JP2007164985A - Substrate for information recording medium, information recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for an information recording medium having high IR irradiation heating efficiency, an information recording medium with a multilayered film including an information recording layer, formed on the substrate, and its manufacturing method. <P>SOLUTION: This substrate for information recording medium is made of glass or crystallized glass, and is characterized in that (1) it has a region with spectral transmittance of 50% or less in a wavelength range from 2,750 to 3,700 nm, (2) it has spectral transmittance of 70% or less in the wavelength range from 2,750 to 3,700 nm, (3) it contains an IR absorbent made of a specific metal oxide and is used for a perpendicular magnetic recording medium, (4) it is used for IR irradiation heating and contains water of >200 ppm, or (5) it contains the IR absorbent made of the specific metal oxide and used for supporting the multilayered film including the information recording layer formed by sputtering after IR irradiation heating. Further, the information recording medium formed of the multilayered film including the information recording layer on the substrate and its manufacturing method are also disclosed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an information recording medium substrate, an information recording medium, and a manufacturing method thereof. More specifically, the present invention is suitable for an information recording medium substrate having high infrared irradiation heating efficiency, an information recording medium in which a multilayer film including an information recording layer is provided on the substrate, and the substrate is suitable for forming a multilayer film. The present invention relates to a method for producing a good information recording medium by maintaining a high temperature state.

  Conventionally, as a substrate for an information recording medium such as a magnetic disk, for example, a high Young's modulus lithium-containing aluminosilicate glass or a material subjected to chemical strengthening treatment (for example, see Patent Document 1) or a specific composition. A substrate made of crystallized glass (for example, see Patent Document 2) in which a crystal layer is deposited by heat-treating glass is used.

  The information recording medium is formed by forming a multilayer film including an information recording layer on these substrates. When forming a multilayer film on the substrate, for example, the substrate is first introduced into a substrate heating region of a film forming apparatus, and the substrate is heated to a temperature at which film formation by a sputtering ring is possible. After the temperature of the substrate is sufficiently raised, the substrate is transferred to the first film formation region, and a film corresponding to the lowermost layer of the multilayer film is formed on the substrate. Next, the substrate is transferred to the second film formation region, and film formation is performed on the lowermost layer. In this way, the substrate is sequentially transferred to the subsequent film formation region to form a film, thereby forming a multilayer film including the information recording layer on the substrate. Since the heating and film formation are performed under a low pressure exhausted by a vacuum pump, the heating must be performed in a non-contact manner. Therefore, heating by radiation is suitable for heating the substrate.

  This film formation must be performed before the substrate falls below a temperature suitable for film formation. If the time required for forming each layer is too long, the temperature of the heated substrate is lowered, and there is a problem that a sufficient substrate temperature cannot be obtained in the subsequent film formation region. In order to maintain the temperature at which the substrate can be formed over a long period of time, it is conceivable to heat the substrate to a higher temperature. However, if the heating rate of the substrate is low, the heating time must be longer, The time for the substrate to stay must also be lengthened. Therefore, the residence time of the substrate in each film formation region also becomes long, and a sufficient substrate temperature cannot be maintained in the subsequent film formation region. Furthermore, the throughput cannot be improved.

In order to increase the heating rate, it is conceivable to irradiate the substrate with high-power light. However, the light absorption of the glass substrate or the crystallized glass substrate is weak, and there is a problem that it is difficult to obtain sufficient heating efficiency.
JP 2001-180969 A JP 2000-119042 A

  Under such circumstances, the present invention provides an information recording medium substrate having high infrared irradiation heating efficiency, an information recording medium in which a multilayer film including an information recording layer is provided on the substrate, and the substrate as a multilayer film. It is an object of the present invention to provide a method for producing a good information recording medium by maintaining a temperature suitable for the film formation or heating the substrate sufficiently in a short time.

As a result of intensive studies to achieve the above object, the present inventors have (1) a substrate made of glass or crystallized glass in which a region having a spectral transmittance of a certain value or less exists in a specific wavelength region. (2) A substrate made of glass or crystallized glass that has a spectral transmittance below a certain value over a specific wavelength range, (3) A substrate made of glass or crystallized glass containing an infrared absorber made of a specific metal oxide Or (4) that a substrate made of glass or crystallized glass containing a certain amount of water can be used as an information recording medium substrate, and that these substrates are heated by irradiating them with infrared rays. By forming a multilayer film including an information recording layer, or by forming a multilayer film including an information recording layer on a substrate heated at an average heating rate equal to or higher than a value that is a heating region, It has been found capable of producing an information recording medium. The present invention has been completed based on such findings.

That is, the present invention
(1) A substrate for an information recording medium (hereinafter referred to as “a substrate for an information recording medium”) having a spectral transmittance of 50% or less converted to a thickness of 2 mm in a wavelength range of 2750 to 3700 nm. , Substrate 1),
(2) An information recording medium substrate (hereinafter referred to as “substrate 2”), which is made of glass or crystallized glass and has a wavelength of 2750 to 3700 nm and a spectral transmittance converted to a thickness of 2 mm of 70% or less. ,
(3) An infrared absorber comprising an oxide of at least one metal selected from iron, copper, cobalt, ytterbium, manganese, neodymium, praseodymium, niobium, cerium, vanadium, chromium, nickel, molybdenum, holmium and erbium. A substrate for information recording medium (hereinafter referred to as substrate 3), characterized in that it is made of glass containing glass or crystallized glass and used for a perpendicular magnetic recording medium.
(4) The information recording medium substrate according to (1), (2) or (3), which is for infrared irradiation heating,
(5) An information recording medium substrate (hereinafter referred to as substrate 4), which is made of glass or crystallized glass, contains moisture of more than 200 ppm, and is used for infrared irradiation heating.
(6) An infrared absorber comprising an oxide of at least one metal selected from iron, copper, cobalt, ytterbium, manganese, neodymium, praseodymium, niobium, cerium, vanadium, chromium, nickel, molybdenum, holmium and erbium. An information recording medium substrate (hereinafter referred to as substrate 5), which is used for supporting a multilayer film including an information recording layer formed by sputtering after infrared irradiation and heating. ),
(7) An information recording medium comprising a multilayer film including an information recording layer provided on the information recording medium substrate according to any one of (1) to (6) above,
(8) In the method for manufacturing an information recording medium in which a multilayer film including an information recording layer is formed on an information recording medium substrate, the substrate heated at an average heating rate of 10 ° C./second or more in a heating region is formed into a plurality of components. A method of manufacturing an information recording medium (hereinafter referred to as manufacturing method 1), wherein the multilayer film is formed by sequentially transferring to a film region and sequentially forming each layer constituting the multilayer film in each film forming region;
(9) The method for producing an information recording medium according to (8) above, wherein the residence time of the information recording medium substrate in the heating region and each film formation region is equalized,
(10) The method for manufacturing the information recording medium according to (8) or (9), wherein the information recording medium substrate is carried into and out of the heating region and each film formation region in synchronization.
(11) The method for producing an information recording medium according to (8), (9) or (10) above, wherein the information recording medium substrate is heated by irradiating infrared rays.
(12) Forming a multilayer film including an information recording layer on the substrate by irradiating the information recording medium substrate described in any one of (1) to (6) with infrared rays and heating the substrate. A method of manufacturing a characteristic information recording medium (hereinafter referred to as manufacturing method 2),
(13) An information recording medium, wherein an information recording layer is formed on the information recording medium substrate according to any one of (1) to (5) above, and then heated by irradiation with infrared rays. (14) selected from iron, copper, cobalt, ytterbium, manganese, neodymium, praseodymium, niobium, cerium, vanadium, chromium, nickel, molybdenum, holmium, and erbium An information recording layer is formed on a substrate for an information recording medium made of glass or crystallized glass containing an infrared absorber made of at least one metal oxide, and then heated by irradiation with infrared rays. Manufacturing method of recording medium (hereinafter referred to as manufacturing method 4)
Is to provide.

