WO2004081444A1

WO2004081444A1 - Light guide plate

Info

Publication number: WO2004081444A1
Application number: PCT/JP2004/003234
Authority: WO
Inventors: Masahiko Hayashi; Kazuyuki Obuchi; Keisuke Tsukada; Toshihiko Hori
Original assignee: Zeon Corporation
Priority date: 2003-03-14
Filing date: 2004-03-11
Publication date: 2004-09-23
Also published as: TW200424565A; JPWO2004081444A1

Abstract

A light guide plate which is light in weight, high in luminance, small in luminance unevenness and excellent in uniformity ratio of luminance is characterized in that it is composed of a plate-like transparent resin molded body having a front surface, a back surface, and four lateral surfaces, in that the front surface serves as a light emitting surface, in that at least two opposite surfaces among the four lateral surfaces serve as light incident surfaces, and in that the back surface is so formed as to have the plate thickness decrease from the light incident surfaces to the center of the back surface and serves as a light reflecting surface.

Description

Description Light guide plate Technical field

The present invention relates to a light guide plate. More specifically, the present invention relates to a light guide plate that is lightweight, has high luminance, has low luminance unevenness, and has excellent luminance uniformity. Background art

Liquid crystal display devices are widely used for display screens such as personal computers, flat-panel televisions, and power navigation systems. The liquid crystal display device uses a light guide plate that converts light from a light source such as a cold cathode discharge tube provided on a side surface into planar light. The light guide plate is required to have a high brightness, make full use of the light from the light source, to have no uneven brightness, and to uniformly irradiate the liquid crystal with the light from the light source. For this reason, various improvements have been attempted for the shape of the light guide plate.

For example, by adjusting the reflective surface to increase the uniformity of luminance, and as a light guide plate with high luminance, the rear surface is directly subjected to reflection processing with a variable reflectivity according to the distance from the light source, and the front surface is provided with multiple light guides. A light guide plate having a linear prism cut has been proposed (Patent Document 1). In addition, as a light guide plate that has a light and thin structure and high light utilization, it has a convex lens-like light introduction part that makes the light from the light source almost parallel at the side end, and the light that is introduced in parallel is incident There has been proposed a light guide plate having an inclined surface which is provided with a light diffusion layer outside the inclined surface (Patent Document 2). However, the brightness and brightness uniformity of these light guide plates have not reached sufficiently satisfactory levels.

The present invention is lightweight, has high luminance, has low luminance unevenness, and has excellent luminance uniformity. The purpose of the present invention is to provide a light guide plate that has the following features.

[Patent Document 1] Japanese Patent Application Laid-Open No. 5_2039447 (Page 2, FIG. 1)

[Patent Document 2] Japanese Patent Application Laid-Open No. 6-166038 (Page 2, FIG. 1) Disclosure of the Invention

The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, a plate-shaped transparent resin molded body having a front surface, a back surface, and four side surfaces, the surface is a light emitting surface, and four The light guide plate, in which at least two opposing surfaces of the side surfaces are light incident surfaces and the back surface is a light reflecting surface composed of a surface formed so that the thickness decreases from the light incident surface toward the center, is lightweight. It was found that the brightness was high, the brightness unevenness was small, and the brightness uniformity was excellent, and the present invention was completed based on this finding.

That is, the present invention

(1) A plate-shaped transparent resin molded body having a front surface, a back surface, and four side surfaces, wherein the surface is a light emission surface, at least two opposing surfaces of the four side surfaces are a light incidence surface, and the back surface Is a light reflecting surface consisting of a surface formed so that the plate thickness decreases from the light incident surface toward the center toward the center,

(2) All four sides of the transparent resin molded body are light incident surfaces, and the back surface is a light reflecting surface composed of a curved surface formed so that the thickness decreases from the four sides toward the center ( 1) Light guide plate described,

(3) The light guide plate according to (2), wherein all four side surfaces that are light incident surfaces are rectangular.

(4) The light guide plate according to (2), wherein the transparent resin is a polymer resin having an alicyclic structure.

(5) The transparent resin is a polymer resin having an alicyclic structure, two of the four side surfaces facing each other are light incident surfaces, and the rear surface has a thickness from the two light incident surfaces toward the center. But The light guide plate according to (1), wherein the light guide surface is a light reflection surface that is formed to have an inclined surface formed so as to have a minimum thickness at the center.

(6) The light guide plate according to (1), wherein the light emitting surface and the Z or light reflecting surface have a fine uneven pattern.

Is provided.

Further, as a preferred embodiment of the present invention,

(7) The light guide plate according to (4) or (5), wherein the polymer resin having an alicyclic structure is a hydrogenated product of a polymer of a norbornene-based monomer or a butyl alicyclic hydrocarbon-based monomer. , as well as,

(8) polymers of norbornene monomers is, tricyclo ^{^{[4. 3.0. I 2 '5}} ] Deka 3,7 Jen and 8 E dust Den tetracyclo ^{^{[4.4.0. I 2 · 5.}} I 7 [ ¹⁰ ] The light guide plate according to (7), which is a copolymer with dodeca-3-ene.

