JPH11142833A - Reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reflection type liquid crystal display device which is small in brightness and darkness difference by a visual angle change, is large in a reflected light quantity, is excellent in utilization efficiency of light, is substantially free of hindrance of visibility by ghost images and is excellent in visibility, such as visual field angle and brightness. SOLUTION: This reflection type liquid crystal display device is constituted by arranging a reflection plate 1 installed with a reflection layer 12 consisting of a vapor deposited metal layer on the prism-like rugged surface of a supporting base material 11 having a repetitive structure of prism-like ruggedness on the visible rear surface side of a liquid crystal cell 4 via an air layer 2 and arranging an anti-glare layer 3 between the air layer 2 and the liquid crystal cell 4. The reflection plate which is capable of controlling the exit direction of the reflected light and exhibits the peak of the reflected light at plural exit angles is formable as well by adjusting the angle of inclination of the prism-like ruggedness of the supporting base material. The formation of a reflection characteristic exhibiting a light quantity distribution of a trapezoidal shape is made possible by forming this plate via the anti-glare layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device using a prism type reflection plate and having excellent viewing characteristics such as viewing angle and luminance.

[0002]

2. Description of the Related Art Conventionally, as a reflection type liquid crystal display device, there has been known a reflection type liquid crystal display device in which a reflection plate provided with a metal deposition layer on a surface whose surface is roughened by a mat treatment or the like is arranged on the viewing back side of a liquid crystal cell. Was. However, there is a problem that the reflected light shows a remarkable peak in the regular reflection direction as shown by a curve C in FIG. 5, the luminance sharply decreases due to a change in the viewing angle, the difference in brightness is large, and the viewing angle range for good visibility is narrow.

[0003]

In view of the above, the present inventor has made prototypes of the reflection plates 5 and 6 shown in FIGS. 6 and 7 showing the reflection characteristics as shown by the curve D in FIG. An attempt was made to form a liquid crystal display. However, based on the critical angle, for example, 40
It has been found that there is a problem that reflected light having a large emission angle, such as a degree or more, is totally reflected in the reflector and the amount of light that can be effectively used is reduced. In addition, when a separately formed trapezoidal reflector having a reflection characteristic was used, a similar loss of the amount of emitted light based on the critical angle was observed. The method in which the light scattering layer is provided on the surface of the reflection plate also involves a loss in the amount of emitted light based on the critical angle.

The reflecting plate 5 is provided with a metal-deposited layer by roughening the surface of the prism-shaped uneven surface of the base material 51 having a repeating structure of prism-shaped unevenness, and has a light scattering property based on the fine unevenness. And a resin coating layer 53 is formed thereon. The reflecting plate 6 has a metal layer deposited on the prismatic irregular surface of a substrate 61 having a repeating structure of prismatic irregularities to form a reflecting layer 62, and a resin coating layer containing light scattering particles 64 thereon. 63 is formed. In these, the directivity of the reflected light is controlled by the prism structure or the scattering of the reflected light to provide the reflection characteristic as indicated by the curve D.

In the above description, it is considered that the light quantity loss of the emitted light is considered to be based on the critical angle of the resin coating layer. Therefore, a prototype of a reflection plate from which the resin coating layer is removed is used to form a reflection type liquid crystal display device. When attempted, loss of the amount of emitted light could be prevented. However, in that case, air will be interposed between the liquid crystal cell and the prismatic irregular surface of the reflector, and an image based on the light reflected on the cell substrate on the back side of the liquid crystal cell will appear and overlap the original image. It was found that a ghost phenomenon occurred and display quality deteriorated.

Accordingly, the present invention provides a reflection device which has a small difference in brightness due to a change in viewing angle, has a large amount of reflected light, is excellent in light use efficiency, and has substantially no visual hindrance due to a ghost image and has excellent viewing characteristics such as a viewing angle and luminance. It is intended to obtain a liquid crystal display device of the type.

[0007]

According to the present invention, a reflector having a reflective layer made of a metal vapor deposition layer provided on the prism-shaped irregular surface of a substrate having a repeating structure of prism-shaped irregularities is visually recognized through an air layer. An object of the present invention is to provide a reflection type liquid crystal display device which is arranged on the back side and wherein an anti-glare layer is arranged between the air layer and the liquid crystal cell.

