JP2010116532A - Re-releasable process film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a re-releasable process film, which has a base material film and a pressure-sensitive adhesive layer arranged on its one side, more specially, when the film is used as the base material sheet for producing a flexible printed wiring board applied to a multilayer printed wiring board, to provide a re-releasable process film which, on removal, is prevented from being fouled at the side of the base material sheet as an adherend while sufficiently increasing adhesion between an adhesive sheet and the base material sheet, or, when the film is applied to a glass part of a CCD or CMOS, to provide a highly heat-resistant re-releasable process film little causing residual adhesive on the adherend and deformation of the base material film even by exposure to high temperature around 260°C. <P>SOLUTION: The re-releasable process film comprises the base material film and the pressure-sensitive adhesive layer formed on one side of the base material film. The pressure-sensitive adhesive layer is formed by using an adhesive comprising an acrylic copolymer (A) having a specific ratio of specific monomer units, and an isocyanate crosslinking agent (B). In the acrylic copolymer, the weight-average molecular weight (Mw) is 300,000-1,000,000; and the molecular-weight distribution (weight-average molecular weight Mw/number-average molecular weight Mn) is 3.0 or lower. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a removable process film, and more particularly, a base sheet for producing a flexible printed wiring board used for a multilayer printed wiring board, or a metal material or other inorganic material such as a charge coupled device or a complementary metal. The present invention relates to a removable process film having a base film and an acrylic pressure-sensitive adhesive layer provided on one surface thereof, which is preferably applied to a glass portion or the like in an oxide film semiconductor element.

The printed wiring board is a wiring board in which a circuit pattern of a conductor necessary for connecting between electrical and electronic components mounted thereon is formed by printing or the like on the surface of the insulating substrate or on the surface thereof.
Such a printed wiring board can be roughly classified into a hard printed wiring board and a flexible printed wiring board from the viewpoint of shape, and is structurally divided into a single layer and two or more layers.
Among these printed wiring boards, flexible printed wiring boards are formed by forming a circuit pattern of conductors on a flexible insulating base sheet, and in a space having a narrow and complicated structure inside an electronic device. It is an indispensable substrate for three-dimensional high-density mounting. Such a flexible printed circuit board is one of the most prominent electronic device members that can meet the recent demands for smaller, lighter, higher density, and higher precision of electronic devices, and the demand is rapidly increasing. It is growing.

In the flexible printed circuit board, since flexibility is required, a plastic sheet excellent in heat resistance and insulation, such as a polyimide sheet and a polyphenylene sulfide sheet, is used as an insulating base sheet. Then, a circuit pattern is formed of a metal material such as copper on the surface of the base sheet or on the surface and inside thereof. As a method for forming a circuit pattern, for example, an additive method is known in addition to a subtractive method in which only a necessary portion of a copper foil of a copper-clad laminate is left and other components are dissolved and removed by an etching process. This additive method is a method of forming a circuit pattern by plating only a necessary portion of a substrate, and includes a semi-additive method and a full additive method.
The performance required for such a flexible printed circuit board includes, for example, dimensional accuracy, low warpage / twist rate, heat resistance, peel strength, bending strength, high volume resistivity, chemical resistance, and heat bending strength. In addition, the processability of the printed wiring board is also important.

  In such a flexible printed wiring board, in the process of circuit formation and mounting of electrical / electronic components described above, in order to suppress solvent contamination, foreign matter mixing, generation of wrinkles, etc., the processing is generally performed. Before performing, a removability process film is previously stuck to the base material sheet used for flexible printed wiring board preparation. This process film is provided with a releasable pressure-sensitive adhesive layer on one surface of a base film, and after being attached to a base sheet for a flexible printed wiring board, it is subjected to a punching process and a solvent. After being subjected to various processes such as immersion and hot pressing, it is peeled off from the produced flexible printed wiring board. Therefore, re-peeling is performed so that no floating or peeling occurs in the process, and no adherence remains on the adherend (base sheet) after peeling, and no curling occurs on the adherend. It is important to have sex.

Therefore, the applicant first performs the above-described processing on the base sheet for producing the flexible printed wiring board, and in the process of producing the flexible printed wiring board, there is no occurrence of displacement, floating, peeling, etc. Re-peeling that can effectively prevent solvent contamination, foreign material contamination, wrinkles, etc. on the substrate surface, and that the adhesive remains less likely to remain on the adherend after peeling. Found a filing process film (see, for example, Patent Document 1).
By the way, in recent years, as electronic devices have higher performance and higher speed, printed wiring boards have been demanded to have high-density mounting and high-density wiring, and multilayer printed wiring boards have attracted attention as satisfying the requirements. ing. Furthermore, with the recent miniaturization of electrical and electronic equipment, multilayer printed wiring boards are increasingly required to be thinner and denser, and multilayer printed wiring boards using adhesive sheets (thermosetting resin sheets). Has come to be used.
In the production of such a multilayer printed wiring board, for example, a flexible printed wiring board provided with a circuit pattern and mounted with electrical / electronic components is connected to another flexible printed circuit via an adhesive sheet such as an epoxy resin sheet. A method of stacking with a wiring board is used.
Specifically, a circuit pattern is generally formed on a substrate sheet to which a removable process film is attached, and electrical and electronic components are mounted thereon, and a cover lay sheet (polyimide sheet, etc.) is provided thereon. 1 unit, peel off the re-peelable process film, face the exposed base sheet and the cover lay sheet of another unit, and interpose an adhesive sheet such as an epoxy resin sheet between them, A method of stacking the units is used. In this method, it is necessary that the adhesion between the units is sufficiently high.

  On the other hand, solid-state imaging devices such as charge coupled devices (CCD) and complementary metal oxide semiconductor devices (CMOS) have recently been mounted in digital cameras, video cameras, camera-equipped mobile phones, and the like. In manufacturing these CCD and CMOS products, a removable process film is usually attached to the glass portion for receiving light for protection. The glass part may be given a high temperature (for example, about 260 ° C.) due to a reflow process, etc. Therefore, the releasable process film used in this application has excellent heat resistance that can withstand this temperature, For example, it is required that the adhesive residue on the adherend and the deformation of the base film are small.

JP 2005-281423 A

As described above, the removable process film described in Patent Document 1 does not cause displacement, floating, peeling, etc. when the base sheet is attached as an adherend, and solvent contamination on the surface of the wiring board. In addition to being able to effectively suppress foreign matter contamination, wrinkle generation, etc., it also has excellent characteristics such as being less likely to cause adhesive residue on the adherend after peeling and also less likely to cause curling on the adherend. When used in a wiring board unit used in a multilayer printed wiring board, when the removable process film is peeled off, the substrate sheet side of the adherend is contaminated, and the epoxy system used for laminating the unit There has been a problem that the adhesive force between an adhesive sheet such as a resin sheet and the base sheet is insufficient, and improvement has been desired.
Moreover, in the application applied to the glass part of CCD and CMOS, the releasable process film which is excellent in heat resistance, for example, can endure the reflow process of 260 degreeC for several minutes is requested | required.
The present invention has been made under such circumstances, and is a removable process film having a base film and an acrylic pressure-sensitive adhesive layer provided on one surface thereof, and used for a multilayer printed wiring board. When it is used for a base sheet for producing a flexible printed wiring board, when the film is removed, the contamination on the base sheet side that is the adherend is suppressed, and adhesion such as an epoxy resin sheet When applied to a re-peelable process film in which the adhesive strength between the sheet and the base sheet is sufficiently high, or a glass part of a CCD or CMOS, even if a temperature around 260 ° C. is applied, the adhesive to the adherend An object of the present invention is to provide a removable process film that is excellent in heat resistance with little deformation of the rest and base film.

