JPH0555600B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] This invention provides a method for forming an inorganic film by decomposing an organometallic compound contained in a solution by heating and coating a substrate with an inorganic film made of a metal or a metal compound; In particular, the present invention relates to prevention of deformation of the substrate due to a decrease in the heating temperature. [Prior art] As a method of forming an inorganic film on a substrate,
Vacuum deposition method, sputtering method, plasma CVD
method, ion plating method, etc. However, the equipment for carrying out these methods must be large-scale. Furthermore, since these methods form the coating in batches, it is not possible to continuously form an inorganic coating over a large area.
Therefore, these methods have the disadvantage that the processing cost must be high as a method for forming an inorganic film on a substrate. A method that can continuously form a large-area inorganic film on a substrate using small-scale equipment is to use an organic metal compound (metal acetylacetonate, metal alcoholate, organic acid) on a substrate such as glass or ceramic. A solution containing a metal salt (metal, etc.) or an inorganic acid metal salt (metal nitrate, metal chloride, etc.) is applied by immersion, and this adhesion solution is applied together with the substrate at a temperature of 400 to 600 ml.
A method is known in which an organic metal compound or an inorganic acid metal salt in an adhesion solution is decomposed by heating at a temperature of about .degree. C. to form an inorganic film made of a metal or a metal compound on a substrate. However, when decomposing the organometallic compound or inorganic acid metal salt in the adhesion solution, this method
Since the substrate is heated to a high temperature of 600℃, if a plastic plate with a low heat resistance temperature is used as the substrate, the substrate will be significantly deformed. Therefore, this method is used to form an inorganic film on the plastic substrate. It is difficult to do so. In addition, even when using a glass plate with a higher heat resistance temperature than a plastic plate as a substrate, the heating temperature for decomposing the organic metal compound or inorganic acid metal salt contained in the solution is close to the softening point temperature of the glass. Therefore, it is inappropriate to form an inorganic film by this method on a substrate that undergoes large deformation due to heating and requires high precision. For this reason, a film forming method (sol-gel method) using hydrolysis of a solution containing a metal alcoholate has been proposed as a method for forming an inorganic film at a low temperature while taking advantage of the immersion method. [Problems to be Solved by the Invention] In the above-mentioned film formation method using hydrolysis of a solution containing a metal alcoholate, the number of organometallic compounds that can form an inorganic film is limited, and moreover, the organometallic compound decomposes. There is a problem that it remains in the inorganic coating without being removed, and only a weak inorganic coating can be formed. This invention was made to solve these problems, and while taking advantage of the immersion method, it
The purpose of this invention is to obtain a method for forming a strong inorganic film by heating at a low temperature below ℃. [Means for Solving the Problems] The method for forming an inorganic film according to the present invention includes heating a plastic substrate to the maximum heat-resistant temperature to saturate oligomer precipitation and thermal shrinkage, wiping off the precipitated oligomer with an organic solvent, Next, a cyclopentadienyl group and Sn, U, Tl,
An organometallic compound consisting of a metal selected from Mo, In, Ni, Th, Pb, Ti, Zn, Hg, Bi, a methylcyclopentadienyl group and In, Ni,
Organometallic compound consisting of one metal selected from Sn, Zn, La, Mg, lower alkyl group and Al, As, B, Be, Bi,
