JP2021145045A - Stiffener with good quality and excellent bending resistance - Google Patents

Abstract

To determine a stiffener with good quality and excellent bendability from compression test characteristics.SOLUTION: A metal rod is used to evaluate the compression characteristics of a stiffener at multiple locations, and satisfy a specific condition. A stiffener that changes the compression rate and has small rate dependence of compressive fracture stress exhibits excellent bendability.SELECTED DRAWING: Figure 4

Description

In the present invention, in order to maintain the strength of a flexible printed circuit board (hereinafter referred to as "FPC board"), a stiffener (support plate or reinforcing plate) used by adhering to the FPC substrate, particularly a plurality of polyimide films are adhered. The present invention relates to a polyimide film laminate stiffener formed by laminating with an agent.

Typical examples of films in which a heat-curable adhesive is provided on one side or both sides of a single-layer or multi-layer polyimide film include "coverlay film" and "TAB (Tape Automated Bonding) film". Be done. As shown in FIG. 1A, the adhesive used in these films is an adhesive in a semi-cured state (B stage) after being applied on a base film 11 made of a polyimide film and then dried. It is said to be layer 12. Then, a separator 13 is usually further laminated on the surface of the adhesive layer 12. This laminate is stored in the form of having an adhesive layer that has been semi-cured before use. Examples of the adhesive layer of the polyimide film of another form include a prepreg obtained by impregnating a reinforcing base material such as a glass cloth with an adhesive varnish and drying the adhesive layer. As for the prepreg, the adhesive is stored in the B stage state. Then, as shown in FIG. 1 (b), the base film 11 of these coverlay films and TAB films is applied to an object such as an FPC substrate 14 via an adhesive layer 2 (consisting of an adhesive or a prepreg). By stacking, heating, and pressurizing, the base film 11 is adhered to an object such as the FPC substrate 14. Further, as shown in FIG. 2, an FPC substrate in which a metal foil 23 such as a copper foil and a polyimide film 11 are bonded with an adhesive 22 is also known, but in these bonding, the metal foil and the polyimide film are used. It is necessary to perform heat aging after laminating.

By the way, the thickness of the FPC substrate is usually thin (for example, 12.5 to 100 μm). However, if the thickness of the substrate is thin, inconvenience is likely to occur in the switch portion and the connector portion. Therefore, conventionally, as shown in FIG. 3, an FPC substrate made of a polyimide film including a portion where this inconvenience is likely to occur or a portion where this inconvenience is likely to occur is passed through a heat-curable adhesive (referred to as a bonding sheet). It is fixed to a support such as a stiffener. In this case, it is a general bonding condition to heat and pressurize at 150 to 180 ° C. for 15 to 45 minutes under a pressure of 1 to 3 MPa. As the stiffener used to support or reinforce the FPC substrate, a single-layer polyimide film is generally used. A single-layer polyimide film having a thickness of 225 μm or less is widely and generally commercially available, and this commercially available single-layer polyimide film is used as a stiffener. Typical examples of these single-layer polyimide films are Kapton H or V type (manufactured by Toray DuPont Co., Ltd.), Upirex S type (manufactured by Ube Industries, Ltd.), Apical AH or NPI type (manufactured by Ube Industries, Ltd.). Examples thereof include polyimide films commercially available under trade names such as (manufactured by Kaneka). The hardness and stiffness of a single-layer polyimide film are constant depending on each product. However, depending on the application, rigidity may be required more than that of a single layer even if the thickness is the same.

Further, the polyimide film is mainly produced by solution film formation by casting, and it is difficult to produce a thick film due to the production method, or the productivity thereof is extremely inferior.

For this reason, a sheet in which a plurality of polyimide films are bonded may be used as a stiffener. If a gap or the like is generated, the strength of the stiffener becomes insufficient at that portion. Even with a single-layer stiffener, the strength may be insufficient if there are voids or scratches generated during film formation.

Further, since the stiffener is often used together with a metal part having a higher rigidity than a polyimide film, bending resistance at a joint with a hard member is important.

If there are gaps, scratches, or foreign matter caught in the bent part, it may cause cracks.

As a result of diligent studies to solve the above problems, the present inventors conducted a compression test of a stiffener using a rod, and if the number of places that do not satisfy a specific condition is 0.1 pieces / square cm or less, there is a drawback. It was found that it can be said that it is a stiffener having sufficient strength for FPC. Further, when the compression test speed is changed from 0.2 mm / min to 10 mm / min, if the strain difference at the fracture point is 15% or less at 0.2 mm / min, the 90-degree bending resistance is excellent. It is a stiffener, and it has been found that it is difficult for creases to be formed at the contact portion with metal parts.

That is, the present invention has the following configuration.
[1] A stiffener made of a polyimide film.
When a compression test in the thickness direction is performed at a compression speed of 0.2 mm / min using a rod having a contact surface with a stiffener of 10 mm × 10 mm, 0.1 places / square do not satisfy the following condition (I). A stiffener characterized by being less than cm.
Condition (I)
In the stress-strain curve of the stiffener obtained with the horizontal axis as the compressive strain and the vertical axis as the compressive stress, the strain value at the transition start point where the stress-strain curve shifts to the linear region is 20% or less of the stiffener thickness.
[2] The stiffener according to the above [1], which satisfies the following condition (II) when a compression test is performed in the thickness direction using a rod having a contact surface with the stiffener of 10 mm × 10 mm. Stiffener featuring.
Condition (II)
In the stress-strain curve of the stiffener obtained with the compression speeds of 10 mm / min and 0.2 mm / min, the horizontal axis as the compressive strain, and the vertical axis as the compressive stress, the compressive stress σ _{10 at the time of the strain that maximizes the stress.} The difference of σ _{0.2 is | σ 10 −} σ _0.2 | <0.15 × σ _0.2
Is.
[3] The stiffener according to the above [1], when the operation of bending at an angle of 60 ° along the iron plate placed on the plate, holding and opening for 3 seconds is repeated 10 times, a crack is formed in the bent portion. A stiffener that is characterized by the fact that

If there is a defect in the stiffener, stress will be concentrated on that part, causing cracks and chips. In addition, the heat resistance generally required for FPC substrates is about 260 ° C, assuming the soldering temperature, and moreover, sites such as internal combustion engines, external combustion engines, nuclear energy facilities, aerospace applications, crustal excavation equipment, and the metal industry. The equipment used in the above is required to have heat resistance for a long time at a higher temperature. Under these high temperatures, thermal and mechanical stress is applied to the stiffener, so it is important that there are fewer defects in the stiffener than when used at room temperature.
The stiffener in the present invention relates to a stiffener having few defects regardless of whether the polyimide film constituting the film is a single layer or a plurality of layers. Further, since the stiffener in the present invention has bending resistance at a contact portion with a component such as a connector, it is preferably used for partial reinforcement of an FPC substrate used in a high temperature region, for example, reinforcement of a connector insertion / removal portion.

FIG. 1 is a schematic cross-sectional view of a PI film (a) provided with an adhesive layer on one side and an FPC substrate (b) to which the PI film is bonded. FIG. 2 is a schematic cross-sectional view of an FPC substrate in which a copper foil and a PI film are bonded together. FIG. 3 is a schematic cross-sectional view of a stiffener in which two thin PI films are bonded together. FIG. 4 is a schematic view of the stiffener bending test in the present invention. FIG. 5 is a schematic configuration diagram showing an example of an apparatus used in the method for treating a silane coupling agent via a gas phase on a film in the present invention. FIG. 6 is a schematic configuration diagram showing an example of an apparatus used in the method for treating a silane coupling agent via a gas phase on a film in the present invention. FIG. 7 is an example of a typical compressive stress-strain curve in the case of failure without showing a yield point. FIG. 8 is an example of a typical compressive stress-strain curve when a yield point appears.

