JP5576636B2 - Resin sheet molded product, manufacturing method thereof, mold for hot press molding - Google Patents

Description

  The present invention relates to a resin sheet molded article, a manufacturing method thereof, and a mold for hot press molding, and more specifically, is suitable for use as a backlight of a liquid crystal display device, and is formed using hot press molding. The present invention relates to a thin and large resin sheet molded product having a concavo-convex pattern on its surface, a manufacturing method thereof, and a hot press mold.

  Liquid crystal display devices have been widely used in personal computers, monitors, liquid crystal televisions, mobile phones and the like. In order to display a display image brightly in the liquid crystal display device, a backlight unit is arranged on the lower surface side of the liquid crystal panel. In order to make the backlight unit thin, a light guide plate is used. For example, a light source is arranged on the side surface of the light guide plate to guide light from the light source to the back of the light guide plate, and light is emitted to the upper surface of the light guide plate. The structure is a so-called edge light structure. As one of the prior art structures showing this edge light structure, for example, there is a structure shown in FIG.

  As shown in FIGS. 4A and 4B, the backlight unit 50 is disposed in the vicinity of the light guide plate 60 and the side surface 61 of the light guide plate 60 with the light emission surface facing the side surface 61. An LED 68 is included. On the first surface (upper surface) 60a that is the light emitting surface of the light guide plate 60, as shown in FIG. 4B, a diffusion sheet 65 and two prism sheets 66 provided on the diffusion sheet 65, 67 is laminated, and a reflection sheet 64 is provided on the second surface (lower surface) 60 b of the light guide plate 60.

  Since 2007, light guide plates used as backlights for liquid crystal display devices have expanded into the fields of electronic signboards and 46-inch and 52-inch information displays (for outdoor advertising, corporate, and public facility information display devices) announced by market demand. In order to do so, it is necessary to secure a product and a manufacturing method that can cope with the trend toward thinning due to, for example, the development and popularization of 0.5 mm thick LEDs simultaneously with the trend toward larger size. Conventionally, large light guide plates for monitors and liquid crystal televisions have been practically sufficient by providing a dot-shaped uneven pattern on a resin sheet reflecting surface by printing and inkjet. In addition, the liquid crystal light guide plate for personal computers is formed by injection molding a transparent resin, and the reflection surface opposite to the emission surface is provided with a very fine uneven pattern such as a dot shape and a prism shape for scattering or totally reflecting light. Installed, mass-produced and accurate products are completed.

  However, the injection molding method has a disadvantage that the thickness of the light guide plate is limited due to the resin filling problem. In order to produce the above-mentioned 0.5mm-thick large-sized light guide plate by injection molding, a large molding machine with ultra-high pressure and ultra-high-speed injection performance and a high-rigidity high-rigidity precision assembly mold with few gaps are required. It becomes. On the other hand, in the case of the printing method and the inkjet method, there is an inconvenience that a dot-shaped concavo-convex pattern can be seen on a transparent sheet having a thickness of 0.5 mm. Thus, until now, it was the actual condition that a thin large-sized flat light-guide plate with a thickness of 0.5 mm or less could not be manufactured. In addition, since there is a limit to thinning the light guide plate, there is a disadvantage that a thin backlight unit cannot be obtained.

  As an improvement measure, there is a hot press molding method. FIG. 5 of Patent Document 1 is a perspective view for explaining a method for manufacturing a light guide plate, and FIG. 6 is a side view showing a state where pressure is applied by a press die in the method for manufacturing a light guide plate in FIG. Show. In the thin large plate light guide plate and its molding method, the concave and convex optical pattern of the light guide plate is obtained by sandwiching a resin sheet between thin plate mold members provided with a concave and convex pattern on the opposite surface and pressurizing the opposing mold under heating. Form. In the method described in Patent Document 1, a belt-shaped thin resin sheet is fed out using a material feeding device between thin sheet metal mold members provided with concave and convex patterns on opposite surfaces, and pressed under heating to form a molded belt The thin light guide plate is cut into a required size of the light guide plate to obtain the light guide plate. According to this method, the process for forming the concave / convex optical pattern is short and the working method is simple and easy, so that the manufacturing cost can be reduced, and the sheet metal mold member provided with the concave / convex pattern on the opposite surface is provided. Since it is only necessary to manufacture a pair of molds, the cost of molds can be reduced.

  Next, in Patent Document 2 below, a planar circular recess having a bottom surface diameter of 0.5 to 2 mm and a depth of 20 to 200 μm is formed in a halftone dot pattern by etching on the surface of a metal plate, and the bottom surface is Prepare a pressing template having a ten-point average roughness Rz of 10 to 45 μm and a transfer portion having a flat surface excluding the recesses and having a mirror surface with a ten-point average roughness Rz of less than 1 μm. A transparent thermoplastic resin plate having a thickness of 3 to 15 mm is placed on top of each other, and the shape in the transfer portion is transferred to the transparent thermoplastic resin plate by hot pressing, so that the shorter side is approximately 600 mm or more. A method of manufacturing a light guide plate, characterized in that a rectangular light guide plate is obtained is described. Further, in Patent Document 3 below, in order to eliminate the distortion of a large injection molded product, synthetic resin is injected and filled in a closed mold cavity in a high-pressure clamping state, and the mold cavity is formed by resin pressure in the mold. After releasing slightly in the thickness direction, the mold gate is mechanically or cooled and sealed, and compression of the synthetic resin in the mold cavity is performed under pressure holding and mold clamping in the high-pressure mold clamping state. An injection molding method of a synthetic resin molded product is disclosed, in which compression molding is performed by reducing the mold clamping force during holding pressure or cooling through the state.

