JP2003119052A - Light transmitting sheet, light emitting device using the same, and method for manufacturing light transmitting sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light transmitting sheet having an antireflective function and high transmittance, and to provide a method for manufacturing the sheet and a light emitting device. SOLUTION: The light transmitting sheet has a light receiving face 3 on one side of a sheet body 1 having light transmitting property and is prepared by forming an aerogel layer 2 on the light receiving face 3. The aerogel layer 2 is formed in such a manner that the refractive index in the sheet body side is higher than the refractive index in the outer face side. The light emitting device is equipped with the light transmitting sheet and a light emitting body 5 in the side of the sheet where the aerogel layer 2 is formed, and emits light in the opposite side to the aerogel layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-transmitting sheet which suppresses the reflection of light on the surface and has a good light-transmitting property, a light emitting device using the same, and a method for manufacturing the light-transmitting sheet. .

[0002]

2. Description of the Related Art A planar light emitting device in which a light emitting layer is formed on a sheet-shaped substrate is used. Examples of the light emitting device include a flat light source in which an organic electroluminescence element is formed on a glass substrate. In this flat light source, the refractive index of glass is about 1.5 and the refractive index of air is 1.0, so due to the difference in the refractive index at the interface between the glass substrate and the outside (air), some Light is reflected and is not extracted to the outside, and the brightness with respect to the emitted light amount is reduced. Therefore, a flat light emitting device with good luminance is required.

Also in a photodetector for detecting and measuring light, a glass substrate is generally used as a light receiving portion of a sensor, and a difference in refractive index between the glass and air, which is a light receiving surface, is present. Therefore, all the received light cannot be transmitted through the glass substrate, and a part of the light is reflected by the light receiving surface. Therefore, high transmittance is required.

[0004]

Therefore, it has been proposed to form an antireflection film in which an inorganic oxide such as SiO ₂ / TiO ₂ is laminated on the above glass substrate. The antireflection film employs a method of forming a plurality of layers while controlling thin films having different refractive indexes on the order of about 1/4 wavelength of light wavelength, but this thickness control is difficult and easier. There is a demand for a sheet such as a glass substrate provided with light reflection prevention.

On the other hand, silica airgel has attracted attention as a material having a refractive index of 1.5 or less. Silica airgel is described in US Pat. No. 4,402,927, US Pat.
As disclosed in US Pat. No. 4,329,956 and US Pat. No. 4,610,863, a gel compound obtained by hydrolyzing an alkoxysilane (also referred to as a silicon alkoxide or an alkyl silicate) and polymerizing the same is
It can be obtained by drying in the presence of a dispersion medium under supercritical conditions at or above the critical point of this dispersion medium. Further, silica airgel is disclosed in JP-A-5-27901.
As disclosed in Japanese Patent Application Laid-Open No. 1 and Japanese Patent Application Laid-Open No. 7-138375, a technology has been developed in which a silica airgel is subjected to a hydrophobic treatment to improve its moisture resistance and prevent deterioration of characteristics. The silica airgel produced by this method has characteristics such as high heat insulation, high electrical insulation, low refractive index, and low dielectric constant. Utilizing these characteristics, it can be applied to various fields. Is expected to do.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a light transmitting sheet having a light reflection preventing function and a high transmittance, and a manufacturing method thereof. is there.

Still another object of the present invention is to provide a light emitting device in which the substrate has high transmittance and good brightness.

[0008]

The present inventors have been developing a silica airgel having characteristics such as high heat insulation, high electrical insulation, low refractive index and low dielectric constant. Since it can be adjusted to a refractive index intermediate between that of glass and air, when silica airgel is formed on the surface of the sheet body such as a glass substrate, the light reflection amount on the light receiving surface decreases and the incident light amount increases. Find out what you can do,
Furthermore, as a result of repeated research, the refractive index of the silica aerogel on the sheet body side is lower than the refractive index of the silica aerogel on the outer surface side, so that the light transmission is achieved by forming the refractive index stepwise or inclined. The inventors have found that the rate is dramatically improved and have completed the present invention.

