JP2009000651A - Film manufacturing method and antireflection substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a film, which has excellent surface strength and antifouling properties, alkali resistance, and is suitable especially for application for an optical system such as application for antireflection. <P>SOLUTION: The film manufacturing method includes the steps of: hydrolyzing alkoxysilane in a solvent, which does not contain alcohol substantially; coating a coating material containing a resultant product on the surface of the substrate and drying; and forming a film having a thickness of 0.05-1 μm on the surface of the substrate. In a hydrolytic reaction of alkoxysilane, alcohol which inhibits this hydrolytic reaction is eliminated from a reaction system to accelerate the hydrolytic reaction, so as to suppress the remaining of alkoxy groups in the product. As a result, even when a high-temperature treatment cannot be performed, the remaining of the alkoxy groups in the film constituted of a hydrolysis condensate of alkoxysilane is suppressed, thereby enhancing the crosslinking density. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a coating film used for coating an optical system member and the like, and an antireflection substrate.

  Conventionally, a coating material obtained by partially hydrolyzing an alkoxysilane, particularly a tetrafunctional alkoxysilane represented by tetraethoxysilane, can form a film having a high surface strength close to that of glass, and a functional filler (fine particles, etc.). It is used for optical system applications such as anti-reflective coatings by adjusting the refractive index in combination with modified alkoxysilanes such as fluorine-modified, vinyl-modified, and amino-modified, and is also put into practical use in other fields ( Patent Document 1).

  Among anti-reflective applications, especially anti-reflective coatings located on the outermost surface of the display, together with excellent anti-reflective performance, dirt such as surface strength (friction resistance) and fingerprints can be easily removed to prevent scratches. Surface water repellency and oil repellency (contamination resistance) that can be produced are required at the same time, but this film is formed by cohydrolysis of porous silica fine particles and tetrafunctional alkoxysilane partial hydrolyzate or tetrafunctional alkoxysilane and fluorine-modified alkoxysilane. By forming it with a film made of a product, it is possible to impart excellent surface hardness together with excellent antireflection performance.

  However, such a coating tends to have a low resistance to an alkaline solution. Particularly, when the film thickness needs to be 1 μm or less depending on the application, etc., when high-temperature heat treatment at 200 ° C. or higher is not possible, the ratio of tetrafunctional alkoxysilane When it is necessary to increase the strength and increase the strength, or when it is necessary to increase the functional filler ratio, the low alkali resistance becomes prominent. As a specific application in which such low alkali resistance becomes prominent, a coating material film containing photocatalyst fine particles typified by titanium oxide is formed on the surface of a high-hardness substrate such as glass. In addition, an optical application for forming a coating film containing high refractive index / low refractive index fine particles can be mentioned. Especially for optical applications, anti-reflection applications need to be formed into a thin film with a thickness of about 0.1 to 0.2 μm. Even if it decreases, the reflected color changes.

In addition, a coating made of a fluororesin is also used as an anti-reflection coating on the display surface, but such a coating has a strong alkali resistance as well as excellent antifouling property, but has a problem of low surface hardness. is there.
JP 2003-201443 A

  The present invention has been made in view of the above points, and has excellent surface strength and antifouling property, and has high alkali resistance and is particularly suitable for optical system applications such as antireflection applications. An object of the present invention is to provide a manufacturing method and an antireflection substrate.

  As a result of diligent research, the present inventors have found that if an unreacted alkoxy group remains during the hydrolysis reaction of alkoxysilane, the alkoxy group cannot be decomposed when it cannot be treated at a high temperature of 200 ° C. or more particularly during film formation. It is possible to improve the alkali resistance of the film by reducing the number of unreacted alkoxy groups as much as possible. Therefore, the present invention has been made.

