JPS6026322A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent coloring phenomenon by using a specified polymer for a transparent film having the polymer oriented in a specified direction and exhibiting birefringence, and forming this film between a linearly polarizing plate on one side and a TN crystal layer. CONSTITUTION:A TN liquid crystal layer 4 is sandwiched with two linearly polarizing plates 6, 7 each having a polarizing axis crossing each other at right angles, and a transparent film 7 having a polymer oriented in a specified direction and exhibiting optical birefringence and erasing coloring display phenomenon is inserted between one of the plates 6, 7 and the layer 4. Polycarbonate, a copolymer of tetrafluoroethylene and hexafluoroethylene, or polyfluoroethylene propylene ether is used for the material of this film 7. The rotation angle of this film 7 is controlled so as to maximize the erasion effect of said phenomenon. As a result, the coloring phenomenon remarkably occurring especially in a large- sized cell can be easily erased, an off-grade rate in manufacture can be lowered, further, occurrence of elliptic polarization can be reduced, and contrast can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a novel liquid crystal display device that eliminates interference colors.

<Prior art> Conventionally, the basic structure of a TN type liquid crystal display device is to form transparent electrodes on the inner surfaces of two transparent substrates, fill the space between the two substrates with liquid crystal, and then It is made by pasting two polarizing plates having mutually orthogonal polarizing axes on the front and back outer sides of a substrate. In the case of a reflective TN type liquid crystal display element, a reflective plate made of aluminum or the like is arranged behind the rear polarizing plate. In the TN type liquid crystal display element having this structure, there has conventionally been a phenomenon in which the light transmittance differs depending on the wavelength due to non-uniformity of the cell thickness, the thickness of the liquid crystal alignment film, the birefringence of the liquid crystal material, and the like. As a result of this phenomenon, a so-called coloring phenomenon in which specific colors such as light color, green, etc. appear on the display element occurs. Recently, technological progress has been remarkable, and the above coloring phenomenon has been prevented to a considerable extent. However, it is difficult to uniformize cell thickness with high accuracy in large cells, etc., and countermeasures against the above coloring phenomenon are especially desired. Ta.

Purpose The present invention has been made to solve the above-mentioned conventional problems, and its purpose is to prevent the above-mentioned coloring phenomenon of a liquid crystal display element by a relatively simple means.

<Examples> Examples of the liquid crystal display element according to the present invention will be described in detail below.

FIG. 1 is an explanatory diagram of the configuration of an embodiment of a liquid crystal display element according to the present invention. 1 is a liquid crystal cell in which twisted nematic liquid crystal is sealed. 2.2fd glass substrate (a transparent plastic film substrate with optical isotropy may also be used)
), 3 is a sole agent, and 4 is a liquid crystal. 5 is a linear polarizing plate on the front side, and 6 is a linear polarizing plate on the back side. The above linear polarizing plate 5
and the linearly polarizing plate 6 have their polarization axes orthogonal to each other. This polarizing plate includes a polarizing layer made of a PVA (polyvinyl alcohol) film doped with iodine or a dye, sandwiched between two protective layers (for example, triacetyl cellulose);
Alternatively, a axial plastic film with dyes oriented in a predetermined direction can be used. 7 is a transparent film in which polymers are oriented in a specific direction and exhibits optical birefringence. The properties of this transparent film 7 are as follows: The transparent film 7 is inserted between two linear polarizing plates whose polarization planes are perpendicular to each other, and while white light is incident on the linear polarizing plates, only the transparent film 7 is rotated. It has the property that the amount of transmitted light changes over time. However, at this time, no interference color occurs. Examples of excellent transparent films 7 include polycarbonate (manufactured by Mitsubishi Gas Chemical Co., Ltd.), copolymer of tetrafluoroethylene and hexafluoride propylene (Toyoflon's FEP film, Toshiku Co., Ltd.), and fluoride. Ethylene propylene ether (Toyoflon EPE film, manufactured by Toshiku Co., Ltd.) was found. Inserting the transparent film 7 between two linear polarizing plates whose polarization planes are orthogonal to each other,
Moreover, the transmitted light has the same positional relationship with respect to the linear polarizing plates 5 and 6 of FIG. 1 as the position where the intermediate state between the bright state and the dark state is shown. When the transparent film 7 is arranged in this way, the transparent film 7
Even if a coloring phenomenon existed when no color was present, the coloring phenomenon could be eliminated by the arrangement of the transparent film 7. The effect of eliminating this coloring phenomenon differs in magnitude depending on the thickness of the transparent film 7. Specifically, when the transparent film 7 was made of polycarbonate, the film thickness was medium at 100 μm, large at 200 μm, and relatively small at 300 μm. In addition, in the case of a copolymer of tetrafluoroethylene and 67-fluoropropylene, the film thickness is 25%.
Although there was no effect at 50 μm and 100 μm, a great effect was obtained at 50 μm and 100 μm.

