JP2009237585A - Reflective liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflective liquid crystal display device having a reflecting plate having a high reflectivity on a display screen of a notebook personal computer or the like. <P>SOLUTION: A substrate having a liquid crystal layer formed thereon is provided, and tilt angles of reflecting irregularities formed on the liquid crystal layer side of the substrate are distributed so that their existence probability has one peak along a first direction and has two peaks along a second direction different from the first direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reflective liquid crystal display device and a manufacturing method thereof, and more particularly to a reflective liquid crystal display device having a scattering reflector structure having a high reflectance by a simple process and a manufacturing method thereof.

  In recent years, a reflection type liquid crystal display device which can realize a light weight, a thin shape, and low power consumption in a liquid crystal panel using an active matrix has been attracting attention. The reflection type liquid crystal display device takes in light from the outside into the display panel and reflects it with a reflector provided on the back side, thereby eliminating the need for a backlight and reducing power consumption. Therefore, it is useful as a display device for a portable information terminal or a cellular phone.

  External light depends on the environment in which the display device is used. Therefore, it is desirable that the reflection plate provided in the display panel has a light scattering reflection structure that reflects light entering from a random direction in a random direction.

  As such a reflective liquid crystal display device, a structure is proposed in which pixel electrodes are formed in a film shape having irregularities, and external light is irregularly reflected by the pixel electrodes having irregularities. For example, JP-A-5-232465 and JP-A-8-338993. The reflection type liquid crystal display devices described in these publications use a photolithographic process using a mask pattern or a combination of a polishing process and an etching process to form irregularities on the pixel electrode. Yes.

  In these conventional examples, a high reflectance can be obtained by forming an arbitrary uneven pattern on the reflective electrode. However, controlling the shape of the reflective electrode using photolithography is a complicated process. Furthermore, there is a problem that the margin of the manufacturing process is narrow because the reflection characteristics greatly change when the shape changes depending on the exposure conditions.

  As a method for improving this, Japanese Patent Laid-Open No. 5-80327 discloses a method of simplifying the process by using a thin film resin layer having a different thermal expansion coefficient from that of the reflective electrode. However, in this method, after forming the organic film, a metal film is formed by a heat sputtering method to form irregularities on the surface of the pixel electrode. However, this method may cause degassing from the organic film during the heating process in vacuum, resulting in a change in the film quality of the reflective film, or formation of minute irregularities on the reflective film that degrade the reflective properties. , Not a practical process.

  Japanese Patent Application Laid-Open No. 2000-193807 discloses a technique for forming a fine concavo-convex shape in an organic film using a fluororesin having a fluoroaliphatic ring structure in the main chain. However, this method requires a baking process at a high temperature of 350 ° C in addition to using a special resin. Further, as shown in this publicly known example, since the resin itself is not photosensitive, when forming irregularities on the pixel electrode connected to the thin film transistor, a resist is separately coated and contacted by a photolithography process. Holes need to be formed, complicating the process.

  In addition, Japanese Patent Application No. 10-253977 has a random uneven distribution by forming unevenness having a variation distribution in the depth direction by using the intensity distribution of speckles generated when irradiated with coherent light. The formation of a reflector is described. However, this method requires a special exposure apparatus, and the exposure apparatus itself is large and expensive, which is not practical.

JP-A-5-232465 JP-A-8-338993 Japanese Patent Laid-Open No. 5-80327 JP 2000-193807 A Japanese Patent Laid-Open No. 11-259018 Japanese Patent Application Laid-Open No. 08-227071 JP 56-156865 A JP-A-6-175126 JP 11-295750 A JP 11-337935 A JP-A-11-337964 JP-A-5-281533

  As described above, various reflection type liquid crystal display devices using the scattering reflection electrode as the pixel electrode have been proposed. In any case, it is possible to form the scattering reflection electrode having sufficient reflectance by a simple manufacturing process. Can not. Furthermore, in order to form an optimal reflective electrode structure, for example, it is necessary to control the average inclination angle of unevenness and the inclination angle distribution within an optimal range. No manufacturing process has been proposed that can be well controlled.

  Further, the inclination angle of the unevenness of the reflector in the conventional reflection type liquid crystal display device is selected so as to obtain the maximum reflectance with respect to the incident light from a specific direction. In the conventionally proposed reflector, the inclination angle of the unevenness is set to, for example, 10 ° to 20 ° (Japanese Patent Laid-Open No. 11-259018), and the inclination angle of the unevenness of the reflection plate is 5 ° to 25 °. A uniform angle (Japanese Patent Laid-Open No. 08-227071), the average inclination angle of the unevenness of the reflector is 30 ° or less (Japanese Patent Laid-Open No. 56-156865), and the height of the unevenness is a Gaussian distribution. Yes, the average inclination angle of the irregularities is 10 ° (Tohru Koizumi and Tatsuo Uchida, Proceedings of the SID, vol.29, p.157, 1988), and the reflector surface is a smooth irregular surface and The uneven average inclination angle is selected to be 4 to 15 ° (Japanese Patent Laid-Open No. 6-175126).

  However, in these conventional examples, no examination is made as to whether the reflectance is highest when external light is incident on the display panel from all directions. Therefore, no reflection type liquid crystal display device is proposed in the prior art, which is brightened by reflection of external light with high reflectivity even in various environments.

  Furthermore, in the conventional example, it is assumed that the external light incident on the display panel of a notebook computer or the like is omnidirectional in a certain direction and has a specific direction in a different direction. No shape has been proposed.

  Further, a reflection plate structure has been conventionally proposed in which a resist film is formed, exposed and developed with a predetermined mask pattern, and then baked to smooth the sectional structure of the resist film to form a desired inclined surface. However, no optimum pattern shape has been proposed in such a manufacturing process. In addition, a method for forming a reflective concavo-convex shape having both directivity and scattering within the same pixel region has not been proposed.

  Furthermore, since the reflective liquid crystal display device uses external light, it is necessary to provide a light source in order to use it in a dark place. However, when a structure in which light from the light source is scattered and incident on the display panel side is employed, there is a problem that the display image is blurred by the scattering structure and the contrast is deteriorated.

  Accordingly, an object of the present invention is to manufacture a liquid crystal display device that can realize a simplified reflector, a yield improvement, a reduction in manufacturing cost, and a reflector that can stably realize high reflection characteristics. It is to provide a method.

  Furthermore, another object of the present invention is to provide a reflection type liquid crystal display device having a reflector having a high reflectance even when external light is incident from various directions.

  Furthermore, another object of the present invention is to provide a reflection type liquid crystal display device having a reflection plate having a high reflectance on a display screen of a notebook personal computer or the like.

  Furthermore, another object of the present invention is to provide a reflective liquid crystal display device having an optimum resist film pattern shape for forming reflective irregularities.

  Furthermore, another object of the present invention is to provide a reflective liquid crystal display device with a front light which can be used in a dark place and has improved contrast by eliminating blurring of the display screen during normal use. is there.

  In order to achieve the above object, according to a first aspect of the present invention, in a method for manufacturing a liquid crystal display device, light having exposure energy is irradiated on the surface of a photosensitive resin layer having a predetermined film thickness, thereby After forming the distribution of thermal deformation characteristics in the thickness direction (or plane direction) of the photosensitive resin layer, heat treatment is performed to cause random irregularities (micro grooves, fine grooves, or fine wrinkles on the surface of the photosensitive resin layer. ).

  The photosensitive resin layer is irradiated with light having exposure energy such as deep ultra violet (DUV), for example, and is partially exposed to partially change the photosensitive resin layer. Thereby, a distribution of thermal deformation characteristics can be formed in the thickness direction (or plane direction) of the photosensitive resin layer. Thereafter, by performing a heat treatment at a glass transition temperature or higher, random irregularities can be formed on the surface of the photosensitive resin layer.

  It is preferable that the DUV irradiation is controlled to energy irradiation that only a part of the surface side in the depth direction of the photosensitive resin layer is exposed. As a result, up to a certain depth on the surface side of the photosensitive resin layer is altered by the crosslinking / decomposition reaction, and the surface side region and the back side region have different thermal deformation characteristics. Therefore, during the subsequent heat treatment, random irregularities are formed on the surface due to the difference in thermal deformation characteristics between the front side and the back side of the photosensitive resin layer.

  Or you may perform energy irradiation of the grade which exposes DUV irradiation only to the one part area | region of the surface of the photosensitive resin layer. In that case, an exposure process using a mask film is required. Even if the distribution of thermal deformation characteristics is formed in the plane direction, different thermal deformation occurs in the plane direction in the subsequent heat treatment process, and random irregularities are formed on the surface.

  The pitch and height difference (roughness and fineness of the unevenness) of the above-mentioned random unevenness-shaped grooves and ridges can be controlled with good reproducibility by the film thickness of the photosensitive resin layer, irradiation energy, and the like. Furthermore, the uneven shape can also be controlled by the heat treatment temperature and time for the photosensitive resin layer before irradiation with energy light.

  For example, when the thickness of the photosensitive resin layer is small, the height difference of the unevenness is small and the pitch is small, and when the thickness of the photosensitive resin layer is large, the height difference of the unevenness is large and the pitch is large. In addition, when the irradiation energy is small, the uneven height difference is small and the pitch is small, and when the irradiation energy is large, the uneven height difference is large and the pitch is large. Furthermore, when the heat treatment temperature before irradiation with energy light is low and the time is short, the uneven height difference is large and the pitch is large, and when the heat treatment temperature is high and the time is long, the uneven height difference is small and the pitch is small.

  Therefore, a random uneven shape can be processed into a desired shape by appropriately selecting the above conditions. Moreover, the process is an extremely simple process of irradiating energy light and then performing heat treatment, and is very practical.

  The photosensitive resin layer of the present invention is preferably used for an insulating film between a source electrode and a pixel electrode of a thin film transistor for driving the pixel electrode. In that case, it is necessary to form a contact hole for connecting the pixel electrode and the source electrode. However, a contact hole is formed by subjecting the photosensitive resin layer to a photolithography process, and partially exposing and developing. can do. And the desired random uneven | corrugated shape can be formed in the surface by performing irradiation of said energy light and subsequent heat processing to the photosensitive resin layer. By forming a pixel electrode on such a photosensitive resin layer, a reflective pixel electrode having desired random irregularities can be formed.

  Instead of irradiation with light having the above-described photosensitive energy, wet treatment with any one of an acid, an alkali solution, a quaternary ammonium salt solution, and HMDS (Hexa-methyl-di-silazane) can be used. By immersing the photosensitive resin layer in such a chemical solution, it is possible to cause a chemical reaction on the surface of the photosensitive resin layer and to change the material into materials having different thermal deformation characteristics.

  In order to achieve the above object, a second aspect of the present invention provides a reflective liquid crystal display device having a substrate on which a liquid crystal layer is formed, and having reflective irregularities formed on the liquid crystal layer side of the substrate. The inclination angle is distributed in a range of at least 0 ° to 20 °, and the existence probability of the inclination angle peaks in a range of 15 ° to 19 °.

  In the case of having the distribution of the inclination angles of the reflection unevenness, the highest reflectance can be obtained in an environment where external light is incident on the display surface from all directions. That is, when considering diffused light from an integrating sphere in which external light is incident on the display surface from all directions, the incident light intensity into the liquid crystal layer is within the range of 30 ° to 38 ° in the liquid crystal layer. The intensity is strongest at other angles, and the incident intensity decreases at other incident angles. Therefore, in order to reflect the incident light in the range of the incident angle of 30 ° to 38 ° where the incident light intensity becomes the highest in the normal direction of the display surface, the existence probability of the inclination angle of the reflection unevenness is 15 °. It is necessary to have a peak in the range of ˜19 °.

  However, since there is an incident angle in a range other than the incident angle of 30 ° to 38 °, it is preferable that the inclination angle of the reflection unevenness is distributed in the range of at least 0 ° to 20 ° accordingly.

  In this case, the inclination angle distribution is more preferably a distribution corresponding to the incident intensity of the incident light in the liquid crystal layer. For example, by setting the distribution of the inclination angle of the reflection unevenness corresponding to the incident intensity distribution of the incident light in the liquid crystal layer specified by the incident state of the external light in the environment where the display panel is used, A high amount of reflected light can be obtained.

  In order to achieve the above object, a third aspect of the present invention provides a reflective liquid crystal display device having a substrate on which a liquid crystal layer is formed, and reflecting irregularities formed on the liquid crystal layer side of the substrate. The inclination angle is distributed so that the existence probability has one peak along the first direction and the existence probability has two peaks along a second direction different from the first direction. It is characterized by.

  According to the above invention, for example, when the display panel of a notebook computer is tilted in a certain direction, external light is incident at a relatively wide range of incident angles in the horizontal direction of the display panel. In the vertical direction of the panel, external light is incident at a relatively narrow incident angle because it is blocked by the keyboard. Under such an environment, along the horizontal direction of the display panel, the inclination angle distribution of the reflection unevenness has a peak in the range where the existence probability is, for example, 15 ° to 19 °, and is along the vertical direction of the display panel. Therefore, it is preferable that the inclination angle distribution of the unevenness for reflection has a peak in two ranges of existence probabilities. In this way, the highest reflected light amount can be realized by changing the inclination angle distribution of the reflection unevenness according to the direction of the incident angle.

  In order to achieve the above object, according to a fourth aspect of the present invention, there is provided a reflective liquid crystal display device having reflective irregularities on a substrate, and a first directivity for reflected light within a single pixel region. And a first convex part having a first scattering property, a second directivity weaker than the first directivity for the reflected light, and a second scattering property stronger than the first scattering property. The two convex portions are mixed randomly.

