JP7003474B2 - Method for manufacturing silicon oxide thin film laminate - Google Patents

Description

The present invention relates to a method for producing a silicon oxide thin film laminate, and more particularly to a method for producing a silicon oxide thin film laminate in which a porous silicon oxide thin film is laminated on the surface of a plastic base material.

As a method for forming a silicon oxide thin film, a sol solution containing an inorganic compound of at least one element selected from the group consisting of silicon, aluminum, zirconium, and hafnium, which is formed by the sol-gel method, is applied onto a substrate. However, there is known a method for forming a silicon oxide thin film that irradiates an ultraviolet ray of at most 100 mJ / cm ² while heat-treating to a temperature not exceeding 200 ° C. (Patent Document 1).

Japanese Unexamined Patent Publication No. 2002-187738

By the way, when the above method, which requires a heating step, is applied to a plastic base material, deterioration of the base material is unavoidable, and it is difficult to obtain a highly accurate optical member such as an antireflection fill. In addition, considering the difficulty of uniform heat treatment, there is a problem that productivity is inferior because it is not possible to form a large area film and it is difficult to form a film in a short time.

The present invention has been made in view of the above circumstances, and an object thereof is a method for manufacturing a silicon oxide thin film laminate in which a porous silicon oxide thin film is laminated on the surface of a plastic base material, and does not require a heating step. Therefore, it is an object of the present invention to provide a method for manufacturing a silicon oxide thin film laminate, which can be applied to a highly accurate optical member and can form a large area and a short time film formation.

In order to achieve the above-mentioned problems, the present inventors skillfully utilize the hydrolyzable silane compound in the sol-gel method, and if ultraviolet irradiation is performed under specific conditions, the plastic base material does not require a heating step. It was found that a porous silicon oxide thin film can be formed on the surface of the sol-gel process.

The present invention has been completed based on the above findings, and the gist thereof is an oxidation containing a binder liquid consisting of a reaction composition obtained by hydrolyzing and condensing a hydrolyzable silane compound and silica fine particles. After applying the coating liquid for forming a silicon thin film to the surface of the plastic substrate, it is dried and cured by irradiating it with ultraviolet rays (excluding ultraviolet rays having an irradiation intensity of 100 mW / cm ² or less) in the presence of oxygen. It exists in a method for producing a characteristic silicon oxide thin film laminate.

Hereinafter, the present invention will be described in detail.

First, a binder liquid composed of a reaction composition obtained by hydrolyzing and condensing a hydrolyzable silane compound will be described.

The binder acts between the silica particles to form a silicon oxide thin film and also has an action of adhering the silicon oxide thin film to the surface of the base material, and the action is the properties of the reaction composition obtained by the difference in the preparation method. The ideal binder is a reaction composition rich in linear structure with a large amount of —OH groups. Then, if such an ideal binder is used, the adhesion of the silicon oxide thin film to the substrate can be remarkably improved.

In the preparation of the binder solution, a hydrolyzable silane compound composed of a bifunctional hydrolyzable silane compound and having a multimeric content of at least 50% by weight thereof is used to prepare the hydrolyzable silane compound in the absence of silica particles. It is preferable to carry out the above reaction by continuously dropping an acid catalyst aqueous solution into the dissolved hydrophilic solvent solution under stirring conditions.

The hydrolyzable silane compound is a silane compound having a hydrolyzable group such as an alkoxy group, an alkoxyalkoxy group, an acyloxy group, an aryloxy group, an aminoxy group, an amide group, a ketooxime group, an isocyanate group and a halogen atom.

Among the above, an alkoxysilane compound is preferably used. Examples of the alkyl group of the alkoxy group (−OR) include lower alkyl groups such as a methyl group, an ethyl group, a propyl group and a butyl group. Those having 1 to 4 functionalities are known depending on the number of hydrolyzable groups.

Typical examples of alkoxysilane compounds are dimethyldimethoxysilane (DMDMS), methyltrimethoxysilane (MTMS), tetramethoxysilane (TMS), dimethyldiethoxysilane (DMDES), methyltriethoxysilane (MTES), and tetraethoxysilane. (TEOS) and the like.

