WO2011093172A1

WO2011093172A1 - Light-guiding plate and lighting device

Info

Publication number: WO2011093172A1
Application number: PCT/JP2011/050753
Authority: WO
Inventors: 一範植木; 啓介塚田; 敏朗鈴木
Original assignee: 日本ゼオン株式会社
Priority date: 2010-01-29
Filing date: 2011-01-18
Publication date: 2011-08-04
Also published as: TW201131224A

Abstract

Disclosed is a light-guiding plate (100) comprising a light introduction face (110) that introduces light; a light extraction face (120) that extracts light that is introduced via the light introduction face (110); and a rear face (130) that is located on the opposite side from the light extraction face (120). The thickness of the light-guiding plate is 0.020mm-0.500mm, at least one of either the light introduction face (120) or the rear face (130) further comprises a pattern of at least either depressions or protrusions; and the share of the pattern is between 0.02 and 0.2 times the thickness of the light-guiding plate (100), inclusive.

Description

Light guide plate and lighting device

The present invention relates to a light guide plate and a lighting device including the same.

As a backlight device used in a liquid crystal display device, a side-ride type backlight device that introduces light from a light source from a side surface of a light guide plate and emits the light from a light extraction surface located on the front surface or the back surface of the light guide plate It has been known. The sidelight type backlight device has an advantage that it can be formed thinner than a direct type backlight device. In such a sidelight type backlight device, adoption of a thinner light guide plate is being studied in order to meet the demand for further thinning of the device. For example, Patent Documents 1 and 2 discuss the thin light guide plate.

JP 2005-228612 A JP 2006-21018 A

From the viewpoint of improving the light extraction efficiency, minute irregularities may be formed on the front and back surfaces of the light guide plate. However, in the case of a thin light guide plate, the number of reflections of the introduced light tends to increase significantly compared to a thick light guide plate. For this reason, when unevenness for light extraction having the same arrangement and size as the conventional thick light guide plate is formed on the thin light guide plate, it is difficult to extract light uniformly on the light extraction surface. Specifically, as the number of times of light reflection increases, the light is easily emitted near the light source, and the light emitted from the terminal portion far from the light source tends to decrease. As a result, in the thin light guide plate, the luminance of the light extraction surface increases in a region close to the side surface where light is introduced, and decreases in a distant region, resulting in luminance unevenness. As a result, it has been desired to develop a technique for suppressing luminance unevenness by allowing light to be extracted with high luminance even on a light extraction surface in a region far from the side where light is introduced.
Further, in the thin light guide plate, when the light extraction unevenness is designed to be the same size as the thick light guide plate, there is a problem that a pattern can be seen, interference fringes are generated, and luminance is not increased.

The present invention has been made in view of the above-described problems, and an object thereof is to provide a thin light guide plate that suppresses luminance unevenness and an illumination device that can suppress luminance unevenness.

As a result of intensive studies to solve the above-described problems, the present inventor has determined that the occupancy ratio (pattern occupancy ratio) of the unevenness formed on the front surface or the back surface of the light guide plate is within a predetermined range in relation to the thickness of the light guide plate. Thus, even when a thin light guide plate is used, it is found that light can be extracted uniformly from the light extraction surface, and no pattern appearance or interference fringes are generated, and the present invention has been completed.
That is, according to the present invention, the following [1] to [6] are provided.

[1] A light guide plate having a light introduction surface for introducing light, a light extraction surface for extracting light introduced from the light introduction surface, and a back surface located on the opposite side of the light extraction surface,
The light guide plate has a thickness of 0.020 mm to 0.500 mm;
At least one of the light extraction surface and the back surface has a pattern consisting of at least one of a concave portion and a convex portion,
The light guide plate whose occupation rate of the pattern is 0.02 to 0.2 times the thickness (mm) of the light guide plate.
[2] The concave portion or the convex portion included in the pattern extends in a predetermined direction, and a cross-sectional shape thereof is a triangular shape or a partial shape of a circle or an ellipse,
The width of the concave portion or the convex portion is 0.02 to 0.5 times the thickness of the light guide plate,
The light guide plate according to [1], wherein the height of the concave portion or the convex portion is 0.01 times or more and 0.25 times or less the thickness of the light guide plate.
[3] The shape of the concave portion or the convex portion included in the pattern is a shape selected from the group consisting of a partial shape of a sphere, a triangular pyramid, a quadrangular pyramid, and a cylinder,
The maximum length of the bottom of the concave or convex portion is 0.02 to 0.5 times the thickness of the light guide plate,
The light guide plate according to [1], wherein the height of the concave portion or the convex portion is 0.01 times or more and 0.25 times or less the thickness of the light guide plate.
[4] The light guide plate according to any one of [1] to [3], wherein an arithmetic average roughness Ra of a portion of the light extraction surface and the back surface where the pattern is not formed is 0.05 μm or less. .
[5] The light guide plate according to any one of [1] to [4], wherein an occupation density of the pattern increases continuously or stepwise as the distance from the light introduction surface increases.
[6] An illumination device comprising: the light guide plate according to any one of [1] to [5]; and a point light source that irradiates light to a light introduction surface of the light guide plate.

According to the light guide plate of the present invention, the thickness can be reduced, and luminance unevenness on the light extraction surface can be suppressed.
According to the illumination device of the present invention, luminance unevenness can be suppressed.

FIG. 1 is a perspective view schematically showing an outline of an illumination device as an embodiment of the present invention. FIG. 2 is a perspective view schematically showing an enlarged portion surrounded by an ellipse II in FIG. FIG. 3 is a perspective view schematically showing an example of the shape of the convex portion included in the pattern. FIG. 4 is a perspective view schematically showing an example of the shape of the convex portion included in the pattern. FIG. 5 is a perspective view schematically showing an example of the shape of the convex portion included in the pattern. FIG. 6 is a perspective view schematically showing an example of the shape of the convex portion included in the pattern. FIG. 7 is a perspective view schematically showing an example of the shape of the convex portion included in the pattern. FIG. 8 is a perspective view schematically showing an example of the shape of the convex portion included in the pattern. FIG. 9 is a cross-sectional view illustrating simulation conditions set in the simulation performed in the first embodiment.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples, but the present invention is not limited to the following embodiments and examples, and the claims of the present invention and equivalents thereof. Any change can be made without departing from the scope.
In the following description, the directions of the components are “parallel” and “orthogonal” unless otherwise specified, including errors within a range that does not impair the effects of the present invention, for example, within ± 5 °. May be. Further, “along” in a certain direction means “in parallel” in a certain direction. Further, unless otherwise specified, in the description of the position of the light guide plate, “near” refers to a position close to the light introduction surface, and “back” refers to a position far from the light introduction surface.

