JP2013140702A - Light distribution layer and light guide device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide device that can exert at least either effect of (1) high luminance or (2) little unevenness of luminance, and a light distribution layer used for the same.SOLUTION: The light distribution layer 11b is arranged between a light guide plate 11 and a reflective layer 12. The light distribution layer 11b includes a light-transmitting matrix and nano hollow silica particles. The nano hollow silica particles have a primary particle size of 500 nm or less, a wall thickness of 30 nm or less, and a porosity of 40% or more. The nano hollow silica particles are coagulated in the matrix, and their secondary aggregated particle diameter is 1,500 nm or less.

Description

  The present invention relates to a light distribution layer formed on a reflective surface side of a light guide plate and a light guide device using the same.

  A light guide device is used in many industrial fields such as a light-emitting device using a liquid crystal television or an LED (for example, Patent Document 1). These light guide devices are required to have high luminance and uniform light emission on the light emitting surface, and each member constituting the light guide device performs the functions required for this, and improves the light intensity. It is necessary to reduce the attenuation.

Japanese Patent Laid-Open No. 2004-6187

  However, the conventional light guide device has a problem that sufficient luminance is not yet obtained and luminance unevenness is large. The present invention has been made in view of the above-described conventional situation, and a light guide device capable of producing at least one of the effects of (1) high luminance and (2) low luminance unevenness, and the same Providing a light distribution layer to be used is a problem to be solved.

1st aspect of this invention is the light distribution layer formed in the reflective surface side of a light-guide plate, Comprising: The light transmissive matrix and the nano hollow silica particle disperse | distributed to this matrix, Comprising: This nano hollow Silica particles have a primary particle diameter of 500 nm or less, a wall thickness of 30 nm or less, a porosity of 40% or more, and are aggregated in the matrix, and a secondary aggregated particle diameter of 1500 nm or less. And a light distribution layer containing nano hollow silica particles.
It should be understood by those skilled in the art that the “light guide plate” in the present specification is not limited to a plate-like object.

The light distribution layer of the present invention is formed on the reflective surface side of the light guide plate. Here, the “reflecting surface side of the light guide plate” refers to the surface opposite to the light emitting surface of the light guide plate. This
(1) The light emission surface is reflected and / or refracted by the nano hollow silica particles in the light distribution layer and returned to the light emission surface side of the light that is about to leak to the surface opposite to the light emission surface of the light guide plate. Light reflection function to increase the brightness of
(2) The light reflected by the reflective layer is diffused by the nano-hollow silica particles in the light distribution layer, and exhibits a reflected light diffusion function of making the light emission on the light emission surface uniform.
The reason will be described below.

  The nano hollow silica particles contained in the light distribution layer of the present invention are dispersed in a light-transmitting matrix, the primary particle diameter is extremely small as 500 nm or less, and the wall thickness is extremely thin as 30 nm or less. ing. For this reason, the particle diameter and wall thickness of the nano hollow silica particles are less than or equal to the wavelength of visible light or infrared light, and transparency to visible light or infrared light is not easily lost. In addition, the nano hollow silica particles have a high light transmittance in combination with the porosity of 40% or higher. For this reason, there is little attenuation of the light intensity in a light distribution layer.

  Moreover, scattering of the nano hollow silica particles occurs not only on the outer surface of the particle but also on the inner surface of the particle (see FIG. 6). Furthermore, since it has a hollow structure, unlike solid particles, energy attenuation of light entering the inside of the particles is small and scattering occurs efficiently (see FIGS. 6 and 7). For this reason, the light distribution layer of the present invention has a scattering effect while ensuring transparency. In other words, the balance between permeability (some of which passes through the inside of the particle) and scattering (some of the inner wall of the particle) are different from solid particles, so that it has a characteristic of uniformly scattering while ensuring transparency. It becomes. Such a characteristic occurs efficiently and uniformly in combination with the high transmittance and high scattering property of the nano hollow silica particles below the aggregate that does not become opaque with visible light.

  According to the test results of the present inventors, the nano hollow silica particles in the light distribution layer of the present invention become secondary agglomerated particles in the light distribution layer, and therefore, as a characteristic of the secondary agglomerated particles enclosing air. Is considered to achieve both high transmittance and high scattering. Further, taking advantage of such characteristics, the balance between transmission and scattering can be adjusted by the secondary aggregated particles. That is, with respect to scattering, the scattering from one particle (there is also an inner wall part of the particle) and the scattering of the outer wall of the secondary aggregated particle overlap, so the primary particle and the secondary particle are adjusted. Specifically, the balance between transmission and scattering can be adjusted by adjusting the primary particle diameter, silica cell wall thickness, porosity and secondary aggregate particle diameter in the nano hollow silica particles.