<Shape of stiffener>
The stiffener in the present invention is a reinforcing material made of resin, and the shape is not particularly limited. For example, the shape of the upper surface may be a square, a rectangle, a circle, or the like. The number of layers may be any number, and a single layer of resin film may be used.

<Polyimide film laminating method>
The polyimide film constituting the stiffener in the present invention may be a single layer or a plurality of polyimide films may be laminated. As a method of laminating the polyimide film, a method of laminating by hot pressing using a thermoplastic resin as an adhesive, a method of applying a reactive liquid such as a silane coupling agent to the bonded surface and laminating, and a method of laminating by applying a silane coupling agent, plasma on the surface of the polyimide film. Examples thereof include a method of performing an easy-adhesion treatment such as treatment and then hot-pressing.

<Silane coupling agent>
The silane coupling agent in the present invention refers to a compound having a silicon element in the molecule, physically and chemically interposing between polyimide films, and having an action of enhancing the adhesive force between the two.
Preferred specific examples of the silane coupling agent include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, and N-2- ( Aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, 2- (3,4-Epoxycyclohexyl) Ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, vinyltricrolsilane, Vinyl trimethoxysilane, vinyl triethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycid Xypropyltriethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-Acryloxypropyltrimethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, 3-ureidopropyltriethoxysilane , 3-Chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3-isocyanuppropyltriethoxysilane, tris- (3-trimethoxy) Cyrilpropyl) isocyanurate, chloromethylphenetyltrimethoxysilane, chloromethyltrimethoxysilane, aminophenyltrimethoxysilane, aminophenyltrimethoxysilane, aminophenylaminomethylphenetyltrimethoxysilane, hexamethyldisilazane and the like.

In addition to the above, silane coupling agents that can be used in the present invention include n-propyltrimethoxysilane, butyltrichlorosilane, 2-cyanoethyltriethoxysilane, cyclohexyltrichlorosilane, decyltrichlorosilane, diacetoxydimethylsilane, and diacetoxydimethylsilane. Ethoxydimethylsilane, dimethoxydimethylsilane, dimethoxydiphenylsilane, dimethoxymethylphenylsilane, dodecyllichlorosilane, dodecyltrimethoxylane, ethyltrichlorosilane, hexyltrimethoxysilane, octadecyltriethoxysilane, octadecyltrimethoxysilane, n-octyltrichlorosilane , N-octyltriethoxysilane, n-octyltrimethoxysilane, triethoxyethylsilane, triethoxymethylsilane, trimethoxymethylsilane, trimethoxyphenylsilane, pentyltriethoxysilane, pentyllichlorosilane, triacetoxymethylsilane, trichloro Hexylsilane, trichloromethylsilane, trichlorooctadecylsilane, trichloropropylsilane, trichlorotetradecylsilane, trimethoxypropylsilane, allyltrichlorosilane, allyltriethoxysilane, allyltrimethoxysilane, diethoxymethylvinylsilane, dimethoxymethylvinylsilane, trichlorovinylsilane , Triethoxyvinylsilane, vinyltris (2-methoxyethoxy) silane, trichloro-2-cyanoethylsilane, diethoxy (3-glycidyloxypropyl) methylsilane, 3-glycidyloxypropyl (dimethoxy) methylsilane, 3-glycidyloxypropyltrimethoxysilane, Etc. can also be used.

Further, other alkoxylans such as tetramethoxysilane and tetraethoxysilane may be appropriately added to the silane coupling agent.

In addition, mixing and heating operations are added to the silane coupling agent, including cases where other alkoxylans such as tetramethoxysilane and tetraethoxylan are appropriately added or not added, to slightly react the reaction. You may use it after proceeding.

Among such silane coupling agents, the silane coupling agent preferably used in the present invention is preferably a silane coupling agent having a chemical structure having one silicon atom per molecule.
In the present invention, particularly preferable silane coupling agents include N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, and N-2. -(Aminoethyl) -3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, aminophenyl Examples thereof include trimethoxysilane, aminophenyl trimethoxysilane, and aminophenyl aminomethylphenyl trimethoxysilane. When particularly high heat resistance is required in the process, it is desirable to connect Si and an amino group with an aromatic group.
In the present invention, a phosphorus-based coupling agent, a titanate-based coupling agent, or the like may be used in combination, if necessary.

<Silane coupling agent treatment>
Generally, the silane coupling agent treatment refers to a treatment of forming a thin film layer composed of a silane coupling agent or a condensate of a silane coupling agent on the surface of an object.
In the silane coupling agent treatment, generally, the silane coupling agent is made into a solution such as alcohol and is not applied to the object, or the object is applied by means such as immersion in the silane coupling agent solution, and then silane is dried and heated. By condensing the coupling agent and at the same time chemically reacting it to the surface of the object.
As a method for applying the silane coupling agent, a spin coating method, a spray coating method, a capillary coating method, a dip method and the like are generally used.
The silane coupling agent treatment is performed on one side or both sides of the polyimide film, if necessary.

In the present invention, preferably, the silane coupling agent coating step can be performed via the gas phase. Dissolving the gas phase is a method of exposing a polyimide film to a vaporized silane coupling agent. The vaporization refers to a state in which the vapor of the silane coupling agent, that is, the silane coupling agent in a substantially gaseous state or the silane coupling agent in a fine particle state is present. Then, the exposure to this means that the polyimide film is brought into contact with the atmosphere containing the vaporized silane coupling agent. Since the silane coupling agent has a constant vapor pressure, there is a constant amount of the silane coupling agent in a gaseous state even in a normal temperature atmosphere. If the liquid silane coupling agent is heated to a temperature from 40 ° C. to the boiling point of the silane coupling agent, a higher concentration of silane coupling agent vapor can be obtained. The vaporized silane coupling agent may be mist-ized due to the dew point and may exist in the form of fine particles in a gas. Such a state can also be used in the present invention. It is also possible to add an operation to increase the steam density by manipulating the temperature and pressure. The boiling point of the silane coupling agent varies depending on the chemical structure, but is generally in the range of 100 to 250 ° C. However, heating at 200 ° C. or higher is not preferable because it may cause a side reaction on the organic group side of the silane coupling agent.
The environment for heating the silane coupling agent may be under pressure, substantially normal pressure, or reduced pressure, but in the case of promoting vaporization of the silane coupling agent, it is preferably under substantially normal pressure or reduced pressure. Since many silane coupling agents are flammable liquids, it is preferable to carry out the vaporization work in a closed container, preferably after replacing the inside of the container with an inert gas. However, from the viewpoint of improving production efficiency and reducing the price of production equipment, it is desirable to apply a silane coupling agent in an environment that does not use a vacuum. The silane coupling agent deposition method that does not use a vacuum in the present invention is not to use a vacuum only at the time of deposition, but to set a polyimide film in an ordinary atmospheric atmosphere and then replace it with a carrier gas to replace the silane coupling agent. It means that the pressure is kept at about atmospheric pressure from the time when the film is deposited until the time when the silane coupling agent is returned to the state without the silane coupling agent.
The time for exposing the polyimide film to the silane coupling agent is not particularly limited, but is 60 minutes or less, preferably 20 minutes or less, and more preferably 10 minutes or less. The exposure time is a process design value determined by the relationship between the concentration of the silane coupling agent and the required amount of the silane coupling agent applied. The lower limit of the exposure time is not particularly limited, but in order to reduce the unevenness of the coating amount that occurs industrially, it is preferable to provide a time of about 10 seconds or more, preferably about 30 seconds or more.