  That is, the present invention hydrolyzes alkoxysilane in a solvent substantially free of alcohol, and after applying the coating material containing the obtained product to the surface of the substrate, it is dried to form the surface of the substrate. A film having a thickness of 0.05 to 1 μm is formed. Conventionally, the hydrolysis reaction of alkoxysilane has been performed in an alcohol solvent in consideration of the compatibility of the solvent with the alkoxysilane and water, but the alcohol is not substantially contained in the solvent in this way. By making the alkoxysilane hydrolysis reaction, alcohol that inhibits the hydrolysis reaction is excluded from the reaction system and the hydrolysis reaction is promoted, and the residual alkoxy group in the product can be suppressed. As a result, even when high temperature treatment is not possible, it is possible to improve the crosslink density by suppressing the residual alkoxy groups in the coating composed of the hydrolysis condensate of alkoxysilane.

  In this case, if the solvent which does not substantially contain the alcohol has no hydroxyl group, the hydrolysis reaction can be prevented from being inhibited even by a compound having a hydroxyl group other than the alcohol. Residual groups can be further suppressed.

  In addition, if the reaction is allowed to proceed while removing the alcohol produced by the hydrolysis reaction from the reaction system during the hydrolysis of the alkoxysilane, the hydrolysis reaction is also inhibited by the alcohol by-produced by the hydrolysis reaction. This can suppress the remaining of the alkoxy group.

  In preparing the coating material, it is also preferable to mix the obtained product with at least one of a filler, a solvent, and a modified alkoxysilane after hydrolysis of the alkoxysilane. Thus, by hydrolyzing the alkoxysilane to obtain a matrix forming material, other components are blended so that these components are effectively incorporated without being incorporated into the matrix forming material. Become.

  In addition, the antireflection substrate according to the present invention is characterized in that a film is formed on the surface of a substrate by the above-described method for producing a film.

  According to the present invention, the coating film is composed of a hydrolyzed condensate of alkoxysilane, so that the surface strength (friction resistance) is high, and the high water and oil repellency provides high antifouling properties. In addition, the crosslink density of the coating can be improved to improve alkali resistance, and the reflective coating changes when the thickness of the coating of the thin film is reduced by alkali and the refractive index is changed. It is possible to prevent a situation in which characteristic changes occur, and is particularly suitable for applications where high-temperature processing cannot be performed and optical system applications.

  Hereinafter, the best mode for carrying out the present invention will be described.

  The matrix-forming material for forming the matrix in the coating material composition of the present invention is a hydrolyzate of alkoxysilane (including a partial hydrolyzate) or a hydrolysis having a siloxane bond formed by condensation of the hydrolyzate. It is a condensate.

  Alkoxysilane is represented by the following formula (A).

R _n SiY _4-n (A)
In formula (A), R represents the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 9 carbon atoms or phenyl group, n represents an integer of 0 to 2, and Y represents an alkoxy group. R is, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group or an octyl group; a cycloalkyl group such as a cyclopentyl group or a cyclohexyl group; a 2-phenylethyl group Aralkyl groups such as 2-phenylpropyl group and 3-phenylpropyl group; aryl groups such as phenyl group and tolyl group; alkenyl groups such as vinyl group and allyl group; chloromethyl group, γ-chloropropyl group, 3 Halogen substituted hydrocarbon groups such as 1,3,3-trifluoropropyl group; substitutions such as γ-methacryloxypropyl group, γ-glycidoxypropyl group, 3,4-epoxycyclohexylethyl group, γ-mercaptopropyl group, etc. A hydrocarbon group etc. can be illustrated. Among these, an alkyl group having 1 to 4 carbon atoms and a phenyl group are preferable because of easy synthesis or availability.

  Examples of such alkoxysilane include di-, tri-, and tetra-functional alkoxysilanes in which n in the general formula (A) is an integer of 0 to 2. Particularly, tetramethoxysilane, tetraethoxysilane and the like can be exemplified as tetraalkoxysilane of n = 0, and methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, n = 1 as organotrialkoxysilane, Examples thereof include phenyltrimethoxysilane, phenyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane and the like. Examples of n = 2 diorganodialkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, and methylphenyldimethoxysilane.

  Hydrolysis of the alkoxysilane is carried out in a solvent. At this time, it is necessary to use a solvent which does not substantially contain alcohol. Here, “substantially does not contain” means not intentionally blended, and those contained as reaction by-products or impurities are allowed. Moreover, it is preferable that this solvent does not contain the compound containing hydroxyl groups other than alcohol.

