JP6164120B2 - Base material and article with antireflection film - Google Patents

Description

  The present invention relates to a substrate with an antireflection film and an article using the same.

For the purpose of reducing external light reflection and improving light transmittance, an antireflection film is provided on the surface of a transparent substrate such as a glass plate.
Various types of antireflection films have been proposed. For example, Patent Document 1 proposes a coating film obtained by applying and baking a coating composition containing a dispersion medium, fine particles dispersed in the dispersion medium, a terpene derivative, and a binder by a wet coating method. When the coating composition is applied and baked, voids are formed around the fine particles in the coating film. When hollow particles are used as the fine particles, the inside of the fine particles in the coating film also becomes voids. Thus, since it has many space | gap, this coating film has a low refractive index, and has a high antireflection effect.

However, the coating film has a problem that the antifouling property is low because there are many fine irregularities and open holes on the surface. For example, oil stains and resin stains are likely to adhere to the coating film, and it is difficult to remove the attached stain from the coating film.
In solar cell modules, cover glasses are placed on the front and back surfaces of solar cells to protect the solar cells. The light incident surface of the cover glass reduces the reflection of sunlight and increases power generation efficiency. In many cases, an antireflection film is provided. In the manufacturing process of a solar cell module using such a cover glass, an antireflection film is previously formed on a glass plate, and then the module is often produced by combining with other components. When the antireflection film is the above-mentioned coating film, dirt such as machine oil and fingerprints tends to adhere to the antireflection film during the production of the module. In addition, dirt is likely to adhere to the antireflection film when the manufactured module is installed. Dirt on the antireflection film must be removed because it impairs antireflection performance and commercial value. However, removal of the once adhering dirt is time-consuming and complete removal is difficult. Further, depending on the color tone of the antireflection film, there is a problem that even if the dirt is removed, the attached dirt mark is easily seen.

International Publication No. 2010/018852

  The coating film tends to have a lower refractive index and higher antireflection performance as the content of fine particles increases. However, as the content of fine particles increases, the coating film tends to have surface irregularities and a decrease in antifouling properties. At the same time, it is difficult to adjust the color tone of the coating film. Therefore, it is difficult to improve the antifouling property while ensuring sufficient antireflection performance.

  An object of this invention is to provide the base material with an anti-reflective film which made the outstanding antifouling property and anti-reflective performance compatible, and an article using the same.

The present invention has the following aspects.
[1] A transparent substrate and an antireflection film formed on the transparent substrate,
The antireflection film is a two-layer film in which a lower layer and an upper layer are laminated in order from the transparent substrate side,
The lower layer is a silica film;
The lower layer has a refractive index of 1.45 to 1.50,
The average thickness of the lower layer is 40-120 nm,
The upper layer is a silica-based porous membrane containing hollow silica particles and a silica-based matrix, the average primary particle diameter of the hollow silica particles is 40 to 80 nm, and the hollow silica particles and the silica-based matrix The mass ratio (hollow silica particles / silica matrix) of the solid content in terms of SiO ₂ is 45/55 to 65/35,
The refractive index of the upper layer is 1.29 to 1.34,
The base material with an antireflection film whose average thickness of the said upper layer is 40-110 nm.
[2] The base material with an antireflection film according to [1], wherein an arithmetic average roughness Ra of the surface of the antireflection film is 0.006 to 0.015 μm.
[3] The base material with an antireflection film according to [1] or [2], wherein a maximum height roughness Rz of the surface of the antireflection film is 0.05 to 0.17 μm.
[4] The substrate with an antireflection film according to any one of [1] to [3], wherein the luminous reflectance of the antireflection film is 0.4% or more.
[5] An article comprising the substrate with an antireflection film according to any one of [1] to [4].
[6] The article according to [5], which is a solar cell module.
[7] The article according to [5], which is a display device.
[8] The article according to [5], which is a lighting device.

  ADVANTAGE OF THE INVENTION According to this invention, the base material with an anti-reflective film which made the outstanding antifouling property and antireflection performance compatible, and an article | item using this can be provided.

It is sectional drawing which shows typically one Embodiment of the base material with an antireflection film of this invention. It is sectional drawing which shows typically a part of base material with an antireflection film shown in FIG. 6 is a spectrum chart obtained by measuring the reflectance of a base material with an antireflection film of Example 2. 6 is a spectrum chart obtained by measuring the reflectance of a base material with an antireflection film of Example 5. 10 is a spectrum chart obtained by measuring the reflectance of a base material with an antireflection film in Example 8. 10 is a spectrum chart obtained by measuring the reflectance of a base material with an antireflection film in Example 11. 14 is a spectrum chart obtained by measuring the reflectance of a base material with an antireflection film in Example 12.

[Base material with antireflection film]
FIG. 1 is a cross-sectional view schematically showing an embodiment of a substrate with an antireflection film of the present invention. FIG. 2 is a cross-sectional view schematically showing a part of the base material with an antireflection film shown in FIG.
The base material 1 with an antireflection film of the present embodiment includes a transparent base material 3 and an antireflection film 5 formed on the transparent base material 3.
The antireflection film 5 is a two-layer film in which a lower layer 7 and an upper layer 9 are laminated in order from the transparent substrate 3 side.

(Transparent substrate)
The transparency in the transparent substrate 3 means that 80% or more of light in the wavelength region of 400 to 1100 nm is transmitted on average.
Examples of the shape of the transparent substrate 3 include a plate and a film.
Examples of the material of the transparent substrate 3 include glass and resin.
Examples of the glass include soda lime glass, borosilicate glass, aluminosilicate glass, and alkali-free glass.
Examples of the resin include polyethylene terephthalate, polycarbonate, triacetyl cellulose, polymethyl methacrylate, and the like.

As the transparent substrate 3, a glass plate is preferable.
The glass plate may be a smooth glass plate formed by a float method, a fusion method, or the like, or may be a template glass having irregularities on the surface formed by a roll-out method or the like. Further, not only flat glass but also glass having a curved surface shape may be used.
The thickness of the glass plate is not particularly limited. For example, a glass plate having a thickness of 10 mm or less can be used. The thinner the thickness, the lower the light absorption, which is preferable for the purpose of improving the transmittance.

When glass is soda-lime glass, what has the following composition is preferable.
In mass percentage display based on oxide,
SiO _2: 65~75%,
Al ₂ O _3: 0~10%,
CaO: 5 to 15%,
MgO: 0 to 15%,
Na ₂ O: 10~20%,
K ₂ O: 0 to 3%,
Li ₂ O: 0 to 5%,
Fe ₂ O ₃ : 0 to 3%,
TiO _2: 0~5%,
CeO ₂ : 0 to 3%,
BaO: 0 to 5%,
SrO: 0 to 5%,
B ₂ O _3: 0~15%,
ZnO: 0 to 5%,
ZrO ₂ : 0 to 5%,
SnO ₂ : 0 to 3%,
SO ₃ : 0 to 0.5%.

