JP2008238610A - Mold part and light diffusion plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold part capable of efficiently molding a flat plate molding superior in optical properties. <P>SOLUTION: A plurality of linear parts 3 arranged along a predetermined direction are formed on a cavity surface for forming the surface of the flat plate molding and this cavity surface is characterized in that the maximum value Ra(max 1) of center line average roughness Ra measured along all of directions within the cavity surface is 3.0-1,000 μm. Linear recesses 4A are formed on the oblique surfaces 4 of the linear parts 3. When the maximum value of center line average roughness Ra(μm) measured along all of the directions within the cavity surface is set to Ra(max 2) and the minimum value of the center line average roughness Ra measured along all of the directions within the cavity surface is set to Ra(min 2), the relation of 0.05>Ra(max 2)>0.005 and Ra(max 2)/Ra(min 2)>1.5 is satisfied by the surface with the linear recesses 4A. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a mold part and a light diffusing plate, and more particularly to a mold part and a light diffusing plate capable of efficiently forming a flat molded product having excellent optical performance.

  Conventionally, a liquid crystal display device may use a direct backlight device having a reflector, a plurality of light sources, and a light diffusing plate. In such a direct type backlight device, a cross-sectional polygon extending substantially parallel to the longitudinal direction of the light source is provided on the surface of the light diffusing plate in order to make the luminance uniform on the light diffusing plate exit surface (increase the luminance uniformity). It has been practiced to provide a prism array in which a plurality of linear prisms are arranged (see Patent Document 1). Such a light diffusing plate can be obtained, for example, by forming a concavo-convex structure corresponding to the prism row on the cavity surface of a mold part and performing injection molding using the mold part. However, when a light diffusing plate having such a linear prism is formed by injection molding, depending on the resin used, the light diffusing plate may stick to the mold part, and it may be difficult to release the light diffusing plate. . For this reason, the molding operation is not always efficient.

  On the other hand, Patent Document 2 discloses that in a mold for injection molding, the surface of the mold has a ten-point average roughness Rz of 0 in order to improve the releasability of the molded article due to adhesion between the mold and the molded article. It is disclosed that the surface has a rough surface of 2 to 3.0 μm.

Japanese Patent Laid-Open No. 2006-066074 Japanese Patent Laid-Open No. 2001-287227

  In order to efficiently perform the injection molding of the light diffusing plate, it is conceivable to roughen the surface of the concavo-convex structure corresponding to the prism row using the technique shown in Patent Document 2. However, simply applying this technique can improve the mold releasability of the molded product, but there are cases where the optical performance such as luminance uniformity cannot be sufficiently exhibited. For this reason, development of mold parts having sufficient optical performance and excellent releasability is desired. Such a problem occurs not only in the case where the molded product is a light diffusion plate, but also in a flat molded product such as a light guide plate.

  An object of the present invention is to provide a mold part capable of efficiently molding a flat molded article having excellent optical performance, and a light diffusing plate manufactured by the mold part.

The present invention relates to a mold part used for a cavity surface of a mold for injection molding a resin flat molded product used as an optical part, and a plurality of the mold parts arranged in a predetermined direction on the cavity surface. In this cavity surface, the maximum value Ra (max1) of the centerline average roughness Ra measured along all directions in the surface is 3.0 μm to 1,000 μm, At least a part of the concavo-convex structure of the plurality of concavo-convex structures has a plurality of micro concavo-convex parts formed on at least a part of the surface, and the surface on which the plurality of micro concavo-convex parts are formed The maximum value of the center line average roughness Ra (μm) measured along all directions in the inside is defined as Ra (max 2), and the center line average roughness Ra (μm) measured along all directions within the plane As the minimum value of Ra (min2), ) And satisfies the relation (2).
0.05> Ra (max2)> 0.005 (1)
Ra (max2) / Ra (min2)> 1.5 (2)

  The mold part can be a mold itself or a stamper disposed on the main surface of the mold. In addition, the surface of the concavo-convex structure can be configured to include two or more planes. Further, the surface of the concavo-convex structure may be configured such that the cross-sectional shape includes a curved surface such as an arc, an elliptical arc, or a parabolic arc. When the surface is a curved surface, the center line average roughness Ra may be measured in a direction along the curved surface.

