WO2015099050A1

WO2015099050A1 - Light guide plate unit, production method therefor, and light-transmitting composition

Info

Publication number: WO2015099050A1
Application number: PCT/JP2014/084327
Authority: WO
Inventors: 小川　修; 藤本　恭一; 林　宏三
Original assignee: 豊田通商株式会社
Priority date: 2013-12-26
Filing date: 2014-12-25
Publication date: 2015-07-02
Also published as: JP2015125836A

Abstract

The light-scattering capability is improved for each dot in a dot pattern of a light-scattering layer from a light guide plate unit. The light-scattering capability of the dot is dramatically increased by adopting a hollow nano-particle having an average particle size of 200 nm to 2000 nm as a light-scattering substance in a light-transmitting composition constituting the dot. As a result, even when the dot diameter is 200 μm or smaller, the dot functions as a dot that constitutes the dot pattern of the light-scattering layer formed on the back face of a backlight-type light guide plate unit, and supplies a sufficient amount of light to the light-emitting face.

Description

Light guide plate unit, method for producing the same, and light transmissive composition

The present invention relates to a light guide plate unit. This light guide plate unit is suitable as a planar light source (backlight or frontlight) for display of electronic equipment.

An edge light type light guide plate unit is used as a planar light source of a display of an electronic device such as a smartphone or a tablet terminal.
The light guide plate unit includes a light guide plate whose one side faces a linear light source, and a light scattering layer that scatters light is formed on one surface of the light guide plate. This light scattering layer is obtained by printing a light scattering pattern composed of dots (hereinafter sometimes simply referred to as “dot pattern”) on one surface of the light guide plate. By making the light scattering layer a dot pattern, the degree of light scattering can be arbitrarily and easily adjusted. This is because the diameter of the dots constituting the dot pattern (dot diameter), the pitch between the dots, and the light-transmitting composition (ink) that is the dot forming material may be adjusted.

Therefore, various studies have been made on dot patterns.
For example, in the case of the backlight type light guide plate unit disclosed in Patent Document 1 using a thin light guide plate (1.5 mm), the coverage by the dot pattern in the vicinity of the light introduction side is set to 3.8% (dot diameter 220 μm). . Thereby, the visibility of dots is reduced while preventing strong light emission in the vicinity of the light introduction side. The dot ink (light transmissive composition) is a mixture of a light transmissive material made of acrylic / vinyl resin and a light scattering material made of titania (particle diameter: 2 μm or less).
See also Patent Document 2 and Patent Document 3 as other documents disclosing techniques related to the present application.

JP-A-7-72479 WO2010 / 004610 Publication JP 2007-87659 A

With diversification of electronic devices, diversification is also demanded for displays mounted on the electronic devices, and thus light guide plate units serving as the planar light sources.
As a direction of diversification of displays, there are large screens and thinnings, but it goes without saying that uniform luminance and chromaticity are required in any case. Therefore, diversity is also required for the dot pattern in the light scattering layer formed on one surface of the light guide plate.
According to the study by the present inventors, for example, in the case of a backlight type light guide plate unit, when the dot diameter is 200 μm or less, the light scattering ability is inferior, and it is difficult to supply a sufficient amount of light to the light emitting surface of the light guide plate. there were. That is, it was impossible to include dots having a diameter of 200 μm or less in the dot pattern.
Accordingly, an object of the present invention is to improve the light scattering ability of dots having a diameter of 200 μm or less.
Another object of the present invention is to improve the light scattering ability of each dot of the dot pattern of the light scattering layer of the light guide plate unit.

As a result of intensive studies to achieve at least one of the above-mentioned purposes, the present inventors have an average particle size of 200 nm to 2000 nm (hereinafter, “ The present inventors have found that the use of nano hollow particles (sometimes abbreviated as “200 nm to 2000 nm”) dramatically improves the light scattering ability of dots.
That is, the first aspect of the present invention is configured as follows.
A light guide plate corresponding to the edge light system;
A light scattering plate unit comprising a light scattering layer formed on one surface of the light guide plate and including a light scattering pattern composed of dots,
The dots are made of a light transmissive composition,
The light transmissive composition comprises a light transmissive material and a light scattering material of nano hollow particles having an average particle size of 200 nm to 2000 nm,
The dots include dots having a diameter of 25 μm or more and 200 μm or less,
Light guide plate unit.

