JP5324278B2 - Hard coating agent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hard coating agent enabling application of a hard coating having low refractive index and high adhesiveness to a substrate using general-purpose materials, i.e. methyltrimethoxysilane and glycidoxyalkyltrialkoxysilane. <P>SOLUTION: The hard coating agent includes a polysilanol composition obtained by hydrolytic condensation of methyltrimethoxysilane compound and glycidoxyalkyltrialkoxysilane, and an aluminum-based curing catalyst, wherein the proportion of Si atoms derived from the methyltrimethoxysilane compound in the entire Si atoms is &ge;50%, and the obtained coating film has a refractive index of &le;1.45. A hard coating is obtained using the hard coating agent. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a hard coating agent for applying a hard coat on a substrate and a method for producing the same.

  It is known that a hard coat using hydrolysis condensation of a silane compound is applied to the surface of glass or a plastic substrate. Hard coatings are required to have various optical properties, one of which is a low refractive index. In order to obtain a low refractive index in a hard coat material using hydrolysis condensation of a silane compound, it is common to use a fluorine-based material (for example, Patent Document 1). However, the fluorine-based material is expensive and has a problem that adhesion with the base material is not good.

In addition, there have been many hard coat compositions using a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane so far (for example, Patent Documents 2 to 7). None was applied as an agent.
JP 2009-025568 A JP-A-56-099668 JP 63-048363 A Japanese Patent Laid-Open No. 03-287627 Japanese Patent Laid-Open No. 04-161435 Japanese Patent Application Laid-Open No. 08-295736 Japanese Patent Laid-Open No. 2004-256609

  An object of the present invention is to provide a hard coating agent capable of applying a hard coat having a low refractive index and high adhesion to a substrate using a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane, which are general-purpose materials. Is to provide.

  The hard coating agent of the present invention comprises a polysilanol composition obtained by hydrolytic condensation of a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane, and an aluminum-based curing catalyst. The proportion of Si atoms derived from the above methyltrimethoxysilane compound is 50% or more, and the refractive index of the resulting coating film is 1.45 or less. Here, the polysilanol composition may have an epoxy group.

  The method for producing a hard coating agent of the present invention comprises a step of hydrolyzing and condensing a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane using an inorganic acid or a Lewis acid as an acid catalyst to obtain a polysilanol composition. And a step of adding an aluminum-based curing catalyst to the polysilanol composition obtained in the above step.

  The hard coat of the present invention is obtained from the previous hard coating agent.

  The hard coating agent of the present invention can provide a hard coat having a low refractive index and good adhesion to a substrate. This is because the methyltrimethoxysilane compound, which is a material with a low refractive index, is hydrolyzed and condensed to a specific ratio with glycidoxyalkyltrialkoxysilane that improves adhesion, and an aluminum-based curing agent is used as a curing catalyst. This is due to the use of a catalyst.

  Moreover, the hard coating agent of this invention can form a firm film | membrane by low temperature heating, when it has an epoxy group. This is because the silanol group obtained from the methyltrimethoxysilane compound is active, and the glycidoxyalkyltrialkoxysilane-derived epoxy group undergoes an addition reaction with the silanol group due to the presence of an aluminum-based curing catalyst. It is thought that this is because.

  The hard coating agent of the present invention contains a polysilanol composition obtained by hydrolytic condensation of a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane and an aluminum-based curing catalyst.

Polysilanol composition The polysilanol composition, which is a component of the hard coating agent of the present invention, is obtained by hydrolytic condensation of the methyltrimethoxysilane compound and glycidoxyalkyltrialkoxysilane. In the present specification, the above two types, or each, may be referred to as “raw material alkoxysilane”. Alkoxysilane compounds other than the above-mentioned methyltrimethoxysilane compound and glycidoxyalkyltrialkoxysilane do not usually need to be used, but do not adversely affect the properties of the hard coating agent of the present invention and the coating film obtained therefrom. If it is an amount, it may be used in combination during hydrolysis condensation.

  The methyltrimethoxysilane compound means both methyltrimethoxysilane itself and its condensate, and is used for imparting a low refractive index to the coating film. In the present specification, the methyltrimethoxysilane compound may be a mixture of methyltrimethoxysilane itself, a condensate thereof, or both. Moreover, when the above-mentioned mixture is used, the mixing ratio can be arbitrarily set so as to exhibit the intended refractive index. As said methyltrimethoxysilane compound, what is generally marketed can be used.

