JPWO2017047056A1 - Light diffusion transmission sheet - Google Patents

Abstract

The light diffusing and transmitting sheet (1) of the present invention includes a base resin (10) and composite particles (20) dispersed in the base resin (10). The composite particles (20) contain a resin binder (21) and fine particles (22) encapsulated in the resin binder (21). The fine particles (22) include glass fine particles (22a).

Description

  The present invention relates to a light diffusing and transmitting sheet.

  With the improvement in image quality of liquid crystal displays, there is an increasing demand for light diffusing and transmitting sheets having high light diffusion characteristics in order to spatially homogenize the light emitted from the backlight of the liquid crystal display. In addition, from the viewpoint of reducing energy consumption, there is an increasing demand for light diffusing and transmitting sheets having high luminance characteristics.

  Patent Document 1 describes a light diffusing and transmitting sheet including a base material resin and silica composite particles dispersed in the resin. The silica composite particles include titanium oxide fine particles having an average particle diameter of 100 nm or less. The light diffusion transmission sheet described in Patent Literature 1 exhibits high total light transmittance and haze ratio. Titanium oxide has a high refractive index (eg, about 2.60).

  Patent Document 2 describes an optical laminate having an internal scattering layer provided on a light-transmitting substrate. The internal scattering layer contains internal scattering particles. The internal scattering particles include fine particles made of an organic material and / or an inorganic material having an average particle diameter of 1 to 10 μm and an average particle diameter of 5 to 300 nm. Examples of the inorganic material forming the fine particles include materials having high refractive index expression such as titanium oxide, zinc oxide, zirconia, and alumina.

  Patent Document 3 describes a transmissive screen for visually recognizing an image projected from a projector. The transmission screen has a light diffusion layer containing light diffusion fine particles and xerogel. The light diffusing fine particles are supported by xerogel. As a result, xerogel voids (air with a refractive index of 1.0) exist on the surface of the light diffusing fine particles, and the relative refractive index of the light diffusing fine particles with respect to the air becomes very high. For this reason, efficient light diffusion of the light diffusing fine particles becomes possible. As a result, it is possible to provide a transmissive screen that has a very wide viewing angle for visually recognizing the image projected from the projector and is excellent in visibility from both sides of the screen. In Patent Document 3, as light diffusing fine particles, composite particles composed of organic fine particles and a small amount of inorganic fine particles (the proportion of inorganic fine particles is less than 50% by mass), or inorganic fine particles and a small amount of organic polymer (the proportion of organic fine particles). It is described that the composite particles can be used. For example, in the embodiment, opt beads 500S and opt beads 6500M, which are composite fine particles of silica and melamine resin, are used as the light diffusing fine particles.

  Patent Document 4 describes a light diffusing plate having a light diffusing layer made of a transparent substrate containing a transparent resin. The light diffusion layer includes first light diffusion particles and second light diffusion particles present inside the transparent substrate. The refractive index of the second light diffusing particles is larger than the refractive index of the first light diffusing particles. The refractive index of the first light diffusing particles is 1.4 to 1.7, and the refractive index of the second light diffusing particles is larger than 2.

JP 2014-48427 A JP 2009-42554 A JP 2013-195548 A JP 2008-40479 A

  According to the technique described in Patent Document 1, there is room for improving the luminance characteristics of the light diffusing and transmitting sheet. Further, according to Patent Document 2, although a specific material such as titanium oxide is exemplified as an inorganic material for forming fine particles, in order to increase the luminance of the optical layered body while ensuring good light diffusion characteristics No specific investigation has been made on advantageous internal scattering particles. According to Patent Document 3, as the light diffusing fine particles that are composite particles, substantially only the opt beads 500S and the opt beads 6500M are described. Further, it is suggested that even if the optobead 500S is used, the luminance characteristics of the light diffusion layer are low depending on the porosity of the light diffusion layer. Patent Document 4 neither describes nor suggests that the composite particles are dispersed in the transparent substrate.

  Under such circumstances, it is an object of the present invention to provide a light diffusing / transmitting sheet provided with novel composite particles that are advantageous for realizing good light diffusion characteristics and high luminance characteristics.

