JP2009116170A - Pressure-sensitive adhesive tape for photomask protection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive tape for high-resolution photomask protection which is excellent in re-peelability (properties of leaving no paste on adherend after peeling), and avoids entry of bubbles even when the pressure-sensitive adhesive tape is stuck on a photomask with a complex pattern having fine dots and thin lines arranged at narrow intervals. <P>SOLUTION: The pressure-sensitive adhesive tape for photomask protection is obtained by disposing, on one surface of a transparent base material (A), a pressure-sensitive adhesive layer (B) comprising a pressure-sensitive adhesive containing an acrylic ester-based resin of which the weight average molecular weight measured as molecular weight in terms of polystyrene by GPC is 1,000,000-2,000,000 and a crosslinking agent, wherein the acrylic ester-based resin is a specific resin and an amount of tensile shear displacement of the pressure-sensitive adhesive layer (B) is 8-25 μm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an adhesive tape for protecting a photomask, and in particular, is excellent in removability (performance that does not leave adhesive residue on an adherend when peeled off), is complex, has small dots, and has thin lines. The present invention relates to a high-resolution photomask protective adhesive tape in which bubbles are not mixed even if a photomask protective adhesive tape is attached to a photomask having a pattern with a narrow interval.

  Fabrication of a printed wiring board includes a step of curing a photoresist by irradiating light from a photomask that is an original for exposure after adhering an adhesive photoresist such as a liquid photoresist. In this process, if the photomask is in direct contact with the photoresist, a part of the photoresist may be transferred to the surface of the photomask when the photomask is peeled off after completion of exposure, and may not be reused. is there. Therefore, conventionally, a photomask protective adhesive tape has been attached to the surface of the photomask facing the photoresist to prevent the photomask from being contaminated or scratched.

  Photomask protective adhesive tape is required to have various performances such as removability, antistatic property, release layer durability, light transmission, etc. Among them, the irradiated light can surely transmit in parallel. Parallel light transmission is most important. For curing the photoresist, ultraviolet rays having a wavelength of 400 nm or less are often used as a light source. For this reason, the transmittance | permeability of the ultraviolet-ray with a wavelength of 400 nm or less is important for the adhesive tape for photomask protection. Also, if the photomask protective adhesive tape has a lot of scattered light (has a high haze value), the parallel ultraviolet light transmission will be insufficient, and the irradiated ultraviolet rays will not reach the photoresist in a sufficiently parallel manner. There were problems such as the occurrence of dimensional defects. Therefore, Patent Document 1 is improved by proposing a photomask-protecting adhesive tape with good transmittance, characterized in that the haze value at a wavelength of 350 nm is 3% or less.

  However, in recent years, more complicated circuit formation is becoming mainstream with the increase in added value of circuits formed on a printed wiring board. For this reason, in conventional photomask protective adhesive tape, bubbles are mixed when the photomask protective adhesive tape is applied to a photomask with a pattern of small dots, fine lines, and narrow line spacing. There is a problem that bubbles are scattered by acting as a lens, the resolution is lowered, and the circuit pattern is disconnected.

JP 2003-206454 A

  The object of the present invention is excellent in removability, complicated, small dots, thin lines, and even if a photomask with a photomask having a pattern with a narrow space between lines is attached to the photomask protective adhesive tape. It is an object of the present invention to provide a high-resolution photomask protective adhesive tape that does not mix.

As a result of intensive studies in order to achieve the above object, the present inventors have obtained a pressure-sensitive adhesive containing a specific acrylic ester resin and a crosslinking agent on one side of a transparent substrate (A). The above-described bubble and resolution are provided by a photomask protecting adhesive tape provided with an adhesive layer (B) having a 200 g load tensile shear displacement amount of 8 to 25 μm by a specific measurement method at a thickness of 4 μm. And found that the problem is solved.
These findings have been further studied and the present invention has been completed.

