JP2007256876A - Application liquid for forming reflection film, reflection film, base material with reflection film and surface light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an application liquid for forming a reflection film easily forming the more uniform and minuter reflection film, to provide the reflection film, to provide a base material with the reflection film and to provide a surface light source. <P>SOLUTION: The application liquid for forming the reflection film contains metal oxide particles comprising secondary particles formed by aggregating a plurality of primary particles consisting of a metal oxide, a resin as a binder and a solvent. The primary particles of the metal oxide particles have 0.1 to 1 μm average particle diameter and secondary particles have 0.1 to 3.0 μm particle diameter of 50 wt.% cumulative percentage of cumulative particle distribution thereof. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reflective film forming coating liquid, a reflective film, a substrate with a reflective film, and a surface light source, and more specifically, a reflective film forming coating capable of easily forming a more uniform and dense reflective film. Liquid, a reflective film obtained by applying and drying this reflective film forming coating liquid and a substrate with a reflective film, and improving the light utilization efficiency by providing this reflective film inside a planar light source body The present invention relates to a surface light source that can be used.

2. Description of the Related Art Conventionally, a liquid crystal display device is provided with a backlight for supplying light to a liquid crystal display because a portion of the liquid crystal display constituting the display unit is non-luminous. As a fluorescent lamp used for the backlight, a cold cathode fluorescent lamp (CCFL) having a thin tube shape is mainly used.
When this cold cathode fluorescent lamp (CCFL) is used, it is divided into the following two systems depending on the mounting position of the cold cathode fluorescent lamp (CCFL).
(1) A method in which a fluorescent lamp is attached to the edge of the liquid crystal display, and the light obtained from the fluorescent lamp is incident on the liquid crystal display in a specific direction by multiple reflection by a light guide plate.
(2) A system in which a surface light-emitting unit having a plurality of fluorescent lamps sandwiched between a diffusing plate and a reflecting plate is disposed on the back side of the liquid crystal display, and light from the surface light-emitting unit is incident on the liquid crystal display in a specific direction .

However, in these methods (1) and (2), since a light guide plate and a diffusion plate are provided on the optical path, there is a disadvantage that light loss is large from the viewpoint of light efficiency. A structure in which a direct reflection layer is provided in a glass tube and light is emitted in a specific direction has been proposed. However, in this structure, the amount of light emitted in the state of the reflection layer and the phosphor layer in the glass tube is large. In contrast, it is difficult to improve the light utilization efficiency.
As a backlight with improved light utilization efficiency, a glass sheet molded body of a reflector and a green sheet molded body of a phosphor are integrally formed on the inner surface of a glass tube, and these are fired. Thus, a fluorescent lamp (Patent Document 1) in which a reflector layer and a phosphor layer having a uniform film thickness are sequentially formed on the inner surface of the glass tube, and the light source body is composed of scattering particles having two or more types of particle sizes. A surface light source device (Patent Document 1) or the like in which a reflective film and a fluorescent film are sequentially formed has been proposed.
As a method for forming this reflective film, a method of applying a suspension containing a reflective material on a glass plate or the inner surface of a glass tube by a flow coating method, a spray coating method, a dip coating method or the like is widely used. .
JP 2000-306550 A JP 2005-268111 A

By the way, in the conventional backlight, when the particle size of the scattering particles constituting the reflective film is large, unevenness is generated on the surface of the film, and light is scattered by the unevenness, so that the light use efficiency is improved. There was a problem that was difficult. Further, when the thickness of the reflective film is not sufficient, light is transmitted, and there is a problem that the reflectance of the reflective film itself is lowered.
Further, when a gap is generated in the reflector layer, there is a problem that scattered light is confined in the gap and the reflectance of the reflector layer itself is lowered. Further, when the thickness of the reflector layer is not sufficient, light is transmitted, and there is a problem that the reflectance of the reflector layer itself is lowered.

On the other hand, when the particle size of the scattering particles constituting the reflective film is small, the irregularities on the surface of the film can be remarkably reduced, but particularly when particles having a particle size smaller than the wavelength of visible light are used, The film is easy to transmit light. Therefore, in order to function as a reflective film, it is necessary to increase the film thickness. However, when the film thickness is increased, there is a problem that defects such as microcracks are likely to occur during film formation.
In addition, when the reflective film is formed using particles having different particle diameters, for example, a mixture of particles having a particle diameter of 1 μm or more and particles having a particle diameter of 1 μm or less, the irregularities on the surface of the reflective film and the internal voids are reduced. Although it is possible, light becomes easy to transmit. Therefore, it is difficult to improve the reflectance, and a sufficient effect may not be obtained.