The present invention
A base material resin;
A resin binder and fine particles encapsulated in the resin binder, and composite particles dispersed in the matrix resin,
The fine particles include glass fine particles,
A light diffusing and transmitting sheet is provided.

  When the fine particles encapsulated in the resin binder contain glass fine particles, the composite particles are advantageous for realizing good light diffusion characteristics and high luminance characteristics. By providing such composite particles, the light diffusing and transmitting sheet has good light diffusing characteristics and high luminance characteristics.

Schematic sectional view of a light diffusion transmission sheet according to an embodiment of the present invention Sectional view schematically showing the structure of the composite particles The figure which shows typically the optical path of the light which injects into the glass fine particle inside a composite particle The figure which shows typically the optical path of the light which injects into the high refractive index fine particle inside a composite particle

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description relates to an example of the present invention, and the present invention is not limited to these.

  As shown in FIG. 1, the light diffusing and transmitting sheet 1 of the present invention includes a base material resin 10 and composite particles 20. The composite particles 20 are dispersed in the base material resin 10. The base material resin 10 is not particularly limited, but is preferably a resin having excellent dispersibility of the composite particles 20 and having transparency to visible light, weather resistance, moisture resistance, and heat resistance. For example, as the base material resin 10, polyester polyol, linear polyester, acrylic resin, amino resin, epoxy resin, melamine resin, silicone resin, urethane resin, vinyl acetate resin, norbornene resin, and polycarbonate Examples include materials such as resins. Various thermosetting resins and various ultraviolet curable resins can also be used. These resins may be appropriately added with an isocyanate-based curing agent and various dispersants. The light diffusing and transmitting sheet 1 may further include a substrate (not shown) such as a PET (polyethylene terephthalate) film, and the base resin 10 in which the composite particles 20 are dispersed may be formed in layers on the substrate.

  As shown in FIG. 2, the composite particle 20 contains a resin binder 21 and fine particles 22. The fine particles 22 are encapsulated in the resin binder 21. The fine particles 22 include glass fine particles 22a.

  As shown in FIG. 3B, when the high refractive index fine particles PH having a higher refractive index than the glass fine particles 22a such as the titanium dioxide fine particles are present inside the composite particles instead of the glass fine particles 22a, the high refractive index fine particles PH. When light is incident on the light, a large amount of light may be confined inside the high refractive index fine particles PH by repeating total reflection inside the high refractive index fine particles PH. This is disadvantageous in improving the luminance characteristics of the light diffusing and transmitting sheet. On the other hand, as shown in FIG. 3A, when the glass fine particles 22a are contained in the composite particles 20, some light may be confined in the glass fine particles 22a, but the refractive index of the glass. Is not so high, a lot of light passes through the glass fine particles 22a while being appropriately refracted on the surface of the glass fine particles 22a. That is, since the fine particles 22 of the composite particles 20 include the glass fine particles 22a, most of the light incident on the glass fine particles 22a travels toward the front of the light diffusion transmission sheet 1, so that the ratio of light confined in the fine particles 22 is reduced. Is done. As a result, the light diffusing and transmitting sheet 1 has high luminance characteristics. Further, the glass tends to have a refractive index having a desirable relationship with the refractive index of the resin binder 21 from the viewpoint of providing the light diffusing and transmitting sheet 1 with good light diffusing characteristics. For this reason, the inclusion of the glass fine particles 22a in the fine particles 22 is advantageous for realizing both good light diffusion characteristics and high luminance characteristics. Thereby, the light diffusion transmission sheet 1 has good light diffusion characteristics and high luminance characteristics.

