Film-equipped translucent base material

Abstract

Provided is a film-equipped translucent base material comprising a translucent base material and a film that is provided on a surface of the translucent base material, wherein the film includes first silicon oxide particles that have an average particle size of greater than 2 μm and second silicon oxide particles that have an average particle size of 0.3 μm to 1.0 μm, the surface has a first region and a second region, the first silicon oxide particles are present in the film on the first region, the first silicon oxide particles are not present in the film on the second region, and the second silicon oxide particles are present in at least a portion of the second region.

Description

Transparent substrate with a film

[0001] The present invention relates to a transparent substrate with a film, particularly a transparent substrate with a film having transparency, light diffusion properties, and opacity.

[0002] A technique of forming a film containing particles on a glass plate to impart light diffusion properties to the glass plate is known. For example, Patent Document 1 discloses greenhouse glass in which a film containing silicon oxide particles and titanium oxide particles is formed on a glass plate. In Examples 1 to 6 of Patent Document 1, a film containing first silicon oxide particles having an average particle size of 3.5 μm, second silicon oxide particles having an average particle size of 0.1 μm, titanium oxide particles having an average particle size of 10 nm, and a binder is disclosed. The haze of the glass plates with the film in Examples 1 to 6 is 41.6 to 62.9%. In Examples 7 to 8 of Patent Document 1, a film similar to that in Examples 1 to 6 is disclosed except that the average particle size of the first silicon oxide particles is 0.9 μm. The haze of the glass plates with the film in Examples 7 to 8 is 49.6 to 74.2%.

[0003] The glass plate with a film of Patent Document 1 enables light to be introduced into a greenhouse while avoiding the appearance of hot spots where light is concentrated.

[0004] International Publication No. 2021 / 182485

[0005] According to the study by the present inventor, the glass plate with a film of Patent Document 1 has room for improvement from the viewpoint of opacity. An object of the present invention is to provide a transparent substrate with a film having opacity as well as transparency and light diffusion properties.

[0006] The present invention provides a transparent substrate with a film, comprising: a transparent substrate; and a film on the surface of the transparent substrate, wherein the film contains first silicon oxide particles having an average particle size greater than 2 μm and second silicon oxide particles having an average particle size of 0.3 μm or more and 1.0 μm or less, the surface has a first region and a second region, the first silicon oxide particles are present in the film on the first region, the first silicon oxide particles are not present in the film on the second region, and the second silicon oxide particles are present in at least a part of the second region.

[0007] According to the present invention, it is possible to provide a translucent substrate with a film that combines light transmission, light diffusion, and opacity.

[0008] This is a cross-sectional view showing an example of a film-coated translucent substrate according to the present invention. This is a cross-sectional view showing another example of a film-coated translucent substrate according to the present invention. This is a cross-sectional view showing yet another example of a film-coated translucent substrate according to the present invention. This is a schematic cross-sectional view for explaining Clarity C. This figure shows the film surface of the film-coated translucent substrate of Example 1 as observed by a scanning electron microscope (SEM).

[0009] Embodiments of the present invention will be described below with reference to the drawings. The following description is an example of the present invention, and the present invention is not limited to the following embodiments. For example, the particle distribution shown in Figures 1 to 3 is merely one example of an embodiment of the present invention. Furthermore, the upper and lower limits of the numerical ranges below can be arbitrarily combined.

[0010] As shown in Figure 1, the film-coated translucent substrate according to this embodiment comprises a translucent substrate 10 and a film 20 on the surface of the translucent substrate 10.

[0011] The translucent substrate 10 may be plate-shaped. In this case, the surface on which the film 20 is formed may be the main surface of the plate-shaped substrate. The plate-shaped substrate has two main surfaces 11 and 12, which are connected by their sides and are parallel to each other. In Figure 1, the film 20 is formed on the first main surface 11 of the translucent substrate 10. Incident light, for example, enters on the second main surface 12 side and exits from the first main surface 11 side.

[0012] The film 20 contains first silicon oxide particles 21 and second silicon oxide particles 22. The average particle size of the first silicon oxide particles 21 is greater than 2 μm, and the average particle size of the second silicon oxide particles 22 is between 0.3 μm and 1.0 μm. The film 20 may further contain third silicon oxide particles 23. The film 20 may further contain a binder 25.