  Therefore, when the light distribution layer of the present invention is used in a light guide device, a light guide device that can solve at least one of high luminance and low luminance unevenness can be obtained. The secondary agglomerated particle diameter of the nano hollow silica particles is 1500 nm or less, preferably 500 nm or more and 1500 nm or less, and more preferably 700 nm or more and 1000 nm or less. When the secondary aggregate particle diameter is less than 500 nm, light scattering and reflection are difficult to occur. On the other hand, if the secondary agglomerated particle diameter exceeds 1500 nm, the light transmittance is deteriorated, and the luminance on the light emission surface of the light guide plate is lowered.

It is a disassembled perspective view of the sidelight type light guide device of an embodiment. It is a schematic cross section of the side light type light guide device of an embodiment. It is a disassembled perspective view of the sidelight type light guide device of Example 1 and Comparative Example 1. It is a schematic cross section of the sidelight type light guide device of Example 1 and Comparative Example 1. It is a top view of the sidelight type light guide device of Example 1 and Comparative Example 1 (numbers surrounded by circles indicate positions where luminance is measured). It is a schematic diagram which shows scattering and permeation | transmission of the light by a nano hollow silica particle. It is a schematic diagram which shows scattering and permeation | transmission of the light by a solid particle.

FIG. 1 is an exploded perspective view of an embodiment in which the light distribution layer of the present invention is applied to a sidelight type light guide device. This side light type light guide device includes a light guide device body 10 and an LED light source 20 installed on a side surface of the light guide device body 10 (a light source such as a fluorescent tube may be disposed instead of the LED light source 20). ).
The light guide device body 10 includes a light guide plate 11, which is opposite to the light guide plate body 11a made of a colorless and transparent acrylic resin and the light emission surface of the light guide plate body 11a, as shown in FIG. The light distribution layer 11b is dot-printed on the side surface (hereinafter also referred to as “back side surface”). The light distribution layer 11b contains nano hollow silica particles, and light scattering fine particles such as silica fume may be added to the light distribution layer 11b. The light distribution layer 11b can be formed by printing a light transmissive resin solution composition described later by screen printing or the like. A reflective layer 12 made of an aluminum plate is laminated on the back side surface of the light guide plate 11. Here, the term “lamination” includes not only the case where the layers are in close contact with each other, but also the case where the layers are simply stacked and not bonded (that is, a case where there is a slight gap between layers). In FIG. 2, the light distribution layer 11b is dot-printed. However, the present invention is not limited to this. The light distribution layer 11b may be applied or printed on the entire surface according to the purpose, or may be a separate sheet from the light guide plate main body 11a. You can also
A reflective sheet 12 is laminated on the back side surface of the light guide plate 11. The reflection sheet 12 has a structure in which a reflection light diffusion layer 12b having a thickness of 3 to 10 μm is laminated on a reflection layer 12a. The reflected light diffusing layer 12b can be formed by printing a light transmissive resin solution composition on the reflective layer 12a by screen printing or the like.

On the other hand, a first emission light diffusion layer 13 is laminated on the light emission surface side of the light guide plate 11. The first emission light diffusion layer 13 has a structure in which a light scattering particle-containing layer 13b for diffusing the emitted light from the light guide plate 11 is laminated on the back side surface of a film 13a made of a colorless transparent resin such as acrylic. Yes. The thickness of the light-scattering particle-containing layer 13b is adjusted as appropriate so that the diffusion effect required for making the brightness of the emitted light uniform and the required light transmittance can be obtained. The light scattering particle-containing layer 13b can be formed by printing a light-transmitting resin solution composition described later on the film 13a by screen printing or the like.
The first emitted light diffusing layer 13 may be formed on the light guide plate body 11a by printing or other deposition methods without using a separate sheet from the light guide plate body 11a.

  Further, on the light emission surface side of the first emission light diffusion layer 13, the light collection layer 14 that functions to improve the front luminance by condensing the emitted light from the first emission light diffusion layer 13 to the front by refraction. Is provided. The condensing layer 14 is made of a colorless and transparent resin, and has a structure in which structural rows having a triangular cross section are arranged. In FIGS. 1 and 2, only one condensing layer 14 is provided, but it is also preferable to insert a plurality of condensing layers so that triangular structure rows are orthogonal to each other. A condensing layer having a microlens structure can also be employed.

  A second emission light diffusion layer 15 for making the brightness of the emitted light from the light collection layer 14 uniform is laminated on the light emission surface side of the light collection layer 14. The second emission light diffusion layer 15 has a structure in which a light scattering particle-containing layer 15b for diffusing emitted light is laminated on the light emission surface side of a film 15a made of a colorless and transparent resin such as acrylic.

