Liquid crystal display Number:7,394,511 from the United States Patent and Trademark Office (PTO) owispatent A liquid crystal display is furnished with: a liquid crystal display element having a pair of substrates, to which alignment members are provided to their respective opposing surfaces, and a liquid crystal layer sandwiched by the pair of substrates; an alignment mechanism for providing at least two different director configurations simultaneously on different arbitrary regions used for display in the liquid crystal layer; and a reflection film provided to at least one of the different arbitrary regions showing different director configurations; wherein the different arbitrary regions showing different director configurations are used for a reflection display section for showing reflection display and a transmission display section for showing transmission display, respectively. Examples of the alignment mechanism include an alignment film to which the alignment treatment is applied in different orientations in the reflection display section and transmission display section, respectively, an insulation film having different film thicknesses in the reflection display section and transmission display section, and so forth.<H display, crystal, Liquid, crystal, , 7394511.html, Patent, pto, 7394511

Title: Liquid crystal display

Abstract: A liquid crystal display is furnished with: a liquid crystal display element having a pair of substrates, to which alignment members are provided to their respective opposing surfaces, and a liquid crystal layer sandwiched by the pair of substrates; an alignment mechanism for providing at least two different director configurations simultaneously on different arbitrary regions used for display in the liquid crystal layer; and a reflection film provided to at least one of the different arbitrary regions showing different director configurations; wherein the different arbitrary regions showing different director configurations are used for a reflection display section for showing reflection display and a transmission display section for showing transmission display, respectively. Examples of the alignment mechanism include an alignment film to which the alignment treatment is applied in different orientations in the reflection display section and transmission display section, respectively, an insulation film having different film thicknesses in the reflection display section and transmission display section, and so forth.

Patent Number: 7,394,511 Issued on 07/01/2008 to Okamoto, et al.

Inventors: Okamoto; Masayuki (Kashiwa, JP), Hiraki; Hajime (Kashiwa, JP), Mitsui; Seiichi (Kashiwa, JP)
Assignee: Sharp Kabushiki Kaisha (Osaka, JP)

Appl. No.: 11/333,304

Filed: January 18, 2006

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
10774625	Feb., 2004	7050132
10177149	May., 2005	6900863
09887442	Jun., 2001	6563554
09217931	Dec., 1998	6281952

Foreign Application Priority Data


Dec 26, 1997 [JP]			9-359036
Dec 22, 1998 [JP]			10-364247

Current U.S. Class: 349/114 ; 349/106

Current International Class: G02F 1/1335 (20060101)

Field of Search: 349/106,109,113,114 345/88

References Cited [Referenced By]

U.S. Patent Documents


5220444	June 1993	Mitsui et al.
5578241	November 1996	Plach et al.
5598285	January 1997	Kondo et al.
5684551	November 1997	Nakamura et al.
5691791	November 1997	Nakamura et al.
5737051	April 1998	Kondo et al.
5753937	May 1998	Shimomaki et al.
5847789	December 1998	Nakamura et al.
6108064	August 2000	Minoura et al.
6147728	November 2000	Okumura et al.
6195140	February 2001	Kubo et al.
6211992	April 2001	Van Aerle et al.
6327010	December 2001	Scheuble et al.
6496241	December 2002	Tillin
6580484	June 2003	Okamoto et al.
6791640	September 2004	Okamoto et al.

Foreign Patent Documents


59-017530	Jan., 1984	JP
59218483	Dec., 1984	JP
61-230101	Oct., 1986	JP
03-11514	Jan., 1991	JP
03-245122	Oct., 1991	JP
07-114020	May., 1995	JP
07-218923	Aug., 1995	JP
7-318929	Dec., 1995	JP
07-333598	Dec., 1995	JP
7-333598	Dec., 1995	JP
07318929	Dec., 1995	JP
08-292413	Nov., 1996	JP
09-274327	Oct., 1997	JP
10-142621	May., 1998	JP
10-282488	Oct., 1998	JP
10-325953	Dec., 1998	JP
11-052366	Feb., 1999	JP
11-52366	Feb., 1999	JP
11-101992	Apr., 1999	JP
11-183892	Jul., 1999	JP
WO-98/48320	Oct., 1998	WO

Other References

"Brightness Function: Effects of Adaptation," J. C. Stevens et al., Journal of the Optical Society of America, vol. 53, No. 3, pp. 375-385 (Mar. 1963). cited by other.

Primary Examiner: Nguyen; Dung T.
Assistant Examiner: Duong; Tai
Attorney, Agent or Firm: Birch, Stewart, Kolasch & Birch, LLP

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 10/774,625 filed on Feb. 10, 2004, now U.S. Pat. No. 7,050,132 which is a divisional of application Ser. No. 10/177,149 filed on Jun. 24, 2002, now U.S. Pat. No. 6,900,863 B2 issued May 31, 2005, which is a divisional of application Ser. No. 09/887,442, filed Jun. 25, 2001, now U.S. Pat. No. 6,563,554 B2, which is a divisional of application Ser. No. 09/217,931 filed on Dec. 22, 1998, now U.S. Pat. No. 6,281,952, for which priority is claimed under 35 U.S.C. .sctn. 120; and this application claims priority of Application No. 9-359036 filed in Japan on Dec. 26, 1997 and Application No. 10-364247 filed in Japan on Dec. 22, 1998, under 35 U.S.C. .sctn. 119. The entire contents of all of these applications are hereby incorporated by reference.