[0008]

According to the present invention, even when a reflector having a sharper reflected light peak than the conventional curve C, such as the curve A in FIG. 2, is used, the light scattering function of the anti-glare layer can be used. As shown by the curve B in FIG. 2, the peak is alleviated, the difference in brightness due to the change in the viewing angle can be reduced, and the emission direction of the reflected light can be controlled by adjusting the inclination angle of the prismatic irregularities on the base material, as shown in FIG. A reflection plate showing a peak of reflected light at a plurality of emission angles can be formed, and a reflection characteristic having a trapezoidal light quantity distribution as shown in FIG. 4 can be formed by passing the reflection plate through an antiglare layer. The trapezoidal light quantity distribution is particularly excellent in suppressing a difference in brightness due to a change in viewing angle.

Further, as described above, by arranging the reflectors through the air layer, it is possible to prevent the loss due to the total reflection of the reflected light, thereby increasing the amount of reflected light and improving the efficiency of use of light, and the anti-glare layer between the air layer and the liquid crystal cell. By intervening, the surface reflection on the viewing back side of the liquid crystal cell can be reduced, and viewing inhibition by a ghost image can be substantially prevented.

As a result of the above, the reflection type which has a small difference in brightness and darkness due to a change in the viewing angle, is excellent in the amount of reflected light, is substantially free from obstruction of viewing by a ghost image, is excellent in a wide viewing angle and brightness, etc., and has excellent viewing characteristics. A liquid crystal display device can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A reflection type liquid crystal display device according to the present invention comprises a base plate having a repeating structure of prismatic irregularities, wherein the prismatic irregularity surface is provided with a reflecting plate comprising a metal deposition layer on an air layer. And an anti-glare layer disposed between the air layer and the liquid crystal cell. An example is shown in FIG. 1 is a reflector, 11 is a base material, 12 is a reflective layer, 2 is an air layer, 3 is an antiglare layer, and 4 is a liquid crystal cell.

The substrate can be formed of a suitable substance such as glass or polymer, and the material for forming the substrate is not particularly limited. In general, for example, polyolefins and various synthetic rubbers, polycarbonate and polystyrene, polyimide and polyamide, cellulosic polymers and polyvinyl alcohol, polyacrylate and polymethacrylate, polyurethane and polyurethane acrylate, polyvinyl chloride and polyester, epoxy resin and A polymer such as epoxy acrylate is used.

The prismatic irregularities on the base material are provided as a repetitive structure of a large number of irregularities, but the form of the prismatic irregularities is not particularly limited. For example, a sectional shape such as a triangle or a trapezoid, or a curved surface such as a record disk is used. Or an appropriate shape such as a shape having a circular surface, a shape having a triangular prism, a triangular pyramid, or a dome shape, or a multi-step shape having a stepped or stepped portion. Further, the prism-shaped irregularities may be formed as a continuous surface or as a discontinuous surface.

Further, the repeating structure of the prism-shaped unevenness may be formed by the same shape of the unevenness, or may be formed by the different shape of the unevenness. Further, the repeating structure may be one in which prismatic irregularities are regularly arranged,
They may be arranged irregularly. A repetitive structure in which prism-shaped irregularities having substantially the same form are regularly arranged is preferable to unifying the emission direction over the entire surface.

The above-mentioned regular arrangement includes, for example, columns, rows, diagonal rows, diagonal rows, diagonal rows, diagonal rows, diagonal rows, diagonal rows, diagonal rows, diagonal rows, and diagonal rows. An array composed of a combination with a column is exemplified. Therefore, a stripe-like arrangement, a polygonal arrangement such as a triangular or lattice-like arrangement and the like are also included. Therefore, the prismatic irregularities may be one-dimensionally arranged in one direction, or two-dimensionally arranged in a predetermined arrangement state in which concave portions are formed in multiple directions such as vertical and horizontal, and discontinuous convex portions are formed. They may be arranged.

The emission angle of the reflected light can be adjusted by controlling the form such as the inclination angle of the above-mentioned prismatic irregularities and the repeating structure thereof. Incidentally, in FIG. 1, the inclination angles α, β, γ of the prismatic irregularities are 30 degrees and 20 degrees.
By setting the inclination angles α, β, and γ at 10 ° and 10 °, a reflector having reflected light peaks at three different emission angles as shown in FIG. 3 can be obtained. In order to improve the vertical and horizontal viewing angle characteristics of a liquid crystal display device or the like, a regular arrangement of a triangular or trapezoidal uneven pattern with a constant pitch such as a stripe or a grid is advantageous.

