JPH01114822A - Manufacture of liquid crystal display device - Google Patents

Abstract

PURPOSE:To almost completely seal a liquid crystal cell by a simple manufacturing method by providing a process for pressing a liquid crystal by a pressure body and injecting a liquid crystal, and a process for pressing the liquid crystal cell by the pressure body, and applying an adhesive agent for sealing to a liquid crystal injection port. CONSTITUTION:A liquid crystal cell 1 is inserted and held by pressure bodies 2, and placed in a cassette which can be pressed. When a knob 6 is rotated, a spring 5 which has contracted is restored and presses the pressure body 2 and as a result, the liquid crystal cell is pressed. In case of injecting a liquid crystal, the injection port of the liquid crystal cell is immersed into a liquid crystal reservoir in a vacuum and when it is set to the atmospheric pressure in its state, the inside of the liquid crystal cell goes to vacuum, and by a difference of the atmospheric pressure, the liquid crystal is injected into the inside of the liquid crystal cell. In such a state, furthermore, extending from the liquid crystal injecting process to the adhesive agent hardening process for sealing, the liquid crystal cell is pressed by the pressure body, a gap of the liquid crystal cell is corrected, and thereafter, a temperature management is executed. In such a way, uniform liquid crystal layer thickness of a picture element part of the liquid crystal cell can be obtained and a uniform and stable image can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a liquid crystal display device for displaying characters or images, and in particular to a method for manufacturing a liquid crystal display device for displaying characters or images, and in particular, a liquid crystal display device having a structure in which the thickness of the liquid crystal layer in each pixel portion is constant to obtain a uniform image. The present invention relates to a method of manufacturing a display device.

Conventional technology As disclosed in Japanese Patent Laid-Open No. 56-146122, for example, there is a liquid crystal display in which spacers are dispersed within a liquid crystal cell so that the internal pressure of the liquid crystal cell at room temperature and atmospheric pressure is lower than atmospheric pressure. There is a method for manufacturing the device. When this method is used, spacers are dispersed within the liquid crystal cell so that the two substrates of the liquid crystal cell do not come into contact with each other.

Other conventional techniques include, for example, Japanese Patent Application Laid-Open No. 68-193
As shown in Publication No. 518, the diameter of the spacer included in the seal in the liquid crystal cell is made larger than the diameter of the spacer dispersed in the liquid crystal cell, and the internal pressure of the liquid crystal cell at room temperature and atmospheric pressure is lower than atmospheric pressure. There is a method for manufacturing a liquid crystal display device. When this method is used, the diameter of the spacer included in the seal is dispersed within the liquid crystal cell so that the two substrates of the liquid crystal cell do not come into contact with each other, and in order to obtain a tightening effect near the seal from the viewpoint of reliability. larger than the diameter of the spacer.

Here, there are two methods for making the internal pressure of the liquid crystal cell lower than atmospheric pressure at room temperature and atmospheric pressure. The first method is to heat the liquid crystal cell and the liquid crystal at a temperature higher than room temperature and seal the liquid crystal cell.The difference in thermal contraction between the liquid crystal and the liquid crystal inside the liquid crystal cell causes the inside of the liquid crystal cell to be in a depressurized state, and the liquid crystal is heated to a temperature higher than room temperature. This is a method of keeping the liquid crystal layer between the two substrates constant. The second method is to inject liquid crystal into a liquid crystal cell and then forcibly discharge a portion of the liquid crystal and seal it, thereby reducing the internal pressure of the liquid crystal cell to atmospheric pressure. . However, in the first method, the volume of thermal contraction relative to the volume of liquid crystal in the liquid crystal cell is minute, and in order to obtain the effect of thermal contraction to the extent that the two substrates come into contact, the liquid crystal cell and the liquid crystal must be heated at a very high temperature. The disadvantage is that it has to be done. For example, when a liquid crystal cell is heated and liquid crystal is injected into the liquid crystal cell, the liquid crystal is heated at the same time, but it is necessary to adjust the temperature to a temperature that does not cause compositional deformation of the liquid crystal. The temperature at which compositional changes occur in general liquid crystals is about 90°C. If boric acid glass is used for the substrate of a liquid crystal cell, its thermal expansion coefficient is about 10'/C, and the thermal expansion coefficient of liquid crystal is about 10-4/C. Therefore, since the number of digits is different, if we ignore the thermal expansion of the glass and focus on the thermal expansion of the liquid crystal, the volume of the liquid crystal cell is approximately 16 - approximately 7
At a temperature difference of 0'C, the volume change is approximately 0.1-. On the other hand, the warpage of the liquid crystal cell substrate is approximately 3 μm, and the volume change required to flatten the warp is approximately 11 μm, so it is not possible to flatten the warp of the liquid crystal cell substrate by changing the volume of the liquid crystal alone. seems to be difficult.

