JP2003228076A - Liquid crystal display element and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display device in which electro-corrosion is prevented from occurring between electrodes outside main seal. <P>SOLUTION: After arranging an LCD3 filled with a liquid crystal in a pixel area between transparent substrates 1, 2, forming a main seal 11 for partitioning a liquid crystal filling area in the peripheral part of the substrate 1 provided with a common electrode, arranging electrode wiring to be brought into conduction with the common electrode on the substrate 1 at the end part of the substrate 2 faced thereto and provided with segment electrodes, applying a conductive paste 12 onto the electrode wiring, and then letting the area coated with the sealing agent on the substrate 1 and the area with the conductive paste 12 pre-cure, respectively, both substrates 1, 2 are superimposed together with spacers scattered in between, and the conductive paste 12 is coated with the sealing agent by hardening treatment. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a liquid crystal display device and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display element, a liquid crystal display element (hereinafter sometimes referred to as a liquid crystal display section or LCD) in which liquid crystal for display is filled between transparent substrates is known. L
A liquid crystal display device that drives a CD with an LSI (IC) (hereinafter referred to as L
A CM or LC module is sometimes used) is shown in the perspective view of FIG.

In the LCM, a front substrate 1 and a back substrate 2 each having wiring constituting a transparent electrode are superposed on each other, and a liquid crystal is sealed in a pixel region divided by a seal member between the both substrates 1 and 2. A liquid crystal display (LCD) 3 and metallic copper wirings 5 and 6 connected to the wirings from the LCD 3 are formed on a circuit board made of a synthetic resin film such as a polyimide resin, and the metallic copper wirings 5 and 6 are formed. An LSI for controlling conduction of the ITO transparent pixel electrodes of the LCD 3 in the gathered area
(IC) 7 ACF containing conductive paste not shown
(Anisotropic Conductive Film) and a circuit board portion 8 connected to each other. Both the substrates 1 and 2 are made of transparent glass or a transparent resin plate.

The electrode wiring of the LSI (IC) 7 on the circuit board portion 8 is connected to the power source side through an anisotropic conductive film (not shown) or the like. The structure shown in FIG. Then, since the LSI 7 is on the synthetic resin film, it may be called a chip on film module.

Further, FIG. 6 shows an active area 3a, a viewing area 3b and an LSI 7 of the LCD 3 shown in FIG.
FIG. 7 shows a plan view of electrodes and electrode wiring, and FIG. 7 shows the common electrodes and segment electrodes of the LCD 3 shown in FIG. Figure 5,
The electrode wirings 5 and 6 shown in FIG. 6 are provided on the circuit board portion 8 connected to the common electrode and the segment electrode of the LCD 3, respectively.

In the LCD 3, for example, 16 segment electrodes (SEG1 to 16) and 16 common electrodes (COM1 to 16) orthogonal to the segment electrodes are arranged on the transparent substrate 1 and the transparent substrate 2, respectively.

The common electrode and the segment electrode are I
The transparent electrodes are made of TO, for example, the segment electrodes are wired on the transparent substrate 1, and the common electrodes are wired on the transparent substrate 2. The segment electrode is copper electrode wiring 5
Further, the common electrodes are connected to the copper electrode wirings 6, respectively, and the energization is controlled by one LSI 7 of the circuit board portion 8 via the wirings 5 and 6, respectively.

At this time, the 16 segment electrodes of the LCD 3 pass through the viewing area 3b of the LCD 3 as shown in FIG.
Connected to the LSI 7 via the viewing area 3b
It is bent at a right angle inside and wired on the transparent substrate 1. Further, the electrode wiring 6 arranged on the transparent substrate 2 is used as a common electrode, but the common electrode is connected to the LSI 7 through the inside of the active area 3 a of the LCD 3.

Further, the circuit board portion 8 connecting between the LSI 7 and the LCD 3 can be bent because it is composed of a flexible conductive cable, and the LSI 7 can be arranged on the back side of the LCD 3 although not shown. it can.

