JPH0374361B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an optical multilayer interference film (hereinafter simply referred to as "multilayer film"), and more specifically, the present invention relates to an optical multilayer interference film (hereinafter simply referred to as "multilayer film"), and more specifically, it is obtained by alternately laminating a high refractive index film and a low refractive index film on a substrate. The present invention relates to a method for producing a multilayer film with the purpose of increasing light reflection with high durability. Multilayer films that utilize light interference are used to increase light reflection, prevent light reflection, cold mirrors, cold filters, etc. A titanium oxide film (TiO ₂ , n≒2.0-2.4) with a high refractive index (n) is usually used as a high refractive index film constituting a multilayer film. It is common to use a silicon oxide film (SiO ₂ , n≈1.421.50) which has excellent properties such as: In such a multilayer film, when obtaining a light reflection increasing film with a high reflectance, a high refractive index film is used as the outermost layer, and a high refractive index film is used in an odd numbered layer counting from the outermost layer, and a low refractive index film is used in an even numbered layer. For example, as a light reflection increasing film using glass as a substrate, glass/TiO ₂ /
Three-layer structure of SiO ₂ /TiO ₂ , glass / TiO ₂ /SiO ₂ /
A five-layer structure such as TiO ₂ /SiO ₂ /TiO ₂ is adopted, and the light reflectance is about 30% for a single-layer structure of glass/TiO ₂ , while it is about 65% for a three-layer structure.
%, and in the case of a five-layer structure, more than 80% can be obtained. However, when films made of different materials are combined in this way, various problems arise in terms of durability due to differences in physical properties between the materials. For example, cracking or peeling due to the thermal expansion difference between the substrate and the thin film or each thin film, and chemical erosion of the substrate or inner film due to pinholes occur. In particular, the silicon oxide film in the multilayer film system is as stable as other oxide films in the normal usage environment, but it is not suitable for environments such as coastal areas where it is directly exposed to salt water or where there is a lot of salt or flying sand. On the other hand, point peeling and fine cracks occur due to the silicon oxide film, and the outermost titanium oxide film is extremely easily scratched due to surface abrasion caused by solid particles such as dust and sand, and reflections due to abrasion occur. There is a decrease in the rate. As a method of improving the salt resistance of a silicon oxide film, a method of adding tin oxide or zirconium oxide to a silicon oxide film has been proposed in Japanese Patent Laid-Open No. 124301/1983. It is certainly recognized that the salt resistance is improved by this method, but the abrasion resistance of the high refractive index film used as the outermost layer is not improved. An object of the present invention is to provide a multilayer film that has excellent durability and abrasion resistance in salt water and high temperature and high humidity environments, and a method for manufacturing the same. As a result of intensive research to achieve the above object, the present inventors have found that the outermost layer of the multilayer film is a tantalum oxide film alone or a composite film of tantalum oxide and titanium oxide, and that the multilayer film is manufactured by a coating method. The present invention was completed based on the discovery that salt water resistance and abrasion resistance can be significantly improved by using an organic silicon compound solution to which phosphorus pentoxide is added as a coating solution for forming a low refractive index film. The multilayer film of the present invention has a TiO ₂ /Ta ₂ O ₂ ratio in the outermost layer.
It has a high refractive index film consisting of a single film of tantalum oxide or a composite film of tantalum oxide and titanium oxide of 95/5 to 0/100, and the single film of titanium oxide or titanium oxide is placed in the odd numbered layer counting from the outermost layer. This is a light reflection increasing film that utilizes optical interference, in which high refractive index films made of a composite film of tantalum oxide and tantalum oxide are alternately laminated on a substrate, and low refractive index films made of even-numbered silicon oxide films are alternately laminated on a substrate. For example, as a multilayer film using glass as a substrate, glass/TiO ₂ /SiO ₂ /Ta 2 O ₅ , glass/TiO 2 /SiO 2 /Ta ₂ O 5
TiO ₂ /SiO ₂ /TiO ₂・Ta ₂ O ₅ , Glass/TiO ₂・
Ta ₂ O ₅ /SiO ₂ /TiO ₂・Ta ₂ O ₅ , Glass/TiO ₂・
Three-layer film such as Ta ₂ O ₅ /SiO ₂ /Ta ₂ O ₅ , glass /
Examples include five-layer films such as TiO ₂ / _{SiO 2 /} TiO ₂ /SiO 2 /TiO ₂ ·Ta ₂ O ₅ and glass/TiO ₂ /SiO 2 /TiO ₂ / _{SiO 2 /} Ta ₂ O ₅ . In the present invention, as the TiO ₂ /Ta ₂ O ₅ ratio of the high refractive index film of the outermost layer decreases, salt water resistance and abrasion resistance improve, but light reflectance slightly decreases. In particular, the durability is significantly improved when the TiO ₂ /Ta ₂ O ₅ ratio is 95/5 or less. Therefore, if abrasion resistance is required, it is preferable to use tantalum oxide as a single film; conversely, if abrasion resistance is not required, a high reflectance of light can be obtained.
