JP5279015B2 - Light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of moire, maintain high luminance, and realize uniformity of luminance distribution on a light-irradiation face, of a light guide plate with a convex lens column formed. <P>SOLUTION: The light guide plate with at least one side-end face as a light-incident face, and one face crossing the light-incident face as a light-irradiating face has a plurality of convex lens columns extended in a direction nearly crossing the light-incident face formed at given alignment pitches at the light-irradiating face and the rear face opposed to it. Out of the alignment pitches of the convex lens columns formed at the light-irradiating face and those formed at the rear faces, provided the smaller is P1 and the larger is P2, a ratio (P1/P2) is to be 0.55-0.95. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a light guide plate, and more particularly, to a light guide plate suitable for a liquid crystal display device used in a personal computer, a liquid crystal monitor, a liquid crystal television, and the like, an illumination device for indoor and outdoor spaces, and a surface light source device that illuminates from the back of a signboard or the like. .

  A liquid crystal display device widely used in personal computers, mobile phones, and the like includes a surface light source device because the liquid crystal material does not emit light. As the surface light source device, an edge light type surface light source device is often used, and such an edge light type surface light source device generally includes a light guide plate that emits light from the light source to the liquid crystal display panel side. The light source plate includes a light source such as an LED (light emitting diode) or a CCFL (cold cathode tube) disposed on the side of the light source and a prism sheet that directs light emitted from the light guide plate toward the liquid crystal display panel. The light guide plate generally includes a transparent substrate and a light emission mechanism, and repeatedly and totally reflects light incident from the side inside the plate as a light emission mechanism provided on the light guide plate. The light is emitted to the liquid crystal display panel side by the light scattering pattern.

  As the light scattering pattern provided on the light guide plate, a diffusion gradation pattern obtained by dot printing of diffusion ink, or a concavo-convex pattern such as a prism or a grain (rough surface) formed on the light guide plate is used. When the image display size of a mobile phone, PDA, mobile personal computer or the like is a small size of 15 inches or less, a concavo-convex pattern is often used, and the concavo-convex pattern is formed by injection molding, overheating press, or the like.

  In addition, a light guide plate having convex lens rows and prism rows formed on the light exit surface or the back surface in order to increase the light use efficiency of the light guide plate in response to a decrease in light transmittance of the liquid crystal display cell due to high definition display. It is used.

  In recent years, surface light source devices using LED as a point light source as a light source have been used especially for mobile applications, as liquid crystal display devices are increasingly required to be thin from the viewpoint of environmental problems (mercury-free), portability and design. The light guide plate used in the surface light source device is also made thinner by 1.0 mm or less as the resin molding technology is improved. However, as a result, each of the liquid crystal display cell, the convex lens array and the prism array formed on the light emitting surface or the back surface of the light guide plate, the uneven pattern for the light scattering pattern, the diffusion gradation pattern by dot printing, the prism of the prism sheet, Moire (interference fringes) may occur due to interference between the two, which may hinder improvement in luminance uniformity and emission luminance over the entire light emitting surface.

  With respect to the reduction of moire (interference fringes), many techniques have been disclosed so far. For example, a method of suppressing the generation of moire by inclining a prism formed on the light exit surface of the light guide plate by 0 degree or more with respect to the entrance surface (Patent Document 1), disposed on the light exit surface of the light guide plate The method of preventing the occurrence of moire by making the ridges of the fine prisms of the prism sheet to be curved or uneven (Patent Document 2), arranging the dot print pattern of the light guide plate on a straight line intersecting the grooves of the prism sheet A method of preventing the generation of moire (Patent Document 3) and a method of reducing moire due to irregular periods of prism-like irregularities formed on the light exit surface of the light guide plate or the back surface thereof (Patent Document 4) are disclosed. ing.

JP 2005-123046 A JP 2003-337331 A JP 2005-285586 A Japanese Patent No. 3286239

In these prior arts, in a surface light source device having a relatively small image display size of 15 inches or less, such as a mobile phone for mobile use, a PDA, and a mobile personal computer, the light scattering pattern of the light guide plate and the prism pattern of the prism sheet are used. It is possible to prevent the occurrence of the moire caused by it.
By the way, if a thin light guide plate having a thickness of 1.0 mm or less used for a large surface light source device having an image display size of 15 inches or more is formed by injection molding or a hot press, the warp of the molded product becomes large and the thickness distribution varies. Becomes larger. Therefore, in general, such a light guide plate is extruded using an embossing roll having a convex lens array to form a sheet molded body, then cut into a predetermined size, the cut surface is polished, and then light scattering It is formed by forming a diffusion gradation pattern by dot printing as a pattern.
However, the prior art cannot sufficiently prevent the occurrence of moire due to the interference between the diffusion gradation pattern by dot printing and the convex lens array formed by the embossing roll.

As a method for solving this problem, a method of reducing the pitch of the convex lens array or a method of reducing the dot size of the diffusion gradation pattern of dot printing can be considered.
However, it is extremely difficult to form a convex lens array on a roll at a pitch of 40 μm or less in terms of the accuracy of the cutting method and the accuracy of resin molding by extrusion using an embossing roll.
In addition, diffusion gradation pattern dot printing is generally performed by screen printing, and the dot size of screen printing is determined by the mesh of the plate making used for screen printing and the particle size of the scattering material contained in the ink, and is produced stably. The dot size suitable for the above is 100 μm or more. In addition, with the diffusion gradation pattern, the dot size gradually increases as the distance from the light source increases, and eventually the dot size is 400% or more of the dot size near the light source, so it is difficult to reduce the dot size. is there.

An object of the present invention is to prevent the occurrence of moire in a light guide plate on which a convex lens array is formed, to achieve high luminance, and to achieve uniformity in luminance distribution on the light exit surface.
Another object of the present invention is to prevent the generation of moire even when a dot gradation printing gradation pattern is adopted as the light scattering pattern, thereby realizing high luminance and uniformity of luminance distribution.

  As a result of intensive studies to solve the above problems, the present inventors formed a plurality of rows of convex lens rows extending in a direction substantially orthogonal to the light incident surface on the light emitting surface and the back surface of the light guide plate at predetermined intervals. The present invention has been found by setting the arrangement pitch of the convex lens arrays on each surface to a predetermined ratio, thereby preventing moire caused by interference between the convex lens arrays and the light scattering pattern, and further improving the light emission luminance. I came to let you.