  According to the present invention, since the minute concavo-convex portion satisfying the above relationship formed on the surface of the concavo-convex structure is formed with an extremely small size, the molten resin is completely contained in the micro concavo-convex structure during injection molding. Hard to get in. For this reason, a gap is generated between the mold part and the sticking to the mold part can be suppressed, and the shape of the minute uneven part becomes a smooth surface that is not completely transferred, thereby scattering light. It is possible to obtain the desired optical characteristics with suppressed. Further, even if the molten resin enters a part of the minute uneven portion, it becomes smaller than the visible light wavelength, so that the optical performance is not affected. Therefore, it is possible to efficiently mold a flat molded product having excellent optical performance.

  Here, in the mold part, the concavo-convex structure may be configured to include two or more planes inclined with respect to the thickness direction of the mold part.

Here, the concavo-convex structure can be a linear portion extending linearly in parallel with each other. Specifically, for example, a configuration in which the cross section has a polygonal shape such as a triangle, a quadrangle, or a pentagon, and extends linearly can be employed.
In the mold part, the concavo-convex structure may be a pyramid having a pyramid shape or a truncated pyramid shape. As the cone, for example, a triangular pyramid, a quadrangular pyramid, a quadrangular pyramid, and the like can be adopted.

  Further, in the mold part, at least one of the two or more planes is formed with a rough surface portion on which a minute uneven portion is formed and a smooth surface portion formed more smoothly than the minute uneven portion. It can be set as the structure which becomes. According to such a configuration, mold parts can be easily manufactured. At this time, it is preferable that a plurality of rough surface portions and smooth surface portions are alternately provided on one plane.

  In the mold part, in the one plane, a ratio (S1 / S2) of the area S1 of the rough surface portion to the area S2 of the smooth surface portion is preferably 0.05 to 20, and 0.1 10 is more preferable. By making the area ratio within the above-mentioned preferable range, it is possible to easily produce mold parts while having sufficient releasability.

  The present invention is a light diffusing plate manufactured by injection molding using the above mold parts. According to such a light diffusing plate, sufficient optical performance can be exhibited. In particular, when a direct-type backlight device in which the light diffusion plate thus obtained, a plurality of linear light sources, and a reflecting plate are arranged in this order is configured, the interval between the linear light sources is a, When the distance b between the center of the linear light source and the light diffusing plate is set, sufficient optical performance can be exhibited even when the ratio (a / b) is 2.3 or more.

  According to the present invention, by forming a predetermined minute uneven portion on the surface of the uneven structure, there is an effect that it is possible to efficiently form a flat molded product excellent in optical performance while suppressing sticking to a mold part.

A mold part according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view schematically showing a stamper 1 which is a mold part according to the present embodiment. FIG. 2 is a view partially showing a cross section along the thickness direction of the stamper 1. The stamper 1 is a member for forming a resin-made flat molded product used for an optical component, and is disposed at a position corresponding to a cavity surface of an injection mold (not shown). Examples of the molded flat product include optical components such as a light diffusion plate and a light guide plate.

  Here, as the resin constituting the flat plate molded product, a transparent resin can be used from the viewpoint of not reducing the luminance. The transparent resin is a resin having a total light transmittance of 70% or more measured with a 2 mm-thick plate smooth on both sides based on JIS K7361-1, for example, polyethylene, propylene-ethylene copolymer, polypropylene , Polystyrene, a copolymer of an aromatic vinyl monomer and a (meth) acrylic acid alkyl ester having a lower alkyl group, polyethylene terephthalate, terephthalic acid-ethylene glycol-cyclohexanedimethanol copolymer, polycarbonate, acrylic resin, and Examples thereof include a resin having an alicyclic structure. In addition, (meth) acrylic acid is acrylic acid and methacrylic acid. Here, as the resin, a resin obtained by adding a light diffusing agent to the transparent resin may be used. The light diffusing agent is a particle having a property of diffusing light, and examples thereof include an inorganic filler and an organic filler.

  As shown in FIGS. 1 and 2, the stamper 1 has a concavo-convex structure 2 formed on a surface serving as a cavity surface. The concavo-convex structure 2 is a sawtooth cross-sectional structure in which a plurality of linear portions 3 which are concavo-convex structures are arranged substantially parallel to each other and the bottom angles of the linear portions 3 are continuous.

  As shown in FIG. 2, the linear portion 3 has a slope 4 which is two planes inclined with respect to the thickness direction of the stamper 1 and is formed in a triangular shape having a convex section. The apex angle θ of the linear portion 3 is 60 ° to 170 °, preferably 70 ° to 160 °. The width dimension W of the bottom part of the linear part 3 is 20 micrometers-700 micrometers, Preferably it is 30 micrometers-600 micrometers. The height H of the linear portion 3 is 0.9 μm to 606 μm, and preferably 2.6 μm to 428 μm. The cross-sectional shape of the linear portion 3 is preferably an isosceles triangle in that the optical performance of the molded flat plate product is improved. Moreover, the space | interval (pitch) P between the adjacent linear parts 3 is 20 micrometers-700 micrometers, Preferably they are 30 micrometers-600 micrometers.

