JP2006168034A - Press molding method and thermoplastic resin molded product - Google Patents

Abstract

The present invention relates to a press molding method in which press molding is performed simply and with a molding cycle shortened, and a thermoplastic resin molded body in which a thermoplastic resin is molded by the press molding method.
A press molding apparatus (1) heats only a mold (6) to a glass transition temperature or higher, presses the heated mold (6) against a thermoplastic resin (20), and molds the thermoplastic resin (20) with the mold (6). As the glass transition temperature rises from the contact surface, the softening proceeds and transfer molding proceeds. Finally, the entire surface of the thermoplastic resin 20 is brought into close contact with the mold 6 to complete the transfer. Therefore, compared with the case where the entire molds 2 and 3 are heated and press-molded, the heat capacity is small, the heating / cooling rate is increased, the molding cycle time can be greatly shortened, and the high accuracy is achieved. A thermoplastic resin molded product can be obtained.
[Selection] Figure 1

Description

  The present invention relates to a press molding method and a thermoplastic resin molded body, and more specifically, a press molding method for performing press molding simply and by shortening a molding cycle, and a large and thin type in which a thermoplastic resin is molded by the press molding method. The present invention relates to a thermoplastic resin molding for optical use.

  Optical molded bodies such as optical lenses and mirrors for cameras and printers and compact discs are conventionally manufactured by injection molding a transparent thermoplastic resin such as polycarbonate or acrylic resin.

  However, in recent years, as parts using these optical molded bodies have become larger, thinner, and higher performance, the thermoplastic resin molded bodies used for optical parts are also larger, thinner, and Therefore, a material having excellent optical properties such as low birefringence has been demanded.

  In order to produce such a molded article having excellent optical characteristics, there is a limit in conventional injection molding, and thus special molding methods such as press molding and injection compression molding have been proposed. .

  Among these special molding methods, the press molding method can set the melting temperature of the resin lower than that in the case of injection molding, so that it can prevent thermal degradation of the resin, and can produce an optical molded body with excellent transparency. Obtainable. In addition, the press molding method has no flow orientation of the resin and does not need to be molded at a high pressure, so that the residual stress can be reduced, the birefringence is small, and the deformation with time is not easily caused. Further, it is possible to obtain a molded body that is less susceptible to cracking due to oils and fats or organic solvents. Furthermore, in the press molding method, since the thermoplastic resin is heated, melted again, and pressed, the stress can be relieved and a molded article excellent in low birefringence can be obtained.

  However, unlike the injection molding, the press molding method requires time for raising and lowering the temperatures of the upper and lower molds, and there is a problem that the cycle time becomes longer.

  Thus, various techniques have been proposed in which a press mold is provided with a cooling mechanism in addition to a heating mechanism to shorten the molding cycle (see Patent Documents 1 to 4).

  Conventionally, the lower female mold is divided into a fixed lower mold part and a movable receiving plate on which a thermoplastic resin is placed, and this receiving plate is attached to and detached from the lower female die. As a possible technique, a technique has been proposed in which only the backing plate and the thermoplastic resin are heated and cooled to save time for heating and cooling the mold and to speed up the manufacturing time (see Patent Document 5).

JP 07-016917 A JP 2000-223338 A JP 2001-260163 A JP 2002-046136 A Japanese Patent No. 2922396

  However, in the prior art described in Patent Document 1 to Patent Document 4, since a mold having a large heat capacity is heated to a temperature higher than the glass transition temperature and then cooled, a long time is required for heating and cooling. There was a need to improve the cycle time. Further, in these conventional techniques, when the pressure is released at a temperature equal to or higher than the glass transition temperature of the resin when cooling is performed, sink marks are generated in the molded product and the quality is deteriorated. Therefore, the temperature management of the molded product is complicated. At the same time, adding a cooling mechanism to the molding apparatus complicates the molding apparatus and increases the cost.

  Moreover, in the prior art described in Patent Document 5, since the mold and the transfer surface are below the glass transition temperature, the resin and the transfer surface come into contact with each other, so that the resin is rapidly cooled and the viscosity is increased. However, it is impossible to completely fill the resin in the molding of an optical element having a fine structure, which deteriorates the transferability of press molding and lowers the quality of the molded body. There was a problem.