JP 2008-52940 A JP 2008-175996 A Japanese Patent No. 2510441

  However, the above-described background art injection molding method and hot press molding method have the following disadvantages. First, the problem to be solved in the present situation is that there is no manufacturing method that can replace the injection molding method in which the thickness is about 0.5 mm. For example, according to the relational expression between tube radius and tube length of volume flow rate described in Katsuhiko Ito, James M. Mckelvey, “Polymer Processing Optics”, Maruzen Co., Ltd., page 61, It is known that the volume flow rate as a non-Newtonian fluid with respect to the isothermal flow of the thermoplastic resin in the flow path is generally proportional to the cube of the flow path (thickness) and inversely proportional to the flow length (size of the light guide plate). Yes. Therefore, in the injection molding method, when the thickness is 0.5 mm or less, it is difficult to secure a flow volume even with ultra-high pressure / ultra-high speed injection, and in addition, a large light guide plate having a flow length 600 times the thickness is melted. The flow length of the resin becomes longer, the flow pressure loss becomes larger, the filling property into the mold cavity becomes worse, and the fine uneven pattern of the light guide plate, in particular, the fine prism pattern cannot be accurately transferred. . Further, Patent Document 3 described above discloses an injection molding method for eliminating the distortion of a large injection molded product. However, when injection molding is performed at an ultra-high pressure / ultra-high speed in the technology, the molten resin is removed from the mold surface. There is an inconvenience that it becomes difficult to release due to the close contact.

  Next, in the hot press molding method described in Patent Documents 1 and 2 described above, there is a disadvantage that a step of obtaining a light guide plate by cutting into a predetermined dimension from a molded product obtained after the molding step is required. . In addition, the hot press molding method that puts a thin resin sheet into the mold does not take into account the dimensional accuracy and weighing accuracy of the thin resin sheet and the management of the space between the mold cavity and emphasizes the uneven pattern. There was a disadvantage that burrs were generated on the side of the molded product.

  The present invention pays attention to the above points, suppresses the generation of burrs, makes the emitted light uniform with excellent transferability, and further eases the adhesion to the mold surface and has excellent releasability, It is an object of the present invention to provide a thin and large resin sheet molded product having a concavo-convex pattern on the surface using hot press molding, which can be easily produced in a plurality, and a method for producing the same. Another object is to provide a hot press molding die suitable for manufacturing the resin sheet molded article.

In order to achieve the above object, a hot press molding die of the present invention accommodates a pair of thin members provided with a concavo-convex pattern on at least one of the opposing main surfaces, and one of the pair of thin members. The required dimension of the molded product is set, and a resin sheet holding frame that forms a cavity for storing a thin resin sheet together with the pair of thin members, one of the pair of thin members, and the resin sheet holding frame are provided. A lower mold and the other of the pair of thin members, the upper mold facing the lower mold, and the upper mold and the lower mold, respectively. At least among the four side surfaces of the temperature adjustment pipe for adjusting the temperature for transferring and forming the concavo-convex pattern by pressing with an appropriate pressure, and the resin sheet holding frame surrounding the outer periphery of the thin resin sheet A slide mechanism that slides one side surface, and adjustment of a space formed between the side surface of the thin resin sheet housed in the cavity and the holding frame of the resin sheet by the slide mechanism; The space formed between the side surface of the thin member housed in the cavity and the resin sheet holding frame is adjusted. According to one of the main forms, an uneven pattern is provided on a side surface slid by the slide mechanism .

The method for producing a resin sheet molded product according to the present invention is a method for producing a resin sheet molded product using any one of the above-described hot press molding dies, and the cavity is cut and polished to the same dimension as the cavity. After feeding the processed thin resin sheet, heat transfer is performed while fixing the thin resin sheet in the cavity at a low pressure, and the pressure is increased before reaching the temperature at which the thermally expanded thin resin sheet softens. The resin sheet is compressed into a mold cavity, and a concavo-convex pattern is transferred and formed on the thin resin sheet at a temperature in a rubber-like flat region exceeding the transfer start temperature and at a pressure capable of suppressing the generation of burrs. To do. In addition, as shown in FIG. 5, the transfer start temperature in this specification is a graph of the phase transition region when the relationship between the temperature of the thermoplastic resin used for molding and the longitudinal elastic modulus (storage elastic modulus) is measured. This temperature is obtained from the intersection of the tangent line LA (the inflection point is called the glass transition temperature, the deflection temperature under load, or the softening temperature) and the graph LB of the rubber-like flat region connected to the high temperature flow region.