The polyimide film temperature during exposure of the polyimide film to the silane coupling agent is controlled to an appropriate temperature between -50 ° C and 200 ° C depending on the type of the silane coupling agent and the desired thickness of the silane coupling agent layer. Is preferable.
The polyimide film exposed to the silane coupling agent is preferably heated to 70 ° C. to 200 ° C., more preferably 75 ° C. to 150 ° C. after exposure. By such heating, the hydroxyl group and the like on the surface of the polyimide film react with the alkoxy group and the silazane group of the silane coupling agent, and the silane coupling agent treatment is completed. The time required for heating is 10 seconds or more and 10 minutes or less. If the temperature is too high or the time is too long, the coupling agent may deteriorate. If it is too short, the processing effect cannot be obtained. If the substrate temperature during exposure to the silane coupling agent is already 80 ° C. or higher, the subsequent heating can be omitted.

In the present invention, it is preferable to hold the silane coupling agent coated surface of the polyimide film downward and expose it to the silane coupling agent vapor. In the conventional method of applying a solution of a silane coupling agent, the coated surface of the polyimide film inevitably faces upward during and before and after coating, so that floating foreign substances in the working environment may be deposited on the surface of the inorganic substrate. I can't deny it. However, in the present invention, the polyimide film can be held downward. It is possible to significantly reduce the adhesion of foreign matter in the environment.
Further, when introducing a gas containing a vaporized silane coupling agent into a room where the polymer substrate is exposed, once the gas is separated into two or more and introduced, the two or more gases collide in the room. It is also effective to generate turbulence by causing the silane coupling agent to be distributed to make the distribution of the silane coupling agent uniform.
As a method of vaporizing the silane coupling agent, in addition to evaporative vaporization by heating, there may be a method of introducing a gas into the silane coupling agent liquid to generate bubbles. This is hereafter referred to as bubbling. For bubbling, simply put a pipe through which gas passes into a silane coupling agent solution, attach a porous body to the tip of the pipe so that many fine bubbles are emitted, and vaporize by superimposing ultrasonic waves. It is also effective to encourage.

In addition, the vaporized silane coupling agent may be charged. By utilizing this effect and applying an electric field to the film at the time of exposure, many silane coupling agents can be deposited in a short time, and since the silane coupling agent has kinetic energy, the deposited film becomes an island-like film. Can be suppressed. Further, it is known that when the carrier gas used contains water, the reaction between the water and the silane coupling agent starts. Therefore, it is effective that the dew point is low. Desirably, the dew point is 15 ° C. or lower, more preferably 10 ° C. or lower, and even more preferably 5 ° C. or lower.
Silane Coupling Agent Layer The number of silicon-containing foreign substances with a major axis of 10 μm or more present in the silane coupling agent layer of the laminated polyimide film is 2000 pieces / m2 or less, preferably 1000 pieces / m2 or less, and further 500 pieces / m2 or less. Is a preferred embodiment of the present invention. Further, the number of silicon-containing foreign substances can be achieved by combining the above operations.

The amount of the silane coupling agent applied depends on the thickness of the silane coupling agent condensate layer. If the coupling agent layer is too thick, the amount of decomposition products generated during high temperature exposure increases, which may hinder the adhesion between the polyimide films. The thickness of the silane coupling agent condensate layer of the present invention is preferably 0.1 nm or more and 300 nm or less, and more preferably 0.5 nm or more and 200 nm or less. Further, the upper limit of the thickness is preferably less than 200 nm, preferably 150 nm or less, more preferably 100 nm or less, more preferably 70 nm or less, still more preferably 50 nm or less in practical use. In the region of 0.1 nm or less, it is assumed that the coupling agent exists in a cluster form rather than as a uniform coating film, which is not preferable.
The thickness of the silane coupling agent condensate layer is determined by polishing the cross section of the polyimide film laminate in the direction perpendicular to the film surface, then making an ultrathin section with a microtome, taking a cross-sectional photograph with a transmission electron microscope, and measuring the measured value. It was calculated back from the magnification.

The thickness of the polyimide film of the present invention is preferably 3 μm or more, and more preferably 11 μm or more. The upper limit of the thickness of the polyimide film is not particularly limited, but it is preferably 250 μm or less, more preferably 150 μm or less, and further preferably 90 μm or less from the requirement as a flexible electronic device.
The area of the polyimide film of the present invention is preferably large from the viewpoint of production efficiency and cost of the laminate and the flexible electronic device. It is preferably 1000 square cm or more, more preferably 1500 square cm or more, and even more preferably 2000 square cm or more.

In the present invention, aromatic polyimide, alicyclic polyimide, polyamideimide, polyetherimide and the like can be used as the polyimide film. More preferably, it refers to a polymer containing 50% or more of a polyimide skeleton.

Generally, a polyimide film is a green film (“precursor film”) in which a polyamic acid (polyimide precursor) solution obtained by reacting diamines and tetracarboxylic acids in a solvent is applied to a support for producing a polyimide film and dried. (Also referred to as "polyamic acid film"), and further obtained by subjecting the green film to a high-temperature heat treatment to carry out a dehydration ring-closing reaction on a support for producing a polyimide film or in a state of being peeled off from the support.

The diamines constituting the polyamic acid are not particularly limited, and aromatic diamines, aliphatic diamines, alicyclic diamines and the like usually used for polyimide synthesis can be used. From the viewpoint of heat resistance, aromatic diamines are preferable, and among aromatic diamines, aromatic diamines having a benzoxazole structure are more preferable. When aromatic diamines having a benzoxazole structure are used, it is possible to develop high bending elastic modulus, low coefficient of thermal expansion, and low linear expansion coefficient as well as high heat resistance. The diamines may be used alone or in combination of two or more.

The aromatic diamines having a benzoxazole structure are not particularly limited, and are, for example, 5-amino-2- (p-aminophenyl) benzoxazole, 6-amino-2- (p-aminophenyl) benzoxazole, 5 -Amino-2- (m-aminophenyl) benzoxazole, 6-amino-2- (m-aminophenyl) benzoxazole, 2,2'-p-phenylenebis (5-aminobenzoxazole), 2,2' -P-Phenylenebis (6-aminobenzoxazole), 1- (5-aminobenzoxazole) -4- (6-aminobenzoxazole) benzene, 2,6- (4,4'-diaminodiphenyl) benzo [1,2-d: 5,4-d'] bisoxazole, 2,6- (4,4-diaminodiphenyl) benzo [1,2-d: 4,5-d'] bisoxazole, 2, 6- (3,4'-diaminodiphenyl) benzo [1,2-d: 5,4-d'] bisoxazole, 2,6- (3,4'-diaminodiphenyl) benzo [1,2-d: 4,5-d'] bisoxazole, 2,6- (3,3'-diaminodiphenyl) benzo [1,2-d: 5,4-d'] bisoxazole, 2,6- (3,3') -Diaminodiphenyl) benzo [1,2-d: 4,5-d'] bisoxazole and the like can be mentioned.