  According to the above-described invention, it is possible to efficiently reflect the reflected light with respect to the incident light by mixing the convex portion having strong directivity and the convex portion having strong scattering property in a single pixel region.

  In order to achieve the above object, according to a fifth aspect of the present invention, there is provided a reflective liquid crystal display device having a reflective unevenness on a substrate, the unevenness being formed by a photosensitive resin film, The circular patterns are arranged apart from each other by a first distance or more, and a second circular pattern smaller than the first circular pattern is arranged apart from the first circular pattern by less than the first distance. It is characterized by.

  According to the above invention, the relatively large circular pattern is arranged so as not to be merged at the time of post-baking after exposure / development of the photosensitive resin film. it can. In addition, since the relatively small circular pattern is arranged in the vicinity of the large circular pattern, the density of the inclined surface can be increased. Even if a small circular pattern and a large circular pattern are merged during post-baking, the merged area is narrow, so the adverse effects caused by this are limited.

  In order to achieve the above object, according to a sixth aspect of the present invention, there is provided a reflective liquid crystal display device having reflective irregularities on a substrate, wherein the irregularities are formed of a photosensitive resin film, The square pattern is arranged so that sides of adjacent polygons are parallel to each other.

  According to the above invention, the opposing sides are arranged in parallel so that adjacent patterns do not merge at the time of post-baking after exposure / development of the photosensitive resin film. And since the polygonal pattern in which the inclined surface faces in a plurality of directions is arranged with high density, the randomness in the direction of the inclined surface can be made equal to the circular pattern.

  In order to achieve the above object, according to a seventh aspect of the present invention, in a reflective liquid crystal display device, a reflective liquid crystal display panel, a light guide plate provided on the reflective liquid crystal display panel, and the light guide plate A light source arranged at the end of the light source, and a light scattering means that expresses light scattering for light transmitted through the light guide plate when the light source is turned on and reduces the light scattering when the light source is not turned on And a front light.

  According to the above invention, when used in a dark state, the light source is turned on and the display screen is brightened by the incidence of scattered light, and when used in a bright state, the light source is turned off and displayed by outside light. The screen is brightened and the light scattering property of scattering the light from the light source is reduced, thereby preventing the display image from being blurred or distorted.

  As described above, according to the present invention, the reflection unevenness of the reflective liquid crystal display device can be formed by a simple process, and the inclined surface distribution due to the desired unevenness can be formed with good controllability. Furthermore, according to the present invention, it is possible to obtain an inclined surface distribution by the optimum reflection unevenness, and improve the reflectance.

It is an example of the circuit diagram of the liquid crystal display device with which this embodiment is applied. It is a figure which shows the example of sectional drawing of the reflection type liquid crystal display device with which this embodiment is applied. It is sectional drawing which shows a part of manufacturing process of the reflection type liquid crystal display device in this embodiment. It is a figure which shows the microscope picture of the surface shape of the micro groove of the reflection panel formed by changing the film thickness of the photosensitive resin layer 20, and UV irradiation energy. It is a figure which shows the microscope picture of the surface shape of the micro groove of the reflection panel formed by changing the film thickness of the photosensitive resin layer 20, and UV irradiation energy. It is a figure which shows the microscope picture of the surface shape of the micro groove of the reflection panel formed by changing the film thickness of the photosensitive resin layer 20, and UV irradiation energy. It is a figure which shows the microscope picture of the surface shape of the micro groove of the reflection panel formed by changing the film thickness of the photosensitive resin layer 20, and UV irradiation energy. It is a figure which shows the AFM image of the sample of three reflective panels. It is a graph which shows the relationship between the average inclination angle of the reflecting film with respect to a diffused light source, and a reflectance. It is a graph which shows the relationship between the resist film thickness with respect to three samples of FIG. 8, and a reflectance. It is a figure which shows typically the uneven | corrugated shape of the micro groove of the resin layer formed by the example of this Embodiment. It is a figure which shows the example of a plane pattern of the micro groove formed by the example of this embodiment. It is a figure which shows the example of UV irradiation required in order to form a microgroove. It is sectional drawing which shows the manufacturing process of a 1st sample. It is the graph which compared the reflectance when the diffused light source of an integrating sphere is irradiated to the 1st, 2nd, 3rd sample. It is a figure explaining isolation | separation of the photosensitive resin layer. It is sectional drawing which shows the process which forms the separation line of the photosensitive resin layer. It is a figure which shows the microscope picture of the microgroove when not forming with the case where a separation line is formed. It is a figure which shows the real environment where the reflection type liquid crystal display device which the example of this embodiment assumes is used. It is a figure which shows incident angle (theta) i and azimuth angle (phi) i of incident light. It is a figure which shows the case where light injects into a reflective display apparatus, and reflects. FIG. 6 is a diagram showing the relationship between the intensity f (θ _i ′) of light incident on the reflector and the incident angle θ _i ′. It is a figure which shows the relationship between incident angle (theta) _i 'in which the incident light intensity of FIG. 23 becomes the maximum, and the refractive index n of a medium. It is a figure which shows the relationship between the incident angle with respect to the inclined surface of a reflective unevenness | corrugation, a reflection angle, and an inclination angle. It is a figure which shows distribution of the probability of existence of the inclination angle corresponding to the incident light intensity distribution of FIG. It is a figure which shows the simulation result of a reflection characteristic. It is a figure which shows the result of having measured the reflectance with respect to the uniform diffused light of an integrating sphere using the sample actually produced. It is sectional drawing which shows the formation method of the prototyped reflector. It is a figure which shows the example of a pattern of the mask 64 for forming the unevenness | corrugation of a reflecting plate. It is a figure which shows the inclination-angle distribution of the unevenness | corrugation of the reflecting plate from which a high reflectance is obtained with respect to the diffused light of an integrating sphere. It is a figure which shows the state in which the reflection type liquid crystal display device was mounted as a monitor of a notebook type personal computer. It is a figure which shows distribution of the inclination angle of the XY plane direction and XZ plane direction which have a high reflectance when it is utilized as a display device of a notebook personal computer. It is a figure which shows the distribution which turned around inclination angle distribution of FIG. 32 centering on inclination-angle 0 degree. It is sectional drawing which shows the formation method of the reflecting plate of a sample. It is a figure which shows the example of the mask pattern of FIG. It is a figure which shows the example of the plane of a convex part of FIG. 34, and a cross-sectional shape. The measurement result of the tilt angle distribution of the prototyped reflector is shown. It is a schematic sectional drawing of the reflection type liquid crystal display device produced using the prototyped reflector. It is a figure which shows the measurement result of the reflectance of the reflection type liquid crystal display device of FIG. It is a figure which shows the inclination angle range where existence probability becomes the maximum with respect to the inclination angle of a reflection type liquid crystal display device, and the refractive index of a liquid crystal layer. It is sectional drawing which shows two reflective uneven | corrugated shapes mixed in a pixel area. It is a top view of pixel region PK in the present embodiment. FIG. 43 is a cross-sectional view showing a manufacturing process for forming the reflective unevenness of FIG. 42. It is a figure which shows the example of the circular pattern of the conventional resist. It is a figure which shows the example of the circular pattern of the resist in this Embodiment. It is a figure for demonstrating the circular pattern of FIG. It is a figure which shows the example of the polygonal pattern of the resist in this Embodiment. It is a figure which shows the example of the polygonal pattern of the resist in this Embodiment. It is a block diagram of the reflection type liquid crystal display panel with a front light proposed conventionally. It is a figure which shows the 1st example of a reflection type liquid crystal display panel with a front light. It is a figure which shows the 2nd example of the reflection type liquid crystal display panel with a front light. It is a figure which shows the 3rd example of a reflection type liquid crystal display panel with a front light. It is a figure which shows the 4th example of a reflection type liquid crystal display panel with a front light. It is a figure which shows the 5th example of a reflection type liquid crystal display panel with a front light. It is a figure which shows the 6th example of a reflection type liquid crystal display panel with a front light. It is a figure which shows the 7th example of the reflection type liquid crystal display panel with a front light.

  Embodiments of the present invention will be described below with reference to the drawings. However, this embodiment does not limit the technical scope of the present invention.

  FIG. 1 is an example of a circuit diagram of a liquid crystal display device to which this embodiment is applied. Pixels are formed in a matrix in the display area 11 of the insulating substrate 10 on the back side. The pixel has drive transistors T00 to Tmn and pixel electrodes P00 to Pmn, and the drive transistors T00 to Tmn include scanning lines S0 to Sm arranged in the row direction and data lines D0 to Dn arranged in the column direction. And connected respectively. Outside the display area 11, a scanning line driving circuit 12 for driving scanning lines and a data line driving circuit 13 for driving data lines are provided.

  FIG. 2 is a diagram showing an example of a cross-sectional view of a reflective liquid crystal display device to which the present embodiment is applied. In the reflective liquid crystal display device, a liquid crystal layer 34 is provided between the insulating substrate 10 on the back side and the transparent substrate 30 on the display side, and the reflective electrode 22 is formed on the insulating substrate 10 on the back side. The incident external light is reflected on the surface of the reflective electrode 22, passes through the liquid crystal layer 34, and is emitted to the display side again.

  On the insulating substrate 10, a gate electrode 15 connected to a scanning line (not shown), an insulating layer 16, a drain electrode 17 connected to the semiconductor layer 19 and the data line, and a source electrode 18 are formed. Further, a reflective electrode 22 as a pixel electrode is formed on the resin layer 20 of the interlayer insulating film, and the reflective electrode 22 is connected to the source electrode 18 through the contact hole CH. An alignment film 23 made of polyimide or the like is formed on the resin layer 20 and the reflective electrode 22. Random irregularities for irregularly reflecting incident light are formed on the surface of the resin layer 22, and accordingly, random irregularities are also formed on the surface of the pixel electrode (reflecting electrode) 22 deposited thereon.

  The transparent substrate 30 on the display side is formed with a transparent electrode 31 such as ITO (a material containing indium oxide as a main component) and an alignment film 32 on one side and a polarizing plate 33 on the other side. A liquid crystal layer 34 is inserted between the alignment film 32 on the display side and the alignment film 23 on the back side. The alignment direction of the liquid crystal molecules in the liquid crystal layer 34 is a direction corresponding to the surface shape of the alignment films 32 and 23 and the characteristics thereof.

[Method of forming microgrooves]
FIG. 3 is a cross-sectional view showing a part of the manufacturing process of the reflective liquid crystal display device according to the present embodiment. FIG. 3 shows a part of the source electrode 18 of the thin film transistor shown in FIG. As shown in FIG. 3A, after forming the insulating layer 16, each electrode of the thin film transistor, and the semiconductor layer on the insulating substrate 10, the photosensitive resin 20, for example, LC200 (novolak resin), which is a general-purpose resist manufactured by Shipley, is used. , Is applied. The resin layer 20 is spin-coated by a spinner with a film thickness of about 0.5 to 2.0 μm. In this case, for example, the first resist layer is formed by spin coating for 3 seconds at a rotation speed of about 350 rpm, and further the resist layer is formed by spin coating for 20 seconds at a number of lines of about 800 rpm.

  The film thickness of the resin layer 20 affects the roughness (level difference, pitch length) of the microgrooves formed on the surface, so that an appropriate film thickness is selected. As will be described later, when the thickness of the photosensitive resin layer 20 is large, the irregularities become rougher (large difference in elevation and pitch length), and when the film thickness is small, the irregularities become finer (small difference in elevation and pitch length). .

  Thereafter, a pre-bake treatment is performed at a temperature of about 90 ° C. for 30 minutes. In this pre-baking process, the temperature is not so high that the resist reacts, and the solvent is slightly blown away. This prevents the resist layer from dripping due to heat during post-bake described later.

  As shown in FIG. 3B, known stepper exposure processing and development processing using a mask substrate 40 are performed to form contact holes for the display electrodes. As a result, a contact hole CH is formed on the source electrode 18 of the resin layer 20.

  After the contact hole CH is formed, the photosensitive resin layer 20 is subjected to a post-bake treatment. The post-bake treatment is, for example, a heat treatment at 120 ° C. for 40 minutes, and the purpose is to sufficiently remove the solvent of the photosensitive resin. The temperature of the post-baking process is lower than the temperature (for example, about 200 ° C.) at which the photosensitive resin photosensitive agent reacts, and it is necessary to prevent the photosensitive agent from reacting in the post-baking process. Further, the post-baking temperature is lower than the glass transition temperature of the resin (for example, about 200 ° C.), and it is necessary to prevent the resin from curing.

  If the post-baking temperature is high and the time is long, the amount of residual solvent decreases, and the microgroove irregularities become fine. Conversely, if the temperature is low and the time is long, the microgroove irregularities become rough. Accordingly, the conditions for the post-baking process are appropriately selected so that an optimal microgroove shape can be formed.

Next, as shown in FIG. 3C, light having a sufficiently high energy for photosensitivity, for example, far ultraviolet rays (DUV) having a wavelength of λ = 360 nm or less, is applied to the entire surface of the photosensitive resin layer 20. irradiated with 2600mj / cm ^2. By this DUV irradiation, the photosensitive agent undergoes a photosensitive reaction and the novolac resin undergoes a cross-linking reaction from the surface portion (surface side in the film thickness direction) of the photosensitive resin layer 20, and the upper layer portion of the resin layer is denatured. As a result, the resin layer 20 has different thermal deformation characteristics between the front side and the back side. This DUV irradiation was performed using, for example, an ORC UV irradiation apparatus.

