JPH1152110A - Reflection body and reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection body capable of obtaining the high reflection effciency over a wide angle and to provide a reflection type liquid crystal display device whose visual angle is wide even in every direction and which has a brighter display surface. SOLUTION: Many recessed part 4 whose inner surfaces are one part of sphericalities are continuously formed on the surface of a reflection body 1. Then, depths of respective recessed parts 4 are formed at random within the range of 0.1 to 3 μm and pitches among adjacent recessed parts 4 are arranged at random within the range of 5 to 50 μm and inclinations of inner surfaces of the recessed parts 4 are set within the range of -18 to 18 degrees. Moreover, the reflection type liquid crystal display device is provided with this reflection body 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a reflector having uniform brightness and whiteness over a wide range, and a reflection type liquid crystal display device using the reflector.

[0002]

2. Description of the Related Art In recent years, a reflection type liquid crystal display device has been widely used as a display unit of a handy type computer or the like because of particularly low power consumption. This reflective liquid crystal display device includes a reflector for reflecting light incident from the display surface side to perform display. As a conventional reflector, a reflector having a mirror-finished surface or a reflector having random irregularities formed on the surface has been used.
Among them, as shown in FIG. 9, a conventional reflector 60 having a random uneven surface has a thickness of 300 to 500, for example.
By heating a polyester film 61 of μm, an uneven surface 61 a having a height of several μm
And a reflective film 62 made of aluminum, silver, or the like is formed on the uneven surface 61a by a method such as vapor deposition.

As shown in FIG. 10, in a conventional reflection type liquid crystal display device using a reflection plate 60 of this kind, transparent electrode layers 53, 54 are provided on opposite sides of a pair of glass substrates 51, 52, respectively.
Are further provided on each of the transparent electrode layers 53 and 54, and liquid crystal alignment films 55 and 56 are provided.
A liquid crystal layer 57 is provided between the two. Then, the first and second portions are provided outside the glass substrates 51 and 52, respectively.
Are provided, and a reflection plate 60 is attached to the outside of the second polarization plate 59 with the surface on the reflection film 62 side facing the second polarization plate 59 side.

In the reflection type liquid crystal display device 50 having the above-described structure, the light incident on the first polarizing plate 58 is linearly polarized by the polarizing plate 58, and the polarized light is elliptically polarized by transmitting through the liquid crystal layer 57. You. Then, the elliptically polarized light is linearly polarized again by the second polarizing plate 59, and
The linearly polarized light is reflected by the reflecting plate 60, passes through the second polarizing plate 59 and the liquid crystal layer 57, and exits from the first polarizing plate 58.

The reflection plate and the reflection type liquid crystal display have the following reflection characteristics. For example, as shown in FIG.
The incident angle of the incident light J from the point light source disposed on the reflective film 62 is set to an incident angle 30 with respect to the normal to the surface of the reflective film 62.
When the reflectance is measured when the reflection angle θ of the reflected light K is changed from 0 degree to 60 degrees, the reflection angle 30
It was found that the reflectance was almost the lowest when the right and left reflection angles were 20 degrees or less and 40 degrees or more with the reflectance at the peak as the peak. This tendency is similar not only to the measurement using the reflection plate alone, but also to the measurement as a whole of the liquid crystal display device provided with this reflection plate. The reflection angle at a reflection angle of 30 degrees is a peak and the reflection angle is 23 degrees. It has been found that the temperature drops to almost 0% in the range from below to 37 degrees or more.

[0006] With respect to the reflection characteristics of a reflector having a mirror-finished surface, the reflectivity generally shows a very high reflectance at a specific reflection angle with respect to the incident angle, as compared with a reflector having random irregularities on the surface. However, it has the characteristic that the range of the reflection angle with high reflectance is extremely narrow, that is, the viewing angle is narrow.