(Light transmissive resin solution composition)
The light-transmitting resin solution composition described above is a viscous liquid in which nano hollow silica particles are dispersed in a light-transmitting matrix dissolved in a solvent. In addition, when the light diffusibility is insufficient only with the nano hollow silica particles, a medium for light diffusion may be added. In this case, the light diffusion medium is preferably transparent. This is because light attenuation in the light distribution layer 11b is reduced. Moreover, you may add the thickener etc. for providing the viscosity suitable for printing, and thixotropy.

What is necessary is just to determine suitably the addition amount in the case of adding a light-diffusion particle other than a nano hollow silica particle considering the balance of scattering and permeation | transmission of the light irradiated in the light-guide plate. If the amount and ratio of the nano hollow silica particles are increased, both the scattered light and the transmitted light are increased, so that the surface on which the light diffusion layer is provided becomes brighter. On the other hand, when the light diffusing particles are solid particles having a low light transmittance, the scattered light increases, but the transmitted light decreases, so the surface opposite to the side where the light diffusing layer is provided becomes bright. Furthermore, the balance between transmission and scattering can also be adjusted by adjusting the components of the light diffusing particles other than the nano hollow silica particles and the diameter of the primary particles.
The following ranges are usually recommended.
Nano hollow silica particles:
10 wt% to 40 wt%, preferably 15 wt% to 30 wt%, more preferably 20 wt% to 25 wt%.
Light diffusion particles other than nano hollow silica particles:
20 wt% to 80 wt%, preferably 30 wt% to 60 wt%, more preferably 40 wt% to 50 wt%.

  It is good also as a nano hollow silica particle, without adding a light-diffusion particle. Even when the nano hollow silica particle diameter is smaller than the wavelength of light, it aggregates in the light distribution layer to form large secondary particles. This is because it is possible to achieve both.

The light-transmitting matrix 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, acrylonitrile-styrene copolymer (AS) resin, polyethylene. Examples thereof include polyolefin resins such as resins and polypropylene resins, acrylic resins, epoxy resins, silicone resins, and polyimide resins.
In this specification, light includes infrared light and ultraviolet light as well as visible light.

  Nano hollow silica particles dispersed in the light transmissive resin solution composition have a primary particle diameter of 500 nm or less, a wall thickness of 30 nm or less, and a porosity of 40% or more. Preferably, the primary particle size is 10 nm to 450 nm, the wall thickness is 5 nm to 30 nm, and the porosity is 40% to 90%.

Such hollow nanoparticles 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 20 to 200 nm by transmission electron microscopy was prepared in an aqueous system and aged so that the particle size by static light diffusion method was 20 to 700 nm. After that, 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. NH ₃ is added in an amount of 4 to 15 mol with respect to 1 mol of silicon alkoxide, and water is added in an amount of 25 to 200 mol with respect to 1 mol of silicon alkoxide. After preparation, washing with alcohol and water, again as a water-containing cake,
(3) In the third step, by dispersing the water-containing cake of (2) in water, adding an acid, and dissolving the calcium carbonate by adjusting the acid concentration of the liquid to 0.1 to 3 mol / L These are highly dispersed hollow particles composed of a dense silica shell.

  According to this method, the primary particle size by transmission electron microscopy is 30 to 500 nm, the particle size by static light diffusion method is 30 to 800 nm, the wall thickness is 5 to 30 nm, and the pore distribution is measured by mercury porosimetry. Highly dispersed silica nano hollow particles in which pores of 2 to 20 nm are not detected 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, “cubic” means not only a cube but also a shape similar to a cube surrounded by a surface.

  The inventors, following this method, adjust the drug concentration, the stirring method, the temperature, the type of alkali, etc. as appropriate, so that the nano hollow silica has various primary particle diameters, wall thicknesses, and porosity shown below. It has been confirmed that the particles can be produced.

  Further, the nano hollow silica particles may be subjected to a hydrophobic treatment with a surface treatment agent in order to facilitate dispersion in the transparent matrix.

Next, operations and effects of the side light type light guide device of the embodiment will be described.
In this side light type light guide device, the light irradiated from the side surface of the light guide 11 by the LED light source 20 travels while reflecting in the light guide plate body 11a at the boundary surface, and the nano hollow in the light distribution layer 11b. Scattered by the silica particles, part of which proceeds to the back side. The light that has escaped to the back side in this way is reflected by the reflection sheet 12 and returned to the light guide 11 side.

  The light returned to the light guide plate 11 side by the reflection sheet 12 as described above is reflected in the light guide plate 11, and the light that has escaped to the light emission surface side is diffused by the first radiated light diffusion layer 13, resulting in uneven brightness. Is improved and enters the light collecting layer 14. The condensing layer 14 has a function of condensing radiant light on the front surface by a refracting action and improving front luminance. And it diffuses by the 2nd radiation light diffusion layer 15, a brightness nonuniformity is improved, a brightness | luminance with a high brightness | luminance and a little brightness nonuniformity is radiated | emitted on the front side.

