JP2006268949A - Laminate for hdd suspension - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminate for an HDD suspension which has sufficient low moisture absorption and wherein dimensional change due to humidity environmental change can be prevented and etching work can be efficiently and reliably carried out by an alkali aqueous solution, in the laminate for the HDD suspension holding heat resistance and dimensional stability by thermal treatment which used to be required. <P>SOLUTION: The laminate for the HDD suspension provided with a stainless steel foil, at least one polyimide based resin layer and a conductor layer is characterized in that at least the one polyimide based resin layer contains a polyimide resin as a main component obtained by reacting a diamino compound containing 20 to 80 mol% 4-aminophenyl-4'-aminobenzoate and a tetracarboxylic dianhydride with each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminate used for an HDD suspension.

  Conventionally, HDD (hard disk drive) suspensions are manufactured by etching stainless steel foil, and a magnetic head such as a thin film head is mounted on the tip of the suspension and then mounted by wire bonding with a gold wire. However, in recent years, HDD suspensions have been actively studied to reduce the size, increase the density, increase the capacity, and the like, and accordingly, it has become an indispensable problem to lower the flying height of the slider on which the magnetic head is directly mounted. In response to such problems, in the conventional gold wire wire bonding type HDD suspension, the influence of the air resistance, rigidity, etc. of the gold wire has been an obstacle to lowering the slider. In addition, such a wire bonding type HDD suspension manufacturing method using a gold wire has a problem that it is difficult to automate the gold wire connecting process to the magnetic head.

  As a method for solving the problem by such a gold wire wire bonding method, in Japanese Patent Laid-Open No. 60-246015 (Patent Document 1), a polyimide resin which is an insulator is directly formed on a stainless steel foil, and further, A method of forming a signal line instead of the gold wire directly on the suspension by forming a circuit with copper has been proposed. In the so-called wiring-integrated suspension in which the signal lines are directly formed in this way, there is no problem that the slider has a low flying height due to the air resistance and rigidity of the signal lines, and the magnetic head connection process can be automated. Become. On the other hand, Japanese Patent Application Laid-Open No. 5-131604 (Patent Document 2) discloses a method of laminating polyimide on a thin sheet metal. However, in the method described in Patent Document 2, no attention has been paid to the thermal expansion of the polyimide to be used, and the thermal expansion coefficient of the specifically disclosed polyimide is also high. There is a problem that warpage is likely to occur when the metal is etched away. In addition, when a polyimide is laminated on a thin sheet metal by the method described in Patent Document 2, the adhesive force between the sheet metal and the polyimide layer tends to vary, and problems such as heat resistance also occur. There were difficulties in applying the body to the HDD suspension.

  Moreover, in order to solve such a problem, in the international publication 98/08216 pamphlet (patent document 3), in the laminated body by which a polyimide-type resin layer and a conductor layer are sequentially formed on a stainless steel base | substrate. An HDD suspension laminate in which the linear expansion coefficient of the polyimide resin layer is in a predetermined range is disclosed. Such a laminate for an HDD suspension described in Patent Document 3 is a wiring-integrated HDD suspension with less warpage during the etching process. However, in such a laminate for HDD suspension described in Patent Document 3, attention is not paid to the dimensional stability with respect to changes in the humidity environment, and the moisture absorption rate of the polyimide resin layer of the obtained flexible printed circuit board. When the value is large, the coefficient of linear humidity expansion becomes large. Therefore, even if the dimensional stability against a thermal change is excellent, there is a problem that the dimensional stability is impaired due to a change in the humidity environment.

In addition, in International Publication No. 01/028767 pamphlet (Patent Document 4), at least one of the polyimide resin layers contains 20 mol% or more of 4,4′-diamino-2,2′-dimethylbiphenyl. A laminate having a low humidity expansion polyimide resin layer obtained by reacting a compound with a tetracarboxylic acid compound and having a linear humidity expansion coefficient of 20 × 10 ⁻⁶ /% RH or less is disclosed. However, in the processing of a laminate made of such a polyimide resin, a dry etching method using an ultraviolet laser processing method or a plasma processing method is used, and these processing apparatuses are expensive and have a high running cost such as a gas cost to be used. In addition, there was a problem that the mass productivity was poor.