  The energy of UV irradiation also affects the shape of the microgroove. If the energy is too low, the microgroove itself is not formed, but if the energy exceeding a certain threshold is irradiated, the microgroove is formed. In this case, the microgroove is fine when the irradiation energy (energy per unit time × irradiation time) is low, and rough when it is high. Therefore, the irradiation energy amount is also selected according to the optimal microgroove shape.

  Next, as shown in FIG. 3D, the resist 20 is finally baked. This heat treatment is performed, for example, at a temperature of 200 ° C. for about 40 minutes. The temperature of the heat treatment in the final bake needs to be higher than the temperature of the heat treatment (post bake) before UV irradiation. Then, by performing the heat treatment in the final baking, random microgrooves MG are formed on the surface of the resin layer 20 as illustrated.

  The heat treatment temperature of the final baking needs to be a temperature higher than that of the post baking, and is preferably sufficiently higher than the baking temperature of the alignment film, which is a subsequent heat treatment step, so that the resin layer 20 is sufficiently cured.

  Thereafter, as shown in FIG. 2, about 2000 mm of aluminum is grown by sputtering or heat evaporation, and patterned by a known photolithography method to form the pixel electrode 22. As a result, random irregularities are formed on the surface of the pixel electrode 22 and function as a reflective electrode that scatters and reflects light. Further, an alignment film 23 made of, for example, about 5000 mm of polyimide is formed on the entire surface by spin coating and baking (about 120 ° C.). Concavities and convexities are also formed on the surface of the alignment film 23, and the alignment direction of the liquid crystal molecules of the liquid crystal layer 34 inserted thereon is aligned according to the groove direction of the concavities and convexities.

  The reason why the microgroove is formed is not yet certain, but according to the knowledge of the inventors, the surface layer portion of the resin layer 20 is altered by the DUV irradiation, and the surface side and the back surface of the resin layer 20 are subjected to the final baking heat treatment. It seems that micro-grooves (micro-grooves) or micro-links (fine ridges) are formed on the surface due to different thermal deformations on the sides due to stress between the upper and lower layers. For example, it is considered that microgrooves are formed on the surface side when the back side of the resin layer 20 contracts due to heat treatment. This is considered to be due to the fact that the level of cross-linking reaction of the resin in the thickness direction on the resin layer differs due to UV irradiation.

  According to experiments by the inventors, the microgrooves formed in this manner have been confirmed to have random irregularities necessary for irregularly reflecting incident external light as described later.

  The UV irradiation in the above process may be performed only on a partial region in the plane direction using a predetermined mask pattern instead of being performed on the entire surface of the resin layer 20. As a result, the resin layer 20 is partially altered in the planar direction, and a distribution of thermal deformation characteristics is formed in the planar direction. Due to the distribution of the thermal deformation characteristics in the horizontal direction, the same microgroove is formed in the subsequent heat treatment in the final baking.

  Furthermore, in place of the UV irradiation in the above process, a wet treatment with any one of an acid, an alkali solution, a quaternary ammonium salt solution, and HMDS can be used. By immersing the photosensitive resin layer in such a chemical solution, it is possible to cause a chemical reaction on the surface of the photosensitive resin layer and to change the material into materials having different thermal deformation characteristics.

  In this embodiment, the roughness of the microgroove is controlled by the film thickness of the resin layer 20 and the UV irradiation energy. 4 to 7 are micrographs (about 20 times) of the surface shape of the microgroove formed by changing the film thickness of the photosensitive resin layer 20 and the UV irradiation energy. The sample of the micrograph's reflection panel was made by the following process.

A resist (for example, a general-purpose resist LC200 manufactured by Shipley Co., Ltd.) is formed on the panel by spin coating (350 rpm for 3 seconds and 800 rpm for 20 seconds twice), and after pre-baking at 90 ° C. for 30 minutes, the panel is fully exposed. , Develop to the desired film thickness (2.0 μm, 1.7 μm, 1.4 μm, 1.0 μm). Then, 120 ° C., after post-baking for 40 minutes, subjected to DUV radiation of a desired energy ^{(5200mj / cm 2, 3900 mj} / cm 2, 2600 mj / cm 2, 1300 mj / cm 2, 0 mj / cm 2) The final baking was performed at 200 ° C. for 40 minutes. Finally, aluminum was formed as a reflective film on the resist film by an evaporation method of about 2000 mm.

4, the thickness of the photosensitive resin layer 20 in the 2.0 .mu.m, the UV irradiation ^{energy, 5200mj / cm 2, 3900 mj} / cm 2, 2600 mj / cm 2, 1300 mj / cm 2, and to zero It is a microscope picture of five samples. When UV irradiation is not performed or when the irradiation energy is as small as 1300 mj / cm ² , microgrooves are not formed on the surface of the resin layer. However, when the irradiation energy is greater than 1300 mj / cm ^2, it is confirmed that microgrooves are formed on the surface of the resin layer. In that case, the height difference and pitch length (roughness) of the microgroove is rougher when the UV irradiation energy is higher (large difference in height and pitch length) and finer when the irradiation energy is low (small difference in height and pitch length). That is confirmed.

  The shape of the microgroove formed on the surface of the resin layer 20 is random. As shown in the photograph, at least two or more of the curved shape, the curved shape of the sharp curve, the bent shape of the sharp angle, the closed loop shape, the Y-shaped branch shape and the like are mixed. The microgroove according to the present embodiment has a shape that cannot be obtained by unevenness by a lithography process using a conventional artificially created constant mask pattern.

  Then, by controlling the roughness of the microgroove, it is possible to appropriately control the average inclination angle and inclination angle distribution of the unevenness.

Figure 5 is the film thickness of the photosensitive resin layer 20 to 1.7 [mu] m, the UV irradiation ^{energy, 5200mj / cm 2, 3900 mj} / cm 2, 2600 mj / cm 2, 1300 mj / cm 2, and to zero It is a microscope picture of five samples. Since the thickness of the resist layer is made smaller than that of the sample of FIG. 4, it is confirmed that the formed microgroove is finer. The microgrooves are not formed when the UV irradiation energy is too low, as in the sample of FIG.

6, and the film thickness of the photosensitive resin layer 20 to 1.4 [mu] m, the UV irradiation ^{energy, 5200mj / cm 2, 3900 mj} / cm 2, 2600 mj / cm 2, 1300 mj / cm 2, and to zero It is a microscope picture of five samples. In this case, the microgroove is even finer.

Then, Figure 7, the thickness of the photosensitive resin layer 20 in the 1.0 .mu.m, the UV irradiation ^{energy, 5200mj / cm 2, 3900 mj} / cm 2, 2600 mj / cm 2, 1300 mj / cm 2, zero It is the microscope picture of five samples made. In this case, the microgroove becomes finer, and it is confirmed that the formation of the microgroove is not sufficient even when the UV irradiation energy is 2600 mj / cm ² .

  As described above, as is clear from the surface photographs of the 20 samples, the concave and convex shape of the microgroove becomes smaller as the UV irradiation energy becomes lower. Furthermore, the microgroove itself is not formed unless irradiation energy exceeding a certain reference value is given. In addition, there is a film thickness dependency of the resist after the final baking, and the uneven shape of the microgroove becomes smaller as the film thickness is thinner.

FIG. 8 is a diagram showing AFM images of three more reflective panel samples. This sample is the same reflective panel sample as above, the UV irradiation energy is kept constant at 5200 mj / cm ² , the resist film thickness is 1.7 μm, 1.4 μm, 1.0 μm, and the aluminum reflective film is 2000 mm. Is formed on the resist layer.

  As shown in FIG. 8A, in the sample in which the resist film thickness, which is the photosensitive resin layer, is 1.7 μm, the shape of the microgroove on the surface is large, the height difference of the unevenness is 1.3 μm, and the average inclination The angle was measured to be 13 °.

  As shown in FIG. 8B, in the sample in which the film thickness of the resist film as the photosensitive resin layer is 1.4 μm, the shape of the microgroove on the surface is slightly small, the unevenness of the unevenness is 1.1 μm, the average The tilt angle was measured to be 11 °.

  Further, as shown in FIG. 8C, in the sample in which the resist film thickness as the photosensitive resin layer is 1.0 μm, the shape of the microgroove on the surface is further smaller, and the height difference of the unevenness is 0.5 μm. The average tilt angle was measured to be 8 °.

  As is apparent from the observation results in FIG. 8, it is understood that the average inclination angle due to the unevenness also changes depending on the shape of the microgroove. That is, as the resist film becomes thinner, the height difference of the unevenness and the average inclination angle become smaller. Therefore, according to the manufacturing process of the present embodiment, the average tilt angle can be controlled. The average inclination angle is an important factor for increasing the reflectance of the reflective panel. Therefore, the fact that the average inclination angle can be controlled by the manufacturing process of the present embodiment has an important practical significance.

  FIG. 9 is a graph showing the relationship between the average inclination angle of the reflective film and the reflectance with respect to the diffused light source. FIG. 9 shows five integrating spheres having a distribution of incident angles in the range of 0 °, 15 °, 30 °, 45 ° and 0 ° to ± 90 ° as incident light to the reflective panel as diffuse light sources incident on the reflective panel. It is shown that the reflectance Y depends on the average inclination angle k of the unevenness of the reflective film with respect to the type. This dependency can be obtained from the theoretical formula described later. The inclination angle distribution due to the unevenness is a normal distribution, and the average inclination angle of the normal distribution is theoretically set.

  As can be understood from the theoretical values in FIG. 9, when the average inclination angle increases as it exceeds 15 °, the reflected light reflected by the reflective film has an angle at the boundary between the liquid crystal on the surface side of the reflective panel and the glass substrate. In many cases, the critical angle is exceeded, and the reflectivity decreases. On the other hand, when the incident angle is 0 ° or 15 °, the reflectance is higher when the average inclination angle is smaller than 5 °, but the display panel is used in an environment where the incident angle is 0 ° or 15 °. Is not so many. Therefore, it is understood from the theoretical values in FIG. 9 that the reflective film having an average inclination angle of 15 ° or less, preferably 8 ° to 13 °, has a relatively high reflectance for any incident light. The

  Therefore, all the three samples shown in FIG. 8 have an average inclination angle in the range of 8 ° to 13 °. Therefore, it can be understood that the average inclination angle can be controlled within a range in which the reflectance is high by using the manufacturing process of the present embodiment.

  FIG. 10 is a graph showing the relationship between the resist film thickness and the reflectance when the post-baking is performed (black circle) and when it is not performed (white circle) for the three samples in FIG. In this case, an integrating sphere is used as the diffused light. First, as described with reference to the three samples in FIG. 8, when the post-baking is performed, the resist film thickness is 1 as compared with the top data of the reflectance when the unevenness is formed by the conventional process. It has been proved that the samples according to this embodiment of 7 μm, 1.4 μm, and 1.0 μm all have high reflectance. That is, as shown in the theoretical value of FIG. 9, the sample formed so that the average inclination angle falls within the range of 8 ° to 15 ° has a higher reflectance than the top data of the conventional example.

  Next, looking at the sample that has not been post-baked as indicated by the white circles in FIG. 10, in the region where the resist film is thick, the reflectance is lower than the conventional top data, but in the region where the resist film is thin. It is high. From this experimental result, it is understood that the post-baking process is important for increasing the reflectance. The reason is probably that when post-baking is not performed, a lot of solvent remains in the resist film after exposure and development, and the residual solvent is generated as degassing in the final baking process after UV irradiation, resulting in defects on the uneven surface. It is estimated that this occurred.

  Further, it is presumed that the final baking temperature needs to be set higher than the baking temperature for the subsequent alignment film formation. That is, it is estimated from the sample result without post-baking in FIG. 10 that it is necessary to completely remove the solvent in the resist layer in the final baking process so that the degassing phenomenon does not occur in the subsequent heat treatment. Because it is done.

  FIG. 11 is a diagram schematically showing the concave-convex shape of the microgroove of the resin layer formed according to the present embodiment. When the unevenness of FIG. 11A is rough, the undulation of the surface of the resin layer 20 is large, the pitch length L is long, and the height difference H of the unevenness is also large. As a result, the inclination angle k tends to increase. On the other hand, when the unevenness of FIG. 11B is fine, the surface waviness of the resin layer 20 is small, the pitch length L is short, and the unevenness height difference H is also small. As a result, the inclination angle k tends to decrease.

  FIG. 12 is a diagram showing an example of a planar pattern of microgrooves formed according to the present embodiment. As described above, according to the present embodiment, the bending pattern of FIG. 12A, the bending pattern of FIG. 12B, the loop pattern of FIG. 12C, the branching pattern of FIG. Mixed microgrooves are formed on the surface of the resin film.

  FIG. 13 is a diagram showing an example of UV irradiation necessary to form a microgroove. The example of FIG. 13A is a case where the entire surface of the resin layer 20 is irradiated with UV. In this case, a region having a certain depth in the depth direction from the surface indicated by the oblique lines is caused by UV irradiation. Altered by photoreaction. Therefore, it is considered that microgrooves are formed on the surface due to the difference in thermal deformation characteristics between the altered layer and the non-altered layer due to the subsequent heat treatment by the final baking.

  On the other hand, in the example of FIG. 13B, the shaded area is altered by UV irradiation using a mask on the resin layer 20. As a result, a distribution of an altered layer and an unaltered layer is formed in the lateral direction. Therefore, it is considered that microgrooves are formed on the surface due to the difference in thermal deformation characteristics between the altered layer and the non-altered layer due to the subsequent heat treatment by the final baking. In any method, microgrooves are formed on the surface of the resin layer, but the process of FIG. 13A is more advantageous because a mask is not required in the UV irradiation step.

