JP2009227881A - Surface structure-modified polyimide benzoxazole film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide benzoxazole film whose adhesiveness is easily improved and also can be maintained even in a severe environment of high temperature and high humidity. <P>SOLUTION: The surface structure-modified polyimide benzoxazole film is produced by ion beam treatment of a polyimide benzoxazole film, and its surface area factor became ≥1.2 and ≤2.8, and polar component (γ<SB>sh</SB>) of the surface free energy of the film became 5 mN/m or less, and the polar component (γ<SB>sh</SB>) of the surface free energy of the film can be made at least 15 mN/m by electric discharge treatment or by active energy beam treatment of the film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyimide benzoxazole film, and more particularly to a surface-modified polyimide benzoxazole film having improved adhesion to an adhesive and suitable for applications such as flexible printed wiring boards.

  The polyimide benzoxazole film is superior in mechanical properties to other polyimide films (for example, Patent Documents 1 and 2). However, as with general polyimide films, adhesion to metal is also possible using an adhesive. There was a problem of being scarce. Until now, various improvement of adhesiveness by surface modification of a polyimide film has been proposed. For example, a method of surface-modifying a polyimide film by alkali treatment (for example, Patent Document 3), a method of plasma-treating the surface of the polyimide film (for example, Patent Document 4), a method of corona discharge treatment (for example, Patent Document 5) ), A method of irradiating the surface with ion particles having energy while blowing a reactive gas, reducing the contact angle of the surface, and controlling the adhesive force (see Patent Document 6).

However, the surface treatment with alkali has problems that the process is complicated and the strength of the film is lowered because it is immersed in a chemical. In addition, although plasma treatment and corona treatment have some effects at the beginning of the treatment, it has been regarded as a problem that the effects decrease with time.
As described above, many studies have been made on the surface modification technology for polyimide films, but there are few proposals for polyimide benzoxazole films that have better mechanical properties than polyimide films, and the improvement in adhesion is not. It is desired.

Japanese National Patent Publication No. 6-56992 Japanese National Patent Publication No. 10-508059 Japanese Patent Laid-Open No. 7-3055 JP 2004-51712 A JP-A-7-149929 Japanese National Patent Publication No. 11-501696

The present inventors previously obtained a polyimide benzoxazole film having a specific surface structure by, for example, irradiating the film with an ion beam using ions and introducing oxygen in the vicinity of the treated film. The surface structure-modified polyimide benzoxazole film obtained and proposed by finding that the adhesiveness is excellent (Japanese Patent Application No. 2008-8781) is a short period of time under normal temperature, normal pressure and constant humidity. In storage, the initial adhesiveness was maintained, but when used after long-term storage for several months or more, it was confirmed that the adhesiveness could not be maintained.
The present invention has been made against the background of such prior art problems.
That is, the object of the present invention is to maintain the adhesiveness for a long time, and even if the adhesiveness is once lost, the adhesiveness can be recovered by a simple treatment, and after adhesion, it is placed in a severe environment of high temperature and humidity. Is to provide a surface structure modified polyimide benzoxazole film that can maintain adhesion.

As a result of investigating the cause of the present inventors, it has been found that the reason why the adhesiveness cannot be maintained is that the polar component of the surface energy of the surface modified film is reduced, and the present invention has been reached.
That is, the present invention has the following configuration. 1. A film in which a polyimide benzoxazole film has been subjected to ion beam treatment to have a surface area ratio of 1.2 or more and 2.8 or less, and a polar component (γ _sh ) of the surface energy of the film is 5 mN / m or less. A polar component (γ _sh ) of the surface free energy of the film is 5 mN / m or less, and the polar component of the surface free energy is obtained by subjecting the film to discharge treatment or active energy ray treatment. A surface structure modified polyimide benzoxazole film characterized in that (γ _sh ) can be 15 mN / m or more.
2. 1. The polyimide benzoxazole film has a tensile modulus of 4 GPa or more and 10 GPa or less, and a thickness of 7 μm or less and 1 μm or more. Surface modified polyimide benzoxazole film.
3. 1. Gas used for ion beam treatment is a mixed gas of oxygen and nitrogen Or 2. Surface structure modified polyimide film.
4). The ion beam treatment is performed in a roll-to-roll film processing apparatus equipped with an ion gun, and the film obtained by the treatment has a width of 250 mm to 2 m and a length of 10 m to 20000 m. ~ 3. The surface structure-modified polyimide benzoxazole film according to any one of the above.
5. A polyimide benzoxazole film whose surface area ratio is 1.2 to 2.8 and the polar component (γ _sh ) of the surface energy is 5 mN / m or less by ion beam treatment of the polyimide benzoxazole film. A method for treating a surface structure-modified polyimide benzoxazole film, characterized in that the film is subjected to discharge treatment or active energy ray treatment so that the γ _sh is 15 mN / m or more.