Examples of aromatic diamines other than the above-mentioned aromatic diamines having a benzoxazole structure include 2,2'-dimethyl-4,4'-diaminobiphenyl and 1,4-bis [2- (4-aminophenyl). ) -2-propyl] benzene (bisaniline), 1,4-bis (4-amino-2-trifluoromethylphenoxy) benzene, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 4,4 '-Bis (4-aminophenoxy) biphenyl, 4,4'-bis (3-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl ] Sulfates, 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'- Diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4' −Diaminodiphenylsulfoxide, 3,3′-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 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-Aminophenoxy) 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-amino) Phenoxy) 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-amino) benzoyl] Phenoxy) 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'-Diaminodiphenylsulfide, 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-dimethyl) Benzene) 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-dimethylbenzyl] benzene, 1,3-bis [4- (4-amino-) 6-Cyanophenoxy) -α, α-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-bife) Noxybenzoyl) 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) phenoxy] benzonitrile, and some of the hydrogen atoms on the aromatic ring of the aromatic diamine. Alternatively, all of them are halogen atoms, alkyl or alkoxyl groups having 1 to 3 carbon atoms, cyano groups, or halogens having 1 to 3 carbon atoms in which some or all of the hydrogen atoms of the alkyl or alkoxyl groups are substituted with halogen atoms. Examples thereof include aromatic diamines substituted with an alkylated group or an alkoxyl group.

Examples of the aliphatic diamines include 1,2-diaminoethane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,8-diaminooctane and the like.
Examples of the alicyclic diamines include 1,4-diaminocyclohexane and 4,4'-methylenebis (2,6-dimethylcyclohexylamine).
The total amount of diamines other than aromatic diamines (aliphatic diamines and alicyclic diamines) is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less of all diamines. Is. In other words, the aromatic diamines are preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more of all diamines.

The polyimide resin in the present invention may preferably be transparent depending on the intended use. 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,4,5-cyclopentanetetracarboxylic acid dianhydride, 1,2,4, as acid components used in the synthesis of the precursor 5-Cyclohexanetetracarboxylic acid dianhydride, bicyclo [2,2,1] heptane-2,3,5,6-tetracarboxylic acid dianhydride, bicyclo [2,2,2] octane-2,3,5 , 6-Tetracarboxylic acid dianhydride, 3,3', 4,4'-bicyclohexyltetracarboxylic acid dianhydride, 1,2,4-cyclohexanetricarboxylic acid anhydride and the like are exemplified, but are particularly preferable. 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, 3,3', 4,4'-bicyclohexyltetracarboxylic acid dianhydride It is a thing. These aliphatic carboxylic acids may be used alone or in combination of two or more. On the other hand, those containing unsaturated bonds such as bicyclo [2,2,2] octo-7-ene-2,3,5,6-tetracarboxylic dianhydride are colored during heat treatment to improve the optical properties of the film. It is not preferable because it tends to decrease.

Examples of the diamine component used for the synthesis of the polyimide resin of the present invention or a precursor thereof are 1,3-phenylenediamine, 1,4-phenylenediamine, 2,4-diaminotoluene, and 2,6-diamino. Toluene, 3,4-diaminotoluene, 4,5-dimethyl-1,2-phenylenediamine, 2,5-dimethyl-1,4-phenylenediamine, 2,6-dimethyl-1,4-phenylenediamine, 2, 3,5,6-Tetramethyl-1,4-phenylenediamine, 3-aminobenzylamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4 , 4'-diamine, 2,2'-bis (trifluoromethyl) benzidine, 3,3'-dimethoxybenzidine, 4,4'-diaminooctafluorobiphenyl, 3,3'-diaminodiphenylmethane, 3,4'- Diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-methylenebis (2,6-diethylaniline), 4,4'-methylenebis (2-ethyl-6-methylaniline), 4,4'-ethylenedi Aniline, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl ether, 1,3- Bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (4-amino-2-trifluoromethyl) Phenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-diamino-3,3'-dimethyldiphenylmethane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4 -(3-Aminophenoxy) phenyl] sulfone, 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis (3-aminophenyl) hexafluoropropane, 2,2'-bis [4- (4-Aminophenoxy) phenyl] propane, 2,2'-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis (3-amino-4-methylphenyl) hexafluoropropane, α, α'-bis (4-aminophenyl) -1,4-diisopropylbenzene, bis (2-aminophenyl) Rufido, bis (4-aminophenyl) sulfide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminobenzophenone, 3,3' -Diaminobenzophenone, 4,4'-diaminobenzanilide, 1,4-bis (4-aminophenoxy) benzene, bis (4-aminophenyl) terephthalate, 2,7-diaminofluorene, 9,9-bis (4-) Aromatic diamines such as aminophenyl) fluorene can be mentioned. As aliphatic diamines, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,3-bis (aminomethyl) cyclohexane, 1,1-bis (4-aminophenyl) cyclohexane, 4,4'-diaminodicyclohexyl Methane, 4,4'-methylenebis (2-methylcyclohexylamine), 4,4'-methylenebis (2,6-dimethylcyclohexylamine), 4,4'-diaminodicyclohexylpropane, bicyclo [2.2.1] heptane -2,3-diamine, bicyclo [2.2.1] heptane-2,5-diamine, bicyclo [2.2.1] heptane-2,6-diamine, bicyclo [2.2.1] heptane-2 , 7-Diamine, 2,3-bis (aminomethyl) -bicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) -bicyclo [2.2.1] heptane, 2,6-bis (Aminomethyl) -bicyclo [2.2.1] heptane, 3 (4), 8 (9) -bis (aminomethyl) tricyclo [5.2.1.0 (2,6)] decane and the like are exemplified. NS. Of these, particularly preferred are p-phenylenediamine, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-bis (trifluoromethyl) benzidine, 2,2'-bis (trifluoro). Methyl) -4,4'-diaminodiphenyl ether, 1,4-bis (4-amino-2-trifluoromethylphenoxy) benzene, 1,4-diaminocyclohexane, 4,4'-diaminodicyclohexylmethane, 4,4' -Methylenebis (2-methylcyclohexylamine), 4,4'-methylenebis (2,6-dimethylcyclohexylamine). The above amine components may be used alone or in combination of two or more.

Examples of the tetracarboxylic acids constituting the polyamic acid include aromatic tetracarboxylic acids (including the acid anhydride thereof), aliphatic tetracarboxylic acids (including the acid anhydride) and alicyclic tetracarboxylic acids usually used for polyimide synthesis. Acids (including its acid anhydride) can be used. Among them, aromatic tetracarboxylic acid anhydrides and alicyclic tetracarboxylic acid anhydrides are preferable, aromatic tetracarboxylic acid anhydrides are more preferable from the viewpoint of heat resistance, and alicyclics are more preferable from the viewpoint of light transmission. Group tetracarboxylic acids are more preferred. When these are acid anhydrides, the number of anhydride structures in the molecule may be one or two, but those having two anhydride structures (dianhydride) are preferable. good. The tetracarboxylic acids may be used alone or in combination of two or more.

Examples of the alicyclic tetracarboxylic acids include cyclobutanetetracarboxylic acids, 1,2,4,5-cyclohexanetetracarboxylic acids, and 3,3', 4,4'-bicyclohexyltetracarboxylic acids. Examples include carboxylic acids and their acid anhydrides. Among these, dianhydrides having two anhydride structures (eg, cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 3,3', 4,4 '-Bicyclohexyltetracarboxylic dianhydride, etc.) is suitable. The alicyclic tetracarboxylic acids may be used alone or in combination of two or more.
When transparency is important, the alicyclic tetracarboxylic acids are, for example, preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more of all tetracarboxylic acids.