Embodiment
FIG. 1 is a perspective view schematically showing an outline of an illumination device as an embodiment of the present invention. As shown in FIG. 1, the illumination device 1 as an embodiment of the present invention includes a light guide plate 100 and a light source 200.

The light guide plate 100 includes a light introduction surface 110 that introduces light into the light guide plate 100, a light extraction surface 120 that extracts light introduced from the light introduction surface 110 to the outside of the light guide plate 100, and a light extraction surface 120. And a back surface 130 located on the opposite side. In this light guide plate 100, light introduced into the light guide plate 100 from the light introduction surface 110 is guided through the light guide plate 100 while being internally reflected by the light extraction surface 120 and the back surface 130, and is extracted from the light extraction surface 120. It is like that.

Here, the thickness direction of the light guide plate 100 is defined as the Z-axis direction. Further, in a plane orthogonal to the Z-axis direction, a direction along one side of the light guide plate 100 is defined as an X-axis direction, and a direction orthogonal to the X-axis direction is defined as a Y-axis direction. In the light guide plate 100 of the present embodiment, the Z-axis direction is orthogonal to the light extraction surface 120 and the back surface 130, and the X-axis direction is orthogonal to the light introduction surface 110.

The thickness T of the light guide plate 100 is usually 0.020 mm or more, preferably 0.05 mm or more, more preferably 0.10 mm or more, and usually 0.500 mm or less, preferably 0.4 mm or less, more preferably 0.3 mm. It is as follows. Since the light guide plate 100 of the present embodiment can be reduced in thickness as described above, the thickness of the unit when the unit is incorporated into a lighting device or a liquid crystal display device can be reduced. Furthermore, the light extraction from the light extraction surface 120 can be made uniform, and uneven brightness can be suppressed. However, if the thickness T of the light guide plate 100 is excessively thin, it may be difficult to manufacture or the handling property may be impaired. Therefore, the thickness T has a preferable lower limit as described above.
In addition, although the pattern 140 which consists of a recessed part or a convex part is formed in the light extraction surface 120 or the back surface 130 of the light-guide plate 100 so that it may mention later, the thickness T of the light-guide plate 100 is the area | region in which the said pattern 140 is not formed. Means the dimension of the light guide plate 100 in the Z-axis direction.

FIG. 2 is a diagram schematically showing an enlarged portion surrounded by an ellipse II in FIG. The light extraction surface 120 and the back surface 130 are main surfaces of the light guide plate 100, and are generally parallel to each other. As shown in FIG. 2, the light guide plate 100 has a light extraction pattern 140 on at least one of the light extraction surface 120 and the back surface 130.

The pattern 140 is a minute concavo-convex structure for extracting light that is composed of at least one of a concave portion and a convex portion. The pattern 140 may be formed by a recessed portion that is recessed from the surroundings, may be formed by a protruding portion that is protruded from the surroundings, or may be formed by both a recessed portion and a protruding portion. . However, the pattern 140 is a portion where the surface roughness Ra is larger than 0.05 μm when the surface roughness Ra is measured in a direction orthogonal to the light introduction surface 110 (X-axis direction in the present embodiment). . Such a pattern 140 exhibits an effect of extracting light guided through the light guide plate 100 from the light extraction surface 120. However, from the viewpoint of preventing the surface having the pattern 140 (one or both of the light extraction surface 120 and the back surface 130) from being damaged, the pattern 140 preferably has a convex portion.

However, in the light guide plate 100 of the present embodiment, the occupation ratio of the pattern 140 (hereinafter referred to as “pattern occupation ratio” as appropriate. The unit of the pattern occupation ratio is dimensionless) is the same as that of the light guide plate 100. The thickness T (unit: “mm”) is usually 0.02 times or more, preferably 0.04 times or more, more preferably 0.06 times or more, and usually 0.2 times or less, preferably 0. .18 times or less, more preferably 0.15 times or less. By keeping the pattern occupancy within the above range, it becomes possible to uniformly extract light from the light extraction surface 120, so that uneven brightness can be suppressed. When the pattern occupancy exceeds the upper limit of the above range, the light introduced from the light introduction surface 110 is not guided to the back and may be extracted entirely in the near area near the light introduction surface 110. When the pattern occupancy is below the lower limit of the above range, most of the light introduced from the light introduction surface 110 is not extracted from the light extraction surface 120 but is emitted from the side surface opposite to the light introduction surface 110, There is a possibility that the utilization efficiency of will be low.

Here, the pattern occupancy rate refers to the ratio of the area of the portion where the pattern 140 is formed to the area of the surface where the pattern 140 is formed (that is, one or both of the light extraction surface 120 and the back surface 130). Further, the area of the portion where the pattern 140 is formed refers to the area of the bottom surface of the concave portion or the convex portion included in the pattern 140.
The pattern 140 does not necessarily exist uniformly on the surface on which the pattern 140 is formed. Therefore, when the pattern 140 does not exist uniformly, the ratio of the area of the portion where the pattern 140 is formed to the total area of the surface where the pattern 140 is formed is defined as the pattern occupation ratio. Therefore, when the pattern 140 exists on one surface of the light extraction surface 120 and the back surface 130, the ratio of the area of the portion where the pattern is formed to the area of the one surface is defined as the pattern occupation ratio. When the pattern 140 exists on both the light extraction surface 120 and the back surface 130, the ratio of the total area of the portion where the pattern 140 is formed to the total area of the light extraction surface 120 and the back surface 130 is determined as the pattern occupancy rate. And

The shape of the concave portion and the convex portion constituting the pattern 140 is arbitrary as long as the effects of the present invention are not significantly impaired.
Therefore, the concave portion and the convex portion may be, for example, a concave portion or a convex portion extending in a predetermined direction. When the concave portion or the convex portion is a concave portion or a convex portion extending in a predetermined direction, the cross-sectional shape (the shape of a cross section cut by a plane perpendicular to the extending direction) is arbitrary. Furthermore, when the concave or convex portion is a concave or convex portion extending in a predetermined direction, the extending direction is also arbitrary, and the extending directions of the concave and convex portions may be aligned or intersect. May be. Moreover, the recessed part and the convex part may be formed in a dot shape, for example.