[0013] The first main surface 11 has a first region 31 in which first silicon oxide particles 21 are present in the film 20, and a second region 32 in which first silicon oxide particles 21 are not present in the film 20, with second silicon oxide particles 22 present in at least a part of the second region 32. On the surface of the film 20, protrusions 71 originating from the first silicon oxide particles 21 appear in the first region 31. The first region 31 and the second region 32 can be determined by observation from a direction perpendicular to the first main surface 11.

[0014] The translucent substrate 10 may include a glass plate or a resin plate. There are no particular restrictions on the type of glass or resin. The glass plate may be, for example, float glass or patterned glass. The glass plate may also be tempered glass. The strengthening process may be either thermal strengthening or chemical strengthening. The thermal strengthening process may be carried out after the film 20 has been formed.

[0015] As shown in Figure 2, the translucent substrate 10 may include a film 41 on the first main surface 11 side. The film 41 functions as an undercoat, and its surface becomes the first main surface 11. As shown in Figure 3, the translucent substrate 10 may also include a film 42 on the second main surface 12 side opposite to the first main surface 11. Films 41 and 42 may be single-layer or multi-layer. Films 41 and 42 may be optically functional films that block ultraviolet rays, block infrared rays, control visible light reflectance, or perform other functions. Film 42 may also have functions such as anti-fogging and water repellency.

[0016] The average particle size of the silicon oxide particles is greater than 2 μm. The average particle size of the silicon oxide particles may be 2.2 μm or more, 2.4 μm or more, 2.5 μm or more, 2.7 μm or more, or 2.8 μm or more. The average particle size of the silicon oxide particles may be 7 μm or less, 6 μm or less, 5 μm or less, or 4 μm or less. The silicon oxide particles have the function of greatly scattering incident light.

[0017] The average particle size of the silicon diaoxide particles is 0.3 μm or more and 1.0 μm or less. The average particle size of the silicon diaoxide particles may be 0.4 μm or more, 0.6 μm or more, or 0.8 μm or more. The average particle size of the silicon diaoxide particles may be 0.95 μm or less, or 0.9 μm or less. The silicon diaoxide particles also have the function of scattering incident light. However, their light scattering function is limited compared to that of the silicon diaoxide particles. On the other hand, the silicon diaoxide particles are superior to the silicon diaoxide particles in their ability to maintain light transmission.

[0018] Surprisingly, the combination of silicon monoxide particles and silicon doxide particles is suitable for achieving both light diffusion and opacity while maintaining light transmittance. This combination can contribute to achieving both high levels of light diffusion and opacity, in other words, achieving both high haze and low clarity, especially low clarity.

[0019] The average particle size of the silicon trioxide particles is 0.01 μm or more and 0.2 μm or less. The average particle size of the silicon trioxide particles may be 0.05 μm or more, 0.07 μm or more, or 0.1 μm or more. The average particle size of the silicon trioxide particles may be 0.18 μm or less, or 0.15 μm or less. Although the silicon trioxide particles contribute little to the scattering of incident light, they may have the function of improving light transmission.

[0020] In this specification, "average particle size" may refer to the particle size corresponding to 50% of the volume cumulative distribution (d50) obtained from the particle size distribution measured on a volume basis by laser diffraction scattering. Note that the average particle size refers to the average particle size of the primary particles, i.e., the particle size measured when the particles are not aggregated.

[0021] The shape of the first silicon oxide particles, the second silicon oxide particles, and the third silicon oxide particles is not particularly limited and may be fibrous, flaky, spherical, or other. The first silicon oxide particles, the second silicon oxide particles, and the third silicon oxide particles may each be spherical. In this specification, "spherical" does not mean a perfect sphere, but rather means that when the particles are observed with a scanning electron microscope (SEM), the ratio of the maximum diameter to the minimum diameter (maximum diameter / minimum diameter) is 1.0 to 2.0, particularly 1.0 to 1.5. Spherical silicon oxide particles are mass-produced at low cost and are readily available in terms of quantity, quality, and cost.

