Film-coated light-transmitting substrate

Abstract

To provide a translucent substrate with a film that combines light transmission, light diffusion, and opacity. [Solution] A film-coated translucent substrate is provided, comprising a translucent substrate and a film on the translucent substrate, wherein the surface of the film has a surface roughness expressed by RSm of 12 μm or more and Rk of 1.2 μm or more, the total light transmittance Tt is 70% or more, and the clarity C is 40% or less. 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° at the emission angle and Tp is the parallel light transmittance.

Description

Technical Field

[0001] The present invention relates to a light-transmissive substrate with a film, particularly a light-transmissive substrate with a film having both light-transmitting properties and privacy properties.

Background Art

[0002] A technique of forming a film containing particles on a glass plate to impart light diffusing properties to the glass plate is known. Patent Document 1 discloses a glass plate with a film having light diffusing properties and privacy properties. In Patent Document 1, a film is formed by applying a coating liquid containing flaky silicon oxide fine particles onto a glass plate a plurality of times using an electrostatic coating device. According to Patent Document 1, the maximum height of the convex portions among the convex portions of the film, which are referred to as "first convex portions," is in the range of 8.0 μm to 30.0 μm (Claim 1).

[0003] Patent Document 1 provides a light-transmissive substrate with a film having high haze, i.e., light diffusing properties, and low clarity, i.e., privacy properties. Note that the definition of clarity in Patent Document 1 is different from the clarity C in this specification.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The light-transmissive substrate with a film disclosed in Patent Document 1 does not aim to achieve both light-transmitting properties and privacy properties. An object of the present invention is to provide a new light-transmissive substrate with a film having both light-transmitting properties and privacy properties.

Means for Solving the Problems

[0006] The present invention comprises a light-transmissive substrate and a film on the light-transmissive substrate. The surface of the aforementioned film has a surface roughness represented by RSm of 12 μm or more and Rk of 1.2 μm or more. The total light transmittance Tt is 70% or higher, and the clarity C is 40% or lower. We provide a translucent substrate with a film coating. Here, 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° at the emission angle, and Tp is the parallel light transmittance. [Effects of the Invention]

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

[0008] [Figure 1] This is a cross-sectional view showing an example of a film-coated translucent substrate according to the present invention. [Figure 2] This is a cross-sectional view showing another example of a film-coated translucent substrate according to the present invention. [Figure 3] This is a cross-sectional view showing yet another example of a film-coated translucent substrate according to the present invention. [Figure 4] This is a schematic cross-sectional view illustrating Clarity C. [Figure 5] This figure shows the film surface of the translucent substrate with a film coating from Example 1 as observed using a scanning electron microscope (SEM). [Modes for carrying out the invention]

[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. In the following, the upper and lower limits of the numerical range can be combined arbitrarily.

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

[0011] The surface of the film 20 has a surface roughness represented by an RSm of 12 μm or more and an Rk of 1.2 μm or more. The surface of the film 20 forms the interface between the film 20 and the air, and its surface roughness diffuses the incident light. RSm may be 13 μm or more, and in some cases 15 μm or more. Rk may be 1.3 μm or more, 1.4 μm or more, and even 1.6 μm or more. There is no particular upper limit to RSm, but for example, it is 30 μm or less, and even more specifically 25 μm or less. Similarly, there is no upper limit to Rk, but for example, it is 4 μm or less, 3 μm or less, 2.5 μm or less, and even more specifically 2.2 μm or less.

[0012] 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.

[0013] The optical properties that can be achieved with the film-coated translucent substrate of this embodiment are as follows. A film-coated translucent substrate has a total light transmittance Tt of 70% or more. A film-coated translucent substrate may have a total light transmittance Tt of 73% or more, and even more than 75% or more. The film-coated translucent substrate has a clarity of 40% or less. The film-coated translucent substrate may have a clarity C of 30% or less, 25% or less, 20% or less, 15% or less, 13% or less, 11% or less, and in some cases, 10% or less. The lower limit of clarity C is not particularly limited, but may be 3% or more. Furthermore, 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, 88% or more, 90% or more, and even 91% or more.

