JP6942688B2 - Composition for transparent silica glass and its manufacturing method - Google Patents

Description

The present invention relates to a composition for transparent silica glass, transparent silica glass, and a method for producing the same.

At present, the white LED market is expanding greatly, and high heat resistance and high impact resistance of resins are required as the brightness of chips is increased. Currently, silicone resins are mainly used for high brightness LEDs.

Recently, UV LEDs have been developed for sterilization applications. Since UV LEDs mainly emit light in a wavelength region of 400 nm, extremely high heat resistance, impact resistance, and discoloration resistance are required. However, the silicone resin is decomposed when it is continuously exposed to light in the UV region, causing problems such as cracks and discoloration.

Therefore, at present, most of the LED structures have a glass or the like hermetically sealed with a reflector directly above the UV LED chip without adding an organic component. However, quartz glass is the only glass with a short wavelength and low absorption, which is very expensive in terms of price. Further, the LED structure can only be a flat plate structure with quartz glass, and it is difficult to mount a wide variety of lens structures and Fresnel structures.

Conventionally, a glass sintered body produced by molding and sintering a kneaded product of an inorganic powder and a binder has been known, but it has been difficult to obtain a highly pure and highly transparent molded product (). Patent Document 1). Further, there is a method of molding silica using a cellulose derivative such as methyl cellulose or methyl hydroxyethyl cellulose (Patent Documents 2 and 3) or polyvinyl alcohol (PVA) (Patent Document 4) as a binder and sintering the silica to produce transparent silica glass. Has been found. However, when the cellulose derivative is used as a binder, the moldability is good, but impurities in the cellulose derivative remain and it is difficult to exhibit high transparency. Further, when PVA is used as a binder as well, there is a problem in the transparency of the silica glass after sintering due to the inclusion of a plasticizer of PVA as an impurity, which makes mass production difficult. Further, although a method of sintering a silica-containing gel whose pH is adjusted by a sol-gel method is known (Patent Documents 5 and 6), the procedure of this production method is complicated, and mass production is difficult even with this method. Met.

From these facts, it has been required to develop high-purity and highly transparent transparent silica glass and a manufacturing method capable of efficiently mass-producing such transparent silica glass.

Japanese Unexamined Patent Publication No. 2008-266087 JP-A-2009-120444 Japanese Unexamined Patent Publication No. 2013-525156 Japanese Unexamined Patent Publication No. 2009-007185 Japanese Patent Application Laid-Open No. 2011-530468 Special Table 2010-502554

Therefore, in view of the above circumstances, it is an object of the present invention to provide a composition that becomes a highly pure and highly transparent transparent silica glass, and a transparent silica glass obtained from this composition. Another object of the present invention is to provide a manufacturing method capable of efficiently mass-producing high-purity and highly transparent transparent silica glass by converting the binder itself into silica.

In order to solve the above problems, in the present invention, the following components (A) and (B);
(A) Amorphous spherical silica particles having an average particle size of 0.01 to 150 μm and an aspect ratio of 1.00 to 1.50: 80 to 99.9 parts by mass (B) One or more Si Provided is a composition for transparent silica glass, which comprises 0.1 to 20 parts by mass of a binder which is a silazane compound having an −N bond and one or more Si—H groups.

In the case of a composition for transparent silica glass as in the present invention, when the binder which is the component (B) is degreased, all of the composition becomes silica, so that discoloration due to residual organic groups does not occur, and the composition is more transparent and has high purity. A transparent silica glass is obtained.

（式中、Ｒ^１、Ｒ^２、Ｒ^３はそれぞれ独立して、水素原子、または炭素数１〜１０の飽和脂肪族炭化水素基、炭素数６〜１２の芳香族炭化水素基から選ばれる基であり、１分子中の少なくとも１つのＲ^１は水素原子であり、ｎは前記重量平均分子量の範囲を満たす値である。） Further, it is preferable that the component (B) is a polysilazane compound having a weight average molecular weight of 1,000 to 2,000,000 represented by the following general formula (1).

(In the formula, R ¹ , R ² , and R ³ are independently selected from hydrogen atoms, saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms, and aromatic hydrocarbon groups having 6 to 12 carbon atoms. At least one R ¹ in one molecule is a hydrogen atom, and n is a value satisfying the range of the weight average molecular weight.)

By being polymerized in this way, a more dense glass film can be formed, and there is no risk of voids or cracks occurring during degreasing or sintering, resulting in a more transparent transparent silica glass.

Further, in the above formula (1), all of R ¹ , R ² and R ³ may be hydrogen atoms.

As described above ^{, if all of R 1} , R ² , and R ³ are hydrogen atoms, it is preferable because all of those that volatilize during degreasing and sintering do not have any component that affects transparency and are all silica.