That is, the present invention has the following configuration.
A light guide plate having at least one side end surface as a light incident surface and one surface orthogonal to the light incident surface as a light exit surface,
On the back of each of the light emitting surface and facing the convex lens rows extending in the direction the light entrance surface and substantially perpendicular to a plurality of columns formed in a predetermined arrangement pitch,
Of the arrangement pitch of the convex lens array formed on the light exit surface and the arrangement pitch of the convex lens array formed on the back surface, when the smaller one is P1 and the larger one is P2, the ratio P1 / P2 is
A light guide plate of 0.55 to 0.95.

In the light guide plate of the present invention, the phase of the convex lens array is made random by setting the pitch of the convex lens arrays formed on both surfaces to a predetermined ratio, thereby effectively preventing the occurrence of moire due to interference with the light scattering pattern. It becomes possible to do. In particular, according to the present invention, it is possible to prevent the occurrence of moire even when the light scattering pattern is a diffusion gradation pattern formed by dot printing.
Therefore, according to the present invention, there is provided a light guide plate suitable for a display device used for various monitors such as a panel monitor and a television monitor for displaying an image signal, a display device used for a lighting device for indoor and outdoor spaces, a signboard, and the like. can do.

Embodiments of the light guide plate according to the present invention will be specifically described below.
The light guide plate of the present invention is composed of a transparent substrate, and at least one side end surface is a light incident surface, and one surface orthogonal to the light incident surface is a light emitting surface. In such a light guide plate, the light incident on the light guide plate propagates in the light guide plate with light having a distribution within the critical angle repeatedly totally reflected on the surface of the light guide plate. Of these light rays, light rays that hit the light scattering pattern provided on the back surface of the light guide plate are scattered or transmitted through the light scattering pattern, and the scattered light rays are emitted from the light exit surface of the transparent substrate. The transmitted light passes through the back surface, strikes the reflection sheet, is reflected, and is emitted from the light exit surface of the transparent substrate. A light scattering pattern is formed so that these emitted lights have a uniform emission intensity on the entire screen. Specifically, a density distribution is given to the light scattering pattern according to the distance from the light source, and thus, Uniformity of the luminance distribution within the exit surface is realized.
FIG. 7 shows a schematic diagram of an example of the light guide plate of the present invention. In FIG. 7, 71 is a light incident surface, 72 is a light emitting surface, 73 is a back surface facing the light emitting surface, and 74 and 75 are convex lens arrays.

<Disposition and pitch of convex lens array>
In the present invention, measurement evaluation and examination on the uniformity of the luminance distribution of the light guide plate were performed using the uniformity (ΔB) represented by the following equation (1) as a measure of the uniformity of the luminance distribution.
When the luminance measurement values for the measurement points P1 to P25 shown in FIG. 1 are B1 to B25, the degree of uniformity (ΔBi) at each measurement point is expressed by the following equation (1).
ΔBi = Bi / B0 × 100% (i = 1 to 25) (1)
B0: Light guide plate center luminance

An edge light type surface light source device used for a liquid crystal display or the like is required to have high uniformity of brightness, but in addition, the light guide plate center luminance (B0) is the luminance on the light incident surface side (B1 to 25). Higher is also required.
If a convex lens array is formed on the light exit surface of the light guide plate in a direction parallel to the light incident surface, light that exceeds the ridge line of the convex lens array out of the light reaching the ridge line of the convex lens array is refracted. The light beam is emitted outside the light guide plate and reflected within the critical angle, but the light beam reflected by the ridge line of this convex lens array has a large incident angle on the opposite surface, and there is little light beam within the critical angle on the opposite surface. As a result, light rays entering from the light incident light surface almost radiate on the light incident light surface side, and the light incident surface side luminance (B1 to 25) is higher than the light guide plate center luminance (B0). The uniformity (ΔBi) of the measurement points is 100% or more, and the uniformity of the luminance distribution on the light exit surface is deteriorated.
Therefore, the convex lens array needs to be formed such that its ridge line is in a direction perpendicular to the light incident surface of the light guide plate. If the convex lens array is formed in this direction, the function of guiding the light beam entering from the original incident light surface of the light guide plate in the traveling direction is not hindered, and the uniformity (ΔBi) of each measurement point is set to 100. % Or less.

  If a convex lens array is formed only on either the light exit surface or the back surface of the light guide plate, the difference in surface area between the front and back surfaces of the light guide plate increases, and the light guide plate is warped due to environmental temperature and humidity. Regardless of the direction of the warp (irregularity), the liquid crystal unit is pushed up, and therefore the occurrence of warp affects the liquid crystal screen display, which is not preferable. In the present invention, by forming convex lens rows on both the light exit surface and the back surface of the light guide plate, the difference in surface area between the front and back surfaces of the light guide plate is reduced, the occurrence of warpage due to environmental temperature and humidity is prevented, and the liquid crystal screen display The impact is reduced.

  The light guide plate of the present invention has a light scattering pattern on the back surface, that is, the surface facing the light emitting surface. The light scattering pattern is for correcting the angle of light so that a sufficient amount of light entering from the light incident surface reaches the light exit surface. When a diffusion gradation pattern by dot printing is used as the light scattering pattern, for example, constant from the end of the light guide plate surface to the center, or from one end to the other (from the light source to the farthest part of the light source) This is given by providing a dot pattern in which a large number of dots having a constant size are added, or a gradation in which the number of dots of a certain size is gradually increased, and a dot pattern in which a large number of circles, squares, and the like continue.

The ratio of the arrangement pitch of the convex lens rows formed on the light exit surface of the light guide plate to the arrangement pitch of the convex lens rows formed on the back surface thereof is P5 and P1 / P2 is 0.55 where P1 is the larger one. It should be in the range of ~ 0.95. As a result, the phase of the valleys of the convex lens arrays on both sides is randomly arranged, and the moire generated by the interference between the light scattering pattern arranged at a constant pitch or a constant size and the unevenness of the convex lens array is made invisible. be able to.
Here, the arrangement pitch of the convex lens rows refers to the corresponding positions (for example, vertices) of the cross sections of the two adjacent convex lens rows in the cross section that appears when the light guide plate is cut along a plane parallel to the light incident surface. The distance between.
There is no limitation on the arrangement pitch of the convex lens array on the light exit surface and the convex lens array on the back surface, and it can be set to 40 to 200 μm, for example. Further, the arrangement pitch of the convex lens rows on the light exit surface and the arrangement pitch of the convex lens rows on the back surface may be larger as long as the ratio is within the range of the present invention.

