KR20160070193A - Heat-resistant proective film for flexible printed circuit board having high visibility - Google Patents

Abstract

The present invention relates to a heat-resistant protective film for a flexible printed circuit board (FPCB) process having high visibility. The heat-resistant protective film for the FPCB process of the present invention has an adhesive layer and a release layer sequentially stacked on at least one surface of a transparent base film layer, in which the adhesive layer is formed by an adhesive composition containing an optimum content of epoxy hardener and colored nano particles with respect to acrylic polymer resin. Since the adhesive layer contains the colored nano particles, so heat-resistant protective film has high visibility, thereby easily determining whether a residue of the heat-resistant protective film exists after a hot press during the FPCB process, and accordingly easily removing the residue, so that a product defect rate is improved. In addition, since heat-resistance and viscosity of the heat-resistant protective film are maintained, thus productivity is improved without an increase of adhesion, a transfer of adhesive agent, and a tear of the film which are occurred after a hot melt in a condition of high temperature and pressure.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a heat-resistant protective film for a FPCB process,

The present invention relates to a heat-resistant protective film for a flexible printed circuit board (hereinafter referred to as " FPCB ") process to which visibility is imparted, and more particularly, Wherein the pressure-sensitive adhesive layer is formed of a pressure-sensitive adhesive composition containing an epoxy curing agent and colored nanoparticles with respect to the acrylic polymer resin, and the heat resistance of the heat-resistant protective film is improved by optimizing the pressure- The heat resistance for the FPCB process, in which viscoelastic properties are maintained, and visibility is easily determined in order to easily determine whether the heat-resistant protective film remains after hot pressing in the FPCB process due to the colored nano particles contained in the adhesive layer, To a protective film.

2. Description of the Related Art Recently, there has been a demand for a printed circuit board (PCB) that is easy to be embedded even in a narrow space due to miniaturization, thinning, high density and high bending of electronic products. In accordance with this market demand, a flexible printed circuit board (FPCB) capable of miniaturization and high density and having repeated flexing has been developed.

Such FPCBs are becoming more and more necessary due to the rapid use of electronic equipment such as portable terminals, LCDs, cameras, and printer heads, and recently, there has been a rapid increase in the use of a rigid printed circuit board .

Generally, the FPCB is formed by forming a copper-clad laminate on one surface of an insulating film such as a polyimide resin, laminating a dry film to the copper clad laminate, and sequentially exposing, developing, And then a coverlay film is applied to the outside of the copper-clad laminate and laminated using a hot press, followed by a surface treatment and a post-treatment.

Copper Clad Laminate (CCL) needs to protect copper on one side during exposure, development, and double-side etching while these processes are being performed.

In order to meet the demand for miniaturization, thinning, and high density, CCL and CL have been formed as a thin film to improve the workability by attaching a protective film to compensate for the thickness of CCL and CL thinned. However, , The protective film is maintained with the protective film attached to the CCL and CL bonding process. Therefore, the protective film must maintain high heat resistance without increasing the adhesive strength after hot melt (high temperature and high pressure) or transferring the adhesive.

Korean Patent Laid-Open Publication No. 2013-121264 discloses a heat-resistant adhesive composition having a small amount of tacky residue at the time of removing a protective film from a base film after a high-temperature process in a flexible circuit board process, And Korean Patent Laid-Open Publication No. 2014-0084416 discloses a heat treatment process for ITO crystallization of an indium tin oxide (ITO) film and a dimensional stability of an ITO film in a touch screen panel (TSP) process In general, when general protective film is used, deterioration of workability when peeling protective film due to increase of adhesion of protective film after heat treatment, transfer of pressure-sensitive adhesive onto ITO film after transfer of pressure-sensitive adhesive to ITO film, occurrence of curl of ITO film, The present invention provides a heat-resistant protective film for a touch screen panel process which solves the problems of oxidation of the ITO layer caused by the heat-resistant film.

