JP2000206544A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the contamination of liquid crystals which occurs in the contaminants in an end-sealing material, to provide high-grade image quality free from the occurrence of a display unevenness defect and to improve productivity by adopting the constitution to end-seal an liquid crystal injection port after liquid crystal filling by using a high-polymer film and photo- and/or thermosetting resin for adhering and fixing the high-polymer film. SOLUTION: A pair of substrates 1 and 2 are adhered and bonded to each other via a sealing material 3 and a gap, i.e., cell gap, of an effective display region 6 is formed constantly to 5.0 μm, following which liquid crystals are filled from an aperture formed by the sealing material, i.e., the liquid crystal injection port by using a vacuum filling method. The building of a liquid crystal cell is removed by pressing the liquid crystal cell and the excess liquid crystals are wiped away under pressurization after the filling of the liquid crystals. A polyimide film 5 of 25 mm in length slightly longer than the spacing of the liquid crystal injection port, 1.5 mm in width and 10 μm in thickness is thereafter applied to the injection port photosetting epoxy resin is applied from above the same and is cured to effect end-sealing.

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 having good display quality, which eliminates display defects near an injection port for injecting liquid crystal of a liquid crystal display device, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, a liquid crystal display device comprises a liquid crystal cell and a polarizing plate, and a reflecting plate or an illuminating device placed behind the liquid crystal cell. A liquid crystal cell is one in which a liquid crystal composition is filled between two substrates having an electrode and a liquid crystal alignment film inside.
A spacer for controlling the cell thickness to be constant is arranged between the two substrates. Further, the periphery is sealed to prevent deterioration of the liquid crystal due to moisture, oxidation and the like.

In a conventional method of assembling a liquid crystal cell, first, a seal made of a thermosetting resin is printed on an outer portion of a pixel on one of the alignment processing surfaces of two glass substrates, and a seal is formed on the other alignment processing surface. In order to maintain the thickness of the gap between the glass substrates, the spherical spacers are uniformly dispersed. Next, the substrates are bonded together with the alignment-processed surfaces facing inward, and the thermosetting resin is cured by a heating process to complete the empty panel. Then, according to the vacuum injection method, a small hole (so-called liquid crystal injection port) left in the seal portion is immersed in a liquid crystal reservoir in a vacuum degassed chamber, and the liquid crystal composition is introduced and injected using the capillary action of the cell. Finally, the liquid crystal injection port is sealed with an adhesive or the like. As a method of sealing the liquid crystal injection port,
After injection of the liquid crystal, dozens of cells are pressed at once to remove the swelling of the liquid crystal cell, excess liquid crystal is wiped off under pressure, an ultraviolet-curing sealant is applied with a dispenser, and the sealant is drawn into the cell by decompression. Then, it is cured by ultraviolet rays and sealed.

[0004]

The introduction of the sealant into the liquid crystal injection port formed in the seal portion with a width of several mm to several tens of mm depends on the temperature difference from high temperature to low temperature in the cell. A negative pressure in the cell due to a change in pressure or a change from pressurization to decompression is used. Since the sealing agent made of a photo-curable resin or the like that seals the sealing port is in contact with the liquid crystal, if it takes a long time to cure, the resin melts out of these resins, and the sealing agent in the cell is removed. There is a problem that the liquid crystal is contaminated by penetrating to the display region, and the specific resistance and the alignment state of the liquid crystal are partially changed, thereby causing display unevenness failure. Therefore, the following properties are required for the sealant.

(1) High barrier properties such as airtightness, prevention of moisture intrusion, prevention of liquid crystal outflow, etc. (2) Adhesion with the injection port, compatibility with the liquid crystal Cleaning of the liquid crystal attached to the injection port is impossible as it is Therefore, in order to improve the adhesion to the substrate glass, the compatibility of the liquid crystal is required to some extent.

