JP2007264648A - Reflector and reflection type liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflector having a light-diffusing property which suppresses inter-object reflection over a wide angle, and giving particularly high reflectance in an intended range of viewing angle; and to provide a reflection type liquid crystal display device using the same. <P>SOLUTION: Each of the inner surfaces of the concave portions consists of a shape having a longitudinal section passing the deepest part. The longitudinal section has an inner surface shape including a first curve and a second curve. The first curve and the second curve are concave arcs and the average value of the absolute value of the inclination angle of the first curve is set grater than the average value of the absolute value of the inclination angle of the second curve. The reflector has the reflection characteristics deviating from specular reflection with respect to a base material surface by reflection on the surface of the second curve. In addition, the reflected light has the reflection characteristics that the reflected light to the incident light made incident from diagonal above shifts to the perpendicular position direction with respect to the base material surface. When the external light is radiated at an incident angle of 30°, the photodetecting angle is so set as to attain high reflectivity within a range from 15 to 45°. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reflector and a reflective liquid crystal display device, and more particularly to a reflector having a reflection characteristic that looks brighter than other viewing angles when the reflected light is observed from a specific viewing angle, and a reflective type using the reflector The present invention relates to a liquid crystal display device.

Liquid crystal display devices are roughly classified into a transmission type and a reflection type. Among them, the reflective liquid crystal display device depends on outside light or is visually recognized using a front light. A portable computer, a computer, a digital clock, a communication device, a game machine, a measuring instrument, an electronic bulletin board It is often used as a display unit of electronic devices such as.
In the reflective liquid crystal display device, as shown in FIG. 8, for example, a light transmissive display side substrate 20 and a light reflective reflective side substrate 10 are arranged to face each other with a liquid crystal layer 30 interposed therebetween. The outer surface of the display side substrate 20 is a display surface, and the reflective layer 12 is formed on the reflective side substrate 10. In this reflection type liquid crystal display device, external light incident from the display surface is transmitted through the display side substrate 20 and the liquid crystal layer 30 and is reflected by the reflection layer 12 of the reflection side substrate 10, and the reflected light is transmitted through the liquid crystal layer 30 again. And an image is visually recognized by radiating | emitting from a display surface.
In FIG. 8, the reflective substrate 10 is a transparent electrode 16 composed of a glass substrate 11, a reflective layer 12, an intervening layer 13, a color filter layer 14, a planarizing layer 15, an ITO (Indium Tin Oxide) film or a nesa film in order from the lower layer. The display-side substrate 20 on which the alignment layer 17 is laminated and opposed to the display surface side with the liquid crystal layer 30 in between is arranged in order from the liquid crystal layer 30 side, the alignment layer 21, the insulating layer 22, the ITO film, or the NESA film. A transparent electrode 23, a glass substrate 24, and an optical modulation layer (a polarizing plate, a retardation plate, etc.) 25 are laminated.

In the illustrated liquid crystal display device, the color filter layer 14 of the reflection-side substrate 10 is formed by sequentially arranging R (red), G (green), and B (blue) colored films in parallel, Striped transparent electrodes 16 are arranged in parallel corresponding to the respective colored films. Further, in the display side substrate 20, the transparent electrode 23 is arranged in parallel so as to be orthogonal to the transparent electrode 16 of the reflection side substrate, and the portion of the liquid crystal layer 30 where the display side transparent electrode 23 and the reflection side transparent electrode 16 intersect is formed. Pixels corresponding to each color are formed.
In this liquid crystal display device, a front light is disposed on the outer side of the display side substrate 20 as necessary (not shown). In this case, the light of the front light is also displayed on the display side in the same manner as the external light. The light passes through the substrate 20 and the liquid crystal layer 30 and is reflected by the reflective layer 12 of the reflective substrate 10, and the reflected light passes through the liquid crystal layer 30 again and is emitted from the display surface.

