JPH08152621A - Reflection diffusion plate and reflection type liquid crystal display device - Google Patents

Abstract

PURPOSE: To make it possible to obtain a reflection characteristic having good directivity by forming a diffusion layer having a refractive index distribution within a plane having a flat surface between the reflection layer on one substrate and another substrate. CONSTITUTION: Aluminum is formed by sputtering as a reflection film 22 on a glass substrate 21. Next, a liquid mixture composed of a photosensitive copolymer prepd. by adding a methyl methacrylate as a dopant to a chloromethacrylate and toluene sol. of 4wt.% is applied as an org. material film 23a on the substrate 21. This coating is then irradiated with UV light 25 via a prescribed photomask. The parts irradiated with the UV light 25 and the parts not irradiated therewith are formed by this photomask 24 and regions varying in refractive indices are formed in an org. material film 23b. The coating is then subjected to baking again, by which the reflection diffusion plate 20 formed with the org. material film 23 having the regions varying in the refractive index is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective liquid crystal display device which displays by reflecting ambient light.

[0002]

2. Description of the Related Art The most important performance required for a reflective liquid crystal display device is how efficiently the ambient light incident on the liquid crystal display device can be reflected and used effectively for display. is there. Currently, in order to obtain a bright display, a method of optimizing the concavo-convex shape of the reflection plate, providing a reflection film on the surface of the reflection plate, and making the reflection plate have directivity in reflection characteristics is proposed in, for example, JP-A-5-323371. Has been done.

The technique disclosed in Japanese Patent Laid-Open No. 5-323371 will be described below. FIG. 15 is a cross-sectional view of the reflective liquid crystal display device 130, and FIG. 16 is a plan view of the reflecting plate 152 shown in FIG. A plurality of gate bus wirings 132 made of chromium, tantalum, or the like are provided in parallel to each other on an insulating substrate 131 made of glass or the like, and a gate electrode 133 branches from the gate bus wirings 132. The gate bus wiring 132 functions as a scanning line.

On the entire surface of the substrate 131 covering the gate electrode 133, silicon nitride (SiN _x ), silicon oxide (S
A gate insulating film 134 made of, for example, iO _x ) is formed. A semiconductor layer 135 made of amorphous silicon (hereinafter referred to as a-Si), polycrystalline silicon, CdSe, or the like is formed on the gate insulating film 134 above the gate electrode 133. At both ends of the semiconductor layer 135, a-Si is formed.
A contact electrode 141 made of, for example, is formed.
A source electrode 136 made of titanium, molybdenum, aluminum, or the like is overlaid on one contact electrode 141, and a drain electrode 137 made of titanium, molybdenum, aluminum, or the like is formed on the other contact electrode 141, similarly to the source electrode 136. It is formed to overlap.

As shown in FIG. 16, the source electrode 136, the gate bus line 132, and the gate insulating film 134 described above.
Source bus lines 139 intersecting with each other are connected. The source bus line 139 functions as a signal line. The source bus line 139 is also made of the same metal as the source electrode 136. The gate electrode 133, the gate insulating film 134, the semiconductor layer 135, the source electrode 136, and the drain electrode 137 form the TFT 140, and the TF
T140 has a function of a switching element.

Gate bus wiring 132, source bus wiring 1
An organic insulating film 142 is formed on the entire surface of the substrate 131 so as to cover 39 and the TFT 140. Organic insulating film 142
In the region where the reflective electrode 138 is formed, a convex portion having a tapered bottom surface with a diameter of 3 to 20 μm is formed at a height H, and adjacent convex portions are formed at a distance of 1 μm or more. A contact hole 143 is formed in the portion. In order to reduce problems in the method of forming the organic insulating film 142, the process of forming the contact hole 143 in the organic insulating film 142, and variations in cell thickness when the liquid crystal display device 130 is formed, the height H of the convex portion is 10 μm or less. Is preferred. A reflective electrode 138 made of aluminum, silver, or the like is formed on a region where the circular convex portion 142a of the organic insulating film 142 is formed, and the reflective electrode 138 is connected to the drain electrode 137 in the contact hole 143. Further, an alignment film 144 is formed on it.