Furthermore, the resin sheet molded article of the present invention is a thin-walled large-sized resin sheet molded article having a concavo-convex pattern on the surface formed by the method for producing a resin sheet molded article according to claim 3, and having diagonal lines of a substantially rectangular plane. The length is in the range of 600 to 1000 times the thickness, and the thickness is 0.3 to 3.0 mm . One of the major form is pre Symbol thickness, characterized in that a 0.5 mm to 2.0 mm. The resin sheet molded product is a thin and large flat light guide plate. The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

According to the present invention, a pair of thin members provided with a concavo-convex pattern on at least one of the opposing main surfaces, and one of the pair of thin members are accommodated and set to the required dimensions of the molded product. A resin sheet holding frame that forms a cavity for storing a thin resin sheet together with the thin member, a lower mold provided with one of the pair of thin members, the resin sheet holding frame, and the other of the pair of thin members. And provided on each of the upper mold facing the lower mold and each of the upper mold and the lower mold, and pressurizing the thin resin sheet at an appropriate temperature and an appropriate pressure to transfer and form an uneven pattern. A temperature control pipe for adjusting the temperature of the slide, and a slide machine for sliding at least one of the four side surfaces of the resin sheet holding frame surrounding the outer periphery of the thin resin sheet And adjusting the space formed between the side surface of the thin resin sheet accommodated in the cavity and the holding frame of the resin sheet by the slide mechanism, and the thin wall accommodated in the cavity It was decided to perform hot press molding with a mold for adjusting the space formed between the side surface of the member and the resin sheet holding frame . For this reason, the generation of burrs is suppressed, the emitted light is made uniform with excellent transferability, the mold releasability from the mold is good, and a thin and large resin sheet molded product having an uneven pattern on the surface can be obtained efficiently. effective. Moreover, since hot press molding is used, it is easy to produce a plurality.

FIG. 1 is an explanatory view showing the timing of hot press molding of a thin and large resin sheet molded product having an uneven pattern on the surface according to the present invention. FIG. 2 is a view showing a hot press molding die of Example 1, (A) is a simplified cross-sectional view for explaining gap burrs, parting gap burrs, and space protrusion burrs, and (B) is the above-mentioned figure. FIG. 4C is a plan view of the resin sheet holding frame as viewed from above with the mold opened on the parting surface, and FIG. 5C is a plan view for explaining the sliding mechanism of the resin sheet holding frame. FIG. 3 is a cross-sectional view showing a detailed configuration of the hot press molding die of the first embodiment. 4A and 4B are diagrams showing the backlight unit, in which FIG. 4A is an external perspective view, and FIG. 4B is a cross-sectional view. FIG. 5 is an explanatory diagram of the transfer start temperature.

  Hereinafter, the best mode for carrying out the present invention will be described in detail based on examples.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an explanatory view showing the timing of hot press molding of a thin and large resin sheet molded product having an uneven pattern on the surface. 2A and 2B are diagrams showing a hot press molding die according to Example 1. FIG. 2A is a simplified cross-sectional view for explaining gap burrs, parting gap burrs, and space protrusion burrs, and FIG. FIG. 3C is a plan view of the resin sheet holding frame as viewed from above with the mold opened on the parting surface, and FIG. 3C is a plan view illustrating a sliding mechanism of the resin sheet holding frame. FIG. 3 is a cross-sectional view showing a detailed configuration of the hot press molding die of the first embodiment. 4A and 4B are diagrams showing the backlight unit, where FIG. 4A is an external perspective view, and FIG. 4B is a cross-sectional view. The present invention is characterized in that a thin and large resin sheet molded product having a concavo-convex pattern on its surface is obtained by hot press molding continuously produced using a mold.

  <Mold Configuration> First, the configuration of the hot press molding die of the present invention will be described with reference to FIG. 2 and FIG. A hot press molding die (hereinafter referred to as “die”) 10 of the present embodiment includes a pair of thin members 3a and 3b provided with a concavo-convex pattern on at least one of the opposing main surfaces, and one thin member ( In the illustrated example, the resin sheet holding frame that accommodates the thin member 3b) and is set to the required dimensions of the molded product, and forms a cavity 12 for accommodating the thin resin sheet 5 together with the pair of thin members 3a and 3b. 6, a fixed cooling lower die 1 b provided with one thin member 3 b and a resin sheet holding frame 6, and a movable heating upper die 1 a provided with the other thin member 3 a. The movable heating upper mold 1a and the fixed cooling lower mold 1b face each other, the movable heating upper mold 1a is provided with a pipe 2a, and the fixed cooling lower mold 1b is provided with a pipe 2b. In this embodiment, the pipe 2a is for heating and the pipe 2b is for cooling, and each is designed to conduct heat, and the thin resin sheet 5 is pressed at an appropriate temperature and pressure to transfer and form an uneven pattern. Used for temperature control. As the thin resin sheet 5, for example, various known transparent thermoplastic resin sheets are used. The main surface here refers to two opposing surfaces having a large area among the six constituent surfaces. The thin member 3a is accommodated in a plate 11a fixed to the movable heating upper die 1a.