[0010]

In the liquid crystal display device having the above-described structure, the LCD 3 has characteristics such as liquid crystal sandwiched between the two transparent substrates 1 and 2 leaking to the outside or moisture or dirt. In order to prevent the change, a wall is formed between the transparent substrates 1 and 2 by a resin called a main seal 11 which is a seal member to reduce the influence from external factors.

In the liquid crystal display device, the liquid crystal molecules in the portions where the electric field is applied are moved between the segment electrodes and the common electrodes arranged on the transparent substrate 1 and the transparent substrate 2, respectively, to change the amount of light for display. An electric field is usually applied between the upper and lower transparent substrates 1 and 2, but the voltage difference is caused by a portion where the transparent electrodes of the transparent substrates 1 and 2 overlap on the outer side of the main seal 11 or the terminals of the transparent electrodes are narrow. It is known that a conductive material such as impurities or water adheres to a generated portion to cause electricity to flow, resulting in a problem called electric field corrosion or electrolytic corrosion. When this electrolytic corrosion occurs, the liquid crystal display becomes abnormal, so that the liquid crystal display device cannot be used as a display.

8 is a plan view showing the main seal 11 and electrode ends of the transparent substrates 1 and 2 of FIG. 8 with the transparent substrate 2 removed, and a sectional view taken along the line AA of FIG. 8 (including the transparent substrate 2). The above problem will be described with reference to FIG.

Main seal 1 provided on transparent substrate 1
1 and a space S formed between the conductive paste 12 which is a common electrode conduction portion provided outside the seal 11, the moisture reduces and deteriorates the lead portion of the ITO transparent electrode (electrical corrosion). ), The electrical resistance of the transparent electrode wiring may be increased, and the wiring may be broken.

At the end of the transparent substrate 1, there are also provided lead portions 14 for the segment electrodes wired on the transparent substrate 1 and for connecting the common electrodes wired on the transparent substrate 2.
The conductive paste 12 shown in FIGS. 8 and 9 is disposed between the transparent substrate 1 and the transparent substrate 2, and has a lead portion 14 at an end of the transparent substrate 1 and a common electrode wired on the transparent substrate 2. It is provided for electrical continuity. The conductive paste 12
In many cases, an epoxy resin in which fine gold particles are dispersed is applied by screen printing and heat-cured at about 100 ° C. Further, carbon particles may be used in the conductive paste 12 as a conductivity retainer.

In FIG. 8, 16 common electrodes (COM1 to COM16) are provided at the center of the LCD 3, and 8 segment electrodes (SEG1 to SEG1) are provided outside both of them.
8, SEG 9 to 16) are wired.

The lead portion 14 of the transparent substrate 1 is provided with a common electrode wiring to be wired to the transparent substrate 2 in addition to the segment electrode connecting wiring provided to the substrate 1. The common electrode wiring provided on the transparent substrate 1 is connected to the common electrode of the transparent substrate 2 via the conductive paste 12.

Conventionally, by increasing the processing accuracy, the portions where the electrodes (segment electrodes and common electrodes) of the upper and lower transparent substrates 1 and 2 shown in FIG. 5 overlap each other are reduced, and water repellency is prevented so that moisture does not adhere to the electrodes. The method of applying the above-mentioned material or the method of applying a thermosetting synthetic resin or a UV-curing synthetic resin having less shrinkage after curing between the electrodes to insulate them and prevent moisture from adhering to the electrodes has been adopted. However, the number of steps for these measures is complicated, the number of processes is increased, and it is not efficient. In particular, the curable synthetic resin has a drawback that the transparent substrate of the panel is distorted due to the resin shrinkage, and the possibility that air bubbles are generated in the display panel is increased.

Further, as shown in FIG. 10 which is an enlarged view of a portion B of FIG. 9 and FIG. 8, there is a space S between the main seal 11 and the conductive paste 12, in which water is accumulated and the ITO electrode material is corroded. In some cases, the reduction of ITO metallized the metal component to increase the resistance and generated heat, which sometimes caused a state close to disconnection.