A color filter 146 is formed on the other substrate 145. A magenta or green filter 146a is formed at a position of the color filter 146 facing the reflective electrode 138 of the substrate 131.
Black filter 146b at a position not facing 8
Is formed. I on the entire surface of the color filter 146
A transparent electrode 147 made of TO or the like, and an alignment film 148 are further formed thereon.

Both substrates 131 and 145 are provided with a reflective electrode 138.
And the filter 146a are bonded so as to face each other so as to match with each other, and the liquid crystal 149 is injected therebetween to complete the reflective liquid crystal display device 130.

The shape of the convex portion on the organic insulating film 142 can be controlled by the shape of the mask, the thickness of the photoresist, and the dry etching time, but another organic insulating film may be applied.

By making the dry etching time of the organic insulating film 142 longer, it is possible to obtain the substrate 131 in which the respective heights H of the circular convex portions 142a having various radii are 1 μm, and the height H is 1 μm. A reflective liquid crystal display device using the reflective plate 152 having a certain reflective electrode 138 as a substrate can be obtained.

[0011]

When the above-mentioned conventional reflector is manufactured by dry etching or wet etching, there are the following problems. In dry etching, since the etching force can be distributed by the gas flow in the etching tank, the in-plane distribution is poor and a uniform shape cannot be controlled.
In addition, since the entire surface of wet etching is submerged in the liquid, it is difficult to control the uniform shape. Therefore, there is a problem that the conventional reflector cannot control the directivity and the scattering property with high accuracy.

Further, in the conventional reflection type liquid crystal display device, when an uneven reflection plate is formed on the liquid crystal layer side, when alignment treatment such as rubbing is performed, the liquid crystal molecules at the substrate interface do not tilt in a certain direction, and thus the disc There is a problem that a alignment line is generated and the orientation is not stable.

Further, if a substrate having concave and convex portions on the liquid crystal layer side is used, it becomes impossible to achieve a uniform cell thickness within the screen because of the concave and convex portions. This causes a problem of lowering display quality such as lowering of contrast and unevenness on the display screen.

Further, when the reflecting film has an uneven surface, there is a problem that when patterning as a reflective electrode, the unevenness causes patterning failure.

[0015]

DISCLOSURE OF THE INVENTION The present invention comprises:
A reflective diffusion plate having a substantially flat surface and a diffusion layer having an in-plane refractive index distribution formed thereon.

Further, according to the present invention, at least one of the pair of substrates arranged to face each other with the liquid crystal layer interposed therebetween is a transparent substrate, and the liquid crystal layer side on one substrate is connected to the other substrate side. A reflective liquid crystal display device is formed by forming a reflective layer that reflects the incident light on the liquid crystal layer side of the other substrate, and forming a common electrode having translucency over substantially the entire surface of the other substrate. A reflective liquid crystal display device, wherein a diffusion layer having a substantially flat surface and a refractive index distribution within the surface is formed between the reflective layer and the other substrate.

[0017]

According to the reflective diffuser plate of the present invention, it is possible to obtain a reflection characteristic having a good directivity which has never been obtained.

When this reflective diffusion plate is applied to a reflective liquid crystal display device, a structure can be adopted in which an insulating film is not provided between the liquid crystal layer and the electrodes, so that voltage can be applied without loss.

Further, since the substrate is not provided with unevenness to obtain scattered light, but a flat reflecting / diffusing plate is used,
A good alignment state can be obtained because the liquid crystal molecules at the substrate interface are tilted in a certain direction and are stably aligned.

Further, since the surface of the reflective diffuser plate is flat, a uniform cell thickness is obtained in the display area, so that a uniform voltage is applied to the liquid crystal layer, resulting in good uniform display and viewing angle characteristics. can get.

Further, since the reflective diffusion plate is a flat film, each film is well patterned, and a reflective liquid crystal display device excellent in processability can be obtained.

[0022]

【Example】

(Embodiment 1) A reflective diffuser plate and a reflective liquid crystal display device using the same according to a first embodiment of the present invention will be described. FIG. 1 shows a process of forming a reflective diffusion plate 20 using a film having a substantially flat surface and a distribution having different refractive indexes, which is Embodiment 1.

