JP4181017B2 - Mold for molding - Google Patents

Description

The present invention is used for molding dies, especially for plastic substrates for optical disks such as compact disks (CDs) and digital versatile disks (DVDs), liquid crystal display devices used in personal computers, mobile phones, and other applications. The present invention relates to a molding die suitable for forming a transparent resin light guide plate and the like to be used.

  In general, plastic substrates for optical discs such as CD and DVD use movable molds and fixed molds made of metal materials such as steel, and the cavities formed when these molds are combined. A stamper corresponding to the recorded information is arranged, and the cavity is filled with a molten plastic such as polycarbonate resin, and after cooling and solidification, it is separated from the mold.

However, in recent years, with the increase in the density of optical discs, in the molding of such plastic substrates for optical discs, precise transfer of information pits and laser guide grooves on the order of submicron has become the most important issue. In particular, if the thickness of the substrate is reduced to 0.6 mm or less in order to increase the density, it is difficult to transfer the molten plastic resin sufficiently with respect to the groove depth of the stamper, resulting in poor transferability. Such a problem also occurs in the formation of the light guide plate, and in the formation of a minute uneven surface serving as a light reflection surface on the surface of the light guide plate, sufficient transferability cannot be obtained, and a good reflection surface cannot be formed. There is.

In order to solve such problems, it has been proposed to use a molding die in which a heat insulating layer made of a ceramic material is formed between a stamper and a die core by a thermal spraying method. (For example, Patent Document 1)
According to this method, since a heat insulating layer made of a ceramic material is formed between the stamper and the mold core by a thermal spraying method, the molten resin temperature immediately after filling is lower than the inner peripheral portion of the substrate near the gate. The temperature at the interface with the stamper immediately after resin filling exceeds the thermal deformation temperature of the resin, and the same temperature is obtained at the inner and outer peripheral parts of the substrate. Good transferability can be obtained at both the inner and outer peripheral parts. Since the thermal insulation layer is formed by the thermal spraying method, it is difficult to obtain surface accuracy of the surface of the thermal insulation layer that contacts the stamper, and uneven portions due to voids are likely to be formed on the surface, resulting in sliding contact with the stamper. As a result, problems such as generation of stamper wear powder occurred.

  In addition, when such a heat insulating layer made of a ceramic material is used as a cavity surface for forming a surface of a molded body such as a reflecting surface of a light guide plate, the ceramic material is generally large in hardness and has a surface of the heat insulating layer. There is a problem that fine processing is difficult.

JP-A-10-149487

The present invention is intended to solve such problems, and an object of the present invention is to provide a molding die in which a smooth surface of a cavity is easily and reliably formed and generation of wear powder by a stamper is suppressed. To do.

The present invention is formed in the first and second inventions, at least one surface constituting the cavity of the movable mold and the fixed mold made of metallic material, a heat insulating layer of ceramic by thermal spraying By using a molding die with an amorphous diamond-like carbon thin film formed on the surface of this heat insulation layer, the surface is smooth and the wear of the stamper is prevented and the generation of wear powder by the stamper is suppressed. Can do.

Furthermore, the first invention of the present invention, the heat insulation layer, zirconia, titanium oxide, alumina, by a formed shape mold made of a ceramic material selected from at least one of aluminum titanate, The transferability of the molten resin stamper or the information recording portion from the cavity surface or the uneven reflection surface of the light guide plate is improved.

Further, according to a second aspect of the present invention, the heat insulating layer is formed of a first heat insulating layer made of zirconia and chromium oxide, chromium nitride, alumina, aluminum nitride, silicon nitride, silicon carbide laminated thereon. with formed form mold made up of the second insulation layer made of a material selected from at least one, it can be made more smooth the surface of the heat insulating layer.

