JP2002139728A - Reflection type liquid crystal display element and method for forming its light diffusion layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a liquid crystal display easily visible without subjecting the surface of an element to antiglare treatment and the like. SOLUTION: The form of a recessed groove of an inner surface uneven layer 21 to be a light diffusion layer is specified to be an asymmetric form with respect to the normal V of a display surface to shift the angle at which the liquid crystal display is seen in the brightest state and the regular reflection angle of external light on the display surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device and a method of forming a light diffusion layer thereof. More specifically, the present invention relates to a method of forming a brightness peak at a position shifted from a regular reflection angle of external light on the surface of the device. The present invention relates to an internal light diffusion layer having the same.

[0002]

2. Description of the Related Art In a reflection type liquid crystal display element, a light diffusion / reflection layer is formed on the inner surface of a cell so that a bright display can be obtained by effectively utilizing external light. Various forms are known for the diffusion layer. Among them, an inner surface uneven layer formed by a photolithography method utilizing a collimation angle of an exposure machine and light diffraction is generally employed.

By the way, the reflection type liquid crystal display element has an inherent problem in its structure that the liquid crystal display becomes difficult to see due to reflection from the element surface. In order to prevent this, conventionally, an anti-glare treatment or an anti-reflector treatment is applied to the element surface, or a film for changing the angle of incident light is pasted.

Another method is to shift the reflection peak of the inner surface uneven layer from the specular reflection angle of external light on the element surface to make the liquid crystal display easier to see. In some cases, an inclined surface having a predetermined gradient is provided from the upper end to the lower end of the surface, and an inner surface uneven layer is formed on the inclined surface.

[0005]

However, when the above-described treatment is performed on the element surface, not only the cost is increased but also the liquid crystal display itself becomes dark or the contrast is lowered. Occurs. In addition, the method of forming the inner surface uneven layer on the inclined surface is not preferable because the manufacturing process becomes complicated and the gap difference in the surface becomes large, which causes display unevenness.

[0006]

SUMMARY OF THE INVENTION The present invention provides a liquid crystal display device in which an angle at which a liquid crystal display looks brightest is shifted from a regular reflection angle of external light on an element surface so that the liquid crystal display can be easily viewed. In the reflection type liquid crystal display element, which includes a viewing surface side transparent electrode substrate and a rear surface side transparent electrode substrate, which are arranged in a line, and wherein a light diffusion layer having a fine uneven surface is provided on the inner surface of the rear surface side transparent electrode substrate. Most of the concave grooves included in the uneven surface have an asymmetric shape with respect to a normal line of a display surface of the observation surface side transparent electrode substrate.

Further, in order to obtain reflected light having a uniform brightness within the display surface, the asymmetric shape of the groove is smoothly changed from one end to the other end of the display surface. This is another feature of the present invention.

Further, the present invention provides a method in which a photosensitive resin is applied to an inner surface of a rear transparent electrode substrate which sandwiches a liquid crystal layer between the transparent electrode substrate and a viewing surface transparent electrode substrate, and light from an exposing machine is passed through a photomask. By irradiating and developing the photosensitive resin, when forming a light diffusion layer having a fine uneven surface on the inner surface of the back side transparent electrode substrate, a prism is attached to the photomask, and light from the exposure device is exposed to light. The photosensitive resin is exposed at a predetermined angle with respect to the normal line of the photomask.

In this case, the incident angle of light on the photosensitive resin is not more than 80 °, especially not more than 45 ° with respect to the above-mentioned normal line, and furthermore, the conversion of the incident light angle is continuously changed. Is preferred.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the overall structure of a reflection type liquid crystal display device according to the present invention will be described with reference to the sectional view showing the embodiment of FIG. This reflection type liquid crystal display element 1
Includes a back-side transparent electrode substrate 2 and an observation-surface-side transparent electrode substrate 3 on which external light is incident.

An inner surface uneven layer (light diffusion layer) 21 having a fine uneven surface is provided on the inner surface of the rear surface side transparent electrode substrate 2. On the inner surface uneven layer 21, for example, an aluminum film is used. The reflection layer 22 is formed.

On the light reflection layer 22, a surface smoothing layer 23 formed by applying, for example, an acrylic resin by a spinner is formed. In the case of a color display, a color filter layer is provided on the light reflection layer 22 by an electrodeposition method or the like, and a surface smoothing layer 23 is formed thereon.