  The present inventors conducted a comparative study on the case where the process of final baking by UV irradiation according to the present embodiment is applied to the concavo-convex formation process by half exposure using a conventional mask. That is, (1) a first sample in which irregularities by half exposure are formed on the surface and then UV-irradiated and finally baked; (2) a second sample that is UV-irradiated and finally baked without half-exposure; (3) A third sample was formed as a concavo-convex portion by conventional half exposure and UV irradiation was not performed, and the respective reflectances were compared.

  The manufacturing process of the second sample has been described with reference to FIG. Therefore, the manufacturing process of the first sample and the second sample will be described. FIG. 14 is a cross-sectional view showing the manufacturing process of the first sample. The first sample is pre-baked by applying the resist film 20 on the substrate 10 by spin coating. Then, as shown in FIG. 14A, the resist film 20 is half-exposed using a mask 42 having a predetermined pattern. Half exposure is exposure with weak energy that does not expose the entire thickness direction of the resist film 20. Thereafter, when developed, as shown in FIG. 14B, a concave portion having a pattern shape of the mask 42 is formed on the surface of the resist film.

Therefore, the first sample is subjected to UV irradiation (for example, 5200 mj / cm ² ) of the present embodiment after post-baking, and the surface is altered. Then, when the above-described final baking is performed, as shown in FIG. 14C, the surface of the resist film 20 is micro-grooved by UV irradiation and post-baking in addition to the undulations corresponding to the pattern by half exposure. Is formed.

In the third sample, UV irradiation (for example, 1300 mj / cm ² ) with a low energy that does not form microgrooves is performed on the entire surface after the development process of FIG. 14B. After that, when the final baking is performed, irregularities where microgrooves are not formed are formed on the surface of FIG. Since only the very surface of the resist film 20 is deteriorated by the UV irradiation with the low energy, the resist film is prevented from being uneven and flattened in the final baking heating step. However, since the UV irradiation energy is small, microgrooves are not formed.

  FIG. 15 is a graph comparing the reflectance when the first, second, and third samples formed by the above process are irradiated with an integrating sphere diffuse light source. In the figure, the first sample SM1 includes samples that have been half-exposed with a plurality of types of pattern shapes (octagon, quadrangle, cross, pentagon, donut, triangle, ellipse, fan, octagon). The second sample SM2 uses an area that has not been exposed by half exposure. Similarly to the first sample, the third sample SM3 includes a sample that is half-exposed with a plurality of types of pattern shapes.

  As understood from the comparative example of FIG. 15, even when the half exposure process is added and this embodiment is applied, there is a case where a reflectance higher than the top data of the conventional process may be obtained. However, the reflectance is highest when the present embodiment is applied without performing half exposure as in the second sample SM2. The third sample SM3 in which unevenness is formed only by the half exposure process has a low reflectance in any pattern. As described above, the process of final baking by UV irradiation according to the present embodiment can achieve a high reflectance even if a half exposure process and a development process using a predetermined pattern are added.

  It is preferable that the microgroove according to the present embodiment is formed with random irregularities as much as possible. According to the experiments by the present inventors, it was observed that when the surface of the photosensitive resin layer was irradiated with UV and finally baked, thick grooves or ridges were formed to extend long in some places. Such irregularities may be undesirable for the diffuse reflection function of the reflective electrode, for example, the reflection direction is concentrated in a certain direction. Therefore, a method capable of controlling the direction and length of the microgroove to some extent is desired.

  On the other hand, a pixel electrode is used as the reflective electrode in this embodiment. The pixel electrode is formed separately for each pixel, and a voltage is applied independently. Therefore, the present inventors have separated the photosensitive resin layer in pixel units or line units to prevent the above-described thick grooves or ridges from being formed to extend for a long time, and more uniform in the pixel electrode. We found that it was possible to form microgrooves. The photosensitive resin layer may be completely separated, or may be separated by forming a groove with a certain depth on the surface, and further, the film may be formed so that the film thickness is partially reduced. May be. However, since the pixel electrode is designed so that the capacitance between the data line, the scanning line, and the gate electrode falls within a predetermined range, it is necessary to separate the photosensitive resin layer within a range satisfying such conditions.

  FIG. 16 is a diagram for explaining separation of the photosensitive resin layer. 16A and 16B are plan views of the back substrate. As shown in FIG. 16A, data lines D and scanning lines S are formed on the surface of the back substrate, and semiconductor layers 19 and source / drain electrodes 17 and 18 are formed at the intersections. A region partitioned by the data line D and the scanning line S becomes a pixel region PX. Accordingly, as shown in FIG. 16B, a contact hole CH for connecting the source electrode 18 and the pixel electrode 22 is formed, and the pixel electrode 22 is provided separately for each pixel region.

  FIGS. 16C to 16F show examples of separation lines for separating the photosensitive resin layer. (C) is an example in which a separation line 50 is formed along the scanning line S and the data line D, and the photosensitive resin layer is separated into pixel units (pixel electrode region units). (D) is an example in which the separation line 50 is formed along the data line D, and the photosensitive resin layer is separated in data line units. In (E), the separation line 50 is formed along the data line D, and the separation line 50 is also formed in a direction orthogonal thereto. In this case, the separation unit of the photosensitive resin layer is irrelevant to the pixel electrode. (F) is an example in which the separation line 50 is formed along the scanning line S.

  FIG. 17 is a cross-sectional view showing a process for forming a photosensitive resin layer separation line. In FIG. 17A, a gate electrode 15, an insulating film 16, a semiconductor layer 19, and drain / source electrodes 17 and 18 are formed on an insulating substrate 10, and a photosensitive resin layer 20 made of resist is spin-coated. Shows the pre-baked state. In this state, an exposure process for forming a contact hole in the photosensitive resin layer 20 is performed. In the exposure mask 51 at that time, the region 53 corresponding to the contact hole completely transmits light, the region 55 corresponding to the separation line partially transmits light, and the other region 54 completely blocks light. A mask pattern is formed on the transparent substrate 52. For example, the region 54 can be formed of a light shielding film made of chromium, and the region 55 can be made of a half exposure film made of molybdenum silicide. When exposed using such an exposure mask, the position of the contact hole of the photosensitive resin layer 20 is completely exposed, and the region corresponding to the separation line is half-exposed.

  Thereafter, when development is performed, as shown in FIG. 17B, a contact hole CH penetrating the resin layer is formed in the photosensitive resin layer 20 at a position corresponding to the source electrode 18, and is constant on the surface of the resin layer. Are formed as the separation line 50. The contact hole CH is formed only in a narrow region and has little function of separating the resin layer 20. However, since the separation line 50 separates at least the surface of the resin layer 20, it prevents a long groove or wrinkle from being generated in the microgroove formed by the subsequent UV irradiation and the final baking process. be able to.

  In FIG. 17A, a special exposure mask 51 is used. However, patterning of the resin layer shown in FIG. 17B can also be performed by performing normal exposure with the contact hole forming mask and half exposure with the separation line forming mask. Further, the resin layer 20 may be completely separated by the separation line 50 by performing normal exposure with a separation line forming mask.

  Further, the separation line 50 is not necessarily formed on the surface side of the resin layer 20. For example, it can be formed on the back side. In that case, the presence of the data line D formed on the insulating layer 16 itself may have the function of the separation line 50. This is because the thickness of the resin layer 20 is partially reduced at the portion where the data line D exists. As a result, the formation of microgrooves is divided, and the formation of long extending grooves and ridges is prevented.

  As shown in FIG. 17B, the separation line 50 is preferably formed in the separation region of the pixel electrode 22 (shown by a broken line in the drawing) formed on the resin layer 20. This is because the influence on the parasitic capacitance between the pixel electrode 22 and the gate electrode 15 and other electrodes can be minimized.

  FIG. 18 is a diagram showing micrographs of microgrooves with and without a separation line. In this sample, the same reflector as in the samples of FIGS. 6 to 9 described above is formed with and without a separation line. FIG. 18A shows an example of a microgroove when a separation line is formed, and FIG. 18B shows an example of a microgroove when a separation line is not formed.

  As can be seen from this photograph, the example (B) in which the separation line is not formed has a groove or ridge that extends long in part, whereas the example (A) in which the separation line is formed extends. There are no grooves or wrinkles and the shape is more uniform.

  In the sample of the above embodiment, a general-purpose resist LP200 manufactured by Shipley Co. was used as the photosensitive resin layer. It was confirmed that microgrooves were formed in the same manner even when resist AFP750 made by Clariant Japan was used as another photosensitive resin.

  As described above, in this embodiment, a micro-groove having random irregularities on the surface is formed by a simple process of forming a partially altered region in the photosensitive resin layer by UV irradiation or the like and then performing a heat treatment. can do. In addition, the shape and direction of the microgroove can be controlled relatively easily according to various process conditions. Therefore, by forming a reflective layer on the resin layer having such microgrooves, it is possible to realize a reflective function effective for the reflective liquid crystal display device. By using a pixel electrode for the reflective layer, a simpler reflective liquid crystal display device can be realized.

[Control of tilt angle distribution of reflector]
FIG. 19 is a diagram showing an actual environment in which the reflective liquid crystal display device assumed in the present embodiment is used. In an environment where a reflective liquid crystal display device is used, light sources exist in various places. Therefore, considering all usage environments, it is necessary to assume a case where the reflective liquid crystal display device is placed under a uniform diffused light source disposed on the inner surface of the hemisphere, as shown in FIG. Under such a use environment, the display panel is irradiated with all incident light existing within the solid angle of the hemisphere.

Therefore, in order to obtain the light intensity L incident on the reflective liquid crystal display device, the XYZ axis, the incident angle θi, and the azimuth angle φi are defined as shown in FIG. The incident angle θi is an angle between the Z axis and the incident light, and the azimuth angle is an angle between the incident light and the X axis. Assuming that the light intensity per unit area of the hemisphere (hereinafter referred to as an integrating sphere) shown in FIG. 19 is I (θ _i , φ _i ), the light intensity dL is
dL = I (θ _i , φ _i ) · dω
= I (θ _i , φ _i ) · ds / r ²
It becomes. Where ω is a solid angle, ds is the unit area of the spherical surface of the integrating sphere, r is the radius of the integrating sphere, and if the integrating sphere is uniform diffused light, the light intensity I is a constant.

  Furthermore, since the incident light is applied to the display panel from an oblique direction by the incident angle θi, the display panel has a light intensity attenuated by sinθi,

It becomes. The unit area ds is as shown in FIG.

Therefore, if the formula (2) is substituted into the formula (1) and the light intensity dL is integrated over the incident angle θi of 0 to π / 2 and the azimuth angle φi of 0 to 2π, the incident light on the display panel is obtained. The light intensity L is expressed as follows.

Therefore, the light intensity f (θ _i ) incident from the polar angle θ _i direction is expressed by a function in the integral of the equation (3), which is as follows.

  The sin θi in the equation (4) is caused by the area of the diffusion light source of the integrating sphere for each unit incident angle θi, and the light source area of incident light from directly above the display panel (incident angle θi = 0) is narrow. (Sin θi = 0), which means that the light source area of incident light from the horizontal direction of the display panel (incident angle θi = π / 2) is large (sin θi = 1). In addition, cos θi in the equation (4) is an attenuation component due to the incident angle, and there is almost no attenuation of incident light from directly above the display panel (incident angle θi = 0) (cos θi = 1). This means that the attenuation of incident light from the direction (incident angle θi = π / 2) is large (cos θi = 0).

FIG. 21 is a diagram illustrating a case where light is incident on the reflective display device and reflected. In the reflection type liquid crystal display device shown in FIG. 2, the refractive index n of the display side glass substrate and the liquid crystal layer has a value of about 1.5. Therefore, from the substrate having the reflection electrode as shown in FIG. It can be assumed that the reflection plate 60 is covered with a medium 61 having a refractive index n formed of a liquid crystal layer or a display-side substrate formed thereon. Then, the incident light incident at the incident angle θi from the air layer becomes the incident angle θ _i ′ in the medium 61, is reflected by the reflection plate 60 at the reflection angle θ _o ′, and exits at the reflection angle θo in the air layer. Will go.

When entering the medium 61 from the air layer, a part thereof is reflected light R and is not incident on the medium. Therefore, considering this, the intensity f (θ _{i) of} light incident on the reflecting plate 61 at the incident angle θ _i ′. ') Can be expressed as:

Here, R (θ _i ) is the reflectance of light reflected at the interface between the air layer and the medium 61 having a refractive index n. Then, hold the following relationship between the incident angle theta _i 'of within the incident angle theta _i and the medium 61 at the air layer.

Here, the refractive index of the air layer is 1, and the refractive indexes of glass and liquid crystal are n. θ _i is the incident angle in the air layer, and θ _i ′ is the incident angle in the liquid crystal layer.

FIG. 22 is a diagram showing the relationship between the intensity f (θ _i ′) of light incident on the reflector 61 and the incident angle θ _i ′, and calculated by substituting equation (6) into equation (5) above. . However, the light intensity was calculated with I (θ _i , φ _i ) = 1. As is understood from FIG. 22, when uniform diffused light from the integrating sphere is assumed, the incident light intensity increases with respect to the reflector 60 as the incident angle increases from the incident angle θ _i ′ = 0. The incident light intensity becomes maximum within a certain incident angle θ _i ′ range, and the incident light intensity is greatly attenuated near an incident angle of 45 °. That is, it can be seen that there is an incident angle θ _i ′ where the incident light intensity is maximum, and the incident angle varies depending on the refractive index n of the medium.

