JP2006342055A - Method of manufacturing titanium oxide thin film applied glass plate, glass plate manufactured by the method and use for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high strength glass plate having a firm titanium oxide thin film having a function as a photocatalyst and excellent wear resistance. <P>SOLUTION: In the method of manufacturing the titanium oxide thin film applied glass plate, the surface compression stress of the glass substrate becomes 20-250 MPa by applying a liquid containing titanium element on the surface of a glass substrate having ≤10 MPa surface compression stress, heating the surface coated with the liquid to 550-700°C of the maximum temperature and cooling under a condition satisfying following formula (1). The formula is 0.2≤a/t<SP>2</SP>≤5 (1) where (a) is time (sec) required for cooling to 200°C from 500°C and (t) is the thickness (mm) of the glass substrate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a glass plate coated with a titanium oxide thin film, wherein a titanium oxide thin film is formed on the surface of a glass substrate. In particular, the present invention relates to a method for producing a titanium oxide thin film-coated glass plate formed by heat-treating a titanium oxide thin film having a photocatalytic function such as antifogging property and antifouling property under specific temperature conditions. Moreover, it is related with the titanium oxide thin film coating glass plate manufactured by the method, and its use.

  For example, Japanese Patent No. 2756474 (Patent Document 1) describes that antifogging properties can be obtained by forming a titanium oxide thin film on the surface of a glass substrate. This is because the surface of the titanium oxide crystal, which is a photocatalytic semiconductor, is irradiated with light having a wavelength of energy higher than the band gap energy of the semiconductor, so that the surface thereof is highly hydrophilized. Thus, by covering a glass surface with a titanium oxide thin film, it is said that it is widely applicable to the use which a window glass, a windshield glass, a mirror, etc. are clouded and a visibility falls.

  In the above-mentioned Japanese Patent No. 2756474 (Patent Document 1), it is described that the titanium oxide that is hydrophilic in this way by light irradiation may be an anatase type crystal or a rutile type crystal. It is different from the point that the photolysis of chemical substances is observed only in the anatase type. When amorphous titania (titanium oxide) is baked, anatase-type titania is obtained by baking at 400 to 500 ° C. or higher, and rutile-type titania is obtained when baked at a temperature of 600 to 700 ° C. or higher. Specifically, it is described in Example 11 that a rutile type crystal was obtained by baking at 650 ° C. to obtain anatase type and 800 ° C. respectively.

  Japanese Patent No. 2517874 (Patent Document 2) discloses that an anatase-type titanium oxide thin film is formed by coating a titania sol on a substrate and then gradually heating from room temperature to a final temperature of 600 ° C. to 700 ° C. The method of obtaining is described. It is described that when the final temperature is too high or the rate of temperature increase is too fast, rutile crystals with poor photodegradation performance are mixed, specifically when gradually heated to 750 ° C, It is described that when heated immediately to 650 ° C., a considerable amount of rutile crystals are mixed.

  On the other hand, Example 29 of the above-mentioned Japanese Patent No. 2756474 (Patent Document 1) describes an example in which the surface of a glazed tile is coated with a mixture of anatase-type titania sol and colloidal silica sol and baked at 800 ° C. . There, it is described that the abrasion resistance is improved by adding silica to titania, but the pencil hardness of a film made of only titania is said to be 6B.

  In addition, in the above-mentioned Japanese Patent No. 2756474 (Patent Document 1), when the substrate on which titanium oxide is coated is a glass containing alkali metal ions, an intermediate such as silica is previously placed between the substrate and the titania layer. It is described that a layer is formed and then fired. By doing so, it is said that alkali metal ions in the glass can be prevented from diffusing into the titanium oxide coating during firing. Specifically, in the example in which amorphous titania was directly coated on the surface of soda lime glass and baked at 500 ° C., the contact angle with water increased compared to the example in which the intermediate layer was provided, Example 7 describes that the hydrophilization performance is reduced.

  Japanese Patent Laid-Open No. 2001-180980 (Patent Document 3) discloses a bent glass in which a hydrophilic film having a photocatalytic function in which a titanium oxide crystal is dispersed in a film forming component composed of zirconium oxide and silicon oxide is formed on the glass surface. Is described. Specifically, it is described that after applying the raw material solution of the oxide, firing is performed at a temperature of 560 to 700 ° C., and bending is performed simultaneously with the firing. In this publication, when a titanium oxide crystal film is formed without an alkali barrier layer made of silicon oxide and the glass is bent and fired at a high temperature of 560 to 700 ° C., the alkali component in the glass moves into the photocatalytic thin film, so that the photocatalytic function is remarkably increased. In order to solve this problem, it is described that titanium oxide crystals are dispersed in a film-forming component containing not only silicon oxide but also zirconium oxide.

Japanese Patent No. 2756474 Japanese Patent No. 2517874 JP 2001-180980 A

  When considering the practicality of a titanium oxide thin film glass plate having a photocatalytic function, its durability is extremely important. In particular, in outdoor applications where the photocatalytic function is manifested by sunlight, it is often necessary to perform simple cleaning at regular intervals even if the titanium oxide thin film has an antifouling function. In such a case, it is important to have sufficient resistance to friction. As described in the above-mentioned Japanese Patent No. 2756474 (Patent Document 1), the pencil hardness when only titania sol is baked is 6B, which is quite insufficient when considering practical friction resistance. It is. It is the greatest object of the present invention to solve this problem.

