JPH11190803A - Reflection plate, reflection type polarizing plate and reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the display having a bright and good visibility even when the display is viewed from the angle, in which the reflection of external light beams is being avoided, by setting the angle of the recessed or the projected sections formed on the surface section of the reflection plate with respect to a horizontal surface to be within a specific angular range. SOLUTION: The surface section of the reflection plate has the structure in which the groups of recessed or projected sections are densely formed on the whole surface and the angle between the recessed or the projected sections and a horizontal surface is set to 2.5 to 20 degrees. The following is an example of the method in which the surface section of the substrate of the reflection plate is formed, i.e., negative molds having objective shapes are formed on a roll and the shapes are provided by a roll transfer method. The reflection type polarizing plate, which is suitable for a reflection type liquid crystal display device, is formed by laminating the reflection plate on a polarizing plate with acrylic adhesive. By mounting the reflection plate or the reflection type polarizing plate on a liquid crystal display device, the reflection type liquid crystal display device having a superior visibility is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reflection plate, a reflection type polarizing plate and a reflection type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been used in various fields such as notebooks, personal computers, electronic notebooks, portable information terminals, amusement devices, stationery, mobile phones, and the like. Among them, portable devices often use a reflection type liquid crystal display device. As such a reflection type liquid crystal display device, for example, the configuration of a first polarizing plate / liquid crystal cell / second polarizing plate / reflecting plate using a TN type (twisted nematic type) or STN type (super twisted nematic type) as a liquid crystal cell. Liquid crystal display device (reflection type TN type liquid crystal display device, reflection type STN type liquid crystal display device) and a liquid crystal display device having a liquid crystal cell / reflection plate configuration using a GH type liquid crystal cell (guest host type cell) as a liquid crystal cell. (Reflective GH type liquid crystal display device) and the like are known. More recently, a reflection type liquid crystal display device having a configuration in which a reflection plate is provided in a liquid crystal cell is also known.

[0003] However, all display devices tend to be inferior in visibility from an angle where external light is not reflected, so that visibility is better when viewed from an angle where external light is not reflected. Liquid crystal display devices have been desired.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present inventors have proposed a reflection type liquid crystal display device which provides a bright and good visibility display even when viewed from an angle where external light is not reflected. As a result of intensive studies to develop a plate, the present inventors have found that such a problem can be solved by using a reflector having a specific shape, and arrived at the present invention.

[0005]

That is, the present invention has a structure in which the surface of the reflector has a structure in which a group of concaves or convexes is formed densely over the entire surface, and the angle formed by the concaves or convexes with the horizontal plane is 2.5 degrees. A reflection plate, which is 20 degrees to 20 degrees.
It is an object of the present invention to provide a reflection type polarizing plate obtained by laminating the reflection plates, and a reflection type liquid crystal display device provided with the reflection plate. By using the reflection plate of the present invention, a reflective liquid crystal display device which is bright and has good visibility can be obtained at any angle where reflection of external light is avoided.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The surface portion of the reflector of the present invention has a structure in which a group of concave portions or convex portions is formed densely over the entire surface, and the angle formed by the concave portions or convex portions with the horizontal plane is 2.5 to 20 degrees. FIG. 1 is a sectional view showing an example of the reflection plate of the present invention.
It suffices if the elevation angle of the surface with the horizontal plane is 2.5 degrees or more and 20 degrees or less. Preferably, it is 2.5 degrees or more and 15 degrees or less, more preferably 2.5 degrees or more and 10 degrees or less.

The diameter of the circle of the concave portion or the convex portion on the surface of the reflector is not particularly limited, but is preferably 500 μm or less from the viewpoint of reducing the horizontal plane and making the irregularities less noticeable.

Examples of the base material of the reflection plate of the present invention include plastic films such as polyethylene terephthalate film, polyester film, polycarbonate film, polyacryl film and polyolefin film, metal plates such as aluminum plate and copper plate, and glass plate. Can be The thickness of the substrate is not particularly limited, but is, for example, about 10 μm to 5 mm, and may be plate-like, sheet-like, or film-like.

As a method for forming the surface portion of the base material of the reflecting plate into the above-mentioned shape, for example, (1) a method of forming a negative mold having a desired shape on a roll and giving the shape by a roll transfer method, 2) A negative mold of the desired shape is formed on the roll, and an ultraviolet ray or electron beam curable resin is applied and filled into the concave portion. A method of irradiating an electron beam and peeling a base film to which a cured resin is adhered from a roll (JP-A-3-223883, JP-A-6-3242)
No. 05), (3) A method in which a negative mold having a desired shape is formed on a casting belt, and the casting is performed by a solvent casting method to give a desired shape at the time of casting. Examples include a method of directly imparting a desired shape with a cutting tool, and (5) a method of coating a fine particle-dispersed resin.