  It is desirable that the average particle diameter of the composite particles 20 be within a predetermined range so that the composite particles 20 can be uniformly dispersed in the matrix resin 10. From such a viewpoint, the average particle diameter of the composite particles 20 is, for example, 1 μm to 20 μm, desirably 1 μm to 15 μm, and more desirably 4 μm to 15 μm. Thereby, the spatial dispersion | variation in the optical characteristic in the light diffusion transmission sheet 1 can be prevented. In addition, it is possible to reduce light reflection loss due to light entering a gap between primary particles generated when the composite particles 20 are aggregated. Thereby, the luminance characteristic of the light diffusion transmission sheet 1 can be improved. Furthermore, it is possible to sufficiently secure an interface where light is refracted in the light diffusion transmission sheet 1. Thereby, the light-diffusion characteristic of the light-diffusion transmission sheet 1 can be improved. In the present specification, the “average particle diameter” means a volume-based D50 measured by a laser diffraction method. The “average particle size” is 50 or more visible when the cross section of the light diffusing and transmitting sheet 1 or the cross section of the composite particle 20 is observed with a scanning electron microscope (SEM) or a transmission electron microscope (TEM). You may obtain | require as an average value of the largest diameter of particle | grains.

  The shape of the composite particles 20 is desirably granular with an aspect ratio of 1 to 2 from the viewpoint of imparting spatially uniform light diffusion characteristics to the light diffusing and transmitting sheet 1. Here, the aspect ratio means the ratio (da / db) of the major axis da of the composite particle 20 to the minor axis db of the composite particle 20.

  The average particle diameter of the glass fine particles 22a is, for example, 10 nm to 10 μm. The average particle diameter of the glass fine particles 22a is desirably 100 nm to 10 μm, and more desirably 100 nm to 5 μm. As a result, the glass fine particles 22 a are appropriately included in the resin binder 21.

  The refractive index of the glass fine particles 22a is, for example, 1.52 to 1.80. Thereby, the light-diffusion transmission sheet 1 has a favorable light-diffusion characteristic and a high luminance characteristic more reliably. From the viewpoint that the light diffusing and transmitting sheet 1 more reliably has good light diffusing characteristics and high luminance characteristics, the refractive index of the glass fine particles 22a is preferably 1.54 to 1.80, more preferably 1 .55 to 1.80.

  For example, the glass fine particles 22 a have a refractive index larger than that of the resin binder 21. The difference between the refractive index of the glass fine particles 22a and the refractive index of the resin binder 21 is, for example, 0.30 or less. This makes it difficult for light incident on the glass fine particles 22a to be confined by repeating total reflection inside the glass fine particles 22a, and the light diffusion transmission sheet 1 surely has high luminance characteristics. The difference between the refractive index of the glass fine particles 22a and the refractive index of the resin binder 21 is, for example, 0.02 or more. Thereby, the light-diffusion transmission sheet 1 has a favorable light-diffusion characteristic more reliably.

The glass for forming the glass fine particles 22a is not particularly limited, but is, for example, the following glass.
Expressed in mass%,
59% ≦ SiO ₂ ≦ 65%,
8% ≦ Al ₂ O ₃ ≦ 15%,
47% ≦ (SiO ₂ —Al ₂ O ₃ ) ≦ 57%,
1% ≦ MgO ≦ 5%,
20% ≦ CaO ≦ 30%,
0% <(Li ₂ O + Na ₂ O + K ₂ O) <2%,
0% ≦ TiO ₂ ≦ 5%,
Each component _{contains, B 2 O 3, F,} ZnO, BaO, SrO, and not containing ZrO ₂ substantially glass. Here, “substantially does not contain” means, for example, that it is not intentionally included unless it is inevitably mixed into industrial raw materials, and specifically includes the target component. The amount is less than 0.1% by weight, desirably less than 0.05% by weight, more desirably less than 0.03% by weight. As such a glass, the glass of international publication 2006/068255 is illustrated. Thereby, the light-diffusion transmission sheet 1 has a favorable light-diffusion characteristic and high brightness | luminance characteristic more reliably.

  The content rate of the composite particles 20 in the light diffusion transmission sheet 1 is, for example, 55% by mass or more, desirably 60% by mass or more, and more desirably 64% by mass or more. Thereby, the light diffusion transmission sheet 1 more reliably has good light diffusion characteristics and high luminance characteristics. Moreover, the content rate of the composite particle 20 in the light diffusive transmission sheet 1 is, for example, 70% by mass or less, desirably 68% by mass or less, and more desirably 66% by mass or less. Thereby, the composite particles 20 can be appropriately dispersed in the base material resin 10, and for example, the composite particles 20 can be prevented from being exposed on the surface of the light diffusion transmission sheet 1.