Further, as a result of repeated studies, the present inventors have found that even in a planar light source having a light-emitting body such as an organic electroluminescence element, when an airgel layer is formed on the light-emitting body side, the refractive index on the sheet body side is If it is formed to have a refractive index higher than that of the outer surface side, when the light beam that has passed through the airgel layer passes through the sheet body, it becomes closer to being vertical than when it is incident on the light emitting surface. The inventors have found that the amount of reflected light rays is reduced and the brightness is increased, and the present invention has been completed.

The light-transmitting sheet according to claim 1 has a light-transmitting sheet main body having a light-receiving surface on one side, and an airgel layer is formed on the light-receiving surface.

A light transmitting sheet according to a second aspect is the first aspect.
In the light transmitting sheet described above, the refractive index of the airgel layer is such that the refractive index near the sheet body side is higher than the refractive index near the outer surface side.

The light-transmitting sheet according to claim 3 is the same as in claim 1.
Alternatively, in the light-transmitting sheet according to claim 2, the airgel layer is formed of a plurality of layers, and the airgel layer is formed so that the refractive index of the airgel layer becomes higher toward the sheet body side layer.

The light transmitting sheet according to claim 4 is the light transmitting sheet according to claim 1.
4. The light-transmitting sheet according to claim 3, wherein the airgel layer hydrolyzes the alkoxysilane and hydrophobizes the gelled compound obtained by polymerization, or before or during supercritical drying. And is imparted with hydrophobicity.

A light emitting device according to a fifth aspect comprises the light transmitting sheet according to any one of the first to fourth aspects and a light emitting body on the side of the light transmitting sheet on which the airgel layer is formed, and the side opposite to the airgel layer. It is characterized by emitting light on the surface of.

According to a sixth aspect of the present invention, there is provided the light emitting device according to the fifth aspect, wherein the light emitting device includes a light emitting layer made of a light emitting material in contact with the airgel layer.

According to a seventh aspect of the present invention, in the method for producing a light-transmitting sheet, a plurality of alkoxysilane solutions having different concentrations of alkoxysilane are applied on the surface of a sheet body having a light-transmitting property, and the refractive index near the sheet body is The airgel layer is formed so as to have a higher refractive index near the outer surface side.

The method of manufacturing a light-transmitting sheet according to claim 8 is the method of manufacturing a light-transmitting sheet according to claim 7,
The boiling point of the solvent added to the alkoxysilane solution is 1
It is characterized in that it contains a solvent of 00 ° C. or higher.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION A first embodiment of the light transmitting sheet of the present invention will be described with reference to FIG. The light-transmitting sheet has a light-receiving surface 3 on one side of the sheet body 1, and an airgel layer 2 is formed on the light-receiving surface 3.

The sheet body 1 is translucent and can hold the formed airgel layer 2 on its surface. Examples of the material of the sheet body 1 include a glass substrate, an acrylic resin, a polyethylene terephthalate resin (PET), an epoxy resin, a silicone resin, a cycloolefin polymer, a polycarbonate resin, and a plastic substrate such as a fluororesin. The shape of the sheet body 1 is not particularly limited, such as a plate shape and a film shape.

The airgel layer 2 is transparent and has a refractive index intermediate between that of the sheet body 1 and air, and specifically, the one having a refractive index of about 1.003 to 1.45 can be mentioned. .

Since the light transmitting sheet has the airgel layer 2 on the light receiving surface 3, the difference in refractive index between the airgel layer 2 and the air is small, so that at the interface between the airgel layer 2 and the air.
It is possible to reduce the amount of reflection of the received light and improve the amount of light that passes through the airgel layer 2 and is transmitted to the sheet body 1 side.

The airgel forming the airgel layer 2 may be a gel obtained by critically drying a wet gel, but may be a gel obtained by non-critically drying a wet gel. The airgel has a porosity of 40% by volume or more, preferably 60% by volume or more, more preferably 80% by volume or more. The airgel is preferably silica aerogel prepared from alkoxysilane.

