WO2008062638A1

WO2008062638A1 - Optical flat plate member and method for manufacturing optical flat plate member

Info

Publication number: WO2008062638A1
Application number: PCT/JP2007/071101
Authority: WO
Inventors: Kazunori Ueki
Original assignee: Zeon Corporation
Priority date: 2006-11-24
Filing date: 2007-10-30
Publication date: 2008-05-29
Also published as: TW200832001A; JPWO2008062638A1

Abstract

This invention provides an optical flat plate member produced by injection molding a thermoplastic resin using a mold having a gate within an optically effective plane. This optical flat plate member comprises a first plane with a gate mark and a second plane which is a plane opposite to the first plane. The first and second planes satisfy requirement 1: 1 (μm) < Ra1 ≤ 3 (μm), Ra2 ≤ 3 (μm) and Ra1 ≤ Ra2, or requirement 2: Ra1 ≤ 1 (μm) and Ra2 ≤ 3 (μm), wherein r1 represents the radius of the gate mark present within the optically effective surface in the first plane; Ra1 represents the arithmetic mean roughness of the gate mark in the first plane; and Ra2 represents the arithmetic mean roughness, in the second plane, in an area with a radius r2 (r2 = r1 x 30) with a point, as its center, corresponding to the center of the gate mark in the first plane.

Description

Specification

Optical flat plate member and method for manufacturing optical flat plate member

Technical field

The present invention relates to an optical flat plate member which can be easily produced by injection molding of a thermoplastic resin without using a gate trace when it is used as an optical member, and a method of producing the flat plate member for optical use. It is.

Background art

Liquid crystal display devices utilizing the property of liquid crystals that change the alignment of molecules when voltage is applied are widely used in personal computers, flat-screen televisions, car panels, portable information terminals and the like. Since the liquid crystal itself does not emit light, the liquid crystal display device needs an external light source, and as the light source, a side light system in which the light source is disposed at the side edge of the liquid crystal display device and a light source is disposed at the back of the liquid crystal display device The direct system is being put to practical use. Since the sidelight system is capable of reducing the thickness of the device unit S and the luminance is low, the direct system is suitable for a large liquid crystal display device requiring high brightness!

An optical flat member made of a thermoplastic resin plays an important function in both the side light type and the direct type, and in particular, in the direct type, a light diffusion plate is used as the optical flat member. In the direct type liquid crystal display device, a light source such as a plurality of cold cathode tubes is disposed on the back of the device housing, light from the light source is incident on the light diffusion plate, and the incident light is diffused by the light diffusion plate. And convert it into uniform light of uniform brightness. If necessary, a reflection plate is provided behind the cold cathode tube, gradation printing is performed on the back of the light diffusion plate, and a light collection sheet, diffusion sheet, etc. are stacked on the front of the light diffusion plate. The light diffusing plate is required to have a sufficient strength without any warpage between the light transmittance and the light diffusing property, and to reduce the luminance unevenness.

A molded product of a thermoplastic resin containing a light diffusing agent is often used as the material of the light diffusion plate, but it is possible to use only the thermoplastic resin and devise the shape of the surface of the molded product. Ru. As a molding method of the light diffusion plate, an extrusion molding method, a casting method, an injection molding method or the like is used. According to the extrusion molding method, post-processing for forming a light diffusion plate capable of efficiently producing a raw material sheet of the light diffusion plate takes time and labor, and material waste occurs. Queer According to the strike method, it is not high in productivity which can obtain a light diffusion plate without optical distortion with high strength. According to the injection molding method, the light diffusion plate can be manufactured in a short time in which the number of post-processing steps is small, and in the conventional method in which the molten thermoplastic resin flows from the side gate of the cavity side, It is technically difficult to manufacture by one-piece injection molding of light diffusers and by multiple injection molding of small light diffusers.

Therefore, Japanese Patent Application Publication No. 2004-117544 proposes a method of providing a multipoint gate on the light incident surface of a light diffusion plate and performing injection molding. According to this, it becomes possible to manufacture by a single-piece injection molding method for a large light diffusion plate and to manufacture by a multi-piece injection molding method for a small light diffusion plate. By using a mold having a hot runner and a multipoint gate, it is possible to efficiently inject and mold a large single-piece light diffusion plate and a small number of small light diffusion plate in a short molding cycle.

By the way, when using a hot runner for the mold of a precise molded product such as a light diffusion plate, the valve gate is closed by the valve pin after the inflow of molten resin into the mold cavity, and the tip of the valve pin is closed. By transferring the shape into the optically effective surface of the light diffusion plate, the processing of the gate mark is not necessary. However, when a light diffusion plate molded with a mold using this valve pin is mounted on a liquid crystal display device, uneven brightness occurs between the vicinity of the gate mark and the other parts, and the image quality of the display screen is degraded. Yes, further improvement is required. Such a problem occurs not only in the light diffusion plate but also in other flat optical members such as a light guide plate or the like.

Disclosure of the invention

Therefore, it is an object of the present invention to provide an optical flat plate member in which the gate mark is inconspicuous, the luminance unevenness can be suppressed, and the optical resin can be easily manufactured by injection molding of a thermoplastic resin. A flat plate member and a method of manufacturing the flat plate member for optics.

As a result of intensive studies to solve the above problems, the inventor of the present invention has found that the arithmetic mean roughness Ra of the gate mark of the optical flat plate member and the surface on the side opposite to the surface on which the gate mark exists. Arithmetic mean roughness Ra and force S within a predetermined range from the point corresponding to the center of the gate mark As a result, it has been found that the gate mark of the optical flat member when mounted on the device becomes inconspicuous, and the present invention has been completed based on this finding.

According to a first aspect of the present invention, there is provided an optical flat member obtained by injection molding a thermoplastic resin using a mold having a gate in a plane corresponding to the optically effective surface. A first surface on which a gate mark formed corresponding to the gate is present, and a second surface opposite to the first surface, and the first surface The radius of the gate mark existing in the optically effective surface is r, and the arithmetic mean roughness in the range of the radius r is Ra, and in the second surface, the gate mark of the first surface is Let the arithmetic mean roughness Ra in the range of radius r (r = r x 30) centering on the point corresponding to the center

2 2 1 2 When

(Condition 1)

K ^ mX Ra ≤ 3 (111), and Ra ≤ 3 (111), color 1 1⁄2 ≤ Ra

1 2 1 2

Or

(Condition 2)

Ra ≤ 1 (^ m), power, one Ra ≤ 3 (^ m)

1 2

An optical flat member satisfying the above is provided.

