JP6572719B2 - Light guide, surface light source device, and illumination device - Google Patents

Description

  The present invention relates to a light guide for a surface light source device, a surface light source device, and an illumination device. More specifically, the light guide having high illuminance and high uniformity of illuminance on the light exit surface, and the light guide are used. The present invention relates to a surface light source device and an illumination device using the surface light source device.

  LEDs are used in lighting devices because of their low power consumption and long life. As an illumination device using an LED, for example, a direct type illumination that diffuses light emitted from an LED by a diffusion plate to illuminate an emission direction of the LED light, and a rectangular plate-shaped light guide light incident end surface using the LED as a primary light source LED light is incident on the light guide, introduced into the light guide, and emitted from a light exit surface that is one of the two main surfaces of the light guide.

  In the light guide plate type illumination device, light emitted from the light exit surface of the light guide is diffused in a required direction by a light diffusion element such as a light diffusion plate disposed on the light exit surface, for example. Light is also emitted from the back surface facing the light emitting surface of the two main surfaces of the light guide, and in order to return this light to the light guide, a light reflecting element such as a light reflecting sheet facing the back surface Is placed.

  When manufacturing the light guide as described above, for example, a light emitting mechanism for appropriately emitting light guided through the light guide is formed on the surface of the transparent resin molded body that is the material of the light guide. Is done.

  As the light emitting mechanism, for example, a rough surface that is moderately roughened or a micro uneven structure such as a lens array forming surface in which a large number of lens arrays are arranged is used.

  As a method for forming a micro uneven structure, a method for transferring a shape to a translucent material such as an acrylic resin by using a molding device using a molding die member having a shape transfer surface formed by blasting or etching. Is known (Patent Document 1 and Patent Document 2).

  In addition to the above, a light emitting mechanism is disclosed in which a light emitting surface of a light guide is irradiated with laser light to form a recess having a foam surface layer (Patent Document 3).

  Further, as a method for obtaining a light guide having high brightness and excellent in-plane brightness uniformity, a light guide containing a specific amount of inorganic fine particles having a specific average particle diameter in methacrylic resin is disclosed (patent). Reference 4).

International Publication No. 2005 / 073,625 JP 2009-266,830 A International Publication No. 2011 / 115,124 JP 2004-351 649 A

  However, a light guide having a high average illuminance and a high degree of illuminance uniformity on the light exit surface that can be used in a surface light source device or illumination that requires LED light source and thinning has not been obtained.

  An object of the present invention is to provide a light guide having high illuminance and high uniformity of illuminance on a light exit surface, a surface light source device using the light guide, and an illumination device using the surface light source device. is there.

  The above problems are solved by the following inventions [1] to [4].

[1] A light incident end face provided at one end of a plate-like substrate, a light emitting face and a back face provided on the main surface of the substrate substantially orthogonal to the light incident end face and opposed to each other A light guide for an edge light type surface light source device, wherein the base material is made of a transparent resin composition containing a light diffusing agent, and is selected from a light emitting surface and a back surface. has a light emitting mechanism in at least a partial area of the surface state, and are illuminance uniformity of the substrate is 80% or more, the light guide body, the light guide Toru
From the light guide obtained using the resin composition obtained by removing the light diffusing agent from the bright resin composition, the in-plane average illumination is obtained.
A light guide for a surface light source device having a degree of 10% or higher .

[2] A light incident end face provided at one end of the plate-like substrate, a light exit face provided on the main surface of the substrate substantially orthogonal to the light incident end face and opposed to each other; A light guide for a surface light source device, including a base material having a back surface, wherein the base material is made of a transparent resin composition containing titanium oxide, and at least one of at least one surface selected from a light emitting surface and a back surface When having a light emission mechanism in a part of the region, the titanium oxide content in 100 parts by mass of the transparent resin is Y parts by mass, and the distance from the light incident end surface of the substrate to the opposite light emission end surface is X mm, A light guide for a surface light source device in which Y / X satisfies the following formula (1).
0.00000005 ≦ Y / X ≦ 0.000000025 (1)

[3] A surface light source device in which an LED is disposed adjacent to at least one light incident end face of the light guide.
[4] The LED may be disposed adjacent to the two light incident end faces of the light guide facing each other.

