JPH03122036A - Method for forming glass substrate for curved liquid crystal cell - Google Patents

Abstract

PURPOSE:To obtain the title glass substrate having excellent adhesion by fast sticking two laminated glass substrates superposed through a thin film consisting of ceramics or metal under reduced pressure and then forming the laminated glass substrates into a curved shape along a curved mold while heating and softening the substrate. CONSTITUTION:A laminated sheet glass substrate 4 is put on a frame 5 for vacuum tank 6 and the interior of the tank 6 is evacuated to 10<-1> torr. and then allowed to stand and then returned to atmospheric atmosphere. Then a tape 9 is released from the substrate 4 and then the substrate 4 is put on a recessed part of recessed forming mold 12 made of stainless steel in a heating furnace 10 and projected mold forming mold 13 having projected and curved face corresponding to the recessed curved face of mold 12 is put thereon. Then temperature in the furnace is kept to 620 deg.C in this state and heated for 1 hr to soften the substrate 4 and subjected to plastic deformation between these forming molds to form the substrate for curved liquid crystal cell. Furthermore, the forming molds are previously heated to 400 deg.C. A good- quality curved cell having uniform cell gap between substrates of liquid crystal cell and free from domain and unevenness of color can be produced by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a method of manufacturing a glass substrate for a curved liquid crystal cell used in a liquid crystal mirror or the like.

[Prior Art] Conventionally, curved substrates have been used in liquid crystal mirrors used for automobile door mirrors and the like. This curved substrate is made of plastic with good moldability and molded into a curved surface (Japanese Unexamined Patent Publication No. 129830/1983). However, although plastic has good moldability, it has low heat resistance, so it has the problem that it is easily deformed and difficult to maintain a uniform curved surface.

On the other hand, when manufacturing curved glass substrates, flat glass is placed on a pedestal (mold) made of fireproof material, softened by heating, and deformed along the pedestal to form it. A bending method is required.

Furthermore, in order to improve the accuracy of the curvature of the surface, a method has been proposed in which the glass substrate is pressurized to form a curved surface.

For example, Japanese Patent Application Laid-Open No. 62-238526 discloses that when forming a liquid crystal cell, a pair of glass plates on which a gap adjustment material and a sealing material have been provided in advance on opposing surfaces are pressurized in a curved mold. A method of manufacturing a liquid crystal cell is disclosed in which the sealing material hardens when pressed.

[Problems to be Solved by the Invention] When forming a pair of glass plates with a gap adjusting material or a sealing material disposed on opposing surfaces by pressure as described above, the gap adjusting material or sealing material is present. Therefore, it is not possible to heat the glass to a high enough temperature to soften it. Therefore, in this method, the thickness of the glass plate is limited to 0.2% or less. Furthermore, when a curved glass substrate formed from a glass plate by the self-weight bending method is used for a liquid crystal cell, even though the glass plate has fairly good flatness, there are warps in some parts, so the curved glass plate obtained from it There will be variations in curvature. When two curved glass plates are selected and placed facing each other with a predetermined interval between them, the interval between them tends to be uneven.

In addition, when two glass plates are laminated together after cleaning the glass plates to remove foreign matter and dust, even though the flatness of the glass plates is quite good, there are some areas where the adhesion is not good due to warpage. is. Therefore, when this glass plate is sandwiched between molds and heated to be formed, there is a problem that the glass plates are misaligned and the curved surfaces do not match, making it impossible to use it as a glass substrate for TN type liquid crystal cells, which requires uniform gap control. .

An object of the present invention is to improve the adhesion between the two glass plates in a glass substrate for a liquid crystal cell composed of these two glass plates.

[Means for Solving the Problems] The method for forming a glass substrate for a curved liquid crystal cell of the present invention includes forming a thin film made of ceramic or metal on the surface of at least one of two glass plates, Part 1
1. A lamination ITj step in which the two glass plates are stacked with the ill side on the inside to form a laminated glass substrate, and an adhesion step in which the laminated glass substrate is kept under reduced pressure in a vacuum chamber and the two glass plates are brought into close contact with each other. and a molding step of placing the closely adhered laminated glass substrate in a curved mold, heating it to a softening temperature of the glass plate, and molding it into a curved shape that follows the mold surface shape of the curved mold;
It is characterized by consisting of.

As the glass plate, commonly used soda lime glass, borosilicate glass, etc., which have good flatness, can be used.

The softening treatment of the glass plate is performed by heating the glass plate to a temperature higher than its softening point. Here, the softening point temperature is the lower limit temperature of the temperature range in which glass exhibits rubber-like behavior before it becomes a viscous liquid when heated above the transition point temperature.For example,
530℃ for soda lime glass, 6 for borosilicate glass
The temperature is 30°C.

As a thin film formed on a glass plate, for example, ITO
(indium/tin composite oxide), 5i02 film, A
I203 film, ZrO2 film, PT film, AQ film, Ti film, etc. can be used. These thin films are preferably those that can be used as they are as transparent conductive thin films of liquid crystal cells, and may also be ones that prevent glass plates from being fused together during softening treatment. Then, it is formed on the overlapping surface of at least one of the two glass plates. Alternatively, it may be formed on both overlapping surfaces of two glass plates.