  On the other hand, as described above, the form of titanium oxide used as the photocatalyst preferably has an anatase type crystal form. However, amorphous or rutile-type titanium oxide may be formed depending on the firing temperature conditions, and it is not always easy to set conditions for forming a thin film made of anatase-type titanium oxide.

  Furthermore, as described above, when a titanium oxide coating film is directly formed on a glass substrate containing an alkali metal and then baked, alkali metal ions contained in the glass substrate move into the titanium oxide thin film. It was inevitable that the performance of titanium oxide as a photocatalyst would deteriorate due to diffusion. However, if the titanium oxide crystal, which is a photocatalyst, is dispersed in a matrix composed of other components, the catalytic effect may be reduced. Further, when the intermediate layer made of silica or the like is formed between the titanium oxide thin film and the glass substrate, not only the thin film forming operation becomes complicated, but the productivity is lowered, and the yield is also a problem.

  Further, when a titanium oxide thin film is formed on a sheet glass having a large area, it is extremely important to prevent a decrease in yield due to partial nonuniformity and generation of defects. On the other hand, it is also important to form a titanium oxide thin film having a good appearance.

  The present invention has been made to solve the above-described problems. A liquid containing a titanium element is applied to the surface of a glass substrate having a surface compression stress of a certain value or less, and the surface on which the liquid is applied is coated with glass. Titanium oxide thin film coated glass that is heated to a certain maximum temperature close to the softening temperature and then cooled at a specific cooling rate related to the thickness of the glass plate so that the surface compressive stress of the glass substrate becomes a constant value. A method for manufacturing a plate is provided. At the same time, the present invention provides a titanium oxide thin film-coated glass plate produced by the method and its use.

The above-mentioned problem is that a liquid containing titanium element is applied to the surface of a glass substrate having a surface compressive stress of 10 MPa or less, the surface on which the liquid is applied is heated to a maximum temperature of 550 to 700 ° C., and then the following formula ( It achieves by providing the manufacturing method of the titanium oxide thin film covering glass plate which cools on the conditions which satisfy | fill 1), and makes the surface compressive stress of a glass substrate be 20-250 MPa.
0.2 ≦ a / t ² ≦ 5 (1)
However,
a: Time required for cooling from 500 ° C. to 200 ° C. during cooling (seconds)
t: thickness of glass substrate (mm)
It is. By manufacturing under such conditions, it is possible to form a strong titanium oxide thin film excellent in friction resistance on the surface of the glass substrate.

  At this time, it is preferable that the glass substrate is a glass substrate containing 5 to 15% by weight of an alkali metal. This is because such glass can easily improve the surface compressive stress by heat treatment.

  Moreover, it is suitable that the time in which the temperature of the surface on which the liquid is applied is in a temperature range of 550 to 700 ° C. is 20 to 500 seconds. A strong film can be formed by setting it to 20 seconds or longer. Moreover, by using 500 seconds or less, when a glass substrate containing an alkali metal is used, it is possible to suppress the diffusion of alkali metal ions into the titanium oxide thin film.

  It is preferable that the liquid containing titanium element applied to the substrate is a sol containing anatase-type titanium oxide fine particles. This is because it is easy to obtain a strong thin film made of anatase-type titanium oxide crystals in a short baking time. It is also preferable that the photocatalytic thin film is made of anatase-type titanium oxide because of its high photocatalytic activity.

  The above-mentioned problems can also be solved by providing a titanium oxide thin film-coated glass plate produced by the above method. Further, a laminated glass in which glass plates are laminated on both sides of a resin intermediate film, and a laminated glass formed by laminating the glass plate with a titanium oxide thin film coating surface on the outside as at least one glass plate is a preferred embodiment. It is. One useful application of such laminated glass is as a road or railway sound barrier.

  According to the present invention, it is possible to form a strong titanium oxide thin film excellent in friction resistance on a glass substrate. This thin film has a function as a photocatalyst, and can provide a glass having a photocatalyst function having excellent durability. Moreover, since the strength of the glass plate is high, it is possible to provide a glass plate that is optimal for applications that require anti-fogging properties, anti-fouling properties, decomposition of organic substances, strength, and the like.

In the present invention, a liquid containing titanium element is applied to the surface of a glass substrate having a surface compressive stress of 10 MPa or less, and the surface to which the liquid is applied is heated to a maximum temperature of 550 to 700 ° C. It is the manufacturing method of the titanium oxide thin film coating glass plate which cools on the conditions which satisfy (1), and makes the surface compressive stress of a glass substrate be 20-250 MPa.
0.2 ≦ a / t ² ≦ 5 (1)
However,
a: Time required for cooling from 500 ° C. to 200 ° C. during cooling (seconds)
t: thickness of glass substrate (mm)
It is.

  The liquid containing the titanium element applied to the glass substrate is not particularly limited as long as it forms titanium oxide after firing. For example, a solution of an organic titanium compound or an inorganic titanium compound may be used, or a sol containing titanium oxide fine particles may be used.

  Examples of the organic titanium compound used in the solution include tetraethoxy titanium, tetraisopropoxy titanium, tetra n-propoxy titanium, tetrabutoxy titanium, tetramethoxy titanium, and other alkoxides, carboxylates, and chelate compounds. It is also possible to use inorganic titanium compounds such as titanium chloride, titanium sulfate, and peroxotitanic acid. These solutions can be used for coating as they are or after hydrolysis.

