JPWO2007094209A1 - Method for producing flat plate molded product and flat plate molded product - Google Patents

Abstract

A plurality of gates 20 are provided on the substantially rectangular cavity surface 10. The gates 20 are arranged at substantially equal intervals along the vertical direction or the horizontal direction. The plurality of gates are three horizontal gate rows 22 and four vertical gate rows, and among the three horizontal gate rows, the middle horizontal gate row 22B is the first horizontal gate row X, and the lateral gates outside thereof. The columns 20A and 20C are defined as a second horizontal gate column Y. When the resin is injected from the first horizontal gate row X and the injection amount of the resin reaches a predetermined amount, the resin is injected from the second horizontal gate row Y to manufacture a flat plate molded product.

Description

  The present invention relates to a method for producing a flat plate molded product and a flat plate molded product produced by the production method.

  Conventionally, as a backlight device for a liquid crystal display, an edge light type method or a direct type method is used. For example, a general direct type backlight device includes a plurality of light sources arranged in parallel, a reflection plate that reflects light emitted from the light source, light from the light source and light reflected by the reflection plate. And a light diffusing plate for diffusing irradiation.

  The light diffusing plate used in such a direct type backlight device is often molded by an extrusion molding method, a casting method, an injection molding method, or the like. For example, Japanese Patent Application Publication No. 2005-271306 discloses a method of forming a light diffusion plate by an injection molding method. This method is a method of manufacturing a light diffusing plate by using a mold in which a rectangular cavity surface is divided into predetermined rectangles and a gate is provided at the center in the short direction from the intersection of diagonal lines of each rectangle. . According to such a method, since air does not easily accumulate in the cavity, there is an effect that it is possible to efficiently manufacture a high-quality light diffusion plate with few appearance defects due to burning or the like.

  However, in the gate row in the short direction of the rectangular cavity surface, there are a mixture of a part with a wide gate interval and a part with a narrow gate interval. In some cases, it could not be lowered sufficiently. Such a problem occurs not only in the light diffusion plate but also in other optical members such as a light guide plate and a reflection plate and other flat plate molded products.

  An object of the present invention is to provide a method for producing a flat molded product capable of efficiently producing a high quality flat plate molded product while keeping the in-mold pressure low, and a flat molded product obtained by this production method.

  As a result of intensive studies by the present inventors in order to solve the above problems, for example, when three gates in the vertical direction and four gates in the horizontal direction are arranged at equal intervals, three gates arranged in the vertical direction are arranged. Resin is injected from the gate row (first gate row) along the lateral direction including the middle gate, and then the resin is injected from the gate rows (second gate row) on both sides of the first gate row at different timings. It has been found that high-quality flat plate molded products can be efficiently manufactured by suppressing the in-mold pressure by injection.

  Further, the present inventors have found a method for manufacturing a flat plate molded product that can efficiently manufacture a high quality flat plate molded product while suppressing the pressure inside the mold when a plurality of gates are arranged at equal intervals in the vertical direction and the horizontal direction.

  That is, according to the first aspect of the present invention, there is provided a method for producing a resin flat molded article using an injection mold, wherein the mold corresponds to the shape of the flat molded article. And a fixed mold plate provided with a plurality of gates communicating with the cavity surface, wherein the plurality of gates are arranged in a substantially rectangular longitudinal direction and a lateral direction of the cavity surface. When the grid having the vertical pitch L1 and the horizontal pitch L2 is considered, the grid is arranged at the intersection of the grid and is closest to each vertex of the substantially rectangular cavity surface. In the four outermost gates which are gates, the distances LA1 to LA4 between each outermost gate and the nearest side of the lateral side of the cavity surface are 120% to 10% of the pitch L1, and each Outermost gate and front The distances LB1 to LB4 with the nearest side among the vertical sides of the cavity surface are 120% to 10% of the pitch L2, and the plurality of gates are separated from the plurality of gates arranged along the vertical direction. A plurality of vertical gate rows and a plurality of horizontal gate rows composed of a plurality of gates arranged along the horizontal direction, the number of the vertical gate rows and the number of the horizontal gate rows in at least one direction. The number of gate rows is an odd number, and in the gate row in any direction where the number is odd, a plurality of gate rows is a row including a central gate that is a gate closest to an intersection of diagonal lines of the cavity surface. A first gate row, a second gate row including two gate rows close to the first gate row, a third gate row including gate rows close to the gate rows constituting the second gate row,. -Configure 1 gate line A first step of injecting the resin from the first gate row, and injection from the n-1 gate row, wherein each of the n-th gate rows (n is an integer of 2 or more) including each gate row close to each gate row An n-th step of injecting the resin from the n-th gate row when the amount reaches a predetermined amount (when n is k, n holds for all values from 2 to k); A method for producing a flat molded product is provided.

  As described above, in at least one direction, since an odd number of gate rows are provided at a predetermined pitch, the center gate row is the first gate row and the gate row closest to the first gate row is the first gate row. The two gate rows will include a total of two gate rows, one on each side of the first gate row. In addition, since there is one gate line that is closest to each gate line constituting the second gate line, there are also two third gate lines. After that, there are two gate rows all up to the nth gate row.

  In the method for manufacturing a flat molded product according to the first aspect of the present invention, for example, when the number of gate rows is 3, the first resin is injected from the central gate row (first gate row). And a second step of injecting resin from the gate rows (second gate rows) on both sides of the first gate row. If the number of gate rows is five, the first step of injecting resin from the first gate row, and then the resin from each gate row (second gate row) on both sides of the first gate row. A second step of injecting, and then a third step of injecting resin from the gate row (third gate row) closest to each gate row constituting the second gate row. In summary, if the number of gate columns is 2n−1 (n is an integer of 2 or more), the first step, the second step,..., The nth step in the first aspect of the present invention. Will be included.

  According to the method of manufacturing a flat molded product according to the first aspect of the present invention, the first gate row including the center side gate is formed in the direction of the odd number of rows, and the second gates are arranged in order from the first gate row. Since the resin injection timing is shifted in the order of the gate row as a row, even if the plurality of gates are placed at the intersections of the lattice, an air pool does not occur in the cavity, and burning due to the air pool It is possible to prevent appearance defects such as the above. For this reason, a high quality flat plate molded product can be manufactured. In addition, since the plurality of gates are arranged substantially evenly in this way, the pressure does not partially increase in the cavity, and the in-mold pressure can be kept low. As described above, according to the present invention, it is possible to manufacture a high-quality flat plate molded product more efficiently while keeping the in-mold pressure low.

  Here, the number of gate rows is, for example, 4 in the vertical direction × 3 in the horizontal direction, 3 in the vertical direction × 3 in the horizontal direction, 2 in the vertical direction × 3 in the horizontal direction, 4 in the vertical direction × 5 in the horizontal direction. It can be an individual. Further, the direction of the odd number of columns may be either the vertical direction or the horizontal direction. However, the direction in which the number of columns is an odd number is preferably the longer one of the vertical direction and the horizontal direction.

  Further, the distances LA1 to LA4 in the outermost gates may be substantially the same, and the distances LB1 to LB4 in the outermost gates may be substantially the same.

  According to a second aspect of the present invention, there is provided a method for producing a substantially rectangular flat plate molded article by injection molding a resin using an injection mold, wherein the mold comprises: A plurality of gates, each having a movable mold plate and a fixed mold plate having a substantially rectangular cavity surface corresponding to the shape of the flat plate molded product and a plurality of gates communicating with the cavity surface. Is a lattice in which the pitch in the first direction along the first side of the substantially rectangular shape of the cavity surface is L1, and the pitch in the second direction along the second side perpendicular to the first direction is L2. In consideration of the above, the plurality of gates are arranged at the positions of the intersections of the lattice, and the plurality of gates are arranged in the first direction. As a plurality of second gate rows composed of a plurality of gates arranged along In the first gate row, the two gate rows closest to the intersection of the diagonal lines of the cavity surface are the eleventh gate row and the twelfth gate row, and the two gate rows close to the eleventh gate row and the twelfth gate row are respectively set. The thirteenth gate row and the fourteenth gate row, and in the second gate row, the two gate rows closest to the intersection of the diagonal lines of the cavity surface are the 21st gate row and the 22nd gate row, the 21st gate row and the 21st gate row. When two gate rows close to 22 gate rows are respectively referred to as a 23rd gate row and a 24th gate row, and each gate is represented by (first gate row, second gate row), (13, 21), (11 , 22), (12, 21), (14, 22) first group, (13, 22), (11, 21), (12, 22), (14, 21) gates Including A first step of injecting the resin from each gate included in one of the second groups, and when the injection amount in the first step reaches a predetermined amount, it is included in the other group A second step of injecting the resin from each gate, and a third step of injecting the resin from each gate of the 23rd gate row and the 24th gate row when the injection amount in the second step reaches a predetermined amount. A method for producing a flat molded article including the steps is provided.

