JP4636573B2 - Method for forming light diffusion layer of reflective liquid crystal display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention also relates to a method for preparation of light-diffusing layer in the reflection type liquid crystal display element, more particularly, formation of the inner surface light diffusion layer having a brightness peak at offset specular reflection angle of the external light on the element surface It is about the method .
[0002]
[Prior art]
In the reflective liquid crystal display element, a light diffusing / reflecting layer is formed on the inner surface of the cell so that a bright display can be obtained by effectively using light from the outside. Various forms are known for the diffusion layer. Among them, an inner surface uneven layer by a photolithography method utilizing a collimation angle of an exposure machine and light diffraction is generally employed.
[0003]
By the way, the reflection type liquid crystal display element has a unique problem that the liquid crystal display becomes difficult to see due to reflection from the surface of the element due to its structure. In order to prevent this, conventionally, an antiglare process or an antireflector process is applied to the element surface, or a film for converting the angle of incident light is attached.
[0004]
As another method, the upper end of the display surface is applied to the photosensitive resin applied to the inner surface of the substrate in order to make the liquid crystal display easier to see by shifting the reflection peak of the inner concavo-convex layer from the regular reflection angle of the external light on the element surface. An inclined surface having a predetermined gradient from the bottom to the bottom is formed, and an inner surface uneven layer is formed on the inclined surface.
[0005]
[Problems to be solved by the invention]
However, when the above-described treatment is performed on the element surface, not only is the cost high, but there is a problem that the liquid crystal display itself becomes dark or the contrast is lowered. Further, 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.
[0008]
[Means for Solving the Problems]
In order to make the liquid crystal display easier to see by shifting the angle at which the liquid crystal display looks brightest and the regular reflection angle of external light on the element surface, the back surface sandwiching the liquid crystal layer with the transparent electrode substrate on the observation surface side By applying a photosensitive resin to the inner surface of the side transparent electrode substrate, and irradiating the photosensitive resin with light from an exposure device through a photomask and developing the surface, a fine uneven surface is formed on the inner surface of the rear surface side transparent electrode substrate. When the light diffusing layer having the above structure is formed, a prism whose light inclination angle with respect to the normal line of the photomask is gradually changed is attached to the photomask, and the light from the exposure device is set at a predetermined angle with respect to the normal line of the photomask. The photosensitive resin is exposed at an angle.
[0009]
In this case, it is preferable that the incident angle of light with respect to the photosensitive resin is 80 ° or less, particularly 45 ° or less with respect to the normal line, and that the conversion amount of the light incident angle is continuously changed. The photosensitive resin is preferably a positive photosensitive resin.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
First, the overall configuration of a reflective liquid crystal display device according to the present invention will be described with reference to a cross-sectional view illustrating the embodiment of FIG. The reflective liquid crystal display element 1 includes a back surface side transparent electrode substrate 2 and an observation surface side transparent electrode substrate 3 on which external light is incident.
[0011]
An inner surface uneven layer (light diffusion layer) 21 having a fine uneven surface is provided on the inner surface of the back surface side transparent electrode substrate 2, and a light reflection layer 22 made of, for example, an aluminum film is provided on the inner surface uneven layer 21. Is formed.
[0012]
On the light reflection layer 22, for example, a surface smoothing layer 23 formed by applying an acrylic resin with a spinner is formed. In the case of 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.
[0013]
The back surface side transparent electrode substrate 2 is formed by sputtering ITO (Indium Tin Oxide) as a transparent conductive film on the surface smoothing layer 23, and the display portion has a predetermined patterned display electrode. An ITO pattern 2a is formed.
[0014]
In this embodiment, a terminal portion 31 for forming an extraction electrode is connected to the observation surface side transparent electrode substrate 3, and a display electrode and an extraction electrode are provided on the display portion and the terminal portion 31 of the observation surface side transparent electrode substrate 3. An ITO pattern 3a is formed.
[0015]
The back surface side transparent electrode substrate 2 and the observation surface side transparent electrode substrate 3 are bonded to each other via the peripheral sealing material 4 with their respective display portions facing each other. An in-plane spacer (not shown) for keeping the cell gap constant is disposed between the display portions, and a predetermined liquid crystal layer 6 is sealed in the cell gap.
[0016]
The peripheral sealing material 4 includes a transfer material 41 made of, for example, conductive beads, and the ITO pattern 2a of the back surface side transparent electrode substrate 2 is formed on the observation surface side transparent electrode substrate 3 via the transfer material 41. It is connected to an extraction electrode formed on the terminal portion 31. On the display surface side of the observation surface side transparent electrode substrate 3, a retardation film 7 and a polarizing plate 8 are attached.
[0017]
FIG. 2 shows an enlarged part of the inner surface uneven layer 21 formed on the back side transparent electrode substrate 2. As can be seen from this figure, the concave groove 211 of the inner surface uneven layer 21 is formed to be asymmetric with respect to the normal V of the element surface (display surface) of the observation surface side transparent electrode substrate 3.
[0018]
That is, the concave groove 211 includes a slope 212 having a gentle slope and a long slope, and a slope 213 having a short slope and a short slope with respect to a plane parallel to the element surface of the observation surface side transparent electrode substrate 3. As a result, the reflection peak of the inner uneven layer 21 is shifted from the regular reflection angle of the external light on the element surface, so that the liquid crystal display is easy to see. FIG. 2 ideally shows the concave groove 211, and actually includes a considerably deformed slope.
[0019]
The concave groove 211 is formed by applying a photosensitive resin on the back side transparent electrode substrate 2 to a uniform thickness, exposing and developing ultraviolet rays through a photomask, and baking at a predetermined temperature. By using the photomask 100 shown in FIG. 3 as an example, the groove 211 can be asymmetrical.
