JPH05255631A - Ultraviolet-curable ink composition, formation of cured coating films and use of ultraviolet-curable ink composition - Google Patents

Abstract

PURPOSE:To provide an ultraviolet-curable ink composition which can be suitably used to form tentative coatings for protecting flexible substrates by using urethane (meth)acrylate oligomer, reactive diluents and ultraviolet-polymerization initiator as the major components. CONSTITUTION:The ultraviolet-curable ink composition comprises (A) 30 to 60wt.% of a urethane oligomer having more than 4,000 molecular weight and bears 2 or 3 (meth)acryloyl groups in one molecule, (B) 10 to 40wt.% of a reactive diluent such as N-vinyl-2-pyrrolidone, polyfunctional (meth)acrylate), and (C) 1 to 10wt.% of an ultraviolet-polymerization initiator such as benzoin, azoisobutyronitrile, as major components. Coating films are formed with the composition, irradiated with ultraviolet rays to give cured, films of 50 to 200kg/cm<2> tensile strength, more than 200% elongation, having rubber elastic properties. When a flexible print circuit is plated, the coating films of the composition are formed on the parts not to be plated and cured by irradiation of ultraviolet rays.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet curable ink composition, a method for forming a cured film and a method for using the ultraviolet curable ink composition.

[0002]

2. Description of the Related Art Flexible printed circuit board
When plating the (FPC board), it is necessary to temporarily protect the parts that do not require plating (non-plating parts). Conventionally, an adhesive tape made by laminating an adhesive on a film such as polyester, polyethylene, polypropylene, etc., or crepe paper was attached to the non-plated part of the FPC board, plated, and then cooled to room temperature. There was a method of peeling off the adhesive tape. There is also a method in which a heat-curable screen printing ink is screen-printed on the non-plated portion of the FPC board, and then heat treatment is performed to cure and form a temporary protective coating film. Then, the FPC board is subjected to plating treatment, and after the plating treatment, the FPC board is cooled to room temperature and the temporary protective coating film is physically peeled off.

[0003]

In the method of attaching the adhesive tape described above, since the non-plating treated portion of the FPC board is scattered, the adhesive tape is cut according to the shape and size of the non-plating treated portion. , Must be pasted.
Further, after the plating treatment, it is necessary to peel off each adhesive tape by hand one by one, which causes a great cost demerit in man-hours, labor and time. In addition, since the adhesive strength of the adhesive tape to the FPC board varies considerably, it is necessary to increase the adhesive strength considerably in order to prevent adhesive failure. Therefore, when peeling the adhesive tape from the FPC board, the flexible FPC board may be bent, which is a cause of failure. Furthermore, when the adhesive tape is peeled from the non-plated part after the FPC board is plated, the adhesive of the adhesive tape is partially transferred to the FPC board side, and the adhesive remains on the FPC board. It is difficult to remove this pressure-sensitive adhesive, which causes a defect.

Next, in the method of using the heat-curable screen printing ink, since the screen-printed ink is heat-cured on the non-plated portion of the FPC board,
The board should be subjected to essentially unnecessary heat treatment. As a result, the FPC board may be thermally deformed due to the heat treatment, which is one of the causes of defects. Furthermore, since the heat-curable screen printing ink requires a heat-curing time of at least about 5 to 10 minutes, the number of man-hours in the pre-treatment step of the plating treatment is large and the pre-treatment ability is deteriorated. It has become a neck. Further, a long heating furnace line must be provided for the heat treatment, which wastes a large amount of space and energy.

An object of the present invention is to enable a cured coating to be easily formed on the surface of an FPC board or the like without heat treatment, and to allow the cured coating to be rapidly peeled from the FPC board or the like.

[0006]

Means for Solving the Problems As a result of earnest research to solve the above problems, the present inventor has blended a urethane (meth) acrylate oligomer, a reactive diluent, and an ultraviolet polymerization initiator in a fixed ratio. It was found that a surprising synergistic effect can be exerted by using as a main component of the ink composition, and the present invention has been completed.