  In the method for manufacturing a flat molded product according to the second aspect of the present invention, as the first step, resin is injected from each gate included in the first group or each gate included in the second group as the second step, and as the second step. Injecting resin from each gate included in the second group or each gate included in the first group, and injecting resin from each gate of the 23rd gate row and the 24th gate row as the third step, Since the timing of resin injection from the gates has been shifted, even if a plurality of gates are arranged at the intersections of the lattice, the air does not collect in the cavity, and appearance defects such as burning due to air accumulation It can be prevented from occurring. For this reason, a high quality flat plate molded product can be manufactured. In addition, since the plurality of gates are arranged substantially evenly in this way, the pressure does not partially increase in the cavity, and the in-mold pressure can be kept low. Therefore, a high-quality flat plate molded product can be manufactured more efficiently while keeping the in-mold pressure low.

  According to a third aspect of the present invention, there is provided a method for producing a substantially rectangular flat plate molded article by injection molding a resin using an injection mold, wherein the mold comprises: A plurality of gates, each having a movable mold plate and a fixed mold plate having a substantially rectangular cavity surface corresponding to the shape of the flat plate molded product and a plurality of gates communicating with the cavity surface. Is a lattice in which the pitch in the first direction along the first side of the substantially rectangular shape of the cavity surface is L1, and the pitch in the second direction along the second side perpendicular to the first direction is L2. In consideration of the above, the plurality of gates are arranged at the positions of the intersections of the lattice, and the plurality of gates are arranged in the first direction. As a plurality of second gate rows composed of a plurality of gates arranged along In the first gate row, the two gate rows closest to the intersection of the diagonal lines of the cavity surface are the eleventh gate row and the twelfth gate row, and the two gate rows close to the eleventh gate row and the twelfth gate row are respectively set. The thirteenth gate row and the fourteenth gate row, and in the second gate row, the two gate rows closest to the intersection of the diagonal lines of the cavity surface are the 21st gate row and the 22nd gate row, the 21st gate row and the 21st gate row. When two gate rows close to 22 gate rows are respectively referred to as a 23rd gate row and a 24th gate row, and each gate is represented by (first gate row, second gate row), (11, 22), (12 , 21) and the first group including the gates of (11, 21), (12, 22), and the second group including the gates of (12, 22). A first step of injecting the resin, a second step of injecting the resin from each gate included in the other group when the injection amount in the first step reaches a predetermined amount, and the second step And a third step of injecting the resin from the gates of the thirteenth gate row, the fourteenth gate row, the twenty-third gate row, and the twenty-fourth gate row when the injection amount of the first plate reaches a predetermined amount. A manufacturing method is provided.

  In the manufacturing method of the flat molded product according to the third aspect of the present invention, as the first step, the resin is injected from each gate included in the first group or each gate included in the second group, and as the second step. Resin is injected from each gate included in the second group or each gate included in the first group, and as a third step, each of the thirteenth gate row, the fourteenth gate row, the twenty-third gate row, and the twenty-fourth gate row Since the injection timing of the resin from each gate is shifted so that the resin is injected from the gate, even if the plurality of gates are arranged at the intersections of the lattice, there is no air pocket in the cavity. It is possible to prevent appearance defects such as burning due to air accumulation. For this reason, a high quality flat plate molded product can be manufactured. In addition, since the plurality of gates are arranged substantially evenly in this way, the pressure does not partially increase in the cavity, and the in-mold pressure can be kept low. Therefore, a high-quality flat plate molded product can be manufactured more efficiently while keeping the in-mold pressure low.

  Further, in the method for manufacturing a flat molded product according to the second and third aspects of the present invention, in the four outermost gates which are the gates closest to each vertex of the substantially rectangular cavity surface, each outermost gate And distances LA1 to LA4 between the sides in the second direction of the cavity surface that are the closest to each other are 120% to 10% of the pitch L1, and each outermost gate and the first direction of the cavity surface are in the first direction. It is preferable that the distances LB1 to LB4 with the closest side among the sides are 120% to 10% of the pitch L2.

  Further, it is preferable that the distances LA1 to LA4 in the outermost gates are substantially the same, and the distances LB1 to LB4 in the outermost gates are substantially the same. According to the method for producing a flat plate molded product of the present invention, the resin can be injected well even near the apexes of the substantially rectangular cavity surface, and a high quality flat plate molded product without thickness unevenness can be more efficiently obtained. Can be manufactured.

In the method for manufacturing a flat molded product according to the first to third aspects of the present invention, the number of the gates is N (pieces), and the depth of the cavity formed in the fixed mold is t (mm). When the area of the cavity surface is S (mm ² ), it is preferable that the following mathematical formula (1) is satisfied.

(Equation 1)
(S / (t + 6)) × 10 ⁻⁴ ≦ N ≦ (2S / t) × 10 ⁻⁴ (1)
Moreover, according to the 4th aspect of this invention, the flat molded product without the appearance defect manufactured by the manufacturing method of the flat molded product of this invention can be provided. Examples of such flat plate molded products include optical members such as a light diffusion plate and a light guide plate.

It is a top view which shows typically the cavity surface formed in the fixed metal mold | die which concerns on the 1st Embodiment of this invention. It is a top view for demonstrating the position of the gate formed in the cavity surface which concerns on the 1st Embodiment of this invention. It is a top view of the cavity surface for demonstrating the manufacturing method of the light diffusing plate which concerns on the 1st Embodiment of this invention. It is a flowchart for demonstrating the procedure of the method of manufacturing the light diffusing plate which concerns on the 1st Embodiment of this invention. It is a top view which shows typically the cavity surface formed in the stationary template which concerns on the 2nd Embodiment of this invention. It is a top view for demonstrating the position of the gate formed in the cavity surface which concerns on the 2nd Embodiment of this invention. It is a top view of the cavity surface for demonstrating the manufacturing method of the light diffusing plate which concerns on the 2nd Embodiment of this invention. It is a flowchart for demonstrating the procedure of the method of manufacturing the light diffusing plate which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the state of the flow of resin at the time of manufacturing the light diffusing plate which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the state of the flow of resin at the time of manufacturing the light diffusing plate which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the state of the flow of resin at the time of manufacturing the light diffusing plate which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the opening-and-closing timing of a gate in case the number of gates formed in the stationary mold plate which concerns on the 2nd Embodiment of this invention is 6x8. It is a figure for demonstrating the state of the flow of resin at the time of manufacturing the light diffusing plate which concerns on the 3rd Embodiment of this invention. It is a figure which shows the structure of the liquid crystal display device which concerns on embodiment of this invention. It is a top view which shows typically the cavity surface of the fixed metal mold | die in the comparative example 2 as a prior art. It is a top view which shows typically the cavity surface of the fixed metal mold | die in the comparative example 3 as a prior art. It is a top view which shows typically the cavity surface of the stationary mold plate in the comparative example 4 as a prior art.

  Hereinafter, with reference to the drawings, a method for producing a resin flat plate molded article using the injection mold according to the first embodiment of the present invention will be described. First, the injection mold used in the first embodiment will be described. An injection mold includes a fixed mold (fixed mold plate) and a movable mold (movable mold plate), and a resin is injected into a cavity that is a gap between the fixed mold and the movable mold. For example, a light diffusing plate which is a flat molded product is manufactured.

  Here, a gas vent for releasing air in the cavity at the time of injection molding is provided on the outer peripheral edge of the injection mold. The fixed mold can be provided with a hot runner or a cold runner. Further, a vacuum pulling hole for releasing air in the cavity or the like can be provided in the fixed mold or the movable mold.

  The depth of the cavity is preferably 0.1 mm to 15.0 mm, more preferably 0.2 mm to 5.0 mm, and still more preferably 0.5 mm to 3.0 mm. Note that the depth of the cavity substantially matches the thickness of the obtained flat plate molded product.

  FIG. 1 is a plan view schematically showing a cavity surface formed in a fixed mold. As shown in FIG. 1, the cavity surface 10 is formed in a substantially rectangular shape. In the substantially rectangular cavity surface 10, the vertices of the rectangle are 10A to 10D, the vertical side connecting the vertices 10A and 10B is 11A, and the vertical side connecting the vertices 10C and 10D is 11B. A lateral side connecting the vertex 10A and the vertex 10C is 12A, and a lateral side connecting the vertex 10B and the vertex 10D is 12B. The vertical direction is the vertical direction in FIG. 1, and the horizontal direction is the horizontal direction in FIG.

  The diagonal length of the cavity surface 10 (distance between vertex 10A and vertex 10D, distance between vertex 10B and vertex 10C) is preferably 400 mm or more, and more preferably 650 mm or more. According to the manufacturing method according to an embodiment of the present invention to be described later, even if the diagonal length is larger than the numerical value, it is possible to efficiently manufacture a flat molded product with little thickness unevenness.

  Here, as an aspect of the substantially rectangular cavity surface, for example, (1) when the entire cavity surface is rectangular, (2) the entire cavity surface is around the rectangular main body portion and the main body portion. Examples include a case where the peripheral edge portion is provided, the peripheral edge portion is formed in an arbitrary shape, and the entire cavity surface is not rectangular.

