WO2009101890A1

WO2009101890A1 - Injection molding method

Info

Publication number: WO2009101890A1
Application number: PCT/JP2009/051942
Authority: WO
Inventors: Kazuma Kurihara; Takashi Nakano; Junji Tominaga; Yuji Saito; Hirohisa Kato; Shogo Makihara; Norito Soma
Original assignee: National Institute Of Advanced Industrial Science And Technology; Itoh Optical Industrial Co., Ltd.; Tokai Seimitsu Industrial Co., Ltd.
Priority date: 2008-02-14
Filing date: 2009-02-05
Publication date: 2009-08-20
Also published as: JP2009190276A; KR20100114041A

Abstract

A molded product of an antireflection nanostructure having an aspect ratio of 1 or above is produced while a high productivity is maintained without using a mold release agent or the like by making it possible to fill a die having a nanostructure of high aspect ratio with resin up to the deep part of the nanostructure. After heating the surfaces of a core (4) on the fixed side and a core (5) on the movable side to a temperature higher than the softening temperature of resin being molded, the core (4) on the fixed side and the core (5) on the movable side are mold-clamped, the core (4) on the fixed side and the core (5) on the movable side are filled with resin following the mold clamping, the pressure of the filling resin is held while the core (4) on the fixed side and the core (5) on the movable side are cooled down to a temperature lower than the softening temperature of the resin, the resin molding is held at a low temperature and then the core (4) on the fixed side and the core (5) on the movable side are mold-opened, thus injection molding a molded product having a structure of nanometer size on the surface thereof.

Description

Injection molding method

The present invention relates to an injection molding method for a molded product such as an optical element or an optical component having a nanometer-sized structure (hereinafter referred to as “nanostructure”) having an aspect ratio of 1 or more and 10 or less.

Conventionally, in an optical element made of glass, resin, or the like, surface treatment is performed in order to reduce return light due to surface reflection and increase transmitted light. As a specific method of this surface treatment, a method of forming a fine and dense uneven shape on the surface of the optical element is known.

When a periodic uneven shape is provided on the surface of the optical element in this way, the light is diffracted when passing through the surface of the optical element, and the linear component of the transmitted light is greatly reduced, but it is formed on the surface of the optical element. When the light transmitted through the concavo-convex pitch is a short concavo-convex shape that is shorter than the wavelength, the light is not diffracted, so effective antireflection for light of a single wavelength corresponding to the pitch, depth, etc. An effect can be obtained.

Furthermore, instead of shortening the concave and convex shape, by forming a so-called cone shape (cone-shaped pattern) in which the volume ratio between the crest and trough, that is, the optical element material side and the air side, changes continuously. It is known that an antireflection effect can be obtained even for light having a wide wavelength range (see, for example, Patent Document 1 and Patent Document 2).

In order to realize such a structure for preventing reflection with respect to a wide wavelength range, it is known that a nanostructure having a fine pattern of a wavelength or less and an aspect ratio of 1 or more is required. .

Therefore, in order to realize these anti-reflection structures at low cost, the structure can be reduced by press molding, injection molding, cast molding, etc., using a mold having a nanostructure with an aspect ratio of 1 or more on the surface. It is expected to be realized at a cost.

Also, as an optical component having a fine structure, there is a high-density optical disk substrate or the like. For example, in a Blu-ray disc, the shortest pit width is 150 nm, and the pit depth at that time is designed to be (λ / 4n to λ / 8n: λ = 405, n = 1.5) for tracking control. It is possible to perform injection molding at a low cost by using a nanostructure having a low aspect ratio of about 0.45 to 0.22 having a nanostructure aspect ratio of about 0.45 to 0.22 that is 67.5 nm to 33.75 nm. (Refer to Patent Document 3 and Patent Document 4).

As described in

Patent Documents

5 and 6, injection molding of a molded product such as an optical disk substrate using a mold having a low aspect ratio nanostructure with an aspect ratio of 0.5 or less, This can be realized by optimizing the resin temperature, optimizing the mold temperature, controlling the release timing by air, and the like (see Patent Document 5 and Patent Document 6).

JP 2001-272505 A JP 2006-243633 A Japanese Patent Laid-Open No. 8-281692 JP 11-31256 A JP-A-8-197593 JP-A-11-45463

As in the conventional example, it has been possible to injection-mold a molded product using a mold having a low aspect ratio nanostructure with an aspect ratio of 0.5 or less (Patent Documents 5 and 6). reference).

However, for an optical element having an antireflection function, in order to obtain an optical characteristic having a low reflectance characteristic and a high transmittance characteristic, molding is performed using a nanostructure mold having an aspect ratio of 1 or more. There is a need.

Therefore, when the optical disk molding method is used for a mold with a high aspect ratio structure, the resin is not sufficiently filled to the deep part of the nanostructure mold with a high aspect ratio, and the molded product has a low aspect ratio nanostructure on the surface. Therefore, there is a problem that good optical characteristics cannot be obtained.

Also, even if transfer of a high aspect ratio structure can be realized, the high aspect ratio structure is filled with resin or the like in detail, so that there is a problem that release is impossible.