[5] An illumination device using the surface light source device.

  Since the illumination using the light guide of the present invention can maintain a high degree of uniformity and can obtain high illuminance, the light guide used in a thin surface light source device or illumination device using LEDs. It is suitable as a body.

It is a typical block diagram which shows one Embodiment of the surface light source device of the edge light system of this invention. It is a schematic diagram of the laser processing shape which shows one Embodiment of a light-projection mechanism in the back surface of the light guide used for the surface light source device of FIG.

  The present invention will be specifically described below, but the present invention is not limited to only these embodiments.

  FIG. 1 is a schematic configuration diagram showing an embodiment of an edge light type surface light source device of the present invention. The surface light source device includes a light guide 1, LEDs 3 a and 3 b as point-like primary light sources, a light diffusing element 4, and a light reflecting element 5. The light guide 1 includes the light emitting mechanism 2 in at least a partial region of at least one surface of the light emitting surface 14 and the back surface 13 of the base material 15.

<Base material>
The base material 15 is a plate-like base material made of a transparent resin composition containing a light diffusing agent, and is provided at one end of the base material 15 in order to make the light of the LED incident on the light guide 1. It has at least one incident end face A11 and a light emitting face 14 and a back face 13 provided substantially orthogonal to the light incident end face A11 and facing each other.

  The light emitting mechanism 2 is formed in at least a partial region of at least one of the light emitting surface 14 and the back surface 13 of the base material 15.

  The base material 15 is obtained by molding a transparent resin composition containing a light diffusing agent to be described later.

<Transparent resin composition>
The transparent resin composition contains a transparent resin and a light diffusing agent.

<Transparent resin>
Examples of the transparent resin include (meth) acrylic resins, polycarbonate resins, polyester resins, and vinyl chloride resins. Among these, a (meth) acrylic resin is preferable because of its high light transmittance, heat resistance, mechanical properties, and molding processability.

  Examples of the (meth) acrylic resin include a resin containing 50% by mass or more of a methyl methacrylate unit. From the viewpoint of a balance of high light transmittance, heat resistance, mechanical properties, and moldability, What contains 80 weight% or more of methyl methacrylate units is preferable.

<Light diffusing agent>
The light diffusing agent is a light diffusing substance having a light diffusing function that is used by being added to a transparent medium such as a transparent resin, and examples thereof include organic fine particles and inorganic fine particles having a refractive index different from that of the transparent resin. . Specific examples of the light diffusing agent include inorganic fine particles such as silica, calcium carbonate, barium sulfate, titanium oxide, and aluminum oxide, silicone beads, polymethyl methacrylate resin beads, methyl methacrylate / styrene copolymer resin beads, polystyrene. Organic fine particles such as beads may be mentioned.

  As the light diffusing agent, titanium oxide is preferable because the larger the difference in the refractive index between the transparent resin and the light diffusing agent, the greater the light diffusing effect.

  Examples of the shape of the light diffusing agent include a true spherical shape, a spherical shape, a scale shape, and an indefinite shape. The average particle size of the light diffusing agent is preferably 0.1 μm or more and 50 μm or less. When the average particle size of the light diffusing agent is 0.1 μm or more, the wavelength dependence of light scattering tends to be small. Moreover, when the average particle diameter of the light diffusing agent is 50 μm or less, the occurrence of glare and uneven brightness due to scattered light tends to be suppressed.

  In the present invention, the upper limit of the thickness of the light guide 1 is preferably 6 mm or less, and more preferably 4 mm or less in terms of weight reduction of the surface light source. The lower limit of the thickness of the light guide 1 is preferably 1.5 mm or more, and more preferably 3 mm or more in that light emitted from the LED light sources 3a and 3b is efficiently incident on the inside of the light guide 1.

<Light incident end face>
In the present invention, at least one of the four end surfaces of the substrate 1 can be a light incident end surface, and the light incident end surfaces can be 1 to 4 according to the purpose. FIG. 1 shows a case where there are two light incident end faces, a light incident end face A11 is provided at one end of the base material 15, and the light incident end face A11 is provided at the end of the other one side of the base material 15. Opposing end faces B12 are provided so as to face each other.