[0014] As shown in Fig. 4, haze Hz is calculated by Td / Tt, and clarity C is calculated by (Tp - Tn) / (Tp + Tn). Tt is the total light transmittance, Td is the total diffused light transmittance, Tp is the parallel light transmittance, and Tn is the angular diffused light transmittance. Tn is measured within the range where the emission angle θ is ±2.5°. The smaller the value of clarity C, the higher the opacity of the sample S. The total light transmittance Tt, haze Hz, and clarity C can be measured, for example, using haze-gard i manufactured by BYK. The above characteristics are defined in ISO 13468, 14782, and ASTM D1003, D1004.

[0015] The inventors have found that a surface structure with RSm and Rk being large enough as described above enables the coexistence of a high total light transmittance Tt and a low clarity C. That is, in order for the surface of the film to have a sufficient influence on light diffusion, or rather, in order for light to sufficiently recognize the irregularities on the surface of the film, it is desirable that Rk be above a certain value. In order to scatter light at a narrow emission angle, it is desirable that the change in the inclination of the irregularities on the surface of the film be small, or rather, that RSm be above a certain value. More surprisingly, although it is usually difficult to achieve the coexistence of a high total light transmittance Tt and a high haze Hz, the inventors have also found that a surface structure with RSm and Rk being large enough as described above can simultaneously achieve a high haze Hz.

[0016] The maximum thickness Tmax of the film 20 (see Fig. 1) may be less than 8 μm. Considering that the maximum height of the convex portion of the film disclosed in Patent Document 1 is 8.0 μm or more, it is considered that the maximum thickness Tmax does not fall below 8 μm. The maximum thickness Tmax may be 2 μm or more and 7.5 μm or less. The maximum thickness Tmax may be 3 μm or more, 4 μm or more, 7 μm or less, or 6 μm or less. There are advantages in mass production in that the film 20 that is not too thick can achieve light diffusibility and opacity.

[0017] As can be understood from the section of the embodiments, the film-coated light-transmissive substrate of the present embodiment can be manufactured without using a device that may be a factor inhibiting mass productivity such as an electrostatic coating device, and is also advantageous for mass production in this regard.

[0018] The shape of the light-transmissive substrate 10 may be plate-like. In this case, the surface on which the film 20 is formed may be the main surface of the plate-like substrate. The plate-like substrate has two main surfaces 11 and 12, and the two main surfaces 11 and 12 are connected by side surfaces and are parallel to each other. In FIG. 1, the film 20 is formed on the first main surface 11 of the light-transmissive substrate 10. Incident light enters, for example, from the second main surface 12 side and exits from the first main surface 11 side.

[0019] The light-transmissive substrate 10 may include a glass plate or a resin plate. There is no particular limitation on the types of glass and resin. The glass plate is, for example, float glass or plate glass. The glass plate may be tempered glass. The tempering process may be either thermal tempering or chemical tempering. The thermal tempering process may be carried out after forming the film 20. As shown in FIG. 2, the light-transmissive substrate 10 may include a film 41 on the first main surface 11 side. The film 41 functions as a base film, and its surface becomes the first main surface 11. As shown in FIG. 3, the light-transmissive substrate 10 may include a film 42 on the second main surface 12 side opposite to the first main surface 11. The films 41 and 42 may be single-layer or multi-layer. The films 41 and 42 may be ultraviolet-blocking, infrared-blocking, visible light reflectance control, or other optical functional films. The film 42 may have functions such as anti-fogging and water repellency.

[0020] An example of a method for making the RSm and Rk of the film 20 within a desired range is to add oxide particles to the film, more specifically, to add two or more types of oxide particles having different average particle diameters to the film. The oxide particles are not particularly limited, but may be silicon oxide particles. However, the film-coated light-transmissive substrate of the present embodiment is not limited to those in which the film contains two or more types of oxide particles as long as the film has a surface roughness with RSm and Rk within a predetermined range.

[0021] The film 20 may contain first silicon oxide particles 21 and second silicon oxide particles 22. For example, 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 0.8 μm. The film 20 may further contain third silicon oxide particles 23. The film 20 may further contain a binder 25.

[0022] The first main surface 11 may have a first region 31 in which first silicon oxide particles 21 are arranged in the film 20, and a second region 32 in which the first silicon oxide particles 21 are not present in the film 20. Second silicon oxide particles 22 are present in at least a portion 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.

[0023] The average particle size of the first silicon oxide particles may be greater than 2 μm, and 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 first silicon oxide particles may be 7 μm or less, 6 μm or less, 5 μm or less, or 4 μm or less.