As a result of intensive studies to achieve the above object, the present inventors have peeled off the removable process film when used for a base sheet for producing a flexible printed wiring board used for a multilayer printed wiring board. At that time, it was found that the pollutant migrating to the adherend side was an oligomer component in the acrylic pressure-sensitive adhesive layer in the removable process film. As a result of further research to reduce the content of the oligomer component in the acrylic pressure-sensitive adhesive layer, the present inventors have found that when producing the acrylic pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, The oligomer in the pressure-sensitive adhesive is controlled by controlling the molecular weight distribution of the acrylate copolymer, which is the resin component in the pressure-sensitive adhesive, to a certain value or less, and preferably suppressing the residual monomer content within a certain range. For application of the base sheet for flexible printed wiring board production by using a non-silicone release agent layer as a release agent layer for the release material that protects the adhesive layer until use. As a result, it was found that a more suitable removable process film can be obtained.
Furthermore, in the case of pasting a glass part of a CCD or CMOS, a re-peeling excellent in heat resistance can be achieved by using a base film whose rate of change in storage elastic modulus defined by a specific formula is less than a certain value. It has been found that a process film can be obtained. The present invention has been completed based on such findings.

That is, the present invention
[1] A removable process film having a base film and a pressure-sensitive adhesive layer provided on one surface thereof, wherein the pressure-sensitive adhesive layer is (A) 40 to 80% by mass of butyl acrylate units, and styrene 1 to 15% by mass of units, 1 to 30% by mass of methyl methacrylate units, 1 to 30% by mass of methyl acrylate units, 1 to 10% by mass of a hydroxyl group-containing vinyl monomer unit, and a carboxyl group-containing vinyl system Including an acrylate copolymer having a monomer unit of 0.1 to 1% by mass, and (B) an isocyanate crosslinking agent, the weight average molecular weight Mw of the acrylate copolymer is 300,000 to 1,000,000. A removable process film characterized by being formed using an adhesive having a molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of 3.0 or less,
[2] The releasable process film according to the above [1], wherein an adhesive having a residual monomer content of 5 to 20% by mass with respect to the acrylate copolymer is used,
[3] The releasable process film according to the above [1] or [2], wherein the pressure-sensitive adhesive layer is laminated with a release material having a non-silicone release agent layer,
[4] The removable process film according to any one of [1] to [3], wherein the non-silicone release agent layer is a polypropylene resin.
[5] The adhesive according to any one of [1] to [4] above, wherein the pressure-sensitive adhesive is obtained by using together a tolylene diisocyanate crosslinking agent and a xylylene diisocyanate crosslinking agent as an isocyanate crosslinking agent. Re-peelable process film,
[6] The removable film according to any one of [1] to [5], which is for a flexible printed wiring board used for a multilayer printed wiring board,
[7] (a) When the adherence of the adherend to the plastic sheet used for the flexible printed wiring board is 70,000 seconds or more and 70,000 seconds as measured according to JIS Z 0237 There is virtually no discrepancy,
(B) The adhesive strength of the adherend to the plastic sheet used for the flexible printed wiring board is 0.01 to 0.5 N / 25 mm in a measurement method according to JIS Z 0237 before hot pressing.
After application to the plastic sheet used in (c) adherend of the flexible printed wiring board, a temperature 180 ° C., the adhesive strength after the 60 minutes of heat pressing under a pressure of 4.3 N / mm ² is, JIS Z The measurement method according to 0237 is 2.0 N / 25 mm or less, and (d) the gel fraction of the pressure-sensitive adhesive layer is 95% or more.
The removable process film according to the above item [6],
[8] The removable process film according to [6] or [7], wherein the flexible printed wiring board is obtained using a polyimide sheet or a polyphenylene sulfide sheet.
[9] The removable process film according to any one of [6] to [8], wherein the base film is a polyethylene terephthalate film,
[10] The releasable process film according to any one of [1] to [4], which is applied to a metal material or other inorganic material,
[11] The removable process film according to [10], which is applied to a glass portion in a charge coupled device or a complementary metal oxide film semiconductor device,
[12] The adhesive described in any one of [1] to [4] above, or [10] or [11], wherein the pressure-sensitive adhesive is obtained by using a xylylene diisocyanate crosslinking agent as the isocyanate crosslinking agent. Re-peelable process film,
[13] When the storage elastic modulus at 23 ° C. is G ′ ₂₃ and the storage elastic modulus at 260 ° C. is G ′ ₂₆₀ , the change rate X of the storage elastic modulus represented by the following formula is 85% or less. The removable film according to any one of the above items [1] to [4] and [10] to [12],
X (%) = [(G ′ ₂₃ −G ′ ₂₆₀ ) / G ′ ₂₃ ] × 100
[14] The removable film according to any one of [1] to [8], [10] to [13], wherein the substrate film is a polyimide film,
Is to provide.

  According to the present invention, a removable process film having a base film and an acrylic pressure-sensitive adhesive layer provided on one surface thereof, (1) Fabrication of a flexible printed wiring board used for a multilayer printed wiring board When used for a base material sheet, when the removable film is peeled off, contamination on the base material sheet side as an adherend is suppressed, and an adhesive sheet such as an epoxy resin sheet and the base material sheet It is possible to provide a removable process film that can suppress a decrease in adhesive strength. In addition, (2) when applied to a metal material or other inorganic material such as a glass part of a CCD or CMOS, even if a temperature around 260 ° C. is applied, the adhesive residue on the adherend or deformation of the substrate film It is possible to provide a removable process film having a low heat resistance and excellent heat resistance.

The removable process film of the present invention (hereinafter sometimes abbreviated as “process film”) is a removable process film having a base film and an adhesive layer provided on one surface thereof. The pressure-sensitive adhesive layer contains (A) an acrylate copolymer having a specific monomer unit shown below at a specific ratio, and (B) an isocyanate cross-linking agent. It is formed using an adhesive having a weight average molecular weight Mw of 300,000 to 1,000,000 and a molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) of 3.0 or less.
The removable process film of the present invention having such a pressure-sensitive adhesive layer has a removable process film A (hereinafter sometimes abbreviated as “process film A”) and a removable process film depending on the application. B (hereinafter sometimes abbreviated as “process film B”).
The process film A is for a flexible printed wiring board used for a multilayer printed wiring board, and the process film B is for a metal material or other inorganic material such as a glass part of a CCD or CMOS.

