JP2002226588A - Organic-inorganic composite gradient material and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an organic-inorganic composite gradient material with which a coating film having a relatively thick film thickness, controlling crack occurrence can be formed by a spray coating and deterioration of the coating film by a photocatalyst can be controlled when used as an intermediate film of a photocatalytically active material layer. SOLUTION: This organic-inorganic composite gradient material is formed by using (A) an organic polymer compound having a hydrolyzable metal- containing group and (B) a substance obtained by hydrolyzing a mixture comprising (b1) a specific hydrolyzable metal-containing compound and (b2) a specified hydrolyzable phenyl group-containing compound in a specific ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an organic-inorganic composite gradient material and its use. More specifically, the present invention is an organic-inorganic composite gradient material having a component gradient structure by adsorbing an organic polymer compound to an organic substrate, and has a relatively large film thickness by a spray coating method or the like,
In addition to being able to form a film in which the generation of cracks is suppressed and, when used as an intermediate film of the photocatalytic active material layer, an organic-inorganic composite gradient material capable of suppressing deterioration of the film due to the photocatalyst, from the gradient material, The present invention relates to a coating agent for forming a film, particularly a coating agent used for an intermediate film interposed between an organic base material and a photocatalytic active material layer, and a structure having a film formed of the gradient material on the surface.

[0002]

2. Description of the Related Art In recent years, with the diversification of requirements concerning the performance and functions of organic polymer materials, it has become difficult to satisfy with a single polymer compound, and different materials having different properties are added to the polymer compound. Compounding is being done.

[0003] For example, the modification of physical properties by dispersing a reinforcing material in an organic polymer material is widely performed, and specifically, organic fibers such as carbon fiber, glass fiber, metal fiber, ceramic fiber, and aramid fiber are used. And inorganic fibrous substances, or powdered inorganic fillers such as calcium carbonate, silica, and alumina are added and uniformly dispersed. In addition, studies are being actively conducted to mix new polymer compounds, optionally compatibilize them via a compatibilizer, and form a polymer alloy, thereby expressing new functions. On the other hand, recently, a functionally graded material, which is a composite material whose properties are completely different between the front and the back, has been attracting attention by gradually changing the composition of the material.For example, a metal-ceramic composite gradient function that has both the heat resistance of ceramics and the strength of metal Materials have been developed as airframe materials for supersonic aircraft.

[0004] Such functionally graded materials are classified into inorganic graded materials, organic graded materials and organic-inorganic composite graded materials, and a plurality of materials, for example, a plurality of different kinds of inorganic materials, a plurality of different kinds of organic materials. By mixing each other or one or more organic materials and one or more inorganic materials, and controlling the distribution density, orientation, etc., depending on the location, the physical properties of a plurality of component materials can be expressed.
It is expected to be used in the aviation, automotive, electronics, medical, energy, and radiation and electromagnetic shielding fields.

[0005] The present inventors have previously proposed various uses as a novel functional material, for example, a coating film, an adhesive between an organic material and an inorganic or metal material, and a coating material between an organic substrate and a photocatalytic coating film. An organic polymer compound that is provided and is useful for applications such as an intermediate film that prevents deterioration of the organic base material and an intermediate film that improves the adhesion between the organic base material and the inorganic or metal material layer. Organic compounds whose composition changes in the thickness direction by adsorbing on
An inorganic composite gradient material was found (Japanese Patent Application No. Hei 11-26459).
No. 2).

[0006] The organic-inorganic composite gradient material is an organic-inorganic composite material containing a chemical bond of an organic polymer compound and a metal compound. It is a novel material that has a component gradient structure in which the content of the metal-based compound changes in the thickness direction of the material, and is extremely useful for the various uses described above.

However, since the organic-inorganic composite gradient material is formed by utilizing the adsorption ability of the polymer portion to the substrate, the optimum film thickness is 50 to 100 nm in order to develop a good gradient structure. Therefore, it is important that the film is homogeneous within the range described above, and therefore, a spin coating method is generally used for forming a film. In practice, spray coating is more advantageous than spin coating in forming a relatively thick coating over a wide area on a substrate, but spray coating is more effective than spin coating. As a result, there is a problem that the inclined structure is hardly developed and cracks are easily generated.

In order to prevent the occurrence of cracks, in the formation of the organic-inorganic composite gradient material, a metal-containing compound capable of forming a metal oxide by hydrolysis may be, for example, an alkoxysilane having a non-hydrolyzable organic group. It is conceivable that a compound is used to impart flexibility to the formed composite gradient film, but when such a composite gradient film is used as an intermediate film of the photocatalytic active material layer, the metal component in the composite gradient film is It is feared that the non-hydrolyzable organic group remaining in the polymer is degraded by the photocatalyst.

[0009]

Under such circumstances, the present invention provides an organic-inorganic composite material having a component gradient structure in which the content of a metal component changes continuously in the thickness direction of the material. In addition, it is possible to form a film having a relatively large thickness and suppressed crack generation by a spray coating method or the like, and when the film is used as an intermediate film of a photocatalytic active material layer, the film is deteriorated by the photocatalyst. Organic-
It is an object of the present invention to provide an inorganic composite gradient material and its use.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have found that an organic polymer having a metal-containing group which can be bonded to a metal oxide by hydrolysis in the molecule. The object is achieved by using, as a hydrolyzable metal-containing compound to be hydrolyzed and condensed with a compound, a mixture containing a metal-containing compound having a specific structure and a phenyl-containing metal-containing compound having a specific structure in a predetermined ratio. The present inventors have found that the present invention can be performed, and have completed the present invention based on this finding.