[0010] In the optical flat member of the present invention, the total light transmittance is preferably 50 to 90% when light is applied to the surface on which the gate mark is present.

In addition, it is preferable that the flat member for optics of the present invention be used for a light diffusion plate.

Further, according to a second aspect of the present invention, in the method of manufacturing an optical flat member of the present invention, the optical flat member is injection molded using a mold including a hot runner having a valve gate. The manufacturing method of is provided.

According to the present invention, when used as a flat optical plate member, it is possible to make the gate mark inconspicuous and to suppress the luminance mark S. Also, the optical flat member can be easily manufactured by injection molding of a thermoplastic resin.

Brief description of the drawings

FIG. 1 is a cross-sectional view showing the shape of a triangular prism formed on the flat member for optics according to the embodiment. FIG. 2 is a cross-sectional view showing the shape of a triangular prism formed on the optical flat member according to the embodiment.

FIG. 3 is a cross-sectional view showing the shape of a composite prism formed on the optical flat member according to the embodiment.

FIG. 4 is a cross-sectional view showing the shape of a lenticular lens-shaped prism formed on the flat optical member according to the embodiment.

FIG. 5 is a cross-sectional view showing the shape of a hemispherical protrusion formed on the optical flat member according to the embodiment.

FIG. 6 is a perspective view showing the shape of a quadrangular pyramid formed on the optical flat member according to the embodiment.

FIG. 7 is a cross-sectional view showing a configuration of a mold having a hot runner according to the embodiment.

FIG. 8 is a cross-sectional view showing a method of manufacturing an optical flat member using a mold according to an embodiment.

FIG. 9 is a cross-sectional view showing a method of manufacturing an optical flat member using a mold according to the embodiment.

FIG. 10 is a cross-sectional view showing a method of manufacturing an optical flat member using a mold according to the embodiment.

FIG. 11 is a view for explaining a gate mark angle according to the embodiment.

FIG. 12 is a perspective view showing the configuration of a direct-type backlight device according to the embodiment.

FIG. 13 is a view showing the gate position of the mold used in the example.

FIG. 14 is a diagram showing measurement positions of luminance in the vicinity of the gate in the embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the optical flat member according to the embodiment of the present invention will be described. The flat member for optics according to the present embodiment is obtained by injection molding a thermoplastic resin using a mold having a gate in a plane corresponding to the optically effective surface of the flat member for optics. The optical flat member includes a first surface on which a gate mark formed corresponding to the gate is present, and a second surface opposite to the first surface, The radius of the gate trace existing in the optically effective plane is r, and the range of the radius r is The arithmetic mean roughness of the surface of in the second surface, in the range of radius r (r = r X 30) centered on the point corresponding to the center of the gate mark of the first surface in the second surface table

2 2 1

In order to satisfy the following (condition 1) or (condition 2) when the arithmetic mean roughness of the surface is Ra

2

It is set.

(Condition 1)

K ^ mXRa ≤ 3 (111), and Ra ≤ 3 (111), color 1 1⁄2 ≤ Ra

1 2 1 2

(Condition 2)

Ra ≤ 1 (^ m), power, one Ra ≤ 3 (^ m)

1 2

In this optical flat member, the total light transmittance when light is applied to the surface (first surface) on which the gate mark is present is 50 to 90%, preferably 60 to 90%.

Here, the optically effective surface is a portion that can be confirmed by the observer when the optical member is incorporated into a liquid crystal display device or the like for observation, and, for example, if it is a light diffusion plate, its main surface The portion excluding the liquid crystal display incorporating margin existing near the side wall of the.

In addition, a plurality of gates are installed and installed in a plane corresponding to the optical effective surface of the optical flat plate member for injection molding of the optical flat plate member. Assuming that the number of gates is N (number), the area of the optical flat plate member is S (mm ² ), and the thickness of the optical flat plate member is t (mm), the number of gates N satisfies the following (formula 1) It is more preferable to satisfy the following (formula 2) that is preferred.

(Formula 1) (S / (t + 6)) X 10 ^{_ 4} ≤ N ≤ (2 S / t) X 10 ⁴

(Eq. 2) (S / (t + 4)) X 10 ^{_ 4} ≤ N ≤ (2 S / t) X 10 ⁴

When the gate number N is less than (S / (t + 6) ) X 10_ 4, flow distance is too long in the mold of the molten resin, the temperature of the molten resin in the fluid is reduced, optical There is a possibility that distortion, uneven thickness, weld line, etc. may occur on the flat plate member. In addition, when the gate number N exceeds (2S / t) × 10 ⁴ , the number of gates is too large, which may make it difficult to manufacture a mold. Also, optical flat plate member according to the present embodiment 15 inch or more, i.e., force S preferably the area is to 76,000Mm ² or more, a 24 inch or more, i.e., area 180,00 Omm ² or more It is more preferable to When a large number of flat plate members are taken from one mold, the area of the optical flat plate member is the entire flat plate provided in one mold. It is the sum of the area of a member. Also, the thickness of the flat plate member is properly selected in the range of 0.2 to 50 mm.

In the first surface of the optical flat member, the arithmetic mean roughness Ra of the gate marks present in the optically effective surface is plural for the gate marks of the optical flat member in order to provide a light diffusion function. In the case where a micro-specific shape is formed! /, It means the arithmetic mean roughness of the surface (range of radius r) forming this micro-specific shape, and the micro-specific shape is formed on the gate trace. If not, it is the arithmetic mean roughness of the plane of the gate mark (range of radius r). In addition, such a fine specified shape forms the corresponding fine specified shape at the tip of the valve pin 12a (see FIG. 8) of the hot runner nozzle 12 described later, and transfers this fine specified shape to the resin. It is formed by Such a fine specified shape of the gate mark is the same as that of the other part except for the gate mark when the fine specified shape is formed in the part other than the gate mark of the surface on which the gate mark of the optical flat plate material is present. A particular shape is formed.

In the second surface, which is the surface opposite to the surface on which the gate marks are present, the radius r force = r × 30 from the point corresponding to the center of the gate marks on the first surface. Arithmetic mean roughness Ra

2 2 1

In order to provide a light diffusion function, a plurality of fines are formed on the surface (second surface) of the optical flat member.

2

When a thin specified shape is formed, it means the arithmetic mean roughness in the relevant range of the surface forming this fine specified shape, and it is fine specified on the surface (second surface) of the optical flat member. When the shape is not formed, it means the arithmetic mean roughness in the relevant range of the surface of the optical flat member. Such a fine specified shape is formed on the surface of the stamper provided on the fixed mold 4 (see FIG. 7) of the mold described later (see FIG. 7), and this fine specified shape is used as a resin. It is formed by transferring.