[Base film for process film A]
As the base film in the removable process film A of the present invention, it is important that the film is excellent in heat resistance, and specifically, a polyethylene terephthalate film, a polycarbonate film, an amorphous polyolefin film, an aramid film, polyethylene. Super engineering plastic films such as naphthalate film, polyphenylene sulfide film, aromatic polysulfone film, polyetherimide film, polyarylate film, polyetheretherketone film, and various liquid crystal polymer films can be mentioned. Among them, polyethylene terephthalate film is preferred because of its excellent balance of mechanical properties, electrical insulation, barrier properties, heat resistance, chemical resistance, economy, etc. Although there is no restriction | limiting in particular about the thickness of this base film, Usually, 16-200 micrometers, Preferably it is the range of 25-100 micrometers.

[Base film for process film B]
The base film for the process film B is for a metal material or other inorganic material, and more excellent heat resistance is required than the base film for the process film A. For example, when the process film B is applied to a glass part of a CCD or a CMOS, a high temperature around 260 ° C. due to a reflow process or the like may be applied. There is a demand for a small amount of adhesive residue and deformation of the base film on the adherend.
In addition, as a metal material to which the process film B is applied, for example, gold, platinum, silver, copper, iron, aluminum, or an alloy thereof, a semiconductor metal used for a wafer, and the like, an inorganic material other than the metal material is used. Examples thereof include a glass plate and a ceramic plate.
As the base film for the process film B, when the storage elastic modulus at 23 ° C. is G ′ ₂₃ and the storage elastic modulus at 260 ° C. is G ′ ₂₆₀ , the change rate X of the storage elastic modulus represented by the following formula is 85. It is preferable to use a film that is not more than%.
X (%) = [(G ′ ₂₃ −G ′ ₂₆₀ ) / G ′ ₂₃ ] × 100
Examples of such a base film include a polyimide film and a polyaramid film, and a polyimide film is particularly preferable.
The storage elastic modulus G ′ ₂₃ and the storage elastic modulus G ′ ₂₆₀ are values measured by the following method.
The base film is mounted on a dynamic viscoelasticity measuring apparatus [TA Instruments, trade name “DMA-Q800”] with a measurement length (distance between chucks) of 20 mm, a frequency of 11 Hz, an amplitude of 20 μm, and a temperature increase rate of 5 ° C. / under the conditions of min, 'measures the storage modulus G at 23 ° C.' temperature range 15 to 300 storage modulus G ° C. was _23, 260 ° C. the storage modulus G _'260 at.
Although there is no restriction | limiting in particular about the thickness of the said base film for process films B, Usually, 16-200 micrometers, Preferably it is the range of 25-100 micrometers.

  For the purpose of improving the adhesiveness with the pressure-sensitive adhesive layer at least on the surface on which the pressure-sensitive adhesive layer is provided, the base film for process films A and B is optionally oxidized or uneven. Surface treatment can be applied. Moreover, primer treatment can also be performed. Examples of the oxidation method include corona discharge treatment, plasma treatment, chromic acid treatment (wet), flame treatment, hot air treatment, ozone / ultraviolet irradiation treatment, and the like. Etc. are used. These surface treatment methods are appropriately selected according to the type of the base film, but generally, the corona discharge treatment method is preferably used from the viewpoints of effects and operability.

[Adhesive layer for process film A and B]
In the removable process films A and B of the present invention, the pressure-sensitive adhesive layer provided on one surface of the base film is (A) a butyl acrylate unit, a styrene unit, a methyl methacrylate unit, and an acrylic acid. It is formed using an adhesive containing an acrylate copolymer having at least a methyl unit, a hydroxyl group-containing vinyl monomer unit, and a carboxyl group-containing vinyl monomer unit, and (B) an isocyanate crosslinking agent. The

((A) acrylate copolymer)
In the pressure-sensitive adhesive used in the present invention, the methyl methacrylate unit and the styrene unit in the acrylate copolymer of the component (A) increase the cohesive force and glass transition temperature. In the process film A, the flexible printed wiring after hot pressing It has the effect of suppressing displacement with respect to the substrate and an increase in adhesive force. On the other hand, the methyl acrylate unit has the effect of stabilizing the polymerization and increasing the molecular weight in the production of the acrylate copolymer. The hydroxyl group-containing vinyl monomer unit and the carboxyl group-containing vinyl monomer unit in the acrylate copolymer have a crosslinkable functional group (hydroxyl group, carboxyl group) that can react with a crosslinking agent described later. Introduced to impart to the polymer.

  Examples of the monomer forming the hydroxyl group-containing vinyl monomer unit include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, Examples include (meth) acrylic acid hydroxyalkyl esters such as (meth) acrylic acid 2-hydroxybutyl, (meth) acrylic acid 3-hydroxybutyl, and (meth) acrylic acid 4-hydroxybutyl. These may be used individually by 1 type and may be used in combination of 2 or more type. Of these, 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate are preferred.

On the other hand, examples of the monomer that forms the carboxyl group-containing vinyl monomer unit include ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, citraconic acid, and the like. Can be mentioned. These may be used individually by 1 type and may be used in combination of 2 or more type. Of these, methacrylic acid and acrylic acid are preferred.
In the present invention, by introducing both the hydroxyl group-containing vinyl monomer unit and the carboxylic acid-containing vinyl monomer unit into the acrylate copolymer, the acrylate copolymer and the crosslinking agent are introduced. The reactivity with is good.
In the acrylate copolymer that is the resin component of the pressure-sensitive adhesive, if the content of the butyl acrylate unit is 40.0% by mass or more as will be shown later, the process film A is formed on the flexible printed wiring board production base. When affixed to a material sheet and, for example, hot-pressed, misalignment is unlikely to occur between the substrate sheet and the process film.

  The content ratio of each unit in the acrylate copolymer is 40 to 80% by mass of butyl acrylate units, 1 to 15% by mass of styrene units, and 1 to 30% by mass of methyl methacrylate units from the viewpoint of the performance of the pressure-sensitive adhesive. 1 to 30% by mass of a methyl acrylate unit, 1 to 10% by mass of a hydroxyl group-containing vinyl monomer unit and 0.1 to 1% by mass of a carboxyl group-containing vinyl monomer unit, and 50 to 50% of a butyl acrylate unit 65% by mass, styrene units 2 to 10% by mass, methyl methacrylate units 3 to 20% by mass, methyl acrylate units 5 to 20% by mass, hydroxyl group-containing vinyl monomer units 2 to 7% by mass and carboxyl group-containing vinyl It is preferable that it is 0.1-0.5 mass% of system monomer units.

  Furthermore, in the acrylate copolymer, if desired, another monomer copolymerizable with the monomer can be used as a copolymerization component. Examples of this other monomer include ethyl (meth) acrylate, propyl (meth) acrylate, butyl methacrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate (Meth) acrylic acid ester having 2 to 20 carbon atoms in the alkyl group of the ester moiety other than butyl acrylate and methyl (meth) acrylate; vinyl esters such as vinyl acetate and vinyl propionate; ethylene, propylene, Olefins such as isobutylene; Halogenated olefins such as vinyl chloride and vinylidene chloride; Pig Diene monomers such as diene, isoprene and chloroprene; nitrile monomers such as acrylonitrile and methacrylonitrile; acrylamides such as acrylamide, N-methylacrylamide and N, N-dimethylacrylamide; α-methylstyrene and the like Can be mentioned. These may be used alone or in combination of two or more.