That is, the present invention provides (1) a composite comprising an organic polymer compound and a metal oxide compound chemically bonded, and wherein the content of the metal component is continuous from the surface of the material in the depth direction. An organic-inorganic composite gradient material having a component gradient structure that changes gradually, wherein the composite comprises (A) an organic polymer compound having a metal-containing group capable of bonding to a metal oxide by hydrolysis in a molecule. , (B) (a) general formula (I) R ¹ _mm ¹ (I) wherein R ¹ is a hydrolyzable group, M ¹ is a metal atom,
m is the valence of the metal atom M ^1. ) And a condensed oligomer thereof, and (b) a general formula (I)
_{^{I) Ph p-q M 2}} R 2 q ... (II) ( wherein, ^{R 2} is a hydrolyzable group, Ph refers to a phenyl group, ^{M 2}
It represents a metal atom, p is the valence of the metal atom M ^2, q
Is an integer satisfying the relationship 0 <q <p-1. Wherein the mixture is formed by subjecting a mixture containing a phenyl group-containing metal-containing compound represented by the formula (1) or a condensation oligomer thereof to a metal atom ratio of 95: 5 to 10:90 by hydrolysis. A gradient material, (2) a coating agent characterized in that a coating comprising the organic-inorganic composite gradient material is formed on a substrate, and (3) a coating comprising the organic-inorganic composite gradient material. Structure,
Is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The organic-inorganic composite gradient material of the present invention is an organic-inorganic composite material including a composite obtained by chemically bonding an organic polymer compound and a metal oxide compound, preferably the composite Comprising an organic-inorganic composite material having a component gradient structure developed by adsorption of an organic polymer compound onto an organic base material.

[0013] The confirmation of the component gradient structure accompanying the adsorption of the organic polymer compound can be performed, for example, by examining the surface of the coating film of the organic-inorganic composite gradient material provided on the substrate made of an organic material and peeling the coating film from the substrate. It can be carried out by measuring the content of carbon atoms and metal atoms on the film surface, the content of organic polymer compound, and the like on both of the separated surfaces by X-ray photoelectron spectroscopy or the like.

The content of the metal component in such a gradient material is not particularly limited, but is usually 5 to 98% by weight, preferably 20 to 98% by weight, particularly preferably 20 to 98% by weight in terms of the weight ratio of the metal alkoxide charged. 50-90% by weight
Range. The degree of polymerization or molecular weight of the organic polymer compound is not particularly limited as long as it can form a film,
What is necessary is just to select suitably according to the kind of a high molecular compound, desired film property, etc.

The kind of the metal component in the composite gradient material of the present invention is not particularly limited. For example, a metal containing a metal atom selected from among silicon, titanium, zirconium, indium, tin and aluminum atoms. Oxide compounds are preferred. The metal oxide-based compound may be contained alone or as a mixture of two or more kinds, and may be contained in the form of a composite metal oxide having two or more kinds of metal atoms. You may.

Further, when the thickness of the composite gradient material of the present invention is usually in the range of 0.05 to 10 μm, cracks do not occur, the composite gradient material has a good gradient structure, and the light-catalyst has good deterioration. is there. The preferred thickness is 0.1 to
It is in the range of 5.0 μm.

Such an organic-inorganic composite gradient material can be efficiently produced by the following method. First, together with (A) an organic polymer compound having a metal-containing group capable of bonding to a metal oxide by hydrolysis (hereinafter sometimes referred to as a hydrolyzable metal-containing group) in a molecule, and (B)
After preparing a coating solution containing a mixture of a specific hydrolyzable metal-containing compound and a specific hydrolyzable phenyl-containing metal-containing compound (b), the mixture is treated with an organic solvent. The organic-inorganic composite gradient material of the present invention can be obtained by forming a coating film composed of the coating liquid on a substrate and then subjecting it to a heat drying treatment.

The organic polymer compound having a hydrolyzable metal-containing group as the component (A) includes, for example, (a) an ethylenically unsaturated monomer having a hydrolyzable metal-containing group, and (b) a metal. Can be obtained by copolymerizing ethylenically unsaturated monomers.

The ethylenically unsaturated monomer having a hydrolyzable metal-containing group as the component (A) (a) is represented by the general formula (III):

[0020]

Embedded image

(Wherein R ⁶ is a hydrogen atom or a methyl group;
A is an alkylene group, preferably an alkylene group having 1 to 4 carbon atoms, and R ⁷ is a hydrolyzable group or a non-hydrolyzable group, at least one of which is hydrolyzed to form (B)
It must be a hydrolyzable group capable of components chemically bonded, and when R ⁷ is plural, each R ⁷ may be the mutually the same or different, M ³ is silicon, titanium, zirconium, indium, tin, metal atoms such as aluminum, r is a valence of the metal atom M ^3. )).

In the above formula (III), examples of the hydrolyzable group of R ⁷ which can be chemically bonded to the component (B) by hydrolysis include, for example, a halogen atom such as an alkoxyl group, an isocyanate group, a chlorine atom, an oxy group. Halogen group,
An acetylacetonate group, a hydroxyl group and the like are mentioned. On the other hand, as the non-hydrolyzable group which does not chemically bond to the component (B), for example, a lower alkyl group is preferably mentioned.

In the general formula (III), -M ³ R ⁷ _r-1
As the metal-containing group represented by, for example, a trimethoxysilyl group, a triethoxysilyl group, a tri-n-propoxysilyl group, a triisopropoxysilyl group, a tri-n-
Butoxysilyl group, triisobutoxysilyl group, tri-
sec-butoxysilyl group, tri-tert-butoxysilyl group, trichlorosilyl group, dimethylmethoxysilyl group,
Methyldimethoxysilyl group, dimethylchlorosilyl group,
Methyldichlorosilyl group, triisocyanatosilyl group,
Such as methyldiisocyanatosilyl group, trimethoxy titanium group, triethoxy titanium group, tri-n-propoxy titanium group, triisopropoxy titanium group, tri-n-butoxy titanium group, triisobutoxy titanium group, tri-sec- Butoxy titanium group,
Tri-tert-butoxytitanium group, trichlorotitanium group, further, trimethoxyzirconium group, triethoxyzirconium group, tri-n-propoxyzirconium group, triisopropoxyzirconium group, tri-
n-butoxyzirconium group, triisobutoxyzirconium group, tri-sec-butoxyzirconium group, tri-tert-butoxyzirconium group, trichlorozirconium group, and further, dimethoxyaluminum group, diethoxyaluminum group, di-n-propoxy Examples include an aluminum group, a diisopropoxyaluminum group, a di-n-butoxyaluminum group, a diisobutoxyaluminum group, a di-sec-butoxyaluminum group, a di-tert-butoxyaluminum group, and a trichloroaluminum group. One type of the ethylenically unsaturated monomer as the component (a) may be used alone, or two or more types may be used in combination.