  The length in the vertical direction of the cavity surface 10 (the length of the sides 11A and 11B) and the length in the horizontal direction (the lengths of the sides 12A and 12B) are not particularly limited. The length in the direction can be described as length 740 mm × width 430 mm, length 1,020 mm × width 600 mm, or the like. The cavity surface 10 is usually formed so that the length in the horizontal direction is larger than the length in the vertical direction, but the length in the vertical direction and the length in the horizontal direction may be substantially the same.

  A plurality of gates (pin point gates) 20 communicating with the cavity surface 10 are formed in the fixed mold. Here, FIG. 2 is a schematic diagram for explaining the position of the gate 20 on the cavity surface 10. As shown in FIG. 2, each gate 20 has a lattice composed of a vertical line A along the vertical side 11A (11B) of the cavity surface 10 and a horizontal line B along the horizontal side 12A (12B). When considered, it is provided at the position of the intersection point P of this lattice. In this lattice, the vertical pitch (the pitch between the gates 20 arranged in the vertical direction) is L1, and the horizontal pitch (the pitch between the gates 20 arranged in the horizontal direction) is L2. In other words, the plurality of gates are formed at substantially equal intervals along the vertical direction and the horizontal direction of the cavity surface 10. Here, the substantially equal interval means that each interval falls within an error range of about 10% or less with respect to an average interval obtained by averaging all intervals in a certain direction. The error range is preferably within about 5%, more preferably within about 1%. As described above, since the gates 20 are arranged substantially evenly, the pressure inside the mold can be kept low, and the one having a small mold clamping force can be used. Specifically, for example, when the dimension of the cavity surface 10 is 740 mm long × 430 mm wide, the vertical pitch L1 can be 143.3 mm and the horizontal pitch L2 can be 185 mm.

  Moreover, as shown in FIG. 2, let the gate nearest from each vertex 10A-10D be the outermost gates 20A-20D among the some gates 10, respectively. Here, the distance LA1 between the lateral side 12A closest to the outermost gate 20A and the outermost gate 20A is 120% to 10%, preferably 100% to 20% of the pitch L1. Further, the distance LB1 between the vertical side 11A closest to the outermost gate 20A and the outermost gate 20A is 120% to 10%, preferably 100% to 20% of the pitch L2.

  In the outermost gate 20B, the distance LA2 between the lateral side 12B closest to the outermost gate 20B and the outermost gate 20B is 120% to 10%, preferably 100% to 20% of the pitch L1. It is. The distance LB2 between the vertical side 11A closest to the outermost gate 20B and the outermost gate 20B is 120% to 10%, preferably 100% to 20% of the pitch L2.

  In the outermost gate 20C, the distance LA3 between the lateral side 12A closest to the outermost gate 20C and the outermost gate 20C is 120% to 10%, preferably 100% to 20% of the pitch L1. . The distance LB3 between the vertical side 11B closest to the outermost gate 20C and the outermost gate 20C is 120% to 10%, preferably 100% to 20% of the pitch L2.

  In the outermost gate 20D, the distance LA4 between the lateral side 12B closest to the outermost gate 20D and the outermost gate 20D is 120% to 10%, preferably 100% to 20% of the pitch L1. . The distance LB4 between the vertical side 11B closest to the outermost gate 20D and the outermost gate 20D is 120% to 10%, preferably 100% to 20% of the pitch L2.

  The pitch L1 can be an average value of the intervals. Similarly, the pitch L2 can be an average value of each interval.

  Here, the distances LA1 to LA4 are preferably substantially equal to each other. The distances LB1 to LB4 are preferably substantially equal to each other. Note that “approximately equal” means that the distances LA1 to LA4 have an error of 10% or less with respect to the average distance obtained by averaging the distances LA1 to LA4. The error is preferably 5% or less, and more preferably 1% or less. By setting it as such a structure, it can suppress that thickness nonuniformity arises in the obtained flat plate molded article.

In the injection mold used in the present embodiment, the number N (pieces) of gates to be installed is expressed by the following formula (t) when the cavity depth is t (mm) and the cavity area is S (mm ² ): It is preferable to satisfy 1).

(Equation 1)
(S / (t + 6)) × 10 ⁻⁴ ≦ N ≦ (2S / t) × 10 ⁻⁴ (1)
If the number of gates is less than the preferred range, there is a risk that unevenness in the thickness of the flat plate molded product due to an increase in the resin flow distance in the cavity. Further, when the number of gates is larger than the preferable range, it may be difficult to manufacture a mold. For this reason, there exists an effect that a high quality flat plate molded product can be simply shape | molded by making the number of gates into the said suitable range.

  As described above, since the plurality of gates 20 are arranged on the intersection P of the lattice, as shown in FIG. 1, the plurality of gates 20 are connected to the vertical gate row 21 which is a vertical gate row and the horizontal gate row 21. It can be classified into a horizontal gate row 22 which is a gate row in the direction. In the present embodiment, the number of vertical gate rows 21 is four, and the number of horizontal gate rows 22 is three (odd number). The number of gates 20 constituting the vertical gate row 21 is three, and the number of gates 20 constituting the horizontal gate row 22 is four.

  Next, the resin that is a constituent material of the flat molded product will be described. Examples of the resin used in the present embodiment include a resin having an alicyclic structure, a copolymer of an aromatic vinyl monomer and a (meth) acrylic acid alkyl ester monomer, a methacrylic resin, a polycarbonate, polystyrene, and acrylonitrile. -Styrene copolymer resin, ABS resin, polyethersulfone, etc. can be mentioned. Among these, a resin having an alicyclic structure, a methacrylic resin, and a copolymer of an aromatic vinyl monomer and a (meth) acrylic acid alkyl ester monomer can be suitably used. A resin having a structure can be particularly preferably used.

  A resin having an alicyclic structure has good flowability of the molten resin, so it can fill the cavity of the mold with a low injection pressure, and has extremely low hygroscopicity. There is no warpage and the specific gravity is small, so that the flat plate molded product can be reduced in weight. In addition, the resin having an alicyclic structure has an advantage that a weld line is hardly generated.

  The resin having an alicyclic structure is a resin having an alicyclic structure in the main chain or side chain. Among these, a resin having an alicyclic structure in the main chain can be particularly suitably used because it has 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, more preferably 5 to 20, and further preferably 5 to 15. . The ratio of the repeating unit having an alicyclic structure in the resin having an alicyclic structure is preferably 50% by weight or more, more preferably 70% by weight or more, and 90% by weight or more. Further preferred.

  Examples of the resin having an alicyclic structure include a ring-opening polymer or a ring-opening copolymer of a norbornene monomer or a hydrogenated product thereof, an addition polymer or an addition copolymer of a norbornene monomer, or Those hydrogenated products, polymers of monocyclic olefin monomers or hydrogenated products thereof, polymers of cyclic conjugated diene monomers or hydrogenated products thereof, vinyl alicyclic hydrocarbon monomers Or a hydrogenated product thereof, a polymer of a vinyl aromatic hydrocarbon monomer, or a hydrogenated product of an unsaturated bond part containing an aromatic ring of the copolymer. Among these, hydrogenated products of norbornene-based monomer polymers and hydrogenated products of unsaturated bonds containing aromatic rings of vinyl aromatic hydrocarbon-based monomer polymers have mechanical strength and heat resistance. Since it is excellent in property, it can be used especially suitably.

  The methacrylic resin is excellent in transparency, tough and hardly cracked, and thus is suitable for an optical member. Examples of the methacrylic resin include a methacrylic resin molding material containing 80% or more of a methyl methacrylate polymer defined in Japanese Industrial Standard JIS K 6717. Among the methacrylic resins specified in this standard, methacrylic resins having a specified classification code 100-120 having a Vicat softening point temperature of 96 to 100 ° C. and a melt flow rate of 8 to 16 have suitable fluidity and strength, and thus are suitable. Can be used.

  The aromatic vinyl monomer constituting the copolymer of the aromatic vinyl monomer and the (meth) acrylic acid alkyl ester is an aromatic vinyl monomer or a derivative thereof such as styrene, α-methyl. Mention may be made of styrene, m-methylstyrene, p-methylstyrene, o-chlorostyrene, p-chlorostyrene and the like. Examples of (meth) acrylic acid alkyl esters include (meth) acrylic acid alkyl esters having an alkyl group having 1 to 4 carbon atoms. As the (meth) acrylic acid alkyl ester, methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate can be suitably used. A copolymer of an aromatic vinyl monomer and an alkyl (meth) acrylate is a copolymer of an aromatic vinyl monomer 20 to 60% by weight and an alkyl (meth) acrylate 40 to 80% by weight. It is preferable that Note that (meth) acrylic acid refers to methacrylic acid and acrylic acid, and (meth) acrylic refers to methacrylic and acrylic.