As a technique for solving such a problem, Japanese Patent Laid-Open No. 2002-245609 (Patent Document 5) is a laminate in which an insulating resin layer and a metal foil layer are sequentially laminated on a stainless steel base, and the insulating resin layer Consists of a plurality of polyimide resin layers, and all the layers constituting the insulating resin layer have an average etching rate of 0.5 μm / min or more by 80 ° C. and 50 wt% potassium hydroxide aqueous solution, and are insulated. There is disclosed a suspension for HDD obtained by processing a laminate in which a layer in contact with a stainless steel substrate and a metal foil layer of a resin layer is a polyimide resin layer (B) having a glass transition temperature of 300 ° C. or lower. However, even the laminate described in Patent Document 5 is not yet sufficient in terms of dimensional changes with respect to changes in the humidity environment, and a HDD suspension laminate having a lower moisture absorption rate is desired.
JP 60-246015 A JP-A-5-131604 International Publication No. 98/08216 Pamphlet International Publication No. 01/028767 Pamphlet Japanese Patent Laid-Open No. 2002-245609

  The present invention has been made in view of the above-described problems of the prior art, and is a laminate for an HDD suspension that retains heat resistance and dimensional stability by heat treatment, which have been conventionally required, and has a sufficient moisture absorption rate. An object of the present invention is to provide a laminate for an HDD suspension that is low, can sufficiently prevent a dimensional change due to a change in humidity environment, and can be etched efficiently and reliably with an alkaline aqueous solution.

  As a result of intensive studies to achieve the above object, the inventors of the present invention, in a laminate for an HDD suspension comprising a stainless steel foil, at least one polyimide resin layer, and a conductor layer, By containing as a main component a polyimide resin obtained by reacting a diamino compound containing 20 mol% to 80 mol% of 4-aminophenyl-4′-aminobenzoate with tetracarboxylic dianhydride in at least one layer of It has been found that the moisture absorption rate can be sufficiently lowered, the dimensional change due to a change in humidity environment can be sufficiently prevented, and the etching process can be efficiently and reliably performed with an alkaline aqueous solution. It came to be completed.

  In other words, the HDD suspension laminate of the present invention is a HDD suspension laminate comprising a stainless steel foil, at least one polyimide resin layer, and a conductor layer, wherein at least one of the polyimide resin layers is at least one layer. The main component is a polyimide resin obtained by reacting a diamino compound containing 20 to 80 mol% of 4-aminophenyl-4′-aminobenzoate with tetracarboxylic dianhydride. Is.

  In the laminate for HDD suspension of the present invention, the polyimide resin is represented by the following general formula (1):

(In the formula, Ar represents a tetravalent hydrocarbon group.)
A repeating unit represented by the following general formula (2):

(In the formula, Ar represents a tetravalent hydrocarbon group, and R represents a divalent hydrocarbon group.)
It is preferable to contain the repeating unit represented by these.

  In the laminate for HDD suspension according to the present invention, the diamino compound preferably contains 20 mol% to 60 mol% of 4-aminophenyl-4′-aminobenzoate.

  Furthermore, in the laminate for an HDD suspension of the present invention, the polyimide resin layer has a moisture absorption rate of 1.2% or less after being allowed to stand for 24 hours at (i) 23 ° C. and 50% relative humidity. And / or (ii) in an etching process using an aqueous solution of potassium hydroxide 33.5 wt%, ethylene diamine 11 wt%, ethylene glycol 22 wt% as an etchant, when the etching solution at 80 ° C. is used, It is preferable that the average value of the etching rate is 5 μm / min or more.