  On the other hand, the glycidoxyalkyltrialkoxysilane is used for the purpose of imparting adhesion to the substrate of the coating film and enhancing curability. Examples of the glycidoxyalkyltrialkoxysilane include glycidoxyethyltrimethoxysilane, glycidoxyethyltriethoxysilane, glycidoxypropyltrimethoxysilane, and glycidoxypropyltriethoxysilane. From the viewpoint of reactivity and material availability, glycidoxypropyltrimethoxysilane is preferred.

  The hydrolytic condensation of the methyltrimethoxysilane compound and the glycidoxyalkyltrialkoxysilane can be performed simultaneously or separately. The ratio in the case of simultaneously hydrolyzing and condensing a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane is set so that the ratio of Si atoms derived from the methyltrimethoxysilane compound to the total Si atoms is 50% or more. . If it is less than 50%, the refractive index exceeds 1.45. The upper limit of the proportion of Si atoms derived from the methyltrimethoxysilane compound in the total Si atoms is preferably 99.95%, and more preferably 99.5%. A preferable lower limit of the ratio of Si atoms derived from the methyltrimethoxysilane compound to the total Si atoms is 70%.

  In the present invention, the ratio of the Si atoms derived from the methyltrimethoxysilane compound to the total Si atoms is determined as follows. It is considered that the alkoxysilyl group of the raw material alkoxysilane substantially disappears due to the progress of the hydrolysis reaction and the condensation reaction. However, it is difficult to accurately determine how much the condensation reaction has progressed. Therefore, it is assumed that the alkoxysilyl group of the raw material alkoxysilane is changed to 100% by polyhydroxysilane hydrolyzed to all silanol groups and the condensation reaction does not proceed at all. That is, the number of moles that the raw material alkoxysilane is considered to have changed to polyhydroxysilane is the value of the total Si atoms, whereas the ratio of the number of moles that the methyltrimethoxysilane compound is considered to have changed to polyhydroxysilane Is the ratio of Si atoms derived from the methyltrimethoxysilane compound to the total Si atoms.

  The hydrolysis condensation of the raw material alkoxysilane can be performed by dissolving the raw material alkoxysilane in a polar organic solvent and adding water and an acid catalyst.

As the polar organic solvent, it is preferable to use a solvent capable of dissolving the raw material alkoxysilane, water and a hydrolysis-condensation product thereof. As the polar organic solvent, a hydrophilic organic solvent can be used. Examples of the organic solvent include alcohol, glycol, glycol ether or ester, and ketone. Specifically, methanol, ethanol, propanol, isopropyl alcohol, R ₂ —O— (CH ₂ CH (R ₃ ) O) _m —H (wherein R ₂ is an alkyl group having 1 to 4 carbon atoms, R ₃ is H or CH ₃ , m is an integer of 1 to 3), CH ₃ —O— (CH ₂ CH (R ₄ ) O) ₁ —CH ₃ (wherein R ₄ is H or CH ₃ and l is 1 or 2.), acetone, methyl ethyl ketone, diacetone alcohol, 3-methoxy-3-methyl-1-butanol and the like can be preferably used. The solubility can be controlled by using an organic solvent other than the hydrophilic organic solvent in combination with the hydrophilic organic solvent. Examples of organic solvents that are not hydrophilic organic solvents include methyl isobutyl ketone, toluene, xylene, diethylene glycol dibutyl ether, and the like, and 2,2,4-trimethyl, which is known as a film-forming auxiliary agent added to paints. -1,3-pentanediol monoisobutyrate (product name “CS-12” manufactured by Chisso Corporation) can also be used. Incidentally, the solubility in water of the hydrophilic organic solvent as (20 ° C.) is preferably 5g / 100gH ₂ O or more, more preferably 20g / 100gH ₂ O or more, still more preferably 100g / 100gH ₂ O or more.

  The amount of the polar organic solvent is preferably 0.5 to 5 times the mass of the raw material alkoxysilane, and more preferably the upper limit amount is 2 times.

  The amount of water used for the hydrolysis and condensation of the raw material alkoxysilane is preferably half to the same amount as the molar amount of the alkoxysilyl group of the raw material alkoxysilane.