[0024] The average particle size of the silicon dioxide particles may be between 0.3 μm and 1.0 μm. The average particle size of the silicon dioxide particles may be between 0.4 μm and 0.6 μm and 0.8 μm and 0.95 μm or less and 0.9 μm or less.

[0025] The average particle size of the silicon tertiary oxide particles is 0.01 μm or more and 0.2 μm or less. The average particle size of the silicon tertiary oxide 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 tertiary oxide particles may be 0.18 μm or less, or 0.15 μm or less.

[0026] In this specification, "average particle size" may refer to the particle size corresponding to 50% of the volume cumulative (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.

[0027] The shape of the first silicon oxide particles, second silicon oxide particles, and third silicon oxide particles is not particularly limited and may be fibrous, flaky, spherical, or other. The first silicon oxide particles, second silicon oxide particles, and 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.

[0028] Referring again to Figure 1, the desirable 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 portion 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 portion 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 portion of the second region 32. Third silicon oxide particles 23 may be present in the first region 31 or in the second region 32.

[0029] The number N1 of first silicon oxide particles 21 present on a line segment of length 50 μm set on the surface of the film-coated translucent substrate, specifically on the first main surface 11, may be between 3 and 20. The number N1 may be between 5 and 7, between 18 and 15, or even between 12 and 18.

[0030] 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 between 0.1 and 0.9. The ratio TL1 / (TL1+TL2) may be between 0.2 and 0.4, or between 0.8 and 0.6.

[0031] The ratio TL1 / (TL1+TL2) and the number N1 can be determined by observing the surface of the translucent substrate 10 at at least 10 locations over a length of 50 μm and taking the simple average.

[0032] 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.

[0033] Furthermore, the maximum thickness Tmax of the film 2 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.

[0034] Binder 25 has the function of holding silicon oxide particles in the film. Binder 23 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, particularly silicon oxide. Binder 25 may consist only of silicon oxide. Binder 25 can be introduced into film 2, for example, by the so-called sol-gel method.

[0035] Next, the ratios of each silicon oxide particle and binder in film 2 will be explained. All numerical values ​​describing the ratios and proportions below are based on mass. The ratio R1 of first silicon oxide particles 21 to second silicon oxide particles 22 is, for example, 0.1 or more and 4 or less. The ratio R1 may also 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 silicon tertiary oxide particles 23 to silicon tertiary oxide particles 22 is, for example, 0.1 or more and less than 7. The ratio R3 may also be 0.5 or more, 1 or more, 1.2 or more, 5 or less, or 4 or less. The ratio RB of binder 25 to the total amount of total silicon oxide particles 21, 22, and 23 and binder 25 is, for example, 5% or more and 40% or less. The ratio RB may also be 10% or more, 13% or more, 15% or more, or 35% or less, 30% or less, or 25% or less.

[0036] The film 20 may contain other components besides silicon oxide particles and binders. 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.

[0037] As described above, this specification discloses the following technologies. The first technology is, The invention comprises a translucent substrate and a film on the translucent substrate, The surface of the aforementioned film has a surface roughness represented by RSm of 12 μm or more and Rk of 1.2 μm or more. The total light transmittance Tt is 70% or higher, and the clarity C is 40% or lower. It is a translucent substrate with a film coating. 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° of the emission angle, and Tp is the parallel light transmittance.

[0038] The second technology is, The haze frequency is 75% or higher. The first technology is a translucent substrate with a film.

[0039] The third technology is, The RSm is 13 μm or more, and the Rk is 1.5 μm or more. The aforementioned clarity C is less than 12%, and the film-coated translucent substrate is a first or second technology.

[0040] The fourth technology is, The second technology is a film-coated translucent substrate in which the haze Hz is 90% or more and the clarity C is 10% or less.

[0041] The fifth technology is, The film-coated translucent substrate is one of the first to fourth technologies, wherein the maximum film thickness Tmax of the aforementioned film is 8 μm or less.

[0042] The sixth technology is, The aforementioned film is a translucent substrate with a film of any one of the first to fifth technologies, wherein the film contains oxide particles.