  In the concavo-convex structure 2 constituted by such a plurality of linear portions 3, the centerline average roughness Ra (max1) measured in the A direction which is a direction perpendicular to the thickness direction of the stamper 1 is 3.0 μm to 1, 000 μm, preferably 4.0 μm to 900 μm. The A direction is the direction showing the maximum value of the center line average roughness Ra measured along all directions in the plane. The centerline average roughness Ra can be obtained based on JIS B0601.

  On the surface of each inclined surface 4 of the linear part 3, a plurality of linear concave parts 4A which are minute uneven parts are formed. 4 A of linear recessed parts are extended substantially parallel to the longitudinal direction (direction perpendicular | vertical to the paper surface of FIG. 2) of the linear part 3. As shown in FIG. These linear recesses 4A are substantially parallel to each other. In the slope 4, between the center line average roughness Ra (max2) measured along the B direction and the C direction, which are directions along the slope 4A in the figure, and the Ra (max1), 0.05> The relationship (1) of Ra (max2)> 0.005 is satisfied. The B direction and the C direction are directions indicating the maximum value of the center line average roughness Ra measured along all directions in the plane.

  On the surface of the slope 4 where the linear recess 4A is formed, Ra (max2) is between the centerline average roughness Ra (min2) measured in the longitudinal direction of the linear recess 4A and the Ra (max2). ) / Ra (min2)> 1.5 (2) is satisfied. In addition, the longitudinal direction of 4 A of linear recessed parts is a direction which shows the minimum value of the centerline average roughness Ra measured along all the directions in the said surface.

  The average distance Sm between the adjacent linear recesses 4A measured in the B direction and the C direction is Ra (max1) × 10> Sm> Ra (max1) × 0 between the Ra (max1). It is preferable that the relationship of .001 is satisfied, and it is more preferable that the relationship of Ra (max1) × 9> Sm> Ra (max1) × 0.002 is satisfied.

The stamper 1 as described above is manufactured as follows, for example.
First, a nickel-phosphorus electroless plating layer having a thickness of, for example, about 100 μm is applied to the entire surface of a metal rectangular plate. Next, a fine processing machine tool (for example, Nano Gruber AMG71P, manufactured by Fujikoshi Co., Ltd.) provided with a single crystal diamond bit having a vertex angle of a predetermined angle on the surface of the plating layer and processing corresponding to the linear recess 4A. ), The concavo-convex structure 2 having a plurality of linear portions 3 having a triangular cross section is formed by cutting at a predetermined pitch along the longitudinal side of the plate material. Here, the processing corresponding to the linear recess 4A can be performed by using the diamond bit having the uneven portion formed thereon by using a high energy beam processing apparatus such as a focused ion beam apparatus. For this reason, a plurality of linear recesses 4 </ b> A are formed on the slope 4 of the linear part 3 along the longitudinal direction of the linear part 3 due to the uneven part of the diamond tool. The stamper 1 is produced as described above.

  The stamper 1 produced in this way is arranged so that the surface on which the concavo-convex structure 2 is formed becomes the cavity surface of an injection mold, and is injection-molded using the resin. Flat plate molded products used as optical parts can be molded.

  According to the present embodiment, by providing the linear recess 4A in which the center line average roughness Ra satisfies the relationships (1) and (2) on the slope 4 of the linear portion 3 of the stamper 1, this fineness is achieved. Since the resin for molding does not easily enter the linear recess 4A, the flat plate molded product can be easily released from the stamper 1 due to the occurrence of a gap between the stamper 1 and the flat plate molded product. For this reason, a flat plate molded product can be molded efficiently. In addition, the flat plate molded product is formed with a prism row composed of linear prisms having a triangular cross section corresponding to the concavo-convex structure 2 composed of a plurality of linear portions 3. When a molded product is used as a light diffusing plate and this light diffusing plate is arranged on a plurality of light sources to produce a direct type backlight device, the luminance unevenness is reduced while maintaining sufficient luminance (luminance uniformity). A device having a light emitting surface with a high degree of lightness can be obtained. At this time, since the resin hardly enters the fine concavo-convex portions, light scattering caused by the fine concavo-convex portions can be suppressed, and desired optical characteristics can be obtained.