（式中、Ｒ^２及びＲ^３はそれぞれ独立して、水素原子、または炭素数１〜１０の飽和脂肪族炭化水素基、炭素数６〜１２の芳香族炭化水素基から選ばれる基であり、ｘは１〜３の整数である。）
で示されるシラザンモノマーを含み、上記一般式（１）で表されるポリシラザン化合物と、上記一般式（２）で表されるシラザンモノマーとの割合が質量比で９９：１〜９９．９：０．１であることが好ましい。 In addition, the following general formula (2) is added to the component (B).

(In the formula, R ² and R ³ are independently selected from hydrogen atoms, saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms, and aromatic hydrocarbon groups having 6 to 12 carbon atoms. x is an integer from 1 to 3.)
The ratio of the polysilazane compound represented by the general formula (1) to the silazane monomer represented by the general formula (2) is 99: 1 to 99.9: 0 in terms of mass ratio. It is preferably 1.

If such a silazane monomer is contained, the wettability between silica and the polysilazane compound during molding can be improved, and voids and the like during molding can be reduced.

The present invention also provides transparent silica glass, which is a sintered body of the composition for transparent silica glass.

The transparent silica glass shown in the present invention is a highly pure and highly transparent transparent silica glass.

Further, the present invention relates to the following components (A) and (B);
(A) Amorphous spherical silica particles having an average particle size of 0.01 to 150 μm and an aspect ratio of 1.00 to 1.50: 80 to 99.9 parts by mass (B) One or more Si Binder, which is a silican compound having an −N bond and one or more Si—H groups: After the step of preparing a composition containing 0.1 to 20 parts by mass, the composition is molded to form a molded product. Step, then the step of heating the molded product at 400 to 1,200 ° C. for 10 minutes to 12 hours to degrease, and further heating the degreased molded product at 1,400 to 1,900 ° C. for 1 to 60 minutes. Provided is a method for producing transparent silica glass, which comprises a step of sintering.

With the production method as in the present invention, since all the silicon species constituting the binder are changed to silica, high-purity and highly transparent transparent silica glass can be efficiently mass-produced.

（式中、Ｒ^１、Ｒ^２、Ｒ^３はそれぞれ独立して、水素原子、または炭素数１〜１０の飽和脂肪族炭化水素基、炭素数６〜１２の芳香族炭化水素基から選ばれる基であり、１分子中の少なくとも１つのＲ^１は水素原子であり、ｎは前記重量平均分子量の範囲を満たす値である。） Further, as the component (B), it is preferable to use a polysilazane compound having a weight average molecular weight of 1,000 to 2,000,000 represented by the following general formula (1).

(In the formula, R ¹ , R ² , and R ³ are independently selected from hydrogen atoms, saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms, and aromatic hydrocarbon groups having 6 to 12 carbon atoms. At least one R ¹ in one molecule is a hydrogen atom, and n is a value satisfying the range of the weight average molecular weight.)

With such a manufacturing method using the component (B), a finer glass film can be formed, and there is no risk of voids or cracks occurring during degreasing or sintering, and a more transparent transparent silica glass. Can be manufactured.

At this time, in the above formula (1), all of R ¹ , R ² , and R ³ may be hydrogen atoms.

A production method using such a component (B) is preferable because all of the components that volatilize during degreasing and sintering do not remain and are all silica.

（式中、Ｒ^２及びＲ^３はそれぞれ独立して、水素原子、または炭素数１〜１０の飽和脂肪族炭化水素基、炭素数６〜１２の芳香族炭化水素基から選ばれる基であり、ｘは１〜３の整数である。）
で示されるシラザンモノマーを含み、上記一般式（１）で表されるポリシラザン化合物と、上記一般式（２）で表されるシラザンモノマーとの割合が質量比で９９：１〜９９．９：０．１であることが好ましい。 Further, the following general formula (2) is added to the component (B).

(In the formula, R ² and R ³ are independently selected from hydrogen atoms, saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms, and aromatic hydrocarbon groups having 6 to 12 carbon atoms. x is an integer from 1 to 3.)
The ratio of the polysilazane compound represented by the general formula (1) to the silazane monomer represented by the general formula (2) is 99: 1 to 99.9: 0 in terms of mass ratio. It is preferably 1.

With such a production method using the component (B), the wettability between silica and the polysilazane compound during molding can be improved, and voids and the like during molding can be reduced.