The surface structure-modified polyimide benzoxazole film of the present invention can be obtained by simple plasma treatment, etc., even if the adhesiveness is low as it is after long-term storage for several months or more under normal temperature, normal pressure, and constant humidity. Since the polar component of the surface free energy can be easily increased, the adhesiveness can be improved. Moreover, film mechanical properties equivalent to those of the untreated polyimide benzoxazole film can be retained.
In addition, since the surface structure modified polyimide benzoxazole film of the present invention has a high value for its unique surface structure and the polar component of surface free energy, it can be used in a severe environment of high temperature and high humidity such as heat treatment or wet heat treatment after bonding. High adhesiveness can be maintained, and it can be suitably used for electronic components such as a printed wiring board (PWB), FPC, and TAB tape that require reliability.

The polyimide benzoxazole film in the present invention is composed of aromatic diamines having a benzoxazole structure (hereinafter collectively referred to as amines and amide-bonded derivatives), and aromatic tetracarboxylic acid anhydrides (anhydrides, It is a film mainly composed of polyimide obtained by reacting acid and amide bond derivatives generically, referred to below as the same). In the reaction, diamines and tetracarboxylic acid anhydrides are first subjected to a ring-opening polyaddition reaction in a solvent to obtain a polyamic acid solution, and then a green film or the like is formed from the polyamic acid solution, followed by dehydration condensation. (Imidization) is performed.
<Aromatic diamines>
The molecular structure of aromatic diamines having a benzoxazole structure used in the present invention is not particularly limited, and specific examples include the following.

  Among these, from the viewpoint of easy synthesis, each isomer of amino (aminophenyl) benzoxazole is preferable, and 5-amino-2- (p-aminophenyl) benzoxazole is more preferable. Here, “each isomer” refers to each isomer in which two amino groups of amino (aminophenyl) benzoxazole are determined according to the coordination position (eg, the above “formula 1” to “formula 4”). Each compound described in the above. These diamines may be used alone or in combination of two or more.

  In the present invention, one or two or more diamines having no benzoxazole structure exemplified below may be used as long as they are 30 mol% or less of the total diamine. Examples of such diamines include 4,4′-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, and bis [4- (3-aminophenoxy) phenyl]. Sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 3,3′-diamino Diphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-dia Nodiphenyl sulfide, 3,3′-diaminodiphenyl sulfoxide, 3,4′-diaminodiphenyl sulfoxide, 4,4′-diaminodiphenyl sulfoxide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4 , 4′-diaminodiphenylsulfone, 3,3′-diaminobenzophenone, 3,4′-diaminobenzophenone, 4,4′-diaminobenzophenone,

3,3′-diaminodiphenylmethane, 3,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylmethane, bis [4- (4-aminophenoxy) phenyl] methane, 1,1-bis [4- (4-amino) Phenoxy) phenyl] ethane, 1,2-bis [4- (4-aminophenoxy) phenyl] ethane, 1,1-bis [4- (4-aminophenoxy) phenyl] propane, 1,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,3-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 1,1- Bis [4- (4-aminophenoxy) phenyl] butane, 1,3-bis [4- (4-aminophenoxy) phenyl] butane, 1,4-bis [4- 4-aminophenoxy) phenyl] butane, 2,2-bis [4- (4-aminophenoxy) phenyl] butane, 2,3-bis [4- (4-aminophenoxy) phenyl] butane, 2- [4- (4-aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3-methylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) -3-methylphenyl] propane, 2- [4- (4-Aminophenoxy) phenyl] -2- [4- (4-aminophenoxy) -3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy)- 3,5-dimethylphenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane,

1,4-bis (3-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 4,4′-bis (4-aminophenoxy) ) Biphenyl, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfoxide, bis [4- ( 4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 1,3-bis [4- (4-aminophenoxy) ) Benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (3 Aminophenoxy) benzoyl] benzene, 4,4-bis [(3-aminophenoxy) benzoyl] benzene,

