Patent Application
20050083456
1. Field of the Invention
The present invention relates to a reflector and a liquid crystal display device using the same.
2. Description of the Related Art
Generally, liquid crystal display devices are classified into different types such as a transflective liquid crystal display device having a back light unit, a transmissive liquid crystal display device, and a reflective liquid crystal display device. The reflective liquid crystal display device performs display without the back light unit, instead it makes use of external light such as solar light or illumination light, and is mainly used in, for example, a thin personal digital assistant having light weight and low power consumption. While, the transflective liquid crystal display device operates in a transmissive mode by turning on a back light unit when external light is not sufficient obtained and operates in a reflective mode without turning on the back light unit in the presence of sufficient external light, and is mainly used in a portable electronic equipment such as a portable telephone or a notebook computer.
In the display performance of the transflective or the reflective liquid crystal display device, a bright display performance is typically required in the reflective mode. In order to accomplish this, it is important that the light input from the outside is reflected in the liquid crystal panel and the scattering performance of the light emitted to the outside is controlled. Thereby, in order to reflect the incident light through various angles to the display direction (viewer side) with respect to the display surface in these liquid crystal display device, the liquid crystal display device is often implemented with a method for causing the reflecting plate on the inside or the outside of the liquid crystal panel to have a scattering function or with a forward scattering method in which a scattering layer is formed in the liquid crystal panel to scatter the transmitted light.
The reflective liquid crystal display device comprises an opposite transmissive substrate 101, a liquid crystal layer 110, and a reflective element substrate 102 in this order when viewed from the incident direction of the light. The element substrate 102 is provided with a scattering band for reflecting and scattering the light Q transmitting the opposite substrate 101. The scattering band is composed of a high reflective metal film 122 having irregularities 122a at the surface thereof and a reflecting plate 130 which is made of an insulating layer 128 below the metal film. One pixel of the reflecting plate 130 is divided into two regions, that is, a region B having reflective characteristics of high directivity and a region A having reflective characteristics of high diffusivity. Each region is formed with irregularities each having a different average inclination angle.
The reflecting plate 130 is manufactured by forming initial irregularities on a glass or silicon oxide film by a sand blast method, etching it in hydrofluoric acid solution, and forming an Al film thereon. As shown in
However, in case that the liquid crystal display device is accommodated in the display portion of an electronic equipment used in a state that the display surface thereof is oblique, such as a portable telephone or the notebook computer, it is mainly viewed from the direction close to the normal direction H to the display surface, as shown in
As it can be seen from the drawing, the viewing direction ob of the viewer is generally lies in the direction of the reflected light R2 close to the normal direction H, and, more specifically, the direction in a range from the normal direction H to 10°. As such, the reflected light R1, R3 becomes the direction for viewing the display surface, and thus it is typically difficult to view the display surface. Accordingly, in view of providing a clear visibility to a viewer, it is required that wide viewing angle should be wide and the reflection intensity (reflectivity) of the direction of the reflecting angle smaller than the specular reflection angle should be high.
However, in the conventional reflective liquid crystal display device shown in
An object of the present invention is to provide a reflector of which the viewing angle characteristics for the reflected light intensity can become wide and the intensity of the reflected light in a direction having a reflection angle smaller than the specular-reflection angle can be improved.
In addition, the another object of the present invention is to provide a liquid crystal display device of which the viewing angle characteristics for a reflected light intensity can become wide and the visibility can be improved when the display surface is viewed from the direction close to the normal direction for the display surface of the liquid crystal display device.
In order to accomplish the above-mentioned objects, the present invention provides the following configuration.
In the reflector according to a first aspect of the present invention, a plurality of large-diameter concave portions having light reflectivity are formed on a surface of a base material or a metal film formed on the base material in irregular pitches, a plurality of small-diameter concave portions each having a diameter smaller than that of the large-diameter concave portion are formed between the large-diameter concave portions, an inner surface of the large-diameter concave portion has a curved surface which is a portion of a sphere or a non-sphere, an inner surface of the small-diameter concave portion has a curved surface which is a portion of a sphere or a non-sphere, and, in the metal film or the base material having formed with the plurality of the large-diameter concave portions and the plurality of the small-diameter concave portions on the surface thereof, an inclination of the sectional curved line of the vertical surface between the adjacent concave portions or at the boundary of the concave portions is discontinuous.