  The reflection layer 12 of the reflection side substrate 10 can be roughly classified into a smooth reflection type and a diffuse reflection type. In the smooth reflection type shown in FIG. 9 (a), the reflection surface of the reflection layer 12 (a) has a smooth finish, and the incident angle (absolute value) and the emission angle (absolute value) of the light across the normal line perpendicular to the display surface ( (Absolute value) is equal. Accordingly, when observing the display surface, there arises a problem that the brightness of the display surface is uneven due to the positional relationship between the light source and the viewpoint, and the visibility of the light source and the viewer's face is reflected to reduce visibility. In order to solve this problem, in the diffuse reflection type, as shown in FIG. 9B and FIG. 10, the reflective surface of the reflective layer 12 (b) does not have many fine irregularities (the concave portions 31 in FIG. 10). It is formed adjacent to the rule. For this reason, in the diffuse reflection type, external light incident at a certain angle is diffusely reflected on the surface of the reflection layer 12 (b) and the reflected light is diffused. A reflection type liquid crystal display device with a small so-called wide viewing angle can be obtained.

Various proposals have been made on the material of the diffuse reflection type reflection layer 12 (b), the shape and distribution of the unevenness, the formation method of the unevenness, and the like from the viewpoint of reflection characteristics and productivity.
As a method for forming irregularities, for example, the surface of a flat resin substrate made of a photosensitive resin layer or the like is irradiated with light through a pattern mask to form a large number of adjacent fine spherical concave portions 31 by development processing, A method in which aluminum or silver or the like is deposited or plated to form a mirror surface on the surface where the recesses are formed, or a punch having a hemispherical tip is pushed into a smooth substrate surface such as an aluminum plate or silver plate. A method of forming a large number of adjacent fine spherical concave portions 31 is known.
The shape of the recesses 31 is conventionally a spherical surface having a depth distributed within a range of 0.1 μm to 3 μm, and the mutual distance is such that the pitch between adjacent recesses (the distance between the centers) is 5 μm to 50 μm. It is set to vary within the range.
Japanese Patent Laid-Open No. 11-52367 Japanese Patent Laid-Open No. 11-52110

  For example, as shown in FIG. 11A, an electronic device such as a desktop computer or a portable computer is shown in FIG. 11A and an example of a portable computer is shown in FIG. When viewing the display surface of the display device, the display surface is often observed obliquely from below. That is, the observer's viewpoint Ob is inclined below the display surface by an angle θ with respect to the normal X perpendicular to the display surface.

  On the other hand, in a reflection type liquid crystal display device, illumination often depends on external light. The external light is an optical modulation layer 25 such as a polarizing plate, two transparent electrodes 16 and 23, a liquid crystal layer 30, and a color filter. In the diffuse reflection type, incident light is diffused in a wide range by the reflection layer 12 (b), so that the display screen at the observation viewpoint Ob is generally used. It is very dark. For this reason, if there is little external light, visibility will fall significantly. In particular, in the conventional reflective liquid crystal display device, the shape and arrangement of the recesses are designed so as to eliminate the variation in brightness depending on the viewing angle as much as possible, so that the observation is performed from a specific viewing angle range obliquely below the normal X. When doing so, there was a problem that sufficient brightness could not be obtained. Also, when using a front light, there is a problem of attenuation and diffusion like external light, so that sufficient brightness in a specific visual range is ensured without increasing the power consumption for lighting. Was difficult.

Therefore, there has been a demand for a reflective liquid crystal display device that can suppress reflection in a wide viewing angle range and can observe a display screen particularly brightly in a specific viewing angle range.
The present invention has been made in order to solve the above-described problems. Therefore, the object of the present invention is to have a light diffusibility that suppresses reflection in a wide viewing angle range and to appear particularly bright in a specific viewing angle range. And a reflective liquid crystal display device using the reflector.