The case of silica airgel will be described below. Silica airgel is an alkoxysilane (also called silicon alkoxide or alkyl silicate).
It is possible to use an alkoxysilane solution prepared by mixing, a catalyst for hydrolytic polymerization reaction of alkoxysilane, water, and, if necessary, a solvent.

As the above-mentioned alkoxysilane, various kinds of conventionally known ones as raw materials for silica airgel can be used. Examples thereof include difunctional alkoxysilane such as dimethyldimethoxysilane and dimethyldiethoxysilane, and methyltrimethoxy. Examples thereof include trifunctional alkoxysilane such as silane and methyltriethoxysilane, and tetrafunctional alkoxysilane such as tetramethoxysilane and tetraethoxysilane. Further, as a catalyst for the hydrolysis and polymerization reaction of the alkoxysilane, a basic catalyst such as ammonia, ammonium fluoride or sodium hydroxide can be used.

Further, as the solvent of the alkoxysilane solution, it is preferable to use a solvent which is compatible with water and dissolves the alkoxysilane, for example, methanol,
Examples thereof include ethanol and isopropanol, and it is preferable that the solvent further contains a solvent having a boiling point of 100 ° C. or higher. As the solvent having a boiling point of 100 ° C. or higher, N, N-
Examples thereof include ethylene glycol derivatives such as dimethylformamide, dimethyl sulfoxide, diacetone alcohol, ethylene glycol, ethylene glycol monobutyl ether, and ethylene glycol monoethyl ether acetate, and diethylene glycol derivatives such as diethylene glycol and diethylene glycol monobutyl ether. When the solvent contains a solvent having a boiling point of 100 ° C. or higher, volatilization of the solvent is suppressed, which is preferable in that cracks can be prevented from occurring during the production of the airgel.

The silica aerogel is obtained by hydrolyzing an alkoxysilane and polymerizing the same to obtain a wet gel-like compound having a silica skeleton in the presence of a solvent (also referred to as a dispersion medium) of alcohol or carbon dioxide. Then, it can be produced by drying under supercritical conditions above the critical point of this solvent. Supercritical drying is, for example, immersing a gelled compound in liquefied carbon dioxide, replacing all or part of the solvent contained in the gelled compound with liquefied carbon dioxide having a lower critical point than this solvent, and thereafter, It can be carried out by drying under supercritical conditions of carbon alone or a mixture of carbon dioxide and a solvent.

The silica aerogel is preferably hydrophobized and hydrophobized to give a gel-like compound obtained by hydrolyzing an alkoxysilane and polymerizing the same. The silica airgel imparted with hydrophobicity can prevent moisture and water from entering and prevent deterioration of refractive index and light transmittance.

The above-mentioned hydrophobizing treatment can be carried out before or during the supercritical drying of the gel compound. As a method for performing the hydrophobizing treatment, for example, the gelling compound is immersed in a hydrophobizing treatment solution prepared by dissolving the hydrophobizing treatment agent in a solvent and mixed to infiltrate the hydrophobizing treatment agent into the gel-like compound. After the treatment, a method of heating as necessary to carry out the hydrophobizing treatment reaction and the like can be mentioned. The above-mentioned hydrophobization treatment, the hydroxyl group of the silanol group present on the surface of the gel-like compound,
It is carried out in order to react with the functional group of the hydrophobizing agent to make it hydrophobic.

Examples of the solvent used for the hydrophobic treatment include methanol, ethanol, isopropanol, xylene, toluene, benzene, N, N-dimethylformamide, hexamethyldisiloxane and the like.
If the hydrophobic treatment agent is easily dissolved, and can be replaced with the solvent contained in the gel compound before the hydrophobic treatment,
It is not limited to the above. Further, when performing supercritical drying in a later step, an easy solvent for supercritical drying, for example,
Methanol, ethanol, isopropanol, liquid carbon dioxide and the like are preferably of the same type or those which can be easily replaced.

