JP2005001296A - Method for manufacturing transparent molded body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a transparent molded body by which the generation of a black spot (a scorch of resin) can be restrained and production efficiency, especially yield can be increased. <P>SOLUTION: This method for manufacturing a transparent molded body is to inject a resin loaded inside a screw cylinder 20 into a cavity 50 formed of a cavity-side half 10 and a movable half 30 of a mold and mold the resin. After the molding, the resin loaded inside the screw cylinder 20 is treated by at least, either of oxygen shut-off process or heat retaining process until a following molding is performed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a transparent molded body, and more particularly to a method for producing a transparent molded body used for an optical disk substrate or the like.
[0002]
[Prior art]
At present, as the demand for improvement in recording density increases, the diameter of laser light is reduced. When the diameter of the laser beam is reduced, mixing of foreign matters into the molded product (substrate) becomes a big problem. Examples of such foreign substances include black spots generated by burning the resin.
[0003]
It has been considered that the above-mentioned resin burn (black spots) occurs during molding. However, previous studies have shown that the method of preserving the resin in the cylinder (particularly up to the cylinder injection nozzle) while the molding machine is stopped is important. Also, the resin is burned by oxidation of the resin.
[0004]
Once a black spot or the like occurs, purging (resin emptying), cleaning the inside of the cylinder, replacing the nozzle, and the like are necessary, and production efficiency is greatly reduced. Further, the quality of the molded product is greatly influenced by the resin temperature at the time of molding, and the influence of the resin temperature of the nozzle portion is particularly great.
[0005]
In view of this, there has been proposed a resin burn prevention device that removes air in a cylinder by a vacuum device when the cylinder temperature in the cylinder is higher than a set temperature (see, for example, Patent Document 1).
According to this apparatus, it is possible to create an environment in which resin burning does not occur by removing air in the cylinder with a vacuum pump and lowering the oxygen concentration. However, according to the study of the present inventor, it has been found that resin burning occurs when air enters from a nozzle after the resin is injected to oxidize the resin in the cylinder. That is, even if the air in the cylinder is removed, the resin burn cannot be sufficiently prevented unless air intrusion or oxidation from the vicinity of the nozzle is prevented. Moreover, when using a vacuum apparatus, there also exists a problem that an apparatus mechanism becomes complicated.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-76292 [0007]
[Problems to be solved by the invention]
In view of the above, an object of the present invention is to solve the above conventional problems. That is, an object of the present invention is to provide a method for producing a transparent molded product capable of suppressing production of black spots (resin burn) and improving production efficiency, particularly yield.
[0008]
[Means for Solving the Problems]
As a result of intensive studies to achieve the above object, the present inventor has found that the object can be achieved by the present invention described below.
That is, the present invention is a method for producing a transparent molded body that performs molding by injecting a resin in a screw cylinder into a cavity formed from a fixed mold and a movable mold,
In a method for producing a transparent molded article, the resin in the screw cylinder is subjected to at least one of an oxygen blocking treatment and a heat retaining treatment before the next molding after molding. is there.
[0009]
Moreover, it is preferable that this invention has a structure of any one of following (1)-(4). That is,
(1) The oxygen blocking process is a process of pushing the screw in the screw cylinder to the most advanced end immediately after performing the molding.
(2) The oxygen blocking process is a process of covering the nozzle tip of the screw cylinder with a sealing means immediately after performing the molding.
(3) The heat retention temperature by the heat retention treatment is not less than the glass transition point of the resin and not more than the decomposition temperature of the resin.
(4) The transparent molded body is an optical disk substrate.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
[Method for producing transparent molded article]
The method for producing a transparent molded body of the present invention is a method for producing a transparent molded body in which molding is performed by injecting a resin in a screw cylinder into a cavity formed by a fixed side mold and a movable side mold. Thus, at least one of the oxygen blocking treatment and the heat retaining treatment is performed on the resin in the screw cylinder after the molding and before the next molding.
The manufacturing method can be performed by adding an improvement as described later to a generally used injection molding machine.
