WO2001039960A1 - Plastic molding and stamper used therefor - Google Patents

Abstract

Plastic molding, wherein a base material provided with a transfer surface and consisting of a plastic material is provided, the base material is fixed with the transfer surface exposed, the shaping surface of a stamper consisting at at least a part thereof of an infrared transmitting material is kept in close contact with the transfer surface of the base material, and an infrared beam is applied to the stamper in a base material orienting direction. At least main body portion excluding the shaping surface of the stamper is formed of an infrared transmitting material.

Description

 Description Plastic molding process and stamper used for it

 The present invention relates to a plastic molding method, and more particularly, to an improvement in a technique for producing a molded article made of a plastic material such as a component for precision equipment, a storage medium for electronic equipment and a lens for optical equipment, and a method for manufacturing the same. The present invention relates to a molding stamper used.

 In this specification, the “transfer surface” refers to a surface portion on a substrate to be subjected to an intended molding process. For example, a pit of a substrate used for manufacturing a CD-ROM which is a storage medium for electronic equipment is used. It refers to the surface to be formed and the surface used for manufacturing precision lenses.

 The “imprinted surface” refers to the surface on the stamper where the desired molding process is to be performed on the transfer surface of the substrate.

 In addition, the “shape element” refers to a protruding piece existing on the shape face, for example, corresponding to a bit of CD-ROM,

 In plastic molding, the plastic material is melt-plasticized, filled at high temperature into the mold cavities (with pre-installed stanbars) at high speed and high pressure by an injection molding machine, and then cooled and solidified. A molded product with the following shape is obtained. This technology is widely used in the industry because of its higher productivity than press molding.

However, during this injection molding, the plastic material is a viscoelastic substance, and the flow and cooling of the plastic material occur simultaneously in parallel. 9 and plastic materials have low thermal conductivity and uneven cooling, resulting in unavoidable stresses and strains in the part:外部 External structural defects such as sinks are likely to occur;

 Other external structural inconveniences include defects such as short shots (poor injection) and weld lines (poor fusion) resulting from the above defects:

 In addition, in the vicinity of the mold wall on the side opposite to the injection port in the cavity, the high-temperature plastic material suddenly comes into contact with the low-temperature mold wall, so that its viscosity increases and the transferability (the ability to follow the mold shape) decreases. Therefore, when the molded product is a storage medium for electronic equipment having a portion in which a large number of fine grooves or projections are juxtaposed, for example, there is a problem that the intended groove or projection structure cannot be obtained precisely. is there.

In addition, near the mold wall, similar high and low temperature contact causes a layer of different viscosity in the plastic material, which generates a shearing force, and the polymer of the plastic material forms a highly oriented (orientation) layer. You. As a result local change in birefringence and refractive index occurs, get an Hen'ayaginu optical characteristics: _c for this reason the molded article is an internal structural problems when used like a lens for an optical instrument

 To avoid these external and internal structural inconveniences inherent in injection molding, solutions such as reducing the cooling rate, increasing the plastic material temperature, and increasing the injection pressure by increasing the molding pressure, etc. Some measures can be considered:

As a specific method of reducing the cooling rate, there are methods such as gradually cooling the plastic material or raising the temperature of the molding die. However, with these methods, a large number of molded products can be produced in a shorter time than in press working. There are some basic disadvantages that impair high productivity, which is the biggest advantage of injection molding technology that can be done:

 In addition, according to the results of the research by the present inventors, it was apparent that the method of raising the temperature of the plastic material could not be expected to have any substantial effect:

 Even with the method of increasing the molding pressure, according to the results of the present inventors' research, it has become clear that no substantial effect can be expected yet. Further, a fundamental problem is that in the case of injection molding, Can be quite high pressure (sometimes several tonnes), and the equipment must be large in order to withstand it. It is difficult to produce customized products at the distribution end of unformed articles, for example, at CD retailers.

 In view of the current state of the prior art, the basic object of the present invention is to maintain high productivity such as injection molding, improve the transferability of plastic materials, and also achieve uniform physical properties (eg, optical To provide a molded article having the following characteristics.

 It is another object of the present invention to reduce the size of the apparatus and make it possible to produce on demand at the distribution end of a molded article. Disclosure of the invention

 For this reason, in the first technical idea of the present invention, a base material having a transfer surface and made of a plastic material is prepared, and the base material is fixed in a state where the transfer surface is exposed. The aim is to hold the imprinting surface of the stan-hae made of a material in close contact with the transfer surface of the substrate, and to irradiate the stern bar with infrared rays in the direction toward the substrate.

As a result of absorbing the energy from infrared irradiation, plastic near the transfer surface The temperature of the packing material rises and its viscosity decreases. The stamper, on the other hand, does not absorb energy and does not heat up at all because it is infrared permeable:

 By the way, in the above process, it is indispensable that the stancher has infrared transmittance. However, since the conventional stancher is made of a metal that absorbs infrared rays, it does not satisfy this requirement and is used in the process. I can't.

 In view of the circumstances of the prior art, another object of the present invention is to provide a stamper suitable for the plastic molding method as described above: Therefore, in a second technical idea of the present invention, The gist is that at least the body other than the stamper having a shaping surface is formed of an infrared transmitting material except for the shaping surface.

 In one embodiment, a shaping element is integrally formed on the shaping surface of the main body.

 In another embodiment, a shaping element is attached and fixed to a shaping surface. In still another embodiment, the shaping surface is formed by a metal ultra-thin plate integrally provided with a shaping element.

 Infrared rays pass through the main body made of infrared transmitting material and reach the base material side, and the energy absorption causes the base material to be heated and melted near the imprinting surface of the stamper.