  According to the present invention, a laminate for an HDD suspension that retains heat resistance and dimensional stability caused by heat treatment, which have been conventionally required, has a sufficiently low moisture absorption rate, and can sufficiently prevent dimensional changes due to changes in humidity environment. At the same time, it is possible to provide a laminate for an HDD suspension that can be etched efficiently and reliably with an alkaline aqueous solution.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  The laminate for HDD suspension of the present invention is a laminate for HDD suspension comprising a stainless steel foil, at least one polyimide resin layer, and a conductor layer, and at least one of the polyimide resin layers is 4 -The main component is a polyimide resin obtained by reacting a diamino compound containing 20 mol% to 80 mol% of aminophenyl-4'-aminobenzoate with tetracarboxylic dianhydride.

  The molar ratio of 4-aminophenyl-4'-aminobenzoate contained in the diamino compound is 20 mol% to 80 mol%. When the content molar ratio of 4-aminophenyl-4′-aminobenzoate is less than the lower limit, the etching rate of the resulting polyimide resin is lowered, and the moisture absorption rate is increased. The resulting polyimide resin becomes brittle, making it difficult to use it in a laminate for an HDD suspension. Further, the content molar ratio of such 4-aminophenyl-4'-aminobenzoate is more preferably 20 mol% to 60 mol%.

  In the present invention, the 4-aminophenyl-4'-aminobenzoate and other diamino compounds are used in combination. Such a diamino compound is not particularly limited, and examples thereof include 1,4-diaminobenzene, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diamino-2,2′-dimethyl. Biphenyl, 4,4′-diamino-2′-methoxybenzanilide, 4,4′-diaminobenzanilide, 3,4′-diaminobenzanilide, 1,4-bis (4-aminophenoxy) benzene, 1,3 -Bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-diaminobenzene, 1,3-diaminobenzene, 2,4-diaminotoluene, 4,4'-diamino Diphenylmethane, 4,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 4,4′- Aminobiphenyl, 4,4-diaminobenzophenone, 4,4-diaminodiphenyl sulfide, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 4,4′-bis (4-aminophenoxy) biphenyl, Bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (2-aminophenoxy) phenyl] sulfone, bis [4- (4-amino Phenoxy) phenyl] ether, bis (3-methyl-4-aminophenyl) methane, bis (3-chloro-4-aminophenyl) methane, 2,2′-dimethoxy-4,4′-diaminobiphenyl, 2,2 '-Dichloro-4,4'-diaminobiphenyl, 2,2', 5,5'-tetrachloro-4,4'-diamy Nobiphenyl, 2,2'-dicarboxy-4,4'-diaminobiphenyl, 2,2'-dihydroxy-4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl ether And aromatic diamino compounds such as 4,4′-diaminooctafluorobiphenyl. Such diamino compounds can be used singly or in combination of two or more.

  Further, among diamino compounds other than such 4-aminophenyl-4′-aminobenzoate, the etching rate of the resulting polyimide resin layer can be further improved, and the moisture absorption rate can be further reduced. From this viewpoint, 4,4′-diaminodiphenyl ether, 4,4′-diamino-2,2′-dimethylbiphenyl, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) It is preferable to use benzene, 1,3-bis (3-aminophenoxy) benzene, or 1,4-diaminobenzene.

  Further, the tetracarboxylic dianhydride is not particularly limited, and a known tetracarboxylic acid compound can be appropriately used. From the viewpoint of improving the heat resistance of the obtained polyimide resin layer, aromatic tetracarboxylic acid dianhydride can be used. Acid dianhydride is preferred. Examples of the tetracarboxylic dianhydride include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, and 2,3,3 ′, 4-biphenyltetracarboxylic dianhydride. Anhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2,2-bis (2,3- or 3,4-di Carboxyphenyl) -propane dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3.4-dicarboxyphenyl) Tan dianhydride, bis (2,3-carboxyphenyl) sulfone dianhydride, bis (3,4-carboxyphenyl) sulfone dianhydride, and the like. Such tetracarboxylic acid compounds can be used alone or in combination of two or more.