That is, according to the first invention of the present invention, an acrylic ester resin having a weight average molecular weight of 500,000 to 1,500,000 measured as a polystyrene-equivalent molecular weight by the GPC method on one side of the transparent substrate (A). And a pressure-sensitive adhesive tape for photomask protection comprising a pressure-sensitive adhesive layer (B) comprising a pressure-sensitive adhesive containing a crosslinking agent,
The acrylic ester resin is obtained by copolymerizing a vinyl monomer having a hydroxyl group or a carboxyl group, the main component of which is a (meth) acrylic ester monomer having 4 to 12 carbon atoms in the alkyl group. And
The pressure-sensitive adhesive layer (B) has a thickness of 4 μm and a tensile shear displacement amount of 8 to 25 μm at a load of 200 g.
In the present invention, “(meth) acrylate” means “methacrylate or acrylate”. Similarly, “(meth) acrylic acid” means “methacrylic acid or acrylic acid”, and “tensile shear displacement” means JIS having a width of 5 mm using a Yamamoto-type cohesive force measuring device. A 25 mm × 5 mm pressure-sensitive adhesive tape for photomask protection is pressed on a mirror-finished flat plate made of SUS304 steel plate specified in G4305, and a load of 17 g is applied to both ends of the pressure-sensitive adhesive tape for photomask protection immediately after pressure bonding via a thread. After that, a measurement load of 200 g is further added to one of the loads, which means a deviation between the flat plate and the photomask protecting adhesive tape that occurs after 30 seconds.

  According to a second aspect of the present invention, in the first aspect, the (meth) acrylic acid ester monomer is butyl acrylate and / or 2-ethylhexyl acrylate. An adhesive tape for mask protection is provided.

  According to the third invention of the present invention, in the first or second invention, the vinyl monomer is 2-hydroxyethyl (meth) acrylate and / or (meth) acrylic acid. An adhesive tape is provided.

  According to a fourth aspect of the present invention, there is provided the pressure-sensitive adhesive tape for photomask protection according to any one of the first to third aspects, wherein the crosslinking agent is an isocyanate compound.

According to a fifth invention of the present invention, in any one of the first to fourth inventions, the adhesive is obtained by immersing an adhesive whose weight has been measured in advance in ethyl acetate at 23 ° C. for 24 hours. Then, when the residue taken out from ethyl acetate and filtered through a 200 mesh wire net was dried at 110 ° C. for 1 hour, the gel fraction (Y) represented by the following formula was 50 to 75% by weight. An adhesive tape for protecting a photomask is provided.
Y = 100 × W2 / W1
(W1 means the initial weight of the pressure-sensitive adhesive measured before dipping, and W2 means the remaining weight of the pressure-sensitive adhesive after dipping and drying.)

  According to a sixth invention of the present invention, in any one of the first to fifth inventions, the pressure-sensitive adhesive layer (B) has a thickness of 2 to 9 μm, and is a photomask protecting pressure-sensitive adhesive tape. Is provided.

  According to the pressure-sensitive adhesive tape for protecting a photomask of the present invention, in the first invention, a (meth) acrylic acid ester monomer having 4 to 12 carbon atoms in the alkyl group is formed on one side of the transparent substrate (A). 200 g by a specific measuring method at a thickness of 4 μm, comprising a pressure-sensitive adhesive containing an acrylic ester resin obtained by copolymerizing a vinyl monomer having a hydroxyl group or a carboxyl group and a crosslinking agent. Since it is an adhesive tape for protecting a photomask provided with an adhesive layer (B) having a load tensile shear displacement amount of 8 to 25 μm, it is easy to remove and is complicated, has small dots, thin lines, Effect of high-resolution photomask protective adhesive tape that does not contain bubbles even when a photomask protective adhesive tape is applied to a photomask with a narrow line spacing pattern There is.

In the second invention, since the (meth) acrylic acid ester monomer is specified to be butyl acrylate and / or 2-ethylhexyl acrylate, the above effects can be further improved. There is an effect.
In the third invention, since the vinyl monomer is specified to be 2-hydroxyethyl (meth) acrylate and / or (meth) acrylic acid, the above effect can be further improved. There is an effect that can be done.

  In the fourth aspect of the invention, since the crosslinking agent is specified as an isocyanate compound, the above-described effects can be further improved, and the peel stress generated by the deformation of the adherend can be used. There is an effect that the pressure-sensitive adhesive tape is a photomask protecting pressure-sensitive adhesive tape comprising a preferable pressure-sensitive adhesive layer (B) in that it can be made difficult to peel off from the bag.

