JP2506833B2 - Liquid crystal display manufacturing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device for displaying characters or images, and more particularly to a liquid crystal display in which a liquid crystal cell is filled with liquid crystal and then an adhesive is sucked and sealed. The present invention relates to a method for manufacturing a device.

2. Description of the Related Art As a conventional technique, there is a method of manufacturing a liquid crystal display device having a structure as shown in FIG. 8 as disclosed in Japanese Patent Laid-Open No. 24518/1985. FIG. 8a is a sectional view of the liquid crystal cell, and FIG. 8b is a plan view of the liquid crystal cell. In these figures, 19 and 20 are flexible substrates, which are made of a plastic film or sheet, 21 is an adhesive layer provided around the substrate, 22 is a cell thickness control material, various substances, For example, there are glass fibers, polymer fine particles, films and the like, but it is said that the use of polymer fine particles is particularly preferable. 23 is a space for accommodating the liquid crystal. When injecting liquid crystal from the liquid crystal inlet 24 into the liquid crystal cell of this structure,
As a method for injecting this liquid crystal, for example, the liquid crystal cell is left in a vacuum system to depressurize the inside of the cell, then the liquid crystal injection port of the cell is introduced into the liquid crystal, and the liquid crystal is brought to atmospheric pressure. By utilizing the pressure difference from the internal pressure of the liquid crystal cell and the capillary phenomenon, liquid crystal is injected and filled in the liquid crystal cell so that an excessive liquid crystal content is generated. When the liquid crystal is filled in the liquid crystal cell, the surface of the liquid crystal cell is uniformly pressed to remove the excess liquid crystal component from the liquid crystal inlet of the liquid crystal cell to the outside of the system, and then the liquid crystal inlet is sealed. In this case, the liquid crystal cell surface can be pressed with any pressure as long as it has a smooth surface such as a roller or a pressing plate, and the liquid phase injection port of the cell is sealed using an ultrasonic welder or the like. You can do it. However, in this method, since the liquid crystal cell is sealed under pressure, a considerable amount of time is required to suck the adhesive used for the sealing into the liquid crystal cell, which is not suitable for mass production. When sealing in a short time, the amount of adhesive to be sucked into the liquid crystal cell is small, which is considered to be unfavorable for reliability in terms of moisture resistance and image quality. After sandwiched between plates having a smooth surface, such as plates, and pressing and fixing, liquid crystal is injected into the liquid crystal cell from the liquid crystal injection port of the liquid crystal cell. When the liquid crystal is injected, both sides of the liquid crystal cell are pressed by the smooth surfaces, so that the liquid crystal cell is filled with the liquid, and therefore, after the liquid crystal is injected into the cell, the injection port may be sealed as it is. . According to this method, since there is no change in the volume of the liquid crystal during inhalation of the adhesive required for sealing in the panel, the adhesive applied to the liquid crystal inlet is only sucked into the liquid crystal cell by the capillary phenomenon. Inhalation time is considerably required, and it has a drawback that it is not suitable for mass production.

Still another conventional technique is, for example, JP-A-59-21.
As shown in Japanese Patent No. 8424, there is a manufacturing method of a liquid crystal display device as shown in FIG. 9a is a sectional view showing the first manufacturing method thereof, and FIG. 9b is a sectional view showing the second manufacturing method thereof and a plan view of an adhesive reservoir by the manufacturing method. In FIG. 9A, 25 is a squeegee, 26 is a screen, 27 is a pattern of the screen 26, 28 is a liquid crystal cell, 29 is a liquid crystal cell sealing port, 30 is a printing stage, and 31 is a sealing adhesive. The screen used is 50 mesh, emulsion thickness 40μ
The printing conditions were a squeegee pressure of about 5 kg / cm ² and a squeegee speed of about 5 mm / sec. At this time, when a resin of about 200 poise was used as a sealing adhesive, the cell thickness was uniform, and a liquid crystal cell in which the sealing adhesive appropriately penetrated into the cell injection port was formed. According to another second manufacturing method, as shown in FIG. 9B, 25 is a squeegee, 32 is a screen without a pattern, 28 is a liquid crystal cell, 29 is a liquid crystal cell sealing port, and 30 is a printing stage. Reference numerals 33 are films provided with an adhesive reservoir 33 'for sealing. As shown in FIG. 9b, a screen 32 having no pattern is used, and a polyester film 33 provided with a sealing adhesive reservoir 33 'is placed below the screen 32, and the adhesive is stored in the adhesive reservoir 33'. It is said that the same cells as in the above-mentioned embodiment were formed when the same cells as in the above-mentioned embodiment were stored. However, according to this method, the movement of the liquid crystal will occur with the movement of the squeegee, but the movement trace of the squeegee is the drawback that the gap of the liquid crystal cell does not appear accurately due to the restoration of the warp of the glass substrate and the elastic deformation of the spacer. In addition, it is necessary to make the speed at which the liquid crystal flows out from the liquid crystal inlet of the liquid crystal cell and the moving speed of the squeegee almost equal, but it is extremely difficult, and from the viewpoint of the configuration, the squeegee can prevent the liquid crystal cell from moving. Since the adhesive is applied to the liquid crystal injection port at the same time as it passes, the amount of the sealing adhesive that is sucked into the liquid crystal cell is small, and it is inferior in terms of moisture resistance, which significantly affects the image quality, resulting in reliability. It seems to have a defect that there is a defect in.