Hereinafter, the oxygen blocking process and the heat retaining process will be described in detail.
[0011]
(Oxygen blocking treatment)
The oxygen blocking process is a process for preventing “resin burn” in which the resin is oxidized by oxygen entering from the nozzle after one transparent molded body is molded and before the next transparent molded body is molded.
Specifically, (1) Immediately after forming, a process of pushing the screw in the screw cylinder to the most advanced end, or (2) Immediately after forming, the nozzle tip of the screw cylinder is sealed with sealing means. The covering process etc. can be mentioned.
[0012]
FIG. 1 illustrates a part of an injection molding machine and a mold applied to the method for producing a transparent molded body of the present invention. The injection molding machine or the like has a movable mold 30, a fixed mold 10 and a screw cylinder 20, and a cavity 50 is formed by the movable mold 30 and the fixed mold 10.
A stamper 40 fixed by a stamper fixing means (not shown) is provided on the cavity 50 side of the movable mold 30. The stamper 40 is used when producing an optical disk substrate as a transparent molded body.
[0013]
The screw cylinder 20 has a molten resin inside, and is disposed so as to be close to or away from the stationary mold 10. Then, the nozzle 22 of the screw cylinder 20 is in close contact with the resin inlet 14 of the sprue portion 12 of the stationary mold 10.
Here, the “nozzle” is a portion that is connected to the tip of the screw cylinder and forms a flow path of molten resin by being in close contact with the resin inlet of the sprue portion of the fixed mold during injection. Therefore, in the case of FIG. 1, the resin in the screw cylinder 20 is injected into the cavity 50 through the nozzle 22.
[0014]
In the process (1), first, as shown in FIG. 1A, the resin is injected into the cavity 50 by the screw 24 in accordance with normal conditions. The screw 24 after injecting a certain amount is held in a fixed position in the screw cylinder 20. Thereafter, a predetermined clamping force (for example, 300 to 400 kN) is applied, and the molded product is taken out by cooling. Immediately after being separated from the fixed mold 10, the screw cylinder 20 pushes the screw 24 in the screw cylinder 20 to the inner wall of the cap 22 that is the most advanced end, as shown in FIG. By doing so, it is possible to prevent air from entering the cylinder from the tip of the cap 22. As a result, oxidation of the resin can be prevented, so that resin burn can be prevented.
[0015]
Next, as the process (2), first, the resin is injected into the cavity 50 in the same manner as the process (1). Thereafter, as shown in FIG. 2, immediately after the screw cylinder 20 is separated from the fixed mold 10, the tip of the nozzle 22 is covered with a sealing means 60. By covering the tip of the nozzle 22 with the sealing means 60, it is possible to prevent air from entering through the nozzle 22. As a result, oxidation of the resin can be prevented, so that resin burn can be prevented.
[0016]
The sealing means 60 is not particularly limited as long as it does not cause deformation or alteration even if it contacts the nozzle 22 immediately after separation, and a lid or plate made of metal or glass can be used.
In order to prevent air from entering more reliably, after the screw 24 in the screw cylinder 20 is pushed to the inner wall of the cap, which is the most advanced end, in the process (1), the tip of the nozzle 22 is sealed by the sealing means 60. It is preferable to perform a process of covering the surface.
[0017]
In addition, before the next molding is performed after the molding, the heat retaining treatment may be performed instead of the oxygen shielding treatment described above or together with the oxygen shielding treatment.
The heat retention process is a process that prevents the resin from being burnt by keeping the temperature in the screw cylinder constant, and preventing the resin from burning as well as the oxygen blocking process. A specific method of the heat retaining process is not particularly limited, but a known heater or the like may be installed outside the screw cylinder. In particular, if a heat insulating treatment is performed by providing a heater at the tip of a nozzle where air enters, oxidation of the resin can be prevented more efficiently.
[0018]
The heat retention temperature by the heat treatment is preferably not less than the glass transition point of the resin and not more than the decomposition temperature of the resin. Keeping the temperature within this range prevents the resin from degrading and decomposing, causing the resin degradation product to adhere to the inner walls of the nozzle, screw, and screw cylinder, and preventing the degradation product from adhering to the inner wall from entering the molded product after molding begins. be able to. As a result, it is possible to shorten the startup time from the stop of molding to the start of mass production molding.