<Light exit surface>
In the present invention, the light emitting surface 14 is one of the main surfaces substantially orthogonal to the light incident end surface of the substrate 1. In FIG. 1, the upper surface of the light guide 1 is the light emitting surface of the substrate 1.

<Back side>
In the present invention, the back surface 13 is one of the main surfaces substantially orthogonal to the light incident end surface of the substrate, and is the main surface opposite to the light emitting surface 14. In FIG. 1, the lower surface of the light guide 1 is the back surface of the substrate.

<Light output mechanism>
In the present invention, the light emitting mechanism 2 is provided in at least a partial region of at least one surface selected from the light emitting surface 14 and the back surface 13, and transmits light incident from the light incident end surface to the light emitting surface. 14 has a function for emitting light from the light source 14.

  Examples of the shape of the light emitting mechanism 2 include a convex shape and a concave shape. In FIG. 1, a convex light emitting mechanism 2 is formed in a partial region of the lower surface (back surface 13) of the light guide 1. Of course, a convex light emitting mechanism can be formed in a partial region of the upper surface (light emitting surface 14) of the light guide 1.

  FIG. 2 is a schematic diagram showing the light emitting mechanism 2 formed on the back surface 13 of the light guide 1. The light emitting mechanism 2 includes a plurality of grooves 6 provided on the back surface 13, and has a shape and pattern such as a groove length 7, a groove interval 8, a groove pitch 9, a groove thickness 10, and a groove depth (not shown). By controlling the above, it is possible to obtain a light guide plate having an illuminance uniformity of 80% or more described later, and to obtain a light guide plate having a high illuminance of 10% or more in-plane average illuminance described later. .

  Examples of the method for forming the convex light emitting mechanism include a printing method. Moreover, as a formation method of a concave-shaped light emission mechanism, the method of forming a some recessed part in the surface of a light guide so that it may become a desired pattern by embossing or laser processing, for example is mentioned.

  In the present invention, the shape and pattern of the light emitting mechanism 2 are not particularly limited, and a known light emitting mechanism can be formed according to the purpose, but the uniformity of the light emitted from the light emitting surface It is preferable to form a light emitting mechanism in which a gradation pattern is formed.

  As the pattern having gradation, for example, a pattern in which the light emitting mechanism is formed so that the pitch between the linear light emitting mechanisms becomes narrower as the distance from the light incident end face is increased. For example, in FIG. 1, the pitch between the linear light emitting mechanisms has a minimum value at the intermediate portion between the light incident end surface A11 adjacent to the left LED 3a and the light incident end surface B12 adjacent to the right LED 3b. The width is gradually widened from the left to the right and left LEDs. With such a pattern, as the distance from the LEDs 3a and 3b to the region where the light is emitted increases, the light emission rate from the light emission surface 14 in the region where the light is emitted is increased. The amount of light emitted from each region of the surface 14 can be made more uniform.

  Examples of the method for forming the light emitting mechanism on the surface of the substrate 15 include a method of hot pressing using a mold member having a desired surface structure on the surface of the substrate, and a printing method such as screen printing on the surface of the substrate. A method of forming a light emitting mechanism with, a method of obtaining a substrate by molding such as extrusion molding, injection molding and the like, and simultaneously imparting a shape of the light emitting mechanism, a thermosetting composition or a photocurable composition on the surface of the substrate A method of forming a light emitting mechanism by applying and curing a curable composition such as the above.

  In addition to the above methods, a curable composition such as a thermosetting composition or a photocurable composition on a transparent sheet such as a polyester resin, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, or a polymethacrylimide resin. A method of laminating a laminated sheet on which a light emitting mechanism is formed by applying and curing an object on the surface of the substrate, or forming a light emitting mechanism on the surface of the substrate by forming a recess on the surface of the substrate by laser irradiation processing The method of doing is mentioned.

  When the transparent resin is a resin mainly composed of methyl methacrylate made by the casting method, the foamed part is formed by laser processing, and a light diffusing mechanism with higher diffusibility can be obtained. As a method for forming the emission mechanism, laser processing is preferable.