The multimer of the hydrolyzable silane compound is a multimerized polymerization (oligomerization) of the above-mentioned monomers by condensation. In this reaction, first, a silanol group (-Si-OH) is formed by hydrolysis of the alkoxy group. At the same time, alcohol (R-OH) is produced. Next, a siloxane bond (—Si—O—Si—O—) is formed by (dehydration) condensation of silanol groups, and this condensation is repeated to form a siloxane oligomer. As the multimer of the alkoxysilane compound, a multimer of tetramethoxysilane in which R is a methyl group or a multimer of tetraethoxysilane in which R is an ethyl group is preferable from the viewpoint of hydrolyzability and condensability of the alkoxy group. ..

The structure of the multimer includes a linear structure, a branched structure, a cyclic structure, and a network structure. If the multimer of tetraalkoxysilane is shown as having a linear structure, it is represented by the following general formula. ..
[Chemical 1]
RO (Si (OR) ₂ O) _n R ... (I)

In the general formula, n represents the degree of mulching of multimers. Usually available multimers are compositions of multimers with different n and therefore have a molecular weight distribution. The degree of mass increase is represented by an average of n.

The degree of increase in the amount of a tetrafunctional hydrolyzable silane compound such as tetraalkoxysilane or a multimer thereof may be expressed by "silica content". The "silica content" is the mass ratio of silica (SiO ₂ ) produced from the compound, and is obtained by stably hydrolyzing the compound and measuring the amount of silica produced by firing. Further, "silica content" also indicates the ratio of silica produced to one molecule of the compound, and is a value calculated by the following equation.
[Number 1]
Silica content (parts by mass) = degree of mass increase x molecular weight of SiO ₂ / molecular weight of the compound

The degree of mulching n is usually 2 to 100, preferably 2 to 70, and more preferably 2 to 50. Since such a multimer is already on the market, it is convenient to use it. As the degree of mulching n increases, the molecular weight of the produced binder increases and the molecular weight distribution becomes wider. Therefore, a multimer having a degree of mulching n of more than 100 is inappropriate.

Commercially available products of multimers of hydrolyzable silane compounds include MKC silicate MS51, MKC silicate MS56, MKC silicate MS57, MKC silicate MS56S (all are tetramethoxysilane multimers) manufactured by Mitsubishi Chemical Co., Ltd., and methyl manufactured by Corcote. Examples thereof include silicate 51 (multimer of tetramethoxysilane), methyl silicate 53A, ethyl silicate 40, ethyl silicate 48, ethyl silicate 40 manufactured by Tama Chemical Industry Co., Ltd., and silicate 45 (all of which are multimers of tetraethoxysilane).

The multimer ratio in the bifunctional hydrolyzable silane compound is preferably 70% by weight or more. When the amount of the multimer used is small, the hydrolysis and condensation reactions of the monomer reduce the OH groups and increase the branched, cyclic and reticulated structures in the reaction composition.

The hydrolysis and condensation reactions are carried out sequentially, and if silica particles are present in the reaction process (by heating), each component generated during the reaction is adsorbed on the surface of the silica particles. This adsorption is a strong state in which the OH groups of the binder component and the OH groups of the silica particles are hydrogen-bonded or siloxane bonds are formed, and the OH groups that contribute to the adhesion of the binder to the substrate and the increase in the strength of the silicon oxide thin film are present. It will decrease. In addition, the binder component adsorbed on the silica particles becomes a cross-linking point, which increases the branched structure and the network structure. On the other hand, the reaction product prepared in the absence of silica particles is rich in a linear structure having a large amount of OH groups. Therefore, a binder liquid is prepared in the absence of silica particles, and the obtained binder liquid and silica fine particles are mixed at room temperature to prepare a coating liquid for forming a silicon oxide thin film.

The above reaction is carried out by continuously dropping an acid catalyst aqueous solution into a hydrophilic solvent solution in which a hydrolyzable silane compound is dissolved under stirring conditions.

