JPH06148653A - Liquid crystal display element - Google Patents

Abstract

(57) [Summary] [Object] To provide a liquid crystal display device capable of reliably improving display quality by preventing generation of bright spots in a dark display region due to interposition of spacers. In a liquid crystal display element in which a polymer dispersed liquid crystal layer 7 is provided between a pair of transparent substrates 1 and 2 having transparent electrodes 3 and 4, a portion on one transparent substrate 1 and avoiding a pixel region A. Further, the spacer 5 is fixedly provided by the resin film 10, and the gap between the substrates 1 and 2 is kept substantially uniform by the spacer 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using a polymer dispersed liquid crystal.

[0002]

2. Description of the Related Art A polymer dispersed liquid crystal is a nematic liquid crystal dispersed in a transparent polymer material, and a liquid crystal display device using this polymer dispersed liquid crystal has a structure in which a transparent electrode is formed between a pair of transparent substrates. It has a structure in which a polymer dispersed liquid crystal layer is provided.

FIG. 5 shows the structure of a TFT active matrix type liquid crystal display device using polymer dispersed liquid crystal. In this liquid crystal display device, a polymer dispersed liquid crystal layer 7 is provided between a pair of transparent substrates (eg glass substrates) 1 and 2 on which transparent electrodes 3 and 4 are formed.
Spacers 5 are interspersed between the two so as to keep the gap between the substrates 1 and 2 substantially uniform.

The spacer 5 is composed of spherical glass particles, glass fibers cut into short pieces, and the like, and the pair of transparent substrates 1 and 2 are joined together at their peripheral portions via a frame-shaped sealing material 6, so that the polymer The dispersed liquid crystal layer 7 is composed of both substrates 1 and 2.
It is provided in a region surrounded by the sealing material 6 between.

The one electrode 3 is a pixel electrode, the other electrode 4 is a counter electrode, and a pixel area A is provided between the counter electrodes. The transparent substrate 2 is provided with a black mask 8 for preventing light leakage in a portion corresponding to each other between the pixel regions A arranged adjacent to each other, and the black mask 8 is covered with an insulating film 9. The transparent electrode 4 is formed on the substrate 9.

Such a liquid crystal display device has a transparent electrode 3,
After assembling the pair of substrates 1 and 2 on which the substrate 4 is formed with the spacer 5 sandwiched between them and joining the substrates 1 and 2 with the sealant 6 in between (both substrates A mixed liquid of a photo-curable polymer monomer and a liquid crystal is injected and filled in a gap surrounded by the seal material 6 between the first and second substrates by a vacuum injection method, and then the outer surface side of one substrate 1 Is irradiated with light (ultraviolet light) to polymerize the polymer monomer by photopolymerization to form the polymer dispersed liquid crystal layer 7.

The display is driven by applying an electric field between the electrodes 3 and 4 of the substrates 1 and 2, and the molecules of the liquid crystal in the polymer dispersed liquid crystal layer 7 are in a state where no electric field is applied. Since the light is directed in various directions and in this state, the light incident on the polymer-dispersed liquid crystal layer 7 is scattered by the light scattering action of the liquid crystal and the light scattering action at the interface between the liquid crystal and the polymer material, there is no electric field. The light transmittance of the portion becomes low, and in the case of a transmissive liquid crystal display element, a dark display state occurs.

When an electric field higher than the threshold voltage of the liquid crystal is applied between the electrodes 3 and 4, the molecules of the liquid crystal are uniformly arranged so as to be perpendicular to the surfaces of the substrates 1 and 2, and transmitted light is transmitted. Since the light is transmitted through the polymer-dispersed liquid crystal layer 7 with almost no light scattering effect, the light transmittance in the portion to which the electric field is applied is increased, and a transmissive liquid crystal display element is in a bright display state.

[0009]

However, in such a conventional liquid crystal display element, as shown in FIG. 6, the light incident on the portion where the spacer 5 is arranged is the polymer liquid crystal layer of this portion. Since 7 is excluded by the spacer 5, even if it is in a non-electric field state, it does not scatter and passes through the spacer 5 as it is, and exits. There is a problem that the bright spots are scattered and the display quality is degraded as a result.

Such a problem becomes remarkable in a projection type display device in which a display image of a liquid crystal display element is enlarged and projected on a screen surface by a projection lens, that is, in this case, bright spots in a dark display area of the liquid crystal display element. Is magnified and becomes considerably conspicuous, so that the quality of the screen projection image is significantly deteriorated.

It should be noted that since a black mask 8 for preventing light leakage is provided in a portion of the spacer 5 arranged at a position separated from the pixel region A between the electrodes facing each other, light is prevented. No emission, no problem.

The present invention has been made by paying attention to such a point, and an object thereof is to prevent the generation of bright spots in the dark display area due to the interposition of the spacers and ensure the display quality. It is to provide a liquid crystal display device that can be improved.

[0013]

In order to achieve such an object, the present invention provides a liquid crystal display device in which a polymer dispersed liquid crystal layer is provided between a pair of transparent substrates on which transparent electrodes are formed.
A spacer is fixedly provided by a resin film on one transparent substrate and in a portion avoiding the pixel region, and the gap between the substrates is kept substantially uniform by this spacer.