In the reflector of the first aspect of the present invention, since a plurality of large-diameter concave portions having light reflectivity are formed on a surface of a base material and on a metal film formed on the base material in irregular pitches, the reflection intensity (reflectivity) in a direction having a reflecting angle smaller than the specular reflection angle can be improved. Also, since a plurality of small-diameter concave portions each having a diameter smaller than that of the large-diameter concave portion are formed between the large-diameter concave portions, the base of the graph representing the viewing angle characteristic of the reflection intensity can become sufficiently wide, thereby the incident light from the inclination direction (for example, the incident light of which the angle from the normal direction is beyond 45°) can be efficiently reflected in the main viewing direction of the user (the direction close to the line of the sight of the user).
According to the first aspect of the present invention, it is possible to provide a reflector, which has reflection characteristics of which the intensity of the reflected light is high through a wide angle range and the incident light at various angles is reflected and collected to the viewing direction.
In the reflector according to a second aspect of the present invention, a plurality of large-diameter convex portions having light reflectivity are formed on a surface of a base material or a metal film formed on the base material in irregular pitches, a plurality of small-diameter convex portions each having a diameter smaller than that of the large-diameter convex portion are formed between the large-diameter convex portions, an outer surface of the large-diameter convex portion has a curved surface which is a portion of a sphere or a non-sphere, an outer surface of the small-diameter convex portion has a curved surface which is a portion of a sphere or a non-sphere, and, in the metal film or the base material having formed with the plurality of the large-diameter convex portions and the plurality of the small-diameter convex portions on the surface thereof, an inclination of the sectional curve of the vertical surface between the adjacent convex portions or at the boundary of the convex portions is discontinuous.
According to the second aspect of the present invention, since a plurality of large-diameter convex portions having light reflectivity are formed on the surface of a base material or on a metal film formed on the base material in irregular pitches, the reflection intensity (reflectivity) in the direction having a reflecting angle smaller than the specular reflection angle can be improved. Also, since a plurality of small-diameter convex portions each having a diameter smaller than that of the large-diameter convex portion are formed between the large-diameter convex portions, the base of the graph representing the viewing angle characteristics for the reflectivity can become sufficiently wide, thereby the incident light from the inclination direction (for example, the incident light of which the angle in the normal direction is beyond 45°) can be efficiently reflected to the main viewing direction of the user (the direction close to the line of the sight of the user).
According to the second aspect of the present invention, it is possible to provide a reflector, which has reflection characteristics of which the intensity of the reflected light is high through a wide angle range and the incident light having various angles is reflected and collected to the viewing direction.
In addition, in the reflector according the first and second aspects, it is preferable that the area ratio of the plurality of the large-diameter concave portions to the plurality of the small-diameter concave portions or the area ratio of the plurality of the large-diameter convex portions to the plurality of the small-diameter convex portions is about 1:1 to 400:1 in the metal film or the base material.
Moreover, in the reflector according to the first and second aspects, it is preferable that the diameter of the large-diameter concave portion or the large-diameter convex portion is in a range of about 5 μm to 100 μm, and the thickness or the height thereof is in a range of about 0.1 μm to 3 μm.
Also, according to the first and second aspects, it is preferable that, in the inner surface of the large-diameter concave portion or the outer surface of the large-diameter convex portion has a curved surface which is a portion of a sphere, the inclination angle distribution of the curved surface is in a range of about −30° to about +30°.
Further, according to the first and second aspects, it is preferable that, in the inner surface of the large-diameter concave portion or the outer surface of the large-diameter convex portion has a curved surface which is a portion of a non-sphere, the inclination angle in one side of the large-diameter concave portion or the large-diameter convex portion (the absolute value of the angle between the tangent plane and the surface of the base material in any point of the curved surface) becomes maximum.
In addition, in the reflector according to the first and second aspects, it is preferable that the inner surface of the small-diameter concave portion or the outer surface of the small-diameter convex portion has a curved surface which is a portion a sphere or a non-sphere having a radius of the curvature of about 1 μm to abut 11 μm, and the maximum inclination angle of the curved surface is in a range of about 15° to about 60°.