It is preferable to use a composite film of tantalum oxide and titanium oxide with a large TiO ₂ /Ta ₂ O ₅ ratio. Further, depending on the case, a single film of titanium oxide may be used. In the present invention, an organic titanium compound solution or a mixed solution of an organic titanium compound and an organic tantalum is applied as a coating solution for forming a high refractive index film onto a substrate or a low refractive index film, and then heated to form a high refractive index film. Then, an organic silicon compound solution containing phosphorus pentoxide is applied as a coating liquid for forming a low refractive index film on the high refractive index film, and a low refractive index film is formed by heat treatment, and an organic tantalum compound solution or A mixed solution of an organic tantalum compound and an organic titanium compound is applied as a coating solution for forming the top layer of high refractive index film onto the next layer of low refractive index film, and then heated to form the top layer of high refractive index film. A multilayer film is thereby produced. The organic titanium compound used in the coating solution for forming the high refractive index film and the top layer high refractive index film is soluble in organic solvents, and the organic solvent solution is applied onto the substrate or silicon oxide (SiO ₂ ) film. Any material that can form a titanium oxide (TiO ₂ ) film by heat treatment can be used. For example, the following general formula (1) Ti(Cl) _x (OR) _(4-x) ...(1)
~4 alkyl group, x is 0 and 1-3
is an integer. ) Organotitanium compounds represented by and general formula (1)
A polymer containing 2 to 20 Ti atoms in one molecule obtained by polymerizing tetraalkoxytitanium in which x is 0 using water is preferably used.
In addition, organic tantalum compounds are also soluble in organic solvents, and a tantalum oxide (Ta ₂ O ₅ ) film can be formed by coating the organic solvent solution on a substrate or silicon oxide (SiO ₂ ) film and heat-treating it. Any of these can be used, but preferably pentaalkoxytantalum represented by the following general formula (2) Ta(OR) ₅ ...(2) (wherein R represents the same meaning as above), and pentaalkoxytantalum A polymer containing 2 to 20 Ta atoms in one molecule obtained by polymerizing alkoxy tantalum with water is used. A metal oxide (TiO 2 , Ta ₂ O 5 or TiO 2 +Ta ₂ O ₅ ) produced by oxidizing the organic titanium compound, organic tantalum compound, or a mixture of an organic _titanium compound and an _{organic tantalum} compound. Contains 1 to 10% by weight in terms of a concentration converted to
Preferably, an organic solvent solution to which 1.5 to 5 times the mole is added is used as a coating liquid for forming a high refractive index film. Alcohols and esters having 8 or less carbon atoms as organic solvents;
Hydrocarbons and halogenated hydrocarbons can be used. Stabilizers include β-diketones such as acetylacetone and benzoylacetone, ketonic acids such as acetoacetic acid, propionylbutyric acid, and benzoylformic acid, esters of these ketonic acids, lactic acid, glycolic acid, α-oxybutyric acid, salicylic acid, etc. Oxyacids, esters of oxyacids, oxyketones such as diacetone alcohol and acetoin, α-amino acids such as glycine and alanine,
One or more selected from the group consisting of amino alcohols such as aminoethyl alcohol and organic carboxylic acids such as acetic acid are used. Also, if necessary, add phosphorus pentoxide to 0.5% based on metal oxides.