Can be mentioned. BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is a schematic plan view, a side view, and a cross-sectional view of one embodiment of the light guide plate of the present invention, and Fig. 2 is a schematic plan view, a side view, and another embodiment of the light guide plate of the present invention. FIG. 3 is a cross-sectional view, FIG. 3 is a schematic plan view, a side view, and a cross-sectional view of another embodiment of the light guide plate of the present invention, and FIG. 4 is a schematic perspective view of an example of a continuous triangular prism shape. Yes, Fig. 5 is a schematic perspective view of an example of a continuous arc prism shape, and Fig. 6 is a schematic cross-sectional view of another example of a continuous triangular prism shape. In Figs. 1 to 3, 1 is the light exit surface, 2 is the light entrance surface, and 3 is the light reflection surface. BEST MODE FOR CARRYING OUT THE INVENTION

The light guide plate of the present invention is a plate-shaped transparent resin molded body having a front surface, a back surface, and four side surfaces, the surface being a light emission surface, and at least two opposing surfaces of the four side surfaces being light incidence surfaces. The light guide plate is a light reflection surface including a surface formed such that the back surface is formed such that the thickness decreases toward the center from the light incident surface. The light guide plate of the present invention has a light reflection surface formed of a curved surface formed such that all four side surfaces of the transparent resin molded body are light incident surfaces, and the back surface is formed so that the thickness decreases from the four side surfaces toward the center. can do.

FIG. 1 is a schematic plan view, a side view, a sectional view taken along line AA, and a sectional view taken along line BB of one embodiment of the light guide plate of the present invention. The light guide plate of this embodiment is a plate-shaped transparent resin molded body having a front surface, a back surface, and four side surfaces, the surface being a light exit surface 1, and all four side surfaces being a light incident surface 2. On the other hand, the light reflecting surface 3 is formed of a concave curved surface whose back surface is formed so that the plate thickness decreases from the side surface toward the center. The light guide plate of this aspect can be called a dome-shaped light guide plate because the light reflection surface is a concave curved surface.

In the light guide plate of the embodiment shown in Fig. 1, all four sides, which are the light incident surfaces, are rectangular. By making all four sides rectangular, installing light sources in all of them, and entering light from four directions, a light guide plate with high brightness and less uneven brightness can be obtained.

In the light guide plate shown in Fig. 1, the light reflecting surface is a curved surface, so that light incident parallel to the light guide plate is reflected on the curved surface and reflected in multiple directions, so that the light use efficiency is high. As a result, the brightness of the light guide plate is improved, and uneven brightness is reduced. Further, in the light guide plate of the embodiment shown in Fig. 1, since the light reflection surface is a concave curved surface, the amount of transparent resin used for the light guide plate is small, and the weight can be reduced. In the light guide plate shown in Fig. 1, the light reflecting surface is a curved surface and there is no part where stress concentrates. It is possible to make it W-shaped and lighter.

In the light guide plate of the embodiment shown in Fig. 1, the center is the lower part of each side corresponding to the four sides from the center of the substantially rectangular shape which is the surface of the plate-shaped molded body having the front and back sides and four sides. It is a region that passes through the midpoint of the vertical line and is divided by four straight lines drawn parallel to each side. In the light guide plate of the embodiment shown in Fig. 1, the back surface is a curved surface formed so that the thickness decreases from the four side surfaces toward the center, and the minimum point of the light guide plate thickness is in the above-mentioned region. Exists within. The center of the substantially rectangular shape, which is the surface of the plate-like molded body, can be obtained as the intersection of two diagonal lines of the substantially rectangular shape. If the approximate rectangular shape deviates from the exact rectangular shape and it is difficult to find the center as the intersection of two diagonals, the center of gravity of the approximate rectangle can be used as the center of the approximate rectangle. In addition, the substantially rectangular center of gravity is a substantially rectangular center of gravity as a geometric shape, and is not the center of gravity of the light guide plate itself.

In the light guide plate of the present invention, the transparent resin is a polymer resin having an alicyclic structure, two opposing surfaces of the four side surfaces are light incident surfaces, and the back surface is a medium from the two light incident surfaces. The light guide plate can be a light reflecting surface formed of an inclined surface formed such that the plate thickness decreases toward the center and has a minimum plate thickness at the center.

FIG. 2 is a schematic plan view, a side view, a sectional view taken along line AA, and a sectional view taken along line BB of another embodiment of the light guide plate of the present invention. The light guide plate of the present embodiment is a plate-shaped molded body of a polymer resin having an alicyclic structure composed of a front surface, a back surface, and side surfaces, wherein the surface is a light emission surface 1 and two of the four side surfaces are opposed to each other. The surface is a light incident surface 2, and the back surface is a light reflecting surface 3 consisting of an inclined surface formed so that the thickness decreases from the two light incident surfaces toward the center and becomes the minimum thickness at the center. is there. The size of the light source that can be installed on the side of the light guide plate is determined by the size of the side surface. The weight can be reduced as compared with a flat light guide plate that can be used. In addition, light incident parallel to the light exit surface from the light placed on the side surface is reflected on the inclined light reflection surface, and is therefore used more efficiently and has higher brightness than a flat light guide plate. And brightness uniformity can be obtained.