Examples of the hydrophobizing agent include hexamethyldisilazane, hexamethyldisiloxane, trimethylmethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, trimethylethoxysilane and dimethyldiethoxy. Examples thereof include silane and methyltriethoxysilane.

The silica airgel is porous and
By adjusting the concentration of the alkoxysilane contained in the above-mentioned alkoxysilane solution, it is possible to manufacture from a refractive index of 1.003, which is close to the refractive index of air, to a refractive index of about 1.3.

As the aerogel, other than the silica aerogel prepared from the above-mentioned alkoxysilane may be used as long as it has the above-mentioned refractive index. The silica airgel prepared from others may be one produced from sodium silicate as a raw material. Furthermore, as the airgel other than the silica airgel, those obtained by forming a wet gel of a melamine resin and then supercritically forming the wet gel may be used. Among these aerogels, silica aerogel obtained from the above-mentioned production method from alkoxysilane has a low refractive index, excellent moisture resistance, high thermal insulation properties, high electrical insulation properties, and the like. It is the most suitable because it can be used in the environment and applications.

In the method of manufacturing the light transmitting sheet, for example, in the case of silica airgel, the alkoxysilane solution having the concentration of alkoxysilane adjusted is applied to the surface of the sheet body 1. The method of applying the alkoxysilane solution is spin coating, dip coating,
Any method such as bar coating, roll coating and spray coating can be used. An appropriate method can be adopted according to the viscosity due to the composition of the alkoxysilane solution, the gelation time, the change with time in the properties until gelation, etc. Among them, the spin coating method is the most suitable in consideration of versatility. preferable.

In the above manufacturing method, the alkoxysilane in the alkoxysilane solution is hydrolyzed with water by the action of the hydrolysis polymerization reaction catalyst and undergoes a polymerization reaction to gel to form a gel compound in a wet state having a silica skeleton. It Then, the gel compound on the surface of the sheet body 1 is cured. If this curing step is omitted, the silica airgel will undergo whitening or shrinkage in the supercritical drying step due to its weak structure. If this curing is not performed in a non-dry atmosphere, whitening or shrinkage may occur and cracks may occur.

Then, in the above-mentioned manufacturing method, after curing the gel-like compound on the surface of the sheet body 1, the gel-like compound is supercritically dried. Prior to this supercritical drying, the gel compound may be subjected to a hydrophobizing treatment, or may be subjected to a hydrophobizing treatment during supercritical drying. Supercritical drying can be carried out in a high-pressure container by placing the sheet body 1 having the gel compound on its surface in the high-pressure container.

Next, a second embodiment of the light transmitting sheet of the present invention will be described with reference to FIG. Only points different from the first embodiment will be described.

In the above light transmitting sheet, the airgel layer 2 is
The airgel layer 2 is composed of two or more layers, and is formed so that the airgel layer 2 on the outer surface side has a lower refractive index. That is, as shown in FIG. 1B, three airgel layers 2a,
The light-transmitting sheet on which 2b and 2c are formed has a refractive index of the airgel layer 2a on the sheet body side that is an intermediate airgel layer 2b.
The refractive index of the outer airgel layer 2c is lower than that of the intermediate airgel layer 2b. For example,
If the sheet body 1 is a glass base material having a refractive index of 1.5, the airgel layer 2a on the sheet body side has a refractive index of about 1.30.
The refractive index of the intermediate airgel layer 2b is about 1.20, and the refractive index of the outer airgel layer 2c is about 1.10.
The outer airgel layer 2c has a refractive index closer to that of air (1.0). The amount of light reflected at the interface between layers increases as the difference in refractive index between layers increases. The above light-transmitting sheet can reduce the amount of reflected light by gradually changing the refractive index to reduce the difference in the refractive index of the layers. As shown in FIG. 2, the light-transmitting sheet transmits a light ray 4 incident on the light-receiving surface 3 at a small angle at a larger angle with respect to the light-receiving surface 3 every time it passes through the airgel layer 2. Is.