  An acid catalyst is used for the hydrolysis and condensation of the raw material alkoxysilane. This is because the acid catalyst has an appropriate catalytic action, so that the condensation of the produced polyhydroxysiloxane proceeds to an appropriate degree. As the acid catalyst, any appropriate one can be used as long as it is a protonic acid or Lewis acid having a catalytic action on the hydrolysis reaction of the alkoxysilyl group. Specifically, as the protonic acid, for example, inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid, and organic acids such as acetic acid, lactic acid and p-toluenesulfonic acid, and Lewis acids include metals such as titanium, aluminum and zirconium. Examples thereof include alkoxides and chelate compounds.

  In the hydrolysis condensation, an inorganic acid such as hydrochloric acid, nitric acid or sulfuric acid is preferably used in order to leave the epoxy group. The adhesion and curability are expected to be improved due to the remaining epoxy group. Moreover, a condensation reaction can be controlled by using an aluminum catalyst, and the molecular weight of polyhydroxysiloxane and the content of silanol groups can be adjusted. Examples of the aluminum catalyst include aluminum trisacetylacetonate, aluminum bisethylacetoacetate / monoacetylacetonate, ethylacetoacetate aluminum diisopropylate, aluminum isopropylatebis (oleyl acetoacetate), and the like.

  The acid catalyst may be used in an amount that is at least an amount that exhibits a catalytic action for the hydrolysis reaction of the alkoxysilyl group of the raw material alkoxysilane. Specifically, it is preferably 0.1 ppm to 10% with respect to the mass of the raw material alkoxysilane. A more preferred upper limit is 5%.

  The temperature of hydrolysis condensation of the raw material alkoxysilane is preferably performed in the range of room temperature to about 150 ° C. It is possible to advance the hydrolysis reaction at room temperature and then heat to advance the condensation reaction, or heat from the beginning to advance the hydrolysis reaction and the condensation reaction simultaneously. Moreover, it is also possible to distill off the alcohol and water produced by hydrolysis and condensation as needed.

  The hydrolysis condensation of the raw material alkoxysilane is preferably performed until no peak based on the alkoxysilyl group is observed by infrared spectrum (IR) or nuclear magnetic resonance analysis (H-NMR). Although time changes with the conditions, it is not specifically limited, It can be performed in about 1 to 10 hours.

  When the hydrolytic condensation of the methyltrimethoxysilane compound and the glycidoxyalkyltrialkoxysilane is performed simultaneously, the resulting hydrolytic condensate becomes a polysilanol composition which is one component of the hard coating agent of the present invention. In this case, the polysilanol composition is composed of a mixture in which a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane are condensed at various ratios and do not have an alkoxysilyl group.

  In addition, when the hydrolytic condensation of the methyltrimethoxysilane compound and the glycidoxyalkyltrialkoxysilane is carried out separately, the resulting two kinds of hydrolytic condensates are mixed to obtain the hard coating agent of the present invention. A polysilanol composition which is one component is obtained. In this mixing method, if the ratio of the hydrolysis condensate of glycidoxyalkyltrialkoxysilane in the mixture obtained by the above mixing becomes high, the mixture may become turbid. For this reason, it is preferable that the ratio of the Si atom derived from the hydrolysis condensate of glycidoxyalkyltrialkoxysilane in the polysilanol composition obtained by mixing is 20% or less.

  In addition, when hydrolytic condensation of a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane is performed simultaneously, turbidity is not recognized in the obtained hydrolysis condensate. Considering such characteristics, when emphasizing the low refractive index property of the hard coating agent, that is, when using a large amount of methyltrimethoxysilane compound, methyltrimethoxysilane compound and glycidoxyalkyltrialkoxy It is preferable to adopt a method in which the hydrolysis and condensation of silanes are performed separately and mixed. On the other hand, when the curability is important, that is, when the amount of the glycidoxyalkyltrialkoxysilane in the raw material alkoxysilane is 20% or more, the hydrolysis of the methyltrimethoxysilane compound and the glycidoxyalkyltrialkoxysilane is difficult. It is preferable to carry out decomposition condensation at the same time to obtain a polysilanol composition.

  In the polysilanol composition, the proportion of Si atoms derived from the methyltrimethoxysilane compound in all Si atoms contained therein is 50% or more. It is preferable that it is 70% or more. The upper limit is preferably 99.95%, and more preferably 99.5%.

  Moreover, it is preferable from the point of adhesiveness and sclerosis | hardenability that the said polysilanol composition has an epoxy group. The presence of the epoxy group in the polysilanol compound and confirmation of its content can be confirmed by H-NMR. It is preferable that 30% or more of the epoxy group which the glycidoxyalkyltrialkoxysilane used as a raw material has remained after hydrolysis condensation.