The hydrophilic solvent is not particularly limited as long as it can dissolve a multimer of the hydrolyzable silane compound, but is generally limited to alcohols such as methanol, ethanol, propanol and butanol, ethyl cellosolve, butyl cellosolve and propyl cellosolve. Cellulosolves such as, ethylene glycol, propylene glycol, glycols such as hexylene glycol are used.

The amount of the hydrophilic solvent used is not particularly limited, but is a ratio to 100 parts by weight of the hydrolyzable silane compound in consideration of the coatability of the coating liquid for forming a silicon oxide thin film prepared by mixing silica fine particles with the binder liquid. It is usually 0.1 to 100 times by weight, preferably 1 to 10 times by weight. Incidentally, the multimer of the hydrolyzable silane compound is a composition composed of components having different degrees of polymerization as described above, and the viscosity increases as the degree of polymerization increases. On the other hand, the commercially available product of the monomer, for example, dimethyldimethoxysilane, is usually a solution having a purity of 99% by weight.

The acid concentration in the aqueous acid catalyst solution is usually in the range of 0.1 to 0.0001% by weight, preferably 0.01 to 0.001% by weight. When the acid catalyst is used as such a low-concentration aqueous solution, a large amount of water is involved in the reaction system, and as a result, the reaction rate of the condensation reaction, which is a competitive reaction, can be suppressed. Therefore, the tendency is that the OH groups generated by hydrolysis disappear at an appropriate rate, and it becomes easy to obtain a reaction composition rich in a linear structure having a large amount of OH groups.

The amount of the acid catalyst used is usually 0.001 to 10 mmol, preferably 0, based on 100 mol of the total amount of hydrolyzable groups (typically alkoxy groups) of the hydrolyzable silane compound in the hydrophilic solvent solution. It is 0.01 to 10 mmol.

The acid catalyst aqueous solution is continuously dropped, and the dropping rate is appropriately selected so that the temperature in the reaction system does not rise sharply. The dropping rate of the acid catalyst aqueous solution is usually 1 to 10 ml / min, preferably 3 to 5 ml / min per 100 ml of the hydrophilic solvent solution. The dropped catalyst aqueous solution is immediately and uniformly diffused by stirring, and uniform hydrolysis is performed. As the stirring method, the method adopted in a normal chemical reaction can be adopted.

The hydrolysis and condensation reactions of the hydrolyzable silane compound are practically carried out sequentially and in parallel. From the viewpoint of obtaining a reaction composition rich in a linear structure containing a large amount of OH groups, it is preferable to carry out the hydrolysis and condensation reactions separately in the following three steps as much as possible. ..

(1) Hydrolysis reaction step:
This is done by dropping an acid catalyst aqueous solution into a hydrophilic solvent solution under stirring conditions. The reaction temperature is usually 5 to 50 ° C, preferably 10 to 40 ° C. If the reaction temperature is less than the above range, the hydrolysis reaction becomes too slow, and if it exceeds the above range, it becomes difficult to avoid the condensation reaction. The reaction temperature is controlled by the temperature and circulation amount of the refrigerant conducted on the jacket of the reactor, the dropping speed of the acid catalyst aqueous solution, and the like. If the boiling point of the hydrophilic solvent is low, the hydrolysis reaction is carried out under reflux conditions. The reaction time is usually 1 to 60 minutes, preferably 5 to 30 minutes.

The hydrolysis reaction is an exothermic reaction, and the temperature of the reaction solution usually rises by 1 to 15 ° C. In order to confirm that the hydrolysis reaction is substantially completed, it is preferable to continue stirring until the reaction temperature drops by 5 to 10 ° C. after the completion of dropping the acid catalyst aqueous solution.

(2) Condensation reaction step:
Following the above steps, the reaction temperature is raised as necessary and the reaction is carried out under stirring conditions. The reaction temperature is usually 40 to 80 ° C, preferably 50 to 60 ° C. If the reaction temperature is less than the above range, the condensation reaction becomes too slow, and if the reaction temperature exceeds the above range, it becomes difficult to avoid an excessive condensation reaction. The rate of temperature rise is usually 0.1 to 10 ° C./min.
The reaction time is usually 1 to 120 minutes, preferably 5 to 60 minutes.