  On the light diffusing plate obtained by the stamper 1, prism rows corresponding to the uneven structure 2 of the stamper 1 are formed. A minute concavo-convex structure corresponding to the linear concave portion 4A can be formed on each inclined surface of each linear prism constituting the prism row. As described above, the releasability between the flat plate molded product and the mold part can be reduced. In consideration of optical characteristics, it is preferable that the uneven structure corresponding to the linear recess 4A is not transferred.

<Modification>
In addition, this invention is not limited to the said embodiment.
For example, in the above-described embodiment, the concavo-convex portion of the slope 4 of the linear portion 3 is the linear concave portion 4A, but it may be a linear convex portion (linear convex portion), or a linear concave portion and a linear convex portion. It is good also as a structure which has both. In addition, a plurality of linear recesses 4 </ b> A are formed on the slope 4 so as to be substantially parallel to the longitudinal direction of the linear portion 3, but the plurality of linear recesses 4 </ b> A are substantially parallel to the longitudinal direction of the linear portion 3. It does not have to be. However, it is preferable that the plurality of linear recesses 4A are substantially parallel to each other.

  Moreover, in the said embodiment, although the linear part 3 was made into the cross-sectional triangle shape, it is good also as polygonal shapes other than a triangular shape, and the shape in which a cross section contains curves, such as a circular arc, an elliptical arc, a parabolic arc, what is called a lenticular lens shape It is good. Here, as the polygonal linear portion, for example, as shown in FIG. 3, the concavo-convex structure 2 includes at least four surfaces 11 to 14, and two of the at least four surfaces 11 to 14 are provided. A configuration in which the surfaces 11 and 12 and the other two surfaces 13 and 14 are inclined in directions opposite to each other with respect to a surface including the thickness direction of the stamper 1 (a surface including the vertical direction in the figure and perpendicular to the paper surface). Also good. By configuring the direct type backlight device using the light diffusing plate formed using the stamper having such a configuration and a plurality of light sources, the luminance and the luminance uniformity of the light emitting surface can be increased. Therefore, the light diffusing plate has sufficient optical performance.

  Moreover, in the said embodiment, although all apex angle (theta) of the linear part 3 was made into the same angle, you may make it apex angle (theta) differ. For example, as shown in FIG. 4, the angle formed by the two inclined surfaces 4 of each linear portion 3 and the surface in the direction orthogonal to the thickness direction of the stamper 1 is formed to be equal. The angle θ is continuous or stepwise as it moves away from the point X and the point Y between the point Y and the point Y that is separated from the point Y by a predetermined distance along the direction perpendicular to the longitudinal direction of the linear portion 3 (left and right direction in the figure). You may form so that it may become small. By arranging a light source at a position corresponding to the point X and the point Y of the light diffusing plate formed using the stamper having such a configuration to constitute a direct type backlight device, the luminance and luminance uniformity of the light emitting surface Can be increased. Therefore, the light diffusing plate has sufficient optical performance.

  Moreover, in the said embodiment, the uneven structure 2 is good also as a convex structure or a concave structure which has a slope which is three or more planes inclined with respect to the thickness direction of a stamper. As the concave structure or the convex structure having three or more inclined surfaces, for example, a pyramid including a polygonal pyramid such as a quadrangular pyramid as shown in FIG. By configuring a direct type backlight device using a light diffusing plate formed using a stamper having such a cone and a plurality of light sources, the luminance and luminance uniformity of the light emitting surface can be increased. Therefore, the light diffusing plate has sufficient optical performance.

  The cone is formed by forming a linear portion having a polygonal shape with a concave or convex cross section, and then making a V-shaped cut into the linear portion in a direction different from the longitudinal direction of the linear portion. can do.

  In the above embodiment, the linear recesses 4A are formed on the entire slopes 4 of all the linear parts 3 over substantially the entire surface of the slopes 4. However, the present invention is not limited to this, The structure which provided the flat surface (mirror surface shape) without the linear recessed part 4A in the part of all the slopes 4 of the some linear part 3 is also contained. By providing a flat surface in this way, there is an advantage that it is possible to obtain a molded product with a higher luminance uniformity (with less luminance unevenness) while ensuring sufficient molding efficiency. A specific configuration of a stamper having a part of a flat surface is shown below.

FIG. 7 is a cross-sectional view showing a stamper 201 according to a fourth modification.
As shown in FIG. 7, the stamper 201 has a configuration in which a linear recess 4 </ b> A is formed only on the slope 4 of a part of the linear portions 3 among the plurality of linear portions 3. Such a stamper 201 can be easily produced by using both the sintered diamond bite and the single crystal diamond bite.

