JPH035564B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a substrate for a liquid crystal cell,
In particular, the present invention relates to a method for manufacturing a substrate for a liquid crystal cell in which an insulating thin film forming process is streamlined. It is well known that liquid crystal can be used as a display device by utilizing its electro-optic effect, and a liquid crystal cell having the basic configuration as shown in FIG. 1 is usually used. That is, a liquid crystal cell consists of a pair of glass substrates 1 and 1' arranged approximately half a row apart from each other with a gap of about 10 μm, a liquid crystal layer 4 filled between them, and a liquid crystal layer 4 to prevent the liquid crystal from flowing out.
It also includes a sealing part 3 provided around the liquid crystal layer 4 in order to keep the thickness of the liquid crystal layer 4 constant. Transparent conductive films 2, 2' for applying electrical signals to the liquid crystal layer 4 are provided on the surfaces of the glass substrates 1, 1' in contact with the liquid crystal layer 4, depending on the pattern desired to be displayed. It extends to the outside of the stop portion 3 to form a lead terminal portion. However, for various reasons, a structure in which the transparent conductive films 2, 2' and the liquid crystal layer 4 are in direct contact with each other is difficult to provide a practical liquid crystal cell. One is that an undesirable electrochemical reaction occurs on the surface of the transparent conductive film when voltage is applied, which accelerates the deterioration of the liquid crystal cell. The other is that in many cases, such as TN type liquid crystals, it is necessary to control the arrangement of liquid crystals within the liquid crystal cell using interfacial forces, which requires surface treatments such as rubbing and oblique vapor deposition. However, on a surface as shown in FIG. 1 where a glass substrate surface and a transparent conductive film surface coexist, uniform surface treatment is difficult due to surface irregularities or differences in materials, resulting in poor appearance of the liquid crystal cell. (This is called alignment failure.) In order to solve these difficulties, a practical liquid crystal cell has the structure shown in FIGS. 2a and 2b. That is, the surfaces of the glass substrates 1, 1' on which the transparent conductive films 2, 2' are located are coated with insulating thin films 6, 6'. The insulating thin films 6, 6' used here include inorganic insulating films containing oxides such as silicon oxide, titanium oxide, and cerium oxide, and fluorides such as magnesium fluoride, and silicon oxide is generally used. It is being It is desirable that the insulating thin films 6, 6' be formed not on the entire surface of the substrate, but only on the parts that contact the liquid crystal layer 4, and the transparent conductive films 2, 2'
It would be inconvenient if the insulating thin films 6, 6' were attached to the internal connection part 5 and the external terminal parts 2a, 2a' between them. It is also preferable that the portions corresponding to the insulating thin films 6, 6' are not attached. However, in reality, the insulating thin film 6 is applied only to the part that contacts the liquid crystal layer 4.
It is difficult to form the insulating thin films 6, 6' in the liquid crystal cell in the vicinity of the sealing part 3, and an alignment defect may be observed there. In the present invention, in order to prevent these problems and obtain reliable strength of the sealing part 3, an insulating thin film 6' is provided in an area of 1/3 to 1/2 of the width of the sealing part 3, as shown in FIG. It is designed so that it is formed by digging into it. When actually forming an insulating thin film, the method of masking the areas where you do not want to apply the insulating thin film in advance and forming the insulating thin film on the remaining areas is generally used because the process is shorter than other methods. However, since an insulating thin film will also be formed on the mask, we need to consider how to remove this and prevent chemical reactions between the mask and the insulating thin film when forming the mask. It is necessary to select the material. Several methods have been tried in the past based on this idea. One method is to use a low melting point alloy such as solder as a mask. Masks are formed by vacuum evaporation or screen printing of paste-like solder, but screen printing uses a paste-like solder that is stabilized by heating in order to chemically stabilize the insulating thin film. Usually 200~
It is processed at 300°C, but since the substrate is glass at this time, the solder becomes spherical on the glass substrate, rendering it useless as a mask.