A method for producing a light-transmitting sheet having a plurality of airgel layers 2 is, for example, using a plurality of alkoxysilane solutions having different concentrations of alkoxysilane, and the surface of the sheet body 1 is first provided with a higher concentration of alkoxysilane. An alkoxysilane solution is applied by spin coating or the like to form a gel compound of alkoxysilane, and then an alkoxysilane solution having a lower concentration of alkoxysilane is applied thereon to form a gel compound. In the above-mentioned manufacturing method, an alkoxysilane solution is applied in the order of the concentration of alkoxysilane to form gel-like compounds, and then these gel-like compounds are cured, and thereafter, hydrophobic treatment and supercritical drying are performed.

The airgel layer 2 of the light-transmitting sheet is preferably formed so that the refractive index on the sheet body side is higher than the refractive index on the outer surface side. In addition to forming a plurality of airgel layers 2a, 2b ... As in the embodiment, a single layer is also possible. A method of changing the refractive index in the single-layer airgel layer 2 is, for example, using two liquids of alkoxysilane solutions having different concentrations of alkoxysilane, and the first alkoxy having a higher concentration of alkoxysilane is first formed on the surface of the sheet body 1. The silane solution is applied by spin coating or the like, and immediately after the alkoxysilane gels, the second alkoxysilane solution is applied. Immediately after gelling, 0-3
It's about a minute. At this time, part of the second alkoxysilane solution diffuses inside the gelled product of the first alkoxysilane solution and bonds with the unreacted silicate remaining when the first alkoxysilane solution gels. Then, the concentration of alkoxysilane at these interfaces becomes an intermediate concentration between the first and second levels, and even the single layer becomes the airgel layer 2 in which the refractive index gradually changes.

The light-transmitting sheet has a high light transmittance by suppressing the reflection of light on the light receiving surface 3. The light transmitting sheet can be used as a light receiving portion of a sensor, a lens of eyeglasses, or the like.

Next, an embodiment of the light emitting device of the present invention will be described.
It will be described with reference to FIG. The light emitting device includes a light emitting body 5 on the side of the light transmitting sheet on which the airgel layer 2 is formed, and emits light on the side 6 opposite to the airgel layer 2.

Examples of the light emitting body 5 include anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin,
Oxadiazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxyquinolinato) aluminum complex, tris (4-methyl-8-quinolinato) aluminum complex, tris (5-phenyl-8) -Quinolinato) aluminum complex, aminoquinoline metal complex, benzoquinoline metal complex, tri- (p-terphenyl-4-yl) amine, 1-aryl-2,5-di (2-thienyl) pyrrole derivative, pyran, quinacridone , Rubrene, a distilbenzene derivative, a distilarylene derivative, and various fluorescent dyes.

When the luminous body 5 is formed on the surface of the airgel layer 2, it can be formed by a vacuum vapor deposition method, an electron beam vapor deposition method, an ion plating method, a solution printing method, or the like.

In the above light emitting device, the refractive index of the airgel layer 2 is changed stepwise or inclining so that the refractive index of the silica airgel 2a on the sheet body side becomes lower than the refractive index 2b of the silica airgel on the outer surface side. Is preferred. Reference numeral 7 in the drawing is a means for causing the light emitting body 5 such as a black light to emit light. An organic electroluminescence element (not shown) can be used as the light emitting body 5.

In the above-mentioned light emitting device, since the light rays passing through the airgel layer 2 become closer to vertical when passing through the sheet body 1, the amount of light rays reflected at the interface between the sheet body 1 and air and remaining inside is reduced. However, since the amount of light rays that pass through is increased, the brightness is increased. The light emitting device can be used as a flat light source for a display using an organic electroluminescence element.

[0046]

EXAMPLES The effects of the present invention were confirmed in Examples and Comparative Examples. The refractive index is a spectroscopic ellipsometer (JA
It was measured using Ulm Japan Co., Ltd.).