  Assuming that the epoxy group of the raw material alkoxysilane used does not disappear and remains completely, the content of the epoxy group contained in the polysilanol composition is 0 with respect to the solid content of the polysilanol composition. It is preferably 0.02 to 15% by mass.

  It is difficult to directly determine the solid content of the polysilanol composition. Therefore, in the present specification, the polysilanol composition is composed of all the alkoxysilyl groups of the raw material alkoxysilane as silanol groups in the same manner as the method for determining the ratio of Si atoms derived from the methyltrimethoxysilane compound to the total Si atoms. It is assumed that the polysilanol compound hydrolyzed to 100% is changed 100%, and the solid content of the polysilanol composition is calculated. And based on this, content of the said epoxy group is prescribed | regulated.

Aluminum-based curing catalyst The aluminum-based curing catalyst, which is another component of the present invention, is used to accelerate the curing of the coating film. By using an aluminum-based curing catalyst, in addition to the condensation between silanol groups and the condensation between epoxy groups, the addition reaction between silanol groups and epoxy groups proceeds, and it is expected that a stronger coating film can be obtained. The
For the aluminum-based curing catalyst, the contents described in the previous hydrolytic condensation are applied.

Hard coating agent The hard coating agent of the present invention contains the above polysilanol composition and an aluminum-based curing catalyst. The content of the aluminum-based curing catalyst is preferably 0.1 to 10% with respect to the solid content of the polysilanol composition. If it is less than 0.1%, curing may be insufficient and the expected physical properties of the coating film may not be obtained. Moreover, even if it exceeds 10%, a further effect corresponding to it cannot be expected.

  The hard coating agent is produced by mixing a polysilanol composition, an aluminum-based curing catalyst, and other components as necessary. Here, when the aluminum-based curing catalyst is already used in the production of the polysilanol composition and the amount thereof is within the above range as the hard coating material, it is not necessary to additionally mix the aluminum-based curing catalyst.

  Examples of the other components include ultraviolet absorbers, surface conditioners, thickeners, solvents, and low refractive index particles represented by fluorinated acrylic particles. These components are generally used in an amount that can exhibit the function of the addition and do not adversely affect the properties of the hard coating agent and the coating film obtained therefrom.

  It is preferable that the solid content of the polysilanol composition calculated | required in the hard coating agent of this invention is 1-50 mass%. If the amount is less than 1% by mass, the thickness of the resulting coating film is insufficient.

Manufacturing method of hard coating agent The hard coating agent of the present invention is obtained by the above method, but the manufacturing method of the hard coating agent of the present invention comprises a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane, A step of obtaining a polysilanol composition by hydrolytic condensation using an inorganic acid or a Lewis acid as an acid catalyst, an aluminum-based curing catalyst in the polysilanol composition obtained in the above step, and other if necessary Adding the ingredients of: For details, the contents already described apply. The hard coating agent obtained by this production method can be expected to have excellent adhesion and curability since epoxy groups remain.

Hard coat The hard coat of the present invention is obtained from the previous hard coating agent, and its refractive index is 1.45 or less, preferably from 1.371 to 1.45 from the refractive index of methyltrimethoxysilane. is there.

  Examples of the base material for forming the hard coat include plastic and glass. Hard coat formation is performed by coating the previous hard coating agent to a dry film thickness of 1 to 30 μm and heating at 60 to 150 ° C. for 10 to 120 minutes. For coating, a spin coater, slit coater, spray, dip coater or the like is used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these Examples. Unless otherwise specified, parts and% in the examples are based on mass.

Production Example 1 Production of Hydrolytic Condensate of Methyltrimethoxysilane Compound Part 1
408 parts of methyltrimethoxysilane was dissolved in 450 parts of isopropyl alcohol. To this, 162 parts of water having the same number of moles as the number of moles of methoxysilyl group and 1 part of hydrochloric acid as an acid catalyst were added, stirred at 40 ° C. for 1 hour, and further stirred at 75 ° C. for 1 hour. Thus, a hydrolyzed condensate of a methyltrimethoxysilane compound was obtained. In the analysis by IR, the absorption of C—H based on the methoxysilyl group was not confirmed. The solid content calculated by assuming that all methoxysilyl groups of the methyltrimethoxysilane compound were hydrolyzed and condensation did not proceed was 27.6% by mass.