  It can be said that the opposing main surfaces of the thin members 3 a and 3 b constitute a part of the cavity 12. In the present embodiment, a heat insulating sheet 4 for adjusting heat dissipation is provided on the other main surface of the thin member 3b as necessary. The thin members 3a and 3b are made of metal, and as the material thereof, for example, stainless steel, nickel, copper alloy or the like is used, and the thickness is set to about 0.3 mm to 0.7 mm, for example. The inner side of the resin sheet holding frame 6 constitutes four side surfaces of the cavity 12, and its thickness, long side (corresponding to 6a and 6b in FIG. 2 (C)), short side (in FIG. 2 (C)). 6c, 6d) roughly corresponds to the required thickness and length of the molded product. The gap 13 between the resin sheet holding frame 6 and the thin member 3b is set within a predetermined tolerance by precision cutting and polishing the thin member 3b. Moreover, you may make it provide many degassing grooves 15 shown in FIG.2 (B) in the parting surface of the resin sheet holding frame 6 as needed.

  As shown in FIG. 3, the resin sheet holding frame 6 has a claw portion 16 for holding the thin member 3b. Further, the resin sheet holding frame 6 may include a slide mechanism for sliding at least one of the four side surfaces facing the outer peripheral portion of the thin resin sheet 5. For example, in the example shown in FIG. 2C, the resin sheet holding frame 6 is divided into four blocks: blocks 14a and 14b including the long sides 6a and 6b, and blocks 14c and 14d including the short sides 6c and 6d. At least one of these blocks 14a to 14d is slidable by a slide mechanism (not shown) in the direction indicated by the arrow in FIG.

  The slide mechanism slides at least one of the side surfaces of the resin sheet holding frame 6 by a distance that adjusts the thickness variation of the thin members 3a and 3b by about 10 μm, and the side surface of the resin sheet holding frame 6 and the thin resin sheet As a preferred embodiment, the space 9 is slid so as to be adjusted within 50 μm. Further, the slide mechanism may include a mold clamping force adjusting mechanism in order to suppress burrs in the parting gap 7 generated when the thin resin sheet 5 is heated and pressed to transfer the uneven pattern. is there. Further, in order to eliminate burrs in the gap 8 (gap between the thin member 3 b and the resin sheet holding frame 6) in FIG. 2, the outer diameter dimensions of the thin members 3 a and 3 b may be larger than those of the thin resin sheet 6. . 2C is provided on the side surface of the resin sheet holding frame 6 on the long side 6a side, and the concavo-convex pattern is transferred to the side surface of the thin resin sheet 5 on the long side side. Also good. In this way, when the present embodiment is applied to the manufacture of the light guide plate, the uneven pattern on the light incident surface of the light guide plate 60 can be suppressed by transferring the uneven pattern to the light incident surface of the light guide plate.

  In FIG. 3, a heat insulating sheet 4 is provided on the lower surface of the resin sheet holding frame 6. The heat insulating sheet 4 is mounted in order to shorten the heating time to the transfer temperature and stabilize the transferability, and is housed in a plate 11b provided in the fixed cooling lower mold 1b. ing. The resin sheet holding frame 6 is provided on the plate 11b.

  As a method of mounting the thin member 3a on the movable heating upper die 1a and the thin member 3b on the fixed cooling lower die 1b, for example, a method of vacuum adsorption, a method of adhering with an adhesive, or a method of fixing using a magnet. Can be mentioned. Moreover, the fixing method which combined the method of vacuum-sucking and a pressing ring may be utilized. Since the main body of the present invention is to manufacture a thin and large resin sheet molded product having a concavo-convex pattern on the surface, description of the method for forming the concavo-convex pattern on the thin members 3a and 3b is omitted.

  <Method for Producing Resin Sheet Molded Product> Next, a method for producing a thin and large resin sheet molded product using the mold 10 will be described with reference to FIG. First, the thin resin sheet 5 cut and polished with a tool such as an end mill, for example, is inserted into the cavity 12 formed by the pair of thin members 3a and 3b and the resin sheet holding frame 6 in substantially the same dimensions as the cavity 12. The inside of the mold 10 is evacuated (T1 in FIG. 1). As shown in FIG. 1, the thin resin sheet 5 is, for example, in a range of 1 to 3 MPa in a temperature range of 50 ° C. or less from a solidified state of the resin to a load deflection temperature inherent to the resin, for example, 99 ° C. or less in a methacryl resin sheet The heat is heated while being fixedly adhered to the cavity 12 at a low pressure (T1 to T2), and the softening is started over the deflection temperature under load indicated by the one-dot chain line in FIG. 1 (T3). The pressure starts (T2 to T3), and the thin resin sheet 5 that thermally expands is compressed into the cavity 12. When the rubber-like flat region that is the transfer start temperature is reached, the uneven pattern is transferred and formed at a pressure that can suppress the generation of burrs, for example, a pressure in the range of 5 to 9 MPa (T4 to T5). When cooling and decompression are completed, the resin sheet molded product is taken out from the mold 10 (T6).