According to the present invention, a urethane oligomer having a molecular weight of 4000 or more and having 2 to 3 acryloyl groups or methacryloyl groups in one molecule is 30 to 60% by weight, a reactive diluent is 10 to 40% by weight, and an ultraviolet ray is used. The present invention relates to an ultraviolet-curable ink composition containing a compounding agent of 1 to 10% by weight as a main component.

Further, according to the present invention, by forming a film of the above ultraviolet curable ink composition and irradiating the film with ultraviolet rays, the tensile strength according to the physical characteristics of the rubber test method of JIS-K-6301 is 50. The present invention relates to a method for forming a cured coating, which comprises a cured coating having a rubber elasticity of about 200 kg / cm ² and an elongation of 200% or more.

Further, in the present invention, when the flexible printed circuit board is plated, a coating film of the above ultraviolet curable ink composition is formed on a portion of the surface of the flexible printed circuit board which does not require plating. The present invention relates to a method for using an ultraviolet-curable ink composition, which comprises forming a cured film by irradiating the film with ultraviolet rays and protecting unnecessary portions of the plating treatment with the cured film.

(Urethane oligomer) "Urethane oligomer having a molecular weight of 4000 or more and having 2-3 acryloyl groups or methacryloyl groups in one molecule" includes polyester type, polyether type, butadiene type and the like. If necessary, one kind or two or more kinds can be used in combination. When the molecular weight of the urethane oligomer is less than 4000, the ultraviolet curable ink composition lacks flexibility as a base oligomer. When a urethane oligomer having a molecular weight of 4000 or more is selected, the above flexibility is exhibited and the flexibility of the FPC board can be followed. As this urethane oligomer,
2 acryloyl groups or methacryloyl groups per molecule
By using one having 3 to 3, the cured film has an appropriate rubber elasticity when it is ultraviolet-cured, and exhibits flexibility.

When a urethane oligomer having a molecular weight of 4,000 or less and four or more acryloyl groups or methacryloyl groups in one molecule is used, the crosslinking density after ultraviolet curing becomes extremely large, and the adhesion and followability to the FPC board is increased. The property is extremely deteriorated and a sufficient cured film cannot be obtained. In addition, the increase in crosslink density causes shrinkage upon curing, which causes deformation of the FPC board. In addition, one (meth) acryloyl group is included in one molecule.
If you use urethane oligomers that you have, there is a problem with ultraviolet curing, the cured coating develops tackiness, and the strength of the cured coating is insufficient, so the cured coating will break when peeled from the FPC board. There's a problem.

When polyester (meth) acrylate or epoxy (meth) acrylate is used as the base oligomer of the UV-curable ink composition, the physical properties of the cured film are such that tensile strength of 200 kg / cm ² or more is exhibited. The growth rate is 10% or less. That is, it has strong plasticity, and when the cured coating is bent, cracks may occur,
When the crosslink density increases, curing shrinkage occurs and the FPC board is deformed, or the adhesion to the FPC board rises and peeling becomes difficult, and the flexibility to follow the FPC board disappears and the adhesion increases. There is a problem of. However, if the urethane oligomer is used as a base oligomer, it can be used as a modifier for the physical properties of the cured film after UV curing.
The above photopolymerizable polyester (meth) acrylate oligomer and epoxy (meth) acrylate oligomer may be blended alone or in combination of two or more.