  Moreover, as said polyimide resin obtained by making such a diamino compound and the said tetracarboxylic dianhydride react, following General formula (1):

(In the formula, Ar represents a tetravalent hydrocarbon group.)
A repeating unit represented by the following general formula (2):

(In the formula, Ar represents a tetravalent hydrocarbon group, and R represents a divalent hydrocarbon group.)
The polyimide resin containing the repeating unit represented by these is preferable.

  Ar in the above formulas (1) and (2) is a tetravalent hydrocarbon group derived from the main skeleton of tetracarboxylic dianhydride as described above. Moreover, General formula (2) is a repeating unit contained as a copolymer composition. R in the formula (2) is a divalent hydrocarbon group, and is derived from the main skeleton of a diamino compound other than the aforementioned 4-aminophenyl-4'-aminobenzoate.

  Here, the ratio of the repeating unit of the formula (1) and the repeating unit of the formula (2) in the polyimide resin is the 4-aminophenyl-4′-amino in the diamino compound when the polyimide resin is produced. This corresponds to the compounding molar ratio of benzoate and diamino compounds other than 4-aminophenyl-4′-aminobenzoate. The ratio of the repeating unit of the formula (1) and the repeating unit of the formula (2) in such a polyimide resin is the ratio of the repeating unit of the formula (1) and the repeating unit of the formula (2). Is preferably 20/80 to 80/20. When the proportion of the repeating unit of the formula (1) exceeds 80%, the polyimide resin layer (polyimide film) tends to be fragile and difficult to be used as a film. If it is less than the range, the etching rate tends to decrease and the moisture absorption rate tends to increase.

  Further, the weight average molecular weight of the polyimide resin obtained by reacting a diamino compound containing 4-aminophenyl-4′-aminobenzoate with 20 mol% to 80 mol% and the tetracarboxylic dianhydride is not particularly limited. Is preferably about 30,000 to 300,000.

  The polyimide resin layer according to the present invention preferably has a moisture absorption rate of 1.2% or less after standing for 24 hours at 23 ° C. and a relative humidity of 50%, preferably 1% or less. More preferred. When such a moisture absorption rate exceeds the upper limit, a dimensional change occurs due to a change in humidity environment, and there is a tendency for curling and warping to occur.

  Furthermore, as the polyimide resin layer according to the present invention, the etching solution at 80 ° C. was used in an etching process using an aqueous solution of potassium hydroxide 33.5 wt%, ethylenediamine 11 wt%, and ethylene glycol 22 wt% as an etching solution. In this case, it is preferable that the average value of the etching rate is 5 μm / min or more. When the average value of such etching rates is less than 5 μm / min, it tends to be difficult to perform etching processing efficiently and reliably with an alkaline aqueous solution.

  Further, the thickness range of the polyimide resin layer according to the present invention is not particularly limited, but is preferably 3 μm to 75 μm, and more preferably 8 μm to 50 μm. When the thickness range of the polyimide resin layer is less than the lower limit, the reliability of electrical insulation tends to decrease when used as an HDD suspension. On the other hand, when the polyimide resin layer exceeds the upper limit, the polyimide resin layer is formed. In addition, the drying efficiency tends to decrease, and the dimensional stability due to heat treatment tends to decrease.

  The stainless steel foil according to the present invention is not particularly limited, but SUS304 is preferable from the viewpoint of spring characteristics and dimensional stability required for use as an HDD suspension, and tension is applied at a temperature of 300 ° C. or higher. More preferably, it is SUS304 that has been annealed. Moreover, as a range of the preferable thickness of the stainless steel foil concerning this invention, it is preferable that they are 10 micrometers-70 micrometers, and it is more preferable that they are 15 micrometers-30 micrometers. In addition, about such a stainless steel foil, you may perform a chemical or mechanical surface treatment for the purpose of improvement, such as the adhesive force with the other layer in a laminated body.

