JP2014229553A - Light guide plate and lighting device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate which does not cause failure due to interference fringe (Moire).SOLUTION: A light guide plate 1a includes: a light incident surface 10 which makes light emitted from a light source incident; a light emission surface 12 which emits light made incident to the light incident surface 10; and a light deflection surface 14 which faces the light emission surface 12 and deflects light made incident to the light incident surface 10 to the light emission surface 12. On the light emission surface 12, a number of unit lenticular lenses 2a each of which comprises a convex cylindrical lens and is extended in a first direction X are arrayed in a second direction Y crossing orthogonally to the first direction X at regular intervals. On the light deflection surface 14, a number of ridge-like structures 2b extended in the first direction X are disposed in the second direction Y at regular intervals. A trough part 16 extended in the first direction X is formed between the unit lenticular lenses 2a adjacent to each other. Upon a planar view of the light deflection surface 14, the trough part 16 presents such a wavy shape that an amplitude along the second direction Y of the trough part 16 is aperiodically changed.

Description

  The present invention relates to a light guide used mainly for illumination light path control, an illumination device, and a display device.

  In recent large-sized liquid crystal televisions, flat display panels and the like, a direct type illumination device and an edge light illumination device are mainly used. In the direct type illumination device, a plurality of cold cathode tubes and LEDs (Light Emitting Diodes) are regularly arranged as light sources on the back surface of the panel. A light diffusing plate is used between the image display element such as a liquid crystal panel and the light source so that a cold cathode tube or LED as a light source is not visually recognized.

  On the other hand, in an edge light type lighting device, a plurality of cold-cathode tubes and LEDs are arranged on an end face of a translucent plate called a light guide plate. In general, light that efficiently enters incident light that is incident from an end surface of the light guide plate onto a surface (light deflection surface) opposite to the light emission surface (surface that faces the image display element) of the light guide plate. A deflection element is formed. At present, the light deflection element formed on the light deflection surface is generally one in which white ink is printed in the form of dots (for example, Patent Document 1). However, since the light incident on the white dots is diffusely reflected almost omnidirectionally, the light extraction efficiency to the exit surface side of the light guide plate is low. Light absorption by white ink cannot be ignored.

  Therefore, recently, a method of forming a microlens on the light deflection surface of a light guide plate by an ink jet method, a method of forming a light deflection element by a laser ablation method, and the like have been proposed. Unlike white ink, light absorption hardly occurs because it uses reflection, refraction, and transmission due to the difference in refractive index between the resin of the light guide plate and air. Therefore, a light guide plate having a higher light extraction efficiency than that of white ink can be obtained.

  However, the formation of the light deflection element by the ink jet method or the laser ablation method is formed in a separate process after the light guide plate is formed into a flat plate, as in the case of printing with white ink, so the number of manufacturing steps is not reduced. Rather, there is a problem that the tact time is longer than the white ink printing process and the initial cost of the equipment is high, resulting in high costs.

  Therefore, a method has been proposed in which the light guide plate is formed by an injection molding method or an extrusion molding method, and the light deflection element is directly shaped at the time of extrusion (for example, Patent Document 2). Since the light deflection element is formed simultaneously with the formation of the light guide plate, the number of processes is reduced, and the cost can be reduced.

JP-A-1-241590 JP 2000-89033 A

  In the light guide plate, a lenticular lens is formed on the exit surface in order to adjust the luminance distribution on the exit surface, the light deflection element is disposed on the surface facing the light exit surface, and the object (mainly a reflective sheet) adjacent to the facing surface. In general, a shape having a surface structure in which a saddle-like structure is mixed is reduced in order to reduce problems (white spots) due to close contact with (). However, if the lenticular lens and the bowl-shaped structure are provided on both surfaces of the light guide plate, the period of the unit lens and the unit structure that are arranged interfere with each other, causing interference fringes (moire) and causing a problem. There is a need for improvement.

  An object of the present invention is to provide a light guide plate formed by forming a light deflection element for a backlight provided in a liquid crystal display body and the like, which is free from defects due to interference fringes (moire).