However, it has been pointed out that the conventional protective film produced by applying to the transparent substrate film layer has a problem of an increase in the defective ratio due to the inability to distinguish the protective film after hot pressing. Although an opaque mat (Matt) film is used to reduce such a defective ratio, it causes a problem of productivity deterioration due to tearing of the film after hot pressing.

Accordingly, the present inventors have made efforts to improve the problems of the conventional transparent protective film. As a result, the present inventors have found that when an adhesive layer and a release layer are sequentially layered on at least one side of a transparent substrate film layer, an epoxy curing agent and colored nanoparticles It is easy to determine the presence or absence of the heat-resistant protective film after the hot pressing in the FPCB process by forming the pressure-sensitive adhesive layer by the pressure-sensitive adhesive composition containing the optimum content and imparting visibility to the heat- Whereby the residue can be easily removed, thereby confirming the reduction of the product defective rate and the improvement of the productivity, thereby completing the present invention.

An object of the present invention is to provide a heat-resistant protective film for FPCB process to which visibility is imparted.

The present invention relates to a heat-resistant protective film for an FPCB process in which an adhesive layer and a release layer are sequentially layered on at least one surface of a transparent base film layer, wherein the adhesive layer comprises 5 to 10 parts by weight of an epoxy curing agent per 100 parts by weight of the acrylic polymer resin , And 0.001 to 0.01 part by weight of colored nanoparticles are provided with visibility by the pressure-sensitive adhesive composition.

Preferred colored nanoparticles used in the heat-resistant protective film of the present invention are carbon black of 500 nm or less.

In the heat-resistant protective film, the thickness of the adhesive layer is preferably 5 to 20 占 퐉, and the peel strength of the adhesive layer is 10 to 100 gf / 25 mm.

The heat-resistant protective film of the present invention has a transparent base film layer, a pressure-sensitive adhesive layer and a release layer successively laminated, and imparts visibility to the pressure-sensitive adhesive layer due to the presence of colored nanoparticles. It is easy to judge and the residue can be easily removed thereby improving the defective product rate.

Thus, the heat-resistant protective film of the present invention maintains the heat resistance and adhesive property by optimizing the components and the content of the pressure-sensitive adhesive composition, thereby improving the productivity without increasing pressure-sensitive adhesive force after hot-melt at high temperature and high pressure, .

1 is a schematic cross-sectional view of a heat-resistant protective film for FPCB process of the present invention,
2 is a comparative photograph of the visibility evaluation of the heat-resistant protective film for FPCB process of the present invention.

Hereinafter, the present invention will be described in detail.

1 is a schematic cross-sectional view of a heat-resistant protective film for FPCB process according to the present invention, in which an adhesive layer 2 and a release layer 3 are sequentially laminated on at least one surface of a transparent substrate film layer 1, .

Accordingly, the present invention provides a heat-resistant protective film for FPCB process wherein the pressure-sensitive adhesive layer (2) and the release layer (3) are sequentially layered on at least one surface of the transparent base film layer (1) Provided is a heat-resistant protective film for FPCB process to which visibility is imparted by a pressure-sensitive adhesive composition comprising 5 to 10 parts by weight of an epoxy curing agent and 0.001 to 0.01 part by weight of colored nanoparticles based on 100 parts by weight of an acrylic polymer resin.

In the heat-resistant protective film for FPCB process according to the present invention, the thickness of the pressure-sensitive adhesive layer (2) is 5 to 20 탆 in dry film thickness and 10 to 100 gf / 25 mm in adhesive force.

At this time, if the thickness of the adhesive layer 2 is as thin as less than 5 mu m, the adhesiveness to CCL and CL is lowered, the CCL and CL are pressed by the R chip roughness of the film, The workability may be lowered due to the increase of the adhesive force, and the pressure-sensitive adhesive may be transferred after hot pressing.

If the adhesive strength of the adhesive layer 2 is less than 10 gf / 25 mm, peeling and penetration of the etchant may occur in the process. If the adhesive force exceeds 100 gf / 25 mm, the FPCB surface may be damaged or warped during removal.

