JPH09133924A - Liquid crystal panel and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the spacing for packing liquid crystals uniform by forming a seal of an easily electrifiable adhesive into which electrification decreasing materials are incorporated, thereby averting the adhesion of foreign matter (dust) in the atm. on the seal-forming adhesive prior to tight adhesion of substrates. SOLUTION: A UV curing type adhesive 8 is applied along the periphery of the surface of the one substrate 2. Spacers 5 and a large amt. of carbon powder 9 are incorporated as the material for lowering the electrification of the adhesive 8 into the adhesive 8. Many spacers 6 for limiting the thickness of liquid crystals 7 are sprayed on the front surface of the other substrate 3. The substrate 3 is pressed to the substrate 2 onto the central part of the surface of which a prescribed amt. of liquid crystals 7 are dropped. The liquid crystals 7 are then packed into the inter- substrate spacing encircled by the adhesive 8 simultaneously when the adhesive 8 grows to a prescribed thickness. The material to lower the electrification, for example, the carbon powder 9, is incorporated into the easily electrifiable adhesive 8 for forming the seal in the manner described above, by which the adhesion the dust suspended in the atm. by electrification is substantially prevented and the seal is formed to the prescribed thickness. Cell defects are thus decreased.

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 panel in which liquid crystal is filled between a pair of substrates and a method for manufacturing the same, and more particularly,
Regarding a liquid crystal display panel using an easily chargeable adhesive, for example, an ultraviolet curable adhesive for forming a liquid crystal filling area, and a method for forming a liquid crystal filling area setting seal using the adhesive, forming a seal before adhering a pair of substrates The liquid crystal filling gap is made uniform by preventing foreign matter (dust) in the atmosphere from adhering to the adhesive for use due to the easily charged property of the adhesive.

[0002]

2. Description of the Related Art In a liquid crystal display panel, a peripheral portion of a pair of substrates having a desired electrode pattern or the like is bonded (sealed) with an adhesive, and liquid crystals are filled between the substrates surrounded by the seals. The gap between the pair of substrates facing each other is generally made uniform by the spherical spacers scattered on the substrates and the fiber-like spacers mixed in the sealing adhesive. Adhesives and UV curable adhesives are used.

In the liquid crystal display panel, a liquid crystal filling method includes a vacuum filling method in which a liquid crystal is injected from an opening of the seal into a gap between substrates surrounded by a seal that joins a pair of substrates in a vacuum, and a loop shape. After dropping an appropriate amount of liquid crystal on one substrate coated with adhesive, press the other substrate over the substrate in a vacuum and press it to spread the liquid crystal into the liquid crystal filling area. A drop filling method for curing is known.

Generally, the vacuum filling method, in which a thermosetting type adhesive is used as the seal forming adhesive, requires a long time for filling the liquid crystal and a long time for hardening the adhesive, for example, a panel of about 10 inches. Therefore, it takes about 5 hours to fill the liquid crystal and about 2 to 3 hours for pre-baking and post-baking to heat the adhesive, so that a large amount of expensive liquid crystal is wasted, and the sealing opening is sealed after filling the liquid crystal. A process and a process of cleaning the liquid crystal attached to the outside of the substrate are required.

The drop filling method is a method developed to shorten the liquid crystal filling time and to omit the waste of liquid crystal and the sealing and cleaning steps after filling the liquid crystal. An appropriate amount of liquid crystal is dropped on the substrate, the other substrate is placed on the substrate, and the pair of substrates are attached in a state where the liquid crystal is spread and spread, and then the adhesive is cured.

In such a drop filling method, both a thermosetting type and an ultraviolet curing type can be used as the seal forming adhesive. However, when the solvent contained in the thermosetting adhesive enters the liquid crystal, The display characteristics of the liquid crystal display panel deteriorate. Therefore, when the thermosetting adhesive is used, the solvent is removed by prebaking.

However, it is difficult to completely remove the conventional solvent contained in the thermosetting adhesive by prebaking, and according to the results of our study, the ultraviolet curable adhesive is used as the adhesive used in the drop filling method. It was confirmed that the display panel using the agent has a better display quality than the display panel using the thermosetting adhesive.

[0008]

While conventional thermosetting adhesives containing a solvent are non-electrostatic, ordinary ultraviolet curable adhesives have the property of being easily charged.