The invention according to claim 1 of the present invention includes a light incident surface on which light emitted from a light source is incident, a light emission surface that emits light incident on the light incident surface, and the light facing the light emission surface. A light deflecting surface for deflecting light incident on the incident surface to the light exit surface, and the light exit surface is made of a convex cylindrical lens and a unit lenticular lens extending in the first direction is orthogonal to the first direction. A plurality of the light deflection surfaces are arranged at equal intervals in the second direction, and the light deflection surfaces are arranged at equal intervals in the second direction. A light guide plate having a valley extending in the first direction between the adjacent unit lenticular lenses, and when the light deflection surface is viewed in plan, the valley is the portion of the valley Waveform whose amplitude along the second direction varies aperiodically Characterized in that it exhibits.
According to a second aspect of the present invention, in the light guide plate according to the first aspect, the corrugated shape of the valley portion is such that the height of the unit lenticular lens changes aperiodically in the first direction. It is formed.
According to a third aspect of the present invention, in the light guide plate according to the first or second aspect, the trough has an amplitude of 5 μm or more and 10 μm or less.
According to a fourth aspect of the present invention, in the light guide plate according to any one of the first to third aspects, an interval between the unit lenticular lenses in the second direction is an optical axis of the adjacent unit lenticular lenses. The distance is not less than 30 μm and not more than 200 μm.
According to a fifth aspect of the present invention, in the light guide plate according to any one of the first to fourth aspects, the unit lenticular lens has a radius of curvature of not less than 30 μm and not more than 200 μm.
The invention which concerns on Claim 6 of this invention is an illuminating device using the light-guide plate of any one of Claims 1-5.

  According to a first aspect of the present invention, a light incident surface for entering light emitted from a light source, a light exit surface for emitting light incident on the light incident surface, and the light incident surface facing the light exit surface A light deflecting surface for deflecting light incident on the surface to the light exit surface, and the light exit surface is made of a convex cylindrical lens and a unit lenticular lens extending in the first direction is orthogonal to the first direction. A plurality of the light deflecting surfaces are arranged at equal intervals in the second direction, and the light deflection surface is provided with a plurality of hook-shaped structures extending in the first direction at equal intervals, and adjacent to each other. In the light guide plate that is a trough extending in the first direction between the matching unit lenticular lenses, when the light deflection surface is viewed in plan, the trough is the second of the trough. Waveform shape whose amplitude along the direction changes aperiodically By, it is possible to provide a light guide plate capable of improving a defect by Moire for the periodicity of the unit lenticular lens and ribbed structure is relaxed.

According to the second aspect, it is advantageous to easily form the corrugated shape of the valley.
According to the third to fifth aspects, it is advantageous in producing a high-quality light guide plate that effectively suppresses moire.
According to the sixth aspect, it is advantageous to provide a high-quality lighting device that effectively suppresses moire.

Schematic of the light-guide plate which is embodiment of this invention. Schematic of the light-guide plate which is a conventional embodiment. Schematic of the roll metal mold | die for the light emission surfaces of the light-guide plate which concerns on this invention. The schematic of the roll metal mold | die for the light deflection | deviation surface of the light-guide plate which concerns on this invention. Schematic of the conventional roll metal mold | die for micro lens formation. Schematic of the manufacturing apparatus of the light-guide plate which is embodiment of this invention. Explanatory drawing of evaluation of a light-guide plate. FIG. 4 is an explanatory diagram of specifications of Examples and Comparative Examples. Explanatory drawing of an external appearance evaluation result. Explanatory drawing of the roll metal mold | die for the light emission surfaces of the conventional light-guide plate. (A), (B) is explanatory drawing of the roll metal mold | die for the light emission surfaces of the light-guide plate of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a development view of a light guide plate according to an embodiment of the present invention. As shown in FIG. 1, the light guide plate 1a of the present invention has a lenticular lens formed of a large number of unit lenticular lenses 2a formed continuously on one surface (light exit surface). At the same time, on the other surface (light deflection surface), a ridge-like structure 2b extending in the same direction as the lenticular lens, and a substantially hemispherical microlens 3 that becomes a light deflection element concave with respect to the light deflection surface. The microlenses 3 are arranged so that the number of microlenses per unit area increases as the distance from the light incident surface increases.
FIG. 2 is a development view of a conventional light guide plate 1b.