As shown in the cross-sectional view of FIG. 1, as a micro-specific shape formed on the surface of the gate mark or one or both surfaces of the optical flat member, the cross section formed on the surface of the optical flat member is A triangular prism row composed of triangular linear prisms (triangular prisms) may be mentioned. In this case, the arithmetic mean roughness of the surface forming the triangular prism indicated by R1 in the figure is measured.

Further, as shown in the cross-sectional view of FIG. 2, the triangular prism is formed so that the angle formed by the two slopes forming the triangle and the plane orthogonal to the thickness direction of the optical flat plate member becomes equal. , This angle is a certain X point of the optical flat plate member and the short side of the triangular prism from this X point You may form so that it may become small continuously or intermittently as it leaves | separates from X point and a saddle point between Y points which separated by predetermined distance in the hand direction. In this case, the arithmetic mean roughness of the surface forming the triangular prism indicated by R2 in the figure is measured.

In addition, as shown in the cross-sectional view of FIG. 3, it is possible to cite a composite prism row in which linear prisms are formed in a polygonal shape in cross section including at least four planes. In this case, the arithmetic mean roughness of the surface forming the composite prism indicated by R3 in the figure is measured. Here, when the shapes shown in FIGS. 1 to 3 are formed, when the optical flat member is placed on the light source and the gate mark is observed, the gate mark appears to be split and the gate mark appears. Becomes more noticeable. For this reason, it is possible to make it difficult to see the gate mark by providing the suitable surface roughness shown in this embodiment.

In addition, as shown in the cross-sectional view of FIG. 4, there can be mentioned a lenticular lens-like prism row having a convex arc-shaped cross section. In this case, the arithmetic mean roughness of the surface forming the convex arc-shaped lenticular lens-like prism indicated by R4 in the drawing is measured.

Further, as shown in the cross-sectional view of FIG. 5, it is possible to cite a shape in which hemispherical projections are arranged in the longitudinal direction and the lateral direction. In this case, the arithmetic mean roughness of the surface forming a hemispherical protrusion indicated by R5 in the figure is measured. Here, when the shapes shown in FIG. 4 and FIG. 5 are formed, when the flat plate member for optics is placed on the light source and the gate mark is observed, the gate mark appears to be apparently enlarged. Becomes more noticeable. Therefore, the gate mark can be made less visible by providing the suitable surface roughness described in this embodiment.

Further, as shown in FIG. 6, it is possible to cite a shape in which multipyramidal projections such as quadrangular pyramids are arrayed. In this case, the arithmetic mean roughness of the surface forming a multipyramidal projection such as a quadrangular pyramid shown by R6 in the drawing is measured. The multipyramidal protrusion such as a quadrangular pyramid may be a multipyramidal recess such as a quadrilateral pyramid. Here, when the shape shown in FIG. 6 is formed, when the optical flat member is placed on the light source! /, And the gate mark is observed, the gate mark appears to be split in appearance, which is noticeable It will be easier. For this reason, the gate mark can be made visible by giving the suitable surface roughness shown in the present embodiment.

Arithmetic mean roughness Ra is a value defined in Japanese Industrial Standard JIS B06013.1, and can be measured using an ultra-deep microscope or the like. In addition, the flat plate for optics is used as a light source When arranged at the facing position, the gate mark is provided on the surface on the light source side of the optical flat plate member! /, Or may be! /, Provided on the surface opposite to the light source! / , Even!

[0027] The thermoplastic resin used in the present embodiment is not particularly limited. For example, a resin having an alicyclic structure, a copolymer of an aromatic boule monomer and a (meth) acrylic acid alkyl ester monomer is used. Examples thereof include polymers, methacrylic resins, polycarbonates, polystyrenes, acrylonitrile-styrene copolymer resins, ABS resins, and polyether sulfones. Among these, resins having an alicyclic structure, copolymers of an aromatic boule monomer and a (meth) acrylic acid alkyl ester monomer, and a polycarbonate have a low water absorption coefficient and are tough. Can be suitably used. A resin having an alicyclic structure can be filled into a mold cavity at a low injection pressure because the fluidity of the molten resin is good, and has extremely low hygroscopicity, so it is excellent in dimensional stability, and is a flat member for optics The weight of the flat optical member can be reduced because the specific weight that causes no warping is small. In addition, a resin having an alicyclic structure is less likely to generate a weld line.

The resin having an alicyclic structure is a resin having an alicyclic structure in the main chain or side chain! Among these, resins having an alicyclic structure in the main chain can be particularly preferably used because they have good mechanical strength and heat resistance. The alicyclic structure is preferably a saturated cyclic hydrocarbon structure, and the carbon number thereof is preferably 4 to 30 and more preferably 5 to 20. 5 to 15 Is more preferred. The proportion of the repeating unit having an alicyclic structure in the resin having an alicyclic structure is preferably 50% by weight or more, and more preferably 70% by weight or more, and is 90% by weight or more. Is more preferred.

Examples of the resin having an alicyclic structure include a ring-opened polymer or ring-opened copolymer of a norbornene-based monomer, a hydrogenated product thereof, an addition polymer or addition-copolymer of a norbornene-based monomer, and the like. Polymer or hydrogenated product thereof, polymer of monocyclic cyclic olefin group monomer or hydrogenated product thereof, polymer of cyclic conjugated diene monomer or hydrogenated product thereof, alicyclic cycloaliphatic hydrocarbon Polymers or copolymers of monomers of the above type or their hydrogen additives, hydrogenates of unsaturated bonds including aromatic rings of polymers or copolymers of bure aromatic hydrocarbon monomers, etc. Can be mentioned. Among these, hydrogenation products of polymers of norbornene type monomers and polymerization of bure aromatic hydrocarbon type monomers The hydrogenated substance of the unsaturated bond part including the aromatic ring of the body can be particularly preferably used because it is excellent in mechanical strength and heat resistance.

[0030] Methacrylic resin is excellent in transparency, and thus can be suitably used as an optical member. As a methacrylic resin, the methacrylic resin molding material which contains 80 weight% or more of methyl methacrylate polymers prescribed | regulated to Japanese Industrial Standard JISK6717 can be mentioned. Among the methacrylic resins defined in this standard, the methacrylic resins having a Vicat softening point temperature of 96 to 100 ° C. and melt flow rates 8 to 16; classified classification codes 100 to 120 have appropriate fluidity and strength. Therefore, it can be used suitably.

