WO2014042129A1

WO2014042129A1 - Product having low-reflection film

Info

Publication number: WO2014042129A1
Application number: PCT/JP2013/074280
Authority: WO
Inventors: 義美大谷; 敏本谷
Original assignee: 旭硝子株式会社
Priority date: 2012-09-14
Filing date: 2013-09-09
Publication date: 2014-03-20
Also published as: JP2015222277A

Abstract

Provided is a product having a low-reflection film having good weather resistance and durability, as well as low reflectivity, and that is capable of adequately reducing reflected colors such as red-violet and blue in particular. A product (10) having a low-reflection film, having a transparent substrate (12) and a low-reflection film (14) formed on the transparent substrate (12), the low-reflection film (14) comprising two layers including a lower layer (16) on the transparent substrate (12) side and an upper layer (18) formed on the lower layer (16), the refractive index of the lower layer (16) being 1.40-1.44, the film thickness of the lower layer (16) being 70-130 nm, the refractive index of the upper layer (18) being 1.17-1.30, and the film thickness of the upper layer (18) being 70-130 nm.

Description

Article having a low-reflection film

The present invention relates to an article having a low reflection film on a transparent substrate.

Articles having a low reflection film on the surface of a transparent substrate are used as cover glasses for solar cells, various displays and their front plates, various window glasses, cover glasses for touch panels, and the like.

As the low reflection film, for example, the following low reflection films (i) and (ii) are known.
(I) A single-layer low-reflection film containing hollow SiO ₂ fine particles and a matrix (see Patent Document 1).
(Ii) A low-reflection film comprising three or more thin film layers, each layer having a refractive index of 1.0 to 2.5 and gradually increased from the outermost layer toward the transparent substrate (Patent Document 2) reference).

However, the low reflection film (i) has a high average reflectance of light incident from an oblique angle with a wavelength of 400 to 1200 nm (that is, light having a large incident angle). In addition, when the porosity of the low reflective film (i) is increased in order to keep the reflectance low, moisture and the like easily penetrate into the transparent substrate, and the weather resistance is low. In particular, when the transparent substrate is glass, alkali is eluted from the glass due to moisture and the film deteriorates, so that it is difficult to obtain sufficient weather resistance.
Moreover, since the low reflection film (ii) has a large number of interfaces between layers, there is a large risk of delamination at the interfaces and wear resistance is low.

Therefore, the following low reflection film (iii) has been proposed as a low reflection film having a low reflectance even in light having a large incident angle in a wide wavelength region and having good weather resistance and durability.
(Iii) It consists of two layers, a lower layer on the transparent substrate side and an upper layer formed on the lower layer, the refractive index of the lower layer is 1.30 to 1.44, and the refractive index of the upper layer is 1.10. A low reflection film having a thickness of ˜1.29 (see Patent Document 3).

Japanese Unexamined Patent Publication No. 2001-233611 Japanese Unexamined Patent Publication No. 2007-052345 International Publication No. 2012/086806

However, it is difficult to reduce reflection colors such as magenta and blue even with the low reflection film (iii). As a result, color unevenness may occur in the low-reflection film, dirt on the attached surface (for example, dust, fingerprints) may be noticeable, and the color of the low-reflection film itself may be a problem. .

The present invention provides an article having a low reflection film that has good weather resistance and durability, low reflectance, and can sufficiently reduce the reflection color, particularly reddish purple and blue.

The article of the present invention has a transparent substrate and a low reflection film formed on the transparent substrate, and the low reflection film is formed on the lower layer on the transparent substrate side and on the lower layer. The lower layer has a refractive index of 1.40 to 1.44, the lower layer has a thickness of 70 to 130 nm, and the upper layer has a refractive index of 1.17 to 1.30. The upper layer has a thickness of 70 to 130 nm.

It is preferable that the lower layer has independent pores and does not have pores communicating from the upper layer to the transparent substrate.
The lower layer is preferably a layer mainly composed of SiO _2.
The upper layer is preferably a layer mainly composed of SiO ₂ .
The lower layer preferably contains hollow SiO ₂ fine particles.
The upper layer preferably contains solid SiO ₂ fine particles.
The difference between the refractive index of the lower layer and the refractive index of the upper layer is preferably 0.10 to 0.27.
The porosity of the lower layer is preferably less than 15% by volume.
The lower layer preferably has independent pores, and the average pore diameter of the independent pores is preferably 10 to 100 nm.
In the article of the present invention, the reflectivity at 5 ° incidence in light of wavelengths 380 nm and 780 nm is 0.7% or less, and the difference between the maximum value and the minimum value of reflectivity in light in the wavelength range of 380 nm to 780 nm. Is preferably 0.5% or less.
The article of the present invention is preferably a cover glass for solar cells.

The article of the present invention has good weather resistance and durability and low reflectivity, and particularly, reflection colors such as reddish purple and blue are sufficiently suppressed.