FIG. 3 is a schematic plan view, a side view, an A-A line sectional view, and a BB line sectional view of another embodiment of the light guide plate of the present invention. The light guide plate of this embodiment is a plate-shaped molded body of a polymer resin having an alicyclic structure composed of a front surface, a back surface, and side surfaces, and the surface is a light emission surface 1.

The two opposing surfaces of the four side surfaces are the light incident surfaces 2, and the back surface is formed so that the plate thickness decreases from the two light incident surfaces toward the center and becomes the minimum plate thickness at the center. The light reflecting surface 3 is formed of an inclined curved surface. Since the size of the light source that can be installed on the side surface of the light guide plate is determined by the size of the side surface, the light guide plate of this embodiment is lighter in weight than a flat light guide plate on which a light source of the same scale can be installed. can do. In the light guide plate of this embodiment, since the light reflection surface is a curved surface, light incident parallel to the light guide plate has different angles of incidence on the light reflection surface at each point on the light reflection surface, and is reflected in multiple directions. As a result, the light use efficiency is increased, the luminance of the light guide plate is improved, and the luminance unevenness is reduced. In addition, the light guide plate of this embodiment has a curved light reflection surface and does not have a portion where stress is concentrated. Therefore, the light guide plate can be reduced in thickness and weight while maintaining sufficient strength.

In the light guide plate of the embodiment shown in Fig. 2 and Fig. 3, the center is the light incident surface from the center of the substantially rectangular shape which is the surface of the plate-shaped molded body having the front and back surfaces and the four side surfaces. This is a region that passes through the midpoint of the perpendicular line drawn on each side corresponding to the two side surfaces and is surrounded by two straight lines drawn parallel to each side. In the light guide plate shown in Fig. 2 or Fig. 3, the back surface is a surface formed so that the thickness decreases from the two side surfaces, which are the light incident surfaces, toward the center. The minimum point of the thickness is Exists within. The center of the substantially rectangular shape, which is the surface of the plate-like molded body, can be obtained as the intersection of two diagonal lines of the substantially rectangular shape. If the approximate rectangular shape deviates from the exact rectangular shape and it is difficult to find the center as the intersection of the two diagonal lines, the center of the approximate rectangle can be used as the center of the approximate rectangle. In addition, the substantially rectangular center of gravity is a substantially rectangular center of gravity as a geometric shape, and is not the center of gravity of the light guide plate itself.

In the light guide plate of the present invention, the plate thickness does not need to be reduced immediately as the light reflecting surface moves away from the side surface.For example, after maintaining a constant thickness of 5 to 20 mm from the side surface, the plate thickness is reduced. Can be thin. The part where the plate thickness is kept constant can be used as the part for attaching the light guide plate when assembling the liquid crystal display device.

In the light guide plate of the present invention, the thickness of the side surface serving as the light incident surface is preferably from 0.2 to 50 mm, more preferably from 0.5 to 40 mm, and from 1 to 3 mm. More preferably, it is 0 mm. In addition, the thickness of the central portion is preferably 0.05 to 0.95 times the thickness of the side portion, more preferably 0.1 to 0.9 times, and 0.15 to 0.95 times. It is particularly preferred that the ratio be 0.5 times.

The light guide plate of the present invention preferably has a fine concavo-convex pattern on the light emitting surface and / or the light reflecting surface. By having a fine concavo-convex pattern, a light guide plate having more uniform luminance can be obtained. The fine concavo-convex pattern is not particularly limited as long as it has a shape having a light reflecting function. However, it is preferable that the fine concavo-convex pattern has a shape having a plurality of surfaces reflecting light incident from the side surface. As such a shape, it is preferable that the light emitting surface is a shape composed of a plurality of parallel V-shaped grooves, a continuous triangular prism shape, a continuous arc-shaped prism shape, or a fine uneven pattern having a satin finish. The light reflecting surface should be a hemispherical, cylindrical, elliptical, square prism, truncated square pyramid, or linear fine uneven pattern. Is preferred. Fig. 4 is a schematic perspective view of an example of a continuous triangular prism shape, Fig. 5 is a schematic perspective view of an example of a continuous arc prism shape, and Fig. 6 is a schematic perspective view of the continuous triangular prism shape. It is a typical sectional view of other examples. ·