The aromatic tetracarboxylic acid is not particularly limited, but is preferably a pyromellitic acid residue (that is, one having a structure derived from pyromellitic acid), and more preferably an acid anhydride thereof. Examples of such aromatic tetracarboxylic acids include pyromellitic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid dianhydride, and 3 , 3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic acid dianhydride, 2,2-bis [4- (3,4-di) Carboxylic phenoxy) phenyl] propanoic acid anhydride and the like can be mentioned.
When heat resistance is important, the aromatic tetracarboxylic acids are, for example, preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 95% by mass or more of all tetracarboxylic acids.

In the polyimide film of the present invention, it is preferable that the glass transition temperature is 250 ° C. or higher, preferably 300 ° C. or higher, more preferably 350 ° C. or higher, or no glass transition point is observed in the region of 500 ° C. or lower. The glass transition temperature in the present invention is determined by differential thermal analysis (DSC).

The coefficient of linear expansion (CTE) of the polyimide film of the present invention is preferably -5 ppm / K to + 20 ppm / K, more preferably -5 ppm / K to + 15 ppm / K, and even more preferably 1 ppm / K to +10 ppm. / K. When the CTE is in the above range, the difference in the coefficient of linear expansion from that of a general support can be kept small, and it is possible to prevent the polyimide film and the support made of an inorganic substance from peeling off even when subjected to a process of applying heat. .. Further, although the coefficient of linear expansion of the polyimide film in the present invention in question uses an average value between 30 and 200 ° C., the temperature range of interest varies depending on the application, and the process at high temperature is taken into consideration. When examining the range of 30 ° C to 400 ° C, it may be in the range of 100 ° C to 400 ° C, and when examining the range of 50 ° C to 280 ° C with the reflow process in mind, the operating temperature range is -50 ° C to 150. In some cases, the temperature range may be emphasized.

The breaking strength of the polyimide film in the present invention is 60 MPa or more, preferably 120 MPa or more, and more preferably 240 MPa or more. There is no limit to the upper limit of breaking strength, but it is practically less than about 1000 MPa. Here, the breaking strength of the polyimide film refers to an average value in the length direction and the width direction of the polyimide film.

The thickness unevenness of the polyimide film in the present invention is preferably 20% or less, more preferably 12% or less, still more preferably 7% or less, and particularly preferably 4% or less. If the thickness spots exceed 20%, it tends to be difficult to apply to narrow areas. The thickness unevenness of the film can be obtained, for example, by randomly extracting about 10 positions from the film to be measured with a contact-type film thickness meter and measuring the film thickness based on the following formula.
Film thickness spots (%)
= 100 x (maximum film thickness-minimum film thickness) / average film thickness

The polyimide film in the present invention is preferably obtained in the form of being wound as a long polyimide film having a width of 300 mm or more and a length of 10 m or more at the time of its manufacture, and is a roll-shaped polyimide wound around a winding core. The one in the form of a film is more preferable.

In the polyimide film, in order to secure handleability and productivity, it is preferable to add and contain a lubricant (particles) in the film to impart fine irregularities on the surface of the polyimide film to ensure slipperiness. The lubricant (particles) is preferably fine particles made of an inorganic substance, such as metal, metal oxide, metal nitride, metal carbonized product, metal salt salt, phosphate, carbonate, talc, mica, clay, and the like. Particles composed of clay minerals, etc. can be used. Preferably, metal oxides such as silicon oxide, calcium phosphate, calcium hydrogen phosphate, calcium dihydrogen phosphate, calcium pyrophosphate, hydroxyapatite, calcium carbonate, and glass filler, phosphates, and carbonates can be used. The lubricant may be only one type or two or more types.

The volume average particle size of the lubricant (particle) is usually 0.001 to 10 μm, preferably 0.03 to 2.5 μm, more preferably 0.05 to 0.7 μm, and further preferably 0.05 to 0.05. It is 0.3 μm. The volume average particle size is based on the measured value obtained by the light scattering method. If the particle size is smaller than the lower limit, industrial production of the polyimide film becomes difficult, and if it exceeds the upper limit, the unevenness of the surface becomes too large and the sticking strength becomes weak, which may cause a practical problem.

The amount of the lubricant added to the polymer component in the polyimide film is 0.02 to 50% by mass, preferably 0.04 to 3% by mass, and more preferably 0.08 to 1.2. It is mass%. If the amount of the lubricant added is too small, it is difficult to expect the effect of the lubricant added, and the slipperiness is not so ensured, which may hinder the production of the polyimide film. If the amount is too large, the surface unevenness of the film becomes too large. Even if the slipperiness is ensured, there may be problems such as a decrease in smoothness, a decrease in breaking strength and breaking elongation of the polyimide film, and an increase in CTE.

When a lubricant (particle) is added / contained in the polyimide film, it may be a single-layer polyimide film in which the lubricant is uniformly dispersed. For example, one surface is composed of a polyimide film containing the lubricant. A lubricant concentration gradient type polyimide film composed of a polyimide film having a lubricant content of a small amount even if the other surface does not contain or contains a lubricant may be used. In such a lubricant concentration gradient type film, fine irregularities are imparted to the surface of one layer (film) so that the layer (film) can secure slipperiness, and good handleability and productivity can be achieved. Can be secured.

In the case of a film produced by the melt-stretching film-forming method, for example, the lubricant concentration-inclined polyimide film is first formed into a film using a polyimide film raw material containing no lubricant, and placed in the middle of the process on at least one side of the film. It can be obtained by applying a resin layer containing a lubricant. Of course, on the contrary, a film may be formed using a polyimide film raw material containing a lubricant, and a film may be obtained by applying a polyimide film raw material containing no lubricant during the process or after the film formation is completed. I can do it.
The same applies to a polyimide film obtained by using a solution film forming method such as a polyimide film. For example, as a polyamic acid solution (polyimide precursor solution), a lubricant (preferably an average particle diameter of 0.05 to 2) is used. (Approximately 5.5 μm) is contained in 0.02% by mass to 50% by mass (preferably 0.04 to 3% by mass, more preferably 0.08 to 1.2% by mass) with respect to the polymer solid content in the polyamic acid solution. The polyimide solution is free of lubricant or its content is small (preferably less than 0.02% by mass, more preferably less than 0.01% by mass based on the polymer solid content in the polyimide solution). It can be produced by using two kinds of polyamic acid solutions.

The method for tilting the lubricant concentration (lamination) of the lubricant concentration gradient type polyimide film is not particularly limited as long as there is no problem in the adhesion between the two layers, and the lubricant concentration gradient type polyimide film adheres without interposing an adhesive layer or the like. All you need is.
In the case of a polyimide film, for example, i) a method of producing one polyimide film and then continuously applying the other polyamic acid solution on the polyimide film for imidization, ii) casting the one polyamic acid solution. After preparing the polyamic acid film, the other polyamic acid solution is continuously applied onto the polyamic acid film and then imidized, iii) the method by co-extrusion, iv) the lubricant is not contained or the content thereof is high. Examples thereof include a method of applying a polyamic acid solution containing a large amount of lubricating material on a film formed of a small amount of the polyamic acid solution by spray coating, T-die coating, or the like to imidize the film. In the present invention, it is preferable to use the methods i) to ii) above.