(3) Low curing shrinkage In order to improve the sealing property, it is preferable that the curing shrinkage is small and the hardness is somewhat soft so that the peeling stress can be reduced. Especially in large-screen LCD panels with thin substrates and large openings in the inlet, the curing shrinkage of the sealing cured product and the difference in the coefficient of thermal expansion may affect the peeling of the adhesive surface and the cell gap, so the low-temperature curing shrinkage Is required.

(4) High-purity, non-staining properties Since the sealant comes in contact with the liquid crystal, there is a problem in the case where a material or a liquid crystal contaminant which is uncured or contaminates the liquid crystal after curing is mixed as an additive. It is.

(5) Chemical resistance It is necessary to have chemical resistance to washing after completion of sealing.

Conventionally, in order to satisfy the above characteristics, the size of the sealing port sealed by a sealing agent, which is a source of liquid crystal contamination, has been reduced, or a sealing material has been provided between the display section and the sealing port. It has been proposed to use it to form a bank. However, when the sealing opening is made smaller or a bank made of a sealing material is formed, the speed at which the liquid crystal is sealed is reduced, which causes a problem that the throughput is reduced. Also, the bank made of the sealing material may itself be a source of contamination of the liquid crystal.
Furthermore, space for forming a bank with a sealing material has been reduced due to the recent reduction in the width around the display screen of the liquid crystal display module.

An object of the present invention is to solve the problems of the prior art, suppress contamination of liquid crystal due to contaminants in a sealing agent, and have high-quality image quality free from display unevenness defects. Another object of the present invention is to provide a liquid crystal display device having excellent productivity.

[0011]

The object of the present invention is to provide a liquid crystal display device comprising: a pair of substrates at least one of which is transparent; a liquid crystal layer disposed between the pair of substrates; A plurality of active elements connected to the electrode group or the electrode group and the electrodes for applying an electric field to the liquid crystal layer formed on at least one of the pair of substrates, In a liquid crystal display device comprising an optical means for changing optical characteristics according to a molecular orientation state of the liquid crystal layer, a liquid crystal injection port after liquid crystal injection is exposed to light and / or thermosetting for tightly fixing the polymer film to the polymer film. This is achieved by a configuration in which sealing is performed using a conductive resin.

According to the present invention, also in a liquid crystal display device provided with an injection port for injecting liquid crystal on one or both of the pair of substrates, the liquid crystal injection port after injecting the liquid crystal is provided with a polymer film. This is achieved by using a light and / or thermosetting resin for tightly fixing the polymer film.

Further, the present invention is characterized in that a polymer film used for the sealing and a light and / or thermosetting resin holding the polymer film form a layer structure.

The method for manufacturing a liquid crystal display device according to the present invention is characterized in that a liquid crystal is sandwiched between respective glass substrates having thin-film electrodes, switching elements, and a liquid crystal alignment control film provided on the inner surface of the panel. A liquid crystal sealing seal made of a cured resin is formed. The air inside the cell is exchanged for the liquid crystal material in a vacuum, and then the opening (injection port) used for injecting the liquid crystal is closed with a polymer film. Alternatively, the panel is characterized in that the polymer film and the panel are completely adhered and sealed using a photocurable resin. This polymer film makes it possible to prevent the liquid uncured resin from dissolving into the liquid crystal layer.

In the liquid crystal display device and the method of manufacturing the same according to the present invention, the polymer film used for sealing the injection port needs to be a material that does not deteriorate the characteristics of the liquid crystal upon contact with the liquid crystal material. For example, a polymer film in which the plasticizer or the like is reduced as much as possible is preferable, and polyimide, polyamide, polyamideimide,
Polyester, polycarbonate, acrylic resin, epoxy resin and the like are desirable.

Further, in the conventional sealing method, the deterioration of the liquid crystal material in the vicinity of the ultraviolet light curable resin used for the sealing may be recognized in some cases. Therefore, if the polymer film used in the present invention is a material that absorbs light having a wavelength used for photocuring, deterioration of liquid crystal due to light can be reduced, which is more effective.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the liquid crystal display device of the present invention will be described in detail with reference to examples.