In the present invention, the acrylate copolymer is not particularly limited as to its copolymerization form, and may be any of random, block, and graft copolymers. The molecular weight is 300,000 to 1,000,000 in terms of weight average molecular weight Mw and the molecular weight distribution (weight average molecular weight Mw / number average molecular weight Mn) is 3.0 or less.
If the weight average molecular weight Mw is in the range of 300,000 to 1,000,000, the resulting adhesive exhibits good adhesive performance. Moreover, if molecular weight distribution Mw / Mn is 3.0 or less, content of the oligomer whose weight average molecular weight is about 1,000-30,000 is small, and the objective of this invention can be achieved. A preferred molecular weight distribution Mw / Mn is 2.8 or less.
In addition, the said weight average molecular weight Mw and number average molecular weight Mn are the values of polystyrene conversion measured by the gel permeation chromatography (GPC) method.

Conventionally, in the production of an acrylate copolymer, which is a resin component in an acrylic pressure-sensitive adhesive, usually a (meth) acrylic acid ester, a vinyl monomer having a functional group having active hydrogen, and other monomers used as desired are used. In order to eliminate the remaining unreacted monomer as much as possible after performing the first radical polymerization until about 40% of the monomer is consumed in the presence of a radical polymerization initiator and a suitable solvent, a further two-stage A two-stage polymerization method that performs radical polymerization of the eye is employed.
However, according to the inventor's research, when such a two-stage polymerization method is adopted, the formation of the oligomer described above often occurs in the second-stage polymerization, and this oligomer adheres to the removable process film A. When it peeled from the base material sheet | seat of a body, it moved to this adherend side, and it discovered that the adhesive force of adhesive films, such as an epoxy resin film, and this adherend was reduced. Therefore, the present inventor conducted further research, and in the first-stage radical polymerization, the residual amount of unreacted monomer was about 5 to 20% by mass with respect to the acrylate copolymer in the produced pressure-sensitive adhesive. The formation of oligomers could be reduced by adopting a one-stage polymerization method in which the reaction was stopped preferably at 5 to 15% by mass. The resulting acrylate copolymer has succeeded in controlling the weight average molecular weight Mw in the range of 300,000 to 1,000,000 and the molecular weight distribution Mw / Mn to 3.0 or less. It was also found that the remaining unreacted monomer contained in the pressure-sensitive adhesive dissipates during the heating and drying processes when forming the pressure-sensitive adhesive layer and does not substantially remain in the pressure-sensitive adhesive layer.

((B) Isocyanate-based crosslinking agent)
In the present invention, an isocyanate-based crosslinking agent is used as an essential component as a crosslinking agent for the pressure-sensitive adhesive. Examples of the isocyanate-based crosslinking agent include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated diphenylmethane. Diisocyanate-based alicyclic polyisocyanates and the like, and their biurets, isocyanurates, and low molecular active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, castor oil, etc. The adduct body which is a reaction material can be mentioned.

Among these isocyanate-based crosslinking agents, in the process film A, the reactivity and the adhesion between the base material and the pressure-sensitive adhesive are excellent, the adhesive residue is small, and an appropriate pressure-sensitive adhesive force is obtained after hot pressing, etc. From this point, it is desirable to use a tolylene diisocyanate and a xylylene diisocyanate in combination. In this case, the amount used is the total amount of tolylene diisocyanate and xylylene diisocyanate based on 100 parts by mass of the acrylate copolymer, usually 0.5 to 30 parts by mass, preferably 1.0 to 20 parts. The pressure-sensitive adhesive layer having the properties described later is selected within the range of parts by mass.
On the other hand, in the process film B, xylylene diisocyanate is preferable from the viewpoint of heat resistance. The usage-amount is 0.5-30 mass parts normally with respect to 100 mass parts of said acrylate-type copolymers, Preferably it is the range of 1.0-20 mass parts.

  In this pressure-sensitive adhesive, various additives usually used for acrylic pressure-sensitive adhesives as desired, such as antioxidants, ultraviolet absorbers, light stabilizers, softeners, fillings, etc., as long as the object of the present invention is not impaired. An agent, a crosslinking accelerator and the like can be appropriately added. Although a tackifier can be used in combination, it is not preferable because it leads to an increase in adhesive strength.

[Properties of Removable Process Film A]
The re-peelable process film A of the present invention formed using the pressure-sensitive adhesive desirably has the following properties.
First, the holding force of the adherend to the base sheet for producing a flexible printed wiring board is usually 70,000 seconds or more, and it is preferable that no deviation is substantially observed at the time point of 70,000 seconds. If the holding force is less than 70,000 seconds, the process film is affixed to the substrate sheet of the adherend, and the process film and the adherend are subjected to operations such as punching, immersion in a solvent, and hot press. There is a risk of misalignment. In addition, the said retention strength is the value measured by the method shown below. Further, “substantially no occurrence of deviation” means that the deviation at 70,000 seconds is less than 0.1 mm.

(Holding power)
In accordance with JIS Z 0237, a polyimide sheet was bonded as a base sheet used for the production of a flexible wiring board to a test film attaching portion of a test piece of a test plate for holding power measurement made of SUS to obtain a test plate. Next, the process film was cut to prepare a test piece having a width of 25 mm and a length of 150 mm. The pressure-sensitive adhesive layer surface of one end of this test piece is attached to one end of the test plate so that the area of 25 mm × 25 mm is in contact with the test plate, and the pressure is reciprocated 5 times with a 2 kg roller. After 15 minutes, set in a creep tester and leave at 40 ° C. for 15 minutes. A load of 9.807 N is applied vertically downward, and the time until it falls or the occurrence of deviation and the amount of deviation at 70,000 seconds are measured.

Next, it is preferable that the adhesive force with respect to the base material sheet used for preparation of the flexible printed wiring board of the adherend is 0.01 to 0.5 N / 25 mm before hot pressing, the temperature is 180 ° C., and the pressure is 4. It is preferably 2.0 N / 25 mm or less after hot pressing for 60 minutes under the condition of 3 N / mm ² . If the adhesive strength before hot pressing is within the above range, the process film is affixed to the substrate sheet for printed circuit board production of the adherend, and mechanical operations such as punching and immersion in a solvent are performed before hot pressing. Adhesive strength is sufficient even if it is performed, and it is difficult for deviation to occur between the process film and the adherend, and the process film is easy to peel off. Occurrence can be suppressed. The adhesive strength before hot pressing is preferably 0.03 to 0.4 N / 25 mm. Also, if the adhesive strength after hot pressing is 2.0 N / 25 mm or less, the process film is affixed to the substrate sheet for printed circuit board production of the adherend, and the process film is peeled off after performing the hot press operation. It is relatively easy, and it is possible to suppress the occurrence of adhesive residue and curling of the adherend after peeling. In addition, when a hot press operation is performed, the lower limit of the adhesive strength after hot pressing is 0, because it has sufficient adhesive strength and suppresses the occurrence of displacement between the process film and the adherend. It is about 08 N / 25 mm. Preferable adhesive strength after hot pressing is 0.12 to 1.0 N / 25 mm. In addition, the adhesive force before hot press and after hot press is the value measured by the method shown below.