When glass is an alkali free glass, what has the following composition is preferable.
In mass percentage display based on oxide,
SiO _2: 39~70%,
Al ₂ O ₃ : 3 to 25%,
B ₂ O _3: 1~30%,
MgO: 0 to 10%,
CaO: 0 to 17%,
SrO: 0 to 20%,
BaO: 0 to 30%.

When glass is aluminosilicate glass, what has the following composition is preferable.
In mole percentage display on oxide basis,
SiO _2: 62~68%,
Al ₂ O _3: 6~12%,
MgO: 7-13%,
Na ₂ O: 9~17%,
K ₂ O: 0~7%,
ZrO ₂ : 0 to 8%.

  When using the base material 1 with an antireflective film as a cover glass for solar cells, the transparent base material 3 is preferably a matte pattern template glass with an uneven surface. As the template glass, soda lime glass (white plate glass) having a lower iron component ratio (high transparency) than soda lime glass (blue plate glass) used for ordinary window glass or the like is preferable.

The glass plate may be tempered in advance. By the strengthening treatment, the strength of the glass is improved, and for example, it is possible to reduce the plate thickness while maintaining the strength.
The strengthening treatment includes physical strengthening in which the glass plate is air-cooled after being exposed to a high temperature, or an alkali with a small atomic diameter present on the outermost surface of the glass substrate by immersing the glass plate in a molten salt containing an alkali metal. Examples include chemical strengthening that replaces a metal (ion) with an alkali metal (ion) having a large atomic diameter present in a molten salt. In the case of subjecting a glass plate to chemical strengthening treatment, it is particularly preferable to use an aluminosilicate glass.

(Antireflection film)
The antireflection film 5 is a two-layer film in which a lower layer 7 and an upper layer 9 are laminated in order from the transparent substrate 3 side.

The refractive index of the lower layer 7 is 1.45 to 1.50, and the average thickness of the lower layer 7 is 40 to 120 nm. The refractive index of the upper layer 9 is 1.29 to 1.34, and the average thickness of the upper layer 9 is 40 to 110 nm.
When the refractive index and average thickness of the lower layer 7 and the upper layer 9 are within the above ranges, the reflectance in a wide wavelength range, particularly the reflectance of light in a relatively short wavelength range such as purple and blue, is reduced. The reflected color becomes neutral. A conventional silica-based antireflection film tends to have a bluish reflection color as the antireflection performance increases. The human eye has a high sensitivity to blue colors, and when the reflection color of the antireflection film is blue, there is a tendency that other parts (stains, dirt marks, etc.) are not easily detected. Since the reflection color of the antireflection film 5 is a neutral color, even if the antireflection film 5 is soiled or stained, it is difficult to stand out.

  The difference between the refractive index of the lower layer 7 and the refractive index of the upper layer 9 is preferably 0.11 to 0.21, and particularly preferably 0.10 to 0.20. When the difference in refractive index is equal to or greater than the lower limit of the above range, reflection of light having a large incident angle is sufficiently suppressed. If the difference in refractive index is less than or equal to the upper limit of the above range, light reflection at the interface between the lower layer 7 and the upper layer 9 is sufficiently suppressed.

  The ratio of the average thickness of the lower layer 7 to the average thickness of the upper layer 9 (average thickness of the lower layer 7 / average thickness of the upper layer 9) is preferably 40/40 to 120/110, particularly 50/50 to 110/110. preferable. If the ratio of the average thickness is not less than the lower limit of the above range, a sufficient antireflection function can be obtained. If the ratio of the average thickness is not more than the upper limit of the above range, sufficient antifouling properties can be obtained.

In the present invention, the refractive index n and average thickness d of the lower layer 7 and the upper layer 9 are determined by the following measuring method.
A single layer film of the lower layer 7 or the upper layer 9 is formed on a transparent substrate, and the reflectance within a wavelength range of 380 to 780 nm on the surface of the single layer film is measured with a spectrophotometer. The incident angle of light is 5 °.
From the minimum reflectance (so-called bottom reflectance) R _min within the wavelength range of 380 to 780 nm and the refractive index ns of the transparent substrate, the refraction of the single-layer film (lower layer 7 or upper layer 9) by the following equation (1) The rate n is calculated.
R _min = (n−ns) ² / (n + ns) ² (1).
From the refractive index n of the single layer film and the wavelength λ (nm) at the bottom reflectance R _min , the average thickness d (nm) of the single layer film (lower layer 7 or upper layer 9) is calculated by the following equation (2). To do.
n × d = λ / 4 (2).

<Lower layer>
The lower layer 7 is a silica film.
The silica film is a film containing silica as a main component. To have silica as a main component means that the proportion of silica is 90% by mass or more of the entire film (100% by mass).
The silica film is preferably a film substantially made of silica. The phrase “consisting essentially of silica” means that it is composed only of silica excluding inevitable impurities.

  The silica film may contain a small amount of components other than silica. The components include Li, B, C, N, F, Na, Mg, Al, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, and Sr. , Y, Zr, Nb, Ru, Pd, Ag, In, Sn, Hf, Ta, W, Pt, Au, Bi and compounds such as one or more ions and oxides selected from lanthanoid elements .

  As described above, the refractive index of the silica film, that is, the refractive index of the lower layer 7 is 1.45 to 1.50. When the refractive index of the lower layer 7 is within the above range, the reflectance of the antireflection film 5 is lowered, and in particular, reflection colors such as purple and blue are reduced. Moreover, the silica film having a refractive index in the above range is dense, and is excellent in adhesion to the transparent substrate 3 such as a glass plate, durability, and the like.

Examples of the silica film having a refractive index of 1.45 to 1.50 include those made of a hydrolysis polymer of alkoxysilane, those made of polysilazane (fired product of silazane), and the like.
The silica film may contain fine particles, other additives, and the like as necessary.
Examples of the fine particles include hollow silica particles and other fine particles. Examples of these fine particles include the same fine particles as those described in the description of the upper layer.
Other additives will be described in detail later.
The refractive index of the silica film can be adjusted by hollow silica particles or components other than silica (fine particles having a high refractive index). When the silica film contains hollow silica particles, the refractive index is lowered. If the silica film contains fine particles having a higher refractive index than silica (for example, alumina particles, zirconia particles, titania particles, etc.) as other fine particles, the refractive index becomes high.
The lower layer 7 is preferably a silica film made of a hydrolysis polymer of alkoxysilane.