The ratio of the thickness of each layer in the lubricant concentration gradient type polyimide film is not particularly limited, but the polymer layer containing a large amount of lubricant is the layer (a), and the layer does not contain or contains a small amount of lubricant. When the polymer layer is the layer (b), the layer (a) / layer (b) is preferably 0.05 to 0.95. If the number of the (a) layer / (b) layer exceeds 0.95, the smoothness of the (b) layer tends to be lost, while if it is less than 0.05, the effect of improving the surface characteristics is insufficient and the slipperiness is lost. May be struck.

<Surface activation treatment of polyimide film>
It is preferable that the polyimide film used in the present invention is subjected to a surface activation treatment. By the surface activation treatment, the surface of the polyimide film is modified to a state in which functional groups are present (so-called activated state), and the affinity with the silane coupling agent is improved.
The surface activation treatment in the present invention is a dry or wet surface treatment. As the dry treatment of the present invention, treatment of irradiating the surface with active energy rays such as ultraviolet rays, electron beams, and X-rays, corona treatment, vacuum plasma treatment, atmospheric pressure plasma treatment, flame treatment, itro treatment, and the like can be used. .. As the wet treatment, a treatment in which the film surface is brought into contact with an acid or alkaline solution can be exemplified. The surface activation treatment preferably used in the present invention is a plasma treatment, which is a combination of a plasma treatment and a wet acid treatment.

The plasma treatment is not particularly limited, but includes RF plasma treatment in vacuum, microwave plasma treatment, microwave ECR plasma treatment, atmospheric pressure plasma treatment, corona treatment, etc., and gas treatment containing fluorine and ions. It also includes ion implantation treatment using a source, treatment using the PBII method, flame treatment exposed to thermal plasma, and itro treatment. Among these, RF plasma treatment in vacuum, microwave plasma treatment, and atmospheric pressure plasma treatment are preferable.

Suitable conditions for plasma treatment include oxygen plasma, plasma containing fluorine such as CF4 and C2F6, and plasma known to have a high chemical etching effect, or physical such as Ne, Ar, Kr, Xe, and plasma. It is desirable to use plasma, which has a high effect of physically etching by applying a large amount of energy to the surface of the polymer. It is _{also preferable to add plasma such as CO 2} , CO, H ₂ , N ₂ , NH ₄ , CH ₄ and a mixed gas thereof, and further water vapor. In addition to these, OH, N ₂ , N, CO, CO ₂ , H, H ₂ , O ₂ , NH, NH ₂ , NH ₃ , COOH, NO, NO ₂ , He, Ne, Ar, Kr, Xe, CH _At least selected from the group consisting of 2 O, Si (OCH ₃ ) ₄ , Si (OC ₂ H ₅ ) ₄ , C ₃ H ₇ Si (OCH ₃ ) ₃ , C ₃ H ₇ Si (OC ₂ H ₅ ) _3. It is necessary to make a plasma containing one or more components as a gas or as a decomposition product in the plasma. When aiming for processing in a short time, plasma with high energy density, high kinetic energy of ions in plasma, and plasma with high number density of active species are desirable, but energy is required because surface smoothness is required. There is a limit to increasing the density. When oxygen plasma is used, surface oxidation progresses, which is good in terms of forming OH groups, but it is easy to form a surface that already has poor adhesion to the film itself, and the surface roughness (roughness) increases. Adhesion also deteriorates.
Further, in plasma using Ar gas, the influence of purely physical collision occurs on the surface, and in this case as well, the surface roughness becomes large. Considering all of these, microwave plasma treatment, microwave ECR plasma treatment, plasma irradiation with an ion source that can easily shoot high-energy ions, PBII method, and the like are also desirable.

Such surface activation treatment cleans the polymer surface and produces more active functional groups. The generated functional group is bonded to the coupling agent layer by a hydrogen bond or a chemical reaction, and the polyimide film layer and the coupling agent layer can be firmly adhered to each other.
In the plasma treatment, the effect of etching the surface of the polyimide film can also be obtained. In particular, in a polyimide film containing a relatively large amount of lubricant particles, protrusions due to the lubricant may hinder the adhesion between the film and the inorganic substrate. In this case, if the surface of the polyimide film is thinly etched by plasma treatment to expose a part of the lubricant particles and then treated with hydrofluoric acid, the lubricant particles in the vicinity of the film surface can be removed.

The surface activation treatment may be applied to only one side of the polyimide film or may be applied to both sides. When plasma treatment is performed on one side, plasma treatment can be performed only on the side of the polyimide film that is not in contact with the electrode by placing the polyimide film in contact with the electrode on one side in the plasma treatment with the parallel plate type electrode. can. Further, if the polyimide film is placed in a state of being electrically floated in the space between the two electrodes, plasma treatment can be performed on both sides. Further, one-sided treatment is possible by performing plasma treatment with a protective film attached to one side of the polyimide film. As the protective film, a PET film with an adhesive, an olefin film, or the like can be used.

<Surface roughness of polyimide film>
The surface roughness Ra of the polyimide film in the present invention is preferably 70 nm or less, more preferably 30 nm or less, and further preferably 1.5 nm or less. If Ra is larger than 70 nm, it causes uneven coating of the silane coupling agent and uneven peeling due to the uneven coating of the silane coupling agent when a plurality of polyimide films are laminated via the silane coupling agent layer.

<Film laminating method>
In the present invention, by laminating a polyimide film via a silane coupling agent layer, a polyimide film laminate in which a polyimide film layer and a silane coupling agent condensate layer are alternately laminated is obtained.
The polyimide film is laminated by laminating and pressurizing the polyimide film so that the surface treated with the silane coupling agent is arranged between the polyimide film layers. The combination of pressurization and heating is effective.
The pressurization treatment may be performed, for example, in an atmospheric pressure atmosphere or in a vacuum while heating a press, a laminate, a roll laminate, or the like. In addition, a method of pressurizing and heating in a flexible bag can also be applied. From the viewpoint of improving productivity and reducing the processing cost brought about by high productivity, pressing or roll laminating in an atmospheric atmosphere is preferable, and a method using rolls (roll laminating or the like) is particularly preferable.

In the present invention, a polyimide film laminate is obtained by laminating a polyimide film having a thermoplastic polyimide coated on one side or a polyimide film having undergone an easy adhesion treatment such as plasma treatment by a hot press.
The pressurization treatment may be performed while heating the press, laminate, and roll laminate, for example, in an atmospheric pressure atmosphere or in a vacuum.

The pressure during the pressurization treatment is preferably 1 MPa to 30 MPa, more preferably 3 MPa to 10 MPa. If the pressure is too high, the support may be damaged, and if the pressure is too low, some parts may not adhere to each other, resulting in insufficient adhesion. The temperature at the time of the pressure treatment is within a range not exceeding the heat resistant temperature of the polyimide film to be used. In the case of a non-thermoplastic polyimide film, treatment at 10 ° C. to 400 ° C., more preferably 150 ° C. to 350 ° C. is preferable.
Further, the pressurization treatment can be performed in an atmospheric pressure atmosphere as described above, but it is preferable to perform the pressure treatment under vacuum in order to obtain stable adhesive strength on the entire surface. At this time, the degree of vacuum is sufficient with the degree of vacuum by a normal oil rotary pump, and about 10 Torr or less is sufficient.
As a device that can be used for pressure heat treatment, for example, "11FD" manufactured by Imoto Seisakusho can be used for pressing in a vacuum, and a roll-type film laminator in a vacuum or a vacuum is used. For vacuum laminating such as a film laminator that applies pressure to the entire surface of the glass at once with a thin rubber film, for example, "MVLP" manufactured by Meiki Seisakusho can be used.