In the present invention, the inclination angle represents the sectional inclination of a minute region of 0.5 μm (generally, measured by a precise roughness meter or an AFM) when the main section of the concave portion or the convex portion is viewed.
A liquid crystal display device according to a third aspect of the present invention comprises a liquid crystal cell, wherein an electrode and an alignment film are provided on an inner surface of one substrate (second substrate) which is at an viewing side between a pair of opposite substrates through a liquid crystal layer sandwiched therebetween and another electrode and alignment film are provided on an inner surface of the other substrate (first substrate) far from the viewing side, and wherein the reflector according to the first or second aspect is provided between the first substrate and the alignment film provided on the inner surface thereof or on the outer surface of the first substrate.
In the liquid crystal display device according to the third aspect of the present invention, since the first or second reflector which has reflection characteristics in which the intensity of the reflected light becomes high in a wide angle range and the incident light having various angles is reflected and collected to the viewing direction is included, the intensity of the reflected light becomes high in a wide angle range, and the display surface is bright when it is viewed the direction close to the normal direction for the display surface of the liquid crystal display device, and thus the visibility can be improved.
A liquid crystal display device according to a fourth aspect of the present invention comprises a liquid crystal cell, wherein an electrode and an alignment film are provided on an inner surface of one substrate (second substrate) which is at an viewing side between a pair of opposite substrates through a liquid crystal layer sandwiched therebetween and another electrode and an alignment film are provided on an inner surface of the other substrate (first substrate) far from the viewing side, wherein a reflector is provided between the first substrate and the polarization film provided on the inner surface thereof and the outer surface of the other substrate, and a light scattering layer is provided on one substrate, wherein the reflector is formed such that a plurality of large-diameter concave portions or plurality of large-diameter convex portions having light reflectivity are formed on a surface of a base material or on a metal film formed on the base material in irregular pitches, an inner surface of the large-diameter concave portion or the outer surface of the large-diameter convex portion has a curved surface which is a portion of a sphere or a non-sphere, and, in the metal film or the base material formed with the plurality of the large-diameter concave portions or the plurality of the large-diameter convex portions on the surface thereof, the inclination of the sectional curved line of the vertical surface at the boundary of the adjacent concave portions or convex portions is discontinuous, and wherein the light scattering layer is made by dispersing fine particles in a matrix composed of transparent resin or transparent adhesive.
In the liquid crystal display device according to the fourth aspect of the present invention, since the above-mentioned reflector is attached at the inside or the outside of the liquid crystal cell, the reflection intensity (reflectivity) in the direction having an angle smaller than the specular reflection angle can be improved. Also, since the light scattering layer is provided on the outside of the liquid crystal cell, the light is scattered when the light reflected from the reflector passes through the light scattering layer, and thus the range of the reflecting angle can be enlarged.
According to the liquid crystal display device according to the fourth aspect of the present invention, the intensity of the reflected light can be high through the wide angle range, and the display surface is bright when it is viewed at the direction close to the normal direction for the display surface of the liquid crystal display device to improve the visibility.
Moreover, in the liquid crystal display device according to the fourth aspect of the present invention, it is preferable that the haze ratio of the light scattering layer is in a range of about 15% to about 30%.
Here, the haze ratio becomes an index of the degree of the light scattering. When the light scattering property of the light scattering layer is too much, the display characteristics in the display screen is remarkably deteriorated, and, when the light scattering property of the light scattering layer is too little, the moiré can be generated in the display screen. When the haze of the light scattering layer is in a range of about 15% to about 30%, the deterioration of the display characteristics of the liquid crystal display device can be suppressed and the moiré can be prevented in the display screen.
As mentioned above, according to the present invention, it is possible to provide a reflector capable of widening a viewing angle characteristics for the reflected light intensity and capable of increasing the intensity of the reflected light. (reflectivity) in the direction having a reflecting angle smaller than the specular reflection angle.
Also, according to the liquid crystal display device of the present invention, it is possible to widen the range of viewing angle in which a display can be seen brightly and the visibility can be improved when the display surface is viewed in the direction close to the normal direction for the display surface of the liquid crystal display device.
Hereinafter, embodiments of the present invention will now be described with reference to the drawings. In the below drawings, the film thickness or the size ratio of each of the components is adequately set in order to easily understand the drawings.