In order to solve the above-described problems, a reflector according to claim 1 of the present invention has a plurality of concave portions having light reflectivity, and an inner surface of the concave portion has a shape having a longitudinal section passing through the deepest portion. In the longitudinal section, the inner shape includes a first curve and a second curve, the first curve and the second curve are concave arcs, and the average value of the absolute values of the inclination angles of the first curve is: It is set larger than the average value of the absolute value of the inclination angle of the second curve, has a reflection characteristic deviated from the direction of regular reflection with respect to the substrate surface by being reflected by the surface of the second curve, and oblique The reflected light with respect to the incident light incident from above has reflection characteristics shifted in the direction of the vertical position with respect to the substrate surface, and when the external light is irradiated at an incident angle of 30 °, the light receiving angle is 15 ° to 45 °. It is characterized by being set to have a high reflectance in the range of °.
Further, in the reflector according to claim 2 of the present invention, in the reflector according to claim 1, the integral value of the reflectance in the reflection angle range smaller than the angle of regular reflection with respect to the substrate surface is the angle of regular reflection. It is characterized by being larger than the integral value of the reflectance in a larger reflection angle range.
Further, the reflector according to claim 3 of the present invention is the reflector according to claim 1 or 2, wherein the reflector has a maximum reflectance in a reflection angle range smaller than a regular reflection angle with respect to the substrate surface. Features.
A reflector according to a fourth aspect of the present invention is the reflector according to any one of the first to third aspects, wherein the external light having the incident angle is incident obliquely from above. When observing in an obliquely installed state, the second curve in the plurality of recesses is oriented so as to be in a downward direction with respect to the observer.
A reflector according to claim 5 of the present invention is the reflector according to any one of claims 1 to 4, wherein the plurality of recesses are arranged irregularly adjacent to each other. The longitudinal sections have the same direction, and each of the second curves is formed so as to be oriented in a single direction.
A reflection type liquid crystal display device according to a sixth aspect is provided with the reflector according to any one of the first to fifth aspects.

  According to the reflector of the present invention, it has light diffusibility that suppresses reflection in a wide viewing angle range, and can increase the amount of reflected light in the normal viewing angle range of the observer. The reflective liquid crystal display device according to the present invention equipped with the reflector according to the present invention is capable of suppressing reflection in a wide viewing angle range, and having improved visibility so that the display surface looks bright when viewed from a specific viewing angle. Type liquid crystal display device.

Next, embodiments of the present invention will be specifically described with reference to the drawings. However, the following embodiments do not limit the present invention.
FIG. 1 is a diagram showing a reflector according to this embodiment. As shown in FIG. 1, the reflector 1 of the present embodiment has a large number of light-reflective recesses 3a, 3b, 3c,... On a surface S (reference surface) of a flat substrate 2 made of, for example, aluminum. Are generally irregularly adjacent to each other.

As shown in FIG. 2 for the perspective view and FIG. 3 for the sectional view, these concave portions 3 have an inner surface shape in the specific longitudinal section X of the concave portion 3 from the peripheral portion S1 of the concave portion to the deepest point D. It consists of a first curve A and a second curve B that is continuous with the first curve A and extends from the deepest point D of the recess to the other peripheral portion S2. These two curves are connected to each other at the deepest point D with the inclination angle with respect to the substrate surface S being zero.
The inclination angle of the first curve A with respect to the substrate surface S is steeper than the inclination angle of the second curve D, and the deepest point D is at a position shifted from the center O of the recess 3 in the x direction. That is, the average value of the absolute value of the inclination angle of the first curve A with respect to the substrate surface S is larger than the average value of the absolute value of the inclination angle of the second curve B with respect to the substrate surface S. The average value of the absolute value of the inclination angle of the first curve A with respect to the substrate surface S in the recesses 3a, 3b, 3c, ... varies irregularly in the range of 1 to 89 °. Moreover, the average value of the absolute value of the inclination angle of the second curve B with respect to the substrate surface S in the recesses 3a, 3b, 3c,... Varies irregularly in the range of 0.5 to 88 °.
Since the inclination angles of both curves change smoothly, the maximum inclination angle δmax (absolute value) of the first curve A is larger than the maximum inclination angle (absolute value) δb of the second curve. . Further, the inclination angle of the deepest point D where the first curve A and the second curve B are in contact with the substrate surface is zero, and the first curve A and the inclination angle having a negative inclination angle are positive values. The second curve B is smoothly continuous.
In the reflector of the present embodiment, the maximum inclination angles δmax in the recesses 3a, 3b, 3c,... Vary irregularly within a range of 2 to 90 °. However, many recesses vary irregularly within a range of the maximum inclination angle δmax of 4 ° to 35 °.