Hereinafter, the preferable shape of the pattern 140 will be described with an example.
3 to 8 are perspective views schematically showing examples of the shape of the protrusions included in the pattern 140. FIG. When the pattern 140 includes a convex portion, the convex portion may be, for example, a convex portion 141 that extends in a predetermined direction and has a triangular cross section as shown in FIG. Hereinafter, this shape is referred to as “triangular prism shape” as appropriate. In addition, for example, as shown in FIG. 4, the convex portion may be a convex portion 142 that extends in a predetermined direction and whose cross-sectional shape is a partial shape of a circle or an ellipse. Hereinafter, this shape is referred to as a “lenticular shape” as appropriate. Further, the convex portion may be, for example, a convex portion 143 having a shape of a part of a sphere as shown in FIG. Further, the convex portion may be, for example, a triangular pyramid-shaped convex portion 144 as shown in FIG. Further, the convex portion may be, for example, a quadrangular pyramid-shaped convex portion 145 as shown in FIG. Further, the convex portion may be, for example, a cylindrical convex portion 146 as shown in FIG. On the other hand, when the pattern 140 includes a recess, the shape of the recess may be, for example, a recess having the same shape as the protrusion shown in FIGS.

However, when the concave portion or the convex portion included in the pattern 140 is a triangular prism shape or a lenticular shape as shown in FIG. 3 in FIG. 4, the width (that is, the concave portion) among the dimensions of the shape of the concave portion or the convex portion. Alternatively, the length (W) and the height H of the bottom of the cross section obtained by cutting the convex portion by a plane perpendicular to the extending direction preferably satisfy the following conditions.
That is, the width W of the concave portion or the convex portion is preferably 0.02 times or more, more preferably 0.04 times or more, particularly preferably 0.06 times or more of the thickness T of the light guide plate 100, and 0.5. Is preferably not more than twice, more preferably not more than 0.4 times, and particularly preferably not more than 0.3 times. Further, the height H of the concave portion or the convex portion is preferably 0.01 times or more, more preferably 0.02 times or more, and particularly preferably 0.03 times or more of the thickness T of the light guide plate 100. 25 times or less is preferable, 0.20 times or less is more preferable, and 0.18 times or less is particularly preferable. If the width W and the height H are too small, the extracted light may interfere with the light extraction surface 120 to generate interference fringes. If it is too large, the light extraction efficiency from the light extraction surface 120 will not be sufficiently high. there is a possibility.

In addition, when the concave portion or the convex portion included in the pattern 140 is a shape selected from the group consisting of a partial shape of a sphere, a triangular pyramid, a quadrangular pyramid, and a cylinder as shown in FIGS. Among the dimensions of the shape of the convex portion, the maximum length N and the height H of the base preferably satisfy the following conditions.
That is, the maximum length N of the bottom of the concave portion or the convex portion is preferably 0.02 times or more, more preferably 0.04 times or more, and particularly preferably 0.06 times or more of the thickness T of the light guide plate 100. 0.5 times or less is preferable, 0.4 times or less is more preferable, and 0.3 times or less is particularly preferable. Further, the height H of the concave portion or the convex portion is preferably 0.01 times or more, more preferably 0.02 times or more, and particularly preferably 0.03 times or more of the thickness T of the light guide plate 100. 25 times or less is preferable, 0.20 times or less is more preferable, and 0.18 times or less is particularly preferable. If the maximum length N and the height H are too small, the extracted light may interfere with the light extraction surface 120 to cause interference fringes. If it is too large, the light extraction efficiency from the light extraction surface 120 is sufficiently high. It may disappear.

The pattern 140 may be formed uniformly on each of the light extraction surface 120 and the back surface 130, but may be formed non-uniformly. In the case of non-uniformity, the occupation density of the pattern 140 in the light extraction surface 120 and the back surface 130 is preferably increased continuously or stepwise as the distance from the light introduction surface 110 increases. That is, in the present embodiment, it is preferable that the occupation density of the pattern 140 is lowered in a region close to the light guide plate 110 in the X-axis direction, and the occupation density of the pattern 140 is lowered in a far region. As a result, the light can be extracted more efficiently by the pattern 140 as the distance from the light introduction surface 110 increases. Usually, since the amount of light guided is smaller as the distance from the light introduction surface 110 is smaller, the occupation density of the pattern 140 is set so that the light can be extracted with higher extraction efficiency as the distance from the light introduction surface 110 increases. Light can be extracted more uniformly from the surface 120.

Note that the occupation density of the pattern 140 is the area of the light extraction surface 120 and the back surface 130 in each region where the pattern 140 is formed, and the pattern 140 formed on the light extraction surface 120 and the back surface 130 in the region. It means the ratio. Therefore, the pattern occupancy indicates the ratio to the total area of the light extraction surface 120 and the back surface 130 where the pattern 140 is formed, whereas the occupation density is the light extraction surface 120 in each region where the pattern 140 is formed. And the ratio with respect to the area of each of the back surface 130 is pointed out.

As shown in FIG. 2, the light extraction surface 120 and the back surface 130 have a portion 121 where the pattern 140 is not formed. Thus, in this invention, the part in which the pattern is not formed can be made into a flat surface. The arithmetic mean roughness Ra of the portion 121 where the pattern 140 is not formed is usually 0.05 μm or less, preferably 0.02 μm or less, more preferably 0.01 μm or less. Thus, since arithmetic mean roughness Ra is small, the emission of light from the portion 121 where the pattern 140 is not formed can be suppressed. Therefore, unintentional extraction of light from the portion 121 where the pattern 140 is not formed can be prevented, and luminance unevenness can be more reliably suppressed. Moreover, although there is no restriction | limiting in a lower limit, it is 0.001 micrometer or more normally.
The arithmetic average roughness Ra of the portion 121 where the pattern 140 is not formed is measured in a direction orthogonal to the light introduction surface 110, and the method defined in JIS B601-2001 is used for the measurement.