The aromatic bule monomer constituting a copolymer of an aromatic bule monomer and a (meth) acrylic acid alkyl ester refers to an aromatic bule monomer and a derivative thereof, for example, And styrene, α-methylstyrene, m-methylstyrene, p-methylstyrene, o-chloro-styrene, p-chlorostyrene and the like. As a (meth) acrylic acid alkyl ester which comprises the copolymer of an aromatic bure type | system | group monomer and (meth) acrylic-acid alkylester, it has a C1-C4 alkyl group, for example, (meth) acryl Acid alkyl esters and the like can be mentioned, and among them, methyl acrylate, ethyl acrylate, methyl methacrylate, and methyl methacrylate can be suitably used. The copolymer of the aromatic bule monomer and the (meth) acrylic acid alkyl ester is composed of 20 to 60% by weight of the aromatic bule monomer and 40 to 80% by weight of the (meth) acrylic acid ester. It is preferable that it is a copolymer. The (meth) acrylic acid alkyl ester means acrylic acid alkyl ester, methacrylic acid alkyl ester.

The polycarbonate used in the present embodiment is generally obtained by reacting dihydric phenol with a carbonate precursor by an interfacial polymerization method or a melt polymerization method. Representative examples of divalent phenols include: 2,2 bis (4 hydroxy phenyl) propane (generally called bis pheno nore A), 2, 2 bis {(4 hydroxy mono methenore) phe di none} propane, 2 2, 2-bis (4-hydroxy-phenylonitrile) butane, 2, 2-bis (4-hydroxy-phenylonitrile) -3 methyl butan, 2, 2-bis (4-hydroxy-phenylonitrile) -3, 3-dimethinolebutane, 2, 2-bis (4- Hydroxyphenone) 1,4-methylpentane, 1,1-bis (4-hydroxyphenyle) cyclohexane, 1,1 bis (4-hydroxyphenenone) -3,3,3,5-trimethyonecyclo Xan, 9, Examples thereof include 9-bis {(4-hydroxy-1-methinole) phenone} fluorene and α, a-bis (4-hydroxyphenyl) m diisopropylbenzene and the like, with preference given to bisphenyl A. These divalent phenols can be used alone or in combination of two or more.

Yes

As the carbonate precursor, carbonyl halide, carbonate ester, haloformate and the like are used, and specific examples thereof include phosgene, diphenyl carbonate and dihaloforme of divalent phenol.

When producing the polycarbonate resin by reacting the above divalent phenol with the carbonate precursor by the interfacial polymerization method or the melt polymerization method, a catalyst, an end terminator, an antioxidant for divalent phenol, etc. You may use it. The polycarbonate may be a branched polycarbonate obtained by copolymerizing a trifunctional or higher polyfunctional aromatic compound, or a polyester carbonate obtained by copolymerizing an aromatic or aliphatic difunctional carboxylic acid. It may be a mixture of two or more of the polycarbonates listed above.

[0035] The polystyrene resin used in this embodiment is styrene, α-methylstyrene, 0-methylstyrene, メチル -methylstyrene, ρ-chlorostyrene, ρ-nitrostyrene, ρ-aminostyrene, ρ-carboxystyrene, PS resin consisting of aromatic boule such as --phenylstyrene HIPS resin obtained by graft-polymerizing aromatic boule onto rubbery polymer AS resin obtained by copolymerizing cyanide boule such as acrylonitrile with aromatic bule ABS polymer, which is a mixture of a cyanide bule and an aromatic bure grafted on a rubbery polymer and a copolymer of a cyanide boule and an aromatic vinyl, and a rubbery polymer such as methyl methacrylate and an aroma. MBS resin, etc., which is a graft polymer obtained by grafting a family bule, and is required to meet the required performances such as water absorption rate, refractive index, heat resistance and impact resistance. Flip may be selected.

In the present embodiment, as the thermoplastic resin, one in which a thermoplastic elastomer, an additive and the like are blended can be used as needed. Examples of thermoplastic elastomers include polybutadiene, styrene-butadiene block copolymer and its hydrogenated compound, styrene-isoprene block copolymer and its hydrogenated compound, and the like. The blending amount of the thermoplastic elastomer is usually from 0. 0 to! 50% by weight, preferably 0. It is 05-30% by weight. Examples of additives include light diffusing agents, antioxidants, ultraviolet light absorbing agents, light stabilizers, coloring agents such as dyes and pigments, lubricants, plasticizers, antistatic agents, fluorescent whitening agents and the like. S can. As the light diffusing agent, for example, fine particles comprising a polystyrene polymer, a polysiloxane polymer or a crosslinked product thereof, a fluorine resin, barium sulfate, calcium carbonate, silica, talc and the like can be mentioned. Among these, fine particles composed of a polystyrene polymer, a polysiloxane polymer, or a crosslinked product thereof are particularly preferable because they have good dispersibility, are excellent in heat resistance, and do not cause yellowing at the time of molding. It can be used. The amount of these additives to be added is not particularly limited, and is usually from 0. 0;! To 30% by weight, preferably from 0. 05 to 20% by weight. The particle diameter of the light diffusing agent in the case of incorporating the light diffusing agent as a compounding agent is not particularly limited, but the average particle diameter is usually in the range of 0.5-lOO ^ m, preferably 0.5 to 80 111. is there.

The optical flat member according to the present embodiment corresponds to the arithmetic mean roughness Ra of the range of radius r related to the gate mark and the center of the gate mark on the surface opposite to the surface on which the gate mark exists. Arithmetic mean roughness Ra in the range of radius r (= r x 30) from the point to be

2 1 2

Since the total light transmittance of the flat member for optics is set within the above-described predetermined range while setting 2) to satisfy the condition 2), even if the gate mark is in the optically effective surface, the optical unevenness is reduced. The mark of the gate is noticeable when mounted on the device.

The flat optical plate member according to the present embodiment is manufactured by injection molding using a mold provided with a hot runner. FIG. 7 is a view showing the configuration of a mold provided with a hot runner.

