JP7563265B2 - Method and apparatus for manufacturing plastic elements - Google Patents

Description

The present invention relates to a method for manufacturing a plastic element and an apparatus for manufacturing a plastic element.

In recent years, optical elements with micro- and nano-order fine structures, such as microlens arrays and diffractive optical elements, have been used to improve the uniformity of illumination in 3D sensing using Tof (Time of Flight) and thereby improve distance measurement accuracy.

A known method for manufacturing such optical elements involves sandwiching liquid thermosetting resin between flat upper and lower molds on which the inverted shape of the desired optical surface has already been formed, and then heating the resin to transfer the inverted shape to the resin and harden it.

In addition, thermosetting resins that are liquid at room temperature undergo volumetric shrinkage during the curing process due to a crosslinking reaction caused by heating, resulting in poor transfer such as sink marks and reduced shape accuracy. To address this issue, a system is known that detects the negative pressure that occurs due to curing shrinkage at the gel point where the viscosity of the thermosetting resin increases and then applies pressure (for example, Patent Document 1).

However, conventional technology requires highly accurate sensors and complex control mechanisms to detect the gel point and provide feedback. In addition, the faster the heating speed is increased to increase productivity, the more difficult it becomes to control, which leads to a problem of reduced transfer accuracy of the plastic elements.

The objective of the present invention is to provide a method for manufacturing plastic elements that can improve the transfer accuracy of plastic elements with a simple configuration.

One aspect of the present invention is a method for manufacturing a plastic element in which a thermosetting resin to which a predetermined pattern has been transferred is heated to harden it to form a plastic element, the method comprising the steps of: sandwiching the thermosetting resin between a pair of molds and fixing the pair of molds; and heating the pair of molds to harden the thermosetting resin, at least one of the pair of molds having a transfer section that contacts the thermosetting resin to transfer the pattern and an expansion section that expands in a compression direction in which the transfer section compresses the thermosetting resin due to heating, and the amount of expansion of the expansion section is equal to or greater than the amount of cure contraction of the thermosetting resin.

According to one aspect of the present invention, it is possible to improve the transfer accuracy of plastic elements with a simple configuration.

FIG. 2 is a schematic diagram showing a manufacturing apparatus for a plastic element. 4 is a flow chart showing a method for manufacturing a plastic element. 4 is a flow chart showing a method for manufacturing a plastic element. 4 is a flow chart showing a method for manufacturing a plastic element. 4 is a flow chart showing a method for manufacturing a plastic element. 1 is a schematic diagram showing a manufacturing apparatus (manufacturing process) according to a first embodiment; Schematic diagram showing a manufacturing process of the first embodiment. Schematic diagram showing a manufacturing process of the first embodiment. Schematic diagram showing a manufacturing process of the first embodiment. Schematic diagram showing a manufacturing process of the first embodiment. 5A to 5C are diagrams showing the relationship between the manufacturing process of a plastic element and pressure due to thermal expansion. 1A and 1B are images showing the transfer surface of a mold, where (a) is a laser microscope image and (b) is a three-dimensional display image of (a). 1A and 1B are images showing a lens surface of a plastic element according to an embodiment, where (a) is a laser microscope image and (b) is a three-dimensional display image of (a). 1A and 1B are images showing the lens surface of a conventional plastic element, where (a) is a laser microscope image and (b) is a three-dimensional display image of (a). FIG. 13 is a schematic diagram showing a manufacturing apparatus (manufacturing process) according to a second embodiment. Schematic diagram showing a manufacturing process of the second embodiment. Schematic diagram showing a manufacturing process of the second embodiment. Schematic diagram showing a manufacturing process of the second embodiment. Schematic diagram showing a manufacturing process of the second embodiment. Schematic diagram showing a manufacturing process of the second embodiment. FIG. 13 is a schematic diagram showing a manufacturing apparatus according to a third embodiment. FIG. 13 is a diagram showing a state before heating of an upper mold constituting a manufacturing apparatus according to a third embodiment. FIG. 13 is a diagram showing a state in which an upper mold constituting the manufacturing apparatus according to the third embodiment is being heated. 13A to 13C are schematic diagrams showing a manufacturing process of the third embodiment. 13A to 13C are schematic diagrams showing a manufacturing process of the third embodiment. 13A to 13C are views showing a plastic element obtained in a manufacturing process according to a third embodiment. FIG. 13 is a schematic diagram showing a manufacturing apparatus according to a fourth embodiment. 13A to 13C are schematic diagrams showing a manufacturing process of the fourth embodiment. 13A to 13C are schematic diagrams showing a manufacturing process of the fourth embodiment. 13A to 13C are schematic diagrams showing a manufacturing process of the fourth embodiment. 13A to 13C are schematic diagrams showing a manufacturing process of the fourth embodiment. 13A to 13C are schematic diagrams showing a manufacturing process of the fourth embodiment. FIG. 13 is a diagram showing an example of a lower mold constituting a manufacturing apparatus according to a fourth embodiment. FIG. 13 is a diagram showing an example of a lower mold constituting a manufacturing apparatus according to a fourth embodiment.