  Moreover, it does not restrict | limit especially as a conductor used for the conductor layer concerning this invention, However, It is preferable to use copper foil, copper alloy foil, etc. of thickness 3 micrometers-20 micrometers. The copper alloy foil is an alloy foil made of different elements such as copper and nickel, silicon, zinc, beryllium and the like and having a copper content of 80% or more. Such a conductor layer may also be subjected to chemical or mechanical surface treatment for the purpose of improving the adhesive strength with other layers in the laminate.

  The laminate for an HDD suspension of the present invention includes the stainless steel foil, at least one polyimide resin layer, and the conductor layer. With such a laminate for HDD suspension, it is possible to sufficiently reduce the moisture absorption rate, sufficiently prevent dimensional changes due to changes in the humidity environment, and enable efficient and reliable etching with an alkaline aqueous solution. Become.

  Further, when there are a plurality of the polyimide resin layers, at least one layer reacts with a diamino compound containing 4-aminophenyl-4′-aminobenzoate in an amount of 20 mol% to 80 mol% and tetracarboxylic dianhydride. Any polyimide resin layer containing a polyimide resin obtained as a main component may be used.

  Thus, the HDD suspension laminate of the present invention may include at least one polyimide resin layer other than the polyimide resin layer. Although it does not restrict | limit especially as such other polyimide-type resin layers, From a viewpoint of the processability of the etching process by the alkaline aqueous solution of the laminated body for HDD suspensions, potassium hydroxide 33.5 wt%, ethylenediamine 11 wt%, ethylene glycol 22 wt% In the etching process using an aqueous solution of the above as an etching solution, when the etching solution at 80 ° C. is used, the polyimide resin layer preferably has an average etching rate of 5 μm / min or more.

  Below, the method to manufacture the laminated body for HDD suspensions of this invention is demonstrated.

  The method for producing the laminate for an HDD suspension of the present invention is not particularly limited. For example, the following method is preferably employed. That is, first, a diamino compound containing 4-aminophenyl-4'-aminobenzoate and the tetracarboxylic dianhydride are reacted to synthesize a resin solution of polyamic acid. Next, after applying the resin solution of the polyamic acid on the stainless steel foil, heat treatment (drying and curing) is performed to form a polyimide resin layer on the stainless steel foil, and then a conductor layer is formed on the surface of the polyimide resin layer. Stick together. In this way, the laminate for HDD suspension of the present invention can be manufactured.

  First, a method of synthesizing a resin solution of polyamic acid by reacting the diamino compound containing 4-aminophenyl-4'-aminobenzoate with the tetracarboxylic dianhydride will be described.

  The reaction between the diamino compound containing 4-aminophenyl-4'-aminobenzoate and the tetracarboxylic dianhydride compound is preferably performed in an organic solvent. Although it does not restrict | limit especially as such an organic solvent, Specifically, a dimethyl sulfoxide, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, hexamethyl phosphoramide, phenol , Cresol, γ-butyrolactone and the like, and these can be used alone or in combination. In addition, the amount of such organic solvent used is not particularly limited, but the amount used is adjusted so that the concentration of the polyamic acid solution obtained by the polymerization reaction is about 5 to 30% by weight. Are preferably used.

  Moreover, in the reaction using such a solvent, the mixing ratio of the diamino compound to be used and the tetracarboxylic dianhydride is such that the molar ratio of the tetracarboxylic dianhydride is 95 with respect to the molar ratio 100 of all the diamino compounds. It is preferable to mix at a ratio of 1 to 105. When the ratio of the tetracarboxylic dianhydride is less than 95 or exceeds 105, the influence of the etching rate and the moisture absorption rate is small, but the molecular weight of the polymer is not sufficiently increased, and the resulting polyimide resin layer Tends to be difficult to use as a laminate for HDD suspensions.

  The reaction between the diamino compound containing 4-aminophenyl-4′-aminobenzoate and the tetracarboxylic dianhydride may be allowed to react for 1 to 24 hours at a temperature range of 0 ° C. to 60 ° C. preferable. If such a temperature condition is less than the lower limit, the reaction rate tends to be slow and the molecular weight does not increase. On the other hand, if the upper limit is exceeded, imidation proceeds and the reaction solution tends to be easily gelled. . By making it react on such temperature conditions, the resin solution of polyamic acid can be obtained efficiently.