  As above-mentioned, the average thickness of the lower layer 7 is 40-120 nm, 50-110 nm is preferable and 60-110 nm is especially preferable. When the average thickness of the lower layer 7 is within the above range, the reflectance is lowered, and particularly the reflection colors such as purple and blue are reduced. Moreover, if the average thickness of the lower layer 7 is more than the lower limit of the said range, it will become difficult to permeate | transmit moisture etc. to the transparent base material 3, and the outstanding weather resistance will be obtained. If the average thickness of the lower layer 7 is not more than the upper limit of the above range, the reflectance of light having a wavelength of 400 to 1100 nm can be kept low.

<Upper layer>
The upper layer 9 is a silica-based porous film containing hollow silica particles 11 and a silica-based matrix 13.
The surface of the upper layer 9, that is, the surface of the antireflection film 5 has gentle irregularities corresponding to the shape of the hollow silica particles 11 closest to the surface.
From the viewpoint of antifouling properties, the surface side of the upper layer 9 preferably has few open holes, and more preferably has no open holes.

Since the hollow silica particles 11 have cavities inside, the refractive index is lower than that of the silica-based matrix 13. Therefore, the upper layer 9 containing the hollow silica particles 11 has a lower refractive index than the film made of the silica matrix 13.
As described above, the refractive index of the upper layer 9 is 1.29 to 1.34, preferably 1.30 to 1.33. If the refractive index of the upper layer 9 is within the above range, the reflectance will be low, and in particular, the reflection colors such as purple and blue will be reduced. Moreover, if the refractive index of the upper layer 9 is more than the lower limit of the said range, the upper layer 9 will not become too sparse and the outstanding durability will be acquired. If the refractive index of the upper layer 9 is not more than the upper limit of the above range, the reflectance of the antireflection film 5 can be lowered.
The refractive index of the upper layer 9 can be adjusted by the mass ratio of the solid content in terms of SiO ₂ between the hollow silica particles 11 and the silica matrix 13, the average primary particle diameter of the hollow silica particles 11, the porosity of the hollow silica particles, and the like.

Hollow silica particles:
Examples of the hollow silica particles 11 include those having an outer shell of silica and a hollow inside of the outer shell. In the hollow silica particles 11, the particles may exist in an independent state, the particles may be linked in a chain shape, or the particles may be aggregated.
The average primary particle diameter of the hollow silica particles 11 is 40 to 80 nm, and preferably 50 to 70 nm. If the average primary particle diameter of the hollow silica particles 11 is 40 nm or more, the reflectance of the upper layer 9 is sufficiently low. If the average primary particle diameter of the hollow silica particles 11 is 80 nm or less, the surface roughness of the upper layer 9 is reduced, the antifouling property is improved, and the hollow silica particles 11 are densely packed and the refractive index is lowered. .

The average primary particle diameter of the hollow silica particles 11 is obtained as follows.
The hollow silica particles 11 are observed with a scanning electron microscope (hereinafter referred to as SEM) or a transmission electron microscope (hereinafter referred to as TEM), and 100 hollow silica particles 11 are randomly selected to form each hollow silica particle 11. The particle diameter of the silica particles 11 is measured, and the average particle diameter of 100 hollow silica particles 11 is obtained.

  The variation coefficient of the average primary particle diameter of the hollow silica particles 11 is preferably 0.5 or less, and more preferably 0.3 or less. If the coefficient of variation is 0.5 or less, that is, if the particle size distribution is sufficiently narrow and the particle diameters of the hollow silica particles 11 are uniform, the hollow silica particles 11 are easily packed closely, and the space between the hollow silica particles 11 is reduced. Can be reduced. Moreover, the variation in the space between the hollow silica particles 11 is reduced, and the silica-based matrix 13 easily enters the space between the hollow silica particles 11. Further, the surface roughness of the upper layer 9 is reduced, and the antifouling property is improved.

The variation coefficient of the average primary particle diameter of the hollow silica particles 11 is obtained as follows.
The hollow silica particles 11 are observed by SEM or TEM, 100 hollow silica particles 11 are randomly selected, the particle diameter of each hollow silica particle 11 is measured, and the standard deviation of the particle size distribution and the average primary particle diameter are determined. Obtain the coefficient of variation (standard deviation / average primary particle size).

  The sphericity of the hollow silica particles 11 is preferably 0.8 or more, and more preferably 0.9 or more. If the sphericity of the hollow silica particles 11 is 0.8 or more, that is, close to a true sphere, the hollow silica particles 11 are easily packed densely, and the voids between the hollow silica particles 11 can be reduced. Moreover, the variation in the space between the hollow silica particles 11 is reduced, and the silica-based matrix 13 easily enters the space between the hollow silica particles 11. Further, the surface roughness of the upper layer 9 is reduced, and the antifouling property is improved.

The sphericity of the hollow silica particles 11 is obtained as follows.
The hollow silica particles 11 are observed by SEM or TEM, 100 hollow silica particles 11 are randomly selected, and the major axis and minor axis of each hollow silica particle 11 are measured to obtain the sphericity (minor axis / major axis). The sphericity of 100 hollow silica particles 11 is averaged.

Silica matrix:
The silica matrix 13 fills the voids between the hollow silica particles 11. The silica matrix 13 may cover the upper side of the hollow silica particles 11 (the side opposite to the lower layer 7 side) so that the hollow silica particles 11 are not exposed.

“Silica-based matrix” refers to a matrix mainly composed of silica. To have silica as a main component means that the proportion of silica is 90% by mass or more in the matrix (100% by mass).
If the matrix is mainly composed of silica, the refractive index (reflectance) of the upper layer 9 tends to be low. In addition, chemical stability, wear resistance and the like are improved.
As the silica-based matrix 13, those substantially consisting of silica are preferable. The phrase “consisting essentially of silica” means that it is composed only of silica excluding inevitable impurities.

  The silica matrix 13 may contain a small amount of components other than silica. The components include Li, B, C, N, F, Na, Mg, Al, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, and Sr. , Y, Zr, Nb, Ru, Pd, Ag, In, Sn, Hf, Ta, W, Pt, Au, Bi and compounds such as one or more ions and oxides selected from lanthanoid elements .

Examples of the silica-based matrix 13 include hydrolysis polymers of alkoxysilanes (calcined products of hydrolyzed alkoxysilanes), polysilazanes (calcined products of silazanes), and the like.
The silica matrix 13 is preferably an alkoxysilane hydrolyzed polymer.