The following describes an embodiment of the present invention.

<Method of manufacturing plastic elements>
In the method for producing a plastic element according to this embodiment, the thermosetting resin to which a predetermined pattern has been transferred is hardened by heating to form a plastic element.

The method for producing a plastic element according to this embodiment includes the steps of: fixing a pair of molds by sandwiching a thermosetting resin between the pair of molds with the liquid composition according to this embodiment; and heating the pair of molds to harden the thermosetting resin.

At least one of the pair of molds has a transfer section that contacts the thermosetting resin to transfer a pattern, and an expansion section that expands in a compression direction in which the transfer section compresses the thermosetting resin when heated, and the amount of expansion of the expansion section is equal to or greater than the amount of cure contraction of the thermosetting resin.

The method for manufacturing a plastic element according to this embodiment is specifically implemented by the apparatus shown in FIG. 1. FIG. 1 is a schematic diagram showing the apparatus for manufacturing a plastic element.

The plastic element manufacturing apparatus 100 shown in FIG. 1 has an upper die plate 10, a lower die plate 20, a drive unit having guides 70 and 80, a temperature control unit 30 formed on the upper die plate 10 and having a heat transfer unit 31, a heating unit 32, and a cooling unit 33, and a temperature control unit 40 formed on the lower die plate 20 and having a heat transfer unit 41, a heating unit 42, and a cooling unit 43.

The plastic element manufacturing apparatus 100 further has a control unit (not shown), which controls the drive unit and the temperature adjustment units 30 and 40. The control unit has a central processing unit (CPU) and memory, and is connected to the drive unit and the temperature adjustment units 30 and 40 in a wired or wireless manner so as to be able to communicate with them.

The upper mold 50 is formed on the upper die plate 10 via the temperature control section 30. The upper mold 50 has an expansion section 51 that thermally expands when heated, and a transfer section 52. In the first embodiment, the transfer section 52 constitutes the transfer surface of the upper mold 50, and a predetermined pattern shape to be transferred to a plastic element is formed in the transfer section 52. In the upper mold 50, the expansion section 51 and the transfer section 52 are formed integrally.

A lower mold 60 is formed on the lower die plate 20 via a temperature control section 40. The lower mold 60 has an expansion section 61 that thermally expands when heated, and a transfer section 62. In the first embodiment, the transfer section 62 constitutes the transfer surface of the lower mold 60, and is configured with a predetermined mirror shape that is transferred to the plastic element. In the lower mold 60, the expansion section 61 and the transfer section 62 are formed integrally.

In this specification, the upper mold 50 and the lower mold 60 are an example of a pair of molds in this embodiment, and the upper mold 50 is an example of at least one of the pair of molds in this embodiment.

The transfer section 62 may be formed with a predetermined pattern shape to be transferred to the plastic element, similar to the transfer section 52 of the upper mold 50. Alternatively, the transfer section 62 may be formed with a predetermined pattern shape to be transferred to the plastic element, instead of the transfer section 52.

Thermosetting resin 90 is placed between the upper mold 50 and the lower mold 60. In this embodiment, as the drive unit operates, the upper mold 50 moves toward the fixed lower mold 60, and the transfer unit 52 comes into contact with the thermosetting resin 90, deforming the shape of the thermosetting resin 90. In addition, the temperatures of the upper and lower molds 50, 60 are controlled by the temperatures of the temperature adjustment units 30, 40, and the thermosetting resin 90 is heated, hardened, and cooled.

In this specification, a thermosetting resin refers to a synthetic resin that has thermosetting properties, does not dissolve in a solvent after curing, and does not soften even when reheated. There are no particular limitations on the thermosetting resin, and examples of the thermosetting resin include epoxy resin, urethane resin, acrylic resin, urea resin, melamine resin, phenolic resin, and resin.