[0007]

As described above, the conventional reflector having a random concave-convex reflecting surface has a low reflectance as a whole due to poor reflection efficiency, so that incident light can be reflected over a wider range of reflection angles. It has not been possible to sufficiently meet the need for a reflector that reflects light efficiently. Therefore, a reflection type liquid crystal display device using this type of reflector has a viewing angle of about 2
There is a problem that the range of 5 to 35 degrees is narrow and the brightness of the display surface is not sufficient. In addition, whiteness as well as brightness is required for the characteristics of the reflector, but this type of conventional reflector does not uniformly reflect light having various wavelengths in a well-balanced manner, and therefore is insufficient in terms of whiteness of the reflection surface. Met. Further, the reflection characteristics such as the reflection angle and the reflection light intensity of this type of reflection plate are determined automatically by randomly formed irregularities, and are not controlled by optical design.

Therefore, in order to solve these problems,
A reflector having a large number of stripe grooves extending linearly on the surface has been proposed. However, in the case of this reflector, in the direction perpendicular to the stripe groove, although a desired brightness can be obtained at a certain range of reflection angle, the reflection angle range is narrow, and further, in the direction other than the direction perpendicular to the stripe groove, The reflectivity was originally low and the reflection angle was extremely narrow. Therefore, when this type of reflector is applied to a liquid crystal display device, the above-mentioned problems such as a narrow viewing angle and insufficient brightness and whiteness of the display surface, particularly in a direction parallel to the stripe groove, can be solved. Did not.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a reflector capable of obtaining high reflection efficiency over a wide angle, and using such a reflector in any direction. It is another object of the present invention to provide a reflective liquid crystal display device having a wide viewing angle and a brighter display surface.

[0010]

In order to achieve the above object, a reflector according to the present invention comprises a plurality of recesses whose inner surfaces form a part of a spherical surface formed continuously on a reflector surface. Is formed at a depth of 0.1 to 3 μm at random,
The pitch of the adjacent concave portions is randomly arranged in a range of 5 to 50 μm, and the inclination angle of the inner surface of the concave portion is -18 to +
It is characterized by being set within a range of 18 degrees.

In the reflector of the present invention, a large number of concave portions having an inner surface forming a part of a spherical surface are formed on the surface, and parameters such as the depth of the concave portions and the pitch between adjacent concave portions are set as described above. By setting the angle in the range, the inclination angle (inclination angle in a minute unit area) of the inner surface of the concave portion, which is considered to dominate the reflection angle of the reflected light, shows a constant distribution within a certain angle range. Since the inner surface of the concave portion has a spherical shape, the constant inclination angle distribution is realized not only in a specific direction but also in all directions in the reflector. Therefore, according to the reflector of the present invention, a high reflection efficiency can be obtained uniformly in all directions, and light having various wavelengths can be reflected with good balance. That is, it is possible to realize a brighter and whiter reflector when viewed from any direction as compared with the conventional reflector.

The "depth of the concave portion" is the distance from the reflector surface to the bottom of the concave portion, and the "pitch between adjacent concave portions" is the distance between the centers of the concave portions which is circular when viewed in plan. That is. Further, as shown in FIG. 8, the “inclination angle of the inner surface of the concave portion” refers to the horizontal plane of the inclined surface within the minute range when a minute range of 0.5 μm width is taken at an arbitrary position on the inner surface of the concave portion 4. Angle θ with respect to The sign of the angle θ defines, for example, the right slope in FIG. 8 as positive and the left slope in FIG. 8 as negative with respect to the normal line on the reflector surface.

As described above, regarding the depth of these recesses, the pitch between adjacent recesses, and the inclination angle of the inner surface of the recesses, the depth of the recesses is 0.1 to 3 μm, the pitch of the adjacent recesses is 5 to 50 μm, -18 to +
It is desirable to set the range to 18 degrees. In particular, it is important to set the inclination angle distribution in the range of −18 to +18 degrees, and to arrange the pitch of the adjacent concave portions at random in all directions in the plane. This is because, if the pitch of the adjacent concave portions has regularity, there is a problem that an interference color of light appears and the reflected light is colored. On the other hand, when the inclination angle distribution of the inner surface of the concave portion exceeds the range of −18 to +18 degrees, the diffusion angle of the reflected light is too wide, the reflection intensity is reduced, and a bright reflector cannot be obtained. In the liquid crystal display device, the reflection intensity peak inside the liquid crystal display device decreases, and the total reflection loss increases.) On the other hand, if the depth of the concave portion exceeds 3 μm, the top of the convex portion cannot be filled with the flattening film when the concave portion is flattened in a later step, and desired flatness cannot be obtained. When the pitch of the adjacent concave portions is less than 5 μm, there is a restriction in the production of the reflector forming matrix, the processing time becomes extremely long, a shape which can obtain desired reflection characteristics cannot be formed, and interference light is generated. Problems occur. Further, in practice, when a diamond indenter having a diameter of 30 to 100 μm that can be used for manufacturing a master for forming a reflector is used, it is preferable that the pitch between adjacent concave portions is 5 to 50 μm.