(Embodiment 1)
In
On the inner side (the side facing the liquid crystal layer 30) of the first substrate 10, a reflector 47, a transparent inserting layer 53 formed by request, a color filter 13 for displaying the color, an overcoat film 14 (transparent planarization layer) for flattening the irregularities caused by the color filter 13, a transparent electrode layer (electrode) 15 for driving the liquid crystal layer 30, and an alignment film 16 for controlling the orientation of the liquid crystal molecules are laminated in this order. In addition, on the inner side (the side facing the liquid crystal layer 30) of the second substrate 20, a transparent electrode layer (electrode) 25, an overcoat film 24, and a polarization film 26 are laminated in this order.
Further, the transparent electrode layers 15 and 25 having the liquid crystal layer 30 sandwiched therebetween are formed in stripe shape perpendicularly to each other and an intersection region thereof becomes a pixel to construct a passive matrix type liquid crystal display device.
A liquid crystal cell 35b is comprised of a first substrate 10, a second substrate 20, and components provided between the substrates.
On the side opposite to the side facing a liquid crystal layer 30 of the second substrate 20 (the outer side of the second substrate 20), a phase difference plate 27 and a polarization plate 28 are laminated in this order.
This reflector 47 includes an organic film 11 and a metallic reflecting film (metal film) 12 formed on the organic film 11. The organic film 11 is provided so as to form irregularities on the metallic reflecting film 12 to efficiently scatter the reflected light.
The surface of the metallic reflecting film 12 is formed with a plurality of large-diameter concave portions 70 having light reflectivity in irregular pitches, as shown in
The inner surface of the large-diameter concave portion 70 has a curved surface which is a portion of non-spherical surface in this embodiment, and is configured such that the reflection intensity distribution of the diffused light incident to the metallic reflecting film formed with a plurality of the large-diameter concave portions 70 at a predetermined angle (for example, 30°) becomes asymmetrical on the basis of the specular reflection angle.
Specifically, in the cross section along Y-axis direction in
The deepest point D is in a location deviated from the center O of the large-diameter concave portion 70 to the y-direction, the average absolute values of the inclination angles of the first curved line A1 and the second curved line B1 from a horizontal plane of the substrate 10 are set to be irregularly distributed in a range of about 1° to about 89° and in a range of about 0.5° to about 88°, respectively, and the average inclination angle of the first curved line A1 is larger than that of the second curved line B1. Also, the inclination angle δa in the peripheral portion S1 of the first curved line A1 representing the maximum inclination angle is irregularly distributed in a range of about 4° to about 35°, in the large-diameter concave portion 70.
Thereby, the depth of the large-diameter concave portions 70 is irregularly distributed in a range of about 0.25 to about 3 μm. When the depth d of the large-diameter concave portion 70 is less than 0.25 μm, it is difficult to sufficiently obtain the diffusing effect of the reflected light, and, when the depth is more than 3 μm, the top thereof is not buried by the planarization film in a post-process and thus the desired flatness is not obtained. Also, when the depth d is more than 3 μm, since the thickness of the planarization film exceeds than 3 μm, the planarization film adjacent to the peripheral portion or the terminal portion of the panel is apt to be contracted or cracked in the condition of a high temperature and a high humidity.
In addition, the diameter L of the large-diameter concave portions 70 (the maximum diameter of the opening of the concave portion 70 in the Y-axis directional section in
Further, the pitches between the adjacent large-diameter concave portions 70 are randomly positioned, and moiré due to the interference between the array of the large-diameter concave portion 70 and another regular patterns in the liquid crystal display panel can be prevented.
Here, the term ‘depth of the large-diameter concave portion’ means the distance from the surface S of the portion of the metallic reflecting film 12 without concave portion to the bottom of the large-diameter concave portion. The term ‘pitch between the adjacent large-diameter concave portions’ means the distance between the centers of the large-diameter concave portions in the plan view.
The inner surface of the small-diameter concave portion 60 has a curved surface, which is a portion of a spherical or non-spherical surface, and the small-diameter concave portions 60 are formed between the large-diameter concave portions 70. Thus, the base of the graph representing the reflection intensity distribution of the diffused light incident to the metallic reflecting film 12 at a predetermined angle (for example, 30°) can become sufficiently wide.