First, as shown in FIG. 1A, a reflective film 22 is formed by sputtering aluminum to a uniform thickness of 300 nm on an insulative substrate 21 made of glass (Corning 7059). . The reflective film 22 is not limited to aluminum, but Ti, Ta,
Other metals such as Cu, Ag, and Pt may be used, and they may be formed by a method such as vapor deposition other than the sputtering method. Further, the film thickness of the reflective film may be in the range that sufficiently reflects light. After this, aluminum is patterned into stripe electrodes,
This is used as a reflective electrode.

Next, as shown in FIG. 1B, a mixed solution of a photosensitive copolymer in which methyl methacrylate is added as a dopant to chloromethacrylate as an organic material film 23a and a 4 wt% toluene solution. Is uniformly applied onto the substrate 21 by spin coating. The film thickness is preferably 0.5 μm to 4 μm. If the film thickness is thinner than 0.5 μm, it is difficult to form the film, and if it is thicker than 4 μm, uneven film thickness occurs. After coating, baking is performed in an oven at 60 ° C. for 30 minutes.

Next, as shown in FIG. 1C, ultraviolet light (UV light) 25 is irradiated through a predetermined photomask 24. With this photomask 24, ultraviolet light (UV light)
Since there are a portion irradiated with 25 and a portion not irradiated, a region having a different refractive index can be formed in the organic material film 23b.

The photomask 24 has a pattern in which the organic material film 23 formed by the spin coating has a random refractive index distribution in one pixel and is uniform over the entire display portion in which a large number of the pixels are arranged. I used one.

FIG. 2 shows an example of the photomask 24. The photomask 24 of FIG. 2A has a side of 100 to 200 μm.
The unit pattern shown by F in the square of m is used as a reference, and the unit patterns are repeatedly arranged vertically and horizontally. Further, this photomask may be a photomask designed by using mirror inversion as shown in FIG.

In addition to these, a photomask may be used in which the refractive index distribution is random over the entire display portion.

In this embodiment, one photomask is used to form a random refractive index distribution. However, it is also possible to stack a plurality of masks and perform exposure once to produce the same. It is also possible to perform the operation of exposing a plurality of masks one by one a plurality of times.

Further, there is a correlation between the light irradiation amount and the refractive index, for example, as shown in FIG. 3, and the result is that the larger the light irradiation amount, the larger the change in the refractive index. As a result, it is possible to change the refractive index by changing the light irradiation amount.

Next, re-baking is performed in an oven at 95 ° C. for 5 hours, and as shown in FIG. 1D, the reflective diffuser plate 20 having the organic material film 23 having regions having different refractive indexes is formed.
Is completed.

FIG. 4 shows a method for measuring the reflection characteristics of the reflection / diffusion plate 20 thus obtained. In order to make the reflective diffusion plate 20 the same condition as when it is used in an actual liquid crystal display device, the refractive index of the liquid crystal layer and the glass substrate are both approximately equal to about 1.5, so that the refractive index of 1 on the reflective diffusion plate 20. The glass substrate 43 is brought into close contact with the ultraviolet curing adhesive resin 42 of No. 5 to manufacture the measuring device 40.

A photomultimeter 45 for measuring the intensity of light is arranged above the glass substrate 43. The photomultimeter 45 reflects the scattered light 46 that is reflected by the reflective diffusion plate 20 in the normal direction of the measuring device 40 from the incident light 44 that is incident on the reflective diffusion plate 20 at the incident angle θ. The diffusion plate 20 is fixed in the normal direction.

The reflection characteristic can be obtained by changing the incident angle θ of the incident light 44 incident on the measuring device 40 and measuring the scattered light 46 in the normal direction by the reflection / diffusion plate 20.

FIG. 5 shows the results of measuring the reflection characteristics by producing reflection diffusion plates having different reflection characteristics by changing the manufacturing conditions of the reflection diffusion plate described above. In FIG. 5, the reflection intensity of light incident at the incident angle θ is represented as the distance from the origin 0 in the direction of the angle θ with respect to the line of θ = 0 °. The reflection characteristic curve indicated by a white circle is measured on a standard white plate (magnesium oxide). The reflection characteristic 31 indicates a reflection diffusion plate having a strong directivity, the reflection characteristic 33 indicates a reflection diffusion plate having a strong scattering property, and the reflection characteristic 32 indicates a reflection diffusion plate having a reflection characteristic between them. For example, the reflection characteristic 33
It can be seen that the reflective diffusion plate of No. 2 has better reflection characteristics than the standard white plate in the range of θ of about ± 40 °, a bright display is obtained, and ambient light is effectively used.