The expansion section 51 of the upper mold 50 is made of a high thermal expansion material. The high thermal expansion material is preferably a material having a linear expansion coefficient of 10×10 ⁻⁶ /° C. or more and 50×10 ⁻⁶ /° C. or less, more preferably a material having a linear expansion coefficient of 15×10 ⁻⁶ /° C. or more and 45×10 ⁻⁶ /° C. or less, and even more preferably a material having a linear expansion coefficient of 20×10 ⁻⁶ /° C. or more and 35×10 ⁻⁶ /° C. or less. For example, aluminum (linear expansion coefficient: 27×10 ⁻⁶ /° C.) can be used as such a high thermal expansion material.

The thickness of the upper mold 50 is arbitrary, but if the expansion section 51 of the upper mold 50 is made of a high thermal expansion material, it is preferable to make the thickness, for example, 20 mm or more and 60 mm or less, more preferably 30 mm or more and 50 mm or less, and even more preferably 35 mm or more and 45 mm or less, taking into consideration thermal conduction.

The expansion section 61 of the lower mold 60 is made of a low thermal expansion material. The low thermal expansion material is preferably a material with a linear expansion coefficient of less than 10×10 ⁻⁶ /°C, more preferably a material with a linear expansion coefficient of 8×10 ⁻⁶ /°C or less, and even more preferably a material with a linear expansion coefficient of 5×10 ⁻⁶ /°C or less. The lower limit of the linear expansion coefficient of the low thermal expansion material is not limited, and is usually 0.1×10 ⁻⁶ /°C. For example, silicon (linear expansion coefficient: 3.9×10 ⁻⁶ /°C) can be used as such a low thermal expansion material.

In this embodiment, the upper side is made of a high thermal expansion material and the lower side is made of a low thermal expansion material, but as long as compressive stress is applied to the transfer surface by heating, the upper side may be made of a low thermal expansion material and the lower side of a high thermal expansion material, or both the top and bottom may be made of high thermal expansion material. This creates an action mechanism in which the high thermal expansion material thermally expands in response to the temperature of the temperature adjustment units 30 and 40, applying compressive stress in the transfer direction.

Here, the steps of the process for carrying out the manufacturing method of the plastic element of this embodiment will be described. Figures 2 to 5 are flowcharts showing the manufacturing method of the plastic element. Figures 6 to 10 show the manufacturing process of the first embodiment. Figure 11 shows the relationship between the manufacturing process of the plastic element and pressure due to thermal expansion.

The manufacturing method for the plastic element of this embodiment includes a resin application process, a mold closing process, a heating process, a cooling process, and a mold opening process (Figure 2, steps S1 to S5).

In the resin application process (FIG. 2, step S1), the upper die plate 10 and the lower die plate 20 wait in separate positions (FIG. 3, step S11). At this time, the transfer unit 52 of the upper mold 50 waits in a position separate from the thermosetting resin 90 (FIG. 6). The temperature adjustment units 30 and 40 are maintained in a preheated state at a constant temperature (FIG. 4, step S21). Liquid thermosetting resin 90 is applied to the lower mold 60 (FIG. 5, step S31).

In the mold closing process (FIG. 2, step S2), the upper die plate 10 is lowered and stopped at a position that is a distance D1 from the standby position (FIG. 3, steps S12 and S13). This fixes the upper mold 50 to the lower mold 60. The transfer part 52 of the upper mold 50 also stops at a position that is the distance D1 below the standby position and comes into contact with the thermosetting resin 90 (FIG. 7).

At this time, the pressure behavior is close to zero (to the left of the solid line in Figure 11). Note that a slight positive pressure is generated by contact with the resin material, but since it is a liquid, it can be considered to be almost zero.

In this embodiment, the mold closing process (FIG. 2, step S2) is an example of a process in which a pair of molds is fixed together by sandwiching a thermosetting resin between the pair of molds.

In the heating process (FIG. 2, step S3), heating is started by the temperature control units 30 and 40 (FIG. 4, step S22). This causes the upper mold 50 and the lower mold 60 to be heated as well. At this time, the upper mold 50, which is made of a high thermal expansion material, thermally expands.

Therefore, even though the drive unit (upper die plate 10) is not moving, the transfer unit 52 of the upper mold 50 further descends by a distance D2 (Figure 8). As a result, even if the thermosetting resin 90 cures and shrinks, a compressive stress is applied in the transfer direction (points (A) and (B) in Figure 11).