[0043] The present invention will be described in more detail below with reference to examples. (Sample 1) Commercially available propylene glycol monomethyl ether, tetraethoxysilane, purified water, dispersions of silicon oxide particles (average particle size 3.2 μm), silicon oxide particles (average particle size 0.8 μm), silicon oxide particles (average particle size 0.075 μm), and binder converted to SiO2 were weighed into a glass container to obtain a high-concentration solution. The mixture consisted of commercially available propylene glycol monomethyl ether, tetraethoxysilane, purified water, dispersions of silicon oxide particles (average particle size 3.2 μm), silicon oxide particles (average particle size 0.8 μm), and silicon oxide particles (average particle size 0.075 μm), with a solid content concentration of 12%. This glass container was stirred in an oven maintained at 40°C for 8 hours.

[0044] A coating solution was obtained by stirring and mixing 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 zirconium compound (concentration of 25 wt% as ZrO2), and 0.02 g of surfactant (Shin-Etsu Silicone Co., Ltd., KP-341, diluted to 10 wt% with propylene glycol monomethyl ether). The solid content concentration in the coating solution was 7.8%. The solid content concentration relative to the entire coating solution in Example 1 was 7.8% by mass. In the solid content of the coating solution in Example 1, 23.1% by mass of first silicon oxide fine particles were present, 23.1% by mass of second silicon oxide fine particles were present, 30.8% by mass of third silicon oxide fine particles were present, 19.2% by mass of tetraethoxysilane converted to SiO2 was present, and 3.8% by mass of zirconium compound converted to ZrO2 was present. The mass of solids in the coating solution is defined as the sum of the mass of tetraethoxysilane (the source of silicon oxide in the binder) converted to SiO2, the mass of solids in the first silicon oxide fine particle dispersion, the mass of solids in the second silicon oxide fine particle dispersion, the mass of solids in the third silicon oxide fine particle dispersion, and the mass of any optionally added zirconium compound converted to ZrO2.

[0045] The coating solution was applied to the surface of a cleaned glass plate (100 x 100 mm; 3 mm thick; float glass) by spin coating at 200 rpm. The coating solution was continuously stirred until immediately before application. The coated glass plate was dried in an oven set to 200°C to obtain a translucent substrate with a film according to Example 1. The results of observing the film by SEM are shown in Figure 1.

[0046] The surface shape of the film on the translucent substrate with the film obtained was measured using a Lasertec hybrid laser microscope OPTELICS, and the RSm and Rk values ​​were obtained. In addition, the optical properties (total light transmittance Tt, haze Hz, and clarity C) of the film-coated glass plate were measured using the BYK haze-gard-i mentioned above. The optical properties were measured with the surface of the translucent substrate without the film as the incident surface of light. The results are shown in Table 2.

[0047] (Samples 2-7) As shown in Table 1, glass plates with films were prepared in the same manner as Sample 1, except that the mixing ratio of each silicon oxide particle, the coating method, and the drying method were appropriately changed, and the surface shape and optical properties were measured. Note that the speed in the "Coating" column for Samples 2 to 5 in Table 1 is the transport speed of the glass plate.

[0048] [Table 1]

[0049] [Table 2]

[0050] Samples 1-5, with an RSm of 12 μm or higher and an Rk of 1.2 μm or higher, showed high total light transmittance Tt and haze Hz, and low clarity C. Samples 2-4, with an RSm of 13 μm or higher and an Rk of 1.5 μm or higher, showed even lower clarity C. Sample 5 was heated with infrared radiation for drying, which required time to dry the film. As a result, the binder and the second and third silicon oxide particles shifted towards the substrate side, resulting in a slightly lower Rk value and a slightly increased clarity C.

[0051] 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. The invention comprises a translucent substrate and a film on the translucent substrate, The surface of the aforementioned film has a surface roughness represented by RSm of 12 μm or more and Rk of 1.2 μm or more. The total light transmittance Tt is 70% or higher, and the clarity C is 40% or lower. Translucent base material with membrane. 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° of the emission angle, and Tp is the parallel light transmittance.

2. A translucent substrate with a film according to claim 1, wherein the haze Hz is 75% or more.

3. The RSm is 13 μm or larger, and the Rk is 1.5 μm or larger. The translucent substrate with a film according to claim 1, wherein the clarity C is less than 12%.

4. The translucent substrate with a film according to claim 2, wherein the haze Hz is 90% or more and the clarity C is 10% or less.

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

6. The translucent substrate with a film according to claim 1, wherein the film contains oxide particles.

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