<Convex lens array>
The light emitting surface and the convex lens array formed on the back surface of the light guide plate of the present invention refer to convex portions extending in one direction. There is no limitation on the height of the convex lens array (the difference between the height of the apex and the height of the valley), and the height can be, for example, 1 to 200 μm.
The shape of the cross section of the convex lens array parallel to the light incident surface is not limited as long as it is a convex shape. A preferred specific example is a shape in which the apex angle tip portion of the substantially isosceles triangle is formed in an arc shape, and the apex angle of the approximately isosceles triangle is preferably in the range of 50 to 150 degrees. When the apex angle of the substantially isosceles triangle is 50 degrees or more, the emitted light from the light guide plate is collected, and the luminance as the surface light source device can be improved. In addition, when the angle is 150 degrees or less, it is possible to impart an appropriate spread of the emitted light distribution according to the target observation angle range. In the case of a convex lens array on the light exit surface, the apex angle of the substantially isosceles triangle is preferably 50 to 100 degrees, and in the case of a convex lens on the back side of the light exit surface, 50 to 80 degrees, or 100 to 150 degrees. It is preferable to do.
By forming the apex tip of the isosceles triangle of the cross-sectional shape of the convex lens array in the shape of an arc, light is scattered from the vicinity of the ridge line of the convex lens array to prevent generation of bright lines, and light emitted from the light guide plate The distribution is improved, the light use efficiency is improved, and the precise formation of the fine convex lens array on the light guide plate at the time of manufacture can be facilitated. In addition, the prism sheet is caused by friction and pressure with the prism sheet, the diffusion sheet, and the reflection sheet that are arranged in contact with the front end of the isosceles triangle formed on the light guide plate due to long-time vibration such as transportation and carrying. In addition, it is possible to prevent the diffusion sheet and the reflection sheet from being damaged or the tip portion of the approximately isosceles triangle shape from being damaged, thereby improving the durability of the light guide plate. The ratio (r / P) between the radius of curvature (r) of the arc at the apex tip portion and the pitch (P (P1 or P2)) of the convex lens array is preferably 0.1-5.
Moreover, as a specific example of another cross-sectional shape of the convex lens array, a shape composed of an elliptical arc or a part of an arc can be mentioned. In this case, although the degree of light collection is reduced, the luminance distribution is widened and the viewing angle that appears bright can be widened. Therefore, this is a preferable form suitable for a large screen with a wide observation direction.
It is preferable that the cross-sectional shape of the convex lens array does not change in the extending direction.

<Crosslinked resin fine particles constituting the mat surface and laminated structure>
In the present invention, when a mat surface (rough surface) is formed on at least one surface of the light guide plate on which the convex lens array is formed, the light incident from the side end surface of the light guide plate enters the mat surface and is diffused, or the mat. Since the amount of light rays that reach the surface exceeds the critical angle and are radiated from the light exit surface of the light guide plate to the outside increases, the luminance is preferably increased. The mat surface is preferably formed in the entire area of the surface of the convex lens array.
As a method for forming the matte surface (rough surface), for example, chemical etching, sand blasting method using glass beads; a method in which a transparent substrate is heated and pressed using a die having a concavo-convex pattern formed by laser processing, etc .; transparent A method of applying an active energy ray-curable resin on a substrate and curing it by irradiation with active energy rays to transfer a concavo-convex pattern; a method of forming an uneven pattern; a light guide plate by chemical etching, sandblasting, laser processing, etc. Examples include a method of directly processing; a method of providing a mat layer containing crosslinkable resin fine particles. Among them, a method of providing a mat layer containing crosslinkable resin fine particles is preferable, and in particular, multiple extrusion of a transparent thermoplastic resin composition for forming a mat layer containing transparent resin fine particles and a transparent thermoplastic resin for forming a transparent substrate. A method of forming, laminating and integrally forming is preferable.

Examples of the crosslinked resin fine particles contained in the mat layer include organic fine particles such as crosslinked methacrylic resin fine particles, crosslinked styrene resin fine particles, crosslinked MS resin fine particles, and crosslinked siloxane-based fine particles. Further, hollow cross-linked fine particles made of a highly transparent resin material such as methacrylic resin, styrene resin, and MS resin are also included.
Particularly preferred among these are crosslinked methacrylic resin fine particles. The average particle diameter of the crosslinked methacrylic resin fine particles is preferably in the range of 2 μm to 30 μm, more preferably in the range of 5 μm to 20 μm.

Moreover, when forming the mat | matte layer formed by a multilayer extrusion molding method, the range of the thickness is 5 micrometers-200 micrometers normally, Preferably it is 10-100 micrometers, More preferably, it is the range of 10-80 micrometers, More preferably, it is the range of 15-50 micrometers. Is within. The content of the crosslinked resin fine particles dispersed in the transparent thermoplastic resin used for the matte layer is 0.05 to 10 parts by weight, preferably 0.05 to 5 parts by weight with respect to 100 parts by weight of the transparent thermoplastic resin. Parts, more preferably 0.1 to 3 parts by weight.
The manufacturing method of the transparent thermoplastic resin composition for forming the mat layer is not particularly limited, and can be manufactured by a well-known and usual method. For example, there is a method in which transparent thermoplastic resin and crosslinked resin fine particles are mixed by a well-known and commonly used mixing method such as a Henschel mixer, a super floater, and a tumbler, mixed by these methods, and then granulated using an extruder. The temperature of the extruder can be arbitrarily set depending on the type of thermoplastic resin used. For example, in the case of a methacrylic resin, it is around 180-260 degreeC.

<Manufacturing method of light guide plate>
The method for forming a plurality of convex lens rows on the surface of the light guide plate of the present invention is not particularly limited. For example, a method of forming a mold with a convex lens pattern formed by chemical etching, via cutting, laser processing, etc., and heating and forming a transparent substrate, and applying an active energy ray curable resin on the transparent substrate to activate A method of forming a convex lens pattern by forming and curing by irradiation of energy rays, a method of forming by injection molding, a method of directly processing the light guide plate by etching, cutting by cutting, laser processing, etc. are preferable, This is an extrusion method that enables stable mass production. Specifically, an extrusion molding method using an embossing roll having a convex lens array shape is exemplified, and a multilayer extrusion molding method is more preferred.
According to the extrusion molding method, a uniform light guide plate having no moiré due to interference of the convex lens rows formed on both surfaces of the light guide plate is obtained without any slight deviation of the ridgelines or valleys of the convex lens rows formed on both surfaces. I can do it.