FIG. 23 is a diagram showing the relationship between the incident angle θ _i ′ at which the incident light intensity in FIG. 22 is maximum and the refractive index n of the medium. From FIG. 23, it is understood that the incident angle θ _i ′ at which the incident light intensity becomes maximum decreases as the refractive index n of the liquid crystal increases. Since the refractive index of a typical liquid crystal is about 1.4 to 1.8, the incident angle θ _i ′ at which the incident light intensity is maximum is about 30 to 38 °.

Next, it is considered that the incident light having the incident light intensity distribution as shown in FIG. 22 is reflected by the uneven inclined surface of the reflector 61. FIG. 24 is a diagram illustrating a relationship between an incident angle, a reflection angle, and an inclination angle with respect to the inclined surface of the reflection unevenness. The incident light and the reflected light are symmetric with respect to a line perpendicular to the inclined surface, and the local incident angle α in the micro mirror surface is equal to the local reflected angle β. Therefore, the inclined angle ξ, the incident angle θ _i ′, The reflection angle θ _o ′ has the following relationship.

In general, the display is often observed from the vertical direction on the display panel. Therefore, considering that light incident at an incident angle _i θ ′ is reflected in the 0 ° direction on the uneven reflector, the above equation (7) becomes ξ = θ _i ′ / 2. That is, if the tilt angle ξ is ½ of the incident angle θ _i ′, the light can be reflected in the direction perpendicular to the display panel.

  As shown in FIG. 22, the distribution of incident light that is incident on the uneven surface of the reflecting plate with respect to the diffused light of the integrating sphere has a peak that is a region with an incident angle of 0 to 45 °. Therefore, it is desirable that the distribution of the inclined surface of the uneven surface of the reflector is also a distribution corresponding to the light intensity distribution of FIG. In other words, it is desirable to increase the reflected light intensity as a whole by increasing the existence probability of the inclination angle corresponding to the incident angle where the light intensity is high and decreasing the existence probability of the inclination angle corresponding to the incident angle where the light intensity is low. .

  FIG. 25 is a diagram showing a distribution of existence probability of inclination angles corresponding to the incident light intensity distribution of FIG. The example of FIG. 25 shows the case where the refractive index n = 1.5 in FIG. 22 and is normalized so that the sum of the probabilities becomes 1. The horizontal axis represents the inclination angle ξ of the reflective uneven surface, and the vertical axis represents the existence probability (%). Therefore, in the sample having the inclination angle existence probability distribution as shown in FIG. 25, the reflectance when the inclination angle that maximizes the existence probability is changed is obtained. FIG. 26 is a diagram showing a simulation result of such reflection characteristics. More specifically, the slope w at which the existence probability is maximized is changed by changing the width w of the distribution shown in FIG. 25, and the reflectance Y at that time is calculated.

As apparent from FIG. 26, the range of the inclination angle ξ (= θ _i '/ 2) where the existence probability is maximum is reflected in the region where ξ = about 15 to 19 ° (θ _i ' = about 30 to 38 °). It is understood that the rate is the highest. That is, the existence probability of the inclination angle ξ = 15 to 19 ° at which the incident light having the peak incident light intensity θ _i ′ = 30 to 38 ° shown in FIG. 22 can be reflected in the direction perpendicular to the display panel. It is desirable to increase the maximum value in order to increase the overall reflectivity.

  As described above, in order to reflect light effectively under the uniform diffused light of the integrating sphere, it is necessary that the inclination angle due to the unevenness for reflection should be maximized in the region of about 15-19 °. It became clear theoretically.

  FIG. 27 is a diagram showing a result of measuring the reflectance of the integrating sphere with respect to uniform diffused light using a sample that was actually made as an experiment. In the prototype reflector, the relationship between the tilt angle ξp with the highest existence probability and the measured reflectance is shown.

  FIG. 28 is a sectional view showing a method for forming the prototyped reflector. First, as shown in FIG. 28A, a resist (LC-200 manufactured by Shipley Co.) 63 is spin-coated on a glass substrate 62 at 1000 to 2000 rpm for 20 seconds. Then, after pre-baking at 90 ° C. for 30 minutes, ultraviolet exposure is performed using a mask 64 as shown in FIG. Next, development is performed using a developer (MF319 manufactured by Shipley Co., Ltd.), and convex portions are formed on the glass substrate as shown in FIG. Next, as shown in FIG. 28 (d), post-baking was performed at 120 to 200 ° C. for 60 minutes to round the convex portions. Thereafter, as shown in FIG. 28 (e), an aluminum layer 65 was deposited by 200 nm to prepare a reflector.

A liquid crystal layer was formed between the reflection plate formed as described above and the glass substrate, and a reflection type liquid crystal display device as shown in FIG. Here, the liquid crystal layer was made of Merck's liquid crystal material MJ961213, and its thickness was controlled by a 3.5 μm diameter spacer. Using the integrating sphere, we measured the reflectivity when diffused light was incident on the prototype reflective LCD. Furthermore, the inclination angle distribution of the unevenness of the reflector of the prototype was measured, and the inclination angle ξ _p that maximized the existence probability was also obtained. The result is shown in FIG.

From this experimental result, it can be seen that the maximum reflectivity is obtained by setting the inclination angle ξ _{p at} which the existence probability is maximum near 16 to 19 °. This experimental result almost supports the simulation result shown in FIG. It can be seen that the sample with the inclination angle ξ _{p at} which the existence probability is maximum around 16-19 ° has higher reflectivity even when compared with the conventional case where the inclination angle is 10 °. .

  FIG. 29 is a diagram showing a pattern example of the mask 64 for forming the unevenness of the reflecting plate. FIG. 29A is an example in which patterns of large and small circles having different sizes are mixed, and FIG. 29B is an example in which polygons such as triangles, quadrangles, hexagons, and octagons are mixed. However, the present invention is not limited to these patterns.

As another example of forming the unevenness for reflection, the process shown in FIGS. 3 to 6 can be adopted in which the distribution of thermal deformation characteristics is formed by UV irradiation and then the final baking is performed to form microgrooves. Since the concave and convex shape of the microgroove can be controlled under the above-described process conditions, the concave and convex shape is controlled so that the inclination angle ξ _p at which the existence probability is maximized is about 15 to 19 °.

  As described above, in the present embodiment, the inclination angle due to the unevenness of the reflector is distributed in the range of at least 0 ° to 25 °, and the distribution probability is maximized in the vicinity of 15 to 19 °. In various environments, it is possible to provide a reflective liquid crystal display device having a higher reflectance.

[Control of tilt angle distribution of reflector (part 2)]
FIG. 30 is a diagram showing the inclination angle distribution of the unevenness of the reflector plate that provides a high reflectance with respect to the diffused light of the integrating sphere described above. The horizontal axis represents the inclination angle ξ, and the vertical axis represents the existence probability. That is, as already described, it is desirable that the existence probability of the inclination angle be distributed so as to reflect more incident light having an incident angle with a high incident intensity on the reflector in a direction perpendicular to the display panel. FIG. 30 shows a distribution in which the existence probabilities of the inclination angle near +15 to 19 ° and the inclination angle near −15 to 19 ° are maximized. The positive side and negative side exist when the tilt angle is viewed along a certain direction of the display panel, the tilt angle corresponding to the incident light from one direction is the positive side, and the tilt corresponding to the incident light from the opposite direction. Corners are shown on the-side. Therefore, when the distribution diagram of FIG. 30 is bent around an inclination angle of 0 °, an inclination angle distribution as shown in FIG. 25 is obtained.

  By the way, the liquid crystal display device is often used as a display panel of a notebook personal computer. FIG. 31 is a diagram illustrating a state in which the reflective liquid crystal display device is mounted as a monitor of a notebook personal computer. As shown in the figure, the reflective liquid crystal display device 70 is often used in a state where it is inclined by an angle α with respect to the horizontal direction. In that case, as shown in FIG. 31, the display device 70 is a surface perpendicular to the paper surface. Then, the directions of the XYZ axes are defined as shown.

Examining the incident light on the display device 70, the incident angle θ _i distribution along the XY plane of coordinates is θ _i = −90 to 90 ° because there is nothing to block the incident light. On the other hand, the incident angle distribution along the XZ plane of coordinates is not necessarily θ _i = −90 to 90 ° because incident light is blocked by the keyboard portion. That is, the incident angle range differs between the highest position 70A and the lowest position 70B of the display device 70. The highest position 70A is θ _i = −90 to α + β ° in the widest incident angle range, and the lowest position 70B is θ _i = −90 to α ° in the narrowest incident angle range.

  Therefore, the incident light in the XZ plane direction along the vertical direction of the display panel has almost no light incident from an incident angle α to 90 ° (or α + β ° to 90 °). Accordingly, the inclination angle of the micro mirror surface arranged in the XZ plane direction of the display panel does not need an inclination angle that reflects the light incident from this angle range in the normal (0 °) direction of the display panel.

For example, if the inclination α of the display panel is 30 ° and the refractive index n _LC = 1.5 of the liquid crystal layer and the glass substrate, the inclination angle that reflects the light incident at 30 to 90 ° in the 0 ° direction is It becomes 10 to 21 ° from the equations (6) and (7). That is, an inclination angle of 10 to 21 ° is not necessary for the uneven distribution of the unevenness facing the vertical direction (XZ plane direction) of the display panel.

  Therefore, it is desirable that the distribution of the inclination angles in the XY plane direction and the XZ plane direction is as shown in FIG. That is, the inclination angle distribution in the XY plane direction is the same as that shown in FIG. 30, the inclination angle distribution in the XZ plane direction is the same as that in FIG. 30, and the plus side is 10 to 21 °. The distribution does not exist in the range. When the distribution of FIG. 32 is folded around an inclination angle of 0 °, it is as shown in FIG.

  FIG. 33 shows a distribution of inclined surfaces in the XY plane direction and a distribution of inclined surfaces in the XZ plane direction with respect to the inclination angle distribution formed by the unevenness of the reflector. As is clear from this figure, when using it with a tilt, such as a notebook personal computer, the distribution of the inclined surface in the horizontal direction on the display panel is such that the existence probability is maximized within the inclination angle range of 15 to 19 °. It is desirable that the distribution of the inclined surface in the vertical direction of the display panel has a peak existence probability in the range of the tilt angle of 8 to 10 ° and the tilt angle of 15 to 19 °. Thus, according to the direction of the display panel, the angle distribution of the inclined surface due to the unevenness for reflection, one direction has one existence probability peak, and the other direction has two existence probability peaks. Thus, even when used in an environment where the incident light direction is anisotropic, the maximum reflectance can be realized.

  The inventors made a prototype of the reflector having the above-described inclined surface distribution and confirmed the reflectance. FIG. 34 is a cross-sectional view showing a method for forming a sample reflector. First, as shown in FIG. 34A, a resist (for example, LC-200 manufactured by Shipley Co.) 63 is formed on a glass substrate 62 by spin coating at 1000 rpm for 20 seconds. Then, after pre-baking at 90 ° C. for 20 minutes, ultraviolet exposure is performed using a mask 64 as shown in FIG. Next, development is performed using a developer (for example, MF319 manufactured by Shipley Co., Ltd.), and a convex portion made of resist is formed on the glass substrate as shown in FIG. 34 (a) to (c) are repeated four times using the mask patterns (a) to (d) shown in FIG. 35 in order, and the convex portions having different inclination angles as shown in FIG. 34 (d). Form. Next, as shown in FIG. 34 (e), post-baking was performed at 200 ° C. for 80 minutes to round the convex portions. Thereafter, as shown in FIG. 34 (f), aluminum 66 was vapor-deposited to a thickness of 200 nm to produce a reflector.

  FIG. 36 is a diagram showing a planar shape and a cross-sectional shape of the convex portion of the reflecting plate formed as described above. The planar shape of the projection 67 has different inclined surfaces in the vertical direction V of the substrate 62 and has the same inclined surface in the horizontal direction H of the substrate 62. In the plan view shown in FIG. 36, contour lines are shown on the convex portion 67 and the inclined surface shape is shown. Since the convex portion is rounded by post-baking, the inclination angle distribution is distributed in a range of approximately 0 to 20 °. Since the inclined surface (ξ1> ξ2) is different in the vertical direction V of the substrate, there are two regions where the existence probability peaks as shown in FIG. 33. In the horizontal direction H of the substrate, the inclined surface Since (ξ1) is symmetric, there is one region where the existence probability peaks as shown in FIG.

  As described above, the distribution of the inclination angle in the horizontal direction and the distribution of the inclination angle in the vertical direction can be made different by changing the shape of the unevenness for reflection in the horizontal direction and the vertical direction. In addition, as shown in FIG. 36, the distribution of the inclination angle in the horizontal direction and the inclination angle in the vertical direction can be made different by combining the semicircular shape and the semielliptical shape.

  The inventors measured the shape using a non-contact three-dimensional shape measuring device nh-3 manufactured by Ryoko Co., Ltd., and found the inclination distribution of the prototyped reflector. FIG. 37 shows the measurement result of the inclination angle distribution of the prototyped reflector. As shown in the figure, the prototyped reflectors had absolute probabilities at 8 ° and 18 ° in absolute values. For comparison, FIG. 37 also shows the tilt angle distributions of the reflectors having the maximum existence probability at 0 ° and 10 °, and Conventional Example 1 and Conventional Example 2, respectively.