  The concave portion 3 has a single minimum point D (a point on the curved surface where the inclination angle becomes zero) D. And the distance of this minimum point D and the base-material surface S of a base material forms the depth d of the recessed part 3, and this depth d is the range of 0.1 micrometer-3 micrometers about recessed part 3a, 3b, 3c, ..., respectively. It varies irregularly within.

  In the present embodiment, the specific longitudinal sections X in the recesses 3a, 3b, 3c,... Are all in the same direction. Each first curve A is formed so as to be oriented in a single direction. That is, in any recess, the x direction shown in FIGS. 2 and 3 is formed to be the same.

In the reflector 1 of this embodiment, since each 1st curve A is formed so that it may orient in a single direction, the reflection characteristic is regular reflection with respect to the base-material surface S, as shown in FIG. It is shifted from the direction of. That is, as shown in FIG. 4, the reflected light K with respect to the incident light J obliquely from above in the x direction has a bright display range in a direction shifted in the direction H with respect to the base material surface S rather than the regular reflection direction K _0. It is a shifted one.

As a result, the overall reflection characteristics in the specific longitudinal section X are those in which the reflectance in the direction reflected by the surface around the second curve B is increased. Therefore, it is possible to obtain a reflection characteristic in which reflected light is appropriately concentrated in a specific direction.
That is, FIG. 5 irradiates the display surface of the reflection device 1 of the present embodiment with external light at an incident angle of 30 °, and the light receiving angle is centered on 30 ° which is the direction of regular reflection with respect to the display surface (base material surface). The relationship between the light receiving angle (θ °) and the brightness (reflectance) when swung from the perpendicular position (0 °) to 60 ° is shown. In FIG. 5, as a comparative example, the relationship between the light receiving angle and the reflectance of a reflection type liquid crystal display device using a reflector having a spherical concave portion that has been conventionally used is also shown.
As apparent from FIG. 5, the comparative example showed a substantially uniform reflectivity within the range of the light receiving angle of about 15 ° to about 45 °, whereas in the reflection device 1 of the present embodiment, the substrate surface The integral value of the reflectance in the reflection angle range smaller than 30 ° which is the angle of regular reflection with respect to S is larger than the integral value of the reflectance in the reflection angle range larger than the angle of regular reflection. That is, sufficient brightness can be achieved in a field of view around an angle of 20 °.

  As described above, according to the reflector of the present invention, a reflector that looks particularly bright in a specific viewing angle range can be obtained. Moreover, according to the reflector of this invention, it is also possible to have a light diffusibility which suppresses reflection in a wide viewing angle range. According to the reflective liquid crystal display device of the present invention provided with the reflector having such a configuration, the reflection is suppressed in a wide viewing angle range, and the visibility that looks particularly bright when the display surface is observed from a specific viewing angle. The reflection type liquid crystal display device improved.

  Further, in the reflector of the present invention, the reflected light with respect to the incident light incident obliquely from above has a reflection characteristic in which the bright display range is shifted in the direction shifted to the vertical position with respect to the substrate surface rather than the regular reflection direction. The integrated value of the reflectance in the reflection angle range smaller than the angle of specular reflection with respect to the substrate surface may be larger than the integral value of the reflectance in the reflection angle range larger than the angle of specular reflection. Alternatively, a reflection characteristic having a maximum reflectance in a reflection angle range smaller than a regular reflection angle with respect to the substrate surface may be used. According to such a reflector, when the normal viewing angle of the observer is deviated from the regular reflection direction, the reflector can reflect light mainly in the normal viewing angle direction. Can do.