When the reflecting surface of the reflecting plate base material is made of a base material having low reflectivity such as plastic, a metal having high reflectivity such as aluminum or silver is deposited on the surface. The method of depositing a metal with high reflectivity and the thickness of the deposition are not limited at all, and include, for example, a method usually used for forming a metal thin film such as a vacuum deposition method, a sputtering method, and an ion plating method. What is necessary is just to select and use suitably according to the kind of base material. The thickness of the deposition is, for example, 50
nm to about 100 nm.

When deposition is performed using silver as a metal having a high reflectance characteristic, in order to prevent deterioration of the deposited layer,
It is preferable to provide a protective film on the front and back surfaces of the silver deposition layer. Although there is no particular limitation as the protective film, for example, acrylic resin,
Examples include a coating film of an epoxy resin, a polyester resin, a urethane resin, and an alkyd resin. For example, the coating film can be applied by a usual method such as roll coating, gravure coating, or spray coating. In addition, SiO2
Alternatively, an inorganic thin film such as an inorganic thin film can be used, and in this case, a vapor deposition method may be used. The thickness of the protective film is not particularly limited, but is, for example, in the range of 5 nm to 20 μm.

When a metal plate such as an aluminum plate is used as the substrate, it can be used as a light reflection layer of a reflection plate without depositing a metal having a high reflectance.

In many cases, it is necessary to appropriately scatter reflected light from the light reflecting layer having a high reflectance. In this case, the reflecting surface may be roughened, or the upper surface of the reflecting surface may be roughened. A light diffusion layer may be provided.

When the reflective surface is roughened, the surface roughness is preferably in the range of 200 nm to 1500 nm in terms of center line average roughness (for example, measured by 3ST manufactured by Dektac). 2
If it is less than 00 nm, sufficient irregular reflection characteristics cannot be obtained.
If it is larger than 1500 nm, the maximum reflectance decreases, which is not preferable. Examples of a method of making the surface have such a center line average roughness include a method of previously roughening the surface of a negative plate, a method of pressing a resin mixed with organic / inorganic fine particles against the negative plate, After forming the desired shape, a method of sandblasting the surface, after forming the desired shape, a method of coating the surface with a coating liquid containing inorganic / organic fine particles, and the like can be mentioned.

Examples of the method of providing the light diffusion layer on the reflection surface include a method of coating fine particles on the reflection surface using a resin binder, and a method of laminating a film having light diffusion characteristics.

The fine particles used when coating the fine particles on the reflecting surface using a resin binder include:
Inorganic fine particles such as silica, calcium carbonate, pearl pigments such as synthetic or natural mica coated with titanium dioxide, pearlescent fine particles such as plate-like fish scale foil, hexagonal plate-like basic lead carbonate, and polymethyl methacrylate beads,
Organic fine particles such as polycarbonate beads, polystyrene beads, and silicon beads are exemplified. Such fine particles may be used alone or in combination of two or more.
The resin binder is not particularly limited, but examples thereof include an acrylic resin, a urethane resin, an epoxy resin, a polyester resin, and an alkyd resin. These resin binders may have adhesive properties. In order to form the light diffusion layer, for example, after mixing the fine particles and the resin, it may be applied by a usual method such as roll coating, gravure coating, spray coating and the like. The coating thickness is about 5 to 50 μm.

Examples of the film used when laminating a film having light diffusion properties include a film coated with a resin mixed with the same organic and / or inorganic fine particles as described above, or an organic and / or inorganic fine particle. Examples thereof include a film obtained by casting the mixed resin, a film in which the surface of the film is embossed, and the like, but are not particularly limited as long as the film has a diffusion property. The method of laminating the film may be an ordinary method such as using a known acrylic pressure-sensitive adhesive, and is not particularly limited.

The reflection plate of the present invention can be laminated on a polarization plate with, for example, an acrylic adhesive to form a reflection type polarization plate suitable for a reflection type liquid crystal display device. By mounting such a reflection plate or a reflection type polarizing plate on a liquid crystal display device, a reflection type liquid crystal display device having excellent visibility can be obtained. Examples of the configuration of the reflection type liquid crystal display device include (polarizing plate /
A reflection type liquid crystal display device having a configuration of TN type liquid crystal cell / polarizing plate / reflection plate, (polarization plate / phase difference plate / STN type liquid crystal cell /
A reflection type liquid crystal display device having a configuration of a polarizing plate / reflection plate;
Examples thereof include a reflection type liquid crystal display device having a configuration of (H cell / reflection plate), but are not limited thereto. In addition, one or two or more retardation plates may be arranged on the upper surface and / or the lower surface of the liquid crystal cell in these configurations.

[0020]

The reflection type liquid crystal display device using the reflection plate according to the present invention has a brighter display screen when viewed from an angle where external light is not reflected, as compared with the conventional reflection type liquid crystal display device. Excellent in nature.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples.