  FIG. 38 is a schematic cross-sectional view of a reflective liquid crystal display device prepared using the above-described reflector. A liquid crystal layer (for example, a liquid crystal material MJ961213 manufactured by Merck & Co., Inc.) was injected between the reflector and the glass substrate while controlling the thickness with a 3.5 μm diameter spacer. Then, the reflective liquid crystal display device is fixed at an angle of 30 ° from the vertical direction, irradiated with uniform diffused light from an integrating sphere, and the reflectance is measured using a luminance meter (for example, BM-5 manufactured by Topcon). It was measured. FIG. 39 is a diagram showing the measurement results of the reflectance. As is apparent from this chart, when the reflector of the present invention is used, the reflectance is 61%, and the reflectance is improved by 10 to 25% compared to 31% and 53% of the conventional examples 1 and 2. It was confirmed.

FIG. 33 shows an ideal tilt angle distribution. As a precondition, the refractive index n of the liquid crystal layer or the glass substrate is 1.5, and the angle with respect to the horizontal line of the reflective liquid crystal display device (the tilt α shown in FIG. 31). Was set to α = 30 °. Therefore, we investigated the range of tilt angles where the probability of existence is maximized in the ideal reflection unevenness when the refractive index n _LC of the liquid crystal layer and the tilt angle α of the reflective liquid crystal display device are changed.

FIG. 40 is a diagram illustrating a tilt angle range in which the existence probability is maximized with respect to the tilt angle of the reflective liquid crystal display device and the refractive index of the liquid crystal layer. Since the refractive index n _LC of a typical liquid crystal material is about 1.4 to 1.8, the refractive index n _LC was changed from 1.4 to 1.8. In a general use state, the inclination α tends to increase as the size of the reflective liquid crystal display device decreases, and the inclination α of the display panel is changed in the range of 0 to 45 °.

  First, when the inclination angle α of the display panel is 30 °, as shown in FIGS. 32 and 33, the existence probability of the uneven inclination angle is maximized in the range of 15 to 19 °, and on the other hand, it is 8 to 10 It is desirable that the existence probability of the inclination angle of the unevenness is maximized in two ranges of a range of ° and a range of 15 to 19 °. When the display panel tilt angle α is 0 °, the display panel is placed vertically, and the vertical tilt angle ξ of the display panel mainly reflects incident light from above in the vertical direction. Therefore, the existence probability of the uneven inclination angle becomes maximum in the range of 15 to 19 °, and since there is not much incident light from below, an inclined surface facing downward is not necessary. When the display panel tilt angle α is 90 °, the display panel is placed horizontally and is not shown in FIG. 40, but the existence probability of the uneven tilt angle is maximized in the range of 15 to 19 °. It is desirable to become. When the display panel is horizontal, the distribution example is the same as that shown in FIG.

As shown in FIG. 40, when the inclination angle α of the display panel is in the range of 0 ° to 45 °, one inclination angle at which the existence probability in the reflection unevenness is maximized is 0 to 16 °, and the other inclination angle is It was found that the reflectivity can be maximized if it is within the range of 14 to 19 °. As the refractive index n _LC is smaller, the inclination angle at which each is maximized tends to increase.

  A notebook personal computer has a display panel tilted differently depending on the preference of the operator. Therefore, it is desirable to form a plurality of regions in which the existence probability of the inclination angle of the reflection unevenness is maximized in the pixel region so that the maximum reflectance can be realized at a plurality of inclinations. For example, as shown in FIG. 40, the inclination angle region where the inclination probability α of the display device is found corresponding to 30 ° and 40 ° and where the existence probability is maximized is 8 to 10 ° and 15 to 19 °. The first combination and the second combination of 10 to 12 ° and 15 to 19 ° coexist in the same pixel region. Alternatively, the three combinations of regions obtained corresponding to the inclination angle α of the display device corresponding to 30 °, 35 °, and 40 ° coexist. Alternatively, three types of convex patterns are allowed to coexist. Thereby, even if the inclination of the display panel differs to some extent, a relatively large reflectance can be realized.

  A reflective liquid crystal display device having the structure shown in FIG. 2 is formed by using the reflective electrode having the inclination angle distribution of the reflective irregularities described above as the pixel electrode, and the pixel electrode and the transparent electrode on the display side are formed on the liquid crystal layer 34. By applying a predetermined electric field to the liquid crystal layer 34, the liquid crystal layer 34 can have a birefringence action and desired display can be performed. That is, the liquid crystal layer 34 is driven in the field effect birefringence mode. Further, a pigment can be included in the liquid crystal layer 34 to form a guest-host type liquid crystal display device.

[Examples of reflective irregularities with different directivities]
Japanese Patent Application Laid-Open No. 11-295750 describes a reflective liquid crystal display device that uses a pixel electrode as a reflective electrode. In this publication, the pixel electrode is divided into two regions, and an uneven shape having a highly directional reflection characteristic is formed in one region, and an uneven shape having a highly diffusive reflection property is formed in the other region. Form.

  However, in the case of a higher-definition liquid crystal display device, the pixel area becomes narrower, and it becomes more difficult to divide the pixel area into two areas and form different uneven shapes as in the conventional example. Is expected.

  Therefore, in the present embodiment, an uneven shape having a highly directional reflection characteristic and an uneven shape having a highly diffusive reflection characteristic are mixed in the pixel region. FIG. 41 is a cross-sectional view showing two reflective uneven shapes mixed in such a pixel region. Since the unevenness A has a gentle inclined surface with a thin film thickness and a relatively flat upper surface, the direction of reflected light has directivity in the vertical direction. On the other hand, the unevenness B is thick and has a steeply inclined surface, and the upper surface has a protruding shape.

  FIG. 42 is a plan view of the pixel region PX in the present embodiment. As shown in the drawing, the unevenness A and the unevenness B shown in FIG. 41 are mixedly provided in the pixel region PX.

  FIG. 43 is a cross-sectional view showing a manufacturing process for forming the reflective irregularities of FIG. First, as shown in FIG. 42A, a resist (for example, LC-200 manufactured by Shipley Co., Ltd.), which is a photosensitive resin, is spin-coated on a glass substrate 62 at 2000 rpm for 20 seconds. Then, after prebaking at 90 ° C. for 20 minutes, ultraviolet exposure is performed using a mask 64A as shown in FIG. Next, development is performed using a developing solution (for example, MF319 manufactured by Shipley Co., Ltd.), and convex portions corresponding to the concave and convex portions A are formed on the glass substrate 62 as shown in FIG. Thereafter, as shown in FIG. 42 (d), post-baking is performed at 200 ° for 80 minutes, and the projections are rounded to form the projections and depressions A.

  Next, as shown in FIG. 42E, the resist is spin-coated at 1000 rpm for 20 seconds. Thereby, a thicker resist layer than the above-mentioned resist can be formed. Then, after prebaking at 90 ° C. for 20 minutes, ultraviolet exposure is performed using a mask 64B as shown in FIG. Next, development is performed using the developer described above, and convex portions corresponding to the irregularities B are formed on the glass substrate as shown in FIG. Then, as shown in FIG. 42 (h), post-baking is performed at 120 ° C. for 80 minutes so that the convex portions are rounded to form the concave and convex portions B. Since this post-baking is at a lower temperature than that for forming the unevenness A, the degree of sagging due to the heating of the thick resist film is small, and the unevenness B having a higher diffusibility is formed.

  Thereafter, as shown in FIG. 42 (i), aluminum 64 was deposited to a thickness of 200 nm to produce a reflector (pixel electrode). As described above, it is possible to change the roundness of the unevenness by changing the resist film thickness and the post-baking temperature between the unevenness A and the unevenness B, and to create a reflective surface in which unevenness having different directivities at the time of scattering is mixed. Could be configured.

  As described above, it is desirable that the reflection plate of the reflective liquid crystal display device reflects incident light from all directions in a direction perpendicular to the display surface. Therefore, when the resist layer is patterned and rounded by baking to form an inclined surface, the inclined surface is preferably directed in the direction of 360 °. Thus, conventionally, a circular pattern has been proposed as a resist film pattern. For example, JP-A-11-337935, JP-A-11-337964, JP-A-5-215533, and the like. In these publications, a circular pattern is randomly formed to prevent a moire pattern due to interference of reflected light, or a donut pattern having a large radius and a circular pattern having a small radius are formed randomly. It has been proposed to improve the reflection characteristics.

  Japanese Patent Application Laid-Open No. 5-215533 shows that a large circular pattern and a small circular pattern are randomly mixed. For example, as shown in FIG. However, when circular patterns having a large radius are randomly arranged, the resist patterns that are close to each other are merged due to sagging of the cross-sectional shape due to heating during the post-baking process after exposure and development. The circular pattern shown by diagonal lines in FIG. 44 shows a state in which they are too close together and merged during baking.

  Therefore, in this embodiment, as shown in FIG. 45, the resist pattern is a mixture of a circular pattern with a large radius and a circular pattern with a small radius, and a large circular pattern and a small circular pattern. The distance is always smaller than the distance between large circular patterns. That is, it is prohibited to bring another large circular pattern close to the large circular pattern. If possible, a small circular pattern is arranged around the large circular pattern so that the large circular patterns do not come close to each other. As a result, the density of the inclined surfaces can be increased, and the area where the patterns are merged during baking can be reduced.

  FIG. 46 is a diagram for explaining a resist pattern in the present embodiment.

 FIG. 46A shows an example in which a relatively large circular pattern is arranged. Four large circular patterns P1 are arranged in the pixel region PX. The resist pattern needs to have a certain size. This is because if the pattern is too small, the inclination angle will not be sufficiently large due to the sagging of the cross-sectional shape during post-baking. However, in the pattern of FIG. 46A, the density of the inclined surface formed is thin, and the reflectance cannot be increased.

  Therefore, as shown in FIG. 46B, it is conceivable to increase the density of the large circular pattern P1. However, when the large circular patterns P1 are close to each other, the peripheral portions of the circular patterns may be merged as shown by the hatched lines due to sagging due to heat during post-baking. Such coalescence is not preferable because it reduces the area of the inclined surface as designed.

  Therefore, in the present embodiment, as described in FIG. 45, the density of the relatively large circular pattern P1 is sparse as shown in FIG. The distance L1 between the patterns P1 is kept relatively large, and a relatively small circular pattern P2 is arranged in the gap between the large circular patterns P1 so as to increase the inclined surface density. As a result, the coalescence of relatively large circular patterns is reduced, and even if coalescence occurs, it is limited to only between the large circular pattern P1 and the small circular pattern P2 (hatched line in FIG. 46C). . Such a merged region is narrower than the merged region of the large circular patterns P1, and the reduction of the inclined surface region can be minimized.

  As shown in FIG. 46C, the distance L1 between the large circular patterns P1 is made long to the extent that coalescence does not occur, and the small circular patterns P2 are arranged in the area between the circular patterns P1. As a result, the distance L2 between the large circular pattern P1 and the small circular pattern P2 closest thereto is always shorter than the distance L1 between the large circular pattern P1 and the large circular pattern P1 closest thereto.

  FIG. 47 is a diagram showing another resist pattern. In the above example, a circular pattern is used so that the inclined surface of the reflecting irregularities faces in the direction of 360 °. However, even if it is not circular, it is a polygon having a plurality of directions, preferably three or more directions on each side. Even if it exists, the same high reflectance can be implement | achieved.

  FIG. 47 shows an example of a resist pattern in which a large number of hexagons are brought close to each other in the pixel region PX so that adjacent sides are parallel to each other. The entire periphery of the pixel area PX cannot be accommodated in the entire hexagon, but has a trapezoidal shape or a pentagonal shape, but is basically a resist pattern in which the hexagonal shape is spread like a tile. By making each side parallel, even when the hexagonal patterns are as close as possible, coalescence during post-baking can be prevented.

  By exposing and developing the resist layer using such a mask pattern and performing post-baking, the cross-sectional shape is sagging due to heat, thereby forming reflective irregularities having inclined surfaces facing at least three directions. Can do.

  FIG. 48 is a diagram showing another resist pattern. In the example of FIG. 48, not a hexagon but a plurality of regular triangles are arranged in the pixel region so that the sides are close to each other in parallel. Also in this case, by exposing and developing the resist layer and performing post-baking, it is possible to form reflection irregularities whose cross-sectional shape is bent by heat and whose inclined surfaces are directed in at least three directions. In the present embodiment, even if it is another polygonal shape, it is possible to form reflective irregularities having a high-density inclined surface.

  The process of forming the unevenness for reflection when the patterns of FIGS. 45, 47 and 48 are used is the same as the process shown in FIG. 45, 47 and 48 are used for the mask 64 in the resist layer exposure process. Thereby, in a post-bake process, a high-density inclined surface distribution can be formed, without patterns combining, and the reflectance of a reflecting plate can be made high.

[Front light structure]
The reflective liquid crystal display device brightens the display surface by reflecting external light without providing a backlight. Therefore, it consumes less power and is useful as a display panel for portable information terminals, mobile phones and the like. However, since external light is used, there is a problem that is limited to use in bright places. Therefore, a liquid crystal display device with a front light that is turned on only when used in a dark place has been proposed.

  FIG. 49 is a configuration diagram of a reflection type liquid crystal display panel with a front light which has been conventionally proposed. As illustrated, a front light 70 is provided on the display side of the reflective liquid crystal display panel 73. In the reflective liquid crystal display panel 73, a liquid crystal layer (not shown) is inserted between a back substrate 73B having a reflective plate structure and a display substrate 73A. A front light 70 is provided on the display-side substrate 73A. The front light 70 guides light from the light source 71 and the light source to the entire display surface, and displays it by a scattering layer or a prism layer formed on the surface. And a transparent substrate 72 scattered on the panel 73 side. Due to the difference in refractive index between the scattering layer or the prism layer formed on the surface of the transparent substrate 72 and the air layer, the light from the light source 71 is scattered and a part thereof is scattered to the display panel 73 side.