In addition, in the second method, if the liquid crystal discharge port is on the substrate, this method is suitable for reducing the pressure inside the liquid crystal cell, but if the liquid crystal injection port is between the substrates, the discharge port is provided on the substrate. It seems difficult to reduce the pressure inside the liquid crystal cell unless there is a problem.

Further, as other conventional techniques, for example, Japanese Patent Application Laid-Open No. 60-2
As shown in Publication No. 0724, in the step of sealing after injecting liquid crystal into the liquid crystal filling port of a liquid crystal cell, a photocurable resin is applied while maintaining the temperature at 10 to 26 degrees Celsius higher than room temperature, After further cooling to room temperature, the room temperature is about 6 degrees Celsius.
The above examples were cured and sealed under conditions that would not cause any rise in temperature.

FIG. 7 shows a relationship between temperature and process of a conventional liquid crystal cell and a plan view of the liquid crystal cell. Section a indicates the liquid crystal injection step. The section indicates that the temperature of the liquid crystal cell decreases when moving from the liquid crystal injection process to the sealing adhesive coating process. Section C indicates that the temperature is raised from room temperature until the sealing adhesive curing step.

At this time, the sealing adhesive 32 sucked into the liquid crystal cell 31
flows back due to thermal expansion of the volume of the liquid crystal 33. Section d is a sealing adhesive curing step, and is characterized by a temperature lower than room temperature and 95° C. or lower. Adhesive for board bonding 3
A sealing adhesive 32 is applied to a liquid crystal injection port 35 provided in a part of 4.
is applied and sucked into the liquid crystal cell due to volumetric contraction of the liquid crystal as the temperature drops.

FIG. 7(b) is a diagram showing the details of the entrance in FIG. 7(IL), and shows the state of the liquid crystal cell after the liquid crystal is injected and the sealing adhesive is applied. A liquid crystal cell 31 is filled with liquid crystal 33, and a sealing adhesive 32 is sucked into the liquid crystal cell.

As described above, when a liquid crystal cell is manufactured using this method under conditions where the temperature is returned to room temperature and then raised, the adhesive used for sealing is sucked into the layer edge liquid crystal cell. 7th
Figure (0) K As shown in detail in part B of Figure (1), backflow occurs and a backflow trace 36 of the adhesive used for sealing is formed, resulting in poor sealing reliability and severe cases. Although the liquid crystal cell is sealed, a passage connecting the inside and outside of the liquid crystal cell is formed due to the backflow of the sealing adhesive, causing air bubbles to flow into the liquid crystal cell.

Problems to be Solved by the Invention In such a conventional manufacturing method of a liquid crystal display device, the internal pressure of a liquid crystal cell injected with liquid crystal at room temperature and atmospheric pressure is lower than atmospheric pressure, and a uniform liquid crystal layer in the pixel area is created. It was difficult to obtain this by simply utilizing the difference in thermal contraction of liquid crystals. In addition, it was possible to inhale the sealing adhesive into the liquid crystal cell by utilizing the difference in thermal contraction of the liquid crystal, but it was difficult for the sealing adhesive to harden without flowing back into the liquid crystal cell after being sucked into the liquid crystal cell. was also extremely difficult.