Production Example 2 Production of Hydrolysis Condensate of Glycidoxyalkyltrialkoxysilane 460 parts of glycidoxypropyltrimethoxysilane were dissolved in 390 parts of isopropyl alcohol. To this, 105 parts of water having the same number of moles as the methoxysilyl group and 1 part of hydrochloric acid as an acid catalyst were added, stirred at 40 ° C. for 1 hour, and further stirred at 75 ° C. for 1 hour. Thus, a hydrolysis condensate of glycidoxypropyltrimethoxysilane was obtained. In the analysis by IR, the absorption of C—H based on the methoxysilyl group was not confirmed. Moreover, it was confirmed by H-NMR analysis that 95% of the epoxy groups remained before and after the hydrolysis condensation reaction. The solid content calculated by assuming that the methoxysilyl group of glycidoxypropyltrimethoxysilane was completely hydrolyzed and the condensation and the ring opening of the epoxy group did not proceed was 39% by mass.

Production Example 3 Production of Hydrolytic Condensate of Methyltrimethoxysilane Compound 2
In Production Example 1, 1 part of hydrochloric acid as an acid catalyst was changed to 1.6 parts of aluminum chelate D (trade name, aluminum bisethylacetoacetate / monoacetylacetonate manufactured by Kawaken Fine Chemical Co., Ltd.) as an aluminum catalyst. A hydrolyzed condensate of a methyltrimethoxysilane compound was obtained in the same manner except that the reaction temperature after stirring at 40 ° C. for 1 hour was changed to 85 ° C. In the analysis by IR, the absorption of C—H based on the methoxysilyl group was not confirmed. The solid content calculated by assuming that all methoxysilyl groups of the methyltrimethoxysilane compound were hydrolyzed and condensation did not proceed was 27.6% by mass.

Production Example 4 Production of Hydrolytic Condensate of Methyltrimethoxysilane Compound 3
202 parts of X-40-9225 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) 405 parts of Echinen F6 (trade name, ethanol / methanol = 89/11 (mass ratio) manufactured by Nippon Alcohol Sales Co., Ltd.) Dissolved in. To this, 56 parts of water corresponding to twice the number of moles of methoxysilyl group and 3 parts of aluminum chelate D as an aluminum chelate catalyst were added and stirred at 40 ° C. for 6 hours to hydrolyze polymethylmethoxysiloxane. A decomposition condensate was obtained. In the analysis by IR, the absorption of C—H based on the methoxysilyl group was not confirmed. The solid content calculated as all the methoxysilyl groups of polymethylmethoxysiloxane hydrolyzed and condensation did not proceed was 27% by mass.

Example 1
47.7 parts of methyltrimethoxysilane and 79.8 parts of glycidoxypropyltrimethoxysilane were dissolved in 154 parts of a 2/1 (mass ratio) mixture of isopropyl alcohol and methyl isobutyl ketone. To this, 37.2 parts of water having the same number of moles as the number of methoxysilyl groups in the system and 1.9 parts of hydrochloric acid as an acid catalyst were added, stirred at 40 ° C. for 2 hours, and further 80 ° C. The mixture was stirred for 3 hours to obtain a polysilanol composition. In the analysis by IR, the absorption of C—H based on the methoxysilyl group was not confirmed. Analysis by H-NMR confirmed that 97% of the epoxy group derived from glycidoxypropyltrimethoxysilane remained. The solid content calculated on the assumption that all the methoxysilyl groups of the methyltrimethoxysilane compound and glycidoxypropyltrimethoxysilane were hydrolyzed and the condensation and the ring opening of the epoxy group did not proceed was 31% by mass. Further, the proportion of Si atoms derived from the methyltrimethoxysilane compound in the total Si atoms was calculated to be 50%.

  To the obtained polysilanol composition, 6.5 parts of aluminum chelate D as an aluminum-based curing catalyst and 2 parts of Tinuvin 928 (trade name, UV absorber manufactured by Ciba Specialty Chemicals) are added to form a hard coating. An agent was obtained. The content of the epoxy group with respect to the solid content of the hard coating agent was calculated to be 14.5% by mass.