Furthermore, even if a resin with a high aspect ratio is filled with resin, it has been developed to release the mold by applying a release agent to the mold surface. There is a problem that the service life of the agent is small and productivity cannot be maintained.

The present invention aims to solve the above problems, and enables filling of the resin up to the deep part of the nanostructure with respect to the mold (fixed side core and movable side core) having a high aspect ratio nanostructure, Furthermore, an object of the present invention is to realize an injection molding method for manufacturing a molded article of an antireflection nanostructure having an aspect ratio of 1 or more while maintaining high productivity without using a release agent or the like.

In order to solve the above problems, the present invention provides a fixed-side core and a movable-side core provided with a nanometer-sized structure on the surface, heating means for heating the surfaces of the fixed-side core and the movable-side core, and the fixed-side An injection molding method for molding a molded product having a nanometer-sized structure on the surface using an injection molding apparatus comprising a core and a cooling means for cooling the movable core, wherein the fixed core and the movable core The surface of the mold is heated to a temperature higher than the softening temperature of the resin to be molded, and then the fixed side core and the movable side core are clamped, and after the mold clamping, the resin is placed in the fixed side core and the movable side core. After filling, holding the filled resin while cooling the fixed side core and the movable side core to a temperature lower than the softening temperature of the resin, holding the resin molded product cooled at the low temperature, The fixed core and the movable core The mold is opened to provide an injection molding method of the molded article having a structure of nanometer size on a surface characterized by.

The temperature higher than the softening temperature of the resin is preferably lower than the decomposition temperature of the resin.

The temperature lower than the softening temperature of the resin is preferably 60 ° C. lower than the softening temperature of the resin.

The average pitch of the nanometer-sized structures formed on the surfaces of the fixed core and the movable core is 30 nm to 1000 nm, and the aspect ratio is preferably 1 or more.

The injection molding method according to the present invention has the following effects.
(1) The surfaces of the fixed core and the movable core are heated to a temperature higher than the softening temperature of the resin to be molded, the fixed core and the movable core are clamped, filled with resin, and fixed after filling. Holding the filled resin while cooling the side core and the movable side core to a temperature lower than the softening temperature of the resin, holding the resin molded product in a cooled state, and then opening the mold, the filling rate and releasability are improved, It is possible to mold a molded product having a nanostructure with an aspect ratio of 1 or more on the surface and having good optical characteristics.

(2) In this injection molding method, the fixed side mold and the movable side mold are partially made of a material having a lower thermal conductivity than the metal material forming the fixed side mold and the movable side mold (low thermal conductivity material). ), The heat capacity of the surface side of the fixed side core and the surface side of the movable side core can be reduced, and when heat energy is applied, the surface side of the fixed side core and The surface of the movable core can be heated at a high speed, and molding can be performed in a short time. Thereby, a shaping | molding cycle can be shortened and productivity of shaping | molding of an optical element, an optical component, etc. which were equipped with the nanostructure on the surface can be improved.

(3) By using a fixed-side core and a movable-side core with nanometer-sized structures on the surface as nanostructure molds, optical elements, optical components, etc. that have low reflectivity and good optical properties can be obtained. Can be molded.

(4) Therefore, a nanostructure that imparts a high-precision antireflection function even on a large area, curved surface, and micrometer-sized uneven surface can be formed in a high molding cycle (one molding cycle can be shortened). Meaning that it is possible to repeatedly perform a number of molding cycles in a certain time.), And is extremely useful for an optical element having an antireflection structure and an injection molding method of an optical component.

It is a figure which shows the structure of the injection molding apparatus for enforcing the injection molding method which concerns on this invention, (a) provides a heating means inside a metal mold | die, and provides a cooling means (cooling medium flow path) in the back surface of a core. (B) shows the structure which provided the heating means in the metal mold | die surface, and provided the cooling means (cooling medium flow path) in the back surface of the core. It is a figure which shows another structural example of the injection molding apparatus for enforcing the injection molding method which concerns on this invention, (a) provides a heating means inside a metal mold | die, a cooling means (cooling medium) also around a cavity (B) shows a configuration in which heating means is provided on the mold surface, and cooling means (cooling medium passage) is also provided around the cavity. It is a flowchart which shows the series of process of the injection molding method which concerns on this invention, and shows the mold temperature of the core surface. It is a figure explaining a series of processes of the injection molding method concerning the present invention. It is a figure which shows the mold temperature of the core surface by having employ | adopted the injection molding method which concerns on this invention, and the filling rate of a molded article. It is a table | surface which shows the external appearance test result of the molded article obtained by the injection molding method which concerns on this invention. It is a table | surface which shows the temperature rising time by the injection molding method which concerns on this invention. It is a figure which shows the antireflection effect of the nanostructure of the optical element obtained by the injection molding method which concerns on this invention. It is sectional drawing of the injection molding apparatus for demonstrating the structure of the cooling means (cooling medium channel | path) provided in the circumference | surroundings of the cavity shown in FIG.2 (b), (a) is a vertical cross section, (b) is horizontal. It is a figure which shows a cross section, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resin introduction path 2 Fixed side base metal mold 3 Movable side base metal mold 4 Fixed side core 5 Movable side core 6 Fixed side core surface (nanostructure)
7 Movable core surface (nanostructure)
8, 9 Cooling