Example 1 A soda glass substrate was used as the sheet body, and two airgel layers were formed on this glass substrate as follows.

An oligomer of tetramethoxysilane ("Methyl silicate 51" manufactured by Colcoat) and methanol were mixed at a mass ratio of 34:47 to prepare an A1 liquid. Further, water, 28% by mass ammonia water, and methanol were mixed at a mass ratio of 210: 1: 143 to prepare a B1 liquid. Then, the A1 liquid and the B1 liquid were mixed at a mass ratio of 17:18 to obtain a first alkoxysilane solution. One minute after starting the mixing of the first alkoxysilane solution, the solution was dropped onto a soda glass plate whose surface had been alkali-cleaned in advance, the glass plate was put in the rotation chamber of the spin coater, and the glass plate was rotated. Then, the surface of the glass plate was spin-coated with the alkoxysilane solution. Here, methanol was previously put into the rotation chamber of the spin coater so as to be in a methanol atmosphere, and the glass plate was rotated at 500 rpm for 2 seconds. Like this first
After spin coating the alkoxysilane solution of
The alkoxysilane was allowed to gel for 3 minutes.

After being left for 10 minutes, a second alkoxysilane solution was applied thereon. The second alkoxysilane solution was obtained as follows. An oligomer of tetramethoxysilane (“Methyl silicate 51” manufactured by Colcoat Co., Ltd.) and methanol were mixed at a mass ratio of 47:81 to prepare an A2 liquid. In addition, water, 28 mass% ammonia water, and methanol each have a mass ratio of 50: 1: 8.
The solution B2 was prepared by mixing in 1. And A2 liquid and B2
The liquids were mixed at a mass ratio of 16:17 to obtain a second alkoxysilane solution. 1 minute and 30 seconds after the completion of mixing the second alkoxysilane solution, the solution was dropped on the gelled glass plate and spin-coated under the same conditions as described above to form a two-layer gel compound. Formed. Then
The glass plate on which this gel-like compound was formed was immersed in a curing solution having a composition of water: 28 mass% ammonia water: methanol = 210: 1: 418 in a mass ratio, and cured at room temperature for one day. Next, the gel-like compound formed on the surface of the glass plate was immersed in a 10% by mass solution of hexamethyldisilazane in isopropanol for hydrophobic treatment. Then, put in a high-pressure container, fill the high-pressure container with liquefied carbon dioxide,
Supercritical drying was performed under the conditions of 0 ° C., 16 MPa, and 2 hours.
As a result, a light transmitting sheet was obtained in which a silica airgel layer consisting of two layers having a film thickness of 2 μm and a refractive index of 1.2, and a film thickness of 2 μm and a refractive index of 1.1 was formed on the surface of the glass plate.

Example 2 The same soda glass substrate as in Example 1 was used as the sheet body, and three airgel layers were formed on this glass substrate.

In the same manner as in Example 1, the first alkoxysilane solution was spin-coated and then left for 3 minutes to gel the alkoxysilane. Furthermore, after standing for 10 minutes, a third alkoxysilane solution was applied onto this. The third alkoxysilane solution was obtained as follows. Tetramethoxysilane oligomer ("Methyl silicate 51" manufactured by Colcoat) and methanol,
A3 liquid was prepared by mixing at a mass ratio of 40:62. Also,
Water, 28 mass% ammonia water, and methanol were mixed at a mass ratio of 112: 1: 130 to prepare a B3 solution. Then, the liquid A3 and the liquid B3 were mixed at a mass ratio of 16:17 to obtain a third alkoxysilane solution. This third
1 minute and 30 seconds after the completion of mixing, the alkoxysilane solution of was added dropwise onto the gelled glass plate and spin-coated under the same conditions as described above. Furthermore, 10
After standing for a minute, a second alkoxysilane solution prepared in the same manner as in Example 1 was added dropwise thereto, and spin coating was performed under the same conditions as described above to form a gel compound in three layers. Then, it was aged, hydrophobized and supercritically dried in the same manner as in Example 1. As a result, the film thickness is 2 μm on the surface of the glass plate, the refractive index is 1.2, the film thickness is 2 μm on it, the refractive index is 1.15, and the film thickness is 2 on it.
There was obtained a light-transmitting sheet having a silica airgel layer consisting of three layers of μm and a refractive index of 1.1.