  Further, it is preferable to apply a sol containing titanium oxide fine particles on a glass substrate. At this time, the titanium oxide particles contained in the sol may be amorphous, or particles made of anatase type or rutile type crystals. Among them, a sol containing anatase-type titanium oxide fine particles can provide a strong thin film made of titanium oxide crystals even in a short baking time, and even when a glass substrate containing an alkali metal is used, It is preferable because diffusion into the titanium oxide thin film can be prevented. Moreover, since such a sol originally contains solid fine particles, it is effective for forming fine irregularities on the surface.

  The average particle diameter of such a titanium oxide sol is not particularly limited, but is usually 100 nm or less, and is preferably 30 nm or less in order to obtain a homogeneous film with little whitening. The medium of the sol is not particularly limited, but it is preferable that the main component is water from the viewpoint of the safety of the working environment during the coating operation.

  The titanium element content in the liquid applied to the glass substrate is preferably 10% by weight or less. When the concentration is higher than this, the depth of the irregularities on the surface becomes too deep, and the transparency of the thin film may be lowered, and it may be difficult to form a uniform film. It is preferably 5% by weight or less, more preferably 3% by weight or less, and most preferably 1% by weight or less. When a low-concentration liquid is used, the film thickness obtained by a single coating operation becomes small, but the thickness of the titanium oxide thin film tends to be uniform, and the unevenness formed on the surface can be made fine. In consideration of productivity, the content of titanium element is usually 0.1% by weight or more.

  The pH of the liquid containing titanium element is preferably 3 or more. The use of a neutral or alkaline liquid can prevent the diffusion of alkali metal ions into the titanium oxide thin film when using a glass substrate containing an alkali metal. The pH is preferably 5 or more. Moreover, it is preferable that it is 14 or less.

  Further, the liquid applied to the glass substrate may contain a metal element other than the titanium element or a metalloid element such as silicon as long as the effects of the present invention are not impaired. However, for efficient expression of the photocatalytic function, it is preferable that the content of metal elements and metalloid elements other than titanium elements is small. Specifically, the content is preferably 1/10 or less by weight ratio with respect to the content of titanium element, and more preferably not contained at all.

  Among those used in the present invention as a liquid containing a titanium element, a liquid containing peroxytitanic acid in an anatase-type titanium oxide sol is preferable. Although this liquid is neutral, titanium oxide particles are well dispersed in water and is suitable for the practice of the present invention.

  The glass substrate used as a raw material in the present invention is a glass substrate having a surface compressive stress of 10 MPa or less. This value is measured according to JIS R3222. Thus, by heating the glass substrate having a small surface compressive stress to near the softening temperature and then cooling it under a certain condition, a glass plate coated with a titanium oxide thin film having a large compressive stress on the glass substrate surface can be obtained. .

  Although the material of a glass plate is not specifically limited, The glass substrate containing 5 to 15 weight% of alkali metals is suitable. By containing an alkali metal, the softening point of the glass is lowered, but by containing this amount of alkali metal, the softening point of the glass substrate is lowered to a point close to the maximum temperature reached by the heat treatment of the present invention. Can be made. Thereby, the elastic modulus of the glass substrate can be lowered in the vicinity of the temperature at which anatase-type titania crystals can be grown, and appropriate surface compressive stress can be generated according to the heating conditions of the present invention. As a result, a titanium oxide thin film having excellent friction resistance can be obtained. As such a glass substrate, soda lime glass is optimal because it has great industrial importance and needs to be tempered.

Although the dimension of a glass substrate is not specifically limited, Usually, thickness is about 2.5-25 mm. In addition, although the area is usually 0.01 m ² or more, it is often used in a large area in applications where the strength of glass is required, so a titanium oxide thin film is applied to a substrate having an area of 0.5 m ² or more. It is preferable to form. More preferably, it is 1 m ² or more.

  Before applying the liquid containing the titanium element, it is preferable to clean the surface of the glass substrate in order to prevent application unevenness and defects and improve the adhesion of the titanium oxide thin film. Although it may be cleaned only with a surfactant, it is preferable to clean with both an acidic aqueous solution and a surfactant-containing aqueous solution. Wash with an acid-containing aqueous solution, for example, acetic acid water, then with a surfactant-containing water, and finally with water to properly clean the dirt adhered during the transportation of the glass. Is possible.

  The method for applying the liquid containing titanium element to the surface of the glass substrate is not particularly limited, and various coating methods such as spray coating, flow coating, spin coating, dip coating, roll coating and the like are employed.

  Among them, in order to form a thin film with no interference color observed and excellent transparency, it is possible to apply by attaching mist-like fine particles made of a liquid containing a titanium element to the surface of the glass substrate. Is preferred. By carrying out like this, it is possible to form a fine unevenness | corrugation on the surface of a titanium oxide thin film, and can form the thin film from which interference color is not visually recognized. In particular, since anatase-type titanium oxide crystals have a high refractive index of about 2.5, this is important because interference colors tend to cause problems in appearance. In addition, since even a slight film thickness unevenness is easily visually recognized as a change in interference color or interference fringes, the above method is also suitable for obtaining a titanium oxide thin film with inconspicuous appearance unevenness. This method is particularly effective when uniformly coating a large area where film thickness unevenness is likely to occur.