Therefore, the ultraviolet curable adhesive has a drawback that dust in the atmosphere is likely to adhere in the process of applying it on a substrate for forming a seal, and a spacer (generally having a diameter of about 5 μm) contained in the adhesive is used. (Glass fiber)
If larger dust adheres to the adhesive, or if it adheres so as to overlap the spacer even if it is smaller than the spacer, the liquid crystal filling gap becomes large at that portion (thickness of the liquid crystal) and the display quality of the panel deteriorates. Like

As a matter of course, the application of the ultraviolet curable adhesive, the dropping of the liquid crystal, and the attachment of the pair of substrates are performed in a clean atmosphere. Therefore, if the cleanliness of the atmosphere is further increased, the deterioration of the display quality due to the above-mentioned defects can be solved.
However, the equipment cost and the cost for maintaining and maintaining such a highly clean atmosphere are high, which lowers the productivity of the liquid crystal display panel and increases the cost.

Thermosetting adhesives for sealing liquid crystal display panels include epoxy-based and acrylic-based adhesives, and use of a solvent-free adhesive is also under consideration. However, if the adhesive for sealing has a property of being easily charged, the above-mentioned problem that the display quality of the panel is deteriorated occurs as in the case of the conventional ultraviolet curable adhesive.

[0012]

According to the present invention, a seal is provided in a liquid crystal display panel in which a peripheral portion of a pair of substrates facing each other is joined by a seal, and liquid crystal is filled in a gap between the substrates surrounded by the seal. The purpose is to prevent foreign substances in the air from adhering to the adhesive applied for forming.

In the first liquid crystal display panel of the present invention for achieving the above object, the seal is formed of the easily chargeable adhesive containing a charge reducing substance, and the easily chargeable adhesive is further provided. The agent is an ultraviolet curable adhesive, and the antistatic substance uses an appropriate amount of carbon powder or a solvent that is removed before the curing treatment.

In the second liquid crystal display panel of the present invention which achieves the above object, a groundable conductive layer is formed in an adhesive application region of one of a pair of substrates to which the easily chargeable adhesive is applied. It was done.

In the first method for producing a liquid crystal display panel of the present invention which achieves the above object, a charge reducing substance is mixed with an easily chargeable adhesive for forming a seal, and the easily chargeable adhesive is used. The agent is an ultraviolet curable adhesive, and the one in which the antistatic substance is mixed with an appropriate amount of carbon powder or a solvent which is removed before the curing treatment is used.

According to a second method for manufacturing a liquid crystal display panel of the present invention which achieves the above object, a conductive material capable of being grounded is provided in one adhesive application region of one of a pair of substrates to which the adhesive agent having an easily chargeable property is applied. Forming a layer.

In the liquid crystal display panel of the present invention and the method for manufacturing the same, dusts floating in the atmosphere are less likely to be charged and adhered by mixing a substance that reduces charge in the easily chargeable adhesive for seal formation. As a result, the seal has a predetermined uniform thickness without adhering dust in the atmosphere, and cell defects due to the dust adhering are significantly reduced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a first embodiment of the present invention. 1, the liquid crystal display panel 1 is shown in FIG.
As shown in (e), a pair of substrates 2 and 3 are joined to each other in the vicinity of the periphery by a seal 4, and the opposing gap between the substrates 2 and 3 is a spacer 5 in the seal 4 and spacers 6 scattered between the substrates 2 and 3.
The liquid crystal 7 is filled in the area surrounded by the seal 4 with a predetermined gap.

In FIG. 1A, on the surface of one of the substrates 2, for example, the surface of the rectangular substrate 2 on which a color filter is formed, an ultraviolet curable adhesive 8 is formed along the periphery in a looped square shape. Apply.

The adhesive 8 applied using a dispenser is partially enlarged and broken in the longitudinal direction as shown in FIG.
As shown in (b), a large number of carbon powders 9 are mixed as spacers (generally glass fibers) 5 and substances that reduce the charging of the adhesive 8. However, in this embodiment, the carbon powder 9 mixed together with the spacer 5 having a diameter of 5 μm has an average diameter of 0.5 μm, and the mixing ratio thereof is 0.5 wt%.

In FIG. 1C, on the surface of the other substrate 3, for example, the surface of the TFT (thin film transistor) substrate 3, a large number of spacers 6 that define the thickness of the liquid crystal 7 (the gap between the substrates 2 and 3) are provided. Disperse.

The spacer 6 is, for example, a spherical body made of plastic having a diameter of about 5 μm coated with an adhesive agent.
By heating at 50 ° C. for about 30 minutes, it comes into close contact with the sprayed position.

Then, as shown in FIG. 1D, in a vacuum furnace 10 of the substrate bonding apparatus, a substrate 3 having a surface facing downward with respect to a substrate 2 on which a predetermined amount of liquid crystal 7 is dropped at the center of the surface. After adjusting the position of the
The substrate 3 is pressed against the substrate 2 with an appropriate pressing force F for about 5 minutes in the vacuum furnace 10 at orrr.