On the back side transparent electrode substrate 2, an ITO (Indium) as a transparent conductive film is formed on the surface smoothing layer 23.
Tin oxide (sputtered Tin Oxide) is used, and an ITO pattern 2a as a predetermined patterned display electrode is formed on a display portion thereof.

In this embodiment, the observation surface side transparent electrode substrate 3 is provided with a terminal portion 31 for forming an extraction electrode, and the display portion and the terminal portion 31 of the observation surface side transparent electrode substrate 3 are provided.
Has an ITO pattern 3 as a display electrode and an extraction electrode
a is formed.

The rear transparent electrode substrate 2 and the observation surface transparent electrode substrate 3 are bonded to each other via a peripheral sealing material 4 with their respective display portions facing each other. In addition,
An in-plane spacer (not shown) for keeping the cell gap constant is arranged between the display portions, and a predetermined liquid crystal layer 6 is sealed in the cell gap.

The peripheral sealing material 4 includes a transfer material 41 made of, for example, conductive beads. The ITO pattern 2a of the rear transparent electrode substrate 2 is connected to the observation surface transparent electrode through the transfer material 41. It is connected to an extraction electrode formed on the terminal portion 31 of the substrate 3. A retardation plate 7 and a polarizing plate 8 are adhered to the display surface side of the observation surface side transparent electrode substrate 3.

FIG. 2 shows an enlarged view of a part of the inner surface uneven layer 21 formed on the back transparent electrode substrate 2. As can be seen from this figure, the concave groove 211 of the inner surface uneven layer 21 is formed so as to be asymmetric with respect to the normal V of the element surface (display surface) of the observation surface side transparent electrode substrate 3.

That is, the concave groove 211 is composed of a slope 212 having a gentle slope and a long slope, and a slope 213 having a steep slope and a short slope, using a plane parallel to the element surface of the observation surface side transparent electrode substrate 3 as a reference plane. As a result, the peak of reflection of the inner surface uneven layer 21 is shifted from the angle of regular reflection of external light on the element surface, and the liquid crystal display becomes easier to see. FIG. 2 ideally shows the concave groove 211, and actually includes a considerably deformed slope.

The concave groove 211 is provided on the back side transparent electrode substrate 2.
It is formed by applying a photosensitive resin to a uniform thickness thereon, exposing it to ultraviolet light through a photomask, developing it, and baking it at a predetermined temperature. As an example, use the photomask 100 shown in FIG. Thereby, the concave groove 211 can be formed in an asymmetric shape.

The photomask 100 includes a glass substrate 101
A mask 102 made of, for example, a chromium film having a large number of light transmitting holes may be formed on the back side of the substrate. A prism 103 is attached to the upper surface of the mask 102 in close contact therewith. The size of the prism 103 may be either a screen size or a pixel size.

According to the photomask 100, as shown in an enlarged view in FIG. 4, light (ultraviolet rays) irradiated from a not-shown exposing machine along the mask normal is changed in direction by the prism 103, and the photosensitive resin Are incident from an oblique direction. Therefore, the amount of exposure increases on one side of the groove 211 and the amount of exposure decreases on the opposite side, so that an asymmetric groove 211 is formed.

Here, the inclination angle of the inclined surface 212 with respect to the reference surface is α
And the angle of inclination of light with respect to the normal to the mask is β,
The inclination angle α depends on the inclination angle β. Is preferably 80 ° or less (especially 45 ° or less).

According to the experiment, when the inclination angle β was 45 °, an inclination angle α of about 5 ° was obtained. When the reflection measurement of this experimental sample was performed, as shown in FIG. 5, assuming that the regular reflection angle of external light on the element surface was θ, the reflection intensity of the inner surface uneven layer 21 was shifted by 2α from the regular reflection angle θ. A peak was observed.

As described above, even if the peak of the reflection intensity by the inner surface uneven layer 21 is set at a position shifted from the regular reflection angle of the external light on the element surface, depending on the angle at which a person views the display, the display surface may be changed. In some cases, the angle formed between the normal line of the display surface and the line of sight differs between the upper end side and the lower end side, and therefore, the reflection intensity also differs within the display surface, and the display brightness may not be uniform.

To cope with this, as another embodiment of the present invention, as shown in FIG. 6, a photomask 100 having a prism 104 whose light inclination angle β with respect to the normal line of the mask gradually changes may be used. . The prism angle is preferably changed in a curved shape, but may be changed in a step shape in some cases.