In the example shown in Fig. 6, a unit prism with a vertex angle of 0, a height of h, and a base of b is provided with pitch p and width w. In the light guide plate of the present invention, the vertex angle 6 of the triangular prism is preferably 40 to 175 degrees, more preferably 45 to 170 degrees, and further preferably 50 to 165 degrees. The pitch p of the triangular prism is preferably 10 to 500 μιη, more preferably 20 to 400 μιη, and even more preferably 30 to 300 μπι. The radius of curvature of the arc-shaped prism is preferably 5 to 50 tm, more preferably 10 to 40 μπι, and further preferably 15 to 30 m. The pitch of the arc-shaped prism is preferably from 5 to 500 m, more preferably from 10 to 400 im, even more preferably from 15 to 300 μπι. In the light guide plate of the present invention, a cylinder provided on the light reflecting surface is preferably that the ratio h ZW _max of the height or depth h and the maximum open port width W _max is 0.3 or more, and this is 0.4 or more Is more preferable, and more preferably 0.5 or more. Preferably, the elliptic cylinder has a major axis of 50 to 600 μm, a minor axis of 5 to 300 m, and a major / minor axis ratio of 1 to L 0. The square pillar preferably has a long side of 50 to 600 // m, a short side of 5 to 300 μm, a ratio of long side / short side of 1 to 10, and a height or depth and a maximum opening width W _mM . preferably the ratio h / W _max of is 0.3 or more, more preferably 0.4 or more, and still more preferably 0.5 or more. It is preferable that the truncated pyramid has a slope angle of 25 to 45 degrees, a base of 100 m or less, and a height of 2 to 15 μπι. It is preferable that the cross section of the fine linear uneven pattern is triangular, circular, square, trapezoidal, etc. Les ,.

In the light guide plate of the present invention, the pitch of the projections or depressions of the light reflecting surface is preferably 10,000 μm or less, more preferably 8, OOO / m or less, and 5,000 m or less. More preferably, there is. The ratio of the dot figure occupied between the pitches is preferably 0.1 to 95%, more preferably 30 to 95%. The height or depth of the projections or depressions is preferably 0.1 to 500 zm, more preferably 1 to 5 μηι, and even more preferably 5 to 40 μm. Projected area of the convex or times lower is preferably at 0.5 5 mm ² or less, more preferably 0.4 mm ² or less, it is further favorable preferable 0.5 is 3 mm ² or less.

In the light guide plate of the present invention, the upper part of the convex pattern on the light reflecting surface can be made rough. The surface roughness of the rough surface is preferably as R _z is 0. 2 to 1 5 m, and more preferably 0. 5~7 μιη. In the present invention, the convex pattern or the concave pattern of the light reflecting surface can be regularly arranged like a lattice, or can be randomly arranged. By randomly arranging convex or concave patterns on the light reflecting surface, it is possible to prevent optical interference with the liquid crystal panel. It is preferable that the distribution of the convex pattern or the concave pattern on the light reflecting surface is made sparse near the light source provided on the side surface of the light guide plate and dense near the light source provided on the side surface of the light guide plate. By making the area closer to the light source sparse and the area farther from the light source dense, the brightness of the entire surface of the liquid crystal display device can be made almost equal, and uneven brightness can be reduced. When the light emitting surface is matte, the surface roughness of the matte is preferably such that the maximum height _Ry is 0.0.1 to 100 μιη, more preferably 0.1 to 50 m, It is particularly preferred that it is 1-3 μιη. The transparent resin used for the light guide plate of the present invention is not particularly limited, but the total light transmittance of the molded plate having a thickness of 3 mm is preferably 70% or more, more preferably 75% or more, More preferably, it is at least 80%. Examples of such a transparent resin include methacrylate resin, polycarbonate, polystyrene, ABS, methyl methacrylate-styrene copolymer resin, polymer resin having an alicyclic structure, polyethylene terephthalate, polyether sulfone, and the like. be able to. Among these, a polymer resin having an alicyclic structure can be particularly preferably used. The polymer resin having an alicyclic structure has a small specific gravity, so that the light guide plate can be reduced in weight, and has extremely low hygroscopicity, so that it has excellent dimensional stability and does not warp the light guide plate. Since the moldability is good, even if a large thin light guide plate is injection-molded, no sink marks will occur.

Examples of the polymer resin having an alicyclic structure include a polymer resin having an alicyclic structure in a main chain or a side chain. A polymer resin having an alicyclic structure in the main chain can be particularly preferably used because it has good mechanical strength and heat resistance. The alicyclic structure is preferably a saturated cyclic hydrocarbon structure, and preferably has 4 to 30 carbon atoms, more preferably 5 to 20 carbon atoms, and 6 to 15 carbon atoms. Is more preferred. The proportion 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. More preferably, it is the above.