FIG. 6 shows a sectional view of a reflection type liquid crystal display device using the reflection diffusion plate manufactured by the above method. An alignment film 51 is formed on the reflection-diffusion plate-side substrate 56 by applying polyimide by a spin coater and baking it. An ITO film (indium thin ox) is formed on the insulating counter substrate 52 made of glass (Corning 7059).
The side) 53 is formed with a film thickness of 0.1 μm, and is patterned into a desired shape as a stripe electrode, which is used as a counter electrode. An alignment film 51 is formed on the reflective diffusion plate side substrate 56 in the same manner. Both upper and lower alignment films 51.5
Reference numeral 1 is a felt which is used for rubbing.

An adhesive sealing material 57, in which the counter substrate 52 and the reflection diffusion plate side substrate 56 are mixed with a spacer of 6 μm, for example, is used.
Liquid crystal 54 (manufactured by Merck & Co., Inc .: ZLI2)
After injecting 459), the injection port is sealed with resin. Next, the polarizing plate 55 is installed outside the counter substrate 52 located on the light incident side, and the reflective liquid crystal display device 50 is completed.

According to the present reflection type liquid crystal display device, good reflection characteristics can be obtained, and a uniform display can be obtained which is extremely bright when displaying white and has a high contrast and is easy to see.

(Second Embodiment) A reflective liquid crystal display device according to a second embodiment of the present invention will be described below. Example 2
FIG. 7 shows a reflective diffusion plate forming process of the reflective diffusion plate 60 using a film having a substantially flat surface and a distribution having different refractive indexes.
Shown in

First, as shown in FIG. 7A, a reflective film 62 having a uniform thickness is formed on an insulating substrate 61 made of glass or the like as in the first embodiment.

Next, as shown in FIG. 7B, a mixture of a photosensitive copolymer obtained by adding methyl methacrylate as a dopant to chloromethacrylate and a 4% by weight toluene solution as an organic material film 63a. Is uniformly applied onto the substrate 61 by spin coating. After coating, baking is performed in an oven at 60 ° C. for 30 minutes.

Next, as shown in FIG. 7C, ultraviolet light (UV light) 65 is irradiated through a predetermined photomask 64. With this photomask 64, ultraviolet light (UV light)
Since there are a portion irradiated with 65 and a portion not irradiated, a region having a different refractive index can be formed in the organic material film 63b.

After the irradiation, rebaking is performed in an oven at 95 ° C. for 5 hours, and an organic material film 63 as shown in FIG.
Is completed. After that, an ITO film 66 is formed with a film thickness of 0.1 μm, patterned into a desired shape as a stripe electrode, and the reflection diffusion plate 60 using this as a reflection electrode 66.
Is completed.

With this structure, it is possible to effectively apply a voltage to the liquid crystal layer without a voltage loss due to the insulating layer.

FIG. 8 is a sectional view of a reflection type liquid crystal display device using the reflection diffusion plate produced by the above method. An alignment film 71 is formed on the reflection / diffusion plate side substrate 76 by coating polyimide with a spin coater and baking it. An ITO film (indium thin ox) is formed on an insulating counter substrate 72 made of glass (Corning 7059).
The side) 73 is formed with a film thickness of 0.1 μm, and is patterned into a desired shape as a stripe electrode, which is used as a counter electrode. An alignment film 71 is formed thereon by the same method as that for the reflective diffusion plate side substrate 76. Both upper and lower alignment films 71, 7
Reference numeral 1 is a felt which is used for rubbing.

An adhesive sealing material 77, in which the counter substrate 72 and the reflection diffusion plate side substrate 76 are mixed with a spacer of 6 μm, for example, is used.
Liquid crystal 74 (Merck & Co .: ZLI2)
After injecting 459), the injection port is sealed with resin. Next, the polarizing plate 75 is installed outside the counter substrate 72 located on the light incident side, and the reflective liquid crystal display device 70 is completed.