The inventors of the present invention have a molding die in which a heat insulating layer made of ceramics is formed by a thermal spraying method between a conventionally known stamper and a die core, so that good transferability can be obtained in both the outer periphery and the outer periphery of the stamper for an optical disk substrate However, since the heat insulating layer made of ceramics is formed by a thermal spraying method, it is difficult to obtain the surface accuracy of the ceramics in contact with the stamper, and uneven portions due to voids are easily formed on the surface. As a result of investigating that the stamper is worn by sliding contact, and that the wear powder of the stamper is generated, and based on this investigation, the solution was examined.

Easily forms chromium oxide flat coating over by thermal spraying of zirconia even heat-insulating layers by ceramic formed by thermal spraying, method having a heat insulating function on the cavity surface first insulation layer, chromium nitride, alumina Even when the second heat insulating layer is formed by a thermal spraying method made of a material selected from at least one of aluminum nitride, silicon nitride, and silicon carbide, a good surface smooth surface can be obtained. In other words, the first heat insulating layer of zirconia has almost the same adhesion and thermal expansion coefficient as the steel mold, and cracks are generated in response to the thermal expansion and contraction of the mold during molding. Although it can be suppressed and is preferable, in order to obtain good transferability, a thickness of 100 μm or more is sufficient, and the transferability improves as the thickness increases. However, as the thickness is increased, the transferability is improved. On the other hand, the time required for cooling is increased, and the molding cycle is lengthened and the productivity is lowered. Therefore, the thickness is preferably set to 1000 μm or less from the balance of transferability and productivity. In this heat insulating layer made of zirconia, gaps are easily formed between the weld particles, and as a result, irregularities due to voids are easily formed on the surface, and it is difficult to obtain good surface flatness. On the other hand, a coating formed by thermal spraying using chromium oxide, chromium nitride, alumina, aluminum nitride, silicon nitride, silicon carbide, etc. as a raw material is unlikely to form a gap between the molten particles, and good surface smoothness is obtained. easy. In consideration of these characteristics, it is selected from at least one of chromium oxide, chromium nitride, alumina, aluminum nitride, silicon nitride, and silicon carbide, which can easily form a flat film on the first heat insulating layer by the zirconia thermal spraying method. When the second heat insulating layer made of a different material is formed by the thermal spraying method, the advantages of both are exhibited synergistically, and a heat insulating layer with good surface smoothness as well as good transferability can be easily obtained. In this case, the second heat insulating layer may be in the range of 1/10 to 1/2 of the total thickness of the first heat insulating layer and the second heat insulating layer.

Furthermore this second insulation layer, further surface smoothness to form a diamond-like carbonaceous thin film of amorphous is improved, which is preferable.

The movable side mold and the fixed side mold used in the present invention are generally formed of a metal such as cemented carbide, stainless steel, carbon steel, mild steel, etc., and are used as molds suitable for injection molding of plastic materials. be able to.

As the thermal spraying method referred to in the present invention, using the ceramic powder, the powder is fed into a high-temperature, high-speed plasma jet generated by ionizing nitrogen gas, hydrogen gas, inert gas, etc., and melted in the jet. Using a plasma powder spray method or a ceramic sintered rod that accelerates and collides with the mold base material to form a coating, it melts in an oxygen-acetylene flame at about 3000 ° C. Locoid rod spray method that forms a film by accelerating spraying with air jet flow, thermospray method in which ceramic powder is melted in an oxygen-acetylene flame and sprayed while being heated in the flow of the combustion flame from the nozzle opening There Ru available.

As the plastic material molded using the molding die of the present invention, any thermoplastic resin such as polycarbonate, polyetherimide, polyethersulfone, acrylic resin, methacrylic resin, polyolefin resin, etc. can be used. it can.

In the present invention, it is possible to provide a molding die in which a smooth-surfaced cavity surface is easily and reliably formed and generation of wear powder by a stamper is suppressed.

An embodiment of a molding die for molding a DVD disk substrate having a diameter of 120 mm and a thickness of 0.2 mm according to the present invention will be described below with reference to the drawings.