It is sectional drawing which shows an example of the articles | goods of this invention. 2 is a scanning electron micrograph of a part of a cross section of the article of Example 1. 3 is a spectrum chart in which the reflectance of the article of Example 1 is measured. 6 is a spectrum chart obtained by measuring the reflectance of the article of Example 2. 10 is a spectrum chart obtained by measuring the reflectance of the article of Example 3. 10 is a spectrum chart obtained by measuring the reflectance of the article of Example 4. 10 is a spectrum chart obtained by measuring the reflectance of the article of Example 5. 10 is a spectrum chart obtained by measuring the reflectance of the article of Example 6. 10 is a spectrum chart obtained by measuring the reflectance of the article of Example 7. 10 is a spectrum chart obtained by measuring the reflectance of the article of Example 8. 10 is a spectrum chart obtained by measuring the reflectance of the article of Example 9. 12 is a spectrum chart obtained by measuring the reflectance of the article of Example 10.

FIG. 1 is a cross-sectional view showing an example of the article of the present invention.
The article 10 includes a transparent substrate 12 and a low reflection film 14 formed on the surface of the transparent substrate 12.

(Transparent substrate)
The transparency in the transparent substrate means that 80% or more of light in the wavelength region of 400 to 1200 nm is transmitted on average.
Examples of the shape of the transparent substrate 12 include a plate and a film.
On the surface of the transparent substrate 12, a layer other than the low reflection film such as an alkali barrier layer may be formed in advance.

Examples of the material of the transparent substrate 12 include glass and resin.
Examples of the glass include soda lime glass, borosilicate glass, aluminosilicate glass, and alkali-free glass. Moreover, as glass, the smooth glass shape | molded by the float method etc. may be sufficient and the template glass which has an unevenness | corrugation on the surface may be sufficient. In the case of glass, surface treatment such as physical strengthening or chemical strengthening may be performed.
Examples of the resin include polyethylene terephthalate, polycarbonate, triacetyl cellulose, polymethyl methacrylate, and the like.

When the article 10 is an architectural or vehicle window glass, the transparent substrate 12 is expressed in terms of an oxide-based mass percentage (hereinafter, “mass percentage display” is also simply referred to as “%”; hereinafter the same). Soda lime glass having the following composition is preferred.
SiO ₂ : 65 to 75%,
Al ₂ O ₃ : 0 to 10%,
CaO: 5-15%,
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 to 5%,
CeO ₂ : 0 to 3%
BaO: 0-5%,
SrO: 0-5%
B ₂ O ₃ : 0 to 15%,
ZnO: 0 to 5%,
ZrO ₂ : 0 to 5%,
SnO ₂ : 0 to 3%
SO ₃ : 0 to 0.5%.

In the case where the transparent substrate 12 is alkali-free glass, those having the following composition in terms of oxide-based mass percentage are preferable.
SiO ₂ : 39 to 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: 0-30%.

When the transparent substrate 12 is a mixed alkali glass, those having the following composition in terms of mass percentage based on oxide are preferable.
SiO ₂ : 50 to 75%,
Al ₂ O ₃ : 0 to 15%,
MgO + CaO + SrO + BaO + ZnO: 6 to 24%,
Na ₂ O + K ₂ O: 6-24%.

When the article 10 is a cover glass for a solar cell, the transparent substrate 12 is preferably a satin-patterned template glass with an uneven surface. As a template glass, the composition ratio of iron is less than the soda lime glass used in ordinary window glass (so-called blue plate glass: the so-called name of soda lime glass with a slight bluish tint). Non-white glass is preferred. White plate glass is a glass in which the transmittance of light having a wavelength of 400 to 800 nm with respect to a glass plate having a thickness of 4 mm is 90% or more.

(Low reflective film)
The low reflection film 14 includes two layers, a lower layer 16 on the transparent substrate 12 side and an upper layer 18 formed on the lower layer 16.
The refractive index of the lower layer 16 is 1.40 to 1.44. The film thickness of the lower layer 16 is 70 to 130 nm. The refractive index of the upper layer 18 is 1.17 to 1.30. The thickness of the upper layer 18 is 70 to 130 nm. When the refractive index and the film thickness of the lower layer 16 and the upper layer 18 are within the above ranges, the reflectance is lowered, and particularly the reflected colors such as reddish purple and blue are sufficiently reduced.

In the present invention, the refractive index n of each layer constituting the low-reflection film is measured with a spectrophotometer on the surface of the transparent substrate formed by forming a single-layer film of the layer whose refractive index is desired. Based on the minimum reflectance (so-called bottom reflectance) Rmin in the wavelength range of 380 to 780 nm and the refractive index ns of the transparent base material, the following formula (1) is used.
Rmin = (n−ns) ² / (n + ns) ² (1).