According to the reflective liquid crystal display device of this embodiment,
It is possible to obtain good reflection characteristics, drive at a low voltage, and achieve a bright, high-contrast reflective liquid crystal display.

(Embodiment 3) A reflective diffuser plate and a reflective liquid crystal display device using the same according to a third embodiment of the present invention will be described. FIG. 9 shows a process of forming the reflective diffusion plate 80 using a film having a substantially flat surface and a distribution having different refractive indexes, which is Embodiment 3.

First, as shown in FIG. 9A, a reflective film 82 is formed by sputtering aluminum to a uniform thickness of 300 nm on an insulative substrate 81 made of glass (Corning 7059). . The reflective film 82 is not limited to aluminum, but Ti, Ta,
Other metals such as Cu, Ag, and Pt may be used, and they may be formed by a method such as vapor deposition other than the sputtering method. Further, the film thickness of the reflective film may be in the range that sufficiently reflects light. After this, aluminum is patterned into stripe electrodes,
This is used as a reflective electrode.

Next, as shown in FIG. 9B, a polyimide resin (H manufactured by Dainippon Ink and Chemicals, Inc.) is used as the organic material film 83.
NA-101) and acrylic resin (Nitto Denko Td-1
A mixture of 1) is uniformly applied onto the aluminum reflective electrode 82 by spin coating. The refractive indices of the mixed resins are 1.37 and 1.59 at a wavelength of 600 nm, respectively, and the difference in the refractive indices causes a light diffusion effect.

At this time, by changing the difference in refractive index due to the difference in resin or changing the film thickness,
It is possible to control the diffusion intensity of light. FIG. 10 shows how the transmittance changes due to the difference in refractive index.
It can be seen from FIG. 10 that almost all light is transmitted when the difference in refractive index is smaller than 0.1, and the degree of light scattering is high when the difference in refractive index is 0.1 or more. Therefore, the difference in refractive index should preferably be 0.1 or more. The thickness of the organic material film 83 is preferably 0.5 μm to 10 μm. If the film thickness is less than 0.5 μm, it is difficult to form the film,
If it is thicker than 10 μm, the voltage drop becomes a problem. In that case, the problem of voltage drop can be avoided by forming an ITO film on the organic material film 83 and using it as a display electrode.

In the third embodiment, two kinds of insulating resins having different refractive indexes are mixed as the organic material film 83, but at least two kinds of insulating resins having different refractive indexes may be mixed.

The type of resin is not limited to the polyimide resin and acrylic resin used in the third embodiment, but may be polyimide resin, epoxy resin, or the like.

Further, the light diffusion layer which is the organic material film 83 does not necessarily have to be provided on the reflection plate 82, and the same effect can be obtained even if it is provided on the upper substrate, and when it is provided under the upper substrate electrode. Also, the voltage drop due to the light diffusion layer which is the organic material film 83 can be prevented.

FIG. 11 shows a method for measuring the reflection characteristics of the reflection diffusion plate 80 thus obtained. In order to make the reflective diffusion plate 80 the same condition as when it is used in an actual liquid crystal display device, the refractive index of the liquid crystal layer and the glass substrate are both approximately equal to about 1.5, so that the refractive index of 1 on the reflective diffusion plate 80. The glass substrate 85 is brought into close contact with the ultraviolet curing adhesive resin 84 of No. 5, and the measuring device 89 is manufactured.

A photomultimeter 45 for measuring the intensity of light is arranged above the glass substrate 85. The photomultimeter 45 reflects the scattered light 46 that is reflected by the reflective diffusion plate 80 in the normal direction of the measuring device 89 from the incident light 44 that is incident on the reflective diffusion plate 80 at the incident angle θ. It is fixed in the direction normal to the diffusion plate 80.

The reflection characteristic can be obtained by changing the incident angle θ of the incident light 44 incident on the measuring device 89 and measuring the scattered light 46 in the normal direction by the reflective diffusion plate 80.