  Here, when one of the opposing main surfaces of the thin-walled members 3a and 3b has an uneven pattern and the other main surface is a mirror surface, the uneven pattern is formed only on one of the main surfaces of the resin sheet molded product. And when the uneven | corrugated pattern is provided in the both surfaces which the said thin member 3a, 3b opposes, it forms in both the main surfaces of a molded article. Examples of the concave / convex pattern include a dot-like, grain-like, and prism-like pattern for guiding light incident on a light incident surface of a resin sheet molded product facing from a light source (not shown), reflecting the light on the back surface, and emitting the light on the front surface. Are appropriately arranged. Further, the molding conditions such as the hot press temperature, time, and pressure are appropriately adjusted depending on the type, size, and pressure of the transparent thermoplastic resin sheet (that is, the thin film resin sheet 5). For example, as the thin film resin sheet 5, A methacrylic resin sheet having a thickness of 0.5 mm (corresponding to t in FIG. 4 (A)) and a planar rectangular diagonal (corresponding to L in FIG. 4 (A)) 15.4 inches (386 mm, thickness ratio 772 times) was used. In this case, a heating press temperature of 160 ° C. for a temperature rising time of 15 seconds, a cooling to 40 ° C. and a time for taking out a molded product of 15 seconds, and a transfer press pressure of 5 MPa at that time are given as examples of suitable conditions.

  <Gap burrs, parting gap burrs, space protrusion burrs> Next, with reference to FIG. 2, gap burrs, parting gap burrs, and space protrusions generated by the hot press molding method using the mold 10 are described. Describe Bali. As shown in FIG. 2, the main problem is the gap 8 between the resin sheet holding frame 6 of the cavity 12 and the thin-walled member 3b. In some cases. This is caused by a defect in the external dimension accuracy of the thin member 3b which is a mold replacement member. Therefore, if the tolerance of the outer dimension of the thin member is 0.1 mm or less, preferably 0.05 mm or less, no gap burrs are generated. Next, the parting gap 7 is a gap between the parting surfaces of the movable heating upper die 1a and the fixed cooling lower die 1b. As is well known in the work press method, the uneven pattern is transferred to the thin resin sheet 5. This is a gap in the mold slightly open state that is generated because the pressure to be applied is larger due to insufficient setting of the clamping force. For example, when the temperature for transferring the concavo-convex pattern is 160 ° C. and the pressure is 5 MPa, the mold clamping force needs to be set to a pressure of 6 MPa or more.

  Finally, the space protrusion burr is generated in the space 9 between the thin resin sheet 5 and the resin sheet holding frame 6, and if a space protrusion burr occurs here, a problem may occur in the arrangement of inspection standards. Yes, it is caused by a defect in the external dimensional accuracy of the thin resin sheet 5 to be input. The space protrusion burr is characterized in that a circular wave-like protrusion burr is generated independently in the space 9 and has a thickness of 50 μm and a radius (length) of 100 to 500 μm. Accordingly, the cutting and polishing accuracy of the outer dimensions of the thin resin sheet 5 is 300 μm or less, preferably 100 μm or less, in the case of a diagonal 15.4-inch light guide plate, which is a dimensional accuracy that does not cause space protrusion burrs.

  <Application example> ... Next, the light guide plate (resin sheet molded product) obtained by the mold 10 of the present embodiment and the resin sheet molded product manufacturing method using the mold 10 is used in the lighting device of the liquid crystal display device. An application example applied to a certain backlight unit will be described. As shown in FIGS. 4A and 4B, the backlight unit 50 has a configuration in which the LEDs 68 are arranged in the vicinity of the side surface 61 of the light guide plate 60 with the light emission surface facing the side surface 61. Yes. A diffusion sheet 65 is provided on a first surface (upper surface) 60 a which is a light emission surface of the light guide plate 60, and two prism sheets 66 and 67 are laminated on the diffusion sheet 65. Yes. On the other hand, a reflection sheet 64 is provided on the second surface (lower surface) 60 b of the light guide plate 60.

  In the example shown in FIG. 4, as the resin sheet for the light guide plate 60, a transparent thermoplastic resin is preferably used. For example, PMMA, MMA / styrene copolymer, Polystyrene, or the like is used. The thickness is 0.3 mm to 3.0 mm, preferably 0.5 mm to 2.0 mm. For example, when the thickness is 0.5 mm or less, the diagonal dimension of the active area is 600 times or more of the thickness. . Among these, considering hot press moldability, transparency and light resistance, PMMA and MMA / styrene copolymers are preferable, and extruded sheets of these are more preferable.

  That the thickness t of the thermoplastic resin sheet (thin resin sheet 5) is 0.5 mm or less corresponds to the development and popularization of thin LEDs, and the length L of the substantially rectangular diagonal line is 600, which is the thickness t. Being more than double is a region that exceeds the molding limit of injection molding, and can therefore be an object of the present invention. As an embodiment of the present invention, the thin resin sheet 5 is cut and polished to the same dimension as the cavity 12 of the resin sheet holding frame 6 of the mold 10 designed and manufactured with the required size and dimensions of the light guide plate. By managing the space between the resin sheet 5 and the cavity 12, a thin large-sized flat light guide plate 60 can be manufactured by a hot press molding method using the mold 10. For example, the tolerance of the external dimension accuracy, the plate thickness variation accuracy, and the plate thickness distribution of the thin resin sheet 5 is determined and monitored, and the thin resin sheet 5, the resin sheet holding frame 6, and the space 9 include a space. In order to suppress protrusion burrs, it is preferable to manage with a tolerance of 50 μm.