As described above, since the composition for transparent silica glass of the present invention uses a silazane compound in which all silicon species become silica when degreased as a binder, the affinity with amorphous spherical silica particles is dramatically improved. It is improved and cracks, voids, and devitrification are suppressed, so that the glass becomes highly transparent transparent silica glass. In addition, there are very few impurities that cause devitrification, resulting in high-purity transparent silica glass. Furthermore, the Si—N bond contained in the binder binds to the amorphous spherical silica particles and changes to a Si—O bond during degreasing and sintering, which further contributes to the formation of a chemical bond with silica, and thus is transparent. Is very high, and it becomes silica glass with excellent transmittance in a wide range of wavelengths.

Further, in the method for producing transparent silica glass of the present invention, by using a silazane compound as a binder, discoloration during degreasing and sintering can be reduced to the utmost, and all silicon species are converted to silica. Therefore, the volume shrinkage during degreasing and sintering can be reduced as much as possible as compared with the conventional binder. Furthermore, since it is not necessary to use a condensation catalyst or the like when kneading the binder and the amorphous spherical silica particles, metal impurities such as metal elements caused by the catalyst can be reduced, so that high-quality transparent silica glass can be inexpensively produced. It can be easily manufactured, and the process can be rationalized at the time of mass production.

As described above, there has been a demand for the development of high-purity and highly transparent transparent silica glass and a manufacturing method capable of efficiently mass-producing such transparent silica glass.

As a result of diligent studies to achieve the above object, the present inventors have found that high-purity and highly transparent transparent silica glass can be produced inexpensively and easily by using a silazane compound as a binder. Completed.

That is, the present invention describes the following components (A) and (B);
(A) Amorphous spherical silica particles having an average particle size of 0.01 to 150 μm and an aspect ratio of 1.00 to 1.50: 80 to 99.9 parts by mass (B) One or more Si A binder which is a silazane compound having an −N bond and one or more Si—H groups: a composition for transparent silica glass, which comprises 0.1 to 20 parts by mass.

Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

<Composition for transparent silica glass>
(A) Amorphous Spherical Silica Particles The amorphous spherical silica particles used in the present invention have an average particle size in the range of 0.01 to 150 μm and an aspect ratio of 1.00 to 1.50. belongs to. The average particle size of the amorphous spherical silica particles is preferably 0.05 to 100 μm, more preferably 0.1 to 10 μm. If the average particle size is less than 0.01 μm, micro voids are generated during sintering, which is not preferable, and if it exceeds 150 μm, voids between silicas are generated during sintering, which is not preferable.

The aspect ratio of the amorphous spherical silica particles is preferably 1.00 to 1.40, more preferably 1.00 to 1.20. If the aspect ratio exceeds 1.50, high filling of silica causes voids during sintering, which is not preferable. The lower limit of the aspect ratio is also limited in the same manner as the upper limit, but it is desirable that the amorphous spherical silica particles are closer to a sphere.

In the present invention, the average particle size of the amorphous spherical silica particles refers to the value of the volume average diameter of the particles measured by the dynamic light scattering method, and the aspect ratio is the major axis (D) according to the image taken by SEM. ) And the minor axis (d), that is, the value measured as D / d.

Further, as the amorphous spherical silica particles used in the present invention, metallic silicon called a sol-gel method, hydrolysis of chlorosilane, or VMC method is used in an oxygen stream rather than those produced from natural silica. It is preferable to use one that is synthesized by dispersing, igniting, and cooling, and the amount of impurities often contained in spherical silica particles such as aluminum, sodium, and iron is reduced to the utmost by metal removal purification. In the present invention, the amount of impurities refers to the element content measured by an inductively coupled plasma emission spectrophotometer (ICP-OES) and quantified by an absolute calibration curve method. The aluminum content in the amorphous spherical silica particles is preferably 0.1 to 50 ppm, more preferably 0.1 to 10 ppm. The smaller the aluminum content, the better, but considering the cost, it is sufficient to remove up to 0.1 ppm, and if it is 50 ppm or less, amorphous spherical silica particles at the time of sintering that cause devitrification. The progress of crystallization of silica can be suppressed. The sodium content in the amorphous spherical silica particles is preferably 0.01 to 1 ppm, more preferably 0.05 to 1 ppm. The smaller the sodium content, the better, but considering the cost and the like, it is sufficient to remove up to 0.01 ppm, and if it is 1 ppm or less, the occurrence of devitrification during sintering can be suppressed. Further, the iron content in the amorphous spherical silica particles is preferably 0.1 to 5 ppm, more preferably 0.1 to 2 ppm. The smaller the iron content, the better, but considering the cost and the like, it is sufficient if the iron content can be removed up to 0.1 ppm, and if it is 5 ppm or less, the occurrence of devitrification during sintering can be suppressed.

Examples of the types of amorphous spherical silica particles include amorphous silica balloons, mesoporous silica, silica gel and stechobite, and quartz.