On the other hand, the metal-free ethylenically unsaturated monomer as the component (b) is, for example, a compound represented by the following general formula (I)
V)

[0025]

Embedded image

(Wherein R ⁸ is a hydrogen atom or a methyl group;
X is a monovalent organic group. )), Preferably an ethylenically unsaturated monomer represented by the general formula (IV-a)

[0027]

Embedded image

(Wherein R ⁸ is the same as described above, and R ⁹ represents a hydrocarbon group), or an ethylenically unsaturated monomer represented by the general formula (IV-a) General formula (IV-b) as an ethylenically unsaturated monomer and an adhesion improver optionally added

[0029]

Embedded image

(Wherein R ¹⁰ represents a hydrogen atom or a methyl group, and R ¹¹ represents an epoxy group, a halogen atom or a hydrocarbon group having an ether bond) and a mixture with an ethylenically unsaturated monomer represented by the formula: Can be mentioned.

In the ethylenically unsaturated monomer represented by the general formula (IV-a), the hydrocarbon group represented by R ⁹ is a linear or branched alkyl group having 1 to 10 carbon atoms. A cycloalkyl group having 3 to 10 carbon atoms, 6 carbon atoms
Preferred examples include aryl groups having 10 to 10 and aralkyl groups having 7 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and various butyl groups, a pentyl group, a hexyl group, an octyl group, and a decyl group. Examples of the cycloalkyl group having 3 to 10 carbon atoms include:
Examples of the aryl group having 6 to 10 carbon atoms such as a cyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, and a cyclooctyl group include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a methylnaphthyl group, and the like. Examples of the aralkyl group of 10 to 10 include a benzyl group, a methylbenzyl group, a phenethyl group, a naphthylmethyl group and the like.

Examples of the ethylenically unsaturated monomer represented by the general formula (IV-a) include methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth)
Examples include acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, and benzyl (meth) acrylate. These may be used alone or in combination of two or more.

[0033] In the ethylenically unsaturated monomer represented by formula (IV-b), an epoxy group represented by R ^11, the hydrocarbon groups having a halogen atom or an ether bond, C1-10 A linear or branched alkyl group, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. As the halogen atom of the above substituent, a chlorine atom and a bromine atom are preferable. Specific examples of the hydrocarbon group include the same groups as those exemplified in the description of R ⁹ in the general formula (IV-a).

Examples of the ethylenically unsaturated monomer represented by the general formula (IV-b) include glycidyl (meth) acrylate, 3-glycidoxypropyl (meth) acrylate, 2- (3,4 -Epoxycyclohexyl) ethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-bromoethyl (meth) acrylate and the like can be preferably mentioned.

Further, as the ethylenically unsaturated monomer represented by the general formula (IV), styrene,
α-methylstyrene, α-acetoxystyrene, m-,
o- or p-bromostyrene, m-, o- or p-
Stabilizers for polymerizable polymers having chlorostyrene, m-, o- or p-vinylphenol, 1- or 2-vinylnaphthalene, and further having an ethylenically unsaturated group, for example, oxidation having an ethylenically unsaturated group, Inhibitors, ultraviolet absorbers, light stabilizers and the like can also be used. These may be used alone or in combination of two or more.

When the ethylenically unsaturated monomer represented by the general formula (IV-a) and the ethylenically unsaturated monomer represented by the general formula (IV-b) are used in combination, It is preferred to use the latter ethylenically unsaturated monomer in a proportion of 1 to 100 mol% with respect to the ethylenically unsaturated monomer.

The ethylenically unsaturated monomer having a hydrolyzable metal-containing group as the component (a) and the metal-free ethylenically unsaturated monomer as the component (b) are used in the presence of a radical polymerization initiator. Under the radical copolymerization, (A)
An organic polymer compound having a hydrolyzable metal-containing group as a component is obtained.

On the other hand, as the hydrolyzable metal-containing compound as the component (B) (A), the following general formula (I): R ¹ _mM ¹ (I) wherein R ¹ is a hydrolyzable group; M ¹ represents a metal atom,
m is the valence of the metal atom M ^1. ), A hydrolyzate thereof or a condensation oligomer thereof.

In the above general formula (I), examples of the hydrolyzable group represented by R ¹ include a hydroxyl group, an alkoxyl group, an isocyanate group, a halogen atom such as a chlorine atom,
An oxyhalogen group, an acetylacetonate group and the like can be mentioned. Examples of the metal atom represented by M ¹ include silicon, titanium, zirconium, indium, tin,
Aluminum and the like can be mentioned.

Examples of the compound represented by the general formula (I) or the condensation oligomer thereof include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, Isobutoxysilane, tetra-sec
-Butoxysilane, tetra-tert-butoxysilane and the like, and the corresponding tetraalkoxytitanium and tetraalkoxyzirconium, furthermore, trimethoxyaluminum, triethoxyaluminum, tri-
Metal alkoxides such as n-propoxyaluminum, triisopropoxyaluminum, tri-n-butoxyaluminum, triisobutoxyaluminum, tri-sec-butoxyaluminum, tri-tert-butoxyaluminum, or metal alkoxide oligomers, for example, commercially available alkoxy Silane oligomers "methyl silicate 51", "ethyl silicate 40" (all trade names manufactured by Colcoat), "MS-51", "MS"
-56 "(all trade names manufactured by Mitsubishi Chemical Corporation), and further, tetraisocyanatosilane, methyltriisocyanatosilane, tetrachlorosilane, methyltrichlorosilane and the like. In the present invention, this (B)
(B) as component, represented particularly by the general formula _{^{(I-a) (R 3}} O) 4 Si ... (I-a) ( wherein, ^{R 3} represents an alkyl group having 1 to 6 carbon atoms.) Tetraalkoxysilanes or condensation oligomers thereof are preferred. In the general formula (Ia), four R ³ Os may be the same or different. In addition, the hydrolyzable metal-containing compound as the component (B) (a) may be used alone or in a combination of two or more.