  The content rate of the fine particles 22 in the composite particles 20 is, for example, 30% by mass to 99% by mass, desirably 30% by mass to 95% by mass, and more desirably 50% by mass to 90% by mass. The content rate of the resin binder 21 in the composite particle 20 is, for example, 1% by mass to 70% by mass, desirably 5% by mass to 70% by mass, and more desirably 10% by mass to 50% by mass. Thereby, the light diffusion transmission sheet 1 more reliably has good light diffusion characteristics and high luminance characteristics.

  As shown in FIG. 2, the fine particles 22 may contain fine particles other than the glass fine particles 22a. For example, the fine particles 22 include at least one fine particle selected from the group consisting of silica, silicone, fluororesin, titanium dioxide, zinc oxide, zirconium oxide, calcium carbonate, barium sulfate, zinc sulfide, aluminum hydroxide, and extender pigment. In addition. Thereby, the light diffusion transmission sheet 1 which has various optical characteristics can be provided. In some cases, a predetermined mechanical strength can be imparted to the composite particles 20.

  The composite particle 20 includes, for example, glass fine particles 22a and silica fine particles. Thereby, the light diffusion transmission sheet 1 more reliably has good light diffusion characteristics and high luminance characteristics. In this case, the average particle diameter of the silica fine particles is smaller than the average particle diameter of the glass fine particles 22a, for example, 1 nm to 1 μm, preferably 2 nm to 600 nm, and more preferably 2 nm to 400 nm. The content of the silica fine particles in the composite particle 20 is, for example, 10% by mass to 98% by mass, desirably 15% by mass to 94% by mass, and more desirably 40% by mass to 87% by mass. Thereby, since the silica fine particles easily surround the glass fine particles 22 a together with the resin binder 21, the composite particles 20 have desirable mechanical strength. The silica fine particles have, for example, a spherical shape. The composite particle 20 may include only glass fine particles 22 a and silica fine particles as the fine particles 22.

  The resin binder 21 can enclose the fine particles 22 and has transparency to visible light. From the viewpoint of reducing the possibility of damaging the member in contact with the light diffusing and transmitting sheet 1 by reducing the hardness of the composite particles 20, the resin binder 21 is desirably at least selected from the group consisting of an acrylic resin, a polyurethane resin, and nylon. Contains one resin. Among these, the resin binder 21 is desirably a polyurethane resin.

  Next, an example of a method for manufacturing the light diffusing and transmitting sheet 1 will be described. A sol solution in which the raw material of the resin binder 21 and the fine particles 22 including at least the glass fine particles 22a are dispersed is prepared. If necessary, fine particles 22 (for example, silica fine particles), fluorescent dyes, fluorescent brighteners, dyes, or pigments different from the glass fine particles 22a are dispersed in the sol solution. The composite particles 20 can be obtained by spray drying using the prepared sol solution. By adjusting the content of the solid component in the sol liquid and the spraying conditions in the spray drying, aggregation of the primary particles can be suppressed and the particle size of the composite particles 20 can be controlled within an appropriate range.

  Further, fine particles 22 containing at least glass fine particles 22a are added to the molten resin to be the resin binder 21, and if necessary, fine particles 22 (for example, silica fine particles) different from the glass fine particles 22a, fluorescent dyes, fluorescent whitening. Agents, dyes, or pigments are added and kneaded, and these additives are mixed uniformly into the molten resin. The composite particles 20 can also be obtained by pulverizing the resin mass obtained in this way and adjusting it to a predetermined particle size. However, from the viewpoint of uniformly dispersing the fine particles 22 and the like in the resin binder 21 or efficiently producing the composite particles 20 having a desired particle size and shape, the composite particles 20 are prepared by preparing a sol solution and spray drying. Is desirable.

  The composite particles 20 produced as described above are uniformly dispersed in a fluid containing the raw material of the base material resin 10. In this way, an ink containing the raw material of the base resin 10 and the composite particles 20 is prepared. The light diffusing and transmitting sheet 1 can be obtained by applying this ink on a substrate such as a PET film and solidifying the ink.

  The present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples.