  In the present embodiment, as the resin, a resin in which a thermoplastic elastomer or an additive is blended can be used as necessary. Examples of the thermoplastic elastomer include polybutadiene, styrene-butadiene block copolymer and hydrogenated product thereof, and styrene-isoprene block copolymer and hydrogenated product thereof. Examples of additives include light diffusing agents, antioxidants, ultraviolet absorbers, light stabilizers, colorants such as dyes and pigments, lubricants, plasticizers, antistatic agents, and fluorescent whitening agents. it can. Examples of the light diffusing agent include fine particles comprising a polystyrene polymer, a polysiloxane polymer or a cross-linked product thereof, (meth) acrylic resin, fluororesin, barium sulfate, calcium carbonate, silica, and talc. Can do. Among these, the fine particles made of polystyrene polymer, polysiloxane polymer, or cross-linked products thereof are particularly suitable because they have good dispersibility, excellent heat resistance, and no yellowing during molding. .

  The blending amount of the thermoplastic elastomer is usually 0.01% to 50% by weight, preferably 0.05% to 30% by weight. Moreover, the compounding quantity of the said additive is 0.01 to 30 weight% normally, Preferably it is 0.05 to 20 weight%. In the case of blending a light diffusing agent as a blending agent, the particle size of the light diffusing agent is usually 0.5 μm to 100 μm in average particle size, and preferably 0.5 μm to 80 μm.

  Next, a method for manufacturing a light diffusing plate, which is a resin flat plate molded product, using the injection mold according to the first embodiment will be described. FIG. 3 is a plan view of the cavity surface for explaining the method of manufacturing the light diffusing plate. FIG. 4 is a flowchart for explaining the procedure of the method of manufacturing the light diffusing plate.

  As shown in FIG. 3, the horizontal gate row 22 includes three horizontal gate rows 22A, 22B, and 22C. Of these horizontal gate rows 22A, 22B, and 22C, a row including the gates 20S and 20T that are closest to the intersection C of the diagonal line of the cavity surface 10 is defined as a first horizontal gate row X. Two close gate rows are defined as a second horizontal gate row Y. In the first embodiment, the lateral gate row 22B is the first lateral gate row X, and the lateral gate row 22A and the lateral gate row 22C that are substantially the same distance from the first lateral gate row X are the second lateral gate row X. This is a gate row Y.

  First, as shown in FIG. 4, the mold for injection molding is clamped at a predetermined pressure using a mold clamping device (not shown) (step S1). Next, the gate of the first horizontal gate row X is opened, and the resin is injected from the gate of the first horizontal gate row X at a constant injection rate (step S2: first step). At this time, the resin injected into the cavity flows out from the portion corresponding to the first gate row X toward the outer peripheral side of the cavity surface 10. The injection amount of the resin can be grasped by the injection time since the injection rate (injection speed) is constant.

  Next, it is determined whether or not the injection amount from the gate of the first horizontal gate row X has become a predetermined amount (step S3). Specifically, this determination may be performed based on, for example, the injection time, but if necessary, the resin injected from the gates of the first gate row X may be used as the first horizontal gate row X and the second horizontal gate row. You may carry out by whether it flowed to the position of about half of the distance of Y.

  If the resin injection amount has not reached the predetermined amount, step S2 is repeated. When the resin injection amount reaches a predetermined amount, the gates of the second lateral gate row Y are opened while the gates of the first lateral gate row X are opened, and the gates of the first lateral gate row X and the second lateral gate row X are opened. The resin is injected from the gate of the gate row Y at the injection rate (step S4: second step).

  Next, it is determined whether or not the injection amounts from the gates of the first lateral gate row X and the gates of the second lateral gate row Y have become the predetermined amounts as described above (step S5). If the resin injection amount has not reached the predetermined amount, step S4 is repeated. When the resin injection amount reaches a predetermined amount, the gates of the first horizontal gate row X and the second horizontal gate row Y are closed, and injection from the gates of these gate rows X and Y is stopped ( Step S6). Thereafter, the injection mold is cooled (step S7), and the light diffusion plate is taken out from the mold (step S8). As described above, one cycle of manufacturing the light diffusing plate is completed.

  In step S6, the timing of closing the gate is normally performed when the resin injection amount reaches a predetermined amount. For example, the resin filling state of the surface portion of the molded product is observed, and this filling state is good. You may make it perform when it becomes. The light diffusing plate is manufactured by repeating such a cycle a plurality of times.

  According to the first embodiment, in the direction of the odd number of columns, the first gate column including the center side gate is formed, and the second gate column is arranged in the order of the first gate column. Since the resin injection timing has been shifted, even if the gates are arranged in an approximately equal position at the intersection of the grids, there is no air accumulation in the cavity, and appearance defects such as burning due to the air accumulation occur. Can be prevented. For this reason, a high quality flat plate molded product can be manufactured. In addition, since the plurality of gates are arranged substantially evenly in this way, the pressure does not partially increase in the cavity, and the in-mold pressure can be kept low. Therefore, a high-quality flat plate molded product can be manufactured more efficiently while keeping the in-mold pressure low.

  Further, according to the first embodiment, there are the following effects. Since the gates 20 are arranged on the cavity surface 10 so that the distance between the adjacent gates 20 is substantially constant, the mold internal pressure becomes substantially the same at any position in the cavity. For this reason, since the mold internal pressure can be kept low, a mold clamping device with a small mold clamping force can be used, and space saving can be achieved.

  In addition, after the resin is injected from the gate 20 of the lateral gate row X which is the center side of the cavity surface 10 separately into the first lateral gate X and the second lateral gate row Y, the gate of the lateral gate row Y outside the first lateral gate X and the second lateral gate row Y Since the injection timing is shifted so as to inject the resin from 20, even if the gates 20 are arranged approximately evenly, air does not accumulate in the cavity. For this reason, since the appearance defects such as burning caused by air accumulation do not occur in the obtained flat plate molded product, a high-quality light diffusion plate can be efficiently manufactured.

  In addition, this invention is not limited to the said embodiment. For example, in the above embodiment, the number of vertical gate rows × the number of horizontal gate rows is 4 × 3. However, if the number of gate rows in at least one of the vertical direction and the horizontal direction is an odd number, The number of is not limited to the above number. Further, the size of the cavity surface is not limited to the above size. Moreover, in the said embodiment, although the obtained flat plate molded article was used as the light diffusing plate, it is good also as optical members, such as a light-guide plate, and good also as members other than an optical use.

  In the embodiment, the injection timing is adjusted based on the horizontal gate row 22. However, when the number of the vertical gate rows 21 is an odd number, the injection timing may be adjusted based on the vertical gate rows 21. Good. Further, although the gate row for timing adjustment is a gate row along the horizontal direction which is the long side, it may be a gate row along the vertical direction which is the short side.

  The lateral distances LB1 to LB4 are preferably about 30% to 70% of the lateral distance L2 (for example, the average distance), and 45% to 55%. Is more preferable, and it is further more preferable that it is 49%-51%. The vertical distances LA1 to LA4 are preferably about 30% to 70% of the vertical distance L1, more preferably 45% to 55%, and 49%. More preferably, it is ˜51%. According to such a configuration, the molten resin flows more suitably, so that a high-quality flat plate molded product with improved thickness unevenness and appearance defects can be molded.

  Next, a method for manufacturing a resin flat molded product using the injection mold according to the second embodiment of the present invention will be described with reference to the drawings.

  The second embodiment relates to the first embodiment described above in terms of the arrangement and number of gates provided in the injection mold, the timing of opening and closing the gate when manufacturing a flat molded product, and the like. Although it is different from the method of manufacturing the injection mold and the resin flat plate molded product, in other respects, using the same injection mold as used in the first embodiment, flat plate molding is performed. Manufacture products. Therefore, in the following, detailed description of parts common to the first embodiment will be omitted, and only different parts will be described in detail. The same components as those in the first embodiment will be described using the same reference numerals.

  As in the first embodiment, the injection mold used in the second embodiment includes a fixed mold plate and a movable mold plate, and a cavity is formed by a gap between the fixed mold plate and the movable mold plate. The depth of the cavity is substantially the same as the thickness of the obtained flat plate molded product.

  FIG. 5 is a plan view schematically showing a cavity surface formed on the fixed mold plate, and corresponds to FIG. 1 in the first embodiment. As shown in FIG. 5, the cavity surface 10 is formed in a substantially rectangular shape, and the diagonal length is preferably 400 mm or more, and more preferably 650 mm or more. Note that the length in the vertical direction and the length in the horizontal direction of the cavity surface 10 are not particularly limited, and are usually formed so that the length in the horizontal direction is larger than the length in the vertical direction. And the length in the horizontal direction may substantially coincide with each other.

  FIG. 6 is a schematic diagram for explaining the position of the gate 20 on the cavity surface 10 and corresponds to FIG. 2 in the first embodiment. As shown in FIG. 6, a plurality of gates 20 communicating with the cavity surface 10 are formed on the fixed template, and each gate 20 has a vertical pitch L1 and a horizontal pitch of the cavity surface 10. L2 is formed at substantially equal intervals along the vertical direction and the horizontal direction. Further, as shown in FIG. 6, the gates closest to the vertices 10A to 10D are the outermost gates 20A to 20D, respectively, and the distances LA1 to LA4 between the outermost gates 20A to 20D and the lateral sides with respect to each of them. Is 120% to 10% of L1, preferably 100% to 20%. Further, the distances LB1 to LB4 between the outermost gates 20A to 20D and the vertical sides thereof are 120 to 10%, preferably 100 to 20% of L2.