  In other words, press molding has the advantages of low birefringence and good surface transfer compared to injection molding, but has the disadvantage of a long molding cycle, but the prior art shortens this molding cycle. Therefore, there is a problem that the advantage that the surface transferability is good is lost or the cost is increased.

  Therefore, the present invention provides a press molding method that reduces the molding cycle time at a low cost while taking advantage of the press molding that surface transferability is good, and a thermoplastic resin molded body molded by the press molding method. It is an object.

  In the press molding method according to the first aspect of the present invention, a mold having a transfer surface on at least one surface of a pair of molds arranged opposite to each other is detachably mounted, and at least one of the pair of molds is the other. A mold preheating step of preheating the pair of molds to a predetermined temperature not higher than the glass transition temperature of the thermoplastic resin; A resin supplying step of supplying the thermoplastic resin between molds, a mold heating step of heating only the mold to a predetermined temperature equal to or higher than a glass transition temperature of the thermoplastic resin by a heating means, and the heated mold A mold disposing step of disposing the mold between the thermoplastic resin and the mold in a state where the transfer surface of the mold faces the thermoplastic resin side, and moving the mold to move the mold A pressing step of pressing the thermoplastic resin at a predetermined pressure with a mold, and cooling the thermoplastic resin at a predetermined cooling rate in a state in which the mold, the mold and the thermoplastic resin are kept in contact after the pressing. The above-described object is achieved by sequentially executing a cooling step of causing the mold to open and a taking-out step of taking out the molded thermoplastic resin by opening the mold.

  In this case, for example, as described in claim 2, the mold is set such that its heat capacity is larger than the heat capacity of the molded thermoplastic resin and smaller than the heat capacity of the mold. There may be.

  For example, as described in claim 3, the press molding method may control a cooling rate of the thermoplastic resin in the cooling step by changing a heat capacity of the mold.

  Furthermore, for example, as described in claim 4, in the press molding method, the mold includes a transfer surface portion on which the transfer surface is formed and a temperature adjusting unit for adjusting the heat capacity of the mold. You may change the heat capacity of the said mold by changing the magnitude | size of a temperature control part, and may control the cooling rate of the said thermoplastic resin in the said cooling process.

  For example, as described in claim 5, the heating unit may be an electromagnetic wave heating unit that heats the mold using heat transfer by radiation of electromagnetic waves.

  Further, for example, as described in claim 6, in the mold, at least a surface irradiated with electromagnetic waves from the electromagnetic wave heating means may be formed of an electromagnetic wave absorbing material.

  For example, as described in claim 7, the mold includes a transfer surface portion on which the transfer surface is formed and a temperature adjustment unit for adjusting the heat capacity of the mold, and the temperature adjustment unit emits electromagnetic waves. You may form with the electromagnetic wave absorption material which absorbs.

  Further, for example, as described in claim 8, the press molding method includes at least the pressing step in which the mold and the thermoplastic are in a state where a gap between the mold and the thermoplastic resin is in a vacuum atmosphere. The resin may be pressed.

  For example, as described in claim 9, in the press molding method, the thermoplastic resin may be cooled at a cooling rate of 1 ° C./second or more in the cooling step.

  Furthermore, for example, as described in claim 10, the press molding method includes the mold preheating step, the resin supply step, the mold heating step, the mold arrangement step, the pressing step, the cooling step, and the takeout step. When pressing a plurality of thermoplastic resins by executing a molding cycle that sequentially executes a plurality of molding cycles, a plurality of the molds are prepared, and the next molding is performed while performing the steps after the predetermined mold arranging step. You may perform the said mold heating process which heats the said mold used by a cycle simultaneously.

  The thermoplastic resin molded article according to an eleventh aspect of the invention is a thermoplastic resin molded article produced by press-molding a thermoplastic resin by a predetermined press molding method. The said objective is achieved by being press-molded using the press molding method in any one of Claims 11.

  According to the press molding method of the present invention, only the molding that is detachable from the mold and has a transfer surface formed thereon is heated and attached to the mold at the time of pressing, so that the surface transferability is good. It is possible to reduce the molding cycle time at low cost while taking advantage of the advantage of press molding.

