JPS6256492B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrode substrate used in optical devices and the like, and particularly to an electrode substrate having an inorganic compound thin film obtained by applying and then heating the solution described in the claims.

It is a well-known fact that in recent years, metal oxides or films similar to them have been used for insulating films of semiconductor devices, or insulating films or alignment control films of liquid crystal display elements.

In particular, in the case of a liquid crystal display element, it consists of a pair of electrode substrates in which a transparent conductor thin film and an organic or inorganic compound film are sequentially formed on an insulating substrate such as glass, and the surface on which the organic or inorganic compound film is formed is They are assembled facing each other with a spacer interposed therebetween, and liquid crystal is sealed inside. In this case, there are dynamic scattering mode types that utilize the specific orientation of the organic or inorganic compound with respect to the liquid crystal, chiral nematics, and display systems that utilize the phase transition between nematics. A display method is known in which the orientation of the liquid crystal in contact with the organic or inorganic compound is controlled in a twisted nematic type by rubbing in the direction of the organic or inorganic compound.

Generally required characteristics of an organic or inorganic compound film formed for the above purpose are good adhesion between the film to be formed and the underlying insulating substrate and transparent conductor thin film, and defects such as pinholes in the film itself. The film has sufficient strength, has a uniform chemical composition over the entire film, has good visible light transparency, and has a uniform film thickness over the surface of the substrate on which it is formed. be. Furthermore, the method for forming the thin film needs to be as mass-producible as possible. From this perspective, organic compound films are generally colored, have low visible light transmittance, have poor adhesion to insulating substrates, and have poor heat resistance compared to inorganic compound films. For this reason, it is desirable that the film formed on the electrode forming substrate be an inorganic compound film.

The desired inorganic compound film can be formed on the electrode forming substrate by (1) vapor phase growth, (2) vapor deposition, (3) sputtering, or (4) using an appropriate method of forming the desired inorganic compound powder. A so-called coating method is known in which the compound is dispersed in a suitable solvent or dispersant and coated by spraying, spinning, dipping, or printing. However, each of these methods has the following drawbacks. In other words, in the vapor phase growth method, for example, aluminum chloride is oxidized in the vapor phase to form aluminum oxide, and titanium chloride is oxidized in the vapor phase to form titanium oxide, but in both cases, the deposition substrate is It must be heated. Further, in order to form a film with a uniform thickness over the entire surface of the substrate, special measures are required for the gas flow system. Therefore, the size of the substrate is limited, and it is difficult to form a uniform film on a substrate with a complicated shape. Furthermore, it is unsuitable for mass production because it must be large in size if gas piping systems, heating systems, etc. are included, and batch processing is required. Vapor deposition is a method in which raw materials are evaporated using resistance heating or electron beam heating, and the desired film is formed on the substrate under reduced pressure. However, because this method uses a vacuum device, it is difficult to form a uniform film on a large substrate. It is difficult to form, and the equipment is expensive, making the product expensive.

The method of forming a film by sputtering has almost the same drawbacks as the vapor deposition method, but since the substrate to be adhered to is exposed to plasma, the previously formed transparent conductive film etc. will change in quality and resistance will increase. No impact.

Although the coating method can form the desired film on large substrates or substrates with complex shapes, the bond between particles is weak and the adhesion to the substrate is also weak, so it is difficult to form a film that can be rubbed with a cloth. It has the disadvantage that it easily peels off. This is because a solution containing powder dispersed therein was used as the coating solution, and in order to form a strong film with good adhesion, it is essential to use a solution in which the solute is uniformly dissolved.