The difference between the refractive index of the lower layer 16 and the refractive index of the upper layer 18 is preferably 0.10 to 0.27, and particularly preferably 0.11 to 0.26. If the difference in refractive index is greater than or equal to the lower limit value, 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, light reflection at the interface between the lower layer 16 and the upper layer 18 is sufficiently suppressed.

(Underlayer)
The refractive index of the lower layer 16 is 1.40 to 1.44, preferably 1.40 to 1.43. When the refractive index of the lower layer 16 is within the above range, the reflectance is lowered, and particularly the reflection colors such as magenta and blue are reduced. Further, if the refractive index of the lower layer 16 is equal to or higher than the lower limit value, the porosity of the lower layer 16 can be easily lowered even when the refractive index of the lower layer 16 is adjusted by the porosity of the lower layer 16. Thereby, it becomes difficult for water | moisture content etc. to osmose | permeate to the transparent base material 12, and the outstanding weather resistance is obtained. If the refractive index of the lower layer 16 is less than or equal to the upper limit value, it is easy to suppress warping of the transparent substrate 12 that occurs when the porosity of the lower layer 16 is low.

The refractive index of the lower layer 16 can be adjusted by adjusting the porosity of the lower layer 16 or adding a substance having a specific refractive index to the lower layer 16. For example, the refractive index of the lower layer 16 can be lowered by increasing the porosity of the lower layer 16. Moreover, the refractive index of the lower layer 16 can be lowered by adding a substance having a low refractive index to the lower layer 16.
Examples of the substance having a low refractive index include fluorine compounds such as magnesium fluoride.

The film thickness of the lower layer 16 is 70 to 130 nm, preferably 70 to 120 nm, and particularly preferably 80 to 120 nm. When the film thickness of the lower layer 16 is within the above range, the reflectance is lowered, and particularly the reflection colors such as magenta and blue are reduced. Moreover, if the film thickness of the lower layer 16 is more than a lower limit, it will become difficult to permeate | transmit moisture etc. to the transparent base material 12, and the outstanding weather resistance will be obtained. If the film thickness of the lower layer 16 is not more than the upper limit value, the reflectance of light having a wavelength of 400 to 1200 nm can be kept low.
The film thickness of the lower layer 16 is measured by the method described in the examples.

The lower layer 16 preferably has independent pores and does not have pores communicating from the upper layer 18 to the transparent substrate 12, that is, the upper layer 18 and the transparent substrate 12 are preferably not connected by a gap. . The presence or absence of the communicated vacancy can be confirmed by observing the lower section with a scanning electron microscope. If the pores in the lower layer 16 are not pores communicating from the upper layer 18 to the transparent base material 12 but are almost independent pores, moisture or the like hardly penetrates to the transparent base material 12 and has excellent weather resistance. can get. In particular, when the transparent substrate 12 is glass, it is easy to suppress deterioration of the low reflection film 14 due to the elution of alkali from the glass due to moisture.

The average pore diameter of the pores in the lower layer 16 is preferably 10 to 100 nm, and more preferably 20 to 70 nm. If the average hole diameter of the holes is equal to or greater than the lower limit value, the refractive index of the lower layer 16 is easily set to 1.44 or less. If the average pore diameter of the pores is not more than the upper limit value, moisture or the like hardly penetrates to the transparent substrate 12, and excellent weather resistance is obtained.
The average pore diameter of the lower layer pores can be obtained by averaging the diameters of 100 pores measured from an image obtained by observing the cross section of the lower layer with a scanning electron microscope.

The porosity of the lower layer 16 is preferably less than 15% by volume and particularly preferably 13% by volume or less from the viewpoint that moisture or the like hardly penetrates to the transparent substrate 12 and excellent weather resistance is obtained. The porosity of the lower layer 16 is preferably 2% by volume or more, and particularly preferably 4% by volume or more, from the viewpoint that the refractive index of the lower layer 16 can easily be 1.44 or less.
The porosity can be calculated by the method described in the examples.

As the lower layer 16, a layer mainly composed of SiO ₂ is preferable from the viewpoint of relatively low refractive index, excellent chemical stability, and excellent adhesion to glass, and a layer substantially composed of SiO ₂ is particularly preferable. preferable.
In the present invention, the layer containing SiO ₂ as a main component means that the proportion of SiO ₂ is 90% by mass or more of the entire layer (100% by mass). The layer substantially composed of SiO ₂ means a layer composed only of SiO ₂ excluding inevitable impurities.

The lower layer 16 is preferably composed of SiO ₂ fine particles and a matrix.
Examples of the SiO ₂ fine particles used for the lower layer 16 include hollow SiO ₂ fine particles and solid SiO ₂ fine particles. The SiO ₂ fine particles used for the lower layer 16 are preferably hollow SiO ₂ fine particles because they can form the lower layer 16 having independent pores and not having pores communicating from the upper layer 18 to the transparent substrate 12.