  In addition, the thermoplastic resin molded body of the present invention is molded by a press picture molding method that is used for press molding by heating only a molding that is detachable from a mold and has a transfer surface formed thereon. It can have good surface transferability.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, since the Example described below is a suitable Example of this invention, various technically preferable restrictions are attached | subjected, However, The scope of the present invention limits this invention especially in the following description. As long as there is no description of the effect, it is not restricted to these aspects.

  FIGS. 1-8 is a figure which shows 1st Example of the press molding method and thermoplastic resin molding of this invention, and FIG. 1 is 1st implementation of the press molding method of this invention and thermoplastic resin molding. It is a principal part front view of the press molding apparatus 1 to which the example is applied.

  In FIG. 1, a press molding apparatus 1 is disposed in a state where a pair of upper mold 2 and lower mold 3 face each other in the vertical direction. 4, 5 are arranged. In addition, as the heaters 4 and 5, for example, a temperature control circuit for flowing warm water can be used.

  The properties required for the materials of the molds 2 and 3 generally include good machinability and grindability, excellent wear resistance, and excellent mirror finish. Have sufficient strength and toughness, have high corrosion resistance, have good texture, good heat treatment characteristics, high thermal conductivity, low thermal expansion coefficient, welding Examples thereof include mechanical characteristics such as good repairability and processing characteristics. Specific examples of metals that satisfy these mechanical characteristics and processing characteristics and can be used for the molds 2 and 3 include mechanical structural steels, alloy tool steels, and stainless steels. If the cooling performance is particularly important, copper alloys and aluminum alloys with high thermal conductivity may be used, but stainless steel is used from the viewpoint of strength, corrosion resistance, wear resistance, mirror finish, etc. It is preferable.

  A mold 6 is detachably provided on the upper mold 2, and the mold 6 includes a transfer surface portion 7 and a temperature adjusting portion 8. In the vicinity of the press dies 2 and 3, an infrared heater 9 is installed as a heating means for heating the mold 6. The infrared heater 9 is held and fixed to a reflecting plate 10 that reflects infrared rays, and heats the mold 6 using heat transfer by radiation of electromagnetic waves.

  The transfer surface portion 7 is cut into a predetermined shape by cutting a steel blank with a cutting tool, and then subjected to a heat treatment, and the processed surface is subjected to electroless nickel plating, and the nickel plated material is heat treated to increase the hardness. The transfer surface 7a having a mirror surface having a desired shape is formed by cutting the processed surface with a diamond cutting tool.

  The temperature control unit 8 is made of a steel material that is black-coated with a heat-resistant paint so as to efficiently absorb infrared rays from the infrared heater 9 when the mold 6 is heated. The target thermoplastic resin 20 is designed to have a cooling rate of 2 ° C./second, which is 1 ° C./second or more. The heat capacity of the mold 6 composed of the two members of the transfer surface portion 7 and the temperature adjusting portion 8 is larger than the heat capacity of the thermoplastic resin 20 to be molded and smaller than the heat capacities of the press dies 2 and 3. Is set.

  Examples of the thermoplastic resin 20 include alicyclic structure-containing resins, acrylic resins, polycarbonate resins, and the like, but are not limited thereto, and the transparency, heat resistance, low water absorption, and low birefringence of the molded body. It can be appropriately selected in consideration of the properties and the like. Moreover, as a to-be-molded body, what mix | blended microparticles | fine-particles, such as an inorganic or organic filler and bead, can be used for a thermoplastic resin.

  Next, the operation of this embodiment will be described. The press molding apparatus 1 of the present embodiment performs molding of the thermoplastic resin 20 that is a molding target in the order of steps described below. In this embodiment, a description will be given assuming that a Fresnel lens is manufactured using an acrylic resin sheet having a thickness of 1 mm as the thermoplastic resin 20.