In order to eliminate the above-mentioned drawbacks regarding the coating method, a solution in which a β-diketone metal complex such as acetylacetonate is dissolved in an organic solvent is coated on the substrate and then thermally decomposed to obtain the desired inorganic compound. There is a way. In this case, in addition to β-diketone, low-viscosity alcohols such as methanol, ethanol, and propanol, ketones such as acetone, or esters are used as the solvent. Further, oxidizing ions or compounds such as nitrate ions may be added to rapidly decompose the complex by heating after application of the solution and promote oxidation. The inorganic compound film obtained by applying such a solution onto a glass substrate on which an indium oxide conductor thin film electrode is formed and then heating it is relatively strong if the film thickness is 500 Å or less, but the adhesion is not sufficient. In many cases, the film thickness over the entire surface of the substrate is non-uniform. Furthermore, as the film thickness increases, the adhesion further decreases. This may be due to the fact that the above-mentioned solvent is relatively easily volatile at room temperature, that the solute aggregates after application due to its cohesive property, or that it has low thixotropy, so a high viscosity solution suitable for printing is created and applied by printing. This is thought to be due to the movement of the printed matter. Therefore, in order to form an inorganic compound film that has good adhesion even when the film thickness is sufficiently large and has a uniform thickness over the entire surface of the substrate, it is necessary to use a solvent that is relatively difficult to volatilize at room temperature, and that the solvent itself is It must have good affinity with the substrate, be non-agglomerative, and be easily volatilized by heating at relatively low temperatures (below 400°C). In addition, in order to apply the printing method, which has high mass production among coating methods, it is essential that the solution has a sufficiently high viscosity and also has transferability and swingability. Furthermore, it goes without saying that it is essential that the solvent used to make the solution highly viscous has sufficient compatibility with the solute and that segregation does not occur.

The present invention was made as a result of various studies to satisfy the above-mentioned requirements, and is a method for forming an inorganic compound film by a coating method on an insulating substrate on which electrodes such as a transparent conductive film are formed. It is an object of the present invention to provide an electrode substrate having an improved inorganic compound coating having sufficiently high adhesion to the substrate, uniform thickness over the entire surface of the substrate, and high strength, with good mass production.

The present invention relates to an electrode substrate in which an inorganic compound film is formed on an insulating substrate such as glass, and an element that forms a complex with β-diketone, β-diketone, or a β-diketone complex is prepared from an organic or inorganic solvent. The coating solution is obtained by adding polyethylene glycol or nitrocellulose to the solution. Application method is spray method,
The amount of the polyethylene glycol and nitrocellulose added may be adjusted depending on the coating method, such as a rotation method, a dipping method, or a printing method. Further, it is also possible to add oxidizing ions or compounds such as nitrate ions to this solution in order to speed up the decomposition of the complex.

The method for preparing the coating solution is as follows. In the first method, a β-diketone such as acetylacetone is added to a salt such as a nitrate of an element that forms a complex with a β-diketone, and the mixture is dissolved while stirring for a long time at room temperature. At this time, heating facilitates dissolution. Additionally, alcohols, ketones, esters, etc. are added as necessary. Next, an appropriate amount of a nitrocellulose solution dissolved in a solvent that dissolves nitrocellulose, such as polyethylene glycol or butyl carbitol acetate, is added depending on the coating method to adjust the viscosity. In the second method, an appropriate amount of the polyethylene glycol or nitrocellulose solution described in the first method is added to a solution of the β-diketone complex dissolved in an organic solvent such as acetylacetone to prepare a coating solution. At this time, it is also possible to add oxidizing ions or compounds such as nitric acid. It is also possible to add organic solvents such as alcohols, ketones, and esters.

The coating liquid is characterized in that polyethylene glycol or nitrocellulose is contained in a solution of an element that forms a complex with β-diketone and β-diketone or a β-diketone complex. Since the complex has the effect of firmly adhering the complex to the substrate to be coated, the adhesion of the film obtained by applying and heating the solution to the substrate is high. Furthermore, since polyethylene glycol or nitrocellulose does not easily volatilize at room temperature, a situation where solutes are partially deposited during the coating operation does not occur, and the resulting film has good uniformity in thickness. Moreover, by selecting the amounts of polyethylene glycol and nitrocellulose added, it is possible to obtain a solution having a viscosity of several centipoises to several hundred thousand centipoises, so that all coating methods including printing methods can be applied. Furthermore, since solutions containing polyethylene glycol or nitrocellulose have greater thixotropy than solutions that do not contain these, there is no movement of the applied substance after the solution is applied, making it difficult for the film to become uneven.