Hollow silica particle / silica matrix ratio:
In the upper layer 9, the mass ratio (hollow silica particles / silica matrix) of the solid content in terms of SiO ₂ between the hollow silica particles 11 and the silica matrix 13 is 45/55 to 65/35, and 50/50 to 60 / 40 is preferable, and 55/45 to 60/40 is particularly preferable.
If the hollow silica particles / silica-based matrix is at least the lower limit of the above range, the hollow silica particles 11 are densely packed in the upper layer 9, so that the refractive index is low and the reflectance can be kept sufficiently low. .
If the hollow silica particles / silica matrix is not more than the upper limit of the above range, the silica matrix 13 is sufficiently filled between the hollow silica particles 11 and it is difficult to form voids between the hollow silica particles 11. Further, the surface roughness of the upper layer 9, that is, the surface roughness of the antireflection film 5 is reduced. Therefore, the antifouling property is improved.
As described above, the silica-based matrix 13 is substantially made of silica, but may contain inevitable impurities. In the present specification, the mass of SiO ₂ converted solid content of the silica-based matrix means the mass of only silica excluding the inevitable impurities.

Other fine particles:
The upper layer 9 may contain fine particles other than the hollow silica particles 11.
Examples of the other fine particles include metal oxide fine particles, metal fine particles, pigment-based fine particles, and resin fine particles. Other fine particles may have a hollow structure or a solid structure.

As the material of the metal oxide fine particles, Al ₂ O ₃ , SiO ₂ , SnO ₂ , TiO ₂ , ZrO ₂ , ZnO, CeO ₂ , Sb-containing SnO _X (ATO), Sn-containing In ₂ O ₃ (ITO), RuO ₂ etc. are mentioned.
Examples of the material of the metal fine particles include metals (Ag, Ru, etc.), alloys (AgPd, RuAu, etc.) and the like.
Examples of the pigment-based fine particles include inorganic pigments (titanium black, carbon black, etc.) and organic pigments.
Examples of the resin fine particle material include polystyrene and melanin resin.

Examples of the shape of the other fine particles include a spherical shape, an elliptical shape, a needle shape, a plate shape, a rod shape, a cone shape, a columnar shape, a cube shape, a rectangular shape, a diamond shape, a star shape, and an indefinite shape. The other fine particles may be present in a state where each fine particle is independent, each fine particle may be linked in a chain, or each fine particle may be aggregated.
Other fine particles may be used alone or in combination of two or more.

The content of the other fine particles in the upper layer 9 is preferably such that the effects of the present invention are not impaired. Specifically, the content is preferably 50 parts by mass or less, and 30 parts by mass or less with respect to 100 parts by mass of the hollow silica particles 11. Is more preferable.
The average primary particle diameter of other fine particles, the coefficient of variation of the average primary particle diameter, and the sphericity are preferably the same as those of the hollow silica particles 11.

Other optional ingredients:
The upper layer 9 may contain other optional components such as terpene derivatives and additives in addition to the hollow silica particles 11, the silica-based matrix 13, and other fine particles.
The terpene derivative, additive and the like will be described in detail later.

Average thickness of upper layer 9:
As described above, the average thickness of the upper layer 9 is 40 to 110 nm, preferably 50 to 100 nm, and more preferably 60 to 90 nm. If the average thickness of the upper layer 9 is within the above range, the reflectance will be low, and in particular, reflection colors such as purple and blue will be suppressed. Moreover, if the average thickness of the upper layer 9 is not more than the upper limit value, a sufficient antifouling effect can be obtained.

<Surface roughness>
The surface of the antireflection film 5, that is, the surface of the upper layer 9 is usually the outermost surface of the substrate 1 with the antireflection film. Therefore, the surface roughness of the antireflection film 5, that is, the surface roughness of the upper layer 9, is preferably as small as possible from the viewpoint of antifouling properties.
The surface roughness of the antireflection film 5 can be expressed by various surface property parameters defined in JIS B0601: 2001. Examples of the surface property parameter include arithmetic average roughness Ra, maximum height roughness Rz, and the like. Detailed measurement conditions for these parameters are as shown in the Examples.

Ra is an index indicating the average height of the ridges and valleys on the surface.
Ra of the surface of the antireflection film 5 is preferably 0.006 to 0.015 μm, more preferably 0.006 to 0.014 μm, and particularly preferably 0.006 to 0.013 μm. If Ra is below the upper limit of the said range, the antifouling property of the antireflection film 5 will be excellent. If Ra is not less than the lower limit of the above range, the reflectance of the upper layer 9 is sufficiently low, and sufficient antireflection performance can be ensured.

Rz is an index indicating the maximum height of the ridges and valleys on the surface.
Rz on the surface of the antireflection film 5 is preferably 0.05 to 0.17 μm, more preferably 0.05 to 0.16 μm, and particularly preferably 0.05 to 0.15 μm. When Rz is not more than the upper limit of the above range, the antifouling property of the antireflection film 5 is excellent. If Rz is not less than the lower limit of the above range, the reflectance of the upper layer 9 is sufficiently low, and sufficient antireflection performance can be ensured.

The values of these parameters can be adjusted by the hollow silica particle / silica matrix ratio, the average primary particle diameter of the hollow silica particles, the average thickness of the upper layer 9, and the like.
For example, the smaller the ratio of hollow silica particles in the hollow silica particle / silica matrix ratio in the upper layer 9, the smaller Rz and Ra tend to be. In particular, Ra has a large change before and after hollow silica particles / silica matrix = 65/35.

<Visual reflectance>
The luminous reflectance of the antireflection film 5 is preferably 0.4% or more, preferably 0.4 to 1.4%, particularly preferably 0.4 to 1.3%. When the luminous reflectance is 0.4% or more, there is a sufficient antifouling effect. When the luminous reflectance is not more than the upper limit of the above range, there is sufficient antireflection property.
The luminous reflectance is a reflectance averaged by multiplying the reflectance at a wavelength of 380 to 780 nm by a weight function.
The luminous reflectance can be adjusted by the film thickness and refractive index of each layer.

(Manufacturing method of substrate with antireflection film)
As a manufacturing method of the base material 1 with an antireflection film, for example, a coating composition for forming a lower layer and a coating composition for forming an upper layer are sequentially applied on the transparent base material 3 by a wet coating method. The method of preheating and finally baking is mentioned.
In the above method, after applying the coating composition for forming the lower layer, after baking the coating film of the coating composition for forming the lower layer, the coating composition for forming the upper layer may be applied thereon, After applying the coating composition for lower layer formation, you may apply | coat the coating composition for upper layer formation on it, without baking the coating film of the formed coating composition for lower layer formation in a wet state.
The lower layer forming coating composition and the upper layer forming coating composition will be described later.

As a coating method for each of the coating composition for forming the lower layer and the coating composition for forming the upper layer, a known wet coat method can be employed.
Wet coating methods include spin coating, spray coating, dip coating, die coating, curtain coating, screen coating, inkjet coating, flow coating, gravure coating, bar coating, flexo coating, and slit coating. Method, roll coat method and the like.
Among them, the roll coating method is preferable because it can cope with a wide transparent substrate 3, can transport the transparent substrate 3 at a relatively high speed, and requires a relatively small amount of coating composition. The reverse roll coating method is more preferable from the viewpoint of easily forming a coating film having an arbitrary film thickness with a uniform film thickness (excelling in film thickness controllability).
The coating temperature (atmosphere) of each of the lower layer forming coating composition and the upper layer forming coating composition is preferably room temperature to 80 ° C, more preferably room temperature to 60 ° C.