Furthermore, the hydrolyzable phenyl group-containing metal-containing compound (B) (b) is a compound represented by the general formula (I)
_{^{I) Ph p-q M 2}} R 2 q ... (II) ( wherein, ^{R 2} is a hydrolyzable group, Ph refers to a phenyl group, ^{M 2}
It represents a metal atom, p is the valence of the metal atom M ^2, q
Is an integer satisfying the relationship 0 <q <p-1. The compound containing a phenyl group metal represented by the formula (1) or a condensation oligomer thereof is used.

The above general formula (II), when R ² is more than one, a plurality of R ² may be different even in the same. The hydrolyzable group represented by R ² and the metal atom represented by M ² are each a group represented by R in the aforementioned general formula (I).
It includes the same as those exemplified in the description of ¹ and M ^1. Note that a substituent that is not easily deteriorated by a photocatalyst can be introduced on the ring of the phenyl group.

In the present invention, as the component (B) (b), in particular, the general formula (II-a) Ph _4-k Si (OR ⁵ ) _k (II-a) (wherein R ⁵ is carbon The alkyl group represented by Formulas 1 to 6, Ph represents a phenyl group, and k represents 2 or 3) or a condensed oligomer thereof. General formula (II-
In a), a plurality of OR ⁵ may be the same or different.

Examples of the compound represented by the general formula (II-a) include phenyltrimethoxysilane, phenyltriethoxysilane, phenyltri-n-propoxysilane, phenyltriisopropoxysilane, phenyltri-n- Butoxysilane, phenyltriisobutoxysilane, phenyltri-sec-butoxysilane, phenyltri-tert-butoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diphenyldi-n-
Examples thereof include propoxysilane, diphenyldiisopropoxysilane, diphenyldi-n-butoxysilane, diphenyldiisobutoxysilane, diphenyldi-sec-butoxysilane, diphenyldi-tert-butoxysilane, and condensation oligomers thereof. In the present invention, the hydrolyzable phenyl group-containing metal-containing compound (B) (b) may be used alone or in combination of two or more.

In the present invention, as the hydrolyzable metal-containing compound of the component (B), the components (a) and (b) are used.
A mixture having a metal atomic ratio of 95: 5 to 10:90 with the components is used. As described above, by using a mixture in which the ratio of the component (a) to the component (b) is within the above range, a thick film of about 0.5 to 5.0 μm can be formed by a spray coating method or the like. In addition, the generation of cracks is suppressed, and even if uneven coating occurs, a favorable inclined structure is developed. When this coating is used as an intermediate film of the photocatalytic active material layer,
Deterioration of the film by the photocatalyst is suppressed. A preferable ratio of the component (a) to the component (b) is 70:30 in terms of metal atom ratio.
10:90, especially 50:50 to 10: 9.
A range of 0 is preferred.

In the present invention, alcohols, ketones,
In a suitable polar solvent such as ether, the above (A)
Using a mixture of the metal-containing compound (B) and the component (B) together with the organic polymer compound as the component, an acid such as hydrochloric acid, sulfuric acid, nitric acid, or a cation exchange resin as a solid acid is used. , Usually 0 to 100 ° C, preferably 2
Hydrolysis is performed at a temperature of 0 to 60 ° C., and when a solid acid is used, after removing the solid acid, the solvent is further distilled off or added, if necessary, to adjust the viscosity to be suitable for coating. To prepare a coating solution. If the temperature is too low, hydrolysis does not proceed, while if it is too high, the hydrolysis / polymerization reaction proceeds too quickly, making control difficult, and as a result, the gradient of the resulting gradient coating film may be reduced.

Depending on the type of the inorganic component, even after the coating solution is prepared, hydrolysis and polycondensation gradually progress and the coating conditions may fluctuate. Therefore, a solid dehydrating agent insoluble in the coating solution may be used. For example, addition of anhydrous magnesium sulfate or the like can prevent a decrease in pot life. In this case, the coating liquid is used for coating after removing the dehydrating agent.

Next, using the coating solution thus obtained, the thickness of the dried coating film on the organic substrate is usually 0.05 to 0.05.
10 μm, especially for interlayer film, preferably 0.05
Dip coating method, spin coating method, spray coating method, bar coating method, knife coating method, roll coating method, blade coating method, and so on so as to be in a range of from 5.0 to 5.0 μm, more preferably from 0.07 to 3.0 μm. The organic-inorganic composite gradient material of the present invention is obtained by forming a coating film by a known means such as a die coating method and a gravure coating method, and performing a known drying treatment, for example, heating and drying at a temperature of about 40 to 150 ° C. Can be In the present invention, it is possible to form a wide and thick film, particularly by a spray coating method, which is advantageous in practical use.

Examples of the organic substrate include acrylic resins such as polymethyl methacrylate, polystyrene and A
Styrene resins such as BS resin, olefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyamide resins such as 6-nylon and 6,6-nylon, polyvinyl chloride resins, Examples of the base material include polycarbonate resins, polyphenylene sulfide resins, polyphenylene ether resins, polyimide resins, and cellulose resins such as cellulose acetate.

These organic base materials can be subjected to a surface treatment by an oxidation method or a concavo-convex method, if desired, in order to further improve the adhesion to the gradient material of the present invention.
Examples of the oxidation method include corona discharge treatment, chromic acid treatment (wet method), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, and examples of the unevenness method include a sand blast method and a solvent treatment method. Is mentioned. These surface treatment methods are appropriately selected according to the type of the base material.

In the present invention, the organic base material is applied to a surface of a base material made of a material other than the organic material, for example, a metal material, a glass or ceramic material, or other various inorganic or metal materials. Those having a membrane are also included.

In the thus obtained organic-inorganic composite gradient material of the present invention, the surface layer contains almost 100% of the metal oxide compound in the material.
It becomes almost 0% near the base material.

The organic-inorganic composite gradient material of the present invention is particularly suitable as an intermediate film of a photocatalytically active material layer. The present invention also provides a coating agent for forming a coating comprising the organic-inorganic composite gradient material on a substrate.

As the coating agent, (A)
Coatings including those obtained by hydrolyzing a mixture of an organic polymer compound having a hydrolyzable metal-containing group as a component and a metal-containing compound as a component (B) [component (a) and component (b)]. A working liquid can be used.