  Moreover, in the fifth invention, since the adhesive is specified as a photomask protecting adhesive tape having a gel fraction (Y) of 50 to 75% by weight, the above effect is obtained. There is an effect that the performance can be further improved.

  Moreover, in the sixth invention, since the pressure-sensitive adhesive layer (B) has been specified as having a thickness of 2 to 9 μm, there is an effect that the above effect can be further improved.

Hereinafter, the adhesive tape for protecting a photomask of the present invention will be described in detail.
The pressure-sensitive adhesive tape for protecting a photomask of the present invention is one in which a pressure-sensitive adhesive layer (B) is provided on one side of a transparent substrate (A).
1. Base material (A)
In the present invention, the transparent base material (A) may be any material having a high transmittance of ultraviolet rays used in exposure. For example, polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polypropylene, A polymer film having excellent transparency made of a resin such as polyethylene, polyvinyl chloride, polystyrene, polycarbonate, triacetyl cellulose, polyimide, and acrylic is preferably used. In particular, a biaxially stretched PET film is preferably used because of its excellent mechanical strength and dimensional stability.

  The thickness of the substrate film can be appropriately determined in consideration of light transmittance, handling properties, and the like. Specifically, the thickness is preferably 2 to 50 μm, more preferably 4 to 12 μm. If the thickness is less than 2 μm, the strength of the tape may be insufficient and handling may be difficult, and wrinkling may occur when the tape is applied. If the thickness exceeds 50 μm, sufficient light transmission may not be obtained.

  Moreover, in order for the transparent base film of this invention to improve adhesiveness with an adhesive layer, it can surface-treat on a transparent base film. For example, there are discharge treatments such as corona treatment and plasma treatment. In order to perform uniform treatment on a thin base material, a weak discharge with low processing energy is desirable to prevent problems such as base material breakage and perforation. As another method, saponification treatment with alkali is known.

2. Adhesive layer (B)
The pressure-sensitive adhesive layer (B) used in the present invention is affixed to the surface of an exposure original document that is a photomask, and has a weight average molecular weight of 500,000 to 1,500,000 measured as a polystyrene-converted molecular weight by the GPC method. It consists of an adhesive containing an acrylic ester resin and a crosslinking agent.
Furthermore, the pressure-sensitive adhesive layer (B) is required to have a 200 g load tensile shear displacement amount of 8 to 25 μm at a thickness of 4 μm in a specific measurement method.
The amount of tensile shear displacement is determined by using a 25 mm × 5 mm photomask protective adhesive tape on a mirror-finished flat plate of SUS304 steel specified in JIS G4305 of 5 mm width using a Yamamoto-type cohesive force measuring device. Immediately after the pressure bonding, a load of 17 g is applied to both ends of the pressure-sensitive adhesive tape for photomask protection via a thread, and then a measurement load of 200 g is further added to one of the loads, and the flat plate generated after 30 seconds and the above-mentioned It means deviation from the photomask protective adhesive tape.

(1) Raw material of pressure-sensitive adhesive Among the pressure-sensitive adhesives used in the present invention, a specific acrylic pressure-sensitive adhesive is particularly optimal.
The acrylic pressure-sensitive adhesive is obtained by crosslinking an acrylic ester resin (hereinafter also referred to as “acrylic copolymer”) with a crosslinking agent. In the present invention, “(meth) acrylic acid” means “methacrylic acid or acrylic acid”.

