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Injection molding method

A technology of injection molding and molded products, which is applied in the direction of sound recording carriers, home appliances, and other home appliances. It can solve the problems of increasing the injection speed of the mold temperature, easily increasing the birefringence difference, and increasing the cost. It can reduce the resin temperature, Effect of shortening cooling time and improving productivity

Inactive Publication Date: 2008-06-04
HITACHT MAXELL LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, even with the above method, a solidified layer is formed between the mold wall surface and the flowing resin during filling, and shear stress occurs, which is the main cause of increased birefringence.
In addition, since the growth of the cured layer, that is, the skin layer is different between the inner and outer circumferences, the difference in birefringence between the inner and outer sides tends to increase.
As a method of reducing these, for example, there are ways to increase the mold temperature, increase the injection speed, etc., so that although the in-plane birefringence (related to the stress difference in the radial direction and the circumferential direction) can be controlled to a certain extent, the substrate The control of the birefringence of the oblique incident component is very difficult because it is greatly affected by the photoelastic constant of the resin material.
In addition, there is still a method of increasing the temperature of the mold to bake the product at a high temperature close to the heat distortion temperature, but this is limited
The method of reducing the photoelastic constant of the resin material is also adopted, but there are disadvantages such as high cost and low rigidity
[0007] In addition, when the above-mentioned conventional filling method is used, there is also the following problem: since the viscosity of the resin increases closer to the outer periphery, the temperature at the interface of the stamper 7 drops, resulting in poor transferability, and it is difficult to obtain uniform transferability inside and outside.
In these methods, due to the large heat capacity of the mold, it takes at least 1 minute for slow cooling, so multiple molds must be prepared, which will inevitably increase the cost
In addition, the above-mentioned essential problems inherent in injection molding such as having to flow through a short tube etc. to the end of the cavity are not solved
In the manufacturing method of the glass substrate, a kind of forming method of heating the glass original disc put into the mold to the glass softening temperature or higher, and pressing the mold to obtain the shape accuracy is proposed (Japanese Patent Application Laid-Open No. 11-92159, etc.), but There is a problem that it takes a long time to heat and melt the solidified original plate
In addition, even if the fine structure can be fully filled, the separation of the resin forming the structure with a high aspect ratio is poor, such as Figure 30 As shown, it is difficult to obtain shape accuracy due to deformation during demolding

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Examples

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Effect test

Embodiment 1

[0087] using the present invention Figure 2 to Figure 8 The injection molding apparatus of the present invention manufactures disc-shaped substrates for optical disks with an inner diameter of φ8 mm, an outer diameter of φ50 mm, and a plate thickness of 0.4 mm. On the stamper 7, helical pregrooves with a track pitch of 0.5 μm, a groove width of 0.25 μm, and a groove depth of 70 nm were provided within a range from an inner diameter of φ12 mm to an outer diameter of φ48 mm.

[0088] exist figure 2 Among them, the thickness H of the movable mold 3 is preferably below 15mm, but it is determined as 10mm in the present embodiment. The thermal conductivity of the mold is preferably 20w / m.k (200°C) or higher, but in this example, HPM38 manufactured by Hitachi Metals Co., Ltd. with a temperature of 21.5w / m.k (200°C) was used. The vacuum degree in the vacuum furnace 1 is expected to be in the range that can suppress the foaming of the molten resin due to air entering from the surfa...

Embodiment 2

[0105] In addition to changing the shape of the nozzle tip 2 in the injection process to Figure 9 Except as shown, injection molding was performed in the same manner using the same injection molding machine as in Example 1. The temperature of the heater 20 at the tip of the nozzle was controlled to 250°C. The temperature of the heating plate 8 is 250°C, and the nozzle faces Figure 10 Move in the arrow direction of the sealing stopper 50, by contacting the sealing stopper front end 52 of the sealing stopper 50 with the inner diameter pin 4 of the movable mold 3, pushing up the sealing stopper 50 in the nozzle, and passing through the outer peripheral portion of the sealing stopper 50 The resin flow groove 53 is used to fill the mold with molten resin 23 . At this time, it was confirmed that the fluid resin 23 filled in the moving mold 3 was close to the final product shape, and the transfer surface 54 of the stamper was also maintained flat.

[0106] Thereafter, pressing a...

Embodiment 3

[0114] Figure 21 to Figure 26 A molding method is schematically shown. In this molding method, polycarbonate having a glass transition temperature of 140° C. is used as a thermoplastic resin material and a supercritical fluid containing CO2 gas is used. Figure 21 ~ Figure 22 A filling process of molten resin is shown, but a moving mold 101 provided with a stamper 103 for forming a fine structure is placed on a moving table 102, and the moving mold 101 moves in each step together with the moving table.

[0115] The microstructure of the stamper 103 is made as Figure 28 As shown, a groove pattern with a depth D of 0.6 μm, a width W of 0.15 μm, and an aspect ratio of 4 is formed by using Ni to form a structure of high aspect ratio lines and spaces connected at an interval of 0.2 μm. The inner wall forms a disc-shaped cavity of φ50mm.

[0116] The moving mold is heated at least above the glass transition temperature Tg of the thermoplastic resin, and the heating method is arbit...

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Abstract

An injection molding method that ensures, in the molding of optical disks and the like, accurate transferability, optical characteristics and mechanical characteristics for accurately transferring a super fine structure that could not be transferred satisfactorily by the conventional molding method, mass production of replicas, and so on, thus improving the production efficiency. It comprises the steps of using a cavity forming mold composed of at least two members, charging molten resin into the mold, obtaining a molding, wherein one of the members constituting the mold passes through a stage that is separated into at least three steps, a charging step, a press step and a molding take-out step, and molten resin is charged into the unclosed cavity of the one member in the charging step and then a molding is formed in the press step.

Description

technical field [0001] The present invention relates to an injection molding method excellent in transferability, optical characteristics and productivity. Background technique [0002] In the injection molding of thermoplastics, the following steps are repeated: installing the mold in the injection molding machine, injecting the heated and melted resin into the mold whose temperature is controlled below the glass transition temperature of the resin material used, and then molding Pressurize the clamping pressure of the machine, wait for cooling and solidification, and then take out the product. In addition, in products such as optical discs that require precise transfer of ultra-micro-sized molds, it is of course necessary to control the optical and mechanical properties of the transfer by such a molding method. [0003] Figure 14 ~ Figure 17 It shows the molding method of conventional optical discs such as CD and DVD. Such as Figure 14 As shown, the cavity 37 filling ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B29C43/04B29C43/34B29L17/00B29C33/36B29C33/42B29C43/02B29C43/08
CPCB29L2017/003B29C2043/3433B29C2043/025B29C43/08B29C43/34B29C2043/3488B29C43/021B29C2043/3689B29C33/36B29C33/424B29C43/14
Inventor 遊佐敦
Owner HITACHT MAXELL LTD