Examples of the polymer resin having an alicyclic structure include a ring-opening polymer or a ring-opening copolymer of a norponene-based monomer, a hydrogenated product thereof, and an addition polymer or addition copolymer of a nor- polene-based monomer. Polymer or hydrogenated product thereof, polymer of monocyclic cyclic olefin monomer or hydrogenated product thereof, polymer of cyclic conjugated diene monomer or Is a hydrogenated product, a polymer or copolymer of a vinyl alicyclic hydrocarbon monomer or a hydrogenated product thereof, a polymer or copolymer of a vinyl aromatic hydrocarbon monomer. Examples include hydrogenated products of an unsaturated bond portion containing a ring. Among these, the hydrogenated product of the polymer of the norponene-based monomer and the hydrogenated product of the unsaturated bond portion including the aromatic ring of the polymer of the vinyl aromatic hydrocarbon-based monomer have a high mechanical strength and resistance to resistance. Since it has excellent thermal properties, it can be suitably used. Tricyclo [4. 3. 0. I 2 '5] dec-one 3,7-diene and 8 E dust Den tetracyclo [4. 4. 0. I 2 · 5. I 7 · 10] with Dodeka 3 En The hydrogenated copolymer has a low specific gravity, can reduce the weight of the light guide plate, has a very low hygroscopic property, and can provide a light guide plate that is not easily deformed even when used under high temperature and high humidity. It can be particularly preferably used.

Although the method for producing the light guide plate of the present invention is not particularly limited, an injection molding method can be preferably used, and an injection compression molding method can be particularly preferably used. According to the injection compression molding method, the resin filled in the mold cavity is pressurized in a timely manner, the internal pressure of the cavity is increased, and the amount of shrinkage due to cooling is compensated for, thereby transferring the fine uneven pattern on the mold surface. Accuracy can be improved and warpage of the light guide plate can be corrected.

The light guide plate of the present invention has high luminance and luminance uniformity, can reduce the weight of the light reflection surface as a surface formed so that the plate thickness decreases toward the center, and has an alicyclic structure. By molding using a polymer resin, a light guide plate having excellent dimensional stability can be obtained.

Example

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

In the examples and comparative examples, the light guide plate was evaluated by the following method. (1) Average brightness

A straight tubular cold cathode fluorescent lamp, Lison Toshiba Lighting Co., Ltd., MB SM24 J N10WX3 70NLU] or an L-shaped tubular cold cathode fluorescent lamp

Attach [Norrison Toshiba Lighting Co., Ltd., ML VM24N 10WX3 70/2 75 NL H] and assemble the liquid crystal display device, temperature 20 ° C, relative humidity 65% or temperature 60 ° C, relative humidity 90 After standing for 72 hours in a constant temperature / humidity room, the luminance was measured. On the light exit surface side of the light guide plate, it is assumed that the surface formed 10 mm inward from each side forming the light exit surface is divided into four lines at equal intervals in the vertical and horizontal directions, each with five lines. Then, at a total of 25 intersections of each line, the luminance was measured using a luminance meter [Minolta Co., Ltd., CA-1500W], and the average value was calculated.

(2) Brightness uniformity

The ratio of the maximum value to the minimum value of the above 25 measured luminance values, that is, {(minimum value) / (maximum value)} X I 00 (%) was defined as the luminance uniformity.

(3) Moisture absorption deformation

After leaving the light guide plate in a constant temperature and humidity room at a temperature of 60 ° C and a relative humidity of 90% for 72 hours, it was placed on a flat plate and the four sides were measured using a gap gauge [Tokyo Cycnes Corporation, 100ML]. The gap with the flat plate was measured at a total of eight points at each midpoint and four corners, and the maximum value was taken as the amount of hygroscopic deformation.

Production Example 1 (Production of polymer resin having alicyclic structure)

500 parts by weight of dehydrated cyclohexane, 0.82 parts by weight of 1-hexene, 0.15 parts by weight of dibutyl ether and 0.30 parts by weight of triisobutylaluminum After mixing in a steel pressure vessel and mixing at 45 ° C, tricyclo [4. 3. 0. I ² ' ⁵ ] decal 3,7-gen (dicyclo Pentajen) 170 parts by weight of 8-E Chile den tetracyclo and ^{^{[4.4.0. I 2 · 5.}} 1 7 '10]' de de force one 3- E emissions (E dust Den tetra consequent opening dodecene) 30 parts by weight 40 parts by weight of a 0.7% by weight solution of tungsten hexachloride in toluene was continuously added over 2 hours to carry out polymerization. Next, 1.06 parts by weight of butyl glycidyl ether and 0.52 parts by weight of isopropyl alcohol were added to the polymerization solution to inactivate the polymerization catalyst and stop the polymerization reaction.

35 parts by weight of cyclohexane was added to 100 parts by weight of the reaction solution containing the obtained ring-opening polymer, and 5 parts by weight of a nickel-alumina catalyst [Nikki Chemical Co., Ltd.] was added as a hydrogenation catalyst. The mixture is heated to 200 ° C with stirring while pressurizing to 5 MPa with hydrogen and reacted for 4 hours, and contains 20% by weight of hydrogenated dicyclopentadiene ethylidene tetracycline dodecene ring-opening polymer. A reaction solution was obtained. After removing the hydrogenation catalyst by filtration, pentaerythrityl tetrakis [3- ( 3,5-Di-t-butyl-4-hydroxyphenyl) propionate] was added and dissolved. Then, at a temperature of 270 ° C and a pressure of 1 kPa or less, a cylindrical concentrator / dryer [Tachi Seisakusho Co., Ltd.] was used to remove hexane and other volatile components as a solvent from the solution while removing the solvent. extruded into strands the Jishiku port Pentaji E Hmm E dust Den tetracyclododecene ring-opening polymer hydrogenation product from the extruder in a molten state, and Peretz preparative reduction after cooling, it was recovered resin Peretsuto ₀

Example 1

Polymer resin with alicyclic structure [Nippon Zeon Co., Ltd., Zeonor 106 OR] Force, et al., Short side 276.4 mm, long side 344.0 mm, side thickness 8.0 mm, center thickness 2. Omm dome-shaped 17-inch light guide plate was molded by injection compression molding. The curve formed when the central part of the light guide plate is cut along a plane parallel to the short side is an arc with a radius of curvature of 1,592 mm.