  Such a solvent is preferably water or a mixture of water and another liquid. Examples of the other liquid include toluene, xylene, hexane, ethyl heptane acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methyl ethyl ketoxime. 1 type, or 2 or more types can be used.

  In addition, a catalyst can be used as necessary during the hydrolysis. The catalyst is not particularly limited. Examples of the acid catalyst (or acidic catalyst) include organic acids (for example, acetic acid, chloroacetic acid, citric acid, benzoic acid, dimethylmalonic acid, formic acid, propionic acid, glutaric acid, glycol). Acid, maleic acid, malonic acid, toluenesulfonic acid, oxalic acid, etc.), inorganic acid (eg hydrochloric acid, nitric acid, halogenated silane, etc.), acidic sol-like filler (eg, acidic colloidal silica, oxidized titania sol, etc.). . Examples of the basic catalyst (or basic catalyst) include aqueous solutions of hydroxides of alkali metals or alkaline earth metals such as sodium hydroxide and calcium hydroxide, aqueous ammonia, and aqueous solutions of amines. These catalysts may be used alone or in combination of two or more.

  The alkoxysilane may be hydrolyzed as necessary (for example, when not so high mechanical strength is required), for example, in the range of 30 to 80 ° C. for 10 minutes to 24 hours. The reaction can proceed.

  Here, hydrolysis of alkoxysilane proceeds in the following reaction formula in the case of tetraethoxysilane, for example.

Si (OC ₂ H ₅ ) ₄ + 2H ₂ O → SiO ₂ + 4C ₂ H ₅ OH
In this reaction, alcohol is produced as a by-product, so the presence of alcohol in the reaction system promotes an increase in the reaction rate of the reverse reaction and inhibits the hydrolysis reaction, causing unreacted alkoxy groups to remain. . This tendency is particularly remarkable in the case of hydrolysis of tetrafunctional tetraalkoxysilane.

  However, if the solvent in the hydrolysis reaction system does not substantially contain the alcohol that inhibits the hydrolysis reaction as described above, the residual alkoxy group in the hydrolyzate is suppressed, and The crosslink density of the decomposition polycondensate can be improved, and the alkali resistance of the coating can be improved.

  In addition to alcohols, compounds having other hydroxyl groups such as compounds having phenolic hydroxyl groups may also inhibit the hydrolysis reaction in the same manner as alcohols, but have such other hydroxides. If the compound is not contained in the solvent in the reaction system, the remaining alkoxy group in the hydrolyzate can be further suppressed.

  Moreover, it is also preferable to advance the hydrolysis reaction while distilling off the alcohol by performing the hydrolysis under reduced pressure. In this case, the alcohol by-produced by the hydrolysis reaction as described above can be removed from the reaction system, and the hydrolysis reaction can be further promoted, whereby the alkoxy group residue can be further suppressed. .

  The weight-average molecular weight of the matrix-forming material thus obtained, measured as a standard polystyrene equivalent value by GPC (gel permeation chromatography), is preferably in the range of 800 to 2000.

  After generating the matrix forming material by the hydrolysis, a coating material can be prepared by blending the matrix forming material with a filler, a solvent, a modified alkoxysilane, or the like as necessary. By adding the other components after the formation of the matrix forming material by hydrolysis in this way, the other components are not taken into the matrix forming material, and the action is effectively exhibited.

  As the filler, appropriate ones such as airgel fine particles, hollow silica fine particles, polymer hollow fine particles, organic polymer fine particles, metal oxide fine particles and the like can be used. By including such a filler, it is possible to adjust various properties of the coating, for example, to adjust the refractive index.

  Examples of the airgel fine particles include silica airgel fine particles, composite airgel fine particles such as silica / alumina airgel, and organic airgel fine particles such as melamine airgel.

