JP2005125606A - Mold and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold which enables the higher-precision molding of a product, and its manufacturing method. <P>SOLUTION: In this mold 1, an alumina layer 3 using sputtering is formed on an Al<SB>2</SB>O<SB>3</SB>-TiC substrate 2 or an alumina substrate 2; a tantalum layer 5 is formed on the polished surface of the alumina layer 3; and a required mold pattern is formed on the surface of the tantalum layer 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an injection mold having a highly accurate mold pattern and a method for manufacturing the same.

Conventionally, a method of forming a mold using machining is to form nickel phosphorus (NiP) on a stainless steel substrate by electroless plating, reduce the surface roughness by polishing the surface, and then use a NC lathe or the like to determine the surface roughness. The mold of the shape is made. In this mold forming method using a lathe, two constraint conditions appear. One can form only patterns having rotational symmetry. The other is that the pattern pitch is about 5 μm.
In addition, NiP is formed on a stainless steel substrate in the same manner as machining, tantalum is sputtered on the polished NiP substrate, and then photolithography and etching (physical etching or reactive etching) are used to form a desired gold. There is a method of forming a mold pattern (see Patent Document 1).
JP 2003-103525 A

  By the way, when trying to form a high-precision mold by machining with an NC lathe or the like, as shown in FIG. 3, for example, in a step-shaped mold pattern, a lathe is formed at a portion corresponding to the step edge 63 of the mold 60. Since the blade 61 does not touch, the step edge 63 is distorted. For example, when a hologram lens for CD / DVD compatibility is molded with the edge 62 of the mold edge 63 left, the edge of the mold is also transferred and the lens is molded. It cannot be formed. That is, in the optical pickup of the optical disk, as shown in FIGS. 4A and 4B, the CD / DVD is placed on the light source side of the objective lenses 11 and 12 so that the CD recording medium 13 and the DVD recording medium 14 can be reproduced by one optical pickup. A lens having a compatible hologram lens 10 is known. The lens structure has a large number of ring-shaped staircase shapes from the center toward the outer periphery. This CD / DVD compatible hologram lens 10 corrects the spherical aberration caused by the difference in the substrate thickness between the CD and the DVD by the spherical aberration of the hologram caused by the difference in the wavelengths of the laser beams L1 and L2 as the reproduction light. . 4A and 4B, a CD recording medium 13 having a substrate thickness t1 of 1.2 mm and a recording medium 14 having a substrate thickness t2 of 0.6 mm are respectively subjected to laser light L1, L2 indicates a state of focusing on the recording layer. When such a CD / DVD compatible hologram lens 10 is molded by a mold by machining, the above-mentioned step edge portion 62 does not function as a lens, so the minimum width of a staircase as a mold is limited to 5 μm. It was difficult to reduce the stairs width beyond that.

In addition, as described above, in the method of forming tantalum by forming NiP on a stainless steel substrate, it is possible to form a free-form pattern unlike the method by machining, and the pattern pitch is 1 μm. It is possible to form even a pattern that is lower than that. However, by using a stainless steel substrate as the substrate, the mold has a thermal expansion coefficient of 11 to 17 × 10 ⁻⁶ (1 / K). The mold is deformed, and as a result, the pattern accuracy of the molded product is deteriorated.

  In view of the above-mentioned points, the present invention provides a mold capable of molding a product with higher accuracy and a manufacturing method thereof.

  In the mold according to the present invention, an alumina layer is formed by sputtering on an Altic substrate or an alumina substrate, a tantalum layer is formed on the polished surface of the alumina layer, and a desired mold pattern is formed on the surface of the tantalum layer. The configuration.

The surface roughness Ra of the polished surface of the alumina layer is preferably 0.2 to 0.5 nm.
The mold pattern of the tantalum layer is preferably formed by reactive ion etching by a photolithography method.

  The method for producing a mold according to the present invention includes a step of forming an alumina layer by sputtering on an Altic substrate or an alumina substrate, and a surface roughness Ra of the surface of the alumina layer to be 0.2 to 0.5 nm. A step of polishing, a step of forming a tantalum layer on the surface of the polished alumina layer by sputtering, and a step of forming a required mold pattern by reactive ion etching on the tantalum layer by photolithography. And

In the metal mold | die which concerns on this invention, the deformation | transformation of the metal mold | die by the heat | fever at the time of a product shaping | molding is suppressed since the Altic or alumina used as a board | substrate is used. Further, by selecting tantalum as the mold material, the thermal expansion coefficient of tantalum is 6.5 × 10 ⁻⁶ , so that it is close to the thermal expansion coefficient of the Altic substrate, and the mold surface material due to the thermal history during product formation. Durability is also improved. The durability of the mold is also excellent in deformation due to pressure during product molding because it uses an Altic or alumina substrate.