A substrate having a repeating structure of prismatic irregularities is manufactured by, for example, a liquid substrate which can be polymerized by heat, radiation or the like onto a mold on which a predetermined shape (repeating structure of prismatic irregularities) is transferred and formed. A method of casting a forming material and performing a polymerization treatment, a method of pressing a thermoplastic resin onto a mold or the like in which a predetermined shape is formed, and transferring a surface shape of the mold or the like, or a method in which the thermoplastic is applied to the predetermined mold or the like A method of filling and molding a resin, a method of extruding and solidifying a polymer, such as a solvent solution or a melt, from a nozzle having a molding opening of a predetermined shape onto a table, and a repeating structure of prism-shaped irregularities separately formed on a base material And an appropriate method such as a mask exposure method of irradiating the polymer layer with ultraviolet rays or the like via a mask. Further, the repeating structure of the prismatic irregularities can be formed by a method of providing the substrate with the prismatic irregularities.

The angle of inclination of the inclined surface forming the prismatic irregularities is appropriately determined according to the desired emission direction of reflected light, light utilization efficiency, cut angle of obliquely incident light, and the like. Generally, 70 degrees or less, particularly 1
It has a structure having at least one inclined surface of 度 60 degrees, especially 5 to 50 degrees. Therefore, in the present invention, a structure having a surface having a tilt angle of 90 degrees is also allowed, and this can be preferably used when the emission direction of reflected light is controlled in one direction.

The width (pitch) of the prismatic irregularities can be appropriately determined according to the purpose of use and the like, and is generally 5 mm or less, preferably 1 μm to 1 mm or less, and particularly preferably 5 to 500 μm. When used in a liquid crystal display device, the pitch is smaller than the pixel pitch of the liquid crystal cell, preferably 以下 or less, especially １ ／.
It is particularly preferable to form a repeating structure of prismatic irregularities at the following pitches from the viewpoint of preventing moiré and expanding the viewing angle.

The thickness of the substrate provided with the prismatic irregularities can be appropriately determined according to the purpose of use and the like, but is generally preferably as thin as possible, usually 3 mm or less, especially 10 μm to 1 mm, especially 30 to 500 μm. You. The height or depth of the prismatic irregularities can also be appropriately determined according to the purpose of use and the like, and is generally 1 mm or less, preferably 0.1 to 800 μm, particularly 1 to 30 μm.
0 μm.

The reflection plate can be formed by providing a reflection layer made of a metal deposition layer on the prismatic uneven surface of the substrate. The vapor deposition treatment may be performed by an appropriate method such as a vacuum vapor deposition method or a sputtering method, and an appropriate metal such as aluminum or silver may be used as a metal for vapor deposition. The reflective layer can be formed of a single layer or two or more metal vapor-deposited layers, and can provide reflected light exhibiting polarization characteristics such as linearly polarized light as a multilayer laminated structure of the metal vapor-deposited layers. The thickness of the metal deposition layer forming the reflective layer is 80 nm or more, especially 100 nm or more, particularly 200
It is preferably at least nm.

As shown in FIG. 6, the reflecting layer may have a light scattering property due to a fine uneven structure through roughening of a prism-shaped uneven surface by a mat treatment or the like. The purpose can be sufficiently achieved even with a reflective layer having excellent characteristics and poor light scattering. It requires advanced technology to roughen the prismatic irregular surface and provide a metal deposition layer on it.In the case of silver deposition that requires a base treatment or formation of a protective layer to improve durability, it is necessary to form it. Although it is particularly difficult, the deposition process on a smooth surface can be easily performed even in the case of silver deposition, and a metal deposition layer in a good state such as excellent adhesion can be provided. The practical significance of achieving the object with an excellent reflective layer is significant.

As shown in FIG. 1, the reflection plate 1 is disposed on the viewing back side of the liquid crystal cell 4 via the air layer 2 and the anti-glare layer 3. By placing an anti-glare layer on the prismatic irregular surface of the reflector, an air layer automatically intervenes through the concave portion of the prismatic irregular surface, but in the present invention, a gap is provided between the reflector and the antiglare layer The air layer may be interposed by arranging the air layers. In that case, a gap between the reflector and the anti-glare layer is maintained via an appropriate support frame such as an outer case of the liquid crystal display device.

The antiglare layer is made of, for example, transparent fine particles made of a suitable inorganic substance such as silica particles or calcium oxide particles and / or crosslinked or uncrosslinked transparent fine particles made of a suitable polymer such as polymethyl methacrylate or polyurethane in a transparent resin layer. Can be formed by an appropriate method such as a material having a fine uneven structure on the surface by an appropriate method such as embossing roll, sand blasting, etching or the like.

From the viewpoint of suppressing the difference in brightness due to a change in the viewing angle,
An antiglare layer having excellent light scattering properties is preferred. By optimizing the light scattering characteristics, it is possible to prevent the prism-shaped uneven structure on the surface of the reflector from being seen, and to prevent the occurrence of moire due to interference with the liquid crystal cell.