Specifically, the radius of the curvature of the curved surface of the small-diameter concave portions 60 is irregularly distributed in a range of about 1 μm to about 11 μm, and the maximum inclination angle of the curved surface thereof is irregularly distributed in a range of about 15° to about 60°, and, preferably, in a range of about 18° to about 60°.
When the radius of the curvature of the curved surface of the small diameter concave portion 60 is less than 1 μm, it is difficult to perform the stable process used in the forming the reflector when forming a base mold, and, when the radius of the curvature of the curved surface is more than 11 μm, it is difficult to obtain the effect of the present invention because the shape thereof becomes equal to that of the large-diameter concave portion 70. It is preferable that the radius of the curvature of the curved surface is irregularly distributed in a range of about 1 μm to about 10 μm.
When the maximum inclination angle of the curved surface of the small-diameter concave portion 60 is less than about 15°, it is difficult to obtain the effect of the present invention because the reflection characteristics thereof become equal to that of the large-diameter concave portion 70, and, when the maximum inclination angle of the curved surface of the small-diameter concave portion 60 is more than about 60°, the reflectivity decreases.
In addition, the depth d1 of the small-diameter concave portion 60 is irregularly distributed in a range of about 0.25 μm to about 3 μm. When the depth d1 of the small-diameter concave portion 60 is less than 0.25 μm, it is difficult to sufficiently obtain the diffusing effect of the reflected light, and, when the depth d1 is more than 3 μm, the peak thereof is not buried by the planarization film in the post-process and thus desired flatness is not obtained. Also, when the depth d1 is more than 3 μm, the thickness of the planarization film also exceeds 3 μm, the reliability of the liquid crystal display device on condition of a high temperature and a high humidity is reduced.
In addition, the diameter L1 of the small-diameter concave portion 60 (the maximum diameter of the opening of the concave portion 60 in the Y-axis directional cross section in
Further, the pitches between the adjacent small-diameter concave portions 60 are randomly positioned, and moiré due to the array of the small-diameter concave portions 60 can be prevented.
Here, the term ‘depth of the small-diameter concave portion’ means the distance from the surface S of the portion of the metallic reflecting film 12 without the concave portion to the bottom of the small-diameter concave portion. The term ‘pitch between the adjacent small-diameter concave portions’ means the distance between the centers of the small-diameter concave portions in the plan view.
In the reflector 47 of the present embodiment, it is preferable that the area ratio of the plurality of large-diameter concave portions to the plurality of small-diameter concave portions is about 1:1 to about 400:1 and the total area of the plurality of large-diameter concave portions 70 is about 1 to 400 times of that of the plurality of small-diameter concave portion 60.
When the total area of the plurality of large-diameter concave portions 70 is less than that of the plurality of small-diameter concave portions 60, the reflectivity of the region having a reflection characteristic obtained by the large-diameter concave portion 70 decreases. Also, when the total area of the plurality large-diameter concave portions 70 is more than 400 times of that of the plurality of small-diameter concave portions 60, the effect for widening the base of the reflection characteristics become low.
The solid line in
In addition, the size of each component of the reflector having the reflection characteristics shown in the solid line in
In the plurality of large-diameter concave portions 70, the indentation diameter is irregularly distributed in a range of about 5.9 μm to about 7.7 μm, the depth d is irregularly distributed in a range of about 0.8 μm to abut 1.4 μm (the mix of 0.8 μm, 1.0 μm, 1.1 μm, 1.4 μm), the maximum inclination angle of the curved surface is irregularly distributed in a range of about 15.6° to about 20.5°, and the radius of the curvature of the curved surface is about 22 μm.
In the plurality of small-diameter concave portions 60, the indentation diameter is irregularly distributed in a range of about 3.5 μm to about 5.0 μm, the depth d1 is irregularly distributed in a range of abut 0.6 μm to about 1.2 μm (the mix of 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm), the maximum inclination angle of the curved surface is irregularly distributed in a range of about 18.6° to about 27.0°, and the radius of the curvature of the curved surface is about 11 μm.
Further, in
In addition, in
In the reflector of the first example in which the small-diameter concave portions are formed between the large-diameter concave portions, as shown in
The reflector 47 of the present embodiment has the reflection characteristics that the intensity of the reflected light becomes high in the wide angle range and the light incident thereto at various angles can be more reflected to the viewing direction to be collected.