In the hollow SiO ₂ fine particles, each particle may exist in an independent state, each particle may be linked in a chain shape, or each particle may be aggregated. Among them, as the hollow fine SiO ₂ particles, a state where the particles are present independently from the viewpoint of suppression of the communication Tonghua the pores.
The average primary particle diameter of the hollow SiO ₂ fine particles is preferably 5 to 150 nm, more preferably 50 to 100 nm. If the average primary particle diameter of the hollow SiO ₂ fine particles is equal to or greater than the lower limit value, the reflectance of the low reflective film 14 is sufficiently low. If the average primary particle diameter of the hollow SiO ₂ fine particles is not more than the upper limit value, the haze of the low reflective film 14 can be suppressed low.

In the solid SiO ₂ fine particles, each particle may exist in an independent state, each particle may be linked in a chain shape, or each particle may be aggregated.
The average primary particle diameter of the solid SiO ₂ fine particles is preferably 5 to 150 nm, more preferably 50 to 100 nm. If the average primary particle diameter of the solid SiO ₂ fine particles is not less than the lower limit value, the reflectance of the low reflective film 14 is sufficiently low. If the average primary particle diameter of the solid SiO ₂ fine particles is not more than the upper limit value, the haze of the low reflective film 14 can be suppressed low.

The average primary particle size of the fine particles is obtained by randomly selecting 100 fine particles from an electron micrograph, measuring the particle size of each fine particle, and averaging the particle sizes of the 100 fine particles.

Examples of the matrix include a calcined product of an alkoxysilane hydrolyzate (sol-gel silica), a silazane calcined product, and the like.
As the matrix, a calcined product of a hydrolyzate of alkoxysilane is preferable.
As a catalyst used for hydrolysis of alkoxysilane, a catalyst that does not hinder the dispersion of SiO ₂ fine particles is preferable.

Examples of the alkoxysilane include tetraalkoxysilane (tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, etc.), alkoxysilane having a perfluoropolyether group (perfluoropolyether triethoxysilane, etc.), perfluorosilane. Alkoxysilanes having a fluoroalkyl group (perfluoroethyltriethoxysilane, etc.), alkoxysilanes having a vinyl group (vinyltrimethoxysilane, vinyltriethoxysilane, etc.), alkoxysilanes having an epoxy group (2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysila Etc..) Acryloyloxy group alkoxysilane (3-acryloyloxypropyltrimethoxysilane having like.) And the like.

In the case of tetraalkoxysilane, hydrolysis of the alkoxysilane is carried out using 4 times or more moles of water of the alkoxysilane and an acid or alkali as a catalyst.
Examples of the acid include inorganic acids (such as nitric acid, sulfuric acid, and hydrochloric acid) and organic acids (such as formic acid, oxalic acid, monochloroacetic acid, dichloroacetic acid, and trichloroacetic acid). 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.

If the lower layer 16 using a hollow fine SiO ₂ particles, to the average agglomerated particle size of the hollow fine SiO ₂ particles in the lower layer coating liquid for forming a lower layer (90% volume average) (d1), the average of the hollow fine SiO ₂ particles The ratio (d2 / d1) of the primary particle diameter (d2) is preferably 0.5 or more, particularly preferably 0.52 or more. If the ratio (d2 / d1) is equal to or greater than the lower limit, excellent weather resistance can be obtained, and even when the transparent substrate is glass, alkali is eluted from the glass due to moisture and the low reflective film is prevented from deteriorating. It's easy to do.
The average aggregate particle diameter (d1) of the hollow SiO ₂ fine particles in the coating solution is measured by the method described in the examples.

When the lower layer 16 is formed using the hydrolyzate of alkoxysilane obtained using an acid as a catalyst, the lower layer 16 is preferably formed of a lower layer coating solution having an acid concentration of 50 to 200 ppm by mass. It is particularly preferable that the lower layer coating solution is 50 to 100 ppm by mass. Moreover, if the said acid concentration is more than a lower limit, hydrolysis of alkoxysilane will fully advance. If the acid concentration is less than or equal to the upper limit value, the ratio (d2 / d1) is likely to be 0.5 or more. Thereby, a low reflective film having excellent weather resistance can be formed, and even when the transparent base material is glass, it is easy to suppress deterioration of the low reflective film due to alkali elution from the glass due to moisture.

(Upper layer)
The refractive index of the upper layer 18 is 1.17 to 1.30, preferably 1.17 to 1.29, and particularly preferably 1.17 to 1.27. If the refractive index of the upper layer 18 is within the above range, the reflectance will be low, and in particular, the reflection colors such as reddish purple and blue will be reduced. Moreover, if the refractive index of the upper layer 18 is more than a lower limit, the upper layer 18 will not become sparse too much and the outstanding durability will be obtained. If the refractive index of the upper layer 18 is not more than the upper limit value, the reflectance of the low reflective film 14 can be lowered.
Similar to the refractive index of the lower layer 16, the refractive index of the upper layer 18 can be adjusted by adjusting the porosity and adding a substance having a specific refractive index.