[0022] Referring again to Figure 1, the arrangement of each silicon oxide particle will be described. The surface of the translucent substrate 10 has a first region 31 in the film 20 where the first silicon oxide particles 21 are present, and a second region 32 in the film 20 where the first silicon oxide particles 21 are not present. Second silicon oxide particles 22 are present in at least a part of the second region 32. In the first region 31 and the second region 32, the first silicon oxide particles 21 and the second silicon oxide particles 22 exert effects such as scattering on incident light. As illustrated in Figure 1, a part of the second silicon oxide particles 22 may be present in the first region 31. Second silicon oxide particles 22 may not be present in a part of the second region 32. Third silicon oxide particles 23 may be present in the first region 31 or in the second region 32.

[0023] The number N1 of first silicon oxide particles 21 present on a line segment with a length of 50 μm set on the surface of the film-coated translucent substrate, specifically on the first main surface 11, may be 3 or more and 20 or less. The number N1 may be 5 or more, 7 or more, 18 or less, 15 or less, or even 12 or less.

[0024] On the surface of the translucent substrate with a film, specifically on the first main surface 11, along a line segment of length 50 μm, the ratio TL1 / (TL1+TL2) calculated from the total length TL1 of the first region 31 and the total length TL2 of the second region 32 may be 0.1 or more and 0.9 or less. The ratio TL1 / (TL1+TL2) may be 0.2 or more, 0.4 or more, 0.8 or less, or 0.6 or less.

[0025] The number N1 and the ratio TL1 / (TL1+TL2) can be determined by observing the surface of the film 20 at at least 10 locations over a length of 50 μm and taking a simple average of the measured values.

[0026] It is desirable that the first silicon oxide particles 21 exist without overlapping in the thickness direction of the film 20. However, the second silicon oxide particles 22 and the third silicon oxide particles 23 may overlap with the first silicon oxide particles 21, or with each other, in the thickness direction of the film 20. As shown in Figure 1, the first silicon oxide particles 21 may be in contact with each other in the direction along the first main surface 11.

[0027] The maximum thickness Tmax of the film 20 may be less than twice the average particle size of the first silicon oxide particles 21, and even less than or equal to 1.5 times. The maximum thickness Tmax may be less than 8 μm. The maximum thickness Tmax may be between 2 μm and 7.5 μm. The maximum thickness Tmax may be 3 μm or more, 4 μm or more, 7 μm or less, or 6 μm or less. Achieving light diffusion and opacity with a film 20 that is not too thick has advantages for mass production.

[0028] The binder 25 has the function of holding silicon oxide particles in the film. The binder 25 may contain an oxide, specifically at least one selected from the group consisting of silicon oxide, zirconium oxide, aluminum oxide, niobium oxide, and tantalum oxide, and further at least one selected from the group consisting of silicon oxide and zirconium oxide, particularly silicon oxide. The binder 25 may also consist only of silicon oxide. The oxides constituting the binder 25 can be introduced into the film 20, for example, by the so-called sol-gel method.

[0029] Next, the ratios of each silicon oxide particle and the binder in the film 20 will be explained. The following numerical values ​​describing ratios and proportions are all based on mass. The ratio R1 of the first silicon oxide particle 21 to the second silicon oxide particle 22 is, for example, 0.1 or more and 4 or less. Ratio R1 may be 0.5 or more, 0.7 or more, 0.9 or more, 1 or more, or 3 or less, 2.5 or less, 2.3 or less, or 2.1 or less. The ratio R3 of the third silicon oxide particle 23 to the second silicon oxide particle 22 is, for example, 0.1 or more and less than 7. Ratio R3 may be 0.5 or more, 1 or more, 1.2 or more, or 5 or less, or 4 or less. The ratio RB of the binder 25 to the total amount of all silicon oxide particles 21, 22, and 23 and the binder 25 is, for example, 5% or more and 40% or less. The ratio RB may be 10% or more, 13% or more, 15% or more, or 35% or less, 30% or less, or 25% or less.