Claims

What is claimed is:

1. A liquid crystal display device comprising: a pair of substrates and a liquid crystal layer interposed between said substrates, said device including a plurality of pixels; at least some of said pixels each including a light reflecting display section and a light transmitting display section; wherein said light reflecting display sections are provided with color filters, and said light transmitting display sections are partially provided with color filters.

2. The liquid crystal display of claim 1, wherein the characteristics of the color filters in the light transmitting display sections are substantially the same as the characteristics of the color filters in the light reflecting display sections.

3. The liquid crystal display device of claim 1, wherein the color filters in said light transmitting display sections have a transmission color with chroma at least as good as the chroma of the color filters in said light reflecting display sections.

Description

FIELD OF THE INVENTION

The present invention relates to liquid crystal displays used for information systems, such as word processors and notebook-type personal computers, video equipment of various kinds, video game machines, portable VCRs, digital cameras, etc. More particularly, the present invention relates to liquid crystal displays used indoors and outdoors, or in automobiles, air-planes, marine vessels, etc. where a variety of ambient light conditions occurs.

BACKGROUND OF THE INVENTION

Conventionally, CRTs (Cathode Ray Tubes), EL (Electroluminescence) elements, PDPs (Plasma Display Panels), etc. have been put into practical use as displays of the light emissive type in which display contents can be overwritten electrically.

However, since this type of displays emit display light and use the same directly for the display, there arises a problem that their power consumption is quite large. Further since a light-emitting surface of the displays of this type serves as a display surface having high reflectance, if the displays of this type are used under the circumstances where ambient light is brighter than the luminance, for example, in direct sunlight, there always occurs a phenomenon known as "wash-out" in which the display light cannot be observed.

On the other hand, liquid crystal displays have been put into practical use as color displays which display characters and/or images not by emitting the display light, but by adjusting an amount of transmitted light from a particular light source. These liquid crystal displays include a transmission type and a reflection type.

Of the two types, particularly popular are the liquid crystal displays of the transmission type which employ a light source called "back light" at the back side, namely, behind the liquid crystal cell. Since the liquid crystal displays of the transmission type are advantageous in thinness and lightness, they have been used in diversified fields. On the other hand, the liquid crystal displays of the transmission type consume a large amount of power to keep the back light turned ON. Thus, regardless of the advantage that only a small amount of power is consumed to adjust transmittance of the liquid crystal, a relatively large amount of power is consumed as a whole.

However, the liquid crystal displays of the transmission type (that is, color liquid crystal displays of the transmission type) wash out less frequently compared with the displays of the light emissive type. This is because, in the color liquid crystal displays of the transmission type, the reflectance on the display surface of a color filter layer is reduced by the reflectance reducing technique using a black matrix.

Nevertheless, it becomes too difficult to observe the display light on the color liquid crystal displays of the transmission type when they are used under the circumstances where the ambient light is very strong and the display light is relatively weak. This problem can be eliminated by using brighter back light, but this solution raises another problem that the power consumption is further increased.

Unlike the displays of the light emissive type and liquid crystal displays of the transmission type, the liquid crystal displays of the reflection type show the display using the ambient light, thereby obtaining display light proportional to an amount of the ambient light. Thus, the liquid crystal displays of the reflection type are advantageous in a principle that they do not wash out, and when used in a very bright place in direct sunlight, for example, the display can be observed all the more sharply. Further, the liquid crystal displays of the reflection type do not use the back light for the display, and therefore, have another advantage that the power for keeping the back light turned ON can be saved. For the above reasons, the liquid crystal displays of the reflection type are particularly suitable as the devices for the outdoor use, such as portable information terminals, digital cameras, and portable video cameras.

However, since these conventional liquid crystal displays of the reflection type use the ambient light for the display, the display luminance largely depends on the surrounding environment, and when used under the circumstances where the ambient light is weak, there arises a problem that the display content can not be observed. Particularly, in case that a color filter is used for realizing the color display, the color filter absorbs the light and the display becomes darker. Thus, when used under these circumstances, the above problem becomes more apparent.

To eliminate the above problem, a lighting device called "front light" has been developed as an auxiliary light, so that the liquid crystal displays of the reflection type can be used under the circumstances where the ambient light is weak. Since the liquid crystal displays of the reflection type have a reflection layer behind the liquid crystal layer, they can not use the back light as do the liquid crystal displays of the transmission type. For this reason, the lighting device (front light) lights the liquid crystal displays of the reflection type from the front side, that is, from the display surface side.

On the other hand, liquid crystal displays, employing a transflective film which transmits a part of incident light and reflects the rest, have been put into practical use as the liquid crystal displays which can be used under the circumstances where the ambient light is weak while maintaining the advantages of the liquid crystal displays of the reflection type. The liquid crystal displays using both the transmitted light and reflected light are generally referred to as the liquid crystal displays of the transflective type.