(I) Acrylic ester resin As the acrylic ester resin constituting the pressure-sensitive adhesive of the present invention, the main component is a (meth) acrylic ester monomer having 4 to 12 carbon atoms in the alkyl group, It is obtained by copolymerizing a vinyl monomer having a carboxyl group.
Examples of the (meth) acrylic acid ester having 4 to 12 carbon atoms of the alkyl group that provides adhesiveness include butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, and the like. Even if it is used independently, 2 or more types can also be used together. Of these, butyl acrylate and -2-ethylhexyl acrylate are preferable from the viewpoint of low Tg and viscoelasticity.
Examples of vinyl monomers having a hydroxyl group or a carboxyl group that form a cross-linked structure between the main chains of the acrylic ester resin include (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid glycidyl, and allyl glycidyl ether. Etc. The vinyl monomer containing a hydroxyl group or a carboxyl group is preferably (meth) acrylic acid-2-hydroxyethyl when an isocyanate compound capable of enhancing the cohesive strength of the acrylate resin is used as a crosslinking agent. .
When the amount of (meth) acrylic acid-2-hydroxyethyl is small, the crosslinking points are reduced, and even when a crosslinking agent is used, the gel fraction is lowered and the adhesive residue is generated. If the blending amount is too large, the amount of tensile shear displacement is lowered and foaming becomes worse. For this reason, as a desirable range, it is 0.01-5 weight part with respect to 100 weight part of the (meth) acrylic acid ester monomer which is a main component.
As the vinyl monomer having a carboxyl group that increases the cohesive strength of the (meth) acrylic acid ester having 4 to 12 carbon atoms of the alkyl group and improves the adhesive force, (meth) acrylic acid, crotonic acid, maleic acid, Examples include itaconic acid. Of these, acrylic acid is preferred from the viewpoint of adhesive performance. If the amount of acrylic acid is too large, the adhesive strength becomes too large, making it difficult to remove again, and if it is too small, it may be peeled off from the photomask during use and may become unusable. For this reason, as a desirable range, it is 0.05-5 weight part with respect to 100 weight part of (meth) acrylic acid ester monomers which are main components.

(Ii) Crosslinker
The crosslinking agent is not particularly limited, and examples thereof include an isocyanate crosslinking agent, an aziridine crosslinking agent, an epoxy crosslinking agent, and a metal chelate crosslinking agent. Among these, an isocyanate-based crosslinking agent is preferable from the viewpoint that the pressure-sensitive adhesive layer formed by this pressure-sensitive adhesive can be made difficult to peel from the adherend due to the peeling stress caused by the deformation of the adherend. As the isocyanate crosslinking agent, a polyfunctional isocyanate compound containing two or more isocyanate groups in the molecule is used. For example, tolylene diisocyanate, hydrogenated tolylene diisocyanate, naphthylene-1,5-diisocyanate, diphenylmethane diisocyanate, Hexamethylene diisocyanate, trimethylolpropane modified tolylene diisocyanate, triphenylmethane triisocyanate, methylenebis (4-phenylmethane) triisocyanate and the like.
In addition, since the isocyanate compound is highly reactive and dangerous when touched with steam, a modified isocyanate having a low vapor pressure and high safety is preferably used, and a commercially available product is manufactured by Sumika Bayer Urethane Co., Ltd. And “Coronate (registered trademark) L-45” manufactured by Nippon Polyurethane Industry Co., Ltd. are preferably used.

  A crosslinking agent may be used independently and may be used together 2 or more types. When the amount of the crosslinking agent added decreases, the tensile shear displacement amount of the resulting acrylic pressure-sensitive adhesive layer increases, but the gel fraction decreases, and adhesive residue on the photomask tends to occur during re-peeling and increases. The gel fraction of the resulting acrylic pressure-sensitive adhesive is high, and adhesive residue on the photomask is less likely to occur during re-peeling, but the tensile shear displacement is reduced and bubbles are more likely to occur when a photomask is applied. It is necessary to mix appropriately in the range of about 0.01 to 5 parts by weight with respect to 100 parts by weight of the acrylic copolymer.

(Iii) Other ingredients
In the present invention, a so-called tackifying resin component can be blended and used in order to improve the adhesive strength. The tackifier resin component is a substance that is mixed with an elastomer to improve the adhesive function, and is usually an amorphous oligomer having a molecular weight of several hundred to several thousand and is a liquid resin or a solid thermoplastic resin at room temperature.
The tackifying resin component usually has an influence on the transmittance and haze because it inhibits the transmission of light, so care must be taken when selecting it. For example, there are rosin-based resins, terpene phenol-based resins and the like that achieve small adhesiveness and light adhesion and small adhesiveness.