  However, in the reflection type liquid crystal display device configured as shown in FIG. 49, a scattering layer or a prism layer is formed on the surface of the transparent substrate 72, and an observer can display the display panel 73 via the scattering layer or the prism layer. You will see characters and images. For this reason, characters and images are distorted or blurred by the scattering layer or the prism layer, resulting in a decrease in image quality.

  Therefore, in this embodiment, the front light structure has a scattering property for the transparent substrate that guides light only when the light source is turned on, and the scattering property of the transparent substrate is lost when the light source is not turned on. With such a configuration, during normal use using external light, the front light structure does not have a scattering function, so that the characters and images on the display panel to be observed and distortion and blur are eliminated. On the other hand, in limited cases such as when used in dark places, the front light structure gives light from the light source. Therefore, even if characters and images are slightly distorted or blurred, the display panel is brightened. As a minimum, it is possible to secure the functions.

  FIG. 50 is a diagram illustrating a first example of the front light. The front light 70 shown in FIG. 50 is filled with a transparent substrate 74 having a scattering layer 75 on the surface thereof by sandblasting the surface of the transparent substrate made of acrylic, an acrylic transparent substrate 76, and the space between the substrates. A fluid 77 such as silicone oil, a fluid pump 78, and a fluid tank 79. The front light 70 further includes a linear light source 71 using a cold cathode fluorescent tube. The fluid stored in the fluid tank 79 is filled or extracted between the substrates 74 and 76 by the fluid pump 78. The refractive index of the fluid 77 is substantially the same as that of the transparent substrates 74 and 76, n = 1.5.

  As shown in FIG. 50A, when the reflective liquid crystal display panel is used in a bright place, the light source 71 is in the off state, and the fluid 77 is filled in the gap between the transparent substrates 74 and 76. Thereby, the scattering layer 75 is not visible from the viewer side because there is no difference in refractive index from the fluid 77. Therefore, when used in a bright place, characters and images on the display panel 73 are not blurred or distorted.

  On the other hand, as shown in FIG. 50B, when the reflective display panel is used in a dark place, the light source is turned on, and the fluid 77 is fluid pump 78 from the gap between the transparent substrates 74 and 76. The gap between the substrates is filled with an air layer. Therefore, in the scattering layer 75, a refractive index difference is generated between acrylic (refractive index: about 1.5) and air (refractive index: 1.0), which are transparent substrate materials, and functions as an original scattering layer. Therefore, the light guided by repeated internal reflection from the light source 71 at the ends of the transparent substrates 74 and 76 is scattered by the scattering layer 75 and illuminates the reflective liquid crystal display panel 73. Therefore, a bright display panel can be realized even in a dark place.

  However, when the front light 70 is viewed from the viewer side, the scattering layer 75 of the transparent substrate 74 is seen, and the display of the reflective liquid crystal display panel 73 is distorted. However, such distortion is equivalent to that of a conventional reflective liquid crystal display panel with front light.

  As described above, when used in a bright place, the same display as a reflective display panel without a front light can be obtained, and when used in a dark place, the light from the lit light source is effectively reflected. It can be used to illuminate liquid crystal display panels and can achieve bright display.

  FIG. 51 is a diagram showing a second example of the reflective liquid crystal display panel with a front light in the present embodiment. In this example, a transparent electrode (ITO) 81 mainly composed of indium oxide is formed on the surface of two transparent substrates 74 and 76 such as glass, and a liquid crystal layer 80 whose state is changed by an electric field is sandwiched between the electrodes. Yes. The voltage V1 may or may not be applied between the transparent electrodes 81 by the switch SW. Normally, such a liquid crystal layer 80 is in a transparent state when a voltage V1 is applied between the transparent electrodes, and is in a scattering state when the voltage between the transparent electrodes is zero. Accordingly, in a bright place, the switch SW is turned on to make the liquid crystal layer 80 transparent, and in a dark place, the switch SW is turned off to bring the liquid crystal layer 80 into a scattering state.

  Liquid crystal materials that can be switched between a scattering state and a transmission state include (1) liquid crystal using dynamic scattering effect, (2) liquid crystal using phase transition effect between cholesteric phase and nematic phase, (3) There is a polymer-dispersed liquid crystal, and either liquid crystal can be used.

  Compared with the example of FIG. 50, the example of FIG. 51 does not require a transparent substrate with a scattering layer, a pump, a tank, or the like, and does not require time for filling or withdrawing a fluid. Furthermore, in the case of a polymer dispersion type liquid crystal, the degree of refractive index anisotropy of the spherical liquid crystal in the polymer can be adjusted by an applied voltage. Therefore, by adjusting the applied voltage, the scattering degree of the liquid crystal layer 80 can be adjusted. Whether to increase the scattering degree with respect to the light of the light source 71 to make it brighter or reduce the scattering degree to suppress distortion of the display screen. , Can be adjusted according to the observer's preference.

  Also in the example of FIG. 51, when the light source 71 is turned on and the liquid crystal layer 80 has a scattering property, the display of the reflective liquid crystal display panel seems to pass through the frosted glass. This is equivalent to a reflective liquid crystal display panel. In a bright state where the light source 71 is off, the liquid crystal layer 80 is transparent, and the display is not blurred or distorted. In other words, this example is a reflective liquid crystal display panel with a front light, but when the front light is not lit, display quality equivalent to that of a reflective liquid crystal display panel without a front light is possible. It has the same display quality as a reflective liquid crystal display panel.

  FIG. 52 is a diagram showing a third example of the reflective liquid crystal display panel with front light. In this example, a transparent electrode 81 is formed on the inner surface of transparent substrates 74 and 76 such as glass, and a prism layer 82 having prism-shaped fine irregularities is formed inside the transparent substrate 74. A liquid crystal layer 80 having refractive index anisotropy is sealed between the transparent substrates 74 and 76. In liquid crystal molecules having refractive index anisotropy, the orientation direction of the molecules changes depending on the electric field, and the direction of refractive index anisotropy changes. Therefore, the refractive index of the prism layer 82 is matched with one refractive index of the liquid crystal layer 80 having refractive index anisotropy.

  As shown in FIG. 52 (a), when used in a bright place, a voltage is applied to the liquid crystal layer 80 or no voltage is applied, and the refraction of the prism layer 82 in the direction from the display side toward the reflective display panel 73 is performed. And the refractive index of the liquid crystal layer 80 are matched. In this state, in the direction from the display side toward the reflective display panel 73, the refractive index is the same between the prism layer 82 and the liquid crystal layer 80, the scattering state by the prism layer 82 is eliminated, and the front light structure becomes transparent. . As a result, the reflective liquid crystal display panel without the front light is brought into the same state, and the display screen is not blurred or distorted.

  On the other hand, as shown in FIG. 52 (b), when used in a dark place, the prism layer 82 is applied to the liquid crystal layer 80 in a state in which no voltage is applied or is applied, and in the direction from the display side toward the reflective display panel 73. And the refractive index of the liquid crystal layer 80 are made different. As a result, a difference in refractive index occurs between the prism layer 82 and the liquid crystal layer 80, and the light from the light source 71 is refracted. This refracted light becomes illumination light for the reflective liquid crystal display panel 73, and a bright display can be realized.

  In this example, a prism shape is formed on the surface of the transparent substrate 74, but the same effect can be expected even if a scattering layer is formed on the surface of the transparent substrate 74 by a sandblasting process.

  By applying this structure, the same effects as those of Example 2 can be obtained, and the switching speed between the transmission state and the scattering state can be further improved due to the properties of the liquid crystal layer 80. Compared with the polymer dispersion type liquid crystal of Example 2, the voltage applied to the liquid crystal layer 80 can be directly applied to the liquid crystal layer 80, so that the applied voltage can be kept lower than when the polymer dispersion type liquid crystal is used. Then, by applying the refractive index of the liquid crystal layer to the refractive index of the prism layer 82 in a state where no voltage is applied to the liquid crystal layer 80, voltage application to the light source 71 and the transparent electrode 81 is possible when used in a bright place. It becomes unnecessary and can further reduce power consumption.

  FIG. 53 is a diagram showing a fourth example of the reflective liquid crystal display panel with front light. In this example, the transparent electrode 81A formed on the transparent substrate 74 which is the light guide plate of the front light 70 is divided into strips, and voltage application 81A-1 and voltage non-application 81A-2 can be selected for each. ing. A liquid crystal layer whose state is changed by application of a voltage is filled between the transparent substrates 74 and 76. 53A shows a cross-sectional structure, and FIG. 53B shows a planar structure of the divided transparent electrode 81A.

  With this structure, by changing the number of transparent electrodes 81A to which a voltage is applied, the area of the liquid crystal layer that is in a scattering state can be changed as appropriate, and the amount of illumination light can be adjusted to some extent. Therefore, in this configuration, the liquid crystal layer 80 uses a scattering type liquid crystal whose scattering degree cannot be adjusted, a liquid crystal using a dynamic scattering effect, a liquid crystal using a phase transition effect between a cholesteric phase and a nematic phase, and the like. However, the degree of scattering can be adjusted by selecting a transparent electrode to which a voltage is applied.

  A reflection type liquid crystal display panel with a front light scatters light from the light source 71 well and can illuminate the reflection type liquid crystal display panel 73 well if the degree of scattering by the liquid crystal layer of the front light is large. The brightness can be increased. However, since a scattering layer is inserted between the viewer and the reflective liquid crystal display panel, the displayed image becomes cloudy and the resolution appears to be lowered. Therefore, if the degree of scattering can be adjusted, the observer can adjust it to obtain the optimum display quality for the observer.

  FIG. 54 is a diagram showing a fifth example of the reflective liquid crystal display panel with front light. In this example, as in the second example shown in FIG. 52, the front light 70 has a transparent electrode 81 formed inside two transparent substrates 74 and 76, and a liquid crystal layer 80 filled between them. Yes. The liquid crystal layer 80 is a polymer-dispersed liquid crystal, and a refractive index anisotropic resin is used for the polymer. The ordinary light refractive index and the extraordinary light refractive index of the liquid crystal grains 90 are not applied with a voltage between the transparent electrodes. It is configured to match the refractive index of the polymer in two directions.

  Details of the polymer-dispersed liquid crystal are shown on the right side of FIG. In the polymer dispersed liquid crystal A, liquid crystal grains 90 having refractive index anisotropy are dispersed in a polymer having no refractive index anisotropy, whereas in the polymer dispersed liquid crystal B, the refractive index anisotropy is present. Liquid crystal grains 90 having refractive index anisotropy are dispersed in a certain polymer.

  The crystal grains 90 are aligned in the thickness direction of the front light 70 with no voltage applied between the transparent electrodes, and the refractive index in the thickness direction of the front light matches the polymer 92 and the transparent substrates 74 and 76. Assume that the refractive index is inconsistent when a voltage is applied between the transparent electrodes.

  In that case, the polymer dispersed liquid crystal A has a refractive index in the vertical direction of the liquid crystal grains 90 matching the polymer 92 and the transparent substrates 74 and 76 as shown in the figure, and there is no refractive index difference between the light beams in the vertical direction. No refraction or scattering occurs. However, since there is a difference in the refractive index in the horizontal direction between the polymer 92 and the liquid crystal grains 90, not only horizontal light but also light from an oblique direction, that is, with respect to the horizontal vector component of the light ray, Refraction occurs. For this reason, when the reflective liquid crystal display panel 73 is viewed obliquely, the front panel 70 appears cloudy due to this refraction.

  On the other hand, when the polymer dispersed liquid crystal B is filled between the transparent substrates 74 and 76, liquid crystal molecules are aligned in the thickness direction of the front light without applying a voltage between the transparent electrodes, and the refractive index of the liquid crystal grains 90 The direction of anisotropy coincides with the direction of refractive index anisotropy of the polymer 92. Accordingly, in this state, the refractive index difference between the liquid crystal grains 90 and the polymer 92 is completely eliminated from any direction, and the front light becomes transparent from any direction. Therefore, as compared with the case where the polymer dispersion type liquid crystal A is used, it is possible to prevent image distortion and fogging from an oblique direction when used in a bright place.

  On the other hand, when used in a dark place, when a voltage is applied between the transparent electrodes, the direction of the refractive index anisotropy of the liquid crystal grains 90 is different from the direction of the refractive index anisotropy of the polymer 92 as shown in the figure. It becomes inconsistent state. This is because the anisotropy direction of the polymer 92 is not changed by the electric field. Therefore, the front light 70 is in a scattering state, light from the light source 71 is scattered toward the reflective liquid crystal display panel 73, and the liquid crystal display surface is brightened. However, the liquid crystal layer 80 becomes a cream color, and the display screen is blurred or distorted.

  In that case, the direction of the refractive index anisotropy of the liquid crystal grains 90 can be adjusted by adjusting the voltage applied between the transparent electrodes. That is, when the applied voltage is increased, the degree of scattering in the liquid crystal layer increases, and the incident light on the reflective liquid crystal display panel 73 increases and the screen becomes brighter, but the screen becomes too white and difficult to see. On the other hand, when the applied voltage is lowered, the degree of scattering in the liquid crystal layer decreases and the screen becomes darker, but the transparency of the screen increases. Therefore, by adjusting this applied voltage, the degree of screen brightness and the degree of contrast can be set according to the preference of the observer.