(Embodiment 1) FIG. 1 is a schematic plan view for explaining a first embodiment of a liquid crystal display device according to the present invention, and FIG.
FIG. 4 is a cross-sectional view of a portion of the liquid crystal injection port region taken along line AA ′ of FIG. At least a transparent electrode was formed on the opposing surfaces of a pair of glass substrates having a thickness of 1.1 mm, and an orientation control film was formed on the transparent electrode. Further, spacer beads for keeping the cell gap constant were sprayed on at least one of the effective display regions 6 of both substrates by a spray method or the like. In addition, spacer beads having an average particle diameter larger than that of the spacer beads dispersed in the effective display region 6 in the epoxy resin were mixed in the sealing material 3 in advance. In this manner, the pair of substrates are bonded and adhered via the sealing material 3, and the gap of the effective display area 6, that is, the so-called cell gap is set to 5.
After the liquid crystal was uniformly formed to a thickness of 0 μm, liquid crystal was injected from an opening formed by the sealing material 3, a so-called liquid crystal injection port, using a vacuum injection method.

After the injection of the liquid crystal, the liquid crystal cell was pressed to remove the swelling of the liquid crystal cell, and excess liquid crystal was wiped off under pressure. Thereafter, a polyimide film having a length of 25 mm, a width of 1.5 mm, and a thickness of 10 μm, which is slightly longer than the distance between the liquid crystal injection ports, is applied to the injection port, and a photocurable epoxy resin is applied from above, cured, and sealed. Then, the cross section of the sealing port portion was configured as shown in FIG.

After the liquid crystal cell was subjected to an aging treatment at about 100 ° C., the temperature was returned to room temperature, and the alignment of the liquid crystal was disturbed and contamination was observed. However, no display unevenness near the liquid crystal injection port was observed.

On the other hand, for comparison, a similar liquid crystal cell was prepared by encapsulating only a photocurable epoxy resin without using a polyimide film, and after aging at 100 ° C., the same observation was performed at room temperature. From the vicinity of the entrance, it was observed that the region in which the orientation of the liquid crystal was disturbed spread in a half-moon shape. Analysis of the half-moon-shaped disorder of orientation revealed that the disorder of orientation was mainly caused by contamination by unreacted monomer dissolved in the liquid crystal from the sealant. Therefore, when sealing the injection port of the liquid crystal cell, it is first closed with a polyimide film and then sealed with a photocurable resin, thereby causing uneven alignment or uneven brightness due to unreacted components of the photocurable resin. Was effectively prevented, and it was confirmed that high-quality image display was obtained.

In this embodiment, a polyimide film is used for sealing the injection port of the liquid crystal cell. However, other than that, polyamide, polyamideimide, polyester, polycarbonate,
It was found that a similar effect could be obtained by using a film made of an acrylic resin or an epoxy resin.

In this embodiment, a liquid crystal cell having a transparent electrode on the entire surface of the substrate is used.
TN-LCD and TFT with active elements formed
-LCD, and furthermore, the same effect is obtained with a lateral electric field type TFT-LCD, and there is no limitation.

(Embodiment 2) As shown in the schematic plan view of the cell of the liquid crystal display device of this embodiment in FIG. 3, the liquid crystal injection port 7 is located at one corner inside the sealing material 3 of one glass substrate. It is formed as a circular hole. A liquid crystal cell having such a liquid crystal injection port 7 is prepared as an empty cell in the same manner as in Example 1, and then a mounting jig is directly attached to the injection port 7 without using a vacuum chamber, and degassing in the cell and injection of liquid crystal are performed. went. Thereafter, as in Example 1, the liquid crystal cell was pressed to remove the swelling of the liquid crystal cell, and excess liquid crystal was wiped off under pressure. Thereafter, a film made of an acrylic resin having a diameter of 10 mm and a thickness of 10 μm, which is larger than the diameter of the liquid crystal injection port 7, is applied to the injection port, and a photo-curable acrylic resin is applied thereon, and the photo-cured acrylic resin is sealed. The cross section of the sealing port was configured as shown in FIG.