This coating agent can be used for the following purposes. First, it is used for application as a coating film.
Since the organic-inorganic composite gradient material has excellent adhesiveness to an organic substrate and the surface of a coating film has the property of a metal oxide, for example, a coating layer made of the material is provided on various plastic films. Thereby, it is possible to obtain a hard coat film having excellent scratch resistance and heat resistance, as well as good adhesion.

Next, it is used for application as an adhesive.
As described above, the graded material of the present invention has excellent adhesion to an organic base material and has excellent adhesion to an inorganic or metal material because its surface is a metal oxide compound. Therefore, it is suitable as an adhesive between an organic material and an inorganic or metal material.

Further, it is used as an intermediate film interposed between an organic base material and a coat layer containing at least an inorganic or metallic material. When a coating layer containing an inorganic or metal material is formed on an organic substrate, generally, the adhesion between the organic substrate and the coating layer is insufficient, the durability is poor, and peeling over time, Alternatively, there is a problem that the film is easily peeled off by heat or moisture.

By using the gradient material of the present invention as an intermediate film and interposing it between the organic substrate and the coat layer containing an inorganic or metallic material, the intermediate film has a gradient as described above. From the excellent adhesion to the organic substrate, and also excellent adhesion to the coating layer containing an inorganic or metal-based material provided thereon, as a result, the inorganic or metal-based material on the organic substrate Can be formed with extremely good adhesion. In the present invention,
The thickness of the intermediate film is usually 0.05 to 10 μm or less, preferably 0.05 to 5.0 μm, and more preferably 0.07 to 5.0 μm.
範 囲 3.0 μm.

The coat layer containing the inorganic or metal material is not particularly limited, and various coat layers can be formed. For example, (1) a photocatalytic active material layer,
(2) an inorganic or metallic conductive material layer, (3) a hard coat layer containing an inorganic or metallic material, (4) an inorganic or metallic optical recording material layer or an inorganic or metallic dielectric layer, etc. Are preferred.

Next, the coat layer containing each inorganic or metal material will be described. (1) Photocatalytic active material layer: When a coat layer of a photocatalytic active material such as titanium dioxide is provided on the surface of an organic base material, the photocatalytic action causes a problem that the organic base material is deteriorated in a short time. Therefore, it has been attempted to provide a coating layer of a photocatalytically active material such as titanium dioxide on an organic substrate via an inorganic binder which is hardly deteriorated by photocatalysis. However, there is a problem that the inorganic binder has insufficient adhesion to an organic base material and is inferior in durability.

When the gradient material of the present invention is used as an intermediate film and is interposed between an organic substrate and a coat layer of a photocatalytically active material, the adhesion to the organic substrate is excellent, and the surface is almost metal oxide-based. Since it is a compound, it has good adhesion to the coat layer of the photocatalytically active material, and the intermediate film is not easily degraded by the photocatalytic action, so that the organic base material can be sufficiently protected.

The gradient material of the present invention can be interposed as an intermediate film between a metal-based substrate having an organic coating film on the surface and the photocatalytically active material layer. This intermediate film has excellent adhesion with an organic coating film, and has good adhesion with a coating layer of a photocatalytically active material, as well as the organic base material, and is hardly deteriorated by a photocatalytic action. The coating film can be sufficiently protected. Such a use is particularly useful when a photocatalytically active material layer is provided on a steel sheet for automobiles having an organic coating film on the surface.

Examples of the metal base having an organic coating film on its surface include metal bases such as cold-rolled steel sheets, galvanized steel sheets, aluminum / zinc alloy-plated steel sheets, stainless steel sheets, aluminum sheets, and aluminum alloy sheets. An organic coating film can be used. When the gradient material of the present invention is used as such an intermediate film, it is particularly effective when the coating layer of the photocatalytically active material provided thereon is titanium dioxide having a high photocatalytic ability.

(2) Inorganic or metallic conductive material layer:
Organic substrates having a conductive material layer on the surface, particularly plastic films, are used for electroluminescence devices (EL devices), liquid crystal display devices (LCD devices), solar cells, etc., and further include electromagnetic wave shielding films and antistatic films. It is used as Examples of the conductive material used in such applications include metal oxides such as indium oxide, tin oxide, zinc oxide, cadmium oxide, and ITO (indium tin oxide); gold, platinum, silver, nickel, aluminum, and copper. Inorganic or metallic conductive materials such as metals as described above are used. And these inorganic or metallic conductive materials are usually formed on an organic substrate such as a plastic film by a known means such as a vacuum deposition method, a sputtering method, and an ion plating method.
It is formed as a thin film having a thickness of about 5 to 200 nm.

Since the inorganic or metallic conductive material layer thus formed has insufficient adhesion to the organic substrate, the gradient material of the present invention is used as an intermediate film and the organic substrate and By interposing between the inorganic or metal-based conductive material layer, the adhesion between the organic base and the inorganic or metal-based conductive material layer can be improved. Further, even when a transparent conductive film is required, transparency is hardly impaired by interposing the intermediate film made of the gradient material of the present invention.

(3) Hard coat layer containing inorganic or metallic material: A hard coat film having a good surface hardness and excellent scratch resistance and abrasion resistance is, for example, a vehicle,
It is widely used for attaching surfaces such as window glass of buildings and plastic boards for windows, and for protecting CRT displays and flat panel displays.

On the other hand, plastic lenses have become increasingly popular in recent years because they are lighter and have better safety, workability, fashionability, etc. than glass lenses. However, this plastic lens has a drawback that it is easily damaged as compared with a glass lens, and therefore, its surface is coated with a hard coat layer.

Examples of the material of the hard coat layer provided on such a hard coat film or a plastic lens include, for example, a mixture of an alkyltrihydroxysilane and a partial condensate thereof, colloidal silica and a silicon-modified acrylic resin, and an organotrialkoxysilane. Inorganic or metallic materials such as a mixture of a hydrolysis condensate, a mixture of an alkoxysilane hydrolysis condensate and colloidal silica, a zirconium, a metal selected from aluminum and titanium and a chelate compound and a silicon-modified acrylic resin. Hard coating agents are frequently used.