Further, in the reflection type liquid crystal display device of the present invention, a large number of concave portions whose inner surface forms a part of a spherical surface are formed on the reflector, that is, the reflector surface, and the concave portion has a depth of 0.1 mm. 1 to 3 μm, the pitch between adjacent concave portions is 5 to 50 μm, and the inclination angle of the inner surface of the concave portion is −18 to +18.
It is characterized by having a reflector which is a degree.
The reflector may be installed in either an external type installed outside the liquid crystal cell or a built-in type installed inside the substrate of the liquid crystal cell.

According to the reflection type liquid crystal display device of the present invention, the reflector itself has high reflection efficiency in all directions and reflects light having various wavelengths in a well-balanced manner. The viewing angle is wider than that of the liquid crystal display device, and the display surface can be made brighter.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a reflector according to the present embodiment. As shown in this figure, a reflector 1 of the present embodiment is a flat resin substrate 3 (a substrate for a reflector) made of a photosensitive resin layer or the like provided on a substrate 2 made of, for example, glass. A large number of concave portions 4 whose inner surfaces are part of a spherical surface are continuously formed so as to overlap each other, and a reflective film 5 made of a thin film of, for example, aluminum or silver is formed thereon by vapor deposition or printing. It is a thing.

The depth of the concave portions 4 is randomly formed within a range of 0.1 to 3 μm, and the pitch of the adjacent concave portions 4 is 5 μm.
And randomly arranged in the range of 50 μm to 50 μm.
It is desirable to set the inclination angle of the inner surface in the range of −18 to +18 degrees. In particular, the inclination angle distribution of the inner surface of the recess 4 is -1.
Point set in the range of 8 to +18 degrees, adjacent recess 4
It is important that the pitches are randomly arranged in all directions in the plane. This is because if the pitch of the adjacent concave portions 4 is regular, there is a problem that interference colors of light appear and reflected light is colored. If the inclination angle distribution of the inner surface of the recess 4 exceeds the range of −18 to +18 degrees, the diffusion angle of the reflected light becomes too wide, and the reflection intensity decreases.
This is because a bright reflector cannot be obtained (the diffusion angle of the reflected light becomes 36 degrees or more in air, the reflection intensity peak inside the liquid crystal display device decreases, and the total reflection loss increases). If the depth of the concave portion 4 exceeds 3 μm, the concave portion 4
In the case of flattening, the tops of the projections cannot be filled with the flattening film, and desired flatness cannot be obtained. When the pitch of the adjacent recesses 4 is less than 5 μm, there is a restriction in the production of the reflector forming matrix, the processing time becomes extremely long, a shape that can obtain desired reflection characteristics cannot be formed, and interference light is not generated. And other problems arise. Further, in practice, when a diamond indenter having a diameter of 30 to 100 μm that can be used for manufacturing a reflector forming base is used, it is desirable that the pitch of the adjacent concave portions 4 is 5 to 50 μm.