medium flow path

10, 11 Extrusion pin 12 Vacuum discharge path 13 in the cavity 13 Reflecting mirror
14 Cavity 15A Heating means (when installed inside the base)
15B Heating means (when installed on the base surface)
16 Cooling medium introduction port 17 Cooling medium discharge port 20 Injection molding device 21 Fixed side mold (consisting of a fixed side core and a fixed side base mold group)
22 Movable mold (consisting of movable core and movable base mold group)
23 Fixed-side base mold group (consisting of multiple fixed-side base molds)
24 Movable base mold group (consisting of a plurality of movable base molds 25 Cooling medium passage

The best mode for carrying out the injection molding method according to the present invention will be described below with reference to the drawings based on the embodiments.

1 and 2 show an injection molding apparatus 20 used in an injection molding method according to the present invention. The injection molding apparatus 20 includes a fixed-side mold 21 and a movable-side mold 22 that are a pair facing each other. The fixed-side mold 21 and the movable-side mold 22 include a fixed-side core 4 and a movable-side core 5, and further, a fixed-side base mold so as to surround the fixed-side core 4 and the movable-side core 5 from around. A group 23 and a movable base mold group 24 are provided.

In the example shown in FIGS. 1A, 1B, 2A, and 2B, two pairs of the fixed core 4 and the movable core 5 are provided, but one pair or a plurality of pairs are provided. Nanostructures are formed on the surface 6 of the fixed core 4 and the surface of the movable core 5 facing each other.

This nanostructure has an irregular surface configuration with an aspect ratio of 1 or more, and the surface of the resin filled between the fixed core 4 and the movable core 5 is molded, and the aspect ratio is 1 or more. It forms a molded article such as an optical element or optical component having an uneven surface of nanostructure. The average pitch of such nanostructures is 30 nm to 1000 nm.

The fixed-side base mold group 23 includes one or a plurality of fixed-side base molds 2, and a resin introduction path 1 is formed in the fixed-side base mold 2. The movable side base mold group 24 includes one or a plurality of movable side base molds 2.

The movable base mold 3 is formed with a cavity 14 communicating with the resin introduction path 1 and the molding space of the fixed core 4 and the movable core 5. The cavity 14 may be provided not in the movable side base mold 3 but in the fixed side base mold 2, or may be provided in both the fixed side base mold 2 and the movable side base mold 3.

An in-cavity vacuum exhaust passage 12 communicating with the cavity 14 is formed in the movable-side base mold 3. The cavity 14 may be provided in the fixed base mold 2.

Extrusion pins 10 and 11 are provided so that the front end faces the surface of the fixed core 4 so as to be able to slide through the movable base mold 3 and the movable core 5. The projecting pins 10 and 11 are used by abutting against the stationary core 4 when the stationary mold 21 and the movable mold 22 are opened.

The fixed-side base mold group 23 and the movable-side mold group 22 are provided with heating means 15A and 15B, temperature sensors and cooling means 8 and 9, respectively. The heating means 15A and 15B heat the surfaces of the fixed side core 4 and the movable side core 5, and the temperature sensor measures the temperature of the surfaces of the fixed side core 4 and the movable side core 5, and the cooling means. 8 and 9 cool the fixed core 4 and the movable core 5.

As shown in FIGS. 1A and 2A, the heating means 15A and 15B have heaters such as heaters embedded in the fixed base mold 2 and the movable base mold 3, respectively. It is good also as a structure.

Alternatively, as shown in FIGS. 1B and 2B, the heating means 15A and 15B are formed on the surfaces of the fixed-side base mold 2 and the movable-side base mold 3, for example, infrared rays, electromagnetic waves, laser beams, etc. The heater may be embedded.

In the configuration in which heaters such as infrared rays, electromagnetic waves, and laser beams are provided as the heating means 15A and 15B, when the fixed-side mold 21 and the movable-side mold 22 face each other and perform the clamping operation, the opposed fixed-side molds face each other. 21 and the movable mold 22 approach each other. Then, multiple reflections such as infrared rays, electromagnetic waves, and laser beams occur between the fixed mold 21 and the movable mold 22, and the

surfaces

6 and 7 of the fixed core 4 and the movable core 5 are uniformly and efficiently heated. This produces an effect (see FIG. 4B).

In addition, for example, when the reflecting mirror 13 is provided around the heater using infrared rays in the heating means 15A and 15B, the heating effect is further increased. The reflecting mirror 13 has a substantially V-shaped cross-section and is embedded so as to be in contact with the recesses of the substantially V-shaped cross sections of the fixed-side base mold 2 and the movable-side base mold 3.