1,1-bis [4- (3-aminophenoxy) phenyl] propane, 1,3-bis [4- (3-aminophenoxy) phenyl] propane, 3,4'-diaminodiphenyl sulfide, 2,2-bis [3- (3-Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, bis [4- (3-aminophenoxy) phenyl] methane, 1,1-bis [4- (3-aminophenoxy) phenyl] ethane, 1,2-bis [4- (3-aminophenoxy) phenyl] ethane, bis [4- (3-aminophenoxy) phenyl] sulfoxide, 4,4′-bis [3 -(4-aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [3- (3-aminophenoxy) benzoyl] diphenyl ether, 4,4'-bis [4 (4-Amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenylsulfone, bis [4- {4- ( 4-aminophenoxy) phenoxy} phenyl] sulfone, 1,4-bis [4- (4-aminophenoxy) phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) Phenoxy-α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-trifluoromethylphenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- ( 4-amino-6-fluorophenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-6-methylphenoxy) -α, α- Methylbenzyl] benzene, 1,3-bis [4- (4-amino-6-cyanophenoxy)-.alpha., alpha-dimethylbenzyl] benzene,

3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-5,5′-diphenoxybenzophenone, 3,4′-diamino-4,5′-diphenoxybenzophenone, 3, 3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3 '-Diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 3,3'- Diamino-4-biphenoxybenzophenone, 4,4′-diamino-5-biphenoxybenzophenone, 3,4 -Diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis (3-amino-4-phenoxybenzoyl) benzene, 1,4-bis (3-amino- 4-phenoxybenzoyl) benzene, 1,3-bis (4-amino-5-phenoxybenzoyl) benzene, 1,4-bis (4-amino-5-phenoxybenzoyl) benzene, 1,3-bis (3-amino) -4-biphenoxybenzoyl) benzene, 1,4-bis (3-amino-4-biphenoxybenzoyl) benzene, 1,3-bis (4-amino-5-biphenoxybenzoyl) benzene, 1,4-bis (4-Amino-5-biphenoxybenzoyl) benzene, 2,6-bis [4- (4-amino-α, α-dimethylbenzyl) pheno Si] A part or all of hydrogen atoms on the aromatic ring of benzonitrile and the above aromatic diamine are halogen atoms, alkyl groups having 1 to 3 carbon atoms or alkoxyl groups, cyano groups, or hydrogen atoms of alkyl groups or alkoxyl groups. Examples thereof include aromatic diamines substituted with a halogenated alkyl group having 1 to 3 carbon atoms partially or wholly substituted with a halogen atom or an alkoxyl group.

<Aromatic tetracarboxylic acid anhydrides>
The tetracarboxylic acid anhydrides used in the present invention are aromatic tetracarboxylic acid anhydrides. Specific examples of the aromatic tetracarboxylic acid anhydrides include the following.

これらのテトラカルボン酸二無水物は単独で用いてもよいし、二種以上を併用してもよい。

These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  In the present invention, one or two or more non-aromatic tetracarboxylic dianhydrides exemplified below may be used in combination as long as they are 30 mol% or less of the total tetracarboxylic dianhydrides. Examples of such tetracarboxylic acid anhydrides include butane-1,2,3,4-tetracarboxylic dianhydride, pentane-1,2,4,5-tetracarboxylic dianhydride, and cyclobutanetetracarboxylic acid. Acid dianhydride, cyclopentane-1,2,3,4-tetracarboxylic dianhydride, cyclohexane-1,2,4,5-tetracarboxylic dianhydride, cyclohex-1-ene-2,3 5,6-tetracarboxylic dianhydride, 3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohexane-3 -(1,2), 5,6-tetracarboxylic dianhydride, 1-methyl-3-ethylcyclohex-1-ene-3- (1,2), 5,6-tetracarboxylic dianhydride 1-ethylcyclohexane -(1,2), 3,4-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane- 1- (2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ′, 4′-tetracarboxylic dianhydride, bicyclo [2.2.1] Heptane-2,3,5,6-tetracarboxylic dianhydride, 1-propylcyclohexane-1- (2,3), 3,4-tetracarboxylic dianhydride, 1,3-dipropylcyclohexane-1 -(2,3), 3- (2,3) -tetracarboxylic dianhydride, dicyclohexyl-3,4,3 ', 4'-tetracarboxylic dianhydride, bicyclo [2.2.1] heptane -2,3,5,6-tetracarboxylic dianhydride, Cyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic acid A dianhydride etc. are mentioned. These tetracarboxylic dianhydrides may be used alone or in combination of two or more.