  Next, after applying the polyamic acid resin solution on the stainless steel foil, heat treatment (drying and curing) is performed to form a polyimide resin layer on the stainless steel foil. The polyamic acid resin solution is applied on the stainless steel foil. The method of applying is not particularly limited, and it is possible to apply with a coater such as a comma, die, knife, lip or the like.

  Moreover, the method of the said heat processing (drying and hardening) is not restrict | limited in particular, For example, the heat processing of heating for 1 to 60 minutes on the temperature conditions of 80 to 400 degreeC is employ | adopted suitably. By performing such heat treatment, dehydration and ring closure of the polyamic acid proceeds, so that a polyimide resin layer can be formed on the stainless steel foil.

  Thereafter, a conductor layer is bonded to the surface of the polyimide resin layer, but the method is not particularly limited, and a known method can be adopted as appropriate. Examples of the method for laminating such a conductor layer include a normal hydro press, a vacuum type hydro press, an autoclave pressurizing vacuum press, a continuous thermal laminator and the like. Among such methods of laminating the conductor layers, it is possible to use a vacuum hydropress from the viewpoint that a sufficient pressing pressure is obtained, residual volatiles can be easily removed, and oxidation of the conductor can be prevented. preferable. In addition, when the conductor layers are bonded together in this way, it is preferable to press the conductor layer while heating to about 200 to 400 ° C. Moreover, about press pressure, although depending on the kind of press apparatus to be used, about 1-50 MPa is suitable.

  Thus, the laminated body for HDD suspension of this invention can be manufactured by bonding a conductor layer on the surface of the said polyimide-type resin layer.

  In the above production method, the polyamic acid resin solution is applied onto a stainless steel foil and the conductor layer is laminated after heat treatment. However, as another production method, the polyamic acid resin solution is applied onto the conductor layer. The HDD suspension laminate of the present invention can also be obtained by performing a heat treatment (drying and curing) to form a polyimide resin layer and then attaching a stainless steel foil to the surface of the polyimide resin layer. Alternatively, a polyimide film may be prepared in advance using the resin solution of the polyamic acid, and the HDD suspension laminate of the present invention may be formed by a means such as thermocompression bonding with one or both of the formed polyimide film and the stainless steel or conductor layer.

  Further, in the manufacturing method, an HDD suspension laminate including the stainless steel foil, the polyimide resin layer, and the conductor layer is manufactured. However, the HDD suspension laminate of the present invention may include other components as needed. It is also possible to laminate the polyimide resin layer. The method for laminating such other polyimide resin layers is not particularly limited, and for example, the following method is suitably employed. That is, as a method of laminating such another polyimide resin layer, for example, a resin solution for forming another polyimide resin layer and the aforementioned 4-aminophenyl-4′-aminobenzoate are 20 mol%. A resin solution obtained by reacting a diamino compound containing ˜80 mol% with tetracarboxylic dianhydride is sequentially applied, dried, and then heat-treated in a lump to repeatedly laminate a polyimide resin, A method of laminating by simultaneously applying the resin solution and then heat-treating it to form a plurality of layers can be exemplified.

  A method for forming a circuit in the thus obtained HDD suspension laminate of the present invention is not particularly limited, and an HDD suspension can be obtained by appropriately forming a circuit by a known method.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example. The etching rate and the moisture absorption rate were measured as follows.

<Measurement of etching rate>
The measurement of the etching rate of the laminated body obtained in Examples 1-4 and Comparative Examples 1-4 was performed on condition of the following. That is, an aqueous solution composed of 33.5 wt% potassium hydroxide, 11 wt% ethylenediamine, and 22 wt% ethylene glycol was used as an etching solution, and the etching solutions heated to 80 ° C. were obtained in Examples 1 to 4 and Comparative Examples 1 to 4. The obtained laminate was immersed for 10 to 60 seconds. Then, the etching rate was calculated by dividing the difference between the thickness of the polyimide layer before immersion and the thickness of the polyimide layer after immersion by the immersion time. The obtained results are shown in Table 1.