In the present invention, firing includes heating and curing a coating film obtained by applying a coating composition.
Firing may be performed by applying a coating composition for forming a lower layer or a coating composition for forming an upper layer, followed by heating. The transparent substrate 3 is heated to a firing temperature in advance, and the transparent substrate 3 ( You may carry out by apply | coating the coating composition for silica-type porous film formation to the surface of the transparent base material 3 or the coating film surface of the coating composition for lower layer formation).
The firing temperature is preferably 30 ° C. or higher, and may be appropriately determined according to the material of the transparent substrate, the lower layer forming coating composition, the upper layer forming coating composition, or the like.
In order to rapidly convert the hydrolyzate of alkoxysilane into a calcined product (hydrolyzed polymer), it may be calcined at 80 ° C. or higher, preferably 100 ° C. or higher, and more preferably 200 to 700 ° C. When the firing temperature is 100 ° C. or higher, the fired product is densified and durability is improved.
When the material of the transparent substrate 3 is a resin, the firing temperature is equal to or lower than the heat resistant temperature of the resin. Even in this case, the obtained base material 1 with an antireflection film has a sufficient antireflection effect.
When the transparent substrate is glass, the firing temperature is preferably 200 ° C. or higher and the glass softening point or lower. When the firing temperature is 200 ° C. or higher, the lower layer 7 is densified and the durability is improved.
When the material of the transparent base material 3 is glass, it can also serve as the baking process at the time of forming the anti-reflective film 5, and the physical strengthening process of glass. In the physical strengthening step, the glass is heated to near the softening temperature. In this case, the firing temperature is set to about 600 to 700 ° C. The firing temperature is usually preferably equal to or lower than the heat distortion temperature of the transparent substrate 3. The lower limit of the firing temperature is determined in accordance with the respective formulations of the lower layer forming coating composition and the upper layer forming coating composition.
Since the polymerization proceeds to some extent even in natural drying, it is theoretically possible to set the drying or calcination temperature to a temperature setting near room temperature if there is no restriction on time.

<Coating composition for lower layer formation>
As a coating composition for lower layer formation, the solution of a silica type matrix precursor is mentioned.
The coating composition for lower layer formation may contain fine particles, other additives, etc. as needed.

Silica-based matrix precursor:
Examples of the silica-based matrix precursor include hydrolyzate of alkoxysilane, silazane and the like.
As the silica-based matrix precursor, a hydrolyzate of alkoxysilane is preferable. When the silica-based matrix precursor is an alkoxysilane hydrolyzate, the silica-based matrix is composed of an alkoxysilane hydrolyzate (a calcined product of the alkoxysilane hydrolyzate (SiO ₂ )).

  Examples of the alkoxysilane include tetraalkoxysilane (tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, etc.), alkoxysilane having a perfluoropolyether group (perfluoropolyether triethoxysilane, etc.), perfluorosilane. An alkoxysilane having a fluoroalkyl group (perfluoroethyltriethoxysilane, etc.), an alkoxysilane having a vinyl group (vinyltrimethoxysilane, vinyltriethoxysilane, etc.), an alkoxysilane having an epoxy group (2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane .), Alkoxysilane (3-acryloyloxy propyl trimethoxysilane having an acryloyloxy group.), And the like.

Hydrolysis of the alkoxysilane can be performed by a known method.
For example, when the alkoxysilane is tetraalkoxysilane, the reaction is carried out using at least 4 moles of water of alkoxysilane and an acid or alkali as a catalyst.
Examples of the acid include inorganic acids (HNO ₃ , H ₂ SO ₄ , HCl, etc.) and organic acids (formic acid, oxalic acid, monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, etc.). Examples of the alkali include ammonia, sodium hydroxide, potassium hydroxide and the like. The catalyst is preferably an acid from the viewpoint of long-term storage stability of the hydrolyzate of alkoxysilane.
When the coating composition for forming the lower layer contains fine particles, the catalyst used for hydrolysis of the alkoxysilane is preferably one that does not interfere with the dispersion of the fine particles.
When using an acid as a catalyst when obtaining the hydrolyzate of alkoxysilane, the acid concentration in the coating composition for forming the lower layer is preferably 100 to 1000 mass ppm, particularly preferably 200 to 700 mass ppm.

The solvent for the silica matrix precursor solution is not particularly limited.
In the case where the silica-based matrix precursor is a hydrolyzate of alkoxysilane, water is required for hydrolysis, and therefore, the dispersion medium preferably contains at least water. Water and other liquids may be used in combination. Examples of the other liquid include alcohols (methanol, ethanol, isopropanol, butanol, diacetone alcohol, etc.), ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), ethers (tetrahydrofuran, 1,4-dioxane, etc.). ), Cellosolves (methyl cellosolve, ethyl cellosolve, etc.), esters (methyl acetate, ethyl acetate, etc.), glycol ethers (ethylene glycol monoalkyl ether, etc.), nitrogen-containing compounds (N, N-dimethylacetamide, N, N -Dimethylformamide, N-methylpyrrolidone, etc.), sulfur-containing compounds (dimethylsulfoxide, etc.) and the like.
As a solvent of the alkoxysilane hydrolyzate solution, a mixed solvent of water and alcohols (methanol, ethanol, isopropanol, butanol, diacetone alcohol, etc.) is preferable.

Fine particles:
The description of the fine particles is the same as described above.

Other additives:
Examples of other additives include surfactants for improving leveling properties and metal compounds for improving durability of coating films.
Examples of the surfactant include silicone oil and acrylic.
As a metal compound, a zirconium chelate compound, a titanium chelate compound, and an aluminum chelate compound are preferable. Examples of the zirconium chelate compound include zirconium tetraacetylacetonate and zirconium tributoxy systemate.

SiO ₂ solid concentration in terms of the lower layer-forming coating composition is preferably 1 to 9 wt%, more preferably 2 to 6 wt%. If the SiO ₂ equivalent solid content concentration is equal to or higher than the lower limit of the above range, it is easy to control the film thickness of the coating film of the lower layer forming coating composition. If terms of SiO ₂ solid concentration than the upper limit of the above range, tends to the thickness of the coating film of the lower layer-forming coating composition uniformly.
The terms of SiO ₂ solid content of the lower layer-forming coating composition, means the terms of SiO ₂ solid content of the silica-based matrix precursor. The SiO ₂ conversion solid content of the silica-based matrix precursor is a solid content when all Si of the silica-based matrix precursor is converted to SiO ₂ .