<Light guide>
The light guide 1 of the present invention can be used for an edge light type surface light source device, for example, as shown in FIG.

  In the light guide 1 of the present invention, the light emitting mechanism 2 is formed in at least a partial region of at least one surface selected from the light emitting surface 14 and the back surface 13 of the substrate 15.

  The light guide 1 of the present invention is characterized in that the illuminance uniformity of the LED light emitted from the light emitting surface 14 is 80% or more when the LED light is incident from the light incident end surface. By setting the illuminance uniformity of the LED light emitted from the light emitting surface 14 to 80% or more, the appearance brightness spots in the light emitting surface 14 when the light guide plate is used for illumination as a surface light source are reduced. Can improve the aesthetics of lighting.

  The light guide 1 of the present invention uses a base material molded using a transparent resin composition containing a light diffusing agent.

  The light guide 1 of the present invention has an illuminance with an in-plane average illuminance higher by 10% or more than when a resin material molded using a resin composition obtained by removing a light diffusing agent from a transparent resin composition is used. Is. When the in-plane average illuminance is 10% or more higher than when using a resin material molded using a resin composition that does not contain a light diffusing agent, the light guide plate is used for illumination as a surface light source. In addition, illumination with high luminous efficiency can be obtained.

The light guide 1 of the present invention is, for example, a plate-like base material containing titanium oxide, and at least a region of at least one surface selected from the light emitting surface 14 and the back surface 13 of the base material. And a light guide that satisfies the following formula (1) when the content of titanium oxide contained in 100 parts by mass of the substrate is Y parts by mass and the development length of the substrate is X mm: Is mentioned.
0.00000005 ≦ Y / X ≦ 0.000000025 (1)

  When Y / X is 0.00000005 or more, the light diffusion effect by the diffusing agent is sufficiently obtained, and a surface light source with high illuminance can be obtained. When Y / X is 0.000000025 or less, the light diffusing effect of the diffusing agent is not too strong, and the amount of light emitted from the light emitting surface 14 in the vicinity of the light incident end surfaces 11 and 12 of the light guide 1 is large. Since the amount of light emitted from the light exit surface 14 to the outside of the light guide 1 can be suppressed as it advances through the light guide, the amount of light emitted from the light exit surface 14 by the light exit mechanism 2 can be reduced. It is easy to adjust, and the uniformity of the light emitted from the light exit surface 14 can be improved.

  Furthermore, when the light guide 1 includes the light emitting mechanism 2, the content of titanium oxide contained in the base material satisfies the formula (1). Combined with the effect of making the amount of light emitted from each region of the light exit surface 14 produced by the mechanism 2 more uniform, the illuminance uniformity and the in-plane average illuminance of the light guide plate can be controlled to desired values.

<Surface light source device>
In the surface light source device of the present invention, an LED is disposed adjacent to at least one light incident end face of the light guide 1. In view of the uniformity of illuminance on the light exit surface 14, it is preferable that the LED is disposed adjacent to each of the two light incident end surfaces 11 and 12 facing the light guide 1.

  Examples of the surface light source device of the present invention include an embodiment shown in FIG. The surface light source device includes a light guide 1, LEDs 3 a and 3 b as point-like primary light sources, a light diffusing element 4, and a light reflecting element 5.

<Light diffusion element>
The light diffusing element 4 is used to diffuse light emitted from the light guide in a desired direction. For example, as shown in FIG. 1, the light diffusing element 4 is disposed on the light exit surface 14 of the light guide 1. .

  Examples of the light diffusing element include a light diffusing film. In the present invention, the light diffusing element 4 may be omitted when the directivity of light emitted from the light emitting surface 14 has a desired emission angle and viewing angle.

<Light reflection element>
The light reflecting element 5 is used to return the light passing through the opposite surface of the light emitting surface back to the light guide plate, and to promote light emission from the light emitting surface. For example, as shown in FIG. 1 is disposed under the back surface of the first.

  Examples of the light reflecting element 5 include a plastic sheet (light reflecting sheet) having a metal vapor deposition reflection layer on the surface, and the surface of the metal vapor deposition reflection layer is disposed so as to face the back surface of the light guide 1. In the present invention, the light reflecting element 5 may be omitted when the amount of light emitted from the back surface of the light guide is small enough to be ignored.