Means for solving the problems The means for solving the above problems of the present invention are as follows. Manufacturing a liquid crystal cell consisting of a set of electrode-equipped substrates and an adhesive/spacer for bonding the substrates interposed between the substrates, injecting liquid crystal between the glass substrates, and applying the adhesive for bonding the substrates. When manufacturing a liquid crystal display device consisting of a sealing adhesive present in a partially opened liquid crystal injection port, the liquid crystal cell is pressurized with a pressure body to inject liquid crystal, and the liquid crystal cell is pressurized. applying the adhesive for sealing to the liquid crystal injection port under pressure with a pressure body at a temperature of t1°C; It consists of a step of leaving the liquid crystal cell coated with the adhesive still, and a step of pressurizing the liquid crystal cell with a pressure body and curing the adhesive for sealing at a temperature of t5°C, tl>t2 It is characterized by having the relationship of ≧t3 and t5°C being equal to or higher than room temperature.

action The effect of this technical means is as follows.

In other words, the rough edges of the substrate of the liquid crystal cell are flattened by pressurizing the liquid crystal cell with a pressurizing body, and the liquid crystal sealed in the liquid crystal cell is heated and then air-cooled to room temperature, causing thermal contraction of the liquid crystal. At room temperature and atmospheric pressure, the internal pressure of the liquid crystal cell becomes lower than atmospheric pressure, the remaining warpage of the substrate of the liquid crystal cell is corrected, and a uniform liquid crystal layer in the pixel portion of the liquid crystal cell is obtained. In addition, the liquid crystal cell is heated under pressure with a pressure body, liquid crystal is injected, a sealing adhesive is applied to the liquid crystal injection port, the heating temperature is lowered, and the sealing adhesive is injected into the liquid crystal cell. Inhale. Furthermore, by curing the sealing adhesive at a temperature lower than the temperature at which it is sucked, almost complete sealing can be obtained without causing the sealing adhesive sucked into the Shibanel to flow back.

EXAMPLE Hereinafter, an example of the present invention will be described based on the drawings. A liquid crystal display device manufactured based on the manufacturing method of the present invention is shown in FIGS.

In FIG. 6, the liquid crystal display device includes a front glass plate 21 having a transparent electrode 19 and an alignment film 20 thereon, a TPTJ element (transistor element composed of a thin film transistor and used for switching the voltage applied to the pixel electrode) part 22, and Between the pixel part 23 and the liquid crystal display substrate 26 on which the alignment film 24 is attached, there is a sealant 26 mixed with a predetermined spacer in the peripheral part, and the inside of the panel surrounded by the sealant 21 is LCD 27. A number of spacers 28 are present.

The polarizing plates 29 and 30 are pasted on both sides of the front glass plate 21 and the liquid crystal display substrate 26.

FIG. 6 shows the structure on the substrate 26 side, where G is TPT.
The gate electrode of the device, I is an insulating film, M is a channel active region made of amorphous silicon, and M is a source and drain electrode.

Here, a description will be given of applying and sealing a sealing adhesive to a liquid crystal injection port of a liquid crystal cell while the liquid crystal cell is pressurized by a pressurizing body. FIG. 1 is a perspective view of a liquid crystal cell and a cassette to show one embodiment of the present invention. A liquid crystal cell 1 is sandwiched between pressurizing bodies 2 and placed in a pressurizable cassette. Here, the structure of the cassette will be briefly explained. The cassette forms a container consisting of six side plates 3, one side plate 3a has a hole 4 in the center, and a spring 6. Knob 6, needle roller bearing 71 rotations for smooth rotation of the knob! ! ! ! Link ball that converts a groove into a linear mechanism 8. It is composed of a spring slippage prevention plate 9, and when the knob 6 is rotated, the compressed spring 6 restores itself and presses the pressurizing body 2, and as a result, the liquid crystal cell is pressed.

The spring 6 used for this was designed to have a pressing force of 6 kq.