In addition, when using the former vacuum evaporation method, it is chemically stable and an insulating thin film can be formed on it, but when removing this solder mask, it must be heated to about 250℃ in an electric furnace. However, the solder tends to become spheroidized as in Stareen printing. At this time, since there is an insulating thin film on the solder mask, the solder does not actually become spherical, but since this thin film is porous, it focuses toward the hole in an attempt to become spherical. The solder, which is the material of the mask, evaporates to the outside through these holes and is finally lost. For this reason, it takes two to three hours to remove the solder mask, and it is also very difficult to dispose of the toxic gas generated from the solder. A more serious drawback is that when the solder mask is removed from the glass substrate, the insulating thin film formed thereon sags as the solder evaporates, and eventually comes into close contact with the glass substrate. After this, when the insulating thin film is fired at 500°C, it completely adheres to the glass substrate, and even if you try to remove it afterwards, it is almost impossible to remove, making it unsuitable as a mask material. Another method is to use a depolymerizable polymer. This method uses screen printing to form a mask, but this method is also not safe;
After forming the insulating thin film, it is not possible to remove all of the insulating thin film on the mask, and a mechanical peeling process is required. In addition, this polymer mask uses toluene as a solvent, so it is highly volatile, and the screen printing process takes a short time, resulting in clogging.
Not suitable for practical use. In this way, conventionally known methods cannot completely remove the insulating thin film on the mask, or even if it can be removed, a mechanical removal method is required, which increases the number of steps and takes time to remove. Not much is actually done to increase the number of people. This is also the case in the prior art and is generally considered to be the case, but in the case of mask formation using polymers, the above-mentioned problems occur for the following reasons. The film thickness was made as thin as the thickness of an insulating thin film such as silicon oxide (usually 800 to 2000 Å is the optimal value), and the polymer mask was peeled off as shown in Figure 7. In the later state, we want the height B of the protrusion to be as small as possible, ideally to be the same as the thickness A of the insulating thin film, so the thickness of the mask is generally 4000 Å to 1 μ.
The thickness is about 5 μm at most. In this way, it is possible to make a polymer mask as thick as the insulating thin film using the spinner method, vacuum evaporation method, etc., but the state in which the polymer mask is applied is shown in Figure 4. However, as mentioned above, even if the polymer mask 7 decomposes or disappears due to heating, the insulating thin film 6 formed on top of it will not be destroyed at all, and on the contrary, the glass mask 7 will not be destroyed at all. Mask 7 made of polymer etc. decomposes because it is too close to substrate 1.
As it disappears, the glass substrate 1 and the insulating thin film 6
The masks become stuck together and eventually become glued together, making the mask useless considering its original purpose. This is almost the same even when using the screen printing method, and as shown in Figure 5, the film thickness of the mask 7 made of polymer or the like is generally 1 to 5 μm, which is 5 to 50 times that of the insulating thin film 6. . This is because the height B of the protrusion shown in FIG. 7 mentioned above was considered not to be too high, but even with this method, the insulating thin film 6 cannot be destroyed by the force of decomposing or disappearing the mask 7 made of polymer or the like. It is difficult to remove the insulating thin film 6 by a mechanical method as a post-processing, and even with this, some parts may not be completely removed. After removal and peeling, the height B of the protrusions in FIG. 7 was measured and found to be 4,000 to 10,000 Å. The purpose of the present invention is to eliminate these conventional drawbacks, to make it possible to easily remove the insulating thin film on the mask made of polymers, etc., and to make the height B of the protrusion approximately the same as the thickness A of the insulating thin film. The aim is to provide a method that is of practical value. This will be explained in detail below with reference to the drawings. Figures 6 and 8
Figures a, b, and c are of the present invention, and Figure 6 is a state in which an insulating thin film 6 is formed on a mask 7 made of polymer or the like with a film thickness, and Figure 8 is a state of the present invention. The manufacturing process is shown, and FIG. 3 shows the range of forming a mask made of polymer or the like for forming the insulating thin film 6' near the sealing part. To explain with reference to FIG. 8, the present invention first begins in FIG.
As shown in FIG.