FIG. 8 is a cross-sectional view showing a stamper 202 according to a fifth modification.
As shown in FIG. 8, the stamper 202 has a configuration in which the linear protrusions 4 </ b> B are formed only on a part of the inclined surfaces 4 on the inclined surfaces 4 of the plurality of linear portions 3. Specifically, in the stamper 202, on the slope 4 constituting the linear portion 3, the linear convex portion 4B is formed only at the central portion of the slope 4 excluding the root side and the top side of the linear portion 3. ing. By forming the linear protrusion 4B only at the center portion, there is an advantage that the processing of the linear portion 3 can be facilitated.

  As shown in FIG. 8, the range of the central portion is D in the length in the direction along each inclined surface 4, and this length D is divided into three regions extending from the root side to the top side of the linear portion 3. When the length of each region is set to D1, D2, and D3 in the order described above, for example, the length D2 is 1% to 98% of the length D, the length D1 is 1% to 98% of the length D, The length D3 can be 1% to 98% of the length D. Further, it is preferable that the length D2 is 5% to 90% of the length D, the length D1 is 5% to 90% of the length D, and the length D3 is 5% to 90% of the length D. More preferably, the length D2 is 10% to 80% of the length D, the length D1 is 10% to 80% of the length D, and the length D3 is 10% to 80% of the length D. Specifically, for example, when the length D is 45.7 μm, the lengths D1 and D3 can be 4.6 μm and the length D2 can be 36.5 μm, respectively. In addition, although the length D2 and the length D3 were made into the same dimension, it is good also as a different dimension.

  Such a stamper 202 is prepared by, for example, producing a chip on which the surface of the single crystal diamond chip is finely processed by using, for example, a focused ion beam device to form a linear convex portion in part, and then, It can be manufactured by performing the same processing as described above using the attached tool.

Here, the detailed shape of the central portion will be described.
FIG. 9 is an enlarged cross-sectional view of the range X in FIG. As shown in FIG. 9, the central portion of the inclined surface 4 has a row portion 4 </ b> X as a rough surface portion in which two linear convex portions 4 </ b> B (micro uneven portions) having a cross section of 90 ° in apex are connected. A plurality are formed at intervals. That is, on the slope 4, a plurality of row portions 4X and smooth surface portions as rough surface portions are alternately provided. At this time, the ratio (S1 / S2) between the area S1 of the row portion 4X and the area S2 of the smooth surface portion is preferably 0.05 to 20.

  By providing such a row portion 4X, a concave portion Z is formed between the two linear convex portions 4B. When a molded product is formed using the stamper 202 having the recesses Z, it is difficult to enter the molding resin into the recesses Z. Therefore, a stamper is formed due to the formation of voids in the deepest part of the recesses Z. There exists a tendency for the mold release property of the molded article from 202 to improve. For this reason, it is possible to improve the moldability of the molded product by deliberately providing a portion such as the concave portion Z on the slope 4 of the linear portion that is difficult for the resin to enter. However, the shape of the recess Z needs to be a shape in which an undercut portion does not occur so that when the molded product is released from the stamper 202, the release is not hindered.

  In this modification, the central portion of the slope 4 has a configuration in which a plurality of row portions 4X are formed at intervals, but there is no interval between the row portions 4X, that is, a linear convex portion 4B. It can be set as the structure which mutually continued. Even in such a configuration, since the root portion and the top portion of the linear portion are flat surfaces, it is possible to obtain a molded product with higher brightness uniformity while ensuring sufficient molding efficiency. Can be played.

  Moreover, although the row | line | column part 4X was formed only in the said center part, you may form a structure as shown in FIG. In this case, since the flat portion as described above is provided between the row portions 4X, there is an advantage that a molded product with a higher luminance uniformity can be obtained while ensuring sufficient molding efficiency. be able to.

  Further, in this modification, the configuration of the row portion 4X is a configuration in which two linear convex portions 4B are connected, but may be a shape in which three or more linear concave portions are connected. Moreover, it is good also as a structure with which the multiple types of row | line | column part was combined. For example, as shown in FIG. 10, a configuration in which a row portion 4X in which two linear convex portions 4B are continuous and a row portion 4Y in which three linear convex portions 4B are continuous is mixed. it can.

FIG. 11 is a cross-sectional view showing a stamper 203 according to a sixth modification.
As shown in FIG. 11, the stamper 203 has a configuration in which the linear convex portions 4 </ b> B are formed only on any one of the slopes 4 of the linear portions 3. The stamper 203 can be manufactured by using a cutting tool provided with the single crystal diamond tip and a cutting tool finely processed by the focused ion beam apparatus or the like.

