GLASS FLAKE MATERIAL CONTAINING AN ORGANIC COMPOUND,

AND METHOD OF MANUFACTURING THE SAME

FIELD OF THE INVENTION

The present invention relates to a glass flake material containing an organic compound such as an organic pigment, and a method of manufacturing the glass flake material. BACKGROUND OF THE INVENTION

A glass flake material containing an organic pigment is manufactured by a so-called sol-gel process. For example, JP 4-292430A discloses a method for obtaining a glass flake material by applying onto a substrate a solution containing an organic pigment and a metallic compound that can be hydrolyzed and dehydration-condensed (e.g. tetramethoxysilane) and peeling off the applied matter from the substrate.

JP 8-60019A discloses a method of manufacturing a glass flake material by adding an acid dye, used as the organic pigment, to a solution containing a metallic compound that can be hydrolyzed and dehydration-condensed, then applying the solution onto a substrate, then drying to peel off the resultant material from the substrate, and further subjecting the resultant material to a predetermined heat treatment. This method makes it possible to obtain a glass flake material that contains a pigment (dye) at high concentrations (from 0.5 wt.% to 30 wt.%). However, leaching resistance, for example water resistance of the dye in this glass flake material, is not sufficient, and the organic pigment (acid dye) is

dissolved out from the glass flake material under severe conditions.

JP 8-245341A discloses a method of manufacturing a glass flake material by curing a solution containing a metallic compound that can be hydrolyzed and dehydration-condensed (condensation polymerized) to condensation-polymerize the metallic compound so that the polymerization degree becomes from 100 to 3500, then adding an acid dye to the solution containing the polymer, subsequently applying the resultant solution onto a substrate, then drying the applied solution to peel off the resultant substance from the substrate, and further heating the resultant substance. This method can improve the leaching resistance of the organic pigment.

The manufacturing method disclosed in JP 8-245341A requires that the polymerization degree of the metallic compound polymer be controlled in the solution so as to be within a predetermined range. However, the foregoing condensation polymerization of the metallic compound represented by tetramethoxysilane keeps proceeding as time passes, and the rate of the reaction is affected by various conditions such as temperature; therefore, it is not easy to control the polymerization degree in the condensation polymerization of the metallic compound. Moreover, if the control were possible, the time during which the solution is usable would be very limited. For these reasons, the manufacturing method disclosed in JP 8-245341A is not suitable for mass production of the glass flake material. DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a glass flake material in which the leaching resistance of the organic compound is improved and that can be manufactured by a method suitable for mass production. It is another object of the present invention to provide a method

of manufacturing the glass flake material.

A glass flake material of the present invention contains^ an oxide of an element other than phosphorus as its main component; an organic compound; and one substance selected from the group consisting of a phosphoric acid and a phosphate compound.

The present invention also provides, as a method of manufacturing the glass flake material according to the invention, a method of manufacturing a glass flake material including: applying onto a substrate a solution containing a hydrolysate of a hydrolyzable compound free from phosphorus, at least one substance selected from the group consisting of a phosphoric acid and a phosphate compound, and an organic compound, to form a film; and peeling the film off from the substrate to obtain the glass flake material.

In the present invention, the leaching resistance of the organic compound is enhanced by changing the component of the glass flake material. Therefore, the manufacturing method of the invention does not require that the polymerization degree of a polymer of a compound used as a source material be controlled within a predetermined range to improve the leaching resistance. The glass flake material of the invention can be manufactured by a method that is suitable for mass production while the organic compound has an improved leaching resistance. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view illustrating the shape of a glass flake material according to the present invention. Fig. 2 is a plan view illustrating the shape of the glass flake material according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A glass flake material according to the present invention contains, as its main component, an oxide of an element other than phosphorus. The term "main component" in the present specification is, according to conventional usage, intended to mean a component that accounts for 50 mass % or greater, and in the glass flake material according to the present invention, the oxide may account for 70 mass % or more, or 90 mass % or more.

It is preferable that the element other than phosphorus be at least one element selected from the group consisting of silicon, titanium, aluminum, zirconium, and tantalum.