Hereinafter, the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer (2) in the heat-resistant protective film for FPCB process of the present invention will be described in detail.

a) Acrylic polymer resin

The pressure-sensitive adhesive composition is characterized by comprising 5 to 10 parts by weight of an epoxy curing agent and 0.001 to 0.01 part by weight of colored nanoparticles based on 100 parts by weight of the acrylic polymer resin.

More specifically, the acrylic polymer resin contained as a main component of the pressure-sensitive adhesive composition comprises 50 to 98% by weight of a soft acrylic monomer having a glass transition temperature of 0 DEG C or less, 1 to 48% by weight of a hard acrylic monomer having a glass transition temperature of 0 DEG C or more, By weight to 2% by weight.

At this time, the soft acrylic monomer may be any known acrylic monomer that imparts flexibility and adhesion to the acrylic polymer resin and satisfies the above-mentioned glass transition temperature requirement.

Thus, it is preferable to use at least one monomer selected from the group consisting of butyl (meth) acrylate, hexyl acrylate, hexyl methacrylate, n-propyl (meth) acrylate, n-tetradecyl (meth) Ethylhexyl acrylate, and mixtures of two or more thereof.

The soft acrylic monomer is preferably contained in the adhesive composition in an amount of 50 to 98% by weight, and the content of the soft acrylic monomer can be controlled according to the content of the hard monomer.

The hard acrylic monomer serves to impart cohesive force to the pressure sensitive adhesive of the present invention, and is preferably selected from the group consisting of methyl acrylate, methyl methacrylate, ethyl methacrylate, vinyl acetate, styrene and acrylonitrile A single type or a mixture of two or more types is used. In this case, the hard acrylic monomer preferably contains 1 to 48% by weight in the pressure-sensitive adhesive composition. When the content is less than 1% by weight, the content of the hard monomer is small and the glass transition temperature of the protective film is too low, The components are transferred. On the other hand, if the content of the hard monomer exceeds 48% by weight, the glass transition temperature of the protective film becomes excessively high and the adhesion with the base film layer is lowered.

In the pressure-sensitive adhesive composition of the present invention, the crosslinking monomer is used for copolymerizing the soft acrylic monomer and the hard acrylic monomer.

As a preferable example of the crosslinking monomer, at least one selected from the group consisting of a monomer containing a hydroxy group, a monomer containing a carboxyl group and a monomer containing nitrogen can be used.

Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth)

(Meth) acrylate, 2-hydroxyethyleneglycol (meth) acrylate or 2-hydroxypropyleneglycol (meth) acrylate. Examples of the monomer containing a carboxyl group include , Maleic acid or fumaric acid, and the nitrogen-containing monomer is acrylamide, N-vinylpyrrolidone or N-vinylcaprolactam. The above crosslinking monomers may be used alone or in combination of two or more.

The glass transition temperature of the acrylic polymer resin copolymerized from the above composition is -50 ° C to 0 ° C, preferably -45 ° C to -10 ° C. If the glass transition temperature of the acrylic polymer resin is less than -50 캜, the glass transition temperature of the polymer itself is low even if the pressure-sensitive adhesive composition is cured and has a three-dimensional network structure.

On the other hand, when the glass transition temperature of the acrylic polymer resin is more than 0 ° C, the molecular structure of the adhesive composition becomes more dense and has a three-dimensional network structure than that of a composition having a low glass transition temperature. The adhesive itself is viscoelastic, which in this case is more biased toward elasticity. In this case, the protective film has to protect against foreign matter or external impact, and has high elasticity. When the viscosity is low, the product can not absorb the external impact and damage the product.

In order to obtain a glass transition temperature of -50 ° C or higher, the type and polymerization ratio of each monomer must be optimized.