(Iv) Method for producing acrylic ester resin
In order to obtain the acrylic copolymer, a main component and other components may be mixed and subjected to radical reaction in the presence of a polymerization initiator. In addition, as a polymerization method, a conventionally well-known method is used, for example, solution polymerization, emulsion polymerization, suspension polymerization, block polymerization, etc. are mentioned.
The polymerization initiator is not particularly limited. For example, di (t-hexylperoxy) trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5-dimethyl-2 , 5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxylaurate, and the like, and t-hexylperoxypivalate (“Perhexyl (registered trademark) PV” Japanese fat product) preferable. In addition, the said polymerization initiator may be used independently, or 2 or more types may be used together.

(V) Weight average molecular weight of acrylic ester resin
The weight average molecular weight of the acrylate-based resin of the present invention thus polymerized is a weight average molecular weight measured as a polystyrene equivalent molecular weight by a GPC (Gel Permeation Chromatography) method. Specifically, an acrylic copolymer is dissolved in tetrahydrofuran to form a 0.5 to 1.0% by weight solution, and separated by a gel-filled column using tetrahydrofuran as a dispersion medium. It is calculated | required by measuring the relationship of a rate with a gel permeation chromatograph. As said gel permeation chromatograph, what is marketed as a brand name "2690 separation module" from Water company etc. can be used, for example.

  As for the weight average molecular weight of the acrylic copolymer, it is necessary that the weight average molecular weight measured as the polystyrene-reduced molecular weight by the GPC method is 500,000 to 1,500,000. Preferably, it is 700,000 to 1,200,000. When the molecular weight is less than 500,000, adhesive residue tends to occur due to an increase in low molecular weight, and when it exceeds 1.5 million, the amount of tensile shear displacement tends to decrease, and it is difficult to adjust by the amount of crosslinking agent. In the acrylic ester resin, a desirable molecular weight can be obtained by adjusting the blending amount of the crosslinking agent, the polymerization initiator, the polymerization solvent, the monomer (monomer) concentration, the amount of the chain transfer agent, and the polymerization temperature.

(2) Gel fraction of the pressure-sensitive adhesive As a method for measuring the gel fraction of the pressure-sensitive adhesive of the present invention, the pressure-sensitive adhesive is applied to a release film in the same manner as the production of the photomask-protecting pressure-sensitive adhesive tape, and transparent to the bonding. Cover with a release film instead of a PET substrate and cure at 40 ± 2 ° C. for 4 days. The pressure-sensitive adhesive of the present invention was sampled, previously weighed, immersed in ethyl acetate at 23 ° C. for 24 hours, and then filtered through a 200-mesh wire mesh. The residue after drying was dried at 110 ° C. for 3 hours. The weight ratio is calculated as a gel fraction (Y) using the following formula as a percentage.
Y (% by weight) = 100 × W2 / W1
(W1: Weight of adhesive measured before immersion, W2: Residual weight of adhesive after immersion and drying)

  If the gel fraction of the pressure-sensitive adhesive in the present invention is high, it will be easy to peel off from the adherend, so there will be no adhesive residue at the time of re-peeling, but bubbles will remain when sticking the pressure-sensitive adhesive. Conversely, when the gel fraction is low, bubbles do not enter, but the glue remains when re-peeling. Therefore, in the present invention, when the weight average molecular weight of the acrylate resin is 500,000 to 1,500,000, the gel fraction of the pressure-sensitive adhesive is preferably 50 to 75% by weight, and more preferably 55 to 70% by weight. If it is less than 50% by weight, the paste tends to remain on the photomask, and if it exceeds 75% by weight, bubbles tend to enter. In the appropriate range of the relationship between the weight average molecular weight of the acrylic ester resin and the gel fraction of the pressure-sensitive adhesive, the problem of bubbles and adhesive residue (removability) as described above is more preferably solved.

(3) Method for forming pressure-sensitive adhesive layer (B) As a method for forming the pressure-sensitive adhesive layer, the pressure-sensitive adhesive is prepared, used as it is as a pressure-sensitive adhesive solution, and this pressure-sensitive adhesive solution is applied to a substrate. The pressure-sensitive adhesive layer can be formed by completely drying and removing the solvent in the pressure-sensitive adhesive solution.
As a method for forming the pressure-sensitive adhesive layer, it is possible to use a method in which a pressure-sensitive adhesive is directly applied to one side of a separator and dried using a roll coater such as a gravure, a comma coater, or a die coater.
Moreover, at the time of manufacture of an adhesive solution, additives, such as a tackifier, a plasticizer, a stabilizer, and an ultraviolet absorber, can be added as necessary. These are preferably blended within a range that does not impair optical properties such as light transmittance and hue.