(Adhesive strength before hot pressing)
According to JIS Z 0237, a polyimide sheet having a width of 120 mm and a length of 150 mm is prepared as a base material sheet for use in the production of a flexible wiring board in a process film sticking portion of a test piece of an adhesive strength measurement test plate made of SUS. A test plate was bonded. On the other hand, the process film is cut into a width of 25 mm and a length of 250 mm to obtain a test piece. The pressure-sensitive adhesive layer surface at one end of the test piece is attached to a test plate so that the application area is 25 mm wide × about 90 mm long, and is reciprocated once by a 2 kg roller and is pressed. After 24 hours from the pasting, the adhesive strength when the test piece is peeled off at a peeling angle of 180 degrees and a peeling speed of 300 mm / min is measured. The average value of the central part 70% of the chart excluding 15% of the measurement start area and the end area is taken as the adhesive strength before hot pressing.
(Adhesive strength after hot pressing)
A base sheet (polyimide sheet) used for producing a flexible printed wiring board cut to a size of 120 mm in width and 150 mm in length is prepared, while the process film is cut into a width of 100 mm and a length of 250 mm to obtain a test piece. . The pressure-sensitive adhesive layer surface at one end of the test piece was attached to the base sheet so that the sticking area was 100 mm wide × about 90 mm long, and then the pressure was applied from above the test piece with a press plate at a temperature of 180 ° C. Add 3 N / mm ² and heat press for 60 minutes. Thereafter, the sheet obtained by bonding the hot-pressed test piece and the base sheet is cut into a width of 25 mm and a length of 250 mm, and the base sheet side is bonded to a SUS adhesive pressure test plate. According to 0237, the adhesive strength when the test piece is peeled off at a peeling angle of 180 degrees and a peeling speed of 300 mm / min is measured. The average value of the central portion 70% of the chart excluding 15% of the measurement start region and the end region is taken as the adhesive strength after hot pressing.

  Furthermore, the gel fraction of the pressure-sensitive adhesive layer in the removable process films A and B of the present invention is usually 95% or more. When the gel fraction is less than 95%, in the process film A, the pressure-sensitive adhesive layer surface of the process film is affixed to the substrate sheet for preparing the printed wiring board of the adherend, and after various operations, the process film is peeled off. At this time, adhesive residue is liable to occur, causing the adherend to be contaminated, and further, the process film is liable to be displaced at the time of hot pressing, thereby causing a problem that the circuit printing accuracy is lowered. A preferable gel fraction is 96% or more. The gel fraction is a value measured by the following method.

(Measurement method of gel fraction)
The pressure-sensitive adhesive is applied on the release agent layer surface of a release film in which a silicone resin is applied as a release agent to a polyethylene terephthalate film with a thickness of 25 μm, and is crosslinked under the same conditions as in the re-removable process film preparation of the present invention. Then, the adhesive (50 mm × 100 mm) is peeled off from the release film. Next, wrap the two cross-linked pressure-sensitive adhesives (total mass Ag) on a metal mesh of 200 mesh of 100 × 130 mm size with a wire mesh, set this in a Soxhlet extractor, and extract for 16 hours under reflux of ethyl acetate To do. Next, after the extraction treatment, the pressure-sensitive adhesive remaining on the wire mesh is dried at 100 ° C. for 24 hours, and after conditioning in an atmosphere of 23 ° C. and 50% RH for 3 hours or more, the mass of the pressure-sensitive adhesive is measured (Bg ), The following formula Gel fraction (%) = (B / A) × 100
To calculate the gel fraction.

[Release material for process films A and B]
A release material can be laminated on the pressure-sensitive adhesive layers of the process films A and B. Examples of the release material include paper substrates such as glassine paper, coated paper, and cast coated paper, laminated paper obtained by laminating a thermoplastic resin such as polyethylene on these paper substrates, or polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate. Polyester films such as phthalates, plastic films such as polyolefin films such as polypropylene and polyethylene, olefin resins, isoprene resins, rubber elastomers such as butadiene resins, long-chain alkyl resins, alkyd resins, fluorine resins, etc. And the like applied with a release agent. Moreover, what made these release agents into a sheet form as it is is mentioned. In particular, when the process film A of the present invention is used for a base sheet for producing a flexible printed wiring board, if a silicone release agent is used, a small amount of the silicone component is transferred from the release agent layer to the adhesive layer. It may adhere to the sheet and contaminate it. Therefore, when using the process film A of this invention for a flexible wiring board preparation use, use of a non-silicone release agent is preferable. Among the release agents, a polypropylene resin, which is an olefin-based resin that causes little component migration and results in a large adhesive force, is preferably used. The thickness of the release agent layer is about 0.01 to 100 μm. The thickness of the release material is not particularly limited, but is usually about 20 to 150 μm.

[Preparation of removable film A and B]
The re-peelable process films A and B of the present invention are coated by directly applying the above-mentioned pressure-sensitive adhesive according to the present invention on one surface of a base film, and then dried by heating at about 100 to 130 ° C. for about 1 to 5 minutes. It can be produced by forming an adhesive layer and providing a release material on the pressure-sensitive adhesive layer surface. Moreover, after apply | coating an adhesive to the peeling process surface of a peeling material and heat-drying as mentioned above and forming an adhesive layer, this can also be produced by sticking to one side of a base film. . Considering the adhesion between the pressure-sensitive adhesive layer and the substrate film, the former production method is preferably applied.
In addition, in the said production operation, it is desirable to fully perform the drying process after adhesive application. Insufficient drying may cause a shift after being applied to the adherend and increase residual solvent and residual monomer. Furthermore, when the drying is insufficient, in the process film A, a shift is likely to occur between the pressure-sensitive adhesive layer and the substrate sheet for producing a printed wiring board, and the adhesive strength after hot pressing greatly increases and peels off. In this case, curling and adhesive residue of the base sheet for producing a printed wiring board is likely to occur.
The thickness of the pressure-sensitive adhesive layer in the removable process films A and B of the present invention is usually 5 to 60 μm, preferably about 5 to 30 μm.