  ADVANTAGE OF THE INVENTION According to this invention, the information recording medium provided with the board | substrate for information recording media with high infrared irradiation heating efficiency and the said board | substrate can be provided. In addition, it is possible to provide a method for producing a good information recording medium by maintaining the substrate at a temperature suitable for forming a multilayer film or by efficiently heating the substrate on which the information recording layer is formed. it can. Furthermore, since the throughput is dramatically improved, a high-quality information recording medium can be provided to the market at a low cost.

Embodiments of the invention will be described in the order of an information recording medium substrate, an information recording medium, and an information recording medium manufacturing method.
<Substrate for information recording medium>
The information recording medium substrate of the present invention has been completed based on the following knowledge.

Glass, there is an absorption peak in the region including the wavelength 2750~3700nm the glass containing a suitable _SiO 2, _Al 2 _{O 3} or _{SiO 2,} B 2 _{O 3} as a substrate for particular information recording medium. The above characteristics also exist in crystallized glass.

  In order to efficiently heat a glass substrate or a crystallized glass substrate by infrared irradiation, it is desirable to use infrared rays having a spectrum maximum in the wavelength range.

  In the substrate heating by infrared irradiation, since a part of infrared rays is reflected by the film on the substrate on which the film is formed and the power of the infrared ray absorbed by the substrate is reduced, it is desirable to heat before starting the film formation. Even when the substrate is heated by irradiation with infrared rays after the information recording layer is formed, a sufficient heating effect can be obtained by using a substrate having a large absorption of infrared rays.

In order to increase the heating rate, it is conceivable to match the infrared spectral maximum wavelength with the absorption peak wavelength of the substrate and increase the infrared power. Taking a high-temperature carbon heater as an example of the infrared source, the input of the carbon heater may be increased to increase the infrared power. However, when the radiation from the carbon heater is considered as black body radiation, the heater temperature rises due to an increase in input, so that the maximum wavelength of the infrared spectrum shifts to the short wavelength side and deviates from the above absorption wavelength range of the glass. For this reason, in order to increase the heating rate of the substrate, the power consumption of the heater must be excessive, and problems such as shortening the life of the heater occur.

  In view of these points, by increasing the absorption of the glass in the above wavelength region, the infrared radiation should be performed with the infrared spectral maximum wavelength close to the absorption peak wavelength of the substrate, and the heater input should not be excessive. Is desirable.

  Since the substrate shape is a thin plate shape such as a disk shape, the following information recording medium substrates are desired to increase the heating efficiency.

Based on the above knowledge, before formation of a multilayer film including an information recording layer (however, a layer formed before forming the information recording layer may be removed from the multilayer film without being heated) or It has been found that the following substrates 1 to 5 are substrates for information recording media that can be efficiently heated by infrared irradiation after forming the information recording layer.
(Substrate 1)
The substrate 1 is made of glass or crystallized glass, and is an information recording medium substrate in which a region having a spectral transmittance of 50% or less converted to a thickness of 2 mm exists in a wavelength range of 2750 to 3700 nm.

  The substrate 1 includes those that have been chemically strengthened and those that have not been chemically strengthened. When chemically strengthened, there is an ion-exchanged layer in the vicinity of the surface, except for this part, the substrate is made of homogeneous glass, and when not chemically strengthened, the entire substrate is made of homogeneous glass or Consists of crystallized glass. Since the absorption coefficient and the scattering coefficient are constant in the homogeneous portion, the spectral transmittance can be converted by a known conversion method even for substrates having different thicknesses. In addition, even if the ion exchange layer by chemical strengthening exists, it can be considered that the absorption coefficient is constant throughout the substrate. Note that the spectral transmittance is measured by allowing measurement light to enter perpendicularly to the surface of the substrate on which the information recording layer is formed (referred to as the main surface). Spectral transmittance includes the influence of reflection and scattering on the substrate surface in addition to light absorption and scattering inside the substrate. High flatness and smoothness are required for the main surface of the information recording medium substrate.

Since the substrate 1 has the above-described spectral transmittance characteristics, the heating efficiency by infrared irradiation can be increased, and the substrate can be heated at a high heating rate when forming the multilayer film including the information recording layer. Further, the substrate on which the information recording layer is formed can be sufficiently heated by infrared irradiation.
(Substrate 2)
The substrate 2 is made of glass or crystallized glass, and is an information recording medium substrate having a spectral transmittance of 70% or less converted to a thickness of 2 mm over a wavelength range of 2750 to 3700 nm.

  The same effect as that of the substrate 1 can be obtained by the substrate 2 that can obtain high absorption over the above wavelength range. The homogeneity of the substrate 2, the measurement of the spectral transmittance, and the conversion method are the same as those for the substrate 1. The substrate 2 preferably has the characteristics of the substrate 1. That is, since the spectrum of the infrared rays emitted from the infrared source has a broadening, it is more preferable that the wavelength region having a large absorption exists over the range including the infrared spectral maximum wavelength region in order to efficiently absorb the light.

  Since the substrate 2 has the above-described spectral transmittance characteristics, the heating efficiency by infrared irradiation can be increased, and the substrate can be heated at the time of forming the multilayer film including the information recording layer at a high heating rate. Further, the substrate on which the information recording layer is formed can be sufficiently heated by infrared irradiation.

When the substrate 1 or the substrate 2 is made of crystallized glass, the spectral transmittance depends on the size and density of crystal particles in the crystallized glass. When the size of the crystal particles is large, the proportion of scattering by the crystal particles increases in the reduction of the spectral transmittance, and the spectral transmittance may be smaller than the predetermined value even if the absorption is small. When the substrate of the present invention is made of crystallized glass, the size of the crystal particles is preferably 100 nm or less. If the size is within this range, the scattering of infrared rays by the crystal particles is small, and the density of the crystal particles It is thought that it is not influenced by. Therefore, the main factor determining the spectral transmittance is infrared absorption by the crystallized glass. Therefore, when the substrate is made of crystallized glass in the substrate 1 and the substrate 2, the preferred size of the crystal particles is as described above. A more preferable range is 50 nm or less, and a particularly preferable range is 1 to 50 nm.
(Substrate 3)
The substrate 3 is an infrared ray absorption composed of an oxide of at least one metal selected from iron, copper, cobalt, ytterbium, manganese, neodymium, praseodymium, niobium, cerium, vanadium, chromium, nickel, molybdenum, holmium and erbium. It is a substrate for an information recording medium made of glass containing an agent or crystallized glass and used for a perpendicular magnetic recording medium.

  The infrared absorber exhibits strong light absorption in the infrared region in glass or crystallized glass. The substrate 3 is used for a perpendicular magnetic recording medium. In the manufacture of the perpendicular magnetic recording medium, the multilayer film including the magnetic recording layer is subjected to a high temperature annealing treatment. Therefore, heat treatment is performed at a higher temperature than the longitudinal magnetic recording system medium, and the substrate needs to be heated to a higher temperature. Also, when a substrate is provided with a seed layer and a soft magnetic layer and then heated by infrared irradiation, the substrate must be heated to a desired temperature in a short time. Further, when infrared irradiation heating is performed after forming the magnetic recording layer, the infrared rays that have reached the substrate are sufficiently absorbed, and the temperature of the substrate must be sufficiently high. Therefore, the heating efficiency of the substrate by infrared irradiation must be increased. According to the substrate 3, the light absorption in the infrared region is increased by the addition of the infrared absorber, so that heating suitable for the manufacture of the perpendicular magnetic recording medium can be efficiently performed.

  In addition, since the substrate temperature of 200 ° C. or higher is necessary for manufacturing the perpendicular magnetic recording medium to be heated, the substrate is heated to 200 ° C. or higher and lower than the glass transition temperature of the material constituting the substrate. The substrate heating temperature is preferably 250 ° C. or higher and lower than the glass transition temperature of the material constituting the substrate, more preferably 300 ° C. or higher and lower than the glass transition temperature of the material constituting the substrate, and a more preferable range is 450 ° C. or higher. Is less than the glass transition temperature of the material. A particularly preferable range is a range of 550 ° C. or less in the above range.

Among the above infrared absorbers, when an iron oxide is contained alone, the content thereof is preferably 500 ppm to 5% on a weight basis as Fe ₂ O ₃ , and is 2000 ppm to 5%. Is more preferable, 2000 ppm to 2% is more preferable, and 4000 ppm to 2% is even more preferable. By introducing an iron oxide, absorption near a wavelength of 1000 nm can be increased. A preferable spectral transmittance at a wavelength of 1000 nm is 90% or less in terms of a thickness of 2 mm.