  The hollow silica fine particles have an outer shell composed of a silica-based inorganic oxide. For example, the outer shell has a silica single layer, a single layer of a composite oxide composed of silica and an inorganic oxide other than silica, Examples thereof include a laminated layer having two or more layers. At this time, the thickness of the outer shell can be, for example, in the range of 1 to 50 nm, preferably 5 to 20 nm, and this thickness is in the range of 1/50 to 1/5 of the average particle diameter of the hollow fine particles. Things can be used. The average particle diameter of the hollow silica fine particles can be set in the range of 5 nm to 2 μm, for example.

  As the polymer hollow fine particles, for example, those having an outer shell made of a polymer material such as a fluorine-based polymer can be used.

  Examples of the organic polymer fine particles include fine particles such as silicone resin, acrylic resin, and styrene resin.

  Examples of the metal oxide fine particles include titania fine particles, indium tin oxide fine particles, silica fine particles, and alumina fine particles. These can be mixed with the coating material composition using a sol that is commercially available as a dispersion sol in advance.

  These fillers can be contained in the coating material in an appropriate ratio according to the purpose, but for example, it is preferably contained in the range of 10 to 500 parts by weight with respect to 100 parts by weight of the matrix forming material.

  Moreover, as a solvent, the solvent used for the synthesis | combination of the said matrix formation material can be used as it is, or another solvent can be mix | blended further. At this time, since the hydrolysis reaction has already been completed, a solvent having a hydroxyl group such as alcohol can be added. Examples of such a solvent include water and an appropriate hydrophilic solvent. Examples of the hydrophilic solvent include lower aliphatic alcohols such as methanol, ethanol, isopropanol (IPA), n-butanol and isobutanol, ethylene glycol derivatives such as ethylene glycol, ethylene glycol monobutyl ether and ethylene glycol monoethyl ether, Examples include diethylene glycol derivatives such as diethylene glycol and diethylene glycol monobutyl ether, and diacetone alcohol. These may be used alone or in combination of two or more. Further, in combination with these hydrophilic organic solvents, toluene, xylene, hexane, ethyl heptane acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methyl ethyl ketoxime, etc. can be used. More than one species can be used in combination. The content of the solvent is appropriately adjusted according to the composition of the coating material, the film formation method, the desired thickness of the film, etc., but is preferably in the range of 80 to 99% by weight with respect to the total amount of the coating material.

  The modified alkoxysilane is used for various purposes separately from the alkoxysilane for obtaining the matrix forming material, such as fluorine-modified alkoxysilane, vinyl-modified alkoxysilane, amino-modified alkoxysilane, etc. Appropriate ones can be mentioned. If such a modified alkoxysilane is mixed after the formation of the matrix forming material by hydrolysis of the alkoxysilane so that it is not taken into the matrix forming material, the modified alkoxysilane is present in a free monomer state in the coating material. When the coating is formed, the modified alkoxysilane bleeds out on the surface of the coating and is easily fixed to the surface of the coating, so that the modified alkoxysilane can be unevenly distributed on the surface of the coating. As a result, the action of the modified alkoxysilane is effectively exhibited. For example, when fluorine-modified alkoxysilane is used, high water repellency can be imparted to the coating.

Further, a silicone diol may be contained in the coating material. In this case, by introducing silicone diol into the coating, it is possible to reduce the surface frictional resistance of the coating, reduce the catch on the surface of the coating, and make it difficult for scratches to enter. It is possible to improve the scratch resistance. The silicone diol is preferably a dimethyl type silicone diol (HO [Si (CH ₃ ) ₂ O] _n H). At this time, the number of repeating dimethylsiloxane units (n) in the silicone diol is particularly limited. However, in order to sufficiently exhibit the effect of reducing the frictional resistance and ensure compatibility with the matrix forming material to prevent the transparency of the coating and uneven appearance, n = 20 to 100. Is preferred. The content of the silicone diol is not particularly limited, but is preferably in the range of 1 to 10% by weight with respect to the total solid content of the coating material.

  A coating material having a thickness of 0.05 to 1 μm is formed by applying the coating material thus obtained to the surface of an appropriate base material and drying it while heating, if necessary, or by further proceeding a condensation polymerization reaction. To do. When performing heat processing, it is preferable to heat at 60-200 degreeC for 1 minute-2 hours.