The reactive diluent used in the present invention may be monofunctional or polyfunctional. For example, N-vinyl-2
-Pyrrolidone, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxylethyl (meth) acrylate, N-acroylmorpholine, dicyclopentanyl (meth) acrylate, isobornyl (meth) ) Monofunctional polymerizable monomers such as acrylate, phenoxyethyl (meth) acrylate, glycidyl (meth) acrylate;
4-butanediol di (meth) acrylate, 1,5-pentanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,8-octanediol di (meth) acrylate, 1,9- Nonanediol di (meth) acrylate, bisphenol A-modified di (meth) acrylate, bis (acryloxy neopentyl glycol) adipate, dicyclopentenyl di (meth) acrylate, hydroxybivalic acid neopentyl glycol di (meth) acrylate, Triethylene glycol di (meth) acrylate, bisphenol F-modified di (meth) acrylate, tripropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethylene oxide adduct tri (meth) acrylate There are polyfunctional (meth) acrylates such as acrylate, pentaerythritol tetra (meth) acrylate and dipentaerythritol hexa (meth) acrylate. If necessary, one kind or two or more kinds can be used in combination.

The amount of the reactive diluent used here is 10 to 40% by weight. If it is less than 10% by weight, the viscosity of the ink composition becomes too high, which is not practical as a printing ink. On the other hand, if it is more than 40% by weight, the crosslink density of the ink composition becomes extremely high, the curing shrinkage becomes large, the FPC board is deformed, and the adhesion to the FPC board becomes problematic, which is not preferable. As the reactive diluent, it is preferable to use a monofunctional or difunctional polymerizable monomer in order to secure rubber elasticity from the viewpoint of physical properties of a cured film after irradiation with ultraviolet rays.
However, from the viewpoint of curability, a required amount of a trifunctional or higher polymerizable monomer may be blended and used.

As the UV polymerization initiator, benzoin,
Benzoin alkyl ether, benzyl, benzyl methyl ketal, benzophenone, Michler's ketone, azoisobutyronitrile, 1-azobis-1-cyclohexanecarbonitrile, naphthalenesulfonyl chloride,
There are anthraquinones, biimidazoles, amylphosphine oxides, and thioxanthones. If necessary, one kind or a combination of two or more kinds is used. As for the mixing ratio,
1 to 10% by weight. If it is less than 1% by weight, the curability of the ink composition is poor, and if it is more than 10% by weight, the cost for producing the ink composition becomes too high, which is not preferable.

A photopolymerizable oligomer, a synthetic resin, a filler, a pigment, a defoaming agent, a leveling agent, a release agent, and a release agent can be added to the ink composition of the present invention, if necessary. p-
Sensitization aids for tertiary amines such as dimethylaminobenzoic acid ethyl ester and p-dimethylaminobenzoic acid isoamyl ester can be used in an amount of 30 to 100% by weight of the UV polymerization initiator. As the filler, commercially available inorganic fillers and organic fillers can be used, but from the aspect of UV transparency, printability as an ink composition, physical properties of the cured film after UV irradiation, 10 to 35% by weight. It can be used in combination. Various additives such as a flow control agent for imparting printability, a defoaming agent for keeping the film state constant, and a leveling agent can be blended in an amount of 0.2 to 4.0% by weight, if desired.

When releasing the cured coating film after UV irradiation from the FPC board, a commercially available release agent,
A release agent such as a fluorine-based resin, a silicone-based resin, an acrylic resin, a fatty acid-based metal soap, a surfactant, or a wax can be compounded and used as a release agent.
If this release agent is used in an amount of 0 to 5% by weight, an appropriate release force of the cured film can be obtained. The ultraviolet curable ink composition of the present invention can be obtained by kneading and dispersing the mixture of the above-mentioned raw materials by an appropriate method such as a roller mill.

[0018]

According to the ultraviolet curable ink composition of the present invention,
Since the above urethane oligomer is used as the base oligomer, a cured coating having flexibility and rubber elasticity capable of following a flexible substrate such as an FPC board can be obtained.
Moreover, by incorporating the reactive diluent, a cured film having a desired tensile strength can be obtained. As described above, according to the ultraviolet curable ink composition of the present invention, a cured coating suitable for a flexible substrate such as an FPC board can be formed.
As a result, there is no problem of extremely complicated work, bending of the FPC board or the like, and remaining of the adhesive on the surface of the FPC board, which would occur when using an adhesive tape. Further, unlike the case of using the heat-curable screen printing ink, it is not necessary to heat the FPC board or the like.