  Specifically, it is preferable to apply using an air spray gun or an ultrasonic sprayer. By applying using such an apparatus, for example, titanium oxide sol can be applied. Since such a sol originally contains solid fine particles, it is effective for forming fine irregularities on the surface. At this time, in order to obtain a highly transparent coating film, it is preferable that the content of titanium element in the liquid containing titanium element is 0.1 to 10% by weight. This is because by applying a dilute liquid, it is possible to minimize the occurrence of large irregularities on the surface of the titanium oxide thin film and deterioration of transparency.

  When an air spray gun is used when applying a liquid containing titanium element, it is preferable that the discharge rate per unit time from the nozzle is 1 to 10 ml / min. By spraying with a relatively small discharge amount in this way, bubbles are not caught, fine irregularities can be formed, and it becomes easy to apply with a uniform thickness. The discharge amount is more preferably 7 ml / min or less. Moreover, the suitable air pressure supplied to a spray gun is 0.13-0.8 MPa. Since it is easier to realize a desirable surface shape when the air pressure is set lower, the air pressure is more preferably 0.4 MPa or less, and even more preferably 0.3 MPa or less. The air pressure here is an absolute pressure, and the differential pressure from the atmospheric pressure is a value obtained by subtracting about 0.1 MPa from this value. If necessary, recoating can be performed by repeating coating and drying.

  Moreover, when using an ultrasonic atomizer when apply | coating the liquid containing a titanium element, it is suitable to set the liquid temperature in the liquid tank of an ultrasonic atomizer 5 to 90 degreeC higher than the surface temperature of a glass substrate. is there. The droplets generated from the ultrasonic sprayer are smaller than the droplets generated by an air spray gun and are not sprayed with a strong airflow, but the glass substrate surface is kept lower than the droplet temperature by keeping it on the glass substrate. Can be applied uniformly. This method is useful because it can form a titanium oxide thin film having fine irregularities on the surface, particularly when applied extremely thinly and uniformly.

  The applied coating is dried and then subjected to a heat treatment. The drying method is not particularly limited, and examples thereof include a method of heating at a relatively low temperature and a method of blowing dry air. For example, when applying using an air type spray gun as mentioned above, the method of interrupting | blocking the liquid supplied to the nozzle of a spray gun, and spraying only air and drying is employ | adopted suitably. Moreover, when using an ultrasonic atomizer, the coating film thickness may be thin, and it is possible to dry only by contacting with dry air.

  A fired titanium oxide thin film is formed by subjecting a glass plate coated with a liquid containing a titanium element to a heat treatment. In the present invention, it is important to heat the surface coated with the liquid to a maximum temperature of 550 to 700 ° C. By heating in this temperature range, the titanium oxide thin film can be strengthened, and at the same time, by heating to a temperature close to the softening point of the glass substrate, the cooled titanium oxide thin film can easily adhere to the substrate. Because. In a typical soda lime glass, the softening point of the glass specified by ASTM C338-57 is 720 to 730 ° C. When the maximum temperature is less than 550 ° C., the titanium oxide thin film does not become strong, and the titanium oxide thin film has insufficient adhesion because it has a value that is considerably lower than the softening point of the glass. The maximum temperature is preferably 600 ° C. or higher. On the other hand, if the maximum temperature exceeds 700 ° C., signs of glass softening are observed, the flatness of the glass substrate is impaired during firing, and the resulting glass plate is distorted. The maximum temperature is preferably 650 ° C. or lower.

The temperature increase rate when heating the glass plate coated with the liquid containing titanium element is not particularly limited. However, it is preferable to raise the temperature at a speed that satisfies the following formula (2).
5 ≦ b / t ≦ 30 (2)
However,
b: Time required for heating from 200 ° C. to 500 ° C. when heating (seconds)
t: the thickness (mm) of the glass substrate.

  By raising the temperature relatively quickly in this way, it can be raised in a short time to a temperature at which anatase-type titanium oxide crystals can be grown, and when using a glass substrate containing an alkali metal as a glass substrate, It is possible to prevent alkali metal ions from unnecessarily diffusing. Especially when titanium oxide is amorphous, incomplete crystal form, or contains volatile components, alkali metal ions tend to diffuse, so the temperature rises rapidly and anatase-type crystals grow. It is preferable to quickly reach a possible temperature. Therefore, the value of b / t is preferably 5 or more, and more preferably 10 or more. However, if the glass substrate having a large thickness is heated too quickly, the temperature difference between the surface and the center of the substrate becomes too large, and the glass substrate may be damaged during heating due to excessive stress generated. It is preferable that the value of b / t is 30 or less. More preferably, it is 20 or less.

  Moreover, it is suitable that the time in which the temperature of the surface on which the liquid is applied is in a temperature range of 550 to 700 ° C. is 20 to 500 seconds. If the time in this temperature range is a certain time, anatase-type crystals can grow sufficiently on a relatively soft glass substrate, and as a result, a strong thin film can adhere to the glass substrate. It is thought that there is not. When this time is less than 20 seconds, the photocatalytic function may not be sufficiently exhibited, the film hardness and strength may be insufficient, and the adhesion to the substrate may be reduced. More preferably, it is 40 seconds or more. On the other hand, if this time exceeds 500 seconds, the glass substrate may be distorted, alkali metal ions may diffuse into the titanium oxide thin film, or crystals having a rutile crystal structure may increase. It is not preferable. More preferably, it is 300 seconds or less.