The adhesive strength between the polyimide film layers of the polyimide film laminate in the present invention is 0.1 N / cm or more and 20 N / cm or less, preferably 0.1 N / cm or more and 18 N / cm in the 90 degree peeling method. More preferably, it is 0.15 N / cm or more and 15 N / cm or less.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The method for evaluating the physical properties in the following examples is as follows.

<Stiffener compression test>
A compression test was carried out under the following equipment and conditions.
Device name; Minebea TGI-50kN
Measurement temperature; room temperature compression rate; 0.2 mm / min and 10 mm / min
Atmosphere; Atmosphere measurement sample size; 30 cm x 30 cm
In the measurement, a basket-type jig, a stage on which the stiffener was placed, and a compression rod (made of SUS, indenter area 10 mm × 10 mm) were used.

Based on the results of the compression test, the stress-strain curve of the stiffener was drawn with the horizontal axis as the compressive strain and the vertical axis as the compressive stress, and the transition start point at which the stress-strain curve transitioned to the linear region was obtained.
As shown in FIGS. 7 and 8, the transition start point in the present invention intersects the extension line of the slope of the initial region where strain is applied and the extension line of the linear region according to Hooke's law in the stress-strain curve. It is the value of the strain at the point where the strain is applied.
In this test, the strain value at the transition start point where the stress-strain curve transitions to the linear region is 20% or less of the stiffener thickness, which means that there are no major defects in the indenter contact area. There is. If there is a major drawback, the stress-strain curve will widen the interval from the beginning of stress to the transition to the linear region, and the strain amount at the transition start point will be 20% or more of the thickness of the stiffener. The major drawbacks here are the blister defects or the defects that become the starting point of destruction when the stiffener is used as a reinforcing material.

In this test, when the stress-strain curves were obtained at 10 mm / min and 0.2 mm / min at different compression rates, the compressive stresses σ ₁₀ and σ _0. The difference between _{2 is | σ 10-} σ _0.2 | <0.15 × σ _0.2
This means that the amount of fracture strain does not change significantly even if the speed at which compressive stress is applied changes.
Here, the compressive stress at the time of the strain that maximizes the stress is the fracture point stress in FIG. 7 or the yield point stress in FIG. Assuming that the stiffener in the present invention is used as a reinforcing material for the connector portion, the boundary between the portion joined to the metal part and the portion not joined may be bent by about 90 ° in the handling process. .. This bending is not always a constant speed and varies from process to process. Since compressive stress is generated in the bent stiffener in the thickness direction, the fact that the fracture point stress or the yield point stress does not change significantly with the compression rate indicates that the stiffener is hard to break at the joint.

Adhesive strength by 90 degree method The adhesive strength between the polyimide film layers of the polyimide film laminate was determined according to the 90 degree peeling method of JISK6854-1.
Device name; Shimadzu Autograph AG-IS
Measurement temperature; Room temperature peeling speed; 50 mm / min
Atmosphere; 25 ° C, 60% RH, atmospheric measurement sample width; 1 cm
The sample was measured by making a cut in the surface of a square polyimide film laminate having a side of 100 mm to a depth corresponding to 120% of the thickness of the outermost polyimide film, and peeling off the outermost polyimide film from the edge of the laminate. ..
The adhesive strength was measured after the heat treatment at 200 ° C. for 1 hour.

60 ° bendability test In the atmosphere of 25 ° C and 60% RH normal pressure, as shown in Fig. 4, a stiffener cut to a width of 1 cm and a length of 10 cm is placed on a work table, and the stiffener is located 3 cm from the end of the stiffener. It was pressed down with a 10 mm thick iron plate finished so that the R of the corner on the side that touches was 0.3 mm. The operation of lifting the portion protruding from the iron plate so that the angle formed by the work table and the stiffener was 60 °, holding and opening for 3 seconds was repeated 10 times. Then, the bent portion was observed with a digital microscope VH-Z100R manufactured by KEYENCE at a magnification of 100 times, and the presence or absence of cracks was confirmed. The cracks referred to here are scratches and cracks that reach 1/4 or more of the thickness of the stiffener used in the test.

[Manufacturing example]
(Preparation of polyamic acid solution)
After replacing the inside of the reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirring rod with nitrogen, 223 parts by mass of 5-amino-2- (p-aminophenyl) benzoxazole (DAMBO) and N, N-dimethylacetamide 4416 A dispersion consisting of 217 parts by mass of pyromellitic acid dianhydride (PMDA) and colloidal silica dispersed in dimethylacetamide as a lubricant (Snowtex (Nissan Chemical Industry Co., Ltd.)). Add the registered trademark) DMAC-ST30 ") so that the silica (lubricant) becomes 0.12% by mass of the total amount of polymer solids in the polyamic acid solution), and stir at a reaction temperature of 25 ° C. for 24 hours. A brown and viscous polyamic acid solution V1 was obtained.
(Preparation of polyamic acid solution)
After replacing the inside of the reaction vessel equipped with a nitrogen introduction tube, a thermometer, and a stirring rod with nitrogen, 205.8 g of 1,4-bis (4-amino-2-trifluoromethylphenoxy) benzene (205.8 g) in the reaction vessel under a nitrogen atmosphere. 0.480 mol) and 1200 g of N, N-dimethylacetamide were charged and dissolved, and then 93.8 g (0.478 mol) of cyclobutanetetracarboxylic acid dianhydride was added separately as a solid while cooling the reaction vessel, and the temperature was changed to room temperature. Was stirred for 12 hours. Then, 1.0 g (5.9 mmol) of 4-methylcyclohexane-1,2-dicarboxylic acid anhydride was added, and the mixture was stirred for 4 hours, diluted with 1000 g of N, N-dimethylacetamide, and a polyamide having a reduced viscosity of 5.28 dl / g. An acid solution V2 was obtained. A solution prepared by dispersing colloidal silica fine particles having an average particle size of 0.08 μm in N, N-dimethylacetamide in a polyamic acid solution V2 having an amine terminal amount of 5 eq / t was prepared. In addition to 0% by mass, a fine particle-containing polyamic acid solution V2'was obtained.

(Preparation of polyimide film)
The polyamic acid solution V1 obtained above was applied to a smooth surface (non-slip agent surface) of a long polyester film (“A-4100” manufactured by Toyobo Co., Ltd.) having a width of 1050 mm using a slit die to achieve a final film thickness (imide). The film was applied so that the film thickness after conversion was 40 μm, dried at 105 ° C. for 20 minutes, and then peeled off from the polyester film to obtain a self-supporting polyamic acid film having a width of 920 mm.
After the polyamic acid film obtained above is obtained, it is imidized by heat treatment with a pin tenter at the first stage of 150 ° C. × 5 minutes, the second stage of 220 ° C. × 5 minutes, and the third stage of 495 ° C. × 10 minutes). , The pin gripping portions at both ends were dropped by slits to obtain a long polyimide film F1 (1000 m roll) having a width of 850 mm.

(Preparation of polyimide film)
A fine particle-containing polyamic acid solution V2'is applied onto a polyester film having a thickness of 188 μm using a comma coater so that the final dry thickness is 3 μm, and then a polyamic acid solution V2 is applied onto the polyester film so that the final dry thickness is 40 μm. A thin film was continuously extruded from the slit of. Both polymer solutions were supplied through a defoaming step and a filtering step of passing through a polymer filter having a filtration accuracy of 3 μm. This thin film was heated at 110 ° C. to 135 ° C. for 15 minutes and then peeled off from the support to obtain a self-supporting film having a volatile component of 23.7% by mass.