  In the injection molding die, it is preferable that the number of gates to be installed satisfies the mathematical formula (1) as in the first embodiment.

  In the second embodiment, since the plurality of gates 20 are arranged on the intersection P of the lattice, as shown in FIG. 7, the plurality of gates 20 are connected to a vertical gate row (vertical gate row ( First to 14th gate rows) and horizontal gate rows (21st to 24th gate rows) which are lateral gate rows. In the second embodiment, the number of vertical gate rows is four (even numbers), and the number of horizontal gate rows is four (even numbers). Further, the number of gates 20 constituting the vertical gate row is four, and the number of gates 20 constituting the horizontal gate row is four.

  In addition, since the resin which is a constituent material of the flat molded product is also the same resin as that used in the first embodiment, a detailed description thereof is omitted in the second embodiment.

  Next, a method for producing a light diffusing plate which is the resin flat plate molded product using the above-described injection mold will be described. FIG. 8 is a flowchart for explaining the procedure of the method of manufacturing the light diffusing plate.

  As shown in FIG. 7, in the vertical gate row (first gate row), the two gate rows closest to the intersection of the diagonal lines of the cavity surface are the eleventh gate row and the twelfth gate row, and the eleventh gate row and the twelfth gate. Two gate rows close to the row are defined as a thirteenth gate row and a fourteenth gate row, respectively. In the horizontal gate row (second gate row), the two gate rows closest to the intersection of the diagonal lines of the cavity surface are the 21st gate row and The twenty-second gate row, two gate rows close to the twenty-first gate row and the twenty-second gate row are referred to as a twenty-third gate row and a twenty-fourth gate row, respectively. Column).

  First, as shown in FIG. 8, the mold for injection molding is clamped at a predetermined pressure using a mold clamping device (not shown) (step S11). Next, each gate of the first group, that is, each gate of (13, 21), (11, 22), (12, 21), (14, 22) is opened, and a constant injection rate is obtained from these gates. Then, the resin is injected (step S12: first step). At this time, the resin injected into the cavity flows out from the gates of the first group toward the outer peripheral side of the cavity surface 10 as shown in FIG. The injection amount of the resin can be grasped by the injection time since the injection rate (injection speed) is constant.

  Next, it is determined whether or not the injection amount from each gate of the first group has become a predetermined amount (step S13). Specifically, this determination may be performed based on, for example, the injection time. If necessary, the resin injected from each gate of the first group is about half the distance to the gate of the second group described later. It may be performed depending on whether or not it has flowed to the position. If the resin injection amount has not reached the predetermined amount, the process of step S12 is continued. When the resin injection amount reaches a predetermined amount, each gate of the second group, that is, (13, 22), (11, 21), (12, 22), with each gate of the first group being opened. , (14, 21) are opened, and the resin is injected at the injection rate from the gates of the first group and the second group (step S14: second step). FIG. 10 is a diagram illustrating a state in which resin is injected from each gate of the first group and the second group. In this figure, a portion where the circles indicating the range of the resin flowing out from each gate of the first group overlap, and a portion where the circle indicating the range of the resin flowing out from each gate of the first group protrudes from the cavity surface In reality, however, in this part, the resin flows in the direction of the arrow shown in the figure so as to compensate for the slow resin flow part. Then, as shown by the wavy line in FIG. 11, the resin is filled in the lateral direction of the cavity.

  Next, it is determined whether or not the injection amount from each gate of the second group has become a predetermined amount (step S15). If the resin injection amount has not reached the planned amount, the process of step S14 is continued. When the resin injection amount reaches a predetermined amount, the gates of the third group, that is, the gates of the 23rd gate row and the 24th gate row (with the gates of the first group and the second group being opened) Each gate of (13, 23), (11, 23), (12, 23), (14, 23), (13, 24), (11, 24), (12, 24), (14, 24) ) And the resin is injected from the gates of the first group to the third group at the injection rate (step S16: third step).

  Next, it is determined whether or not the injection amount from each gate of the third group has become a predetermined amount (step S17). If the resin injection amount has not reached the predetermined amount, the process of step S16 is continued. When the resin injection amount reaches the predetermined amount, the gates of the first group to the third group are closed, and the injection from these gates is stopped (step S18). Thereafter, the injection mold is cooled (step S19), and the light diffusion plate is taken out of the mold (step S20). As described above, one cycle of manufacturing the light diffusing plate is completed.

  In the process of step S18, the timing for closing the gate is normally performed when the resin injection amount reaches a predetermined amount. For example, the resin filling state of the surface portion of the molded product is observed, and this filling state is determined. You may make it perform when it becomes favorable. The light diffusing plate is manufactured by repeating such a cycle a plurality of times.

  In the second embodiment, the number of vertical gate rows × the number of horizontal gate rows is 4 × 4. However, if the number of gate rows in the vertical and horizontal directions is an even number, the number of gate rows is as follows. The number is not limited. FIG. 12 is a diagram for explaining the timing of opening the gate when the number of vertical gate rows × the number of horizontal gate rows is 6 × 8. In this case, resin is injected from each gate included in the first group in the first step, and resin is injected from each gate included in the first group and the second group in the second step, or first In the step, resin is injected from each gate included in the second group, and in the second step, resin is injected from each gate included in the first group and the second group. After that, each gate included in each lateral gate row closest to the first group and the second group is opened to inject resin, and each gate included in each lateral gate row on the outer side is opened to inject resin. To do.

  Next, a third embodiment, which is another manufacturing method for manufacturing a light diffusing plate that is a resin-made flat molded product, using the injection mold according to the second embodiment described above will be described. The processing procedure is the same as the procedure in the second embodiment shown in FIG. 8, and will be described with reference to FIG.

  First, as shown in FIG. 8, the mold for injection molding is clamped at a predetermined pressure using a mold clamping device (not shown) (step S11). Next, as shown in FIG. 12, the gates of the first group, that is, the gates of (11, 22) and (12, 21) shown in FIG. The resin is injected (step S12: first step). At this time, the resin injected into the cavity flows out from each gate of the first group toward the outer peripheral side of the cavity surface 10. Here, in FIG. 13, the range of the spread of the resin injected from each gate of the first group is indicated by a solid circle. The injection amount of the resin can be grasped by the injection time since the injection rate (injection speed) is constant.

  Next, it is determined whether or not the injection amount from each gate of the first group has become a predetermined amount (step S13). Specifically, this determination may be performed based on, for example, the injection time. However, if necessary, the resin injected from each gate of the first group flows to a position about half the distance from the adjacent gate. You may go by whether or not. If the resin injection amount has not reached the predetermined amount, the process of step S12 is continued. When the resin injection amount reaches the predetermined amount, as shown in FIG. 13, the gates of the first group are kept open as shown in FIG. 13, that is, the gates of the second group, that is, (11, 21) shown in FIG. The gates (12, 22) are opened, and the resin is injected at the injection rate from the gates of the first group and the second group (step S14: second step). Here, in FIG. 13, the range of the spread of the resin injected from each gate of the second group is indicated by a dotted circle.

  Next, it is determined whether or not the injection amount from each gate of the second group has become the predetermined amount as described above (step S15). If the resin injection amount has not reached the planned amount, the process of step S14 is continued. When the resin injection amount reaches the predetermined amount, each gate of the third group, that is, as shown in FIG. 13, with the gates of the first group and the second group being opened, Each gate of the 14th gate row, the 23rd gate row, and the 24th gate row ((13,23), (13,21), (13,22), (13,24), (14,23), (14, 21), (14, 22), (14, 24), (11, 23), (12, 23), (11, 24), (12, 24) gates)), and the first group The resin is injected from the gates of the third group at the injection rate (step S16: third step).

  Next, it is determined whether or not the injection amount from each gate of the third group has become a predetermined amount (step S17). If the resin injection amount has not reached the predetermined amount, the process of step S16 is continued. When the resin injection amount reaches the predetermined amount, the gates of the first group to the third group are closed, and the injection from these gates is stopped (step S18). Thereafter, the injection mold is cooled (step S19), and the light diffusion plate is taken out of the mold (step S20). As described above, one cycle of manufacturing the light diffusing plate is completed.

  In the process of step S18, the timing for closing the gate is normally performed when the resin injection amount reaches a predetermined amount. For example, the resin filling state of the surface portion of the molded product is observed, and this filling state is determined. You may make it perform when it becomes favorable. The light diffusing plate is manufactured by repeating such a cycle a plurality of times.

  Further, in the third embodiment, the number of vertical gate rows × the number of horizontal gate rows is 4 × 4. However, if the number of vertical and horizontal gate rows is an even number, the number of gate rows is The number is not limited. In that case, after controlling the injection timing of 4 × 4 gates by the above-described method, the gates on the outer side of the cavity are sequentially opened to inject the resin. That is, the gate is opened sequentially from the inside to the outside.