  In the press molding apparatus 1, as the first step (die preheating step), first, as shown in FIG. 2, the heat for forming the press dies 2, 3 by the heaters 4, 5 incorporated therein. The acrylic resin that is the plastic resin 20 is heated to a temperature not higher than the glass transition temperature Tg. The heating rate (temperature increase rate) in this case is not limited, but as the temperature increase rate is larger, the molding cycle time can be shortened and the productivity can be improved. If the temperature raising rate is increased, the load on the press molding apparatus 1 itself and the molds 2 and 3 becomes excessive, so care must be taken.

  As shown in FIG. 3, the press molding apparatus 1, as a second process (resin supply process), removes an acrylic resin sheet, which is a thermoplastic resin 20, between the upper mold 2 and the lower mold 3 by a conveying apparatus (not shown). It is conveyed and arranged at a predetermined position.

  Next, as shown in FIG. 4, the press molding apparatus 1 thermoplastically molds only the mold 6 by an infrared heater 9 disposed in the vicinity of the press molds 2 and 3 as a third process (mold heating process). The resin 20 is heated to a predetermined temperature equal to or higher than the glass transition temperature Tg of the acrylic resin. At this time, the mold 6 and the thermoplastic resin 20 to be molded are not in contact with each other.

  In the heating of the mold 6 by the infrared heater 9, the intended predetermined temperature can be set to the saturation temperature by adjusting the infrared intensity irradiated by the infrared heater 9 and the distance between the mold 6 and the infrared heater 9. The mold 6 can be heated uniformly.

  And a molding cycle time can be shortened by performing the said 1st process (mold preheating process) and a 3rd process (mold heating process).

  As shown in FIG. 5, the press molding apparatus 1 is a predetermined process between the upper mold 2 and the thermoplastic resin 20 as shown in FIG. Place in position.

  As shown in FIG. 6, the press molding apparatus 1 moves the upper mold 2 toward the lower mold 3 as the fifth process (pressing process), and the mold 6 is moved to the lower mold 3 with the upper mold 2. The thermoplastic resin (acrylic resin sheet) 20 is pressed against the thermoplastic resin (acrylic resin sheet) 20 disposed between the mold 6 and the thermoplastic resin (acrylic resin sheet) 20 to the transfer surface 7 a of the transfer surface portion 7 of the mold 6 and the upper surface of the lower mold 3. And press-molding. At this time, the mold 6 and the thermoplastic resin (acrylic resin sheet) 20 are in contact with each other for the first time.

  The pressure during the pressing is usually about several MPa to several tens of MPa, and the thermoplastic resin (acrylic resin sheet) 20 is placed between the transfer surface 7 a of the transfer surface portion 7 of the mold 6 and the upper surface of the lower mold 3. The holding time in the state of being sandwiched between the two is usually about 1 second to 5 minutes, but is appropriately selected in consideration of factors such as the size, shape, and molding accuracy of the molded product.

  As shown in FIG. 7, the press molding apparatus 1 uses the thermoplastic resin (acrylic resin sheet) 20 as the sixth step (cooling step) to transfer the transfer surface 7 a of the transfer surface portion 7 of the mold 6 and the upper surface of the lower mold 3. This state is maintained even after the press state sandwiched between the two, and the heat of the mold 6 having a small heat capacity is rapidly taken away by heat transfer with the molds 2 and 3 having a large heat capacity, and the thermoplastic resin ( The acrylic resin sheet) 20 is cooled to a glass transition temperature Tg or less of the acrylic resin sheet which is the thermoplastic resin 20.

  And when performing the press molding of the plurality of thermoplastic resins 20 using the press molding apparatus 1, a plurality of molds 6 are prepared and the cooling process which is the sixth process is performed. When the third process (mold heating process) for heating the mold 6 used in the next press molding cycle is performed, the molding cycle time can be further shortened.

  Finally, as shown in FIG. 8, the press molding apparatus 1 raises the upper mold 2 and takes out a molded product 30 that is a molded thermoplastic resin product as a seventh process (extraction process). .

  In addition, when the experiment which manufactures a Fresnel lens using the acrylic resin sheet as the thermoplastic resin 20 using the said press molding apparatus 1 was performed, the molding cycle time is 30 seconds and the molded product 30 is a mold. The shape was transferred faithfully, that is, the shape of the transfer surface 7a of the transfer portion 7 of the mold 6 was transferred faithfully.