FIG. 12 shows the results of measuring the reflection characteristics by producing the reflection diffusion plates having different reflection characteristics by changing the manufacturing conditions of the reflection diffusion plate described above. In FIG. 12, the reflection intensity of the light incident at the incident angle θ is represented as the distance from the origin 0 in the direction of the angle θ with respect to the line of θ = 0 °. The reflection characteristic curve indicated by a white circle is measured on a standard white plate (magnesium oxide). The reflection characteristic 86 indicates a reflection diffusion plate having a strong directivity, the reflection characteristic 88 indicates a reflection diffusion plate having a strong scattering property, and the reflection characteristic 86 indicates a reflection diffusion plate having a reflection characteristic between them. For example, it can be seen that the reflection diffusion plate having the reflection characteristic 88 has better reflection characteristics than the standard white plate in the range of θ of about ± 40 °, a bright display is obtained, and ambient light is effectively used.

FIG. 13 is a sectional view of a reflection type liquid crystal display device using the reflection diffusion plate manufactured by the above method. An alignment film 91 is formed on the reflection-diffusion-plate-side substrate 96 by applying polyimide with a spin coater and then baking it. An ITO film (indium thinox) is formed on an insulating counter substrate 92 made of glass (Corning 7059).
side) 93 is formed with a film thickness of 0.1 μm, and is patterned into a desired shape as a stripe electrode, which is used as a counter electrode. An alignment film 91 is formed thereon by the same method as that for the reflection diffusion plate side substrate 96. Both upper and lower alignment films 91.9
Reference numeral 1 is a felt which is used for rubbing.

An adhesive sealing material 97, in which the counter substrate 52 and the reflection diffusion plate side substrate 56 are mixed with a spacer of 6 μm, for example, is used.
Is screen-printed, laminated so that the rubbing direction is a twist of 240 ° to the left, and vacuum degassed to obtain a liquid crystal 9 containing a chiral agent (s-811 manufactured by Merck & Co., Inc.).
After injecting 4 (ZLI4427 manufactured by Merck & Co., Inc.), the injection port is sealed with resin. The retardation value of this liquid crystal layer is 676 nm.

Next, the counter substrate 92 located on the light incident side
Retardation plate 95 with a retardation value of 400 nm outside the
Then, the polarizing plate 98 is installed, and the reflective liquid crystal display device 90 is completed. At this time, the angle formed by the polarization axis of the polarizing plate 98 and the rubbing direction of the light incident side substrate is set to 10 ° counterclockwise, and the slow axis of the retardation plate and the rubbing direction of the light incident side substrate are set. The angle formed by and is set to be orthogonal.

FIG. 14 shows the measurement results of the electro-optical characteristics of the reflection type liquid crystal display device 90 thus manufactured and the reflection type liquid crystal display device using the conventional reflection plate having projections and depressions. In FIG. 14, an electro-optical characteristic 101 indicates a characteristic of the reflective liquid crystal display device 90 of the present invention, and an electro-optical characteristic 10
Reference numeral 2 shows the characteristics of a conventional reflection type liquid crystal display device using a reflection plate having projections and depressions. It can be seen from FIG. 14 that the steepness of the electro-optical characteristics is improved and the range of reflectance is widened.

According to the present reflection type liquid crystal display device, since the reflection plate has no unevenness, the steepness of electro-optical characteristics is improved, and as a result, the display contrast ratio can be improved. Furthermore, an extremely bright white display and a high-contrast display that is easy to see can be obtained. Further, although the specular reflection plate is used as the reflection plate in the present embodiment, a scattering reflection plate may be used, and when this is used, the scattering effect becomes more remarkable.

In the present embodiment, fine particles or resins having different refractive indexes are mixed in the alignment film to such an extent that the function of the alignment film is not impaired, so that the light diffusion layer, which is an organic material film, and the alignment film are formed in one layer. By configuring, simplification of the process can be realized.

In this embodiment, a reflective S with a polarizing plate is used.
Although the TN mode has been described as an example, a mode in which the unevenness of the surface affects the alignment, for example, a light absorption mode such as a guest-host mode, a light scattering mode such as a polymer dispersed liquid crystal display device, a ferroelectric The present invention can be applied to any of the birefringence display modes used in the liquid crystal display device.