  Such a coating is applied to a transparent substrate such as a glass substrate or a plastic substrate to produce an antireflection substrate by, for example, forming a low refractive index coating, and the light transmitted through the antireflection substrate The transmittance or reflectance can be improved. Such applications include, for example, touch panel substrates, backlight unit components (for example, light guide plates, cold cathode tubes, reflective sheets, etc.), liquid crystal brightness enhancement films (for example, prisms, transflective films, etc.), solar cell outermost surface members, There are illumination lamps, reflective lenses, LCD color filters, various reflectors, amplified laser light sources, and the like.

  The film formed in this way is composed of a hydrolyzed condensate of silicon alkoxide, which has high surface strength (friction resistance) and high water repellency and oil repellency, thereby providing high antifouling properties. Become.

  In addition, the coating has a reduced cross-linking of the alkoxy groups therein, a high crosslinking density, and a high alkali resistance. By imparting such high alkali resistance to the thin film, it is possible to prevent the characteristics of the film from being deteriorated or fluctuated due to damage caused by alkali. That is, for example, when the film is used for an optical application such as an antireflection film on the display surface, if the thin film is damaged by alkali, the thickness can be reduced or the refractive index can be reduced even if the film is slightly damaged. Changes in the optical properties such as changes in the reflected color occur due to the change, but such changes in the optical properties can be prevented by improving the alkali resistance of the coating as described above.

  Furthermore, since it is possible to improve the cross-linking density by suppressing the residual alkoxy groups during hydrolysis without applying high-temperature treatment during the formation of the coating, it is possible to coat a substrate such as plastic that is difficult to perform at a high temperature. Even when the film is formed, it is possible to impart high alkali resistance to the coating.

  These effects are particularly prominent when the matrix forming material is obtained from a hydrolyzate of tetraalkoxysilane.

  Hereinafter, the present invention will be specifically described by way of examples. Unless otherwise specified, all “parts” represent “parts by weight”, and “%” represents “% by weight” except for reflectance and haze ratio described later. The weight molecular weight was measured by GPC (Gel Permeation Chromatography) using a model number “HLC8220” manufactured by Tosoh Corporation as a measuring instrument. At this time, a calibration curve was prepared with standard polystyrene and measured as a converted value. .

(Example 1)
Add 152 parts of butyl acetate to 152 parts of tetramethoxysilane, and then add 54 parts of water and 18 parts of 0.4N hydrochloric acid aqueous solution ([H ₂ O] / [OR] = 1.0). Mix well to obtain a mixture. This mixture was stirred in a 30 ° C. constant temperature bath for 2 hours to obtain a silicone hydrolyzate having a weight average molecular weight adjusted to 1250 as a matrix-forming material.

  Next, hollow silica IPA (isopropanol) dispersion sol (manufactured by Catalyst Kasei Kogyo Co., Ltd., trade name “Thruria CS60-IPA”, solid content 20% by weight, average primary particle diameter of about 60 nm, outer shell thickness of about 10 nm) as hollow silica fine particles. Used, 200 parts of this is added to the silicone hydrolyzate, and (hollow silica fine particles) / (silicone hydrolyzate (condensation compound equivalent)) is blended so that the weight ratio is 40/60 based on the solid content, An IPA / butyl cellosolve mixture was mixed to prepare a total solid content of 2%, a butyl cellosolve content of 2%, and a butyl acetate content of 5%.

  Further, a solution obtained by diluting dimethyl silicone diol (n≈40) with ethyl acetate so as to have a solid content of 5% is obtained by adding dimethyl silicone diol to the sum of the solid content of hollow silica fine particles and silicone resin (condensation compound). The coating material composition was prepared by adding so that the solid content was 2 wt%.