  The substrate 3 preferably has the characteristics of the substrate 1, the characteristics of the substrate 2, and the characteristics of the substrate 1 and the substrate 2.

The said board | substrate 1, the board | substrate 2, and the board | substrate 3 are suitable as an object for infrared irradiation heating. The infrared irradiation heating will be described in detail later.
(Substrate 4)
The substrate 4 is an information recording medium substrate that is made of glass or crystallized glass, contains more than 200 ppm of water, and is used for infrared irradiation heating.

Here, the moisture contains OH groups, but the content is displayed in terms of H ₂ O. Moisture or OH groups have strong absorption in the 3 μm band. Therefore, a substrate made of glass or crystallized glass containing moisture exceeding 200 ppm on a weight basis has a large light absorption in the 3 μm band, that is, in the vicinity of a wavelength of 2750 to 3700 nm, increasing the heating efficiency during infrared irradiation heating and increasing the heating rate of the substrate. Improvements can be made. A preferable water content is 220 ppm or more.

In addition, as the board | substrate 4, what combined the characteristic of the board | substrate 1, what combined the characteristic of the board | substrate 2, and also what combined the characteristic of the board | substrate 1 and the board | substrate 2 is preferable. It is also suitable as a perpendicular magnetic recording medium substrate.
(Substrate 5)
The substrate 5 is an infrared ray absorption composed of an oxide of at least one metal selected from iron, copper, cobalt, ytterbium, manganese, neodymium, praseodymium, niobium, cerium, vanadium, chromium, nickel, molybdenum, holmium and erbium. It is a substrate for an information recording medium that is used for supporting a multilayer film including an information recording layer made of glass containing an agent or crystallized glass and formed by sputtering after infrared irradiation heating.

  Here, a multilayer film including an information recording layer formed by sputtering after infrared irradiation heating means (1) an information recording medium substrate heated in a heating area is sequentially transferred to a plurality of film forming areas, and in each film forming area. A multilayer film formed by sputtering film formation; (2) the multilayer film of (1) above, wherein the residence time of the substrate in the heating region and each film formation region is equal; (3) The multilayer film according to the above (1), which means a multilayer film formed by synchronously carrying the substrate into and out of the heating region and each film formation region. In the formation of any of the multilayer films (1) to (3) above, the heating of the substrate and the sputtering film formation are performed in a vacuum or under a low pressure. Heating by infrared irradiation that enables efficient heating in vacuum or under low pressure is preferred. Further, the substrate 5 is suitable as a stationary facing sputtering substrate or an inline sputtering substrate, but is more preferably used as a stationary facing sputtering substrate, and particularly suitable as a single wafer stationary facing sputtering substrate. is there.

  Both the residence time of the substrate in the heating region and the residence time of the substrate in each film formation region are preferably 2 to 10 seconds. The average heating rate of the substrate is preferably 10 ° C./second or more, more preferably 15 ° C./second or more, further preferably 20 ° C./second or more, and 30 ° C./second or more. Is more desirable. The average heating rate is obtained by dividing the difference between the substrate temperature before heating and the substrate temperature at the end of heating by the heating time. In order to prevent damage to the substrate due to rapid heating, the average heating rate is preferably set to 200 ° C./second or less.

  The infrared absorber is an additive that increases infrared absorption, as in the case of the substrate 3. The amount of the infrared absorber introduced is the same as that of the substrate 3.

  The substrate 5 has the characteristics of the substrate 1, the characteristics of the substrate 2, the characteristics of the substrate 1 and the substrate 2, and the characteristics of the substrate 4. Are preferred respectively. It is also suitable for a perpendicular magnetic recording medium.

  The infrared irradiation heating of the substrates 1 to 5 is performed when a multilayer film including an information recording layer is formed on the substrate or immediately before the film formation. For infrared irradiation heating, an infrared source having a maximum wavelength of the emission spectrum in the wavelength region of 2750 to 3700 nm is suitable. A heating element is suitable as such an infrared source. When this heating body can be regarded as a black body, the temperature of the heating body is preferably 600K to 1000K, and more preferably 700K to 900K in order to match the maximum wavelength of the radiation spectrum to the vicinity of the absorption peak of the substrate.

  A carbon heater is suitable as the heating element. By disposing the heating element in the heating chamber, the oxygen partial pressure in the heating atmosphere is reduced, so that deterioration due to oxidation of the carbon heater can also be reduced.

The center line average roughness Ra of the main surface of the substrate is preferably 0.05 to 1 nm for the reason of reducing the smoothness required for the information recording medium substrate and the surface scattering of infrared rays.
What is necessary is just to determine the flatness and parallelism of a board | substrate according to the request | requirement in each information recording medium.

  Each substrate has a disk shape having a central hole, and the outer diameter is about 10 to 95 mm. The substrate should have a uniform thickness and the thickness should be in the range of 0.1 to 2 mm.

  The substrate heating is preferably performed by irradiating the surface (main surface) on which the multilayer film including the information recording layer of the substrate is formed with infrared rays.

Since infrared rays are reflected to some extent by the multilayer film, infrared irradiation heating is performed before film formation or after a layer that can be formed without heating is formed (for example, in a perpendicular magnetic recording medium, a seed layer, a soft magnetic layer It is desirable to carry out after the formation. However, even when the substrate on which the information recording layer is formed is heated by infrared irradiation, since the infrared absorption of the substrate is enhanced, the infrared power reaching the substrate is reduced by reflection on the surface of the information recording layer. In addition, a sufficient heating effect can be obtained.

  Since each of the substrates has a large infrared absorption, the rate of temperature drop due to infrared radiation is slower than a substrate having a small infrared absorption. Therefore, the substrate temperature suitable for film formation is maintained for a relatively long time. The slow cooling rate of the glass constituting the substrate and the base glass of the crystallized glass constituting the substrate is also advantageous from the following points. The substrate is processed into a desired shape by molding glass in a high-temperature state that can be plastically deformed, or by performing machining after the molding. According to the glass, since the cooling rate in a high temperature state is slow, the molding time can be afforded and molding becomes easy. For these reasons, press molding and float molding are suitable for the above molding, and press molding is particularly suitable.

  Next, the composition of glass, crystallized glass or its base glass (glass for making crystallized glass by heat treatment) suitable for the substrates 1 to 5 will be described.

The preferred composition for each substrate is that the absorption of infrared rays is enhanced by adding moisture or an infrared absorbent to the following basic composition. The common point regarding the basic composition is that it contains SiO ₂ and Al ₂ O ₃ . A composition containing SiO ₂ and Al ₂ O ₃ originally has a relatively clear absorption peak around a wavelength of 3 μm and is preferable as a basic composition. In addition, as for the addition method of an infrared absorber, it is preferable to add each additive to a preparation raw material as an oxide. The addition of moisture is performed using hydroxide as a raw material, or by bubbling a gas containing water vapor into the molten glass, or by using the hydroxide raw material and the bubbling in combination. It is preferable to do. In particular, in the case of containing SiO ₂ and Al ₂ O ₃ , it is preferable to use aluminum hydroxide so that a desired water content can be obtained.

The glass or crystallized glass containing SiO ₂ and _B 2 _{O 3} is preferable. In that case, the glass is preferably used _H 3 BO ₃ as a raw material.

A preferred basic composition is as follows.
(Composition 1)
Composition 1, in weight _percent, comprises _{SiO 2 62~75%, Al 2 O} 3 5~15%, Li 2 O 4~10%, Na 2 O 4~12%, a ZrO 2 5.5 to 15% , Na ₂ O / ZrO _{2 has} a weight ratio of 0.5 to 2.0, and Al ₂ O ₃ / ZrO _{2 has} a weight ratio of 0.4 to 2.5. The glass having this composition is preferably applied to the substrate as an amorphous glass.