Tunnel furnaces, batch furnaces, hot plate heating, etc. are used for heating after applying the solution. Heating is convenient for solvent volatilization process, complex and organic matter decomposition process,
The products are divided into calcination processes and are selected depending on the respective solvent and the desired product. Rapid heating is advantageous for the decomposition process of complexes and organic substances.

The present invention will be explained below using Examples.

Example 1 A beaker containing 1 mol of cerium nitrate {Ce(NO ₃ ) ₃ } and 5 mol of acetylacetone is heated and stirred at 50° C. on a hot stirrer equipped with a temperature control device. As the reaction progresses, a viscous, cutlet-colored solution is formed. When the reaction was stopped after about 15 hours and the relationship between rotor rotational speed and viscosity was measured using a rotational viscometer, a curve as shown in Figure 1a was obtained, and the extrapolated value of viscosity at zero rotational speed was approximately 3. It will be 11,000 poise. However, as is clear from FIG. 1a, the change in viscosity with respect to rotational speed is small and the thixotropy is very small. Next, this solution was added to nitrocellulose [HE-2000 manufactured by Asahi Kasei Corporation] 7
g in 100 ml of butyl carbitol acetate and stirred to form a solution. The relationship between the rotor rotational speed and viscosity of this solution in a rotational viscometer is as shown in FIG. 1b, and the extrapolated value of the viscosity at zero rotational speed is about 80,000 centipoise.

As is clear from the figure, it can be seen that the addition of nitrocellulose not only increases the viscosity, but also causes a large change in the viscosity with respect to the rotational speed and an increase in thixotropy. Such properties are essential for print coating methods.

Next, solutions a and b shown in FIG. 1 are printed using an offset printing machine on a glass substrate for a liquid crystal display device on which a transparent conductive film electrode is formed. A manual offset proofing machine (model KD, manufactured by Nakanishi Tekkosho Co., Ltd.) is used as the offset printing machine.

The printed layer printed on the upper and lower substrates of a liquid crystal display device
Heat at 80°C for 30 minutes, then at 250°C for 20 minutes. Next, it is heated rapidly in a furnace preheated to 500°C and held for 30 minutes to bake. As a result, the thickness of the film obtained from solution a is about 2000 Å ± 1500 Å, showing a non-uniform thickness distribution, whereas the thickness of the film obtained from solution b is about 2000 Å ± 1500 Å.
800 ű100 Å, showing a very uniform distribution.
In this way, the reason why the film thickness distribution of the film obtained from the solution containing nitrocellulose is uniform is that the adhesion between the solution and the substrate increases by adding nitrocellulose, and the viscosity is high and the thixotropy is low. This is thought to be because the printing layer becomes uniform due to the large size, and because the coating layer does not move during the standing and heating process compared to acetylacetone alone solution.

Next, as a result of the MIL Standard Cr-6-75A rubber rubbing test (eraser: JIS standard S-50), the presence or absence of damage and peeling was visually observed.
The film formed from the solution showed no damage or peeling, and a dense film with good adhesion was formed, whereas the film formed from the solution a showed partial peeling.

