JP2004093941A - Liquid crystal display element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display element in which the direction of the maximum reflection intensity is controlled to be near the observation direction so that the luminance in the observation direction is increased to give good appearance. <P>SOLUTION: The element has a diffusion layer 8 on a substrate 3 in the back side, and a reflection layer 11 formed on the diffusion layer 8. The diffusion layer 8 has a first diffusion layer 9 in which a plurality of grooves having inclined faces are regularly arranged, and a second diffusion layer 10 having a random rough pattern irregularly arranged on the first diffusion layer 9. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a liquid crystal display element for displaying by reflecting light from the front surface and a method for manufacturing the same, and more particularly, to a liquid crystal display element having a diffusion layer for scattering light and a method for manufacturing the same.
[0002]
[Prior art]
As a liquid crystal display element which reflects and displays light from the front, a reflective liquid crystal display element and a transflective liquid crystal display element are known. These liquid crystal display elements can be displayed with low power consumption and can be made thin and lightweight, and thus are used in various applications. In particular, it is widely used in mobile devices such as mobile phones, mobile terminals, video cameras, notebook computers, and portable game machines.
[0003]
A liquid crystal display element that reflects light from the front surface to display is provided with a reflective layer for reflecting light from the front surface. Is regularly reflected, the visibility is significantly reduced in directions other than the regular reflection direction. For this reason, a diffusion layer for scattering light was required.
[0004]
As the diffusion layer, a method of attaching a film having a scattering function to the front side of the liquid crystal display element, a method of providing a scattering function to an adhesive for attaching a polarizing plate or a retardation plate, the inside of the liquid crystal display element A method of forming a layer having a scattering function has been developed. Recently, from the viewpoint of reflection characteristics, the mainstream method is to form a diffusion layer with irregular irregularities irregularly arranged on the rear substrate of the liquid crystal display element and provide a reflective layer on the diffusion layer along the irregular shape. Has become.
[0005]
The diffusion layer having such uneven unevenness and having fine irregularities has an effect of diffusely reflecting the reflected light to widen the viewing angle, but the reflection intensity is also highest in the regular reflection direction.
[0006]
[Problems to be solved by the invention]
However, in portable devices, light with an incident angle of about 30 ° is often used from above the screen of the liquid crystal display element in order to view the display surface as the front. For this reason, the observation direction in front of the display surface did not match the bright reflection direction with high reflection intensity. The fine unevenness of the diffusion layer is formed using photolithography technology, and although it was possible to control the scattering distribution, the direction in which the reflection intensity was maximized (hereinafter referred to as “maximum reflection intensity”). Direction)).
[0007]
Referring to the drawing, as shown in FIG. 7, the observation direction is generally perpendicular (front) to the liquid crystal display element, but since the incident light is incident at an incident angle of θ, the specular reflection light Is reflected at a reflection angle of θ. For this reason, when a portable device is used, light incident at an incident angle of 30 ° from above the screen of the liquid crystal display element has the highest luminance in a direction of a reflection angle of 30 ° below the screen. Therefore, in the conventional liquid crystal display device, the direction in which the display is performed at the maximum luminance is shifted from the observation direction, and the display in the observation direction has a low luminance and has a poor appearance.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display element having a good appearance by controlling the direction of the maximum reflection intensity and bringing it closer to the observation direction to increase the luminance in the observation direction. It is another object of the present invention to provide a method for easily manufacturing the liquid crystal display device.
[0009]
[Means for Solving the Problems]
In order to achieve the above-described object, a liquid crystal display device of the present invention has a diffusion layer and a reflection layer formed on the diffusion layer on a substrate on the back side, and the diffusion layers each have a slope. A plurality of provided grooves have a regularly arranged shape, and at least a part of the slope is roughened.
[0010]
By adopting such a configuration, it is possible to control the maximum reflection intensity direction by the slope of the diffusion layer, and to scatter the reflected light by the rough surface to give the liquid crystal display element a practical viewing angle. be able to.
[0011]
In another liquid crystal display device according to the present invention, the diffusion layer has a first diffusion layer in which a plurality of grooves each having a slope are regularly arranged, and a non-uniform diffusion layer is provided on the first diffusion layer. And a second diffusion layer in which irregularities in shape are irregularly arranged.
[0012]
Further, the liquid crystal display element of the present invention is used for a portable device.