The thickness of the thin film formed on this glass plate is 100~2
Preferably, it is 5006. If the thickness is too large, it will be difficult to separate the laminated glass plates from each other after the softening treatment, which is not preferable. Fusion cannot be effectively prevented. Also,
If it is too thick, the coloring of the glass plate may become noticeable, which is not preferable. This thin film can be formed on a glass plate by a vacuum evaporation method, a sputtering method, an ion blating method, or the like.

In the lamination process, two glass plates, each of which has a thin film formed on at least one of the glass plates as described above, are stacked one on top of the other so that the special film is on the inside. At this time, it is preferable to perform ultrasonic cleaning on the glass plates before stacking them to prevent foreign matter, lumps, etc. from entering between the stacked surfaces. To prevent the stacked glass plates from shifting, the edges are fixed using, for example, adhesive tape. At this time, it is preferable to partially fix the edges of the glass plates so that air can exit from the center of the overlapping surfaces.

In the adhesion process, the stacked laminated glass substrates are placed in a vacuum chamber, and the interior of the tank is maintained in a reduced pressure state to expel any air remaining between the stacks and bring the stacked surfaces into sufficient contact. For this purpose, the degree of vacuum is preferably greater than or equal to 0-ITorr. The degree of adhesion of the bonded glass substrate can be easily confirmed by the fact that the interference fringes observed on the glass substrate surface become smaller.

In the molding process, the laminated glass substrate that is in close contact with the glass substrate is placed and supported on a metal concave mold placed in a heating furnace equipped with a heater, and a convex mold is roughly placed on top of the laminated glass substrate. . This concave mold has a hemispherical concave curved surface formed with a predetermined radius of curvature on the upper surface. Moreover, this convex mold has a convex curved surface corresponding to the concave curved surface of the above-described concave mold on the lower surface. In this state, the glass plate is heated to a temperature higher than the softening point of the glass using a heater, and the glass plate is plastically deformed and formed between the box molds. Note that it is advisable to heat the box mold beforehand.

The laminated glass substrate, which becomes plastic when heated above its softening point temperature, comes into close contact with the upper and lower molds and assumes a predetermined curved shape. Since these laminated glass substrates are in close contact with each other, they do not shift during molding.

[Function] According to the forming method of the present invention, the laminated glass substrates laminated and fixed in the adhesion process are kept in a reduced pressure state, and the air present on the bonded surfaces is blown out to the center to form the surface between the two glass plates. The number of laminated glass bases is made closer to each other. Even after this laminated glass substrate is removed from the vacuum chamber, it is pressed down by the atmospheric pressure on both outer surfaces of the glass plate and maintains its adhesion, so air will not penetrate again and reduce the adhesion. do not have.

In the molding process, two glass plates are molded into a predetermined curved surface while maintaining close contact, so that a curved glass substrate for a liquid crystal cell with good gap controllability is molded without shifting of the glass plates.

[Example] Hereinafter, this will be explained in detail using examples.

Lamination process FIG. 3 shows a cross-sectional view of this laminated glass substrate 4.

This laminated glass substrate 4 consists of a soda lime glass plate 1 (softening temperature 530'C) with good flatness on which an ITO film 2 with a thickness of 100 to 500 mm is formed on the surface by sputtering or the like;
A laminated glass substrate 4 is obtained by stacking a soda lime glass plate 3 with good flatness on which the TO film is not formed so that the TO film 2 is on the inside. At this time, in order to prevent foreign matter, dust, etc. from entering between the overlapping surfaces, the glass plate 1.3
After ultrasonic cleaning, dry and stack them in a clean booth. If left as is for a while, interference fringes as shown in FIG. 9 will be observed. This laminated glass substrate 4 is fixed by pasting and fixing tape 9 for preventing glue residue at two places on both sides of the end portion.

Adhesion process FIG. 1 shows a schematic side view of the vacuum chamber, and FIG. 2 shows a schematic plan view.

The vacuum chamber 6 is provided with a pedestal 5 on which the laminated glass substrate 4 is mounted within a closed housing having an exhaust pipe having an exhaust valve 7 and an intake pipe having an intake valve 8.

The laminated glass substrates 4 are shown in FIG.
As shown in the figure, place the vacuum chamber 6 on the pedestal 5, close the intake valve 8, listen to the exhaust valve 7, connect the exhaust pipe to the vacuum pump, maintain the pressure inside the chamber at 10-11-orr, and leave it for 5 minutes. After that,
Returned to atmospheric pressure. As shown in FIG. 7, this laminated glass substrate 4 has a reduced range and number of interference fringes compared to the one shown in FIG. 9 before the adhesion process, and is in close contact with the laminated glass substrate 4. This laminated glass substrate 4
When the degree of adhesion was optically measured using a gap measuring device, there was a gap of 10 to 20 μm before the adhesion process (Figure 9), but a gap of 2 μm at maximum after the adhesion process (Figure 7).
It had decreased to a certain extent.