Furthermore, after reaching the maximum temperature, it is important to cool under conditions that satisfy the following formula (1).
0.2 ≦ a / t ² ≦ 5 (1)
However,
a: Time required for cooling from 500 ° C. to 200 ° C. during cooling (seconds)
t: the thickness (mm) of the glass substrate.

It has been empirically known that the value obtained by dividing the temperature drop rate by the square of the thickness of the glass substrate has a correlation with the value of the surface compressive stress remaining in the glass plate obtained after the temperature drop. By rapidly cooling in this way, it is possible to cool the substrate in such a way that compressive stress remains on the substrate surface. By remaining compressive stress on the substrate surface, it seems that not only the strength of the glass substrate itself is improved, but also the titanium oxide film formed on the substrate surface can be made difficult to peel. (1) When the value of a / t ^{2 in} the formula is less than 0.2, the cooling rate is too fast and the glass substrate may be damaged during the temperature drop. Preferably it is 0.3 or more, more preferably 0.5 or more. On the other hand, when the value of a / t ^{2 in} the formula (1) exceeds 5, the adhesion of the resulting titanium oxide thin film becomes insufficient. It is preferably 3 or less, more preferably 2 or less.

  As described above, the apparatus for raising the temperature of the glass substrate, maintaining it at a high temperature, and then lowering the temperature is not particularly limited as long as the processing conditions of the present invention can be satisfied. For example, a tempering furnace that performs a tempering treatment of glass can be suitably used.

  For example, a glass plate coated with a liquid containing titanium element is introduced into a heating furnace maintained at a high temperature. It is preferable to rotate a plurality of rollers and introduce them into the heating furnace. The method for heating the inside of the heating furnace is not particularly limited, and heating by an electric heater may be used, or a method of heating by burning a fuel such as gas or petroleum may be used. In the heating furnace, the glass plate is preferably heated under conditions that satisfy the formula (2). During this time, it is preferable to swing the glass plate in the horizontal direction by switching the rotation direction of the rollers in the heating furnace. By doing so, local heating unevenness can be prevented and the glass plate can be prevented from being damaged. Conveyor conveyance and hanging conveyance can also be adopted as a conveyance method other than roller conveyance.

  The temperature of the glass substrate surface in the heating furnace can be continuously monitored by a non-contact type infrared thermometer. After reaching the maximum temperature, it is taken out from the heating furnace and cooled under the condition satisfying the formula (1). When taking out from a heating furnace, it is possible to take out by rotating a roller, for example. In cooling, a method of cooling by blowing pressurized air at once in a cooling tank is suitable. Air is preferably blown from a number of nozzles arranged on both sides of the substrate so that it can be cooled uniformly. At this time, as in the heating furnace, it is possible to prevent the occurrence of local cooling unevenness by oscillating the glass plate in the horizontal direction by switching the rotation direction of the roller, and the glass plate is damaged. Is preferable.

  The glass substrate thus obtained has a surface compressive stress of 20 to 250 MPa. This value is measured according to JIS R3222. Thus, by making a certain surface compressive stress remain, the adhesiveness of a titanium oxide thin film and a glass substrate becomes favorable. When the surface compressive stress remaining on the glass substrate is too small, the obtained titanium oxide thin film has insufficient adhesion, and is preferably 50 MPa or more. On the other hand, if it is too large, the glass substrate may be damaged during the temperature drop, and is preferably 200 MPa or less. As a result of setting the heat treatment conditions to form a strong and highly adherent titanium oxide thin film having high performance photocatalytic performance, so-called double-strength glass, tempered glass or super-tempered glass is formed simultaneously with the formation of the titanium oxide thin film. Since a glass plate having a strength equivalent to that of glass called can be produced, it is extremely excellent in terms of production efficiency. The surface compressive stress can be measured on the surface where the titanium oxide thin film is not formed.

  The crystal structure of the titanium oxide thin film thus obtained is not particularly limited, but it is preferable that the titanium oxide thin film mainly contains anatase type, and that it is a thin film substantially consisting only of anatase type crystals is the point of photocatalytic activity. Is more preferable. The crystal structure of the formed titanium oxide can be confirmed by wide-angle X-ray diffraction measurement or the like.

  The film thickness to be formed is not particularly limited, and an average film thickness of about 0.02 to 1 μm is exemplified. From the viewpoint of catalytic activity, it is preferable to have a film thickness of a certain level or more, and when it is too thin, it is easily affected by the diffusion of alkali metal ions from the substrate. More preferably, it is 0.05 micrometer or more, More preferably, it is 0.1 micrometer or more. On the other hand, even if the film thickness increases beyond a certain level, no further improvement in the photocatalytic effect can be expected, and only the raw material cost increases. More preferably, it is 0.7 μm or less, and further preferably 0.5 μm or less.

  The refractive index of the titanium oxide crystal is about 2.5 for the anatase type, which is considerably larger than the refractive index of general glass (about 1.5), so that interference color derived from reflection at the interface occurs. The potential is great. For example, since a film having a thickness of about 0.1 to 1 μm is a film thickness that easily generates interference colors, slight thickness unevenness is likely to be visually recognized as interference fringes. From this point, it is preferable to apply the mist-like fine particles made of a liquid containing a titanium element by adhering to the surface of the glass substrate. By doing so, it is possible to form fine irregularities on the surface of the titanium oxide thin film, no interference color is observed, and a thin film having excellent transparency can be formed.