In the mold manufacturing method according to the present invention, since the mold pattern is formed on the tantalum layer by reactive ion etching by photolithography, the mold pattern can be finely processed. Since Altic or alumina is used as the substrate, deformation of the mold due to heat during product molding can be suppressed. In addition, by selecting tantalum as a mold material having a thermal expansion coefficient of 6.5 × 10 ⁻⁶ , it is possible to approach the thermal expansion coefficient of the Altic substrate, and the surface of the mold surface material due to the thermal history during product formation. Durability is improved. Most of the material of the mold is an AlTiC or alumina substrate, so that the mold is a curable mold having a Vickers hardness of 2000. Since a mold Altic or alumina substrate is used, it does not deform to the pressure at the time of product molding.

  As the surface roughness Ra of the polished surface of the alumina layer, the lower limit of 0.2 nm is the limit of polishing. On the other hand, if the surface roughness Ra exceeds the upper limit of 0.5 nm, the performance of products produced using this mold cannot be ensured.

According to the mold of the present invention, an alumina layer is formed by sputtering on one main surface of the Altic substrate, and after surface polishing, a tantalum layer is formed. A mold by reactive ion etching is formed on the surface of the tantalum layer. Since the pattern is formed, the mold pattern is formed, so that a mold with high mold pattern accuracy can be obtained. Since the thermal expansion coefficient of the AlTiC (Al ₂ O ₃ —TiC) substrate as the substrate is 7.6 × 10 ⁻⁶ , the product is almost half compared to 11-17 × 10 ⁻⁶ of the conventional stainless steel substrate. High-precision product molding can be realized by suppressing the deformation of the mold by heat during molding, that is, heat during injection molding, to about half. Further, if tantalum is selected as the mold material, the thermal expansion coefficient of tantalum is 6.5 × 10 ⁻⁶ , so that the thermal expansion coefficient of the AlTiC (Al ₂ O ₃ —TiC) substrate is higher than the thermal expansion coefficient of stainless steel. Therefore, the durability of the mold surface material due to the thermal history during product formation is also improved. Since most of the material of this mold is an Al ₂ O ₃ —TiC substrate, the mold has a Vickers hardness of 2000. On the other hand, a mold using a stainless steel substrate has a hardness of about 700 at most even if a stainless steel having a high hardness is used. Therefore, the durability of the mold is better when the Al ₂ O ₃ —TiC substrate is used, and the mold made by the method of the present embodiment is also superior in deformation due to pressure during product molding. The use of an alumina substrate has the same effect as an Altic substrate.

When the surface roughness Ra of the polished surface of the alumina layer is 0.2 to 0.5 nm, the tantalum layer can be sputtered with high accuracy.
When forming the mold pattern of the tantalum layer by reactive ion etching by photolithography, a general semiconductor process can be used, and a mold having a more accurate mold pattern can be provided.

  According to the mold manufacturing method of the present invention, fine processing is possible, and therefore a mold having a more accurate mold pattern can be manufactured.

According to the mold manufacturing method of the present invention, an alumina layer is formed by sputtering on one main surface of an Altic substrate, a tantalum layer is formed on the surface-polished alumina layer, and the surface of the tantalum layer is reactive. By forming a mold pattern by ion etching, a mold having a high mold pattern accuracy can be manufactured.
Since the mold is formed using an Altic substrate, an alumina layer, and a tantalum layer that have similar thermal expansion coefficients to each other, a mold that suppresses heat deformation during injection molding and enables high-precision product molding. Can be manufactured. In addition, it is possible to manufacture a mold that has high hardness and excellent durability and does not undergo deformation due to pressure during product molding.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an embodiment showing a mold according to the present embodiment, a so-called tantalum mold and a manufacturing method thereof. Hereinafter, it demonstrates in order of a manufacturing process.
As shown in FIG. 1A, an AlTiC (Al ₂ O ₃ —TiC) substrate 2 is prepared, and an alumina (Al ₂ O ₃ ) layer 3 suitable for sputtering is formed on the AlTiC substrate 2.
Next, as shown in FIG. 1B, the surface roughness Ra of the alumina layer 3 is reduced by polishing the surface of the alumina layer 3 with a lapping plate 4. The surface roughness Ra is preferably about 0.2 to 0.5 nm. By sputtering alumina on the surface of the Altic substrate 2, the sputtered particles of alumina fill the holes on the surface of the Altic substrate 2, so that the polished surface is clean.