[0013]
With such a configuration, a bright and good-looking display can be performed on a portable device in which external light often enters at a specific angle.
[0014]
Further, in the method for manufacturing a liquid crystal display element of the present invention, in the method for manufacturing a liquid crystal display element having a diffusion layer and a reflective layer formed on the diffusion layer, Forming a first diffusion layer in which a plurality of grooves each having a slope are regularly arranged; and forming a layer in which irregularities having a non-uniform shape are irregularly arranged on the first diffusion layer. The method includes a step of forming a second diffusion layer by sticking, and a step of forming a reflection layer on the first and second diffusion layers.
[0015]
By adopting such a configuration, the second diffusion layer is simply stuck on a layer in which irregularities of irregular shape are irregularly arranged, so that the second diffusion layer can be easily formed on the first diffusion layer having a plurality of grooves. The irregularities having a non-uniform shape can be irregularly arranged.
[0016]
In the method for manufacturing a liquid crystal display element, the step of forming the second diffusion layer may include, using a roller, a film provided with a layer in which irregularities having the uneven shape are irregularly arranged and a base layer. The first diffusion layer is thermocompression-bonded to the first diffusion layer, and a layer in which the unevenness having the non-uniform shape is irregularly arranged is attached to the first diffusion layer.
[0017]
In the method for manufacturing a liquid crystal display element, the step of forming the first diffusion layer may include exposing and developing a photosensitive resin using a grayscale mask, thereby forming each slope of the first diffusion layer. It is characterized by forming.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
FIG. 1 is a schematic view of a cross-sectional structure of the liquid crystal display element 1, and FIG. 2 is an enlarged view of a portion A surrounded by a dotted line in FIG.
[0020]
The liquid crystal display element 1 includes a front substrate 2 and a rear substrate 3. The front-side substrate has an electrode 4 and an alignment film 5 on the inner surface, and a retardation plate 6 and a polarizing plate 7 on the outer surface. The rear substrate 3 has a diffusion layer 8, a reflection layer 11 (see FIG. 2), a smooth layer 12, an electrode 13, and an alignment film 14 on the inner surface.
[0021]
The substrate 2 and the substrate 3 face each other so that the electrodes 4 and 13 face each other, and a sealing material 16 is applied around the two substrates 2 and 3 in a state where spacers 15 for keeping the cell gap at a constant distance are dispersed therebetween. Surrounded by Further, a liquid crystal material 17 is sealed in a space formed by the substrates 2 and 3 and the sealing material 16.
[0022]
When the liquid crystal display element 1 performs color display, a color filter 18 is further provided. In FIG. 1, the color filter 18 is formed directly on the reflective layer 11, but the present invention is not limited to this position. The color filter may be provided on the smoothing layer 12 or on the front substrate 2.
[0023]
Transparent materials such as glass and synthetic resin are usually used for the substrates 2 and 3. However, when a reflective liquid crystal display element is manufactured, the substrate 3 on the back side may not be translucent. .
[0024]
The diffusion layer 8 formed on the substrate 3 on the back side includes a first diffusion layer 9 and a second diffusion layer 10. 3A to 3D show cross-sectional shapes of the diffusion layer 8, and arrows in the drawings show the incident directions of incident light.
[0025]
A plurality of grooves each having a slope are regularly arranged in the first diffusion layer 9, and the first diffusion layer 9 controls the maximum reflection intensity direction by the slope of the slope. I have. The shape of the groove may be configured so that incident light (at least a part thereof) can be reflected on the slope. That is, as shown in FIG. 1, a two-sided configuration of a vertical plane and a slope, a three-sided configuration of a slope and a slope as shown in FIG. 3A, and a three-sided configuration of a vertical plane, a horizontal plane and a slope as shown in FIG. 3B. As shown in FIG. 3C, a three-sided configuration of a slope, a horizontal plane and a slope may be used. If the direction of the maximum reflection intensity can be controlled, the slope of the groove may be slightly curved. Regarding the arrangement of the grooves, grooves having the same shape may be continuously arranged as shown in FIG. 1 or may be arranged with regular intervals as shown in FIG. 3D.
[0026]
The shape of the groove is arranged such that the slope faces the incident direction of the light source, the slope is preferably in the range of 2 to 15 ° from the horizontal plane, and the width of the groove is preferably in the range of 30 to 60 μm, particularly preferably in the range of 40 to 50 μm. .