[0019]
The transparent molded body produced by the production method of the present invention is preferably used for an optical disk substrate.
In the case of a substrate for an optical disc, various materials used as conventional substrate materials can be arbitrarily selected and used as the resin.
Specific examples include acrylic resins such as polycarbonate and polymethylmethacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins; amorphous polyolefins; polyesters; You may use together.
Among the above materials, amorphous polyolefin and polycarbonate are preferable, and polycarbonate is particularly preferable from the viewpoints of moisture resistance, dimensional stability, and low cost. Further, the thickness of the substrate is preferably 0.5 to 1.2 mm, and more preferably 0.6 to 1.1 mm.
[0020]
When the optical disk substrate manufactured by the manufacturing method of the present invention is used for, for example, a recordable optical disk such as a CD-R or DVD-R, a tracking guide groove or an address signal is formed on the molded substrate. Concavities and convexities (pregrooves) representing the above information are formed by the stamper 40.
In the case of DVD-R or DVD-RW, the track pitch of the pregroove is preferably in the range of 300 to 900 nm, more preferably 350 to 850 nm, and still more preferably 400 to 800 nm.
If the thickness is less than 300 nm, it is difficult to form the pregroove accurately, and a crosstalk problem may occur. If the thickness exceeds 900 nm, the recording density may decrease.
The depth of the pregroove (groove depth) is preferably in the range of 100 to 160 nm, more preferably 120 to 150 nm, and still more preferably 130 to 140 nm.
If the thickness is less than 100 nm, a sufficient recording modulation degree may not be obtained. If the thickness exceeds 160 nm, the reflectance may be significantly reduced.
Furthermore, the half width of the pregroove is preferably in the range of 200 to 400 nm, more preferably 230 to 380 nm, and even more preferably 250 to 350 nm.
If the thickness is less than 200 nm, the grooves may not be sufficiently transferred at the time of molding or the recording error rate may be increased. If the thickness exceeds 400 nm, the pits formed at the time of recording spread and cause crosstalk. Or a sufficient degree of modulation may not be obtained.
[0021]
In the case of CD-R or CD-RW, the pregroove track pitch is preferably in the range of 1.2 to 2.0 μm, more preferably in the range of 1.4 to 1.8 μm, More preferably, it is 1.65 μm.
The depth of the pregroove (groove depth) is preferably in the range of 100 to 250 nm, more preferably 150 to 230 nm, and even more preferably 170 to 210 nm.
The half width of the pregroove is preferably in the range of 400 to 650 nm, more preferably 480 to 600 nm, and further preferably 500 to 580 nm.
The critical meaning of the numerical range of the pregroove is the same as that of the DVD-R or DVD-RW.
[0022]
After the resin is filled into the cavity 50 through the nozzle 22, a clamping force is applied under the same conditions as in a general molding method, and the mold temperature (for example, about 115 to 125 ° C. for a DVD substrate). ) Cooling to near, open the movable mold 30 and take out the molded substrate. The molded substrate is free from defects such as black spots, and the pits or grooves formed on the stamper 40 are well transferred.
[0023]
[Optical Disc Manufacturing Method]
The optical disk substrate (transparent molded body) produced as described above has an optical disk having a recording layer capable of recording and reproducing information by laser light, and a recording section (information recorded by laser light). It can be applied to an optical disc having pits.
The former is a write-once or rewritable optical disk such as CD-R, CD-RW, DVD-R, DVD-RW, DVD-RAM, etc., and the latter is a CD, DVD, etc. An optical disc on which information is written.
[0024]
For example, as a configuration of an optical disc having a recording layer, a configuration in which a recording layer, a light reflection layer, and a protective layer are sequentially formed on a substrate manufactured according to the present invention, or at least a recording layer on the substrate, A configuration in which a light reflection layer, an adhesive layer, and a protective substrate (dummy substrate) are sequentially formed is exemplified.