A light source 200 illustrated in FIG. 1 is a device that irradiates light to a light introduction surface 110 of a light guide plate 100. The light source 200 is usually installed such that its axis (that is, the direction of the principal ray of emitted light) is parallel to the X-axis direction.
As the light source 200, a surface light source, a point light source, or the like may be used, but a point light source is preferably used. This is because when a point light source is used, the light source can be designed to be small. This is because if the light source cannot be made small, the light incident efficiency will deteriorate.

Examples of the point light source include an LED (Light Emitting Diode). LEDs are high light emission efficiency and are excellent light sources from the viewpoint of energy saving. In the present embodiment, it is assumed that an LED is used as the light source 200. The light source 200 is supplied with electric power from a power source (not shown), and can individually emit light by the supplied electric power.

The lighting device 1 as an embodiment of the present invention is configured as described above. For this reason, in use, the light source 200 emits light and the light guide surface 110 is irradiated with light. The light irradiated on the light guide surface 110 enters the light introduction surface 110 and is introduced into the light guide plate 100. The introduced light is guided through the light guide plate 100 while repeating internal reflection on the surfaces of the light extraction surface 120 and the back surface 130. The guided light is extracted by being emitted from the light extraction surface 120 to the outside by the pattern 140. Thereby, the illuminating device 1 functions as a surface light emitting device having the light extraction surface 120 as a light emitting surface.

Furthermore, in the lighting device 1 of the present embodiment, the thin light guide plate 100 has the pattern 140 on at least one of the light extraction surface 120 and the back surface 130 and the pattern occupancy is within a predetermined range. The light can be uniformly extracted from the light extraction surface 120 while using. Therefore, the illuminating device 1 can achieve both reduction in size and thickness and suppression of luminance unevenness.

The embodiment of the present invention has been specifically described above, but the above-described embodiment may be further modified.
For example, the light guide plate 100 may have a shape other than the rectangle as shown in FIG.
For example, the light introduction surface 110 may not be a surface orthogonal to the X-axis direction.
Further, for example, the light introduction surface 110 may be not only one surface but also two or more surfaces. As a specific example, in addition to the light introduction surface 110, a side surface 150 other than the light introduction surface 110 of the light guide plate 100 may be used as the light introduction surface. In particular, it is useful to set the side surface opposite to the light introduction surface 110 as the light introduction surface.
In addition, for example, the shape, size, occupation density, and the like of the pattern 140 may be the same on the light extraction surface 120 and the back surface 130, but may be different.
Further, for example, two or more types of patterns 140 having different shapes and sizes may be combined on each of the light extraction surface 120 and the back surface 130.
Further, for example, the pattern 140 need not be provided on the light extraction surface 120 or the back surface 130 in the entire region of the light guide plate 100. Therefore, the pattern 140 may be provided only on a part of the light extraction surface 120 and the back surface 130 as long as it is provided on the light extraction surface 120 or the back surface 130 in at least a desired region where light is to be extracted.
In addition, for example, a metal may be vapor-deposited or a white scattering plate (white reflection plate) may be disposed in close contact with the surface of the back surface 130 in order to increase internal reflection efficiency on the back surface 130.

[Light guide plate materials and manufacturing method]
Hereinafter, the material and manufacturing method of the light guide plate will be described.
Examples of the material of the light guide plate include glass and transparent resin. In addition, the material of a light-guide plate may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Examples of the transparent resin include propylene-ethylene copolymer, polystyrene, (meth) acrylic acid ester-aromatic vinyl compound copolymer, polyethylene terephthalate, terephthalic acid-ethylene glycol-cyclohexanedimethanol copolymer, polycarbonate. , Methacrylic resin, and resin having an alicyclic structure (for example, norbornene-based resin). Among these, resins having an alicyclic structure, methacrylic resins, and (meth) acrylic acid ester-aromatic vinyl compound copolymer resins are preferable, and resins having an alicyclic structure are particularly preferable.

A resin having an alicyclic structure has good fluidity of the molten resin. Therefore, for example, when a light guide plate is manufactured by injection molding, the mold cavity can be filled with a low injection pressure, so that a thin light guide plate can be formed relatively easily and weld lines are not easily generated. Moreover, when manufacturing a light-guide plate by extrusion molding, for example, there is little thickness nonuniformity at the time of shaping | molding, and the shaping | molding after shaping | molding is easy. Furthermore, since the resin having an alicyclic structure has extremely low hygroscopicity, it has excellent dimensional stability and hardly warps the light guide plate. Furthermore, since the specific gravity of the resin having an alicyclic structure is small, the light guide plate can be reduced in weight.

Examples of the resin having an alicyclic structure include polymer resins having an alicyclic structure in the main chain or side chain. Among them, a polymer resin having an alicyclic structure in the main chain is particularly suitable because it has good mechanical strength and heat resistance.
The alicyclic structure is preferably a saturated cyclic hydrocarbon structure.
The number of carbon atoms constituting the alicyclic structure is preferably 4 or more, more preferably 5 or more, preferably 30 or less, more preferably 20 or less, and particularly preferably 15 or less.
The ratio of the repeating unit having an alicyclic structure in the polymer resin having an alicyclic structure is preferably 50% by weight or more, more preferably 70% by weight or more, and 90% by weight or more. More preferably.

Examples of the resin having an alicyclic structure include a ring-opening polymer or a ring-opening copolymer of a norbornene monomer or a hydrogenated product thereof; an addition polymer or an addition copolymer of a norbornene monomer; Polymers of monocyclic olefin monomers or their hydrogenated products; Polymers of cyclic conjugated diene monomers or their hydrogenated products; Vinyl alicyclic hydrocarbon monomers Or a hydrogenated product thereof; a polymer of a vinyl aromatic hydrocarbon monomer or a hydrogenated product of an unsaturated bond part containing an aromatic ring of the copolymer; and the like. Among these, hydrogenated products of norbornene-based monomer polymers and hydrogenated products of unsaturated bonds including aromatic rings of vinyl aromatic hydrocarbon-based monomer polymers have mechanical strength and heat resistance. It is particularly suitable because of its excellent properties.