  In the present invention, the light reflecting element can be arranged on the end face other than the end face used as the light incident end face of the light guide according to the purpose, in addition to the back face of the light guide.

<Lighting device>
The illumination device of the present invention uses the surface light source device of the present invention.

  Hereinafter, the present invention will be described with reference to examples. The illuminance uniformity and in-plane average illuminance of the light guide were evaluated by the following methods. In the following, “part” means “part by mass”.

(Illuminance uniformity and in-plane average illuminance)
A region of 560 mm × 560 mm in the central portion of the upper plane of the plate-like base material having a length of 595 mm × width of 595 mm × thickness of 10 mm is used as a light emission surface, and a light emission mechanism is formed on the lower plane opposite to the upper plane. A light guide was formed. An LED edge light in which 40 LED light sources (5 mm surface mount type) were arranged at intervals of 9 mm was arranged so that each of the two light emitting end faces opposed to the light guide were adjacent to each other. An illuminator L # 432-2mm is installed on the light emitting end face of the light guide, and a reflector film with adhesive (trade name: MTN-W400, manufactured by Tsujiden Co., Ltd.) is installed on the back surface. Got. Next, a reflector film with an adhesive (trade name: MTN-W400, manufactured by Tsujiden Co., Ltd.) was attached to the entire surface of the two end faces of the light guide where no LED edge light was arranged.

  At a total of 28 measurement points provided at a pitch of 20 mm on a line connecting the center of the light incident end face on one side of the light exit surface of the illumination device and the center of the light incident end face on the other side, the illuminance meter ( Illuminance was measured using Konica Minolta Co., Ltd. product name: T-1). In the measurement, in order to avoid the influence of incident light from the side surface of the terminal, a cover in which a black acrylic plate (thickness 3 mm) was hollowed into a terminal shape was installed on the side surface of the terminal.

  The illuminance uniformity was a value obtained by dividing the minimum value of illuminance by the maximum value of illuminance in the measured values of illuminance at 28 locations.

  The in-plane average illuminance was an average value of measured values of illuminance at 28 locations.

[Example 1]
(Production of light guide)
In 100 parts of a monomer solution containing 20% by mass of polymethyl methacrylate and 80% by mass of methyl methacrylate (hereinafter referred to as “syrup”), 0.00006 part of titanium oxide having an average particle size of 0.255 μm is dispersed. Dispersed syrup was obtained.

  Subsequently, 0.03 part of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator and 2- (5-methyl-2-hydroxyphenyl)-as an ultraviolet absorber were added to 100 parts of the dispersion syrup. 0.005 part of benzotriazole was added and stirred for 30 minutes to prepare a polymerizable raw material syrup.

  Two tempered glass plates (length 700 mm, width 700 mm and thickness 6 mm) are placed in a mold obtained by placing them on the periphery of the tempered glass plate facing each other through an endless tube made of polyvinyl chloride. The polymerizable raw material syrup is injected, adjusted to a predetermined interval so as to have a plate thickness of 3 mm, immersed in warm water at 70 ° C. for 2 hours, and then polymerized in a 130 ° C. air bath for 1 hour. An acrylic resin plate having a length of 650 mm, a width of 650 mm, and a thickness of 3 mm was obtained.

  The obtained acrylic resin plate was cut to a size of 573 mm × 573 mm with a panel saw (trade name: SZIVG-4000, manufactured by Shinx Corp.), and the four end surfaces were ground and polished by a grinder (Koho Sangyo Co., Ltd., product name). : CGS-1600) to obtain a substrate by mirror polishing.

  Laser processing was performed on one surface of the main surface of the base material at a processing speed of 3,000 m / min using a laser processing machine (manufactured by LTS. Co. Ltd., trade name: EMMLS-001), as shown in FIG. A plurality of grooves 6 (groove length 7: 1.5 mm, groove interval 8: 1.5 mm, groove thickness 10: 100 μm) having a pitch between grooves shown in Table 2 in the pattern are formed with the light guide light incident end surface 11. Light emitting mechanisms arranged in parallel were formed to obtain a light guide. The obtained light guide was evaluated for illuminance uniformity and in-plane average illuminance. The evaluation results are shown in Table 1.