For example, Japanese Laid-open Patent Application No. 218483/1984 (Tokukaisho No. 59-21843) (Japanese Patent Application No. 92885/1983 (Tokugansho No. 58-92885)) discloses a liquid crystal display of the transflective type which modulates the brightness by the TN (Twisted Nematic) mode, STN (Super-Twisted Nematic) mode, etc., which are known as the liquid crystal display modes for modulating the luminance of the transmitted light. Also, Japanese Laid-open Patent Application No. 318929/1995 (Tokukaihei No. 7-318929) discloses a liquid crystal display of the transflective type, in which a transflective film is provided in close proximity to the liquid crystal layer. Further, Japanese Laid-open Patent Application No. 160878/1994 (Tokukaihei No. 6-160878) (U.S. Pat. Nos. 5,598,285 and 5,737,051) discloses a liquid crystal display of the transmission type adopting the in-plane switching method as a technique for realizing a wider range of viewing angles. However, since the liquid crystal display of the transflective type disclosed in Japanese Patent Application No. 218483/1984 (Tokukaisho No. 59-218483) has the transflective film behind the liquid crystal cell seen from the viewer's side, there occur the following problems (1) and (2).

(1) It is very difficult to set the brightness which affects a visibility of the display device. More specifically, when the brightness of the liquid crystal display of the transflective type is set adequately for the reflection display, the brightness is set high, so that it can be used under the circumstances where the ambient light is insufficient. However, if the brightness is set high by using a polarization plate having high transmittance in the TN method, for example, a contrast ratio, which is defined as a quotient obtained by dividing the brightness in the light display by the brightness in the dark display, becomes too low for the transmission display, thereby deteriorating the visibility. Conversely, when the brightness of the liquid crystal display of the transflective type is set adequately for the transmission display, it is preferable to set the brightness in such a manner as to raise the contrast ratio. However, in this case, the brightness becomes too low for the reflection display, thereby deteriorating the visibility as well.

(2) In the reflection display, since the display is observed by reflecting the light having passed through the liquid crystal layer sandwiched by the two substrates by the reflection film provided behind the liquid crystal cell, there occurs parallax (double image) and the resolution deteriorates, thereby making high-resolution display very difficult.

Also, in the liquid crystal display of the transflective type disclosed in Japanese Laid-open Patent Application No. 318929/1995 (Tokukaihei No. 7-318929), since the transflective film is used as the reflection film, there arises another problem that there is no optical design such that can be suitable for both the reflection display section and transmission display section.

Further, although the in-plane switching method disclosed in Japanese Laid-open Patent Application No. 160878/1994 (Tokukaihei No. 6-160878) is employed in the liquid crystal displays of the transmission type, the director configuration of the liquid crystal on the comb-shaped electrode does not contribute to the display. This is not because, in most cases, the electrode lines are made of metal that does not transmit light, but because the director configuration of the liquid crystal is not changed sufficiently for the transmission display.

SUMMARY OF THE INVENTION

Thus, to eliminate the above problems, the inventors of the present invention tried to apply the display method capable of eliminating the parallax and employed in the liquid crystal displays of the reflection type to the liquid crystal displays of the transflective type. More specifically, the inventors conducted an assiduous study by applying the two following methods to the transflective display:

(a) the GH (Guest-Host) method for filling liquid crystal composition blended with a dichroic dye into the liquid crystal layer; and

(b) the reflection type liquid crystal display method using a single polarization plate (hereinafter, referred to as the single polarization plate method).

To apply the above two display methods (a) and (b) which eliminate the parallax to the liquid crystal displays of the transflective type, the reflection layer is provided to touch or almost touch the liquid crystal layer, and a transmission opening is made through the reflection layer to use the transmitted light for the display in addition to the reflected light.

Then, the study revealed the following problems. In case of (a) GH method, when a concentration of the dichroic dye blended with the liquid crystal composition is adjusted adequately for the reflection display, the brightness is sufficiently high but the contrast ratio becomes too low in the transmission display section, thereby failing to obtain satisfactory display. On the other hand, when a concentration of the dichroic dye blended with the liquid crystal composition is adjusted adequately for the transmission display, the contrast ratio is sufficiently high in the transmission display section, but the brightness becomes too low in the reflection display section, thereby failing to obtain satisfactory display.

Also, in case of (b) single polarization plate method, the director configuration of the liquid crystal and a thickness of the liquid crystal layer which determine the optical characteristics, a voltage applied to the liquid crystal for driving the same, etc. are set adequately for either the reflection display section or the transmission display realized by additionally providing a polarization plate or the like behind the display surface (double polarization plate method).

Firstly, the display in the transmission display section when the thickness of the liquid crystal layer is set adequately for the reflection display will be explained. In this case, an amount of change in the polarization state caused when the director configuration of the liquid crystal layer is changed by an external field, such as an electric field, is about a strength such that can realize a satisfactory contrast ratio when incident light from the front, that is, from the display surface side, passes through the liquid crystal layer and exits to the display surface side by passing through the liquid crystal layer again. However, when set in this manner, an amount of the change of the polarization state of the light having passed through the liquid crystal layer is not sufficient in the transmission display section. Thus, even if the polarization plate used for the transmission display alone is provided behind the liquid crystal cell seen from the viewer's side in addition to the polarization plate used for the reflection display and provided to the viewer's side of the liquid crystal cell, that is, the display surface side, the display in the transmission display section is not satisfactory. In other words, when the director configurations (thickness of the liquid crystal layer, director configuration of the liquid crystal, etc.) of the liquid crystal layer are set to be suitable for the reflection display, in the transmission display section, either the brightness is not sufficient or even if the brightness is sufficient, the transmittance does not decrease in the dark display, thereby failing to attain a sufficient contrast ratio for the display.