  The present invention has been made in order to solve the above-described problems, and is capable of easily forming a more uniform and dense reflective film, a reflective film-forming coating solution, a reflective film, and a base with a reflective film. An object is to provide a material and a surface light source.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have selected metal oxide particles as the inorganic component of the reflective film, and these metal oxide particles are used as primary particles made of a metal oxide. A secondary particle in which a plurality of particles are aggregated, the average particle size of the primary particles is 0.1 μm or more and 1 μm or less, and the cumulative particle size distribution of the secondary particles is 50% by weight. It has been found that by setting the thickness to 1 μm or more and 3.0 μm or less, a more uniform and dense reflective film can be easily formed, and the present invention has been completed.

That is, the coating liquid for forming a reflective film of the present invention is characterized in that it contains metal oxide particles composed of secondary particles obtained by collecting a plurality of primary particles composed of metal oxides.
The average particle size of the primary particles is 0.1 μm or more and 1 μm or less, and the particle size value when the cumulative percentage of the cumulative particle size distribution of the secondary particles is 50% by weight is 0.1 μm or more and 3.0 μm or less. It is preferable that

  The metal oxide is preferably one or more selected from the group consisting of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, zinc oxide, magnesium oxide, and yttrium oxide.

The reflective film of the present invention is characterized in that the reflective film-forming coating liquid of the present invention is applied and dried or heat-treated.
The base material with a reflective film of the present invention is formed by forming the reflective film of the present invention on a base material.
The surface light source of the present invention is characterized in that the reflective film of the present invention is provided at least inside a planar light source body.

  According to the coating liquid for forming a reflective film of the present invention, since the metal oxide particles composed of secondary particles obtained by collecting a plurality of primary particles composed of metal oxide are contained, the metal oxide particles are contained in the coating liquid. By uniformly dispersing, a more uniform and dense reflection film can be easily formed.

  In addition, since the metal oxide particles are secondary particles in which a plurality of primary particles made of metal oxide are aggregated, the mechanical strength of the reflective film is higher than that of metal oxide particles made of primary particles having the same diameter. And the risk of micro cracks and the like is reduced.

  Furthermore, the average particle size of the primary particles is 0.1 μm or more and 1 μm or less, and the particle size value when the cumulative percentage of the cumulative particle size distribution of the secondary particles is 50% by weight is 0.1 μm or more and 3.0 μm. By making it below, the dispersibility of the metal oxide particles in the reflective film can be improved, and a partial bias in the distribution of the metal oxide particles in the reflective film can be eliminated and the metal oxide particles can be made more uniform. Therefore, even if the thickness of the reflective film is increased, there is less possibility that micro cracks will occur. Further, since the distribution of the metal oxide particles is made uniform, flatness is not lost even if the film thickness is reduced, and a smooth reflective film having a small thickness can be easily obtained. Therefore, a reflective film corresponding to a wide film thickness can be easily obtained. Further, the material cost can be reduced by reducing the thickness.

The best mode for carrying out the reflective film-forming coating liquid, the reflective film, the substrate with the reflective film, and the surface light source of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

"Coating liquid for reflective film formation"
The coating liquid for forming a reflective film according to this embodiment is a coating liquid containing particles made of a metal oxide, a resin as a binder, and a solvent.
The metal oxide particles are preferably particles composed of secondary particles obtained by collecting a plurality of primary particles composed of metal oxide.

The average particle size of the primary particles of the metal oxide is preferably 0.1 μm or more and 1 μm or less, more preferably 0.3 μm or more and 0.8 μm or less.
In addition, the particle size value (D50) when the cumulative percentage of the cumulative particle size distribution of the secondary particles obtained by collecting a plurality of primary particles is 50% by weight is preferably 0.1 μm or more and 3.0 μm or less, more preferably 0.00. 3 μm or more and 1.5 μm or less.
Further, the particle size value (D90) at which the cumulative percentage of the cumulative particle size distribution of the secondary particles is 90% by weight is preferably 0.3 μm or more and 10 μm or less, more preferably 0.3 μm or more and 5 μm or less.