As shown in FIG. A mask is formed in advance using a mask 7 made of polymer or the like. The mask 7 used was the following organic polymer compound (OLI-S2) manufactured by Tokyo Ohka Kogyo Co., Ltd. That is, epoxy resin is used as the main ingredient. 2-hydroxypropyl methacrylate monopolymer _CH2 =C( _CH3 ) _COOCH2CH (OH) _CH3 ,
2-hydroxyethyl methacrylate monopolymer

[Formula] is mixed. This reaction accelerator acts so that when the mask 7 made of epoxy resin is pre-baked as described later, the mask 7 is not completely cured but remains in a semi-cured state. As a result, the mask 7 is easily swollen and peeled off by the solution described below. Furthermore, mask 7 was made into a gel by adding methyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, and televisionneol as diluents to make it suitable for screen printing, which will be described later. There is.
This mask 7 is formed in a part where the formation of the insulating thin film 6 is not desired, but especially in the sealing part 3, as shown in FIG.
A mask 7 is formed so that the insulating thin film 6' is formed over 1/2 of the area. By doing this, it was confirmed that the defective orientation of the inner periphery of the sealing part 3 that had been observed up to now was eliminated and that sufficient sealing strength of the sealing part 3 was obtained. As mentioned above, the mask 7 formed in this manner has been formed with a relatively thin film thickness (4000 Å to 5 μm) in the conventional example, but in the present invention, the film is shown in FIG. In this way, the mask 7 of an extremely thick film was formed. This is a major feature of the present invention; the film thickness is selected to be 10 to 100 μm, and the thickness of the insulating thin film 6 formed thereon (800 to 2000 Å) is 50 to 100 μm.
The value will be 1000 times higher. Especially within this range, from 50 to
The film thickness of the mask 7 of 100 μm gives good results. When the film thickness is increased in this way, the height B of the protrusion in Figure 7 becomes a concern, but in reality it is the opposite.
As shown in FIG. 6, among the insulating thin films 6, the glass substrate 1
The insulating thin film 6c on the mask 7 and the insulating thin film 6a on the mask 7 have normal film thicknesses, but the insulating thin film 6b on the sides of the mask 7 is extremely thin (200 to 500 Å), and at this point The insulating thin film 6b is now in a state where it is easily destroyed. In order to increase the film thickness of the mask 7, the pattern for the mask 7 was formed using a photosensitive film instead of forming the pattern for the mask 7 using a photosensitive emulsion as in conventional screen printing. Generally, a thick film can be formed by making the mesh of the screen rougher, and this is fine, but as the mesh becomes rougher, the transferability of the screen-printed mask 7 becomes less accurate.
In addition, due to the rough mesh, the mask 7
If the viscosity is low, it may bleed out before screen printing, rendering it useless. After this, the screen-printed mask 7 was heated at 140-180℃ for 15 minutes.
Heat and cure for ~30 minutes. This is because no chemical reaction occurs with the insulating thin film 6 formed on the mask 7. Conventional solder masks and depolymerizable polymer masks are not compatible when the insulating thin film is made of silicon oxide, and chemical reactions occur on both sides of the mask, resulting in incomplete insulation. A thin film is formed. On the glass substrate 1 with the heated and hardened mask 7 attached, an insulating thin film 6 of silicon oxide or the like is then formed as shown in FIGS. 6 and 8. In the embodiment of the present invention, a dipping method was adopted in which the glass substrate 1 is immersed in the liquid of the insulating thin film 6, but other methods may of course be used. The formed insulating thin film 6 did not take the form shown by the broken line in FIG. 6 as was generally thought;
On the contrary, the side surface 6b of the mask became extremely thin and easily destroyed. Next, for this insulating thin film 6, 140 to 180
Temporary calcination is performed at ℃ for 15 to 30 minutes. This is to bring the insulating thin film 6 into a metastable state and to ensure that the mask 7 under the insulating thin film 6 does not burn and carbonize due to high temperatures and maintains its chemical properties. This is because it is necessary that the mask 7 is dissolved by the solvent treatment in the subsequent process, but the insulating thin film 6 is not dissolved. Therefore, regarding the pre-firing conditions, if the temperature is too low or the time is too short, the insulating thin film 6 will not melt, whereas if the temperature is too high or the time is too long, the mask 7 will be formed more than necessary. Care must be taken because it may solidify or in some cases burn, making it difficult to dissolve or not dissolving at all. After this calcining, it is immersed in a methylene chloride or trichlene solution. There are no restrictions on soaking time, but the work is usually completed in 5 to 30 minutes. At this time, a solvent such as methylene chloride or trichlene permeates into the mask 7 from places such as the thin insulating thin film 6b shown in FIG. 6, causing the mask 7 to swell. This swelling effect is greater for trichlene than for methylene chloride. After the mask 7 is swollen, it is immersed in a trichloroethane solution and subjected to ultrasonic cleaning. The mask 7 swollen by the ultrasonic vibration shock wave is peeled off from the substrate 1. During this peeling, the insulating thin film 6 on the mask 7 is removed from the mask 7.