  The solvent used when polymerizing diamines and tetracarboxylic acid anhydrides to obtain polyamic acid is not particularly limited as long as it dissolves both the raw material monomer and the polyamic acid to be produced. Organic solvents are preferred, such as N-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N, N-dimethylformamide, N, N-diethylformamide, N, N-dimethylacetamide, dimethyl sulfoxide, hexamethylphos Examples include hollic amide, ethyl cellosolve acetate, diethylene glycol dimethyl ether, sulfolane, and halogenated phenols. These solvents can be used alone or in combination. The amount of the solvent used may be an amount sufficient to dissolve the monomer as a raw material. As a specific amount used, the mass of the monomer in the solution in which the monomer is dissolved is usually 5 to 40% by mass, The amount is preferably 10 to 30% by mass.

  Conventionally known conditions may be applied for the polymerization reaction for obtaining the polyamic acid (hereinafter also simply referred to as “polymerization reaction”). As a specific example, in a temperature range of 0 to 80 ° C., 10 Stirring and / or mixing continuously for 30 minutes. If necessary, the polymerization reaction may be divided or the temperature may be increased or decreased. In this case, the order of adding both monomers is not particularly limited, but it is preferable to add aromatic tetracarboxylic anhydrides to the solution of aromatic diamines. The mass of the polyamic acid in the polyamic acid solution obtained by the polymerization reaction is preferably 5 to 40 mass%, more preferably 10 to 30 mass%, and the viscosity of the solution is measured by a Brookfield viscometer (25 ° C.). And from the stability point of liquid feeding, Preferably it is 10-2000 Pa.s, More preferably, it is 100-1000 Pa.s.

Vacuum defoaming during the polymerization reaction is effective for producing a good quality polyamic acid solution. Moreover, you may perform superposition | polymerization by adding a small amount of terminal blockers to aromatic diamines before a polymerization reaction. Examples of the end capping agent include compounds having a carbon-carbon double bond such as maleic anhydride. The amount of maleic anhydride used is preferably 0.001 to 1.0 mol per mol of aromatic diamine.
In order to form a polyimide film from the polyamic acid solution obtained by the polymerization reaction, a green film (a self-supporting precursor film is obtained by applying the polyamic acid solution on a support and drying, then, A method of imidizing the green film by subjecting it to a heat treatment can be mentioned.
Application of the polyamic acid solution to the support includes, for example, casting from a die with a slit and extrusion by an extruder, but is not limited thereto, and conventionally known solution application means can be appropriately used.

  The conditions for drying the polyamic acid coated on the support to obtain a green sheet are not particularly limited, and examples include a temperature of 70 to 150 ° C. and a drying time of 5 to 180 minutes. A conventionally known drying apparatus that satisfies such conditions can be applied, and examples thereof include hot air, hot nitrogen, far infrared rays, and high frequency induction heating. Subsequently, in order to obtain the target polyimide benzoxazole film from the obtained green sheet, an imidization reaction is performed. As a specific method thereof, a conventionally known imidization reaction can be appropriately used. For example, there may be mentioned a method (so-called thermal ring closure method) in which an imidization reaction proceeds by subjecting to a heat treatment after performing a stretching treatment as necessary using a polyamic acid solution not containing a ring closure catalyst or a dehydrating agent. The heating temperature in this case is exemplified by 100 to 500 ° C., and from the viewpoint of film physical properties, more preferably, a two-stage heat treatment in which treatment is performed at 350 to 500 ° C. for 3 to 20 minutes after treatment at 150 to 250 ° C. for 3 to 20 minutes. Is mentioned.

As another example of the imidization reaction, a chemical ring closure method in which a ring-closing catalyst and a dehydrating agent are contained in a polyamic acid solution and the imidization reaction is performed by the action of the ring-closing catalyst and the dehydrating agent can be exemplified. In this method, after applying the polyamic acid solution to the support, the imidization reaction is allowed to partially proceed to form a film having self-supporting properties, and then imidization can be performed completely by heating. In this case, the condition for partially proceeding with the imidization reaction is preferably a heat treatment for 3 to 20 minutes at 100 to 200 ° C., and the condition for allowing the imidization reaction to be completely performed is preferably 200 to 400 ° C. For 3 to 20 minutes.