<Measurement of moisture absorption rate>
The moisture absorption rate of the laminates obtained in Examples 1 to 4 and Comparative Examples 1 to 4 was measured as follows. That is, first, the copper foil was removed by etching from the laminates obtained in Examples 1 to 4 and Comparative Examples 1 to 4 to obtain a polyimide resin film. Thereafter, the polyimide resin film was dried at 80 ° C. for 2 hours, and the mass of the polyimide resin film after drying was measured. Next, the dried polyimide resin film was allowed to stand under constant temperature and humidity of 23 ° C. and 50% relative humidity for 24 hours, and the mass of the polyimide resin film after being left for 24 hours was measured. And using the mass value thus measured, the following formula:
[Hygroscopic rate (%)] = {(Mass of polyimide resin film after standing for 24 hours−Mass of polyimide resin film after drying) / Weight after drying} × 100
The moisture absorption rate was determined according to The obtained results are shown in Table 1.

Example 1
First, in a 300 ml three-necked flask, 2.4 g of 4-aminophenyl-4′-aminobenzoate and 6.4 g of 4,4′-diaminodiphenyl ether were dissolved in 82 g of N, N-dimethylacetamide while flowing nitrogen. Solution was obtained. Then, 9.2 g of pyromellitic dianhydride was added at room temperature while stirring the solution, and then reacted for 3 hours to obtain a resin solution. Then, after apply | coating the said resin solution on copper foil (Corporation | KK Nikko Materials company make, brand name; NK-120, thickness 12 micrometers) using an applicator, it is 130 degreeC temperature conditions for 3 minutes in oven. Drying was performed. Next, the dried coating material is heated for 7 minutes at a temperature of 130 to 220 ° C., and further heated for 3 minutes at a temperature of 280 to 360 ° C. to perform a curing process by thermal imidization to give a polyimide of about 20 μm. The laminated body which the system resin layer laminated | stacked on copper foil was obtained. An etching rate and a moisture absorption rate were measured using a part of the laminate thus obtained.

  Next, a stainless steel foil (manufactured by Nippon Steel Co., Ltd., SUS304, tension annealed product, thickness 20 μm) is superposed on the surface of the polyimide resin layer of the laminate, and a press pressure of 13 MPa and a temperature are used using a vacuum press machine. A press was performed for 15 minutes at 320 ° C. to laminate a stainless steel foil on the laminate, thereby obtaining a laminate for HDD suspension of the present invention.

(Examples 2-3)
A laminate in the same manner as in Example 1, except that the blending amounts of 4-aminophenyl-4′-aminobenzoate, 4,4′-diaminodiphenyl ether and pyromellitic dianhydride were changed to the blending amounts shown in Table 1, respectively. And the laminated body for HDD suspensions of this invention was obtained.

Example 4
Instead of 4,4′-diaminodiphenyl ether, 4,4′-diamino-2,2′-dimethylbiphenyl was used, and 4-aminophenyl-4′-aminobenzoate, 4,4′-diamino-2,2′- A laminate and a laminate for an HDD suspension of the present invention were obtained in the same manner as in Example 1 except that the amounts of dimethylbiphenyl and pyromellitic dianhydride were changed to the amounts shown in Table 1.

(Comparative Example 1)
4,4′-diamino-2′-methoxybenzanilide is used instead of 4-aminophenyl-4′-aminobenzoate, and 4,4′-diamino-2′-methoxybenzanilide, 4,4′-diaminodiphenyl ether And the laminated body and the laminated body for HDD suspension as a comparison object were obtained like Example 1 except having set the compounding quantity of pyromellitic dianhydride to the compounding quantity shown in Table 1.