FIG. 2 shows a schematic diagram of a multilayer extruder, and a method for forming a convex lens array by a multilayer extrusion molding method will be described.
When a transparent substrate having a convex lens array is formed by a multilayer extrusion molding method, materials having a difference in viscosity are used as the material (transparent thermoplastic resin) of the layer 22 and the base material layer 21 for forming the convex lens array. preferable. Specifically, a transparent thermoplastic resin having a low viscosity is used for the layer 22 for forming the convex lens array, and a convex lens array shape is formed on the embossing roll 26 on the transparent thermoplastic resin. At that time, the base material layer 21 made of a transparent thermoplastic resin having a higher viscosity than the transparent thermoplastic resin of the layer 22 serves as a core to support the entire molten sheet. In this way, the molten sheet that has been easily processed into the convex lens array shape is fed between the embossing roll 26 and the embossing roll 27, and the convex lens array shape is applied to both surfaces by the embossing roll 26 and the embossing roll 27.
The transparent thermoplastic resin forming the layer 22 for forming the convex lens array may be any one having a lower viscosity than the transparent thermoplastic resin of the base material layer 21 and is different from the transparent thermoplastic resin different from the base material layer 21. It may be a resin. The layer thickness of the layer 22 for forming the convex lens array is appropriately selected depending on the application and the plate thickness, but is usually preferably in the range of 10 μm to 500 μm.

<Light scattering fine particles>
Light scattering particles may be dispersed in the transparent substrate constituting the light guide plate in the present invention. As the light scattering fine particles to be dispersed, known fine particles such as aluminum oxide and titanium dioxide can be preferably used. Among these, titanium dioxide fine particles having an average primary particle diameter in the range of 0.24 μm to 0.3 μm are preferable. When the primary particle diameter is within this range, the light incident on the light guide plate from the light source is scattered by the fine particles, and a phenomenon in which the emitted light color tone is different between the vicinity of the light source and the central portion of the plate, so-called color tone unevenness, hardly occurs. Also, light loss due to back reflection or the like is small. Furthermore, when the primary particle diameter is within this range, light incident from the light source can be efficiently scattered to the exit surface side. Thereby, the balance of the improvement effect of light-emitting luminance and the suppression of color tone unevenness in the exit surface can be improved. Since titanium dioxide has a high refractive index, it has a characteristic that high brightness can be obtained even if the concentration relative to the transparent thermoplastic resin is relatively low, but there is a tendency for uneven color tone to become severe if the particle size is too large or too small. . When the primary particle diameter is 0.2 μm or less, blue light having a relatively short wavelength in the wavelength range of visible light is scattered by the fine particles, so that the color unevenness of the light exit surface tends to increase. Further, if the primary particle diameter is 0.4 μm or more, the light scattering effect may be lowered, and the amount of added fine particles must be increased in order to increase the luminance of the light guide plate. As the amount of added fine particles increases, the amount of light transmitted through the fine particles increases, and the fine particles absorb the light in the visible light range, so the light transmitted through the fine particles changes color before transmission, Color unevenness increases.
Next, the amount of fine particles dispersed in the transparent thermoplastic resin substrate is preferably 0.01 to 20 ppm, more preferably 0.05 to 10 ppm, based on the weight of the transparent thermoplastic resin. Preferably it is 0.1-4 ppm. When the amount of the fine particles is within a range of 0.01 ppm to 20 ppm, for example, in a relatively large liquid crystal display device of 15 inches or more, even if the light guide plate does not give a light scattering pattern on the back surface of the light exit surface, The incident light from the light source has no difference between the luminance in the vicinity of the light source and the luminance at the farthest position from the light source, and the entire light exit surface has a uniform light distribution. Therefore, even if the light scattering pattern for correcting the emitted light is applied to the back surface of the light emitting surface of the light guide plate, the portion farthest from the light source is not darkened, and the light distribution on the light emitting surface is appropriately balanced. Can do. Furthermore, when the proportion of fine particles is 20 ppm or less, the change in the color tone in the vicinity of the light guide plate light source is small due to scattering, and the color tone distribution of the emitted light in the light exit surface can be suppressed.
Examples of the crystal structure of titanium dioxide include, but are not limited to, a rutile type and an anatase type.

<Transparent thermoplastic resin constituting the light guide plate>
In the present invention, a specific example of a material constituting the transparent substrate of the light guide plate is a transparent thermoplastic resin. Specific examples of the transparent thermoplastic resin include methacrylic resin, polycarbonate resin, styrene resin, cyclic olefin resin, and amorphous polyester. Particularly preferred is a methacrylic resin.

Specific examples of the methacrylic resin include a copolymer of 70% by weight or more of methyl methacrylate or ethyl methacrylate and a monomer copolymerizable therewith. Examples of the monomer copolymerizable with methyl methacrylate or ethyl methacrylate include, for example, butyl methacrylate, ethyl methacrylate, methyl methacrylate, propyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-ethylhexyl methacrylate, and the like. Methacrylic acid esters; acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, 2-ethylhexyl acrylate; unsaturated acids such as methacrylic acid and acrylic acid However, it is not limited to these. Further, the polymerization method is not limited at all.
Other specific examples of the methacrylic resin include a heat-resistant methacrylic resin, a low hygroscopic methacrylic resin, and an impact-resistant methacrylic resin. Specific examples of the impact-resistant methacrylic resin include, for example, those obtained by blending a rubber elastic body with a methacrylic resin. The rubber elastic bodies are disclosed in JP-A-53-58554, JP-A-55-94917, JP-A-61. -32346 and the like.

  The polycarbonate resin is a polymer derived from a dihydric phenol-based compound typified by bisphenol A, and the method for producing the polycarbonate resin is not particularly limited, and the phosgene method, the transesterification method or the solid phase weight is not limited. What was manufactured by well-known and usual methods, such as a legal method, can be used.

The cyclic olefin resin is a polymer containing a cyclic olefin skeleton in a polymer chain, such as norbornene or cyclohexadiene, or a copolymer containing these, and belongs to an amorphous thermoplastic resin. The manufacturing method is not particularly limited. For example, as cyclic olefin resins mainly composed of norbornene, JP-A-60-168708, JP-A-62-252406, JP-A-2-133413, JP-A-63-145324, JP Resins described in JP-A-63-264626, JP-A-1-240517, JP-B-57-8815 and the like can be used. Moreover, you may add a soft polymer as needed.
For example, an olefin-based soft polymer composed of α-olefin, an isobutylene-based soft polymer composed of isobutylene, a diene-based soft polymer composed of conjugated dienes such as butadiene and isoprene, and a cyclic olefin-based soft composed of a cyclic olefin such as norbornene and cyclopentene. Polymer, organopolysiloxane-based soft polymer, soft polymer composed of α, β-unsaturated acid and its derivative, soft polymer composed of unsaturated alcohol and amine or acyl derivative or acetal thereof, polymer of epoxy compound, Fluorine rubber is exemplified.