Example 2
In Example 1, except that the amount of methyltrimethoxysilane was changed to 95.5 parts, the amount of glycidoxypropyltrimethoxysilane was changed to 40.5 parts, and the amount of hydrochloric acid was changed to 2.4 parts. In the same manner, a polysilanol composition was obtained. In the analysis by IR, the absorption of C—H based on the methoxysilyl group was not confirmed. Analysis by H-NMR confirmed that 94% of the epoxy groups derived from glycidoxypropyltrimethoxysilane remained. The solid content calculated as the methoxysilyl group of the methyltrimethoxysilane compound and glycidoxypropyltrimethoxysilane was all hydrolyzed and condensation and ring opening of the epoxy group did not proceed was 29% by mass. Further, the proportion of Si atoms derived from the methyltrimethoxysilane compound in the total Si atoms was calculated to be 80%.

  To the obtained polysilanol composition, 6.5 parts of aluminum chelate D and 2 parts of tinuvin 928 were added as an aluminum-based curing catalyst to obtain a hard coating agent. The content of the epoxy group with respect to the solid content of the hard coating agent was calculated to be 7% by mass.

Example 3
In Example 1, the amount of methyltrimethoxysilane was 117.2 parts, the amount of glycidoxypropyltrimethoxysilane was 22.6 parts, and 1.9 parts of hydrochloric acid was 0% of aluminum chelate D as an aluminum catalyst. A polysilanol composition was obtained in the same manner except that the content was changed to 6 parts. In the analysis by IR, the absorption of C—H based on the methoxysilyl group was not confirmed. Analysis by 1 H-NMR confirmed that 50% of the epoxy group derived from glycidoxypropyltrimethoxysilane remained. The solid content calculated as the methoxysilyl group of the methyltrimethoxysilane compound and glycidoxypropyltrimethoxysilane was all hydrolyzed and condensation and ring opening of the epoxy group did not proceed was 29% by mass. Further, the proportion of Si atoms derived from the methyltrimethoxysilane compound in the total Si atoms was calculated to be 90%.

  The obtained polysilanol composition already contains 0.5% by mass of an aluminum-based curing catalyst with respect to the solid content of the polysilanol composition in the production process. Further, 6 parts of aluminum chelate D and 3 parts of tinuvin 1130 (trade name, UV absorber manufactured by Ciba Specialty Chemicals) were added to obtain a hard coating agent. The content of the epoxy group based on the solid content of the hard coating agent was calculated to be 2% by mass.

Example 4
A mixture of 361 parts of the hydrolyzed condensate of methyltrimethoxysilane compound obtained in Production Example 1 and 0.5 part of the hydrolyzed condensate of glycidoxypropyltrimethoxysilane obtained in Production Example 2 A silanol composition was obtained. The proportion of Si atoms derived from the methyltrimethoxysilane compound in the total Si atoms was calculated to be 99.9%.

  To this polysilanol composition, 6.5 parts of aluminum chelate D and 2 parts of tinuvin 928 were added as an aluminum-based curing catalyst to obtain a hard coating agent. The content of the epoxy group with respect to the solid content of the hard coating agent was calculated to be 0.04% by mass.

Example 5
A polysilanol composition was prepared by mixing 190 parts of the hydrolyzed condensate of the methyltrimethoxysilane compound obtained in Production Example 3 and 122 parts of the hydrolyzed condensate of glycidoxypropyltrimethoxysilane obtained in Production Example 2. I got a thing. The proportion of Si atoms derived from the methyltrimethoxysilane compound in the total Si atoms was calculated to be 70%.

  This polysilanol composition already contains 0.3% by mass of an aluminum-based curing catalyst with respect to the solid content of the polysilanol composition in the production process. Further, 6.2 parts of aluminum chelate D and 2 parts of tinuvin 928 were added to obtain a hard coating agent. The content of the epoxy group based on the solid content of the hard coating agent was calculated to be 10% by mass.

Example 6
A polysilanol was obtained by mixing 363 parts of the polymethylmethoxysiloxane hydrolysis condensate obtained in Production Example 4 with 5.1 parts of the glycidoxypropyltrimethoxysilane hydrolysis condensate obtained in Production Example 2. A composition was obtained. The proportion of Si atoms derived from the methyltrimethoxysilane compound in the total Si atoms was calculated to be 99%.

  To this polysilanol composition, 5 parts of aluminum chelate D and 2 parts of tinuvin 928 were added as an aluminum-based curing catalyst to obtain a hard coating agent. The content of the epoxy group with respect to the solid content of the hard coating agent was calculated to be 0.4% by mass.