Furthermore, when heating is maintained by the temperature control units 30 and 40 (FIG. 4, step S23), the heating temperature by the temperature control units 30 and 40 becomes constant, and the amount of thermal expansion also settles at a constant value, so the pressure becomes constant (point (C) in FIG. 11). At this time, the descent of the transfer unit 52 of the upper mold 50 stops (FIG. 8).

Thermosetting resin 90 becomes gelled thermosetting resin 91 and undergoes volumetric shrinkage (curing shrinkage), but remains in close contact with the transfer section 52 due to the compressive stress from the expanded upper mold 50 (Figure 8).

On the other hand, in the case of a normal molding method (upper mold 150 and lower mold 160) that does not use a high thermal expansion material, volumetric shrinkage (curing shrinkage) occurs when heating is started and the thermosetting resin 190 gels (point (E) in Figure 11).

At this time, as long as the transfer surface of the upper mold 150 and the gelled thermosetting resin 191 are in close contact with each other, a tensile stress acts, generating a negative pressure. When the contraction progresses further and the resin can no longer withstand the pressure, the gelled thermosetting resin 191 peels off from the transfer surface of the upper mold 150, and the pressure becomes zero (Figure 11 (F)).

In addition, in the case of the prior art (Patent Document 1), complex feedback control is implemented in this process, in which the negative pressure is detected and the drive unit is controlled to fine-tune the die plate position. However, in this embodiment, transferability can be improved simply by heating, without such complex configuration or control.

In this specification, the heating process is an example of a process in which the pair of molds in this embodiment are heated to harden the thermosetting resin.

In the cooling process (FIG. 2, step S4), cooling by the temperature adjustment units 30 and 40 is started (FIG. 4, step S24). As a result, the upper mold 50 in an expanded state contracts and returns to its original state. As a result, the transfer unit 52 of the upper mold 50 rises and returns to its original position (a position a distance D1 from the standby position). Thereafter, cooling by the temperature adjustment units 30 and 40 is terminated (FIG. 4, step S25).

In addition, the hardened and solidified thermosetting resin (molded product) 92 also thermally shrinks when cooled, so a force acts in the direction in which the upper mold 50 and the molded product peel away from each other (Figure 9). As a result, the pressure approaches zero (point (D) in Figure 11). At this point, the molded product 92 has hardened sufficiently and is solid, so even if it peels away from the mold, the transfer accuracy is maintained as a plastic element.

In the mold opening process (FIG. 2, step S5), the upper die plate 10 is raised and placed on standby, and the transfer part 52 of the upper mold 50 is raised and returns to a standby state (FIG. 3, steps S14 and S15). This allows the molded product 92 to be removed as a plastic element (FIG. 5, step S32).

If steps S1 to S5 are to be repeated after the mold opening process (step S5 in FIG. 2), the process returns to the resin application process (step S1 in FIG. 2) and steps S1 to S5 are executed. If steps S1 to S5 are not to be repeated, the process ends.

When steps S1 to S5 are repeated (FIG. 2, step S6), the upper die plate 10 remains elevated and waits (FIG. 3, steps S15 and S16). At this time, the temperature adjustment units 30 and 40 are maintained in a preheated state at a constant temperature in preparation for the next molding (FIG. 4, steps S26 and S27), and liquid thermosetting resin 90 is applied to the lower mold 60 again (FIG. 5, step S33).

In the case of molding methods that do not use high thermal expansion materials, as shown in Figure 11, the thermosetting resin peels off from the transfer surface during the heating process, and the pressure becomes zero. Because the thermosetting resin peels off while still in an uncured state, sink marks appear in the molded product and the shape precision deteriorates (Figures 12 and 14).

In contrast, in this embodiment, a high thermal expansion material is used, so that even if the thermosetting resin cures and shrinks during the heating process, a compressive stress is applied in the transfer direction due to the thermal expansion of the upper mold 50 (expansion section 51). This makes it possible to suppress sink marks in the molded product 92 and improve shape accuracy (Figures 12 and 13).

If the amount of movement of the transfer section 52 due to the thermal expansion of the upper mold 50 (distance D2 in FIG. 11), i.e., the amount of expansion of the expansion section 51, is equal to or greater than the amount of hardening and shrinkage of the resin, the resin will not separate from the transfer surface. In this case, the pattern of the transfer section 52 can be reliably transferred to the thermosetting resin 90.