  According to each of the second and third embodiments described above, as the first step, resin is injected from each gate included in the first group or each gate included in the second group, and as the second step, the second step is performed. Resin is injected from each gate included in the group or each gate included in the first group, and as a third step, resin is injected from each gate of the 23rd gate row and the 24th gate row. Resin injection timing is shifted, or as the first step, the resin is injected from each gate included in the first group or each gate included in the second group, and included in the second group as the second step. Resin is injected from each gate or each gate included in the first group, and as a third step, each gate of the thirteenth gate row, the fourteenth gate row, the twenty-third gate row, and the twenty-fourth gate row is used. Since the injection timing of the resin from each gate is shifted so as to inject the resin, even if the plurality of gates are arranged at the intersection of the lattice, the air does not accumulate in the cavity, and the air It is possible to prevent appearance defects such as burning due to accumulation. For this reason, a high quality flat plate molded product can be manufactured. In addition, since the plurality of gates are arranged substantially evenly in this way, the pressure does not partially increase in the cavity, and the in-mold pressure can be kept low. Therefore, a high-quality flat plate molded product can be manufactured more efficiently while keeping the in-mold pressure low.

  Further, according to the second and third embodiments described above, there are the following effects. Since the gates 20 are arranged on the cavity surface 10 so that the distance between the adjacent gates 20 is substantially constant, the mold internal pressure becomes substantially the same at any position in the cavity. For this reason, since the mold internal pressure can be kept low, a mold clamping device with a small mold clamping force can be used, and space saving can be achieved. In addition, since the plurality of gates are divided into the first group to the third group, the injection timing is shifted so that the resin is injected from each gate 20 in the order of the first group, the second group, and the third group. Even if 20 are arranged substantially evenly, no air pockets are produced in the cavity. For this reason, since the appearance defects such as burning caused by air accumulation do not occur in the obtained flat plate molded product, a high-quality light diffusion plate can be efficiently manufactured.

  In each of the second and third embodiments described above, resin is injected from each gate included in the first group in the first step, and resin is injected from each gate included in the second group in the second step. However, the resin may be injected from each gate included in the second group in the first step, and the resin may be injected from each gate included in the first group in the second step.

  In each of the second and third embodiments described above, the size of the cavity surface is not limited to the above size. In the second and third embodiments described above, the obtained flat plate molded article is a light diffusing plate, but it may be an optical member such as a light guide plate or a member other than an optical application.

  In the second and third embodiments described above, the horizontal distances LB1 to LB4 are approximately 30% to 70% of the horizontal distance L2 (for example, the average distance). Preferably, the length is 45% to 55%, more preferably 49% to 51%. The vertical distances LA1 to LA4 are preferably about 30% to 70% of the vertical distance L1, more preferably 45% to 55%, and 49%. More preferably, it is ˜51%. According to such a configuration, the molten resin flows more suitably, so that a high-quality flat plate molded product with improved thickness unevenness and appearance defects can be molded.

  Next, a liquid crystal display device including the light diffusing plate manufactured according to each of the above embodiments will be described. FIG. 14 is a diagram illustrating a configuration of a liquid crystal display device. The liquid crystal display device 30 includes a pair of liquid crystal substrates 31 disposed opposite to each other, a liquid crystal panel including a liquid crystal layer 32 sandwiched between the pair of liquid crystal substrates 31, and a pair of polarizing plates disposed so as to sandwich the liquid crystal panel. 33, a direct-type backlight 34 that irradiates the liquid crystal panel from the back, and a function that is disposed between the liquid crystal panel and the direct-type backlight 34 to make the light uniform and diffuse or condense the light. And an optical film 35 having the light diffusion plate 36 manufactured by the manufacturing method according to each of the above-described embodiments. Here, the direct type backlight 34 includes a plurality of lamps 37 and a reflecting plate 38 made of a cold cathode fluorescent lamp or the like.

  According to the liquid crystal display device according to this embodiment, since the light diffusion plate 36 manufactured by the manufacturing method according to the above-described embodiment is provided, the liquid crystal panel can be illuminated well.

  The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2006-34655 filed on February 13, 2006 and Japanese Patent Application No. 2006-225259 filed on August 22, 2006. The entire disclosure of which is expressly incorporated herein by reference.

  Next, the present invention will be described in more detail with reference to examples and comparative examples. In addition, this invention is not limited to the following Example.

<Production Example 1 (Production of norbornene polymer)>
500 parts by weight of dehydrated cyclohexane, 0.82 part by weight of 1-hexene, 0.15 part by weight of dibutyl ether, and 0.30 part by weight of triisobutylaluminum are thoroughly dried at room temperature and placed in a stainless steel pressure-resistant container purged with nitrogen. After mixing, 170 parts by weight of tricyclo [4.3.0.1 ^2.5 ] deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as “DCP”) and 8-ethylidene while being kept at 45 ° C. - tetracyclo [4.4.0.1 ^2.5 .1 ^7.10] - dodeca-3-ene (ethylidene tetracyclododecene, hereinafter abbreviated as "ETD") and 30 parts by weight of tungsten hexachloride (0.7 wt % Toluene solution) and 30 parts by weight were continuously added over 2 hours for polymerization. To the polymerization solution, 1.06 parts by weight of butyl glycidyl ether and 0.52 parts by weight of isopropyl alcohol were added to inactivate the polymerization catalyst, and the polymerization reaction was stopped.

  Next, 270 parts by weight of cyclohexane is added to 100 parts by weight of the reaction solution containing the obtained ring-opening polymer, and 5 parts by weight of a nickel-alumina catalyst (manufactured by JGC Chemical Co., Ltd.) is added as a hydrogenation catalyst. The mixture was heated to 200 ° C. with stirring under pressure of 5 MPa and then reacted for 4 hours to obtain a reaction solution containing 20% by weight of a DCP / ETD ring-opening polymer hydrogenated product. After removing the hydrogenation catalyst by filtration, 0.1 parts by weight of a phenolic antioxidant per 100 parts by weight of the hydrogenated product is pentaerythrityl-tetrakis (3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate) was added to and dissolved in the resulting solution.

  Next, using a cylindrical concentrating dryer (manufactured by Hitachi, Ltd.), an extruder in which the hydrogenated product is melted while removing the solvent cyclohexane and other volatile components from the solution at a temperature of 270 ° C. and a pressure of 1 kPa or less. Were extruded into strands, cooled and pelletized to recover the pellets. This hydrogenated ring-opened polymer had a weight average molecular weight (Mw) of 35,000, a hydrogenation rate of 99.9%, and a glass transition temperature (Tg) of 100 ° C.

<Example 1>
99 parts by weight of the DCP / ETD ring-opening polymer hydrogenated product obtained in Production Example 1 and 1 part by weight of fine particles (GE Toshiba Silicone Co., Ltd., Tospearl 120) composed of a crosslinked product of a polysiloxane polymer were mixed, Extruded into a strand using a twin screw extruder (Toshiba Machine Co., Ltd., TEM-35B) and cut with a pelletizer to produce a pellet for a light diffusion plate.

  Using this light diffusion plate pellet, a light diffusion plate was formed by an injection molding machine (screw diameter φ90 mm, maximum clamping force 850 t). In the mold, a substantially rectangular cavity surface is formed on the main surface of the fixed mold plate. The dimensions of the cavity surface were length 430 mm, width 740 mm, and diagonal length 856 mm. The depth of the cavity was 2.0 mm.

  As shown in FIGS. 1 and 2, twelve hot runner type valve gates having a diameter of 2 mm are provided on the cavity surface of the fixed mold and communicate with the cavity surface. The horizontal gate interval L2 was 185 mm, and the vertical gate interval L1 was 143.3 mm. The spacing error in each direction was 0%. Also, the distance LA1 between the outermost gate 20A and the longitudinal side 11A of the cavity surface shown in FIG. 1 is 71.7 mm, and the distance LB1 between the outermost gate 20A and the lateral side 12A of the cavity surface is 92. It was 0.5 mm. The distance LA2 was 71.7 mm, and the distance LB2 was 92.5 mm. The distance LA3 was 71.7 mm, and the distance LB3 was 92.5 mm. The distance LA4 was 71.7 mm, and the distance LB4 was 92.5 mm. Therefore, the error in distance was 0%. Each distance LA1 to LA4 was 50% of the distance L1, and each distance LB1 to LB4 was 50% of the distance L2. The injection molding conditions were a cylinder temperature of 275 ° C., a hot runner temperature of 275 ° C., a mold temperature of 78 ° C., an injection speed of 100 mm / second, and a cooling time of 30 seconds.

After the mold was clamped, the valve gate of the first lateral gate row was opened, and the resin was injected from the valve gate of the first lateral gate row. Subsequently, 1.5 seconds after the resin injection from the valve gate of the first horizontal gate row, the valve gate of the second horizontal gate row is opened, and the valve gate of the first horizontal gate row and the valve of the second horizontal gate row are opened. The resin was injected from the gate. Next, when it was determined that the resin injection amount reached a predetermined amount and the resin filling state in the vicinity of the cavity surface was a sufficient state without sinks or the like, all the valve gates were closed to stop the injection. At this time, the in-mold pressure at the time of injection was 180 kgf / cm ² (18 MPa). Then, after cooling a metal mold | die on the said conditions, the light-diffusion board was picked out from the metal mold | die, and the light-diffusion board was obtained.

