JPH11190840A - Reflection plate, reflection type polarizing plate and reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a bright and good visibility even though the device is viewed from the angle, in which the reflection of external light beams is avoided, by having the reflection plate display section of the device whose cross section has the shape of circular-arcs being connected together and setting the angle between a base line and the tangent of the circle at the point of intersection of the circular-arc and the base to be within a specific range. SOLUTION: The reflection plate has a reflection plate display section whose cross section has the shape of circular-arcs being connected together and the angle (an angle of elevation) between the base line and the tangent of the circle at the intersection of the circular-arc and the base line is set to be within the range of 2.5 to 20 degrees. The following method is used, for example, to form the shape of the substrate surface section of the reflection plate, i.e., negative types having the objective shapes are formed on a roll and the forms are made by a roll transfer method. The reflection plate is made by laminating on a polarizing plate with acrylic adhesive and the plate is made into a reflection type polarizing 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, 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]

In other words, according to the present invention, the surface of the reflector has a cross section formed by a series of arcs, and the angle (elevation angle) between the tangent of the circle and the base at the intersection of the base and the arc is 2 degrees. A reflective plate characterized by a range of 0.5 to 20 degrees, a reflective polarizing plate obtained by laminating the reflective plates, and a reflective liquid crystal display device provided with the reflective plate. It is. 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.

In the reflector of the present invention, the cross section of the surface of the reflector is formed by a series of arcs, and the angle (elevation angle) between the tangent of the circle and the base at the intersection of the base and the arc is 2.5 to 20 degrees. It is. FIG. 1 shows an example of the reflection plate of the present invention. In such a reflector, the elevation angle is 2.5 to 20 degrees, preferably 2.
5 degrees to 15 degrees, more preferably 2.5 degrees to 10 degrees.

The pitch of the circular arc of the cross section, that is, the length of the base of the circular arc parallel to the reflecting plate surface is not particularly limited. However, from the viewpoint of obtaining a regular shape and the fact that the streak is not so noticeable, it is 10 μm. To 500 μm is preferred. If it is less than 10 μm, it is difficult to obtain a regular shape, and if it is more than 500 μm, streaks are noticeable, which is not preferable.

When the reflector of the present invention is incorporated in a liquid crystal display device, the pixel pitch of the liquid crystal cell and the pitch of the reflector may interfere to generate moire fringes. In order to prevent the occurrence of moiré fringes, it is practically necessary to match the pixel pitch of the liquid crystal cell with the pitch of the reflector, to change the length of the base of adjacent polygons, or to reduce the pitch of the polygons to 100 μm or less. preferable.

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.

In order to make 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 type having a desired shape on a roll and giving the shape by a roll transfer method; 2)
After forming a negative mold of the desired shape on the roll, applying an ultraviolet or electron beam curable resin and filling the recess, the ultraviolet or electron beam is applied while the transparent substrate film is covered on the roll intaglio through the resin liquid. Irradiating the substrate film to which the cured resin is adhered from a roll
(2) JP-A-223883, JP-A-6-324205), (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 the desired shape at the time of casting. Or (4) a method of directly imparting a desired shape to a reflecting plate base material with a cutting tool.

When the reflecting surface of the reflecting plate base material is made of a base material having low reflectivity such as plastic,
For example, a metal with high reflectivity such as aluminum or silver is deposited. 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, SiO ₂
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 the reflection plate without depositing a metal having a high reflectance.

In many cases, it is necessary to appropriately scatter the light reflected from the light-reflecting layer having a high reflectivity. In this case, for example, the surface may be roughened, or the light-diffusing layer may be provided above the surface. May be provided. When the surface is roughened, the surface roughness is determined by the center line average roughness (for example, 3ST manufactured by Dektac).
In the range of 200 nm to 1500 nm. If it is less than 200 nm, sufficient irregular reflection characteristics cannot be obtained,
On the other hand, if it is larger than 1500 nm, the maximum reflectance is undesirably lowered. As a method of making the surface have such a center line average roughness, specifically, for example, a method in which the surface of a negative plate is roughened in advance, or a resin in which organic / inorganic fine particles are mixed is converted into a negative plate. Examples of the method include a pressing method, a method of forming a desired shape and then sandblasting the surface, and a method of forming a desired shape and coating the surface with a coating liquid containing inorganic / organic fine particles. When a light diffusion layer is provided on the reflection surface, examples of the method for providing the light diffusion layer include a method in which fine particles are coated on the reflection surface using a resin binder, a method in which a film having light diffusion characteristics is laminated, and the like. Is mentioned.