  As for the shape of the unevenness formed on the surface of the titanium oxide thin film, it is preferable that the unevenness is deepened to the extent that no interference color is generated. On the other hand, if the depth of the unevenness is more than a certain level, the film surface is now whitened and the haze value is increased, which is not preferable. Therefore, it is desirable to make the concavo-convex shape satisfying both simultaneously. The measurement method of such unevenness is not limited, and it is possible to use a stylus type, but the depth of the unevenness to prevent whitening is smaller than the wavelength of light. Therefore, an observation method using the principle of an atomic force microscope or a tunnel microscope is preferable.

  The depth of the unevenness may be an unevenness that does not generate an interference color and does not increase the haze, but specifically, JIS B0601 when scanned over a length of 13 μm using an atomic force microscope. It is preferable that the value of the ten-point average roughness (Rz) specified in (5) is 5 to 50 nm. In order not to generate an interference color, the value of Rz is more preferably 10 nm or more. In order to prevent whitening of the titanium oxide thin film, the Rz value is more preferably 30 nm or less. If it is this uneven | corrugated depth, since it is sufficiently small compared with the wavelength (380-780 nm) in the air of visible light, it is hard to whiten. On the other hand, the optical path length reciprocating in the titanium oxide thin film is a value obtained by multiplying the concave and convex portions by twice the depth of the concave and convex portions and a refractive index of 2.5. Even so, the difference in optical path length is large, and interference colors are unlikely to occur.

  The haze value (haze value) of the obtained glass plate having a titanium oxide thin film is preferably 5% or less, and more preferably 2% or less. Here, the haze value is a value measured according to the method described in JIS R3212. For applications that require high visibility, the haze value is more preferably 1% or less, and even more preferably 0.5% or less. Furthermore, it is preferable to have a light transmittance of 70% or more over the entire visible light (380 to 780 nm). The light transmittance is more preferably 75% or more over the entire wavelength range, and further preferably 80% or more.

  As described above, a high-strength glass plate having an excellent photocatalytic function, having a strong titanium oxide thin film with good adhesion, and high surface compressive stress can be obtained. In addition, a titanium oxide thin film with a good appearance can be formed on a large area glass plate, and at the same time it is possible to improve the strength of the glass, and the productivity is also good, so it is used for many applications. can do. Photocatalytic functions that can be exhibited include, in addition to surface hydrophilization, antifouling functions, antibacterial functions, toxic gas decomposition functions, and deodorizing functions. For example, building window glass, building exterior glass, skylight, handrail glass plate, automotive window glass, railway vehicle window glass, aircraft window glass, ship window glass, elevator window glass, and other various vehicles. Window glass for roads, sound barriers for roads or railways, cover glass for photovoltaic power generation, cover glass for solar water heaters, protective goggles or masks for sports, glass plates for frozen refrigerated food display cases, glass plates for vegetable display cases Examples thereof include cover glasses of measuring instruments, various mirrors, and the like.

  Furthermore, a laminated glass in which glass plates are laminated on both sides of the resin intermediate film, and laminated glass with the above-mentioned glass plate as the at least one glass plate with the titanium oxide thin film coating surface on the outside is also extremely useful. Examples of the resin intermediate film used here include polyvinyl butyral, ethylene-vinyl acetate copolymer, and polyurethane. Examples of the method for producing such a laminated glass include a method of thermocompression bonding under normal pressure and a method of bonding by heating under reduced pressure. Laminated glass with improved safety by having a titanium oxide thin film with photocatalytic performance and good adhesion and having a high strength glass plate to form a so-called laminated glass. Can be provided. Applications requiring such a high level of safety performance include road and railway soundproof walls, building exterior walls, building window glass, skylights, and handrail glass plates.

  Among them, sound barriers for roads and railways are required to have a high level of safety, are easily contaminated with dust and exhaust gas, and are highly demanded to reduce the number of cleanings. It is a particularly useful application.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
As a raw material, soda lime glass having a length of 1000 mm, a width of 1000 mm, and a thickness of 4 mm was used. This soda lime glass contains 10% by weight of sodium as an alkali metal, and has a softening temperature of 720 to 730 ° C. measured according to ASTM C338-57. When the surface compressive stress of the surface of the soda lime glass substrate on the tin diffusion layer side was measured according to JIS R3222, it was 6.3 MPa. Wash the front and back of soda lime glass with a sponge using 1N acetic acid aqueous solution, and then wash with water, and then use a diluted surfactant with water to clean the surface of the glass substrate with a sponge. Washed. Thereafter, the surfactant was washed away with a large amount of water and then air blown to remove moisture.

  The cleaned glass substrate was stood against the wall surface, and the sol containing titanium oxide fine particles was applied to the surface opposite to the tin diffusion layer side using an air spray gun “Small LPH-100-124LVG” manufactured by Anest Iwata Corporation. The titanium oxide fine particle-containing sol used here is “YAL-COAT” manufactured by Yamanaka Sangyo Co., Ltd., which contains anatase-type titanium oxide fine particles and also contains peroxytitanic acid. The content of elemental titanium is about 0.5% by weight, the medium is mainly water, and the pH of the liquid is 6.8. The air pressure supplied to the spray gun was set to 0.2 MPa (the differential pressure from the atmospheric pressure was about 0.1 MPa), and the coating amount per unit time from the nozzle was set to 5 ml / min. It was applied while moving in a horizontal direction while maintaining a certain distance from the position. When reaching the left end or the right end, the whole was applied by shifting the position in the vertical direction. Fine and uniform mist droplets adhered uniformly on the glass substrate. At this time, the entire glass substrate was not evenly wetted, and the liquid did not flow.