Hereinafter, each of the above layers will be described. Note that the layer configuration, materials, and the like are merely examples.
[0025]
(Recording layer)
In the case of CD-R or DVD-R, the recording layer is prepared by dissolving a dye as a recording material in a suitable solvent together with a binder or the like to prepare a coating solution. It forms by apply | coating to the surface in which the groove was formed, forming a coating film, and then drying.
The temperature at the time of applying the spin coating method is preferably 23 ° C. or higher, and more preferably 25 ° C. or higher. The upper limit of the temperature is not particularly limited, but the temperature needs to be lower than the flash point of the solvent, and preferably 35 ° C.
When the temperature is lower than 23 ° C., the drying of the solvent becomes slow, and the target dye film thickness (recording layer thickness) cannot be obtained, or the coating and drying time becomes long, and the productivity may decrease.
[0026]
Examples of the dye include cyanine dyes, oxonol dyes, metal complex dyes, azo dyes, and phthalocyanine dyes. Among these, phthalocyanine dyes are preferable.
JP-A-4-74690, JP-A-8-127174, 11-53758, 11-334204, 11-334205, 11-334206, 11-334207 The dyes described in JP-A-2000-43423, JP-A-2000-108513, JP-A-2000-158818, and the like are also preferably used.
[0027]
Examples of the solvent for the coating solution include esters such as butyl acetate, ethyl lactate and 2-methoxyethyl acetate; ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone; chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane and chloroform; Amides such as formamide; Hydrocarbons such as methylcyclohexane; Ethers such as tetrahydrofuran, ethyl ether, and dioxane; Alcohols such as ethanol, n-propanol, isopropanol, and n-butanol diacetone alcohol; 2,2,3,3-tetrafluoro Fluorinated solvents such as propanol; Glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether; Door can be.
The above solvents can be used alone or in combination of two or more in consideration of the solubility of the recording material used. Various additives such as an antioxidant, a UV absorber, a plasticizer, and a lubricant may be further added to the coating solution depending on the purpose.
[0028]
In the case of using a binder, examples of the binder include natural organic polymer materials such as gelatin, cellulose derivatives, dextran, rosin, and rubber; hydrocarbon resins such as polyethylene, polypropylene, polystyrene, and polyisobutylene; Vinyl resins such as vinyl chloride, polyvinylidene chloride, polyvinyl chloride / polyvinyl acetate copolymer, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyethylene, epoxy resin, butyral resin, And synthetic organic polymers such as rubber derivatives and initial condensates of thermosetting resins such as phenol / formaldehyde resins. When a binder is used in combination as a material for the recording layer, the amount of binder used is generally in the range of 0.01 times to 50 times (mass ratio), preferably 0.1 times the recording substance. The amount is in the range of 5 to 5 times (mass ratio). The concentration of the recording substance in the coating solution thus prepared is generally in the range of 0.01 to 10% by mass, preferably in the range of 0.1 to 5% by mass.
[0029]
As the coating method, the spin coating method is applied as described above, and conventionally known devices can be used for the device and the like used at that time.
The recording layer may be a single layer or a multilayer, and the layer thickness is generally in the range of 20 to 500 nm, preferably in the range of 30 to 300 nm, and more preferably in the range of 50 to 100 nm.
[0030]
The recording layer can contain various anti-fading agents in order to improve the light resistance of the recording layer.
As the antifading agent, a singlet oxygen quencher is generally used. As the singlet oxygen quencher, those described in publications such as known patent specifications can be used.
Specific examples thereof include JP-A Nos. 58-175893, 59-81194, 60-18387, 60-19586, 60-19587, and 60-35054. 60-36190, 60-36191, 60-44554, 60-44555, 60-44389, 60-44390, 60-54892, JP-A-60-47069, JP-A-63-209995, JP-A-4-25492, JP-B-1-38680, JP-A-6-26028, etc., German Patent 350399, and Japan Examples include those described in Chemical Society Journal, October 1992, page 1141.