When the fine particles are coated on the reflection surface using a resin binder, the fine particles used 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.

In the case of laminating a film having a light diffusion property, the film may be a film coated with a resin in which organic and / or inorganic fine particles are mixed as described above, or a mixture of organic and / or inorganic fine particles. Film obtained by casting the resin, or
Examples thereof include a film in which the surface of the film is embossed, and the like is not particularly limited as long as the film has diffusion characteristics. 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 the 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. As a configuration example of the reflection type liquid crystal display device, for example, a reflection type liquid crystal display device having a configuration of (polarization plate / TN type liquid crystal cell / polarization plate / reflection plate) (polarization plate / phase difference plate / STN type liquid crystal cell / polarization plate) / Reflection plate), but are not limited to, a reflection type liquid crystal display device having a configuration of (GH cell / reflection plate). 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.

[0019]

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.

[0020]

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 reflective substrate (plastic) in which the cross section has a shape in which arcs are connected, the angle (elevation angle) between the tangent of the circle and the base at the intersection of the base and the arc is 10 degrees, and the repetition pitch is 100 μm. Sheet] is subjected to aluminum evaporation to obtain a reflection plate. This reflective plate is bonded to a polarizing plate (SJ grade manufactured by Sumitomo Chemical Co., Ltd.) via an acrylic adhesive to obtain 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.
A 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 on the outermost surface of the liquid crystal display device is avoided.

Example 2 The center line average roughness of the reflector in Example 1 was 500 μm.
Even in this case, the reflection plate is bonded to a polarizing plate (SJ grade manufactured by Sumitomo Chemical Co., Ltd.) via an acrylic adhesive to obtain a reflection type polarizing plate (polarizing plate / reflecting 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 when viewed from an angle where reflection of external light on the outermost surface of the liquid crystal display device is avoided,
Good visibility.

Embodiment 3 A light diffusing layer is provided on the reflecting surface of the reflector obtained in Embodiment 1,
Polarizing plate (for example, SJ grade manufactured by Sumitomo Chemical Co., Ltd.)
Are laminated to obtain a reflection type polarizing plate (polarizing plate / reflecting plate). This reflective plate is bonded to a polarizing plate (SJ grade manufactured by Sumitomo Chemical Co., Ltd.) via an acrylic adhesive to obtain 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. A 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 on the outermost surface of the liquid crystal display device is avoided.

Example 4 A reflective substrate (plastic) whose cross section has a shape of a series of arcs, an angle (elevation angle) between the tangent of the circle and the base at the intersection of the base and the arc is 6 degrees, and the repetition pitch is 100 μm. Sheet] is subjected to aluminum evaporation to obtain a reflection plate. This reflective plate is bonded to a polarizing plate (for example, SJ grade manufactured by Sumitomo Chemical Co., Ltd.) via an acrylic adhesive to obtain 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. A 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 on the outermost surface of the liquid crystal display device is avoided.

Example 5 A light-diffusing layer is provided on the reflector obtained in Example 4 and is bonded to a polarizing plate (for example, SJ grade manufactured by Sumitomo Chemical Co., Ltd.) 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. A 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 on the outermost surface of the liquid crystal display device is avoided.

[Brief description of the drawings]

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

Claims (4)

[Claims] The cross section of the surface of the reflector is a series of arcs, and the angle (elevation angle) between the tangent of the circle and the base at the intersection of the base and the arc is 2.5 to 20 degrees. A 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.