  According to the reflective liquid crystal display device of the present invention provided with the reflector having such a configuration, usually, external light incident mainly from above is directed in the normal direction to the surface of the base material rather than the viewer's feet. Can be shifted. For this reason, for example, when used as a display device for a mobile phone or a notebook personal computer, the amount of light reflected in the direction of the line of sight of the observer increases, and a reflective liquid crystal display device with a bright screen can be realized from a practical viewpoint.

  The direction of regular reflection is an angle (light receiving angle) that is symmetric with respect to the incident angle of incident light incident on the display surface (the surface of the substrate) (the axis of symmetry is the normal direction to the display surface). If it changes, the direction of regular reflection (light receiving angle) also changes.

Although the manufacturing method of the reflector 1 is not specifically limited, For example, it can manufacture as follows.
First, a punch having a tip shape obtained by converting the shape of the concave portion into a convex surface (a punching tool) is manufactured, the tip of the punch is opposed to the aluminum base material, and the relative orientation direction of the punch with respect to the aluminum base material is made constant. While keeping it, the stamping stroke is irregularly changed, and the stamping interval is irregularly changed to stamp the entire predetermined region of the aluminum base material. The stamping stroke is adjusted so that the depth of the recess falls within a predetermined range. The stamping interval is adjusted so that moire patterns do not occur.

FIG. 6 is a cross-sectional view showing the layer configuration of a reflective liquid crystal display device 100 incorporating the reflective device 1 of this embodiment.
In FIG. 6, the reflective liquid crystal display device 100 is configured such that a light-transmissive display side substrate 20 and a light-reflective reflective side substrate 10 are disposed to face each other with a liquid crystal layer 30 interposed therebetween. The outer surface of the display side substrate 20 is a display surface, and the reflector 1 is incorporated in the reflection side substrate 10.

The reflective substrate 10 is, in order from the lower layer, a glass substrate 11, a reflector 1, a transparent intervening layer 13, a color filter layer 14, a transparent flattening layer 15, a transparent electrode 16 made of an ITO (Indium Tin Oxide) film or a nesa film, Further, the display-side substrate 20 on which the alignment layer 17 is laminated and opposed to the display surface side with the liquid crystal layer 30 in between is arranged in order from the liquid crystal layer 30 side, such as an alignment layer 21, an insulating layer 22, an ITO film, or a NESA film. A transparent electrode 23, a glass substrate 24, and an optical modulation layer (polarizing plate, retardation plate, etc.) 25 are laminated.
In addition, the transparent electrode 16 and the transparent electrode 23 sandwiching the liquid crystal layer 30 are formed in a stripe shape orthogonal to each other, and constitute a simple matrix type liquid crystal device in which the intersection area is a pixel.

  In the reflective liquid crystal display device 100, the reflector 1 is mounted such that the first curve A of each of the recesses 3a, 3b, 3c,... Is closer to the x direction than the second curve B having a gentle slope. Yes. Characters and the like are displayed with the x direction as the upper side.

FIG. 7 is an explanatory diagram showing a usage state of the liquid crystal display device 100. In FIG. 7, for convenience of explanation, only the first curve A and the second curve B of the reflective liquid crystal display device 100 are shown, and other components are not shown.
Such a reflective liquid crystal display device 100 is incorporated in a mobile phone, a notebook computer, or the like with the x direction facing upward. In this case, the reflective liquid crystal display device 100 is usually installed or held obliquely with respect to the horizontal plane with the x direction obliquely upward as shown in FIG. That is, in use, the first curve A in each recess is provided so as to be positioned above the second curve B as viewed from the observer. The observer usually looks down at the reflective liquid crystal display device 100 from obliquely above the horizontal.
In this case, the reflected light K of the external light (incident light J) incident mainly from above is reflected mainly by the surface around the second curve B, and therefore, in the direction of the viewer's feet as described in FIG. It is hardly reflected, so intensively reflected in a direction above the direction K ₀ of the specular reflection. Therefore, the normal observation range of the observer matches the bright display range, and a practically bright display device can be realized.