The film thickness of the upper layer 18 is 70 to 130 nm, preferably 70 to 120 nm, and particularly preferably 70 to 110 nm. When the film thickness of the upper layer 18 is within the above range, the reflectance is lowered, and particularly the reflection colors such as reddish purple and blue are suppressed. Moreover, if the film thickness of the upper layer 18 is not more than the upper limit value, practical wear resistance can be ensured.
The film thickness of the upper layer 18 is measured by the method described in the examples.

As the upper layer 18, a layer mainly composed of SiO ₂ is preferable from the viewpoint of relatively low refractive index, excellent chemical stability, and excellent adhesion to the lower layer 16, and a layer substantially composed of SiO ₂ is preferable. Particularly preferred.
The upper layer 18 is preferably composed of SiO ₂ fine particles and a matrix.
Examples of the SiO ₂ fine particles used for the upper layer 18 include hollow SiO ₂ fine particles and solid SiO ₂ fine particles. As the SiO ₂ fine particles used for the upper layer 18, solid SiO ₂ fine particles are preferable from the viewpoint of cost.

Examples of the hollow SiO ₂ fine particles, the solid SiO ₂ fine particles, and the matrix used for the upper layer 18 include the same as those mentioned in the lower layer 16.

(Product manufacturing method)
As a method for producing the article of the present invention, for example, a coating solution for forming each layer of a low reflection film is sequentially applied on a transparent substrate, preheated as necessary, and finally fired. Can be mentioned. In the present invention, firing includes heating and curing a coating film obtained by coating a coating solution on the transparent substrate surface.
Examples of the coating solution include a mixture of a dispersion of SiO ₂ fine particles and a matrix precursor solution (a solution of an alkoxysilane hydrolyzate, a silazane solution, etc.).

Examples of the dispersion medium for the dispersion of SiO ₂ fine particles include water, alcohols, ketones, ethers, cellosolves, esters, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds.
As a solvent of the alkoxysilane hydrolyzate solution, a mixed solvent of water and alcohols (methanol, ethanol, isopropanol, butanol, diacetone alcohol, etc.) is preferable.

The coating liquid may contain an additive.
Examples of the additive include a terpene derivative for reducing reflectance, a surfactant for improving leveling properties, and a metal compound for improving durability of a coating film.

The terpene means a hydrocarbon having a composition of (C ₅ H ₈ ) _k (where k 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.
Terpene derivatives include terpene alcohols (α-terpineol, terpinene 4-ol, L-menthol, (±) citronellol, myrtenol, nerol, borneol, farnesol, phytol, etc.), terpene aldehyde (citral, β-cyclocitral, Perylaldehyde, etc.), terpene ketones ((±) camphor, β-ionone, etc.), terpene carboxylic acids (citronellic acid, abietic acid, etc.), terpene esters (terpinyl acetate, menthyl acetate, etc.) and the like. It is done.

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.

As a coating method of the coating solution, a known wet coating 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.

When hollow SiO ₂ fine particles are used for forming the lower layer, it is preferable to use a lower layer coating solution in which the ratio (d2 / d1) is within the above range.
When an acid is used as a catalyst when obtaining a hydrolyzate of alkoxysilane, the acid concentration in the lower layer coating solution is preferably 50 to 200 ppm by mass, and particularly preferably 50 to 100 ppm by mass.

The coating temperature is preferably room temperature to 80 ° C., more preferably room temperature to 60 ° C.
The firing temperature is preferably 30 ° C. or higher, and may be appropriately determined according to the material of the transparent substrate, fine particles or matrix.

For example, when the material of the transparent substrate 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 article has a sufficient antireflection effect.
Moreover, when a transparent base material is glass, baking temperature is 200 degreeC or more and below the softening point temperature of glass. When the firing temperature is 200 ° C. or higher, the lower layer is densified and the durability is improved. If the firing temperature is equal to or lower than the softening point temperature of glass (for example, 800 ° C. or lower), voids in the low reflection film are not lost, and the reflectance of the low reflection film is sufficiently low.

(Function and effect)
In the article of the present invention described above, a lower layer having a refractive index of 1.40 to 1.44 and a film thickness of 70 to 130 nm formed in order from the transparent substrate side, and a refractive index of 1.17 to Since it has a low reflection film having a thickness of 1.30 and an upper layer of 70 to 130 nm, the reflectivity is low, and the reflected colors such as reddish purple and blue are sufficiently reduced. The human eye has a high sensitivity to blue colors, and if the low reflection film has a slight amount of blue reflection color, it tends to feel the color. However, in the article of the present invention, the refractive index and film thickness of the lower layer that forms the low reflection film and the refractive index and film thickness of the upper layer are controlled in specific ranges, respectively, so that the blue color that is easily perceived by human eyes. The color of the system is highly suppressed.
Moreover, in the article of the present invention, since the refractive index of the lower layer is in the above range, the lower layer is dense, moisture and the like hardly penetrate into the transparent substrate, and weather resistance is good.
Moreover, in the article of the present invention, since the low reflection film is composed of two layers, the friction durability is better than that of the three or more low reflection films.