  Styrenic resins include homopolymers, copolymers, or polymer blends obtained from these polymers and other resins, which contain styrene as an essential component. In particular, polystyrene, AS resin which is a copolymer resin of acrylonitrile and styrene, and MS resin which is a copolymer resin of methacrylic acid ester and styrene are preferable. Furthermore, transparent reinforced polystyrene in which rubber is distributed in the styrene resin phase can also be preferably used. The manufacturing method of a styrene resin can use what was manufactured by the well-known and usual method.

Amorphous polyester means aliphatic glycols such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, hexamethylene glycol; alicyclic glycols such as cyclohexanedimethanol; bisphenol, 1,3-bis Aromatic dihydroxy compounds such as (2-hydroxyethoxy) benzene and 1,4-bis (hydroxyethoxy) benzene; or dihydroxy compound units selected from two or more of these, terephthalic acid, isophthalic acid, 2,6- Aromatic dicarboxylic acids such as naphthalene dicarboxylic acid; Aliphatic dicarboxylic acids such as oxalic acid, adipic acid, sebacic acid, succinic acid, and undecadicarboxylic acid; Alicyclic dicarboxylic acids such as hexahydroterephthalic acid, or these two types Zikaru selected from the above Among the polyester formed from the phosphate unit is of the non-crystalline.
As the method for producing the amorphous polyester, those produced by a well-known and commonly used method can be used. Commercially available brands that can be easily obtained as amorphous polyester include KODAR PETG and PCTA, which are products of Eastman Kodak Company.

Further, in the present invention, coloring due to ultraviolet rays generated when the light source disposed along the side end surface is a fluorescent tube is suppressed, so that the color tone on the monitor screen is always constant even when used for a long time. For the purpose of suppressing the occurrence of color unevenness, and further for the purpose of suppressing the decrease in luminance, an ultraviolet absorber can be added to the transparent thermoplastic resin substrate as necessary.
<Addition of UV absorbers, etc.>
Examples of the ultraviolet absorber include 2- (5-methyl-2hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α′dimethylbenzyl) phenyl] benzotriazole, 2- ( Benzotriazole ultraviolet absorbers such as 3,5-di-t-amyl-2-hydroxyphenyl) benzotriazole; 2-hydroxy-4-methoxybenzophenone, 2,2′-dihydroxy-4-methoxybenzophenone, 2- Benzophenone UV absorbers such as hydroxy-4-n-octoxybenzophenone; salicylic acid UV absorbers such as phenyl salicylate and 4-tbutylphenyl salicylate, and one or more selected from these 30 to 2000 ppm of UV absorber for the transparent thermoplastic resin, Mashiku can be added at a concentration of 80～500Ppm.

  Furthermore, in the present invention, for example, a glycerol fatty acid ester such as glycerol monostearate, a higher alcohol such as stearyl alcohol; a higher fatty acid such as stearic acid; It is possible to add antioxidants such as phosphites and phosphites. These are used within a range that does not impair the object of the present invention, and are usually preferably added at a concentration of 5000 ppm or less.

<Addition of light scattering fine particles>
Examples of a method for obtaining a resin composition containing fine particles include the following methods.
1. A method of producing a resin composition by uniformly dispersing fine particles in an organic liquid using, for example, an ultrasonic generator. The organic liquid referred to here is a general organic liquid, a polymerizable monomer constituting a transparent thermoplastic resin, or the like, and the fine particles hardly dissolve and swell, and can be uniformly dispersed. It is not limited at all. You may mix and use several types of organic liquids in arbitrary ratios by the dispersion state of microparticles | fine-particles. Examples of the organic liquid include ketones such as acetone and methyl ethyl ketone, aromatics such as xylene and toluene, and alcohols such as methanol and ethanol. As the polymerizable monomer, for example, when the transparent thermoplastic resin is a methacrylic resin, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, 2-ethylhexyl methacrylate, etc. Acrylic acid esters such as methacrylic acid esters, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate and 2-ethylhexyl acrylate; unsaturated acids such as methacrylic acid and acrylic acid It is done. When the resin composition is melt-kneaded with an extruder, the mixing ratio between the fine particles and the organic liquid may be arbitrarily determined in consideration of the dispersibility of the fine particles. For example, the fine particles are in the range of 0.001 to 80 parts by mass with respect to 100 parts by mass of the organic liquid. Further, the mixing ratio of the dispersion and the transparent thermoplastic resin can be arbitrarily determined in consideration of the handling property in the mixing extrusion process. For example, it is preferable that it is the range of 0.001-10 mass parts with respect to 100 mass parts of transparent thermoplastic resins.

2. Fine particles are uniformly dispersed in a syrup containing a monomer or a partial polymer constituting a transparent thermoplastic resin using, for example, an ultrasonic generator, and then polymerized by a casting method by a known method. The amount ratio between the fine particles and the raw material monomer in which the fine particles are dispersed can be arbitrarily determined from the dispersibility, the viscosity at the time of preparation, the handling property, and the like. Further, the other conditions are not particularly limited, and well-known and usual conditions of the casting method can be applied.

3. A master batch pellet in which high-concentration fine particles are contained in the transparent thermoplastic resin composition is prepared, and diluted with a transparent thermoplastic resin to a desired concentration at the time of molding. As a guide, it is preferable to disperse the fine particles into a transparent thermoplastic resin composition 5 to 300 times the fine particles to be finally included in the light guide plate to form pellets.
In the above method, examples of the ultrasonic generator used for dispersing the particles include a commercially available ultrasonic cleaner or an ultrasonic stirrer. For example, an ultrasonic cleaner having an ultrasonic frequency of 28 KHz to 100 KHz is generally used. The irradiation time by the ultrasonic generator can be arbitrarily set according to the dispersion state of the fine particles, but it is generally preferable to irradiate for 1 minute to 60 minutes.
In order to melt-knead and shape the resin composition thus obtained, for example, an extruder is generally used. When melt-kneading with an extruder, the resin composition can be mixed with a transparent thermoplastic resin using, for example, a well-known and conventional apparatus such as a Henschel mixer, a super floater, or a tumbler. Examples of the extruder for melt-kneading the mixture include a single-screw or twin-screw extruder, but it is preferable to use a twin-screw extruder because secondary aggregation of fine particles can be prevented. Moreover, in order to remove the volatile component of the organic liquid used for dispersion of the fine particles, it is preferable to perform degassing under reduced pressure at the vent port. The pressure at this time is preferably 300 Torr or less. Furthermore, the temperature of the extruder can be arbitrarily set depending on the type of transparent thermoplastic resin used. For example, in the case of a methacrylic resin, it is around 180-260 degreeC.