According to the light guide plate unit defined in the first aspect thus configured, each dot has sufficient light even if the dot diameter is 25 μm or more and 200 μm or less (hereinafter sometimes abbreviated as “25 μm to 200 μm”). Has scattering ability. Therefore, even if a dot pattern composed of such dots is applied to the back surface of the light guide plate, a sufficient amount of light is supplied from the dot pattern to the upper surface (light emitting surface) of the light guide plate, which is sufficient as a planar light source for the display. Function.

The second aspect of the present invention is defined as follows.
In the light guide plate unit defined in the first aspect, the nano hollow particles have an average primary particle size of 200 nm to 2000 nm.
According to the light guide plate unit specified in the second aspect, as a result of adopting relatively large particles (average particle size (primary particle size) of 200 nm to 2000 nm) as the nano hollow particles, the color difference on the light emitting surface of the light guide plate unit Can be suppressed. More preferably, the average particle size (primary particle size) is 500 nm or more and 1000 nm or less.

The third aspect of the present invention is defined as follows.
The light guide plate unit defined in the first or second aspect, wherein in the light transmissive composition, the light transmissive material is made of a light transmissive synthetic resin material, and 100 parts by weight of the synthetic resin material. 10 parts by weight or more and 40 parts by weight or less of the light scattering material is blended.
According to the light guide plate unit of the third aspect defined as described above, the blending amount of the light-transmitting synthetic resin material and the light-scattering substance is in a suitable range, and is formed from the light-transmitting composition having such a blending. The dots exhibit excellent light scattering ability.

The fourth aspect of the present invention is defined as follows.
The light guide plate unit defined in any one of the first to third aspects, wherein the light guide plate has a thickness of 1.5 mm or less, and the dot pitch is 4 to 20 times the dot diameter ( Hereinafter, the light scattering layer may be simply referred to as “4 to 20 times”), and the light scattering layer is formed on the back surface of the light guide plate for backlight.
According to the light guide plate unit of the fourth aspect defined in this way, even if the light guide plate is made as thin as 1.5 mm or less, the dots are hardly visible when viewed from the light emitting surface, or even if they are visible, they are diffused. The visual recognition can be easily eliminated with a sheet or the like.

The fifth aspect of the present invention is defined as follows.
The light guide plate unit defined in the fourth aspect, wherein the light guide plate is for a display of 7 inches (17.8 cm) or more and 10 inches (25.4 cm) or less.
According to the light guide plate unit thus defined, the entire light emitting surface of the light guide plate emits light with uniform luminance and chromaticity.

The sixth aspect of the present invention is defined as follows.
A light guide plate corresponding to the edge light system;
A light-transmitting composition that forms the dots in a light guide plate unit that is formed on one surface of the light guide plate and includes a light scattering layer including dots having a diameter of 25 μm or more and 200 μm or less,
A light transmissive composition comprising a light transmissive material and a light scattering material of nano hollow particles having an average particle diameter of 200 nm to 2000 nm.
The dots formed on one surface of the light guide plate using the light-transmitting composition of the sixth aspect defined in this way have a high light scattering ability. Therefore, even if the dot pattern constituting the light scattering layer includes a dot diameter of 200 μm or less, a sufficient amount of light can be supplied to the light emitting layer side in the light scattering layer of the backlight type light guide plate unit.

The seventh aspect of the present invention is defined as follows.
The light-transmitting composition defined in the sixth aspect, wherein the light-transmitting material is made of a light-transmitting synthetic resin material, and 10 weights of the light scattering material with respect to 100 parts by weight of the synthetic resin material. More than 40 parts by weight is blended.
According to the light-transmitting composition of the seventh aspect defined as described above, the blending amount of the light-transmitting synthetic resin material and the light-scattering substance is in a suitable range. The formed dots exhibit excellent light scattering ability.