The composition 1 has excellent characteristics as a chemically strengthened substrate because it can realize a deep compressive stress layer, high bending strength and high Knoop hardness by chemical strengthening, and also has large Knoop hardness and Vickers hardness. This chemical strengthening is preferably performed by an ion exchange treatment in a treatment bath containing Na ions and / or K ions. As the treatment bath containing Na ions and / or K ions, it is preferable to use a treatment bath containing sodium nitrate and / or potassium nitrate, but the treatment bath is not limited to nitrates, but sulfates, hydrogen sulfates, carbonates, Hydrogen carbonate and halide may be used. When the treatment bath contains Na ions, the Na ions exchange with Li ions in the glass, and when the treatment bath contains K ions, the K ions exchange with Na ions in the glass. When the treatment bath further contains Na ions and K ions, these Na ions and K ions exchange with Li ions and Na ions in the glass, respectively. By this ion exchange, alkali metal ions in the glass surface layer portion are replaced with alkali metal ions having a larger ion radius, and a compressive stress layer is formed in the glass surface layer portion to chemically strengthen the glass.

A more preferred range of composition 1, in _{weight%, SiO 2 63~71%, Al} 2 O 3 7~14%, Li 2 O 4~7%, Na 2 O 6~11%, ZrO 2 6~12% The weight ratio of Na ₂ O / ZrO ₂ is 0.7 to 1.8, and the weight ratio of Al ₂ O ₃ / ZrO ₂ is 0.6 to 2.0.
The composition 1 can contain a commonly used fining agent such as Sb ₂ O ₃ .

  According to the above basic composition, since it has a strong action of binding to hydroxyl groups in the glass and retaining moisture in the glass, suitable infrared absorption characteristics can be obtained by adding a desired amount of moisture. Moreover, suitable infrared absorption characteristics can be easily obtained by adding an infrared absorber.

Such glass can be manufactured as follows. First, a glass material prepared so as to obtain a desired composition is heated and melted at about 1500 to 1600 ° C. for about 5 to 8 hours to obtain a desired shape. Composition 1 is suitable for press molding.
(Composition 2)
Composition 2 in _{molar%, SiO 2 40~65%, Al} 2 O 3 1~10%, Li 2 O 5~25%, Na 2 O 0~15%, CaO 0~30%, MgO 0~20 % (However, the total amount of CaO and MgO is 2 to 30%), TiO ₂ 0 to 10% and ZrO ₂ 0 to 10% (however, the total amount of TiO ₂ and ZrO ₂ is 2 to 20%), The composition has a total content of 95% or more. The glass having this composition is preferably applied to the substrate as an amorphous glass. In addition, since the substrate strength can be increased efficiently by chemical strengthening, it has excellent characteristics as a chemically strengthened substrate and a chemically strengthened substrate.

A first preferred range of composition 2 in _{molar%, SiO 2 40~65%, Al} 2 O 3 1~10%, Li 2 O 5~25%, Na 2 O 1~15%, CaO 1~30 %, MgO
0-10% (provided that 2 to 30 _percent the total amount of CaO and MgO), TiO 2 0.1 to 10% and _ZrO 2 1 to 10% (although, TiO ₂ and ZrO ₂ in a total amount 2-15% And the total content of the components is 95% or more. However, more preferably, the amount of ZrO ₂ is larger than that of TiO ₂ .

A second preferred composition ranges _{2, SiO 2 45~65%, Al 2} O 3 2~8%, Li 2 O 8~20%, Na 2 O 1~10%, CaO 5~25%, MgO 0 8% (however, _5-25% total of CaO and MgO), TiO 2 0.1 to 8% and _ZrO 2 3 to 8% (provided that the total amount of TiO ₂ and ZrO ₂ 3.1-12 %), And the total content of the components is 95% or more. However, more preferably, the amount of ZrO ₂ is larger than that of TiO ₂ .

In the preferable range, the total content of Li ₂ O and Na ₂ O is preferably 10 to 25%, and the content of SiO ₂ is preferably more than 50% and less than 65%. The content of Al ₂ O ₃ is preferably 2% or more and less than 6%, and the content of CaO is preferably more than 9% and 25% or less. The Li ₂ O content is preferably 10% or more, and the TiO ₂ content is preferably 0.2% or more and less than 5%.

Particularly preferable in these compositions are those in which the total content of SiO ₂ , Al ₂ O ₃ , Li ₂ O, Na ₂ O, ZrO ₂ , TiO ₂ , CaO, and MgO is 100%, or each of the above components And Sb ₂ O ₃ up to less than 1% by weight is added.

According to the above basic composition, since it has a strong action of binding to hydroxyl groups in the glass and retaining moisture in the glass, suitable infrared absorption characteristics can be obtained by adding a desired amount of moisture. Moreover, suitable infrared absorption characteristics can be easily obtained by adding an infrared absorber.

  The composition 2 has excellent water resistance. The water resistance is determined by determining the surface centerline average roughness Raf when a glass substrate having the basic composition 2 is kept in water at a temperature of 80 ° C. for 24 hours. When the center line average roughness of the surface before holding is Rab, it can be expressed by Rab / Raf. In the glass substrate of composition 2, the value of Rab / Raf is usually 0.8-1. The closer the Rab / Raf value is to 1, the better the water resistance and the smaller the surface roughness is. The preferred Rab / Raf value is 0.84-1. Further, the center line average roughness Rab of the surface before being held in water is preferably in the range of 0.1 to 0.5 nm. The Rab and Raf can be measured using an atomic force microscope (AFM).

  The Young's modulus is preferably 90 to 120 GPa, and more preferably 95 to 120 GPa.

  In this way, a substrate for an information recording medium that can be applied to an information recording medium excellent in stability during high-speed rotation and has extremely high surface smoothness is provided.

In order to match the thermal expansion characteristics with the fixture of the information recording medium, the average linear thermal expansion coefficient at 100 to 300 ° C. is preferably 80 × 10 ⁻⁷ / ° C. or more.

Furthermore, after satisfying the water resistance, Young's modulus, and expansion coefficient, the specific gravity is preferably 3.1 or less, and more preferably 2.9 or less. For example, what is necessary is just to determine a glass composition on the basis of specific gravity 2.3-2.9. Moreover, lowering the specific gravity is also preferable for reducing the heat capacity of the substrate.
The chemical strengthening of the glass substrate of composition 2 is the same as the chemical strengthening of the glass substrate of composition 1.

  From the viewpoint of such a chemical strengthening step and / or an information recording layer forming step, it is desirable that the glass transition temperature Tg of the glass substrate material be 500 ° C. or higher. If the glass transition temperature is too low, salts such as sodium nitrate and potassium nitrate used for chemical strengthening cannot be melted under the above temperature conditions, or the substrate is deformed by heating when forming an information recording layer on the glass substrate. The problem will end up. In consideration of such points, the glass composition may be determined based on the glass transition temperature Tg of 500 to 600 ° C.

Note that the Young's modulus, the expansion coefficient, the glass transition temperature, the specific gravity, and the like of the glass substrate hardly change before and after chemical strengthening, and Rab / Raf is the same or increased (the upper limit is 1).
The above composition has excellent water resistance, and the substrate surface is not roughened even after cleaning.

Composition 2 is suitable for press molding.
(Composition 3)
Composition 3 in _{molar%, SiO 2 35~70%, Al} 2 O 3 1~15%, CaO 1~45%, 3~45% of MgO and CaO in a total amount, the Li ₂ O and Na ₂ O The total amount includes 3 to 30% and TiO ₂ 0.1 to 10%. The composition is suitable as a basic composition of an amorphous glass substrate, and has a high Young's modulus and good press formability. It is also suitable for a chemically strengthened glass substrate.