(3) Condensation reaction stop step:
The reaction solution is cooled to stop the condensation reaction. The cooling temperature is usually 10 to 30 ° C. At this time, it is more effective to stop the condensation reaction by cooling dilution with which a hydrophilic solvent is added in order to reduce the concentration of the condensation reaction composition. The hydrophilic solvent is preferably the same as the reaction solvent, but another hydrophilic solvent may be used for adjusting the liquid property.

The amount of the hydrophilic solvent added is usually in the range of 50 to 150% by weight when expressed as the concentration of the hydrophilic solvent with respect to the total amount of the hydrolyzable silane compound, the hydrophilic solvent used for the reaction and the acid catalyst aqueous solution.

According to the above-mentioned step of stopping the condensation reaction by cooling dilution, the storage stability of the obtained binder liquid is improved, and it becomes possible to prepare a binder liquid that can be adjusted to a concentration that meets the requirements of each application.

The weight average molecular weight of the obtained reaction composition is determined by the above-mentioned condensation reaction step. The weight average molecular weight is usually 1000 to 5000, preferably 2000 to 4000. Such a molecular weight corresponds to a multimer having a degree of equalization n of 2 to 100.

The above weight average molecular weight is a value measured by gel permeation chromatography (GPC) under the following conditions.

[Solvent] Tetrahydrofuran [Device name] TOSOH HLC-8220GPC
[Column] TOSOH TSKgel Super HM-N (2) and HZ1000 (1) are connected and used.
[Column temperature] 40 ° C
[Sample concentration] 0.01% by mass
[Flow velocity] 0.6 ml / min
[Calibration curve] PEG (calibration curve based on 4-point cubic approximation with molecular weights of 20000, 4000, 1000, and 200 is used.

The binder liquid for forming a silicon oxide thin film composed of the above reaction composition is substantially transparent, and the turbidity is 10 or less as a result of measurement using a kaolin turbidity meter.

Next, the coating liquid for forming a silicon oxide thin film will be described. The coating liquid for forming a silicon oxide thin film is prepared by mixing the binder liquid obtained above with the silica fine particles.

The silica fine particles are not particularly limited, and are spherical non-aggregated silica fine particles having an average particle diameter of 5 to 100 nm, hollow non-aggregated silica fine particles having an average particle diameter of 10 to 100 nm, and chain aggregate having an average primary particle diameter of 5 to 100 nm. Examples thereof include silica fine particles composed of at least one type of silica fine particles. These are appropriately selected depending on the purpose of the silicon oxide thin film to be formed.

Specific examples of spherical non-aggregated silica fine particles include "Snowtex (registered trademark) -O", "Snowtex (registered trademark) -O-40", and "Snowtex (registered trademark)-" manufactured by Nissan Chemical Industries, Ltd. Examples include "OL", "Quatron (registered trademark) -PL-1", "Quatron (registered trademark) -PL-3", and "Quatron (registered trademark) -PL-7" manufactured by Fuso Chemical Industries.

Specific examples of the chain-aggregated silica fine particles include "Snowtex (registered trademark) -UP" (average length: 40 to 100 nm) and "Snowtex (registered trademark) -UP" (average) manufactured by Nissan Chemical Industry Co., Ltd. Length: 40-100 nm), "Snowtex® PS-M" (average length: 80-150 nm), "Snowtex® PS-MO" (average length: 80-150 nm), "Snowtex (registered trademark) PS-S" (average length: 80 to 120 nm), "Snowtex (registered trademark) PS-SO" (average length: 80 to 120 nm), "IPA-ST-UP" ( (Average length: 40 to 100 nm), "Fine Cataloid F-120" manufactured by Japan Catalytic Chemical Industry Co., Ltd. and the like can be mentioned.

The coating liquid for forming a silicon oxide thin film is prepared at an appropriate concentration in consideration of coatability when applied to a substrate, film thickness and smoothness of the coating film, and the like. The concentration adjustment is performed by adding the above-mentioned hydrophilic solvent, and this concentration adjustment can be performed before or after mixing the silica fine particles.