Problems to be Solved by the Invention As described above, the conventional method is a method of sucking the adhesive applied to the liquid crystal injection port of the liquid crystal cell into the liquid crystal cell by a capillary phenomenon, and it takes time to suck the adhesive. Not only is it not suitable for mass production, but if time efficiency is emphasized, the amount of adhesive taken into the liquid crystal cell will be small, which will adversely affect the image quality due to moisture absorption, etc. It is difficult to perform proper liquid crystal sealing.

The present invention has been made in view of the above points, and it is possible to manufacture a liquid crystal display device suitable for mass production with a simple configuration, and perform complete liquid crystal sealing.

Means for Solving the Problems In order to solve the above problems, the present invention fills and seals a liquid crystal in a liquid crystal cell consisting of a pair of substrates with electrodes and a first adhesive interposed between the substrates. When manufacturing a display device, a step of injecting the liquid crystal into the liquid crystal cell in a vacuum without pressurizing the liquid phase cell at room temperature, and a step of pressurizing the liquid crystal cell with a pressurizing body in a heated state. , A step of standing still for ₁ second under pressure in a heated state, a step of applying a second adhesive to the liquid crystal inlet of the liquid crystal cell in a heated state, and a step of applying the second adhesive to the liquid crystal cell in a heated state. It consists of a step of allowing the pressurized body to stand still for a second and then sucking a certain amount of the second adhesive into the liquid phase cell from the liquid crystal inlet, and a step of curing the second adhesive. A method for manufacturing a liquid crystal display device is obtained.

Action According to the above-mentioned manufacturing method, after injecting liquid crystal without pressurizing the liquid crystal cell at room temperature, the liquid crystal cell is pressed by a pressurizing body in a heated state thereafter to remove excess liquid crystal outside the liquid crystal cell,
Apply a sealing adhesive to the liquid crystal inlet, remove the pressure body of the liquid crystal cell, and suck a certain amount of adhesive into the liquid crystal cell from the liquid crystal inlet due to elastic deformation of the glass substrate of the liquid crystal cell. , It cures, and the penetration time is extremely short,
Moreover, the amount of the adhesive can be easily controlled, and it has an effect of being suitable for mass production.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. The basic structure of a liquid crystal display device is a combination of a panel filled with liquid crystal between a pair of electrode substrates and a polarizing plate, and is composed of liquid crystal molecules that are initially aligned and rearranged with voltage applied to the electrodes. The light and shade are displayed by the difference in refraction. A liquid crystal display device manufactured based on the manufacturing method of the present invention is shown in FIGS. 6 and 7.

In FIG. 6, the liquid crystal display device includes a transparent electrode 7, a front glass plate 9 having an alignment film 8 formed thereon, a TFT element (transistor element formed of a thin film transistor and used for switching a voltage applied to a pixel electrode) section 10, Between the pixel portion 11 and the liquid crystal display substrate 13 having the alignment film 12 thereon,
A sealant 14 with a predetermined spacer mixed in the periphery
The liquid crystal 15 and many spacers 16 are present in the panel surrounded by the sealant 14. Then, the polarizing plates 17 and 18 are formed by being attached to both surfaces of the front glass plate 9 and the liquid crystal display substrate 13.