  A preferable thickness of the pressure-sensitive adhesive layer is 2 to 9 μm. If it is less than 2 μm, the adhesive strength to the photomask may be insufficient, bubbles may easily be caught in the unevenness of the photomask, and if it exceeds 9 μm, sufficient light transmission may not be obtained. In an exposure apparatus using scattered light, the resolution of the pattern may be affected.

  In addition, about the tensile shear displacement amount of this invention explained in full detail below, it has prescribed | regulated by the displacement amount per 4 micrometers in thickness of the adhesive layer of a general product.

(4) Tensile shear displacement amount of the pressure-sensitive adhesive layer (B) The tensile shear displacement amount in the cohesive force test of the pressure-sensitive adhesive layer is obtained when the pressure-sensitive adhesive layer (B) has a thickness of 4 μm and is smaller than 8 μm. When the tape is pasted on the photomask, bubbles easily enter. When the adhesive mask for protecting the photomask obtained when the tape is larger than 25 μm is pasted on the photomask, the bubbles are difficult to enter, but the adhesive remains on the photomask at the time of re-peeling. ˜25 μm is preferred.

  In addition, the measurement of the amount of tensile shear displacement after 30 seconds using the Yamamoto-type cohesive force measuring device of the pressure-sensitive adhesive tape for photomask protection requires measurement in a state where the performance of the pressure-sensitive adhesive layer is stable. For this reason, the measurement is carried out after curing for 4 days in an environment of 40 ± 2 ° C. after forming the adhesive. This is because variations in measured values occur if the crosslinking reaction of the pressure-sensitive adhesive does not proceed sufficiently.

  The Yamamoto-type cohesive force measuring apparatus used in the present invention is commercially available from, for example, a measuring machine manufactured by Asahi Seiko Co., Ltd., and can obtain measured values in units of μm. As shown in FIG. 1, a measuring method of the tensile shear displacement amount in the cohesive force test is a stainless steel plate (JIS width 25 × length 5 mm) as shown in FIG. 1 under the environmental condition of temperature 23 ± 2 ° C. and relative humidity 50 ± 5%. A SUS304 steel plate specified in G4305 and a mirror-finished flat plate (1) is fixed, and this is placed and pasted at approximately the center of a photomask protective tape having a width of 25 × 200 mm so that the entire surface is in contact with the entire width. In addition, 21 is a base material layer, 22 is an adhesive layer, 20 is an adhesive tape for photomask protection. At this time, a polyethylene terephthalate film (PET) 5 is provided so that the photomask adhesive tape does not stick between the pulleys 3. Next, a 200 g weight 41 is added to one weight mounting jig 40, and the displacement after 30 seconds is measured by the detection means. Further, the displacement of the PET of the photomask protective tape is negligible.

3. Photomask protective tape
The pressure-sensitive adhesive tape for protecting a photomask of the present invention is one in which a pressure-sensitive adhesive layer (B) is provided on one side of a transparent substrate (A). In order to prevent sticking to another member or adhesion of dust to the pressure-sensitive adhesive layer, a release film may be releasably laminated on the surface of the pressure-sensitive adhesive layer.
Further, if necessary, an intermediate layer provided for improving the adhesion of each layer or an antistatic layer having a role of preventing the tape from being charged and attracting dust in the air may be provided.
The pressure-sensitive adhesive tape for protecting a photomask of the present invention is produced by providing the pressure-sensitive adhesive layer (B) on one side of the substrate (A) by the method as described above. Even when an intermediate layer or an antistatic layer is provided as necessary, these layers are stacked, and these layers are stacked or pressed simultaneously or simultaneously with a rubber roller to protect the photomask on which the layers are stacked. A method for obtaining a pressure-sensitive adhesive tape for use in the present invention.