FIG. 2 is a perspective view of the liquid crystal cell. Two boards 10.1
An adhesive 12 for bonding the substrates was interposed between the two, and a part of the adhesive was opened to provide a liquid crystal injection port 13. FIG. 3 is a side view of a cassette containing the liquid crystal cell 1 shown in FIG. 2. A part of the side plate 3 of the cassette is cut out in order to inject liquid crystal from the injection port 13 of the liquid crystal cell and to apply a sealing adhesive. FIG. 4 shows a diagram showing the relationship between liquid crystal cell temperature and steps based on the manufacturing method of the present invention, and a plan view of the liquid crystal cell. This will be explained based on FIG. 4 (&). The method of injecting liquid crystal is to immerse the injection port of the liquid crystal cell in a liquid crystal reservoir in a vacuum, and then raise atmospheric pressure in that state.The inside of the liquid crystal cell is a vacuum, and the difference in atmospheric pressure causes the liquid crystal to be injected into the inside of the liquid crystal cell. It is something. The present invention further includes pressing the liquid crystal cell with a pressurizing body from the liquid crystal injection process to the sealing adhesive curing process to correct the gap between the liquid crystal cells, and furthermore, performs temperature control. Section a indicates the liquid crystal injection step. The insulating temperature of the liquid crystal cell at this time is about 50'C. Since the cassette containing the liquid crystal cell has a large heat capacity and may be difficult to heat, the cassette containing the liquid crystal cell is heated at approximately 55° C. for 16 minutes before injecting the liquid crystal. Secondly, since it has a large heat capacity, it is difficult for the temperature to drop, and as mentioned above, it retains heat, so it is easy to obtain the effect of temperature preservation. The section indicates that the temperature of the liquid crystal cell decreases when moving from the liquid crystal injection process to the sealing adhesive coating process.

Section C shows a sealing adhesive application step. Next, sealing adhesive is placed in a syringe and dispensed by a dispenser to apply it to the liquid crystal injection port. Section d indicates that the temperature of the liquid crystal cell decreases from the sealing adhesive application process to the curing process. Here, in a cassette with a large heat capacity, the temperature decreases gradually, and as the temperature decreases, the volume of the liquid crystal shrinks and the sealing adhesive is sucked into the panel. This state is shown in FIG. 4 (1), which shows the details of the arm portion in FIG. 4 (IL). A sealing adhesive 16 is applied to a liquid crystal inlet 16 provided in a part of the adhesive 14 for bonding the substrates, and is drawn into the liquid crystal cell by volumetric contraction of the liquid crystal as the temperature decreases. FIG. 4(b) shows the state of the liquid crystal cell after the liquid crystal is injected and the sealing adhesive is applied. A liquid crystal cell 17 is filled with liquid crystal 18.

If the cross-sectional area of the liquid crystal injection port after application is about 0.02-, about 1ff of the sealing adhesive is sucked in about 10 minutes after application.

For the sealing adhesive, an ultraviolet curing resin with a viscosity of about 600 cps or a thermosetting epoxy resin with a similar viscosity was used. The temperature at which the sealing adhesive was applied was about 45° C., and the cassette was placed on a hot plate to keep it warm. As mentioned above, the temperature of the cassette gradually decreases due to its large heat capacity, so if the cassette is left standing for about 10 minutes after application of the sealing adhesive, it will never reach room temperature. After confirming that the sealing adhesive has been sucked into the panel, the sealing adhesive is cured. This state is shown in FIG. 4(C), which shows details of section B in FIG. 4(a). When an ultraviolet curable resin is used, it can be cured by irradiating it with ultraviolet light. The curing conditions were 100 mW/d and 3 minutes. The temperature at this time was about 40'C and was maintained by the radiant heat of the ultraviolet lamp. In addition, in the case of thermosetting resins, the temperature of about 40'C is 60°C, similar to the case of ultraviolet curing.
The liquid crystal cell was placed in a cassette and kept warm in an oven for about 0 minutes to harden the sealing adhesive. Although the time may vary by changing the size and number of liquid crystal injection ports, it seems that the temperature conditions are almost satisfactory. Even when liquid crystal is experimentally injected under heating and a sealing adhesive is applied and cured at room temperature, a predetermined amount of the sealing adhesive is sucked into the liquid crystal cell and directly affects the image quality of the liquid crystal. There was no unevenness in cell thickness. From the above examples, the temperature at which the liquid crystal is pressed by the pressurizing body is 31°C, the temperature at which the sealing adhesive is applied is 2°C, the temperature at which the sealing adhesive is cured is t,
6c, it has been found that it is possible to manufacture a liquid crystal display device that can be almost completely sealed under the relationship tl>t2≧t3.