Next, a method of manufacturing the reflector having the above-described structure will be described with reference to FIG.
This will be described with reference to FIG. First, as shown in FIG. 2A, a flat base material 7 made of, for example, brass, stainless steel, tool steel or the like and having a flat surface is fixed on a table of a rolling device. Then, the surface of the matrix base 7 is pressed by a spherical diamond indenter 8 having a predetermined diameter R at the tip, and the matrix base 7 is moved in the horizontal direction.
Is repeatedly rolled on the surface of the matrix base member 7 by repeating the operation of vertically moving and pressing many times to form a plurality of recesses 7a having different depths and arrangement pitches on the surface of the matrix substrate 7, and a reflector as shown in FIG. The forming matrix 9 is used. As shown in FIG. 3, the rolling device used here has a table for fixing the matrix base material 7.
It moves in the X and Y directions in a horizontal plane with a resolution of 1 μm,
The diamond indenter 8 has a function of moving in the vertical direction (Z direction) with a resolution of 1 μm. The diameter R of the tip of the diamond indenter 8 is desirably about 20 to 100 μm. For example, the depth of the concave portion 7a is 2 μm.
m, a diameter R of 30 to 50 μm,
When the depth of the recess 7a is about 1 μm, it is preferable to use one having a diameter R of 50 to 100 μm.

The procedure of rolling with a diamond indenter is as follows. FIG. 4 is a plan view showing a rolling pattern. As shown in FIG. 4, pitches of adjacent recesses in one horizontal row are t1 (= 17 μm) and t3 in order from the left.
(= 15 μm), t2 (= 16 μm), t3, t4 (=
14 μm), t4, t5 (= 13 μm), t2, t3, t3
It has become. In addition, the pitches of the concave portions adjacent to each other in one vertical line have the same pattern in order from the top. By pressing four different depths in the range of 1.1 to 2.1 μm (shown as d 1, d 2, d 3, and d 4 in the figure), the radius of the circular concave portion which is an indentation after the pressing is also reduced. r1
(= 11 μm), r2 (= 10 μm), r3 (= 9 μm)
m) and r4 (= 8 μm). For example, the radii of the concave portions in one vertical line are r1, r2, r3, r
1, r4, r2, r4, r3, r1, r4, r1.

The order of the actual rolling is, for example, that after forming all the recesses of the depth d1 in the uppermost horizontal row, the recesses of the depth d2, the recesses of the depth d3, The rolling operation of four patterns of depths is repeated to form a concave portion having a depth d4, and all the concave portions in the uppermost row are formed. Then, it moves to the second horizontal row from the top and repeats the same operation. Thus, all the concave portions in the pattern are formed. FIG.
= 150 μm square showing a rolling pattern,
By repeating this pattern, the entire reflector is formed. As shown in FIG. 4, since the indentations of the adjacent concave portions partially overlap, the planar shape of the entire concave portion after all the rolling operations are completed is as shown in FIG.

Thereafter, as shown in FIG.
Is placed and placed in a box-shaped container 10, a resin material 11 such as silicone is poured into the container 10, left to cure at room temperature, and the cured resin product is taken out of the container 10 and unnecessary portions are cut off. As shown in FIG. 2D, a transfer mold 12 having a mold surface 12a having a large number of concave portions forming the mold surface of the matrix 9 and a large number of convex portions having the opposite concave and convex shape is formed.

Next, a photosensitive resin liquid such as an acrylic resist, a polystyrene resist, an azide rubber resist, or an imide resist is applied on the upper surface of the glass substrate by a coating method such as spin coating, screen printing, or spraying. I do. After completion of the coating, the photosensitive resin liquid on the substrate is prebaked by using a heating device such as a heating furnace or a hot plate in a temperature range of, for example, 80 to 100 ° C. for 1 minute or more. Form a layer. However, since the pre-bake conditions differ depending on the type of the photosensitive resin used, it is needless to say that the treatment may be performed at a temperature and a time outside the above range. The thickness of the photosensitive resin layer formed here is preferably in the range of 2 to 5 μm.

Thereafter, as shown in FIG.
After using the transfer mold 12 shown in (d) and pressing the mold surface 12a of the transfer mold 12 against the photosensitive resin layer 3 on the glass substrate for a predetermined time, the transfer mold 12 is removed from the photosensitive resin layer 3. In this way, as shown in FIG. 2 (f), the convex portions of the transfer mold surface 12a are transferred to the surface of the photosensitive resin layer 3 to form a large number of concave portions 4. Further, it is preferable to select a value corresponding to the type of the photosensitive resin to be used for the pressing pressure at the time of embossing,
For example, the pressure is preferably about 30 to 50 kg / cm ² . It is preferable to select a value corresponding to the type of the photosensitive resin to be used for the pressing time, for example, 30 seconds to 10 seconds.
It takes about a minute.

