JP2014223751A - Microstructure molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microstructure molding method that can mold a thin and planar microstructure by one molding in which there is not a burr, and a microstructure is included in a plane part and an edge end part.SOLUTION: A microstructure molding method is that a coated film that is formed by that a molten resin applied to a lower mold is pressed by the lower mold and an upper mold, performed by isovolume temperature change, a microstructure is performed by transfer molding to a plane part and an edge end part of the coated film, and the same is performed by cooling solidification, and a planar microstructure that has the microstructure in the plane part and the edge end part and in which there is not a burr in the edge end part is molded, and includes: a step in which a planar coated film is formed to the lower mold; a step in which heating of the upper mold and the lower mold is begun and mold closing is performed, temperature rising is performed to a prescribed mold temperature and transfer molding of the microstructure is performed; and a step in which cooling of the upper mold and the lower mold is begun, the mold temperature becomes a prescribed temperature, then mold opening is performed, and a molded microstructure is taken out.

Description

  The present invention presses a molten resin clamped to a mold having a fine structure to change the isovolumetric temperature, and molds a flat-plate-like fine structure in which the fine structure is transferred and formed on a flat part and an edge part. On how to do.

  By pressing a thermoplastic resin melt into a mold having a fine structure by injection molding or extrusion molding, and cooling and solidifying it, a thin flat microlens array having a fine structure, a light guide plate, etc. A plate-like body is formed. These plate-like bodies are required to have various fine structures on the front and back surfaces.

  For example, Patent Document 1 discloses a light guide plate having a maximum thickness of 1.5 mm or less obtained by injection molding, and a fine unevenness or lens having a 10-point average roughness of less than 200 μm based on JIS B0601 on at least one surface of the light guide plate. A light guide plate having a shape is disclosed. Then, the fan gate of the light guide plate obtained by injection molding of methacrylic resin is cut with a cutter, and one surface of this gate is polished with Asahi Megaro Plasticity to make this surface the light incident surface. Examples are disclosed. The mold used at this time is 10inch (4: 3) 1mm thick, with a half-width, 1mm thick fan gate at the center of the long side, apex angle 100 ° parallel to the flow direction on the core surface, pitch 150μm The linear prism was provided, the mold surface was provided with a fine irregular shaped satin pattern, and the remaining surface was a mirror surface.

  In the case where a flat microstructure is formed by such an injection molding method, there is a problem that burrs are likely to occur on the die mating surface. To solve this problem, for example, in Patent Document 2, the alignment accuracy of the movable side mold part and the movable side mold part is increased by using an alignment pin, and the clearance between the mold alignment surfaces is reduced to the extent that no burr is generated. A method is disclosed. According to this method, a molded product such as a light guide plate of a liquid crystal display element can be satisfactorily molded without causing short shots, reproducibility of a finely processed surface, distortion of the molded product, and burrs.

  On the other hand, Patent Document 3 discloses a method of forming a light guide plate by an extrusion molding method. That is, a microstructure sheet forming method is disclosed in which a molten thermoplastic resin is supplied to a gap between two rotating rolls, and this is pressed with the rolls to transfer and mold the ridge-like microstructure provided on each roll peripheral surface. Yes. A light guide plate is obtained by cutting the microstructure sheet into a desired size.

JP 2007-291230 JP Japanese Patent Laid-Open No. 2002-292686 JP 2012-233984 A

  The injection molding method has a problem of occurrence of burrs as described above because of the presence of the mold mating surface. In the injection molding method, the temperature of the resin decreases and the viscosity increases or solidifies during the process of flowing the molten resin from the gate filling the molten resin into the mold cavity to every corner of the thin flat cavity. There is a problem that it is difficult to fill every corner of the cavity. Furthermore, since it is difficult for the injection molding method to transfer the microstructure processed at the edge of the cavity to the molten resin, it is necessary to form a thin flat plate-like microstructure having a microstructure at the edge. Not easy. For this reason, as shown in Patent Document 1, the injection-molded light guide plate material has a problem that it is necessary to polish the edge surface where the light source of the light guide plate serving as the light entrance surface is provided.

  In addition, as shown in Patent Document 3, the extrusion molding method is a method in which a molten thermoplastic resin is pressed into a gap between two rotating rolls and pressed to form a microstructure. In addition, there is a problem that the shape of the side edge portion of the sheet-like molten thermoplastic resin is not easy. For this reason, in order to shape | mold a light-guide plate from the microstructure sheet | seat shape | molded by the extrusion molding method, the cutting | disconnection of the required part of a microstructure sheet | seat and grinding | polishing of a cut surface are needed.