<Light diffusion treatment (formation of light scattering pattern)>
The light guide plate of the present invention has a light scattering pattern having gradation toward the direction away from the light source from the rear surface of the light output surface or the side end surface where the light source is arranged on the light output surface in order to make the distribution of the emitted light uniform. Can be formed.
Examples of the light scattering pattern include a dot or uneven shape that is a gradation pattern that gradually increases in area as it moves away from the position where the light source is placed, or a dot or uneven shape that is the same size as the distance from the light source. There is a gradation pattern that narrows. In this case, examples of the shape of the dots and irregularities include a circle and a square, and the size is about 0.1 to 2.0 mm.
When forming a gradation pattern by dot printing, the specific method is not particularly limited, and it is made by screen printing using a white or semi-transparent ink mixed with titanium oxide, silica, etc. by making a plate-like gradation pattern. There are a method of applying to the back surface of the light exit surface of the light guide plate, and a method of performing press working or injection molding using a mold having a gradation pattern.

<Shape of light incident end face>
In order to increase the spread of light in the light guide plate on the light incident side end surface of the light guide plate, it is preferable to form a fine prism row or roughen the surface. Examples of a method for forming a fine prism array include a method of cutting with a milling tool and the like, and examples of a method for forming a rough surface include a method for polishing with a grindstone, sandpaper, buff, and the like, and a method for blasting. Blasting particles used for blasting include spherical particles such as glass beads and polygonal particles such as alumina beads, but the use of polygonal particles has a greater effect of spreading light. It is preferable because the surface can be formed. An anisotropic rough surface can also be formed by adjusting the processing direction of cutting or polishing. This rough surface processing can be directly applied to the light incident end face of the light guide plate.

  Although there is no restriction | limiting in particular in the light source which supplies light to the light-incidence end surface of a light-guide plate, For example, point light sources, such as LED, can also be arrange | positioned and used suitably. In addition to the point light source, one or a plurality of linear light sources such as a cold cathode tube can be arranged on the light incident end face.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

<Method for measuring and evaluating average luminance of light guide plate>
Using the sample light guide plate, the edge light type surface light source device shown in FIG. 3 was prepared and evaluated.
One side end face of the light guide plate 33 cut out to have a length of 332 mm and a width of 214 mm is a light incident end face, and 36 LEDs (NSSW108T; Nichia) are used as a light source so as to face the side end face. Chemical Industries) were installed at intervals of 9 mm. A light reflecting sheet 31 (Ray White 75; manufactured by Kimoto), a light guide plate 33, a light diffusing sheet 34 (light diffusing sheet D121; manufactured by Tsujiden) are stacked in this order, and a prism sheet 36 in which a plurality of prism rows are formed in parallel. (BEF2; manufactured by Sumitomo 3M) is placed so that the ridge line of the prism row is substantially parallel to the light incident end face, and a prism sheet 35 (BEF2; manufactured by Sumitomo 3M) is placed thereon, and the ridge line of the prism row is substantially the same as the light incident end face. They were placed so as to be orthogonal. After 30 minutes have passed since the LED light source 11 was turned on, a luminance meter (BM-7Fast / viewing angle 1 degree setting; manufactured by Topcon) installed at a position 0.5 m away from the light emitting surface was used to measure 25 points on the light emitting surface. The brightness of was measured. As shown in FIG. 1, 25 points were divided into a total of 25 sections by dividing the entire exit surface into 5 sections and 5 sections, and the center of each section was used as a measurement point. The average luminance was calculated from the obtained measurement values.

<Observation of moire>
An edge light type light source device is produced in the same manner as the luminance measurement except that the light diffusion sheet 31 and the prism sheets 36 and 35 are not laminated, the LED light source 11 is turned on, and the diffusion gradation pattern printed from the light emitting surface side The presence or absence of moire generated by the interference between the lens 32 and the convex lens array formed on the light guide plate was visually observed.

<Production of methacrylic resin α pellet>
1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane was added to a monomer mixture consisting of 79.9% by weight methyl methacrylate, 5.1% by weight methyl acrylate, and 15% by weight ethylbenzene. 150 ppm and 300 ppm of n-octyl mercaptan were added and mixed uniformly. This mixed solution was continuously supplied to a sealed pressure-resistant reactor having an internal volume of 10 liters, and polymerization was performed with stirring at an average temperature of 130 ° C. and an average residence time of 2 hours. This resin was continuously sent to a storage tank connected to the reactor, and after removing volatile components under reduced pressure, it was continuously transferred to an extruder in a molten state. Using a feed pump from the side part of the extruder, a predetermined amount of an ultraviolet absorber <2- (5-methyl-2hydroxyphenyl) benzotriazole> heated and melted at 140 ° C. is added, and the resulting resin composition is obtained. By extrusion, a pellet of methacrylic resin α was obtained. As a result of analyzing this pellet, the copolymerization rate was 94.0% by weight of methyl methacrylate unit, 6.0% by weight of methyl acrylate unit, and the content of 2- (5-methyl-2hydroxyphenyl) benzotriazole The amount was 150 ppm.