To be more specific, in case of the reflection display, the director configuration of the liquid crystal in the liquid crystal layer is controlled by means of a voltage applied to the liquid crystal layer to impart a phase difference of about 1/4 wavelength to the light passing through the liquid crystal layer only once. When the transmission display is shown with the voltage modulation such that imparts a 1/4 wavelength phase modulation to the light passing through the liquid crystal layer set in such a manner as to impart the above-specified phase difference to the light passing through the same, if the transmittance of the transmission display section for the dark display is lowered sufficiently, about half the luminance of the light is absorbed by the polarization plate at the light outgoing side when the transmission display section shows the light display, thereby failing to obtain satisfactory light display. If optical elements, such as a polarization plate and a phase difference compensation plate, are provided to increase the brightness in the light display in the transmission display section, the brightness in the dark display in the transmission display section is increased to about half the brightness in the light display, and the resulting contrast ratio is not satisfactory for the display.

Next, the display in the reflection display section, in case that the director configurations of the liquid crystal layer are set to be suitable for the transmission display, will be explained. In case that the reflection display is shown when the liquid crystal layer is set adequately for the transmission display, the director configuration of the liquid crystal must be controlled by the voltage modulation in such a manner that the polarization state of the light passing through the liquid crystal layer only once is modulated between the two polarization states which are orthogonal each other. The two orthogonal polarization states include two linearly polarized light beams having oscillation planes intersecting at right angles, two circularly polarized light beams of right and left circularly polarization, or two elliptically polarized light beams having the same ellipticity whose major axis orientations intersect at right angles, thereby having opposite rotation directions in their respective photo-electric fields. To realize the modulation of the polarization state in any combination of the above two polarization states being orthogonal each other, a voltage must be modulated in such a manner that the liquid crystal layer imparts a phase difference of 1/2 wavelength to the light passing through the same. When the polarization state of the light is modulated by any combination of the two orthogonal polarization states in the above manner, satisfactory brightness and contrast ratio can be attained in the transmission display optionally, by the function of the polarization plate, with the help of the phase difference compensation plate.

However, when the liquid crystal layer is set to realize the above control, the reflectance in the reflection display is changed from the light display to the dark display and to the light display again while the transmittance in the transmission display is changed once from the light display to the dark display. Thus, the same display, that is, either the light or dark display, can not be realized simultaneously in the reflection display section and transmission display section by the same liquid crystal alignment changing means (for example, the thickness of the liquid crystal layer is equal, the initial director configuration is identical, and the driving voltage is equal). The problems raised in the methods (a) and (b) are also raised with the liquid crystal display of the transflective type disclosed in aforementioned Japanese Laid-open Patent Application No. 318929/1995 (Tokukaihei No. 7-318929).

In addition, a pressure detecting input device (touch panel) superimposed on the liquid crystal display has light reflecting properties, thereby posing a problem that the visibility is deteriorated. This problem is particularly obvious in the liquid crystal displays of the reflection type.

Also, in general, a front light unit used to improve the visibility of the liquid crystal displays of the reflection type under the circumstances where the ambient light is weak has a planar light pipe structure. Thus, the display content is observed through this light pipe, and there arises a problem that the visibility is deteriorated.

The present invention is devised to solve the above problems, and it is therefore an object of the present invention to provide a liquid crystal display with excellent visibility, capable of showing high-resolution display while using both the reflected light and transmitted light for the display. It is another object of the present invention to provide a liquid crystal display with excellent visibility, capable of showing high-resolution color display while using both the reflected light and transmitted light for the display.

The inventors of the present invention continued an assiduous study to fulfill the above and other objects, and achieved the present invention when they discovered that the cause of the problems occurred in the conventional liquid crystal displays applying either the GH method or polarization plate method is that the director configuration of the liquid crystal layer is set identical in the transmission display section and reflection display section at the same time.

Here, the director configuration of the liquid crystal layer indicates not only the director defined as orientation of the liquid crystal molecules at a specific point in the liquid crystal layer, but also the variation of the director field with respect to the position along the normal axis of the liquid crystal layer.

To be more specific, to fulfill the above and other objects, a liquid crystal display of the present invention is a liquid crystal display furnished with a liquid crystal display element having a pair of substrates, to which alignment members are provided to their respective opposing surfaces, and a liquid crystal layer sandwiched by the pair of substrates, characterized in that:

alignment mechanism for providing at least two different director configurations simultaneously on different arbitrary regions used for display in the liquid crystal layer is provided;

a reflecting member is provided to at least one of the different arbitrary regions showing different director configurations; and

the different arbitrary regions showing different director configurations are used for a reflection display section for showing reflection display and a transmission display section for showing transmission display, respectively.

According to the above arrangement, the director configuration of the liquid crystal can be different simultaneously. Thus, for example, an amplitude of modulation in an opti-physical quantity, such as an amount of absorbed light (absorbance) in case that a light absorber like a dichroic dye is used for the display, and a phase difference in case that optical anisotropy is used for the display, can be changed separately in each region having a different director configuration of the liquid crystal. Thus, according to the above arrangement, the transmittance or reflectance based on an amplitude of modulation in an opti-physical quantity in response to the director configuration of the liquid crystal layer can be obtained, thereby making it possible to set the optical parameters of the transmission display section and those of the reflection display section independently. Consequently, according to the above arrangement, it has become possible to provide a liquid crystal display of the transflective type with excellent visibility, capable of showing high-resolution display while using both the reflected light and transmitted light for the display.