Furthermore, among the above transparent resins, methacrylic resins are excellent in transparency, strong and resistant to cracking, and therefore can be suitably used. Examples of the methacrylic resin include a methacrylic resin molding material containing 80% or more of a methyl methacrylate polymer defined in JIS K6717. Among the methacrylic resins specified in this standard, methacrylic resins having a specified classification code 100-120 having a Vicat softening point temperature of 96 to 100 ° C. and a melt flow rate of 8 to 16 have appropriate fluidity and strength. Is preferred.

An antioxidant may be included in the light guide plate molding material in order to prevent oxidative degradation and thermal degradation during molding. Examples of the antioxidant include a phenolic antioxidant, a phosphorus antioxidant, and a sulfur antioxidant. Of these, phenolic antioxidants are preferred, and alkyl-substituted antioxidants are particularly preferred. In addition, an antioxidant may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. The amount of the antioxidant is preferably 0.01 parts by weight or more, more preferably 0.02 parts by weight or more, preferably 2 parts by weight or less, more preferably 1 part by weight with respect to 100 parts by weight of the resin component. It is as follows.

In the molding material for the light guide plate, a light resistance stabilizer may be included in order to improve the light resistance of the light guide plate. Examples of the light resistance stabilizer include hindered amine light resistance stabilizer (HALS) and benzoate light resistance stabilizer. Among these, hindered amine light resistance stabilizers are preferred. In addition, a light-resistant stabilizer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The amount of the light-resistant stabilizer is preferably 0.01 parts by weight or more, more preferably 0.02 parts by weight or more, particularly preferably 0.05 parts by weight or more, preferably 2 parts by weight with respect to 100 parts by weight of the resin component. The amount is not more than parts by weight, more preferably not more than 1 part by weight, particularly preferably not more than 0.5 parts by weight.

The molding material for the light guide plate may further contain an optional additive as necessary. Optional additives include, for example, stabilizers such as heat stabilizers, ultraviolet absorbers, near infrared absorbers; resin modifiers such as lubricants and plasticizers; colorants such as dyes and pigments; antistatic agents, light Examples include diffusing agents. In addition, arbitrary additives may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The dimensions of the main surface of the light guide plate (in the above embodiment, the dimensions in the X-axis direction and the Y-axis direction) are usually set according to the size of the effective surface of the liquid crystal panel of the liquid crystal display device in which the light guide plate is used. The Further, the thickness of the light guide plate (in the above embodiment, the dimension in the Z-axis direction) is as described above.

As the light guide plate, for example, one having a refractive index of 1.533 (critical angle 40.7 °) can be used.

When the light guide plate is made of resin, the light guide plate may cause a dimensional change (elongation or warpage) due to moisture absorption. If a dimensional change occurs, wrinkles and the like may occur, and optical characteristics may be impaired. In particular, when the size of the light guide plate is large (for example, 40 inches), the relative positional relationship between the light source and the light introduction surface changes in the lighting device due to the change in size, and the light utilization efficiency tends to decrease. . For this reason, the water absorption rate of the light guide plate is preferably set to 0.50% or less, more preferably 0.25% or less, and even more preferably 0.05% or less. In addition, the water absorption rate in this specification is a desiccator after drying a test piece having a disk shape of 50 mm in diameter or a square of 50 mm on a side at 50 ° C. for 24 hours in accordance with JIS K7209 A method. It can be obtained from the weight increase when it is allowed to cool in water and immersed in water at 23 ° C. for 24 hours.

The material for forming the light guide plate is preferably excellent in heat resistance. Specifically, the Vicat softening temperature is preferably 90 ° C. or higher, more preferably 100 ° C. or higher, and particularly preferably 110 ° C. or higher. If the heat resistance of the light guide plate forming material is low, the light guide plate may be melted or deformed by heat generated from a light source or the like, and optical characteristics may be impaired. The Vicat softening temperature can be measured by the method defined in JIS K7206B.

Although there is no restriction | limiting in the manufacturing method of a light-guide plate, For example, when forming a light-guide plate with resin, it can manufacture by the injection molding method and the extrusion molding method.

Also, there is no particular limitation on the method for forming the pattern. For example, a flat light guide plate may be prepared in advance, and a pattern may be formed later on the surface of the light guide plate. In this case, as a method of forming a pattern on the light extraction surface and the back surface of the flat light guide plate, for example, a method by cutting using a tool capable of forming a pattern of a desired shape, a desired method by applying a photocurable resin The method of hardening in the state which transferred the type | mold of this shape etc. is mentioned.

As a method of forming the pattern, for example, the pattern may be formed simultaneously with the formation of the light guide plate. In this case, for example, profile extrusion can be performed using a profile die having a shape corresponding to a desired pattern. Further, for example, prism rows may be formed by embossing after extrusion. Furthermore, for example, a casting mold capable of forming a desired uneven shape may be prepared, and a light guide plate may be produced by casting using this casting mold, and a pattern may be formed simultaneously with the molding of the light guide plate. Further, when the light guide plate is manufactured by injection molding and the pattern is formed at the same time, a mold capable of forming a desired pattern may be used.

In addition, the mold used for processing such as mold shape transfer to the photo-curing resin, extrusion processing with a deformed die, embossing, casting, or injection molding is, for example, a metal mold using a tool capable of forming a desired pattern. It can be obtained by cutting a member or electroforming on a member having a desired shape.

Furthermore, the pattern may be formed by printing with white ink or metal vapor deposition.

〔light source〕
Hereinafter, the light source will be described.
Examples of the light source include an LED, a laser diode, a cold cathode tube (CCFL, EEFL), a hot cathode tube (HCFL), and a point light source is preferably used. Any point light source may be used as long as it can obtain a sufficient amount of light so that light can reach the end surface from the light introduction surface. For example, a semiconductor laser or the like may be used. However, it is usually preferable to use an LED as described in the above embodiment. Examples of the LED include a blue-yellow pseudo white light emitting diode, a three-color (RGB) type white light emitting diode, and the like.