  Thus, since the press molding apparatus 1 of the present embodiment heats only the mold 6 to the glass transition temperature Tg or higher and presses the heated mold 6 against the thermoplastic resin 20, the thermoplastic resin 20. Is softened from the contact surface with the mold 6 as the glass transition temperature Tg or higher, and transfer molding proceeds. Finally, the entire surface of the thermoplastic resin 20 is brought into close contact with the mold 6 to complete the transfer.

  Therefore, compared with the case where the entire molds 2 and 3 are heated and press-molded, the heat capacity is small, the heating / cooling rate is increased, the molding cycle time can be greatly shortened, and the accuracy is extremely high. Temperature control can be performed, overheating due to overshoot and hunting, etc. can be prevented and the molding process can be controlled more easily, and a molded product with higher accuracy than conventional press molding can be obtained. .

  Further, it is not necessary to use a complicated and expensive molding apparatus provided with a heating / cooling mechanism as in the conventional example, and the press molding apparatus 1 can be extremely simple and downsized, and highly accurate and highly efficient. Optical elements (thermoplastic resin moldings) such as Fresnel lenses can be molded.

  Furthermore, since the heat capacity of the mold 6 is changed to be smaller than the heat capacity of the molds 2 and 3, the cooling efficiency can be improved and the molding cycle time can be shortened.

  Further, if the heat capacity of the mold 6 is smaller than the heat capacity of the thermoplastic resin 20 to be molded, the thermoplastic resin is likely to have a temperature distribution, which may reduce the quality. However, in the press molding apparatus 1 of this embodiment, Since the heat capacity of the mold 6 is set larger than the heat capacity of the thermoplastic resin 20 to be molded, the molding quality can be improved.

  Furthermore, since the press molding apparatus 1 of the present embodiment allows the mold 6 to be attached to and detached from the mold 2, the heat capacity of the mold 6 is increased in consideration of factors such as the size, shape, and molding accuracy of the molded product. The speed at which the thermoplastic resin 20 is cooled can be appropriately selected by changing, and a molded product with an intended accuracy can be molded in a short molding cycle time.

  Further, even if the thermoplastic resin 20 is the same, if the thickness of the thermoplastic resin 20 is different, the heat capacity changes. Therefore, the heat capacity of the mold 6 also needs to be changed. It is costly and uneconomical to produce the entire 6, but the press molding apparatus 1 of the present embodiment comprises the mold 6 with the transfer surface portion 7 and the temperature adjusting portion 8. By exchanging, the heat capacity of the entire mold 6 can be changed at low cost, and the transfer surface portion 7 is formed by changing the size of the temperature adjusting portion 8 and controlling the cooling rate of the thermoplastic resin 20. The material suitable for the shape can be freely selected without being restricted.

  Furthermore, since the press molding apparatus 1 of the present embodiment uses the infrared heater 9 utilizing heat transfer by radiation of electromagnetic waves to heat the mold 6 in the third step (mold heating step), the mold 6 Can be efficiently heated in a short time, and the molding cycle time can be further shortened.

  Moreover, the press molding apparatus 1 of a present Example uses the steel material by which the temperature control part 8 of the mold 6 was black-body-coated with the heat-resistant coating so that the infrared rays from the infrared heater 9 might be efficiently absorbed when the mold 6 was heated. Thus, since at least the surface of the mold 6 that irradiates the electromagnetic wave is an electromagnetic wave absorber, the mold 6 can be efficiently heated in a shorter time, and the molding cycle time can be further shortened.

  Furthermore, since the temperature control part 8 of the mold 6 is an electromagnetic wave absorber in the press molding apparatus 1 of the present embodiment, one member can have two functions and is efficient.

  Further, in the press molding apparatus 1 of the present embodiment, since the cooling rate of the thermoplastic resin 20 is set to 1 ° C./second or more in the sixth step (cooling step), the molding cycle time is longer than the molding cycle time of the injection molding. Can be shortened.

  Furthermore, the press molding apparatus 1 according to the present embodiment prepares a plurality of molds 6 and uses them in the next molding cycle while the processes after the sixth process (cooling process) in the certain molding cycle are performed. By performing the 3rd process (mold heating process) which heats 6 simultaneously, cycle time can be shortened further.