  The obtained light diffusing plate was a non-defective product having no appearance defect caused by air accumulation. Further, the variation of the plate thickness was measured by a micrometer (manufactured by Mitutoyo Corporation), and it was 60 μm.

<Example 2>
The dimensions of the cavity surface were changed as follows, and light was emitted in the same manner as in Example 1 except that the valve gates of the second gate row were opened 2.5 seconds after the valve gates of the first horizontal gate row were opened. A diffusion plate was obtained. The dimensions of the cavity surface were 600 mm long, 1,020 mm wide, and a diagonal length of 1,183 mm. As shown in FIG. 2, the horizontal gate interval L2 was 233 mm, and the vertical gate interval L1 was 181.7 mm. The spacing error in each direction was 0%. The distance LA1 between the outermost gate 20A and the longitudinal side 11A of the cavity surface was 118.3 mm, and the distance LB1 between the outermost gate 20A and the lateral side 12A of the cavity surface was 160.5 mm. . The distance LA2 was 118.3 mm, and the distance LB2 was 160.5 mm. The distance LA3 was 118.3 mm, and the distance LB3 was 160.5 mm. The distance LA4 was 118.3 mm, and the distance LB4 was 160.5 mm. Therefore, the error in distance was 0%. Each distance LA1 to LA4 was 65.1% of the distance L1, and each distance LB1 to LB4 was 68.9% of the distance L2. The cavity depth was 2.0 mm. The mold internal pressure at the time of injection was 190 kgf / cm ² (19 MPa). Further, the obtained light diffusing plate was a non-defective product having no appearance defect caused by air accumulation. Furthermore, the variation in the thickness of the light diffusing plate was 100 μm.

<Comparative Example 1>
A light diffusion plate was obtained in the same manner as in Example 1 except that all the valve gates were opened at the same time and the resin was injected at the same time. The obtained light diffusion plate had a poor appearance due to burning caused by air accumulation. Furthermore, the variation in the thickness of the light diffusing plate was 200 μm.

<Comparative example 2>
Example 1 except that the number of valve gates is 8 (2 in the vertical direction and 4 in the horizontal direction) as shown in FIG. 15 and that all the valve gates are opened simultaneously and the resin is injected simultaneously. In the same manner, a light diffusing plate was obtained. The cavity surface dimensions of the mold were 430 mm long, 740 mm wide, and a diagonal length of 856 mm. The depth of the cavity was 2.0 mm. Describing with reference to the reference numerals in FIG. 2, the lateral gate spacing (L2 in FIG. 2) was 185 mm, and the longitudinal gate spacing (L1 in FIG. 2) was 215 mm. The spacing error in the lateral direction was 0%. The distances (LB1 to LB4 in FIG. 2) were each 160.5 mm, and the distances (LA1 to LA4 in FIG. 2) were each 118.3 mm. The error in distance in each direction was 0%. Each distance (LA1 to LA4 in FIG. 2) is 50% of the distance (L1 in FIG. 2), and each distance (LB1 to LB4 in FIG. 2) is equal to the distance (L2 in FIG. 2). It was 50% long. The mold internal pressure at the time of injection was 200 kgf / cm ² (20 MPa). Moreover, the obtained light diffusing plate had a poor appearance due to burning caused by air accumulation. Furthermore, the variation in the thickness of the light diffusing plate was 200 μm.

<Comparative Example 3>
As shown in FIG. 16, except that the number of valve gates is 16 (4 in the vertical direction and 4 in the horizontal direction), the interval between the horizontal gate rows is narrowed, and the dimensions of the cavity surface are changed as follows. A light diffusing plate was obtained in the same manner as in Comparative Example 1. The cavity surface dimensions of the mold were 600 mm long, 1,020 mm wide, and a diagonal length of 1,183 mm. Referring to the reference numerals in FIG. 2, the lateral gate interval (L2 in FIG. 2) was 255 mm, and the vertical gate interval (L1 in FIG. 2) was 50 mm. The spacing error in each direction was 0%. The distances (LB1 to LB4 in FIG. 2) were each 127.5 mm, and the distances (LA1 to LA4 in FIG. 2) were each 112.5 mm. The error in distance in each direction was 0%. Each distance (LA1 to LA4 in FIG. 2) was 225% of the distance (L1 in FIG. 2). Each distance (LB1 to LB4 in FIG. 2) was 50% of the distance (L2 in FIG. 2).

The depth of the cavity was 2.0 mm. The lateral gate spacing was 230 mm and the longitudinal gate spacing was 50 mm. In each direction, the spacing error was 0%. The mold internal pressure at the time of injection was 250 kgf / cm ² (25 MPa). Moreover, it was a good product with no appearance defect caused by air accumulation. Furthermore, the variation in the thickness of the light diffusing plate was 200 μm.

  In Examples 1 and 2, the in-mold pressure could be kept low, and the obtained light diffusing plate had no appearance defect due to gas burning or the like, and suppressed thickness unevenness. On the other hand, in Comparative Examples 1 and 2, the obtained light diffusing plate had poor appearance and uneven thickness due to gas burning or the like. In Comparative Example 3, the in-mold pressure could not be kept low, and thickness unevenness occurred in the obtained light diffusion plate.

<Example 3>
99 parts by weight of the DCP / ETD ring-opening polymer hydrogenated product obtained in Production Example 1 and 1 part by weight of fine particles (GE Toshiba Silicone Co., Ltd., Tospearl 120) composed of a crosslinked product of a polysiloxane polymer were mixed, Extruded into a strand using a twin screw extruder (Toshiba Machine Co., Ltd., TEM-35B) and cut with a pelletizer to produce a pellet for a light diffusion plate.

  Using the light diffusion plate pellets, a light diffusion plate was formed by an injection molding machine (screw diameter φ90 mm, maximum clamping force 850 t). In the mold, a substantially rectangular cavity surface is formed on the main surface of the fixed mold plate. The dimensions of the cavity surface were length 430 mm, width 740 mm, and diagonal length 856 mm. The depth of the cavity was 2.0 mm.

  As shown in FIGS. 5 and 6, the cavity surface of the stationary mold plate is provided with 16 hot runner type valve gates having a diameter of 2 mm that communicate with the cavity surface. The horizontal gate interval L2 was 185 mm, and the vertical gate interval L1 was 107.5 mm. The spacing error in each direction was 0%. Further, the distance LA1 between the outermost gate 20A and the longitudinal side 11A of the cavity surface shown in FIG. 5 is 92.5 mm, and the distance LB1 between the outermost gate 20A and the lateral side 12A of the cavity surface is 53. 0.8 mm. The distance LA2 was 92.5 mm, and the distance LB2 was 53.8 mm. The distance LA3 was 92.5 mm, and the distance LB3 was 53.8 mm. The distance LA4 was 92.5 mm, and the distance LB4 was 53.8 mm. Therefore, the error in distance was 0%. Each distance LA1 to LA4 was 50% of the distance L1, and each distance LB1 to LB4 was 50% of the distance L2. The injection molding conditions were a cylinder temperature of 275 ° C., a hot runner temperature of 275 ° C., a mold temperature of 78 ° C., an injection speed of 100 mm / second, and a cooling time of 30 seconds.

After the mold was clamped, the first group of valve gates was opened, and the resin was injected from the first group of valve gates. Subsequently, 1.5 seconds after resin injection from the first group valve gate, the second group valve gate was opened, and the resin was injected from the first group valve gate and the second group valve gate. Subsequently, 1.5 seconds after resin injection from the second group of valve gates, the third group of valve gates was opened, and the resin was injected from the first to third valve gates. Next, when it was determined that the resin injection amount reached a predetermined amount and the resin filling state in the vicinity of the cavity surface was a sufficient state without sinks or the like, all the valve gates were closed to stop the injection. At this time, the in-mold pressure at the time of injection was 180 kgf / cm ² (18 MPa). Then, after cooling a metal mold | die on the said conditions, the light-diffusion board was picked out from the metal mold | die, and the light-diffusion board was obtained.

  The obtained light diffusing plate was a non-defective product having no appearance defect caused by air accumulation. Further, the variation in the plate thickness was measured by a micrometer (manufactured by Mitutoyo Corporation) and found to be 60 μm.