[Example 1]
A substantially prism-shaped convex lens array 1 having a cross-sectional shape of a substantially isosceles triangle with an apex angle of 80 degrees, the apex angle of which is a part of an arc having a curvature radius of 40 μm, is formed at a pitch of 90 μm (P1). And a convex lens array having a substantially prism shape, the cross-sectional shape of which is a substantially isosceles triangle having a vertex angle of 100 degrees and whose apex angle tip portion is a part of an arc having a curvature radius of 40 μm. The embossing roll 27 and the polishing roll 25 manufactured so that 2 is formed with a pitch of 100 μm (P2) were arranged in the same manner as the apparatus shown in FIG.
Using methacrylic resin pellets α as the substrate resin, extrusion was performed using an extruder 23 with 90 mmφ and L / D = 32. The lip opening and the clearance between the polishing roll 25 and the embossing roll 26 were adjusted so that the thickness of the obtained extruded plate was 0.8 mm, and the temperature of the extruder and the die was 250 to 260 ° C. Thus, an extruded plate having a width of about 400 mm and having convex lens arrays on both sides was obtained.
From the obtained extruded plate, a plate having a width of 214 mm and a length of 332 mm was cut out using a circular saw so that the convex lens array was perpendicular to the length direction. Subsequently, the cut surface of the cut out plate was polished using a precision polishing machine (PLA-BEAUTY: manufactured by Megaro Technica), further subjected to buff polishing, finished to a mirror surface, and a light guide plate substrate was obtained.
As a light diffusion process on the substrate of the obtained light guide plate, the dot diameter φ on the light incident end face side is 100 μm, and the dot diameter on the opposite face side of the light incident end face is φ400 μm. Screen printing plate with a smooth dot gradation, using Matte Medium SR931 (manufactured by Mino Group) as ink, and light scattering pattern (dot printing by screen printing method on the surface where the convex lens array 2 of the light guide plate is formed And a light guide plate having a pitch ratio P1 / P2 of 0.9 between the convex lens rows formed on both sides was obtained. The cross section is shown in FIG.
When the obtained light guide plate was visually evaluated for moire and measured for luminance, no moire was observed, and the average luminance was 3000 cd / m ² .

[Example 2]
A substantially prism-shaped convex lens array 1 having a cross-sectional shape of a substantially isosceles triangle having a vertex angle of 100 degrees and having a vertex part of a vertex having a radius of curvature of 20 μm is formed at a pitch of 50 μm (P1). And a convex lens array having a substantially prism shape, the cross-sectional shape of which is a substantially isosceles triangle having an apex angle of 100 degrees, the tip end portion of which is formed by a part of an arc having a curvature radius of 80 μm. The pitch ratio P1 / P2 of the convex lens arrays formed on both surfaces is 0. 0 in the same manner as in Example 1 except that the embossing roll 27 manufactured so that 2 is formed with a pitch of 80 μm (P2) is used. A light guide plate 625 was obtained.
When the obtained light guide plate was observed and measured in the same manner as in Example 1, no moire was observed, and the average luminance was 3050 cd / m ² .

[Example 3]
A substantially prism-shaped convex lens array 1 having a cross-sectional shape of a substantially isosceles triangle having a vertex angle of 100 degrees and a tip portion of the vertex having a radius of curvature of 40 μm is formed at a pitch of 100 μm (P1). And a convex lens array 2 having a substantially prism shape, the cross-sectional shape of which is a substantially isosceles triangle having an apex angle of 100 degrees, the tip end portion of which is formed by a part of an arc having a curvature radius of 180 μm. Is formed on both sides in the same manner as in Example 1 except that a diffusion gradation pattern is formed on the surface on which the convex lens array 1 is formed, using an embossing roll 27 manufactured so that is formed at a pitch of 180 μm (P2). A light guide plate having a convex lens array pitch ratio P1 / P2 of 0.6 was obtained.
When the obtained light guide plate was observed and measured in the same manner as in Example 1, no moire was observed, and the average luminance was 3100 cd / m ² .

[Comparative Example 1]
The substantially prism-shaped convex lens array 1 whose cross-sectional shape is a substantially isosceles triangle having a vertex angle of 100 degrees and whose apex angle tip portion is formed by a part of an arc having a curvature radius of 40 μm is formed at a pitch of 100 μm (P1). And a convex lens array 2 having a substantially prism shape, the cross-sectional shape of which is a substantially isosceles triangle having a vertex angle of 100 degrees and whose apex angle tip portion is a part of an arc having a curvature radius of 40 μm. The pitch ratio P1 / P2 of the convex lens arrays formed on both surfaces is 1.0 in the same manner as in Example 1 except that the embossing roll 27 manufactured to have a pitch of 100 μm (P2) is used. A light guide plate was obtained.
When the obtained light guide plate was observed and measured in the same manner as in Example 1, moire was observed and the average luminance was 2980 cd / m ² .

[Comparative Example 2]
A substantially prism-shaped convex lens array 1 having a cross-sectional shape of a substantially isosceles triangle having an apex angle of 160 degrees, the apex angle of which is a part of an arc having a curvature radius of 20 μm, is formed at a pitch of 50 μm (P1). An embossing roll 26 manufactured as described above, and a substantially prism-shaped convex lens array 2 having a substantially isosceles triangle having an apex angle of 100 degrees, the cross-sectional shape of which is a part of an arc having a vertex radius of curvature of 40 μm. The pitch ratio P1 / P2 of the convex lens arrays formed on both sides is 0.5 in the same manner as in Example 1 except that the embossing roll 27 manufactured to have a pitch of 100 μm (P2) is used. A light guide plate was obtained. The cross section is shown in FIG.
When the obtained light guide plate was observed and measured in the same manner as in Example 1, moire was observed and the average luminance was 2940 cd / m ² .

[Comparative Example 3]
A substantially prism-shaped convex lens array 1 having a cross-sectional shape of a substantially isosceles triangle having an apex angle of 80 degrees and having a apex angle tip portion formed by a part of an arc having a curvature radius of 80 μm is formed at a pitch of 250 μm (P1). Example where the embossing roll 26 manufactured as described above was used, a polishing roll was used as the embossing roll 27, and a light scattering pattern was formed on the polishing roll surface (the surface opposite to the surface on which the convex lens array 1 was formed). 1 to obtain a light guide plate having a convex lens array formed only on one side.
When the obtained light guide plate was observed and measured in the same manner as in Example 1, moire was observed and the average luminance was 2790 cd / m ² .