According to the above basic composition, since it has a strong action of binding to hydroxyl groups in the glass and retaining moisture in the glass, suitable infrared absorption characteristics can be obtained by adding a desired amount of moisture. Moreover, suitable infrared absorption characteristics can be easily obtained by adding an infrared absorber.
(Composition 4)
Composition 4 in _{molar%, SiO 2 45~70%, Al} 2 O 3 1~15% ( provided that the total amount of SiO ₂ and _Al 2 _{O 3} is 57~85%), CaO 2~25%, BaO 0-15%, MgO 0-15%, SrO 0-15%, ZnO 0-10% (however, the total amount of MgO, CaO, SrO, BaO and ZnO is 2-30%), K ₂ O 2-15 %, Li ₂ O 0-8%, Na ₂ O 0-8% (however, the total amount of K ₂ O, Li ₂ O and Na ₂ O is 2-15%), ZrO ₂ 0-12% and TiO ₂ The composition contains 0 to 10% and the total content of the above components is 95% or more. This composition glass is preferably applied to the substrate as an amorphous glass. Further, in this composition range, a glass having a relatively high glass transition temperature can be stably obtained, which is suitable for a substrate that does not thermally deform even when a high-temperature heat treatment is performed. Therefore, it is a basic composition suitable for a perpendicular magnetic recording medium substrate.

Further preferred composition range, in _{mol%, SiO 2 50~67%, Al} 2 O 3 2~12% ( provided that the total amount of SiO ₂ and _Al 2 _{O 3} is 57~79%), CaO 3~20% BaO 0-14%, MgO 0-10%, SrO 0-10%, ZnO 0-8% (however, the total amount of MgO, CaO, SrO, BaO and ZnO is 3-30%), Li ₂ O
_{0~5%, Na 2 O 0~5%} , K 2 O 4~12% ( _however, K 2 O, the total amount of Li ₂ O and Na ₂ O is _4~12%), ZrO 2 _0~10% And TiO ₂ 0 to 8%.

Among these, a particularly preferable composition is that in which the total content of SiO ₂ , Al ₂ O ₃ , MgO, CaO, BaO, K ₂ O, and ZrO ₂ is 98% or more, and the total amount is 99% or more. Is more preferable, and 100% is more preferable. An appropriate amount of Sb ₂ O ₃ , fluoride, chloride, SO ₃ , As ₂ O ₃ can be added to this composition as a foaming agent, but the total content is 2% by weight or less as a rough guide. It is preferable to make it 1% by weight or less. In consideration of the environment, it is desirable not to use an arsenic compound such as As ₂ O ₃ .
Those not containing TiO ₂ are particularly excellent in terms of reducing the roughness of the substrate surface.

  The excellent point of this composition is that the glass transition temperature is usually 620 ° C. or higher, preferably 650 ° C. or higher, more preferably 680 ° C. or higher, more preferably 700 ° C. or higher, and high heat resistance. . Although there is no restriction | limiting in particular about the upper limit of the transition temperature of the said glass, Usually, it is about 900 degreeC. Due to such high heat resistance, it is possible to prevent deformation of the substrate even if high temperature heat treatment is performed in the process of manufacturing the perpendicular magnetic recording medium.

  According to the above basic composition, since it has a strong action of binding to hydroxyl groups in the glass and retaining moisture in the glass, suitable infrared absorption characteristics can be obtained by adding a desired amount of moisture. Moreover, suitable infrared absorption characteristics can be easily obtained by adding an infrared absorber.

  The above composition can be chemically strengthened. At that time, it is preferable to perform ion exchange by immersing the substrate in a molten salt containing K ions.

  Further, it has excellent resistance to water and water resistance such as silicic acid, and the substrate surface is not roughened even when acid treatment or cleaning is performed.

Composition 4 is suitable for press molding and float molding, and particularly suitable for press molding. However, in the case of float forming, addition of Sb ₂ O ₃ and As ₂ O ₃ should be avoided.
(Composition 5)
Composition 5 in _{molar%, SiO 2 55~70%, Al} 2 O 3 1~12.5%, Li 2 O 5~20%, Na 2 O 0~12%, K 2 O 0~2%, MgO 0-8%, CaO
_{0~10%, SrO 0~6%, BaO} 0~2%, TiO 2 0~8%, a composition comprising a ZrO 2 0 to 4%. The glass having this composition is preferably applied to the substrate as an amorphous glass. In addition, since the substrate strength can be increased efficiently by chemical strengthening, it has excellent characteristics as a chemically strengthened substrate and a chemically strengthened substrate.

  According to the above basic composition, since it has a strong action of binding to hydroxyl groups in the glass and retaining moisture in the glass, suitable infrared absorption characteristics can be obtained by adding a desired amount of moisture. Moreover, suitable infrared absorption characteristics can be easily obtained by adding an infrared absorber.

Composition 4 is suitable for press molding and float molding. However, in the case of float forming, addition of Sb ₂ O ₃ and As ₂ O ₃ should be avoided.
(Composition 6)
Composition 6 is SiO ₂ 58 to 66%, Al ₂ O ₃ 13 to 19%, Li ₂ O by weight%.
3 to 4.5%, Na ₂ O 6 to 13%, K ₂ O 0 to 5%, R ₂ O 10 to 18% (where R ₂ O = Li ₂ O + Na ₂ O + K ₂ O), MgO 0 to 3 0.5%, CaO 1-7%, SrO 0-2%, BaO 0-2%, R'O 2-10% (where R'O = MgO + CaO + SrO + BaO), TiO ₂ 0-2%. . The glass having this composition is preferably applied to the substrate as an amorphous glass. Moreover, since the strength of the substrate can be increased efficiently by chemical strengthening, the composition of the substrate for chemical strengthening is also excellent, so that it may be used after being chemically strengthened as appropriate.

  According to the above basic composition, since it has a strong action of binding to hydroxyl groups in the glass and retaining moisture in the glass, suitable infrared absorption characteristics can be obtained by adding a desired amount of moisture. Moreover, suitable infrared absorption characteristics can be easily obtained by adding an infrared absorber.

Composition 6 is suitable for press molding and float molding. However, in the case of float forming, addition of Sb ₂ O ₃ and As ₂ O ₃ should be avoided.
(Composition 7)
Composition 7, by _{weight%, SiO 2 40~80%, Al} 2 O 3 1~10%, B 2 O 3 0~20%, R 2 O 0~20% ( provided _{that, R 2 O = Li 2 O} + Na ₂ O + K ₂ O), R′O 0 to 20% (where R′O = MgO + CaO + SrO + BaO). The glass having this composition is preferably applied to the substrate as an amorphous glass. In addition, since the substrate strength can be increased efficiently by chemical strengthening, it has excellent characteristics as a chemically strengthened substrate and a chemically strengthened substrate.
(Composition 8)
The composition 8 is applied to the substrate as a crystallized glass (crystallized glass) by heat treatment of the base glass. This crystallized glass is obtained by precipitating a crystal phase containing enstatite and / or an enstatite solid solution by heat-treating a base glass. Enstatite is a crystal seed composed of Si, Mg, and O, and the base glass contains SiO ₂ and MgO as essential components, and further contains Al ₂ O ₃ .

Composition 8 preferably does not contain Li ₂ O or ZnO. Moreover, the thing which does not contain a spinel type crystal phase and a lithium disilicate crystal as a crystal phase is preferable.

Enstatite and its solid solution have a structure in which Si and O, which are tightly bonded, are connected in a chain, and are connected in a planar shape via Mg. For this reason, the crystal particles are firmly bound to the amorphous phase. On the other hand, the lithium disilicate crystal has a spherical shape or a shape with a small difference between the major axis and the minor axis, and is relatively weakly bound to the amorphous phase. The strength of the bond between the crystal grains and the amorphous phase affects the ease of detachment of the crystal grains existing on the substrate surface. When the substrate is heated rapidly, the crystal particles existing on the substrate surface are easily detached due to the difference in thermal expansion coefficient between the crystalline phase and the amorphous phase. However, according to the crystallized glass, it is possible to prevent detachment of crystal particles and to prevent generation of concave defects on the substrate surface. Further, in a crystallized glass containing a crystal phase of enstatite and / or a solid solution thereof, the thermal expansion coefficients of the crystal phase and the amorphous phase are close to each other, so that the force for releasing the crystal particles hardly works. On the other hand, the crystallized glass containing the lithium disilicate crystal phase has a thermal expansion coefficient of 2 to 3 times different between the crystal phase and the amorphous phase.

Note that press molding is suitable for molding the base glass of composition 8. The heat treatment for crystallization is preferably performed after press molding.
(Composition 9)
The composition 9 is applied to the substrate as a crystal (crystallized glass) obtained by heat-treating the base glass. The composition of the matrix glass in _{molar%, SiO 2 35~65%, Al} 2 O 3
The composition contains more than 5% and 20% or less, MgO 10-40%, TiO ₂ 5-15%, and the total content of the above components is 92% or more.