More specifically, the light guide plate 1a is opposed to the light incident surface 10 on which light emitted from the light source is incident, the light emission surface 12 that emits light incident on the light incident surface 10, and the light emission surface 12. And a light deflecting surface 14 for deflecting the light incident on the light incident surface 10 to the light emitting surface 12.
The light exit surface 12 is composed of convex cylindrical lenses, and a large number of unit lenticular lenses 2 a extending in the first direction X are arranged at equal intervals in a second direction Y orthogonal to the first direction X.
The light deflection surface 14 is provided with a large number of bowl-shaped structures 2b extending in the first direction X at equal intervals in the second direction Y. Each bowl-shaped structure 2b has a triangular shape with the same shape and the same size.
Between the unit lenticular lenses 2a adjacent to each other, a trough portion 16 extending in the first direction X is formed.
When the light deflection surface 14 is viewed in plan, the trough portion 16 has a waveform shape in which the amplitude along the second direction Y of the trough portion 16 changes aperiodically.
It is preferable that the amplitude A of the valley portion 16 is 5 μm or more and 10 μm or less in order to effectively suppress the moire caused by the unit lenticular lens 2a and the bowl-shaped structure 2b.
When the amplitude A is out of the above range, the effect of suppressing moire is reduced.

The corrugated shape of the valley portion 16 is formed by the non-periodic change in the height H of the unit lenticular lens 2a in the first direction X.
For this reason, it is advantageous in easily forming the corrugated shape of the valley portion 16.
The interval W1 between the unit lenticular lenses 2a in the second direction Y is the distance between the optical axes of the adjacent unit lenticular lenses 2a, and this distance is 30 μm or more and 200 μm. It is preferable for effectively suppressing moire caused by the bowl-shaped structure 2b.
When the interval W1 is less than 30 μm, the number of valleys 16 of the convex cylindrical lens increases, and the diffusion effect of the valleys 16 becomes strong, and the screen may be whitened.
When the interval W1 exceeds 200 μm, the amount of change in the valley portion 16 with respect to the interval W1 is small, so the effect of suppressing moire is reduced.
In addition, the radius of curvature of the convex cylindrical lens is preferably 30 μm or more and 200 μm or less in terms of suppressing moire caused by the unit lens 2a and the bowl-shaped structure 2b.
When the radius of curvature of the convex cylindrical lens is less than 30 μm, moire may occur due to the pitch of the apex portion of the convex cylindrical lens, and the effect of suppressing moire is reduced.
When the curvature radius of the convex cylindrical lens exceeds 200 μm, the lens effect is lost and the effect of suppressing moire may be reduced.

  Specifically, the light guide plate 1a of the present invention can be manufactured by a manufacturing apparatus as shown in FIG. 6 using a roll die shown in FIGS. That is, a roll mold 100a for forming a lenticular lens as shown in FIG. 3, a bowl-shaped structure 2b as shown in FIG. 4, and a roll mold 100b for forming a microlens are provided, as shown in FIG. The light guide plate 1a can be manufactured by a manufacturing apparatus based on such an extrusion molding method.

More specifically, the resin melted by heating is extruded from the die 7 of the extruder, and sandwiched between the roll mold 100a for forming the lenticular lens, the bowl-shaped structure 2b, and the roll mold 100b for forming the microlens, A light guide plate 1a is produced by forming a continuous lenticular lens on this surface and forming a bowl-like structure 2b and a minute lens on the other surface.
In addition, a sheet plate having the same shape as the shape formed on the surface of the roll mold 100a or the roll mold 100b is wound around, for example, a mirror roll or the like, so that the roll mold 100a or the roll mold 100b It may be used as an alternative.

  Hereinafter, the present invention will be described more specifically with reference to examples.

(1) Production of light guide plate mold <Roll mold for lenticular lens formation>
As shown in FIG. 1, the shape of the unit lenticular lens 2a is such that the height H of the unit lenticular lens 2a is 10 μm when the interval W1 between the unit lenticular lenses 2a is 50 μm, 100 μm and 200 μm, and the interval W2 between the valleys 16 is 100 μm. Aspherical shape. The height H of the unit lenticular lens 2a is the distance from the valley 16 to the top of the unit lenticular lens 2a in the optical axis direction of the unit lenticular lens 2a.