An object of the present invention is to provide a liquid crystal display device in which electric field corrosion does not occur between electrodes outside the main seal.

[0020]

The above-mentioned problems of the present invention can be solved by the following constitutions (1) and (2). (1) A space formed by arranging a first substrate having a first pixel electrode provided on the surface thereof, a second substrate having a second pixel electrode provided on the surface thereof, and the pixel electrodes facing each other. An electrically insulative seal part for hermetically partitioning the liquid crystal to form a display region, and a non-display region outside the seal part on the surface of the second substrate for the second pixel electrode. In a liquid crystal display device having two wiring electrodes and a first wiring electrode for the first pixel electrode, the pixel electrode of the first substrate is a conductive paste electrode embedded in the electrically insulating seal portion. A liquid crystal display element which is formed so as to be electrically connected to the first wiring electrode through the pixel electrode of the second substrate and is integrally formed with the second wiring electrode.

(2) 1) a step of forming a first pixel electrode in a display region forming portion on the surface of the first substrate, 2) forming a second pixel electrode in a display region on the surface of the second substrate, A step of forming a second wiring electrode integrally connected to the second pixel electrode and a first wiring electrode for the first pixel electrode in the non-display area forming portion, 3) the first substrate and the second A step of forming a liquid crystal alignment film on the surface of the substrate on which each pixel electrode is provided,
4) Between the first substrate and the second substrate, it becomes an electrically insulating seal portion for sealing the liquid crystal in the display region forming portion and partitioning the obtained display region from the non-display region. Step of applying a thermosetting resin to the second substrate and pre-curing (semi-curing), 5) A conductive paste electrode using the thermosetting resin as a base material on the surface of the first substrate at the portion corresponding to the seal portion. Pre-curing (semi-curing) so that the hardness is higher than that of the thermosetting resin formed on the surface of the second substrate by spot coating, 6) the first substrate and the second substrate,
The electrically conductive paste electrode is bonded so as to be embedded and embedded in the electrically insulating seal portion, and then the sealing member is heat-cured to form the first pixel electrode and the first wiring electrode through the electrically conductive paste electrode. A method for manufacturing a liquid crystal display element, the method including the step of electrically connecting the two.

The temperature required for curing by heating the base material of the conductive paste electrode for 15 minutes is 120 ° C. or less,
The thermosetting resin may be selected such that the temperature required for curing by heating for 5 minutes is 130 ° C. or higher. Also, the first
The pixel electrode of can be a common electrode, and the second electrode can be a segment electrode.

In this way, it is possible to manufacture with the current equipment without adding or using a special equipment, and it is possible to eliminate the problem called galvanic corrosion by simply changing the design of the main sealant without increasing the man-hours. it can.

The temperature and time for curing the electrically insulative seal member differ depending on the type of resin such as epoxy resin, polyimide resin and phenol resin, and even if the same epoxy resin is used, it depends on the cross-linking portion of the molecular structure. The density of the resulting three-dimensional stitch structure can be adjusted, and thus the curing temperature and time can be adjusted. The curing of the conductive paste electrode is further affected by the content ratio of the conductive fine particles contained in the resin as the base material. Usually, both resins are preferably epoxy resins from the viewpoint of easy formation of the seal portion by screen printing and good adhesion to the glass and the transparent electrode. In order to prevent the conductive paste electrode from sticking out by sticking the glass and expanding the electrically insulating seal part while maintaining the shape of the electrically conductive paste electrode and penetrating it into the inside. Adjustment of the hardness of both is performed in the precure (semi-curing) process.

The conductive paste electrode may contain silver particles or carbon particles.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

[0027]

EXAMPLES Liquid crystal display device (LC module) of this example
1 is a plan view of the transparent substrate 1 with the transparent substrate 2 removed and the surface of the transparent substrate 1 is viewed. FIG.
2 and FIG. 3 shows a view taken along the line AA of FIG. 1 to 3 show transparent electrodes 6 (common electrodes) arranged on the transparent substrates 1 and 2.