FIG. 12 is a cross-sectional view showing a stamper 204 according to a seventh modification.
As shown in FIG. 12, the stamper 204 has a configuration in which the linear convex portion 4 </ b> B is formed only on one of the slopes 4 of each linear portion 3. The stamper 204 can be manufactured by performing the same processing as described above using a tool in which a chip that has been finely processed by the focused ion beam apparatus or the like is attached to only one surface of the single crystal diamond tool. .

  In addition, although the modification of a mold component was mentioned as a modification of this invention, the light diffusing plate obtained using the mold component which concerns on these modifications can also mention the same modification. That is, at least one main surface of the light diffusing plate according to the modified example of the present invention has a shape in which the concavo-convex structure of the mold part is appropriately transferred as long as the releasability is not impaired.

  Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. The present invention is not limited to these examples.

<Example 1>
Nickel-phosphorous electroless plating with a thickness of 100 μm was applied to the entire surface of a rectangular plate made of stainless steel SUS430 having dimensions of 800 mm × 500 mm and a thickness of 2 mm. Next, using a focused ion beam (FIB) apparatus (manufactured by Hitachi High-Technology Corporation) on the surface of a single crystal diamond tip (manufactured by Contool Fine Tooling) having an apex angle of 100 degrees, FIG. A micromachined chip, schematically showing the tip, was produced. This micromachined chip will be described using a surface directed in the upper right direction in the figure. A smooth surface 301 is formed from the tip T to a position having a width of 10 μm, and a width of 0.22 μm from the end of the smooth surface 301 is set to a depth of 0.2 mm. Five triangular portions 302 having an isosceles right triangle of 11 μm are continuously engraved, and a smooth surface 303 is formed from the end of the triangular shape portion 302 to a position having a width of 5.9 μm. From the end of the smooth surface 301, the triangular shape portion is formed. Five triangular portions 304 having the same size as 302 were engraved, and the engraving process was repeated three times at the same location. This chip was attached to a cutting tool to prepare a cutting tool to which a micromachined chip was mounted. Using the obtained cutting tool for a machine tool for fine processing (for example, Nanogruber AMG71P, manufactured by Fujikoshi Co., Ltd.), the width of the plate is 70 μm in height along the short side direction of the plate material with respect to the nickel-phosphorous electroless plating surface. A concavo-convex structure was formed by cutting a plurality of linear portions having an isosceles triangular section of 29.4 μm, a pitch of 70 μm, and an apex angle of 100 degrees to obtain a stamper.

  With respect to the obtained stamper, the Ra (max1) of the linear portion, the Ra (max2), Ra (min2), and Sm of the slope of the linear portion were determined using an ultradeep microscope. As a result, Ra (max1) was 7.2 μm. Further, Ra (max2) was 0.007 μm, Ra (max2) / Ra (min2) was 4.5, and Sm was 70 μm. S1 / S2 was 0.14. The total area of the surfaces formed corresponding to the smooth surface is the area of the smooth surface portion (S2), and the total area of the surfaces where the triangular portions are formed is the area of the rough surface portion (S1).

Next, the resin constituting the molded product will be described.
99.7 parts by mass of a transparent resin having an alicyclic structure (manufactured by ZEON Corporation, ZEONOR 1060R, water absorption 0.01%), and a crosslinked product of a polysiloxane polymer having an average particle size of 2 μm as a light diffusing agent Were mixed with 0.3 parts by mass of fine particles, kneaded with a twin-screw extruder, extruded into a strand, and cut with a pelletizer to produce a pellet for a light diffusion plate. Using this light diffusion plate pellet as a raw material, a 100 mm × 50 mm test plate having a smooth thickness of 2 mm on both sides was formed using an injection molding machine (clamping force 1000 kN). The total light transmittance and haze of this test plate were measured using an integrating sphere type color difference turbidimeter based on JIS K7361-1 and JIS K7136. The test plate had a total light transmittance of 85% and a haze of 99%.

  Next, a mold was prepared, the stamper was attached to one mold constituting the mold, and the cavity surface of the other mold was polished. At this time, Ra of the polished surface was 0.003 μm. Using an injection molding machine having such a mold (clamping force 4,410 kN), the light diffusion plate is molded under the conditions of a cylinder temperature of 280 ° C. and a mold temperature of 85 ° C. using the light diffusion plate pellets as a raw material. did. The light diffusing plate thus obtained was stuck to the stamper only once after 500 shots of injection molding.