The average reflectance at a wavelength of 380 to 780 nm with respect to 5 ° incident light of the low reflection film in the article of the present invention is preferably 0.7% or less. In addition, in the article of the present invention, the reflectance at 5 ° incidence for light with a wavelength of 380 nm and 780 nm is 0.7% or less, and the maximum reflectance (maximum value for light with a wavelength in the range of 380 nm to 780 nm). The difference between the (reflectance) and the minimum value (minimum reflectance) is more preferably 0.5% or less, and each difference is more preferably 0.3% or less. If the above conditions are satisfied, it is difficult to feel the color when viewed with human eyes.

Articles of the present invention include vehicle transparent parts (for example, headlight covers, side mirrors, front transparent substrates, side transparent substrates, rear transparent substrates, instrument panels, etc.), meters, architectural windows, show windows, displays ( For example, notebook computers, monitors, LCDs, PDPs, ELDs, CRTs, PDAs, etc.), LCD color filters, touch panel substrates, pickup lenses, optical lenses, eyeglass lenses, camera components, video components, CCD cover substrates, light Fiber end face, projector parts, copier parts, solar cell cover glass, mobile phone window, backlight unit parts (for example, light guide plate, cold cathode tube, etc.), backlight unit parts, liquid crystal brightness enhancement film (for example, prism, Translucent 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. Useful. Among these, the article of the present invention is particularly useful as a cover glass for solar cells.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description. Examples 1 and 2 are examples, and examples 3 to 10 are comparative examples.
Various measurement methods and various liquids in each example, and adjustment methods of the respective liquids are as follows.
(Average aggregated particle size of fine particles)
The average aggregate particle diameter (90% volume average value) of the fine particles was measured using a dynamic light scattering particle size analyzer (manufactured by Nikkiso Co., Ltd., Microtrac UPA).

(Refractive index)
The refractive index n of each layer of the low reflection film was measured by the following method. A single-layer film of a layer whose refractive index is desired to be obtained was formed on the surface of a transparent substrate, and a black vinyl tape was attached to the surface of the transparent substrate opposite to the single-layer film so as not to contain bubbles. . Each single-layer film was formed under the same conditions as those for forming the lower layer and the upper layer in Examples 1 to 10 described later. Thereafter, the reflectance of the single-layer film is measured in the wavelength range of 300 to 780 nm with a spectrophotometer (Otsuka Electronics Co., Ltd., instantaneous multi-photometry system MCPD-3000), and the bottom reflectance Rmin and the refractive index of the transparent substrate are measured. It calculated by the following formula (1) from the rate ns.
Rmin = (n−ns) ² / (n + ns) ² (1)

(Transmittance)
The transmittance (%) of the article having a low reflection film was measured for light at a wavelength of 400 nm to 1100 nm using a spectrophotometer (manufactured by JASCO Corporation, V670). The incident angle of light was 5 °.
The transmittance difference Td was determined from the following equation (2).
Td = T1-T2 (2)
However, in the said formula, T1 is the transmittance | permeability of the articles | goods which have a low reflective film, and T2 is the transmittance | permeability of only a transparent base material.

(Reflectance)
The reflectance (%) of an article having a low reflection film was measured by the following method. A two-layer film whose reflectance is to be obtained was formed on the surface of the transparent substrate, and a black vinyl tape was attached to the surface of the transparent substrate opposite to the two-layer film so as not to contain bubbles. Thereafter, light at a wavelength of 380 nm to 780 nm was measured using a spectrophotometer (manufactured by Otsuka Electronics Co., Ltd., instantaneous multi-photometry system MCPD-3000). The incident angle of light was 5 °.

(Porosity)
The porosity P of the lower layer of the low reflection film is expressed by the following formula (3) using the refractive index n of the lower layer calculated by the above formula (1), where the refractive index of air is 1 and the refractive index of silica is 1.46. Calculated by
P = (1.46-n) /0.46×100 (3)

(Film thickness)
The film thickness d (nm) of each layer of the low reflection film was calculated by the following equation (4) from the refractive index n and the wavelength λ (nm) at the bottom reflectivity Rmin of the layer whose thickness is to be obtained.
n × d = λ / 4 (4)

(appearance)
The appearance color tone of the article having the low reflection film was visually observed and evaluated according to the following criteria.
○: The reflection color of the low reflection film is neutral and unnoticeable.
Δ: The reflection color of the low reflection film is slightly conspicuous.
X: The reflection color of the low reflection film is very conspicuous