[0027]
In the second diffusion layer 10 formed on the first diffusion layer 9, irregularities having a non-uniform shape are irregularly arranged, and the second diffusion layer 10 is formed by the first diffusion layer 9. Is roughened to irregularly reflect the reflected light to widen the viewing angle. FIG. 1 shows only the unevenness of the second diffusion layer 10, but a layer having unevenness on the surface as shown in FIG. 2 is formed along the groove of the first diffusion layer 9. You may. The unevenness of the second diffusion layer 10 may be arranged on the entire surface. However, as shown in FIGS. 1 and 3A to 3D, the unevenness is not arranged near the bottom of the slope, but near the top of the slope and in the second area. A configuration in which the diffusion layer 10 is disposed on an upper plane (see FIG. 3D) may be employed.
[0028]
Since the second diffusion layer 10 is bent at the bottom of the slope so that the uneven surface approaches, if the uneven surface is arranged on the entire surface, the uneven surface collides with the first diffusion layer and cannot bend well. There may be a gap between the diffusion layers. The gap accumulates water and gas during the manufacturing process and causes a defect, and also reduces the reliability of the liquid crystal display element. Also, near the bottom of the slope, when light is incident from an oblique direction, it becomes a shadow of the adjacent diffusion layer, so that incident light is difficult to enter. Therefore, even if unevenness is not provided, the influence on the display is small. Therefore, when the width of the groove is 30 to 60 μm, the unevenness of the second diffusion layer 10 is preferably arranged in a range of 15 to 30 μm from the top of the slope. The average shape of the unevenness of the second diffusion layer 10 is preferably in the range of 2 to 5 μm in width and 0.5 to 1.5 μm in height.
[0029]
As another embodiment of the diffusion layer 8, the back surface of the substrate itself is formed into a shape in which a plurality of grooves each having a slope are regularly arranged, and at least a part of the slope is roughened. The configuration may be as follows. In this case, the substrate surface also serves as the diffusion layer 8. Further, when a metal having a high reflectance is used as the substrate, the substrate surface also serves as the diffusion layer 8 and the reflection layer 11. Of course, it is also possible to adopt a configuration in which the surface itself of the substrate on the back side is formed into the shape of the first diffusion layer 9 and the second diffusion layer 10 is provided thereon.
[0030]
The reflection layer 11 is formed on the diffusion layer 8 and is formed along the shape constituted by the first diffusion layer 9 and the second diffusion layer 10. The reflection layer 11 is formed by depositing a metal having high reflectance, such as aluminum or silver, by a sputtering method, a vacuum evaporation method, or the like. Since the reflective layer 11 made of metal is conductive, it can be used also as the electrode 13 of the rear substrate. In this case, the reflective layer 11 is patterned, and a driving voltage is applied to each pattern. In the case of a transflective liquid crystal display device, a transflective layer that not only reflects incident light but also transmits part of light from a backlight is used as the reflective layer 11.
[0031]
The smooth layer 12 is for forming the electrode 13 formed thereon on a smooth surface, and is formed by applying a resin or the like.
[0032]
A transparent conductive film such as ITO is usually used for the electrodes 4 and 13. For the back electrode 13, it is also possible to use a light-shielding material such as metal by also using the reflection layer 11.
[0033]
Next, a method for manufacturing the diffusion layer 8 will be described.
[0034]
The first diffusion layer 9 can be formed by exposing and developing a photosensitive resin applied to the rear substrate 3 using a gray scale mask. The gray scale mask is composed of a base material such as glass on which a light shielding band of silver or the like having a plurality of gradations is formed. Is formed by irradiating the substrate with an electron beam in which is changed step by step. Since the amount of resin exposed by the shading of the light-shielding band changes, when the photosensitive resin is exposed using such a grayscale mask, it is possible to form a slope corresponding to the gradual change in shading. .
[0035]
The second diffusion layer 10 can be formed by attaching a layer 41 in which unevenness having a non-uniform shape is irregularly arranged to the first diffusion layer 9. As shown in FIG. 4, a layer 41 in which irregularities having irregular shapes are irregularly arranged is in a state of a film 44 by laminating a base layer 42 on the surface of the irregularities. It is attached to the first diffusion layer 9. After that, the base layer 42 is peeled off to form the second diffusion layer 10.