~3.0% by weight may be added. When coating the coating liquid on a substrate or a low refractive index film, if the concentration of the organometallic compound in the coating liquid is less than 1%, it is difficult to obtain a sufficient coating film thickness, and if it exceeds 10%, the coating will be difficult to obtain. This is not preferable because the film becomes too thick and cracks may occur during heat treatment. A coating liquid to which a stabilizer is added has excellent stability and has an excellent effect of preventing clouding of a coating film applied on a substrate or a low refractive index film. A coating solution consisting of a mixed solution of an organic titanium compound and an organic tantalum compound may be prepared by mixing the organic titanium compound and the organic tantalum compound in a desired ratio and then dissolving the mixture in an organic solvent. The titanium compound solution and the organic tantalum compound solution may be mixed in a desired ratio. The organic silicon compound used in the coating solution for forming a low refractive index film is one that can form a silicon oxide (SiO ₂ ) film by applying its organic solvent solution onto a high refractive index film and heat treating it. If necessary, a tetraalkoxysilane represented by the following general formula (3) Si(OR) ₄ ...(3) (where R represents a methyl group or an ethyl group) is prepared from methanol or ethanol and acetic acid. A siloxane compound obtained by polymerizing a trace amount of mineral acid as a catalyst in a reaction system is preferably used. The coating liquid for forming a low refractive index film contains 1 to 12% by weight of the organosilicon compound in terms of silicon oxide (SiO ₂ ), and phosphorus pentoxide based on the amount of SiO ₂ .
It is an organic solvent solution to which 0.5 to 3% by weight is added.
As the organic solvent, the same type of organic solvent as used in the above-mentioned coating liquid for forming a high refractive index film can be used. If the concentration of the organosilicon compound in the coating solution for forming a low refractive index film is lower than the above range, the thickness of the coating will be insufficient when applied onto a high refractive index film, and if it is higher than the above range, the coating will be thick. This is not preferable because it increases the possibility that cracks will occur during heat treatment. Phosphorus pentoxide added to the coating solution for forming a low refractive index film has the effect of improving the corrosion resistance of the silicon oxide film obtained by heat-treating the coating film and improving the adhesion with the high refractive index film. In the present invention, a coating liquid for forming a high refractive index film consisting of the above-described organic titanium compound solution or a mixed solution of an organic titanium compound and an organic tantalum compound is applied onto a substrate and heat-treated to form a high refractive index film,
Next, a coating solution for forming a low refractive index film made of an organic silicon compound solution is applied onto the high refractive index film and heat-treated to form a low refractive index film on the high refractive index film. Applying a coating liquid for forming an outermost high refractive index film made of an organic tantalum compound solution or a mixed solution of an organic tantalum compound and an organic titanium compound to the uppermost layer formed by alternately laminating the film and the low refractive index film, By heat treatment, a highly durable multilayer film having a single film of tantalum oxide or a composite film of tantalum oxide and titanium oxide as the outermost layer can be obtained. There are no particular limitations on the method of applying the coating liquid for forming a high refractive index film and a low refractive index film onto the substrate and the high or low refractive index film, including the dipping and pulling up method,
Although known methods such as a spinner method and a spray method can be used, the dipping and pulling method is preferred because it allows easy control of the coating film thickness and provides a uniform film thickness. In addition, the heat treatment of the coating film is performed at a temperature higher than the temperature at which the organometallic compound is oxidized and an oxide of the metal is generated for both the high refractive index film and the low refractive index film.