The fixed mold 21 and the movable mold 22 are partially embedded with a material having a lower thermal conductivity (low thermal conductivity material) than the metal material forming the fixed mold 21 and the movable mold 22. Yes. Specifically, a low thermal conductivity material is partially embedded in all or any of the fixed side base mold 2, the movable side base mold 3, the fixed side core 4, and the movable side core 5. The heat capacities of the fixed core 4 and the movable core 5 are reduced, and between the fixed base mold 2 and the fixed core 4 and between the movable base mold 3 and the movable core 5. In this configuration, a low thermal conductivity material is embedded to prevent heat dissipation from the fixed side core 4 and the movable side core 5 due to heat conduction. In particular, the low thermal conductivity material is embedded in the fixed base mold 2 and the movable base mold 3 so that the fixed core 4 and the movable core 5 are surrounded by the embedded low thermal conductivity material. Is preferred.

Thereby, compared with the case where the low thermal conductivity material is not embedded, the heat capacities of the fixed side core 4 and the movable side core 5 are reduced, and further, between the fixed side base mold 2 and the fixed side core 4, and By embedding a low thermal conductivity material between the movable base mold 3 and the movable core 5, heat conduction (dissipation) to the outside of the fixed core 4 and the movable core 5 is reduced. That is, the fixed-side core 4 and the movable-side core 5 have a low heat capacity due to the low thermal conductivity material embedded in them, and the fixed-side base mold 2 and the movable-side base mold 3 are embedded in them. The heat capacity is reduced by the low thermal conductivity material, and heat conduction (dissipation) from the fixed core 4 and the movable core 5 can be suppressed.

Therefore, the fixed side core 4 and the movable side core 5 having nanostructures on their surfaces are embedded with a low thermal conductivity material in themselves, so that the volume of the original material portion of the fixed side core 4 and the movable side core 5 is reduced. Since the heat capacity is reduced because it becomes smaller, the fixed base mold 2 and the movable base mold 3 are similarly reduced in volume and heat capacity due to the low thermal conductivity material embedded in them. Since the low thermal conductivity material is embedded between the side base mold 2 and the fixed side core 4 and between the movable side base mold 3 and the movable side core 5, the fixed side core 4 and the movable side core Since the loss due to heat conduction (dissipation) from 5 to the fixed base mold 2 and the movable base mold 3 side is reduced, the fixed core 4 and the movable core 5 eventually gave the same thermal energy. Place A, can be heated to a high speed, I am possible to short molding.

Here, the low thermal conductivity material is a material having a lower thermal conductivity than the metal material forming the fixed side core, the movable side core, the fixed side base mold, and the movable side base mold. Materials, organic materials, etc. are effective. Specifically, glass, quartz, alumina, forsterite, zirconia, zircon, mullite, cordierite, silicon nitride, silicon carbide and the like are effective.

As shown in FIGS. 1 (a), 1 (b), 2 (a), and 2 (b), the cooling means includes a back surface of the fixed side core 4 and the movable side core 5 (surfaces on which the fixed side and the movable side face each other). The cooling medium flow paths 8 and 9 are formed on the opposite surface), and the cooling medium flow is circulated through the cooling medium flow paths 8 and 9 by a pump provided outside. . As the cooling medium, water, alcohol, or a gas such as carbon dioxide, air, or nitrogen is useful.

As described above, the cooling means flows the cooling medium flow paths 8 and 9 formed on the back surfaces of the fixed side core 4 and the movable side core 5 to cool the molded product in which the nanostructure is formed. Since the surface portion can be rapidly cooled, a short molding cycle can be realized. As the cooling medium, water, alcohol, or a gas such as carbon dioxide, air, or nitrogen is useful.

As described above, the fixed mold 21 and the movable mold 22 are partially made of a material having a lower thermal conductivity (low thermal conductivity material) than the metal material forming the fixed mold 21 and the movable mold 22. Is embedded. Specifically, all of the fixed-side base mold 2, the movable-side base mold 3, the fixed-side core 4 and the movable-side core 5 configured in the fixed-side mold 21 and the movable-side mold 22 or the For any of these, the low thermal conductivity material is embedded so as to surround the fixed side core 4 and the movable side core 5 partially or with a low thermal conductivity material, and is configured to prevent dissipation due to thermal conduction. In particular, when the low thermal conductivity material is embedded in the fixed side core 4 and the movable side core 5, the overall heat capacity is smaller than when the low thermal conductivity material is not embedded.

In particular, when the heat capacities on the surface 6 side of the fixed side core 4 and the surface 7 side of the movable side core 5 are reduced, the surface 6 side of the fixed side core 4 and the surface 7 of the movable side core 5 are absorbed when the same heat energy is absorbed. Cooling at high speed enables molding in a short time. Similarly to the heating means, the cooling means can be cooled at a high speed and can be molded in a short time when the same thermal energy is applied.

As shown in FIGS. 2A and 2B and FIGS. 9A and 9B, the cooling means includes cooling medium flow paths 8 and 9 formed on the back surfaces of the fixed side core 4 and the movable side core 5, respectively. In addition to the configuration in which the cooling medium is provided, a configuration in which a cooling medium is allowed to flow toward the periphery of the cavity 14 may be added. That is, as shown in FIGS. 9A and 9B, the cooling medium may be introduced into the cooling medium passage 25 from the cooling medium introduction port 16 and discharged from the cooling medium discharge port 17 through the cooling medium passage 25. .