Composition 9 preferably does not contain Li ₂ O or ZnO. Moreover, the thing which does not contain a spinel type crystal phase and a lithium disilicate crystal as a crystal phase is preferable.

  By heat-treating the base glass, a crystallized glass containing a crystal phase composed of enstatite and / or enstatite solid solution is obtained. Therefore, as in the case of the composition 7, according to the crystallized glass, it is possible to prevent detachment of crystal particles and to prevent generation of concave defects on the substrate surface.

  Note that press molding is suitable for molding the base glass of composition 9. The heat treatment for crystallization is preferably performed after press molding.

In the case of the composition 8 or the composition 9, the size of the crystal particles is preferably 100 nm or less, and more preferably 50 nm or less. A more preferable range is 1 to 50 nm.
<Information recording medium and manufacturing method thereof>
Next, the information recording medium of the present invention will be described. The information recording medium of the present invention has a multilayer film including an information recording layer on the information recording medium substrate. Information recording media are roughly classified into magnetic recording media, magneto-optical recording media, optical discs, and the like, depending on the recording method, and are particularly suitable for magnetic recording media. Hereinafter, the information recording medium will be described in detail by taking a magnetic recording medium as an example.

  Examples of the structure of the multilayer film including the information recording layer (magnetic recording layer) formed on the main surface of the substrate include an underlayer, a protective layer, and a lubricating layer in addition to the magnetic recording layer. Each layer has a composition and a film configuration according to the intended specification. The magnetic recording layer is composed of a magnetic layer or a magnetic layer and a nonmagnetic layer. As the magnetic layer, an alloy containing Co as a main component is suitable. The underlayer is selected according to the magnetic layer, but in the case of a Co alloy magnetic layer, an alloy containing Cr (for example, an alloy containing CrW, an alloy containing CrMo, an alloy containing CrV, etc.) is preferable. Examples of the protective layer include a carbon protective film, and examples of the lubricating layer formed by applying a perfluoropolyether diluted with a freon solvent or the like. The underlayer, magnetic layer, nonmagnetic layer, and protective layer are preferably formed by sputtering. The above configuration is suitable for the longitudinal magnetic recording medium.

In the longitudinal magnetic recording medium, the substrate is preferably heated before the film forming step. In a perpendicular magnetic recording medium, for example, a seed layer, a soft magnetic layer, a nonmagnetic layer, a magnetic layer (magnetic recording layer), a protective layer, and a lubricating layer are provided on a substrate. The infrared irradiation heating is preferably performed after the soft magnetic layer is formed and before the nonmagnetic layer is formed, or after the magnetic layer is formed and before the protective layer is formed. Such heating improves the characteristics of magnetic recording and makes it possible to align the magnetization anisotropy of the soft magnetic layer. In addition,
A magnetic field may be applied during heating.

  The seed layer is a Ti alloy, Cr alloy, the soft magnetic layer is FeTaC, FeCoB, CoTaZr, CoNbZr, NiFe, FeAlSi, the nonmagnetic layer is a Ti alloy, NiTaZr, and the magnetic layer is a Co alloy. Examples of the protective layer include carbon, and examples of the lubricating layer include the same lubricating layer as described above.

  In recent years, in order to improve various characteristics such as magnetic characteristics and electromagnetic conversion characteristics, a multilayer film structure including a magnetic recording layer is becoming increasingly multilayered, and some magnetic recording media have eight or more sputtering films. In the stationary facing sputtering method, a sputtering apparatus is used in which a plurality of chambers are connected in series and the whole chamber is structured to be evacuated. An appropriate amount of sputtering gas such as argon gas can be introduced into each chamber as required. A substrate is introduced into such an apparatus, and the substrate is heated in the first chamber. Next, a multilayer film structure is formed while sequentially depositing a sputtering film in each chamber while transferring the substrate to the subsequent chamber. Heating to raise the temperature of the substrate whose temperature has decreased may be provided in one of the subsequent chambers, but in order to improve productivity and avoid further increase in the size of the apparatus, the substrate should be formed only in the first chamber. It is desired that all sputtering film formation be completed while heating and the temperature of the substrate is within a range suitable for film formation. However, as the number of layers increases, it becomes difficult to maintain the substrate temperature in an appropriate range until the end. If the substrate temperature is not sufficient, an information recording layer having a sufficient coercive force cannot be formed. When a layer that can be formed without heating is formed and the information recording layer is formed after heating the substrate, the substrate is transferred to the film formation chamber, the heating chamber, and the film formation chamber in the order described above. An information recording medium may be manufactured.

  Also in the in-line sputtering method, a sputtering film is sequentially laminated while transferring the substrate from the heating region to the film formation region. May be formed). Therefore, there are problems similar to those of the static facing sputtering method.

  According to the method of manufacturing the information recording medium of the present invention, the above problem can be solved. The information recording medium manufacturing method of the present invention has four modes, that is, manufacturing methods 1 to 4.

  The production method 1 is a method for producing an information recording medium in which a multilayer film including an information recording layer is formed on an information recording medium substrate, and is 10 ° C./second or more, preferably 15 ° C./second or more, more preferably in a heating region. A substrate heated at an average heating rate of 20 ° C./second or more, more preferably 30 ° C./second or more is sequentially transferred to a plurality of film formation regions, and each layer constituting the multilayer film is sequentially formed in each film formation region. Thus, a multilayer film is formed. The multilayer film may be composed of an information recording layer, or may be composed of an information recording layer and other layers. Furthermore, since the heating time can be shortened, the throughput of the information recording medium can be improved. In the above method, an extremely large amount of information recording medium can be mass-produced on one production line, but by increasing the heating rate of the substrate, a large amount of information recording medium can be produced in a shorter time. Production costs are greatly reduced, and higher performance products can be provided at low cost.

In this manufacturing method 1, it is preferable to make the residence time of the substrate equal in the heating region and each film formation region. In addition, it is preferable that the substrate is carried into and out of the heating region and each film formation region in synchronization. In the above manufacturing method, the substrate residence time in the heating region (heating chamber) and the substrate residence time in each film formation region (each sputtering chamber) increase or decrease in conjunction with each other. The total residence time in each film formation region, that is, the time obtained by multiplying the residence time in each film formation region by the number of layers formed by sputtering is the accumulated time required for sputtering film formation. Since the substrate temperature decreases as the cumulative time increases, the substrate temperature is likely to fall below the appropriate temperature for sputtering film formation. In order to shorten the cumulative time without reducing the number of layers constituting the sputtering film, it is necessary to shorten the residence time in each film formation region. Therefore, the residence time in the heating region is also shortened. However, according to the above manufacturing method, since the average heating rate of the substrate in the heating region is 10 ° C./second or more, the substrate can be heated to a desired temperature in a short time, and an appropriate substrate can be obtained. Sputtering film formation can be performed in a temperature range. In addition, in the manufacture of a magnetic recording medium in which the number of layers has further increased and in the manufacture of a magnetic recording medium that requires film formation at a higher temperature, a heating region may be provided in the middle chamber in addition to the first-stage chamber. Infrared irradiation heating is suitable as a method for heating the substrate, but in the case of infrared irradiation heating, infrared irradiation is reflected by the film when infrared irradiation heating is performed during the film forming process. Power is reduced. Therefore, the infrared irradiation heating is preferably performed before the start of film formation, and more preferably performed immediately before the start of film formation. Such a method is particularly suitable for the production of a longitudinal magnetic recording medium. On the other hand, after a film that can be formed without heating is formed on the substrate, the substrate may be heated in the heating region, and then a multilayer film including the information recording layer may be formed. In this case, when infrared irradiation heating is performed, a part of infrared rays is reflected by the film formed before heating, but a sufficient heating effect can be obtained by using the substrates 1 to 5 for the substrate. This method is suitable for manufacturing a perpendicular magnetic recording medium.