Also, to fulfill the above and other objects, a liquid crystal display of the present invention is a liquid crystal display furnished with a liquid crystal display element having a pair of substrates, to which alignment members are provided to their respective opposing surfaces, and a liquid crystal layer sandwiched by the pair of substrates, characterized in that:

a region used for display in the liquid crystal layer is composed of regions having at least two different thicknesses of the liquid crystal layer;

the regions having at least two different thicknesses are used for a reflection display section and a transmission display section, respectively;

a reflecting member is provided at least to the reflection display section; and

the thickness of the liquid crystal layer is thinner in the reflection display section than in the transmission display section.

According to the above arrangement, the transmittance or reflectance based on an amplitude of modulation in an opti-physical quantity in the regions having different thicknesses of the liquid crystal layer can be obtained, thereby making it possible to set the transmission display section and reflection display section independently. Thus, according to the above arrangement, it has become possible to provide a liquid crystal display of the transflective type with excellent visibility, capable of showing high-resolution display while using both the reflected light and transmitted light for the display.

According to the present invention, satisfactory display can be shown on both the reflection display section and transmission display section by providing the above arrangement to the liquid crystal display. However, there is an optimal ratio of the reflection display section to the transmission display section for showing satisfactory display, and this optimal ratio varies depending on whether color display or monochrome display is desired, or whether the display is shown mainly by the reflection display or transmission display.

In the liquid crystal display of the present invention, in case that both the reflection display section and the transmission display section show color display, it is preferable that an area of the reflection display section accounts for 30% or above and 90% and less of a total of areas of the reflection display section and the transmission display section.

When the color display is shown on the liquid crystal display of the present invention in the above manner, besides the liquid crystal layer, design of the color filter layer, which plays an important role in color reproduction, is critical. According to the study of the inventors of the present invention, the liquid crystal display of the transflective type will be used in typical two styles.

One is a style that mainly shows the transmission display in general use and uses the reflection display supplementarily, so that the wash-out can be prevented under the lighting environment where the ambient light is very strong, and therefore, can be used extensively in diversified lighting environments compared with the displays of the luminous type or the liquid crystal displays of the transmission type. The other is a style that mainly shows the reflection display in general use by exploiting the advantages of the reflection display that the power consumption is small and the lighting device known as the back light is turned ON only when used under the circumstances where the lighting is weak. Hence, like in the former style, this style can be used extensively in diversified lighting environments.

In the former style (the style showing the transmission display mainly), by providing a color filter having a transmission color at least in the transmission display section of the regions making up the region of each pixel in at least one of the pair of substrates, it has become possible to provide a liquid crystal display with excellent visibility, capable of showing high-resolution color display while using both the reflected light and transmitted light for the display.

When the color display is shown in the above manner, it is effective if the color filter having a transmission color is provided at least to the transmission display section in each pixel, and in the reflection display section, either no color film is used or a color filter having the same brightness as the brightness of the color filter provided to the transmission display section or a color filter having a transmission color brighter than the brightness in the color filter provided to the transmission display section, is provided at least partially.

In the latter style (the style showing the reflection display mainly), by providing a color filter having a transmission color at least in the reflection display section of the regions making up the display region of each pixel in at least one of the pair of substrates, it has become possible to provide a liquid crystal display with excellent visibility, capable of showing high-resolution color display while using both the reflected light and transmitted light for the display.

When the color display is shown in the above manner, it is effective if the color filter having a transmission color is provided to at least the reflection display section in each pixel, and in the transmission display section, either no color film is used or a color filter having chroma as good as the chroma of the color filter provided to the reflection display section or a color filter having a transmission color with better chroma than the chroma of the color filter provided to the reflection display section, is provided at least partially.

According to the above arrangement, it has become possible to provide a liquid crystal display with excellent visibility, capable of showing a high-resolution color display while using both the reflected light and transmitted light for the display.

For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section showing a major portion of a liquid crystal display in accordance with Embodiment 1 of the present invention;

FIG. 2 is a view showing display characteristics of a liquid crystal display of Example 1;

FIG. 3 is a view showing display characteristics of liquid crystal displays of Comparative Examples 2 and 3, respectively;

FIG. 4 is a cross section showing a major portion of a liquid crystal display in accordance with Embodiment 2 of the present invention;

FIG. 5 is a view explaining a definition of a crossed rubbing angle;

FIG. 6 is a view showing display characteristics of a liquid crystal display of Example 2;

FIG. 7 is a view showing display characteristics of a liquid crystal display of Example 3;

FIG. 8 is a view showing display characteristics of a liquid crystal display of Example 4;

FIG. 9 is a view showing display characteristics of a liquid crystal display of Example 5;

FIG. 10 is a view showing display characteristics of a liquid crystal display of Example 6;

FIG. 11 is a view showing display characteristics of a liquid crystal display of Example 7;

FIG. 12 is a view showing display characteristics of a liquid crystal display of Comparative Example 3;