  The obtained light diffusing plate has a rectangular shape with a thickness of 2 mm and 727.5 mm × 415 mm to which the uneven structure of the stamper is appropriately transferred, and a plurality of linear prisms having a triangular cross section on one side thereof. Side-by-side prism rows were formed. This linear prism had an apex angle of 100 ° and a pitch of 70 μm. In addition, the plurality of minute uneven portions formed on the plane of the uneven structure in the stamper were hardly transferred.

  Next, a reflective sheet (manufactured by Tsujiden Co., Ltd., RF188) is attached to the inner surface of a milky white plastic case having an inner width of 700 mm, a depth of 400 mm, and a depth of 20 mm to form a reflector, and 5 mm away from the bottom of the reflector Ten cold cathode tubes having a diameter of 3 mm and a length of 750 mm were arranged so that the distance between the centers of the cold cathode tubes was 40 mm, the vicinity of the electrode portion was fixed with a silicone sealant, and an inverter was attached.

  Next, the obtained light diffusing plate was placed so that the prism row was on the opposite side (the opposite light source position) of the cold cathode tube, and was placed on a plastic case to which the cold cathode tube was attached. At this time, the cold cathode tubes were arranged so that the longitudinal direction of the cold cathode tubes and the longitudinal direction of the triangular prisms constituting the prism row were substantially parallel. Furthermore, a diffusion sheet (“188GM3”, manufactured by Kimoto), a prism sheet (“BEFIII”, manufactured by Sumitomo 3M), and a diffusion sheet (“188GM3”, manufactured by Kimoto) are installed in this order on the light diffusion plate. did. In this way, as shown in FIG. 6, a direct type backlight device 100 having a plurality of light sources 101, a reflecting plate 102, and the light diffusion plate was produced.

Next, a cold cathode tube is turned on by applying a tube current of 5 mA to the obtained direct type backlight, and using a two-dimensional color distribution measuring device, 100 front faces are equally spaced on the center line in the short direction. The luminance in the direction was measured, and a luminance average value La and luminance unevenness Lu were obtained according to the following formulas 1 and 2. At this time, the luminance average value was 7,114 cd / m ² and the luminance unevenness was 0.3%.
Luminance average value La = (L1 + L2) / 2 (Formula 1)
Luminance unevenness Lu = ((L1-L2) / La) × 100 (Formula 2)
L1: Average luminance maximum value just above a plurality of cold-cathode tubes installed L2: Average minimum value sandwiched between maximum values Note that luminance unevenness is an index indicating luminance uniformity, and luminance unevenness When it is bad, the figure increases.

<Example 2>
A light diffusing plate and a direct type backlight device are obtained in the same manner as in Example 1 except that the width of the right isosceles triangle is 0.46 μm, the depth is 0.23 μm, and the width of the smooth surface 303 is 4.7 μm. It was. As a result, Ra (max1) of the obtained stamper was 7.2 μm. Further, Ra (max2) was 0.029 μm, Ra (max2) / Ra (min2) was 14.5, and Sm was 70 μm. S1 / S2 was 0.34. In addition, although the several micro uneven | corrugated | grooved part formed in the plane of the uneven | corrugated structure in a stamper was partially transferred, it was not transferred very much as a whole. The obtained light diffusing plate never stuck to the stamper even after 500 shots of injection molding. Further, in the obtained direct type backlight device, the average luminance value was 7,150 cd / m ² and the luminance unevenness was 0.4%.

<Example 3>
The light diffusing plate and the direct type back are the same as in Example 1 except that the width of the smooth surface 301 is 6 μm, the right isosceles triangular shape is 0.46 μm wide, 0.23 μm deep, and 75 engraved. A light device was obtained. As a result, Ra (max1) of the obtained stamper was 7.2 μm. Further, Ra (max2) was 0.089 μm, Ra (max2) / Ra (min2) was 29.7, and Sm was 70 μm. S1 / S2 was 3.08. In addition, although the several uneven | corrugated | grooved part formed in the plane of the uneven | corrugated structure in a stamper was partially transferred, it was not transferred very much as a whole. The obtained light diffusing plate never stuck to the stamper even after 500 shots of injection molding. Further, in the obtained direct type backlight device, the average luminance value was 7,186 cd / m ² and the luminance unevenness was 0.8%.