Next, as shown in FIG. 1C, a metal layer capable of reactive ion etching (RIE), in this example, tantalum (Ta), is sputtered on the polished surface of the alumina layer 3 to form a tantalum layer 5. . In this case, the tantalum layer 5 is formed with a film thickness that is thicker than the maximum pattern height in consideration of the height of the mold pattern formed on the surface.
As shown in FIG. 1D, a photoresist layer 6 is formed on the tantalum layer 5 by coating. The resist layer 6 is applied with a predetermined film thickness in consideration of the selection ratio at the time of reactive ion etching with the tantalum layer 5.

Next, as shown in FIG. 1E, the photoresist layer 6 is exposed using a photomask (not shown) and developed to form a resist mask 6A having openings 7 corresponding to the mold pattern.
Next, as shown in FIG. 1F, the tantalum layer 5 is selectively etched by the reactive ion etching method through the resist mask 6A. For example, the pattern of the resist mask 6 </ b> A is transferred to the tantalum layer 5 by performing etching using a reactive gas such as CF 4 as a gas to be etched. A required mold pattern 8 is formed on the transferred tantalum layer 5.

  Next, as shown in FIG. 1G, the resist mask 6A is peeled and removed, and the target tantalum mold 1 having the mold pattern 8 on the surface of the tantalum layer 5 using the Altic substrate 2 is obtained.

Here, as the surface roughness Ra of the aluminum layer 3 is improved (Ra is reduced), the surface roughness Ra of the tantalum layer 5 formed on the alumina layer 3 is improved.
Incidentally, as will be described later, when the mold is applied to molding a CD / DVD compatible hologram lens, the surface of the tantalum layer 5 becomes an optical surface at the time of lens molding, so that the surface roughness Ra of the tantalum layer 5 is improved. This reduces the light scattering on the surface of the tantalum layer 5 and improves the transmittance of the lens. Further, when the surface roughness Ra of the tantalum layer 5 is improved, the measurement accuracy at the time of measuring the lens surface shape having a step can be improved. And as surface roughness Ra of the alumina layer 3, 0.2 nm is the limit of the present polishing process, and if it is smaller than this, the polishing process becomes difficult. Further, if the surface roughness Ra is 0.5 nm or less, the performance of a product produced using the mold 1, for example, a CD / DVD compatible hologram lens can be ensured, and the surface roughness Ra is 0. If it exceeds 5 nm, it is difficult to confirm the lens performance.

According to the tantalum mold according to the present embodiment, the alumina layer 3 is formed by sputtering on one main surface of the Altic substrate 2, and after surface polishing, the tantalum layer 5 is formed. Since the mold pattern 8 is formed by reactive ion etching, a mold with high mold pattern accuracy can be obtained. Since the thermal expansion coefficient of the AlTiC (Al ₂ O ₃ —TiC) substrate as the substrate is 7.6 × 10 ⁻⁶ , the product is almost half compared to 11-17 × 10 ⁻⁶ of the conventional stainless steel substrate. High-precision product molding can be realized by suppressing the deformation of the mold by heat during molding, that is, heat during injection molding, to about half. Further, if tantalum is selected as the mold material, the thermal expansion coefficient of tantalum is 6.5 × 10 ⁻⁶ , so that the thermal expansion coefficient of the AlTiC (Al ₂ O ₃ —TiC) substrate is higher than the thermal expansion coefficient of stainless steel. Therefore, the durability of the mold surface material due to the thermal history during product formation is also improved. Since most of the material of this mold is an Al ₂ O ₃ —TiC substrate, the mold has a Vickers hardness of 2000. On the other hand, a mold using a stainless steel substrate has a hardness of about 700 at most even if a stainless steel having a high hardness is used. Therefore, the durability of the mold is better when the Al ₂ O ₃ —TiC substrate is used, and the mold made by the method of the present embodiment is also superior in deformation due to pressure during product molding. The use of an alumina substrate has the same effect as an Altic substrate.

In the present embodiment described above, an AlTiC substrate is used as the substrate. However, there is no particular limitation, and an tantalum mold may be similarly formed using an alumina (Al ₂ O ₃ ) substrate.
The sputtered particles need not be limited to alumina, but may be made of a material that becomes a mold pattern, tantalum is used in the present embodiment, and Altic or the like if the material has a thermal expansion coefficient close to that of tantalum. Further, although an AlTiC substrate or an alumina substrate is used as the substrate, it can be formed of tantalum.