The content of the component (A) is 80 to 99.9 parts by mass, preferably 85 to 99.5 parts by mass, more preferably 85 to 99.5 parts by mass, out of a total of 100 parts by mass of the component (A) and the component (B) described later. It is 90 to 99.5 parts by mass. If the content of the component (A) is less than 80 parts by mass, the stress of the binder cannot withstand during sintering and cracks occur, which is not preferable. It is not preferable because the binding effect is not sufficiently exhibited.

(B) Silazane compound The silazane compound used as the component (B) of the present invention closely chemically binds the amorphous spherical silica particles of the component (A) to each other to create voids during sintering as much as possible. It plays the role of a binder added to reduce the amount. The component (B) is characterized by being a silazane compound having one or more Si—N bonds and one or more Si—H groups.

The silazane compound is preferably a polysilazane compound having a weight average molecular weight of 1,000 to 2,000,000 represented by the following general formula (1).

Here, R ¹ , R ² , and R ³ are independently selected from hydrogen atoms, saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms, and aromatic hydrocarbon groups having 6 to 12 carbon atoms. Yes, at least one R ¹ in one molecule is a hydrogen atom, and n is a value satisfying the range of the weight average molecular weight.
The saturated aliphatic hydrocarbon group preferably has 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, and specifically, a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, or an isobutyl group. , T-butyl group, pentyl group, neopentyl group, hexyl group, octyl group, nonyl group, decyl group and other alkyl groups; cyclopentyl group, cyclohexyl group, norbornyl group, adamantyl group and other cycloalkyl groups.
The aromatic hydrocarbon group preferably has 6 to 10 carbon atoms, more preferably 6 to 7 carbon atoms, and specifically, an aryl group such as a phenyl group, a tolyl group, a xsilyl group, or a naphthyl group; a benzyl group. , Phenylethyl group, aralkyl group such as phenylpropyl group and the like, and phenylmethyl group is preferable.

Provided that at least one in one molecule, and preferably 2 or more of ^{R 1} is a hydrogen atom, more preferably all of the ^{R 1,} R 2, ^{R 3} is a hydrogen atom. By using perhydropolysilazane (hereinafter abbreviated as PHPS) in which all of R ¹ , R ² , and R ³ are hydrogen atoms, there are no components that affect the transparency of those that volatilize during degreasing and sintering. It is more preferable because it becomes all silica and a transparent silica glass having high purity can be obtained.

The weight average molecular weight of the polysilazane compound is 1,000 to 2,000,000, more preferably 1,000 to 500,000, and even more preferably 1,000 to 100,000.

In addition, said n is a value satisfying the range of this weight average molecular weight. Specifically, it is 20 to 22,000, preferably 20 to 13,000. In the present invention, the weight average molecular weight refers to the weight average molecular weight using polystyrene as a standard substance measured by gel permeation chromatography (GPC) under the following conditions.

[Measurement condition]
Developing solvent: tetrahydrofuran (THF)
Flow rate: 0.6 mL / min
Detector: Differential Refractometer (RI)
Column: TSK Guardcolum SuperMP-M
TSKgel Supermulti HZ-M (6.0 mm ID x 15 cm x 4) (both manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Sample injection volume: 20 μL (THF solution with a concentration of 0.1 wt%)

As the silazane compound of the component (B), in addition to the polysilazane compound represented by the above formula (1), a silazane monomer represented by the following formula (2) may be used in combination.

In the above formula, R ² and R ³ are independently hydrogen atoms or saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms, preferably 1 to 4 carbon atoms, and 6 to 12 carbon atoms, preferably 6 to 10 carbon atoms. It is a group selected from aromatic hydrocarbon groups, and specifically, the same group as the example given in the above formula (1) can be exemplified. Of these, a combination of a saturated aliphatic hydrocarbon group having 1 to 4 carbon atoms ^{in R 2 and a hydrogen atom in R 3} is preferable. x is an integer of 1-3, preferably 1 or 2.

In addition, these silazane monomers may be used alone or in mixture of 2 or more types. Moreover, it is not limited to these.

The combined use of the silazane monomer is preferable because the wettability between the silica and the polysilazane compound during molding can be improved and voids and the like during molding can be reduced. Further, the compounding ratio (ratio) of (1) polysilazane compound and (2) silazane monomer can be (1) :( 2) = 95: 5-99.9: 0.1 as a mass ratio, which is preferable. Is 99: 1 to 99.9: 0.1. If the amount of the silazane monomer is 0.1 parts by mass or more, the void suppressing effect is easily obtained, and if it is 5 parts by mass or less, the silicon atom bonded to the carbon of the silazane portion is less likely to be distorted, so that the occurrence of cracks is suppressed. preferable.