FIG. 13 is a view showing display characteristics of a liquid crystal display of Example 8;

FIG. 14 is a view showing display characteristics of a liquid crystal display of Comparative Example 4;

FIG. 15 is a view showing display characteristics of a liquid crystal display of Comparative Example 5;

FIG. 16 is a view showing display characteristics of a liquid crystal display of Example 9;

FIG. 17 is a view showing the steps of the alignment treatment applied to the substrates used for a liquid crystal display in accordance with Embodiment 4 of the present invention;

FIGS. 18(a) through 18(e) are cross sections schematically showing the alignment treatment steps of FIG. 17;

FIG. 19 is a view showing display characteristics of a liquid crystal display of Example 10;

FIG. 20 is a view showing display characteristics of a liquid crystal display of Example 11;

FIG. 21(a) is a cross section showing a major portion of a liquid crystal display of Example 12 when no voltage is applied;

FIG. 21(b) is a cross section showing the major portion of the liquid crystal display of FIG. 21(a) when a voltage is applied;

FIG. 22 is a view showing display characteristics of a liquid crystal display of Example 12;

FIG. 23(a) is a plan view showing a major portion of a TFT element substrate for realizing a liquid crystal display of the transmission-main transflective type in accordance with Embodiment 7 of the present invention;

FIG. 23(b) is a view showing a driving electrode of a reflection display section on the TFT element substrate of FIG. 23(a);

FIG. 23(c) is a view showing a transparent pixel electrode on the TFT element substrate of FIG. 23(a);

FIG. 24 is a cross section of the TFT element substrate taken on line A-A' of FIG. 23(a);

FIG. 25 is a cross section of the TFT element substrate taken on line B-B' of FIG. 23(a);

FIG. 26(a) is a plan view showing a major portion of the liquid crystal display of the transmission-main transflective type in accordance with Embodiment 7 of the present invention, and it is a partial cutaway view of a color filter substrate showing an alignment of color filters formed on the color filter substrate used in the above liquid crystal display of the transmission-main transflective type with respect to a transmission display opening of a driving electrode formed in the reflection display section on the TFT element substrate of FIG. 23(a);

FIG. 26(b) is a cross section of the color filter substrate of FIG. 26(a);

FIG. 27 is a cross section showing a major portion of the liquid crystal display taken on line C-C' of FIG. 26(a);

FIG. 28 is a plan view showing a major portion of a TFT element substrate for realizing a liquid crystal display of the reflection-main transflective type in accordance with Embodiment 7 of the present invention;

FIG. 29(a) is a plan view showing a major portion of the liquid crystal display of the reflection-main transflective type in accordance with Embodiment 7 of the present invention, and it is a partial cutaway view of a color filter substrate showing an alignment of color filters formed on the color filter substrate used in the above liquid crystal display of the reflection-main transflective type with respect to a transmission display opening of a driving electrode formed in the reflection display section on the TFT element substrate of FIG. 28;

FIG. 29(b) is a cross section of the color filter substrate of FIG. 29(a);

FIG. 30 is a contour plot showing a relation of adapted luminance which imparts perceived brightness of an equivalent value versus sample luminance;

FIG. 31 is a view showing characteristics of a relation of illuminance versus perceived brightness in a liquid crystal display of the transflective type in accordance with Embodiment 8 of the present invention; and

FIG. 32 is a cross section schematically showing an arrangement of a major portion of a liquid crystal display incorporating an input device in accordance with Embodiment 11 of the present invention.

DESCRIPTION OF THE EMBODIMENTS

A liquid crystal display of the present invention is characterized in that the director configuration of the liquid crystal can take different states respectively in the reflection display section and transmission display section at the same time. Here, the director configuration of the liquid crystal means not only the director defined as orientation of the liquid crystal molecules at a particular point in the liquid crystal layer, but also the variation of the director field with respect to the position along the normal axis of the liquid crystal layer. Thus, in the present invention, methods of realizing different director configurations of the liquid crystal in the reflection display section and transmission display section and alignment mechanisms used for these methods are classified into three categories, and each will be explained separately below.

In a first category method, the liquid crystal is given different director configurations in the reflection display section and transmission display section by means of an alignment mechanism formed to impose a specific condition of the liquid crystal layer differently in the reflection display section and transmission display section.

To be more specific, examples of the first category method include:

(1) using an alignment mechanism that twists the director of the liquid crystal at totally different twist angles in the reflection display section and transmission display section;

(2) using an alignment mechanism that greatly changes the tilt angle of the director of the liquid crystal with respect to the substrates;

(3) providing liquid crystal materials of different kinds in the reflection display section and transmission display section; and

(4) blending different kinds of dyes with the liquid crystal material at different concentrations in the transmission display section and reflection display section (in this case, a liquid crystal material of the same kind may be used in the transmission display section and reflection display section).

The liquid crystal display of the present invention is furnished with the mechanism used for implementing the above methods as the alignment mechanism of the present invention. The first category method and the alignment mechanism used for the first category method may be a combination of any of the above example methods (1) through (4), and different director configurations of the liquid crystal can be realized in the reflection display section and transmission display section by the above example methods and the alignment mechanism used for these example methods.

