JPS5893032A - Liquid crystal display panel - Google Patents

Abstract

PURPOSE:To minimize the appearance of color rings in a visual angle area by disposing the directions of optical axis planes that degrade the characteristics in visual angle in the direction where the frequencies of the visual angle are smallest. CONSTITUTION:Upper and lower substrates 1, 2 consisting of biaxially stretched flexible polymer films are disposed by unifying the planes thereof including two optical axes in one direction so that the direction where color rings appear and the direction where the frequencies of visual angles are largest intersect orthogonally with each other, wherein said planes are unified in the same direction with a polariziing microscope. The substrates are so disposed that their optical axis planes are at a right angle to the directions where the frequencies of visual angles are largest, and transpaent thin film electrodes of, for example, indium oxide, are patterned on the surfaces. The substrates 1, 2 are provided spacially and liquid crystals are sealed therebetween by placing a spacer between the substrates. An upper polarizing plate 3 is laminated on the outer side of the substrate 1 in such a way that the direction of the polarization thereof intersects orthogonally with the optical axis plane and a lower polarizing plate 4 is laminated in such a way that the direction of the polarization thereof parallels with the optical axis direction, whereby the liquid crystal display panel is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid crystal display panel, which is an important component in a liquid crystal display device.

A liquid crystal display panel consists of two upper and lower substrates with thin film electrodes placed one on top of the other with a gap between them, and a liquid crystal substance filled in the gap.#
It is an I-shaped device that displays graphic characters and the like by electro-optically modulating the liquid crystal material by applying a voltage to the electrodes. In this liquid crystal display panel, inorganic glass has traditionally been the mainstream for the transparent substrate used as the substrate, but it has been replaced by inorganic glass for reasons such as heavy fogging, weak impact resistance, and difficulty in processing. Recently, devices using transparent flexible polymer films have been introduced. By using a transparent flexible polymer film, it is possible to solve the problems of using inorganic glass, such as low weight, low impact resistance, and difficulty in processing. , the following undesirable phenomena are observed. That is, a flexible polymer film is used by being stretched with two wheels, but since the polymer takes on a two-wheel crystallinity due to the stress strain generated internally during stretching, the displayed figures, characters, etc. The disadvantage is that the coloring appears in various directions depending on the angle, making the display characteristics inconsistent and difficult to see.

To explain this development with reference to FIGS. 1 and 2, the optical layer refractive index curve of the two-ringed crystal of the polymer is as shown in FIG. 1, and the two refractive index curves intersect on the X-7 plane. As shown in FIG. 2, due to the symmetry of this distribution, there are two optical axes A 1 and A 2 . In this optical axis direction, there is no delay (retardation) between the two light waves, but as the two light waves deviate from the optical axis direction, the retardation increases sequentially from zero, and when the two light waves are sandwiched between polarizing plates, the display becomes colored due to interference between the two light waves. Shows the so-called coloring that appears to the eye. This coloring appears repeatedly in approximately the same color tone as a first-order interference color, a second-order color, and a third-order color depending on the magnitude of retardation. In this case, the order of retardation is 1st and 2nd order, but the lower the order, the clearer the color tone. The above viewing angle characteristics are greatly impaired. Such a phenomenon is not observed in liquid crystal display panels using isotropic and non-directional inorganic glass as a substrate, and conventionally there was no need to take this into account when manufacturing panels.

The present invention solves the above-mentioned drawbacks in liquid crystal display panels having upper and lower substrates using biaxially stretched transparent flexible polymer films. By arranging them in this direction, the appearance of coloring in the viewing angle range is suppressed to the maximum extent possible. That is, the present invention provides i
A liquid crystal layer is formed by placing a liquid crystal material between the upper and lower substrates made of two stretched transparent flexible polymer films, and applying a voltage to the electrodes to electro-optically modulate the liquid crystal material. By doing so, in two liquid crystal display panels that display characters, figures, etc., the surfaces including the two optical axes of the upper and lower substrates are arranged so that the direction in which the coloring appears and the direction with the highest visual frequency are orthogonal to each other. The gist of the present invention is a liquid crystal display panel arranged so as to be aligned in both directions.

The present invention will be explained below based on the drawings. Fig. 3 shows the structure of the liquid crystal display panel of the present invention, and 1.2 is an electrode (
(not shown) and a lower substrate, each consisting of two-wheeled stretched flexible polymer film. Specific examples of the flexible polymer film include synthetic resin films such as polyethylene terephthalate film, polycarbonate film, and polyethersulfone film. In the present invention, the surface including the two optical axes (optical axis surface) of the upper substrate 1 and the lower substrate 2 is arranged in one direction so that the appearance direction of the coloring and the direction of the largest viewing angle are orthogonal to each other. The upper and lower substrates 1.2 can be aligned in the same direction by measuring their respective optical axes using a polarizing microscope. Then, an electrode made of a transparent thin film of indium oxide, tin oxide, or the like is patterned on the surface of the electrode so as to be arranged perpendicular to the direction in which the visual inclination of the front axis is high. Next, place the upper and lower substrates 1.2 into 1Ill.
A spacer is provided and the liquid crystal is sealed in the gap by a known method. Next, an upper polarizing plate 3 is laminated on the outside of the upper substrate 1 so that its polarization direction (indicated by an arrow) is perpendicular to the optical axis plane, and a lower polarizing plate 4 is laminated so that its polarization direction (indicated by an arrow) is in the optical axis direction. They are stacked in parallel to form a liquid crystal display panel. The above explanation is about an example of a TIQ type (twisted nematic type) liquid crystal display panel, but it can of course also be applied to a GH type (guest host type) liquid crystal display panel in which a liquid crystal containing a multicolor pigment is enclosed. Polarizing plate 4 is not necessary.

As described above, in a liquid crystal display panel in which the upper and lower substrates are made of two-wheel-stretched transparent flexible polymer films, the present invention aims to define the planes containing the two optical axes of the upper and lower substrates as follows: - The direction in which coloring appears and the visual field. Conventional LCDs use flexible polymer films as upper and lower substrates, which are manufactured without taking the direction of the optical axis into account, because they are constructed with λ aligned in one direction so that the directions with the largest inclinations are orthogonal to each other. Unlike display panels, which are colored in all visual directions, the display characteristics are not impaired and the display is difficult to see, and the display has the advantage of being easy to see over a wide field of view.

[Brief explanation of drawings]

FIGS. 1 and 2 are explanatory views in the optical axis direction of a two-wheel stretched transparent flexible polymer film, and FIG. 3 is an explanatory perspective view of the structure of the liquid crystal display panel of the present invention. 1... Upper board 2... Lower board 3...
Upper polarizing plate 4... Lower polarizing plate agent Patent attorney Tsutomu Adachi Figure 1

Claims (1)

[Claims] 1. A liquid crystal layer is formed by disposing a liquid crystal material between upper and lower substrates made of two-wheel stretched transparent flexible polymer films having thin film electrodes on their surfaces, and applying a voltage to the electrodes. In a liquid crystal display panel that displays characters, figures, etc. by electro-optically modulating a liquid crystal substance, the surface including the two optical axes between the upper and lower substrates is determined in the direction in which the coloring appears and the visual intensity. A liquid crystal display panel characterized in that the panels are arranged in one direction so that the largest directions are orthogonal to each other. 2. The liquid crystal display panel according to claim 1, wherein the normal direction to the plane including the two optical axes of the upper and lower substrates is parallel to the thickness direction of the liquid crystal display panel.