The removable process film A of the present invention is used as a process film for producing a flexible printed circuit board used for the multilayer printed circuit board described above. When the releasable process film A of the present invention is used for a base sheet for producing a flexible printed wiring board used for a multilayer printed wiring board, when the removable process film is peeled off, the substrate which is an adherend is used. Contamination on the material sheet side is suppressed, a decrease in the adhesive force between the adhesive sheet such as an epoxy resin sheet and the base sheet can be suppressed, and a high-quality multilayer printed wiring board can be produced. Although there is no restriction | limiting in particular about the kind of base material sheet | seat of the flexible printed wiring board to which the removability process film A of this invention is applied, Usually, this heat-resistant plastics, such as a polyimide and polyferylene sulfide, are in this flexible printed wiring board Sheets are being used.
On the other hand, the re-peelable process film B of the present invention is applied as a metal material or other inorganic material, such as a protective film for a glass part of a CCD or CMOS. In this case, although a high temperature around 260 ° C. may be applied, adhesive residue on the glass part of the adherend can be suppressed, and deformation of the base film is small.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
In addition, the various characteristics of the process film produced in each example were evaluated according to the following method.
(1) Adhesion test A process film cut to a size of 20 cm x 20 cm using a base sheet (polyimide sheet) used for production of a flexible printed circuit board cut to a size of 22 cm x 22 cm as a test plate (adhered body) The pressure-sensitive adhesive layer surface was affixed so as not to contain air bubbles, hot-pressed for 1 hour under conditions of a temperature of 180 ° C. and a pressure of 4.3 N / mm ² , and then the process film was peeled off. Adhesive sheet (Pilalux “LF0100” [manufactured by DuPont, registered trademark “Pyralux”, acrylic) between the adherend surface from which the process film has been peeled off and a base sheet (polyimide sheet) used for the production of a new printed wiring board Modified epoxy adhesive sheet], 20 mm wide and 150 mm long), and hot-pressed for 30 minutes under the conditions of a temperature of 180 ° C. and a pressure of 4.3 N / mm ² , and then the base material sheet of the adherend is made of SUS Adhering to a test plate for measuring adhesive strength, the adhesion strength between the polyimide sheet and the other polyimide sheet is measured at a peeling angle of 180 degrees and a peeling speed of 300 mm / min according to JIS Z 0237.
In addition, as for adhesive force, 30 N / 20mm or more is a pass.

(2) Deviation after hot pressing A base sheet (polyimide sheet) used for the production of a flexible printed circuit board cut to a size of 22 cm × 22 cm is cut to a size of 20 cm × 20 cm using a test plate (adhered body). The pressure-sensitive adhesive layer surface of the processed film is affixed so that air bubbles do not enter, and through-holes with a diameter of 6 mm are formed at the four corners. This is hot-pressed for 60 minutes under the conditions of a temperature of 180 ° C. and a pressure of 4.3 N / mm ² , and then the deviation between the process film and the adherend in the four corner through holes is measured, and the average value is taken as the deviation.

(3) Adhesiveness between pressure-sensitive adhesive layer and substrate film In accordance with JIS K 5600-5-6, 100 mm square grids of 1 mm square are attached to the pressure-sensitive adhesive layer of the process film with a rotary cutter, and adhesive tape (cello tape [ Nichiban Co., Ltd., registered trademark]), and after the adhesive tape is peeled off at an angle of about 60 ° in 0.5 seconds to 1.0 seconds, count the number of remaining films in 100 squares. Thus, the adhesion between the base film and the pressure-sensitive adhesive layer in the process film was tested. Evaluation of adhesion was performed according to the following criteria.
90/100 or more: 5
80/100 to less than 90/100: 4
70/100 to less than 80/100: 3
60/100 to less than 70/100: 2
Less than 60/100: 1

(4) Adhesive residue evaluation test -1
The base material sheet (polyimide sheet) used for the production of a flexible printed wiring board cut to a size of 22 cm × 22 cm is used as a test plate (adhered body), and the pressure-sensitive adhesive layer surface of the process film cut to a size of 20 cm × 20 cm is used. Affixed so as not to contain bubbles and hot pressed for 60 minutes under conditions of a temperature of 180 ° C. and a pressure of 4.3 N / mm ² , the process film was peeled off, and the surface of the test plate was subjected to FT-IR (Fourier transform red). IR measurement was performed by external absorption spectrum analysis (ATR method), and the presence or absence of adhesive residue was examined based on the presence or absence of an absorption peak derived from the pressure-sensitive adhesive.

(5) Adhesive residue evaluation test-2
A 7 cm × 15 cm, 2 mm thick float glass plate was used as a test piece (adhered body), and the adhesive layer surface of the process film cut to a size of 3 cm × 5 cm was stuck so as not to contain bubbles, and the maximum temperature was 260 ° C. Then, IR reflow (reflow furnace: WL-15-20DNX type, manufactured by Sagami Riko Co., Ltd.) with a heating time of 3 minutes was performed. Then, after being left at room temperature for 1 hour, the process film was peeled off, and the surface of the adherend was observed with a digital microscope to examine the presence or absence of adhesive residue. Evaluation of adhesive residue was performed according to the following criteria.
Ratio of remaining glue in 1 cm ² Less than 5%: ○
5% to less than 30%: △
30% or more: ×

(6) Residual silicone Process film cut to a size of 20 cm x 20 cm using a base sheet (polyimide sheet) used for the production of a flexible printed circuit board cut to a size of 22 cm x 22 cm as a test plate (adhered body) The pressure-sensitive adhesive layer surface was affixed so as not to contain air bubbles, hot-pressed for 1 hour under conditions of a temperature of 180 ° C. and a pressure of 4.3 N / mm ² , and then the process film was peeled off. Elemental analysis of the test plate surface was performed by X-ray photoelectron spectroscopy (XPS) under the following conditions.
Measuring device: Quantera SXM manufactured by ULVAC-PHI
X-ray source: AlKα (1486.6 eV)
Extraction angle: 45 degrees Measurement elements: silicon (Si), carbon (C) and nitrogen (N)
The amount of Si was expressed in “atomic%” by multiplying the value of Si / (Si + C + N) by 100. If the amount of Si is detected, the silicone has migrated.

(7) Measurement of number average molecular weight and molecular weight distribution (GPC method)
The pressure-sensitive adhesive obtained in each example was dissolved in tetrahydrofuran (polymer concentration: 10 milligram / milliliter), and the weight average molecular weight and molecular weight distribution in terms of standard polystyrene were measured by gel permeation chromatography (GPC). The measurement uses a GPC device [High-speed GPC device “HLC-8120GPC”, manufactured by Tosoh Corporation], high-speed column TSK guard column H _XL- H, TSKgel GMH _XL , TSKgel GMH _XL , TSKgel G2000H _XL (all of which are Tosoh Corporation) )) Was connected to the apparatus in this order and measured. The column temperature was 40 ° C., the liquid feeding speed was 1.0 ml / min, and an ultraviolet-visible detector (detector wavelength: 254 nm) and a differential refractometer (both manufactured by Tosoh Corporation) were used as detectors.
The molecular weight distribution is a ratio (Mw / Mn) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured by the GPC method. The monomer component is the excluded value.