  <Experimental Example> Hereinafter, an example in which a light guide plate is manufactured using the mold 10 of this example will be described. As the molding machine, a hot press molding machine using a mold (manufactured by Meiki Seisakusho: press molding machine MP22) was used. For the purpose of obtaining a light guide plate having a thickness of 0.5 mm and a diagonal plane of 15.4 inches (386 mm, thickness ratio 772 times), a transparent thermoplastic resin (thin resin sheet 5) having a thickness of 0.5 mm A methacrylic resin extruded sheet (manufactured by Kuraray: Comoglas DK) and a 0.3 mm thick stainless steel thin member 3b provided with an uneven pattern were prepared. The concavo-convex pattern was a dot shape with a diameter of 30 μm and a height of 10 μm, and the thin member 3 b was adjusted in outer dimensions, and the gap 8 with the mold 10 was measured with a gap gauge. Since the gap gauge has a measurement limit of 50 μm, the gap that cannot be measured was set to 50 μm or less. The methacrylic resin extrusion sheet was subjected to end mill precision grinding and polishing so as to have substantially the same dimensions as the cavity 12 of the mold 10 designed and manufactured with the required dimensions of the light guide plate. Here, for Experimental Examples 1 to 3 and Comparative Examples 1 and 2, the gap 8 and the space 9 between the mold 10 (resin sheet holding frame 6) and the thin resin sheet 5 have the dimensions shown in Table 1 below. Set.

  Next, a separate stainless steel thin member 3a having a mirror-like transfer surface is prepared and fixed to the movable heating upper die 1a. Then, the methacrylic resin extruded sheet is sandwiched between the movable cooling upper mold 1a and the fixed cooling mold 1b equipped with the thin member 3b provided with the concave / convex pattern, and 3 MPa by a hot press molding machine. The thin resin sheet 5 is heated by heat transfer while being fixed to the cavity 12 by pressure, and the pressure is increased to 5 MPa just before reaching a temperature at which the resin softens. Compress to Then, the pressure was maintained, and when the rubber-like flat region temperature, which is the transfer start temperature, was reached, the concavo-convex pattern was transferred and formed at a predetermined pressure that suppressed the occurrence of parting burr. The required heating time to the heating press temperature of 160 ° C. is 15 seconds, the cooling time to the molded product take-off temperature of 40 ° C. is 15 seconds, a total of 55 including the insertion of the thin resin sheet 5, the removal of the molded product, and the opening and closing time of the mold 10 Heat press molding was performed in seconds, and a heat press molded product (resin sheet molded product) having a mirror surface transferred to one main surface and a concavo-convex pattern transferred to the other main surface was obtained.

As an evaluation of the light guide plates of Experimental Examples 1 to 3 and Comparative Examples 1 and 2 obtained as described above, the presence or absence of burrs, the presence or absence of dot transfer spots under microscope observation, and visual observation under LED lighting The appearance defects (luminance spots etc.) were evaluated for the presence or absence. The burr was measured visually, touch, and under a microscope (MX61 50 magnification manufactured by OLYMPUS), and the dot transferability was evaluated and judged by comparing the transferability and the transfer spots with the dot shape provided on the thin member 3b used. . The results are shown in Table 1 below.

  As is clear from Table 1, the light guide plate of Experimental Example 1 is more effective than the Experimental Example 2 in that the space 9 is set to 300 μm, there are no gap burrs and space burrs, and transfer spots, No appearance defects were observed. Comparing Experimental Example 2 and Experimental Example 3, there is a difference in the gap 8 between the mold 10 (resin sheet holding frame 6) and the thin-walled member 3b, but the setting of the space 9 is common, and transferability and appearance are poor. The space protrusion burr had no problem with 2 to 3 fine protrusions having a thickness of 50 μm and a length of 100 to 500 μm. In the light guide plates of Comparative Examples 1 and 2, small protrusions were generated in the corner space, and it was confirmed that the setting of the gap 8 was not optimal.

  Next, the light guide plates of Experimental Examples 4 to 6 and Comparative Examples 3 to 6 were manufactured and compared under the conditions shown in Table 2 below for the temperature at the time of temperature rise in hot press molding and the pressure and temperature at the time of pressing. These light guide plates were manufactured by the same hot press molding method using the same mold 10 and molding machine as those of Experimental Examples 1 to 3 and Comparative Examples 1 and 2 described above. In all of Experimental Examples 4 to 6 and Comparative Examples 3 to 6, the gap 8 between the thin member 3b and the resin sheet holding frame 6 (or mold 10) is 50 μm or less, and the resin sheet holding frame 6 (or metal mold) is used. The space 9 between the mold 10) and the thin resin sheet 5 was set to 700 μm.

For the purpose of obtaining a light guide plate having a thickness of 0.5 mm and a flat rectangular diagonal of 15.4 inches (386 mm, thickness ratio 772 times), a MMA / styrene copolymer extruded sheet (Nippon Acryase Corporation) as a transparent thermoplastic resin Manufactured by Acryase MS). The resin extruded sheet is sandwiched between a movable heating mold 1a having a thin-walled member 3a having a mirror-like transfer surface and a fixed cooling lower mold 1b having a thin-walled member 3b provided with the concavo-convex pattern opposed thereto. A hot press molding machine was used to perform hot press molding with the heating press temperature and pressure set to the values shown in Table 2 below. About the obtained light-guide plate, the presence or absence of a gap | interval burr | flash and space protrusion burr | flash, the dot transfer property under microscope observation, and the external appearance defect (luminance spot generation | occurrence | production etc.) by visual observation under LED lighting were evaluated. As for burr, visual observation, touch, microscope (MX61 50 magnification manufactured by OLYMPUS), and transferability were evaluated and determined for transferability and transfer spots compared to the dot shape formed on the thin member 3b used. The results are shown in Table 2. As shown in Table 1, the gap burr was omitted because it was known that the gap burr did not occur when the gap 8 was set to 50 μm or less.