Molding process After peeling off the tape 9, the obtained closely laminated glass substrate 4 was placed in a concave mold, heated, and pressure molded.

FIG. 4, FIG. 5, and FIG. 6 are diagrams illustrating the molding process. Figure 4 is a cross-sectional view showing the state of the laminated glass substrate before molding, Figure 5 is a sectional view showing the state after molding, and Figure 6 is a plan view showing the state when the laminated glass substrate is placed in a concave mold. be.

A heater 11 is provided in the heating furnace 10 . A concave mold 12 made of stainless steel is installed inside the heating furnace 10, and the upper surface of the mold 12 forms four cylindrical parts with a curvature of 1800 mm.

The laminated glass substrate 4 described above is placed on this mold 12. A convex mold 13 is placed on this laminated glass substrate 4. The convex mold 13 has a convex curved surface corresponding to the concave curved surface of the concave mold 12 on its lower surface. In this state, the temperature in the furnace was raised to 620'C and heated for 1 hour to soften the laminated glass substrate 4, which was then plastically deformed between molds to form a glass substrate for a curved liquid crystal cell. Note that the mold was previously heated to 400'C.

FIG. 8 shows the state of adhesion of the curved layered glass substrate 4 obtained. When compared with FIG. 10, which shows a curved area laminated glass substrate formed without performing the conventional laminating process and adhesion process, there are fewer interference fringes, indicating that the degree of adhesion is improved. In addition, when measuring the gap in the case of Figure 8, it is 1 to 2μ.
m is 10 to 20 μm in FIG. 10, indicating that the curved layered glass substrate formed by the method of the present invention has an improved degree of adhesion and a predetermined curved surface.

A TN type liquid crystal cell and a phase change type guest-host mode liquid crystal cell were manufactured using this curved layered glass substrate. The resulting liquid crystal cell was a uniform liquid crystal with no domains or color unevenness.

When a glass substrate is used as a phase change type guest-host mode liquid crystal cell, even if it is uniform and the occurrence of domains and color unevenness is small, when a TN type liquid crystal cell is used, domains and color unevenness are likely to occur.

Therefore, in a TN type liquid crystal cell, uniformity of the curved surface of the liquid crystal cell glass substrate is particularly required, and the cell gap is 1 μm.
It is said that uneven coloring can be observed even if the degree of variation is different. Therefore, stricter cell gap control is required. However, according to the method of the present invention, it is possible to obtain a glass substrate for a liquid crystal cell in which such problems are hardly observed.

[Effects] According to the method for molding a glass substrate for a curved liquid crystal cell of the present invention, in order to improve the adhesion between a pair of glass plates, the laminated glass substrates are left under reduced pressure in a vacuum chamber in the adhesion process to overlap them. After removing any existing air and bringing them into close contact, the laminated glass substrates are molded while maintaining their close contact to form a curved surface, thereby making it possible to prevent the glass plates from shifting during molding.

Therefore, by using this laminated glass substrate, it is possible to manufacture a high-quality curved cell in which the cell gap between the substrates of a liquid crystal cell is uniform and there is no domain or color unevenness. Furthermore, it is possible to mold and cover the glass plate regardless of its thickness.

In addition, there is no need to sort out good quality float glass to make glass plates, and there is an advantage that a complicated sorting process can be omitted.

[Brief explanation of drawings]

Figure 1 is a side view showing how the laminated glass substrate is arranged in a vacuum chamber, Figure 2 is a plan view of Figure 1, Figure 3 is a side view of the laminated glass substrate, and Figure 4 is the forming of the laminated glass substrate. Fig. 5 is a schematic diagram of the laminated glass substrate when it is placed in the mold, Fig. 6 is a plan view showing the planar state of the laminated glass substrate and the mold, and Fig. 7 is a schematic diagram of the laminated glass substrate in the mold after molding. A schematic diagram showing the adhesion state of the laminated glass substrate taken out from the vacuum chamber, FIG. 8 is a schematic diagram showing the adhesion state after the laminated glass substrate of FIG. 7 is molded,
FIG. 9 is a schematic diagram showing the adhesion state of the laminated glass substrates after washing and after being overlapped and left for a sufficient period of time, and FIG. 10 is a schematic diagram showing the adhesion state of the laminated glass substrates of FIG. 9 after being molded. . 1.3... Glass plate 2... Thin film 4... Laminated glass substrate 5... Frame 6... Vacuum chamber
9...Fixing tape 10...Heating furnace 11...Heater 12...Concave mold 13...Convex mold

Claims (1)

[Claims] (1) A thin film made of ceramic or metal is formed on the surface of at least one of the two glass plates, and the two glass plates are stacked with the thin film on the inside to form a laminated glass substrate. a laminating step in which the laminated glass substrates are kept in a vacuum chamber under reduced pressure and the two glass plates are brought into close contact with each other, and the adhered laminated glass substrates are placed in a curved mold, A method for molding a glass substrate for a curved liquid crystal cell, comprising a molding step of heating to a softening temperature and molding the glass substrate into a curved shape that follows the mold surface shape of the curved mold.