To form a hard coat layer on an organic substrate such as a plastic film or a plastic lens,
The hard coat agent containing the inorganic or metal-based material, using a known method such as a bar coat method, a knife coat method, a roll coat method, a blade coat method, a die coat method, a gravure coat method, a spray coat method, or the like. A method of applying the composition on an organic substrate so that the dry film thickness is about 1 to 30 μm and performing a drying treatment is usually used.

The thus formed hard coat layer containing an inorganic or metal material has insufficient adhesion to an organic base material. By interposing the hard coat layer between the organic base material and the hard coat layer containing an inorganic or metallic material, the adhesion between the organic base material and the hard coat layer containing an inorganic or metallic material can be improved. Further, in the plastic lens, even if an intermediate film made of the inclined material of the present invention is interposed, it hardly causes a decrease in the transparency of the plastic lens or the generation of interference fringes. (4) Inorganic or metal-based optical recording material layer or inorganic or metal-based dielectric layer: an optical recording medium having characteristics such as rewritable, high-density, large-capacity storage capacity, and non-contact with a recording / reproducing head in recent years. A phase change using a phase change from a magneto-optical disk or crystal to an amorphous phase by recording information using the magnetization reversal of the magnetic film using the heat energy of a semiconductor laser beam and reading it using the magneto-optical effect Discs have been developed and are now in practical use.

Such an optical recording medium is generally provided with an optical recording material layer, a dielectric layer, a metal reflective layer, an organic protective layer on a translucent resin substrate (organic substrate), for example, a substrate such as polycarbonate or polymethyl methacrylate. It has a structure in which layers are sequentially laminated, and a dielectric underlayer may be provided between the substrate and the optical recording material layer in some cases.

The optical recording material layer provided on the substrate includes, for example, Tb-Fe, Tb-Fe-Co, Dy-Fe-C
o, inorganic magneto-optical recording materials such as Tb-Dy-Fe-Co, or TeOx, Te-Ge, Sn-Te-
Ge, Bi-Te-Ge, Sb-Te-Ge, Pb-S
An inorganic phase change recording material such as n-Te or Tl-In-Se is used. If desired, the dielectric underlayer provided between the substrate and the optical recording material layer may include, for example, S
Inorganic materials such as iN, SiO, SiO ₂ and Ta ₂ O ₅ are used. The inorganic optical recording material layer and the dielectric underlayer are usually formed by a known means such as a vacuum evaporation method, a sputtering method, and an ion plating method.

Since the inorganic or metallic optical recording material layer or the inorganic dielectric underlayer formed as described above has insufficient adhesion to the translucent resin substrate, the gradient material of the present invention is not used. As an intermediate film, by interposing between a light-transmitting resin substrate and the optical recording material layer or the dielectric underlayer,
Adhesion between the substrate and the optical recording material layer or the dielectric underlayer can be improved.

Other coating layers containing inorganic or metallic materials include titanium oxide, zinc oxide, indium oxide, tin oxide, zinc sulfide, and antimony-doped tin oxide (AT
O), an inorganic infrared absorbing layer such as tin-doped indium oxide (ITO), and a magnetic layer on which metal is deposited.

The present invention further provides a structure having a coating made of the above-mentioned organic-inorganic composite gradient material. As such a structure, for example, an organic substrate having a coat layer containing at least an inorganic or metal material, with the organic-inorganic composite gradient material of the present invention interposed as an intermediate film,
Alternatively, the organic-inorganic composite gradient material of the present invention is interposed as an intermediate film, and has a photocatalytically active material layer, such as a metal base material provided with an organic coating film on its surface. An article having a coat layer interposed as a film and containing at least an inorganic or metal material can be given.

As a specific example of the article, a coat layer containing at least an inorganic or metal material is composed of (1) a photocatalytic active material layer, (2) an inorganic or metal conductive material layer, and (3)
A hard coat layer containing an inorganic or metal material, and
(4) An inorganic or metallic optical recording material layer or an inorganic or metallic dielectric layer can be preferably exemplified.

As the above structure, a structure having a photocatalytically active material layer on an organic substrate through a coating made of an organic-inorganic composite gradient material is particularly preferable.

[0078]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The properties of the films formed in the respective examples were determined according to the following methods. (1) Weather resistance A sample having a photocatalyst layer was measured using a sunshine weather meter (“Sunshine Weather Meter S300” manufactured by Suga Test Instruments Co., Ltd.) according to JIS K7350-4.
A 1200-hour weathering acceleration test was performed in accordance with. The sample after the weathering test was measured for haze value [using a haze meter manufactured by Nippon Denshoku Industries Co., Ltd.] based on JIS K7361 and compared with the value before the test.

(2) Confirmation of Inclination The X-ray photoelectron spectrometer “PH” manufactured by ULVAC-PHI, Inc.
I-5600 ", an elemental analysis of the film surface was performed to confirm that no organic component (acryl) was present on the surface.
In addition, the film was peeled off from the substrate, and the peeling interface was analyzed in the same manner to confirm that the presence of acryl and silicon atoms of the inorganic component were hardly detected, and that the film had a component gradient structure that caused polymer adsorption to the substrate. I inferred.

Preparation Example 1 Preparation of Organic Component Solution (a) Methyl methacrylate 30.0 g (0.3 mol), γ-
2.48 g of methacryloxypropyltrimethoxysilane
(0.01 mol) of the mixed solution was added with 0.3 g (0.0018 mol) of 2,2'-azobisisobutyronitrile, and stirred to form a uniform solution. When this solution was reacted at 75 ° C. for 3 hours with stirring, a polymer having a number average molecular weight of 110,000 in terms of polystyrene by GPC was obtained. Methyl ethyl ketone (MEK) so that it becomes 3 g / L
To prepare an organic component solution (a).

Preparation Example 2 Preparation of Inorganic Component Liquid A Tetramethoxysilane tetramer (Mitsubishi Chemical Corporation, M
S-51) 25.3 g, phenyltrimethoxysilane 4.7 g (Si ratio 90:10) and water 18.8 g were mixed and dissolved in ethanol 48.0 g. Here 1 mol /
0.3 g of nitric acid aqueous solution of liter
The mixture was stirred for 4 hours to prepare an inorganic component liquid A.