The eighth aspect of the present invention is defined as follows.
A light guide plate corresponding to the edge light system;
A light scattering layer including a light scattering pattern formed on one surface of the light guide plate and including dots, and a method of manufacturing a light guide plate unit,
Providing a light transmissive composition comprising a light transmissive material and a light scattering material of nano hollow particles having an average particle size of 200 nm to 2000 nm;
Printing the light scattering pattern including dots having a dot diameter of 25 μm or more and 200 μm or less on one surface of the light guide plate with the light transmissive composition, and forming the light scattering layer. A method of manufacturing a light guide plate unit .
According to the manufacturing method of the light guide plate unit of the eighth aspect defined in this way, even a dot having a diameter of 200 μm or less has sufficient light scattering performance, so the degree of freedom in selecting the dot diameter is improved, Even if the display is diversified, a light guide plate unit meeting the requirements can be easily provided.

FIG. 1 is a diagram schematically illustrating the configuration of a light guide plate unit according to the present invention. FIG. 2 is a transmission electron micrograph of nano hollow silica particles having an outer diameter of 1000 nm. FIG. 3 is a transmission electron micrograph of nano hollow silica particles having an outer diameter of 500 nm.

Hereinafter, embodiments of the light guide plate unit of the present invention will be described.
As shown in FIG. 1, the light guide plate unit 1 of this embodiment includes a light guide plate 3 and a light scattering layer 5 formed on the back surface of the light guide plate 3. This does not prevent the general-purpose sheet such as a light diffusion sheet, a prism sheet, and DBEF from being laminated on the upper surface of the light guide plate 3.
<Light guide plate>
The light guide plate 3 of the present invention is a flat member made of a light transmissive material.
One side captures light facing a light source (not shown). The taken-in light is scattered on the back surface (light scattering layer 5) of the light guide plate 3, and light is extracted from the upper surface (light emitting surface). The light from the light source is not limited to visible light, and does not exclude infrared light or ultraviolet light.
In order to improve the light extraction efficiency from the light emitting surface, it is preferable to form a light reflecting layer on the side surface other than the side surface that takes in light.
The dots formed with the light-transmitting composition proposed in the present invention not only reflect and scatter incident light, but also have an effect of efficiently transmitting and scattering part of the light. Therefore, in order to return the light transmitted through the dots to the light emitting surface side, it is preferable that at least the surface facing the light scattering layer 5 in the housing for housing the light guide plate unit 1 is a light reflecting surface such as a mirror surface.
The molding material of the light guide plate 3 can be arbitrarily selected according to the purpose and application of the electronic device. From the viewpoint of weight reduction, a transparent synthetic resin can be selected. Examples of such synthetic resins include acrylic resins and polycarbonates.
The back surface and / or the top surface of the light guide plate 3 itself can be subjected to fine surface processing to scatter or reflect light as necessary.

<Light scattering layer>
The light scattering layer 5 is formed on the back surface of the light guide plate 3. The light scattering layer 5 of this invention consists of a dot pattern.
The dot pattern is formed of a light transmissive composition. Screen printing is performed on the back surface of the light guide plate 3 using this light transmissive composition, or dots are formed on the back surface of the light guide plate 3 by spraying the light transmissive composition onto the back surface of the light guide plate 3 by an inkjet method. A pattern (light scattering layer 5) is formed.
Here, the dot refers to a small-area printing region made of the light-transmitting composition, and preferably has a circular shape in plan view, but the shape is not particularly limited. When the dots are circular, the outer diameter is preferably 25 μm or more and 200 μm or less.
The dot pattern may be composed of only dots having the same diameter, or dots having different diameters may be mixed. The distance (pitch) between dots can be arbitrarily selected according to the application and purpose. That is, the dot pitch may be constant or the pitch may be changed.

The light transmissive composition of the dot pattern is a mixture of a light transmissive material and a light scattering material. Of course, other auxiliaries (viscosity adjusting agents and the like) may be included.
The light transmissive material is not particularly limited as long as it is a material that transmits light. For example, light transmissive resin, glass, etc. are mentioned. The light transmissive resin is not particularly limited as long as it is a material that transmits light. For example, transparent resin or inorganic glass is used. Examples of the transparent resin include polycarbonate resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, methacrylic resin, methyl methacrylate-styrene copolymer resin, polystyrene resin, urethane resin, acrylonitrile-styrene copolymer (AS). Examples thereof include polyolefin resins such as resins, polyethylene resins, and polypropylene resins, acrylic resins, epoxy resins, silicone resins, and polyimide resins.