In a second category method, the liquid crystal is given different director configurations in the reflection display section and transmission display section by display content overwriting means for overwriting the display content with a time lapse (in other words, the alignment mechanism that makes the director configurations of the liquid crystal different in the transmission display section and reflection display section is a display content overwriting means). The display content overwriting means adopted in the second category method can be any of the existing display overwriting means.

More specifically, examples of the second category method include:

(5) overwriting the director configuration of the liquid crystal by using different electrodes in the transmission display section and reflection display section as the alignment mechanism, in other words, applying different voltages as the display content overwriting means directly to the reflection display section and transmission display section;

(6) applying substantially different voltages to the reflection display section and transmission display section from the same electrode. In this case, the liquid crystal is given with different director configurations in the reflection display section and transmission display section driven by a common electrode by providing an insulation body (for example, an insulation film) having different layer thicknesses in the reflection display section and transmission display section between the liquid crystal layer and the electrode driving the same; and

(7) making the directions of the electric fields different in the reflection display section and transmission display section. In case that the display is shown by changing the in-plane alignment direction of the liquid crystal of the liquid crystal layer by means of an electrode group provided in parallel with one of the substrates sandwiching the liquid crystal layer for supplying different potentials to the liquid crystal layer, the director configurations of the liquid crystal differ greatly at a region between the electrodes and a region on the electrode. Thus, these regions having different director configurations of the liquid crystal may be used for the reflection display and transmission display, respectively. Further, a method of applying different potentials to the liquid crystal layer aligned perpendicularly to the substrates by the same electrode group may be adopted. In case of adopting the second category method, the electrodes or insulation body used for implementing the above example methods, or a combination thereof corresponds to the alignment mechanism of the present invention, and naturally, the resulting liquid crystal display is furnished with such alignment mechanism.

In a third category method, the director configurations of the liquid crystal do not differ greatly, but the thicknesses of the liquid crystal layer, which are factors that determine the optical characteristics, differ in the reflection display section and transmission display section. To implement the third category method, an insulation film having different thicknesses in the reflection display section and transmission display section, substrates having different layer thicknesses or shapes in the reflection display section and transmission display section, etc. are used as the above alignment mechanism.

In case of adopting the third category method, the director configuration of the liquid crystal may be twisted uniformly like in the TN method adopted in the liquid crystal display employing two polarization plates, for example. In this case, the director configuration of the liquid crystal is parallel to the substrates sandwiching the liquid crystal layer, and the director is twisted while changing its direction in the plane of one of the substrates in accordance with a distance from that substrate. When this director configuration of the liquid crystal is adopted in the reflection display section and transmission display section by varying the thickness of the liquid crystal layer, satisfactory display can be realized both in the reflection display section and transmission display section, because the optical characteristics vary with the thickness of the liquid crystal layer.

Also, in the GH method, since varying the thickness of the liquid crystal layer can offer substantially the same effect as the effect obtained in case of changing the concentration of the dye, satisfactory display can be realized both in the reflection display section and transmission display section, even when the director configurations of the liquid crystal are substantially the same in the reflection display section and transmission display section.

As has been explained, the method for realizing different director configurations of the liquid crystal in the reflection display section and transmission display section and the alignment mechanism used for this method are classified into three categories, and the liquid crystal display method used in the liquid crystal display of the present invention realized by the above method and alignment mechanism is not especially limited, and can be selected from the methods using a change of the director configuration of the liquid crystal for the display. Examples of the liquid crystal display method applicable in the present invention include: a mode using the nematic phase of the liquid crystal composition for the display, such as the TN method, STN method, nematic bistable mode, vertical alignment mode, hybrid alignment mode, and ECB (Electrically Controlled Birefringence) mode. Also, a mode using scattering, such as the polymer dispersing type liquid crystal mode and dynamic scattering method, can be used as the above liquid crystal display method. Further, the surface stabilized ferroelectric liquid crystal display method using ferroelectric liquid crystal composition and the thresholdless switching anti-ferroelectric liquid crystal display method using anti-ferroelectric liquid crystal can be used as the above liquid crystal display method of the present invention, because they also use a change of the director configuration of the liquid crystal for the display.

In case of adopting the third category method, the liquid crystal display method used in the present invention can be a method of using modulation of the optical rotatory polarization like the TN method, a method of using the modulation of the retardation like the ECB mode, or a method of modulating light absorption (absorbance) like the GH method. In case of adopting the third category method, besides the above methods, any method is applicable, provided that the thickness of the liquid crystal layer is a critical factor for determining the optical characteristics, and provided that making the liquid crystal layer thick in the transmission display section and thin in the reflection display section can offer an effect of realizing satisfactory display.

As has been discussed, the liquid crystal display of the present invention is furnished with a liquid crystal display element having a pair of substrates, to which alignment members (alignment means) are provided to their respective opposing surfaces, and a liquid crystal layer sandwiched by the pair of substrates, and it is arranged in such a manner that: it is furnished with alignment mechanism for imparting at least two different director configurations to arbitrary and different areas in the liquid crystal layer used for the display simultaneously; a reflecting member (reflecting means) is provided in at least one of the regions showing the different director configurations in the liquid crystal layer; and the regions showing the different director configurations are used as a reflection display section for showing reflection display and a transmission display section for showing transmission display, respectively. This arrangement makes it possible to obtain transmittance or reflectance based on an amplitude of modulation in an opti-physical quantity in response to the director configuration of the liquid crystal layer, thereby realizing a high contrast ratio without causing any parallax. Consequently, not only can the visibility under dark circumstances be improved, but also satisfactory visibility can be obtained even when the ambient light is strong.