First, the tackiness (degree of stickiness of the pressure-sensitive adhesive) in the film-type pressure-sensitive adhesive of the present invention is determined depending on the combination of the soft monomer and the hard monomer among the monomer components constituting the pressure-sensitive adhesive. At this time, if the content of soft monomer is increased, the glass transition temperature of the pressure sensitive adhesive is lowered and the tack characteristics are increased. If the content of the hard monomer is increased, the glass transition temperature of the pressure sensitive adhesive is increased and the tack characteristics are lowered.

As described above, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer (2) of the heat-resistant protective film for FPCB process of the present invention is prepared by mixing two kinds of soft acrylic monomers and hard monomers having different glass transition temperatures (Tg) By using the acrylic polymer resin, there is no adhesive residue under a high-temperature process, and the adhesive strength is easily controlled.

The weight average molecular weight of the acrylic polymer resin used in the present invention is preferably 300,000 to 2,000,000. If the weight average molecular weight is less than 300,000, the adhesive residual phenomenon occurs due to a decrease in cohesive strength. If the weight average molecular weight exceeds 200,000, And the elasticity and adhesion of the pressure-sensitive adhesive increase.

The adhesive layer 2 made of the acrylic polymer resin may be biased to the elasticity due to the viscoelastic inherent to the adhesive layer depending on the component and its content. In this case, the protective film should have a role of protecting against foreign substances or external impacts, If the viscosity is low, it will not absorb the external impact and damage the product.

b) Epoxy hardener

The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer (2) of the heat-resistant protective film for FPCB process of the present invention contains 5 to 10 parts by weight of an epoxy curing agent per 100 parts by weight of the acrylic polymer resin.

By the inclusion of the epoxy curing agent, the curing rate can be improved and the heat resistance can be improved.

If the amount of the epoxy curing agent is less than 5 parts by weight, crosslinking may not be sufficiently carried out and surface transfer may occur. If the amount is more than 10 parts by weight, excess curing agent exceeding the functional group of the acrylic pressure-

c) Colored nanoparticles

In order to improve the visibility, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer (2) of the heat-resistant protective film for FPCB process of the present invention contains 0.001 to 0.01 part by weight of colored nanoparticles per 100 parts by weight of the acrylic polymer resin.

In the specification of the present invention, the colored nanoparticle means a material having a color enough to impart visibility and a particle size of 1 to 500 nm. The embodiment of the present invention relates to a colored nanoparticle , Which is exemplified by using carbon black having a particle size of 500 nm or less, but the present invention is not limited thereto.

In the colored nanoparticles, when the particle size exceeds 500 nm, visibility due to large particles is ensured but the heat resistance of the film is lowered.

The preferable content of the colored nanoparticles is 0.001 to 0.01 part by weight based on 100 parts by weight of the acrylic polymer resin. If the amount is less than 0.001 part by weight, desired visibility is not exhibited. If the amount is more than 0.01 part by weight, As a result of the measurement of the adhesion force after pressing, all of the adhesive properties are lost.

In the heat-resistant protective film for FPCB process of the present invention, 1) the transparent base film layer (1) may be a polyester polymer such as polyethylene terephthalate or polyethylene naphthalate, an acrylic polymer such as polymethyl methacrylate, a polystyrene or acrylonitrile -Styrene copolymers (AS resins), and polycarbonate-based polymers.

Examples of the polymer include polyolefin polymers such as polyethylene, polypropylene, cycloaliphatic or norbornene structure, polyolefin polymers such as ethylene-propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, Based polymer, a polyether-etherketone-based polymer, a polyphenylene sulfide-based polymer, a vinyl alcohol-based polymer, a vinylidene chloride-based polymer, a vinyl butyral-based polymer, an allylate-based polymer, a polyoxymethylene-based polymer , An epoxy-based polymer, a blend polymer of the polymer, an acrylic-based, urethane-based, acrylic urethane-based, epoxy-based or silicone-based thermosetting or ultraviolet curable resin. Therefore, the transparent base film layer 1 is most preferably a polyethylene terephthalate (PET) film, and the thickness of the transparent base film layer 1 may be variously applied, but it is preferable to use 10 to 200 탆.