Perform at a temperature of at least 350℃ or higher. More preferably, this is carried out by placing the substrate coated with the coating liquid into a furnace that has been heated to a predetermined temperature in advance. The upper limits of heat treatment time and heating temperature are as follows:
It depends on the allowable temperature limit of the substrate used, and there is no particular restriction. Further, if the heating temperature is lower than 350°C, particularly 300°C or lower, it is difficult to obtain a dense film and no improvement in durability can be expected. The substrate used in the present invention can be made of glass, ceramics, metal, etc., as long as it has heat resistance that can withstand heat treatment. Since the multilayer film of the present invention has high durability and high light reflectance, it can be used for reflective mirrors, decorative colored glass, mirrors, optical filters, and the like. The present invention provides a highly durable multilayer film having salt water resistance, abrasion resistance, and high reflectance, and a method for manufacturing the same, and has extremely great industrial significance. Hereinafter, the present invention will be explained in more detail by giving examples. However, the scope of the present invention is not limited by the following examples. Example Preparation of coating solution [-1] Organic titanium compound solution The following general formula was added to a mixed solvent consisting of 65 parts by weight of ethanol, 25 parts by weight of butyl acetate, and 15 parts by weight of acetylacetone. (Here, Bu represents a normal butyl group.) An organic titanium compound having an average structure represented by the following was dissolved to a concentration of 5% by weight in terms of TiO ₂ to prepare a coating liquid for forming a high refractive index film: A. In addition, the above coating liquid for forming a high refractive index film: A
A coating liquid for forming a high refractive index film: B was prepared by adding and dissolving phosphorus pentoxide (P ₂ O ₅ ) corresponding to 2% by weight based on the weight of the organic titanium compound in terms of TiO ₂ . [-2] Organic tantalum compound solution Add 100 parts by weight of reagent special grade lactic acid to 110 parts by weight of pentaethoxy tantalum, and further add isopropanol to give a concentration of 5% by weight in terms of Ta ₂ O ₅ .
The mixture was heated and mixed at a temperature of 80° C. for 2 hours to prepare a coating liquid for forming a high refractive index film: C. [-3] Organosilicon compound solution 219 parts by weight of tetraethoxysilane, ethanol
643 parts by weight of acetic acid, 0.3 parts by weight of hydrochloric acid was added to 206 parts by weight of acetic acid, mixed, and reacted under reflux for 45 hours to obtain a coating solution for forming a low refractive index film consisting of an organosilicon compound solution with a SiO ₂ equivalent concentration of 5.9% by weight: D was prepared. In addition, the above coating liquid for forming a low refractive index film: D
2.5 per organosilicon compound weight converted to SiO ₂
A coating liquid for forming a low refractive index film: E was prepared by adding phosphorus pentoxide (P ₂ O ₅ ) in an amount of % by weight. Manufacture of multilayer film A soda glass measuring 120 mm x 60 mm x 2 mm was thoroughly washed with detergent, washed with water and dried to form a substrate.
The substrate was immersed in coating solution A or B for forming a high refractive index film, pulled up at a rate such that the optical film thickness (nt) was 1200 Å, dried at room temperature, and then heat-treated in an electric furnace for 30 minutes to form a high refractive index film. was formed. Next, it was immersed in coating solution D or E for forming a low refractive index film, pulled up at a speed such that the optical film thickness (nt) was 1200 Å, and heated in an electric furnace for 30 min.
A heat treatment was performed for a minute to form a low refractive index film on the high refractive index film. Furthermore, it is subsequently immersed in a coating solution A, B, C or a mixed solution of B and C for forming a high refractive index film,
Pulled at a speed to achieve an optical film thickness (nt) of 1200 Å,
A high refractive index film was formed on the low refractive index film by heat treatment in an electric furnace for 30 minutes, and a light reflection increasing mirror consisting of three layers on both sides was manufactured. The type of coating liquid used for each layer and the heat treatment temperature for each layer are shown in Table 1 along with the test results described below. Durability test method [-1] Salt water boiling test: a The multilayer film obtained in a 5% by weight NaCl aqueous solution heated to 90°C was immersed for 1 hour and then pulled up.
After being left at room temperature for 1 hour, it was immersed again in the NaCl aqueous solution for 1 hour, dried, and visually observed for the presence or absence of point defects and fine cracks. [-2] Salt water boiling test: b The multilayer film produced above was immersed in a 5% by weight NaCl aqueous solution heated to 103 to 104°C, and the time until point defects or minute cracks appeared was measured. did. [-3] Salt water spray test A salt water spray test was conducted for 200 hours according to the method specified in JIB Z2371, and the presence or absence of point defects and microcracks was visually observed. In addition, the reflectance: _RJ was measured according to JIS D5705. [-4] Abrasion test A 30 mm x 30 mm flannel cloth was impregnated with a polishing liquid with a solid content of 20% in which Cr ₂ O ₃ powder of 200 mesh or less was dispersed in distilled water, and a load of 80 g/cm ² was applied. The multilayer film surface was polished 60 times, and the reduction rate of optical film thickness (nt) before and after polishing and the reduction rate of reflectance: R _J specified in JIB D5705 were measured. The above test results are shown in Table 1.