  After spray application, stop supplying sol to the spray gun, supply only air at an air pressure of 0.2 MPa (difference from atmospheric pressure is about 0.1 MPa), and spray air from a position 15 cm away The coated film was dried by spraying dry air onto the coated surface. Subsequently, the sol was again supplied to the spray gun, the second application was performed in the same manner as the first time, and then the drying was performed in the same manner as the first time. In addition, coating and drying were repeated in the same manner once more, and a total of three times of overcoating was performed. In the above coating operation, although it became slightly cloudy immediately after coating, it became almost transparent when dried. Moreover, the coloring considered to be derived from interference color before and after drying was not recognized.

  The glass plate on which the coating film thus obtained was formed was heat-treated using a tempered furnace “HTF2448” manufactured by Tam Glass Engineering. First, it was placed on a conveying roller with the coating surface facing upward at room temperature, and the roller was rotated and conveyed into a heating furnace. The furnace temperature is maintained at 705 to 735 ° C. by an electric heater. The surface temperature of the coated surface of the glass substrate conveyed therein was monitored over time by a non-contact infrared thermometer installed inside the heating furnace. As a result, it took 64 seconds for the temperature to rise from 200 ° C to 500 ° C. A value (b / t) obtained by dividing the required time (b: second) by the plate thickness (t: mm) was 16. In the heating furnace, the oscillation (oscillation) operation was repeated while reversing the rotation of the roller to prevent heating unevenness.

  Thereafter, when the temperature reached the maximum temperature of 625 ° C., the product was transported from the heating furnace into the cooling tank using a roller and cooled in the cooling tank. During cooling, a large amount of compressed air was blown from both the upper and lower directions of the substrate through a number of nozzles to cool the substrate. During this time, in the cooling tank, in order to prevent uneven cooling, the roller was continuously swung by the reversing operation of the roller in the same manner as during heating.

The time from reaching 550 ° C. in the heating furnace to cooling to 550 ° C. in the cooling bath after reaching the maximum temperature of 625 ° C. was 50 seconds. Further, it took 14 seconds for the temperature to drop from 500 ° C. to 200 ° C. during cooling. A value (a / t ² ) obtained by dividing the required time (a: second) by the square of the plate thickness (t: mm) was 0.88. The glass plate was coated with a titanium oxide thin film by cooling to approximately room temperature in a cooling bath.

  The average thickness of the obtained titanium oxide thin film is about 0.3 μm calculated from the coating amount at the time of application. The appearance was colorless and transparent, and when observed well from an oblique direction close to the direction parallel to the substrate, it was recognized that it was slightly clouded, and at first glance it was transparent and had a good appearance. No interference color was observed. A spectral transmittance measurement chart of the obtained glass plate is shown in FIG. 1 and had a good light transmittance of 80% or more in the entire visible light region (380 nm to 780 nm). Moreover, when the haze value (haze value) was measured according to JIS R3212, it was almost 0% (less than 0.1%).

  FIG. 2 shows the results of wide-angle X-ray diffraction measurement of the obtained titanium oxide thin film. In the figure, a peak indicated by a square is a diffraction peak derived from an anatase type crystal structure, and a peak indicated by an inverted triangle is a diffraction peak derived from a rutile type crystal structure. A peak derived from the anatase type titanium oxide crystal was observed, and a peak derived from the rutile type titanium oxide crystal was not observed.

  The surface of the obtained titanium oxide thin film was observed using a scanning probe microscope JSPM-4200 manufactured by JEOL Ltd. The surface shape is observed by measuring the atomic force between the probe with a sharp tip and the sample surface. FIG. 3 shows the result of measuring the uneven shape of the surface scanned at a distance of 13 μm in the AFM contact mode. The value of the ten-point average roughness Rz defined by JIS B0601 is 18.4 nm, and it can be seen that irregularities considerably smaller than the wavelength of visible light are formed.

  The probe microscope was equipped with a nanomechanical system “Triboscope” manufactured by Hystron and the surface hardness was measured. The hardness (Hardness) of the obtained film was 6.22 GPa. The hardness of the soda lime glass used as a raw material was measured in the same manner to be 7.09 GPa, and it was found that a high-hardness film almost comparable to glass was obtained. Furthermore, when a pencil hardness test was performed, even when rubbed with a pencil having a hardness of 6H, the film was not completely peeled off and the substrate surface was not exposed.

  After irradiating the titanium oxide film surface with sunlight for 3 days, and then actually blowing on it to confirm the anti-fogging effect, interference fringes that seemed to have formed a water film was observed visually. Later, it was recognized that the interference fringes disappeared quickly and had an excellent anti-fogging effect. Moreover, the anti-fogging effect was not lost even if it was exposed outdoors for 6 months. Moreover, when the contact angle with respect to the water of the titanium oxide thin film surface was measured, it was 5 degrees or less.

In addition, regarding the decomposition effect of organic substances, the grease “Epinoc Grease AP2” manufactured by Nisseki Mitsubishi Co., Ltd. was applied to an area of 100 cm ² and left in a place exposed to sunlight for 3 months. It was confirmed that there was a significant difference in the decomposability compared to the control product coated on the glass substrate, and almost disappeared.