According to the reflective liquid crystal display device 1 of the present embodiment, reflector 47 having the reflection characteristics that the intensity of the reflected light becomes high in the wide angle range and more reflecting and collecting the light incident thereto at various angles to the viewing direction is included, thereby the intensity of the reflected light can become high in the wide angle range and the display surface is bright and the visibility can be improved when being viewed from the direction close to the normal direction for the display surface of the liquid crystal display device (particularly, when the angle θ between the main viewing direction α1 of the user and the normal direction H1 is in a range of about 0° to about 20°).
Next, a second example having a plurality of the large-diameter concave portion formed on the metallic reflecting film of the reflector included in the liquid crystal display device of the present example will be explained with reference to FIGS. 6 to 8.
The large-diameter concave portion 80 of the second example is composed by changing the shape of the inner surface of the large-diameter concave portion 70 of the reflector 47 (large-diameter concave portion of the first example) in the liquid crystal display device 1 and has directivity of the reflected light similar to the large-diameter-concave portion 70.
Specifically, similar to the large-diameter concave portion 70 of the first example, the large-diameter concave portion 80 is comprised of a first curved surface having a small curvature and a second curved surface having a large curvature, and the first curved surface and the second curved surface have a shape shown by a first curved line A′ from one peripheral portion S1 of the large-diameter concave portion 80 to its deepest point D and a second curved line B′ from the deepest point D to the other peripheral portion S2 thereof in connection with the first curve, respectively, in the Y-direction section of
This deepest point D is in the location deviated from the center O of the large-diameter concave portion 80 to y-direction, the average absolute values of the inclination angles of the first curved line A′ and the second curved line B′ from the surface S of the metallic reflecting film are set to be irregularly distributed in a range of about 2° to about 90° and about 1° to about 89°, respectively, and the average inclination angle of the first curved line A′ is larger than that of the second curved line B1′. Also, the inclination angle δa in the peripheral portion S1 of the first curve Al representing the maximum inclination angle in the large-diameter concave portion 80 is irregularly distributed in a range of about 4° to about 35°. Thereby, the depth of each large-diameter concave portion 80 is irregularly distributed in a range of about 0.25 μm to about 3 μm.
In addition, the diameter L of the large-diameter concave portion 80 (the maximum diameter of the opening of the concave portion 80 in the Y-axis direction cross section of
Further, the pitches between the adjacent large-diameter concave portions 80 are randomly positioned.
On the other hand, the first curved surface and the second curved surface has a bilateral symmetric shape for the center O in the X-axis direction section shown in
The solid line in
In the metallic reflecting film in which the plurality of large-diameter concave portions 80 are formed (the small-diameter concave portion 60 is not formed), the brightness of the reflected light of the light incident to the liquid crystal display device at the angle 30° from the y-direction side is high, compared with the metallic reflecting film in which a plurality of the below-mentioned large-diameter concave portions 90 of the third example are formed (the small-diameter concave portion 60 is not formed), in the angle (near 20°) smaller than the reflecting angle of 30° which is the specular reflection direction). That is, since the deepest point D of the large-diameter concave portion 80 is deviated from the center O of the large-diameter concave portion 80 toward the y-direction side, the ratio of the light reflected at the second curved surface B′ becomes larger than the light reflected at the first curved surface A′, the reflection display of the side opposite to the y-direction is more bright. Also, since the adjacent region of the deepest point D of the large-diameter concave portion 80 is slowly curved, the reflection intensity of the specular reflection direction becomes high.
Then, the reflection characteristics of the reflector (second example) including the metallic reflecting film formed with the small-diameter concave portions between the large-diameter concave portions 80 can represent the reflection characteristics similar to that of the reflector 47 shown by the solid line in
Next, a third example of a plurality of large-diameter concave portions formed in the metallic reflecting film of the reflector included in the liquid crystal display device of the present embodiment will be explained with reference to
The large-diameter concave portion 90 of the third example is composed by changing the shape of the inner surface of the large-diameter concave portion 70 of the reflector 47 (the large-diameter concave portion of the first example) in the liquid crystal display device 1.