The thickness of the polyimide benzoxazole film of the present invention is not particularly limited, but is preferably 7 μm or less in terms of the manifestation of the effect.
Conventionally, it is difficult to industrially stably produce a long film of a polyimide film of 7 μm or less, particularly 5 μm or less, and these ultrathin polyimide films obtained have extremely large thickness spots, for example, The thickness unevenness of a commercially available 7.5 μm polyimide film is about 25%, and there is a problem in quality in electronic parts that require dimensional accuracy.
The thickness of the polyimide benzoxazole film can be easily controlled by the amount of the polyamic acid solution applied to the support and the concentration of the polyamic acid solution.

  In the present invention, a method for obtaining a polyimide benzoxazole film having a thickness of 7 μm or less, in which these thickness spots are 20% or less, is not particularly limited, but a preferred method is (1) aromatic tetra A polyamic acid obtained by reacting a carboxylic acid with an aromatic diamine having a benzoxazole skeleton is cast and dried to obtain a precursor film (polyamic acid film). A tenter system that transports the film in a state of being stretched in the width direction and / or the transport direction, in which the film edge gripping at both ends is sandwiched by a large number of clips or pierced by a large number of pins provided on the pin sheet. To obtain a polyimide benzoxazole film having a thickness of 7 μm or less. In the manufacturing method of nzooxazole film, the film gripping at both ends in the width direction of the precursor film is easy adhesion by providing an adhesive layer on the precursor (polyamic acid) film to be imidized and the thin polyimide film A method for producing a polyimide benzoxazole film which is fixed by holding and / or piercing with a conductive polyimide film, and (2) the narrow polyimide film reacts with an aromatic tetracarboxylic acid and an aromatic diamine. The method of said (1) which is what is called a precursor film (green film) which slit the precursor film obtained by casting and drying the obtained polyamic acid is mentioned.

Here, the thin film prepared separately is not particularly limited in the case of the precursor film or the easily adhesive polyimide film provided with the adhesive layer, but it is the same as the precursor film to be processed. The diamine and the same tetracarboxylic acid are preferable, and apart from the polyimide film to be produced, the same polyamic acid solution is cast and dried to create another precursor film and prepared in advance by slitting to a narrow width. A polyimide precursor film or a polyimide film obtained by imidizing the precursor film is preferable, and these can be prepared by slitting them as they are or by slitting them as easy-adhesive polyimide films provided with an adhesive layer. The width of the narrow film is preferably 20 to 80 mm. The thickness of the thin film prepared separately is not particularly limited, but preferably the same thickness as the precursor film to be processed (manufactured as a polyimide film), preferably 5 to 13 μm, If it is less than 5 μm, the reinforcing effect of the overlay tends to be reduced, and if it exceeds 13 μm, the reinforcing effect of the overlay tends to be difficult for the precursor film to be produced as a polyimide film.
In the present invention, when a polyimide benzoxazole film having a thickness of 7 μm or less is subjected to ion gun treatment with roll-to-roll, a rigid film such as a polyester film is lined with a polyimide benzoxazole film through a heat-resistant adhesive or the like. It is preferable to employ a method of peeling and removing the backing film after the treatment.

In the present invention, it is essential that the surface area ratio after the surface structure modification treatment is 1.2 or more and 2.8 or less. The surface area ratio in the present invention indicates how many times the surface has a surface area with respect to an ideal plane, and can be suitably obtained by a scanning probe microscope with a surface physical property evaluation function. Specifically, for example, SPA300 / SPI3800N manufactured by SII Nano Technology can be used.
The range of the surface area ratio is more preferably 1.3 or more and 2.6 or less, and further preferably 1.4 or more and 2.5 or less.

The polar component (γ _sh ) in the surface free energy of the film of the present invention is _D.I. K. Owens: J.M. Appl. Polym. Sci. , Vol. 13, p. 1741 (1969), the surface free energy γ _sv (unit: mN / m) is tested on a polyimide benzoxazole film based on the definition that γ _sv = γ _sd + γ _sh. Is required.
That is, the contact angles θ _H2O and θ _CH2I2 of pure water (H ₂ O) and methylene iodide (CH ₂ I ₂ ) on the polyimide benzoxazole film are measured and obtained from the following simultaneous equations a and b. Can do.
a. 1 + cos θ _H2O =
2 (γ _sd ) ^0.5 ((γ _H2Od ) ^0.5 / γ _H2Ov ) +2 (γ _sh ) ^0.5 ((γ _H2Oh ) ^0.5 / γ _H2Ov )
b. 1 + cos θ _CH2I2 =
2 (γ _sd ) ^0.5 ((γ _CH2I2d ) ^0.5 / γ _CH2I2v ) +2 (γ _sh ) ^0.5 ((γ _CH2I2h ) ^0.5 / γC _H2I2v )
γ _H2Od = 21.8, γ _H2Oh = 51.0, γ _H2Ov = 72.8,
γ _CH2I2d = 48.5, _γCH2I2h = 2.3, _γCH2I2v = 50.8
Therefore, the surface free energy γ _sv of the polyimide benzoxazole film is represented by the sum of γ _sd and γ _sh , and the polar component in the present invention means γ _sh .