[0031]
The amount of the antifading agent such as the singlet oxygen quencher used is usually in the range of 0.1 to 50% by weight, preferably in the range of 0.5 to 45% by weight, based on the amount of the dye. Preferably, it is the range of 3-40 mass%, Most preferably, it is the range of 5-25 mass%.
[0032]
In the case of CD-RW or DVD-RW, the recording layer is preferably made of a phase change type optical recording material composed of at least Ag, Al, Te, and Sb that can take at least two states of a crystalline state and an amorphous state. . Such a recording layer can be formed by a known method.
A known dielectric layer is formed on the recording layer as necessary.
[0033]
(Light reflecting layer)
After the recording layer is formed, a light reflecting layer is formed on the recording layer by vapor deposition, sputtering or ion plating of a light reflecting material. In forming the light reflection layer, a mask is usually used, and the formation region of the light reflection layer can be adjusted thereby.
[0034]
For the light reflection layer, a light reflective material having a high reflectance with respect to laser light is used. The reflectance is preferably 70% or more.
As a light reflective material having a high reflectance, Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd , Ir, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, Bi, and other metals and semi-metals or stainless steel. These light reflecting materials may be used alone, or may be used in combination of two or more kinds or as an alloy. Among these, Cr, Ni, Pt, Cu, Ag, Au, Al, and stainless steel are preferable. Particularly preferred is Au, Ag, Al or an alloy thereof, and most preferred is Au, Ag or an alloy thereof.
The thickness of the light reflecting layer is generally in the range of 10 to 300 nm, and preferably in the range of 50 to 200 nm.
[0035]
(Protective layer, protective substrate)
After forming the light reflecting layer, a protective layer is formed on the light reflecting layer.
The protective layer is formed by a spin coating method. By applying the spin coating method, the protective layer can be formed without damaging the recording layer (dissolution of the dye, chemical reaction between the dye and the protective layer material, etc.). The number of rotations during spin coating is preferably 50 to 8000 rpm, more preferably 100 to 5000 rpm, from the viewpoint of uniform layer formation and prevention of damage to the recording layer.
In the case where an ultraviolet curable resin is used for the protective layer, after the protective layer is formed by spin coating, the ultraviolet curable resin is cured by irradiating the protective layer with ultraviolet rays using an ultraviolet irradiation lamp (metal halide lamp). .
Further, in order to eliminate the thickness unevenness of the protective layer to be formed, a treatment such as leaving it for a certain period of time before curing the resin may be appropriately performed.
[0036]
The protective layer prevents moisture from entering and scratching. The material constituting the protective layer is preferably an ultraviolet curable resin, a visible light curable resin, a thermosetting resin, silicon dioxide, or the like, and more preferably an ultraviolet curable resin. Examples of the ultraviolet curable resin include ultraviolet curable resins such as “SD-640” manufactured by Dainippon Ink and Chemicals, Inc. Further, SD-347 (manufactured by Dainippon Ink and Chemicals), SD-694 (manufactured by Dainippon Ink and Chemicals), SKCD1051 (manufactured by SKC) and the like can be used. The thickness of the protective layer is preferably in the range of 1 to 200 μm, and more preferably in the range of 50 to 150 μm.
In addition, the protective layer is required to have transparency in a layer configuration used as a laser optical path. Here, “transparency” means that the recording light and the reproduction light are so transparent that the light is transmitted (transmittance: 90% or more).
[0037]
In the case of DVD-R and DVD-RW, instead of the protective layer, an adhesive layer made of an ultraviolet effect resin or the like and a substrate as a protective substrate (thickness: about 0.6 mm, the material is the same as the above substrate) are laminated. To do.
That is, after forming the light reflection layer, an ultraviolet curable resin (Dai Nippon Ink Chemical Co., Ltd. SD640 or the like) is applied to a thickness of 20 to 60 μm by spin coating to form an adhesive layer. On the formed adhesive layer, for example, a polycarbonate substrate (thickness: 0.6 mm) as a protective substrate is placed, and the ultraviolet curable resin is cured by being irradiated with ultraviolet rays from the substrate, and bonded together.