As the LED, for example, a side-emitting LED, a surface-mounted LED, or a bullet-type LED is used. The dimension of the light emitting part of the LED can be set according to the light distribution characteristic of the LED. Usually, the width and height of the light emitting part of the LED are made equal. However, when the LED has an elliptical or oval cross section, the LED having a different width and height may be used. Good.

A general high dome type LED has a Lambertian light distribution and emits a relatively large divergent light having a half-value angle (full-width at half maximum) of about 120 °. However, from the viewpoint of introducing more of the light emitted from the light source into the light guide plate, the full width at half maximum of the LED is preferably 80 ° or less, more preferably 70 ° or less, and particularly preferably 60 ° or less. Ideally, LEDs that emit as close to parallel light as possible are preferred. From the viewpoint of suppressing darkening of the portion corresponding to the LEDs in the front portion of the light guide, the full width at half maximum of the LED is preferably 90 ° or more, more preferably 100 ° or more, and particularly preferably 110 ° or more. .

In addition, as a light source, you may use combining light emitting elements, such as LED, and optical elements, such as a lens. For example, even when an LED having a wide full width at half maximum is used, a light source that emits light at a full width at half maximum within the above-described preferable range can be realized by combining the LED and the lens.

[Use]
The illumination device of the present invention is suitable as a backlight device that supplies light to a liquid crystal panel of a liquid crystal display device, for example.
The liquid crystal panel is a member in which, for example, an alignment film, a transparent electrode, a glass plate, a color filter, a polarizing plate, and the like are stacked and arranged at appropriate positions with a liquid crystal layer interposed therebetween. When the lighting device of the present invention is applied to a liquid crystal display device, the lighting device of the present invention is usually provided on the back side of the liquid crystal panel so that light can be supplied to the liquid crystal panel from the back side.
Furthermore, you may make it provide arbitrary optical sheets between a liquid crystal panel and an illuminating device as needed. For example, you may provide a light-diffusion sheet from a viewpoint of improving the uniformity of the light irradiated to a liquid crystal panel. For example, a prism sheet, a brightness enhancement film, or the like may be provided from the viewpoint of increasing brightness.
In addition, the lighting device of the present invention can be integrated so as to include the above-described optical sheet and polarizing plate. Here, “integrated” means that a plurality of elements are fixed so as not to be dispersed, and not only a mode in which the integrated elements are joined to each other, but also any element or gap between the integrated elements. The aspect in which is interposed is also included. There are no particular limitations on the method of integration, such as adhesion, adhesion, fusion, and the use of any sheet to wrap a plurality of optical members. However, in order to prevent the light propagating from the light source by total reflection in the light guide plate from moving more than necessary to the integrated member, there is a bonding surface between the integrated member and the light guide plate. It is preferable that many low refractive index layers such as an air layer are interposed.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and may be arbitrarily set within the scope of the claims of the present invention and its equivalents. You can change it to

[Example 1]
FIG. 9 is a cross-sectional view illustrating simulation conditions set in the simulation performed in the first embodiment. In the following examples, an optical model was created and simulated under the conditions described later using optical simulation software “LightTools” (manufactured by Cybernet Co., Ltd.). As the material of the light guide plate, a thermoplastic alicyclic structure-containing resin (trade name: ZEONOR1420, manufactured by Nippon Zeon Co., Ltd., refractive index: 1.533, critical angle: 40.7 °, water absorption: 0.01%) Was set.

As shown in FIG. 9, a rectangular flat light guide plate was set as the light guide plate 301. The dimensions of the light guide plate 301 were 250 mm in length, 50 mm in width, and 0.5 mm in thickness (dimension in the Z-axis direction).
The light extraction surface 302 corresponding to one main surface of the light guide plate 301 has a hemispherical convex portion as a pattern 303 on the entire surface. The maximum length N (diameter) of the bottom of the convex portion was 0.05 mm, the height H was 0.025 mm, and the pitch P was 0.198 mm. In addition, the pattern occupation ratio on the light extraction surface 302 was set to 0.05 (that is, 5%).
The back surface 304 corresponding to the other main surface of the light guide plate 301 is a flat surface.
The arithmetic average roughness Ra of the portion 305 where the pattern 303 of the light extraction surface 302 is not formed and the back surface 304 was 0.02 μm.

The light source 307 is provided at a position in front of the light introduction surface 306 corresponding to the side surface of the light guide plate 301. As the light source 307, a substrate 308 having a width of 5 mm and 10 LEDs 309 (2.5 mm in length, 1.5 mm in width, 0.5 mm in thickness) arranged in the Y-axis direction along the light introduction surface 306 is set. did. The distance L from the light introduction surface 306 to the light emitting portion of the LED 309 was 2.5 mm. Note that the absorption of the light emitting portion of the LED 309 was 15%, and the full width at half maximum was 120 °.

From the end of the light introduction surface 306 of the light guide plate 301 to the end of the substrate 308 of the light source 307, it was set as covered with the lamp cover 310. The reflection on the inner surface 311 of the lamp cover 310 is assumed to be Lambert reflection with a reflectance of 98%.

The illuminance (Lumen) of (i) to (iv) below was calculated by simulation when the light introduction surface 306 was irradiated with light from the light source 307 in the above configuration. The results are shown in Table 1.
(I) Illuminance on a surface perpendicular to the X-axis direction at a position immediately inside the light introduction surface 306 (that is, a position in the light guide plate 301 that is 0 mm away from the light introduction surface 306). This illuminance is hereinafter referred to as “incident illuminance” as appropriate.
(Ii) Illuminance on a surface perpendicular to the Z-axis direction at a position immediately outside the light extraction surface 302 (that is, a position outside the light guide plate 301 away from the light extraction surface 302 by 0 mm). This illuminance is hereinafter referred to as “emergence illuminance” as appropriate.
(Iii) X-axis direction at a position advanced from the light introduction surface 306 by half the dimension of the light guide plate 301 (that is, a position within the light guide plate 301 that is 125 mm away from the light introduction surface 306 in the X-axis direction) Illuminance on a plane perpendicular to This illuminance is hereinafter referred to as “intermediate illuminance” as appropriate.
(Iv) Illuminance on a surface perpendicular to the X-axis direction at a position just outside the side surface opposite to the light introduction surface 306 (that is, a position outside the light guide plate 301 away from the light introduction surface 306 by 250 mm). This illuminance is hereinafter referred to as “terminal illuminance” as appropriate.