It will be peeled off and removed along with it. Needless to say, this step also involves significant difficulties in the method of forming the mask 7 as shown in FIGS. 4 and 5. All of the solvents for swelling and peeling described so far are chlorine-based (Cl-based), which is used not only for the purpose of swelling and peeling off the mask 7, but also for the purpose of swelling and peeling the insulating thin film 6 itself. It also satisfies the condition that it does not dissolve. For example, the pre-fired insulating thin film 6 has a weakness that it will dissolve and peel off if it is immersed in water or a dilute alkaline detergent.
The mask 7 and the insulating thin film 6 on the mask 7 are completely covered.
The substrate 1 after peeling and removal is subjected to main firing in a continuous firing furnace or the like. The firing temperature is 450 to 520°C, which is the highest temperature, for 15 to 30 minutes. After firing, perform general cleaning with alkali, hydrochloric acid, neutral detergent, etc. The glass substrate 1 with the insulating thin film 6 thus obtained is as shown in FIG. Here, when the thickness A of the insulating thin film is 1000 Å, the height B of the protrusion described in the conventional example shows a value of 1000 to 3000 Å, which is almost close to the thickness A of the insulating thin film, and the sealing portion 3 is above this value. Even if it passed through, it was almost negligible because the thickness of the sealing part 3 was 10 μm. The reason why the height B of this protrusion is lower than that of the conventional example can be said to be due to the difference in the method of forming the insulating thin film 6 depending on the thickness of the mask 7 (in other words, the capacitance of the mask). This has been described as one embodiment according to the present invention, but in this method, another embodiment may be used.
As shown in the figure, there is a method in which an insulating thin film 8 of silicon oxide or the like is applied on a glass substrate 1. This first layer of insulating thin film 8 is applied to the entire surface of glass substrate 1, a transparent conductive film is provided on this, the above-mentioned mask 7 is further formed, and second layer of insulating thin film 6 is applied. It is formed. Here, the first insulating thin film 8 on the glass substrate 1 and the second insulating thin film 6 after forming the mask 7 may be made of the same material, and it is generally preferred that they are made of the same material from the production process. many. The adhesion between the mask 7 and the first insulating thin film 8 is weaker than the adhesion between the mask 7 and the glass substrate 1.