  FIG. 9 is a front view of an essential part of a press molding apparatus 40 to which a second embodiment of the press molding method and the thermoplastic resin molded body of the present invention is applied.

  This embodiment is applied to the press molding apparatus 1 similar to the first embodiment, and in the description of the present embodiment, the same components as the press molding apparatus 1 of the first embodiment are not included. The same reference numerals are assigned and detailed description thereof is omitted.

  In FIG. 9, the press molding apparatus 40 is disposed in a state where the upper mold 2 and the lower mold 3 face each other in the vertical direction, and the upper mold 2 and the lower mold 3 include a heater 4, 5 are arranged respectively. In addition, as the heaters 4 and 5, for example, a temperature control circuit for flowing warm water can be used.

  A mold 6 is detachably provided on the upper mold 2, and the mold 6 includes a transfer surface portion 7 and a temperature adjusting portion 8. In the vicinity of the press dies 2 and 3, an infrared heater 9 is installed as a heating means for heating the mold 6. The infrared heater 9 is held and fixed to a reflecting plate 10 that reflects infrared rays, and heats the mold 6 using heat transfer by radiation of electromagnetic waves.

  The transfer surface portion 7 is formed with a transfer surface 7a having a mirror surface having a desired shape.

  The temperature control unit 8 is made of a steel material that is black-coated with a heat-resistant paint so as to efficiently absorb infrared rays from the infrared heater 9 when the mold 6 is heated. The target thermoplastic resin 20 is designed to have a cooling rate of 2 ° C./second, which is 1 ° C. or higher. The heat capacity of the mold 6 composed of the two members of the transfer surface portion 7 and the temperature adjusting portion 8 is larger than the heat capacity of the thermoplastic resin 20 to be molded and smaller than the heat capacities of the press dies 2 and 3. Is set.

  Examples of the thermoplastic resin 20 include alicyclic structure-containing resins, acrylic resins, polycarbonate resins, and the like, but are not limited thereto, and the transparency, heat resistance, low water absorption, and low birefringence of the molded body. It can be appropriately selected in consideration of the properties and the like. Moreover, as a to-be-molded body, what mix | blended microparticles | fine-particles, such as an inorganic or organic filler and bead, can be used for a thermoplastic resin.

  The press molding apparatus 40 is provided in a chamber 41 in which the molds 2 and 3 and the infrared heater 9 having the above-described configuration can be evacuated.

  Next, the operation of this embodiment will be described. The press molding apparatus 40 of the present embodiment performs molding of the thermoplastic resin 20 that is a molding target in the order of processes described below. In the present embodiment, a description will be given assuming that a lenticular lens is manufactured using a polycarbonate resin sheet as the thermoplastic resin 20.

  As a first step (die preheating step), the press molding apparatus 40 first evacuates the chamber 41 and heats the press dies 2, 3 and 3 with the heaters 4 and 5 incorporated therein. Heat to a temperature not higher than the glass transition temperature Tg of the plastic resin 20.

  As a second process (resin supply process), the press molding apparatus 40 transports a polycarbonate resin sheet, which is a thermoplastic resin 20, to a predetermined position between the upper mold 2 and the lower mold 3 by a transport apparatus (not shown). Arrange.

  Next, as a third step (mold heating step), the press molding apparatus 40 uses only an infrared heater 9 disposed in the vicinity of the press molds 2 and 3 to remove only the mold 6 from the polycarbonate resin, which is the thermoplastic resin 20. Heat to a predetermined temperature above the glass transition temperature Tg.

  As the fourth step (mold placement step), the press molding apparatus 40 places the heated mold 6 at a predetermined position between the upper mold 2 and the polycarbonate resin sheet 20 which is the thermoplastic resin 20 by a conveying device (not shown). Deploy.

  The press molding apparatus 40 moves the upper mold 2 toward the lower mold 3 as the fifth process (pressing process), and arranges the mold 6 between the lower mold 3 and the mold 6 with the upper mold 2. The polycarbonate resin sheet as the thermoplastic resin 20 is pressed against the polycarbonate resin sheet, and the polycarbonate resin sheet as the thermoplastic resin 20 is sandwiched between the transfer surface 7a of the transfer surface portion 7 of the mold 6 and the upper surface of the lower mold 3, and then pressed. Mold.