The content of the component (B) is 0.1 to 20 parts by mass, preferably 0.1 to 10 parts by mass, and more preferably 0. 1 to 5 parts by mass. If the content of the component (B) is less than 0.1 parts by mass, the binding effect of the silazane compound of the component (B) is not sufficiently exhibited, which is not preferable. If it exceeds 20 parts by mass, the converted silica is used. It is not preferable because the stress is large and cracks occur.

In addition to the components (A) and (B), any component may be added to the composition for transparent silica glass of the present invention, depending on the intended purpose. Specific examples thereof include an organic solvent capable of diluting (B) such as xylene and dibutyl ether, and a non-functional silicone oil typified by KF-96 (manufactured by Shin-Etsu Chemical Co., Ltd.).

<Transparent silica glass>
The present invention provides transparent silica glass, which is a sintered body of the above composition for transparent silica glass.
Since the transparent silica glass of the present invention is produced using a silazane compound in which all silicon species become silica when degreased as a binder, the affinity with amorphous spherical silica particles is dramatically improved, and cracks and voids are formed. Since the occurrence of devitrification is suppressed, highly transparent transparent silica glass is obtained. In addition, there are very few impurities that cause devitrification, resulting in high-purity transparent silica glass. Furthermore, the Si—N bond contained in the binder binds to the amorphous spherical silica particles and changes to a Si—O bond during degreasing and sintering, which further contributes to the formation of a chemical bond with silica, and thus is transparent. Is very high, and it becomes silica glass with excellent transmittance in a wide range of wavelengths.
The transparent silica glass of the present invention can be produced by the method described below using the composition for transparent silica glass of the present invention.

<Manufacturing method of transparent silica glass>
In the present invention, the following components (A) and (B);
(A) Amorphous spherical silica particles having an average particle size of 0.01 to 150 μm and an aspect ratio of 1.00 to 1.50: 80 to 99.9 parts by mass (B) One or more Si Binder, which is a silican compound having an −N bond and one or more Si—H groups: After the step of preparing a composition containing 0.1 to 20 parts by mass, the composition is molded to form a molded product. Step, then the step of heating the molded product at 400 to 1,200 ° C. for 10 minutes to 12 hours to degrease, and further heating the degreased molded product at 1,400 to 1,900 ° C. for 1 to 60 minutes. Provided is a method for producing transparent silica glass, which comprises a step of sintering. Hereinafter, each step will be described in detail.

Composition Preparation Step In the method for producing transparent silica glass of the present invention, first, a composition for transparent silica glass (composition for sintered body) containing the component (A) and the component (B) is prepared. As the component (A) and the component (B), the same components as those mentioned in the above description of the composition for transparent silica glass can be used, and thus the description thereof will be omitted here. The composition for transparent silica glass can be prepared by stirring, dissolving, mixing and dispersing each of the above-mentioned components simultaneously or separately with heat treatment if necessary, but is usually amorphous. It is preferable to mix the silazane compound (B) component with the spherical silica particle (A) component.

The device used for operations such as stirring when mixing the silazane compound (B) with the amorphous spherical silica particles (A) is not particularly limited, but a Raikai machine equipped with a stirring and heating device, three rolls, a ball mill, and a planeta. A Lee mixer, a rotating / revolving mixer, or the like can be used. Further, a method of diluting the silazane-based binder with an organic solvent and coating the amorphous spherical silica particles by spray-drying, a method of drying the solvent by a wet treatment as it is, a method of freeze-drying, or the like can also be used. Further, these devices and methods may be appropriately combined.

Molding Step In the method for producing transparent silica glass of the present invention, next, the composition for a sintered body prepared as described above is molded to form a molded product. The molding method is not particularly limited, and it may be molded into a desired shape by a known method.

Solventing Step In the method for producing transparent silica glass of the present invention, the molded product formed as described above is then heated at 400 to 1,200 ° C. for 10 minutes to 12 hours to degreas. The carbon component of the sintered body composition is gradually removed by degreasing. Without the degreasing process, the carbon component remaining during sintering will be carbonized, causing devitrification. The degreasing step is carried out at a maximum temperature of 400 to 1,200 ° C., preferably 400 to 1,000 ° C. for 10 minutes to 12 hours, preferably in an atmosphere of an inert gas such as helium gas or nitrogen gas other than hydrogen chloride gas. Treat for 1-6 hours. If the temperature is lower than 400 ° C, degreasing does not proceed sufficiently, and silazane is not converted to silica and remains, which is not preferable because it is devitrified at the time of sintering. Not preferable.