The mold has a hemispherical hole that forms a hemispherical protrusion with a diameter of 60μιη on the surface of the molded body on the surface of the fixed mold cavity that becomes the light reflecting surface of the light guide plate, and an average of 1 Omm from the light incident surface. The intervals were sequentially set from a pitch of 300 μπι to an average pitch of 150 m in the center.

Injection compression molding uses an injection molding machine [Toshiba Machine Co., Ltd., IS 350GS, screw diameter 7 Omm, clamping force 3, 430 kN], molding temperature 275 ° C, mold temperature 70 ° C, molding cycle The test was performed for 90 seconds.

The weight of the obtained light guide plate was 393 g, and the amount of deformation due to moisture absorption was 0.5 mm. A liquid crystal display device is assembled by attaching a total of eight straight tubular cold cathode fluorescent lamps, two on each of the four side surfaces of this light guide plate, and then left at 20 ° C and 65% relative humidity to measure the luminance did. The average luminance was 7, 200 c dZm ^2, the luminance uniformity ratio was 88%.

Example 2

An L-shaped tubular cold-cathode fluorescent lamp, two in each case, was attached to two adjacent side surfaces of the light guide plate obtained in Example 1 on the long side and short side adjacent to each other. After assembling the device and leaving it to stand at 20 ° C and a relative humidity of 65%, the luminance was measured. The average luminance was 5,800 cd / m ² and the luminance uniformity was 87%.

Embodiment 3.

A dome-shaped resin was prepared in the same manner as in Example 1, except that a copolymer of methyl methacrylate and styrene 13 Tetsu Chemical Co., Ltd., styrene MS-600] was used as the transparent resin. The 17-inch light guide plate was molded by an injection compression molding method.

The weight of the obtained light guide plate was 447 g, and the amount of hygroscopic deformation was 3 mm. A liquid crystal display was assembled by attaching a total of eight straight tube cold cathode fluorescent lamps, two each to the four side surfaces of this light guide plate, and then allowed to stand at 20 ° C and a relative humidity of 65%. It was measured. The average luminance was 6,600 cd Zm ² and the luminance uniformity was 86%.

Example 4

Except for using methacrylic resin [Asahi Kasei Corporation, Delpet 70 NHX] as the transparent resin, a dome-shaped 17-inch light guide plate was molded by injection compression molding in the same manner as in Example 1. did.

The weight of the obtained light guide plate was 472 g, and the amount of deformation due to moisture absorption was 5 mm. A liquid crystal display was assembled by attaching a total of eight straight tube cold cathode fluorescent lamps, two each to the four side surfaces of this light guide plate, and then allowed to stand at 20 ° C and a relative humidity of 65%. It was measured. The average luminance was 6, 8 0 0 cd / " m 2, the luminance uniformity ratio in the dark at 8 7%.

Example 5

From the polymer resin having an alicyclic structure obtained in Production Example 1, a short side of 276.4 mm, a long side of 344.4 mm, a thickness of a side portion of the long side of 8.0 mm, center The thickness of the part is 2.0 mm, and the light reflection surface is a flat surface inclined from the short side surface to the center. The 17-inch light guide plate with the shape shown in Fig. 2 is manufactured by injection compression molding. Molded.

The mold has a hemispherical hole that forms a hemispherical projection with a diameter of 60 / zm on the surface of the movable mold cavity, which is the light reflecting surface of the light guide plate, with an average pitch of 300 mm from the side surface. From μm to an average pitch of 150 μm at the center, the intervals were sequentially reduced. Injection compression molding, injection molding machine [Toshiba Machine Co., Ltd., IS 350GS, screw diameter

Using 7 Omm, a mold clamping force of 3,430 kN], the molding temperature was 275 ° C, the mold temperature was 70 ° C, and the molding cycle time was 90 seconds.

The weight of the obtained light guide plate was 481 g, and the amount of deformation due to moisture absorption was 0.5 mm. A liquid crystal display was assembled by attaching four straight-tube cold-cathode fluorescent lamps, two on each of the two long sides of this light guide plate, and the brightness was measured. 20 ° C, the average luminance of the left light guide plate on the relative humidity of 65% is 3, 200 c dZm ^2, the luminance uniformity ratio is 86. /. It was. 60 ° C, the average luminance of the left light guide plate relative humidity of 90% is 3, 1 60 c dZm ^2, the luminance uniformity ratio was 86%.