Further, as shown in FIG. 2, the conductive paste 1
Reference numeral 2 denotes a columnar shape, and a conductive paste 12 connects the transparent electrodes 6 arranged on the transparent substrates 1 and 2 in a bridge shape as shown in FIG. In addition, the width between the two transparent electrodes 6 shown in FIG. 2 is 0.4 mm to 1.0 mm, and the distance between the electrodes is 0.1 mm or more (there is no particular upper limit, but the distance should be about several mm depending on the display accuracy. The distance between the two transparent substrates 1 and 2 is a liquid crystal layer gap of 4 to 19 μm, the width of the main seal 11 is 1 to 1.5 mm, and the diameter of the conductive paste 12 is 0.5 to 1 mm. Is.

The feature of this embodiment is that the outer peripheral surface of the conductive paste 12 except the surface in contact with the transparent substrate is the main seal 11.
That is, the conductive paste 12 is not exposed to the outside. Therefore, on the outside of the main seal 11 which is a problem of the prior art, conductivity of impurities, moisture or the like is generated in a portion where the transparent electrodes 6 of the upper and lower transparent substrates 1 and 2 overlap or a portion where the terminals of the electrodes 6 are narrow and a voltage difference occurs. There is no possibility of causing a problem called electric field corrosion or electrolytic corrosion due to electric current caused by the adherence of the volatile substance.

A manufacturing method for covering the conductive paste 12 with a sealant will be described with reference to FIG.

Preparation of a glass base plate: A 1.1 mm thick float glass plate of soda lime silica composition, which was well washed as the glass base plates of the first and second substrates, was coated with an alkali elution preventive SiO ₂ film by sputtering. A glass plate with a conductive film having a thickness of 20 nm and an ITO film coated by 20 nm by a sputtering method was used. The surface resistance of the ITO film was 100 Ω / square.

Step 1. Electrode formation: The ITO electrode processing (patterning of the ITO conductive film) for forming pixel electrodes and wiring electrodes was performed by a photolithographic method using an etching solution in which 6N hydrochloric acid and a small amount of nitric acid were mixed and a masking resist. Electrode width 300 μm, distance between electrodes 10
32 0 μm stripe-shaped electrodes were formed.

Step 2. Application and curing of liquid crystal alignment film: An alcohol solution of a polyimide precursor (San Ever SE-610 manufactured by Nissan Chemical Industries, Ltd.) is applied on the surface substrate on which the electrode is formed, and the polyimide precursor is heated at 300 ° C. for 5 minutes. It was a heat-cured film of the body.

Step 3. Rubbing treatment: The polyimide film was rubbed with a rag cloth to form a liquid crystal alignment film.

Step 4A. Preparation of sealing member: Epoxy resin (Structbond ES-750, manufactured by Mitsui Toatsu Chemicals, Inc.
A silica columnar spacer (Micro Rod PF manufactured by Nippon Electric Glass Co., Ltd.) was dispersed in 0) to prepare an ink for screen printing.

Step 4B. Preparation of conductive paste electrode material:
A conductive spacer (Everyome 800PT) manufactured by Nippon Graphite Co., Ltd., which uses an epoxy resin as a base material, was dispersed with a conductive spacer (Nickel Micropearl manufactured by Sekisui Fine Chemical Co., Ltd.) to prepare an ink for screen printing.

Step 5A. Application of seal member: Glass is set at a predetermined position by the position mechanism of the screen printing machine, and the thickness of the seal is 75 μm, width except along one of the four edges of the glass plate, which is the liquid crystal injection part. Is 225
μm step 4A. The ink prepared in 1. was screen-printed to obtain a first substrate.