(Preparation of matrix precursor solution (α-1))
While stirring 80.4 g of denatured ethanol (manufactured by Nippon Alcohol Sales Co., Ltd., Solmix AP-11 (trade name), ethanol-based mixed solvent; the same shall apply hereinafter), 11.9 g of ion-exchanged water and A mixed solution of 61 mass% nitric acid with 0.1 g was added and stirred for 5 minutes. To this, 7.6 g of tetraethoxysilane (SiO ₂ equivalent solid content concentration: 29% by mass) was added and stirred at room temperature for 30 minutes, and the solution of the matrix precursor having a SiO ₂ equivalent solid content concentration of 2.2% by mass. (Α-1) was prepared.
Incidentally, SiO ₂ in terms of solid concentration is a solid content concentration when all Si of tetraethoxysilane was converted to SiO _2.

(Preparation of matrix precursor solution (α-2))
While stirring 77.6 g of denatured ethanol, a mixture of 11.9 g of ion-exchanged water and 0.1 g of 61% by mass nitric acid was added thereto and stirred for 5 minutes. To this, 10.4 g of tetraethoxysilane (SiO ₂ equivalent solid content concentration: 29% by mass) is added and stirred at room temperature for 30 minutes, and the solution of the matrix precursor having a SiO ₂ equivalent solid content concentration of 3.0% by mass. (Α-2) was prepared.

(Hollow SiO ₂ fine particle dispersion (β))
JGC Catalysts & Chemicals, Sululia 4110 (trade name), solid content concentration in terms of SiO ₂ : 20.5% by mass, average primary particle size: 60 nm.

(Chain solid SiO ₂ fine particle dispersion (γ))
Manufactured by Nissan Chemical Industries, Snowtex OUP (trade name), solid content concentration in terms of SiO ₂ : 15.5% by mass, average primary particle size: 10 to 20 nm, average aggregated particle size: 40 to 100 nm.

(Preparation of coating solution for lower layer (A))
Using the matrix precursor solution (α-1) as it was, a lower layer coating solution (A) having a SiO ₂ equivalent solid content concentration of 2.2 mass% was prepared.

(Preparation of lower layer coating solution (B))
While stirring 93.0 g of the matrix precursor solution (α-1), 6.2 g of denatured ethanol and 0.8 g of the hollow SiO ₂ fine particle dispersion (β) were added thereto, and the solid content concentration in terms of SiO ₂ was added. Was 2.2% by mass of the lower layer coating solution (B).

(Preparation of lower layer coating solutions (C) and (D))
Except for changing the composition as shown in Table 1, in the same manner as the lower layer coating solution (B), the lower layer coating solutions (C) and (D) having a SiO ₂ equivalent solid content concentration of 2.2% by mass were used. Prepared.

(Preparation of upper layer coating solution (E))
While stirring 10.8 g of denatured ethanol, 24.0 g of isobutyl alcohol, 15.0 g of diacetone alcohol, 1.0 g of β-ionone, and 37.0 g of a solution of matrix precursor (α-2) were added thereto. And 12.2 g of the chain solid SiO ₂ fine particle dispersion (γ) were added to prepare an upper layer coating liquid (E) having a solid content concentration of 3.0% by mass as SiO ₂ .

(Preparation of upper layer coating solutions (F) to (H))
Except for changing the composition as shown in Table 1, in the same manner as the upper layer coating solution (E), the upper layer coating solutions (F) to (H) having a SiO ₂ equivalent solid content concentration of 3.0 mass% were used. Prepared.

[Example 1]
As a transparent substrate, a template glass (manufactured by Asahi Glass Co., Ltd., Solite (trade name), soda lime glass (white plate glass) with a low iron content, on which a satin pattern is formed. Size: 100 mm × 100 mm, thickness: 3.2 mm, refractive index: 1.46). The surface of the pear ground of the template glass was polished with an aqueous cerium oxide dispersion, and the cerium oxide was washed away with water, then rinsed with ion-exchanged water and dried.

The above-mentioned template glass is preheated in a preheating furnace (VTR-115, manufactured by ISUZU), and a reverse roll coater (Sanwa Seiki Co., Ltd.) is placed on the surface of the template glass while the glass surface temperature is kept at 30 ° C. The coating solution (C) for the lower layer was applied with a coating roll manufactured by the company. The coating conditions were such that the rotation speed of the coating roll and the rotation speed of the doctor roll were changed so as to obtain a predetermined film thickness with respect to the conveyance speed of the substrate: 8.5 m / min. The gap between the coating roll and the conveyor belt was 2.9 mm, and the indentation thickness between the coating roll and the doctor roll was 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.
After the template glass after coating was preheated in a preheating furnace, the upper layer coating solution (G) was further coated on the coating film of the lower layer coating solution (C) by a reverse roll coater in the same manner. Thereafter, it was baked at 500 ° C. for 30 minutes in the air to obtain an article having a low reflection film.