Thereafter, ultraviolet rays (g, h, i) for curing the photosensitive resin layer 3 from the back side of the transparent glass substrate.
The photosensitive resin layer 3 is cured by irradiating a light beam such as a line).
In the case of a photosensitive resin layer of the above type, the intensity of 50 mJ / cm ² or more is sufficient to cure the photosensitive resin layer. It is needless to say that the irradiation may be performed at other intensity depending on the case. Then, the photosensitive resin layer 3 on the glass substrate is post-baked by heating the photosensitive resin layer 3 on the glass substrate at, for example, about 240 ° C. for 1 minute or more by using a heating device such as a heating furnace or a hot plate used in the pre-baking. Is baked.

Finally, for example, aluminum is formed on the surface of the photosensitive resin layer 3 by electron beam evaporation or the like, and the reflection film 1 is formed along the surface of the concave portion.
The reflector 1 of the present embodiment is completed.

In the reflector 1 of the present embodiment, a large number of recesses 4 whose inner surface forms a part of a spherical surface are formed on the surface, and the depth of the recesses 4 and the pitch of the adjacent recesses 4 are determined. By setting the value within the above range, the inclination angle of the inner surface of the concave portion shows a constant distribution in a certain angle range. As an example, FIG. 6 shows the distribution of the inclination angle of the inner surface of the concave portion in the reflector 1 of the present embodiment, where the horizontal axis represents the inclination angle,
The vertical axis indicates the frequency at which the inclination angle exists. As shown in this figure, the inclination angle ranges from -18 to +18 degrees,
In particular, it shows a substantially constant distribution in the range of -10 to +10 degrees. Further, since the inner surface of the concave portion 4 is spherical and symmetrical with respect to all directions, this constant inclination angle distribution is realized not only in a specific direction but also in all directions in the reflector. It is considered that the inclination angle of the inner surface of the concave portion governs the reflection angle of the reflected light on the inner surface of the concave portion. In the case of this embodiment, since the inclination angle distribution is constant in all directions of the reflector, As a result, uniform reflection angles and reflection efficiencies can be obtained, and light having various wavelengths can be reflected in a well-balanced manner. That is, it is possible to realize a brighter and whiter reflector when viewed from any direction as compared with the conventional reflector.

When the master 9 for forming the reflector is manufactured, the diamond indenter 8 is simply moved up and down to press the surface of the master substrate 7. The material 7 does not rub against each other. As a result, the surface state of the tip of the diamond indenter 8 is reliably transferred to the matrix 9 side, and if the tip of the indenter 8 is mirror-finished, the inner surface of the concave portion of the mother die 9 and, consequently, the inner surface of the concave portion of the reflector can easily be mirror-finished. can do. Furthermore, unlike the conventional reflector in which the uneven surface is formed by heating a resin film such as polyester, the depth, diameter, pitch, and other dimensions of the recess in the reflector 1 of the present embodiment, and the inner surface of the recess are formed. The surface state and the like are all controlled, and the concave shape of the reflecting plate can be created almost as designed by using a high-precision rolling device. Therefore, according to the present method, the reflection characteristics such as the reflection angle and the reflection efficiency of the reflection plate to be produced become easier to control than in the past, and a desired reflector can be obtained.

It should be noted that specific numerical values such as the depth, diameter and pitch of the concave portion 4 of the reflector 1 in the present embodiment and the rolling pattern of the concave portion shown in FIG. 4 are merely examples, and design changes may be made as appropriate. Is of course possible. Also, a substrate for a reflector,
The materials of various base materials such as the base material for the matrix, the constituent materials of the transfer mold, and the like can be appropriately changed.

Next, an STN (Supe) equipped with the above-described reflector is used.
r Twisted Nematic) type reflective liquid crystal display device will be described. As shown in FIG. 7, this reflection type liquid crystal display device has a liquid crystal layer 15 provided between a pair of display side glass substrates 13 and a rear side glass substrate 14 having a thickness of, for example, 0.7 mm. One retardation plate 1 made of polycarbonate resin, polyarylate resin, etc.
6 and a first polarizing plate 17 is provided on the upper surface side of the phase difference plate 16. Further, on the lower surface side of the rear glass substrate 14, a second polarizing plate 18 and the reflector 1 of the present embodiment shown in FIG. 1 are sequentially provided.