The mold 2 includes a fixed side mold 4 and a movable side mold 6. A predetermined shape is imparted to the optical plane (second surface) of a molded product (hereinafter referred to as a flat plate member for optics if necessary) on the surface of the stationary mold 4 opposed to the movable mold 6. A stamper 8 is provided which has a surface (shape-imparting surface) to be used. The shape-imparting surface of the stamper 8 is processed to have a predetermined arithmetic mean roughness. In addition, a cavity 10 is formed on the surface of the movable side mold 6 opposite to the fixed side mold 4 and has a valve pin 12 a (see FIG. 8) for supplying the molten resin 14 to the cavity 10. A hot run having a plurality of valve gate type hot runner nozzles (gates) 12 in a plane corresponding to the optically effective surface of the optical flat plate member 16 It is equipped with the 13th. The tip of the valve pin 12a is processed to have a predetermined arithmetic average roughness.

In the case of producing a molded product 16 using this mold, first, the mold clamping is performed at a predetermined pressure using a mold clamping device (not shown). At this point, as shown in FIG. 8, the hot runner nozzle 12 is closed by the knob pin 12a. Next, as shown in FIG. 9, the hot runner nozzle 12 is opened by retracting the valve pin 12a of the hot runner nozzle 12, and the molten resin 14 is injected from the hot runner nozzle 12 into the cavity 10.

After a predetermined amount of molten resin 14 is injected into the cavity 10, as shown in FIG. 10, the valve pin 12a is advanced to close the hot runner nozzle 12. At this time, the shape of the tip portion of the valve pin 12 a is transferred to the molded product 16. Thereafter, the mold 2 is cooled and the molded product 16 is taken out of the mold 2.

According to the method of manufacturing an optical flat member according to the present embodiment, the tip end portion of the valve pin 12a is processed to have a predetermined arithmetic mean roughness, and the shape-imparting surface of the stamper 8 is a predetermined arithmetic. Since it is processed to be an average roughness, the arithmetic flatness of the range of radius r related to the gate mark

2

The roughness Ra and the arithmetic mean roughness Ra in the range of the radius r from the point corresponding to the center of the gate trace on the surface opposite to the surface on which the gate trace exists are described above (Condition 1) or (Condition 1) Condition 2) is satisfied

twenty two

Molded articles 16 can be produced. Moreover, in this manufacturing method, since the above-mentioned resin is used, the total light transmittance when light is applied to the surface (first surface) on the side where the gate mark of the molded product 16 satisfying the above conditions is present. Can be set in the range of 50 to 90%, preferably 60 to 90%. Therefore, even if the gate mark is in the optically effective surface, it is possible to manufacture an optical flat member in which the gate mark is not noticeable when mounted on an optical device having a small brightness mark.

Further, according to this manufacturing method, even when the gate mark is in the optically effective surface, when the gate mark is not noticeable when mounted on the optical device having small luminance unevenness, the optical mark of the optical flat member can be reduced. By providing a large number of gates on the mold cavity surface corresponding to the effective surface and shortening the flow distance of the molten resin, it is possible to efficiently manufacture a large thin optical flat member by injection molding. You

In the present embodiment, in order to manufacture the optical flat member 16, the hot runner 1 is used. Using the hot runner 13 with the mold 2 having 3, it is possible to cool and solidify the molten resin at the gate such that the arithmetic mean roughness Ra of the gate mark becomes a predetermined value. In addition, since the use of the hot runner 13 eliminates the generation of runners to be discarded after each injection, the resin can be effectively used, and the amount of resin melted for one injection decreases, so the molding cycle is shortened. It is possible to shorten and improve productivity.

In the mold having a multipoint gate used for manufacturing the molded article according to the present embodiment, since the hot runner 13 has the valve gate 12, the shape of the tip of the valve pin 12a is transferred to the gate mark, and the gate is It is possible to form a gate trace with a predetermined arithmetic mean roughness Ra, which does not carry out the processing of the trace. That is, in the valve gate 12, the flow of the molten resin 14 is squeezed and shear heat generation occurs, so the viscosity of the molten resin 14 in the vicinity of the gate decreases and the shape of the tip of the valve pin 12a is accurately transferred to the gate mark, It is possible to form a gate mark having an arithmetic average roughness Ra, which is approximately equal to the arithmetic average roughness of the tip of the valve pin 12a. In the present embodiment, the method of processing the arithmetic mean roughness Ra of the tip of the valve pin 12a to a predetermined value is not particularly limited. For example, machining, sand blasting, diamond like carbon processing, plating, etc. may be used.

In the present embodiment, the position of the tip of the valve pin is not particularly limited. For example, the tip of the lube pin can be made coincident with the inner surface of the mold cavity to form an optical flat plate having no unevenness at all. . In addition, it is possible to form an optical flat plate member having a depression in the gate mark by sticking the tip of the valve pin beyond the inner surface of the mold cavity. Furthermore, the tip of the valve pin can be drawn into the inner surface of the mold cavity to form an optical flat member having a convex portion on the gate mark.

In the present embodiment, the shape of the tip of the valve pin is not particularly limited, and may be, for example, a cylindrical shape, a wedge shape, or a truncated cone shape. By using a valve pin having such a tip shape, it is possible to form an optical flat plate member having a recess or a convex portion such as a cylindrical shape, a wedge shape, or a truncated cone shape on the gate mark. In the present embodiment, the diameter of the gate mark of the optical flat plate member is preferably 0.5 to 5 mm. In addition, it is preferable that the depth of the depression or the height of the convex portion of the gate mark be 0.01-0.2 mm. If it is smaller than 0.1 mm, molding of the valve pin tip becomes difficult, and if it is larger than 0.2 mm There is a drawback that the marks of marks can be easily seen.

Further, the side wall portion of the gate mark formed by the valve pin may not be provided with an inclination angle (ie, an inclination angle of 0 degrees) or may be provided with an inclination angle. Here, the inclination angle (gate trace angle) provided on the side wall portion of the gate trace is, as shown in FIG. 11, the normal on the optical flat plate member (bottom surface of the gate trace) and the side wall portion of the gate trace. The angle that is made by In the case of providing the inclination angle, for example, this can be achieved by providing an inclined surface at the tip of the valve pin. By providing the side wall portion of the gate mark with an inclination angle, it is possible to facilitate the release of the gate mark portion. In addition, the inclination angle of the side wall portion is preferably 80 degrees or less, more preferably 60 degrees or less, and even more preferably 45 degrees or less. preferable. With such an angle, it is possible to make the gate mark more visible, and it is also easy to process the tip of the valve pin. In addition, it is preferable that the gate mark is a depression because the gate mark can be seen.

[0049] The injection molding conditions for obtaining the flat member for optics according to the present embodiment are: if the glass transition temperature of the thermoplastic resin to be used is Tg, the cylinder temperature is Tg + 80 ° C to Tg + 200 ° C The mold temperature is preferably in the range of Tg-40 ° C to Tg ° C, and the injection rate is in the range of lOcc / sec to 800 cc / sec. The temperature of the hot runner when having a hot runner as a mold is preferably Tg + 80 ° C to Tg + 200 ° C! /.