  On the other hand, micro structures such as microlens arrays and light guide plates are becoming increasingly thin and have complex forms and various forms of fine structures, and light guide plates can be formed by a single molding process that requires no additional processing. There is a need for a method of molding. Furthermore, there is a demand for microstructures having various microstructures at the edges as well as the front and back surfaces of the plate-like body, and a molding method capable of molding such microstructures is further used for applications. There is a possibility of promoting the formation of a fine structure having an enlarged and novel function.

  In view of such conventional problems and requirements, the present invention does not use a die having a special structure by a press molding method, has no burrs, and has a thin flat plate shape having a fine structure on a flat portion and an edge portion. It is an object of the present invention to provide a fine structure forming method capable of forming a fine structure by one forming process.

  In the microstructure forming method according to the present invention, a coating film formed by applying a molten resin to a lower mold is pressed between the lower mold and the upper mold to change the isothermal temperature, A fine structure is transferred and molded on the flat portion and the edge portion, and this is cooled and solidified. The flat structure having the fine structure on the flat portion and the edge portion and having no burr on the edge portion is formed. A method of forming, wherein a step of forming a flat coating film on the lower mold, heating of the upper mold and the lower mold is started and clamping is performed, and the temperature is raised to a predetermined mold temperature. Performing the transfer molding of the microstructure, and starting the cooling of the upper mold and the lower mold, and after the mold temperature reaches a predetermined temperature, opening the mold and taking out the molded microstructure , Has.

In the above invention, the predetermined mold temperature t _d to be raised is preferably t <t _d <t + 50 (° C.) with respect to the mold temperature t at which the molten resin is applied. Further, the predetermined mold temperature t _d for raising the temperature is preferably t _g <t _d <t _g +100 (° C.) with respect to the glass transition temperature t _g of the molten resin.

  The coating film is preferably formed such that the gap δ from the front surface of the lower mold or the upper mold facing the edge is more than 0 mm and 5 mm or less.

  In addition, the thickness of the coating film that is pressed and fluidized by clamping the lower mold and the upper mold is preferably greater than 0% and less than or equal to 20% of the thickness of the microstructure.

  Further, the microstructure forming method according to the present invention includes a coating film formed by applying a molten resin to a lower mold and changing the isothermal temperature of the coating film by closing the upper mold so that the flat portion and the edge of the coating film are formed. It is carried out by forming a flat microstructure without burrs that performs transfer molding of the microstructure at the end.

  In the invention of the microstructure forming method, the coating film is preferably formed so as to satisfy the following expression with respect to the volume of the cavity formed by the lower mold and the upper mold. That is, the coating film is preferably formed so as to satisfy the following relationship: coating film volume + volume increase due to thermal expansion> cavity volume> coating film volume.

  According to the present invention, without using a specially structured mold, a thin flat microstructure having no burrs and having a microstructure transferred and formed on a flat portion and an edge portion can be formed by one molding. it can.

It is explanatory drawing of the microstructure manufacturing method which concerns on this invention. It is explanatory drawing which shows the time chart A of the thermal cycle of molten resin. It is explanatory drawing which shows the time chart B of the thermal cycle of molten resin It is explanatory drawing which shows the time chart C of the thermal cycle of molten resin It is a schematic diagram which shows the mode of the isovolumetric temperature change of molten resin. It is drawing which shows the result of an Example.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the microstructure forming method according to the present invention, a coating film formed by applying a molten resin to a lower mold is pressed between the lower mold and the upper mold to change the isothermal temperature, A fine structure is transferred and molded on the flat portion and the edge portion, and this is cooled and solidified. The flat structure having the fine structure on the flat portion and the edge portion and having no burr on the edge portion is formed. This is a molding method. As shown in FIG. 1, for example, this microstructure forming method includes a step of forming a flat coating film 5 on a stamper 3 held by a lower mold body 11 of a lower mold 1 (see FIG. )), Starting heating of the upper mold 2 and the lower mold 1 and performing mold clamping, raising the temperature to a predetermined mold temperature and performing transfer molding of the fine structure (FIG. 1 (b)), After the mold 2 and the lower mold 1 are cooled and the mold temperature reaches a predetermined temperature, the mold is opened to take out the molded microstructure. The lower mold 1 is heated and cooled by the temperature adjusting means 15 and 16. The upper mold 2 is heated and cooled by the temperature adjusting means 25 and 26.