<Preparation of raw material pellet A>
Titanium dioxide (average primary particle size: 0.29 μm) 0.15 g was mixed with 20 g of mixed organic liquid xylene: methanol = 3: 1 using an ultrasonic cleaner (US-4 manufactured by IUCHI) at a transmission frequency of 38 KHz. It was dispersed for minutes and confirmed to be uniformly dispersed. This dispersion was uniformly sprinkled over 1.5 kg of methacrylic resin α pellets and blended at 1400 rpm for 1 minute using a Henschel mixer (manufactured by Mitsui Miike Kogyo Co., Ltd.). This operation is repeated until the required amount of mixed pellets is obtained, and the obtained mixed pellets are extruded at a temperature of 250 ° C. while being devolatilized to 100 Torr with a 30 mmφ twin screw extruder (manufactured by Nakatani), and methacrylic resin containing 100 ppm of titanium dioxide. A composition was obtained. Hereinafter, this is referred to as raw material pellet A.
<Preparation of raw material pellet B>
1 kg of crosslinked methacrylic resin fine particles having an average particle size of 12.0 μm (MBX-12; manufactured by Sekisui Plastics Co., Ltd.) and methacrylic resin α pellets were uniformly mixed by a tumbler at a mixing weight ratio of 1: 100, and the resulting mixture was obtained. The pellets were extruded at a temperature of 250 ° C. while being devolatilized under reduced pressure to 100 Torr with a 30 mmφ biaxial extruder (manufactured by Nakatani) to obtain a methacrylic resin composition containing 1 part by weight of crosslinked methacrylic resin fine particles. Hereinafter, this is referred to as raw material pellet B.

[Example 4]
The raw material pellet A was formed on both sides containing 0.5 ppm of titanium dioxide as light scattering fine particles in the same manner as in Example 1 except that the mixing weight ratio with the methacrylic resin α pellet was changed to 1: 199. A light guide plate having a convex lens array pitch ratio P1 / P2 of 0.9 was obtained.
When the obtained light guide plate was observed and measured in the same manner as in Example 1, no moire was observed, and the average luminance was 3110 cd / m ² .

[Example 5]
A substantially prism-shaped convex lens array 1 having a cross-sectional shape of a substantially isosceles triangle having an apex angle of 80 degrees and formed by a part of an arc having a curvature radius of 40 μm at the apex end is formed at a pitch of 90 μm (P1). The embossing roll 26 manufactured as described above, and a convex lens array 2 having a substantially prism shape, the cross-sectional shape of which is a substantially isosceles triangle having a vertex angle of 100 degrees and formed by a part of a circular arc having a curvature radius of 40 μm at the apex tip portion. The embossing roll 27 and the polishing roll 25 manufactured so as to be formed with a pitch of 100 μm (P2) were arranged as shown in FIG.
Using methacrylic resin pellets α as the substrate resin, co-extrusion was performed with an extruder 23 of 90 mmφ and L / D = 32 and an extruder 24 (hereinafter referred to as sub-extruder) of 30 mmφ and L / D = 24. The die uses a two-layer, two-layer feedblock type, and the lip opening and the clearance between the polishing roll 25 and the embossing roll 26 are adjusted so that the laminate has a thickness of 0.8 mm. The temperature was 250 to 260 ° C. Using the raw material pellet B forming the mat layer, the mat layer 82 was extruded from the sub-extruder 24 by adjusting the discharge amount to adjust the thickness to 40 μm. Using the obtained extruded plate, a light guide plate having a pitch ratio P1 / P2 of 0.9 between the convex lens rows formed on both surfaces was obtained in the same manner as in Example 1.
When the obtained light guide plate was observed and measured in the same manner as in Example 1, no moire was observed, and the average luminance was 3180 cd / m ² .

<Visual observation evaluation and luminance measurement result of moire>
In all of the light guide plates of Examples 1 to 5, moire due to interference between the dot pattern and the convex lens array was not observed, and the average luminance was excellent. In particular, Example 4 in which light scattering fine particles were added to a transparent substrate and Example 5 in which a mat layer was formed on the surface had higher average luminance and excellent performance.

  The light guide plate of the present invention is a display device used for office automation equipment such as personal computers and word processors, various monitors for displaying image signals, for example, panel monitors, television monitors and the like, and lighting devices for indoor and outdoor spaces. It can be suitably used for signs and signs.

It is explanatory drawing which shows the measurement point at the time of the light-guide plate brightness | luminance measurement of this invention. It is explanatory drawing which shows the manufacturing method of the light-guide plate of this invention. It is the schematic which shows the structure of the surface light source device of the edge light system used when measuring average luminance. It is explanatory drawing of a structure of a light-scattering pattern. It is sectional drawing which shows the form of Example 1 of this invention. It is sectional drawing which shows the form of the comparative example 2 of this invention. It is the schematic of an example of the light-guide plate of this invention. It is explanatory drawing which shows the manufacturing method of the light-guide plate of this invention.

Explanation of symbols

11: LED light source 12: luminance measurement position 21: base material layer 22: layer for forming a convex lens array 23: main extruder 24: sub-extruder 25: polishing roll 26: embossing roll 27: embossing roll 28: dice 31 : Light reflection sheet 32: light scattering pattern 33: light guide plate 34: light diffusion sheet 35: prism sheet 36: prism sheet 51: convex lens array 1
52: Convex lens array 2
71: Light entrance surface 72: Light exit surface 73: Back surface 74 and 75 opposite to the light exit surface 75: Convex lens array 82: Layer for forming a mat layer

Claims (7)

A light guide plate having at least one side end surface as a light incident surface and one surface orthogonal to the light incident surface as a light exit surface,
On the back of each of the light emitting surface and facing the convex lens rows extending in the direction the light entrance surface and substantially perpendicular to a plurality of columns formed in a predetermined arrangement pitch,
Of the arrangement pitch of the convex lens array formed on the light exit surface and the arrangement pitch of the convex lens array formed on the back surface, when the smaller one is P1 and the larger one is P2, the ratio P1 / P2 is
A light guide plate of 0.55 to 0.95. 2. The light guide plate according to claim 1, wherein an arrangement pitch of the convex lens arrays formed on the light emitting surface and an array pitch of the convex lens arrays formed on the back surface are both 40 to 200 μm. At least one of the cross-sectional shape of the convex lens arrays formed in a convex lens column and the back are formed on the light emitting surface, an apex angle of a substantially isosceles triangle is 50 degrees to 150 degrees, apex angle tip The light guide plate according to claim 1, wherein is a circular arc shape. At least one of the cross-sectional shape of the convex lens arrays formed in a convex lens column and the back are formed on the light emitting surface, an ellipse, or a part of a circle, the light guide plate according to claim 1 or 2. The entire area of at least one surface of the convex lens arrays formed in a convex lens column and the back are formed on the light emitting surface was matte surface, the light guide plate according to claim 1. The transparent thermoplastic resin composition containing the crosslinked resin fine particles and the transparent thermoplastic resin are laminated and integrally formed by laminating the mat layer and the substrate by multilayer extrusion molding. Light guide plate. The light guide plate according to claim 1, wherein the transparent thermoplastic resin substrate contains light scattering fine particles.