Example 1 A sectional shape shown in FIG. 2 [an angle (elevation angle) formed by the section is 10 degrees]
When a plastic sheet having aluminum is subjected to aluminum evaporation, it becomes a reflector. This reflective plate is bonded to a polarizing plate (for example, SJ grade manufactured by Sumitomo Chemical Co., Ltd.) via an acrylic adhesive to form a reflective polarizing plate (polarizing plate / reflecting plate).
This reflective polarizing plate is mounted on an STN liquid crystal cell, and a retardation plate (eg, SEF manufactured by Sumitomo Chemical Co., Ltd.) is provided on the opposite side.
And a polarizing plate (for example, SJ manufactured by Sumitomo Chemical Co., Ltd.), and a reflective STN liquid crystal display device (polarizing plate / retardation plate /
STN liquid crystal cell / polarizing plate / reflecting plate). This reflective liquid crystal display device is bright and has good visibility when viewed from an angle where reflection of external light is avoided.

Example 2 Even when the center line average roughness of the reflector obtained in Example 1 was set to 500 nm, when the reflector was bonded to a polarizing plate (for example, SJ grade manufactured by Sumitomo Chemical Co., Ltd.), the reflection type was used. A polarizing plate (polarizing plate / reflecting plate) is obtained. Further, this reflective polarizing plate is mounted on an STN liquid crystal cell, and on the opposite side, a retardation plate (for example, SEF manufactured by Sumitomo Chemical Co., Ltd.) and a polarizing plate (for example, SJ manufactured by Sumitomo Chemical Co., Ltd.) are mounted to reflect the light. A type STN liquid crystal display device (polarizer / retarder / STN liquid crystal cell / polarizer / reflector) is obtained. This reflective liquid crystal display device, when viewed from an angle where reflection of external light is avoided,
Bright and good visibility. Example 3 A light-diffusing layer was provided on the surface of the reflector obtained in Example 1 and bonded to a polarizing plate (for example, SJ grade manufactured by Sumitomo Chemical Co., Ltd.) to obtain a reflective polarizing plate (polarizing plate / reflecting plate). Also, this reflective polarizing plate is mounted on an STN liquid crystal cell, and a phase difference plate (eg, SE manufactured by Sumitomo Chemical Co., Ltd.) is provided on the opposite side.
F) and polarizing plate (for example, SJ manufactured by Sumitomo Chemical Co., Ltd.)
To obtain a reflective STN liquid crystal display device (polarizer / phase plate / STN liquid crystal cell / polarizer / reflector). This reflective liquid crystal display device is bright and has good visibility when viewed from an angle where reflection of external light is avoided. Example 4 A plastic sheet having the cross-sectional shape shown in FIG. 2 (an angle formed by the cross section (elevation angle) is 6 degrees) is subjected to aluminum vapor deposition to form a reflector. This reflective plate is bonded to a polarizing plate (for example, SJ grade manufactured by Sumitomo Chemical Co., Ltd.) via an acrylic adhesive to form a reflective polarizing plate (polarizing plate / reflecting plate). The reflective polarizing plate is mounted on an STN liquid crystal cell, and a retardation plate (for example, SEF manufactured by Sumitomo Chemical Co., Ltd.) and a polarizing plate (for example, SJ manufactured by Sumitomo Chemical Co., Ltd.) are mounted on the opposite sides of the STN liquid crystal cell. Liquid crystal display (Polarizer / Phase plate / S
TN liquid crystal cell / polarizing plate / reflecting plate). This reflective liquid crystal display device is bright and has good visibility when viewed from an angle where reflection of external light is avoided. Example 5 A light-diffusing layer is provided on the surface of the reflection / reflection plate obtained in Example 4, and is laminated with a polarization plate (for example, SJ grade manufactured by Sumitomo Chemical Co., Ltd.) to obtain a reflection-type polarization plate (polarization plate / reflection plate). . Also, this reflective polarizing plate is mounted on an STN liquid crystal cell, and a retardation plate (for example, SEF manufactured by Sumitomo Chemical Co., Ltd.) and a polarizing plate (for example, SJ manufactured by Sumitomo Chemical Co., Ltd.) are mounted on the opposite side to reflect light. A type STN liquid crystal display device (polarizer / retarder / STN liquid crystal cell / polarizer / reflector) is obtained. This reflective liquid crystal display device is bright and has good visibility when viewed from an angle where reflection of external light is avoided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a reflection plate of the present invention.

FIG. 2 is a sectional view of a reflector obtained in Example 1.

FIG. 3 is a sectional view of a reflector obtained in Example 4.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G02F 1/1335 510 G02F 1/1335 510 520 520

Claims (4)

[Claims] The surface portion of the reflector has a structure in which a group of concave portions or convex portions is formed densely over the entire surface, and the angle formed by the concave portions or convex portions with a horizontal plane is 2.5 to 20 degrees. Characteristic reflector. 2. A reflection type polarizing plate obtained by laminating the reflection plate according to claim 1 on a polarizing plate. 3. A reflection type liquid crystal display device comprising the reflection plate according to claim 1. 4. A reflection type liquid crystal display device comprising the reflection type polarizing plate according to claim 2.