Organometallic compound consisting of one metal selected from Cd, Ga, Hg, In, P, Sb, Se, Te, Zn, (C ₆ H ₆ ) ₂ Cr, (C ₆ H ₆ ) ₂ Mo or ( A solution consisting of one or more selected from the group of organometallic compounds selected from C ₆ H ₅ ) ₂ SnH ₂ and an organic solvent from which oxygen and moisture have been removed is heated to remove residual oxygen, The adhesive is deposited under an inert gas atmosphere with moisture content controlled to be 10 ppm or less, and the deposition solution is heated together with the substrate at a heating rate of 2 to 50°C/sec and a maximum holding temperature of 300°C or less. be. Further, the solution for forming an inorganic film according to the present invention is characterized in that it consists of the above-mentioned organometallic compound and an organic solvent from which oxygen and moisture have been removed, and contains the organometallic compound at a concentration of 2 to 30 wt%. That is. [Function] In this invention, since the solution deposited on the substrate contains a predetermined highly reactive organometallic compound, when heated, this organometallic compound becomes 300%
It decomposes at a low temperature of .degree. C. or lower, and an inorganic film made of metal or a metal compound thereof is formed on the substrate. [Example] The invention of this application involves dissolving a predetermined amount of a highly reactive organometallic compound in a low boiling point organic solvent, applying the solution onto a substrate by a dipping method, and applying the solution in a reducing or oxidizing atmosphere. This solution is heated at a low temperature of 300°C or less to form an inorganic film on the substrate. Here, highly reactive organometallic compounds are represented by the general formula M(ClHm)n (where M is a metal, l, m, and n are integers, and n represents the valence of the metal M). For example, an organometallic compound consisting of cyclopentadiene or a derivative thereof and a metal, an organometallic compound consisting of an alkyl metal, benzene, phenyl group or a derivative thereof and a metal, or a mixture of these organometallic compounds. can be mentioned. The highly reactive organometallic compounds that can be used in the present invention are as follows. here,
Cp represents cyclopentadienyl, Me represents methyl, Et represents ethyl, Pr represents propyl, Bu represents butyl, and Ph represents phenyl. ★ Organometallic compound consisting of cyclopentadiene or its derivatives CpNa, Cp ₂ Sn, Cp ₄ U, CpTl,
(MeCp) ₂ Sn, Cp ₄ Mo, Cp ₄ Sn, CpIn, Cp ₂ Ni,
Cp ₄ Th, Cp ₂ Pb, Cp ₂ Ti, Cp ₃ Ti, Cp ₃ In,
_Cp2Zn , MeCpIn, _Cp2Hg , _Cp3Bi ,
(MeCp) ₃ In, (MeCp) ₂ Ni ★ Alkyl metal Me ₃ Al, Et ₃ Al, Pr ₃ Al, Bu ₃ Al, Me ₃ As,
Et ₃ As, Me ₃ B, Et ₃ B, Pr ₃ B, Bu ₃ B, Me ₂ Be,
Et ₂ Be, Pr ₂ Be, Bu ₂ Be, Me ₃ Bi, Me ₂ Cd,
Et ₂ Cd, Pr ₂ Cd, Bu ₂ Cd, Me ₃ Ga, Et ₃ Ga,
Pr ₃ Ga, Bu ₃ Ga, Me ₂ Hg, Et ₂ Hg, Me ₃ In,
Et ₃ In, Pr ₃ In, Bu ₃ In, MeLi, EtLi, PrLi,
BuLi, Me ₃ P, Et ₃ P, Pr ₃ P, Bu ₃ P, Me ₃ Sb,
Et ₃ Sb, Pr ₃ Sb, Bu ₃ Sb, Me ₂ Se, Et ₂ Se,
Me ₂ Te, Et ₂ Te, Me ₂ Zn, Et ₂ Zn,
(MeCp) ₂ Zn, (MeCp) ₃ La, (MeCp) ₂ Mg ★ Benzene compound (C ₆ H ₆ ) ₂ Cr, (C ₆ H ₆ ) ₂ Mo ★ Phenyl compound Ph ₂ SnH _2These organometallic compounds are It is a highly reactive substance that reacts with oxygen in the atmosphere at room temperature, causing spontaneous combustion, heat generation, smoke, and discoloration. However, when these organometallic compounds are dissolved in an organic solvent, their reactivity is considerably reduced. However, when the organic solvent is vaporized and separated from the solution, reactivity appears, so that a decomposition or oxidative decomposition reaction occurs at a low temperature, forming an inorganic film on the substrate. Furthermore, the organometallic compound used in the present invention must be of high purity and, since it is highly reactive, must be protected from deterioration by oxygen remaining in the operating atmosphere. Organometallic compounds that have undergone alteration have a higher oxidative decomposition temperature, and
This is because solubility in organic solvents also deteriorates. The low boiling point organic solvent used in this invention is:
Benzene (bp80.5℃), methylethyltaton (MEK) (bp79.6℃), tetrahydrofuran (THF) (bp88℃), diethyl ether ( _Et2O )
(bp34.6℃), cyclopentane (bp49.5℃), cyclopentadiene (bp41℃), n-pentane (b.