The polyimide benzoxazole film according to the present invention is easily polarized even if the polar component (γ _sh ) of the surface free energy of the film is 5 mN / m or less and the adhesive properties are significantly deteriorated. (Γ _sh ) is a film that can be increased to 15 mN / m or more and can improve adhesive properties. The polar component (γ _sh ) of the surface free energy is preferably 20 mN / m or more, more preferably 25 mN / m or more.
As a method of increasing the polar component (γ _sh ) of the surface free energy to 15 mN / m or more, there is a method of subjecting the film to a discharge treatment or an active energy ray treatment.
Examples of the discharge treatment include reduced-pressure plasma treatment, atmospheric pressure plasma treatment, corona treatment, and the like, and examples of the active energy ray treatment include ultraviolet rays and electron beams.
Therefore, even if the polyimide benzoxazole film of the present invention is subjected to ion beam treatment and the surface area ratio of the film is 1.2 or more and 2.8 or less, the surface free energy is reduced from the beginning or by long-term storage. The film should have a γ _sh of 15 mN / m or more by subjecting a film having a polar component (γ _sh ) of 5 mN / m or less to a discharge treatment or an active energy ray treatment.

In the polyimide benzoxazole film of the present invention, the surface area ratio is in the above range, and the polar component (γ _sh ) of the surface free energy is increased to 15 mN / m or more for the first time, by PCT treatment (saturated water vapor pressure, The peel strength showing the adhesiveness after 96 hours at 121 ° C. and 2 atmospheres is maintained at 4 (N / cm) or more. When the surface area ratio is less than 1.2, the peel strength indicating adhesion after 96 hours of PCT treatment (saturated water vapor pressure, 121 ° C., 2 atm) is less than 4 (N / cm). When the rate exceeds 2.8, even if the peel strength showing adhesion after 96 hours of PCT treatment (saturated water vapor pressure, 121 ° C., 2 atm) is 4 (N / cm) or more, Strength will not withstand practical use. Further, the surface area ratio after the surface structure modification treatment is preferably 1.2 or more and 2.8 or less, and Ra is preferably 12 to 30 (nm). The mechanism is not clear, but the PCT treatment (saturation) The peel strength showing the adhesiveness after 96 hours of water vapor pressure (121 ° C., 2 atm) is not sufficiently practical.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited by a following example. In addition, the evaluation method of the physical property in the following examples is as follows.

1. Reduced viscosity of polyamic acid (ηsp / C)
A solution dissolved in N-methyl-2-pyrrolidone (or N, N-dimethylacetamide) so that the polymer concentration was 0.2 g / dl was measured at 30 ° C. with an Ubbelohde type viscosity tube.
2. Film thickness The film to be measured was measured using a micrometer (Finereuf, Millitron 1245D).

3. Surface Area Ratio, Surface Roughness Ra Measurement Method The surface morphology was measured using a scanning probe microscope with a surface physical property evaluation function (SP300 / SPI3800N manufactured by SII Nanotechnology Inc.). The measurement was performed in the DFM mode, and DF3 or DF20 manufactured by SII Nano Technology Co., Ltd. was used as the cantilever. The scanner used was FS-20A, the scanning range was 2 mm square, and the measurement resolution was 512 × 512 pixels. For the measurement image, after correcting the secondary inclination, the surface area ratio and the surface roughness Ra were calculated by the software attached to the apparatus.
4). Peel strength measurement method The treated surfaces of the films obtained above were bonded face to face, and then the peel strength after 96 hours of PCT treatment (saturated water vapor pressure, 121 ° C., 2 atm) was evaluated. The adhesive was TFA880-CA manufactured by Kyocera Chemical Co., Ltd. as an adhesive, and was cured by press at 160 ° C. for 1 hour after roll lamination at 100 ° C. The peel strength of the sample was determined by a T-shaped peel test under the following measurement conditions.
Device name: Autograph AG-IS, manufactured by Shimadzu Corporation
Measurement temperature; Room temperature Peeling speed; 50mm / min
Atmosphere: Air Measurement sample width: 1cm