[Examples 2 to 10]
An article having a low reflection film was obtained in the same manner as in Example 1 except that the types of the lower layer coating liquid and the upper layer coating liquid and the film thickness were changed as shown in Table 2. Note that 1 to 10 in the first row in Table 2 indicate Examples 1 to 10.
For the articles of Examples 1 to 10, the refractive index and film thickness of the upper layer and the lower layer, the porosity of the lower layer, the transmittance difference Td, the average reflectance (wavelength 380 to 780 nm), the reflectance of light with wavelengths 380 nm and 780 nm, the wavelength 380 nm Table 2 shows the maximum reflectance at 780 nm, the minimum reflectance, the difference between the maximum reflectance and the minimum reflectance, and the appearance evaluation results. A scanning electron micrograph of a part of the cross section of the article of Example 1 is shown in FIG. Further, spectrum charts obtained by measuring the reflectance in Examples 1 to 10 are shown in FIGS.

The low reflection films of Examples 1 and 2 in which the refractive index and film thickness of the lower layer and the upper layer satisfy the conditions of the present invention have a low reflectance, and particularly the reflection colors such as magenta and blue are sufficiently reduced. I did not feel the color with my eyes.
On the other hand, in the low reflection film of Examples 3 to 6 in which either the refractive index or the film thickness of the lower layer does not satisfy the conditions of the present invention, and the low reflection film of Example 10 in which the upper film thickness is larger than 130 nm, The reflected colors of blue and the like were not sufficiently reduced.
In addition, the low reflection film of Example 7 in which the refractive index of the upper layer is smaller than 1.17 has a difference between the maximum reflectance and the minimum reflectance of more than 0.5%, and the reflection colors such as magenta and blue are reduced. It was insufficient. The low reflection film of Example 8 having an upper layer refractive index greater than 1.30 has a reflectance at 780 nm of more than 0.7%, and the low reflection film of Example 9 having an upper layer film thickness of less than 70 nm is 380 nm. The reflectivity at 780 nm exceeds 0.7%, the difference between the maximum reflectivity and the minimum reflectivity is more than 0.5%, and the reflection colors such as magenta and blue are not sufficiently reduced, and sufficient transmission is achieved. The rate could not be obtained.

According to the present invention, it is possible to provide an article having a low reflection film that has good weather resistance and durability, low reflectance, and in particular, reflection colors such as reddish purple and blue are sufficiently suppressed. An article having such a low reflection film is useful as a cover glass for solar cells, a front plate for various displays, various window glasses, a cover glass for touch panels, and the like.
The entire contents of the description, claims, drawings and abstract of Japanese Patent Application No. 2012-203497 filed on September 14, 2012 are incorporated herein by reference. .

10 Article 12 Transparent substrate 14 Low reflection film 16 Lower layer 18 Upper layer

Claims

A transparent base material, and a low reflection film formed on the transparent base material,
The low reflection film is composed of two layers, a lower layer on the transparent substrate side and an upper layer formed on the lower layer,
The lower layer has a refractive index of 1.40 to 1.44,
The lower layer has a thickness of 70 to 130 nm,
The refractive index of the upper layer is 1.17 to 1.30,
An article having a low reflection film, wherein the upper layer has a thickness of 70 to 130 nm.
The article according to claim 1, wherein the lower layer has independent pores and does not have pores communicating from the upper layer to the transparent substrate.
The lower layer is a layer composed mainly of SiO 2, an article having a low reflection film according to claim 1 or 2.
The article having a low reflection film according to any one of claims 1 to 3, wherein the upper layer is a layer containing SiO 2 as a main component.
The article having a low reflection film according to any one of claims 1 to 4, wherein the lower layer contains hollow SiO 2 fine particles.
The article having a low reflection film according to any one of claims 1 to 5, wherein the upper layer contains solid SiO 2 fine particles.
The article having a low reflection film according to any one of claims 1 to 6, wherein a difference between a refractive index of the lower layer and a refractive index of the upper layer is 0.10 to 0.27.
The article having a low reflection film according to any one of claims 1 to 7, wherein the porosity of the lower layer is less than 15% by volume.
The article having a low reflection film according to any one of claims 1 to 8, wherein the lower layer has independent pores, and the average pore diameter of the independent pores is 10 to 100 nm.
The reflectance at 5 ° incidence for light with a wavelength of 380 nm and 780 nm is both 0.7% or less, and the difference between the maximum value and the minimum value for light in the wavelength range of 380 nm to 780 nm is 0.5% or less. The article having a low reflection film according to any one of claims 1 to 9, wherein
The article having a low reflection film according to any one of claims 1 to 10, which is a cover glass for a solar cell.