Sintering Step In the method for producing transparent silica glass of the present invention, the molded product degreased (purified if necessary) as described above is then heated at 1,400 to 1,900 ° C. for 1 to 60 minutes. Transparent silica glass is produced by sintering. The sintering conditions of the composition for transparent silica glass of the present invention after degreasing are not particularly limited, but are usually 1,400 to 1,900 ° C. under an atmosphere of an inert gas such as helium gas or nitrogen gas. , Preferably, can be sintered at 1,500 to 1,900 ° C. If the temperature is lower than 1,400 ° C., sintering due to fusion between silicas does not proceed and devitrification occurs. If the temperature exceeds 1,900 ° C., crystallization of silica is promoted and devitrification occurs. The sintering time is 1 minute to 60 minutes, preferably about 1 to 30 minutes. If it is less than 1 minute, the silicas will not be sufficiently fused and will be devitrified. If it exceeds 60 minutes, the crystallization of silica is further promoted and the silica is devitrified.

Purification Step In the method for producing transparent silica glass of the present invention, a purification step which is a step of removing Al, Na, Fe and the like may be incorporated before the sintering step. When the purification step is performed, the maximum temperature is 1,000 to 1,500 ° C., preferably 1,000 to 1,300 ° C., more preferably 1,100 to 1,300 ° C. in a hydrogen chloride gas atmosphere. The treatment is carried out under the conditions of 5 to 5 hours, preferably 0.5 to 2 hours.

A manufacturing method including a purification step as described above is preferable because it is possible to manufacture transparent silica glass in which the occurrence of devitrification is further suppressed by removing impurities that may cause devitrification during sintering.

Inspection Step In the method for producing transparent silica glass of the present invention, in order to measure the transmittance from the ultraviolet region to the visible region as an inspection step after the sintering step, the method described in JIS K 7105: 1981 is used to make a transparent material having a thickness of 1 mm. A step of measuring the transmittance of silica glass can be added. The transmittance of light in the wavelength range of 250 to 300 nm is preferably 90% or more, and more preferably 92 to 100%. With such a light transmittance, it can be suitably used as a UV lens material having good brightness. By selecting transparent silica glass having light transmittance in the above range by an inspection step, only a high-purity and highly transparent transparent glass molded body can be obtained.

In such a method for producing transparent silica glass of the present invention, by using a silazane compound as a binder, discoloration and curing shrinkage after degreasing and sintering can be reduced to the utmost, and all silicon species are converted to silica. As a result, unlike conventional binders, volume shrinkage during degreasing and sintering can be reduced to the utmost limit. Further, since the catalyst caused by the binder and unnecessary elements can be reduced, high-quality transparent silica glass can be produced inexpensively and easily, and the process can be rationalized at the time of mass production.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. Further, in the following formula, Me is a methyl group.

The materials used in the Examples and Comparative Examples of the present invention are shown.
(A) Spherical silica particles As the spherical silica particles, those listed in Table 1 below were used.
For the average particle size, the value of the volume average diameter by a laser diffraction type particle size distribution measuring device (“Microtrac HRA (X-100)” manufactured by Nikkiso Co., Ltd.) was used.

As the aspect ratio, the ratio of the major axis (D) to the minor axis (d) obtained by using image analysis software (WINROOF2015 manufactured by Mitani Sangyo Co., Ltd.) and the value of D / d of the SEM image taken by the SEM were used.

The amount of metal impurities was measured by ICP-OES (730-ES ICP-OES manufactured by Agilent). After dissolving 0.3 g of the sample with hydrofluoric acid and nitric acid, the solution is heated to dryness, 0.5 mL of concentrated nitric acid and an appropriate amount of water are added to the dried product, and the mixture is heated and concentrated, and then reconstituted with water to 2 mL. The volume was adjusted and a measurement solution was prepared. From the obtained measured values, the amounts of Al, Fe, and Na were quantified by the absolute calibration curve method.

アドマファインＳＯ−Ｅ５、ＳＯ−Ｅ５高純度品：アドマテックス（株）製、非晶質
クリストバライト：フミテック（株）製、結晶性
ＥＭＩＸ−３００：（株）龍森製、非晶質
ＧＢ−ＡＣ：マコー（株）製、非晶質
ＭＫＣシリカ：日本化成（株）製、石英

Admafine SO-E5, SO-E5 High-purity product: Admatex Co., Ltd., Amorphous Cristobalite: Fumitech Co., Ltd., Crystalline EMIX-300: Ryumori Co., Ltd., Amorphous GB-AC : Mako Co., Ltd., Amorphous MKC Silica: Nippon Kasei Co., Ltd., Quartz