is easily peeled off, which has a great effect on the method for producing a glass substrate of the present invention. However, the first insulating thin film 8 and the second insulating thin film 6, and the first insulating thin film 8 and the transparent conductive film 2 on the first insulating thin film 8, The adhesion force is also slightly weaker than the adhesion force between the glass substrate 1 and the insulating thin film 6, and in the conventional example, when trying to peel off and remove the mask 7 using a 2 to 5% NaOH aqueous solution, the first It was observed that the second insulating thin film 6 on the transparent conductive film 2 on the second insulating thin film 8 was peeled off. Ideally, the solvent for removing the mask 7 should be one that can reliably remove the mask 7 and not cause the insulating thin film 6 to peel off. As described above, in the present invention, a chlorine-based solvent such as trichlene, methylene chloride, or trichloroethane is used as a solvent for swelling and peeling off the mask 7. In the example, as described above, trichlene or methylene chloride was used to swell the mask 7, and trichloroethane was used for peeling and removal by ultrasonic cleaning. The peeling time was 3 to 5 minutes, and about 10 minutes at most. As a result, the mask 7 is reliably peeled off, but the second insulating thin film 6 on the transparent conductive film 2 on the first insulating thin film 8 is not completely peeled off. A solid insulating layer was maintained, and the same results as in the method of forming an insulating thin film 6 on the glass substrate 1 shown in FIGS. 8a, b, and c were obtained. The present invention has been described in detail above, and the main ingredient is an epoxy resin, mixed with a reaction accelerator such as a 2-hydroxypropyl methacrylate monopolymer or a 2-hydroxyethyl methacrylate monopolymer, and a diluent such as methyl carbitol. By using a polymer mask made of an organic compound with hydroxyl groups that has been gelled with an agent, the film thickness of the mask is made much thicker than conventional ones, and by making the film extremely thick, The resulting insulating thin film was thinly attached to the mask, making it easy to penetrate. Then, the insulating thin film is calcined, the mask is swollen by dipping in methylene chloride, etc., and the mask and the insulating thin film on the mask are peeled off and removed by ultrasonic cleaning in a trichloroethane solution, and the mask is The insulating thin film in the areas where it was not applied retains its insulating layer without being peeled off. Furthermore, the peeled surface of the insulating thin film on the glass substrate produced in this manner is characterized by the small height of the protrusion at the end, which is highly effective from a practical standpoint. The glass substrate 1 thus produced is then subjected to an orientation treatment using an oblique vapor deposition method, a rubbing method, etc.
They are stacked together as two sheets of glass, liquid crystal is injected, and sealed to form a liquid crystal cell. At that time, an insulating thin film is formed by biting into the sealing part, so the orientation inside and around the sealing part is difficult. Good alignment can be obtained without any damage.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the basic structure of a liquid crystal cell.
FIGS. 2a and 2b are a plan view and a sectional view showing the configuration of a practical liquid crystal cell, FIG. 3 is a plan view of a liquid crystal cell showing an embodiment of the present invention, and FIGS. 6 is a sectional view of a mask according to an embodiment of the present invention, FIG. 7 is a sectional view illustrating a state in which the mask of FIG. 6 is peeled off, and FIGS. FIG. 9 is a process diagram showing the mask forming process of the invention, and a sectional view showing another embodiment of the mask of the invention. 1, 1'... Glass substrate, 2, 2'... Transparent conductive film, 3... Sealing part, 4... Liquid crystal layer, 6, 6', 8
... Insulating thin film, 7... Mask, A... Thickness of insulating thin film, B... Height of protrusion.

Claims (1)

[Scope of Claims] 1. A liquid crystal cell substrate comprising at least one insulating thin film formed on the surface of a glass substrate on which a transparent conductive film is provided and on a part of the transparent conductive film. In the manufacturing method, a mask having a thickness of 50 to 1000 times the thickness of the insulating thin film is formed in advance on the part where the insulating thin film is not desired to be formed, and then the insulating film is coated on the entire surface of the glass substrate. forming a thin film, further calcining the insulating thin film,
Next, after peeling off and removing the mask and the insulating thin film on the mask, the remaining insulating thin film is subjected to main baking. 2. A method for producing a substrate for a liquid crystal cell comprising forming at least one or more insulating thin film on the surface of a glass substrate partially provided with a transparent conductive film and on a part of the conductive film. Forming a first insulating thin film of silicon oxide or the like on the substrate in advance, forming the transparent conductive film on the first insulating thin film, and forming a second insulating thin film. A mask having a thickness of 50 to 1000 times the thickness of the second layer insulating thin film is formed in advance on the areas where the second layer of insulating thin film is not desired, and then the second layer of the insulating thin film is coated on the entire surface of the glass substrate. After forming the second layer of insulating thin film and pre-baking the second layer of insulating thin film, and then peeling off and removing the mask and the second layer of insulating thin film on the mask, the remaining second layer 1. A method for producing a substrate for a liquid crystal cell, which comprises performing main firing of an insulating thin film.