Example 3 The same soda glass substrate as in Example 1 was used as the sheet body, and a single-layer airgel layer having a gradually changing refractive index was formed on this glass substrate.

After spin-coating the first alkoxysilane solution in the same manner as in Example 1, the alkoxysilane was allowed to gel for 3 minutes. Immediately after that, a second alkoxysilane solution prepared in the same manner as in Example 1 was dropped on this, and spin coating was performed under the same conditions as described above. Then, it was aged, hydrophobized and supercritically dried in the same manner as in Example 1. As a result, a light-transmitting sheet was obtained in which a single-layer silica airgel layer having a film thickness of 4 μm and a refractive index changed from 1.2 to 1.1 was formed on the surface of the glass plate from the sheet body side to the outside.

Example 4 The same soda glass substrate as in Example 1 was used as the sheet body, and a single-layer airgel layer was formed on this glass substrate.

The second alkoxysilane solution of Example 1 was used as the alkoxysilane solution. 1 minute and 30 seconds after starting the mixing of the second alkoxysilane solution, the solution was dropped onto a soda glass plate whose surface was previously washed with alkali, and spin-coated under the same conditions as in Example 1 to form a single layer. Of a gel-like compound was formed. Then, Example 1
In the same manner as described above, curing, hydrophobization, and supercritical drying were performed. As a result, a light transmitting sheet was obtained in which a single-layer silica airgel layer having a film thickness of 2 μm and a refractive index of 1.1 was formed on the surface of the glass plate.

Example 5 N, N-dimethylformamide was used as the solvent of the alkoxysilane solution as the solvent having a boiling point of 100 ° C. or higher, and two sheets were formed on the soda glass substrate as in Example 1 as the sheet body. The airgel layer of was formed.

An oligomer of tetramethoxysilane ("Methyl silicate 51" manufactured by Colcoat Co., Ltd.) and methanol were mixed at a mass ratio of 34:47 to prepare an A1 liquid. Further, water, 28 mass% ammonia water, and N, N-dimethylformamide were mixed at a mass ratio of 50: 1: 95 to prepare a B4 solution. Then, add A1 liquid and B4 liquid to 1
A fourth alkoxysilane solution was obtained by mixing in a mass ratio of 6:17.

An airgel layer was formed in the same manner as in Example 1 except that this fourth alkoxysilane solution was used instead of the first alkoxysilane solution. By this, the film thickness of 2 μm on the surface of the glass plate,
Refractive index 1.2, film thickness 2 μm on it, refractive index 1.1 2
A light-transmitting sheet composed of a silica airgel layer composed of layers was obtained.

Comparative Example 1 The soda glass substrate used in Example 1 was used as Comparative Example 1.

(Measurement of Light Transmittance) Obtained Examples 1 to 1
5 and the light transmittance of Comparative Example 1 were measured. A light ray was irradiated from the airgel layer side, and its transmittance was measured with a self-recording spectrophotometer (“U-3400” manufactured by Hitachi, Ltd.). As a result, as shown in Table 1, the transmittance of each of the examples was higher than that of the comparative example.

[0061]

[Table 1]

Example 6 Using the light-transmitting sheet of Example 1, tris (8) was used as a light-emitting body on the airgel layer.
-Hydroxyquinolinate) aluminum complex (manufactured by Dojindo Laboratories Ltd.) is vacuum-deposited to a thickness of 0.1 μm.
Formed by.