To change an amplitude of modulation in an opti-physical quantity (such as absorption of light and a phase difference caused by optical anisotropy) in the reflection display section and transmission display section independently, even if the alignment direction of the liquid crystal determined by the applied voltage is oriented to substantially the same direction across a region of the liquid crystal layer used for the display, regions having different thicknesses of the liquid crystal layer can attain substantially the same effect as the effect obtained when the alignment direction of the liquid crystal layer is changed in these regions. For this reason, another liquid crystal display of the present invention is furnished with a liquid crystal display element having a pair of substrates, to which alignment members (alignment means) are provided to their respective opposing surfaces, and a liquid crystal layer sandwiched by the pair of substrates, and it is arranged in such a manner that:

a region used for display in the liquid crystal layer is composed of regions having at least two different thicknesses of the liquid crystal layer;

the regions having at least two different thicknesses are used for a reflection display section and a transmission display section, respectively;

a reflecting member (reflecting means) is provided at least to the reflection display section; and

the thickness of the liquid crystal layer is thinner in the reflection display section than in the transmission display section.

This arrangement also makes it possible to obtain transmittance or reflectance based on an amplitude of modulation in an opti-physical quantity in regions having different thicknesses of the liquid crystal layer. Accordingly, the transmission display section and reflection display section can be set independently. Thus, according to the above arrangement, a high contrast ratio can be attained without causing any parallax, and not only can the visibility under dark circumstances be improved, but also satisfactory visibility can be obtained even when the ambient light is strong.

A liquid crystal display realizing satisfactory reflection display and transmission display by changing the thickness of the liquid crystal layer in the reflection display section and transmission display section will be explained mainly in Embodiments 1 and 2 below.

Embodiment 1

Mainly referring to FIG. 1, an example liquid crystal display adopting the GH method will be explained in the present embodiment.

FIG. 1 is a cross section of a major portion of the liquid crystal display in accordance with the present embodiment. As shown in the drawing, the liquid crystal display includes a liquid crystal cell 100 (liquid crystal display element), and optionally, a back light 13 (lighting device) serving as back light means. The liquid crystal cell 100 and back light 13 are provided sequentially in this order from the viewer's (user's) side.

As shown in the drawing, the liquid crystal cell 100 is composed of a liquid crystal layer 1 sandwiched by an electrode substrate 101 (first substrate) and an electrode substrate 102 (second substrate). The electrode substrate 101 has an alignment film 2 on a surface touching the liquid crystal layer 1 (an interface between the first substrate and the liquid crystal layer 1), and the electrode substrate 102 has an alignment film 3 on a surface touching the liquid crystal layer 1 (an interface between the second substrate and the liquid crystal layer 1).

The electrode substrate 101 is composed of a substrate 4 made of, for example, a light transmitting glass substrate on which are formed an electrode 6 (voltage applying means) for applying a voltage to the liquid crystal layer 1, and the electrode 6 is covered with the alignment film 2 (alignment mechanism) to which the rubbing treatment has been applied.

On the other hand, the electrode substrate 102 provided in such a manner as to oppose the electrode substrate 101 through the liquid crystal layer 1 is composed of a light transmitting substrate 5 on which are formed counter electrodes 7 (voltage applying means) opposing the electrode 6 through an insulation film 11 for applying a voltage to the liquid crystal layer 1.

The insulation film 11 is made in such a manner as to have different film thicknesses in regions corresponding to a region of the liquid crystal layer 1 used for the display, so that the above region of the liquid crystal layer 1 used for the display has at least two different thicknesses of the liquid crystal layer (herein, exactly two different thicknesses). To be more specific, the insulation film 11 is made thinner in the region corresponding to the transmission display section 10 than in the region corresponding to the reflection display section 9.

In the region of the electrode substrate 102 corresponding to the reflection display section 9, a reflection film 8 (reflecting means) is formed to cover the electrodes 7, and further, the alignment film 3 (alignment member, alignment mechanism) to which the rubbing treatment has been applied is formed to cover the electrodes 7 and reflection film 8.

Here, each of the electrodes 6 and 7 is a transparent electrode made of ITO (Indium Tin Oxide), for example. Also, a voltage is applied to the electrodes 6 and 7 to apply an electric field in the liquid crystal layer 1. Thus, the display is controlled by a voltage applied in accordance with the display content.

Also, the reflection film 8 has light reflecting properties, and is made of metal, such as aluminum or silver, or composed of dielectric multi-layer film mirror. In case that the reflection film 8 is made of a conducting material, the reflection film 8 may also serve as an electrode instead of the electrodes 7. In other words, the reflection film 8 may be a reflective pixel electrode serving both as a liquid crystal driving electrode for driving the liquid crystal layer 1 and the reflecting means. Further, the reflection film 8 may be a color reflection film which reflects light having a wavelength in a range selected from the visible light, as the case may be.

It should be appreciated that the materials and producing methods of each member forming the electrode substrates 101 and 102 are not limited to the above disclosure, and any known material and typical method are applicable. Also, the arrangement of the liquid crystal display is not limited to the above-described arrangement. For example, it may be arranged in such a manner that voltages are applied to the electrodes