Nano hollow particles are used as the light scattering material.
Here, the nano hollow particle refers to a particle having an outer diameter of 2000 nm (= 2 microns) or less and a hollow inside (excluding porous particles).
The particle size of the nano hollow particles used in the present invention can be arbitrarily selected according to the wavelength of light to be reflected, but is preferably 200 nm to 2000 nm. A more preferable range of particle diameter is 500 nm or more and 1000 nm or less.
The particle size may be a primary (non-aggregated) nano hollow particle particle size or a secondary (aggregated) or higher nano hollow particle particle size. According to the study by the present inventors, the use of relatively large nano hollow particles having a primary particle size of 200 nm to 2000 nm can suppress the color difference from appearing on the light emitting surface.
Silica is preferably used as the material for the nano hollow particles from the viewpoint of refractive index, specific gravity, miscibility with light-transmitting materials, and material costs. Of course, titania, light transmissive polystyrene, or other transparent materials can be used.

Nano hollow silica particles having a primary particle size of 200 nm to 2000 nm can be produced, for example, by the method described in JP-A-2005-263550. That is, in the method for producing hollow particles composed of silica shells by the first step of preparing calcium carbonate, the second step of coating calcium carbonate with silica, and the third step of dissolving calcium carbonate,
(1) In the first step, calcium carbonate having a primary particle size of 150 nm to 2000 nm by transmission electron microscopy is prepared in an aqueous system, aged, and then dehydrated to form a water-containing cake.
(2) In the second step, the water-containing cake of (1) is dispersed in alcohol, and ammonia water, water and silicon alkoxide are contained in the ammonia water in a volume ratio of silicon alkoxide / alcohol of 0.002 to 0.1. the NH ₃ to be, with respect to the silicon alkoxide 1 mole, 4 to 15 moles of water to silicon alkoxide 1 mole, by adding so as to be 25-200 mol, the coated calcium carbonate on silica After preparation, washing with alcohol and water, again as a water-containing cake,
(3) In the third step, the water-containing cake of (2) is dispersed in water, acid is added, and the calcium carbonate is dissolved by adjusting the acid concentration of the liquid to 0.1 to 3 mol / L. This is a method of forming highly dispersed hollow particles made of a dense silica shell.

According to this method, a highly dispersed nano hollow silica having a primary particle size of 200 to 2000 nm by transmission electron microscopy, a wall thickness of 10 to 100 nm, and pores of 2 nm or more are not detected in the pore distribution measured by mercury porosimetry. Particles can be produced. Further, the calcium carbonate crystals prepared in the first step are calcite and hexagonal, but by controlling the synthesis conditions, the shape as if it were cubic, that is, “cubic” Can grow. Here, the “cubic shape” means not only a cube but also a shape (spindle shape) similar to a cube surrounded by a surface.
FIG. 2 is a transmission electron micrograph of nano hollow silica particles having an outer diameter of 1000 nm, and FIG. 3 is a transmission electron micrograph of nano hollow silica particles having an outer diameter of 500 nm.

In accordance with this method, the present inventors appropriately adjust the drug concentration, stirring method, temperature, type of alkali, etc., and thereby, nano hollow silica having various primary particle diameters, wall thicknesses, and porosity shown below. It has been confirmed that the particles can be produced.

<Method for producing light-transmitting composition>
The light transmissive composition of the present invention can be produced as follows using the above-described light transmissive material and light scattering material (nano hollow silica particles) as raw materials.
(Preparation process)

The nano hollow silica particles of 200 nm to 2000 nm obtained by the above method are put in a methanol solution of trimethylchlorosilane and stirred, and then filtered, washed with water, and dried to obtain methyl group-modified nano hollow silica. In addition, by using trialkylchlorosilane to which another alkyl group is bonded instead of trimethylchlorosilane, the alkyl group can be changed to various types.
(Dispersion preparation process)