  Each unit lenticular lens is attached to a lathe machine by attaching a plating roll with copper plating for cutting, a diamond tool having a shape corresponding to the above shape at the tip, and contacting the diamond tool while rotating the plating roll at high speed. 2a was processed. By changing the height H of the unit lenticular lens 2a, the amplitude A of the valley portion 16 was changed, and Examples 1 to 3 and Comparative Examples 1 to 4 were obtained as shown in FIG. A roll mold for lenticular lenses corresponding to Comparative Examples 1, 5, and 9 is designated as 100c, and for lenticular lenses corresponding to Examples 1 to 9, Comparative Examples 2 to 4, Comparative Examples 6 to 8, and Comparative Examples 10 to 12. A roll mold 100a was prepared.

As shown in FIG. 10, in the conventional roll mold 100c for the light exit surface of the light guide plate, the interval W1 between the unit lenticular lenses 2a is constant, and the mold part corresponding to the unit lenticular lens 2a is cut. The depth is also constant.
In contrast, as shown in FIGS. 11A and 11B, in the roll mold 100b for the light exit surface of the light guide plate of the present invention, the interval W1 between the unit lenticular lenses 2a is constant. The cutting depth of the mold part is changed so that the height H of each unit lenticular lens 2a changes aperiodically in the first direction X.
In FIG. 11 (A), the solid line portion indicates the cutting portion by the cutting blade, and in FIG. 11 (B), the solid line portion indicates the cross-sectional shape of the mold.

<Roll-shaped structure 2b and roll mold for forming microlenses>
The shape of the bowl-shaped structure 2b was a prism shape (triangular cross section) with a spacing P of 50 μm and a depth D1 of 1 μm. The shape of the microlens 3 was an elliptical hemisphere having a major axis L of 180 μm, a minor axis S of 70 μm, and a depth D2 of 20 μm.

The roll mold 100b was produced by the following method.
Each plating roll to which the copper plating for processing was applied was set on a lathe machine, and the shape corresponding to the bowl-shaped structure 2b was processed on the roll surface.
Subsequently, a diamond tool having a shape corresponding to the shape of the micro lens is attached to the tip, and the diamond tool is taken in and out of the roll in synchronization with the rotation of the roll. 100b was produced.

<Production of light guide plate>
The roll mold 100a or 100c for forming a lenticular lens, the bowl-shaped structure 2b, and the roll mold for forming a microlens corresponding to Examples 1 to 9 and Comparative Examples 1 to 12 as shown in FIGS. The light guide plates 1a and 1b corresponding to Examples 1 to 9 and Comparative Examples 1 to 12 were manufactured using a manufacturing apparatus that includes 100b and is based on the extrusion method as shown in FIG.

  Specifically, a thermoplastic polycarbonate resin manufactured by Teijin Chemicals Ltd. is heated and melted from a die 7 of an extruder and extruded, and a roll mold 100a or mold 100c for forming a lenticular lens, a bowl-shaped structure 2b, and a microlens. Examples 1 to 9 and Examples 1 to 9 are formed by forming a unit lenticular lens 2a which is sandwiched between the forming roll mold 100b and forming a continuous unit lenticular lens 2a on one surface, and forming a bowl-shaped structure 2b and a microlens 3 on the other surface. The light guide plates of Comparative Examples 1 to 12 were produced. The size of the light guide plate was 530 mm × 300 mm and the thickness was 0.4 mm.

(2) Evaluation of light guide plate <Appearance evaluation>
The appearance performance of the light guide plates produced in Examples 1 to 3 and Comparative Examples 1 to 4 was evaluated using the light guide plate evaluation apparatus shown in FIG.
That is, the evaluation device is a liquid crystal display device 20, and the liquid crystal display device 20 includes a liquid crystal panel 22, prism films 23 and 24, a diffusion film 25, a light source lamp 26, a lamp reflector 27, a reflection film 28, and a light guide plate 29. It consists of
In the method, the light guide plates produced in Examples 1 to 3 and Comparative Examples 1 to 4 were replaced with the light guide plate 29 having the configuration of the liquid crystal display device 20, a white screen was displayed, and visual sensitivity evaluation was performed. The evaluation is performed by three evaluators. If all three people cannot confirm the interference fringe (moire) defect, it is judged as good. did.

  In the light guide plates of Comparative Examples 1, 5, and 9, the appearance of interference fringes (moire) was visually recognized due to the period of the interval W1 between the unit lenticular lenses and the interval P between the bowl-shaped structures 2b. This is considered that the period of the space | interval W1 and the space | interval P interfered and the interference fringe (moire) was visually recognized.