p.36.1℃). Alkyl metals form adducts with THF, Et ₂ O, etc., making them more stable. The concentration of the organometallic compound in this invention is 2 to
The content is preferably 30wt%. If it is less than 2wt%, the thickness of the inorganic film formed will be too thin, and
This is because if the amount exceeds 30 wt%, insoluble matter will be generated in the solution. As the substrate, in addition to commonly used glass plates, ceramic plates, and metal plates, heat-resistant plastic plates can also be used. Examples of heat-resistant plastics include polyethylene terephthalate (PET) (heat-resistant temperature 150°C) and polyethylene sulfide (PES).
(heat resistant temperature: 190°C), polyethyl ethyl ketone (PEEK) (heat resistant temperature: 220°C), polyimide resin (heat resistant temperature: 400°C), etc. These plastic plates have good wettability with the above-mentioned organic solvent, but in order to increase the adhesion strength with the inorganic coating, it is necessary to perform surface treatment as necessary. Furthermore, when a plastic plate is used as a substrate, precipitation and shrinkage of oligomers may occur due to heat treatment. Precipitation and shrinkage of oligomers have a negative effect on the adhesion of the inorganic coating, so before use, each plastic substrate is heated to its maximum heat-resistant temperature for about 5 to 15 seconds to saturate the precipitation and thermal shrinkage of oligomers, and to prevent precipitation. The oligomers must be wiped off with an organic solvent. The heat treatment conditions set in the present invention depend on the type of substrate and organometallic compound used, but are preferably as follows. The temperature increase rate shall be 2°C/sec or more. If it is less than 2°C/sec, the decomposition of the organometallic compound will be incomplete and a residue will be produced.If it is too fast, if a plastic substrate is used, the substrate will be deformed and the formed inorganic film will also be damaged. This may cause deformation or cracks. 40-50 at most
C/sec is the upper limit. The maximum holding temperature shall be 300℃ or less. This is because if the temperature exceeds 300°C, the substrate will deform. The holding time is approximately 20 to 90 minutes. When forming an oxide film, the organometallic compound on the substrate is brought into contact with oxygen at the same time as heating is performed. On the other hand, when forming a metal film, heating is performed in a reducing atmosphere (eg, nitrogen gas or Ar gas atmosphere). Depending on the situation, preheating to vaporize the organic solvent may be required, but in that case, contact with oxygen should be sufficiently avoided and the temperature increase rate should be relatively slow. In this invention, the highly reactive organometallic compound is attached to the substrate in a solution state by a dipping method, but it may also be attached to the substrate by an MO-CVD method, a spray method, or the like. The film thickness is controlled by adjusting the concentration of the solution and the speed at which the substrate is pulled up, and by repeating dipping and heat treatment. During the heat treatment process, the organometallic compound layer portion becomes significantly higher than the substrate heating temperature, albeit for a short time, due to heat accumulation due to self-heating. Therefore, the decomposition or oxidative decomposition of the organometallic compound progresses sufficiently, and an inorganic film made of a metal film or a transparent metal oxide film is formed with almost no residual organic matter even when heated at low temperatures. This metal film or metal oxide film exhibits high conductivity and also has fairly strong adhesion to the substrate. The organometallic compound used in this invention includes oxygen,
Changes in quality due to moisture and heat (above room temperature).
The altered substance incorporates oxygen into its molecules, undergoes partial oxidation, becomes a hydroxide, becomes a metal oxide, and becomes mixed with metal precipitates. Therefore, when handling organometallic compounds, it is necessary to do so under an inert gas (e.g., nitrogen gas, argon gas, etc.), and the residual oxygen and moisture content must be approximately 5 to 10 ppm.