Further, a TFT (T
Hin Film Transistor), MIM
It can also be applied to an active matrix substrate using a (Metal Insulator Metal), a diode, a varistor, or the like. Further, it can be applied to color display by combining a color filter and various dyes.

[0067]

As described above, according to the present invention, it is possible to obtain a good reflective diffuser plate in which the directivity and the scattering property can be accurately controlled by changing the manufacturing conditions.

Further, by using this reflection diffusion plate in a reflection type liquid crystal display device, the liquid crystal has a good orientation and a good contrast can be obtained.

Furthermore, good patterning of the reflective electrode can be obtained, and the voltage of the liquid crystal display device can be lowered.

[Brief description of drawings]

FIG. 1 is a diagram showing a cross section and a forming process of a reflective diffusion plate according to a first embodiment.

FIG. 2 is a diagram showing an example of a photomask.

FIG. 3 is a diagram showing characteristics of a light irradiation amount and a change amount of a refractive index.

FIG. 4 is a diagram showing a method for measuring the reflection characteristic of the reflective diffusion plate of the first embodiment.

FIG. 5 is a diagram showing a reflection characteristic of the reflection diffusion plate of the first embodiment.

FIG. 6 is a cross-sectional view of a reflective liquid crystal display device using the reflective diffusion plate of Example 1.

FIG. 7 is a diagram illustrating a process of forming a reflective diffusion plate according to the second embodiment.

FIG. 8 is a sectional view of a reflective liquid crystal display device using the reflective diffusion plate of the second embodiment.

FIG. 9 is a diagram showing a cross section and a forming process of a reflective diffusion plate of Example 3;

FIG. 10 is a diagram showing optical characteristics of refractive index difference and transmittance.

FIG. 11 is a diagram showing a method for measuring the reflection characteristic of the reflection / diffusion plate of Example 3;

FIG. 12 is a diagram showing the reflection characteristics of the reflective diffusion plate of Example 3;

FIG. 13 is a cross-sectional view of a reflective liquid crystal display device using the reflective diffusion plate of Example 3.

FIG. 14 is a diagram showing electro-optical characteristics of a reflective liquid crystal display device.

FIG. 15 is a cross-sectional view of a conventional reflective liquid crystal display device.

16 is a plan view of the substrate shown in FIG.

[Explanation of symbols]

20, 60, 80 Reflective diffusion plate 21, 43, 61, 81, 131, 145 Substrate 22, 62, 82 Reflective film 23, 63, 83 Organic material film 24, 64 Photomask 25, 65 Ultraviolet light (UV light) 31 , 32, 33, 86, 87, 88 Characteristic curve of reflection characteristics of reflective diffuser plate 40, 89 Measuring device 42, 84 UV curable adhesive resin with refractive index of 1.5 45 Photomultimeter 44 Incident light 46 Scattered light 50, 70 , 90, 130 Reflective liquid crystal display device 51, 71, 91, 144, 148 Alignment film 52, 72, 92 Counter substrate 53, 73 93 ITO 54, 74 94 Liquid crystal 55, 75, 98 Polarizing plate 56, 76, 96 Reflection Diffusion plate side substrate 57, 77, 97 Sealing material 66, 93, ITO film 95 Phase difference plate 101 Electro-optical characteristics of reflective liquid crystal display device of Example 3 1 2 conventional reflective electro-optical characteristics of the liquid crystal display device 138 reflective electrode 140 TFT 142 organic insulating film 142a circular protrusion 146 color filter 152 reflector

Claims (2)

[Claims] 1. A reflective diffusion plate comprising a diffusion layer having a substantially flat surface and an in-plane refractive index distribution formed on the reflective layer. 2. A transparent substrate is used for at least one of a pair of substrates arranged to face each other with a liquid crystal layer interposed therebetween, and incident light from the other substrate side is incident on the liquid crystal layer side of the one substrate. In a reflective liquid crystal display device formed by forming a reflective layer that reflects light, and forming a common electrode having a light-transmitting property over substantially the entire surface of the other substrate, the reflective layer on the one substrate. A reflective liquid crystal display device, characterized in that a diffusion layer having a substantially flat surface and a refractive index distribution within the surface is formed between the other substrates.