  Here, the reason why the average particle diameter and D50 of the primary particles are limited as described above is that when the average particle diameter of the primary particles and D50 are larger than the values in the above range, the surface of the obtained reflective film This is because the concavity and convexity of the particles increases and the bonding points between the particles also decrease, so that the bonding force between the secondary particles decreases, and therefore the particles may fall off the surface of the film. If the particles fall off, they can diffuse into the interior of the light source and become contaminated. On the other hand, when the average particle diameter of primary particles and D50 are smaller than the above range, a denser film can be easily obtained, but it is difficult to relieve internal stress in the heat shrinkage process when the coating film is dried. In particular, when the film thickness is increased, cracks may occur in the film.

The refractive index (n) of the metal oxide particles is preferably as large as possible, and particularly preferably (n =) 1.5 or more.
With such a high refractive index, light incident on the film can be efficiently reflected in a certain direction.

Examples of the metal oxide include silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), zinc oxide (ZnO), magnesium oxide (MgO), One or more selected from the group of yttrium oxide (Y ₂ O ₃ ) is preferable, and in particular, aluminum oxide (Al ₂ O ₃ ) in that it is a high refractive index material of (N =) 1.5 or higher. ) And titanium oxide (TiO ₂ ) are preferable.

It is preferable that the amount of alkali metal contained as an impurity in the metal oxide is small. In particular, sodium (Na) reacts with the mercury particles in the fluorescent lamp to form amalgam to reduce the mercury particles, with the result that the luminance of the fluorescent lamp may be deteriorated.
The metal oxide particles may be composed of a plurality of types of metal oxide particles having different compositions.

  Examples of the resin include acrylates such as polymethyl methacrylate (PMMA) and polycyclohexyl methacrylate, polycarbonate (PC), polystyrene (PS), polyether, polyester, polyarylate, polyacrylic ester, polyamide, phenol-formaldehyde (phenol) Resin), diethylene glycol bisallyl carbonate, acrylonitrile / styrene copolymer (AS resin), methyl methacrylate / styrene copolymer (MS resin), poly-4-methylpentene, norbornene polymer, polyurethane, epoxy, silicone, etc. Can be mentioned.

The solvent is basically water and / or an organic solvent, but other polymer monomers and oligomers alone, or mixtures thereof are also preferably used.
Examples of the organic solvent include methanol, ethanol, 2-propanol, butanol, octanol, diacetone alcohol, furfuryl alcohol, ethylene glycol, hexylene glycol, and other alcohols, ethyl acetate, butyl acetate, ethyl lactate, and acetic acid. Esters such as methyl ester, ethyl acetate, acetoacetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, γ-butyrolactone, diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether ( Ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, di Ethers such as tylene glycol monoethyl ether, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, cyclohexanone, aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, dimethylformamide, N, N-dimethylacetoacetamide Amides such as N-methylpyrrolidone are preferably used, and one or more of these solvents can be used.

  In addition to the above, the reflective film-forming coating solution may contain other inorganic oxide particles, a dispersant, a dispersion aid, a coupling agent, a resin monomer, and the like as long as the characteristics are not impaired.

The content of the metal oxide particles in the coating solution for forming a reflective film is preferably 1% by weight or more and 90% by weight or less, more preferably 1% by weight or more and 60% by weight or less.
Here, the reason why the content of the metal oxide particles is limited to 1% by weight or more and 90% by weight or less is that when the content of the metal oxide particles in the coating solution exceeds 90% by weight, it becomes difficult to form a coating. This is because the stability of the paint, the film uniformity during coating, and the coating property may be impaired. On the other hand, if the content of the metal oxide particles in the coating solution is less than 1% by weight, This is because when a film having a film thickness (1 μm or more) is formed, overcoating is required, which is inefficient.

"Reflective film and substrate with reflective film"
The reflective film of this embodiment can be obtained by applying the reflective film-forming coating solution of this embodiment to form a coating film, and then drying or heat-treating this coating film in the atmosphere.
The substrate with a reflective film of the present embodiment is obtained by applying the coating liquid for forming a reflective film of the present embodiment on a substrate, and then drying or heat-treating the substrate with a coated film in the air. be able to.

As a base material, what is necessary is just a base material which can endure the temperature in the case of drying or heat processing, and a glass substrate, a translucent ceramic substrate, etc. are used suitably.
In the case where the heat treatment temperature is about 200 ° C. to 250 ° C., a heat resistant plastic substrate can also be used as long as thermal deformation does not occur.