Next, using two upper and lower glass substrates for a liquid crystal display device having films formed from the solution b, a spacer such as a glass bead is used to remove a small part of the liquid crystal filling opening so as to maintain a gap of 10 μm between the upper and lower glass substrates. After printing the glass paste containing the thin film on the surface of one of the substrates on which the thin film was formed, seal firing is performed by applying a combination load with the surfaces on which the thin film is formed facing each other. Next, apply a thin layer of Cr around the filling opening.
- Forming a Ni-Av layer by vapor deposition. This forms the envelope of the liquid crystal display device. Next, the liquid crystal is sealed in the surrounding air under reduced pressure, and the sealing opening is sealed with solder. The liquid crystal can be of either nematic Nn or Np type, depending on the display method, but Schiff base type, biphenyl type, azoxy type, phenylcyclohexane type, terphenyl type, ester type, phenylcyclohexane type Any type of liquid crystal such as ester type liquid crystal is aligned perpendicularly to the display substrate evenly over the entire surface of the substrate. This is confirmed by suitable observational means such as a conoscope.

Example 2 Aluminum acetylacetonate {Al
1 mol of (C ₅ H ₈ O ₂ ) ₃ } is dissolved in 5 mol of acetylacetone with stirring while heating. Next, 1 mole of 61% nitric acid is added and the reaction is allowed to proceed with heating and stirring. Add polyethylene glycol 400 {Wako Pure Chemical Industries, Ltd.}
A solution of 1 part by weight dissolved in 10 parts by weight of ethanol is added to form a solution with a viscosity of about 10 centipoise, and this is used as a coating solution. The coating liquid is applied using a spinner onto a glass substrate on which a tin oxide-based transparent conductor electrode is formed. Spinner rotation speed is 3000rpm,
Application time is 20 seconds. Visual observation shows that the coating layer is uniform over the entire surface of the substrate, and no shrinkage or movement of the coating layer is observed even after being left in the air for a long time. This is because polyethylene glycol has good affinity with the substrate, improving the wettability of the solution, and even when solvents other than polyethylene glycol evaporate, polyethylene glycol remains in the coating layer, improving adhesion to the substrate. This is thought to be because it prevents the movement of solutes.

After applying the solution, heat it at 70℃ for 30 minutes, then continue
Heated at 500°C for 1 hour. In the latter heating process, decomposition of organic matter, oxidation and firing of metal proceed simultaneously.

The thickness of the obtained film was 1500 ű over the entire surface of the substrate.
It had extremely good uniformity of 150 Å, and was transparent and insulating. Further, in an electron micrograph of the surface of the film, there are few irregularities and no obvious pinholes are observed.
When this substrate is used as a liquid crystal display element, it undergoes a process such as brush cleaning to clean the substrate, but the film formed as described above shows no peeling or damage, and has excellent adhesion and film strength. Yes, it is durable enough for use.

Although only the printing method and the spin coating method were explained in the above embodiments, it is clear that coating methods such as the spray method and the dipping method can be applied. In addition, in the above example, a solution containing only one component of an element that forms a complex with acetylacetone was explained, but it is possible to use not only acetylacetone but also a general β-diketone, and the complex contained in the solution can be made of only one component. Without limitation, it goes without saying that a thin film can be formed from a solution containing a two-component or three-component complex depending on the application.

As explained in the examples above, the present invention allows a thin film with good adhesion to the substrate and excellent strength to be easily formed on the substrate with excellent uniformity using a coating method such as a printing method. A substrate on which an inorganic compound thin film is formed can be provided at a much lower cost than using phase growth, vapor deposition, or sputtering methods.

[Brief explanation of the drawing]

The figure shows the viscosity of a solution prepared from cerium nitrate and acetylacetone as a function of the rotational speed of a rotational viscometer. a... Viscosity of a solution without nitrocellulose added, b... Viscosity of a solution with nitrocellulose added.

Claims (1)

[Claims] 1 General formula R ₁ COCH ₂ COR ₂ or R ₁ COCH=C
(OH)R ₂ (in the general formula, R ₁ and R ₂ represent an alkyl group or an aryl group) and one or more salts selected from the elements that form a complex with the β-diketone; Add polyethylene glycol or nitrocellulose or the above two to a solution consisting of an organic or inorganic solvent containing β-diketone.
1. An electrode substrate characterized in that it has a thin film obtained by applying a solution containing a compound and then heating the solution.