Comparative Example 1
A hard coating for comparison was prepared by adding 6.5 parts of aluminum chelate D and 2 parts of tinuvin 928 as an aluminum-based curing catalyst to 370 parts of the hydrolyzed condensate of the methyltrimethoxysilane compound obtained in Production Example 1. An agent was obtained. The proportion of Si atoms derived from the methyltrimethoxysilane compound in the total Si atoms was calculated as 100%. The content of the epoxy group based on the solid content of the comparative hard coating agent was 0% by mass.

Comparative Example 2
In Example 1, the amount of methyltrimethoxysilane was 34.7 parts and the amount of glycidoxypropyltrimethoxysilane so that the proportion of Si atoms derived from the methyltrimethoxysilane compound in the total Si atoms was 40%. Was similarly changed to 90.6 parts to obtain a polysilanol composition. Analysis by H-NMR confirmed that 96% of the epoxy groups derived from glycidoxypropyltrimethoxysilane remained. The solid content calculated on the assumption that all the methoxysilyl groups of the methyltrimethoxysilane compound and glycidoxypropyltrimethoxysilane were hydrolyzed and the condensation and ring opening of the epoxy group did not proceed was 32% by mass.

  To the obtained polysilanol composition, 6.5 parts of aluminum chelate D and 2 parts of tinuvin 928 were added as an aluminum-based curing catalyst to obtain a comparative hard coating agent. The content of the epoxy group based on the solid content of the comparative hard coating agent was calculated to be 16% by mass.

Comparative Example 3
A hard coating agent for comparison was obtained in the same manner as in Example 4 except that aluminum chelate D as an aluminum-based curing catalyst was not added. The content of the epoxy group based on the solid content of the comparative hard coating agent was calculated to be 16% by mass.

Examples 7-12 and Comparative Examples 4-6
The hard coating agent obtained in the examples and the comparative hard coating agent obtained in the comparative example were coated on non-alkali glass using a # 22 bar coater and heated at 150 ° C. for 30 minutes to be transparent. Each hard coat was obtained.

  The obtained hard coat was evaluated for the following items. The results are shown in Table 1.

<Refractive index>
The refractive index of a 10 μm-thick coating film coated on a silicon wafer was measured at a measurement wavelength of 633 nm and a room temperature of 20.5 ° C. using a prism coupling type measuring device Metricon 2010 (manufactured by Metricon).

<Pencil hardness>
In accordance with JIS K 5600-5-4, a scratch test was performed by applying a load of 750 g from above to a pencil fixed at an angle of 45 degrees.

<Adhesion>
According to JIS K 5600-5-6, the prepared coating film is cut with 6 mm vertical and horizontal cuts at intervals of 1 mm with a cutter, and cellophane tape is affixed thereon to peel off the remaining 25 squares. The number of creaking eyes was counted (cross cut test, remaining creased number / total creased number (25)).

Each of the hard coats obtained from the hard coating agent of the present invention had a refractive index as low as 1.45 or less, a pencil hardness of 3H or more, and good adhesion to the substrate. .
On the other hand, the hard coat obtained from the comparative hard coating agent had problems. That is, in Comparative Example 4 in which glycidoxyalkyltrialkoxysilane was not used as the raw material alkoxysilane, a decrease in adhesion was observed. In Comparative Example 5 in which the proportion of Si atoms derived from the methyltrimethoxysilane compound was 40%, the refractive index exceeded 1.45. Furthermore, in Comparative Example 6 that did not contain an aluminum-based curing catalyst, the pencil hardness decreased.

  The hard coating agent of the present invention is suitably used in the field of display materials.

Claims (4)

A hard coating agent comprising a polysilanol composition obtained by hydrolytic condensation of a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane, and an aluminum-based curing catalyst,
The proportion of Si atoms derived from the methyltrimethoxysilane compound in the total Si atoms is 50% or more,
The refractive index of the resulting coating film is 1.45 or less,
Hard coating agent.   The hard coating agent according to claim 1, wherein the polysilanol composition has an epoxy group.   A step of hydrolyzing and condensing a methyltrimethoxysilane compound and a glycidoxyalkyltrialkoxysilane using an inorganic acid or Lewis acid as an acid catalyst to obtain a polysilanol composition, and the polysilanol obtained in the above step A method for producing a hard coating agent, comprising a step of adding an aluminum-based curing catalyst to a composition.   A hard coat obtained from the hard coating agent according to claim 1.