[0019]

EXAMPLES Specific experimental results will be described below. (Production of UV-curable ink composition of each example) The oligomer, the reactive diluent, the UV polymerization initiator, and the defoaming agent shown in Table 1 were blended, mixed with stirring, and dissolved to obtain a uniform solution.
Inorganic filler is added to this homogenized solution and mixed by stirring, and this mixture is kneaded twice with a three-roll mill,
Each component was dispersed to obtain an ultraviolet curable ink composition.

[0020]

[Table 1]

Here, each numerical value shown in Table 1 represents "% by weight". Moreover, each component shown in Table 1 is shown below. Urethane acrylate oligomer A: molecular weight is 1700
0. There are two acryloyl groups per molecule. Simplified structural formula:

[Chemical 1] R ₁ is a diol residue, R ₂ is a polyisocyanate residue, R ₃
Is a polyol residue. Urethane acrylate oligomer B: The molecular weight is 4000. The number of acryloyl groups per molecule is 2. Simplified structural formula:

[Chemical 2] R ₁ is a diol residue, R ₂ is a polyisocyanate residue, R ₃
Is a polyol residue. Urethane acrylate oligomer C: The molecular weight is 4000. The number of acryloyl groups per molecule is 4. Simplified structural formula:

[Chemical 3] R ₁ is a polyol residue and R ₂ is a polyisocyanate residue. Polyester acrylate oligomer: "Aronix
M-8060 "(manufactured by Toagosei Chemical Industry Co., Ltd.) Epoxy acrylate oligomer:" lipoxy SP-1509
"(Showa Highpolymer Co., Ltd.) Reactive Diluent A: Isobornyl Acrylate Reactive Diluent B:" 1,6-HX-A "(Kyoeisha Oil and Fat Chemical Co., Ltd.), 1,6- Hexanediol diacrylate UV polymerization initiator A: “Darocuta 1173” (manufactured by Merck) UV polymerization initiator B: “Irgacure 651” (manufactured by Ciba Geigy) Inorganic filler: “Nipseal VN ₃ ” (Nippon Silica) Defoamer: "Polyflow No.460" (manufactured by Kyoeisha Oil and Fat Chemical Co., Ltd.)

(Evaluation of UV-curable ink composition) The ink composition of each example was treated with 80 mesh tetron gauze, emulsion and film thickness.
Printing was performed on the following adherend using a screen printing plate prepared under the condition of 200 μm. As the adherend, in the test items shown below, for peelability test, plating resistance test
An ink composition was printed on the polyimide surface using a copper-clad polyimide laminated film for FPC (FPC board). In addition, the ink composition was printed on the release-treated surface of the polyester film which was release-treated on one side for tensile strength, elongation, and 180-degree bending test.

After printing, each adherend was placed on a belt conveyor, and the printing surface was irradiated with ultraviolet rays to cure each ink composition. As the high-pressure mercury lamp, an air-cooled type, 80 W / cm space 3-lamp type manufactured by Oak Manufacturing Co., Ltd. was used. The height of the lamp was 15 cm from the belt surface, and the speed of the belt conveyor was 4 m / min. The following test items were evaluated for each example. The evaluation results are shown in Table 2.

(Tensile Strength, Elongation) The cured coating was removed from the release-treated polyester film and used as a test piece. According to the rubber test method of JIS-k-6301, the test piece was punched with dumbbell No. 3, and the tensile strength and the elongation rate were measured with a tensometer (manufactured by Monsanto Co.) at a pulling speed of 500 mm / min. (180 degree bendability) The cured coating was removed from the release-treated polyester film and used as a test piece. A test piece was punched out to a length of 100 mm and a width of 25 mm, and the length was set on a flat plate.
It was bent 180 degrees starting from the midpoint of 50 mm, and the occurrence of cracks and cracks at the bent portion was visually observed.