Next, the formation of the silicon oxide thin film will be described. The silicon oxide thin film is formed by applying a coating liquid for forming a silicon oxide thin film to the surface of a plastic substrate, and then drying and curing the thin film.

The plastic substrate may be a film (100 μm or less) or a thicker sheet. Incidentally, examples of the plastics include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), polyimide (PI), polymethylmethacrylate (PMMA), cycloolefin polymer (COP) and the like. The surface of the base material can be either surface-modified or untreated.

The application of the coating liquid is not particularly limited, and examples thereof include a dip coating method, a spin coating method, a die coating method, a spray coating method, a gravure coating method, a roll coating method, a curtain coating method, a screen printing method, and an inkjet printing method. can.

The coating film thickness is appropriately selected according to the purpose of the silicon oxide thin film to be formed. It is usually 50 to 5000 nm.

The above-mentioned drying is performed to remove the solvent, the drying temperature is usually 50 to 80 ° C., and a hot air dryer or the like is preferably used. The drying time is usually 1 to 10 minutes, preferably 1 to 5 minutes.

The above curing treatment is mainly performed to bond the silanol group (Si—OH) contained in the binder solution with an oxygen-containing functional group such as a hydroxyl group or a carboxyl group on the surface of the substrate, whereby a silicon oxide thin film is formed. Will be done.

The above curing treatment is performed by irradiating ultraviolet rays in the presence of oxygen. Ultraviolet rays include near ultraviolet rays (near UV, wavelength 200 to 380 nm), far ultraviolet rays (wavelength 10 to 200 nm), and extreme ultraviolet rays (extreme UV, wavelength 1 to 10 nm), but far ultraviolet rays are usually effective. Examples of the ultraviolet source include a low-pressure mercury lamp, a high-pressure mercury lamp, an excimer ultraviolet (excimer UV) lamp, a halide lamp, and a laser. The irradiation time of ultraviolet rays is usually 1 second to 3 minutes.

In the case of a curing treatment in which a plastic base material is used as a base material and ultraviolet rays are irradiated in the presence of oxygen, a silicon oxide thin film having significantly improved base material adhesion is formed. The reason is presumed as follows.

That is, the surface of the plastic base material is activated (modified) by the active oxygen generated by the action of ultraviolet rays, and the silanol group (Si—OH) contained in the binder liquid and the surface of the base material are firmly bonded.

In the method for producing a silicon oxide thin film laminate of the present invention, a heating step is not essential for the curing treatment, so that a large area and a short time film formation are possible. In addition, continuous production using a single-wafer type or a long plastic base material is also possible.

In the continuous production, in particular, the first step of drawing out the plastic base material wound in a roll shape and coating the surface with the coating liquid for forming a silicon oxide thin film, and the plastic base material carried out from the first step. A silicon oxide thin film laminate comprising a second step of drying the surface coating liquid and a third step of irradiating the surface of the plastic substrate carried out from the second step with ultraviolet rays in the presence of oxygen to cure the surface. A continuous manufacturing method is recommended.

Hereinafter, the present invention will be described in more detail than the examples, but the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded. The analysis methods in the following examples are as follows.

Example 1
<Preparation of binder liquid for forming silicon oxide thin film>
(1) Hydrolysis reaction step:
In a 2L reactor with a jacket, 50 parts by mass of Shinetsu Silicone's product "KBM22" (dimethylmethoxysilane content 99% by weight), Mitsubishi Chemical's product "Sylicate MS51" (average mass n: 7, methylsilicate) 200 parts by mass of oligomer content 99.8% by weight) and 500 parts by mass of ethanol were charged, the upper limit reaction temperature was set to 40 ° C., and under stirring conditions, 330 parts by mass of a 0.007% by weight aqueous hydrochloric acid solution was added dropwise over 10 minutes. did. At this time, the reaction temperature increased by 5 to 10 ° C. due to the exothermic reaction. Stirring was continued until the reaction temperature dropped by 5-10 ° C. The ratio of the multimer to the bifunctional hydrolyzable silane compound (ratio of silicate MS51 to the total amount of "KBM22" and "silicate MS51") is 80% by weight.