[Example 2]
The maximum length N of the base of the hemispherical convex portion set as the pattern 303 is changed to 0.1 mm, the height H is changed to 0.05 mm, the pitch P is changed to 0.627 mm, and the pattern occupancy is changed. The incident illuminance, outgoing illuminance, intermediate illuminance, and terminal illuminance were calculated by simulation in the same manner as in Example 1 except that it was changed to 0.02 (that is, 2%). The results are shown in Table 1.

Example 3
The incident illuminance, emitted illuminance, intermediate illuminance, and terminal illuminance were calculated by simulation in the same manner as in Example 1 except that the pattern 303 was changed to exist on the back surface 304 instead of the light extraction surface 302. The results are shown in Table 1.

Example 4
The maximum length N of the base of the hemispherical convex portion set as the pattern 303 is changed to 0.1 mm, the height H is changed to 0.05 mm, the pitch P is changed to 0.295 mm, and the pattern occupancy is changed. Except for the change to 0.09 (that is, 9%), the incident illuminance, outgoing illuminance, intermediate illuminance, and terminal illuminance were calculated by simulation in the same manner as in Example 1. The results are shown in Table 1.

Example 5
The thickness of the light guide plate 301 is changed to 0.2 mm, the pitch P of the hemispherical convex portion set as the pattern 303 is changed to 0.313 mm, and the pattern occupation ratio is changed to 0.02 (ie, 2%). Except that, the incident illuminance, outgoing illuminance, intermediate illuminance, and terminal illuminance were calculated by simulation in the same manner as in Example 1. The results are shown in Table 1.

Example 6
The pattern 303 is a triangular prism-shaped convex portion extending in parallel with the Y-axis direction. The apex angle of the triangular prism-shaped cross section was 90 °. Moreover, the width W of the convex part was 0.01 mm, the height H was 0.005 mm, and the pitch P was 0.333 mm. In addition, the pattern occupation ratio on the light extraction surface 302 was set to 0.03 (that is, 3%). Furthermore, the thickness of the light guide plate 301 was 0.2 mm. Except for the above matters, the incident illuminance, outgoing illuminance, intermediate illuminance and terminal illuminance were calculated by simulation in the same manner as in Example 1. The results are shown in Table 2.

Example 7
The pattern 303 has a quadrangular pyramid shape. Further, the height H of the convex portions was 0.04 mm, and the pitch P was 0.354 mm. In addition, the pattern occupation ratio on the light extraction surface 302 was set to 0.01 (that is, 1%). Furthermore, the thickness of the light guide plate 301 was 0.2 mm. Except for the above matters, the incident illuminance, outgoing illuminance, intermediate illuminance, and terminal illuminance were calculated by simulation in the same manner as in Example 1. The results are shown in Table 2.

Example 8
The thickness of the light guide plate 301 is changed to 0.02 mm, the maximum length N of the hemispherical convex portion set as the pattern 303 is changed to 0.002 mm, the height H is changed to 0.001 mm, and the pitch In the same manner as in Example 1 except that P was changed to 0.032 mm and the pattern occupation ratio was changed to 0.003 (that is, 0.3%), the incident illuminance, outgoing illuminance, intermediate illuminance, and terminal illuminance were changed. Calculated by simulation. The results are shown in Table 2.

Example 9
The pattern 303 is changed to exist on both the light extraction surface 302 and the back surface 304, the maximum length N of the base of the hemispherical convex portion set as the pattern 303 is changed to 0.1 mm, and the height H is set to 0. .05 mm, the pitch P is changed to 0.443 mm, and the pattern occupancy is changed to 0.08 (that is, 8%) on both sides. The intermediate illuminance and terminal illuminance were calculated by simulation. The results are shown in Table 2.

Example 10
Example except that the maximum length N of the base of the hemispherical convex portion set as the pattern 303 is changed to 0.3 mm, the height H is changed to 0.15 mm, and the pitch P is changed to 1.189 mm. In the same manner as in 1, the incident illuminance, outgoing illuminance, intermediate illuminance, and terminal illuminance were calculated by simulation. The results are shown in Table 2.

Example 11
In the same manner as in Example 1, except that a triangular prism-shaped convex portion (vertical angle 90 °, pitch 100 μm) extending in the X-axis direction so as to be orthogonal to the light introduction surface is disposed on the back surface. Light illuminance, light emission illuminance, intermediate illuminance and terminal illuminance were calculated by simulation. The results are shown in Table 2. In Example 11, a pattern appearance that does not affect luminance unevenness was confirmed.

[Comparative Example 1]
The thickness of the light guide plate 301 is changed to 4 mm, the maximum length N of the base of the hemispherical projection set as the pattern 303 is changed to 0.1 mm, the height H is changed to 0.05 mm, and the pitch P is changed. The incident illuminance, outgoing illuminance, intermediate illuminance and terminal illuminance were calculated by simulation in the same manner as in Example 1 except that the pattern occupancy was changed to 0.162 mm and the pattern occupation ratio was changed to 0.30 (ie, 30%). . The results are shown in Table 3.

[Comparative Example 2]
The maximum length N of the base of the hemispherical convex portion set as the pattern 303 is changed to 0.1 mm, the height H is changed to 0.05 mm, the pitch P is changed to 0.162 mm, and the pattern occupancy is changed. The incident illuminance, outgoing illuminance, intermediate illuminance, and terminal illuminance were calculated by simulation in the same manner as in Example 1 except that the value was changed to 0.30 (that is, 30%). The results are shown in Table 3.

[Comparative Example 3]
The maximum length N of the base of the hemispherical convex portion set as the pattern 303 is changed to 0.1 mm, the height H is changed to 0.05 mm, the pitch P is changed to 0.229 mm, and the pattern occupancy is changed. The incident light illuminance, outgoing light illuminance, intermediate illuminance, and terminal illuminance were calculated by simulation in the same manner as in Example 1 except that it was changed to 0.15 (that is, 15%). The results are shown in Table 3.