[0036]
In the case where the photosensitive resin is used as the layer 41 in which irregularities having irregular shapes are irregularly arranged, and the film 44 is formed by irregularly disposing irregularities having irregular shapes on the surface of the base layer 42, After the thermocompression bonding, the layer 41 may be exposed to remove a predetermined portion of the unevenness arranged on the surface of the layer 41.
[0037]
Further, as a method for manufacturing the first diffusion layer 9, similarly to the second diffusion layer 10, a film having a layer in which desired grooves are arranged in advance can be attached to the substrate 3.
[0038]
【Example】
In this example, a reflective liquid crystal display element 1 having the structure shown in FIG. 1 was manufactured. First, a glass substrate having a thickness of 0.7 mm is used as the substrate 3 on the back side, and a photosensitive resin (PC411B manufactured by JSR Corporation) serving as the first diffusion layer 9 is formed on the glass substrate to a thickness of 4 μm by spin coating. Was applied uniformly. After the photosensitive resin was preliminarily dried at 60 ° C., the photosensitive resin was exposed and developed using a gray scale mask. After that, the main diffusion was performed to form the first diffusion layer 9. As shown in FIG. 1, the first diffusion layer 9 of this embodiment has a sawtooth-shaped cross section in which grooves having a two-sided configuration of a vertical surface and an inclined surface are continuously arranged, and the width of the groove is 45 μm. The inclination of the slope was about 5 ° from the horizontal plane.
[0039]
Next, a second diffusion layer 10 was formed on the first diffusion layer 9. As shown in FIG. 4, the second diffusion layer 10 was formed by attaching a layer 41 in which irregularities having a non-uniform shape were irregularly arranged in advance to the first diffusion layer 9. In this example, as the film 44, RF-4053 (δ0) manufactured by Hitachi Chemical Co., Ltd. was used. The film 44 has irregularities of irregular shape irregularly arranged on the surface of the base layer 42, and a resist, which is a photosensitive resin, is laminated thereon. The layers 41 are arranged in a regular manner.
[0040]
The film 44 is overlaid on the first diffusion layer 9, and the film 44 is aligned with the roller 43 so that the unevenness of the layer 41 is arranged near the top of the slope of the groove of the first diffusion layer 9. The layer 41 was attached to the first diffusion layer 9 by pressing the first diffusion layer 9 at a temperature of ° C. After that, the layer 41 as a resist was cured by irradiating ultraviolet rays to fix the irregularities. Finally, the base layer 42 was peeled off to form the second diffusion layer 10. The unevenness of the second diffusion layer 10 in the present example had a shape of 3 μm in width and 1 μm in height on average, and was arranged in a range of 20 μm from the top of the slope in a groove having a width of 45 μm.
[0041]
Then, on the diffusion layer 8, a reflection layer 11 of a silver-palladium alloy was formed along the shape of the diffusion layer 8. Thereafter, a color filter 18, a smoothing layer 12, a transparent electrode 13, and an alignment film 14 were sequentially laminated on the reflective layer 11, thereby producing the rear substrate 3. The front substrate 2 is manufactured by laminating a transparent electrode 4 and an alignment film 5 on the substrate 2. The substrate 2 and the substrate 3 are opposed to each other so that the electrodes 4 and 13 face each other, and a sealing material 16 is applied around the substrates 2 and 3 in a state where spacers 15 for keeping the cell gap at a constant distance are dispersed therebetween. Surrounded by Further, a liquid crystal material 17 was sealed in a space formed by the substrates 2 and 3 and the sealing material 16 to complete the liquid crystal display device 1.
[0042]
As a comparative example, a conventional reflective liquid crystal display device was manufactured. As shown in FIG. 6, a photosensitive resin is applied to the surface of the rear glass substrate 21b of the pair of glass substrates 21a and 21b, exposed using a mask, and then developed. By sintering, a diffusion layer 22 having a bowl-shaped groove in cross section was formed. Further, a reflective layer 23 was formed on the diffusion layer 22, and a smooth layer 24 was formed on the reflective layer 23 so that the surface became flat. Thereafter, a transparent electrode 25 and an alignment film (not shown) were formed in the same manner as in the example of the present invention, and a reflective liquid crystal display element 26 was completed by the same steps.