  As the sixth step (cooling step), the press molding apparatus 40 is a press in which the polycarbonate resin sheet, which is the thermoplastic resin 20, is sandwiched between the transfer surface 7a of the transfer surface portion 7 of the mold 6 and the upper surface of the lower mold 3. After this state, this state is maintained, and the heat of the mold 6 having a small heat capacity is rapidly taken away by heat transfer using the molds 2 and 3 having a large heat capacity, and the polycarbonate resin sheet which is the thermoplastic resin 20 is forcibly applied. The polycarbonate resin sheet which is the thermoplastic resin 20 is cooled to a glass transition temperature Tg or lower.

  Finally, the press molding apparatus 40 raises the upper mold 2 as the seventh step (extraction step), and the lenticular lens as a molded product which is a molded thermoplastic resin molded product (polycarbonate resin molded product). Take out.

  In addition, when the experiment which manufactures a lenticular lens using the polycarbonate resin sheet as the thermoplastic resin 20 using the said press molding apparatus 40 was performed, the molding cycle time is 25 second and the lenticular lens which is a molded article The mold shape was faithfully transferred, that is, the shape of the transfer surface 7a of the transfer portion 7 of the mold 6 was faithfully transferred.

  Thus, since the press molding apparatus 40 of the present embodiment performs a pressing process in a vacuum state by evacuating the chamber 41, in particular, in the fifth process (pressing process), at least the mold 6 and Since the gap with the thermoplastic resin 20 is in a vacuum atmosphere, even when a deep optical surface shape or a complicated optical surface shape is press-molded, resistance by air is eliminated and the thermoplastic resin 20 is filled in a short time. Thus, the molding quality can be improved and the molding cycle time can be further shortened. In other words, when molding an optical element having a fine structure such as a diffraction ring zone on the optical surface, if press molding is performed in an air atmosphere, it is particularly easy to form a minute air reservoir in the fine structure, and the transferability of hot press molding is improved. As described above, when the pressing process is performed at least in the gap between the mold 6 and the thermoplastic resin 20 in a vacuum atmosphere, as described above, a deep optical surface shape or a complicated optical surface is formed. Even when the shape is press-molded, resistance due to air can be eliminated and the resin can be filled in a short time, so that the cycle time can be further shortened.

Here, “vacuum atmosphere” refers to an atmosphere having a degree of vacuum of 1.0 × 10 ⁻¹ Pa or less, preferably 1.0 × 10 ⁻³ Pa or less. As described above, the method of making the gap between the mold 6 and the thermoplastic resin 20 into a vacuum atmosphere is not limited to the method in which the pressing process is performed in the evacuated chamber 41 as described above. A known method can be appropriately used as long as the gap with the plastic resin 20 can be appropriately set to a vacuum atmosphere.

  Then, by using the press molding apparatus 1 of the first embodiment and the press molding apparatus 40 of the second embodiment, various precision lenses such as long lenses and projection lenses, optical information recording medium substrates, guides, etc. Highly functional optical elements such as optical plates, prism sheets, light diffusing sheets, diffraction gratings, lens arrays, and other products with fine concavo-convex structures can be molded easily, with high accuracy, with a short molding cycle time and at low cost. can do.

  The invention made by the present inventor has been specifically described based on the preferred embodiments. However, the present invention is not limited to the above, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention can be applied to a press molding method and a press molding apparatus that mold a high-precision and large optical element or the like with high precision while shortening the molding cycle timing.