[0030] The film 20 may contain other components besides silicon oxide particles and the binder. An example of other components is oxide particles other than silicon oxide particles. Examples of oxide particles other than silicon oxide particles include titanium oxide particles and zirconium oxide particles. The oxide particles may be composite oxide particles or multilayer particles having a core-shell structure. The film 20 does not have to contain titanium oxide particles. The film 20 does not have to contain oxide particles other than silicon oxide particles.

[0031] The optical properties achievable with the film-coated translucent substrate of this embodiment are as follows: The film-coated translucent substrate may have a total light transmittance Tt of 70% or more. The film-coated translucent substrate may have a total light transmittance Tt of 73% or more, and furthermore, of 75% or more. The film-coated translucent substrate may have a haze Hz of 75% or more. The film-coated translucent substrate may have a haze Hz of 78% or more, 80% or more, 85% or more, 87% or more, and furthermore, of 90% or more. The film-coated translucent substrate may have a clarity C of 40% or less, 35% or less, 30% or less, furthermore, of 25% or less, and in some cases, of 20% or less. The lower limit of clarity C is not particularly limited, but may be 3% or more.

[0032] As shown in Figure 4, the haze Hz is calculated by Td / Tt, and the clarity C is calculated by (Tp-Tn) / (Tp+Tn) × 100%. Tt is the total light transmittance, Td is the total diffuse light transmittance, Tp is the parallel light transmittance, and Tn is the narrow-angle diffuse light transmittance. Tn is measured within a range of ±2.5° for the emission angle (see Figure 4θ). The smaller the clarity C value, the higher the opacity of the sample S. The total light transmittance Tt, haze Hz, and clarity C can be measured, for example, using a haze-gard i manufactured by BYK. These characteristics are specified in ISO 13468, 14782, and ASTM D1003, D1004.

[0033] In the film-coated translucent substrate of this embodiment, the surface shape of the protrusions 71 may have a surface roughness indicated by the following indicators. The film-coated translucent substrate may have an RSm of 12 μm or more. The film-coated translucent substrate may have an Rk of 1.2 μm or more, and furthermore, an Rk of 1.5 μm or more.

[0034] Here, RSm is the average length Xs of the contour curve elements at the reference length. Rk is one of the plateau structure surface parameters and is a value that indicates the level difference of the core. RSm is specified in Japanese Industrial Standard (JIS) B0601-2001, and Rk is specified in JIS B0671-2002.

[0035] The coating solution according to this embodiment contains first silicon oxide particles and second silicon oxide particles. The coating solution may further contain third silicon oxide particles. The ratio of these particles is as described above. The coating solution may contain a binder precursor for supplying a binder to the film. The binder precursor is, for example, a hydrolyzable metal compound, typically a metal alkoxide represented by silicon alkoxide. The coating solution may contain a catalyst involved in the hydrolysis of the binder precursor, such as an acid catalyst. The acid catalyst is suitable to be a volatile inorganic acid such as hydrochloric acid or nitric acid, but is not limited to these, and may also be other inorganic acids or organic acids. The coating solution may be a dispersion in which the binder precursor is dissolved and the silicon oxide particles described above are dispersed. Various organic solvents can be used as the liquid component of the coating solution that functions as a solvent and dispersion medium. The organic solvent is preferably a solvent that is miscible with water. The organic solvent is preferably a low-boiling point solvent with a boiling point of 150°C or less, particularly between 70°C and 150°C. The organic solvent may include high-boiling point solvents with a boiling point exceeding 150°C, particularly those with a boiling point between 150°C and 200°C. It is desirable that the organic solvent include both low-boiling point and high-boiling point solvents.

[0036] In the manufacturing method according to this embodiment, the method of applying the coating solution is not particularly limited, and methods such as spin coating, roll coating, bar coating, dip coating, and spray coating can be used. A film is formed on the translucent substrate by heating the translucent substrate to which the coating solution has been applied. The heating is carried out, for example, so that the maximum temperature of the translucent substrate is between 120°C and 250°C.

[0037] As described above, this specification discloses the following technologies. The first technology provides a film-coated translucent substrate comprising: a translucent substrate; and a film on the surface of the translucent substrate, wherein the film comprises first silicon oxide particles having an average particle size greater than 2 μm and second silicon oxide particles having an average particle size of 0.3 μm or more and 0.8 μm or less, the surface having a first region and a second region, the first silicon oxide particles being present in the film on the first region, the first silicon oxide particles being absent in the film on the second region, and the second silicon oxide particles being present in at least a portion of the second region.