Specifically, it is preferable that the phosphate compound be at least one substance selected from the group consisting of a phosphate salt and a phosphoric ester. Examples of the phosphate salt include calcium phosphate, sodium phosphate, and magnesium phosphate. The phosphate salt may be added to the glass flake material as a phosphate salt or may be composed of phosphoric acid(s) and metallic ion(s) such as ion of calcium that are added separately. The phosphoric ester may be any of monoester, diester, or triester. The phosphoric ester may be a hydrophilic organic polymer containing a phosphate ester group and a polyoxyalkylene group, such as commercially available as a surfactant.

It is recommended that the proportion of the total amount of the phosphoric acid and the phosphate compound with respect to the total amount of the oxide that is the main component of the glass flake material be 20 mole % or less, more preferably 10 mole % or less, and still more preferably 2 mole % or less. The lower limit of this proportion should exceed

0, and preferably 0.001 mole % or greater. In calculating the proportion, the total amount of the phosphoric acid and the phosphate compound should be converted into phosphoric acid (orthophosphoric acid: H3PO4).

The organic compound in the glass flake material of the present invention should preferably be a functional organic material that has a predetermined function, such as pigment, nonlinear optical material, laser dye, photochemical burning material, liquid crystal material, photovoltaic material, photochemical sensor material, and photocatalytic material. The glass flake material of the present invention functions as a carrier that carries a functional organic material such as listed above, and it may be mixed into various matrix (base material) or applied on a substrate, depending on the application.

Even with the use of a water-soluble organic compound, the leaching resistance to water improves by applying the present invention. A representative example of a water-soluble organic pigment is an acid dye. Examples of the functional groups that are typical in the acid dye include -SO ₃ Na and -COONa.

Illustrative examples of the acid dye include '• Acid Orange 24, Acid

Black 1, Acid Violet No. 43, Food Blue 2, Acid Blue 74, Acid Blueδ, Acid Blue 9, Acid Green 25, SoIv. Green 7, Acid Green 5, Food Green, Acid Green 1, Acid

Green 3, Acid Yellow 73, Acid Yellow 3, Acid Yellow 23, Acid Yellow 40, Acid

Yellow 1, Acid Yellow 36, Acid Yellow 11, Food Yellow 3, Acid Orange 7, Acid

Red 95, Acid Orange 20, Acid Red 18, Acid Red 92, Acid Red 94, Acid Red 52,

Acid Red 27, Basic Violet 10, Acid Red 33, Acid Red 87, Acid Red 51, Acid Violet 9, Food Red 6, Acid Red 26, Food Red 1, and Acid Red 88.

The content of the organic compound in the glass flake material may

be adjusted as appropriate according to the type of the organic compound or the purpose of the addition thereof. The glass flake material of the present invention may contain the organic compound in an amount of about 0.1 mass % or more, or even about 1 mass % or more, of the glass flake material. The upper limit of the content of the water-soluble organic compound is not particularly limited either, but is normally preferably 20 mass % or less of the glass flake material.

The size and shape of the glass flake material should be adjusted as appropriate according to, for example, its application; typically, the thickness t is within the range of from 0.1 μm to 15 μm and the aspect ratio (particle size a/thickness t) is within the range of from 2 to 1000. An example of the shape of the glass flake material 1 is illustrated in Figs. 1 and 2. As shown in Fig. 2, the particle size a is defined as the square root of area S when the glass flake material 1 is viewed in plan (a = S ⁰ - ⁵ ). In the manufacturing method of the present invention, the glass flake material, the formed product, is obtained from source materials utilizing a technique known as a so-called sol-gel process. In the present invention, an acid catalyst is used as a hydrolysis catalyst. A typical acid catalyst that has conventionally been used is hydrochloric acid. Phosphoric acid may function as an acid catalyst. However, phosphoric acid has been known to be a weaker acid than hydrochloric acid, sulfuric acid, and nitric acid and therefore have inferior catalytic activity! moreover, phosphoric acid has been difficult to use as a catalyst since it is nonvolatile. Because it is widely known that phosphates have poor water resistance, it has been thought that the use of phosphoric acid should be avoided when the water resistance of the product or the leaching resistance of the contained components should be

taken into consideration. For example, only hydrochloric acid, sulfuric acid, and nitric acid are mentioned as the examples of the acid catalyst in the previously-mentioned patent publications, JP 4-292430A, JP 8-60019A, and JP 8-245341A. However, it has been found that the addition of a phosphoric acid and/or a phosphate compound to the glass flake material is desirable when the leaching resistance of an organic compound contained in a glass flake material needs to be improved. Although the reason why the addition of these substance(s) improves the characteristics has not yet been fully understood at present, it is believed that in the glass flake material of the present invention, the retention force that works on the organic compound improves because of an interaction between the phosphoric acid and the organic compound, or an action that occurs among the phosphoric acid or the phosphate compound, the oxide of the element other than phosphorus and the organic compound due to the presence of the phosphoric acid or the phosphate compound, or because the network of the oxide is strengthened due to the presence of the phosphoric acid or the phosphate compound.