FIG. 1 is a side view showing a first step in one embodiment of the processing method of the present invention, and FIG. 2 is a side view showing a second step in one embodiment of the processing method of the present invention. FIG. 3 is a side view showing a third step in one embodiment of the working method of the present invention. FIG. 4 is a side view showing a fourth step in one embodiment of the working method of the present invention. The figure shows this FIG. 6 is a cross-sectional side view showing a first embodiment of the stamper of the present invention, FIG. 6 is a cross-sectional side view showing a second embodiment of the stamper of the present invention, and FIG. FIG. 3 is a cross-sectional side view showing the third embodiment-Best Mode for Carrying Out the Invention

 FIGS. 1 to 4 show an embodiment of the forming method according to the present invention. First, as shown in Fig. 1, a base material 1 made of a plastic material and having a transfer surface 11 is prepared .: The base material is, for example, a thin disk when the molded article is a CD-ROM. Are used. If the plastic material is a thermoplastic material, it is appropriately selected according to the application, for example, polystyrene.

 Next, as shown in FIG. 2, the substrate 1 is fixed to the support frame 3 with its transfer surface 11 facing upward.

 Next, as shown in FIG. 3, a stamper 5 having a shaping surface 51 is prepared. This stamper 5 is formed from an infrared transmitting material. As the infrared transmitting material, selenium zinc (ZnSe), sapphire, infrared glass, etc. are used: In the illustrated case, the entire stamper 5 is formed from the infrared transmitting material. It may be made of a material other than the infrared transmitting material. For example, in the case of a stamper for processing a CD-ROM substrate, the shaping surface 51 is a surface provided with a pit corresponding to the pit.

 Further, as shown in FIG. 4, the stamper 5 and the substrate 1 are held so that the imprinting surface 51 and the transfer surface 11 are in close contact with each other. In this state, infrared rays are applied to the stand 5 in the direction toward the substrate 1.

As an infrared light source, for example, a carbon dioxide gas laser, a YAG laser or the like is used, but an infrared lamp or the like can also be used. The frequency of the infrared radiation to be irradiated is absorbed by the polymer that constitutes the plastic material to be irradiated. Select as appropriate according to the implementation conditions within the acceptable range.

 FIG. 5 shows a first embodiment of a stamper according to the present invention, in which a shaping surface 105 of a body 103 made of an infrared transmitting material of a stub 101 has a large number of shaping surfaces 105. Element 107 is engraved on the body:

 However, in the case of this type of stamper, the engraving of the shaping element requires high precision, and it is extremely difficult to work. However, since the infrared transmitting material generally has a lower hardness than metals used in conventional stampers, the shaping elements formed by engraving are worn out less frequently than the conventional stampers are used. In other words, this type of stamper is a consumable item and needs to be replaced frequently to maintain high transfer accuracy. As a result, we cannot avoid being expensive.

 The embodiment shown in FIG. 6 solves this point. That is, the shaping element 109 is attached and fixed to the shaping surface 105 of the main body 103 made of an infrared transmitting material by photolithography or the like. In the case of this type, the direct engraving of photolithography is easy in terms of work and high accuracy can be obtained. It is advantageous. Also, after use for plastic molding of a certain specification, the shaping element for plastic molding of a new specification can be removed and the shaping element can be attached by photolithography or the like. It is cost effective.

 However, in the case of the above embodiment, since almost all parts of the stamper are formed of an infrared transmitting material, it is necessary to use a long wavelength infrared light, which is costly in terms of equipment. There is a common drawback of being high.

The third embodiment shown in FIG. 7 solves this point. That is, the shaping surface of the main body 103 made of an infrared transmitting material is formed by a metal ultra-thin plate 1 11, and the shaping element 1 13 is formed on the thin plate 1 1 1 It has been. The thickness of the thin plate is several tens of μm. As described above, since the thin metal plate 111 is used, infrared light having a short wavelength can be used, and the equipment is inexpensive. In addition, the heat capacity is small because the structure is extremely thin, and the temperature rises easily and quickly by the absorbed infrared energy. Industrial applicability

 In particular, since the viscosity of the plastic material decreases near the precise imprint surface, the transferability is improved even if the imprint surface has a complicated and precise shape, and the shape accuracy of the molded article is greatly improved. In addition, since the viscosity of the plastic material decreases near the imprinting surface, the orientation of the polymer is relaxed without forming a layer having a different viscosity, and the physical properties become uniform.

 Cooling is not required because the temperature is not elevated, so productivity is not impaired. The process can be separated into two stages: production of the base material and infrared irradiation molding. In addition, since no pressure is applied, the size of the equipment does not increase, so it is possible to equip the equipment at the distribution end. Therefore, if various types of stampers are prepared, it can be manufactured freely on demand at the end of distribution (for example, at a shop selling molded articles).

 Since almost all parts of the stamper are formed of the infrared transmitting material, the energy of the infrared light is smoothly transmitted to the base material side to promote the heating and melting.

Claims

The scope of the claims 1. Prepare a substrate made of a plastic material that has a transfer surface and fix the substrate with the transfer surface exposed. At least a part of the rectangular surface of a stamper made of an infrared transmitting material is used as the substrate. A plastic molding method comprising: holding a stamper in close contact with a transfer surface thereof; and irradiating the stamper with infrared rays in a direction toward the substrate.  2. A stamper for plastic molding, which has a shaping surface and at least a main body other than the shaping surface is made of an infrared transmitting material. 3. The stamper according to claim 2, wherein a shaping element is integrally formed on the shaping surface of the main body.  4. The stamper according to claim 2, wherein the shaping element is fixedly attached to the shaping surface.  5. The stamper according to claim 2, wherein the shaping surface is formed of an extremely thin metal plate integrally provided with a shaping element.