Next, an acrylic resin solution in which an acrylic resin is dissolved in an organic solvent as a light transmissive resin and the nano hollow silica particles obtained in the above preparation step are mixed so as to have a predetermined ratio, and then stirred to obtain nano A silica dispersion in which hollow silica particles are uniformly dispersed in an acrylic resin solution is obtained. In order to adjust the light scattering effect, solid light scattering particles may be added in addition to the nano hollow silica particles.
The mixing ratio of the light transmitting resin and the light scattering material can be adjusted as appropriate, but the light scattering material is preferably 10 to 40 parts by weight with respect to 100 parts by weight of the light transmitting resin.
When the blending amount of the light scattering material is less than 10 parts by weight, the light scattering property is lowered, and the dots are easily visible on the light emitting surface of the light guide plate unit. On the other hand, when the blending amount exceeds 40 parts by weight, the physical properties (viscosity, etc.) of the light-transmitting composition as the ink for forming the dots are not preferable.
A more preferable range of the light scattering material is 25 parts by weight or more and 30 parts by weight or less with respect to 100 parts by weight of the light-transmitting resin.
<Formation of light scattering layer>

The light-scattering layer 5 which consists of a dot pattern is formed in the whole or part on the back surface of the light-guide plate 3 with the light transmissive composition obtained as mentioned above.
The dot diameter d constituting the dot pattern is preferably 25 μm to 200 μm, and the pitch p between dots (the distance between dot centers) is preferably 4 to 20 times the dot diameter d.
When the dot pattern configured in this way is used in a backlight type light guide plate unit, even if the thickness of the light guide plate is 1.5 mm or less, the dots are hardly visible on the light emitting surface, or the dots are formed with a thin diffusion sheet. Can be eliminated.
According to the study by the present inventors, when the dot pattern is formed as described above on a light guide plate of 7 inches (17.8 cm) to 10 inches (25.4 cm), the dots are almost visually recognized on the entire surface of the light emitting surface. Not only is this not done, but the brightness of the entire light emitting surface is uniform, and there is almost no color difference.
The thickness of the dot is preferably 2 μm to 10 μm.
Examples of a method for forming a dot pattern under such conditions include a screen printing method and an ink jet method.

In the above description, the light guide plate unit has been described by taking only the backlight type as an example, but the present invention is naturally applicable to a front light type.
In the case of the front light type, a light scattering layer is formed on the upper surface (light emitting surface) side of the light guide plate unit. In the case of the front light type, the diameter of the dots constituting the light scattering layer is made small (for example, 25 μm or more and 200 μm or less) so that the dots themselves do not hinder display.
Dots formed of a light-transmitting composition containing nano hollow particles have a high ability to absorb light not only inside the light guide plate but also outside, that is, from the light guide plate. Therefore, when such a dot is used in a front light type light guide plate unit, it is preferable to match the background color (default color) of the display with the light source color (for example, white).

Example 1
In Example 1, a silica dispersion having the following composition was prepared, and dot printing was performed on one side of a transparent acrylic plate to produce a light guide plate unit for an LED panel.

Nano balloon XP200 (methyl) manufactured by Grandex Co., Ltd. as nano hollow particles in 333 parts by weight of CAV transparent 800 medium (solid content 30%) manufactured by Seiko Advance Co., Ltd. (primary particle diameter (outer diameter): 202 0.0 nm, see Table 1) 20 parts by weight were mixed. And it disperse | distributed using Kurashiki Boseki Co., Ltd. Maruzester as a planetary-type stirring and defoaming apparatus, and obtained the silica dispersion liquid by which the nano hollow silica particle was disperse | distributed uniformly in the acrylic resin solution.

A 5-inch (12.7 cm) transparent acrylic plate was prepared, and the above silica dispersion was screen-printed on one side so as to have a basis weight of 12 g / m ² (when dry). Then, it was made to dry and it was set as the light-guide plate unit of Example 1. The obtained dots had a minimum diameter of 50 μm and a maximum of 62 μm, and the dot pitch was 500 μm.
(Example 2)
The light guide plate of Example 2 under the same conditions as in Example 1 above, except that Nano Balloon NFB manufactured by Grandex Co., Ltd. (primary particle diameter (outer diameter): 630.0 nm, see Table 1) was adopted as the nano hollow particles. Got a unit.
Example 3
A light guide plate unit of Example 3 was obtained under the same conditions as in Example 1 except that the compounding amount of the nano hollow particles was halved (10 parts by weight).