Here, the cooling medium passage 25 is disposed around the cavity 14, so that the cooling medium flows around the cavity 14. In addition, a wall of about 10 μm to 500 μm is formed between the cavity 14 and the cooling medium passage 25. By cooling the resin filled through the wall, high-speed cooling is possible.

(Molding method)
According to the injection molding method of the present invention using the above-described injection molding apparatus, it is possible to mold a molded product such as an optical element or an optical component having a nanostructure with an aspect ratio of 1 or more on the surface in a short time. Hereinafter, this injection molding method will be described with reference to a flow chart showing a series of steps of the injection molding method shown in FIGS. 4 and 3 and a mold temperature on the core surface.

Charging process (preparation process):
When molding, first, before the clamping of the fixed side mold 21 and the movable side mold 22 facing each other, the mold temperatures of the surfaces of the fixed side core 4 and the movable side core 5 are set by heating means. The temperature is raised to a temperature T1 that is higher than the softening temperature and lower than the decomposition temperature of the resin.

Then, in a state where the fixed side core 4 and the movable side core 5 are set at the temperature T1, the fixed side mold 21 and the movable side mold 22 are clamped (of course, the molds of the fixed side core 4 and the movable side core 5). To complete.)

Injection process:
After completing the mold clamping, the resin is filled from the resin introduction path 1 through the cavity 14. Here, conventionally, since the temperature of the fixed base mold 2 and the movable base mold 3 is set to a temperature lower than the softening temperature of the resin, the fixed base mold is set at a temperature higher than the softening temperature of the resin. Even when injected into the fixed core 4 and the movable core 5 from the cavity 14 of the mold 2, the resin is cooled, the viscosity of the resin increases in relation to the flow length and flow velocity, and a solidified layer is formed on the surface. Fill while forming.

Here, when the molding is performed by the conventional means, the solidified layer on the resin surface is caused, the nanostructure is insufficiently filled with respect to the fixed core 4 and the movable core 5 formed on the surface, and when the aspect ratio becomes 1 or more, the nanostructure is formed. Insufficient transfer of the structure (molded product that is not sufficiently filled in the irregularities of the nanostructure and does not correspond precisely to the irregularities of the nanostructure) occurs.

Therefore, in the present invention, the surface temperatures of the fixed core 4 and the movable core 5 are set to a temperature T1 that is higher than the softening temperature of the resin and lower than the temperature at which the resin is decomposed, and the filling speed is 30 mm / s or less. As a result, the resin is not cooled to a temperature lower than the softening temperature, and formation of a solidified layer can be prevented.

Furthermore, by setting the filling speed to 30 mm / s or less, it becomes possible to suppress the influence of the stay gas due to the nanostructure of the fixed side core 4 and the movable side core 5. Specifically, when the resin is filled at a speed of 30 mm / s or more, the resin has a large force in the flow rate direction. When the resin flows on the surface of the core having a nanostructure formed on the surface, the resin does not fill the details of the nanostructure, and the resin flows only near the top of the nanostructure.

Therefore, when molding is performed using the fixed core 4 and the movable core 5 having a nanostructure, the bottom of the nanostructure is capped with a filled resin, and residual gas accumulates. Therefore, the residual gas capped with the resin is affected, and the filling rate of the resin into the nanostructure is low. However, when filling at a filling speed of 30 mm / s or less, as the filling speed becomes slower, the force in the flow direction decreases, and the resin flows in the direction of divergence from the flow direction.

Therefore, when molding is performed using the stationary core 4 and the movable core 5 having a nanostructure, the bottom and top of the nanostructure are uniformly filled. It is discharged out of the tee 14. Therefore, the influence of the gas remaining in the nanostructure is reduced, so that the nanostructure having an aspect ratio of 1 or more can be sufficiently filled. Therefore, since filling of a molded product having a nanostructure having a high aspect ratio can be realized, a molded product having good optical characteristics can be realized.

Cooling process:
After the resin is filled, the fixed core 4 and the movable core 5 are kept in the mold-clamped state, and the resin is cooled to a temperature T2 lower than the softening temperature of the resin while maintaining the filling pressure to the resin (holding pressure). Cool the molded resin product.

Here, in the conventional molding process, the mold temperature is constant, and when the nanostructure has a high aspect ratio structure, a liquid or monomolecular release film is applied to the surfaces of the fixed core 4 and the movable core 5. Otherwise, it cannot be released.

However, in the injection molding method according to the present invention, the surface temperature of the fixed core 4 and the movable core 5 can be heated and cooled during molding, so that the surface portion of the molded product with the nanostructure formed on the surface can be obtained. Since the shrinkage of the resin can be made larger than usual, it is possible to easily release the nanostructure having an aspect ratio of 1 or more.

Mold opening process:
Finally, after the fixed side core 4 and the movable side core 5 are cooled, the protruding pins 10 and 11 are abutted against the fixed side core 4 to open the fixed side mold 21 and the movable side mold 22, and the aspect A molded product in which a nanostructure having a ratio of 1 or more is formed is taken out.