  In the reflective liquid crystal display device of the embodiment shown in FIG. 6, the reflector 1 is formed as a layer different from the transparent electrode 16, but the transparent electrode 16 itself is formed of the reflector 1 and the transparent electrode 16 is shown in FIG. 6 is formed at the position of the reflector 1, the transparent electrode can also serve as the reflector, and the layer structure of the reflective liquid crystal display device is simplified.

  In addition, when the reflector is formed of a semi-transmissive and semi-reflective substrate such as a half mirror and an illumination plate is arranged on the back of the liquid crystal panel, the reflector becomes a reflective type when the outside light is bright, and the outside light becomes dark. When the illumination plate is turned on, a transflective liquid crystal display device that can be used as a transmissive type is obtained. This transflective liquid crystal display device is also included in the present invention.

  Further, if a front light is provided on the display surface side of the display-side substrate 20, a front light type is used in which only the external light is used when the external light is bright and the front light is turned on when the external light becomes dark. A liquid crystal display device is obtained. This front light type liquid crystal display device is also included in the present invention.

  The liquid crystal driving method of the present invention is not particularly limited, and can be similarly applied to an active matrix type using a thin film transistor or a thin film diode, or a segment type in addition to the simple matrix type. All of these liquid crystal display devices are included in the present invention.

The perspective view which shows the part of the reflector of embodiment. The perspective view which shows one recessed part of embodiment. Sectional drawing in the specific longitudinal cross-section of the said recessed part. Explanatory drawing of the reflective characteristic of the reflector of embodiment. The graph which shows the relationship between a light reception angle and a reflectance. Sectional drawing which shows the layer structure of the reflection type liquid crystal display device of embodiment. Explanatory drawing of the use condition of the reflection type liquid crystal display device of embodiment. Sectional drawing which shows an example of a general reflection type liquid crystal display device. (A) is smooth reflection type, (b) is sectional drawing which shows each reflection side board | substrate of a diffuse reflection type liquid crystal display device. The perspective view which shows the part of the conventional reflector. (A) is a perspective view which shows the viewing angle at the time of visually observing a desktop computer, and (b), respectively.

Explanation of symbols

  1: Reflector 2: Base material 3, 3a, 3b, 3c: Recessed part 10: Reflection side substrate A: First curve B: Second curve X: Specific longitudinal section

Claims (6)

  It has a plurality of concave portions having light reflectivity, and the inner surface of the concave portion has a shape having a longitudinal section that passes through the deepest portion, and the inner surface shape of the longitudinal section includes a first curve and a second curve, The first curve and the second curve are concave arcs, and an average value of absolute values of inclination angles of the first curve is set larger than an average value of absolute values of inclination angles of the second curve, and the second curve Reflected by the curved surface, it has a reflection characteristic deviated from the direction of regular reflection with respect to the substrate surface, and the reflected light with respect to the incident light incident from obliquely above is shifted in the vertical position direction with respect to the substrate surface. A reflector having the above-described reflection characteristics and having a light-receiving angle set to a high reflectance in a range of 15 ° to 45 ° when external light is irradiated at an incident angle of 30 °. .   2. The reflection according to claim 1, wherein the integrated value of the reflectance in the reflection angle range smaller than the angle of regular reflection with respect to the substrate surface is larger than the integrated value of the reflectance in the reflection angle range larger than the angle of regular reflection. body.   The reflector according to claim 1, wherein the reflector has a maximum reflectance in a reflection angle range smaller than an angle of regular reflection with respect to the substrate surface.   When observing in the state where the base material is installed obliquely so that external light of the incident angle is incident obliquely from above, the second curve in the plurality of concave portions is directed downward with respect to the observer. The reflector according to any one of claims 1 to 3, wherein the reflector is oriented in the direction.   The plurality of recesses are arranged irregularly adjacent to each other, are formed such that directions of the longitudinal sections are equal, and the second curves are oriented in a single direction. The reflector according to any one of claims 1 to 4.   A reflective liquid crystal display device comprising the reflector according to claim 1.

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