For example, assume that the preheating temperature is 100° C., the heating temperature is 150° C., the cure shrinkage of the thermosetting resin is 5%, and the thickness of the molded product is 1 mm. As described above, if the material of the upper mold 50 is aluminum (linear expansion coefficient: 27×10 ⁻⁶ /° C.) and the thickness is 40 mm, then the relationship in which the amount of thermal expansion is greater than or equal to the amount of cure shrinkage (amount of thermal expansion≧amount of cure shrinkage) is established as shown below, and the pattern shape of the transfer portion 52 can be reliably transferred to the thermosetting resin 90.

Amount of thermal expansion of upper mold: 27×10 ⁻⁶ /° C.×(150° C.−100° C.)×40 mm=54 um
Amount of shrinkage of thermosetting resin during hardening: 1 mm x 5% = 50 um

In addition, if both the upper mold 50 and the lower mold 60 are made of aluminum, even if the thickness of each mold 50, 60 is half that of the mold, at 20 mm, the combined expansion of the upper and lower molds 50, 60 will exceed the amount of hardening shrinkage.

On the other hand, when both the upper mold 50 and the lower mold 60 are made of silicon (linear expansion coefficient: 3.9×10 ⁻⁶ /° C.),
Amount of thermal expansion of the upper mold: 3.9×10 ⁻⁶ /° C.×(150° C.−100° C.)×40 mm=7.8 um
This is significantly less than the amount of cure shrinkage.

To make the cure shrinkage of the thermosetting resin (50 um) or more, the thickness of the mold must be 128 mm or more for both the top and bottom. A mold with a thickness of more than 100 mm is not practical because it takes too long for heat conduction and significantly extends the tact time. From this perspective, it is preferable to use a high thermal expansion material such as aluminum for at least one of the upper mold 50 and the lower mold 60.

In this way, according to the first embodiment, it is possible to improve the transfer accuracy of plastic elements with a simple configuration.

Figure 15 shows the manufacturing apparatus of the second embodiment. Figures 16 to 20 show the manufacturing process of the second embodiment. Note that parts of the second embodiment that are common to the first embodiment are given the same reference numerals and will not be described.

In the manufacturing device of the second embodiment, the expansion section 51 and the transfer section 52 of the upper mold 50 are constructed from separate members. Specifically, the expansion section 51 is disposed between the transfer section 52 and the temperature adjustment section 30, and expands when heated, thereby forming a pressure adjustment section for the transfer section 52.

In the second embodiment, the material of the transfer part 52 is selected so that the amount of expansion of the transfer part 52 is smaller than the amount of expansion of the expansion part 51. Specifically, the material of the transfer part 52 of the upper mold 50 is made of the same low thermal expansion material as the lower mold 60.

For example, in the case of a microlens array in which the pattern transferred to the plastic element is an array of tens of thousands of microlenses with a diameter of about 100 μm, it is difficult to machine the shape into aluminum, which is a material with high thermal expansion. In this case, it is more desirable to process silicon (linear expansion coefficient: 3.9×10 ⁻⁶ /° C.) or a glass substrate (linear expansion coefficient: 0.6×10 ⁻⁶ /° C.) using a semiconductor process. However, silicon and glass have very small linear expansion coefficients.

Therefore, in the second embodiment, a low thermal expansion material such as silicon is used for the transfer portion 52 of the upper mold 50, and a high thermal expansion material such as aluminum is used for the expansion portion 51 of the upper mold 50, thereby achieving both workability and transferability of the transfer surface. In addition, it is possible to adjust the thickness of the expansion portion 51 according to the amount of cure shrinkage of the resin material to be transferred, and to change the material of the expansion portion 51 to accommodate various resin materials.

For example, the expansion portion 51 is made of aluminum (linear expansion coefficient: 27×10 ⁻⁶ /° C.) with a thickness of 40 mm, the preheating temperature is 100° C., the heating temperature is 150° C., the cure shrinkage amount of the thermosetting resin is 5%, and the thickness of the molded product 92 is 1 mm. In this case, as in the first embodiment, a relationship is established in which the amount of thermal expansion is equal to or greater than the amount of cure shrinkage (amount of thermal expansion≧amount of cure shrinkage), and the pattern shape of the transfer portion 52 can be reliably transferred to the thermosetting resin 90.

When forming a pattern shape on the silicon or glass transfer part 52 of the upper mold 50, the wafer process is used as described above, but the thickness of the transfer part 52 is 1 mm or less, so there is no problem with thermal conductivity.