FIG. 1 is an enlarged cross-sectional view of a portion corresponding to the concavo-convex portion 4 corresponding to the recording information of a DVD disc substrate manufactured using the molding die according to the present invention. , is molded of polycarbonate resin, the depth H of the concave portion 2 is about 85 nm, the interval W between the projections 3 are formed of 0.8 [mu] m.

An embodiment of a molding die and an injection molding apparatus for producing a plastic disc substrate 1 used for such a DVD disc 1 will be described with reference to FIGS.

FIG. 2 is a schematic cross-sectional view of an injection molding apparatus in which a mold is closed. 4 is a stamper made of a nickel material having a surface on which an uneven surface 4 corresponding to recording information of a DVD disc is formed. , A fixed side mold, 6 is a movable side mold, 7 is a stamper outer peripheral holder, and these molds are made of stainless steel. When these molds are combined and closed on the injection molding apparatus, a molded product, in this case, a cavity 8 for molding the substrate 1 is formed. The cavity 8 communicates with a runner 12 and a sprue 11 formed on a gate cut member 10 attached to the gate 9 attached to the fixed die 5 and the movable die 6 so as to move up and down. The injection molding resin supplied from the resin supply port 13 is filled into the cavity 8 through the sprue 11, the runner 12, and the gate portion 9. After the resin is solidified, the gate cut member 10 moves upward, the injected resin is cut at the gate cut part, and then the movable mold 6 moves to open the mold, and the molded product is not shown in the drawing pin. The substrate 1 is manufactured by protruding. The fixed side mold 5 is attached to the fixed side mounting plate 19 and the movable side mold 6 is attached to the movable side mounting plate 20. The above-mentioned stamper 4 is mounted on the movable mold 6 with the outer peripheral portion held by the stamper outer peripheral holder 7 and the inner periphery held by the stamper inner peripheral holder 14.
( Reference Example 1 )

The structure of the movable mold 6 that is a characteristic part of the reference example 1 will be described with reference to FIG. 3. The surface of the movable mold 6 is obtained by sintering zirconia powder on the cavity surface 15 of the movable mold 6. A disk-shaped plate member 16 having a thickness of about 100 μm is fixed on the cavity surface by a silver solder 17 having a thickness of about 50 μm. In this case, the disk-like plate member 16 made of ceramic may be provided in the area of the portion corresponding to the entire surface of the substrate 1 as shown in Reference Example 1. You may arrange | position only to the corresponding part.

  An amorphous diamond-like carbon thin film 18 is formed on the surface of the plate-like member 16 with a thickness of about 3 μm using a carbon target by a magnetron sputtering method or the like. In this case, in order to improve the adhesion between the thin film 18 and the plate member 16 as well as the diamond-like carbon thin film 18, Cr, W, Ti, Si are interposed between the thin film 18 and the plate member 16. A sputtering underlayer made of, for example, may be formed. Furthermore, in order to improve the friction coefficient of the thin film 18, a fluorine-containing diamond-like thin film may be used.

  In this mold portion, a silver solder 17 having a melting point of about 750 ° C. is disposed on the cavity surface 15 of the mold 6, and a disk-like plate-like member 16 made of zirconia material is placed on the surface thereof. Then, the silver braze 17 is melted by heating at 1000 ° C., and then cooled, the silver braze 17 is solidified, and the plate-like member 16 is fixed to the movable side mold 6. In this case, by the heat treatment, the silver component of the silver brazing diffuses into the joining surface of the disk-like plate member 16 made of zirconia material and the mold 6 and is firmly joined.

In this way, the disk-shaped plate member 16 made of the fixed zirconia material is polished by the polishing apparatus, and the surface thereof is polished with high surface accuracy and smooth surface. Thereafter, this mold portion is introduced into a magnetron sputtering apparatus, and an amorphous diamond-like thin film 18 is formed on the surface of the plate-like member 16 using carbon as a target. The stamper 4 is installed on the mold part formed as described above, and the movable mold part is assembled in the molding apparatus.