Step 5B. Application of conductive paste electrode: Glass is set at a predetermined position by a position mechanism of a screen printing machine, and a height of 7 is set at a predetermined position on the periphery of the glass plate.
Step 4B. Of a columnar shape having a diameter of 5 μm and a diameter of 300 μm. The ink prepared in step 1 was screen printed to obtain a second substrate.

Step 6A. First substrate pre-cure: 10
Precure (semi-curing) was performed at 0 ° C. for 13 minutes. At this time, the sealant was in a state of easily penetrating inside by pressing a soft and sharp pencil.

Step 6B. Precure of second substrate: 10
It was pre-cured (semi-cured) at 0 ° C. for 13 minutes to obtain a conductive paste electrode. This conductive paste electrode did not easily penetrate even when pressed with a hard and sharp pencil.

Step 7. Spacer spraying: Epoxy resin microbeads (Micropearl SP manufactured by Sekisui Fine Chemical Co., Ltd.) with a diameter of 5 μm are sprayed onto a glass substrate using a mixed solution of isopropyl alcohol (IPA) and pure water to volatilize alcohol and pure water. Let

Step 8. Lamination of glass substrate: Place the first glass substrate on the pace table of the laminating machine that aligns while observing the mark given to the predetermined position of the glass substrate by the optical lens, and place it in advance on it. Place the second glass substrate on the defined position and pressurize from above,
The columnar conductive paste electrode formed on the first glass substrate penetrated and was embedded so as to push the seal portion of the second substrate separately. As a result, the partition of the display section for sealing the liquid crystal was formed.

Step 9. Heat curing of seal member: 3kg /
It was carried out by heating at 170 ° C. for 33 minutes under a pressure of cm ² .

Step 10. Liquid crystal injection: Liquid crystal was injected and filled from the liquid crystal injection port into the display portion between the two substrates by a method using a depressurized vacuum container.

Step 11. Sealing of injection port: UV resin was applied to the injection port and cured by irradiation with ultraviolet rays.

The segment electrode and the common electrode thus obtained (electrode width 200 μm, distance between electrodes 30 μm)
An electrolytic corrosion occurrence test was conducted on each of the 16 LCD panels. The following test results are average values of 10 panels, and the number of defective display defects is counted while the LCD panel is lit and displayed after a lapse of 95% relative humidity and a temperature of 80 ° C.

[0047]

COMPARATIVE EXAMPLE A liquid crystal display device was manufactured in the same manner as in the above example except that the conductive paste electrode was formed at a position 0.375 mm away from the outer surface of the seal portion.

The results of Examples and Comparative Examples are shown in Table 1.

[0049]

[Table 1]

As shown in Table 1 above, an electrolytic corrosion generation test was conducted on 10 panels having 32 electrodes, and an LCD panel having the conductive paste 12 of the present invention embedded in the seal 11 is shown in FIG. Compared with the case where the conductive paste 12 was provided on the outer side of the seal 11, the number of electrolytic corrosions generated was almost halved.

According to the above-described embodiment of the present invention, a liquid crystal display device which is free from electrolytic corrosion and does not increase the number of working steps by using the equipment currently used without adding or using a special device. Manufacture becomes possible.

Further, according to the present embodiment, by simply changing the design of the main seal 11 for enclosing the liquid crystal region of the LCD panel, the resin can be filled while using the existing equipment to prevent electrolytic corrosion. .

In this embodiment, since the countermeasure against electrolytic corrosion can be taken only by changing the design of the main seal 11, the countermeasure against electrolytic corrosion can be easily carried out in a short time, and a new product can be dealt with, and it is necessary to install new equipment. Absent. Furthermore, the manufacturing cost does not increase because the work man-hours can be unchanged.

[0054]

According to the present invention, it is possible to provide a liquid crystal display device in which electric field corrosion does not occur between electrodes outside the main seal.

[Brief description of drawings]

FIG. 1 is a plan view of the surface of a transparent substrate of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a circle B portion of FIG.

FIG. 3 is a view taken along the line AA of FIG.