The material of the pressurizing body may be rigid or flexible, but the material used this time is aluminum. This is because a rigid body with a smooth surface is desirable, but as an ideal pressing method, a pressing body with a flexible structure such as silicone rubber is also desirable. The reason for pressurizing the liquid crystal cell with a pressurizing body is to flatten the warpage of the liquid crystal cell, and flattening can be achieved with a pressure smaller than 1 kg/c4. If liquid crystal is injected and sealed without a pressurizing body, the gap of the liquid crystal cell cannot be obtained accurately. LCD cell gap,
In order to form a liquid crystal cell, the liquid crystal cell must be sealed while being pressurized, or the liquid crystal must be injected with no load and then pressurized.

In this way, according to this embodiment, the sealing adhesive can be cured without flowing back into the liquid crystal cell after being sucked into the liquid crystal cell, and the internal pressure of the liquid crystal cell can be increased at room temperature by utilizing the volumetric contraction of the liquid crystal. This has the effect of making the air pressure smaller and making it possible to form uniform gaps in the liquid crystal display device.

Effects of the Invention As described above, according to the present invention, a liquid crystal cell can be almost completely sealed with liquid crystal using an extremely simple manufacturing method, and a uniform liquid crystal layer thickness can be obtained in the pixel portion of the liquid crystal cell. It is possible to obtain stable images with this method, making it extremely useful for practical purposes.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a liquid crystal cell and a cassette according to an embodiment of the present invention, FIG. 2 is a perspective view of a liquid crystal cell, FIG. 3 is a side view of a cassette containing the liquid crystal cell shown in FIG. 2, and FIG. The figure is an explanatory diagram showing the relationship between liquid crystal cell temperature and process and the liquid crystal cell based on the manufacturing method of the present invention. Figure 6 is a sectional view of the liquid crystal cell in an embodiment of the present invention. Figure 6 is a diagram of the substrate of the liquid crystal cell. The cross-sectional view and FIG. 7 are explanatory diagrams showing the relationship between temperature and process of a conventional liquid crystal cell and the liquid crystal cell. 1... Liquid crystal cell, 2... Pressure body, 3... Side plate, 4... Hole, 6... Spring, 6... Knob, 7... ...Needle roller bearing, 8...Link ball, 9...Spring slippage prevention plate, 1o/11...
...Substrate, 12...Adhesive for bonding, 13.
...Liquid crystal injection port, 14...Adhesive for bonding substrates, 16...Liquid crystal injection port, 16...Adhesive for sealing, 17... ...Liquid crystal cell, 18...
...Liquid crystal cell, 19...Transparent electrode, 2o...
・Alignment film, 21...Front glass plate, 22...
・TFIJ child part, 23...Pixel part, 24...
・Alignment film, 26...Liquid crystal display substrate, 26...
...Sealant, 27...Liquid crystal, 28...
...Spacer, 29-30...Polarizing plate, 31...
・Liquid crystal cell, 32... Sealing adhesive, 33.
...Liquid crystal, 34...Adhesive for bonding substrates, 35
...Liquid crystal injection port, 36...Adhesive backflow trace. Name of agent: Patent attorney Toshio Nakao and 1 other person
2111 31!1 Figure 4

Claims (1)

[Claims] A liquid crystal cell consisting of four sets of electrode-attached substrates and an adhesive/spacer for bonding the substrates interposed between the substrates, liquid crystal is injected between the glass substrates, and the substrates are bonded. When manufacturing a liquid crystal display device made of a sealing adhesive present in a liquid crystal injection port with a part of the adhesive for bonding opened, a step of pressurizing the liquid crystal cell with a pressure body and injecting liquid crystal; , a step of pressurizing the liquid crystal cell with a pressurizing body and applying the sealing adhesive to the liquid crystal injection port at a temperature of t_1°C; pressurizing the liquid crystal cell with a pressurizing body and maintaining a temperature of t_2°C; a step of leaving the liquid crystal cell coated with the adhesive for sealing still, and a step of pressurizing the liquid crystal cell with a pressure body and curing the adhesive for sealing at a temperature of t_3°C. t_1>t_2≧t_3, and t_3°C is equal to or higher than room temperature.