  Coating methods include spray coating, bar coating, spin coating, dip coating, screen printing, roll coating, meniscus coating, gravure printing, and ink jet coating, etc. The usual wet coating method can be used. Among these, the spray coating method, the bar coating method, and the spin coating method are particularly preferable coating methods because a thin film can be formed in a short time.

The coating film formed on the substrate is dried using a hot air dryer or the like, and then subjected to heat treatment using a heat treatment apparatus such as a high-temperature baking furnace in order to dissipate the resin contained in the coating film. A substrate with a reflective film is obtained.
The atmosphere of the heat treatment is preferably in the air because it is necessary to decompose and dissipate the resin.
The heat treatment temperature is preferably a temperature sufficient to decompose and dissipate the resin, for example, 500 ° C. or higher.

"Surface light source"
The surface light source of the present invention includes the reflective film of the present invention at least inside a planar light source body.
FIG. 1 is a cross-sectional view showing a surface light source device according to an embodiment of the present invention, and shows the vicinity of a peripheral portion of a surface light source device provided on the back side of a liquid crystal display (LCD).
In the figure, reference numerals 1 and 2 denote glass substrates arranged to face each other at a predetermined interval, 3 denotes a sealing member for sealing a peripheral portion of the glass substrates 1 and 2, and 4 and 5 denote spaces between the glass substrates 1 and 2. A partition wall forming a meandering discharge region, 6 is a meandering discharge region formed between the glass substrates 1 and 2 by the partition walls 4, 5, 7 is a reflective film, 8 is a phosphor layer, and 9 is a phosphor layer. These are electrodes provided on both sides of the glass substrate 1.
The electrodes 9 are provided on both sides of the upper surface of the glass substrate 1, and only one of them is shown in FIG.

This surface light source device has a long meandering discharge region 6 between the glass substrates 1 and 2 by extending the partition 4 from one end side of the glass substrates 1 and 2 and the partition 5 from the other end side, respectively. Is forming.
In this surface light source device, a predetermined voltage is applied between a pair of electrodes 9 provided on both sides of the glass substrate 1 to generate a plasma discharge in the discharge region 6, and phosphors are generated by ultraviolet rays generated by the plasma discharge. The layer 8 is excited to emit light of a predetermined wavelength.

In this surface light source device, since the reflection film 6 of the present invention is formed on the glass substrate 1, the surface of the reflection film 6 becomes a smooth surface and can reflect incident light from outside without being scattered, Light utilization efficiency can be improved.
Further, since the reflective film 6 itself is a dense film, there is no possibility that the reflectance will be lowered.
Further, even when the thickness of the reflective film 6 is thin, there is no risk of light passing through the reflective film 6 and high reflectance can be maintained.

FIG. 2 is a cross-sectional view showing a modification of the surface light source device of this embodiment. The surface light source device is different from the surface light source device shown in FIG. 1 in that a reflective film 7 is formed on the entire upper surface of the glass substrate 1. In addition, the sealing member 3, the partition walls 4, 5 and the phosphor layer 8 are formed on the reflective film 7.
Also in this surface light source device, the same effect as the surface light source device shown in FIG. 1 can be produced.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.
A nitrocellulose solution was prepared as a vehicle common to the examples and comparative examples.
10 parts by weight of nitrocellulose and 90 parts by weight of butyl acetate were put into a mixing tank, and then this mixed solution was stirred for 24 hours or more using a stirrer to obtain a nitrocellulose solution.

"Example 1"
Average particle size of primary particles 0.4 μm, secondary particle cumulative particle size distribution D50 value 1.1 μm, D90 value 2.5 μm of alumina particles 30 parts by weight, nitrocellulose solution 9 parts by weight, and butyl acetate 61 The parts by weight were mixed and then mixed and dispersed for 24 hours using a ball mill to obtain the coating solution of Example 1.
Next, this coating solution was applied onto a glass substrate by a spray coating method to obtain a coating film.
Next, this coating film was dried at 100 ° C. for 3 minutes in the air using a heat dryer, and then baked at 500 ° C. for 30 minutes in the air to obtain a substrate A1 with a reflective film.