<Example 4>
The dimensions of the cavity surface were changed as follows, and the opening and closing of the valve gate was controlled in the same manner as in Example 1 to obtain a light diffusing plate. The dimensions of the cavity surface were 600 mm long, 1,020 mm wide, and a diagonal length of 1,183 mm. As shown in FIG. 6, the lateral gate interval L2 was 255 mm, and the longitudinal gate interval L1 was 150 mm. The spacing error in each direction was 0%. The distance LA1 between the outermost gate 20A and the longitudinal side 11A of the cavity surface was 75 mm, and the distance LB1 between the outermost gate 20A and the lateral side 12A of the cavity surface was 127.5 mm. Further, the distance LA2 was 75 mm, and the distance LB2 was 127.5 mm. The distance LA3 was 75 mm, and the distance LB3 was 127.5 mm. The distance LA4 was 75 mm, and the distance LB4 was 127.5 mm. Therefore, the error in distance was 0%. Each distance LA1 to LA4 was 50% of the distance L1, and each distance LB1 to LB4 was 50% of the distance L2. The cavity depth was 2.0 mm. The mold internal pressure at the time of injection was 180 kgf / cm ² (18 MPa). Further, the obtained light diffusing plate was a non-defective product having no appearance defect caused by air accumulation. Furthermore, the thickness variation of the light diffusing plate was 80 μm.

<Comparative example 4>
A light diffusing plate was obtained in the same manner as in Example 3 except that all the valve gates were opened at the same time and the resin was injected at the same time. The obtained light diffusion plate had a poor appearance due to burning caused by air accumulation. Furthermore, the variation in the thickness of the light diffusing plate was 200 μm.

<Comparative Example 5>
As shown in FIG. 17, the number of valve gates is 8 (2 in the vertical direction and 4 in the horizontal direction), the vertical gate interval is made narrower than the horizontal gate interval, and all the valve gates are simultaneously connected. A light diffusing plate was obtained in the same manner as in Example 2 except that it was opened and the resin was injected at the same time and the in-mold pressure at the time of injection was 25 MPa. The obtained light diffusion plate had a poor appearance due to burning caused by air accumulation. Furthermore, the variation in the thickness of the light diffusing plate was 200 μm.

  In Examples 3 and 4, the in-mold pressure could be kept low, and the obtained light diffusion plate had no appearance defects due to gas burning or the like, and suppressed thickness unevenness. On the other hand, in Comparative Example 4, the obtained light diffusing plate had poor appearance and uneven thickness due to gas burning or the like. In Comparative Example 5, the in-mold pressure could not be kept low, and thickness unevenness occurred in the obtained light diffusion plate.

  The method for producing a flat molded product of the present invention is suitable for producing a flat molded product using a mold, and includes optical members such as a light diffusing plate, a light guide plate, and a reflecting plate that constitute a backlight device of a liquid crystal display, and the like. It can be applied to the production of flat plate molded products.

Claims (9)

A method for producing a resin-made flat molded product using a mold for injection molding,
The mold includes a fixed mold plate in which a substantially rectangular cavity surface corresponding to the shape of the flat plate molded product is formed, and a plurality of gates communicating with the cavity surface are provided. When considering a lattice in which the vertical pitch is L1 and the horizontal pitch is L2 along the substantially rectangular vertical and horizontal directions of the cavity surface, it is arranged at the position of the intersection of the lattice. ,
In the four outermost gates that are the gates closest to each vertex of the substantially rectangular cavity surface, the distances LA1 to LA4 between the outermost gates and the nearest side of the lateral sides of the cavity surface are the pitches L1 is 120% to 10%, and distances LB1 to LB4 between each outermost gate and the closest side among the vertical sides of the cavity surface are 120% to 10% of the pitch L2,
The plurality of gates as a plurality of vertical gate rows composed of a plurality of gates arranged along the vertical direction and a plurality of horizontal gate rows composed of a plurality of gates arranged along the horizontal direction,
Of the number of the vertical gate rows and the number of the horizontal gate rows, the number of gate rows in at least one direction is an odd number,
In the odd number of gate rows in any direction, a plurality of gate rows are arranged as a first gate row, and a row including a center side gate which is a gate closest to an intersection of diagonal lines of the cavity surface is a first gate row. A second gate row including two gate rows close to the row, a third gate row including gate rows close to each gate row constituting the second gate row,... Each constituting the n-1 gate row An n-th gate column (n is an integer of 2 or more) including each gate column close to the gate column;
A first step of injecting the resin from the first gate row;
N-th step of injecting the resin from the n-th gate row when the injection amount from the n-th gate row reaches a predetermined amount (when n is k, n is 2 to k) For all values)
The manufacturing method of the flat plate molded article characterized by comprising.   2. The flat molded article according to claim 1, wherein the distances LA1 to LA4 in the outermost gates are substantially the same, and the distances LB1 to LB4 in the outermost gates are substantially the same. Manufacturing method.   3. The method for manufacturing a flat molded article according to claim 1, wherein the odd-numbered gate row direction is the longer direction of either the vertical direction or the horizontal direction. A method of manufacturing a substantially rectangular flat plate molded product by injection molding a resin using a mold for injection molding,
The mold includes a movable mold plate and a fixed mold plate having a substantially rectangular cavity surface corresponding to the shape of the flat plate molded product and provided with a plurality of gates communicating with the cavity surface. ,
The plurality of gates have a pitch in the first direction along the first side of the substantially rectangular shape of the cavity surface as L1, and a pitch in the second direction along the second side orthogonal to the first direction. Is considered at the position of the intersection of the lattice when considering the lattice of L2,
The plurality of gates are a plurality of first gate rows made of a plurality of gates arranged along the first direction and a plurality of second gate rows made of a plurality of gates arranged along the second direction,
In the first gate row, the two gate rows closest to the intersection of the diagonal lines of the cavity surface are the eleventh gate row and the twelfth gate row, and the two gate rows close to the eleventh gate row and the twelfth gate row are respectively set. The thirteenth gate row and the fourteenth gate row, and in the second gate row, the two gate rows closest to the intersection of the diagonal lines of the cavity surface are the 21st gate row and the 22nd gate row, the 21st gate row and the 21st gate row. When two gate rows close to 22 gate rows are respectively referred to as a 23rd gate row and a 24th gate row, and each gate is represented by (first gate row, second gate row),
A first group including the gates (13, 21), (11, 22), (12, 21), (14, 22), (13, 22), (11, 21), (12, 22), A first step of injecting the resin from each gate included in any one of the second groups including each gate of (14, 21);
A second step of injecting the resin from the gate included in the other group when the injection amount in the first step becomes a predetermined amount;
A third step of injecting the resin from each gate of the 23rd gate row and the 24th gate row when the injection amount in the second step becomes a predetermined amount;
The manufacturing method of the flat plate molded article characterized by including. A method of manufacturing a substantially rectangular flat plate molded product by injection molding a resin using a mold for injection molding,
The mold includes a movable mold plate and a fixed mold plate having a substantially rectangular cavity surface corresponding to the shape of the flat plate molded product and provided with a plurality of gates communicating with the cavity surface. ,
The plurality of gates have a pitch in the first direction along the first side of the substantially rectangular shape of the cavity surface as L1, and a pitch in the second direction along the second side orthogonal to the first direction. Is considered at the position of the intersection of the lattice when considering the lattice of L2,
The plurality of gates are a plurality of first gate rows made of a plurality of gates arranged along the first direction and a plurality of second gate rows made of a plurality of gates arranged along the second direction,
In the first gate row, the two gate rows closest to the intersection of the diagonal lines of the cavity surface are the eleventh gate row and the twelfth gate row, and the two gate rows close to the eleventh gate row and the twelfth gate row are respectively set. The thirteenth gate row and the fourteenth gate row, and in the second gate row, the two gate rows closest to the intersection of the diagonal lines of the cavity surface are the 21st gate row and the 22nd gate row, the 21st gate row and the 21st gate row. When two gate rows close to 22 gate rows are respectively referred to as a 23rd gate row and a 24th gate row, and each gate is represented by (first gate row, second gate row),
It is included in any one of the first group including the gates of (11, 22) and (12, 21) and the second group including the gates of (11, 21) and (12, 22). A first step of injecting the resin from each gate;
A second step of injecting the resin from each gate included in the other group when the injection amount in the first step becomes a predetermined amount;
A third step of injecting the resin from each gate of the thirteenth gate row, the fourteenth gate row, the twenty-third gate row, and the twenty-fourth gate row when the injection amount in the second step becomes a predetermined amount;
The manufacturing method of the flat plate molded article characterized by including.   In the four outermost gates, which are the gates closest to the vertices of the substantially rectangular cavity surface, the distances LA1 to LA4 between the outermost gates and the closest sides of the sides of the cavity surface in the second direction are: The distances LB1 to LB4 between each outermost gate and the nearest side of the cavity surface in the first direction are 120% to 10% of the pitch L2, respectively. The method for producing a flat molded article according to claim 4 or 5, wherein the ratio is%.   The flat plate molding according to claim 6, wherein the distances LA1 to LA4 in the outermost gates are substantially the same, and the distances LB1 to LB4 in the outermost gates are substantially the same. Product manufacturing method. When the number of the gates is N (pieces), the depth of the cavity formed in the fixed mold is t (mm), and the area of the cavity surface is S (mm ² ), The manufacturing method of the flat plate molded product according to any one of claims 1 to 7, characterized by satisfying.
(S / (t + 6)) × 10−4 ≦ N ≦ (2S / t) × 10−4 Formula (1)   The flat plate molded product manufactured by the manufacturing method of the flat plate molded product as described in any one of Claims 1-8.

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