Example 6

The 17-inch light guide plate was compressed in the same manner as in Example 1 except that a mold having a movable cavity surface was flat and a hemispherical projection was not formed on the light reflection surface. It was molded by a molding method.

The weight of the obtained light guide plate was 481 g, and the amount of deformation due to moisture absorption was 0.5 mm. A liquid crystal display was assembled by attaching a total of four straight tubular cold cathode fluorescent lamps, two each to the two long sides of this light guide plate, and measured the brightness. The average brightness of the light guide plate left at 20 ° C and a relative humidity of 65% was 2,500 cd / m ² , and the brightness uniformity was 75%. The average brightness of the light guide plate left at 60 ° C and 90% RH was 2, 4

It was 80 cd / i ² and the brightness uniformity was 75%.

Comparative Example 1

Injects a flat 17-inch light guide plate with a short side of 276.4 mm, a long side of 344. Omm, and a thickness of 8. Omm from a polymer resin with an alicyclic structure [ZEONOR 106 OR, Nippon Zeon Co., Ltd.] It was formed by a compression molding method. In the mold, hemispherical holes that form hemispherical protrusions with a diameter of 60 are formed on the surface of the fixed mold cavity that serves as the light reflecting surface of the light guide plate, with an average pitch of 300 μιη at a position 1 Omm from the light incident surface. The intervals were successively reduced to an average pitch of 150 μΐη at the center. Injection compression molding uses an injection molding machine [Toshiba Machine Co., Ltd., IS 350 GS, screw diameter 7 Omm, clamping force 3,430 kN], molding temperature 275 ° C, mold The test was performed at a temperature of 70 ° C. and a molding cycle of 90 seconds.

The weight of the obtained light guide plate was 7688 g, and the amount of hygroscopic deformation was 0.5 mm. A total of eight straight tube cold cathode fluorescent lamps, two each on the four side surfaces of this light guide plate, were attached to assemble a liquid crystal display device.After leaving at 20 ° C and 65% relative humidity, the brightness was reduced. It was measured. The average luminance was 6.00 cd / m ² and the luminance uniformity was 85%.

Comparative Example 2

A liquid crystal display with four L-shaped cold cathode fluorescent lamps, two each, was attached to the adjacent two long sides and short sides of the light guide plate obtained in Comparative Example 1. After assembling the device and leaving it at 20 ° C and 65% relative humidity, the luminance was measured. The average luminance was 4,800 cd / m ² and the luminance uniformity was 84%.

Comparative Example 3

From the polymer resin having an alicyclic structure obtained in Production Example 1, a short-sided 2 76.4 mm, long-sided 3 44.Omm ヽMolded by injection compression molding.

The mold has a hemispherical hole that forms a hemispherical projection with a diameter of 60 / ^ m on the movable cavity surface that is the light reflecting surface of the light guide plate, and an average pitch of 1 Omm from the light incident surface. The intervals were successively reduced from 00 μm to an average pitch of 150 μm at the center. Injection compression molding uses an injection molding machine [Toshiba Machine Co., Ltd., IS 350GS, screw diameter 7 Omm, clamping force 3,430 kN], molding temperature 275 ° C, mold temperature 70 ° C, molding cycle The test was performed for 90 seconds.

The weight of the obtained light guide plate was 768 g, and the amount of hygroscopic deformation was 0.5 mm. A liquid crystal display was assembled by attaching four straight-tube cold-cathode fluorescent lamps, two on each of the two long sides of this light guide plate, and the brightness was measured. The average brightness of the light guide plate left at 20 ° C and a relative humidity of 65% was 2,700 cd / m ² , and the brightness uniformity was 81%. 60 ° C, the average luminance of the left light guide plate to 90% relative humidity is ^2, 6 70 c dZm 2, the luminance uniformity ratio was 81%.

Comparative Example 4

A flat 17-inch light guide plate was formed by an injection compression molding method in the same manner as in Comparative Example 1, except that a methacrylic resin [Asahi Kasei Corporation, Delpet 70NHX] was used as the transparent resin.

The weight of the obtained light guide plate was 913 g, and the amount of deformation due to moisture absorption was 3 mm. A liquid crystal display was assembled by attaching a total of eight straight tubular cold cathode fluorescent lamps, two on each of the four side surfaces of this light guide plate, and was left at 20 ° C and 65% relative humidity before measuring the brightness. . The average brightness was 5,700 cd / m ² and the brightness uniformity was 84%. O

Comparative Example 5

A liquid crystal display was assembled by attaching four straight tubular cold cathode fluorescent lamps, two each, to the two side surfaces on the long side of the light guide plate obtained in Comparative Example 4, and measured the luminance. The average brightness of the light guide plate left at 20 ° C and 65% relative humidity was 2,600 cd / m ² , and the brightness uniformity was 80%. Induction at 60 ° C and 90% RH The average luminance of the light plate is 2, 3 4 0 cd / m 2, the luminance uniformity ratio is 7 4. /. Met. Table 1 shows the shapes of the light guide plates, the type of transparent resin, the presence or absence of convex patterns, the weight and the amount of hygroscopic deformation in Examples 1 to 6 and Comparative Examples 1 to 5, and the mounting state, degree, and brightness uniformity of the cold cathode fluorescent lamp. The degrees are shown in Table 2. Table 1