(8) 'the storage modulus at ₂₃ and 260 ° C. G' storage modulus G at 23 ° C. in storage modulus change rate following method to measure _260, wherein X (%) = [(G _'23 -G _{'260) / G' 23]} × 100
Thus, the change rate X of the storage elastic modulus was obtained.
<G _'23 and G' ₂₆₀ measurements>
The base film is mounted on a dynamic viscoelasticity measuring apparatus [TA Instruments, trade name “DMA-Q800”] with a measurement length (distance between chucks) of 20 mm, a frequency of 11 Hz, an amplitude of 20 μm, and a temperature increase rate of 5 ° C. / under the conditions of min, 'measures the storage modulus G at 23 ° C.' temperature range 15 to 300 storage modulus G ° C. was _23, 260 ° C. the storage modulus G _'260 at.
In addition, the holding power of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive strength before and after hot pressing, and the gel fraction were measured according to the methods described in the specification.

Example 1
Using a reactor equipped with a stirrer, reflux condenser, dropping funnel, nitrogen gas inlet tube and thermometer, butyl acrylate (BA) 61.0 parts by mass, methyl methacrylate (MMA) 18.0 parts by mass, styrene (St) 3.5 parts by mass, methyl acrylate (MA) 12.0 parts by mass, 2-hydroxyethyl methacrylate (HEMA) 5.0 parts by mass, acrylic acid (AAc) 0.15 parts by mass Using 0.01 parts by mass of azobisisobutyronitrile (AIBN) as an agent, adding toluene as a solvent, solution polymerization in a nitrogen gas atmosphere, solid content of 40.0% by mass, weight average molecular weight of about 45 An acrylate copolymer having a molecular weight distribution (Mw / Mn) of 2.60 was produced.
In addition, content of the residual monomer was 10.0 mass% with respect to the acrylate copolymer by the following measuring method.
<Measurement of residual monomer content>
The residual monomer content was calculated by measurement and quantification by gas chromatography.
To 100 parts by mass of this acrylate copolymer, a tolylene diisocyanate (TDI) cross-linking agent [manufactured by Toyo Ink Manufacturing Co., Ltd., trade name “Olivein BHS8515” (solid content: 37.5% by mass)] 8.0 mass Parts, xylylene diisocyanate-based (XDI-based) crosslinker [manufactured by Takeda Pharmaceutical Co., Ltd., trade name “D-110N” (solid content: 75% by mass)], 3.0 parts by mass of toluene, 1.0 mass part of ethyl acetate was mix | blended and the adhesive was prepared.
Next, the coating amount after drying is 10 g / m ² (thickness 10 μm) on one side of a polyethylene terephthalate (PET) film [trade name “Embret TA-50” manufactured by Unitika Ltd.] having a thickness of 50 μm. After direct coating, and drying at 120 ° C. for 1 minute, a release material having a silicone release agent layer (trade name “40RL-01Z” manufactured by Oji Paper Co., Ltd.) is laminated thereon, and a process film And various properties were evaluated. A polyimide sheet was used as the test plate (adhered body). Moreover, the adhesive residue evaluation test-1 was used for the adhesive residue. The results are shown in Table 1.

Example 2
Except that the monomer composition was changed as shown in Table 1, the same procedure as in Example 1 was conducted, except that the solid content was 40.0% by mass, the weight average molecular weight was about 460,000, the molecular weight distribution (Mw / Mn) was 2.70, the residual monomer 12 A 0.0 mass% acrylate copolymer was produced.
Hereafter, the process film was produced like Example 1 and various characteristics were evaluated. The results are shown in Table 1.

Comparative Example 1
In Example 1, an acrylate copolymer was produced in the same manner as in Example 1 except that the solution polymerization was performed and then the polymerization was performed again. The weight average molecular weight of the obtained acrylate copolymer was about 470,000, and the molecular weight distribution (Mw / Mn) was 3.29.
Further, the content of the residual monomer was measured in the same manner as in Example 1, and found to be 3.4% by mass with respect to the acrylate copolymer.
Hereafter, the process film was produced like Example 1 and various characteristics were evaluated. The results are shown in Table 1.

  As can be seen from Table 1, the process film of Example 1 has an extremely high adhesive force in the adhesion test as compared with that of Comparative Example 1.

Example 3
Using a reactor equipped with a stirrer, reflux condenser, dropping funnel, nitrogen gas inlet tube and thermometer, butyl acrylate (BA) 60.0 parts by mass, methyl methacrylate (MMA) 18.0 parts by mass, styrene (St) 3.5 parts by mass, methyl acrylate (MA) 13.0 parts by mass, 2-hydroxyethyl methacrylate (HEMA) 5.0 parts by mass, acrylic acid (AAC) 0.15 parts by mass Using 0.01 parts by mass of azobisisobutyronitrile (AIBN) as an agent, adding toluene as a solvent, solution polymerization in a nitrogen gas atmosphere, solid content of 40.0% by mass, weight average molecular weight of about 47 An acrylate copolymer solution having a molecular weight distribution (Mw / Mn) of 2.4 was produced.
Further, the content of the residual monomer was measured in the same manner as in Example 1, and found to be 11.0% by mass with respect to the acrylate copolymer.
To 100 parts by mass of this acrylate copolymer solution (solid content 40.0% by mass), a tolylene diisocyanate (TDI) crosslinking agent [manufactured by Toyo Ink Mfg. Co., Ltd., trade name “Olivein BHS8515” (solid content 37 .5 mass%)] 8.0 parts by mass and xylylene diisocyanate (XDI) crosslinking agent [manufactured by Takeda Pharmaceutical Co., Ltd., trade name “D-110N” (solid content: 75 mass%)] 3.0 An adhesive was prepared by blending part by mass and 40.0 parts by mass of ethyl acetate.
Next, the coating amount after drying is 10 g / m ² (thickness 10 μm) on one side of a polyethylene terephthalate (PET) film [trade name “Embret TA-50” manufactured by Unitika Ltd.] having a thickness of 50 μm. After coating directly and drying at 120 ° C. for 1 minute, a release material made of polypropylene resin (made by Oji Paper Co., Ltd., trade name “Alphan PP40SD-001”) is laminated thereon, and a process film is formed. It produced and evaluated various characteristics. In addition, the adhesive residue used the adhesive residue evaluation test-1. The results are shown in Table 2.

Example 4
Except for changing the monomer composition as shown in Table 2, the same procedure as in Example 3 was performed, except that the solid content was 40.0% by mass, the weight average molecular weight was about 500,000, the molecular weight distribution (Mw / Mn) 2.7, the residual monomer 8 A 3 mass% acrylate copolymer was produced.
Hereafter, the process film was produced similarly to Example 3 and various characteristics were evaluated. The results are shown in Table 2.

Example 5
A process film was produced in the same manner as in Example 3 except that the release material was changed to a polyethylene terephthalate film having a thickness of 50 μm, which was release-treated with an alkyd resin on one side [trade name “PET50 AL-5”, manufactured by Lintec Corporation]. Various characteristics were evaluated. The results are shown in Table 2.

Example 6
A process film was produced in the same manner as in Example 3 except that [Rintec Co., Ltd., trade name “SP-PET3811]] was used as a release material using a silicone release agent layer. The results are shown in Table 2.