[0043]
With respect to the reflective liquid crystal display element 1 of the embodiment of the present invention and the conventional reflective liquid crystal display element 26, the reflection characteristics when light was irradiated at an incident angle of 30 ° from above the screen of the liquid crystal display element were measured. FIG. 5 shows the measurement results. In FIG. 5, the vertical axis indicates the reflection intensity, and the horizontal axis indicates a direction perpendicular to the liquid crystal display element at 0 °, the upper part of the screen is indicated by a negative angle, and the lower part of the screen is indicated by a positive angle. Therefore, the incident light is incident from the direction of -30 ° in FIG.
[0044]
In FIG. 5, the conventional reflection type liquid crystal display element 26 obtained the maximum reflection intensity near the regular reflection angle of 30 °, whereas the reflection type liquid crystal display element 1 according to the embodiment of the present invention has the specular reflection. The maximum reflection intensity is obtained around 10 ° which is an angle of −20 ° from the angle. Further, it can be seen from FIG. 5 that the viewing angle of the liquid crystal display element 1 according to the embodiment of the present invention is widened to the same extent as the conventional one. As described above, in the embodiment of the present invention, the direction of the maximum reflection intensity can be controlled to approach the observation direction, and at the same time, the same viewing angle as that of the related art is realized.
[0045]
【The invention's effect】
In the liquid crystal display element of the present invention, the surface shape of the diffusion layer has a plurality of grooves each having an inclined surface arranged regularly, and irregularities having an irregular shape are irregularly arranged on at least a part of the inclined surface. Due to the shape, the maximum reflection intensity direction can be controlled by the slope of the diffusion layer, and the reflected light is scattered by unevenness of unevenness arranged on the slope, and the practical viewing angle can be increased. Can be held.
[0046]
In addition, when the liquid crystal display element of the present invention is used in a portable device, a bright and good-looking display can be provided in a portable device in which external light often enters at a specific angle.
[0047]
Furthermore, since the liquid crystal display element of the present invention can be manufactured by simply attaching a layer in which the second diffusion layer has irregular irregularities of irregular shape, the second diffusion layer can be formed on the first diffusion layer having a plurality of grooves. In addition, irregularities having a non-uniform shape can be easily arranged irregularly.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a cross-sectional structure of a liquid crystal display device of the present invention. FIG. 2 is an enlarged view of a diffusion layer portion of the liquid crystal display device. FIG. 3 is a diagram showing an example of a cross-sectional structure of a diffusion layer. FIG. 5 is a view showing a reflection characteristic of a liquid crystal display element. FIG. 6 is a schematic view of a sectional structure of a liquid crystal display element of a comparative example. FIG. 7 is a view showing a relationship between incident light and reflected light. Diagrams [Description of symbols]
REFERENCE SIGNS LIST 1 liquid crystal display element 2, 3 substrate 4, 13 electrode 5, 14 alignment film 6 retardation plate 7 polarizing plate 8 diffusion layer 9 first diffusion layer 10 second diffusion layer 11 reflection layer 12 smooth layer 15 spacer 16 sealing material 17 Liquid crystal substance 18 Color filter

Claims (6)

In a liquid crystal display element having a diffusion layer and a reflection layer formed on the diffusion layer on a substrate on the back side, the diffusion layer has a shape in which a plurality of grooves each having a slope are regularly arranged. Wherein at least a part of the slope is roughened. 2. The diffusion layer according to claim 1, wherein the diffusion layer includes a first diffusion layer in which a plurality of grooves each having a slope are regularly arranged, and irregularities having an uneven shape on the first diffusion layer. A liquid crystal display device comprising: a second diffusion layer disposed thereon. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is used for a portable device. In a method for manufacturing a liquid crystal display element having a diffusion layer and a reflection layer formed on the diffusion layer,
Forming a first diffusion layer in which a plurality of grooves each having a slope are regularly arranged on the rear-side substrate;
Forming a second diffusion layer on the first diffusion layer by attaching a layer in which irregularities having irregular shapes are irregularly arranged;
Forming a reflective layer on the first and second diffusion layers. 5. The method according to claim 4, wherein the step of forming the second diffusion layer comprises: applying a film provided with a layer in which irregularities of the non-uniform shape are irregularly arranged and a base layer to the first diffusion layer by a roller. A method for manufacturing a liquid crystal display element, wherein a layer in which irregularities having the non-uniform shape are irregularly arranged is attached to the first diffusion layer by pressure bonding. The step of forming the first diffusion layer according to claim 4 or 5, wherein each slope of the first diffusion layer is formed by exposing and developing a photosensitive resin using a grayscale mask. A method for manufacturing a liquid crystal display element, comprising:

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