[Table] However, the wavelength at maximum reflection λmax = 480nm
*2 Optical film thickness before abrasion test: noto
Optical film thickness after 60 times abrasion test: nt
Optical thickness reduction rate = 〓(noto−nt)/noto
〓×100(%)
*3 Reflectance before abrasion test: R _J o
Reflectance before 60 times abrasion test: R _J
Decrease rate of reflectance=〓(R _J o−R _J )/R _J o
〓×100(%)
Discussion of test results As is clear from the test results shown in Table 1, the addition of phosphorus pentoxide to the coating solution for forming a low refractive index film
Improve salt water resistance (No. 1 and No. 3, No. 2 and No. 4)
(comparison with). Furthermore, the higher the heating temperature of the first layer and the second layer, the better the salt water resistance. (Comparison between No. 1 and No. 2, and No. 3 and No. 4) Furthermore, by adding tantalum to the top layer, salt water resistance is further improved, and abrasion resistance is also improved. The smaller the TiO ₂ /Ta ₂ O ₅ ratio of the top layer, the lower the reflectance, but the greater the salt water resistance and abrasion resistance.

Claims (1)

[Scope of Claims] 1. A method for producing an optical multilayer interference film in which metal oxide thin films with a high refractive index and metal oxide thin films with a low refractive index are alternately laminated on a substrate, wherein an organic titanium compound solution is used. Alternatively, a mixed solution of an organic titanium compound and an organic tantalum compound is applied as a coating solution for forming a high refractive index film onto a substrate or a low refractive index film, and a high refractive index film is formed by heat treatment. An organic silicon compound solution containing phosphorus pentoxide is applied thereon as a coating solution for forming a low refractive index film, and heat treated to form a low refractive index film, and then an organic tantalum compound solution or an organic tantalum compound and an organic titanium compound are applied. A method for producing a highly durable multilayer film, characterized in that a mixed solution of the above is applied as a coating solution for forming a high refractive index film on a low refractive index film, and then heated to form a high refractive index film as the outermost layer. . 2 The outermost layer has a TiO ₂ /Ta ₂ O ₅ ratio of 95/5 to 5/95
A method for producing a highly durable multilayer film according to claim 1, which is a composite film of tantalum oxide and titanium oxide. 3. The method for producing a highly durable multilayer film according to claim 1, wherein the heat treatment temperature of each layer is at least 350°C or higher. 4 The organic titanium compound solution has the following general formula (1) Ti(Cl) _x (OR) _(4-x) ...(1) (where R represents an alkyl group having 1 to 18 carbon atoms, and x is 0 or an integer from 1 to 3.) From the group consisting of β-diketones, ketonic acids, ketonic acid esters, oxyacids, or organic carboxylic acids of organic titanium compounds or hydropolymerized tetraalkoxytitanium represented by The method for producing a highly durable multilayer film according to claim 1, which is an organic solvent solution containing one or more selected stabilizers. 5 The organic tantalum compound solution is pentaalkoxytantalum or pentaalkoxytantalum represented by the following general formula (2) Ta (OR) ₅ ... (2) (where R represents an alkyl group having 1 to 18 carbon atoms). β- of hydropolymer
diketones, ketonic acids, ketonic acid esters,
The method for producing a highly durable multilayer film according to claim 1, which is an organic solvent solution containing one or more stabilizers selected from the group consisting of oxyacids and organic carboxylic acids. 6 The coating solution for forming a low refractive index film is a tetraalkoxysilane represented by the following general formula (3) Si(OR) ₄ ...(3) (where R represents a methyl group or an ethyl group) in methanol or The highly durable multilayer film according to claim 1, which is obtained by adding phosphorus pentoxide to an organic solvent solution of a siloxane compound obtained by polymerizing using a mineral acid as a catalyst in a reaction system consisting of ethanol and acetic acid. manufacturing method.