  A so-called cavity is formed by the stamper 3, the side mold 12, and the upper mold 2, and the fine structure provided in the stamper 3 is transferred to the coating film 5. Further, the fine structure provided on the inner peripheral surface of the upper mold 2 or the side mold 12 is transferred and molded on the coating film 5. When the inner peripheral surface of the upper mold 2 or the side mold 12 is a mirror surface, the mirror surface is transferred and formed on the coating film 5. A mold surrounding the periphery of the coating film 5 such as the side mold 12 in this example can be provided integrally with the lower mold 1 as shown in FIG. It is also possible to provide the lower mold 1 and the upper mold 2 separately for each component part, or to form an edge mold in a completely independent form.

  In order to obtain a fine structure without burrs using the mold shown in FIG. 1, after the mold is clamped, the coating film 5 is transferred with no gap between the side mold 12 and the upper mold 2. It is necessary to perform molding. However, when there is no gap between the side mold 12 and the upper mold 2, the distance between the upper mold 2 and the lower mold 1 is constant, and the upper mold 2 and the lower mold 1 are coated. It becomes difficult to perform transfer molding by compressing 5. Here, when the mold temperature is raised and the coating film 5 in the cavity is heated, the molten resin forming the coating film 5 undergoes an isovolumetric temperature change to generate an internal resin pressure. The fine structure is transferred and formed on the coating film 5 using the generated internal pressure of the resin. Thereby, according to the present microstructure forming method, a thin flat microstructure having no burrs and having the microstructure transferred and formed on the flat portion and the edge portion can be formed by one molding.

The coating film 5 formed on the lower mold 1 is formed by applying a thermoplastic molten resin to the stamper 3 as shown in FIG. The application of the thermoplastic molten resin is performed in the lower mold 1 whose mold temperature is equal to or higher than the glass transition temperature of the thermoplastic resin. After clamping, the upper mold 2 and lower mold 1 is heated, after being heated to a predetermined mold temperature t _d, performs transfer molding of microstructures holds this temperature. The predetermined mold temperature t _d for raising the temperature is preferably t <t _d <t + 50 (° C.) with respect to the mold temperature t for applying the molten resin. This is because if the mold temperature t _d to be raised is high, the heating time during mold clamping becomes longer, the molding cycle becomes longer, and the productivity becomes lower. The predetermined mold temperature t _d to be raised is preferably t _g <t _d <t _g +100 (° C.) with respect to the glass transition temperature t _g of the molten resin. This is because appropriate fluidity can be secured without impairing the properties of the thermoplastic molten resin. The stamper 3, the lower mold 1 and the upper mold 2 are preferably controlled at substantially the same temperature in each process of mold clamping, temperature rising / transfer molding and cooling. As a result, the thermal strain history on the front and back surfaces of the flat molded body becomes equal, and the occurrence of distortion such as warpage can be suppressed. Therefore, in this microstructure forming method, the mold temperature means the temperature of the stamper 3, the lower mold 1, or the upper mold 2. Here, when using a resin that does not have a clear glass transition temperature t _g, such as a crystalline resin, refer to the softest temperature, the deflection temperature under load, etc. as the alternative index. Can do.

  The coating film 5 has a gap δ from the front surface of the lower mold or the upper mold facing the edge of the transfer molding, that is, the gap δ from the inner peripheral surface of the side mold 12 in the case of FIG. Formed as follows. The gap δ is preferably more than 0 mm and not more than 5 mm. The coating film 5 is formed so as to protrude from the upper end surface (the height h of the cavity) of the side mold 12. The protrusion amount m should be more than 0% and not more than 20% of the thickness of the fine structure. As the protrusion amount m, an optimum value is selected depending on the gap δ, the size of the fine structure, the kind of resin, and the like.

  The coating film 5 is preferably applied with a molten thermoplastic resin on its upper surface so as to give a dynamic pressure of 0.1 to 5 MPa with a gauge pressure. Thereby, the thickness of the coating film 30 can be controlled with high accuracy, and the thickness of the fine structure as the final product can be controlled with high accuracy. In this application, the in-plane thickness distribution (difference between the thickest part and the thinnest part) can be suppressed to around 10 μm. That is, the resin discharge part is brought close to the target film thickness on the coated surface, and a molten resin having a flow rate substantially equal to the required volume is discharged from the discharge part at a predetermined moving speed. Apply while. As a result, the width of the coating film can be made substantially equal to the width of the resin discharge portion of the T die and the length of the coating film can be made substantially equal to the moving distance of the resin discharge portion. And by these, the width | variety, length, and thickness of a coating film can be accurately apply | coated to the shape and thickness substantially equal to the final fine structure obtained after a press.