"Example 2"
Average particle diameter of primary particles 0.4 μm, D50 value of secondary particle cumulative particle size distribution 1.1 μm, 21 parts by weight of alumina particles having D90 value 2.5 μm, average particle diameter of primary particles 0.18 μm, 9 parts by weight of alumina particles having a D50 value of 0.45 μm and a D90 value of 1.25 μm, 9 parts by weight of a nitrocellulose solution, and 61 parts by weight of butyl acetate are mixed, and then a ball mill is used. The coating liquid of Example 2 was obtained by mixing and dispersing for 24 hours.
Next, this coating solution was applied onto a glass substrate by a spray coating method to obtain a coating film.
Subsequently, this coating film was dried in air at 100 ° C. for 3 minutes using a heat dryer, and then baked in air at 500 ° C. for 30 minutes to obtain a substrate A2 with a reflective film.

"Example 3"
Average particle diameter of primary particles 0.23 μm, cumulative particle size distribution of secondary particles D50 value 0.35 μm, D90 value of 0.9 μm, titania particles 30 parts by weight, nitrocellulose solution 9 parts by weight, and butyl acetate 61 The parts by weight were mixed and then mixed and dispersed for 24 hours using a ball mill to obtain a coating solution of Example 3.
Next, this coating solution was applied onto a glass substrate by a spray coating method to obtain a coating film.
Next, this coating film was dried at 100 ° C. for 3 minutes in the air using a heat dryer, and then baked at 500 ° C. for 30 minutes in the air to obtain a substrate T1 with a reflective film.

Example 4
Average particle size of primary particles 0.4 μm, D50 value 1.1 μm of secondary particle cumulative particle size distribution, 15 parts by weight of alumina particles having D90 value 2.5 μm, primary particle average particle size 0.23 μm, 15 parts by weight of titania particles having a D50 value of 0.45 μm and a D90 value of 0.9 μm, 9 parts by weight of a nitrocellulose solution, and 61 parts by weight of butyl acetate are mixed, and then a ball mill is used. The coating liquid of Example 4 was obtained by mixing and dispersing for 24 hours.
Next, this coating solution was applied onto a glass substrate by a spray coating method to obtain a coating film.
Next, this coating film was dried at 100 ° C. for 3 minutes in the air using a thermal dryer, and then baked at 500 ° C. for 30 minutes in the air to obtain a substrate AT1 with a reflective film.

“Comparative Example 1”
Average particle diameter of primary particles 2.0 μm, cumulative particle size distribution of secondary particles D50 value 2.5 μm, D90 value 4.0 μm 30 parts by weight of alumina particles, nitrocellulose solution 9 parts by weight, and butyl acetate 61 The parts by weight were mixed and then mixed and dispersed for 24 hours using a ball mill to obtain a coating solution of Comparative Example 1.
Next, this coating solution was applied onto a glass substrate by a spray coating method to obtain a coating film.
Next, this coating film was dried at 100 ° C. for 3 minutes in the air using a heat dryer, and then baked at 500 ° C. for 30 minutes in the air to obtain a substrate A3 with a reflective film.

"Comparative Example 2"
Average particle size of primary particles: 0.02 μm, D50 value of secondary particle size distribution: 0.4 μm, D90 value: 30 parts by weight of alumina particles, 9 parts by weight of nitrocellulose solution, and butyl acetate 61 The parts by weight were mixed and then mixed and dispersed for 24 hours using a ball mill to obtain a coating solution of Comparative Example 2.
Next, this coating solution was applied onto a glass substrate by a spray coating method to obtain a coating film.
Next, this coating film was dried at 100 ° C. for 3 minutes in the air using a heat dryer, and then baked at 500 ° C. for 30 minutes in the air to obtain a substrate A4 with a reflective film.

“Comparative Example 3”
Average particle size of primary particles: 0.03 μm, D50 value of secondary particle cumulative particle size distribution: 0.45 μm, titania particles having D90 value of 0.8 μm, 30 parts by weight of nitrocellulose solution, and butyl acetate 61 The parts by weight were mixed and then mixed and dispersed for 24 hours using a ball mill to obtain a coating solution of Comparative Example 3.
Next, this coating solution was applied onto a glass substrate by a spray coating method to obtain a coating film.
Next, this coating film was dried at 100 ° C. for 3 minutes in the air using a thermal dryer, and then baked at 500 ° C. for 30 minutes in the air to obtain a substrate T2 with a reflective film.