Comparative Example 2
In Example 3, an acrylate copolymer was produced in the same manner as in Example 3 except that the solution polymerization was performed and then the polymerization was performed again. The weight average molecular weight of the obtained acrylate copolymer was about 550,000, and the molecular weight distribution (Mw / Mn) was 3.4.
Further, the content of the residual monomer was measured in the same manner as in Example 1, and found to be 3.5% by mass relative to the acrylate copolymer.
Hereafter, the process film was produced similarly to Example 3 and various characteristics were evaluated. The results are shown in Table 2.

  As can be seen from Table 2, the process films of Examples 3 to 6 have higher adhesive strength in the adhesion test than those of Comparative Example 2. Moreover, although Examples 3-5 use the release material which has a non-silicone-type release agent layer, since Example 6 uses the release material which has a silicone-type release agent layer, it is adhesion in an adhesion test. The force is inferior compared to Examples 3-5.

Example 7
An acrylate copolymer solution was produced in the same manner as in Example 3.
To 100 parts by mass of this acrylate copolymer solution (solid content 40.0% by mass), a xylene diisocyanate (XDI) crosslinking agent [manufactured by Takeda Pharmaceutical Co., Ltd., trade name “D-110N” (solid content 75 (Mass%)] 9.0 parts by mass and 40.0 parts by mass of ethyl acetate were blended to prepare an adhesive.
Next, a thickness of 50 [mu] m, the polyimide film of the rate of change of 40% storage modulus [Du Pont-Toray Co., Ltd., registered trademark "Kapton"] on one side of the coating amount after drying becomes 10 g / m ² And then drying at 120 ° C. for 1 minute, and then laminating a release material made of polypropylene resin (trade name “Alphan PP40SD-001” manufactured by Oji Paper Co., Ltd.) to produce a process film The adhesive residue was evaluated using Adhesive residue evaluation test-2. The results are shown in Table 3.

Example 8
An acrylate copolymer was produced in the same manner as in Example 1.
To 100 parts by mass of this acrylate copolymer solution (solid content 40.0% by mass), a xylene diisocyanate (XDI) crosslinking agent [manufactured by Takeda Pharmaceutical Co., Ltd., trade name “D-110N” (solid content 75 Mass%)] 7.0 parts by mass and 40.0 parts by mass of ethyl acetate were blended to prepare an adhesive.
Next, on a single side of a polyimide film (trade name “Kapton” (registered trademark), manufactured by Toray DuPont Co., Ltd.) having a thickness of 50 μm and a storage elastic modulus change rate of 40%, the coating amount after drying is 10 g / After coating directly to m ² and drying at 120 ° C. for 1 minute, a release material made of polypropylene resin [manufactured by Oji Paper Co., Ltd., trade name “Alphan PP40SD-001”] was laminated thereon, A process film was produced, and the adhesive residue was evaluated by adopting adhesive residue evaluation test-2. The results are shown in Table 3.

Comparative Example 3
A process film was prepared in the same manner as in Example 7 except that the pressure-sensitive adhesive solution prepared in Comparative Example 1 was used, and the adhesive residue was evaluated using Adhesive Residue Evaluation Test-2. The results are shown in Table 3.

  The removable process film of the present invention is a base material that is an adherend when the removable process film is peeled off when used for a base sheet for producing a flexible printed wiring board used for a multilayer printed wiring board. Contamination on the sheet side is suppressed, and a decrease in the adhesive force between the adhesive sheet such as an epoxy resin sheet and the base sheet can be suppressed. In addition, when applied to a glass part of a CCD or CMOS, even when a temperature around 260 ° C. is applied, the adhesive residue and the base film are less deformed with respect to the adherend and are excellent in heat resistance.

Claims (14)

  It is a removable process film which has a base film and the adhesive layer provided in the one surface, Comprising: The said adhesive layer is (A) butyl acrylate unit 40-80 mass%, styrene unit 1- 15 mass%, 1 to 30 mass% of methyl methacrylate units, 1 to 30 mass% of methyl acrylate units, 1 to 10 mass% of hydroxyl group-containing vinyl monomer units, and carboxyl group-containing vinyl monomers An acrylate copolymer having a unit of 0.1 to 1% by mass and (B) an isocyanate crosslinking agent, and the weight average molecular weight Mw of the acrylate copolymer is 300,000 to 1,000,000; A re-peeling process film characterized by being formed using an adhesive having a distribution (weight average molecular weight Mw / number average molecular weight Mn) of 3.0 or less.   The re-peelable process film according to claim 1, wherein the pressure-sensitive adhesive has a residual monomer content of 5 to 20% by mass with respect to the acrylate copolymer.   The removable process film according to claim 1 or 2, wherein the pressure-sensitive adhesive layer is laminated with a release material having a non-silicone release agent layer.   The re-peelable process film according to any one of claims 1 to 3, wherein the non-silicone release agent layer is a polypropylene resin.   The removable process film according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive is obtained by using a tolylene diisocyanate crosslinking agent and a xylylene diisocyanate crosslinking agent in combination as an isocyanate crosslinking agent.   It is for flexible printed wiring boards used for a multilayer printed wiring board, The removable process film in any one of Claims 1-5. (A) The holding force of the adherend to the plastic sheet used for the flexible printed wiring board is 70,000 seconds or more and a deviation occurs at the time of 70,000 seconds as measured according to JIS Z 0237. Is virtually unacceptable,
(B) The adhesive strength of the adherend to the plastic sheet used for the flexible printed wiring board is 0.01 to 0.5 N / 25 mm in a measurement method according to JIS Z 0237 before hot pressing.
(C) The adhesive strength after 60 minutes of hot pressing under conditions of temperature 180 ° C. and pressure 4.3 N / mm ² after sticking to a plastic sheet used for the flexible printed wiring board of the adherend is JIS Z The measurement method according to 0237 is 2.0 N / 25 mm or less, and (d) the gel fraction of the pressure-sensitive adhesive layer is 95% or more.
The removable process film according to claim 6.   The removable process film according to claim 6 or 7, wherein the flexible printed wiring board is obtained using a polyimide sheet or a polyphenylene sulfide sheet.   The removable process film according to any one of claims 6 to 8, wherein the base film is a polyethylene terephthalate film.   The removable process film according to any one of claims 1 to 4, which is applied to a metal material or other inorganic material.   The removable process film according to claim 10, which is applied to a glass portion in a charge coupled device or a complementary metal oxide semiconductor device.   The removable process film according to any one of claims 1 to 4, or 10 or 11, wherein the pressure-sensitive adhesive is obtained by using a xylylene diisocyanate-based crosslinking agent as the isocyanate-based crosslinking agent. When the base film has a storage elastic modulus at 23 ° C. of G ′ ₂₃ and a storage elastic modulus at 260 ° C. of G ′ ₂₆₀ , the change rate X of the storage elastic modulus represented by the following formula is 85% or less: Item 14. The removable film according to any one of Items 1 to 4 and 10 to 12.
X (%) = [(G ′ ₂₃ −G ′ ₂₆₀ ) / G ′ ₂₃ ] × 100   A base film is a polyimide film, The removable process film in any one of Claims 1-8, 10-13.