FIG. 2 is a comparative photograph of the heat-resistant protective film for FPCB process of the present invention for evaluation of visibility. The left photograph shows the conventional heat-resistant protective film and the right photograph shows the result of attaching the heat-resistant protective film of the present invention. Thus, excellent visibility to the heat-resistant protective film of the present invention can be visually confirmed.

Therefore, it is possible to improve the defect rate of the process even with the structure of the transparent base film layer 1 without the opaque mat film used for determining whether the heat-resistant protective film remains after hot pressing in the conventional FPCB process.

Hereinafter, the present invention will be described in more detail with reference to Examples.

The present invention is intended to more specifically illustrate the present invention, and the scope of the present invention is not limited to these embodiments.

≪ Preparation Examples 1 to 6 &

The pressure-sensitive adhesive composition was prepared by uniformly mixing the components and the contents shown in Table 1 below.

≪ Example 1 >

The pressure-sensitive adhesive composition prepared in the same manner as in Preparation Example 1 was coated on transparent polyethylene terephthalate (PET) to a PSA (Pressure Sensitive Adhesive) thickness of 10 μm and dried at 160 ° C. for 1 minute to form an adhesive layer. Then, a polyester film was laminated on the adhesive layer at a pressure of 2 kgf / cm and a speed of 7 mpm using a laminator to form a release layer to produce a heat-resistant protective film for FPCB process.

≪ Comparative Example 1 &

A heat-resistant protective film for FPCB process was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition prepared in Preparation Example 1 was applied to transparent PET so that the thickness of the PSA layer was 5 μm .

≪ Comparative Example 2 &

A heat-resistant protective film for an FPCB process was prepared in the same manner as in Example 1, except that the pressure-sensitive adhesive composition prepared in Preparation Example 1 was applied to transparent PET so that the thickness of the PSA layer was 20 μm .

≪ Comparative Example 3 &

A heat-resistant protective film for FPCB process was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition prepared in Preparation Example 2 was applied to transparent PET so that the thickness of the PSA layer was 10 μm .

≪ Comparative Example 4 &

A heat-resistant protective film for FPCB process was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive composition prepared in Preparation Example 3 was applied to transparent PET so that the thickness of the PSA was 10 탆 to form an adhesive layer .

≪ Comparative Example 5 &

A heat-resistant protective film for an FPCB process was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition prepared in Preparation Example 4 was applied to transparent PET so that the thickness of the PSA layer was 10 μm .

≪ Comparative Example 6 >

A heat-resistant protective film for FPCB process was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition prepared in Preparation Example 5 was applied to transparent PET so that the thickness of the PSA was 10 탆 to form an adhesive layer .

≪ Comparative Example 7 &

A heat-resistant protective film for FPCB process was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive composition prepared in Preparation Example 1 was applied to opaque PET PET to a PSA thickness of 10 μm to form an adhesive layer Respectively.

≪ Comparative Example 8 >

A heat-resistant protective film for FPCB process was prepared in the same manner as in Example 1 except that the pressure-sensitive adhesive composition prepared in Preparation Example 6 was applied to transparent PET so that the thickness of the PSA layer was 10 μm .

<Experimental Example>

1. Thickness of adhesive layer

The thickness of the adhesive layer of the heat-resistant protective film prepared in Example 1 and Comparative Examples 1 to 8 was measured using a micrometer.

2. Adhesion measurement

The release layer was removed from the heat-resistant protective film prepared in Example 1 and Comparative Examples 1 to 8, and the laminate was laminated with a conventional polyimide (PI) film and a copper foil. After that, the adhesive strength of the adhesive layer was measured by peeling at a rate of 10 m / min and a 180 degree angle using a measurement equipment (AR-1000) at room temperature and hot press at 160 캜 and 7.7 MPa for 30 minutes.