（ｎは重量平均分子量１，２００を満たす平均値）
で示される重量平均分子量１，２００のＰＨＰＳ
シラザン化合物Ｂ：前記式（３）（ただし、式中ｎは重量平均分子量５，０００を満たす平均値）
で示される重量平均分子量５，０００のＰＨＰＳ
シラザン化合物Ｃ：前記式（３）（ただし、式中ｎは重量平均分子量９００，０００を満たす平均値）
で示される重量平均分子量９００，０００のＰＨＰＳ
シラザン化合物Ｄ：下記式（４）

（ｍは重量平均分子量１０，０００を満たす平均値）
で示される重量平均分子量１０，０００の有機ポリシラザン
シラザン化合物Ｅ：下記式（５）

（ｎ，ｍはモル比で５０：５０であり、ｎ＋ｍが重量平均分子量３，０００を満たす平均値）
で示される重量平均分子量３，０００の無機・有機ハイブリッドポリシラザン
シラザンモノマー：ヘキサメチルジシラザン（信越化学工業（株）製 商品名ＳＺ−３１） (B) Cilazan compound As the cilazan compound of (B), the following was used.
Cilazan compound A: The following formula (3)

(N is an average value satisfying a weight average molecular weight of 1,200)
PHPS with a weight average molecular weight of 1,200 indicated by
Cilazan compound B: The above formula (3) (where n is an average value satisfying a weight average molecular weight of 5,000).
PHPS with a weight average molecular weight of 5,000 indicated by
Cilazan compound C: The above formula (3) (where n is an average value satisfying a weight average molecular weight of 900,000)
PHPS with a weight average molecular weight of 900,000 indicated by
Cilazan compound D: The following formula (4)

(M is an average value satisfying a weight average molecular weight of 10,000)
Organic polysilazane compound E with a weight average molecular weight of 10,000 represented by: the following formula (5)

(N and m have a molar ratio of 50:50, and n + m is an average value satisfying a weight average molecular weight of 3,000)
Inorganic / organic hybrid polysilazane with a weight average molecular weight of 3,000 indicated by bisilazan Monomer: Hexamethyldisilazane (trade name SZ-31 manufactured by Shin-Etsu Chemical Co., Ltd.)

Each binder composition was prepared in a comparative preparation example without using the silazane compound of (B).

(Comparative Preparation Example 1)
Instead of (B), 8 g of methyl cellulose (trade name: Metrose SM-4000, manufactured by Shin-Etsu Chemical Co., Ltd.) and 92 g of water were added and mixed with a planetary mixer to prepare a methyl cellulose binder composition.

(Comparative Preparation Example 2)
Instead of (B), 8 g of polyvinyl alcohol (PVA) and 92 g of pure water were added and mixed using a rotating and revolving mixer at 2,000 rpm for 1 minute and then at 2,200 rpm for 1 minute to prepare a PVA binder composition. Made.

(Comparative Preparation Example 3)
Instead of (B), tetramethoxysilane (KBM-04 manufactured by Shin-Etsu Chemical Co., Ltd.) was used.

(Comparative Preparation Example 4)
Vinyl dimethyl silazane (SZ-1021 manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of (B).

(Examples 1 to 12, Comparative Examples 1 to 10)
Each silica particle was mixed with silazane compounds A to E and other binder compositions or organosilicon compounds prepared in Comparative Preparation Examples 1 to 4, and the following characteristics were measured. The results are shown in Tables 2 and 3.

[Moldability]
The composition after mixing the silica particles is injected into a mold of 30 × 30 × 1 mm, and molded by heating at 80 ° C. × 5 minutes at a molding pressure of 0.5 MPa using a compression molding machine (manufactured by TOWA Corporation). It was confirmed whether or not the flow mark, unfilled and cracks were generated in the molded product.

[Transmittance]
A sample molded under the same conditions as the evaluation of moldability was degreased by heating at 500 ° C. for 1 hour, and then heated at 1,750 ° C. for 10 minutes using a firing furnace (VESTA manufactured by Shimadzu Industrial Machinery Systems Co., Ltd.). Sintered. For the sample after sintering, the transmittance of light in the wavelength range of 200 to 800 nm was measured with an ultraviolet-visible spectrophotometer (U-4100 manufactured by Hitachi Techno System Co., Ltd.) at a scanning speed of 300 nm / min, and the wavelength was 250 nm. And the light transmittance at 300 nm was evaluated. If the sintered product had cracks or the like and could not be measured, it was described as "not measurable".

[exterior]
The appearance of the sintered sample used in the evaluation of the transmittance was visually evaluated, and the color tone, transparency, presence or absence of cracks, etc. were evaluated. If it is colorless and transparent and has no cracks, it is described as "colorless and transparent", and if there is any abnormality, it is described in Tables 2 and 3.