  The underlayer-forming coating composition is prepared, for example, by hydrolyzing alkoxysilane and adding an additional solvent, additive, or the like as necessary.

<Coating composition for upper layer formation>
Examples of the upper layer-forming coating composition include those containing a dispersion medium, hollow silica particles, and a silica-based matrix precursor. When the coating film of the coating composition for forming an upper layer is baked, a film in which hollow silica particles are dispersed in a silica-based matrix is formed.
The coating composition for forming an upper layer may contain other fine particles and other optional components as necessary.

Dispersion medium:
The dispersion medium is a liquid that disperses the hollow silica particles. The dispersion medium may be a solvent that dissolves the silica-based matrix precursor.
In the case where the silica-based matrix precursor is a hydrolyzate of alkoxysilane, water is required for hydrolysis, and therefore, the dispersion medium preferably contains at least water.
Water and other liquids may be used in combination. Examples of the other liquid include alcohols (methanol, ethanol, isopropanol, butanol, diacetone alcohol, etc.), ketones (acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), ethers (tetrahydrofuran, 1,4-dioxane, etc.). ), Cellosolves (methyl cellosolve, ethyl cellosolve, etc.), esters (methyl acetate, ethyl acetate, etc.), glycol ethers (ethylene glycol monoalkyl ether, etc.), nitrogen-containing compounds (N, N-dimethylacetamide, N, N -Dimethylformamide, N-methylpyrrolidone, etc.), sulfur-containing compounds (dimethylsulfoxide, etc.) and the like.
Among the other liquids, as the solvent for the silica-based matrix precursor, alcohols are preferable, and methanol and ethanol are particularly preferable.

Hollow silica particles:
The description of the hollow silica particles is the same as described above.

Silica-based matrix precursor:
As a silica type matrix precursor, the thing similar to what was mentioned by description of the coating composition for upper layer formation is mentioned, The hydrolyzate of an alkoxysilane is preferable.
As a catalyst used for hydrolysis of alkoxysilane, a catalyst that does not hinder the dispersion of the hollow silica particles is preferable.

Mixing ratio of hollow fine particle silica particles to silica matrix precursor:
The compounding ratio of the hollow silica particles and the silica-based matrix precursor in the upper layer-forming coating composition is set according to the hollow silica particle / silica-based matrix ratio in the upper layer 9.
And in terms of SiO ₂ solid content of the silica-based matrix, and in terms of SiO ₂ solid content of the silica-based matrix precursor is the same. Therefore, in the coating composition for forming the upper layer, the mass ratio (hollow silica particles / silica matrix precursor) of the solid content in terms of SiO ₂ between the hollow silica particles and the silica matrix precursor is the hollow silica particle / silica matrix ratio. Similarly, it is 45 / 55-65 / 35, 50 / 50-60 / 40 is preferable and 55 / 45-60 / 40 is especially preferable.

Other fine particles:
The explanation for the other fine particles is the same as described above.

Other optional ingredients:
Other optional components include terpene derivatives and other additives.

The terpene means a hydrocarbon having a composition of (C ₅ H ₈ ) _n (where n is an integer of 1 or more) having isoprene (C ₅ H ₈ ) as a structural unit. The terpene derivative means terpenes having a functional group derived from terpene. Terpene derivatives include those with different degrees of unsaturation. Although some terpene derivatives function as a dispersion medium, those having “a hydrocarbon having a composition of (C ₅ H ₈ ) _n having isoprene as a structural unit” fall under the category of terpene derivatives. Shall not apply. As the terpene derivative, those described in International Publication No. 2010/018852 can be used.

Examples of other additives include surfactants for improving leveling properties and metal compounds for improving durability of coating films.
Examples of the surfactant include silicone oil and acrylic.
As the metal compound, a zirconium chelate compound, a titanium chelate compound, an aluminum chelate compound and the like are preferable. Examples of the zirconium chelate compound include zirconium tetraacetylacetonate and zirconium tributoxy systemate.

SiO ₂ solid concentration in terms of the upper layer-forming coating composition is preferably 1 to 9 wt%, more preferably 2 to 6 wt%. If terms of SiO ₂ solid concentration than the lower limit of the range, it is easy to control the thickness of the coating layer-forming coating composition. If the solid content concentration in terms of SiO ₂ is not more than the upper limit of the above range, it is easy to make the film thickness of the coating film of the upper layer forming coating composition uniform.
The SiO ₂ converted solid content of the upper layer forming coating composition means the total of the hollow silica particles and the SiO ₂ converted solid content of the silica-based matrix precursor.

  The upper layer forming coating composition is, for example, mixing a hollow silica particle dispersion, a silica-based matrix precursor solution, and an additional dispersion medium, other fine particle dispersion, and other optional components as necessary. It is prepared by.

In the coating composition for forming the upper layer, since it contains a dispersion medium, hollow silica particles, and a silica-based matrix precursor, a silica-based porous film in which hollow silica particles are dispersed in a silica-based matrix is low-cost, It can be formed even at relatively low temperatures.
When the coating composition for forming the upper layer further contains a terpene derivative, voids are formed around the hollow silica particles, and the antireflection effect is increased. However, the content of the terpene derivative is controlled to such an extent that troubles due to the penetration of dirt into the voids formed around the hollow silica particles do not occur.

(Function and effect)
In the base material 1 with the antireflection film, the antireflection film 5 provided on the transparent base material 3 has a two-layer structure in which the lower layer 7 and the upper layer 9 are laminated in order from the transparent base material 3 side, and the lower layer 7 and the upper layer 9 have a predetermined refractive index and an average thickness, respectively, so that the reflectance in a wide wavelength region, particularly the light reflectance in a relatively short wavelength region such as purple and blue is low as described above. Therefore, the reflected color becomes neutral, and even if there is dirt or dirt marks, it is difficult to stand out.
Moreover, sufficient antireflection performance is ensured by the mass ratio (hollow silica particles / silica matrix) of the solid content in terms of SiO ₂ between the hollow silica particles 11 and the silica matrix 13 in the upper layer 9 being within a predetermined range. However, the antifouling property of the surface of the upper layer 9, that is, the surface of the antireflection film 5, can be made high.

(Use)
The use of the substrate 1 with an antireflection film is not particularly limited. As specific examples, transparent parts for vehicles (headlight covers, side mirrors, front transparent boards, side transparent boards, rear transparent boards, etc.), transparent parts for vehicles (instrument panel surfaces, etc.), meters, architectural windows , Show windows, displays (notebook computers, monitors, LCDs, PDPs, ELDs, CRTs, PDAs, etc.), LCD color filters, touch panel substrates, pickup lenses, optical lenses, eyeglass lenses, camera parts, video parts, CCD covers Substrate, optical fiber end face, projector part, copier part, transparent substrate for solar cell (cover glass, etc.), mobile phone window, backlight unit part (light guide plate, cold cathode tube, etc.), backlight unit part, liquid crystal brightness Improvement film (prism, transflective film, etc.), LCD brightness enhancement film Organic EL light-emitting element parts, inorganic EL light-emitting element parts, phosphor light-emitting element parts, optical filters, end faces of optical parts, illumination lamps, covers for lighting fixtures, amplified laser light sources, antireflection films, polarizing films, agricultural films, etc. Can be mentioned.