[0020]
The photomask 100 may be formed by forming a mask 102 made of, for example, a chromium film having a large number of light transmitting holes on the back surface side of the glass substrate 101, and a prism 103 is attached to the upper surface thereof in close contact. ing. The size of the prism 103 may be either a screen size or a pixel size.
[0021]
According to the photomask 100, as shown in an enlarged view in FIG. 4, light (ultraviolet rays) irradiated along a mask normal from an exposure machine (not shown) is redirected by the prism 103, and is oblique to the photosensitive resin. Incident from the direction. Accordingly, 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.
[0022]
Here, when the inclination angle of the inclined surface 212 of the concave groove 211 with a gentle slope and a long slope with respect to the reference surface is α and the inclination angle of light with respect to the normal of the mask is β, the inclination angle α depends on the inclination angle β. To do. The inclination angle β is preferably 80 ° or less (particularly 45 ° or less).
[0023]
According to experiments, when the inclination angle β is 45 °, an inclination angle α of about 5 ° is obtained. When the reflection measurement of this experimental sample was performed, as shown in FIG. 5, the reflection intensity of the inner uneven layer 21 was shifted by 2α from the regular reflection angle θ, where θ is the regular reflection angle of external light on the element surface. A peak was observed.
[0024]
Thus, even if the peak of the reflection intensity by the inner surface uneven layer 21 is set at a position deviated from the regular reflection angle of the external light on the element surface, depending on the angle at which the person views the display, the upper end side of the display surface Since the angle formed between the normal line of the display surface and the line of sight may be different between the lower end side and the lower end side, the reflection intensity is different within the display surface, and the display brightness may not be uniform.
[0025]
In order 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 depending on circumstances.
[0026]
In this alternative embodiment, the maximum inclination angle γ located at the left end of the prism 104 in FIG. 6 is 65 ° with respect to the mask surface, and the light inclination angle β with respect to the mask normal near the maximum inclination angle γ. Is 45 °.
[0027]
Then, 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 light inclination angle β is also 0 °. In this way, by gradually changing the light inclination angle β, the shape of the groove 211 is smoothly changed from the asymmetric shape of the left portion B to the symmetrical shape of the right portion A as shown in an enlarged manner in FIG. Will change.
[0028]
【Example】
A glass prism having an incident angle gradually changing from 0 to 45 ° depending on the size of the screen was attached to the upper surface of the photomask for forming the inner surface uneven layer. Then, this photomask is set in a Hitachi DECO collective exposure machine LE-4050, and a substrate coated with a positive photosensitive resin PC-403 made by Nippon Synthetic Rubber Co., Ltd. in a thickness of 2.5 μm is exposed, developed and baked. Thus, an inner surface uneven layer was formed. The length from the upper end to the lower end of the screen was 5 cm.
[0029]
After an aluminum reflective film was formed on the concavo-convex surface by sputtering, the reflection characteristics were measured at a total of three locations: the upper end, the center, and the lower end of the substrate. The reflection characteristics were measured by making light incident at −30 ° and setting the detector angle in increments of 2.5 ° from 55 ° to −20 °. As a result, the detector angle at which the peak of reflection changes from the upper end to the center and the lower end changes to about 30 °, 25 °, and 20 °, and visual uniform brightness is obtained. It could be confirmed.
[0030]
【The invention's effect】
As described above, according to the present invention, the groove shape of the inner concavo-convex layer that is the light diffusion layer is asymmetric with respect to the normal of the display surface, and the angle at which the liquid crystal display looks brightest and the By shifting the regular reflection angle of the external light, the liquid crystal display can be easily seen without performing anti-glare treatment or the like on the element surface.
[0031]
In addition, by changing the incident angle of light by a prism and gradually changing the asymmetrical shape of the groove from the upper end side to the lower end side of the screen, a reflective liquid crystal display element having uniform brightness in the display screen is obtained. can get.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an overall configuration of a reflective liquid crystal display element according to an embodiment of the present invention.
FIG. 2 is a partially enlarged cross-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 concavo-convex layer.
FIG. 4 is an explanatory diagram for explaining a method of forming the inner surface uneven layer.
FIG. 5 is a graph showing reflection characteristics of the embodiment.
FIG. 6 is an explanatory view showing another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reflective type liquid crystal display element 2 Back surface side transparent electrode substrate 21 Inner surface uneven | corrugated layer 211 Grooves 212 and 213 Slope 22 Light reflection layer 23 Surface smoothing layer 3 Front surface side transparent electrode substrate 4 Peripheral sealing material 100 Photomask 101 Glass base material 102 Mask 103,104 Prism

Claims (4)

A photosensitive resin is applied to the inner surface of the back surface side transparent electrode substrate that sandwiches the liquid crystal layer with the observation surface side transparent electrode substrate, and the photosensitive resin is irradiated with light from the exposure device through a photomask and developed. By forming a light diffusion layer having a fine irregular surface on the inner surface of the back side transparent electrode substrate,
A prism whose light inclination angle with respect to the normal of the photomask gradually changes is attached to the photomask, and the photosensitive resin is exposed by inclining light from the exposure machine by a predetermined angle with respect to the normal of the photomask. A method for forming a light diffusion layer of a reflective liquid crystal display element . 2. The method of forming a light diffusion layer of a reflective liquid crystal display element according to claim 1 , wherein an incident angle of light with respect to the photosensitive resin is 80 [deg.] Or less with respect to the normal line. The method of forming the light diffusion layer in the reflection type liquid crystal display device according to claim 1 or 2, characterized in that the conversion amount of the light incident angle by the prism is continuously changed. 4. The method for forming a light diffusing layer of a reflective liquid crystal display element according to claim 1, wherein the photosensitive resin is a positive photosensitive resin.

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