[Comparative Example 4]
The pattern 303 is changed to exist on both the light extraction surface 302 and the back surface 304, the maximum length N of the base of the hemispherical convex portion set as the pattern 303 is changed to 0.1 mm, and the height H is set to 0. .05 mm, the pitch P is changed to 1.253 mm, and the pattern occupancy is changed to 0.005 (that is, 0.5%). The intermediate illuminance and terminal illuminance were calculated by simulation. The results are shown in Table 3.

[Comparative Example 5]
The incident illuminance, outgoing illuminance, intermediate illuminance, and terminal illuminance were calculated by simulation in the same manner as in Example 1 except that the pattern 303 was not formed on any of the light extraction surface 302 and the rear surface 304. The results are shown in Table 3.

〔Consideration〕
In Tables 1 to 3, a value α1 obtained by dividing the pattern occupancy by the thickness of the light guide plate, a value α2 obtained by dividing the width W or the maximum length N of the bottom by the thickness of the light guide plate, and the height H of the pattern A value α3 obtained by dividing by the thickness of the light guide plate is also shown. Further, a value obtained by dividing the light emission illuminance by the light incident illuminance is shown as “light emission ratio”, and a value obtained by dividing the intermediate illuminance by the light incident illuminance is shown as “intermediate illuminance ratio”.

From Tables 1 and 2, it can be seen that in Examples 1 to 11, the ratio of light emission is high and the ratio of intermediate illuminance is also high.
The light emission ratio is an index indicating how much of the light introduced from the light introduction surface is extracted from the light extraction surface. Therefore, a high light emission ratio indicates that light emitted from the light source can be used more effectively.
Further, the intermediate illuminance ratio is an index indicating how much light is introduced from the light introduction surface to the back of the intermediate point in the X-axis direction of the light guide plate. Therefore, a high intermediate illuminance ratio indicates that the introduced light is difficult to be extracted from the light extraction surface near the light introduction surface. That is, the luminance at the position near the light introduction surface of the light extraction surface is not excessively increased, and luminance unevenness can be suppressed.
Therefore, it can be confirmed from the above embodiments that the light guide plate and the lighting device of the present invention can both reduce the thickness of the light guide plate and suppress luminance unevenness.

On the other hand, when Table 3 is seen, in Comparative Example 1, good results are obtained. Since the comparative example 1 has a thick light guide plate, such a result is obtained.
Comparative Examples 2 and 3 are examples in which the pattern occupancy is high. In these comparative examples 2 and 3, although the light emission ratio is high, the intermediate illuminance ratio is low. Therefore, most of the light introduced from the light introduction surface is extracted at a position near the light introduction surface of the light extraction surface, and almost no light is emitted at a far position. Therefore, in Comparative Example 2, the near side in the X-axis direction becomes brighter and darker, and luminance unevenness occurs.
Comparative example 4 is an example with a low pattern occupancy, and comparative example 5 is an example without a pattern. In these comparative examples 4 and 5, although the intermediate illuminance ratio is high, the light emission ratio is low. Therefore, most of the light introduced from the light introduction surface is not extracted from the light extraction surface, and most is wasted. Since the terminal illuminance is high, it can be seen that light that has not been extracted from the light extraction surface is extracted from the side surface opposite to the light introduction surface.

By the way, the light emission ratio is not 100% in any of the above-mentioned examples and comparative examples. This is presumably because the light component guided in the light guide plate includes parallel light traveling parallel to the light extraction surface and the back surface. In consideration of the parallel light, it can be determined that the light emitted from the light source can be sufficiently utilized if the light emission ratio is as high as that achieved in the above embodiment.

The light guide plate of the present invention can be arbitrarily applied to optical applications, and is particularly suitable for an illumination device capable of surface light emission.
The illumination device of the present invention is suitable for use in a liquid crystal display device. The lighting device of the present invention can also be used for applications other than the backlight of a liquid crystal display device, for example, as a lighting device such as a show window.

DESCRIPTION OF SYMBOLS 1 Illuminating device 100 Light guide plate 110 Light introduction surface 120 Light extraction surface 121 The part where the pattern is not formed of the light extraction surface and the back surface 130 Back surface 140 Pattern 141-146 Convex part 150 Side surface 200 Light source 301 Light guide plate 302 Light extraction surface 303 pattern 304 back surface 305 portion where light extraction surface pattern is not formed 306 light introduction surface 307 light source 308 substrate 309 LED
310 Lamp cover 311 Inner surface of lamp cover

Claims

A light guide plate having a light introduction surface for introducing light, a light extraction surface for extracting light introduced from the light introduction surface, and a back surface located on the opposite side of the light extraction surface;
The light guide plate has a thickness of 0.020 mm to 0.500 mm;
At least one of the light extraction surface and the back surface has a pattern consisting of at least one of a concave portion and a convex portion,
The light guide plate whose occupation rate of the pattern is 0.02 to 0.2 times the thickness (mm) of the light guide plate.
The concave portion or the convex portion included in the pattern extends in a predetermined direction, and a cross-sectional shape thereof is a triangular shape or a partial shape of a circle or an ellipse,
The width of the concave portion or the convex portion is 0.02 to 0.5 times the thickness of the light guide plate,
The light guide plate according to claim 1, wherein a height of the concave portion or the convex portion is 0.01 to 0.25 times the thickness of the light guide plate.
The shape of the concave portion or the convex portion included in the pattern is a shape selected from the group consisting of a partial shape of a sphere, a triangular pyramid, a quadrangular pyramid, and a cylinder,
The maximum length of the bottom of the concave or convex portion is 0.02 to 0.5 times the thickness of the light guide plate,
The light guide plate according to claim 1, wherein a height of the concave portion or the convex portion is 0.01 to 0.25 times the thickness of the light guide plate.
The light guide plate according to claim 1, wherein the arithmetic average roughness Ra of the portion where the pattern on the light extraction surface and the back surface is not formed is 0.05 μm or less.
The light guide plate according to claim 1, wherein an occupation density of the pattern increases continuously or stepwise as the distance from the light introduction surface increases.
An illumination device comprising: the light guide plate according to claim 1; and a point light source that irradiates light to a light introduction surface of the light guide plate.