Then, at the same time that the adhesive 8 has a predetermined thickness, the liquid crystal 7 spread by the substrate 3 is spread by the adhesive 8
The space between the substrates surrounded by is filled and the substrates 2 and 3 come into close contact with each other.

Therefore, after the inside of the vacuum furnace 10 is returned to the atmospheric pressure, the substrates 2 and 3 in the close contact state are taken out from the vacuum furnace 10 or left in the vacuum furnace 10 and the adhesive 8 is exposed to a predetermined ultraviolet ray 11, for example. When the ultraviolet ray 11 of 5000 mJ / cm ² is irradiated, the adhesive 8 is cured, and the pair of substrates 2 and 3 are joined by the seal 4 in which the adhesive 8 is cured,
Moreover, the liquid crystal display panel 1 in which the liquid crystal 7 is filled between the substrates surrounded by the seal 4 is completed.

In order to confirm the effect of the carbon powder 9, the sample produced by the method of the above-mentioned embodiment and the carbon powder 9
When 100 panels each of which was prepared by using an adhesive agent which did not mix with each other as a seal were manufactured, the cell gap was 5.5 μm or more with respect to the cell defect, that is, the spacer 5 mixed with the adhesive 8 had a diameter of 5 μm. The number of defective panels was 1 panel in the example sample, and 65 panels in the sample manufactured by the conventional method in which the carbon powder 9 was not mixed in the adhesive 8.

Then, electrostatic measurement of a seal formed with an adhesive agent in which the carbon powder 9 was not mixed was 1 KV.
While the above charging was confirmed, the charging of the seal 4 formed by the adhesive 8 mixed with the carbon powder 9 was 100V.
Further, when a defective cell portion of the sample in which the defective cell was obtained was observed with a microscope, mainly fibrous foreign substances were found to be sandwiched in all of them.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2, an ultraviolet curable adhesive 8 '
Is stable to the adhesive 8'and the liquid crystal 7 in place of the adhesive 8 containing the carbon powder 9 and suppresses the charging of the ultraviolet curable adhesive 8 '. ) A suitable removable solvent such as IPA (isopropyl alcohol), which is an alcohol solvent, is added in an appropriate amount, for example, about 0.5 wt%. In the second embodiment of the present invention, the adhesive is used. Adhesive 8'instead of 8
Are used to form the seal 4.

The solvent added to the adhesive 8'is applied to the substrate 8 coated with the adhesive 8'before the superposition of the substrates 2 and 3, for example, when IPA is used as the solvent.
Remove by heating at 0 ° C. for about 10 minutes.

In order to confirm the effect of the added solvent (IPA) in the second embodiment, a sample in which the seal 4 is formed by using the adhesive 8'containing IPA, and the IP
A sample using an adhesive without addition of A and 100 panels each were manufactured, and the cell defects were investigated. As a result, the cell defect of the sample using the adhesive 8'added with IPA was 5, whereas the cell defect of the sample using the adhesive without IPA (panel by the conventional dropping filling method) was found. Was 65 sheets.

There is concern about liquid crystal contamination due to the addition of a solvent to the UV-curable adhesive. Then, when the display characteristics of the 100-panel sample using the IPA-added adhesive 8'were checked, no influence of IPA was detected.

FIG. 3 is a diagram for explaining a third embodiment of the present invention. 3A and 3B, a thin film conductor layer 12 is formed on the surface of the substrate 2 along the periphery of the prism to which the seal 4 (see FIG. 1E) is applied. The adhesive 8 is formed on top. Such a conductor layer 12
For example, when the substrate 2 is a TFT substrate of a liquid crystal display panel, the same IT as the pixel electrode formed on the TFT substrate is used.
It may be formed of an O film, and when the substrate 2 is a color filter substrate of a liquid crystal display panel, an I film for forming a common electrode is formed.
It may be formed from a TO film.

Then, a terminal 13 for external connection is formed on a part of the conductor layer 12 formed wider than the adhesive 8 to be applied. Therefore, the terminal 13 is grounded, the ultraviolet curable adhesive 8 is applied on the conductor layer 12, and then the same process as the conventional drop filling method is performed to complete the liquid crystal display panel.

In the third embodiment, the conductor layer 12
In order to confirm the effect of (1), 100 samples each of the sample having the conductor layer 12 and the sample having the conventional structure without the conductor layer 12 were manufactured, and the cell defects were investigated. The cell defect of No. 1 was 10 panels, whereas the cell defect of the sample in which the conductor layer 12 was not formed (panel by the conventional dropping filling method) was 65 panels.