<Example>
Aqueous dispersion of glass fine particles (refractive index of glass: 1.57, average particle size of glass fine particles: 1.5 μm, concentration of glass fine particles 5.8% by mass) 22.6 parts by weight, colloidal liquid A of silica fine particles ( Manufactured by Nissan Chemical Industries, Ltd., average particle diameter of silica fine particles: 2 nm to 3 nm, refractive index of silica fine particles: about 1.45, trade name: Snowtex XS) and colloid liquid B of silica fine particles (Japan) Made by Chemical Industry Co., Ltd., average particle diameter of silica fine particles: 7 nm to 10 nm, refractive index of silica fine particles: about 1.45, trade name: Silica Doll 30S) and polyurethane emulsion A (Mitsui Chemicals, Product name: Takelac W-6020, polyurethane refractive index: 1.50 to 1.55) 17.7 parts by weight, polyurethane emulsion B (Mitsui Chemicals, product name: Takelac W) -6021, the refractive index of the polyurethane: 1.50 to 1.55) to prepare a sol solution by mixing 2.7 parts by weight. The content of the glass fine particles in the solid content of the sol liquid is 5.8% by mass, the content of the solid content of polyurethane in the solid content of the sol liquid is 20.4% by mass, and the silica fine particles in the solid content of the sol liquid The content of was 73.8% by mass.

The glass forming the glass fine particles is expressed in mass%,
59% ≦ SiO ₂ ≦ 65%,
8% ≦ Al ₂ O ₃ ≦ 15%,
47% ≦ (SiO ₂ —Al ₂ O ₃ ) ≦ 57%
1% ≦ MgO ≦ 5%,
20% ≦ CaO ≦ 30%,
0% <(Li ₂ O + Na ₂ O + K ₂ O) <2%,
0% ≦ TiO ₂ ≦ 5%,
It was glass which contains each of these components and does not substantially contain B ₂ O ₃ , F, ZnO, BaO, SrO, and ZrO ₂ .

  The sol solution prepared as described above was spray-dried using a micro mist spray dryer (manufactured by Fujisaki Electric Co., Ltd., product name: MDL-050) to produce composite particles according to the examples. The average particle size of the composite particles according to the example was 4 to 15 μm. The average particle size of the composite particles was measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Nikkiso Co., Ltd., product name: Microtrac MT-3000II). The sample used for this measurement was prepared by mixing an appropriate amount of the composite particles according to the dried example in pure water and applying ultrasonic vibration (130 W for 1 minute) to disperse the composite particles in pure water.

  Ink was prepared by dispersing the composite particles according to the example produced as described above in an acrylic resin. This ink was applied to a PET film having a thickness of 20 μm by the doctor blade method and solidified to prepare a sample according to the example. The thickness of the coating film in the sample according to the example was 7 to 15 μm, and the content of the composite particles in the coating film of the sample according to the example was 65% by mass.

<Comparative example>
8.4 parts by weight of an aqueous dispersion of fine titanium dioxide particles (refractive index: 2.71, average particle size of fine titanium dioxide particles: 330 nm, concentration of fine titanium dioxide particles: 20% by mass), and an aqueous dispersion of fine zinc oxide particles ( Refractive index: 2.0, average particle diameter of zinc oxide fine particles: 0.15 to 0.16 μm, 9.1 parts by weight of zinc oxide fine particles (concentration 21.7% by mass), and colloidal liquid A of silica fine particles (Nissan Chemical) Manufactured by Kogyo Co., Ltd., average particle diameter of silica fine particles: 2 nm to 3 nm, refractive index of silica fine particles: about 1.45, trade name: Snowtex XS, 16.6 parts by weight, and colloid liquid B of silica fine particles (Nippon Chemical Industry Co., Ltd.) The average particle size of silica fine particles: 7 nm to 10 nm, the refractive index of silica fine particles: about 1.45, 44.3 parts by weight of product name: silica dol 30S, and polyurethane emulsion A (trade name, manufactured by Mitsui Chemicals, Inc.) Product name: Takelac W-6020, 19.4 parts by weight of polyurethane refractive index: 1.50 to 1.55, polyurethane emulsion B (Mitsui Chemicals, trade name: Takelac WS-6021, refractive index of polyurethane: 1 .50 to 1.55) 2.2 parts by weight were mixed to prepare a sol solution. The content of titanium dioxide fine particles in the solid content of the sol liquid is 6.3% by mass, the content of zinc oxide fine particles in the solid content of the sol liquid is 7.4% by mass, and the silica fine particles in the solid content of the sol liquid. The content ratio of polyurethane was 62.1 mass%, and the solid content of polyurethane in the solid content of the sol liquid was 24.2 mass%.