The flat optical plate member according to the present embodiment can be used as a direct-type light diffusion plate, a side-light type light guide plate, a direct-type backlight lighting curtain, or a rear projection TV flare lens. However, it is a power S to use as a direct light diffuser among other things.

FIG. 12 is a diagram showing the configuration of a direct type backlight device provided with a direct type light diffusion plate. As shown in FIG. 12, in the direct-type backlight device, cold cathode tubes 22 are disposed at predetermined intervals on a reflecting plate 20, and the flat plate member for light (light diffusion plate) of the present embodiment is formed thereon. Is arranged so that the surface with the gate mark is the light entrance surface. Therefore, it is possible to provide a surface light source with small luminance unevenness even if the gate mark is in the optically effective surface.

Although the mold may have a cold runner, in the case of using a cold runner, (1) application of in-mold gate cutting technology, (2) pinpoint gate or sub-maritail It is necessary to take measures such as adjusting the mold opening condition appropriately using a gate. If this measure is not taken, gate marks need to be processed after molding, resulting in a drawback that the molding cycle time becomes long.

Example

Hereinafter, the present invention will be described in more detail by way of examples.

Example 1

A mixture of 99 parts by weight of a resin having an alicyclic structure [Nippon Zeon Co., Ltd., Zeonor 1060R] and 1 part by weight of silicone resin fine particles [Zee Toshiba Silicone Co., Ltd., Tospearl 120, average particle diameter 2. O ^ m] The mixture was extruded into strands using a twin-screw extruder, and cut with a pelletizer to prepare pellets for a light diffusion plate. The light diffusion plate was molded from the pellet for light diffusion plate using an injection molding machine (clamping force of 4,410 kN). The diffuser concentration of this light diffuser is 0.2%.

The mold has cavity dimensions of 430 mm in length, 730 mm in width, 847 mm in diagonal length, and 2. O mm in depth, and as shown by ○ in FIG. One valve gate type hot runner nozzle was installed at the center of the 8 divided rectangles. The valve pin (gate pin) opens at the time of injection, the molten resin is sent to the cavity, and the valve pin closes after the injection ends, stopping the supply of molten resin. At this time, the shape of the tip of the valve pin is transferred to the molded product.

The cylindrical portion with the diameter of the tip of the bulb pin of 1.5 mm and the length of 0.1 mm protrudes to the light incident surface of the light diffusion plate, and the diameter of the light incident surface of the light diffusion plate is 1.5 mm and the depth is 0.5. The valve pin was adjusted so that a 1 mm cylindrical depression was formed. The circular portion with a diameter of 1.5 mm at the tip of the valve pin was processed to have an arithmetic mean roughness of 0.2 m. A stamper on which a prism pattern is formed is attached on the side opposite to the side on which the gate is positioned, and the arithmetic mean roughness of the stamper, that is, the arithmetic mean roughness of the surface constituting the prism is 0.1 m. processed. The light diffusion plate was manufactured by injection molding at a cylinder temperature of 275 ° C., a hot runner temperature of 260 ° C., a mold temperature of 80 ° C. and a total cycle time of 70 seconds. The gate trace angle of this light diffusion plate is 0 °.

[0057] Eight centers of gate marks on the surface on the light incident side, and a surface opposite to the surface on which the gate marks exist The arithmetic mean roughness was measured with an ultra-deep microscope in the range where the radius r force = _r × 30 from the point corresponding to the center of the gate trace, where r is the radius of the gate trace. 8 points each

2 2 1

Arithmetic mean roughness of gate mark which is an average value of fixed value Ra is 0.22 m, the gate mark exists Arithmetic mean rough of radius r from the point corresponding to the center of the gate mark on the side opposite to the face The

2

Ra was 0.14 111. Next, apply light from the side where the gate mark of the light diffusion plate exists.

2

The total light transmittance was measured to be 80%.

A white reflective sheet [manufactured by Djiden Co., Ltd., RF188] is attached to the inner surface of a box made of an acrylic plate with an inner dimension of 720 mm wide, 420 mm deep, and 17 mm deep, and the light of the cold cathode fluorescent lamp escapes. To prevent this, 11 cold cathode fluorescent lamps with an outer diameter of 3. O mm were mounted in parallel with a tube center spacing of 40 mm, with the tube surface 2 mm away from the bottom of the box. The light diffusion plate is separated by 12 mm from the tube surface of this cold cathode fluorescent lamp, so that the surface with the gate mark of the light diffusion plate is the light incident surface, and the cold cathode fluorescent light with two gate marks of the light diffusion plate. The lamp was placed so as to be at the middle position of the lamp, and the cold cathode fluorescent lamp was turned on to measure the luminance unevenness of the gate mark of the light diffusion plate.

For luminance, a diffusion sheet [Digden Co., Ltd., D124J] is laminated on the light exit surface of the light diffusion plate, and as shown in FIG. A square that is doubled is drawn virtually so that the center of the square coincides with the center of the circle of the gate mark, and it is 81 points of 81 points where one side is 9 points and the pitch is 1/3 of the gate mark diameter. A grid was considered, and 81 grid points were measured using a luminance meter. Uneven luminance was calculated by dividing the difference between the maximum value and the minimum value of the 81 luminance measurement values by the average value. The average value of the uneven brightness of the eight gate marks is 0.3%, and it was impossible to confirm the gate marks by visual confirmation.

Example 2

As shown in Table 1, a light diffusion plate was molded using a resin having the same alicyclic structure as in Example 1. The gate mark angle of this light diffusion plate is 2 °. The concentration of the diffusing agent in this light diffusing plate is 0.3%. In this case, a mold similar to that of Example 1 was used, but the arithmetic mean roughness of the tip of the valve pin was processed so as to be 0.05 m, and the prismatic pattern was formed into a prism pattern. , I.e., the arithmetic mean roughness of the surface constituting the prism was processed to be 1.3111. As in Example 1, arithmetic mean roughness of the gate trace Ra ^: From the point corresponding to the center of the gate trace on the opposite side surface to the surface on which the gate trace exists, the arithmetic mean roughness of the range of radius r is Ra, all

When the light transmittance was measured, Ra was 0. 08 ^ m, Ra was 1. 27 111, and total light transmittance was

1 2

It was 70%.