  As can be seen from Table 2, the light guide plate of Experimental Example 4 has a pressing temperature of 160 ° C. and higher than the transfer start temperature of 130 ° C., but there is no parting gap burr and space protrusion burr, and transferability The appearance was not good. In Experimental Example 6, since the pressure at the time of temperature rise to 100 ° C. of the deflection temperature under load of the resin was 1 MPa, a space protrusion burr was generated. In Experimental Example 5, since the temperature rise during heating was 3 MPa, even when the thickness of the thin resin sheet 5 is 0.5 mm, heat deformation in the mold 10 can be suppressed, and space burr protrusions are generated. The transferability and appearance were good. Next, since the light guide plate of Comparative Example 3 had a pressing temperature of 173 ° C. close to the resin flow region, parting gap burrs were generated. In the light guide plate of Comparative Example 4, since the heating press pressure of 9 MPa was excessive, the parting surface was opened and burrs were generated. Thereby, it turns out that it is necessary to prevent the metal mold | die 10 from opening by the mold clamping force reinforcement | strengthening of a parting surface.

  Next, the light guide plates of Comparative Example 5 and Comparative Example 6 are low in pressing temperature and difficult to soften, so the resin does not become space protrusion burrs, but the end surface is deformed into a curved shape in the space 9 part, and the light guide plate It was confirmed that this was a cause of luminance unevenness in the outer peripheral portion and was not a preferable condition. The deformation of the end face of the light guide plate, that is, the generation of the curved end surface, is caused by fixed cooling with a movable heating upper die 1a equipped with a thin member 3a having a mirror-like transfer surface and a thin member 3b provided with an uneven pattern facing it. The result was the same as when the lower die 1b was closed and the stamping press type hot press molding was performed.

Thus, according to the first embodiment, the following effects can be obtained.
(1) According to the present embodiment, since the mold 10 is used, a step of cutting the molded product having a concavo-convex pattern on the surface into a light guide plate size is unnecessary.
(2) Further, since there are no various burrs that are likely to occur due to poor dimensional accuracy of the mold 10, the thin members 3a and 3b, and the thin resin sheet 5, the burr processing step that is a subsequent step of the hot press molding step can be omitted. As a result, the manufacturing cost can be reduced.
(3) When a thin large resin sheet having a concavo-convex pattern on the surface is injection-molded by the conventional technique, in order to form a concavo-convex pattern on the surface by inflowing and filling the molten resin from a small gate, for example, 300 MPa or more Manufacturing is difficult because ultra-high pressure and ultra-high-speed injection of 1000 mm / sec or more are required, and a high-rigidity die that can withstand this is required, resulting in high capital investment and high manufacturing costs. However, in this embodiment, the concave / convex pattern can be uniformly transferred and formed on the entire surface at a low pressure of about 5 Mpa using the mold 10, so that the diagonal length L of the substantially rectangular plane of the resin sheet molded product is: A thin and large resin sheet molded product having a size 600 to 1000 times the thickness t can be obtained easily and efficiently.

(4) Uses hot press molding, and the pressure required for transfer formation of the concavo-convex pattern is very low compared to the injection molding method, so the resin sheet molded product can be easily released from the mold 10 and easily Stable production is possible. Moreover, since a gate for inflow of the resin is not required, it is suitable for taking a plurality of pieces, and the manufacturing cost can be reduced.
(5) Since the resin sheet holding frame 6 has a slide mechanism that slides at least one of the side surfaces, the concave / convex pattern 17 is provided on the slide surface, whereby the concave / convex pattern is transferred to the incident surface facing the LED light source and guided. Unevenness of the incident surface luminance of the light plate 60 can be suppressed. Further, the slide mechanism can prevent the occurrence of burrs by adjusting the space 9 between the thin resin sheet 5 and the resin sheet holding frame 6 and the gap 8 between the thin member 3b and the resin sheet holding frame 6. Omission is certain.

  (6) In the thin and large resin sheet molded product having a concavo-convex pattern on the surface produced according to this example, the length L of the diagonal line of the substantially rectangular plane is 600 to 1000 times the thickness t, and the thickness t Is 0.3 mm to 3.0 mm, it can be applied to a light guide plate for a liquid crystal display device such as a personal computer, a monitor, a mobile phone, etc., which cannot be manufactured due to thickness limitation by a conventional injection molding method. Moreover, it can respond also to the large size tendency of a liquid crystal television, an electronic signboard, and a 46-type / 52-type information display (outdoor advertisement / company / public facility information display device). In addition, for example, it is possible to cope with a tendency to reduce the thickness due to the development and popularization of LEDs having a thickness of 0.5 mm or less.