It is recommended that alkoxide, carboxylate, nitrate, chloride, oxychloride, and the like be used as a hydrolyzable compound that is a source material of the oxide, which is the main component of the glass flake material, although alkoxide is preferable. It should be noted that, in the field of sol-gel processes, an alkoxide that is used as a source material is referred to as a "metal alkoxide," including the alkoxide of an element such as silicon that generally should be classified as a non-metallic element. The present specification also follows this convention and uses the term a "metal alkoxide" to include the alkoxides of non-metallic elements such as silicon.

Likewise, a source material such as a metal alkoxide may be generically referred to as a "metallic compound." Because the main component of the glass flake material needs to be an oxide of an element other than phosphorus, a compound free from phosphorus is used as the hydrolyzable compound. This compound may contain at least one element selected from, for example, silicon, titanium, aluminum, zirconium, and tantalum, or may be a metal alkoxide having the element(s) as "metal".

The metal alkoxide that is a source material of the glass flake material may preferably contain an element M and at least one -OR group bonded to the element M. Here, R is an alkyl group, and preferably is an alkyl group having 1 to 5 carbon atoms, such as a methyl group, an ethyl group, a propyl group, and an isopropyl group. The element M, however, may be bonded to a functional group other than the -OR group, for example, to an alkyl group, a phenyl group, or an acyl group. As discussed above, the element M is at least one element selected from, for example, silicon, titanium, aluminum, zirconium, and tantalum.

The metal alkoxide undergoes hydrolysis, whereby at least a part of the bonds represented as M-OR changes into M-OH. It then undergoes condensation polymerization (the condensation polymerization between M-OH and M-OH is dehydration condensation), forming the bonds represented as M-O-M, so that as the condensation polymerization proceeds, a network structure forms in which the bonds M-O-M spread like a net.

A phosphate compound that can supply proton in a polar solvent, such as a phosphoric monoester and a phosphodiester, may function as a hydrolysis catalyst in a sol-gel process, as well as the phosphoric acid. In the case that the phosphate compound does not function as a hydrolysis

catalyst or that the catalytic activity of the phosphate compound is insufficiently low, it is preferable to use an acid catalyst that has been used conventionally as a hydrolysis catalyst, such as hydrochloric acid, nitric acid, and sulfuric acid. It is also possible to use an organic acid such as trichloroacetic acid, trifluoroacetic acid, and para-toluenesulfonic acid as the acid catalyst. Even when the phosphate compound works as the hydrolysis catalyst sufficiently, it is possible to additionally use the acid catalysts that are free from phosphorus and are listed above.

In the manufacturing method of the present invention, a solution containing a hydrolysate of a hydrolyzable compound free from phosphorus, a phosphoric acid and/or a phosphate compound, and an organic compound is prepared as a coating solution. The procedure for preparing the solution is not particularly limited. For example, it may be obtained by preparing a solution in which a metal alkoxide, the compound that can be hydrolyzed and the hydrolysate of which can be dehydration-condensed, is dissolved and an organic pigment, the organic compound having a predetermined function, is dissolved or dispersed, and supplying phosphoric acid into the solution as a hydrolysis catalyst to allow the metal alkoxide to undergo hydrolysis, thereby causing solation of the solution. In this case, a lower alcohol such as methanol, ethanol, and isopropanol is suitable as the solvent.