The inner surface of the large-diameter concave portion 90 of the third example has a curved surface which is a portion of the sphere, and the large-diameter concave portion 90 is composed such that the reflection intensity distribution of the diffused light incident to the metallic reflecting film in which a plurality of the large-diameter concave portions 90 are formed at a predetermined angle (for example, 30°) is symmetrical in the wide range, on the basis of the specular reflection angle. Specifically, the inclination angle θg of the inner surface of the large-diameter concave portion 90 is set in a range of about −30° to about 30°. Also, the diameter L of the large-diameter concave portion L may be called as an indentation diameter.
In addition, the pitches of the adjacent large-diameter concave portions 90 are randomly arranged and the moiré due to the array of the large-diameter concave portions 90 can be prevented from being generated.
Also, the diameter L of the large-diameter concave portion 27 (maximum diameter of the opening of the concave portion 90 in
In addition, the depth of the large-diameter concave portion 90 is irregularly distributed in a range of about 0.1 μm to about 3 μm. When the depth of the large-diameter concave portion 90 is less than 0.1 μm, it is difficult to sufficiently obtain the diffusing effect of the reflected light, and, when the depth is more than 3 μm, the pitch of the large-diameter concave portion 90 must become large in order to satisfy the condition of the inclination angle of the inner surface, and the moiré can be generated.
Here, the term ‘depth of the large-diameter concave portion 90’ means the distance from the surface S of the portion of the metallic reflecting film 12 in which the large-diameter concave portion 90 is not formed to the bottom of the large-diameter concave portion. The term ‘pitch between the adjacent large-diameter concave portions 90’ means the distance between the centers of the large-diameter concave portions 90 each having a circle shape in the plan view. The ‘inclination angle of the inner surface of the large-diameter concave portion 90’ means the angle θg from the horizontal surface of the inclination surface (surface S of the metallic reflecting film 12) in the minute range, when taking the minute range having a width of 0.5 μm in any location of the inner surface of the large-diameter concave portion 90, as shown in
The dotted line in
In the metallic reflecting film in which the a plurality of the large-diameter concave portions 90 are formed (the small-diameter concave portions are not formed), the maximum value of the reflection intensity becomes high to the light-receiving angle which is larger than the specular reflection angle and the light-receiving angle which is smaller than the specular reflection angle on the basis of the specular reflection angle, thereby the region having a high quantity of the reflected light is widened, compared with the reflecting plate of the conventional reflecting plate (first comparative example) having the reflection characteristics of Gaussian distribution, and thus the quantity of the reflected light of which the light-receiving angle is smaller than the specular reflection angle increases and the brightness becomes high.
Then, the reflection characteristics of the reflector (third example) having the metallic reflecting film in which the small-diameter concave portion 60 is formed between the large-diameter concave portions 90 can represent the same reflection characteristics as the reflector 47 shown by the solid line in
(Embodiment 2)
Next, the reflective liquid crystal display device according to the second embodiment of the present invention will be explained.
The reflective liquid crystal display device 100 according to the second embodiment is different from the first reflective liquid crystal display device 1 shown in FIGS. 1 to 3 in that a light scattering layer 29 is formed on the outer surface side of one substrate 20 which becomes the viewing side among a pair of substrates 10 and 20 forming the liquid crystal cell and the structure of the reflector provided in the liquid crystal cell is different.
The reflector 47a included in the reflective liquid crystal display device 100 of the present embodiment is comprised of an organic film 11a and a metallic reflecting film (metal film) 12a formed on the organic film 11a.
The metallic reflecting film 12a included in the reflector 47a of the present embodiment is equal to the metallic reflecting film 12 of the first embodiment, except that the small-diameter concave portions are formed between the large-diameter concave portions 70. In other words, the surface of the reflector 47a (the surface of the metallic reflecting film 12a) according to the present embodiment is formed with a plurality of the large-diameter concave portions 70 in the irregular pitch.
The metallic reflecting film 12a included in the reflector 47a of the present embodiment is formed such that the inclination of the sectional curved line of the vertical section is discontinuous in the boundary of the adjacent large-diameter concave portions 70.
The light scattering layer 29 is made by dispersing particles in the matrix made of transparent resin or transparent adhesive.
The light scattering property in the light scattering layer 29 can be controlled by changing the condition such as the material of the fine particles and the matrix and the content of the fine particles.
In the degree of light scattering in the light scattering layer 29, a haze ratio (%) is preferably in a range of about 15% to about 30%.