The adhesive tape for protecting a photomask of the present invention thus obtained has excellent removability, is complex, has a small dot, a thin line, and a photomask on which a pattern having a narrow line interval is drawn. There is an effect that it is a high-resolution photomask protective adhesive tape in which bubbles do not enter even when a protective adhesive tape is applied.
Therefore, the pressure-sensitive adhesive tape for protecting a photomask of the present invention can be suitably used as a surface protective pressure-sensitive adhesive sheet for protecting the surface of a photomask used for manufacturing a circuit board.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

(Examples 1-5, Comparative Examples 1-4)
Examples 1 to 5 and Comparative Examples 1 to 4 of the present invention will be described below.
1. Preparation of adhesive solution and manufacture of adhesive tape for photomask protection
(Creation of acrylic acid copolymer)
A reactor equipped with a thermometer, a stirrer, and a cooling tube was prepared. A predetermined amount of monomer and ethyl acetate shown in Table 1 were added to the reactor, and N ₂ was added from the bottom of the reactor for one hour. Thereafter, the liquid temperature was set to 70 ° C. To this was added t-hexyl peroxypivalate ("perhexyl PV" Japanese fat product) as a polymerization initiator, and polymerization was carried out in an N ₂ atmosphere to obtain a solution of an acrylic acid copolymer having a weight average molecular weight shown in Table 1. It was.

(Acrylic adhesive formulation)
Next, with respect to 100 parts by weight of the solid content of the acrylic copolymer solution, an isocyanate-based crosslinking agent (trade name “Coronate L-55” manufactured by Nippon Polyurethane Co., Ltd.) was blended as shown in Table 1 in terms of solid content. The mixture was uniformly mixed and crosslinked to obtain an acrylic pressure-sensitive adhesive solution.

(Creation of adhesive tape)
The above-mentioned pressure-sensitive adhesive solution was applied to the release treated surface of a polyethylene terephthalate film having a film thickness of 25 em. After coating, it was dried at 120 ° C. for 60 seconds, and after drying, a pressure-sensitive adhesive layer having a thickness of 4 (8) μm was provided. Next, the pressure-sensitive adhesive layer was laminated with a biaxially stretched transparent PET base film (“F53 # 6C” manufactured by Toray Industries, Inc.) having a thickness of 6 μm to prepare a pressure-sensitive adhesive tape for photomask protection. Moreover, the adhesive was apply | coated to the release film similarly to photomask protective tape preparation for the measurement of a gel fraction, and the sample which covered the release film instead of the transparent PET base material for bonding was created. Table 1 shows the gel fraction of the acrylic pressure-sensitive adhesive sheet obtained by curing these at 40 ± 2 ° C. for 4 days and the tensile shear displacement amount in the cohesive force test.

2. Evaluation
(Evaluation of remaining foam)
Line-and-space (L / S) 50 μm / 50 μm pattern photomask for testing (manufactured by Kodak Company: ARD-7) and the prepared adhesive mask for photomask protection laminating machine DH-5100 (manufactured by FTM) Was bonded at a speed of 1.0 m / min and a laminating pressure of 0.3 MPa. Then, about this test sample, the foamed state immediately after and 4 hours after was evaluated with the microscope. The results are shown in Table 1, and the evaluation criteria are shown in Table 2. In addition, Table 3 shows a specific example of evaluation criteria using a microscope.

(Adhesive residue evaluation)
For the sample prepared under the same conditions as the bubble remaining evaluation, after 40 days at 40 ° C., the photomask is fixed with double-sided tape, and the photomask protecting adhesive tape is perpendicular to the photomask at an angle close to 90 degrees. The adhesive was removed by hand as soon as possible, and the presence or absence of adhesive residue on the photomask of the adhesive was evaluated visually. The results are shown in Table 1, and the evaluation criteria are shown in Table 4.