<Comparative Example 1>
A light diffusing plate and a direct backlight device were obtained in the same manner as in Example 1 except that fine irregularities were not processed on the single crystal diamond chip. As a result, Ra (max1) of the obtained stamper was 7.2 μm. Moreover, Ra (max2) was 0.004 μm, Ra (max2) / Ra (min2) was 6.0, and Sm was 70 μm. The obtained light diffusion plate stuck to the stamper 498 times after performing 500 shots of injection molding. In the direct type backlight device using the light diffusion plate that was not attached, the average luminance value was 7,100 cd / m ² and the luminance unevenness was 0.2%.

<Comparative example 2>
A light diffusing plate and a direct backlight device were obtained in the same manner as in Comparative Example 1 except that a polycrystalline diamond chip was used. As a result, Ra (max1) of the obtained stamper was 7.2 μm. In addition, Ra (max2) was 0.18 μm, Ra (max2) / Ra (min2) was 7.9, and Sm was 70 μm. S1 / S2 was 1.0. The obtained light diffusion plate was never stuck to the stamper after 500 shots of injection molding. In the obtained direct type backlight device, the average luminance value was 7,240 cd / m ² and the luminance unevenness was 1.8%.

  The results of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1.

  In Table 1, formability is a value indicating how many times the flat molded product has stuck to the stamper when 500 shots of injection molding are performed.

  As shown in Table 1, in Examples 1 to 3, it was found that the moldability (mold release property) was excellent and the luminance and luminance unevenness were both good. On the other hand, as shown in Comparative Example 1, in the case where the minute uneven portion is not formed on the surface of each surface of the uneven structure, the releasability was insufficient. In addition, as shown in Comparative Example 2, it was found that when unevenness portions having a predetermined size or more were formed on the surface of each surface of the uneven structure, the luminance unevenness was increased.

1 is a perspective view schematically showing a mold part according to an embodiment of the present invention. It is a fragmentary sectional view which partially shows the cross section along the thickness direction of the said mold components. It is a fragmentary sectional view showing typically the metallic mold parts concerning the 1st modification of the present invention. It is a fragmentary sectional view showing typically a mold part concerning the 2nd modification of the present invention. It is a fragmentary sectional view showing typically the metallic mold parts concerning the 3rd modification of the present invention. It is a perspective view which shows typically the direct type | mold backlight apparatus which concerns on an Example. It is sectional drawing which shows the stamper which concerns on a 4th modification. It is sectional drawing which shows the stamper which concerns on a 5th modification. It is sectional drawing which expands and shows the range X in FIG. It is sectional drawing which shows the modification of a row part. It is sectional drawing which shows the stamper which concerns on a 6th modification. It is sectional drawing which shows the stamper which concerns on a 7th modification. It is typical sectional drawing which expands and shows the front-end | tip part of the microfabricated chip | tip used in Example 1,2.

Explanation of symbols

1,201-204 Stamper (mold parts)
3 Linear parts (concave / convex structure)
4 slope (plane)
4A Linear concave part (micro uneven part)
4B Linear convex part (micro uneven part)

Claims (7)

A mold part used on a cavity surface of a mold for injection molding a resin flat plate product used as an optical part,
A plurality of concavo-convex structures arranged in a predetermined direction are formed on the cavity surface, and the cavity surface is a maximum value Ra of centerline average roughness Ra measured along all directions in the surface. (Max1) is 3.0 μm to 1,000 μm,
At least some of the plurality of concavo-convex structures have a plurality of micro concavo-convex portions formed on at least a part of the surface thereof.
On the surface on which the plurality of micro concavo-convex portions are formed, the maximum value of the center line average roughness Ra (μm) measured along all directions in the surface is defined as Ra (max2), A mold part satisfying the following relations (1) and (2), where Ra (min2) is the minimum value of the centerline average roughness Ra (μm) measured along the direction.
0.05> Ra (max2)> 0.005 (1)
Ra (max2) / Ra (min2)> 1.5 (2) The mold part according to claim 1,
The concavo-convex structure is a mold part including two or more planes inclined with respect to the thickness direction of the mold part. The mold part according to claim 2,
The concavo-convex structure is a mold part which is a linear part extending linearly in parallel with each other. The mold part according to claim 2,
The concavo-convex structure is a mold part which is a pyramid having a pyramid shape or a truncated pyramid shape. The mold part according to claim 2,
At least one of the two or more planes is a mold part in which a rough surface portion on which fine uneven portions are formed and a smooth surface portion formed smoother than the fine uneven portions are formed. The mold part according to claim 5,
The mold part whose ratio (S1 / S2) of the area S1 of the rough surface portion to the area S2 of the smooth surface portion is 0.05 to 20 in the one plane.   The light diffusing plate manufactured by injection molding using the metal mold | die part in any one of Claims 1-6.

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