On the surface of the diamond-like thin film 18 formed in this way, there are almost no voids between zirconia particles, and it has good surface smoothness, and its surface roughness Rmax is as good as 0.01 μm. The surface roughness and low friction coefficient of 0.1 were shown, and no generation of wear powder by the stamper was observed even after molding 1 million times.
( Reference Example 2 )

In the reference example 1 , the amorphous diamond-like carbon thin film 18 was omitted, and a movable mold part was formed in the same manner. On the surface of the disk-shaped plate-like member 16 of the movable mold part formed in this way, there are almost no voids between the zirconia particles, and it has good surface smoothness and its surface roughness Rmax. Exhibited a good surface roughness of 0.02 μm and a low coefficient of friction of 0.05, and no wear powder was generated by the stamper even after 100,000 moldings.
( Reference Example 3 )

As shown in FIG. 4, a heat insulating layer made of zirconia material is formed with a thickness of about 100 μm on the cavity surface 15 of the movable mold 6 by the plasma powder spray method using zirconia powder. After polishing, a sealing layer 22 made of water glass with a thickness of about 50 μm was formed, and the stamper 4 was placed on the sealing layer 22. The surface of the sealing layer 22 formed in this manner is sealed with gaps between zirconia particles and exhibits good surface smoothness, and its surface roughness Rmax is 0.03 μm and has a good surface roughness. It was shown that no abrasion powder was generated by the stamper even after molding 100,000 times.
(Comparative example)

In Reference Example 3 , a movable mold part was produced in the same manner except for the sealing layer 22. A large number of gaps between zirconia particles were observed on the surface of the heat insulating layer, and the surface roughness, Rmax, was as coarse as 0.1 μm, and generation of stamper wear powder was observed after 1000 moldings.

( Reference Example 4 )
In Reference Example 3 , a movable mold part was produced in the same manner except that an electroless Ni—P plating film was used as the sealing layer instead of the water glass film. The surface of the sealing layer is sealed with gaps between zirconia particles and exhibits good surface smoothness, and its surface roughness Rmax is 0.05 μm and exhibits good surface roughness. No wear powder was generated by the stamper even when the test was performed.
( Reference Example 5 )

5 is a plan view of the light guide plate 23 formed according to Reference Example 5 , FIG. 6 is a cross-sectional view taken along the line AA in FIG. 5, and FIG. 7 is a cutaway view of a portion B in FIG. FIG.

The light guide plate 23 formed in Reference Example 5 is made of polycarbonate and is formed by injection molding using a molding die to be described later. As is apparent from FIGS. 5 and 6, the rectangular shape is 46 mm in length and 31 mm in width, and has a reflecting surface 24 that is gradually inclined on the surface, and is incident from the left side of FIG. A light beam from a light source (not shown) is bent and reflected upward by this reflecting surface. As is apparent from FIG. 7, the reflecting surface 24 is 0.3 mm wide, and a partially reflecting surface 24a parallel to the width direction in FIG. 5 is inclined downward by 7 μm stepwise in the longitudinal direction. 160 surfaces are formed. In order to increase the reflection efficiency, such a reflection surface 24 needs to be formed with a large number of inclined partial reflection surfaces 24a that are minute irregularities with high precision, and the reflection surface 24 having such minute irregularities. When using a die with a Ni-P plating film directly formed on a normal metal such as cemented carbide, stainless steel, carbon steel, etc. In a state where the molten resin corresponding to the mold shape with high accuracy is difficult to be transferred, there is a problem in optical characteristics. In Reference Example 5 , the cavity surface corresponding to the minute uneven surface of the mold and the metal mold so that the light guide plate molded body having such a minute uneven surface can be injection-molded with good optical characteristics. A heat insulating layer made of a ceramic material is disposed between the molds so that the injected molten resin can be accurately transferred to the cavity surface, and a cavity surface having a minute uneven surface can be easily and reliably formed. It is a thing.