The reflector 1 is mounted on the lower surface side of the second polarizing plate 18 such that the surfaces on which the concave portions 4 are formed face each other. Between the second polarizing plate 18 and the reflector 1, glycerin or the like is provided. An adhesive 19 made of a material that does not adversely affect the refractive index of the light is filled. Transparent electrode layers 20 and 21 made of ITO (indium tin oxide) or the like are formed on the opposing surfaces of the two glass substrates 13 and 14, respectively, and an alignment film 2 made of a polyimide resin or the like is formed on the transparent electrode layers 20 and 21.
2 and 23 are provided respectively. These alignment films 2
The liquid crystal in the liquid crystal layer 15 is twisted 240 degrees due to the relationship of 2, 23, and the like.

Further, a color filter (not shown) may be formed between the rear glass substrate 14 and the transparent electrode layer 21 by printing or the like so that the liquid crystal display device can display a color image.

In the liquid crystal display of the present embodiment,
As described above, since the reflector 1 itself has a characteristic that the angle of reflection of the incident light is wide in all directions and the reflection efficiency is high, even when the user looks at the display surface from any direction, The viewing angle is wider than that of the liquid crystal display device, and a bright display surface can be obtained.

In the reflection type liquid crystal display device of the present embodiment, an example has been described in which the reflection plate is provided outside the second polarizing plate, that is, a so-called external reflection plate. May be disposed on the opposite surface side to form a built-in type. Also,
An example of the liquid crystal display device has been described in the case of the STN mode.
Of course, the reflector of the present invention can be applied to a (Twisted Nematic) type liquid crystal display device.

[0034]

As described in detail above, in the reflector of the present invention, a large number of concave portions having an inner surface which forms a part of a spherical surface are formed on the surface, and the depth of the concave portion is adjacent to that of the concave portion. By defining the pitch of the concave portions and the like, the inclination angle distribution of the inner surface of the concave portion becomes almost constant in a certain angle range with respect to all directions of the reflector. Can be reflected in a well-balanced manner. That is, it is possible to realize a brighter and whiter reflector when viewed from any direction as compared with the conventional reflector. According to the reflection type liquid crystal display device of the present invention, a liquid crystal display device having a wide viewing angle and a bright display surface can be realized by including the reflector having the above excellent characteristics.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a reflector according to an embodiment of the present invention.

FIG. 2 is a process flow chart showing a manufacturing process of the reflector in order.

FIG. 3 is a view showing a process of manufacturing a matrix used for forming the reflector, and showing a state in which the matrix substrate is pressed by a diamond indenter.

FIG. 4 is a plan view showing a pattern of rolling by a diamond indenter in a manufacturing process of the matrix.

FIG. 5 is a plan view showing the shape of the entire recess after rolling.

FIG. 6 is a diagram showing a distribution of an inclination angle of an inner surface of a concave portion in the reflector.

FIG. 7 is a cross-sectional view illustrating a reflective liquid crystal display device according to an embodiment of the present invention.

FIG. 8 is a view for explaining an inclination angle of an inner surface of a concave portion of the reflector according to the present invention.

FIG. 9 is a perspective view showing an example of a conventional reflector.

FIG. 10 is a cross-sectional view illustrating an example of a conventional reflective liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reflector 2 Substrate 3 Resin base material (reflector base material) 4 Concave part 5 Reflective film 7 Base mold base 8 Diamond indenter 9 Reflector forming base mold 12 Transfer mold

Claims (2)

[Claims] 1. A plurality of recesses whose inner surface forms a part of a spherical surface are continuously formed on a surface of a reflector, and the recesses are formed at random in a depth range of 0.1 to 3 μm. Are randomly arranged in a range of 5 to 50 μm, and the inclination angle of the inner surface of the recess is −18 to +1.
A reflector characterized by being set in a range of 8 degrees. 2. A reflection type liquid crystal display device comprising the reflector according to claim 1.