  In the tantalum mold manufacturing method according to the present embodiment described above, a one-stage mold is formed using the photolithography method, but a complex-shaped mold is formed by repeating the photolithography method more than once. It is also possible to do.

According to the tantalum mold manufacturing method of the present embodiment, the alumina layer 3 is formed by sputtering on one main surface of the Altic substrate 2, and the tantalum layer 5 is formed on the surface-polished alumina layer 3. By forming the mold pattern 8 on the surface of the tantalum layer 5 by reactive ion etching, the mold 1 with high mold pattern accuracy can be manufactured.
Mold 1 is formed using Altic substrate 2, alumina layer 3 and tantalum layer 5 which have similar thermal expansion coefficients to each other, so that deformation due to heat during injection molding can be suppressed and high-precision product molding is possible. Molds can be manufactured. In addition, it is possible to manufacture a mold that has high hardness and excellent durability and does not undergo deformation due to pressure during product molding.

  By using the tantalum mold according to the present embodiment, it becomes possible to form a hologram lens for CD / DVD compatibility that requires a high degree of pattern and precision.

  FIG. 2 shows a mold 21 of a CD / DVD compatible hologram lens manufactured by using the manufacturing method of the present embodiment described above.

  Usually, a CD / DVD compatible hologram lens requires very precise processing and requires a highly accurate mold. Further, when the mold is formed by injection molding, the temperature rises to 140 to 150 ° C. for a resin lens and 580 to 620 ° C. for a glass lens. Therefore, it is difficult to transfer the injection molding due to the thermal expansion of the mold itself. I need it.

  According to the mold 21 for a CD / DVD compatible hologram lens according to the present embodiment, the alumina layer 3 is sputtered on the hard Altic substrate 2 or the alumina substrate 2 having a relatively high thermal conductivity and a low thermal expansion coefficient. After the formation, the alumina layer 3 is polished so that the Ra becomes 0.2 to 0.5 nm, and further, the tantalum layer 5 is formed and the reactive ion etching is performed to form the mold pattern 22. A mold 21 having rigidity can be provided. According to this mold 21, a mold 21 having a width d of 5 μm or less and about 3 μm is obtained.

  In the tantalum mold according to the present embodiment, the formation of the mold of the CD / DVD compatible hologram lens has been described, but this is not particularly limited to the type of the mold, and the advanced pattern and the coefficient of thermal expansion are small. It can be applied to a mold having relatively high thermal conductivity and high rigidity.

It is a manufacturing-process figure which shows one Embodiment of the manufacturing method of the metal mold | die which concerns on this invention. It is sectional drawing which shows one Embodiment of the metal mold | die which concerns on this invention. It is the schematic diagram explaining the conventional metal mold | die formation. It is explanatory drawing of the hologram lens for CD / DVD compatibility shape | molded by the conventional metal mold | die.

Explanation of symbols

  1 .... Tantalum mold, 2 .... Altic substrate or alumina substrate, 3 .... Alumina layer, 4 .... Lap plate, 5 .... Tantalum layer, 6 .... Photoresist layer, 6A ..., Resist mask, ... Aperture, 8, 22 ... Mold pattern, 10 ... CD / DVD compatible hologram lens, 11, 12 ... Objective lens, 13 ... CD recording medium, 14 ... DVD recording medium, 21 ... CD / DVD Compatible hologram lens mold, 60 ... Die, 61 ... Lathe blade, 62 ... Round, 63 ... Step edge

Claims (4)

An alumina layer is formed by sputtering on an Altic substrate or an alumina substrate, and a tantalum layer is formed on the polished surface of the alumina layer,
A mold having a required mold pattern formed on the surface of the tantalum layer. The mold according to claim 1, wherein the surface roughness Ra of the polished surface of the alumina layer is 0.2 to 0.5 nm. The mold according to claim 1, wherein the mold pattern of the tantalum layer is formed by reactive ion etching by a photolithography method. Forming an alumina layer by sputtering on an Altic substrate or an alumina substrate;
Polishing the surface of the alumina layer so that the surface roughness Ra is 0.2 to 0.5 nm;
Forming a tantalum layer by sputtering on the surface of the polished alumina layer;
Forming a required mold pattern on the tantalum layer by reactive ion etching using a photolithography method.

Images