The mechanism by which the transferability is improved in the second embodiment is the same as in the first embodiment. During the heating process, the expansion portion 51 of the upper mold 50 thermally expands, causing the transfer portion 52 to move down a distance D4, applying pressure according to the heating temperature (Figures 17 to 18).

In the second embodiment, the expansion section 61 and the transfer section 62 of the lower mold 60 are integrally formed, but similar to the upper mold 50, the expansion section 61 and the transfer section 62 may be formed of separate members. In that case, the expansion section 61 is disposed between the transfer section 62 and the temperature adjustment section 40, and can form a pressure adjustment section for the transfer section 62 by expanding when heated.

In the second embodiment, the amount of expansion of the transfer section 52 is smaller than the amount of expansion of the expansion section 51, so the shape of the transfer section 52 is less likely to change not only in the compression direction in which the thermosetting resin is compressed, but also in a direction perpendicular to the compression direction. This improves the transfer accuracy of the pattern shape by the transfer section 52 not only with respect to the hardening shrinkage of the thermosetting resin in the compression direction, but also with respect to the hardening shrinkage in the direction perpendicular to the compression direction.

In addition, in the second embodiment, the transfer section 52 of the upper mold 50 is made of a low thermal expansion material that is separate from the expansion section 51, so that even if the upper mold 50 itself thermally expands, the deterioration of the transfer accuracy of the pattern shape can be suppressed.

Figure 21 shows the manufacturing apparatus of the third embodiment. Figure 22 shows the state of the upper mold constituting the manufacturing apparatus of the third embodiment before heating, and Figure 23 shows the state of the upper mold constituting the manufacturing apparatus of the third embodiment when heated. Figures 24 to 25 show the manufacturing process of the third embodiment. Figure 26 shows a plastic element obtained in the manufacturing process of the third embodiment. Note that parts of the third embodiment that are common to the second embodiment are given the same reference numerals and will not be described.

In the manufacturing device of the third embodiment, the upper mold 50 has a non-expanding portion 53 adjacent to the expanding portion 51 in a direction perpendicular to the compression direction. The non-expanding portion 53 is disposed around the expanding portion 51. In the third embodiment, the expanding portion 51 has a rectangular shape in a plan view, and the non-expanding portion 53 has a shape that surrounds the expanding portion 51 in a rectangular shape in a plan view (Figure 22).

The shape of the non-inflatable portion 53 is not particularly limited. In this embodiment, it has an annular shape with a rectangular outline in a plan view.

The non-expanding portion 53 is a portion that does not expand due to heat, or if it does expand, the amount of expansion is small. The material of the non-expanding portion 53 is not particularly limited, but for example, a low thermal expansion material such as silicon can be used, as with the lower mold 60.

In the third embodiment, the transfer portion 52 is provided in the compression direction of the expansion portion 51. As a result, when the upper mold 50 is heated, the expansion portion 51 expands, the transfer portion 52 descends, and the non-expansion portion 53 does not descend. The transfer portion 52 that descends due to heating becomes the effective region 92A of the hardened thermosetting resin (molded product) 92, and the non-expansion portion 53 that does not descend even when heated constitutes the non-effective region 92B of the molded product 92.

The effective area is the area in the plastic element where you want to form the desired pattern shape (or mirror surface). For example, in the case of an optical element, it refers to the area that performs functions such as transmitting and reflecting light. In the case of an exterior part, it refers to the area where you want to ensure the desired appearance. On the other hand, the non-effective area does not necessarily need to have the desired pattern shape (or mirror surface). In other words, it refers to the area where the occurrence of transfer defects such as sink marks will not cause any problems for the element.

In the third embodiment, the transfer portion 52 of the upper mold 50 is provided only on the portion where the effective area 92A of the molded product 92 is projected, so that when heated, the effective area 92A is pressed against the non-effective area 92B in a convex manner (FIG. 23). On the other hand, the non-effective area 92B is not subjected to the pressurizing effect due to thermal expansion, so the thermosetting resin 90 is less constrained against the effective area 92A.

As a result, since the thermosetting resin 90 can shrink inward, the transferability is improved in the effective area 92A on the inside of the hardened thermosetting resin 92, and shrinkage occurs in the non-effective area 92B on the outside. In other words, by allowing the sink marks to escape to the non-effective area 92B, the transferability of the thermosetting resin 90 can be improved.