(Example 1 and Comparative Example 1)
・ Production of light guide plate coated with light distribution layer As shown in Fig. 3, solid SiO2 particles (SR931 white medium ink manufactured by Mino Group) are used on the half surface A of acrylic resinous light guide plate 20 of A4 size / 5mm thickness. Then, the light guide pattern was screen printed by screen printing, and this was used as Comparative Example 1. On the other side, M-group SR930 transparent medium ink and nano hollow silica (GRANDEX NanoBalloon XP200 primary particle size 200nm / secondary particle size) A light guide pattern was printed by screen printing using an ink in which 20% by weight of 1000 nm and a wall thickness of about 10 nm were mixed, and this was used as Example 1 as a light distribution layer.

  Then, as shown in FIG. 4, the LED light source 30 is placed on the side surface in the long side direction of the light guide plate 20, the light guide pattern printing surface 21 of the light guide plate 20 is down, and a white PET film made by Toray is used as the reflection sheet 22. Piled up. Further, Reiko Ruillite was placed as the emitted light diffusion layer 23 on the light emitting surface side of the light guide plate 20.

(Example 2 and Comparative Example 2)
In Example 2 and Comparative Example 2, an aluminum reflective sheet made of Toyo Aluminum was used as the reflective sheet 22 shown in FIG. About others, it is the same as that of Example 1 and the comparative example 1, and attaches | subjects the same code | symbol to the same structure, and abbreviate | omits description.

<Evaluation>
For the light guide devices of Example 1, Example 2, Comparative Example 1 and Comparative Example 2, the luminance of the radiation surface when the LED light source was turned on was measured for each location. As shown in FIG. 5, the luminance measurement points were arranged in two rows and eight places at equal intervals. Konica Minolta Sensing Co., Ltd. CA-1500W was used for measuring the luminance. The results are shown in Table 2 for the case of white PET film (ie, in the case of Example 1 and Comparative Example 1), and in the case of the aluminum reflective sheet (ie, in the case of Example 2 and Comparative Example 2). 3, respectively.

When Comparative Example 1 and Comparative Example 2 were compared, from Table 2 and Table 3 above, the average brightness when a white PET film was used as the reflective sheet was 922 cd / m <2>, whereas the reflective sheet was aluminum reflective. When the sheet was used, the average luminance was 913 cd / m @ 2, which was almost unchanged.
On the other hand, when Example 1 and Example 2 were compared, from Table 2 and Table 3 above, the average luminance when using a white PET film as the reflective sheet was 1081 cd / m 2, When an aluminum reflection sheet was used as the reflection sheet, the average luminance was 1125 cd / m 2 and the luminance was improved by 4% or more.
Moreover, when the comparative example 1 and the example 2 were compared, it turned out that the average brightness | luminance of the example 2 improves about 22% compared with the comparative example 1. FIG.

  In the above embodiment, the panel for LED has been described, but it can be applied to all uses that require light diffusion. Specifically, it is used for light guide plates (for liquid crystal TVs, advertisements, billboards, lighting, automotive meter panels, etc.), automotive instrumentation using LED transmitted light, and display panels for home appliances, and for liquid crystal TVs. Used for diffuser plates, LCD TV reflective sheets, fluorescent / halogen lamp lenses and surface coatings, LED bulbs / LED lighting, various lighting / signboard equipment, headlights / tail lamps for automobiles and bicycles, etc. Can do. For these uses, the surface of the light-transmitting material can be coated by a method such as screen printing, or can be used as a bulk material. In the above embodiment, the LED is the light source. However, the light source is not limited to the LED, and can be applied to a fluorescent light source such as a cold cathode tube.

The present invention is not limited to the description of the embodiments and examples of the invention described above. 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.
In the above embodiment, an example in which nano hollow silica is blended in the light distribution layer has been described. It goes without saying that well-known and widely used members and materials can be used for the elements other than the light distribution layer. In addition, nano hollow silica can be blended into at least one of the reflected light diffusion layer and the emitted light diffusion layer as defined in the present invention.
The number of the emitted light diffusing layer and the condensing layer and the order in which they are stacked are not limited to the above. Free combinations are allowed, such as combining multiple sheets or changing the order of placing each layer from the light emitting surface.

DESCRIPTION OF SYMBOLS 11 ... Light guide plate 11a ... Light guide plate main body 11b ... Light distribution layer 12 ... Reflection sheet

Claims (2)

A light distribution layer formed on the reflective surface side of the light guide plate,
A light transmissive matrix;
Nano hollow silica particles dispersed in the matrix, the nano hollow silica particles having a primary particle diameter of 500 nm or less, a wall thickness of 30 nm or less, and a porosity of 40% or more, And a nano hollow silica particle that is agglomerated and whose secondary agglomerated particle diameter is 1500 nm or less.   A light guide device comprising the light distribution layer according to claim 1.

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