As described above, the fixed-side mold 21 and the movable-side mold 22 are partially made of a material having a lower thermal conductivity (low thermal conductivity material) than the metal material forming the fixed-side mold 21 and the movable-side mold 22. (For example, embedded).

Specifically, all of the fixed-side base mold 2, the movable-side base mold 3, the fixed-side core 4 and the movable-side core 5 configured in the fixed-side mold 21 and the movable-side mold 22 or the In either case, the low thermal conductivity material is embedded so as to surround the fixed side core 4 and the movable side core 5 partially or with a low thermal conductivity material, and is configured to prevent dissipation due to thermal conduction, and fixed When the low thermal conductivity material is embedded in the side core 4 and the movable side core 5, the overall heat capacity is smaller than when the low thermal conductivity material is not embedded.

Embodiments of the injection molding method according to the present invention will be described. In this example, the aspect ratio is 1 or more according to a series of molding steps shown in FIG. 4 using the fixed side core 4 and the movable side core 5 having nanostructures with an aspect ratio of 1 or more and 10 or less on the surface. Create a molded product of optical elements with nanostructures on the surface.

In this embodiment, the fixed core 4 and the movable core 5 are nanostructures having an aspect ratio of 1.5, and the pitch of the nanostructures is about 100 nm and the depth is about 200 nm. Table 1 shows typical molding conditions in the injection molding method according to the present invention. The resin used for the injection molding is Acrypet Grade VH (hereinafter referred to as “Acrypet VH”), a product manufactured by Mitsubishi Rayon. Table 1 shows the molding conditions.

The heating and cooling of the mold temperature (referred to as “the mold temperature of the core surface”) on the surfaces of the fixed core 4 and the movable core 5 to be heated and cooled in the molding step are as shown in the flow diagram of FIG. To do. In the injection molding method according to the present invention, as shown in FIG. 3, the core surface is heated to a set temperature T1 before filling with resin, and then the base mold is clamped.

And after the mold clamping is completed, the resin is filled. Thereafter, the mold clamping state is maintained, the filled resin is held (meaning to maintain the pressure with respect to the filled resin), and the fixed core 4 and the movable core 5 are set to a predetermined temperature lower than the softening temperature of the resin. While cooling to temperature T2, this temperature is maintained and the formed resin molded product is cooled. After such a resin molded product is cooled, the mold is opened and the molded product is taken out.

Specifically, since the softening temperature of the Acripet VH is approximately 107 ° C., the temperature of the fixed base mold 2 and the movable base mold 3 is set to 95 ° C., which is a normal molding condition.

Then, as shown in the flowchart of FIG. 3, the resin is filled after the surface temperature of the fixed core 4 and the movable core 5 before filling the resin is raised to a softening temperature of 107 ° C. or higher. Next, after filling the resin, the surface temperatures of the fixed core 4 and the movable core 5 are cooled to a predetermined temperature lower than the softening temperature 107 ° C. of the resin.

Finally, open the mold and take out the molded product.

The present inventor empirically implements the embodiment described above, and the effects of the temperature conditions of the fixed core 4 and the movable core 5 on the transfer characteristics (referring to the state of the filling rate) are described below. We examined as follows.

FIG. 5 shows a graph of the surface temperature of the fixed core 4 and the movable core 5 (“mold temperature of the core surface” in FIG. 5) and the filling rate (also referred to as “transfer rate”). Here, the filling rate refers to the rate at which the resin fills the uneven space in the nanostructure.

Referring to FIG. 5, it can be seen that when the resin temperature to be injected is 250 ° C., the filling rate is improved by the increase of the mold temperature on the core surface, which is improved. Furthermore, when the mold temperature on the core surface is set to a temperature higher than the softening temperature of the resin, the filling rate is rapidly improved.

That is, by setting the mold temperature on the core surface to a temperature higher than the softening temperature of the resin, it is possible to prevent the formation of a solidified layer of the resin, so that the resin temperature, molding pressure (pressure applied to the resin after filling), etc. It was confirmed that the filling rate can be dramatically improved by maintaining the pressure without increasing the pressure. As a result of examining the optimum transfer temperature range, the filling rate increased from the softening temperature of the resin to around + 30 ° C., and good transfer characteristics were exhibited.

In addition, the case where the resin was changed from acrylic to polycarbonate, arton, ZEONEX as the molding material was examined. At this time, polycarbonate is Iupil, grade H-3000R (all trade name) manufactured by Mitsubishi Engineering Plastics, Arton is (trade name) JSR Corporation, ZEONEX is ZEONEX, grade 330R (manufactured by ZEON Japan) The product name) was examined, and it was confirmed that there was an effect similar to that of acrylic.

Next, the mold-clamping state of the core surface is set higher than the softening temperature of the resin while maintaining the mold-clamping state of the fixed core 4 and the movable core 5 and holding (holding pressure) the filling pressure to the resin. When the temperature is set lower than the decomposition temperature and the resin is filled and then cooled to a predetermined temperature lower than the softening temperature of the resin, the mold temperature on the core surface is lower than the softening temperature of the resin (normal molding) FIG. 6 shows the appearance inspection result of the molded product when it is set to “Condition” and cooled after filling with resin.