Preparation Example 3 Preparation of Inorganic Component Liquid B Tetramethoxysilane tetramer (manufactured by Mitsubishi Chemical Corporation, M
S-51) 10.0 g, phenyltrimethoxysilane 1
6.8 g (Si ratio: 50:50) and 14.5 g of water were mixed and dissolved in 56.5 g of ethanol. Here 1 mol /
0.3 g of nitric acid aqueous solution of liter
The mixture was stirred for 4 hours to prepare an inorganic component liquid B.

Preparation Example 4 Preparation of Inorganic Component Liquid C Tetramethoxysilane tetramer (Mitsubishi Chemical Corporation, M
S-51) 3.3 g, phenyltrimethoxysilane 2
2.0 g (20:80 Si ratio) and 12.7 g of water were mixed and dissolved in 60.2 g of ethanol. Here 1 mol /
0.3 g of nitric acid aqueous solution of liter
The mixture was stirred for 4 hours to prepare an inorganic component liquid C.

Preparation Example 5 Preparation of Inorganic Component Liquid D Tetramethoxysilane tetramer (Mitsubishi Chemical Corporation, M
S-51) 31.4 g (Si ratio 100: 0) and water 2
0.5 g was mixed and dissolved in 44.6 g of ethanol. 0.3 g of a 1 mol / liter nitric acid aqueous solution was added thereto, and the mixture was stirred at 30 ° C. for 24 hours to prepare an inorganic component liquid D.

Preparation Example 6 Preparation of Inorganic Component Liquid E Tetramethoxysilane tetramer (manufactured by Mitsubishi Chemical Corporation, M
S-51) 10.0 g, methyltrimethoxysilane 1
1.5 g (Si ratio 50:50) and 14.5 g of water were mixed and dissolved in 56.5 g of ethanol. Here 1 mol /
0.3 g of nitric acid aqueous solution of liter
The mixture was stirred for 4 hours to prepare an inorganic component liquid E.

Example 1 10 ml of inorganic component solution A and 10 ml of organic component solution (a)
To prepare a coating solution, spin-coated on a polymethyl methacrylate substrate at 1000 rpm / 30 seconds, and then heat-treated at 80 ° C. for 2 hours to form a composite film having a thickness of about 2 μm. did. When this was visually observed and observed with an optical microscope, it was transparent and no cracks or the like were observed. The gradient of the obtained film is represented by X
When confirmed with a line photoelectron spectrometer, no organic polymer component was confirmed on the film surface, and silicon as an inorganic component was hardly detected at the peeling interface, suggesting that the film had an inclined structure.

Next, a photocatalyst coating solution [a solution obtained by diluting NSC-200C manufactured by Nippon Soda Co., Ltd. by 20 times by weight in isopropanol] was formed on the composite film in the same manner as described above. For 1 hour to produce a sample in which a photocatalyst layer having a thickness of 0.05 μm was formed on the intermediate film formed of the composite film. The film had a haze value of 0.3%, a water contact angle of super hydrophilic, and was transparent and no cracks were observed visually and by an optical microscope.
When a weathering acceleration test was performed on this sample, the sample after the test showed a super-hydrophilic property with a haze value of 0.4%, and when observed visually and with an optical microscope, there was almost no change from that before the weathering acceleration test. I couldn't see it.

Example 2 A composite film was formed in the same manner as in Example 1 except that the inorganic component liquid B was used instead of the organic component liquid A. When this was observed visually and with an optical microscope,
It was transparent and no cracks were observed. When the gradient of the obtained film was confirmed by an X-ray photoelectron spectrometer, no organic polymer component was confirmed on the film surface, and almost no inorganic component silicon was detected at the peeling interface. I suspected that.

Next, in the same manner as in Example 1, a sample in which a photocatalyst layer having a thickness of 0.05 μm was formed on an intermediate film composed of a composite film was produced. The film had a haze value of 0.3%, a water contact angle of super hydrophilic, and was transparent and no cracks were observed visually and by an optical microscope. When a weather resistance acceleration test was performed on this product,
The sample after the test showed a superhydrophilicity at a haze value of 0.3%, and when observed visually and with an optical microscope, almost no change was observed from that before the accelerated weathering test.

Example 3 A composite film was formed in the same manner as in Example 1, except that the inorganic component liquid C was used instead of the organic component liquid A. When this was observed visually and with an optical microscope,
It was transparent and no cracks were observed. When the gradient of the obtained film was confirmed with an X-ray photoelectron spectrometer, no organic polymer component was confirmed on the film surface, and almost no inorganic component silicon was detected at the peeling interface. I suspected that.

Next, in the same manner as in Example 1, a sample was prepared in which a photocatalyst layer having a thickness of 0.05 μm was formed on an intermediate film composed of a composite film. The film had a haze value of 0.3%, a water contact angle of super hydrophilic, and was transparent and no cracks were observed visually and by an optical microscope. When a weather resistance acceleration test was performed on this product,
The sample after the test showed a superhydrophilicity at a haze value of 0.3%, and when observed visually and with an optical microscope, almost no change was observed from that before the accelerated weathering test.

Comparative Example 1 The procedure of Example 1 was repeated, except that the inorganic component liquid D was used instead of the inorganic component liquid A.
Was formed. When this was visually observed and observed with an optical microscope, whitening of the film due to the occurrence of cracks was confirmed.

Comparative Example 2 A composite film was formed in the same manner as in Example 1, except that the inorganic component liquid E was used instead of the inorganic component liquid A. When this was observed visually and with an optical microscope,
It was transparent and no cracks were observed. When the gradient of the obtained film was confirmed with an X-ray photoelectron spectrometer, no organic polymer component was confirmed on the film surface, and almost no inorganic component silicon was detected at the peeling interface. I suspected that.

Next, in the same manner as in Example 1, a sample in which a 0.05 μm-thick photocatalyst layer was formed on an intermediate film composed of a composite film was manufactured. This film had a haze value of 0.3%, a water contact angle of super hydrophilic, and was transparent and no cracks were observed visually and by an optical microscope. When this was subjected to a weather resistance acceleration test, the sample after the test had a haze value of 9.8%, a water contact angle of 40 °, and was observed visually and with an optical microscope. Roughness and whitening were confirmed.