  While the present invention has been described with reference to the exemplary embodiments, the present invention is not limited to the above-described embodiments. Each configuration in the above embodiment, a combination thereof, and the like are examples, and the addition, omission, replacement, and other modifications of the configuration can be made without departing from the spirit of the present invention.

[Articles]
The article of the present invention includes the base material with the antireflection film.
The article of the present invention may be composed of the base material with the antireflection film, or may further include a member other than the base material with the antireflection film.

Examples of the article of the present invention include those mentioned above as applications of the base material 1 with an antireflection film, and devices including any one or more of them.
The article of the present invention is preferably a solar cell module, a display device, or a lighting device in that both demands for antifouling properties and antireflection properties are high.
The solar cell module includes a solar cell and a transparent substrate (cover glass or the like) disposed on each of the front and back surfaces of the solar cell in order to protect the solar cell, and at least one of the transparent substrates (preferably a transparent substrate) Are preferably those using the above-mentioned base material with an antireflection film as at least a transparent substrate on the front side.
Examples of the display device include a mobile phone, a smartphone, a tablet, and a car navigation.
Examples of the lighting device include an organic EL (electroluminescence) lighting device and an LED (light emitting diode) lighting device.

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited by the following description.
Among Examples 1 to 12 described later, Examples 1 to 9 are examples, and Examples 10 to 12 are comparative examples.
The evaluation methods and materials used in each example are shown below.

〔Evaluation method〕
(Average primary particle size of fine particles)
The fine particle dispersion was diluted to 0.1% by mass with ethanol, and then applied onto the collodion film and dried to prepare a sample.
The sample was observed using TEM (Hitachi Ltd., H-9000). 100 fine particles were randomly selected from the TEM image, the particle diameter of each fine particle was measured, and the average value was taken as the average primary particle diameter of the fine particles.

(Refractive index and average thickness of the lower layer)
In each example, a substrate with an antireflection film was prepared under the same conditions except that the coating composition for forming a silica-based porous film was not applied (no upper layer was formed), and a two-layer structure of a transparent substrate / lower layer was prepared. A laminate was obtained. A black vinyl tape was affixed to the surface of the laminate on the transparent substrate side to prepare a sample.
The reflectance in the wavelength range of 380 to 780 nm on the surface of the lower layer side of the sample was measured with a spectrophotometer (Otsuka Electronics Co., Ltd., instantaneous multi-photometry system MCPD-3000). The incident angle of light was 5 °.
From the bottom reflectance R _min in the wavelength range of 380 to 780 nm and the refractive index ns of the transparent substrate, the refractive index n of the lower layer was calculated by the following formula (1).
R _min = (n−ns) ² / (n + ns) ² (1).
From the refractive index n and the wavelength λ (nm) at the bottom reflectance R _min , the average thickness d (nm) of the lower layer was calculated by the following formula (2).
n × d = λ / 4 (2).

(Upper layer refractive index and average thickness)
In each example, a substrate with an antireflection film was prepared under the same conditions except that the silica-based matrix precursor solution was not applied (the lower layer was not formed) to obtain a laminate having a two-layer structure of transparent substrate / upper layer. It was. A black vinyl tape was affixed to the surface of the laminate on the transparent substrate side to prepare a sample.
The reflectance was measured in the same manner as described above (refractive index and average thickness of the lower layer) except that the sample was used, and the refractive index and average thickness of the upper layer were calculated.

(Luminous reflectance Y)
The luminous reflectance was measured using a spectrophotometer (Otsuka Electronics Co., Ltd., instantaneous multi-photometry system MCPD-3000).

(Arithmetic mean roughness Ra, maximum height roughness Rz)
The arithmetic average roughness Ra and the maximum height roughness Rz of the surface of the antireflection film are measured by a method described in JIS B0601: 2001 using a surface roughness meter (manufactured by Tokyo Seimitsu Co., Ltd., Surfcom (registered trademark) 1500DX). It was measured. The reference length lr (cut-off value λc) for the roughness curve was 0.08 mm.

(Transmissivity difference Td)
Using a spectrophotometer (manufactured by JASCO Corporation, V670), the transmittance (%) of light at a wavelength of 400 nm to 1100 nm is measured for each of the transparent substrate and the substrate with an antireflection film before forming the antireflection film. The average transmittance (%) was obtained. From the result, the transmittance difference Td (%) was calculated by the following formula (3). It shows that antireflection performance is so high that the transmittance | permeability difference Td is large. The transmittance difference Td is preferably 2.0% or more for practical use.
Transmittance difference Td = average transmittance of substrate with antireflection film−average transmittance of only transparent substrate (3)

(Evaluation of dirt marks)
0.01 g of oleic acid was added dropwise to the surface of the substrate with the antireflection film on the antireflection film side. Then, the dropped oleic acid was wiped once at 9.8 × 10 ⁻² MPa with Kimwipe S-200 (manufactured by Nippon Paper Crecia Co., Ltd.) in which 0.1 g of ion exchange water was soaked in eight folds. Next, the above-mentioned Kimwipe was newly prepared, and the same operation was repeated 15 times in total. The film after the work was visually evaluated for stains (residual oleic acid) according to the following criteria.
(Double-circle): A stain mark is not visible.
○: Slight traces are visible but hardly noticeable.
Δ: Slightly noticeable stains
X: The dirt mark is quite conspicuous.

[Materials used]
(Silica matrix precursor solution)
What was prepared in the following procedures was used.
While stirring 77.6 g of denatured ethanol (manufactured by Nippon Alcohol Sales Co., Ltd., Solmix AP-11, a mixed solvent mainly composed of ethanol, the same applies hereinafter), 11.9 g of ion-exchanged water and 61% by mass of nitric acid A mixed solution with 0.1 g was added and stirred for 5 minutes. To this was added 10.4 g of tetraethoxysilane (TEOS) (solid content concentration of SiO ₂ : 29% by mass), and the mixture was stirred at room temperature for 30 minutes to obtain a silica system having a solid content concentration of SiO ₂ of 3.0% by mass. A matrix solution was prepared.
Incidentally, SiO ₂ in terms of solids concentration here is solid concentration when all Si of tetraethoxysilane was converted to SiO _2.