The luminance unevenness of the gate marks was measured in the same manner as in Example 1. The average value of the luminance unevenness of the eight gate marks is 0.3%, and it is necessary to confirm the gate marks by visual observation. I could not do it.

Example 3

As shown in Table 1, a light diffusion plate was molded using a resin having the same alicyclic structure as in Example 1. The gate mark angle of this light diffusion plate is 30 °. The diffuser concentration of this light diffuser is 0.7%. In this case, the same mold as used in Example 1 was used, but the arithmetic mean roughness of the tip of the valve pin was processed so as to be 1.5 m, and the arithmetic mean roughness of the prism 1 was formed. That is, it was processed such that the arithmetic mean roughness of the surface constituting the prism was 1. 8111.

As in Example 1, the arithmetic mean roughness Ra of the gate trace, the arithmetic mean coarseness of the range of radius r from the point corresponding to the center of the gate trace on the opposite side surface to the surface on which the gate trace exists Ra, all

When 2 2 light transmittances were measured, Ra is 1. 45 ^ 111, Ra is 1. 7: m, total light transmittance is

1 2

It was 70%.

The luminance unevenness of the gate marks was measured in the same manner as in Example 1. The average value of the luminance unevenness of the eight gate marks is 0.2%, and it is necessary to confirm the gate marks by visual observation. I could not do it.

Example 4

As shown in Table 1, a light diffusion plate was molded using a resin having the same alicyclic structure as in Example 1. The gate mark angle of this light diffusion plate is 2 °. The concentration of the diffusing agent in this light diffusing plate is 0.5%. In this case, the same mold as used in Example 1 was used, but the arithmetic mean roughness of the tip end of the valve pin was processed to be 0.2 m, and the arithmetic mean roughness of the lenticular stamper was formed. That is, the arithmetic mean roughness force of the surface constituting the lenticular shape was set to S 1.5 μm. Similar to Example 1, arithmetic mean roughness of gate trace Ra ^: From the point corresponding to the center of the gate trace on the opposite side surface to the surface on which the gate trace exists, the arithmetic mean coarseness in the range of radius r is Ra, all

When 2 2 light transmittances were measured, Ra was 0.18 ^ m, Ra was 1.6 m, and total light transmittance was 7

1 2

It was 2%.

When the luminance unevenness of the gate marks was measured in the same manner as in Example 1, the average value of the luminance unevenness of the eight gate marks was 0.5%, and it was confirmed that the gate marks were visually observed. I could not do it.

Example 5

As shown in Table 1, a light diffusion plate was molded using a resin having the same alicyclic structure as in Example 1. The gate mark angle of this light diffusion plate is 0 °. The concentration of the diffusing agent in this light diffusing plate is 0.1%. In this case, a mold similar to that of Embodiment 1 was used, but it is processed so that the arithmetic mean roughness of the tip end portion of the valve pin is 1.2πι, and the square average is roughly formed. That is, it was processed so that the arithmetic mean roughness of the surface constituting the quadrangular pyramid shape would be 0.3.

When 2 2 light transmittances were measured, Ra was 1.3 111, Ra was 0.35 111, and total light transmittance was 7

1 2

It was 8%.

When the luminance unevenness of the gate marks was measured in the same manner as in Example 1, the average value of the luminance unevenness of the eight gate marks was 0.1%, and it is necessary to confirm the gate marks by visual observation. I could not do it.

Example 6

As shown in Table 1, a light diffusion plate was molded using a resin having the same alicyclic structure as in Example 1. The gate mark angle of this light diffusion plate is 0 °. The concentration of the diffusing agent in this light diffusing plate is 1%. In this case, the same mold as used in Example 1 was used, but processing was performed so that the arithmetic mean roughness of the tip of the valve pin was 0.1 m, and the arithmetic mean roughness of the stamper was 0.5 Hm. Processed to be

[0073] As in Example 1, the arithmetic mean roughness Ra of the gate trace, which is opposite to the surface on which the gate trace exists Arithmetic mean roughness Ra in the range of radius r from the point corresponding to the center of the gate mark on the opposite side

2 2 When the light transmittance was measured, Ra was 0.15 n Ra was 0.45 111, and the total light transmittance was

1 2

It was 63%.

When the luminance unevenness of the gate marks was measured in the same manner as in Example 1, the average value of the luminance unevenness of the eight gate marks was 0.2%, and it was confirmed that the gate marks were visually observed. I could not do it.

Example 7

As shown in Table 1, a light diffusion plate was molded using methacrylic resin (Asahi Kasei Chemicals Corporation, Delpet 70 NHX). The gate mark angle of this light diffusion plate is 0 °. The concentration of the diffusing agent in this light diffusing plate is 2.5%. In this case, a mold similar to that of Example 1 was used, but the arithmetic mean roughness of the stamper on which the prism notch was formed was processed so that the arithmetic mean roughness of the tip of the valve pin was 0.3 m. That is, it was processed so that the arithmetic mean roughness of the surface constituting the prism was 0.8 μm.

As in Example 1, the arithmetic mean roughness Ra of the gate trace, the arithmetic mean coarseness of the range of radius r from the point corresponding to the center of the gate trace on the surface opposite to the surface on which the gate trace exists Ra, all

2 2 When the light transmittance was measured, Ra was 0.8 m, Ra was 0. Q5 ii total light transmittance was 5

1 2

It was 5%.

When the luminance unevenness of the gate marks was measured in the same manner as in Example 1, the average value of the luminance unevenness of the eight gate marks was 0.3%, and it was confirmed that the gate marks were visually observed. I could not do it.

(Example 8)

As shown in Table 1, a light diffusion plate was molded using MS resin (Denki Kagaku Kogyo Co., Ltd., TX-100S). The gate mark angle of this light diffusion plate is 30 °. The diffuser concentration of this light diffuser plate is 1.5%. In this case, the same mold as in Example 1 was used, but the arithmetic mean roughness of the stamper on which the prism pattern was formed by processing so that the arithmetic mean roughness of the tip of the valve pin was 0.1 m, That is, processing was performed such that the arithmetic mean roughness of the surface constituting the prism was 0.7111.

[0079] The arithmetic mean roughness Ra of the gate trace and the surface on which the gate trace exists are the same as in Example 1. Arithmetic mean roughness Ra in the range of radius r from the point corresponding to the center of the gate mark on the opposite side

When 2 2 light transmittances were measured, Ra was 0. 09 111, Ra was 0. 9 ii total light transmittance was 6

1 2

It was 1%.