  The sol solution prepared as described above was spray-dried using a micro mist spray dryer (manufactured by Fujisaki Electric Co., Ltd., product name: MDL-050) to produce composite particles according to a comparative example. The average particle size of the composite particles according to the comparative example was 4 to 15 μm. The average particle size of the composite particles according to the comparative example was measured in the same manner as in the example.

  The composite particles according to the comparative example were dispersed in an acrylic resin to prepare an ink. This ink was applied to a PET film having a thickness of 20 μm by a doctor blade method and solidified to prepare a sample according to a comparative example. The thickness of the coating film in the sample according to the comparative example was 7 to 15 μm, and the content ratio of the composite particles in the coating film of the sample according to the comparative example was 65% by mass.

<Measurement of luminance characteristics>
The luminance and chromaticity y of the sample according to the example and the sample according to the comparative example were measured using a luminance measuring device (product name: RISA-COLOR ONE, manufactured by Highland Corporation). The backlight of Apple's iPhone 5 was used as the light source. “IPhone” is a registered trademark of Apple Inc. Further, the measurement position of the luminance and chromaticity y was located on the side opposite to the light source of the sample, and the distance between the measurement position of the luminance and chromaticity y and the sample was 100 cm. Table 1 shows the results. Note that the luminance value when the relative luminance value is 100% is 10 ⁴ cd / cm ² .

<Measurement of haze ratio>
Using a spectrophotometer (manufactured by Shimadzu Corporation, product name: UV-3600) and an integrating sphere, the haze ratio of the sample according to the example and the sample according to the comparative example with respect to incident light having a wavelength of 555 nm was measured. The results are shown in Table 1.

  As shown in Table 1, it was suggested that the sample according to the example had higher luminance characteristics than the sample according to the comparative example. Moreover, it was suggested that the sample which concerns on an Example has the high haze rate comparable as the sample which concerns on a comparative example, and has a favorable light-diffusion characteristic.

Claims (9)

A base material resin;
A resin binder and fine particles encapsulated in the resin binder, and composite particles dispersed in the matrix resin,
The fine particles include glass fine particles,
Light diffusion transmission sheet.   The light diffusion / transmission sheet according to claim 1, wherein the composite particles have an average particle diameter of 1 μm to 20 μm.   The light diffusion transmission sheet according to claim 1 or 2 whose average particle diameter of said glass particulates is 10 nm-10 micrometers.   The light diffusion transmission sheet according to any one of claims 1 to 3, wherein the glass fine particles have a refractive index of 1.52 to 1.80.   The light diffusion transmission sheet according to any one of claims 1 to 4, wherein a difference between a refractive index of the glass fine particles and a refractive index of the resin binder is 0.30 or less.   The content of the fine particles in the composite particles is 30% by mass to 99% by mass, and the content of the resin binder in the composite particles is 1 to 70% by mass according to any one of claims 1 to 5. The light diffusive transmission sheet of description.   The fine particles are at least one selected from the group consisting of silica, magnesium fluoride, silicone, fluororesin, titanium dioxide, zinc oxide, zirconium oxide, calcium carbonate, barium sulfate, zinc sulfide, aluminum hydroxide, and extender pigments. The light diffusion transmission sheet according to any one of claims 1 to 6, further comprising fine particles.   The light diffusion transmission sheet according to any one of claims 1 to 7, wherein the composite particles include glass fine particles and silica fine particles as the fine particles.   The light diffusion transmission sheet according to claim 1, wherein the resin binder includes at least one resin selected from the group consisting of an acrylic resin, a polyurethane resin, and nylon.

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