(Hollow silica particle dispersion)
As a hollow silica particle dispersion liquid, Throughia 4110 manufactured by JGC Catalysts & Chemicals was used. The solid content concentration in terms of SiO _{2 of} this hollow silica particle dispersion was 20.5% by mass, and the average primary particle diameter of the hollow silica particles was 60 nm.

(Coating compositions for forming a silica-based porous film (A) to (E))
What was prepared in the following procedures was used.
While stirring the solvent with the mass shown in Table 1, the silica-based matrix precursor solution and the hollow silica particle dispersion are added thereto to obtain silica-based porous film-forming coating compositions (A) to (E). It was. The solid content concentration in terms of SiO ₂ was set to 3.0% by mass.

[Example 1]
Template glass (Solite, low iron soda lime glass (white plate glass), size: 400 mm × 400 mm, thickness: 3.2 mm) was used as a transparent substrate.
The surface of the template glass was polished with an aqueous cerium oxide dispersion, and the cerium oxide was washed away with water, rinsed with ion-exchanged water, and dried.

The template glass is preheated in a preheating furnace (VTR-115, manufactured by ISUZU), and a reverse roll coater (manufactured by Sanwa Seiki Co., Ltd.) is placed on the template glass in a state where the glass surface temperature is kept at 30 ° C. The silica-based matrix precursor solution and the silica-based porous film coating composition (B) were sequentially applied by a coating roll.
The coating amounts of the silica-based matrix precursor solution and the silica-based porous membrane coating composition (B) were such that the lower layer and the upper layer had the average thicknesses shown in Table 2, respectively.
The coating conditions were as follows: conveying speed of the template glass: 8.5 m / min, gap between the coating roll and the conveying belt: 2.9 mm, and indentation thickness between the coating roll and the doctor roll: 0.6 mm.
As the coating roll, a rubber lining roll lined with rubber (ethylene propylene diene rubber) having a surface hardness (JIS-A) of 30 was used.
As the doctor roll, a metal roll having lattice-like grooves formed on the surface thereof was used.

Then, it was baked at 500 ° C. for 30 minutes in the atmosphere. This obtained the base material with an antireflection film which has the antireflection film which laminated | stacked the lower layer and the upper layer one by one on the transparent base material.
About the obtained base material with an antireflection film, the transmittance difference Td, the luminous reflectance Y, the stain mark, the arithmetic average roughness Ra, and the maximum height roughness Rz were evaluated. The results are shown in Table 2.

[Examples 2 to 12]
The silica-based porous membrane coating composition shown in Table 2 is used, and the coating amounts of the silica-based matrix precursor solution and the silica-based porous membrane coating composition are expressed by the average thickness of each of the lower layer and the upper layer. A base material with an antireflection film was obtained in the same manner as in Example 1 except that the value shown in 2 was obtained.
About the obtained base material with an antireflection film, the transmittance difference Td, the luminous reflectance Y, the stain mark, the arithmetic average roughness Ra, and the maximum height roughness Rz were evaluated. The results are shown in Table 2.

As shown in the above results, in Examples 1 to 9, in the evaluation of the stain mark, the stain mark was not visible on the antireflection film, or even if it was visible, it was hardly noticeable and excellent in antifouling property. Further, the transmittance difference Td was 2.0% or more, and the antireflection performance was sufficient.
On the other hand, in Example 10 in which the hollow silica particle / silica matrix ratio in the upper layer was 45/55, the transmittance difference Td was as small as 1.7%, and the antireflection performance was insufficient.
In Example 11 in which the average thickness of the upper layer was 127 nm and Example 12 in which the hollow silica particle / silica matrix ratio in the upper layer was 70/30, the antireflection performance was high, but stain marks were conspicuous.

Spectrum charts (horizontal axis: wavelength (nm), vertical axis: reflectance (%)) of the reflectances of the substrates with antireflection films of Examples 2, 5, 8, 11, and 12 are shown in FIGS. Show.
In Examples 2, 5, and 8, as shown in FIGS. 3 to 5, the difference between the maximum value and the minimum value of the reflectance in the wavelength range of 380 to 780 nm is small, and the reflectance in a relatively low wavelength region. Was low.
On the other hand, in Examples 11 and 12, as shown in FIGS. 6 and 7, the difference between the maximum value and the minimum value of the reflectance within the wavelength range of 380 to 780 nm is larger than in Examples 2, 5, and 8. The reflectance in a relatively low wavelength region was high.

From the above results, the reason why the antireflection film in Examples 1 to 9 is excellent in antifouling property is that the surface roughness of the antireflection film is small (Ra and Rz are small), so that attached dirt is easily removed, reflection This is probably because the luminous reflectance of the prevention film is 0.4% or more and shows a relatively neutral reflection spectrum, so that even if dirt remains, it is not noticeable.
In Example 11, since the reflectance in the low wavelength region is high and the color tone of the antireflection film is bluish, it is considered that the remaining dirt is conspicuous.
In Example 12, as in Example 11, in addition to the color tone of the antireflection film being bluish, the luminous reflectance is low, so that the dirt is more conspicuous due to the reflectance difference (refractive index difference) from the dirt trace portion. It is thought that. Further, since the surface roughness is large, it is considered that the residual amount of dirt itself is large.

DESCRIPTION OF SYMBOLS 1 Base material with antireflection film 3 Transparent base material 5 Antireflection film 7 Lower layer 9 Upper layer 11 Hollow silica particle 13 Silica-based matrix

Claims (8)

A transparent substrate, and an antireflection film formed on the transparent substrate,
The antireflection film is a two-layer film in which a lower layer and an upper layer are laminated in order from the transparent substrate side,
The lower layer is a silica film;
The lower layer has a refractive index of 1.45 to 1.50,
The average thickness of the lower layer is 40-120 nm,
The upper layer is a silica-based porous membrane containing hollow silica particles and a silica-based matrix, the average primary particle diameter of the hollow silica particles is 40 to 80 nm, and the hollow silica particles and the silica-based matrix The mass ratio (hollow silica particles / silica matrix) of the solid content in terms of SiO ₂ is 45/55 to 65/35,
The refractive index of the upper layer is 1.29 to 1.34,
The base material with an antireflection film whose average thickness of the said upper layer is 40-110 nm.   The base material with an antireflection film according to claim 1, wherein the arithmetic average roughness Ra of the surface of the antireflection film is 0.006 to 0.015 μm.   The base material with an antireflection film according to claim 1 or 2, wherein a maximum height roughness Rz of the surface of the antireflection film is 0.05 to 0.17 µm.   The substrate with an antireflection film according to any one of claims 1 to 3, wherein the luminous reflectance of the antireflection film is 0.4% or more.   An article comprising the substrate with an antireflection film according to any one of claims 1 to 4.   The article according to claim 5, which is a solar cell module.   The article according to claim 5, which is a display device.   The article of claim 5, wherein the article is a lighting device.

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