Although the carbon powder 9 is used as the conductive material in the first embodiment of the present invention, the conductive material of the present invention is not limited to the carbon powder 9 and may be nickel, molybdenum, or the like. The metal powder and the powder of which the surface of glass, alumina, or the like is made to be gold-cornered can be used, and the same effect as the carbon powder 9 can be obtained. Similarly, in the second embodiment of the present invention, IPA is used as the solvent that imparts the conductive substance, but the solvent in the present invention is not limited to IPA, and for example, methyl carbitol or diethyl carbitol. Etc. are also available.

[0036]

As described above, according to the present invention, in a liquid crystal display panel in which an ultraviolet curable adhesive is used for a seal, cell defects caused by foreign matter adhering to the adhesive are significantly reduced. It is extremely significant that the ultraviolet curable adhesive can be used for sealing liquid crystal display panels without impairing the display quality.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory view of a second embodiment of the present invention.

FIG. 3 is an explanatory view of a third embodiment of the present invention.

[Explanation of symbols]

 1 liquid crystal display panel 2,3 substrate 4 seal 5,6 spacer 7 liquid crystal 8,8 'adhesive 9 carbon powder 12 conductor layer 13 terminal

Claims (9)

[Claims] 1. In a liquid crystal display panel in which a pair of opposing substrates are bonded to each other in the vicinity of their peripheral portions by a seal and a liquid crystal is filled in a gap between the substrates surrounded by the seal, the seal contains a charge reducing substance. A liquid crystal display panel, characterized in that it is formed of the easily chargeable adhesive. 2. The liquid crystal display panel according to claim 1, wherein the easily chargeable adhesive is an ultraviolet curable adhesive and the charge reducing substance is an appropriate amount of carbon powder. 3. The easily chargeable adhesive is an ultraviolet curable adhesive, and the charge reducing substance is a solvent removed before the curing treatment of the applied adhesive. The liquid crystal display panel according to claim 1. 4. A liquid crystal display panel in which the vicinity of a peripheral portion of a pair of opposed substrates is joined by a seal, and a liquid crystal is filled in a gap between the substrates surrounded by the seals. A liquid crystal display panel, wherein a conductive layer that can be connected to ground is formed in the adhesive application region of one of the pair of substrates to which the adhesive is applied. 5. The liquid crystal display panel according to claim 4, wherein the conductive layer is selectively formed from a conductive film deposited on the one substrate to form a conductive pattern required. . 6. A liquid crystal display panel in which a peripheral portion of a pair of opposed substrates are joined by a seal, and liquid crystal is filled in a gap between the substrates surrounded by the seals. A conductive substance is mixed into the agent as the charge reducing substance, and the conductive substance mixed adhesive is applied near the periphery on one surface of the pair of substrates and a predetermined amount of liquid crystal is applied to the center. , The other of the pair of substrates is superposed on one surface of the pair of substrates, and the pair of superposed substrates are pressed and brought into close contact with each other in a vacuum atmosphere, and then the conductive material is irradiated with ultraviolet rays. A method for manufacturing a liquid crystal display panel, which comprises curing the mixed adhesive. 7. A liquid crystal display panel in which a peripheral portion of a pair of opposed substrates are joined by a seal, and liquid crystal is filled in a gap between the substrates surrounded by the seals. The agent is mixed with a solvent that is removed before the adhesive is cured as the charge reducing substance, and the solvent-mixed adhesive is applied to one surface of the pair of substrates in the vicinity of the peripheral portion. A predetermined amount of liquid crystal is dropped onto the central portion, the solvent is removed by heat treatment before or after the dropping of the liquid crystal, and the other of the pair of substrates is superposed on one surface of the pair of substrates. A method for producing a liquid crystal display panel, comprising: pressing a pair of substrates in a vacuum atmosphere to bring them into close contact with each other, and then irradiating ultraviolet rays to cure the conductive substance-containing adhesive. 8. The method for manufacturing a liquid crystal display panel according to claim 8, wherein the easily chargeable adhesive is an ultraviolet curable adhesive and the solvent is an alcohol solvent. 9. A liquid crystal display panel in which the peripheral portions of a pair of opposed substrates are joined by a seal, and a liquid crystal is filled in a gap between the substrates surrounded by the seal, the pair of substrates forming the seal. A conductive layer that can be connected to earth is formed in the vicinity of one of the peripheral parts, and the easily-charged adhesive is applied onto the grounded conductive layer, and an appropriate amount is applied to the central part of the adhesive-coated substrate. A method of manufacturing a liquid crystal display panel, comprising: dropping a liquid crystal, and then stacking and adhering the pair of substrates according to claim 6 and performing an adhesive curing treatment.