  Thus, by increasing the heating rate of the substrate, the film formation time is shortened, so that the film formation can be performed while the substrate is at a sufficiently high temperature. In addition, since the total manufacturing time can be greatly shortened, the production volume can be improved and the manufacturing cost can be reduced, so that high-performance products can be stably supplied to the market. In addition, the said tendency becomes so remarkable that the number of the layers which comprise a multilayer film increases. In this production method 1, it is preferable to heat the substrate by irradiating it with infrared rays.

  On the other hand, the production method 2 is a method of forming a multilayer film including an information recording layer on the substrate by irradiating the information recording medium substrate (substrate 1 to substrate 5) of the present invention with infrared rays and heating the substrate.

  In this manufacturing method 2, while using a board | substrate with high infrared absorption efficiency, a high board | substrate heating rate can be obtained by carrying out infrared irradiation heating of this board | substrate. For the infrared irradiation heating, an infrared source having a maximum wavelength of the emission spectrum in the wavelength region of 2750 to 3700 nm is suitable. A heating element is suitable as such an infrared source. When the heating body can be regarded as a black body, the temperature of the heating body is preferably 600K to 1000K, and more preferably 700K to 900K in order to match the maximum wavelength of the radiation spectrum to the vicinity of the absorption peak of the substrate.

  A carbon heater is suitable as the heating element. By disposing the heating element in the heating chamber, the oxygen partial pressure in the heating atmosphere is reduced, so that deterioration due to oxidation of the carbon heater can also be reduced.

  In addition, it is preferable to perform infrared irradiation heating before the start of film formation (before the start of film formation of a layer that requires heating), and it is more preferably performed immediately before the start of film formation, as in manufacturing method 1. The above manufacturing methods can be combined with each other.

  On the other hand, the production method 3 is a method for producing an information recording medium by forming an information recording layer on the information recording medium substrate (substrate 1 to substrate 5) of the present invention and then irradiating with infrared rays and heating. When the substrate on which the information recording layer is formed is irradiated with infrared rays, part of the infrared rays is reflected by the information recording layer, and the infrared power reaching the substrate is reduced. However, since the substrate is used, the effect of heating the substrate can be sufficiently obtained by absorption of infrared rays that reach the substrate.

On the other hand, production method 4 comprises an oxide of at least one metal selected from iron, copper, cobalt, ytterbium, manganese, neodymium, praseodymium, niobium, cerium, vanadium, chromium, nickel, molybdenum, holmium, and erbium. In this method, an information recording medium is manufactured by forming an information recording layer on a substrate for an information recording medium made of glass containing infrared absorber or crystallized glass, and then irradiating and heating infrared rays.

  Manufacturing method 3 and manufacturing method 4 are both suitable for manufacturing a perpendicular magnetic recording medium. By the infrared irradiation heating, the magnetic recording characteristics can be improved and the magnetization anisotropy of the soft magnetic layer can be made uniform. Note that, after heating, for example, a protective layer may be formed by sputtering.

  Also in manufacturing method 3 and manufacturing method 4, a plurality of film forming regions for forming each layer constituting the multilayer film including the information recording layer and a heating region for heating the substrate are provided, and the substrate is sequentially transferred to each region to transfer the multilayer film. Is preferably formed. At that time, the heating region is disposed after the film formation region in which the information recording layer is provided. Also in such a method, it is preferable to make the residence time in the heating region and each film formation region equal. In such a method, by improving the heating efficiency, sufficient heating efficiency can be obtained by heating in a short time, so that the heating time can be shortened and the time required for the entire process can be greatly shortened. As a result, the throughput can be improved and a large amount of high-quality information recording media can be provided at a low cost. In production method 3 and production method 4, it is preferable to use the same heat source as in production method 2.

  In any of the production methods 1 to 4, it is desirable that the average heating rate be 200 ° C./second or less in consideration of substrate damage due to rapid heating. Moreover, in each manufacturing method, 2-10 seconds are preferable for the residence time of a heating area | region and each film-forming area | region.

  Shortening the heating time and the film formation time is desirable from the viewpoint of reducing the adhesion of foreign matter to the substrate surface and preventing the crystal grains of the magnetic layer from becoming coarse.

Further, in any of the production methods 1 to 4, it is preferable to use a stationary facing type sputtering apparatus, and it is more preferable to use a single wafer stationary facing type sputtering apparatus.
In any of the manufacturing methods, it is preferable to move the substrate between the chambers within 2 seconds.

  The method for producing an information recording medium of the present invention is suitable when the total film formation time is 24 to 300 seconds.

  According to each of the above manufacturing methods, a sufficient coercive force, for example, a coercive force of 3600 aersted or more, preferably 4500 alested or more can be applied to the information recording layer.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

In addition, the measurement of the glass transition temperature and spectral transmittance of each glass, and the identification of the crystal seed | species of crystallized glass were performed in accordance with the following method.
(1) Glass transition temperature A sample having a diameter of 5φ × 20 mm was measured at a rate of temperature increase of + 4 ° C./min using a thermomechanical analyzer (TMA8140) manufactured by Rigaku Corporation. As the standard sample using SiO _2.
(2) Spectral transmittance For a sample processed into a planar shape, a spectrophotometer [wavelength range of 2200 nm to 6000 nm is used FTIR-8400 made by Shimadzu Corporation, and the wavelength range of wavelength 200 to 2500 nm is made by JASCO V-570 Was used]. The spectral transmittance includes a loss due to surface reflection.
(3) Identification of crystal type of crystallized glass X-ray diffraction was measured on the powdered glass using Cu Kα ray (apparatus: X-ray diffractometer MXP18A manufactured by Mac Science, tube voltage: 50 kV, tube current: 300 mA, scanning angle 10-90 °). The deposited crystals were identified from the obtained X-ray diffraction peaks.
Moreover, the chemical strengthening process was performed by the method shown below.

Examples 1-12
After preparing glass raw materials such as SiO ₂ , Al ₂ O ₃ , and Al (OH) ₃ so as to have the compositions shown in Table 1 and Table 2 in terms of mol%, and mixing them well, they are put in a heated melting container and put into the air. The glass was melted at a high temperature of 1000 ° C. or higher. Thoroughly deaerate and agitate the molten glass to make it homogeneous without bubbles, then pour it into a mold, let it cool to near the glass transition temperature, immediately put it in an annealing furnace, hold it for 1 hour, The mixture was allowed to cool to room temperature. The obtained glass had good homogeneity, and no foam or undissolved material was observed.

  About the glass of Examples 1-9, it processed into the flat plate of thickness 2mm, and gave optical polishing to both surfaces.

  The glasses of Examples 10 to 12 were heat treated at around 800 ° C. to precipitate crystal nuclei in the glass, then heated to around 1000 ° C., and subjected to crystallization treatment to precipitate a crystal phase containing enstatite. Crystallized glass was obtained. The size of the crystal particles in the crystallized glass of Examples 10 to 12 was 50 nm or less when observed with a transmission electron microscope. These crystallized glasses were also processed into flat plates with a thickness of 2 mm, and optical polishing was performed on both sides.

The spectral transmittance of each sample processed into a flat plate shape was measured, and the maximum and minimum values of the spectral transmittance at a wavelength of 2750 to 3700 nm and the spectral transmittance at a wavelength of 1000 nm were determined. These values are shown in Table 1 and Table 2 together with the glass transition temperature. In Examples 1, 2, 4, 5, 7, 8, 10, and 11, iron oxides in amounts shown in Tables 1 and 2 (as Fe ₂ O ₃ ) were contained. Moreover, the moisture content of each glass is a value calculated from the OH content of the raw material.

各サンプルとも波長２７５０〜３７００ｎｍにおける分光透過率の最小値は５１％以下、最大値は７０％以下であった。また鉄を導入した実施例１、２、４、５、７、８、１０、１１については波長１０００ｎｍにおける分光透過率が９０％未満であった。

In each sample, the minimum value of the spectral transmittance at a wavelength of 2750 to 3700 nm was 51% or less, and the maximum value was 70% or less. In Examples 1, 2, 4, 5, 7, 8, 10, and 11 into which iron was introduced, the spectral transmittance at a wavelength of 1000 nm was less than 90%.