  Various thermoplastic resins can be used as the thermoplastic resin used in the present microstructure forming method. For example, polycarbonate (PC), polymethyl methacrylate (PMMA), cycloolefin polymer (COP), cyclic olefin copolymer (COC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polystyrene (PS), methyl methacrylate butadiene Resin materials such as styrene (MBS) can be suitably used.

  When the coating film 5 is formed as described above, heating of the upper mold 2 and the lower mold 1 is started and clamping is performed. In this microstructure forming method, with respect to the cavity formed by the lower mold 1 and the upper mold 2, the cavity is filled or slightly adjusted by adjusting the gap δ and the protrusion amount m of the coating film described above. A small volume of molten resin film is formed. And it is characterized in that the microstructure is transferred and molded to the molten resin by utilizing the internal pressure of the resin generated by the change in the isovolumetric temperature of the molten resin heated in the cavity. Therefore, it is important that the molten resin is heated in the cavity. When the upper mold 2 and the lower mold 1 are started to be heated and clamped, the lower mold 1 and the upper mold 2 This means that the heating includes any time when the mold clamping is started, before the mold clamping or after the mold clamping is finished.

  When the coating film 5 is clamped in the cavity, if the volume of the coating film is greater than the volume of the cavity, the resin may flow out of the cavity before the mold clamping is completed, causing burrs. On the other hand, if the volume of the coating film is smaller than the volume of the cavity, the resin in the cavity is insufficient, and transfer molding is appropriately performed by the resin pressure generated by the isovolumetric temperature change of the resin forming the coating film described below. There is no fear. Therefore, adjustment of the gap δ and the protrusion amount m is important, but in order to appropriately fill the resin in the cavity without generating burrs, the volume of the coating film + the volume increase due to thermal expansion> the cavity The volume should be larger than the volume of the coating film.

Examples of time charts A to C for performing mold operations and mold temperature control performed in the present microstructure forming method are shown in FIGS. Fig. 2 shows that the mold (lower mold 1 and upper mold 2) is first heated at the beginning of the molding cycle, and this temperature is maintained when the mold temperature (mold temperature) reaches the target mold set temperature t. Then, the molten resin is applied to form the coating film 5. Then, after the coating film 5 is formed, mold clamping is started and the mold temperature is increased simultaneously with the start of mold clamping. This temperature is maintained when the mold temperature reaches t _d .

In FIG. 3, heating of the mold is first started at the beginning of the molding cycle. When the mold temperature reaches the target mold setting temperature t, this temperature is maintained, and the molten resin is applied to form the coating film 5. Then, after the coating film 5 is formed and the mold clamping is completed, the mold is further heated to raise the mold temperature. This temperature is maintained when the mold temperature reaches t _d . In FIG. 4, the application of the molten resin starts when the mold temperature reaches t, but the mold continues to be heated, the coating film 5 is formed and the mold is clamped one after another, and this temperature is maintained when the mold temperature reaches t _d. This is an example of the case.

After the mold temperature t _d is maintained for a certain period of time, cooling of the mold is started as shown in FIGS. The mold temperature decreases due to cooling of the mold, and the mold opens when the mold temperature reaches t _o . In the thermal cycle, the coating film 5 is subjected to transfer molding with a fine structure. FIG. 5 shows the change in the isovolumetric temperature of the molten resin during this thermal cycle. FIG. 5 shows an example in which polycarbonate is used as the molten resin and transfer molding is performed according to the time chart C of the type shown in FIG. FIG. 5A shows the time change of the mold temperature in the thermal cycle, and FIG. 5B shows the specific volume of the resin at each mold temperature and the internal pressure of the resin generated in the molten resin. FIG.5 (c) shows the time change of the resin internal pressure calculated | required from FIG.5 (b). Microstructure transfer molding is performed on the polycarbonate coating film by the resin internal pressure shown in FIG. In FIGS. 5A to 5C, each point (a to d) indicates a corresponding state.

In FIG. 5B, the horizontal axis indicates the temperature of the resin (mold temperature), the vertical axis indicates the specific volume at each temperature of the resin, and the parameter indicates the internal pressure of the resin when the temperature of the resin is changed at a constant volume. In FIG.5 (b), the resin internal pressure which arises in molten resin is calculated | required as follows. That is, first, the volume (cm ³ ) of the cavity and the weight (g) of the coating film filled in the cavity are obtained, and the specific volume (cm ³ / g) of the resin is obtained. Then, from FIG. 5 (b), the seek resin pressure at the intersection of the mold temperature t _d that was raised and the specific volume. The obtained resin internal pressure is the resin internal pressure in the cavity.