  In the light guide plates of Comparative Examples 2, 6, and 10, the amplitude A of the valley portion 16 of the unit lenticular lens was changed in the range of 3 μm by changing the height H of the unit lenticular lens. Although improved over Comparative Example 1, interference fringes (moire) were generated and visually recognized as defects.

  In the light guide plates of Comparative Examples 3 to 4, 7 to 8, and 11 to 12, the height A of the unit lenticular lens is changed to 12 μm by changing the height H of the unit lenticular lens in the same manner as in Comparative Example 2. It was changed in the range of 15 μm. As a result, interference fringes (moire) did not occur, but the valley 16 of the unit lenticular lens meandered, resulting in uneven defects and poor appearance.

  The light guide plates of Examples 1 to 9 change the amplitude A of the valley portion 16 of the unit lenticular lens in the range of 5 μm, 7 μm, and 10 μm by changing the height H of the unit lenticular lens as in Comparative Example 2. It was. As a result, no interference fringes (moire) occurred. By causing the amplitude A of the valley portion 16 of the unit lenticular lens to meander in the range of 5 μm to 10 μm, the valley portion 16 of the unit lenticular lens has no periodicity, and therefore interference fringes between the unit lenticular lens and the bowl-shaped structure 2b It was confirmed that (moire) was greatly improved. Moreover, the unevenness | corrugation by meandering of the valley part 16 of a unit lenticular lens did not generate | occur | produce.

<Comparison result>
The products of the present invention obtained in Examples 1 to 9 all exhibited high quality performance with very few appearance defects due to interference fringes (moire). On the other hand, the comparative products obtained in Comparative Examples 1 to 12 were not practical because of interference fringes (moire) and unevenness.

  The present invention can be used as a backlight member used in a liquid crystal display such as a large liquid crystal TV.

DESCRIPTION OF SYMBOLS 1a Light-guide plate 1b of this invention Conventional light-guide plate 2a Unit lenticular lens 2b Cascade-shaped structure 3 Micro lens 10 Light-incidence surface 12 Light-projection surface 14 Light-deflection surface 16 Valley part 20 Liquid crystal display device 22 Liquid crystal panel 23 Prism film 24 Prism Film 25 Diffusion film 26 Light source lamp 27 Lamp reflector 28 Reflective film 29 Light guide plate 100a Roll mold 100b for forming a unit lenticular lens according to the light guide plate of the present invention Form of the ridge-like structure 2b and microlenses according to the light guide plate of the present invention Roll mold 100c roll mold H for forming unit lenticular lens of conventional light guide plate height H of unit lenticular lens 2a
P Spacing X of the ridge-like structures 2b First direction Y Second direction W1 Spacing of the unit lenticular lens 2a W2 Spacing of the valleys 16

Claims (6)

A light incident surface on which light emitted from the light source is incident;
A light emitting surface for emitting light incident on the light incident surface;
A light deflection surface that faces the light exit surface and deflects the light incident on the light entrance surface to the light exit surface;
A plurality of unit lenticular lenses made of convex cylindrical lenses and extending in the first direction are arranged at equal intervals in a second direction orthogonal to the first direction,
The light deflection surface is provided with a large number of bowl-shaped structures extending in the first direction at equal intervals in the second direction,
Between the unit lenticular lenses adjacent to each other, a light guide plate that is a trough extending in the first direction,
When the light deflection surface is viewed in plan, the valley portion has a waveform shape in which the amplitude along the second direction of the valley portion changes aperiodically.
A light guide plate characterized by that. The corrugated shape of the valley is formed by aperiodically changing the height of the unit lenticular lens in the first direction.
The light guide plate according to claim 1. The valley has an amplitude of 5 μm or more and 10 μm or less.
The light guide plate according to claim 1 or 2, wherein The interval between the unit lenticular lenses in the second direction is a distance between the optical axes of the adjacent unit lenticular lenses,
The distance is not less than 30 μm and not more than 200 μm.
The light guide plate according to any one of claims 1 to 3. The radius of curvature of the unit lenticular lens is 30 μm or more and 200 μm.
The light guide plate according to claim 1, wherein the light guide plate is a light guide plate.   The illuminating device using the light-guide plate of any one of Claims 1-5.

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