The principal part front view of the press molding apparatus to which the 1st Example of the press molding method of this invention and the thermoplastic resin molded object is applied. The principal part front view at the time of the 1st process (die preheating process) of the shaping | molding process by the press molding apparatus of FIG. The principal part front view at the time of the 2nd process (resin supply process) of the shaping | molding process by the press molding apparatus of FIG. The principal part front view at the time of the 3rd process (mold heating process) of the shaping | molding process by the press molding apparatus of FIG. The principal part front view at the time of the 4th process (mold arrangement | positioning process) of the shaping | molding process by the press molding apparatus of FIG. The principal part front view at the time of the 5th process (press process) of the shaping | molding process by the press molding apparatus of FIG. The principal part front view at the time of the 6th process (cooling process) of the shaping | molding process by the press molding apparatus of FIG. The principal part front view at the time of the 7th process (extraction process) of the shaping | molding process by the press molding apparatus of FIG. The principal part front view of the press molding apparatus which applied the 2nd Example of the press molding method and thermoplastic resin molding of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Press molding apparatus 2 Upper die 3 Lower mold 4, 5 Heater 6 Mold 7 Transfer surface part 7a Transfer surface 8 Temperature control part 9 Infrared heater 10 Reflecting plate 20 Thermoplastic resin 40 Press molding apparatus 41 Chamber

Claims (11)

  A mold having a transfer surface on at least one surface of a pair of molds arranged opposite to each other is detachably mounted, and at least one of the pair of molds moves to the other side to press-mold the thermoplastic resin. In a press molding method, a mold preheating step for preheating the pair of molds to a predetermined temperature not higher than a glass transition temperature of the thermoplastic resin, and supplying the thermoplastic resin between the preheated molds. A resin supplying step, a mold heating step in which only the mold is heated by a heating means to a predetermined temperature equal to or higher than a glass transition temperature of the thermoplastic resin, and the transfer surface of the mold is transferred to the thermoplastic resin. A mold disposing step of disposing the thermoplastic resin between the mold and the mold, and moving the mold to place the thermoplastic resin at a predetermined pressure with the mold. A pressing step for pressing, a cooling step for cooling the thermoplastic resin at a predetermined cooling rate in a state in which contact between the mold, the mold and the thermoplastic resin is maintained after the pressing, and opening the die A press molding method characterized by sequentially executing an extraction step of taking out the molded thermoplastic resin.   The press molding method according to claim 1, wherein the mold has a heat capacity set larger than a heat capacity of the molded thermoplastic resin and smaller than a heat capacity of the mold.   3. The press molding method according to claim 1, wherein the press molding method controls a cooling rate of the thermoplastic resin in the cooling step by changing a heat capacity of the mold.   In the press molding method, the mold includes a transfer surface portion on which the transfer surface is formed and a temperature adjustment unit for adjusting the heat capacity of the mold, and by changing the size of the temperature adjustment unit, The press molding method according to claim 3, wherein the heat capacity of the mold is changed to control the cooling rate of the thermoplastic resin in the cooling step.   5. The press molding method according to claim 1, wherein the heating unit is an electromagnetic wave heating unit that heats the mold using heat transfer by radiation of electromagnetic waves. 6.   6. The press molding method according to claim 5, wherein at least a surface irradiated with electromagnetic waves from the electromagnetic wave heating means is formed of an electromagnetic wave absorbing material.   The mold includes a transfer surface portion on which the transfer surface is formed and a temperature adjusting portion for adjusting the heat capacity of the mold, and the temperature adjusting portion is formed of an electromagnetic wave absorbing material that absorbs electromagnetic waves. The press molding method according to claim 5.   The press molding method is characterized in that at least in the pressing step, the mold and the thermoplastic resin are pressed with at least a gap between the mold and the thermoplastic resin in a vacuum atmosphere. The press molding method according to claim 7.   The press molding method according to any one of claims 1 to 8, wherein the press molding method cools the thermoplastic resin at a cooling rate of 1 ° C / second or more in the cooling step.   In the press molding method, the mold preheating step, the resin supplying step, the mold heating step, the mold arranging step, the pressing step, the cooling step, and the removing step are sequentially executed a plurality of times. When pressing a plurality of thermoplastic resins, the mold heating is performed in which a plurality of the molds are prepared and the mold used in the next molding cycle is heated while performing the steps after the predetermined mold arranging step. The press molding method according to claim 1, wherein the steps are performed simultaneously. A thermoplastic resin molded body produced by pressing a thermoplastic resin by a predetermined press molding method, wherein the press molding method according to any one of claims 1 to 11 is used as the press molding method. A molded thermoplastic resin product, which is press-molded.

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