“Comparative Example 4”
Average particle size of primary particles: 0.02 μm, D50 value of secondary particle cumulative particle size distribution: 0.4 μm, 15 parts by weight of alumina particles having a D90 value of 0.7 μm, average particle size of primary particles: 0.03 μm, 15 parts by weight of titania particles having a D50 value of 0.35 μm and a D90 value of 0.8 μm of the secondary particle distribution, 9 parts by weight of a nitrocellulose solution, and 61 parts by weight of butyl acetate were mixed, and then a ball mill was used. The coating liquid of Comparative Example 4 was obtained by mixing and dispersing for 24 hours.
Next, this coating solution was applied onto a glass substrate by a spray coating method to obtain a coating film.
Next, this coating film was dried at 100 ° C. for 3 minutes in the air using a thermal dryer, and then baked at 500 ° C. for 30 minutes in the air to obtain a substrate AT2 with a reflective film.

"Evaluation of substrate with reflective film"
The following apparatus or method evaluated each item of the film thickness of a board | substrate with a reflecting film of each of Examples 1-4 and Comparative Examples 1-4, a reflectance, a total light transmittance, and a close_contact | adherence degree. Further, the appearance of the film was visually observed.
(1) Film thickness It measured using surface roughness meter Tencor P10 (made by KLC).
(2) Reflectance Using a spectrophotometer V-570 (manufactured by JASCO Corporation), the total reflectance (diffuse reflectance) when irradiated with light having a wavelength of 550 nm was measured.

(3) Total light transmittance It measured using the haze meter NDH-2000 (made by Nippon Denshoku).
(4) Adhesion level Adhesive tape Scotch 811 (manufactured by Sumitomo 3M) was applied to the surface of the coating film, and the peelability of the coating film was visually observed. In the evaluation, “◯” indicates that no peeling was observed, “Δ” indicates that partial peeling was observed, and “×” indicates that the peeling was completely removed.

(5) Appearance of film When the surface of the film is visually observed, “○” indicates that no irregularities or cracks are observed, “△” indicates that irregularities or cracks are slightly observed, and irregularities or cracks are observed. Those clearly recognized were marked with “x”.
The above evaluation results are shown in Table 1.

According to these evaluation results, it was found that in Examples 1 to 4, the film thickness was as thin as 58 μm or less, and the reflectance, total light transmittance, and adhesion were good. Further, it was found that the surface of the film had no irregularities or cracks and was excellent in smoothness.
On the other hand, in Comparative Example 1, the film thickness was as extremely thick as 180 μm, and the reflectivity and total light transmittance were the same as those in Examples 1 to 4, but the degree of adhesion was low. Further, the film surface had large irregularities and was inferior in smoothness.
Moreover, in Comparative Examples 2-4, the film thickness was 100 micrometers, and it turned out that both a reflectance and a total light transmittance are falling. Further, irregularities were observed on the film surface, and it was found that the film was inferior in smoothness.

  The reflective film-forming coating solution of the present invention contains metal oxide particles composed of secondary particles obtained by assembling a plurality of primary particles composed of metal oxides, a resin as a binder, and a solvent. The average particle size of the primary particles of the product particles is 0.1 μm or more and 1 μm or less, and the particle size value where the cumulative percentage of the cumulative particle size distribution of the secondary particles is 50% by weight is 0.1 μm or more and 3.0 μm or less. As a result, it is possible to easily form a more uniform and dense reflective film. Therefore, not only a flat panel display (FPD) such as a liquid crystal display (LCD) but also various other industrial fields. However, the effect is great.

It is sectional drawing which shows the surface light source device of one Embodiment of this invention. It is sectional drawing which shows the modification of the surface light source device of one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Glass substrate 3 Sealing member 4, 5 Bulkhead 6 Discharge area 7 Reflective film 8 Phosphor layer 9 Electrode

Claims (6)

  A coating solution for forming a reflective film, comprising metal oxide particles composed of secondary particles obtained by aggregating a plurality of primary particles composed of metal oxides.   The average particle size of the primary particles is 0.1 μm or more and 1 μm or less, and the particle size value when the cumulative percentage of the cumulative particle size distribution of the secondary particles is 50% by weight is 0.1 μm or more and 3.0 μm or less. The coating liquid for reflecting film formation according to claim 1, wherein:   The metal oxide is one or more selected from the group consisting of silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, zinc oxide, magnesium oxide, and yttrium oxide. The coating liquid for reflecting film formation as described.   A reflective film obtained by applying the coating liquid for forming a reflective film according to claim 1, 2 or 3, and drying or heat-treating it.   A substrate with a reflective film, wherein the reflective film according to claim 4 is formed on a substrate.   A surface light source comprising the reflective film according to claim 4 at least inside a planar light source body.

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