The anti-glare layer may be formed by directly applying an anti-glare treatment to the cell substrate on the viewing back side of the liquid crystal cell, or a separately formed anti-glare sheet may be adhered to the cell substrate on the viewing back side of the liquid crystal cell via an adhesive layer if necessary. It can be formed by an appropriate method such as a method of causing the formation. In the case of an antiglare layer composed of a coating layer of a transparent fine particle-containing resin or an antiglare sheet, the thickness is 1 mm or less, 1 to 500 μm.
m, especially 5 to 300 μm, but is not limited to this.

In the case where the above-mentioned reflected light shows a polarization characteristic, it is difficult to eliminate the polarization state, especially, the polarization state is 95% or more, particularly 99% or more, and more preferably 99.5.
% Is preferable. The antiglare layer exhibiting such a polarization maintaining property can be obtained, for example, as a layer having a small phase difference due to birefringence, especially a layer having a phase difference of 100 nm or less, particularly 50 nm or less.

There is no particular limitation on the liquid crystal cell used to form the reflection type liquid crystal display device.
An appropriate liquid crystal cell such as a mold can be used, and the liquid crystal cell may be provided with a polarizing plate depending on the characteristics of the liquid crystal.

[0029]

EXAMPLE 1 Triangular prisms having different inclination angles (α, β, γ) of 30 °, 20 ° and 10 ° are formed adjacently on one surface of a polycarbonate sheet having a refractive index of 1.60 in a stripe shape at a pitch of 30 μm. Aluminum was vacuum-deposited on the prism-formed surface of the resulting prism sheet to obtain a reflection plate. The deposition amount is an amount that results in a thickness of 150 nm with respect to a flat surface.

As shown in FIG. 3, the reflector has three reflection peaks in the direction perpendicular to the ridge of the prism with respect to the vertically incident light, and does not diffuse light in the direction parallel to the ridge of the prism. It exhibited excellent specular reflection characteristics. Such a reflection plate weights the diffusion direction of the incident light, so that the change in contrast is small for a viewing angle change in a direction that is important for viewing, and is small for a viewing angle change in a direction that is not important for viewing. It is provided with a property showing a diffusivity that is not practically problematic.

Next, a haze composed of a resin containing silica fine particles of 45%, thickness
A μm anti-glare sheet was bonded via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm, and was mounted on the prism surface of the reflector obtained above to obtain a reflection type liquid crystal display device (FIG. 1).

When the above-mentioned reflection type liquid crystal display device was visually recognized, moire caused by the reflection plate and ghost caused by the reflection on the back of the cell were not seen, and the change in the viewing angle in the direction perpendicular to the prism ridge line of the reflection plate was light and dark. There is almost no change in the difference, and the viewing angle change in the direction parallel to the prism ridge line shows the reflection characteristic of a normal diffuse reflector, and the display brightness is generally excellent,
The viewing angle range of good visibility was wide. FIG. 4 shows the characteristics of the reflected light when an anti-glare sheet is placed on the reflector. This indicates that a trapezoidal reflection characteristic is formed in the direction orthogonal to the prism ridge line of the reflector.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is a graph showing the reflection characteristics (curve A) of a reflection plate and the reflection characteristics (curve B) when an antiglare layer is disposed thereon.

FIG. 3 is a graph showing the reflection characteristics of the reflector used in Example 1.

FIG. 4 is a graph showing reflection characteristics when an anti-glare layer is arranged on the reflector used in Example 1.

FIG. 5 is a graph showing the reflection characteristics of a conventional reflector (curve C) or a prototype reflector (curve D).

FIG. 6 is an explanatory sectional view of a prototype reflector.

FIG. 7 is an explanatory sectional view of another prototype reflection plate.

[Explanation of symbols]

 1: Reflector 11: Base material 12: Reflective layer 2: Air layer 3: Anti-glare layer 4: Liquid crystal cell

Claims (3)

[Claims] 1. A reflector having a reflective layer made of a metal deposition layer provided on the prism-shaped irregular surface of a substrate having a repeating structure of prism-shaped irregularities, is disposed on the viewing back side of the liquid crystal cell via an air layer. A reflection type liquid crystal display device, wherein an antiglare layer is disposed between the air layer and the liquid crystal cell. 2. The reflection type liquid crystal display device according to claim 1, wherein the reflection plate has excellent specular reflection characteristics and the antiglare layer has excellent light scattering characteristics. 3. The reflective liquid crystal display device according to claim 1, wherein the antiglare layer has a polarization maintaining property of 95% or more.