The maximum value of the resin internal pressure is determined by the temperature difference between t _d and t and the difference between the volume of the applied resin and the volume of the cavity. For example, when a polycarbonate resin is heated from 145 ° C. to 195 ° C., a volume expansion of about 3% occurs in the open space, and an internal pressure of the resin of about 60 MPa occurs in the closed space. In the mold, a part of the thermally expanded resin flows into the open space in the cavity, so that the thermal expansion force except for this acts as an internal pressure of the resin. For example, if the difference between the volume of the coated resin and the volume of the cavity is 1.5%, the resin internal pressure is 60 MPa × 1.5% ÷ 3% = 30 MPa. At this time, if the clamping force by the press is small, the mold opens due to the internal pressure of the resin, which causes burrs. Therefore, it is preferable to change the isobaric temperature of the molten resin so that the internal pressure of the resin (MPa) × the transfer area (mm ² ) <the clamping force (N) in a state where the resin is filled in the cavity. Thereby, generation | occurrence | production of a burr | flash can be prevented. To satisfy the above equation, it is easily adjusted by changing the volume setting or applied resin t and t _d. The transfer area indicates the area of the cavity portion of the lower mold or the upper mold.

In this microstructure forming method, after the mold temperature t _d is held for a certain time, the lower mold and the upper mold are cooled, and the transfer-formed coating film is cooled and solidified. The transferred microstructure can be taken out from the stamper 3 without any distortion. In addition, the dimensional accuracy of the extracted fine structure can be ensured. This is because the microstructure formed by transfer molding and cooled adheres to the microstructure portion of the lower mold until it is taken out, and has a characteristic of maintaining its shape against shrinkage in the cooling process. .

  The present microstructure forming method has been described above. As described above, since this fine structure molding method performs transfer molding in a closed cavity formed by an upper mold and a lower mold that are clamped by a press mold, there is no burr on the entire surface. Further, fine structures having various fine structures can be formed on the front and back surfaces of the thin flat plate and the peripheral edges. However, when forming a microstructure that does not require transfer molding on any edge of the flat plate, a mold is not provided in the portion surrounding the edge of the coating (open portion is not provided). Can have). This is because the coating film applied by the T-die does not flow out from the opened mold part, and there is no problem in performing transfer molding of the flat part and other edge parts.

  The mold used for this microstructure forming method is not particularly limited. Instead of using the stamper 3, the lower mold 1 with a fine structure may be provided, and the stamper 3 may be provided not in the lower mold 1 but in the upper mold 2. Further, a fine structure (molded product) obtained by transfer molding by providing a thick part or a thin part in a part of the upper mold 1 or the stamper 3 may be formed in an uneven shape. By forming grooves in the lower mold 1 and the upper mold 2, structures such as ribs can be formed on the molded product. Further, a fine structure taking-out mechanism such as a protruding pin can be provided on the mold.

Using a mold equivalent to the mold shown in FIG. 1 (a configuration in which the side mold is provided on the upper mold), a molding test of the microstructure was performed. The side mold used was one that was surrounded by a coating film and had no open part. The mold temperature was adjusted by heating with an electric heater and cooling with water. The inner surface of the cavity formed by the stamper, side mold, and upper mold mounted on the lower mold was a mirror surface without a pattern. The resin used was polycarbonate (glass transition temperature 145 ° C.). The size of the cavity was 126 mm in length, 107 mm in width, and h = 230 μm. The thermal cycle of the molding was performed with a time chart A of the type shown in FIG. The coating film had a length of 123 mm (δ = 1.5 mm), a width of 104 mm (δ = 1.5 mm), and a thickness of 240 μ (t = 10 μm). A molten resin of 285 ° C was applied to a mirror stamper (mold temperature t = 160 ° C) to form a coating film, then the mold was clamped and the mold temperature was raised and held (mold temperature t _d = 185 ° C) . The applied pressure was 10 MPa (= pressing force (N) ÷ cavity area (mm ² )), and the pressurizing time was 30 seconds. Cooling was started 30 seconds after the start of pressurization, and the applied pressure was gradually reduced to 0 MPa until the mold was opened. When the temperature of the upper mold was lowered to 140 ° C. and the temperature of the lower mold was lowered to 120 ° C., the mold was opened and the microstructure (molded product) transferred and molded was taken out. As Comparative Example 1, a molding test was performed under the same conditions as in Example 1 except that the temperature was not increased during mold clamping and the mold temperature t = mold temperature t _d = 160 ° C. Further, as Comparative Example 2, a molding test was performed under the same conditions as in Example 1 except that the temperature was not raised during mold clamping and the mold temperature t = mold temperature t _d = 185 ° C.