FIG. 6 shows the results when using Acrypet VH (softening temperature is approximately 107 ° C.). From FIG. 6, when the mold temperature on the core surface before resin filling is lower than the softening temperature of the resin, the nanostructure is 40 ° C. or higher (in this case, “resin softening temperature−67 ° C.”). Although the resin shrinkage of the portion was small, it was impossible to release the mold, but it was confirmed that the mold could be released at a temperature lower than 40 ° C. Eventually, it was confirmed that the cooling temperature is preferably 67 ° C. lower than the softening temperature of the resin.

However, when the area is large, some defects occur due to insufficient release. On the other hand, if the mold temperature on the core surface is set to a temperature higher than the softening temperature of the resin before filling the resin and the core surface is cooled after filling the resin, the shrinkage of the resin in the nanostructure portion increases. It was confirmed that good release characteristics were obtained.

This also indicates that the core surface mold temperature is set to a temperature higher than the softening temperature of the resin, the resin is filled, and then cooled to a temperature lower than the softening temperature of the resin. In the present invention for taking out, it was confirmed that the present invention is useful as an injection molding method of a high aspect ratio nanostructure having an aspect ratio of 1 or more.

Further, according to the injection molding method according to the present invention, as a result of molding a higher nanostructure, it was confirmed that good molding characteristics were obtained in molding up to an aspect ratio of 10.

(Heating, cooling means, etc.)
The above embodiments of the injection molding method according to the present invention will be described below mainly from the viewpoint of the influence of the configuration of the heating and cooling means of the injection molding apparatus on the injection molding method according to the present invention.

In order to effectively perform the injection molding method according to the present invention, the heating means is important. In the present invention, as the heating means 15A and 15B, as shown in FIGS. 1B and 2B, the surfaces of the fixed base mold 2 and the movable base mold 3 that face the infrared lamp main body, respectively. It was set as the structure embedded in.

By adopting such a configuration, the multiple reflection between the fixed mold 21 and the movable mold 22 occurs when the fixed mold 21 and the movable mold 22 facing each other approach each other during the mold clamping operation. Thus, the surfaces of the fixed side core 4 and the movable side core 5 can be heated from room temperature to 120 ° C., which is higher than the softening temperature of the resin.

In such a temperature rise due to multiple reflection between the fixed side mold 21 and the movable side mold 22 between the molds, the temperature of the surface of the core is 120 ° C. which is higher than the softening temperature of the resin from room temperature in 10 seconds. It was confirmed that the temperature could be increased up to (see the fourth column from the top of the heating modes in the table of FIG. 7). Therefore, it has been confirmed that the use of such a heating means is effective in performing high-throughput cycle molding.

Modification 1 will be described as another embodiment of the heating means 15A and 15B. As shown in FIGS. 1 (a) and 2 (a), this modification 1 has a configuration in which a heater is provided inside the fixed side base mold 2 and the movable side base mold 3, and the heater is There is a configuration in which a heater (electric heating rod heater) is embedded. By such heating means, the mold temperature on the core surface was raised from room temperature to 120 ° C., which is higher than the softening temperature of the resin.

According to this heating means, the arrival time up to 120 ° C. is 5 minutes as described above, and the temperature of the entire fixed side core 4 and the movable side core 5 with the nanostructures formed on the surface is increased. The time required to reach the mold temperature distribution on the core surface was 6 minutes (see the first column from the top in the heating format in the table of FIG. 7).

Modification 2 will be described as another embodiment of the heating means 15A and 15B. As shown in FIGS. 1 (a) and 2 (a), this modification 2 has a configuration in which a heater is provided inside the fixed side base mold 2 and the movable side base mold 3, and the heater is an infrared ray. There is a configuration in which a lamp is embedded. With this heating means, the mold temperature on the core surface was raised from room temperature to 120 ° C., which is higher than the softening temperature of the resin.

According to this heating means, a rapid temperature increase is possible as compared with a heating means using a heater, and the time required to reach a uniform mold temperature distribution on the core surface as a whole is about 1 minute 30 seconds. (Refer to the second column from the top among the heating modes in the table of FIG. 7).

Further, as another embodiment of the heating means 15A and 15B, Modification 3 will be described. In the third modification, although not shown, an infrared lamp is disposed on the side of the fixed mold 21 and the movable mold 22 and heated from the side surfaces of the fixed base mold 2 and the movable base mold 3. The surface of the fixed side core 4 and the movable side core 5 was heated from room temperature to 120 ° C., which is higher than the softening temperature of the resin. According to this heating means, the time required to reach a uniform core surface mold temperature distribution was about 1 minute 30 seconds (see the third column from the top of the heating formats in the table of FIG. 7). ).