In order to obtain a light guide plate having good optical characteristics, the molding die shown in FIG. 8 is to be provided. FIG. 8 shows a cross-sectional view of a molding die insert 25 which is incorporated into the fixed mold 5 or the movable mold 6 of the molding apparatus as shown in FIG. Is composed of a nesting body 26 made of stainless steel, a heat insulating layer 27 and a sealing layer 28. The nesting body 26 is formed with a rectangular recess 29 having a diameter longer than the length and width of the light guide plate and a depth of 0.5 mm on the upper surface thereof. Using a zirconia (ZrO ₂ ) ceramic powder containing the stabilizing material Y ₂ O ₃ , a thermal insulation material is filled by a plasma powder spray spraying method, polished and flattened, and hydrogen fluoride is applied to the surface. The heat insulation layer 27 is formed by roughening the surface by etching with acid. In this case, in order to improve the adhesion between the nesting body 26 and the heat insulating layer 27, the four inner side surfaces of the recess 29 are inclined surfaces 30 inclined by θ degrees as shown in FIG. Further, a sealing layer 28 made of Ni-P electroless plating is formed on the heat insulating layer 27 and on the nesting body 26 around the heat insulating layer 27 with a thickness of about 130 μm. Here, the angle θ of the inclined surface is 30 degrees in this reference example 5. However, the range of 10 to 60 degrees is preferable, and when the angle is small, Adhesion is poor, and the adhesion improves as this angle increases. However, as the angle θ increases, the heat insulating layer thickness decreases and the number of portions where the heat insulating function deteriorates increases. Therefore, the range up to 60 degrees is preferable. In addition, the thicker the heat insulating layer, the better the heat insulating function. However, as the thickness increases, it takes a long time to form the heat insulating layer by the thermal spraying method, so the thickness is preferably 100 to 1000 μm.

  Further, as described above, the thickness of the sealing layer 28 is 1 μm or more, so that the void formed on the surface of the heat insulating layer can be sealed to form a smooth surface. However, when the surface of the sealing layer 28 is used as the cavity surface 33, a certain amount of thickness is necessary for cutting, and as the thickness increases, Ni by the Ni-P electroless plating method is required. Since it takes a long time to form the -P film, the thickness is preferably 500 μm or less.

The sealing layer 28 is improved in adhesion to the heat insulating layer 27 by etching the surface of the heat insulating layer 27 and has a width (h1) of 100 to 500 μm on the outer peripheral side surface of the nested body 26 made of steel. The first step portion 31 and the second step portion 32 having a narrower width than the first step portion 31 having a width (h2) of 10 to 100 μm are formed, and the step portions 31 and 32 are also covered. As a result, the adhesion between the heat insulating layer 27 and the nested body 26 is improved, and the sealing layer 28 can be prevented from being peeled off or damaged during molding .

  The surface of the sealing layer 28 becomes a cavity surface 33. The cavity surface 33 has a fine uneven surface 34 corresponding to the reflecting surface 24 of the light guide plate 23, and uses a diamond tool with the above-mentioned length, width and step. It is formed by cutting. The sealing layer 28 made of Ni-P has better workability than the heat insulating layer 27 made of ceramics, and fine irregularities can be easily formed by cutting using a diamond tool.

As a result of injection molding of the light guide plate 23 with polycarbonate using such a mold, the light guide plate 23 with good optical characteristics could be easily and reliably formed.
( Example)

In this embodiment, a structure of a mold suitable for producing a plastic substrate for DVD is shown, and the structure is shown in a sectional view of FIG. This mold corresponds to the movable mold 6 of the molding apparatus of FIG. 2, and this mold 6 has a width corresponding to at least the recorded information portion of the DVD on the upper surface of the disc-shaped main body 34 made of stainless steel. A donut-shaped recess 35 is formed, and a zirconia (ZrO ₂ ) ceramic powder containing a partial stabilizing material Y ₂ O ₃ is used in the recess 35, and a heat insulating material is formed by a plasma powder spray spraying method. To form a first heat insulation layer 36 having a thickness of 0.4 mm, and then, using a chromium oxide (Cr ₂ O ₃ ) powder, a second heat insulation layer 37 is formed by plasma powder spraying. The first heat insulating layer 36 is laminated to a thickness of 0.1 mm, and the surface of the second heat insulating layer 37 is polished to smooth the surface. The surface of the second heat insulating layer 37 formed in this way had a surface roughness Rmax of 0.03 μm, indicating a good surface roughness.