(Example 9)

As shown in Table 1, the light diffusion plate was molded using polystyrene resin (manufactured by PS Japan Co., Ltd., G9504). The gate trace angle of this light diffusion plate is 5 °. The diffuser concentration of this light diffuser plate is 0.4%. In this case, the same mold as used in Example 1 was used, but the arithmetic mean roughness of the stamper having the lenticular shape formed by processing so that the arithmetic mean roughness of the tip of the bulb pin is 0.2 m, That is, it was processed so that the arithmetic mean roughness of the surface constituting the lenticular shape would be 0 · 1 m.

As in Example 1, the arithmetic mean roughness Ra of the gate trace, the arithmetic mean coarseness of the range of radius r from the point corresponding to the center of the gate trace on the side opposite to the face on which the gate trace exists Ra, all

2 2 When the light transmittance was measured, Ra was 0.21 m, Ra was 0. 08, im, and the total light transmittance was

1 2

It was 65%.

Comparative Example 1

As shown in Table 1, a light diffusion plate was molded using a resin having the same alicyclic structure as in Example 1. The gate trace angle of this light diffusion plate is 5 °. The concentration of the diffusing agent in this light diffusing plate is 1%. In this case, using the same mold as in Example 1, it was processed so that the arithmetic average roughness of the tip of the valve pin is 5 m and processed so that the arithmetic average roughness of the stamper is 2 m. .

As in Example 1, the arithmetic mean roughness Ra of the gate trace, the arithmetic mean coarseness of the range of radius r from the point corresponding to the center of the gate trace on the surface opposite to the surface on which the gate trace exists is Ra, all When the light transmittance was measured, Ra was 4. ΘΟ, ΐ, Ra was 2. l O ^ m, and the total light transmittance was

1 2

It was 63%.

When the luminance unevenness of the gate marks was measured in the same manner as in Example 1, the average value of the luminance unevenness of the eight gate marks was 3.1%, and the gate marks appeared dimly by visual observation.

Comparative Example 2

As shown in Table 1, a light diffusion plate was molded using a resin having the same alicyclic structure as in Example 1. The gate mark angle of this light diffusion plate is 0 °. The concentration of the diffusing agent in this light diffusing plate is 0.2%. In this case, the same mold as used in Example 1 was used, but the arithmetic mean roughness of the stamper on which the prism pattern was formed, was processed so that the arithmetic mean roughness of the tip of the valve pin was 2 ^ m. That is, processing was performed so that the arithmetic mean roughness of the surface constituting the prism was 4.2111.

In the same manner as in Example 1, the arithmetic average roughness Ra of the gate mark, the area of radius r from the point corresponding to the center of the gate mark on the surface opposite to the surface on which the gate mark exists is Ra, all

When 2 2 light transmittances were measured, Ra was 2.2 111, 11⁄2 was 4. l O ^ m, and total light transmittance was 7

1 2

It was 5%.

The luminance unevenness of the gate marks was measured in the same manner as in Example 1. As a result, the average value of the luminance unevenness of the eight gate marks was 3.3%, and the gate marks were clearly seen by visual observation.

(Comparative Example 3)

As shown in Table 1, a light diffusion plate was molded using a resin having the same alicyclic structure as in Example 1. The gate mark angle of this light diffusion plate is 30 °. The diffuser concentration of this light diffuser is 0.3%. In this case, the same mold as in Example 1 was used, but the arithmetic mean roughness of the tip of the valve pin was processed to be 2.8 m and the prismatic pattern was formed to form the prismatic pattern. That is, it was processed so that the arithmetic mean roughness of the surface constituting the prism was 0. δ ..

2 2 When the light transmittance was measured, Ra was 2.6 m, Ra was 0.55 ii total light transmittance was 7

1 2

It was 1%. When the luminance unevenness of the gate marks was measured in the same manner as in Example 1, the average value of the luminance unevenness of the eight gate marks was 2.1%, and the gate marks were clearly visible by visual observation.

(Comparative Example 4)

As shown in Table 1, a light diffusion plate was molded using a resin having the same alicyclic structure as in Example 1. The gate trace angle of this light diffusion plate is 15 °. The diffuser concentration of this light diffuser plate is 0%. In this case, a mold similar to that of Example 1 was used, but processing was performed so that the arithmetic mean roughness at the tip of the valve pin was 0.01 m, and the arithmetic mean roughness of the stamper was 0.10 μm. It was Karoe to become.

As in Example 1, the arithmetic mean roughness Ra of the gate trace, the arithmetic mean coarseness of the range of radius r from the point corresponding to the center of the gate trace on the surface opposite to the surface on which the gate trace exists is Ra, all

When 2 2 light transmittances were measured, Ra is 0. 02 111, Ra is 0. 02 111, total light transmittance is

1 2

It was 92%.

When the luminance unevenness of the gate marks was measured in the same manner as in Example 1, the average value of the luminance unevenness of the eight gate marks was 1.2%, and the gate marks were clearly seen by visual observation.

[Table 1]

[0097] The embodiments and examples described above are described to facilitate the understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiment or example is intended to include all design changes and equivalents that fall within the technical scope of the present invention.

The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2006-316671 filed on Nov. 24, 2006, the entire disclosure of which is expressly incorporated herein by reference. .

Claims

[1] An optical flat member obtained by injection molding a thermoplastic resin using a mold having a gate in a surface corresponding to an optically effective surface, which corresponds to the gate A first surface on which a gate mark to be formed is present, and a second surface opposite to the first surface, the first surface being within the optically effective surface. Let r be the radius of the gate trace and let Ar be the arithmetic mean roughness in the range of the radius r, and in the second plane, a point corresponding to the center of the gate trace of the first surface be a center If the arithmetic mean roughness in the range of radius r (r = r x 30) is Ra, then 2 2 1 2

(Condition 1)

K ^ mX Ra ≤ 3 (111), and Ra ≤ 3 (111), color 1 1⁄2 ≤ Ra

1 2 1 2

Or

(Condition 2)

Ra ≤ 1 (^ m), power, one Ra ≤ 3 (^ m)

1 2

Flat members for optics that satisfy

[2] The optical flat member according to claim 1, wherein the total light transmittance is 50 to 90% when light is applied to the surface on the side where the gate mark of the optical flat member is present.

[3] The flat member for optics according to claim 1 or 2, which is used for a light diffusion plate.

[4] A method of manufacturing an optical flat plate member according to any one of claims 1 to 3,

The manufacturing method of the optical flat plate member which injection-molds using the metal mold | die provided with the hot runner which has a valve gate.