5. Measurement method of polar component (γ _sh ) of surface free energy (γ _sv ) (1) Measurement of contact angle of film After conditioning the film at 20 ° C. and 26% RH for 1 hour or more, pure water ( The contact angles θ _H2O and θ _CH2I2 of H ₂ O) and methylene iodide (CH ₂ I ₂ ) were measured.
That is, using the automatic contact angle meter CA-X type manufactured by Kyowa Interface Science Co., Ltd., the liquid surface at the point where the film and the liquid come into contact with each other by forming 1.8 μl droplets on the film. The angle formed by the tangent to the film surface and the film surface was measured as the contact angle. The contact angle was measured five times for one sample and one kind of liquid, and the average value of the five times was defined as θ _H2O and θ _CH2I2 .
(2) Calculation method of polar component (γ _sh ) of surface free energy The contact angles θ _H2O and θ _CH2I2 obtained above are calculated using the above-mentioned document (DK Owens: J. Appl. Polym. Sci., 13). Volume, p. 1741 (1969)), the surface free energy is calculated by substituting into simultaneous equations a and b in the literature, and γ _sv (surface free energy) = γ _sd + γ _sh (polar component) γ _sh (mN / m) was determined.

<Polymerization Example 1>
<Polymerization of a polyamic acid composed of a diamine having a benzoxazole structure>
After the inside of the reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirring rod was purged with nitrogen, 500 parts by mass of 5-amino-2- (p-aminophenyl) benzoxazole was charged. Next, after 8000 parts by mass of N, N-dimethylacetamide was added and completely dissolved, 485 parts by mass of pyromellitic dianhydride was added and stirred at a reaction temperature of 25 ° C. for 48 hours. A polyamic acid solution (A) was obtained. The solution obtained had a ηsp / C of 4.0 dl / g.

<Film creation example 1>
The polyamic acid solution (A) was coated on a stainless steel belt with a squeegee / belt gap of 450 μm, and as a first drying step, three hot-air drying zones at ambient temperature of 90 ° C. × 7 minutes, 90 ° C. × 7 minutes, Dry at 90 ° C. for 7 minutes.
The precursor film which became self-supporting after drying was peeled from the stainless steel belt to obtain a polyimide benzoxazole precursor film having a thickness of 40 μm.
This peeled precursor film was double-sided dried at an atmospheric temperature of 150 ° C. for 10 minutes in a hot air drying zone.
The residual solvent amount of the polyimide benzoxazole precursor film was 35.5% by mass.
The obtained polyimide benzoxazole precursor film was passed through a continuous drying furnace and heat-treated at 200 ° C. for 3 minutes, then heated to 450 ° C. for about 20 seconds and heat-treated at 450 ° C. for 7 minutes. The mixture was cooled to room temperature over 5 minutes to obtain a brown polyimide benzoxazole film (A). Similarly, brown polyimide benzoxazole films (A2) and (A3) were obtained by changing only the film thickness.

<Reference Examples 1-5>
While these films were rolled in a vacuum chamber, oxygen ions were irradiated with an ion gun to treat the film surface. Surface treatment was performed using a sputtering apparatus. The sputter device is a roll-to-roll type device, in which the film is moved from the roll to the unwinding chamber, the sputtering chamber, the spare chamber, and the winding chamber. It is done.
Each chamber is roughly partitioned by a slit. In the ion gun chamber, the film was in contact with the chill roll, cooled by the temperature of the chill roll (−5 ° C.), and a wide ion gun was used so that ion irradiation was uniform in the roll width direction. As the ion gun, 38CMLIS manufactured by Advanced Energy Industries was used. Oxygen was used as a gas to be introduced into the ion gun, and the ion gun was operated at a discharge voltage of 520 V, a discharge current of 0.6 A, a discharge power of 300 W, a beam gas flow rate of 45 sccm, and a differential pressure of 3 × 10 ⁻¹ Pa. Each polyimide benzoxazole film having a width of 250 mm was used, and the roll feed rate was 0.05 m / min. Oxygen was not introduced from anything other than the ion gun.
Ion gun treatment was carried out in the same manner as above except that the ion gun treatment gas and the film used were changed. Table 1 shows the evaluation results of the films after one day (in air, 20 ° C., 70% RH) after treatment of the obtained surface structure-modified polyimide benzoxazole films as Reference Examples 1 to 5.