FIG. 7 shows the structure on the substrate 13 side, where G is the gate electrode of the TFT element, I is the insulating film, A is the channel active portion made of amorphous silicon, and M is the source and drain electrodes.

Here, a method for manufacturing the liquid crystal display device of the present invention will be described. As described above, in the liquid crystal display device of the present invention, a liquid crystal cell is assembled by a pair of glass plates and an adhesive agent interposed therebetween, and a part of the adhesive agent is opened in the liquid crystal cell to form a liquid crystal injection port. Then, it is manufactured by injecting and sealing liquid crystal.

Also, by forming a gelatin film, a transparent electrode, a metal, an insulating film, an alignment film, etc. on the glass substrate, warpage of the glass substrate occurs, but when the liquid crystal cell is assembled and observed under a single wavelength light source, the liquid crystal It is known that the vicinity of the center of the cell is in a medium-high state of about 1 μm. In this state, the liquid crystal is injected into the liquid crystal cell in vacuum without pressurizing the liquid crystal cell at room temperature. It has been experimentally found that it takes about 30 minutes to fill a liquid crystal cell having a gap gap thickness of about 6 μm and a volume of about 18 mm ³ with liquid crystal by pressurizing the liquid crystal cell.
However, it was found that when the liquid crystal was injected into this liquid crystal cell in a vacuum while keeping the medium and high state, the liquid crystal was filled within 5 minutes. Therefore, this method of manufacturing a liquid crystal display device is advantageous in terms of time and can improve the efficiency of mass production. First
FIG. A is a plan view of the vicinity of the liquid crystal inlet 3 of the liquid crystal cell 2 filled with the liquid crystal 1. FIG. 1b is a plan view of a liquid crystal cell in which the liquid crystal cell 2 is sealed with a sealing adhesive 4. Also, by injecting the liquid crystal at room temperature, the volatile component of the liquid crystal contained in the liquid crystal does not evaporate more easily than when heated in a vacuum, and the viscosity does not change, so it can be reused by passing it through the filter. It is advantageous in cost.

Next, pressure is applied to the liquid crystal cell filled with the liquid crystal using a pressure member to correct the warpage of the liquid crystal cell and to obtain a uniform gap of the liquid crystal cell, which will be described with reference to FIG. It was confirmed that in a liquid crystal cell having a liquid crystal layer having a thickness of 6 μm and a volume of about 18 mm ³ , the outflow of the liquid crystal stopped after about 2 minutes in a heated state at 40 ° C.
It took about 5 minutes at room temperature. It is considered that this is because when the liquid crystal cell was heated, the viscosity of the liquid crystal was lowered and the liquid crystal easily flowed out. The material of the pressurizing body 5 used here may be a metal such as aluminum or stainless steel, a rigid body such as resin such as Teflon, or a flexible structure such as silicon rubber. However, in the case of a rigid body, if a hard rubber or glass chipping is interposed between the liquid crystal cell 6 and the pressing body 5, there is a defect that a local gap defect occurs in the liquid crystal cell. Therefore, it is necessary to devise such as a pressurizing body made of only silicon rubber, or silicon rubber only at the screen portion of the liquid crystal cell and a metal such as aluminum at the periphery. Experimentally, when a pressure member that presses the screen portion of the liquid crystal cell with silicon rubber was used, a uniform liquid crystal layer thickness was obtained, and there was no concern about defects and the image quality was good.

The pressurizing body of the present invention is made up of a rigid body 5a such as aluminum and a flexible member 5b such as silicon rubber, in which a boring is formed inside aluminum and silicon rubber is fitted therein.

FIG. 3 shows a sectional view of the pressurizing body of the embodiment of the present invention. As shown in FIG. 3a, one surface b of the flexible member made of silicon rubber a is processed to be flat, and it is difficult to peel it off when it is brought into contact with the surface of aluminum c having a boring inside. . Further, a cone-shaped convex portion d is provided on the other surface, and FIG. 3b shows a state in which a liquid crystal cell is sandwiched between pressurizing bodies to apply pressure. A layer e is formed so that the layer is easily peeled off from the silicone rubber liquid crystal cell. When the pressure is further applied, the convex portion is deformed and a uniform pressure is applied to the liquid crystal cell, which can be ideally pressed.