[0038]
As described above, an optical disc comprising a laminate in which a recording layer, a light reflecting layer, a protective layer (dummy substrate) via a protective layer or an adhesive layer, etc. are provided on the optical disc substrate manufactured in the present invention. Is produced.
In addition, the track pitch of the pregroove formed on the substrate and the material constituting the recording layer are appropriately set, so that the track pitch is narrower than that of a conventional DVD, etc. The present invention can also be applied to an optical disc capable of recording / reproducing information.
[0039]
【Example】
The present invention will be specifically described with reference to the following examples, but the present invention is not limited thereto.
[0040]
(Example 1)
Using an injection molding machine (manufactured by Sumitomo Heavy Industries, Ltd.), an outer diameter of 120 mm, an inner diameter of 15 mm, and a thickness of 0 having a spiral groove (groove depth of 150 nm, groove width of 300 nm, track pitch of 0.74 μm) 500 continuous optical disk substrates (made of polycarbonate resin) of 6 mm were produced.
Immediately after forming one optical disk substrate, oxygen blocking treatment was performed to push the screw in the screw cylinder to the most advanced end. The clamping force was 400 kN.
[0041]
(Example 2)
In the oxygen shut-off process, 500 optical disk substrates were produced in the same manner as in Example 1 except that after the screw was pushed to the most advanced end, sealing means for covering the nozzle tip with a Ti lid was applied.
[0042]
Example 3
500 optical disk substrates were produced in the same manner as in Example 1 except that a heater was provided around the screw cylinder to perform the heat retaining treatment instead of the oxygen blocking treatment. In addition, the heat insulation temperature by heat insulation processing was 160 degreeC.
[0043]
(Comparative example)
500 optical disk substrates were produced in the same manner as in Example 1 except that the oxygen blocking treatment was not performed.
[0044]
For the optical disk substrates produced in Examples 1 to 3 and the comparative example, the occurrence of black spots was visually confirmed to determine the defect occurrence rate.
[0045]
In the comparative example, it was close to 50% at the beginning of startup and around 5% in the stable production area. On the other hand, in Examples 1-3, it was 1% or less in any case. In the example, the time required for start-up could be reduced from several hours to 10 minutes.
[0046]
【The invention's effect】
As mentioned above, according to the manufacturing method of the transparent molded object of this invention, generation | occurrence | production of a black spot (resin burn) can be suppressed and production efficiency, especially a yield can be improved.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing a part of an injection molding machine or the like for explaining a method for producing a transparent molded body of the present invention, and (a) shows a state in which a screw cylinder is in contact with a stationary mold. (B) shows a state in which the screw cylinder is separated from the fixed mold.
FIG. 2 is a partial cross-sectional view showing a part of an injection molding machine or the like for explaining the method for producing a transparent molded body of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Fixed side metal mold 12 ... Sprue part 14 ... Resin injection port 20 ... Screw cylinder 22 ... Nozzle 24 ... Screw 30 ... Movable side metal mold 40 ... Stamper 50 ... Cavity 60 ... Sealing means

Claims (5)

A method for producing a transparent molded body that performs molding by injecting resin in a screw cylinder into a cavity formed from a fixed side mold and a movable side mold,
A method for producing a transparent molded body, comprising performing at least one of an oxygen blocking treatment and a heat retaining treatment on the resin in the screw cylinder before the next molding after the molding. The method for producing a transparent molded body according to claim 1, wherein the oxygen-blocking process is a process of pushing the screw in the screw cylinder to the most advanced end immediately after performing the molding. 3. The method for producing a transparent molded body according to claim 1, wherein the oxygen blocking treatment is a treatment in which the tip of the nozzle of the screw cylinder is covered with a sealing unit immediately after the molding is performed. The method for producing a transparent molded body according to any one of claims 1 to 3, wherein a heat retaining temperature by the heat retaining treatment is not lower than a glass transition point of the resin and not higher than a decomposition temperature of the resin. The method for producing a transparent molded body according to any one of claims 1 to 4, wherein the transparent molded body is an optical disk substrate.

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