In this alternative embodiment, the prism 10
4, the maximum tilt angle γ located at the left end is 65 ° with respect to the mask surface, and the light tilt angle β with respect to the normal line of the mask near this maximum tilt angle γ is 45 °.

The inclination angle γ of the prism 104 continuously decreases toward the right side in FIG. 6, and finally the inclination angle γ at the right end is 0 °, and the inclination angle β of the light is also 0 °. . In this manner, by gradually changing the inclination angle β of the light, the shape of the concave groove 211 is smoothly changed from the asymmetric shape of the left portion B to the symmetric shape of the right portion A as shown in an enlarged manner in FIG. Will change.

[0028]

EXAMPLE On the upper surface of a photomask for forming an inner surface uneven layer,
A glass prism was attached such that the incident angle gradually changed from 0 to 45 ° depending on the size of the screen. And
This photomask is used as a batch exposure machine LE manufactured by Hitachi DECO.
The substrate was set in −4050 and coated with a 2.5 μm thick positive-type photosensitive resin PC-403 manufactured by Nippon Synthetic Rubber Co., Ltd., and exposed, developed and fired to form an inner surface uneven layer. The length from the upper end to the lower end of the screen was 5 cm.

After a reflective film made of aluminum was formed on the uneven surface by sputtering, reflection characteristics were measured at a total of three places: the upper end, the center, and the lower end of the substrate. For the measurement of the reflection characteristics, light is incident at −30 ° and the detector angle is 55 ° to −20 °.
゜ was performed in 2.5 ゜ increments. As a result, the detector angle at which the peak of the reflection changes from the upper end to the center and then to the lower end changes to about 30 °, 25 °, and 20 °. It could be confirmed.

[0030]

As described above, according to the present invention,
By making the concave groove shape of the inner surface uneven layer which is the light diffusion layer asymmetrical with respect to the normal line of the display surface, by shifting the angle at which the liquid crystal display looks brightest and the specular reflection angle of external light on the display surface In addition, the liquid crystal display can be easily viewed without performing antiglare treatment or the like on the element surface.

Also, by changing the incident angle of light by the prism and gradually changing the asymmetric shape of the concave groove from the upper end side to the lower end side of the screen, a reflection type liquid crystal having uniform brightness in the display screen. A display element is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing the entire configuration of a reflective liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of an inner surface uneven layer included in the reflective liquid crystal display element.

FIG. 3 is a cross-sectional view schematically showing a photomask for forming the inner-surface uneven layer.

FIG. 4 is an explanatory diagram for explaining a method of forming the inner surface unevenness layer.

FIG. 5 is a graph showing reflection characteristics of the embodiment.

FIG. 6 is an explanatory diagram showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflection type liquid crystal display element 2 Back side transparent electrode substrate 21 Inner uneven layer 211 Grooves 212, 213 Slope 22 Light reflection layer 23 Surface smoothing layer 3 Front side transparent electrode substrate 4 Peripheral seal material 100 Photomask 101 Glass base material 102 Mask 103,104 Prism

Claims (5)

[Claims] 1. A light diffusion device comprising: an observation surface side transparent electrode substrate and a back surface side transparent electrode substrate which are opposed to each other with a liquid crystal layer interposed therebetween, and having a fine uneven surface on an inner surface of the back surface side transparent electrode substrate. In the reflective liquid crystal display device provided with a layer, most of the concave grooves included in the uneven surface are asymmetric with respect to a normal line of a display surface of the observation surface side transparent electrode substrate. Reflective liquid crystal display device. 2. The reflective liquid crystal display device according to claim 1, wherein the asymmetric shape of the concave groove changes smoothly from one end to the other end of the display surface. 3. A photosensitive resin is applied to an inner surface of a rear transparent electrode substrate sandwiching a liquid crystal layer between the transparent resin substrate and an observation surface transparent electrode substrate, and light from an exposing machine is applied to the photosensitive resin via a photomask. By irradiating and developing a light diffusion layer having a fine uneven surface on the inner surface of the rear surface side transparent electrode substrate, a prism is attached to the photomask, and light from the exposure machine is irradiated with the light from the photomask. A method for forming a light diffusion layer, comprising exposing the photosensitive resin at a predetermined angle with respect to a normal line. 4. An incident angle of light on the photosensitive resin,
4. The method according to claim 3, wherein the angle is equal to or less than 80 [deg.] With respect to the normal. 5. The method for forming a light diffusion layer according to claim 3, wherein a conversion amount of the light incident angle by the prism changes continuously.