It is necessary to control the following. Further, in order to remove oxygen and moisture mixed in the organic solvent, it is necessary to perform distillation, bubbling with an inert gas, etc. Furthermore, since organometallic compounds gradually deteriorate even at room temperature, they must be stored at low temperatures. The method for forming an inorganic film according to the present invention is based on a simple dipping method, without using vacuum evaporation, sputtering, spraying, etc., and can simplify the coating and baking processes and equipment, so it can continuously cover a large area at low cost. In addition, by using a highly reactive organometallic compound, a nearly complete inorganic film can be formed with low-temperature heat treatment below 300°C, making it possible to form a film even on heat-sensitive substrates such as plastics, making it extremely effective. It's advantageous. Example 1 A solution was applied to a substrate by a dipping method, and a film was formed by heating at a low temperature. As the solvent for this solution, benzene purified by distillation under a nitrogen gas flow state was used, and as the solute, an organometallic compound consisting of cyclopentadiene or its derivative and a metal was used, and the concentration of this organometallic compound was approximately 5 wt%. The substrates used were glass plates, polyimide plates, and PET plates. Glass plates are washed with alkaline detergent and then UV (ultraviolet) irradiation. Polyimide plates and PET plates are washed with 150
The sample was heat-treated at ℃ for 10 minutes, and the precipitated oligomer was wiped off with an organic solvent. For dipping, use a dipping device at a dipping speed of approximately 25cm/min.
I went there. Nitrogen gas is used as the atmosphere, and residual
O ₂ and H ₂ O were kept below about 5 to 10 ppm. Heat treatment was performed using an infrared furnace in nitrogen, air, and oxygen atmospheres at a heating rate of 3 to 5°C/sec and a firing temperature of 100°C.
~400℃. All inorganic coatings after heat treatment had sufficient strength. After heat treatment, the inorganic film formed on the substrate is
Measured by line diffraction. The diffraction patterns of the oxide and metal appeared to overlap, but the metal peak became lower in the order of nitrogen, air, and oxygen. Along with that,
Conductivity also deteriorates. The electrical conductivity of the films fired in a nitrogen atmosphere is shown in Table 1 for the glass substrate, and in Table 2 for the films on the polyimide and PET substrates. Here, the reason why an oxide X-ray diffraction pattern appears in an inorganic film even under a nitrogen atmosphere is because a solution containing an organometallic compound is applied onto a substrate by a dipping method, and then until it is fired. It is thought that this is because oxygen was taken in between them.

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[Table] Example 2 A film formation experiment was conducted using an alkyl metal as a solute. The solvent, substrate, dipping operation, firing conditions, etc. are the same as in Example 1. The experimental results were also almost the same as in Example 1. Table 3 shows the conductivity of coatings on glass substrates.
The conductivity of the coating on the substrate is shown in Table 4.

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[Table] Example 3 A film formation experiment was conducted using a benzene compound and a phenyl compound as solutes. The solvent, substrate, dipping operation, firing conditions, etc. are the same as in Example 1. The experimental results were also almost the same as in Example 1. Table 5 shows the electrical conductivity of the coating on the glass substrate, and Table 6 shows the electrical conductivity of the coating on the polyimide substrate.

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〔Effect of the invention〕

As explained above, this invention enables the formation of an inorganic film with high conductivity and strong adhesion on heat-sensitive substrates such as plastics by low-temperature heating by using a predetermined highly reactive organometallic compound. There is an effect.

Claims (1)

[Claims] 1. Heating the plastic substrate to the highest heat-resistant temperature to saturate oligomer precipitation and heat shrinkage, wiping off the precipitated oligomer with an organic solvent, and then
The substrate has a cyclopentadienyl group and Sn, U, Tl,
An organometallic compound consisting of a metal selected from Mo, In, Ni, Th, Pb, Ti, Zn, Hg, Bi, a methylcyclopentadienyl group and In, Ni,
Organometallic compound consisting of one metal selected from Sn, Zn, La, Mg, lower alkyl group and Al, As, B, Be, Bi,
Organometallic compound consisting of one metal selected from Cd, Ga, Hg, In, P, Sb, Se, Te, Zn, (C ₆ H ₆ ) ₂ Cr, (C ₆ H ₆ ) ₂ Mo or ( A solution consisting of one or more selected from the group of organometallic compounds selected from C ₆ H ₅ ) ₂ SnH ₂ and an organic solvent from which oxygen and moisture have been removed is heated to remove residual oxygen, An inorganic coating characterized by being deposited under an inert gas atmosphere with moisture content controlled to be 10 ppm or less, and heating the deposition solution together with the substrate at a heating rate of 2 to 50°C/sec and a maximum holding temperature of 300°C or less. How to form.