[Amount of impurities after sintering]
The amount of metal impurities after sintering was measured by ICP-OES (Agilent 730-ES ICP-OES). After dissolving 0.3 g of the sample with hydrofluoric acid and nitric acid, the solution is heated to dryness, 0.5 mL of concentrated nitric acid and an appropriate amount of water are added to the dried product, and the mixture is heated and concentrated, and then reconstituted with water to 2 mL. The volume was adjusted and a measurement solution was prepared. From the obtained measured values, the amounts of Al, Fe, and Na were quantified by the absolute calibration curve method. The results are shown in Tables 2 and 3.

As shown in Table 2, the transparent silica glasses produced in Examples 1 to 12 had good moldability, no dullness, high transparency and high purity, and could be easily produced.

As shown in Tables 2 and 3, in Comparative Examples 5 to 7 in which a compound containing no or both of Si—N bond and Si—H group was used as a binder, cracks and uncured during molding occurred. The moldability was very poor, and cracks occurred because the binder and silica were not densely present at the time of sintering. In addition, Comparative Examples 1 to 4 in which methyl cellulose was used instead of the component (B) and Comparative Examples 8 and 9 in which PVA was used contained a large amount of impurities. In Comparative Example 10 using crystalline silica particles, the transmittance was low.

From the above, it has been clarified that according to the present invention, high-purity and highly transparent transparent silica glass can be easily produced.

The present invention is not limited to the above embodiment. The above-described embodiment is an example, and any object having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same effect and effect is the present invention. Is included in the technical scope of.

Claims (8)

The following components (A) and (B);
(A) Amorphous spherical silica particles having an average particle size of 0.01 to 150 μm and an aspect ratio of 1.00 to 1.50: 80 to 99.9 parts by mass (B) One or more Si A composition for transparent silica glass, which comprises 0.1 to 20 parts by mass of a binder, which is a silazane compound having an −N bond and one or more Si—H groups. The composition for transparent silica glass according to claim 1, wherein the component (B) is a polysilazane compound having a weight average molecular weight of 1,000 to 2,000,000 represented by the following general formula (1). ..

(In the formula, R ¹ , R ² , and R ³ are independently selected from hydrogen atoms, saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms, and aromatic hydrocarbon groups having 6 to 12 carbon atoms. At least one R ¹ in one molecule is a hydrogen atom, and n is a value satisfying the range of the weight average molecular weight.) The composition for transparent silica glass according to claim 2, wherein in the formula (1), all of R ¹ , R ² , and R ^{3 are hydrogen atoms.} The following general formula (2) is added to the component (B).

(In the formula, R ² and R ³ are independently selected from hydrogen atoms, saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms, and aromatic hydrocarbon groups having 6 to 12 carbon atoms. x is an integer from 1 to 3.)
The ratio of the polysilazane compound represented by the general formula (1) to the silazane monomer represented by the general formula (2) is 99: 1 to 99.9: 0 in terms of mass ratio. The composition for transparent silica glass according to claim 2 or 3, wherein the composition is 1. The following components (A) and (B);
(A) Amorphous spherical silica particles having an average particle size of 0.01 to 150 μm and an aspect ratio of 1.00 to 1.50: 80 to 99.9 parts by mass (B) One or more Si Binder, which is a silican compound having an −N bond and one or more Si—H groups: After the step of preparing a composition containing 0.1 to 20 parts by mass, the composition is molded to form a molded product. Step, then the step of heating the molded product at 400 to 1,200 ° C. for 10 minutes to 12 hours to degrease, and further heating the degreased molded product at 1,400 to 1,900 ° C. for 1 to 60 minutes. A method for producing transparent silica glass, which comprises a step of sintering. The method for producing transparent silica glass according to claim 5 , wherein a polysilazane compound having a weight average molecular weight of 1,000 to 2,000,000 represented by the following general formula (1) is used as the component (B). ..

(In the formula, R ¹ , R ² , and R ³ are independently selected from hydrogen atoms, saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms, and aromatic hydrocarbon groups having 6 to 12 carbon atoms. At least one R ¹ in one molecule is a hydrogen atom, and n is a value satisfying the range of the weight average molecular weight.) The method for producing transparent silica glass according to claim 6 , wherein in the formula (1), all of R ¹ , R ² , and R ³ are hydrogen atoms. The following general formula (2) is added to the component (B).

(In the formula, R ² and R ³ are independently selected from hydrogen atoms, saturated aliphatic hydrocarbon groups having 1 to 10 carbon atoms, and aromatic hydrocarbon groups having 6 to 12 carbon atoms. x is an integer from 1 to 3.)
The ratio of the polysilazane compound represented by the general formula (1) to the silazane monomer represented by the general formula (2) is 99: 1 to 99.9: 0 in terms of mass ratio. The method for producing a transparent silica glass according to claim 6 or 7 , characterized in that the present invention is 1.