[0014]

In such a structure, the spacer is arranged only in a portion avoiding the pixel region, and the spacer is not present inside the pixel region. Therefore, when light is incident on the pixel region in the non-electric field portion. In addition, all of the light is scattered by the polymer dispersed liquid crystal layer and its emission is suppressed. Therefore, unlike the conventional case, bright spots corresponding to the shape of the spacer do not occur in the dark display region, and the entire dark display region has a uniform darkness.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. The same parts as those of the conventional structure are designated by the same reference numerals and the description thereof will be omitted.

FIG. 1 is a sectional view of the entire TFT active matrix type liquid crystal display device, FIG. 2 is a partially enlarged sectional view, and FIG. 3 is a plan view of the enlarged portion. In this liquid crystal display element, a plurality of spacers 5 are substantially evenly fixed on one transparent substrate 1 at a portion avoiding the pixel region A through a resin film 10, and the spacers 5 serve to form the substrates 1 and 2. The gap between them is kept almost uniform.

As described above, in the present invention, the pixel area A
The spacer 5 is provided at a specific portion while avoiding the above. Next, a work process of disposing and fixing the spacer 5 on the transparent substrate 1 will be described with reference to FIG. First, the transparent substrate 1 on which the transparent electrode 3 is formed is washed. Further, a large number of spacers 5 are put into a resin solution of a photosensitive polyimide precursor and mixed.

Then, a resin solution of the photosensitive polyimide precursor mixed with the spacer 5 is applied to the entire surface of the transparent substrate 1 on which the electrodes are formed, and the resin solution is dried so that the transparent substrate 1 is covered with the resin solution. A large number of spacers 5 are densely attached to.

Next, a photomask M is provided above the transparent substrate 1.
Is disposed, and a part of the resin film 10, that is, a part other than the part which becomes the pixel region A, is irradiated with light (ultraviolet light) by the photomask M and exposed. By this exposure, the photosensitive polyimide precursor as the resin film 10 is photocrosslinked.

Thereafter, by a development process, the resin film 10 in the exposed portion and the resin film 10 in the non-exposed portion are left while leaving the space 5.
Are removed together with the spacer 5 in this portion. Then, by baking the developed resin film 10, the photosensitive polyimide precursor as the resin film 10 is imidized and cured. As a result, the spacer 5 is fixed to the transparent substrate 1 by the resin film 10. Incidentally, as the material of the resin film 10, it is also possible to use photoresist or the like.

In this manner, the spacer 5 is fixed to a specific portion of the transparent substrate, that is, a portion avoiding the pixel area A,
After that, the other transparent substrate 2 is arranged so as to face the transparent substrate 1, the pair of transparent substrates 1 and 2 are joined by a sealing material 6, and the transparent substrates 1 and 2 inside the sealing material 6 Then, a liquid mixture obtained by mixing a photocurable polymer monomer and liquid crystal is injected and filled by a vacuum injection method, and the polymer monomer is polymerized by photopolymerization to form a polymer dispersed liquid crystal layer 7 to form a liquid crystal display. Assemble the elements.

In the transmissive liquid crystal display element having such a structure, the spacer 5 is only arranged in a portion avoiding the pixel region A, and the spacer 5 does not exist inside the pixel region A, and therefore, the spacer 5 is not provided. When light is incident on the pixel area A in the electric field portion, all the light is scattered by the polymer dispersed liquid crystal layer 7 and its emission is suppressed, and therefore, as in the conventional case,
Bright spots corresponding to the shape of the spacer 5 do not occur in the dark display region, and the entire dark display region has a uniform darkness, so that the display quality is surely improved.

Light incident on the spacer 5 arranged at a portion outside the pixel region A passes through the spacer 5 without being scattered, but there is no problem because it is blocked by the black mask 8 and prevented from being emitted.

It is also possible to form the spacer 5 with a non-translucent material such as a black material. In this case, the spacer 5 can also serve as a black mask, and the separate black mask 8 is not required. You can

Needless to say, the present invention can be applied not only to the TFT active matrix type liquid crystal display element but also to a simple matrix type liquid crystal display element.

[0026]

As described above, according to the present invention, the spacers are provided only in the portions avoiding the pixel region, and the spacers keep the gap between the substrates substantially uniform. When light enters the pixel area, all of the light is scattered by the polymer dispersed liquid crystal layer and its emission is suppressed. Therefore, the entire dark display area has a uniform darkness, and the display quality is surely improved. To do.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part of a liquid crystal display element showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an entire liquid crystal display element showing an embodiment of the present invention.

FIG. 3 is a plan view of a main part of a liquid crystal display element showing an embodiment of the present invention.

FIG. 4 is an explanatory view showing a process of disposing spacers in the liquid crystal display element according to the embodiment of the present invention.

FIG. 5 is a partial cross-sectional view of a conventional liquid crystal display element.

FIG. 6 is a sectional view of an entire conventional liquid crystal display element.

[Explanation of symbols]

 1, 2 ... Transparent substrate 3, 4 ... Transparent electrode 5 ... Spacer 7 ... Polymer dispersed liquid crystal layer

Claims (1)

[Claims] 1. In a liquid crystal display device having a polymer dispersed liquid crystal layer provided between a pair of transparent substrates having transparent electrodes formed thereon, a spacer is formed by a resin film on one transparent substrate and at a portion avoiding a pixel region. A liquid crystal display device, wherein the liquid crystal display device is fixedly provided, and a gap between the substrates is held substantially uniform by the spacer.