3. Check whether PSA residue is present

The release layer was removed from the heat-resistant protective film prepared in Example 1 and Comparative Examples 1 to 8, and the laminate was laminated with a conventional polyimide (PI) film and a copper foil. After the hot press at 160 ° C and 7.7 MPa for 30 minutes, the transfer of the adhesive layer was confirmed.

4. Confirm visibility

Visual inspection of transparent protective film products and visibility for commercial FPCB processes was performed.

5. Evaluation of film tear after hot pressing

The release layer was removed from the heat-resistant protective film prepared in Example 1 and Comparative Examples 1 to 8, and the laminate was laminated with a conventional polyimide (PI) film and a copper foil. Thereafter, after the hot press at 160 DEG C and 7.7 MPa for 30 minutes, the produced film was torn by hand to evaluate the degree of tearing.

The physical properties of the degree of tearing were evaluated as good (●) and poor (×).

As shown in Table 2, in Example 1, a pressure-sensitive adhesive composition comprising 5 parts by weight of an epoxy curing agent and 0.005 part by weight of nano-particles, based on 100 parts by weight of an acrylic polymer resin, , The produced film was confirmed to be suitable as a heat-resistant protective film for FPCB process, while maintaining the heat resistance as a pressure-sensitive adhesive and securing visibility.

On the other hand, in the case of Comparative Examples 1 and 2, the physical properties of the produced film depend on the film thickness. If the thickness of the PSA is 5 탆, the PSA is not laminated with CCL and CL at room temperature. The cohesive force between the PSA and the PSA was weakened after the pressing, resulting in increase in adhesion and residue.

In the protective films of Comparative Examples 3 and 4, PSA (Pressure Sensitive Adhesive) residue was determined according to the epoxy curing agent, and Comparative Examples 5 and 6 were obtained by observing the physical properties depending on the content of nanoparticles. , The desired visibility can not be achieved and the adhesive property is lost when an excessive amount is used.

Further, as a result of applying opaque matte PET to the film of Comparative Example 7, basic physical properties and visibility for adhesion were secured, but tearing of the film after hot pressing was confirmed. In Comparative Example 8, when the size of the nanoparticles exceeded 500 nm, the visibility of the film was secured, but the heat resistance was deteriorated.

As described above, the present invention provides a heat-resistant protective film in which a transparent base film layer, a pressure-sensitive adhesive layer and a release layer are sequentially layered, wherein a heat resistance advantageous for FPCB processes imparted with visibility due to the inclusion of colored nanoparticles in the pressure- A protective film was provided.

Since the heat-resistant protective film of the present invention has visibility, it is easy to determine whether the heat-resistant protective film remains after hot pressing in the FPCB process, and thus the residue can be easily removed, thereby improving the defective product.

Further, since the heat-resistant protective film of the present invention maintains the heat resistance and the adhesive property by optimizing the pressure-sensitive adhesive composition, the productivity can be improved without increasing the adhesive strength after hot melt at high temperature and high pressure, and without transferring the pressure-sensitive adhesive and tearing the film.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art.

1: Transparent base film layer
2: Adhesive layer
3:

Claims (4)

A heat-resistant protective film for FPCB process in which an adhesive layer and a release layer are sequentially layered on at least one surface of a transparent base film layer,
Wherein the adhesive layer comprises 5 to 10 parts by weight of an epoxy curing agent and 0.001 to 0.01 part by weight of colored nanoparticles per 100 parts by weight of the acrylic polymer resin, thereby imparting visibility. The heat-resistant protective film for a FPCB process according to claim 1, wherein the colored nanoparticles are carbon black of 500 nm or less. The heat-resistant protective film for FPCB process according to claim 1, wherein the pressure-sensitive adhesive layer has a thickness of 5 to 20 탆. The heat-resistant protective film for FPCB process according to claim 1, wherein the peel strength of the adhesive layer is 10 to 100 gf / 25 mm.

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