(Peelability) After forming a cured coating on the FPC board, plating treatment was performed and the cured coating was peeled by hand.
It was visually observed whether or not the cured coating film was torn during peeling and the cured film component remained on the FPC board after peeling. In Table 2, the mark "○" indicates that the cured film can be easily peeled off from the FPC board. The "X" mark indicates that the FPC board is deformed or the FP
Shows that it is lifted from the C board and cannot be peeled off. (Plating resistance) After forming a cured film on the FPC board,
It was immersed in an electrolytic plating solution and plated. After the plating process, it was confirmed whether the hardened film was deteriorated or the plating solution entered the gap between the hardened film and the FPC board. However, in Comparative Examples 1 to 3, the cured coating cures and shrinks,
The plating resistance test was not performed because the FPC board was deformed. In Table 2, the mark "○" indicates that after the FPC board was plated, the cured coating was not deteriorated, the cured coating could be easily peeled off, and the FPC board after peeling had no abnormalities. (Printability) Printing was performed with a 200 mesh Tetoron (diagonal), screen plate having an emulsion film thickness of 200 μm, and the defoaming property and leveling property of the printed film were visually observed. In Table 2, the mark “◯” indicates that both the defoaming property and the leveling property are good. The mark “Δ” indicates that the defoaming property and the leveling property became good over time.

[0026]

[Table 2]

In Comparative Examples 1, 2, 3 and 4, the cured film was too hard and the elongation was small. Therefore, if you bend it 180 degrees,
Cracking occurs in the cured film and peeling is difficult. In the examples of the present invention, all the properties are good, and the tensile strength of the cured film is sufficiently large, and a flexible film having a large elongation is obtained.

[0028]

According to the ultraviolet curable ink composition of the present invention, since the urethane oligomer is used as the base oligomer, a cured film having flexibility and rubber elasticity capable of following a flexible substrate such as an FPC board. Is obtained. Moreover, by incorporating the reactive diluent, a cured film having a desired tensile strength can be obtained. This cured coating is compatible with flexible substrates such as FPC boards, and can be easily peeled off without bending such substrates. Also, plating resistance is good,
Easy to print.

As a result, there is no problem of extremely complicated work, bending of the FPC board or the like, and remaining of the adhesive on the surface of the FPC board, as in the case of using the adhesive tape. Moreover, because it is possible to form a cured coating suitable for FPC boards by irradiating the printed film with ultraviolet light, there is no need to heat-treat the FPC boards, unlike the case of using heat-curable screen printing ink. .. Therefore, the deformation of the substrate due to heating does not occur, and a heating furnace that takes up space is not required. Therefore, it does not require space, energy, large heating and cooling equipment,
Extremely high productivity. For these reasons, the present invention is extremely useful in industry.

Claims (3)

[Claims] 1. The molecular weight is 4000 or more, and 2 in 1 molecule.
~ 3 to 60 wt% urethane oligomer having 3 acryloyl groups or methacryloyl groups, 10 ~ reactive diluent
An ultraviolet-curable ink composition, which comprises a mixture of 40% by weight and 1 to 10% by weight of an ultraviolet polymerization initiator as a main component. 2. A tensile strength according to the physical properties of the rubber test method of JIS-K-6301 is 50 to 50 by forming a film of the ultraviolet curable ink composition according to claim 1 and irradiating the film with ultraviolet light. A method for forming a cured film, which comprises a cured film having a rubber elasticity of 200 kg / cm ² and an elongation of 200% or more. 3. When the flexible printed circuit board is plated, a film of the ultraviolet curable ink composition according to claim 1 is formed on a portion of the surface of the flexible printed circuit board that does not require plating. A method of using an ultraviolet-curable ink composition, which comprises forming a cured film by irradiating the surface with ultraviolet light and protecting the unnecessary portions of the plating treatment with the cured film.