[0038] The second technology is a film-coated translucent substrate of the first technology, wherein the number N1 of the first silicon oxide particles present on a line segment of length 50 μm on the surface of the film-coated translucent substrate is 3 or more and 20 or less.

[0039] The third technology is a translucent substrate with a film of the first or second technology, wherein the maximum film thickness Tmax of the film is less than 8 μm.

[0040] The fourth technology is a translucent substrate with a film of any one of the first to third technologies, wherein the mass-based ratio R1 of the first silicon oxide particles to the second silicon oxide particles is 0.1 or more and 4 or less.

[0041] The fifth technology is a translucent substrate with a film of any one of the first to fourth technologies, wherein the film further comprises third silicon oxide particles having an average particle size of 0.01 μm or more and 0.2 μm or less.

[0042] The sixth technology is a translucent substrate with a film of the fifth technology, wherein the mass-based ratio R3 of the third silicon oxide particles to the second silicon oxide particles is 0.1 or more and less than 7.

[0043] The seventh technology is a translucent substrate with a film of any one of the first to sixth technologies having a clarity C of 40% or less.

[0044] The eighth technology is a light-transmitting substrate with a film of the seventh technology, having a total light transmittance Tt of 70% or more and a haze Hz of 75% or more.

[0045] Hereinafter, examples will be shown to explain the present invention in more detail. (Example 1) Commercially available propylene glycol monomethyl ether, tetraethoxysilane, purified water, a first silicon oxide fine particle dispersion (average particle size 3.2 μm), a second silicon oxide fine particle dispersion (average particle size 0.8 μm), a third silicon oxide fine particle dispersion (average particle size 0.075 μm), and 1N nitric acid (hydrolysis catalyst) were weighed into a glass container so that the mass ratio of the first silicon oxide fine particles (average particle size 3.2 μm), the second silicon oxide fine particles (average particle size 0.8 μm), the third silicon oxide fine particles (average particle size 0.075 μm), and the binder in terms of SiO2 was 6:6:8:5 and the solid content concentration was 12%. This glass container was stirred in an oven maintained at 40°C for 8 hours to obtain a high-concentration solution.

[0046] 6.25 g of the aforementioned high-concentration solution, 3.23 g of propylene glycol monomethyl ether, 6.25 g of propylene glycol, 0.12 g of a zirconium compound (concentration 25 wt% in terms of ZrO2), and 0.02 g of a surfactant (manufactured by Shin-Etsu Silicone Co., Ltd., KP-341, a solution diluted to 10 wt% with propylene glycol monomethyl ether) were stirred and mixed to obtain a coating solution. The solid content concentration in the coating solution was 7.8%. The solid content concentration with respect to the entire coating solution according to Example 1 was 7.8 mass%. In the solid content of the coating solution according to Example 1, 23.1 mass% of the first silicon oxide fine particles were contained, 23.1 mass% of the second silicon oxide fine particles were contained, 30.8 mass% of the third silicon oxide fine particles were contained, 19.2 mass% of tetraethoxysilane in terms of SiO2 was contained, and 3.8 mass% of the zirconium compound in terms of ZrO2 was contained. The mass of the solid content in the coating solution is defined as the sum of the mass of tetraethoxysilane (the source of silicon oxide in the binder) in terms of SiO2, the mass of the solid content of the first silicon oxide fine particle dispersion, the mass of the solid content of the second silicon oxide fine particle dispersion, the mass of the solid content of the third silicon oxide fine particle dispersion, and the mass of the optionally added zirconium compound in terms of ZrO2.

[0047] The coating solution was spin-coated onto the surface of a cleaned glass plate (100 × 100 mm; thickness 3 mm; float plate glass). The coating solution was continuously stirred until immediately before coating. The glass plate coated with the coating solution was dried in an oven set at 200°C to obtain a light-transmissive substrate with a film according to Example 1.