  A mold having the same configuration as that of Example 1 except that the side mold was a mold in which only two sides in the length direction of the coating film were surrounded and two sides in the width direction were opened (having an open portion). Using a mold, a molding test was performed under the same conditions as in Example 1.

Using a mold having the same configuration as in Example 2, the mold temperature t _d after heating was 175 ° C., the coating film length was 124.5 mm (δ = 0.75 mm), and the coating film thickness was 235 μm (t = 15 μm). A molding test was conducted under the same conditions as in Example 1 except that.

  Table 1 shows the dimensional relationship between the cavity and the formed coating film in the molding test. In the transfer state column of Table 1, o indicates that the molding quality is good, and x indicates that the molding quality is poor.

  6A and 6B show the appearance of the molded product, in which FIG. 6A shows Example 1, FIG. 6B shows Comparative Example 1, and FIG. 6C shows Comparative Example 2. FIG. The molded product of Example 1 has a smooth mirror surface on the front and back surfaces and all edge portions, and the transfer molding is good, as shown in FIG. The dimensions were the same as the cavity dimensions. In the molded product of Comparative Example 1, the front and back surfaces were mirror surfaces, but as shown in FIG. 6B, all the edge portions were not filled with resin, and the molding quality was poor. In the molded product of Comparative Example 2, the front and back surfaces and all edge portions were mirror surfaces. However, as shown in FIG. 6C, the lower mold side mirror surface portion and the side mold side mirror surface portion Burr was generated at the joint. On the other hand, in the molded products of Examples 2 and 3, the front and back surfaces and the edge portions in the length direction had a smooth mirror surface, and as in Example 1, there were no burrs. And it turned out that the dimension of the length direction side of the cavity of a molded article is the same dimension as a cavity, and the target molding quality can be ensured. The cross section in the width direction had the same shape as Comparative Example 1 (FIG. 6B).

1 Lower mold
2 Upper mold
3 Stamper
5 Coating film
11 Lower mold body
12 side type
15, 16, 25, 26 Temperature adjustment means

Claims (7)

The coating film formed by applying molten resin to the lower mold is pressed by the lower mold and the upper mold to change the isovolumetric temperature, and the fine structure is transferred to the flat and edge portions of the coating film. It is a method of forming and cooling and solidifying this, and forming the flat microstructure having the fine structure in the flat part and the edge part and having no burr in the edge part,
Forming a flat coating film on the lower mold; and
Starting heating of the upper mold and the lower mold and performing mold clamping, raising the temperature to a predetermined mold temperature, and performing transfer molding of the fine structure;
A step of starting the cooling of the upper mold and the lower mold, and after the mold temperature reaches a predetermined temperature, performing a mold opening to take out the molded microstructure. 2. The microstructure forming method according to claim 1, wherein the predetermined mold temperature t _d to be raised is t <t _d <t + 50 (° C.) with respect to the mold temperature t for applying the molten resin. . The microstructure according to claim 1, wherein the predetermined mold temperature t _d to be raised is t _g <t _d <t _g +100 (° C.) with respect to the glass transition temperature t _g of the molten resin. Molding method.   The coating film is formed so that a gap δ from the lower mold or the upper mold facing the edge of the upper mold is more than 0 mm and 5 mm or less. The microstructure forming method according to one item.   5. The coating film according to claim 1, wherein a thickness portion flowing by clamping the lower mold and the upper mold is more than 0% and not more than 20% of the thickness of the fine structure. The microstructure forming method according to one item.   The coating film formed by applying molten resin to the lower mold is subjected to thermal expansion by closing the upper mold and changing the isovolumetric temperature to thermally expand the fine structure on the flat and edge portions of the coating film. A fine structure forming method for forming a flat fine structure without burrs. 7. The microstructure forming method according to claim 6, wherein the coating film is formed so as to satisfy the following expression with respect to the volume of the cavity formed by the lower mold and the upper mold.
Volume of coating film + volume increase by thermal expansion> volume of cavity> volume of coating film

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