Also, after the liquid crystal cell is pressurized by the pressure body, while the liquid crystal is flowing out from the liquid crystal inlet, in the pressurized state, the sectional area of the liquid crystal inlet, the volume of the liquid crystal cell, the warpage of the substrate, the pressing force by the pressure body, etc. Therefore, it is known that there is a variation in the stationary time t ₁ second. Experimentally, the pressing force was examined between 5kg and 20kg, and the liquid crystal leaked out when the size of the liquid crystal inlet varied from 1mm to 3mm, and when the warpage of the substrate was larger than the gap of the liquid crystal layer by about 5μm. When the time was measured, it was about 2 minutes. However, in a liquid crystal cell having one liquid crystal inlet, the relationship between the liquid crystal outflow time and the pressing force when the cross-sectional area of the liquid crystal inlet is about 2 × 10 ^-2 mm ² is shown in FIG.
The relationship between the liquid crystal outflow time and the warpage of the substrate is shown in FIG. 4b. As a condition, the pressing force is 5 kg and the liquid crystal cell is about 0.6 kg / c.
A pressure of m ² is applied. When a pressure body with a combination of a rigid body and a flexible structure is used under this pressure level,
No defects such as a local gap defect of the liquid crystal cell, which is a fatal defect in image quality, occurred. The shaded area indicates the range of measured values obtained in the experiment. Further, when there are a plurality of liquid crystal inlets, the liquid crystal outflow time seems to be short.

Next, after the liquid crystal has stopped flowing out of the liquid crystal inlet while the liquid crystal cell is under pressure, a sealing adhesive is applied to the liquid crystal inlet of the liquid crystal cell. Further, the pressurizing body is removed, and the adhesive for sealing is sucked into the liquid crystal cell by elastic deformation of the warp of the substrate. When the heating temperature was experimentally examined from room temperature to about 120 ° C, it was found that from about 100 ° C, the viscosity of the adhesive used for encapsulation decreased, and the adhesive invaded instantaneously, making it unsuitable for mass production. It has been experimentally found that a room temperature to about 80 ° C is suitable for allowing the sealing adhesive to be sucked into the panel in a controlled manner. It was experimentally found that the time t ₂ seconds required for inhaling the sealing adhesive is t ₂ = 20 in a liquid crystal cell having a liquid crystal layer having a thickness of 6 μm and a volume of about 18 mm ³ . In the case of a large A4 size substrate, when the thickness of the liquid crystal layer was 6 μm, the sealing adhesive was inhaled in 10 seconds. In case of small board, warpage is 1μ
A liquid crystal cell having a liquid crystal layer thickness of 6 μm and a volume of 8 mm ³ took about 45 seconds. From the above experimental results, the standing time until the liquid crystal cell pressure body is removed and the sealing adhesive is cured
t ₂ appears to be in the range of 0t ₂ 60.

Fig. 5a shows the relationship between the inhalation time of the sealing adhesive in the liquid crystal cell and the warpage of the substrate when the thickness of the liquid crystal layer is 6 µm and the volume is 18 mm ³ . FIG. 3 is a diagram showing the relationship between the time taken for the adhesive of FIG. It turns out that the above relationships are met. The shaded area shows the range of measurement values obtained in the experiment.

Finally, in order to cure the sealing adhesive, it is necessary to instantly solidify the liquid crystal cell as it can sufficiently cope with the time management after the pressure of the pressure body of the liquid crystal cell is unloaded. An ultraviolet curable resin was used as one satisfying the conditions. Experimentally, a sufficiently good result was obtained by using an ultraviolet curable resin that completely cures under an ultraviolet irradiation condition of 25 mw / cm ² for 180 seconds.

As a method of heating the liquid crystal cell, heat transfer heating by a heater,
There are radiant heating by a heating furnace and radiant heating by infrared rays.
When each method was experimentally tried to keep 40 ° C and the thermocouple was fixed on the surface of the liquid crystal cell and the temperature was measured, the size of the heater was set to the size of the liquid crystal cell in the transfer heating by the heater. The liquid crystal cell surface temperature could be kept at 40 ° C by setting the set temperature to 50 ° C. Moreover, in the radiant heating by the heating furnace, the temperature of the liquid crystal cell surface could be kept at 40 ° C by setting the heating furnace to 40 ° C and heating for 10 minutes or more.

In radiant heating by infrared rays, it was found that when the height of an infrared lamp of 100 W was moved to a position 30 cm away from the liquid crystal cell and irradiation was performed, it reached 40 ° C. in about 5 minutes.