(Comparative Example 1)
The light-guide plate unit of the comparative example 1 was obtained on the same conditions as the said Example 1 except not mix | blending nano hollow particle.
(Comparative Example 2)
The light guide plate of Comparative Example 2 under the same conditions as Example 1 except that solid silica particles (primary particle size 200 nm, manufactured by Admatechs Co., Ltd., trade name: SO-C1) were used instead of the nano hollow particles. Got a unit.

<Evaluation>
It measured about the brightness | luminance and color difference of the light-guide plate unit of an Example and a comparative example.
Table 2 shows the results.

In Table 2, the diffusion plate, the prism, and the DBEF are generally used for the planar light source and are sequentially stacked on the light emission surface side of the light guide plate unit.
The luminance and color difference in Table 2 were measured by the so-called 9-point method. Here, in the nine-point method, the light emission surface is divided into four equal parts vertically and horizontally to provide nine cells, and the luminance and chromaticity at the center of each cell are measured. For measurement, a two-dimensional color luminance meter CA-2000 made by Konica Minolta was used. The luminance is an average luminance of nine points, and the color difference is the difference between the chromaticity at the cell center of the eighth cell and the chromaticity at the cell center of the second cell.
With respect to the luminance, the value of Comparative Example 1 is used as a reference (100%), and the luminance of other examples (Examples and Comparative Examples) is relatively evaluated.
The color difference value is preferably close to zero, and the absolute value is preferably within 0.0100. More preferably, it is within 0.0080.
From the results shown in Table 2, it can be seen that the light guide plate unit of the example can obtain high luminance in a single unit.
From a comparison between Example 1 and Example 2, it can be seen that when the blending amount is a constant ratio, the color difference can be more efficiently suppressed by increasing the primary particle size of the hollow nanosilica (for example, 500 nm or more).

The present invention is not limited to the description of the embodiments and examples of the above invention. Various modifications are also included in the present invention as long as those skilled in the art can easily conceive without departing from the scope of the claims.

1 Light guide plate unit 3 Light guide plate 5 Light scattering layer

Claims

A light guide plate corresponding to the edge light system;
A light scattering plate unit comprising a light scattering layer formed on one surface of the light guide plate and including a light scattering pattern composed of dots,
The dots are made of a light transmissive composition,
The light transmissive composition comprises a light transmissive material and a light scattering material of nano hollow particles having an average particle size of 200 nm to 2000 nm,
The dots include dots having a diameter of 25 μm or more and 200 μm or less,
Light guide plate unit.
The light guide plate unit according to claim 1, wherein the nano hollow particles have an average primary particle size of 200 nm to 2000 nm.
In the light transmissive composition, the light transmissive material is made of a light transmissive synthetic resin material, and 10 parts by weight or more and 40 parts by weight or less of the light scattering material is blended with 100 parts by weight of the synthetic resin material. The light guide plate unit according to claim 1 or 2.
The light guide plate has a thickness of 1.5 mm or less, the dot pitch is 4 to 20 times the dot diameter, and the light scattering layer is formed on the back surface of the light guide plate for backlight. The light guide plate unit according to any one of claims 1 to 3.
The light guide plate unit according to claim 4, wherein the light guide plate is for a display of 7 inches (17.8 cm) or more and 10 inches (25.4 cm) or less.
A light guide plate corresponding to the edge light system;
A light-transmitting composition that forms the dots in a light guide plate unit that is formed on one surface of the light guide plate and includes a light scattering layer including dots having a diameter of 25 μm or more and 200 μm or less,
A light transmissive composition comprising a light transmissive material and a light scattering material of nano hollow particles having an average particle diameter of 200 nm to 2000 nm.
The light transmissive material is made of a light transmissive synthetic resin material, and 10 parts by weight or more and 40 parts by weight or less of the light scattering material is blended with 100 parts by weight of the synthetic resin material. Light transmissive composition.
A light guide plate corresponding to the edge light system;
A light scattering layer including a light scattering pattern formed on one surface of the light guide plate and including dots, and a method of manufacturing a light guide plate unit,
Providing a light transmissive composition comprising a light transmissive material and a light scattering material of nano hollow particles having an average particle size of 200 nm to 2000 nm;
Printing the light scattering pattern including dots having a dot diameter of 25 μm or more and 200 μm or less on one surface of the light guide plate with the light transmissive composition, and forming the light scattering layer. A method of manufacturing a light guide plate unit .