[Note] 1) MS: Methyl methacrylate-styrene copolymer

Table 2

Lamp 20 C 65% RH 60 C 90% RH Light incident

Number of surfaces Luminance uniformity Luminance uniformity Shape.Number (%) (%) Example 1 4 Straight pipe 8 7 200 8 8 1-Example 2 4 L-shaped tube 4 5 8 00 8- 7 1-Example 3 4 Straight pipe 8 6 6 00 86 ― ― Example 4 4 Straight pipe 8 6 8 00 8 7 1

Example 5 2 Straight pipe 4 3 200 8 6 3 1 6 0 8 6 Example 6 2 4 2 500 75 2480 7 5 Comparative example 1 4 Straight pipe 8 6000 8 5 ― ― Comparative example 24 L-shaped pipe 4 48 00 84 ― ― Comparative example 3 2 la.B '4 2 7 00 8 1 26 70 8 1 Comparative example 4 4 Straight pipe 8 5 700 84 ― ― Comparative example 5 2 Straight pipe 4 2600 80 2340 74

One As can be seen in Table 1, the light guide plates of Examples 1 to 4 in which the light reflection surface was a concave curved surface dome shape, and the thickness of the light guide plate was reduced as the light reflection surface became farther from the side surface serving as the light incidence surface. The light guide plates of Examples 5 to 6, which are formed slopes, are lighter in weight and lighter than the light guide plates of Comparative Examples 1 to 5 having a flat plate shape.

In the light guide plates of Examples 1-2 and Examples 4-5 and Comparative Examples 1-3 in which the transparent resin molding material is a resin having an alicyclic structure, the transparent resin molding material is a methylstyrene methacrylate copolymer. The light guide plate of Example 3 and the transparent resin molding material are methacrylic resin, and the amount of deformation by moisture absorption is smaller than that of the light guide plates of Comparative Examples 4 and 5, and the dimensional stability is excellent.

The light guide plates of Examples 1 to 4 in which the light reflecting surface has a concave curved surface are dome-shaped, and all four side surfaces are used as light incident surfaces, so that a large number of lamps can be mounted, and high brightness and uniform brightness The degree is good. On the other hand, the light guide plates of Comparative Examples 1 and 2 and Comparative Example 4 having a flat plate shape have lower brightness and lower brightness than the light guide plates of Examples 1 and 2 and The proportion is also poor.

The light guide plates of Examples 5 to 6 and Comparative Example 3, in which the transparent resin molding material was a resin having an alicyclic structure, had luminance and luminance even after being left in an environment of 60 ° C and a relative humidity of 90%. While the decrease in the uniformity was extremely slight, the light guide plate of Comparative Example 5 in which the transparent resin molding material was methacrylic resin had a brightness after being left in an environment of 60 ° C and a relative humidity of 90%. And the decrease in brightness uniformity is large.

Even though the light guide plates have the same shape, the light guide plate of Example 5 having a convex pattern on the light reflecting surface is superior in both luminance and brightness uniformity to the light guide plate of Example 6 having no convex pattern. ing. Industrial applicability

The light guide plate of the present invention can reduce the weight of the light reflecting surface as a dome-shaped concave curved surface or a slope whose thickness decreases as the distance from the side that becomes the light incident surface decreases, and the brightness and brightness uniformity are high. By molding using a polymer resin having an alicyclic structure, a light guide plate having excellent dimensional stability can be obtained.

Claims

The scope of the claims

1. A plate-shaped transparent resin molded body having a front surface, a back surface, and four side surfaces, wherein the front surface is a light emission surface, at least two opposing surfaces of the four side surfaces are light incidence surfaces, and the back surface is A light guide plate comprising: a light reflection surface formed of a surface formed so that a plate thickness decreases from a light incident surface toward a center.

2. All four side surfaces of the transparent resin molded body are light incident surfaces, and the back surface is a light reflecting surface composed of a curved surface formed so that the thickness decreases from the four side surfaces toward the center. The light guide plate according to 1.

3. The light guide plate according to claim 2, wherein all four side surfaces, which are light incident surfaces, are rectangular.

4. The light guide plate according to claim 2, wherein the transparent resin is a polymer resin having an alicyclic structure.

5. The transparent resin is a polymer resin having an alicyclic structure, two opposing surfaces of the four side surfaces are light incident surfaces, and the back surface decreases in thickness from the two light incident surfaces toward the center. The light guide plate according to claim 1, wherein the light guide plate is a light reflection surface composed of an inclined surface formed so as to have a minimum thickness at the center.

6. The light guide plate according to claim 1, wherein the light exit surface and the Z or light reflection surface have a fine uneven pattern.