[Examples 2 and 3]
A light guide was produced in the same manner as in Example 1 except that the content of titanium oxide in the substrate, the processing speed of the light guide, and the pitch between grooves were the conditions described in Table 1. The obtained light guide was evaluated for illuminance uniformity and in-plane average illuminance. The evaluation results are shown in Table 1.

[Comparative Examples 1 and 2 and Reference Example 1]
A light guide was produced in the same manner as in Example 1 except that the content of titanium oxide in the substrate, the processing speed of the light guide, and the pitch between grooves were the conditions described in Table 1. The obtained light guide was evaluated for illuminance uniformity and in-plane average illuminance. The evaluation results are shown in Table 1.

  In Comparative Example 1, since the content of the light diffusing agent (titanium oxide) is high, the illuminance uniformity of the LED light is low, and it is unsuitable for a surface light source device or an illuminating device that requires the LED light source to be made thinner and thinner. I understand.

  In Comparative Example 2, since the content of the light diffusing agent (titanium oxide) is low, the in-plane average for the light guide (Reference Example 1) using the base material obtained from the resin composition not containing the light diffusing agent. Since the increase rate of illuminance is a low level of less than 10%, it is understood that the light source is unsuitable for a surface light source device or an illuminating device that is required to be made into an LED and thin.

1: Light guide 2: Light emitting mechanism 3a, 3b: LED
4: Light diffusing element 5: Light reflecting element 6: Groove 7: Groove length 8: Groove interval 9: Groove pitch 10: Groove thickness 11: Light incident end face A
12: Light incident end face B
13: Back surface 14: Light exit surface 15: Base material

Claims (5)

A light incident end face provided at one end of the plate-like substrate;
A light guide for an edge-light-type surface light source device, including a base material having a light exit surface and a back surface substantially orthogonal to the light incident end face and provided opposite to each other on the main surface of the base material. Body,
The base material comprises a transparent resin composition containing a light diffusing agent,
It has a light emission mechanism in at least a partial region of at least one surface selected from the light emission surface and the back surface, and the illuminance uniformity of the substrate measured by the following measurement method 1 is 80% or more.
The
The light guide uses a resin composition obtained by removing a light diffusing agent from the transparent resin composition of the light guide.
From the obtained light guide, the in-plane average illuminance measured by the following measurement method 2 is 10% or more higher,
A light guide for a surface light source device.
<Measurement method 1>
The LED light sources are arranged adjacent to the two light emitting end faces facing the light guide. The illuminance at a plurality of points on the line connecting the center of the light incident end face on one side and the center of the light incident end face on the other side on the light exit surface of the light guide is measured using an illuminometer. The value obtained by dividing the minimum value of illuminance by the maximum value of illuminance was defined as the illuminance uniformity.
<Measurement method 2>
The LED light sources are arranged adjacent to the two light emitting end faces facing the light guide. Light guide
Connect the center of the light incident end surface on one side to the center of the light incident end surface on the other side
The illuminance at multiple points on the ellipse is measured using a luminometer, and the average value of the illuminance is calculated as in-plane average illumination.
Degree. A light incident end face provided at one end of the plate-like substrate;
A light guide for a surface light source device, including a base material having a light exit surface and a back surface provided on the main surface of the base material and substantially perpendicular to the light incident end face and facing each other. ,
The substrate comprises a transparent resin composition containing titanium oxide,
Having a light emission mechanism in at least a partial region of at least one surface selected from the light emission surface and the back surface;
When the titanium oxide content in 100 parts by mass of the transparent resin is Y parts by mass, and the distance from the light incident end surface of the substrate to the opposite light emitting end surface is X mm, Y / X satisfies the following formula (1). A light guide for a surface light source device.
0.00000005 ≦ Y / X ≦ 0.000000025 (1) The surface light source device by which LED was arrange | positioned adjacent to the at least 1 light-incidence end surface of the light guide of Claim 1 or 2 . The LED is positioned adjacent to the two light entrance end face facing the light guide, according to claim 3
The surface light source device described in 1. The illuminating device using the surface light source device of Claim 3 or 4 .