In the case of fluorinated ethylene propylene ether, the film thickness is 5
A great effect was obtained at 0 μm. Incidentally, since the effect of eliminating the coloring phenomenon varies depending on the rotation angle of the transparent film 7, this rotation angle may be adjusted as appropriate so that the effect of eliminating the coloring phenomenon is maximized.

In addition to the material of the transparent film 7 mentioned above, the effect was obtained with the following materials (however, the above-mentioned transparent film 7 was more useful.) Namely, polyether sulfone with a film thickness of 100 μm (manufactured by Susumu Kagaku) Aromatic epoxy with a film thickness of 100 μm, nocellophane with a film thickness of 50 μm, film thickness 12
5 μm of 47-fluoroethylene and perfluoroalkoxyethylene co-MIF0 Yoflon PFA (manufactured by Toshiku Co., Ltd.), and polypropylene (Torefan BO (manufactured by Toshishiku Co., Ltd.)) with a film thickness of 50 μm.

The present invention is applicable to liquid crystal display devices having various structures other than the structure shown in FIG. That is, as shown in FIG. 2, a transparent film 7 in which polymers are oriented in a specific direction may be placed between the liquid crystal cell 1 and the linear polarizing plate 6 on the back side. Further, as shown in FIG. 3, one substrate of the liquid crystal cell 1 may be a transparent film 7 in which polymers are oriented in a specific direction. In addition, as shown in FIG. 4, a polarizing layer 8 (PVA (polyvinyl alcohol)
A structure in which a film doped with iodine or a dye) is sandwiched between an optically isotropic film 9 and a transparent film 7 in which a polymer is oriented in a specific direction may be used. In this case, this linear polarizing plate 5 may be used as the front substrate of the liquid crystal cell 1. Further, as shown in FIG. 5, the front linear polarizing plate 5 is constructed by integrating a uniaxially anisotropic polymer film IO with dyes oriented and a transparent film 7 with polymers oriented in a specific direction. Good too. In this case, the linear polarizing plate 5 may be used as the front substrate of the liquid crystal cell 1. Note that the above configuration can also be applied to the linear polarizing plate 6 on the back side.

In the following second embodiment, the present invention was applied to a transmissive type liquid crystal display element, but when used as a reflective type, a reflective layer can be integrated behind the rear polarizing plate. good.

<Effects> According to the present invention, it is possible to eliminate the discoloration phenomenon that occurs particularly in large cells by relatively simple means, and it is possible to change what was conventionally considered defective due to discoloration to a good product. This has excellent effects. Furthermore, the occurrence of elliptically polarized light can be reduced, and contrast can be improved.

[Brief explanation of the drawing]

1 to 5 show side cross-sectional configuration explanatory views of various embodiments of a liquid crystal display device according to the present invention. In the figure, 1: liquid crystal cell 2 glass substrate 3: glue agent
4: Liquid crystal 5: Linear polarizing plate on the front side 6: Linear polarizing plate on the back side 7: Transparent film 8: Polarizing layer 9: Isotropic film 10: Dye orientation - axially anisotropic polymer film Agent Patent attorney Ai Fukuji Hiko (2 others) Figure 2 Figure 4 Figure 5

Claims (1)

[Claims]! , comprising two linearly polarizing plates sandwiching a twisted nematic liquid crystal layer and having polarization axes orthogonal to each other, and between one linearly polarizing plate of the two linearly polarizing plates and the twisted nematic liquid crystal layer, a specific direction is provided. A liquid crystal display device in which a transparent film exhibiting optical birefringence in which polymers are oriented and arranged in a direction that eliminates the coloring phenomenon of the display, the material of the transparent film being polycarbonate or polycarbonate. A liquid crystal display device characterized in that it is a copolymer of ethylene and 67-fluorinated propylene or fluorinated ethylene propylene ether.