When a liquid crystal display device was manufactured by the above process using an experimentally easy heating furnace, a liquid crystal display device with a uniform liquid crystal layer thickness was obtained, and the image quality was good.

As described above, according to the present embodiment, the liquid crystal injection time can be shortened as compared with the conventional case, and the sealing adhesive can be uniformly sucked and sealed in the liquid crystal cell in a shorter time than the conventional case, and the liquid crystal layer of the liquid crystal display device can be uniformly formed. It has been found that it has the effect of maintaining various thicknesses and having good image quality.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

(1) The uniform thickness of the liquid crystal layer of the liquid crystal display device can be maintained to the extent that there is no practical problem.

(2) Liquid crystal sealing of a liquid crystal display device can be carried out stably and uniformly in a relatively short time.

(3) A liquid crystal display with excellent display quality can be obtained.

(4) A large amount of processing can be performed relatively stably.

[Brief description of drawings]

FIG. 1 is a plan view of a liquid crystal display device that has been subjected to the method for manufacturing a liquid crystal display device of the present invention, FIG. 2 is a perspective view showing the method of manufacturing a liquid crystal display device of the present invention, and FIG. FIG. 4 is a relational diagram showing the liquid crystal outflow time, FIG. 5 is a relational view showing the sealing agent inhalation time, and FIG. 6 is a liquid crystal display manufactured using the method for manufacturing a liquid crystal display device of the present invention. FIG. 7 is a sectional view of the device, FIG. 7 is a sectional view of a TFT element portion and a pixel portion of the liquid crystal display device, FIG. 8 is a plan view showing a manufacturing method of the liquid crystal display device in a conventional example, and FIG. 9 is another conventional example. FIG. 6 is an explanatory view showing a manufacturing method of. 1 ... Liquid crystal, 2 ... Liquid crystal cell, 3 ... Liquid crystal inlet, 4 ...
... Sealing adhesive, 5a, 5b ... Pressurizing body, 6 ... Liquid crystal cell, 7 ... Transparent electrode, 8 ... Alignment film, 9 ... Front glass, 10 ... TFT element section, 11 ... … Pixel part, 12 …… Alignment film, 1
3 …… Liquid crystal display substrate, 14 …… Sealant, 15 …… Liquid crystal, 1
6 …… Spacer, 17 …… Polarizer, 18 …… Polarizer, 19,20…
… Flexible substrate, 21 …… Adhesive layer, 22 …… Cell thickness control material,
23: Space for accommodating liquid crystal, 24: Liquid crystal inlet, G ...
... Gate electrode, I ... Insulating film, A ... Channel active part made of amorphous silicon, M ... Source / drain electrode, 25 ... Squeegee, 26 ... Screen, 27 ... Screen pattern, 28 ... Liquid crystal cell , 29 …… liquid crystal cell sealing port, 30 …… printing stage, 31 …… sealing adhesive,
32 …… Screen without pattern, 33 …… Film, 33 ′…
... Adhesive for sealing.

Claims (2)

(57) [Claims] 1. When manufacturing a liquid crystal display device by injecting and sealing a liquid crystal into a liquid crystal cell consisting of a pair of substrates with electrodes and a first adhesive interposed between the substrates, the liquid crystal cell is kept at room temperature. A step of injecting the liquid crystal into the liquid crystal cell in a vacuum without applying pressure, a step of pressurizing the liquid crystal cell with a pressurizing body in a heated state, and a standing state for a predetermined time in the heated state A step of applying a second adhesive to the liquid crystal injection port of the liquid crystal cell in a heated state; A method of manufacturing a liquid crystal display device, which comprises a step of sucking a substantially constant amount of the second adhesive from the liquid crystal inlet into the liquid crystal cell, and a step of curing the second adhesive. . 2. The pressing body comprises a rigid body and a member having a flexible structure, the rigid body has a boring, and the member having the flexible structure has a flat first surface and a predetermined second surface. A plurality of convex portions, the convex portions are formed in a conical shape and are arranged at predetermined intervals, the second surface is a surface contacting the liquid crystal cell, and the first surface is the rigid body. The method for manufacturing a liquid crystal display device according to claim 1, wherein the pressure member presses the liquid crystal cell after the liquid crystal is injected, the surface being in contact with the boring.