  FIG. 55 is a diagram showing a sixth example of the reflective liquid crystal display panel with front light. 50 to 54, the light from the light source 71 is guided through the two transparent substrates. On the other hand, in the example of FIG. 55, the light source 71 is arranged on the side surface of the substrate 74 on the display surface side of the two transparent substrates, and the light is mainly guided through the display surface side substrate 74. Then, light is scattered by the prism-shaped irregularities 82 arranged on the side surface of the reflective liquid crystal display panel 73 of the substrate 74 to illuminate the reflective liquid crystal display panel 73. Transparent electrodes (not shown) are formed on the transparent substrates 74 and 76, and the liquid crystal layer 80 is filled therebetween.

  As shown in FIGS. 50 to 54, when light is guided to the upper and lower transparent substrates 74 and 76, the light guided from the upper and lower transparent substrates hits the prism-shaped unevenness 82. In that case, it is desirable that the light from the upper transparent substrate 74 is refracted and transmitted downward, and the light from the lower transparent substrate 76 is reflected and scattered and is also reflected downward. In practice, however, light is refracted and transmitted more than light is reflected and scattered and travels downward, making it difficult to efficiently reflect and scatter light from the lower substrate.

  On the other hand, in the configuration of FIG. 55, the prism layer 82 is provided on the display panel 73 side of the transparent substrate 74 that transmits the light from the light source. Accordingly, the light applied to the prism layer 82 is light transmitted through the upper transparent substrate 74, and more light enters the reflective liquid crystal display panel 73 side by being refracted and scattered by the prism layer 82. Therefore, the prism-shaped irregularities 82 may be formed into a refractive scattering shape, and the shape can be simplified and the illumination efficiency can be improved.

  Similarly, when the liquid crystal layer 80 exhibiting scattering properties is sealed, more light is scattered from the upper side to the liquid crystal layer 80 and passes downward, and the amount of reflected and scattered light is small. Therefore, the illumination efficiency can be increased with the above structure. Further, the light from the light source 71 guides only one transparent substrate 74 and the amount of incident light from the light source decreases. However, by increasing the thickness of the transparent substrate 74, the amount of incident light from the light source 71 is improved. can do.

  FIG. 56 is a diagram showing a seventh example of a reflective liquid crystal display panel with a front light. The configuration of FIG. 56 is an improvement of the configuration of FIG. That is, FIG. 56 shows a structure in which a transparent light guide plate 94 having a light source 71 arranged on the side surface and a substrate in which elements exhibiting scattering properties are sealed are bonded to two transparent substrates 74 and 76. Specifically, a scattering substrate in which a prism layer 82 is formed between transparent substrates 74 and 76 made of glass or the like and a liquid crystal layer 80 whose refractive index state is changed by an electric field is filled in a transparent light guide plate 94. Bonded by optical adhesive 96. In the case of this structure, it is possible to separate the production of the two transparent substrates 74 and 76 encapsulating the element that expresses the scattering property and the production of the light guide plate 94 with the light source, so that the production process is separated and the yield is improved. It becomes possible. Further, the glass substrates 74 and 76 sandwiching the liquid crystal layer 80 are as thin as, for example, 0.5 to 0.7 mm, and the thickness of the transparent light guide plate 94 on which the light source 71 is disposed is increased accordingly, so It is also easy to improve the light incidence efficiency.

  As described above, the front light structure according to the present embodiment normally scatters the incident light from the light source and makes it incident on the reflective liquid crystal display panel only when the light source is turned on in a dark place, and does not turn on the light source. When in use, the scattering is lost. Accordingly, it is possible to eliminate blurring and distortion of characters and images on the display screen during normal use, and to improve contrast. In addition, a bright display screen can be realized even in a dark place.

  The above embodiment is summarized as follows.

(Supplementary note 1) In the manufacturing method of the reflective liquid crystal display device,
(A) irradiating the surface of the photosensitive resin layer having a predetermined film thickness with light having exposure energy to form a distribution of thermal deformation characteristics in the thickness direction or planar direction of the photosensitive resin layer;
(B) A method of forming a reflective liquid crystal display device, comprising: performing a heat treatment thereafter to form random irregularities on the surface of the photosensitive resin layer.

(Supplementary Note 2) In the manufacturing method of the reflective liquid crystal display device,
(A) A photosensitive resin layer having a predetermined film thickness is immersed in a chemical solution containing any one of an acid, an alkali solution, a quaternary ammonium salt solution, and HMDS, and heated in the thickness direction or the plane direction of the photosensitive resin layer. Forming a distribution of dynamic deformation characteristics;
(B) A method of forming a reflective liquid crystal display device, comprising: performing a heat treatment thereafter to form random irregularities on the surface of the photosensitive resin layer.

(Appendix 3) In Appendix 1,
In the step (a), the light having the exposure energy is far ultraviolet rays.

(Appendix 4) In Appendix 1,
In the step (a), the entire surface of the photosensitive resin layer is irradiated with light having the exposure energy to change its quality, and a distribution of thermal deformation characteristics is formed in the thickness direction of the photosensitive resin layer. A method for forming a reflective liquid crystal display device.

(Appendix 5) In Appendix 1,
In the step (a), the light having the exposure energy is irradiated to a part of the surface of the photosensitive resin layer to change its quality and form a distribution of thermal deformation characteristics in the plane direction of the photosensitive resin layer. A method for forming a reflective liquid crystal display device.

(Appendix 6) In Appendix 1 or 2,
A method of forming a reflective liquid crystal display device, further comprising the step of forming a separation line with a reduced film thickness in the photosensitive resin layer before the step (a).

(Supplementary note 7) In the manufacturing method of the reflective liquid crystal display device,
(A) forming a photosensitive resin layer having a predetermined film thickness on a substrate having a transistor formed on the surface;
(B) forming a contact hole to the electrode of the transistor by a photolithography process of partially exposing and developing the photosensitive resin layer;
(C) a post-baking step of heating the photosensitive resin layer to a first temperature;
(D) irradiating the surface of the photosensitive resin layer with light having exposure energy to form a distribution of thermal deformation characteristics in the thickness direction or planar direction of the photosensitive resin layer;
(E) a reflective liquid crystal display comprising: a final baking step in which random unevenness is formed on the surface of the photosensitive resin layer by performing heat treatment at a second temperature higher than the first temperature. Device forming method.

(Appendix 8) In Appendix 7,
A reflective liquid crystal display device comprising: a step of forming a pixel electrode connected to the electrode of the transistor through the through hole on the photosensitive resin layer after the step (e); Forming method.

(Appendix 9) In Appendix 7,
Before the step (c), the method further comprises a step of forming a separation line for separating the photosensitive resin layer by exposing or developing the photosensitive resin layer in a predetermined pattern or developing it, and developing the photosensitive resin layer. A reflective liquid crystal display device forming method.

(Appendix 10) In Appendix 7,
By controlling the film thickness of the photosensitive resin layer in the step (a), the post-baking temperature and time in the step (c), and the irradiation energy amount in the step (d), the average inclination angle of the unevenness is 0-15. A method for forming a reflective liquid crystal display device, characterized by:

(Appendix 11) In Appendix 10,
And forming a liquid crystal layer between the alignment film and the alignment film of the display-side substrate after the pixel electrode forming step.

(Supplementary note 12) In a reflective liquid crystal display device,
A substrate on which the liquid crystal layer is formed, the inclination angle of the reflection irregularities formed on the liquid crystal layer side of the substrate is distributed in a range of at least 0 ° to 20 °, and the existence probability of the inclination angle is 15 ° to A reflective liquid crystal display device having a peak in a range of 19 °.

(Appendix 13) In Appendix 12,
A reflective liquid crystal display device, wherein the planar pattern of the concave and convex portions for reflection has a circular shape, a polygonal shape, a stripe shape, or a combination thereof.

(Supplementary note 14) In a reflective liquid crystal display device,
A substrate on which a liquid crystal layer is formed, and the inclination angle of the unevenness for reflection formed on the liquid crystal layer side of the substrate has a peak of existence probability along the first direction; A reflection-type liquid crystal display device, wherein the existence probability is distributed so as to have two peaks along a second direction different from the first direction.

(Appendix 15) In Appendix 14,
The display surface of the reflective liquid crystal display device is disposed at an angle,
The reflective liquid crystal display device, wherein the first direction is a horizontal direction and the second direction is a vertical direction.

(Supplementary Note 16) In Supplementary Note 14 or 15,
The existence probability along the first direction peaks once in the range of 15 ° to 19 °, and the existence probability along the second direction ranges from 15 ° to 19 ° and 0 ° to 14 °. A reflection type liquid crystal display device having a peak in each range of °.

(Supplementary note 17) In Supplementary note 14 or 15,
In each of the pixel regions in the display surface, the existence probability along the second direction in the first region has a peak in the first angle range and the second angle range, and the second region has the second probability in the second region. A reflection-type liquid crystal display device, wherein the existence probability along the direction has a peak in the first angle range and the third angle range.

(Supplementary note 18) In any one of Supplementary notes 12 to 15,
And a display side substrate sandwiching the liquid crystal layer with the substrate, and a polarizing plate formed on the display side of the display side substrate, wherein the liquid crystal layer is driven in a field effect birefringence mode. Reflective liquid crystal display device.

(Supplementary note 19) In a reflective liquid crystal display device,
Reflective irregularities on the substrate, and within a single pixel region, a first convex portion having a first directivity and a first scattering property for reflected light, and the first directivity for the reflected light A reflective liquid crystal display device comprising: a second directivity weaker than the second directivity and a second convex portion having a second scattering property stronger than the first scattering property, which are randomly mixed.

(Supplementary note 20) In a reflective liquid crystal display device,
Reflective irregularities are formed on the substrate, and the irregularities are formed of a photosensitive resin film, and the first circular patterns are spaced apart by a first distance or more, and are smaller than the first circular pattern. The reflective liquid crystal display device is characterized in that the circular pattern is spaced apart from the first circular pattern by less than the first distance.

(Supplementary note 21) In a reflective liquid crystal display device,
The substrate has reflection irregularities, the irregularities are formed of a photosensitive resin film, and a plurality of polygon patterns are arranged so that adjacent polygon sides are parallel to each other. Reflective liquid crystal display device.

(Supplementary Note 22) In a reflective liquid crystal display device,
A reflective liquid crystal display panel;
Provided on the reflective liquid crystal display panel, a light guide plate, a light source disposed at an end of the light guide plate, and expresses light scattering with respect to light transmitted through the light guide plate when the light source is turned on, A reflective liquid crystal display device comprising: a front light having light scattering means for reducing the light scattering property when the light source is not turned on.

(Appendix 23) In Appendix 22,
The light guide plate and the light scattering means have a liquid crystal panel having a pair of transparent substrates, a transparent electrode formed on the opposing surface thereof, and a liquid crystal layer formed between the pair of transparent substrates. Is a reflective liquid crystal display device that exhibits light scattering properties according to an electric field applied between the transparent electrodes.

(Appendix 24) In Appendix 23,
The light source is disposed on a side surface of the transparent substrate on the display side of the pair of transparent substrates;
A reflective liquid crystal display device, wherein the liquid crystal layer is provided between the transparent substrate on the display side and the transparent substrate on the reflective liquid crystal display panel side.

(Appendix 25) In Appendix 22,
The light scattering means includes a liquid crystal panel having a pair of transparent substrates, a transparent electrode formed on the opposing surface thereof, and a liquid crystal layer formed between the transparent substrate pairs. A reflection type liquid crystal display device, which exhibits light scattering properties according to an electric field applied between transparent electrodes, and wherein the pair of transparent substrates are bonded to the light guide plate.

(Supplementary note 26) In any one of Supplementary notes 23 to 25,
In the liquid crystal layer, the direction of refractive index anisotropy changes according to the applied electric field,
A transparent prism-like uneven layer is provided between any one of the transparent substrates and the liquid crystal layer, and the refractive index of the uneven layer matches the refractive index of one of the liquid crystal layers. Reflective liquid crystal display device.

(Supplementary note 27) In any one of Supplementary notes 23 to 25,
A reflective liquid crystal display device, wherein the transparent electrode is separated into a plurality of portions, and a voltage is selectively applied to the separated transparent electrodes to adjust the degree of light scattering of the liquid crystal layer.

(Supplementary note 28) In any one of Supplementary notes 23 to 25,
The liquid crystal layer includes a liquid crystal material using a dynamic scattering effect, a liquid crystal material using a phase conversion effect between a cholesteric phase and a nematic phase, and a liquid crystal particle having a refractive index anisotropy in a polymer. A reflective liquid crystal material which is one of a polymer dispersed liquid crystal material and a second polymer dispersed liquid crystal material having liquid crystal grains having refractive index anisotropy in a polymer having refractive index anisotropy Display device.

10 Insulating substrate 20 Photosensitive resin layer (resist layer)
22 Reflecting electrode 34 Liquid crystal layer 60 Reflecting plate CH Contact hole MG Micro groove, unevenness for reflection

Claims (3)

In reflective liquid crystal display devices,
A substrate on which a liquid crystal layer is formed, and the inclination angle of the unevenness for reflection formed on the liquid crystal layer side of the substrate has a peak of existence probability along the first direction; A reflection-type liquid crystal display device, wherein the existence probability is distributed so as to have two peaks along a second direction different from the first direction. In claim 1,
The existence probability along the first direction peaks once in the range of 15 ° to 19 °, and the existence probability along the second direction ranges from 15 ° to 19 ° and 0 ° to 14 °. A reflection type liquid crystal display device having a peak in each range of °. In reflective liquid crystal display devices,
A substrate on which the liquid crystal layer is formed, the inclination angle of the reflection irregularities formed on the liquid crystal layer side of the substrate is distributed in a range of at least 0 ° to 20 °, and the existence probability of the inclination angle is 15 ° to A reflective liquid crystal display device having a peak in a range of 19 °.

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