<Reference Examples 6-8>
The polyimide benzoxazole film (A) not subjected to ion gun treatment was evaluated in the same manner as described above, and the results are shown in Table 2 as Reference Example 6.
Table 2 shows the evaluation results for the surface-treated film in the same manner as in Example 1 except that the film feed rate was set to 0.2 m / min in order to reduce the energy applied to the unit area.
A polyimide benzoxazole film (A) having a width of 250 mm was subjected to oxygen glow discharge to treat the surface of the polyimide film. The processing conditions are O ₂ (oxygen) gas pressure 2 × 10 ⁻³ Torr, flow rate 50 SCCM, discharge frequency 13.56 MHz, output 450 W, and processing time is effective plasma irradiation at a film feed rate of 0.1 m / min. Since the width is about 10 cm, the plasma irradiation time at one place is 1 minute. The evaluation results of the treated film are shown in Table 2 as Reference Example 8.
In addition, evaluation of each process film was implemented about the film after 1 day (in air, 20 degreeC, 70% RH) progress after a process.

Change over time of polar components of surface free energy when the films of Reference Examples 1 to 8 are stored in air at 20 ° C. and 70% RH (1 day (initial), 60 days and 120 days). Table 3 shows.

  In addition, about each polyimide benzoxazole film after 60-day and 120-day preservation | save progress, after bonding a process surface facing each other, PCT process (saturated water vapor pressure, 121 degreeC, 2 atmospheres) after 96 hours peel strength All were 2 mN / m or less.

<Examples 1-5, Comparative Examples 1-3>
Each of the polyimide benzoxazole films in Reference Examples 1 to 8 after storage for 120 days is cut to A4 size, and is used in a RIE mode with a batch-type sputtering apparatus, and polyimide benzoxazole by glow discharge of oxygen. The surface of the film was plasma treated. The processing conditions are O ₂ gas pressure 2 × 10 ⁻³ Torr, flow rate 50 SCCM, discharge frequency 13.56 MHz, output 450 W, and processing time is plasma irradiation time 1 minute.
Table 4 shows the evaluation results for each polyimide benzoxazole film obtained by these simple plasma treatments.

  The surface structure-modified polyimide benzoxazole film of the present invention has a high value of the polar component of the surface free energy by simple plasma treatment, high peel strength by an adhesion peel test, and improved adhesion. I understand.

  The surface structure-modified polyimide benzoxazole film of the present invention can improve the adhesion by a simple treatment, and the adhesion (peel strength) after the PCT treatment of the polyimide benzoxazole film should be a practical value. Can do. For this reason, it can be used even in harsh environments of high temperature and high humidity in electronic parts such as flexible printed wiring boards, and the surface structure modification treatment method is very easy. We can expect to contribute.

Claims (5)

This is a film in which a polyimide benzoxazole film has been subjected to ion beam treatment to have a surface area ratio of 1.2 or more and 2.8 or less and a polar component (γ _sh ) of the surface free energy of the film of 5 mN / m or less. The surface structure modified polyimide benzo, wherein the film can be subjected to a discharge treatment or an active energy ray treatment so that the polar component (γ _sh ) of the surface free energy can be 15 mN / m or more. Oxazole film.   The surface structure-modified polyimide benzoxazole film according to claim 1, wherein the polyimide benzoxazole film has a tensile modulus of 4 GPa to 10 GPa and a thickness of 7 µm to 1 µm.   The surface structure-modified polyimide benzoxazole film according to claim 1 or 2, wherein the gas used for the ion beam treatment is a mixed gas of oxygen and nitrogen. The ion beam treatment is performed in a roll-to-roll film processing apparatus equipped with an ion gun, and the film obtained by the treatment has a width of 250 mm or more and 2 m or less and a length of 10 m or more and 20000 m or less. Surface structure modified polyimide benzoxazole film. The polyimide benzoxazole film is subjected to ion beam treatment so that the surface area ratio of the film is 1.2 or more and 2.8 or less, and the polar component (γ _sh ) of the surface free energy is 5 mN / m or less. A method for treating a surface structure-modified polyimide benzoxazole film, characterized in that an oxazole film is subjected to discharge treatment or active energy ray treatment so that the γ _sh is set to 15 mN / m or more.