The four heating means described above, that is, the configuration in which the infrared lamp main body is embedded in the respective surfaces of the fixed base mold 2 and the movable base mold 3 facing each other, and the heating means of the first to third modifications, Any of them can be applied as a heating means in the present invention. The structure in which the infrared lamp body is embedded in the surfaces of the fixed base mold 2 and the movable base mold 3 facing each other, as shown in the table of FIG. It is particularly suitable as a means for realizing a high-throughput cycle.

As described above, the cooling means flows the cooling medium flow paths 8 and 9 formed on the back surfaces of the fixed side core 4 and the movable side core 5 to cool the molded product in which the nanostructure is formed. It was confirmed that the surface portion can be rapidly cooled and a short molding cycle can be realized.

As the cooling medium, water, alcohol, carbon dioxide, air, nitrogen and other gases were examined and confirmed to be useful in any case.

Further, when the cooling medium flow path 8 or 9 is formed on the back surface of the fixed side core 4 and the movable side core 5 as the cooling means as in the present invention, the fixed side base mold 2 and the movable side base mold are used. It was found that the surface portions of the fixed-side core 4 and the movable-side core 5 can be cooled approximately five times faster than when a configuration in which a flow path for cooling is formed inside 3 is adopted.

Furthermore, as described above, the fixed-side mold 21 and the movable-side mold 22 are partially made of a material having a lower thermal conductivity (low thermal conductivity) than the metal material forming the fixed-side mold 21 and the movable-side mold 22. Material) is embedded. Specifically, all of the fixed-side base mold 2, the movable-side base mold 3, the fixed-side core 4 and the movable-side core 5 configured in the fixed-side mold 21 and the movable-side mold 22 or the In either case, the low thermal conductivity material is embedded so as to surround the fixed side core 4 and the movable side core 5 partially or with a low thermal conductivity material, and is configured to prevent dissipation due to thermal conduction, and fixed When the low thermal conductivity material is embedded in the side core 4 and the movable side core 5, the overall heat capacity is smaller than when the low thermal conductivity material is not embedded.

In particular, if the heat capacities on the surface 6 side of the fixed-side core 4 and the surface 7 side of the movable-side core 5 are small, when the same thermal energy is absorbed, the surface 6 side of the fixed-side core 4 and the surface of the movable-side core 5 7 Cooling at high speed enables molding in a short time. Similarly to the heating means, the cooling means can be cooled at a high speed and can be molded in a short time when the same thermal energy is applied.

By the injection molding method according to the present invention described above, a molded product having a high aspect ratio nanostructure and good optical characteristics can be molded. FIG. 8 shows optical characteristics of an antireflection structure, which is an optical element having a nanostructure, obtained by the conventional injection molding method and the injection molding method of the present invention.

It is generally known that the anti-reflection effect due to the nanostructure is such that the higher the aspect ratio structure, the lower the reflectivity. As shown in FIG. 8, according to the molding method of the present invention, the filling rate and releasability of the nanostructures are improved, and a molded product having a high aspect ratio structure can be produced, which is better than the conventional molding method. A good antireflection effect could be obtained.

The best mode for carrying out the injection molding method according to the present invention has been described based on the embodiments. However, the present invention is not limited to such embodiments, and is described in the claims. It goes without saying that there are various embodiments within the scope of technical matters.

If the injection molding method according to the present invention is used, a highly accurate optical element such as an antireflection structure, an optical component, etc. can be formed even on a large surface and a curved surface, so that an antireflection effect is required. It can be widely applied to optical elements such as lenses, prisms, mirrors, and lens barrels, optical components, and the like.

Therefore, the injection molding method according to the present invention includes an optical pickup optical system of an optical reproduction recording apparatus in which these optical elements are used, a photographing optical system such as a digital still camera, a projection system and an illumination system of a projector, an optical scanning optical system, It is suitable for manufacturing fields such as displays, panels, IU filters, and LEDs.

Claims

A fixed-side core and a movable-side core provided with a nanometer-sized structure on the surface; heating means for heating the surfaces of the fixed-side core and the movable-side core; and cooling means for cooling the fixed-side core and the movable-side core; An injection molding method for molding a molded product having a nanometer-sized structure on the surface using an injection molding apparatus comprising:
After heating the surfaces of the fixed core and the movable core to a temperature higher than the softening temperature of the resin to be molded, the fixed core and the movable core are clamped,
After the mold clamping, the fixed side core and the movable side core are filled with resin,
After the filling, the filled resin is held while cooling the fixed side core and the movable side core to a temperature lower than the softening temperature of the resin, the resin molded product is cooled and held at the low temperature, and then the fixed side An injection molding method for a molded article having a nanometer-sized structure on the surface, wherein the core and the movable core are opened.
The method for injection molding of a molded product according to claim 1, wherein the temperature higher than the softening temperature of the resin is lower than the decomposition temperature of the resin.
The method for injection molding of a molded product according to claim 1, wherein the temperature lower than the softening temperature of the resin is 67 ° C lower than the softening temperature of the resin.
The injection molding method according to claim 1, wherein an average pitch of the nanometer-sized structures formed on the surfaces of the fixed side core and the movable side core is 30 nm to 1000 nm and an aspect ratio is 1 or more.