JPH087361Y2 - Phase difference plate and liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a novel retardation plate used in a liquid crystal display device and the like and a liquid crystal display device using the same.

<Prior Art> A conventional retardation plate is composed of a birefringent polymer film having in-plane uniaxial orientation.

The retardation plate can be used as an optical compensation plate in a liquid crystal display device to improve the display quality of the liquid crystal display device.

<Problems to be Solved by the Invention> A liquid crystal display device using a conventional retardation plate can perform relatively good black and white display, but has a problem of a narrow viewing angle.

<Means for Solving the Problems> The retardation plate of the present invention is a retardation plate composed of a polymer film having in-plane uniaxial orientation and a polymer film having uniaxial orientation in the thickness direction. It is a novel retardation plate that can improve the viewing angle of a liquid crystal display device by using it as an optical compensation plate of an STN type liquid crystal display device in which the twist angle of liquid crystal molecules is 180 ° or more.

Hereinafter, the retardation plate of the present invention will be described in comparison with a conventional one. 2 and 3 show a conventional retardation plate. Reference numeral 1 is a birefringent polymer film having in-plane uniaxial orientation. Here, having in-plane uniaxial orientation means, for example, when a polymer film having no orientation is stretched in a certain direction, a polymer film having uniaxial orientation in that direction can be obtained. I shall say. The means for imparting the uniaxial orientation is not particularly limited.

An example of an STN type liquid crystal display device using a retardation plate as an optical compensation plate is shown in FIG.

In FIG. 4, 4 (4a, 4b and 4c) is a retardation plate, 5 is a pair of polarizing plates, and 6 is an STN liquid crystal cell. The STN liquid crystal display device using the conventional retardation plate (4b) shown in FIG.
There is little coloring peculiar to the liquid crystal display device, and the display is close to its own black, but there is a problem that the viewing angle is narrow.

For the purpose of improving the viewing angle, a retardation plate (Fig. 3) has been proposed in which two films having in-plane uniaxial orientation are laminated by changing the orientation axis angle. In Figure 3, 1,
1'is a birefringent polymer film having in-plane uniaxial orientation, and 3 is an adhesive or pressure-sensitive adhesive for adhering them.

When the retardation plate 4c shown in FIG. 3 is used as an optical compensation plate, the viewing angle is slightly improved as compared with the case where the retardation plate shown in FIG. 2 is used. However, in order to improve the viewing angle by using a polymer having in-plane uniaxial orientation as described above, it is necessary to stack about 10 sheets, which results in poor productivity and high cost. It was

Therefore, the present invention provides a retardation plate having two black and white polymer films and a black-and-white display of an STN type liquid crystal display device and good viewing angle characteristics in view of the above-mentioned drawbacks of the conventional retardation plate. The purpose is to do.

That is, the present invention relates to a retardation plate comprising a polymer film having in-plane uniaxial orientation and a polymer film having uniaxial orientation in the thickness direction, and a liquid crystal display device using the same. is there.

 Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a retardation plate according to the present invention. In FIG. 1, reference numeral 1 denotes a polymer film having in-plane uniaxial orientation, which is obtained, for example, by copolymerizing a polycarbonate resin, methyl polymethylmethacrylate (meth) acrylate as a main component with another ethylene comonomer. Poly (meth) acrylate resin such as methyl (meth) acrylate copolymer, polystyrene, polystyrene resin such as styrene copolymer obtained by copolymerizing polystyrene, styrene as a main component with other ethylene-based comonomer, poly Acrylonitrile, acrylonitrile resin such as acrylonitrile copolymer, polyester resin such as polyethylene terephthalate, polyester copolymer,
Polyamide resin such as nylon 6 and nylon 66, polyvinyl chloride resin such as polyvinyl chloride and vinyl chloride copolymer, polyolefin resin such as polyethylene, polypropylene, ethylene copolymer and propylene copolymer, polysulfone, poly At least one or more selected from ether sulfone, fluorine-based resin and the like and their modified products, and blending these resins with a transparent low-molecular compound or a transparent inorganic compound such as a high-molecular liquid crystal or a low-molecular liquid crystal. It is obtained by uniaxially stretching a film or sheet by a known method such as a roll stretching method, a tenter stretching method, or a roll compression stretching method. Reference numeral 2 denotes a polymer film having uniaxial orientation in the thickness direction, which is obtained by imparting uniaxial orientation in the thickness direction by compression molding or the like of the polymer compound or the like exemplified in the above description of 1. 3 is an adhesive layer or pressure-sensitive adhesive layer for laminating 1 and 2, and as the adhesive or pressure-sensitive adhesive, a known one having excellent transparency and durability can be used.

The method of applying the retardation plate of the present invention to an STN type liquid crystal display device is not particularly limited, and for example, one side or both sides of the retardation plate shown in FIG. Use by pasting. Either 1 or 2 may be disposed on the liquid crystal cell side, or may be disposed between the upper polarizing plate and the liquid crystal cell or between the lower polarizing plate and the liquid crystal cell. Further, 1 and 2 do not necessarily have to be laminated, and as a configuration of the liquid crystal display device, they do not necessarily have to be in contact with adjacent positions.

STN without laminating the films 1 and 2 in Fig. 1
The objects and effects of the present invention can also be achieved by appropriately arranging the liquid crystal display devices individually.

The retardation plate of FIG. 1 exemplifying the present invention works in a direction in which the retardation when viewed from an oblique direction cancels out. Therefore, if the retardation plate is used as an optical compensation plate of an STN type liquid crystal display device,
In addition to black and white display, the viewing angle is widened and the viewing angle characteristics are improved, so that the display characteristics of the STN type liquid crystal display device can be significantly improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a retardation plate according to the present invention, FIGS. 2 and 3 are conventional retardation plates, and FIG. 4 is an example of an STN type liquid crystal display device using the retardation plate. . 1,1 ′ …… Polymer film having uniaxial orientation in the plane 2 …… Polymer film having uniaxial orientation in the thickness direction 3 …… Adhesives or adhesives 4a, 4b and 4c …… Phase retarder 5 ...... Polarizing plate 6 …… STN liquid crystal cell

Claims (2)

[Scope of utility model registration request] 1. A retardation plate comprising a polymer film having in-plane uniaxial orientation and a polymer film having uniaxial orientation in the thickness direction. 2. A liquid crystal display device having a polymer film layer having in-plane uniaxial orientation and a polymer film layer having uniaxial orientation in the thickness direction.