After the liquid crystal cell was aged at about 100 ° C., the temperature was returned to room temperature, and the alignment of the liquid crystal was disordered and the state of contamination was observed, but no display unevenness near the liquid crystal injection port was observed.

On the other hand, for comparison, a similar liquid crystal cell was prepared, which was encapsulated only with a photocurable acrylic resin without using an acrylic resin film, and was similarly observed at room temperature after aging at 100 ° C. In addition, it was observed that the region where the orientation of the liquid crystal was disordered in a half-moon shape spread from the vicinity of the sealing opening. Analysis of the half-moon-shaped disorder of orientation revealed that the disorder of orientation was mainly caused by contamination by unreacted monomer dissolved in the liquid crystal from the sealant. Therefore, when sealing the injection port of the liquid crystal cell, first by closing with an acrylic resin film, and then by sealing with a photocurable resin, uneven alignment or luminance unevenness due to unreacted components of the photocurable resin. It was confirmed that the generation was effectively prevented, and high-quality image display was obtained.

In this embodiment, an acrylic resin film is used to seal the injection port of the liquid crystal cell. However, the same effect can be obtained by using a film made of polyimide, polyamide, polyamideimide, polyester, polycarbonate, or epoxy resin. Was obtained.

In this embodiment, a liquid crystal cell having a transparent electrode formed on the entire surface of the substrate is used.
TN-LCD and TFT with active elements formed
-LCD, and furthermore, the same effect is obtained with a lateral electric field type TFT-LCD, and there is no limitation.

[0029]

According to the present invention, in a liquid crystal display device, contamination of liquid crystal due to contaminants in a sealing agent is suppressed, and high quality image with no display unevenness is generated. It is to provide a liquid crystal display device excellent in performance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic diagram of a cell of a liquid crystal display device used in an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic sectional view of a cell of a liquid crystal display device used in an embodiment of the present invention.

FIG. 3 is a diagram showing a schematic view of a cell of a liquid crystal display device used in an example of the present invention.

FIG. 4 is a schematic cross-sectional view of a cell of a liquid crystal display device used in an example of the present invention.

[Explanation of symbols]

1, 1 ', 2 ... substrate, 3 ... sealant, 4 ... sealant, 5 ...
Sealing polymer film, 6: effective display area, 7: liquid crystal injection port formed in substrate, 8: liquid crystal layer.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Terao 3300 Hayano, Mobara-shi, Chiba F-term in the Electronic Devices Division, Hitachi, Ltd. 2H089 LA07 LA33 MA03Z NA09 NA25 PA12 PA13 QA02 QA12 QA16 RA10 TA04 TA09

Claims (4)

[Claims] 1. A pair of substrates, at least one of which is transparent; a liquid crystal layer disposed between the pair of substrates; and an alignment control film formed on a surface of the pair of substrates that contacts the liquid crystal layer. An electrode group formed on at least one of the pair of substrates and a plurality of active elements connected to the electrode group and the electrode for applying an electric field to the liquid crystal layer; and A liquid crystal display device comprising an optical means for changing optical characteristics according to the liquid crystal, wherein a liquid crystal injection port after liquid crystal injection is sealed with a polymer film and light and / or a thermosetting resin for tightly fixing the polymer film. A liquid crystal display device comprising: 2. The liquid crystal display device according to claim 1, wherein said liquid crystal injection port is provided on one or both substrates of said pair of substrates. 3. The liquid crystal display device according to claim 1, wherein the polymer film used for the sealing and a light and / or thermosetting resin holding the polymer film form a layer structure. . 4. The liquid crystal display device according to claim 1, wherein said polymer film is made of at least one resin selected from the group consisting of polyimide, polyamide, polyamideimide, polyester, polycarbonate, acrylic resin and epoxy resin. .