Subsequently, this self-supporting film is gripped at both ends by a film gripping device attached to a chain driven along a rail, and inserted into a continuous heating furnace heated to 150 ° C. to 320 ° C. at the maximum temperature in the furnace. The heat treatment was performed under the condition that the treatment was 5 minutes or less. The oxygen concentration in the furnace at that time was 20.6%. By completing the imidization with the amount of volatile components of 1% by mass or less by the above step, a long polyimide film F2 (200 m roll) having a thickness of 40 μm was obtained.

In addition to these, a commercially available heat-resistant film was used in the same manner as in Examples and Comparative Examples.
F3: Upirex 75S (polyimide film manufactured by Ube Industries, Ltd., thickness 75 μm)

<Vacuum plasma treatment of polyimide film>
As a pre-process for treating the polyimide film with a silane coupling agent, the polyimide film was subjected to vacuum plasma treatment. For vacuum plasma treatment, a device for single-wafer glass is used, a metal mask is placed on the silane coupling agent-treated surface of the glass and set in the device, and the inside of the vacuum chamber is evacuated until it becomes 1 × 10-3 Pa or less, and vacuum is applied. Argon gas was introduced into the chamber, and the surface of the glass plate was subjected to plasma treatment with argon gas for 20 seconds under the conditions of a discharge power of 100 W and a frequency of 15 kHz.

<Silane coupling agent treatment 1>
The silane coupling agent was applied to the polyimide film under the following conditions using the device for generating the silane coupling agent vapor outlined in FIG.
A container containing 100 g of a silane coupling agent (“KBM-903” manufactured by Shin-Etsu Chemical Co., Ltd .: 3-aminopropyltrimethoxysilane) was adjusted to 40 ° C., and then nitrogen gas was bubbling at 20 L / min. A nitrogen gas containing the silane coupling agent vapor that was fed and generated was introduced into the chamber in the previous period through a pipe, and both sides of the polyimide film were exposed to the gas for 3 minutes to apply a silane coupling agent-coated polyimide film (40 cm × 40 cm). Got

<Silane Coupling Agent Treatment Example 2>
The silane coupling agent was applied to the polyimide film under the following conditions using the device for generating the silane coupling agent vapor outlined in FIG.
A polyimide film having a width of 350 mm was passed through a chamber of 750 mm × 200 mm × 400 mm having a slit of 20 mm × 370 mm at a speed of 240 mm / min.
A container containing 100 g of a silane coupling agent (“KBM-903” manufactured by Shin-Etsu Chemical Co., Ltd .: 3-aminopropyltrimethoxysilane) was adjusted to 40 ° C., and then nitrogen gas was bubbling at 20 L / min. Nitrogen gas containing the generated silane coupling agent vapor was introduced into the chamber in the previous period through a pipe, both sides of the polyimide film were exposed to the gas for 3 minutes, and immediately laminated with the second polyimide film F1 at 100 MPa. , A temporary adhesive was obtained. This laminated body was repeatedly put into the unwinding portion and laminated a plurality of times to obtain a temporary adhesive having a desired thickness.

<Example 1>
The plasma-treated polyimide film F1 is laminated until the final thickness becomes 0.1 mm, and a release sheet is sandwiched, and a pressure of 400 ° C. and 30 MPa is applied for 60 minutes to reduce the pressure by a vacuum press, and a stiffener is applied. Made.

<Example 2>
A stiffener was produced in the same manner as in Example 1 except that the final thickness was 0.2 mm.

<Example 3>
A temporary adhesive having a thickness of 0.5 mm was prepared using the polyimide film F1 by the method of Example 2 of silane coupling agent treatment, and a stiffener was prepared by performing a 20 hr heat treatment at 110 ° C. while being wound around the PP core.

<Example 4>
The polyimide film F2 was laminated until the final thickness became 0.1 mm, and a release sheet was sandwiched and a pressure of 350 ° C. and 30 MPa was applied for 20 minutes to reduce the pressure by a vacuum press to prepare a stiffener.

<Example 5>
A stiffener was produced in the same manner as in Example 4 except that F3 was used as the polyimide film.

<Example 6>
F2 and silane coupling agent treatment 1 were used as the polyimide film to prepare a polyimide film with a silane coupling agent. This polyimide film with a silane coupling agent was laminated until the final thickness became 0.1 mm, and a pressure of 100 Pa was applied to reduce the pressure by sandwiching a release sheet and vacuum pressing to perform temporary bonding. Next, the obtained temporary adhesive laminate was placed in a clean oven and heated at 180 ° C. for 1 hour in a nitrogen atmosphere to obtain a stiffener.
<Example 7>
A stiffener was produced in the same manner as in Example 1 except that the final thickness was 1 mm.

<Comparative example 1>
A stiffener was prepared in the same manner as in Example 3 except that the laminator roll was not passed during the temporary bonding.

<Comparative example 2>
A stiffener was prepared in the same manner as in Example 1 except that the final thickness was 0.3 mm and the pressing pressure was 5 MPa.

Table 1 shows the results of evaluating the obtained laminate. It can be said that the film used is the same as that of Comparative Examples 1 and 2 in which voids are generated between the layers, but the example is a stiffener with few defects. Further, the stiffener having a small difference in compressive stress when the compression speed is changed has high bending resistance.

Since the stiffener of the present invention has no gaps between layers and is excellent in bendability, it can be used not only for reinforcing FPC substrates but also for applications where a combination of a polyimide stiffener and a metal member can be considered.

11 Base film 12, 22, 32 Adhesive layer 13 Separator 14 Flexible printed substrate 23 Copper foil 31 Polyimide film 41 Metal plate 42 Stiffener 61 Film unwinding part 62 Coating liquid supply part 63 Coating liquid discharge part 64 Coating liquid Steam exhaust port 65 Long base material unwinding part 66 Pressurizing part 67 Winding part 68 Long base material height adjustment roll

Claims (3)

A stiffener made of polyimide film
When a compression test in the thickness direction is performed at a compression speed of 0.2 mm / min using a rod having a contact surface with a stiffener of 10 mm × 10 mm, 0.1 places / square do not satisfy the following condition (I). A stiffener characterized by being less than cm.
Condition (I)
In the stress-strain curve of the stiffener obtained with the horizontal axis as the compressive strain and the vertical axis as the compressive stress, the strain value at the transition start point where the stress-strain curve shifts to the linear region is 20% or less of the stiffener thickness. The stiffener according to claim 1, wherein a rod having a contact surface with the stiffener of 10 mm × 10 mm is used to perform a compression test in the thickness direction, and the following condition (II) is satisfied. Stiffener.
Condition (II)
In the stress-strain curve of the stiffener obtained with the compression speeds of 10 mm / min and 0.2 mm / min, the horizontal axis as the compressive strain, and the vertical axis as the compressive stress, the compressive stress σ _{10 at the time of the strain that maximizes the stress.} The difference of σ _{0.2 is | σ 10 −} σ _0.2 | <0.15 × σ _0.2
Is. The stiffener according to claim 1, wherein the bent portion is not cracked when the operation of bending at an angle of 60 ° along the iron plate placed on the plate, holding and opening for 3 seconds is repeated 10 times. A stiffener featuring.

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