In addition, after the thermosetting resin 90 hardens, the outer periphery (non-effective area 92B) of the solidified thermosetting resin (molded product) 92 peels off from the non-expanding portion 53 of the upper mold 50, making it easier to release the molded product 92 during subsequent steps after mold opening.

In addition, in the third embodiment, the expansion portion 51 is restricted by the surrounding non-expansion portion 53, so the amount of movement of the transfer portion 52 due to thermal expansion can be increased.

Figure 27 shows a manufacturing apparatus of the fourth embodiment. Figures 28 to 32 show the manufacturing process of the fourth embodiment. Figure 33 shows an example of a lower mold that constitutes the manufacturing apparatus of the fourth embodiment. Figure 34 shows an example of a lower mold that constitutes the manufacturing apparatus of the fourth embodiment. Note that parts of the fourth embodiment that are common to the second embodiment are given the same reference numerals and will not be described.

In the manufacturing apparatus of the fourth embodiment, a spacer portion 63 is formed between the upper mold 50 and the lower mold 60 to regulate the distance between the upper mold 50 and the lower mold 60 (Figure 27).

Since the manufacturing of plastic elements involves a heating process, heat accumulates throughout the device when the device is operated continuously. In the case of the second embodiment described above, the amount of thermal expansion of the expansion section 51 of the upper mold 50 also changes slightly, causing dimensional variations in the molded product. Furthermore, if there are temperature unevenness in the temperature control sections 30 and 40, pressure unevenness may also occur within the transfer section 52 of the upper mold 50, resulting in a decrease in the parallelism of the transfer section 52.

In contrast, in the fourth embodiment, a spacer portion 63 is provided between the upper mold 50 and the lower mold 60. This regulates the distance between the upper mold 50 and the lower mold 60, and allows the distance at which the thermosetting resin is compressed to be adjusted, improving the shape accuracy of the molded product in the thickness direction.

Specifically, the spacer portion 63 is provided in a ring shape in a plan view on the outer periphery of the surface of the lower mold 60 (Figure 33). During the heating process in Figure 30, the transfer portion 52 of the upper mold 50 hits the spacer portion 63 provided on the lower mold 60 as it descends. This fixes the distance between the transfer portion 52 of the upper mold 50 and the transfer portion 62 of the lower mold 60 at a constant value.

In addition, in the fourth embodiment, the parallelism of the transfer surface is improved by hitting the spacer portion 63 provided on the outer periphery of the lower mold 60. This has the effect of further improving the shape accuracy of the molded product in the thickness direction.

In addition, in the fourth embodiment, it is preferable that the height of the spacer portion 63 in the compression direction is lower than the thickness of the thermosetting resin 90 in the compression direction before heating (FIGS. 28 and 29). By making the height of the spacer portion 63 in the compression direction lower than the thickness of the thermosetting resin 90 in the compression direction before heating, it is possible to prevent insufficient pressure from the upper mold 50.

The material of the spacer portion 63 is not particularly limited, but is preferably a material that has a smaller linear expansion coefficient than the expansion portion 51 and is not easily broken. For example, by integrating the lower mold 60 and the spacer portion 63 from a nickel-phosphorus alloy (linear expansion coefficient: 12×10 ⁻⁶ /° C.), the shape accuracy in the thickness direction of the molded product is further improved.

In the example of FIG. 33, the spacer portion 63 is configured as a single spacer around the entire outer periphery of the lower mold 60, but the shape of the spacer portion 63 is not limited to this form. For example, as shown in FIG. 34, multiple spacer portions 63 may be formed at the four corners of the lower mold 60. By partially providing multiple spacer portions 63 in this manner, the spacer portion 63 is less likely to get in the way when releasing the molded product 92 in the process after mold opening.

In the fourth embodiment, the spacer portion that regulates the distance between the upper mold 50 and the lower mold 60 is provided on the lower mold 60, but the location where the spacer is provided is not limited to this. For example, the spacer portion may be formed on the upper mold 50, or the spacer portion may be formed on both the upper mold 50 and the lower mold 60.

Although the embodiment of the present invention has been described above, the present invention is not limited to a specific embodiment, and various modifications and variations are possible within the scope of the invention described in the claims.

<Plastic elements>
The plastic element of this embodiment is manufactured by the above-mentioned manufacturing method of a plastic element. Specifically, by using the above-mentioned manufacturing apparatus 100 for a plastic element, a cured body (molded product) of a thermosetting resin obtained can become the plastic element of this embodiment.