Here, the haze ratio is a value representing the ratio the scattering-transmittance to the total light-beams transmittance (unit: %), and becomes an index of the degree of light scattering. The value of the haze ratio in the present invention is the value obtained by the measuring method based on JIS K 7105.
The diameter of the fine particles is preferably in a range of about 1 μm to about 20 μm, and, more preferably about 3 μm to -about 15 μm. As the specific example, the particle is composed of silica, stylene butadiene copolymer, divinylbenzene, urethane resin, silicon resin, epoxy resin, or polyethylene.
In addition, as an example of the matrix, there are acrylic resin and urethane resin.
The content of the fine particles in the matrix is preferably in a range of about 0.1 mass % to about 10 mass %. When the content is less than 0.1 mass %, the effect of adding the fine particles does not appear, and, when the content is more than 10 mass %, the light scattering becomes too much large, and thus the light reflection efficiency is deteriorated to darken the screen or the contrast in the display screen is deteriorated.
The thickness of the light scattering layer 29 is preferably in a range of about 30 μm to about 200 μm. When the thickness is less than 30 μm, the light scattering effect is not sufficient, and, when the thickness is more than 200 μm, the light is too much scattered.
In the reflective liquid crystal display device 100 of the present embodiment, the reflector 47a is provided in the liquid crystal cell 35c, thereby the reflection intensity (reflectivity) of the direction of which the reflecting angle is smaller than the specular reflection angle can be improved. Also, the light scattering layer 29 is provided on the outer surface side of the liquid crystal cell 35c, thereby the light reflected at the reflector 47a is scattered when passing through the light scattering layer 29 and thus the range of the reflection angle can become wide. Therefore, according to the reflective liquid crystal display device of the present embodiment, the intensity of the reflected light can become high in the wide range, and the display surface become bright when being viewed from the direction close to the normal direction for the display surface of the liquid crystal display device and the visibility can be improved.
In addition, although the reflector for reflecting the incident light from the outside is provided between the substrate 10 and 20 in the reflective liquid crystal display device of the first and second embodiments, the reflector can be provided on the outside of the substrate 10.
In addition, although one phase difference plate is provided between the second substrate 20 and the polarization plate 28 in the first and second embodiments, a plurality of the phase difference plates can be provided.
Further, although the liquid crystal display device of the present invention is applied to the reflective liquid crystal display device in the first and second embodiments, it can be applied to the transflective liquid crystal display device. In this case, the minute opening is provided in the metallic reflecting film of the reflector 47 or the metallic reflecting film is composed of a transflective thin film and the back light unit is provided on the outer surface side of the first substrate 10.
Also, although the reflector is composed of the organic film and the metallic reflecting-film (metal film) in the first and second embodiments, it may be composed by forming base material made of the metal film having the light reflectivity such as an aluminum plate, by perforating the surface of the base material by the tip of a punch to form a plurality of the concave portions, and by forming small-diameter concave portions between the large-diameter concave portion if necessary.
In addition, although one of the large-diameter concave portions of the first to third examples are employed as a plurality of the large-diameter concave portions formed in the metal reflecting film of the reflector in the first and second embodiments, the large-diameter convex portion formed on the metallic reflecting film of the reflector according to the present invention can be employed, if any one of the large-diameter concave portions of the first to third examples is formed such that the concave portion side is directed to the side of the substrate 10 (the lower side)(in other words, such that the convex portion (the side opposite to the concave portion) is directed to side of the substrate 20 (the upper side)).
Also, although the small-diameter concave portion 60 is employed as a plurality of the small-diameter concave portions formed in the metallic reflecting film of the reflector in the first embodiment, the small-diameter convex portion formed on the metallic reflecting film of the reflector according to the present invention can be employed, if the small-diameter concave portions is formed such that the concave portion side is directed to the side of the substrate 10 (the lower side)(in other words, such that the convex portion (the side opposite to the concave portion) is directed to side of the substrate 20 (the upper side)).
Also, although the passive matrix type reflective liquid crystal display device is applied in the first and second embodiments, an active matrix type liquid crystal display device using a thin film transistor or a thin film diode, or a segment type liquid crystal display device can be applied. These liquid crystal display device can be included in the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-344916 | Oct 2003 | JP | national |