(Comparative Example 2)
Instead of 4-aminophenyl-4′-aminobenzoate, 4,4′-diamino-2,2′-dimethylbiphenyl was used, and 4,4′-diamino-2,2′-dimethylbiphenyl, 4,4′- A laminate and a laminate for an HDD suspension as a comparative object were obtained in the same manner as in Example 1 except that the amounts of diaminodiphenyl ether and pyromellitic dianhydride were changed to the amounts shown in Table 1.

(Comparative Example 3)
The same procedure as in Example 1 was conducted except that 4,4′-diaminodiphenyl ether was not blended and the blending amounts of 4-aminophenyl-4′-aminobenzoate and pyromellitic dianhydride were changed to the blending amounts shown in Table 1. To obtain a laminate. In addition, since the obtained laminated body was very brittle, a moisture absorption rate and an etching rate could not be measured, and furthermore, a laminated body for HDD suspension could not be produced.

(Comparative Example 4)
Instead of pyromellitic dianhydride, 4,4′-biphenyltetracarboxylic dianhydride was used, and 4,4′-diaminodiphenyl ether was not blended, and 4-aminophenyl-4′-aminobenzoate and 4,4 A laminate was obtained in the same manner as in Example 1 except that the amount of '-biphenyltetracarboxylic dianhydride was changed to the amount shown in Table 1. In addition, since the obtained laminated body was very brittle, a moisture absorption rate and an etching rate could not be measured, and furthermore, a laminated body for HDD suspension could not be produced.

  As is clear from the results shown in Table 1, it was confirmed that the laminates obtained in each Example had a sufficiently low moisture absorption rate and a high etching rate. On the other hand, it was confirmed that the laminate obtained in Comparative Example 1 had a high moisture absorption rate of 1.5, and that the laminate obtained in Comparative Example 2 had a slow etching rate of 4 μm.

  Therefore, the laminate for HDD suspension of the present invention is excellent in stability due to changes in humidity environment, can sufficiently prevent curling and warping, and is etched efficiently and reliably with an alkaline solution during etching processing. It was confirmed that it was possible.

  As described above, according to the present invention, a laminate for an HDD suspension that retains the conventionally required heat resistance and dimensional stability by heat treatment, the moisture absorption rate is sufficiently low, and the dimensions due to changes in the humidity environment. It is possible to provide a laminate for an HDD suspension that can sufficiently prevent changes and that can be etched efficiently and reliably with an alkaline aqueous solution.

  Therefore, the laminate for an HDD suspension according to the present invention is excellent in stability due to a change in humidity environment and can sufficiently prevent curling and warping, and thus is useful as a material for a wiring-integrated HDD suspension.

Claims (5)

  A laminate for an HDD suspension comprising a stainless steel foil, at least one polyimide resin layer, and a conductor layer, wherein at least one of the polyimide resin layers comprises 4-aminophenyl-4′-aminobenzoate. A laminate for an HDD suspension comprising, as a main component, a polyimide resin obtained by reacting 20 mol% to 80 mol% of a diamino compound and tetracarboxylic dianhydride. The polyimide resin has the following general formula (1):

(In the formula, Ar represents a tetravalent hydrocarbon group.)
A repeating unit represented by the following general formula (2):

(In the formula, Ar represents a tetravalent hydrocarbon group, and R represents a divalent hydrocarbon group.)
The HDD suspension laminate according to claim 1, comprising: a repeating unit represented by:   The laminate for an HDD suspension according to claim 1 or 2, wherein the diamino compound contains 20 to 60 mol% of 4-aminophenyl-4'-aminobenzoate.   4. The moisture absorption rate after the polyimide resin layer is allowed to stand for 24 hours under conditions of 23 ° C. and a relative humidity of 50% is 1.2% or less. 5. The laminate for an HDD suspension according to one item.   In the etching process in which the polyimide-based resin layer uses an aqueous solution of potassium hydroxide 33.5 wt%, ethylene diamine 11 wt%, and ethylene glycol 22 wt% as an etchant, an etching rate of 80 ° C. is used. The laminate for an HDD suspension according to any one of claims 1 to 4, wherein the average value is 5 µm / min or more.