As mentioned above, the plastic element obtained in this way has excellent shape precision and suppresses sink marks in the molded product, which is a hardened body of thermosetting resin (Figure 13). Therefore, such plastic elements can be used for optical elements with fine structures on the micro- and nano-order, such as microlens arrays and diffractive optical elements.

<Plastic element manufacturing equipment>
The plastic element manufacturing apparatus of this embodiment is a plastic element manufacturing apparatus that heats and hardens thermosetting resin to which a predetermined pattern has been transferred to form a plastic element, and has a pair of molds, a drive unit that moves at least one of the pair of molds to a position where the thermosetting resin is sandwiched between the pair of molds, and a heating unit that heats the pair of molds to harden the thermosetting resin, and at least one of the pair of molds has a transfer unit that contacts the thermosetting resin to transfer the pattern, and an expansion unit that expands in a compression direction in which the transfer unit compresses the thermosetting resin due to heating, and the amount of expansion of the expansion unit is greater than or equal to the amount of hardening contraction of the thermosetting resin.

Specifically, the manufacturing apparatus for the plastic element of this embodiment can use the manufacturing apparatus 100 that realizes the manufacturing method for the plastic element described above (Figures 1 to 10).

As described above, in the manufacturing apparatus for plastic elements of this embodiment, a high thermal expansion member is used, so that even if the thermosetting resin cures and shrinks during the heating process, a compressive stress is applied in the transfer direction due to the thermal expansion of the upper mold 50 (expansion portion 51). This makes it possible to suppress sink marks in the molded product 92 and improve shape accuracy (Figures 12 and 13).

100 Manufacturing apparatus 10 Upper die plate 20 Lower die plate 30 Temperature control section 31 Heat transfer section 32 Heating section 33 Cooling section 40 Temperature control section 41 Heat transfer section 42 Heating section 43 Cooling section 50 Upper mold 51 Expansion section 52 Transfer section 53 Non-expansion section 60 Lower mold 61 Expansion section 62 Transfer section 63 Spacer section 70 Guide 80 Guide 90 Thermosetting resin 91 Gelled thermosetting resin 92 Solidified thermosetting resin (molded product)
92A: Effective area 92B: Non-effective area

JP 2013-75499 A

Claims (8)

A method for manufacturing a plastic element, comprising the steps of: curing a thermosetting resin onto which a predetermined pattern has been transferred by heating to form a plastic element, the method comprising the steps of:
a step of fixing the pair of molds by sandwiching a thermosetting resin between the pair of molds;
and heating the pair of molds to harden the thermosetting resin.
At least one of the pair of molds is
a transfer unit that contacts the thermosetting resin and transfers the pattern;
an expansion portion that expands in a compression direction in which the transfer portion compresses the thermosetting resin by heating;
A method for manufacturing a plastic element, wherein an amount of expansion of the expansion portion is equal to or greater than an amount of cure contraction of the thermosetting resin. The method for manufacturing a plastic element according to claim 1, wherein the amount of expansion of the transfer portion is smaller than the amount of expansion of the expansion portion. The method for manufacturing a plastic element according to claim 1 or 2, wherein at least one of the pair of molds has a non-expanded portion adjacent to the expanded portion in a direction perpendicular to the compression direction. The method for manufacturing a plastic element according to claim 3, wherein the non-expanding portion is disposed around the expanding portion. The method for manufacturing a plastic element according to any one of claims 1 to 4, wherein a spacer portion is formed between the pair of molds to regulate the distance between the pair of molds. The method for manufacturing a plastic element according to claim 5, wherein the height of the spacer portion in the compression direction is less than the thickness of the thermosetting resin in the compression direction before heating. A plastic element manufactured by the manufacturing method according to any one of claims 1 to 6. A manufacturing apparatus for a plastic element, which molds a plastic element by heating and curing a thermosetting resin to which a predetermined pattern has been transferred, comprising:
A pair of molds;
a drive unit that moves at least one of the pair of molds to a position where the thermosetting resin is sandwiched between the pair of molds;
a heating unit that heats the pair of molds to harden the thermosetting resin,
At least one of the pair of molds is
a transfer unit that contacts the thermosetting resin and transfers the pattern;
an expansion portion that expands in a compression direction in which the transfer portion compresses the thermosetting resin by heating;
An apparatus for manufacturing a plastic element, wherein an amount of expansion of the expansion section is equal to or greater than an amount of cure contraction of the thermosetting resin.

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