In addition, this invention is not limited to the Example mentioned above, A various change can be added in the range which does not deviate from the summary of this invention. For example, the following are also included.
(1) The shapes and dimensions shown in the above-described embodiments are merely examples, and may be appropriately changed within a range where similar effects can be obtained.
(2) Similarly, the materials constituting the embodiments may be appropriately changed as necessary.
(3) The concavo-convex pattern provided on the thin member 3a or 3b can be appropriately changed in design according to the use of the resin sheet molded product. The same applies to the case where the uneven pattern is provided inside the resin sheet holding frame 6.
(4) Examples of the use of the resin sheet molded product formed according to the present invention include a light guide plate used for a backlight of a liquid crystal display device, a Fresnel lens sheet for collecting sunlight of a solar power generation device, a liquid crystal A diffusion light guide plate of a television device is a suitable application example, but does not prevent application to various other known uses.

According to the present invention, a pair of thin members provided with a concavo-convex pattern on at least one of the opposing main surfaces, and one of the pair of thin members are accommodated and set to the required dimensions of the molded product. A resin sheet holding frame that forms a cavity for storing a thin resin sheet together with the thin member, a lower mold provided with one of the pair of thin members, the resin sheet holding frame, and the other of the pair of thin members. And provided on each of the upper mold facing the lower mold and each of the upper mold and the lower mold, and pressurizing the thin resin sheet at an appropriate temperature and an appropriate pressure to transfer and form an uneven pattern. A temperature control pipe for adjusting the temperature of the slide, and a slide machine for sliding at least one of the four side surfaces of the resin sheet holding frame surrounding the outer periphery of the thin resin sheet And adjusting the space formed between the side surface of the thin resin sheet accommodated in the cavity and the holding frame of the resin sheet by the slide mechanism, and the thin wall accommodated in the cavity It was decided to perform hot press molding with a mold for adjusting the space formed between the side surface of the member and the resin sheet holding frame . At this time, the generation of burrs is suppressed, the emitted light is made uniform with excellent transferability, and the releasability from the mold is also good, so it is used for a light guide plate used in a backlight unit of a liquid crystal display device. It can be used for thin and large resin sheet molded products.

1a Movable heating upper die 1b Fixed cooling lower die 2a, 2b Pipe 3a, 3b Thin member 4 Thermal insulation sheet 5 Thin resin sheet 6 Resin sheet holding frame 6a, 6b Long side 6c, 6d Short side 7 Parting gap 8 Clearance 9 Space 10 Molds 11a and 11b for hot press molding Plate 12 Cavity 13 Gaps 14a to 14d Block 15 Gas vent groove 16 Claw portion 17 Concave and convex pattern 50 Backlight unit 60 Light guide plate 60a First surface (upper surface)
60b 2nd surface (lower surface)
61 Side surface 64 Reflective sheet 65 Diffusion sheet 66, 67 Prism sheet 68 LED

Claims (6)

A pair of thin members provided with a concavo-convex pattern on at least one of the opposing main surfaces;
A resin sheet holding frame that accommodates one of the pair of thin members and is set to a required dimension of the molded product, and forms a cavity for storing the thin resin sheet together with the pair of thin members;
A lower die provided with one of the pair of thin members and the resin sheet holding frame;
The pair of the other is provided with a thin member, and the upper mold facing the lower mold,
A temperature adjusting pipe which is provided in each of the upper mold and the lower mold and performs temperature adjustment for transferring and forming a concavo-convex pattern by pressing the thin resin sheet at an appropriate temperature and an appropriate pressure;
A sliding mechanism that slides at least one of the four side surfaces of the resin sheet holding frame that surrounds the outer periphery of the thin resin sheet;
With
By the slide mechanism,
Adjustment of the space formed between the side surface of the thin resin sheet accommodated in the cavity and the holding frame of the resin sheet;
Adjustment of the space formed between the side surface of the thin member housed in the cavity and the resin sheet holding frame;
A mold for hot press molding, characterized in that Wherein the side surface is slid by the slide mechanism, according to claim 1 hot press molding die, wherein in that a concavo-convex pattern. A method for producing a resin sheet molded article using the hot press molding die according to claim 1 or 2,
After throwing into the cavity a thin resin sheet cut and polished to the same dimensions as the cavity,
Heat transfer heating while fixing the thin resin sheet in the cavity at a low pressure,
Compress the thin resin sheet into a mold cavity by increasing the pressure before reaching a temperature at which the thin resin sheet that has been thermally expanded softens,
A method for producing a resin sheet molded article, comprising: forming a concavo-convex pattern on the thin resin sheet at a temperature in a rubber-like flat region exceeding a transfer start temperature and a pressure capable of suppressing generation of burrs. A thin and large resin sheet molded product having a concavo-convex pattern on the surface formed by the method for producing a resin sheet molded product according to claim 3 ,
A resin sheet molded product, wherein the length of a diagonal line of a substantially rectangular plane is in a range of 600 to 1000 times the thickness, and the thickness is 0.3 mm to 3.0 mm. Before Symbol thickness, claim 4 resin sheet molded article, wherein a is 0.5 mm to 2.0 mm. The resin sheet molded article according to claim 4 or 5 , wherein the resin sheet molded article is a thin-walled large flat light guide plate.

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