Subsequently, the prepared solution is applied onto a substrate. The material for the substrate is not particularly limited, and such materials as glass, metal, semiconductor, ceramic, and resin may be used. In the case of using resin, however, it is preferable to select a material that has heat resistance that is higher than the boiling point of the solvent contained in the applied solution. From the viewpoint that a glass flake material with a flat

shape and a uniform thickness are desired, it is preferable that the surface on which the solution is applied be flat and smooth. An example of the substrate from which the glass flake material can easily peel off is stainless steel. The application of the solution onto the substrate may be carried out using known techniques. Specific examples that may be used include roll coating (such as flexographic printing), various printing techniques such as screen printing, spin coating, spray coating, curtain coating, dip coating, and flow coating. The film formed by applying the solution is dried on the substrate.

There are no restrictions on the technique for the drying. In order to promote the removal of the solvent, it is preferable that the solution be dried by heating the substrate at a temperature that does not decompose the organic compound contained in the glass flake material and is lower than the heat resistance temperature of the substrate. Preferable temperatures in the drying process by heating the substrate are in the range of from 8O ⁰ C to 250 ⁰ C, for example.

As the drying proceeds, the film on the substrate shrinks, developing cracks due to the stress associated with the shrinkage. These cracks extend and finally the film peels off from the substrate, forming the glass flake material. In the case that the glass flake material does not peel off automatically, it may be peeled off from the substrate by applying an external force thereto. To peel off and collect the glass flake material, it may be drawn by vacuum, scraped with a brush or the like. It should be noted that although the above-described method according to the present invention is most simple and suitable for mass

production for producing the glass flake material according to the present invention, it should not be construed that the method of manufacturing a glass flake material of the present invention is limited to the method according to the present invention. The glass flake material of the present invention may also be manufactured by, for example, forming flat-shaped liquid of metal oxide in the air by spraying the coating solution into the air at high speed, and drying it as it is. In addition, although the glass flake material of the present invention contains an organic compound and has the above-described oxide as its main component, it may contain other components, such as hydroxide, halide, and nitride. EXAMPLES

Hereinbelow, the present invention is described in further detail with reference to examples thereof, but it should be noted that the following examples as well as the foregoing are merely illustrative examples of the preferable embodiments of the present invention. (Example 1)

In Example 1, tetramethoxysilane was used as the hydrolyzable compound, and phosphoric acid (orthophosphoric acid^ H3PO4) was used as the hydrolysis catalyst for tetramethoxysilane. Acid Red 27 (trisodium 3-hydroxy4-(4-sulfonato-l-naphthylazo)-2,7-naphthalenedisulf onate), which is an organic pigment (acid dye), was used as the water-soluble organic compound.

66.0 g of isopropanol, 57.5 g of tetramethoxysilane (made by Tokyo Kasei Corp.) and 0.06 g of Acid Red 27 were mixed together, and 102 g of a 0.05 mol/L (O.IN) aqueous phosphoric acid solution was dropped thereto and stirred at 25°C for 24 hours, to thus obtain a sol.

Next, the resultant sol was applied onto a stainless steel (SUS304) substrate with a size of 100 mm x 100 mm by spin coating at a rate of 10 revolutions per second (600 rpm), to thus form a film. The resultant substrate was set aside for 30 seconds after the application, and thereafter put into a muffle furnace the temperature of which had been elevated in advance to 200 ⁰ C, for 60 seconds for drying. In this drying process, water and methanol that are generated in the condensation polymerization as well as isopropanol used as the solvent come off from the film. After the drying, a glass flake material that automatically peeled off from the substrate was collected.

The thickness t of the resultant glass flake material was about 1 μm. The particle size a thereof was about 5 μm to 50 μm. It should be noted that the glass flake materials obtained in the following examples and comparative examples as well had like thickness t and like particle size a. The glass flake material obtained from Example 1 was glass flakes containing Acid Red 27 in an amount of about 2.5 mass % of the total, and phosphoric acid equivalent to about 1.4 mole % of the oxide.

The leaching property of the resultant glass flake material was measured in the following manner. First, 50 mg of the glass flake material was measured off in a sample bottle, and 10 g of water was added thereto, followed by stirring with a magnetic stirrer at a speed of 8.33 revolutions per second (500 rpm) for 1 hour. It should be noted that this rotation speed of the stirrer is high enough so that the leaching amount will not change if the stirring is made at a higher rate. After the glass flake material was removed from this suspension by suction filtration, the absorption peak intensity at 522 nm, originated from Acid Red 27, was observed with a visible

spectrophotometer (Shimadzu Corp.: UV- 3100), and from the peak intensity, the amount of the pigment that was eluted from the glass flake material was determined.