Next, each of the various molten glasses was cut out from the feeder, and a predetermined weight of molten glass gob was supplied onto a lower mold for press molding maintained in a temperature range in which the molten glass was not fused. Next, the gob was pressed with a lower mold and an upper mold facing the lower mold to form a disk-shaped thin plate. At this time, since each glass has a large absorption in the infrared region, the cooling speed by radiation is relatively slow. Therefore, since the glass is difficult to cool in the direct press in which press molding is performed while the molten glass is in a softened state, the molding conditions can be easily set.

  After the press-molded glass is annealed, a through hole is provided in the center, and inner and outer peripheral processing, double-side grinding processing, double-side polishing processing, etc. are performed, outer diameter 65.0 mm, plate thickness 0.635 mm, center hole diameter 20. The magnetic disk substrate shape was 0 mm. In addition, in the case of Examples 10-12, the process for crystallization was further performed to the said process process.

  The substrates made of the glass of Examples 1 to 9 were subjected to a chemical strengthening treatment by being immersed in a molten salt. In Examples 1 to 6, it was immersed in a molten salt of sodium nitrate and potassium nitrate (380 ° C.) for 4 hours, and in Examples 7 to 9 it was immersed in a molten salt of potassium nitrate (420 ° C.) for 4 hours.

Example 13
A multi-layer film including a magnetic layer is formed on a large number of magnetic disk substrates made of the glass of Examples 1 to 6 and the crystallized glass of Examples 10 to 12 obtained above using a single wafer stationary facing sputtering apparatus. Filmed. The single wafer stationary type sputtering apparatus has a function in which a plurality of chambers are connected in series, and a substrate in a front chamber is transferred to a rear chamber. Transfer of substrates between all chambers is performed one by one in synchronization. When the delivery of the substrate is completed, the substrate stays in the chamber for a certain time. During this staying time, the substrate is heated in the front chamber, the first layer in the second chamber, the second layer in the third chamber, and the upper layer in the further chamber. Is formed by sputtering.

  A carbon heater is placed in the foremost chamber and energized to raise the temperature to 800K or higher to be an infrared source. The input of the heater was 1 kW. The substrate is heated by stopping the substrate at a position facing the heater. Since each of the above substrates exhibits a large light absorption around a wavelength of 3 μm, it efficiently absorbs the infrared rays emitted from the infrared source and is heated rapidly. In the foremost chamber, which is the heating region, the substrate is heated at an average heating rate of approximately 30 ° C./second or higher and reaches a high temperature of 200 ° C. or higher in a short time. The residence time of the substrate in the chamber was 6.4 seconds.

  Next, the heated substrate moves to the second-stage chamber and stops at a position facing the sputtering target. Then, a Cr alloy underlayer is formed on the substrate by sputtering. The movement time of the substrate between the chambers was 1 second.

  In the third and subsequent chambers, a nonmagnetic layer and a magnetic layer made of a Co alloy are alternately formed by sputtering. Then, a hydrogenated carbon film as a protective layer was formed by sputtering to sequentially produce magnetic disks having a multilayer film of eight or more layers. In addition, on the surface of the disk taken out from the sputtering apparatus, a perfluoropolyether diluted with a freon solvent or the like was applied and dried to form a lubricating layer. Since the substrate temperature of each magnetic disk was sufficiently high until the entire sputtering film formation was completed, the magnetic characteristics and electromagnetic conversion characteristics of the magnetic disk taken out from the sputtering apparatus were good. For example, a sufficient coercive force of 3600 aersted or more is obtained.

The tact time of the manufacturing process is 7.4 seconds, which is a chamber residence time of 6.4 seconds plus a travel time of 1 second. In contrast, a glass substrate that does not contain an infrared absorber and does not reach a predetermined amount of water requires approximately 1.5 times the heating time until it is heated to the same temperature. Even if the movement between the chambers is set to 1 second, the tact time is approximately 1.5 times longer, and an enormous difference in production occurs in mass production. In addition, the glass of Examples 1 and 3 can improve the average heating rate of 12% or more for the glass of Example 1 and 20% or more for the glass of Example 3 compared to the case where moisture and iron are not added. it can. The average heating rate can be similarly improved for the substrates shown in the other embodiments.

  Next, a multilayer film was formed on the magnetic disk substrate made of the glass of Examples 7 to 9 using a single wafer stationary opposed sputtering apparatus. A perpendicular magnetic recording type film structure in which a seed layer and a soft magnetic layer are formed on a substrate between chambers, heated by a carbon heater between heating chambers, and then a nonmagnetic layer and a magnetic layer are sequentially formed. did. Also in this case, the substrate residence time in each chamber is equal to each other, and the movement of the substrate between the chambers is also performed in synchronization. Even when the substrates made of the glass of Examples 7 to 9 are used, the substrate can be heated to a sufficiently high temperature without increasing the residence time in the chamber because the infrared irradiation heating efficiency is high. Therefore, the magnetic characteristics and electromagnetic conversion characteristics of the manufactured perpendicular recording magnetic disk were good. In addition, after using the substrate made of the glass of Examples 7 to 9 to form a seed layer, a soft magnetic layer, a nonmagnetic layer, and a magnetic layer by sputtering, the substrate is heated using a carbon heater in a heating chamber to perform a heat treatment. And a protective layer may be formed.

  In the above embodiment, the single wafer stationary type sputtering apparatus is used. However, good film formation is possible even with an in-line type sputtering apparatus.

Claims (14)

A substrate for an information recording medium, which is made of glass or crystallized glass and has a region in which a spectral transmittance converted to a thickness of 2 mm is 50% or less in a wavelength region of 2750 to 3700 nm. A substrate for an information recording medium, which is made of glass or crystallized glass and has a wavelength of 2750 to 3700 nm and a spectral transmittance converted to a thickness of 2 mm of 70% or less. Glass containing an infrared absorber made of an oxide of at least one metal selected from iron, copper, cobalt, ytterbium, manganese, neodymium, praseodymium, niobium, cerium, vanadium, chromium, nickel, molybdenum, holmium and erbium Alternatively, an information recording medium substrate made of crystallized glass and used for a perpendicular magnetic recording medium. 4. The information recording medium substrate according to claim 1, wherein the substrate is for infrared irradiation heating. A substrate for an information recording medium, comprising glass or crystallized glass, containing water of more than 200 ppm, and used for infrared irradiation heating. Glass containing an infrared absorber made of an oxide of at least one metal selected from iron, copper, cobalt, ytterbium, manganese, neodymium, praseodymium, niobium, cerium, vanadium, chromium, nickel, molybdenum, holmium and erbium Alternatively, a substrate for an information recording medium comprising a crystallized glass and used for supporting a multilayer film including an information recording layer formed by sputtering after infrared irradiation heating. An information recording medium comprising a multilayer film including an information recording layer provided on the information recording medium substrate according to claim 1. In a method for manufacturing an information recording medium in which a multilayer film including an information recording layer is formed on an information recording medium substrate, the substrate heated at an average heating rate of 10 ° C./second or more in a heating region is formed into a plurality of film forming regions. A method of manufacturing an information recording medium, wherein the multilayer film is formed by sequentially transferring and sequentially forming each layer constituting the multilayer film in each film formation region. The method for manufacturing an information recording medium according to claim 8, wherein the residence time of the information recording medium substrate in the heating region and each film formation region is equalized. 10. The method for manufacturing an information recording medium according to claim 8, wherein the information recording medium substrate is carried into and out of the heating area and each film formation area in synchronization. The method for producing an information recording medium according to claim 8, 9 or 10, wherein the information recording medium substrate is heated by irradiating infrared rays. An information recording medium, comprising: an information recording medium substrate according to claim 1, wherein the information recording medium substrate is heated by irradiating infrared rays to form a multilayer film including an information recording layer on the substrate. Production method. 6. A method of manufacturing an information recording medium, comprising: forming an information recording layer on the information recording medium substrate according to claim 1; Glass containing an infrared absorber made of an oxide of at least one metal selected from iron, copper, cobalt, ytterbium, manganese, neodymium, praseodymium, niobium, cerium, vanadium, chromium, nickel, molybdenum, holmium and erbium Alternatively, a method for producing an information recording medium, comprising: forming an information recording layer on an information recording medium substrate made of crystallized glass;