FIG. 4 is a flowchart showing a manufacturing procedure of the liquid crystal display device according to the embodiment of the present invention.

FIG. 5 is a perspective view of a conventional liquid crystal display device.

6 is a plan view of an active area, a viewing area, an LSI, an electrode wiring, etc. of the LCD shown in FIG.

7 is a diagram showing a common electrode and a segment electrode of the LCD shown in FIG.

FIG. 8 is a plan view showing a main seal and an electrode end portion in a state in which one transparent substrate of a conventional liquid crystal display device is removed.

9 is a cross-sectional view taken along the line AA of FIG. 8 (including both transparent substrates).

10 is an enlarged view of a circle B portion in FIG.

[Explanation of symbols]

1 front substrate 2 back substrate 3 LCD 3a Active area 3b Viewing area 5, 6 Wiring 7 LSI 8 Circuit board part 11 Main seal 12 Conductive paste 14 Lead

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuya Sato             7 nano at 6 Nagasaki, Okajima, Fukushima City, Fukushima Prefecture             X Co., Ltd. F-term (reference) 2H089 LA19 LA41 QA16 TA01                 2H092 GA48 HA26 NA25 PA01 PA03

Claims (6)

[Claims] 1. A first substrate having a first pixel electrode provided on the surface thereof, a second substrate having a second pixel electrode provided on the surface thereof, and the two pixel electrodes arranged to face each other. An electrically insulative seal part for forming a display area by liquid-sealing the liquid crystal in a space that can be formed, and the second pixel electrode in a non-display area outside the seal part on the surface of the second substrate. A second wiring electrode and a first wiring electrode for the first pixel electrode, wherein the pixel electrode of the first substrate is a conductive paste embedded in the electrically insulating seal portion. A liquid crystal display, which is formed so as to be electrically connected to the first wiring electrode through an electrode, and the pixel electrode of the second substrate is formed integrally with the second wiring electrode. element. 2. The base material of the conductive paste electrode and the electrically insulating seal member are formed of an epoxy resin, and the conductive paste electrode contains silver particles or carbon particles. Item 3. A liquid crystal display device according to item 1. 3. The liquid crystal display element according to claim 1, wherein the first pixel electrode is a common electrode and the second electrode is a segment electrode. 4. A step of 1) forming a first pixel electrode in a display area forming portion of a surface of a first substrate, 2) forming a second pixel electrode in a display area of a surface of a second substrate, and A step of forming a second wiring electrode integrally connected to the second pixel electrode and a first wiring electrode for the first pixel electrode in the display region forming portion, 3) first substrate and second substrate A step of forming a liquid crystal alignment film on the surface on which each pixel electrode is provided, 4) A display obtained by sealing the liquid crystal in the display region forming portion between the first substrate and the second substrate. A step of applying a thermosetting resin, which serves as an electrically insulating seal portion for partitioning the area to the non-display area, to the second substrate and pre-curing it. 5) A thermosetting resin is formed on the surface of the first substrate. A conductive paste electrode as a material is spot-applied to the portion corresponding to the seal portion, and the second base is applied. A step of pre-curing so as to have hardness higher than that of the thermosetting resin formed on the surface, 6) embedding the first substrate and the second substrate in the electrically insulating seal portion by embedding the electrically conductive paste electrode And electrically connecting the first pixel electrode and the first wiring electrode through the conductive paste electrode by a step of heat-bonding the sealing member, and then, the manufacturing method of the liquid crystal display element. . 5. The method of manufacturing a liquid crystal display element according to claim 4, wherein the base material of the conductive paste electrode provided on the first substrate and the sealing member provided on the surface of the second substrate are made of epoxy resin. . 6. The temperature required for curing by heating the base material of the conductive paste electrode for 15 minutes is 120.degree.
6. The thermosetting resin is selected so that the temperature required for curing by partial heating is 130 ° C. or higher.
A method for producing the liquid crystal display element described.