(Example 7) Using the light-transmitting sheet of Example 3, tris (8) was used as a luminous body on the airgel layer.
-Hydroxyquinolinate) aluminum complex (manufactured by Dojindo Laboratories Ltd.) is vacuum-deposited to a thickness of 0.1 μm.
Formed by.

Comparative Example 2 A tris (8-hydroxyquinolinato) aluminum complex (manufactured by Dojindo Laboratories Co., Ltd.) was vacuum-deposited as a light-emitting material on the glass substrate of Comparative Example 1 to give a thickness of 0. It was formed with a thickness of 0.1 μm.

(Measurement of Luminance) The luminances of the obtained Examples 6 and 7 and Comparative Example 2 were measured. 4 W of black light was irradiated from the light emitter side from a height of 80 mm, and the luminance emitted from the glass substrate side was measured. As a result, as shown in Table 2, the brightness of each of the examples was better than that of the comparative example.

[0066]

[Table 2]

[0067]

Since the light transmitting sheet according to the first to fourth aspects has the airgel layer on the light receiving surface, it has a light reflection preventing function and a high transmittance.

In the light emitting device according to the fifth to sixth aspects, the substrate has a high transmittance and a good luminance.

In the method for manufacturing a light transmitting sheet according to the seventh aspect, a light transmitting sheet having a light reflection preventing function and a high transmittance can be obtained.

[Brief description of drawings]

FIG. 1A is a schematic diagram showing a first embodiment of the present invention, and FIG. 1B is a schematic diagram showing a second embodiment of the present invention.

FIG. 2 is a schematic diagram schematically showing a light beam received in a second embodiment.

FIG. 3 is a schematic view showing an embodiment of a light emitting device of the present invention.

[Explanation of symbols]

1 seat body 2, 2a, 2b, 2c aerogel layer, 3 Light receiving surface 4 rays 5 luminous body

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masaru Yokoyama             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company F-term (reference) 2K009 AA02 AA05 CC03 CC09 CC42                       DD02                 4F100 AA20B AA20C AA20D AA20E                       AG00 AR00A AR00B AR00C                       AR00D AR00E BA02 BA03                       BA04 BA05 BA10A BA10E                       BA42 EH462 EJ212 EJ862                       JB06B JB06C JB06D JB06E                       JM01B JN01A JN06 JN18B                       JN18C JN18D JN18E JN28E                 4G059 AA01 AB09 AC04 CB05

Claims (8)

[Claims] 1. A light-transmitting sheet having a light-transmitting sheet main body having a light-receiving surface on one side, and an airgel layer formed on the light-receiving surface. 2. The light-transmitting sheet according to claim 1, wherein the airgel layer has a refractive index higher in the vicinity of the sheet body than in the vicinity of the outer surface. 3. The light transmission according to claim 1, wherein the airgel layer is composed of a plurality of layers, and the airgel layer has a higher refractive index toward the sheet body side layer. Sheet. 4. The airgel layer is rendered hydrophobic by subjecting a gel compound obtained by hydrolyzing and polymerizing an alkoxysilane to supercritical drying of a gelled compound or during supercritical drying to impart hydrophobicity thereto. It is a thing, The light transmission sheet in any one of Claim 1 thru | or 3 characterized by the above-mentioned. 5. The light-transmitting sheet according to claim 1, and a light-emitting body on the side of the light-transmitting sheet on which the airgel layer is formed, wherein light is emitted on the surface opposite to the airgel layer. Characterized light emitting device. 6. The light emitting device according to claim 5, wherein the light emitting body includes a light emitting layer made of a light emitting material in contact with the airgel layer. 7. A plurality of alkoxysilane solutions having different concentrations of alkoxysilane are applied to the surface of a light-transmitting sheet body so that the refractive index near the sheet body side is higher than the refractive index near the outer surface side. A method for producing a light-transmitting sheet, characterized in that an airgel layer is formed on. 8. The method for producing a light-transmitting sheet according to claim 7, wherein the solvent mixed with the alkoxysilane solution contains a solvent having a boiling point of 100 ° C. or higher.