[0048] Regarding the light-transmissive substrate with a film thus obtained, the optical properties (total light transmittance Tt, haze Hz, and clarity C) were measured using the above-mentioned haze gard i. The optical properties were measured with the surface of the light-transmissive substrate without forming a film as the light incident surface. The results are shown in Table 1.

[0049] (Examples 2 to 6, Comparative Examples 1 to 5) As shown in Tables 1 and 2, a glass plate with a film was produced and the optical properties were measured in the same manner as in Example 1, except that the mixing ratio of each silicon oxide particle and the binder was changed. However, in Examples 3 to 5, the coating solution was applied by the spray coating method. Further, the glass plate coated with the coating solution was dried using a hot air dryer or an IR heater under the condition that the glass surface temperature became 150°C.

[0050]

[0051]

[0052] In each of the examples containing the first silicon oxide particles (average particle size 3 μm) and the second silicon oxide particles (average particle size 0.6 μm), a clarity C of 40% or less was achieved while maintaining a high total light transmittance Tt and haze Hz. In particular, in Examples 1 to 5 where the mass-based ratio R1 of the first silicon oxide particles to the second silicon oxide particles was 0.1 or more and 4 or less, a clarity C of 20% or less was achieved. In contrast, in each of the comparative examples not containing the first silicon oxide particles or the second silicon oxide particles, the clarity C exceeded 40%. The influence of the content of the third silicon oxide particles (average particle size 0.075 μm) on the haze ratio was extremely limited.

[0053] The surface shape of the films in each example and comparative example was measured using a Lasertec OPTELICS hybrid laser microscope. A 100x objective lens was used for the measurements. In Example 1, the RSm of the film-coated glass plate was 12.09 μm and the Rk was 1.601 μm. In Examples 2 to 5, the RSm was 12 μm or more and the Rk was 1.2 μm or more. In contrast, in Comparative Example 1, the RSm was 11.21 μm, and in Comparative Example 3, the RSm was 9.98 μm and the Rk was 0.762 μm.

[0054] Using a Hitachi High-Tech SU8220 field emission scanning electron microscope, the above-mentioned number N1 and ratio TL1 / (TL1+TL2) were measured. The number N1 was in the range of 3 to 11. The ratio TL1 / (TL1+TL2) was in the range of 0.1 to 0.7. In addition, the maximum film thickness Tmax of each example was in the range of 2 μm to 7.5 μm.

Claims

1. A translucent substrate with a film, comprising: a translucent substrate; and a film on the surface of the translucent substrate, wherein the film contains first silicon oxide particles having an average particle size greater than 2 μm and second silicon oxide particles having an average particle size of 0.3 μm or more and 1.0 μm or less, and the surface has a first region and a second region, wherein the film on the first region contains the first silicon oxide particles, the film on the second region does not contain the first silicon oxide particles, and the film on the second region contains the second silicon oxide particles.

2. The film-coated translucent substrate according to claim 1, wherein the number N1 of the first silicon oxide particles present on a line segment of length 50 μm on the surface of the film-coated translucent substrate is 3 or more and 20 or less.

3. The translucent substrate with a film according to claim 1, wherein the maximum film thickness Tmax of the film is less than 8 μm.

4. The film-coated translucent substrate according to claim 1, wherein the mass-based ratio R1 of the first silicon oxide particles to the second silicon oxide particles is 0.1 or more and 4 or less.

5. The film-coated translucent substrate according to claim 1, wherein the film further comprises third silicon oxide particles having an average particle size of 0.01 μm or more and 0.2 μm or less.

6. The film-coated translucent substrate according to claim 5, wherein the mass-based ratio R3 of the third silicon oxide particles to the second silicon oxide particles is 0.1 or more and less than 7.

7. A translucent substrate with a film according to claim 1, having a clarity C of 40% or less. Here, the clarity C is a ratio calculated by [(Tp - Tn) / (Tp + Tn)] × 100 (%), where Tn is the narrow-angle diffuse light transmittance measured within a range of ±2.5° for the emission angle θ, and Tp is the parallel light transmittance.

8. A film-coated translucent substrate according to claim 7, having a total light transmittance Tt of 70% or more and a haze Hz of 75% or more.

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