  After leaving this coating material composition for 1 hour, an acrylic plate (trade name “Delagrass HA”, double-sided hard coat treatment, surface-cleaned in advance with a UV-ozone cleaner (excimer lamp, manufactured by USHIO, model “H0011”), A hard bar having a refractive index of 1.52 and a haze of 0.10) is applied to the surface of the hard coat by a wire bar coater to form a film having a thickness of about 100 nm, and the film is heat-treated at 80 ° C. for 1 hour in an oxygen atmosphere. A coating was obtained.

(Example 2)
Add 152 parts of butyl acetate to 152 parts of tetraethoxysilane, add 54 parts of water and 18 parts of 0.4N aqueous hydrochloric acid ([H ₂ O] / [OR] = 1.0), and use a disper. A well mixed solution was obtained. The mixture was stirred in a thermostat at 30 ° C. for 2 hours while removing methanol generated by the reaction with an evaporator, and then the removed methanol was returned to the system to adjust the weight average molecular weight to 1300. The degradation product was obtained as a matrix forming material.

  Using this silicone hydrolyzate, a coating material composition was prepared in the same manner as in Example 1, and a film was obtained in the same manner as in Example 1.

(Comparative Example 1)
Add 152 parts of IPA (isopropanol) to 152 parts of tetramethoxysilane, add 54 parts of water and 18 parts of 0.4N hydrochloric acid aqueous solution ([H ₂ O] / [OR] = 1.0). Mix well to obtain a mixture. This mixture was stirred for 2 hours in a 30 ° C. constant temperature bath to obtain a silicone hydrolyzate having a weight average molecular weight adjusted to 1250 as a matrix-forming material.

  Using this silicone hydrolyzate, a coating material composition was prepared in the same manner as in Example 1, and a film was obtained in the same manner as in Example 1.

  The coatings obtained in Examples 1 and 2 and Comparative Example 1 were measured for reflectivity, haze rate, refractive index, mechanical strength, alkali resistance, and fingerprint removability, and the performance of the coating was evaluated.

(5 ° relative reflectance)
The minimum reflectance was measured using a spectrophotometer (“U-3400” manufactured by Hitachi, Ltd.).

(Haze rate)
It measured using the haze meter (Nippon Denshoku Industries "NDH2000").

(Refractive index)
The refractive index was measured using a simple ellipsometer (manufactured by FILMETRICS, product number “F20”).

(Mechanical strength)
The film was rubbed with an abrasion tester (manufactured by Shinto Kagaku, product number “HEIDON-14DR”, steel wool # 0000, 250 g load, 10 reciprocations), and the number of scratches generated on the film was measured.

(Alkali resistance)
A 1% NaOH aqueous solution was dropped on the surface of the coating, left at room temperature for 30 minutes, then washed with water and air-dried, and the reflected color change of the coating before and after the test was compared visually.

(Fingerprint removal)
Fingerprints were attached to the surface of the coating, and the number of wipings required for removing the fingerprint when wiping with Toraysee (registered trademark, manufactured by Toray Industries, Inc.) was evaluated.

  The results are shown in Table 1.

  As a result, Example 1 and Example 2 have high alkali resistance compared to Comparative Example 1 while having the same reflectance, haze ratio, refractive index mechanical strength and fingerprint removability as Comparative Example 1. In particular, it was confirmed that the alkali resistance was remarkably improved in Example 2.

Claims (5)

  The alkoxysilane is hydrolyzed in a solvent substantially free of alcohol, the coating material containing the obtained product is applied to the surface of the base material, and then dried to obtain a thickness of 0.05 to 1 μm on the surface of the base material. A method for producing a coating, comprising:   The method for producing a coating film according to claim 1, wherein the solvent substantially not containing an alcohol has no hydroxyl group.   The method for producing a coating film according to claim 1 or 2, wherein the reaction is allowed to proceed while removing the alcohol produced by the hydrolysis reaction from the reaction system during the hydrolysis of the alkoxysilane.   At the time of preparation of the coating material, after hydrolysis of the alkoxysilane, the obtained product is mixed with at least one of a filler, a solvent, and a modified alkoxysilane. The manufacturing method of the film as described in one term.   An antireflection substrate comprising a film formed on the surface of a base material by the method for producing a film according to any one of claims 1 to 4.