  Further, an amorphous diamond-like carbon thin film 38 is formed on the second heat insulating layer 37 by a magnetron sputtering method so as to have a thickness of 3 μm. The surface roughness Rmax of the carbon thin film 38 is further 0.01 μm. Smoothness is improved.

As a result of placing the stamper 4 on the carbon thin film 38, incorporating the movable side mold part into the molding apparatus, and performing injection molding , generation of wear powder by the stamper was recognized even after one million moldings. There wasn't.

Light guide plate made of transparent resin for use in plastic substrates for optical disks such as CDs and DVDs, liquid crystal display devices used in personal computers, mobile phones, etc., or other applications using the molding die according to the present invention It can be effectively used also in such fields. In addition, although the example of the optical substrate for optical disks was shown as an Example of this invention, the metal mold | die of this invention is applicable not only to the plastic substrate for optical disks but to the plastic substrate for hard disks, a plastic lens, etc. It is.

It is an expanded sectional view of the part corresponding to the uneven | corrugated | grooved part 2 corresponding to the recording information of the board | substrate for DVD disc manufactured using the metal mold | die by this invention. It is a schematic sectional drawing of the injection molding apparatus with which the shaping die used by this invention was closed. 5 is a cross-sectional view of a movable mold part of Reference Example 1. FIG. 10 is a cross-sectional view of a movable mold part of Reference Example 3. FIG. It is a top view of the light-guide plate manufactured using the shaping die by the reference example 5 . It is sectional drawing cut | disconnected on the AA line of FIG. It is an expanded sectional view of the B section of FIG. It is sectional drawing of the nest | insert which becomes a part of shaping die by the reference example 5. FIG. It is sectional drawing of the movable mold part of the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 DVD disc board | substrate 2 Uneven part 3 Concave part 4 Stamper 5 Fixed side metal mold 6 Movable side metal mold 7 Stamper outer periphery holder 8 Cavity 9 Gate part 10 Gate cut member 15 Cavity surface (fixed side metal mold)
DESCRIPTION OF SYMBOLS 16 Plate-shaped member 17 Silver brazing 18 Diamond-like thin film 19 Fixed side mounting plate 20 Movable side mounting plate 21 Heat insulation layer 22 Sealing layer 23 Light guide plate 24 Reflecting surface 24a Partial reflecting surface 25 Nesting 26 Nesting body 27 Thermal insulation layer 28 by thermal spraying method 28 Sealing layer 29 Indented portion 30 Inclined surface 31 First step portion 32 Second step portion 33 Cavity surface 34 Mold body 35 Donut-shaped indentation portion 36 First heat insulating layer 37 Second heat insulating layer 38 Carbonaceous thin film

Claims (2)

A heat insulating layer made of ceramic is formed on the surface of at least one of the cavities of the movable mold and the fixed mold made of a metal material, and an amorphous diamond-like carbon thin film is formed on the surface of the heat insulating layer. And the heat insulation layer is made of a ceramic material selected from at least one of zirconia, titanium oxide, alumina, and aluminum titanate . A heat insulating layer made of ceramic is formed on the surface of at least one of the cavities of the movable mold and the fixed mold made of a metal material, and an amorphous diamond-like carbon thin film is formed on the surface of the heat insulating layer. And the heat insulating layer is selected from at least one of a first heat insulating layer made of zirconia and chromium oxide, chromium nitride, alumina, aluminum nitride, silicon nitride, and silicon carbide laminated thereon. A molding die comprising a second heat insulating layer made of the above-described material .

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