  When the surface compressive stress of the obtained plate glass was measured according to JIS R3222, the surface compressive stress of the surface on which the titanium oxide thin film was not formed was 104 MPa, which was about the same as that of a general 4 mm thick tempered glass. It had surface compressive stress.

Example 2
The same titanium oxide fine particle-containing sol as in Example 1 was applied to a soda-lime glass substrate that had been cleaned and dried in the same manner as in Example 1. For application, a commercially available ultrasonic sprayer for humidification was used. The temperature of the sol in the sprayer tank was heated to 90 ° C., and then spray-coated on a glass substrate having a surface temperature of 23 ° C. The mist-like droplets were uniformly deposited on the glass substrate from a position 20 cm away from the glass substrate. After adhering to the glass substrate, it was dried using a dryer. Also in the above-described coating operation, as in Example 1, although it became slightly cloudy immediately after coating, it became almost transparent when dried. Moreover, the coloring considered to be derived from interference color before and after drying was not recognized.

  The glass plate on which the coating film thus obtained was formed was heat-treated by the same operation as in Example 1 to form a titanium oxide thin film. The appearance is colorless and transparent, and the degree of cloudiness that can be confirmed by well observing from an oblique direction close to the direction parallel to the substrate is even lower than that of Example 1, and the transparency is better than that of Example 1. It was. In addition, no interference color was observed.

Comparative Example 1
Before the heat treatment, a coating film was applied to the glass substrate in the same manner as in Example 1. The obtained glass substrate was introduced into a heating furnace heated in the same manner as in Example 1, and the same operation as in Example 1 was performed until the maximum temperature of 625 ° C. was reached. When it reached the maximum temperature, it was transported from the heating furnace into the cooling tank using a roller and introduced into the cooling tank, where it was gradually cooled without blowing cooling air. In the meantime, in the cooling tank, in order to prevent uneven cooling, the roller was continuously swung by the reversing operation.

The time from reaching 550 ° C. in the heating furnace to cooling to 550 ° C. in the cooling bath through the maximum temperature of 625 ° C. was 110 seconds. In addition, it took 300 seconds for the temperature to drop from 500 ° C. to 200 ° C. during cooling. A value (a / t ² ) obtained by dividing the required time (a: second) by the square of the plate thickness (t: mm) was 18.8. The glass plate was coated with a titanium oxide thin film by gradually cooling to approximately room temperature in a cooling bath.

  The average thickness of the obtained titanium oxide thin film is about 0.3 μm calculated from the coating amount at the time of application. The appearance was colorless and transparent, and when observed well from an oblique direction close to the direction parallel to the substrate, it was recognized that it was slightly clouded, and at first glance it was transparent and had a good appearance. No interference color was observed. In terms of appearance, no significant difference from Example 1 was observed.

  When the obtained titanium oxide thin film was subjected to a pencil hardness test, the film was completely peeled off and the substrate surface was exposed even when rubbed with a pencil having a hardness of 2H. The hardness or adhesion of the film was greatly reduced as compared with Example 1. When the contact angle with respect to the water of the titanium oxide thin film surface was measured, it was 5 degrees or less, and this point was not different from Example 1.

  When the surface compressive stress of the obtained plate glass was measured according to JIS R3222, the surface compressive stress of the surface on which the titanium oxide thin film was not formed was 0.7 MPa, and the surface compressive stress was almost zero. Met. That is, when the surface compressive stress is reduced by slow cooling, a strong titanium oxide thin film cannot be formed, and the adhesion is insufficient. From this, it became clear that it is very effective to form a titanium oxide thin film under the condition that the surface compressive stress remains by cooling at a constant rate as in the present invention.

4 is a spectral transmittance measurement chart of the glass plate obtained in Example 1. FIG. 2 is a wide-angle X-ray diffraction chart of the titanium oxide thin film formed in Example 1. 3 shows the uneven shape of the surface of the titanium oxide thin film formed in Example 1.

Claims (8)

A liquid containing titanium element is applied to the surface of a glass substrate having a surface compressive stress of 10 MPa or less, and the surface on which the liquid is applied is heated to a maximum temperature of 550 to 700 ° C. A method for producing a titanium oxide thin film-coated glass plate that is cooled under satisfying conditions so that the surface compressive stress of the glass substrate is 20 to 250 MPa:
0.2 ≦ a / t ² ≦ 5 (1)
However,
a: Time required for cooling from 500 ° C. to 200 ° C. during cooling (seconds)
t: The thickness (mm) of the glass substrate. The method for producing a glass plate coated with a titanium oxide thin film according to claim 1, wherein the glass substrate is a glass substrate containing 5 to 15% by weight of an alkali metal. The method for producing a glass plate coated with a titanium oxide thin film according to claim 1 or 2, wherein the time during which the temperature of the surface to which the liquid is applied is in the temperature range of 550 to 700 ° C is 20 to 500 seconds. The method for producing a titanium oxide thin film-coated glass plate according to any one of claims 1 to 3, wherein the liquid containing the titanium element is a sol containing anatase-type titanium oxide fine particles. The method for producing a titanium oxide thin film-coated glass plate according to any one of claims 1 to 4, wherein the titanium oxide thin film comprises anatase-type titanium oxide. A titanium oxide thin film-coated glass plate produced by the method according to claim 1. A laminated glass in which glass plates are laminated on both sides of a resin intermediate film, the laminated glass comprising at least one glass plate laminated with the titanium oxide thin film-coated surface on the outside. A road or railway noise barrier made of the laminated glass according to claim 7.

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