Example 4 A coating liquid was prepared by mixing 2 ml of the inorganic component solution A, 8 ml of ethyl cellosolve and 10 ml of the organic component solution (a). Next, this coating liquid was applied onto a polymethyl methacrylate substrate by using “Spray Gun FSAG-0” manufactured by Meiji Kikai Seisakusho.
5 "(air pressure: 0.2 MPa, coating amount: 0.4 ml / min, operation speed: 15 m / min), and then heat-treated at 80 ° C. for 2 hours to obtain a minimum film thickness of 0.05 μm
Thus, a composite film having a maximum thickness of 2.5 μm and an uneven thickness was obtained. When this was visually observed and observed with an optical microscope, it was transparent and no crack was observed. When the gradient of the obtained film was confirmed by an X-ray photoelectron spectrometer, no organic polymer component was confirmed on the film surface, and almost no inorganic component silicon was detected at the peeling interface. I suspected that.

Next, a photocatalyst coating liquid [a liquid obtained by diluting NSC-200C manufactured by Nippon Soda Co., Ltd. by 20 times by weight with isopropanol] was coated on the composite membrane with “Spray Gun FSAG-” manufactured by Meiji Kikai Seisakusho Co., Ltd. 05 "(air pressure 0.2MP
a, coating amount: 0.4 ml / min, operation speed: 12 m / min), and then heat-treated in an oven at 80 ° C. for 2 hours to form a 0.05 μm-thick film on the intermediate film composed of a composite film.
The sample on which the photocatalyst layer was formed was prepared. This film had a haze value of 0.5%, showed a water contact angle of super-hydrophilic, and was transparent and no cracks were observed visually and with an optical microscope. When a weathering acceleration test was performed on this sample, the sample after the test showed a super-hydrophilic property with a haze value of 0.5%, and when observed visually and with an optical microscope, there was almost no change from that before the weathering acceleration test. I couldn't see it.

Comparative Example 3 A composite film was formed in the same manner as in Example 4 except that the inorganic component liquid E was used instead of the inorganic component liquid A. When this was observed visually and with an optical microscope,
The occurrence of cracks and whitening of the film were confirmed in the thick portion.

[0099]

The organic-inorganic composite gradient material of the present invention has a component gradient structure in which the content of the metal component changes continuously in the thickness direction of the material. Is relatively thick, and a film in which cracks are suppressed can be formed, and when used as an intermediate film of a photocatalytically active material layer, deterioration of the film due to photocatalyst can be suppressed, and a functional material It is useful for various applications.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 185/00 C09D 185/00 // C08F 230/04 C08F 230/04 C08L 43:00 C08L 43:00 ( 72) Inventor Akihiro Kobayashi 2-1-1 Yabuta Nishi, Gifu City, Gifu Prefecture Ube Nitto Kasei Co., Ltd. Term (reference) 4F006 AA22 AB24 AB39 AB52 BA01 DA04 4J031 AA20 AA59 AB01 AC13 AD01 AF12 4J035 BA05 CA06N CA061 GA02 GB08 LA03 LB01 4J038 CG141 CJ181 CL001 DL131 DM021 PB14 4J100 AB00Q AB02Q AB07QAB08QBA09 AL08BA03 BB01Q BB03Q BC04Q BC43Q BC54Q CA04 JA01

Claims (9)

[Claims] 1. An organic-inorganic material comprising a complex in which an organic polymer compound and a metal oxide compound are chemically bonded, and having a component gradient structure due to adsorption of the organic polymer compound to an organic substrate. A composite gradient material, wherein the composite comprises (A) an organic polymer compound having a metal-containing group capable of bonding to a metal oxide by hydrolysis in a molecule,
(B) (A) Formula (I) R ¹ _mm ¹ (I) wherein R ¹ is a hydrolyzable group, M ¹ is a metal atom,
m is the valence of the metal atom M ^1. A) a metal-containing compound represented by the general formula (I)
_{^{I) Ph p-q M 2}} R 2 q ... (II) ( wherein, ^{R 2} is a hydrolyzable group, Ph refers to a phenyl group, ^{M 2}
It represents a metal atom, p is the valence of the metal atom M ^2, q
Is an integer satisfying the relationship 0 <q <p-1. Wherein the mixture is formed by subjecting a mixture having a metal atom ratio of 95: 5 to 10:90 with the phenyl group-containing metal-containing compound represented by the formula (1) or a condensation oligomer thereof to a hydrolysis treatment. Graded material. (B) The metal-containing compound of the component (A) is:
Formula _{^{(I-a) (R 3}} O) ( wherein, ^{R 3} represents an alkyl group having 1 to 6 carbon atoms.) 4 Si ... (I- a) a compound represented by or a hydrolyzate thereof The organic-inorganic composite gradient material according to claim 1, which is a condensation oligomer thereof. Wherein (B) (ii) containing a phenyl group metal-containing compound of the component, the general formula _{(II-a) Ph 4-} k Si (OR 4) k ... (II-a) ( wherein, ^{R 4} Is an alkyl group having 1 to 6 carbon atoms, Ph is a phenyl group, and k is 2 or 3.), a hydrolyzate thereof or a condensed oligomer thereof. Inorganic composite gradient material. 4. The organic polymer compound of component (A),
(A) an ethylenically unsaturated monomer having a metal-containing group capable of bonding to a metal oxide by hydrolysis in a molecule;
The organic-inorganic composite gradient material according to claim 1, 2 or 3, which is obtained by copolymerizing an ethylenically unsaturated monomer containing no metal. 5. The organic-inorganic composite gradient material according to claim 1, which has a thickness of 0.05 to 10 μm. 6. The organic-inorganic composite gradient material according to claim 1, which is used as an intermediate film of a photocatalytic active material layer. 7. A coating agent, wherein a coating comprising the organic-inorganic composite gradient material according to any one of claims 1 to 6 is formed on a substrate. 8. A structure comprising a coating made of the organic-inorganic composite gradient material according to any one of claims 1 to 6. 9. A photocatalytically active material layer having an organic-inorganic composite gradient material on an organic substrate via a coating.
Structure according to.