(2) Condensation reaction step:
After dropping the aqueous hydrochloric acid solution, the temperature was raised to 60 ° C. over 30 minutes under stirring conditions, and the temperature was maintained at 60 ° C. for 30 minutes. Then, it cooled to room temperature.

(3) Condensation reaction stop step:
After cooling, 1100 parts by mass of ethanol was mixed and stirred for 30 minutes to obtain 2180 parts by mass of the alkoxysilane composition (A).

<Preparation of coating liquid for forming silicon oxide thin film>
12000 parts by mass of ethanol was added to 2180 parts by mass of the alkoxylan composition (A) obtained above, and the mixture was stirred for 30 minutes to obtain 14180 parts of the alkoxysilane composition (B).

A silicon oxide thin film is formed by adding 2040 parts by mass of spherical non-aggregated silica (product "Snowtex O" manufactured by Nissan Chemical Industries, Ltd.) to 14180 parts by mass of the alkoxysilane composition (B) obtained above and stirring for 30 minutes. A coating liquid for forming was obtained.

<Manufacturing of silicon oxide thin film laminate>
Coating for forming a silicon oxide thin film obtained in Example 1 on the easily adhesive-treated surface of a polyethylene terephthalate (PET) film (“Cosmo Shine A-4100” manufactured by Toyobo Co., Ltd.) having a thickness of 125 μm cut to 52 × 76 mm. The liquid was dropped and coated with a spin coater (“MS-A150” manufactured by Mikasa) at 1200 rpm for 30 seconds to prepare a thin film.

Then, in order to remove the solvent, it was placed in a constant temperature constant temperature blower (manufactured by Yamato Kagaku Co., Ltd.) and dried at 70 ° C. for 1 minute. Next, by irradiating ultraviolet rays with an illuminance of 130 mW / cm ² and an integrated light intensity of 1000 mJ / cm ² using a high-pressure mercury lamp (manufactured by Eye Graphics) in the atmosphere, a silicon oxide thin film laminated PET having a thickness of 100 nm was formed. Obtained.

[Adhesion test method]
Adhesion was evaluated by a cross-cut method using an industrial 24 mm cellophane tape (registered trademark) manufactured by Nichiban Co., Ltd. as an adhesive tape in accordance with JIS K5600.
That is, 25 grids at 5 mm intervals were made with a cutter knife, cellophane tape was attached to the surface of the film, and after pulling apart, the number of remaining sheets without peeling of the film was counted and evaluated.
Since the silicon oxide thin film has a property close to that of glass, cracks are likely to occur when making a grid with a cutter knife, which makes it difficult to perform an accurate adhesion test. Although it is 1 mm or 2 mm, the interval between the grids was changed to 5 mm.
The ratio of the number of squares that did not peel off (membrane residual ratio) to the total number of squares (25) was determined. The results are shown in Table 1.

[Moisture resistance test]
The silicon oxide thin film laminated PET prepared in the examples and comparative examples was held in an environmental tester (SH-641 manufactured by ESPEC) set in an environment of a temperature of 60 ° C. and a relative humidity of 95% for 30 minutes to evaluate the durability. went. The state of reduced adhesion was evaluated by the above-mentioned adhesion test method. The results are shown in Table 1.

Comparative Example 1:
A silicon oxide thin film laminated PET was produced in the same manner as in Example 1 except that it was not irradiated with ultraviolet rays. The results are shown in Table 1.

Comparative Example 2:
The silicon oxide thin film laminated PET was prepared in the same manner as in Example 1 except that the solvent was removed at 120 ° C. for 10 minutes and no ultraviolet light was irradiated. The results are shown in Table 1.

Claims (1)

A coating solution for forming a silicon oxide thin film containing a binder solution composed of a reaction composition obtained by hydrolyzing and condensing a hydrolyzable silane compound and silica fine particles is applied to the surface of a plastic substrate, and then dried. A method for producing a silicon oxide thin film laminate, which comprises irradiating an ultraviolet ray (excluding an ultraviolet ray having an irradiation intensity of 100 mW / cm ² or less) in the presence of oxygen to cure the silicon oxide thin film laminate.