As the result of the above-described measurement, it was found that 0.19% of the pigment contained in the glass flake material leached out. (Example 2)

In Example 2, the concentration of the phosphate acid was varied from that in Example 1.

A glass flake material was obtained in the same manner as in Example 1 including the amount of phosphoric acid dropped, except that the concentration of the phosphoric acid dropped was changed from 0.05 mol/L to 0.005 mol/L (0.01N).

With the resultant glass flake material, the amount of the pigment that leached out was measured in the same manner as in Example 1 and found to be 0.16%.

The glass flake material obtained from Example 2 contains phosphoric acid equivalent to about 0.14 mole % of the oxide. (Example 3)

In Example 3 also, the concentration of the phosphate acid was varied from that in Example 1.

A glass flake material was obtained in the same manner as in Example 1 including the amount of phosphoric acid dropped, except that the concentration of the phosphoric acid dropped was changed from 0.05 mol/L to 0.5 mol/L (IN). With the resultant glass flake material, the amount of the pigment that leached out was measured in the same manner as in Example 1 and

found to be 0.22%.

The glass flake material obtained from Example 3 contains phosphoric acid equivalent to about 14 mole % of the oxide. (Example 4) In Example 4, a glass flake material was obtained in the same manner as in Example 1, except that the organic compound (organic pigment) was changed.

A glass flake material was obtained in the same manner as in Example 1, except that the organic pigment added to the solution was changed from 0.06 g of Acid Red 27 to 0.11 g of Acid Green 1 (sodium tris(l,2-naphthalenedione l-oximato-O,O')ferrate(II)).

With the resultant glass flake material, the amount of the pigment that leached out was measured in the same manner as in Example 1 and found to be 0.08%. The absorption peak intensity measured in the present example was 715 nm, originating from Acid Green 1.

The glass flake material obtained from Example 4 contains Acid Green 1 in an amount of about 5 mass % of the total. (Comparative Example l)

In Comparative Example 1, a glass flake material was obtained in the same manner as in Example 1, except that the acid was changed.

A glass flake material was obtained in the same manner as in Example 1, except that 0.1 mol/L (0.1N) nitric acid was used in place of the phosphoric acid. With the resultant glass flake material, the amount of the pigment that leached out was measured in the same manner as in Example 1 and found to be 0.58%. (Comparative Example 2)

In Comparative Example 2 as well, a glass flake material was obtained in the same manner as in Example 1, except that the acid was changed.

A glass flake material was obtained in the same manner as in Example 1, except that 0.05 mol/L (0.1N) sulfuric acid was used in place of the phosphoric acid. With the resultant glass flake material, the amount of the pigment that leached out was measured in the same manner as in Example 1 and found to be 0.69%. (Comparative Example 3) In Comparative Example 3, a glass flake material was obtained in the same manner as in Example 4, except that the acid was changed.

A glass flake material was obtained in the same manner as in

Example 4, except that 0.1 mol/L (0.1N) nitric acid was used in place of the phosphoric acid. With the resultant glass flake material, the amount of the pigment that leached out was measured in the same manner as in Example 1 and found to be 0.42%.

The results in the foregoing examples and comparative examples are summarized in Table 1 below.

As shown in Table 1, the leaching resistance of the organic compounds (Acid Red 27, Acid Green l) to water is greatly improved by introducing phosphorus. Regarding Acid Red 27, it was demonstrated that, by adding phosphorus, the amount of the water-soluble organic compound (organic pigment) that leached out was reduced to 0.5% or less of the total when 50 mg of the glass flake material having the above-described dimensions and containing Acid Red 27 in an amount of 2.5 mass % of the total was stirred with 10 g of water at a sufficient speed for 1 hour.

In the foregoing examples, silicon and phosphoric acid were used as the element other than phosphorus and the source of phosphorus, respectively. However, it is possible to obtain the advantageous effect of improving the leaching resistance of the organic compound likewise by using an oxide of an element other than silicon or adding a phosphate compound in place of the phosphoric acid.

TABLE 1

The present invention makes available a glass flake material in which the leaching resistance of the organic compound is improved and that can be manufactured by a method suitable for mass production. This glass flake material containing the organic compound has great utility value since it can improve the leaching resistance of the organic compound in various products in which the conventional glass flake materials have been used.