From the results shown in Table 1, when Examples 1 to 5 and Comparative Examples 1 to 4 are compared, Comparative Example 1 is obtained by increasing the amount of the cross-linking agent of Example 1, and the displacement does not reach the specified amount. There were many bubbles immediately after applying the mask protective tape to the photomask, and the state of the bubbles remained almost unchanged after 4 hours. However, no adhesive residue was generated during peeling. Therefore, Comparative Example 1 which does not satisfy the requirement that “the pressure-sensitive adhesive layer (B) has a tensile shear displacement amount of 8 to 25 μm at a thickness of 4 μm”, which is a specific matter of the present invention, is a foam residue and an adhesive residue. In the evaluation of, both were not satisfied.
In Comparative Example 2, the low molecular weight pressure-sensitive adhesive of Example 2 was prepared by changing the polymerization conditions of the acrylic copolymer. An adhesive residue occurred. Therefore, Comparative Example 2, which is a specific matter of the present invention and does not satisfy the requirement that “the pressure-sensitive adhesive layer (B) has a tensile shear displacement amount of 8 to 25 μm at a thickness of 4 μm”, evaluates the adhesive residue. It was not satisfied.
Moreover, the comparative example 3 created the high molecular weight adhesive of Example 2 by changing the polymerization conditions of an acrylic copolymer. The amount of displacement decreased, and foaming occurred during lamination. Also, the bubble removal was bad after 4 hours. Therefore, Comparative Example 3 which does not satisfy the requirement that “the pressure-sensitive adhesive layer (B) has a tensile shear displacement amount of 8 to 25 μm at a thickness of 4 μm”, which is a specific matter of the present invention, is a foam residue and an adhesive residue. In the evaluation of, both were not satisfied.
In Comparative Example 4, the amount of hydroxyethyl methacrylate in Example 5 was further reduced, and the amount of displacement was greatly increased and no foam was generated, but adhesive residue was generated at the time of peeling. Therefore, Comparative Example 4 which does not satisfy the requirement that “the pressure-sensitive adhesive layer (B) has a tensile shear displacement amount of 8 to 25 μm at a thickness of 4 μm”, which is a specific matter of the present invention, is a foam residue and an adhesive residue. In the evaluation of, both were not satisfied.

Compared with these comparative examples, all of Examples 1 to 5 satisfied both the foam residue and the adhesive residue.
That is, in Example 1, the amount of displacement of the adhesive is larger than the specified amount, and there is little foaming immediately after the photomask protective tape is attached to the photomask, but there is almost no foaming after 4 hours, and adhesive residue is generated even after peeling. There was no.
Moreover, in Example 2 and Example 3, the displacement amount increased from Example 1 due to the composition change, and there was almost no bubbles immediately after the photomask protective tape was attached to the photomask. Also, good evaluation results were obtained without generation of adhesive residue at the time of peeling.
In Example 4, the pressure-sensitive adhesive thickness of Example 3 was doubled, and the tensile shear displacement amount per 4 μm was reduced, but bubbles increased immediately after the lamination due to an increase in the absolute displacement amount. There wasn't.
Moreover, about Example 5, the quantity of the hydroxyethyl methacrylate which contributes to a crosslinked structure was reduced, and the gel fraction was reduced within the regulation range. There were few bubbles immediately after pasting on the photomask, and the bubbles almost disappeared after 4 hours. Also, good evaluation results were obtained without generation of adhesive residue at the time of peeling.
Accordingly, the photomask protecting adhesive tapes obtained in Examples 1 to 5 are more suitable as photomask protecting adhesive tapes than the photomask protecting adhesive tapes obtained in Comparative Examples 1 to 5, respectively. Since the problem of foam residue and adhesive residue was solved, it was found that when used as an adhesive tape for protecting a photomask, it had excellent performance.

  The pressure-sensitive adhesive tape for protecting a photomask of the present invention is excellent in removability (performance in which no adhesive remains on the adherend when peeled off), is complex, has small dots, thin lines, and narrow line intervals. High-resolution photomask protective adhesive tape that does not contain air bubbles even when a photomask with a pattern is applied to it, so it can be used for pattern formation when making printed wiring boards. It is suitable as an adhesive tape for protecting a photomask that is used for the purpose of protecting the exposed photomask from the contamination of the photoresist and the damage caused by the substrate unevenness.

It is explanatory drawing which shows the measuring method of the tensile shear displacement amount in the cohesion force test using the Yamamoto type cohesion force measuring apparatus of this invention.

Explanation of symbols

1 Stainless steel plate (SUS304)
3 pulley 5 PET film 6 detector 20 photomask protective tape 21 base material layer (PET)
22 Adhesive layer 40 Weight attachment jig 41 200g weight

Claims (6)

From a pressure-sensitive adhesive comprising, on one side of a transparent substrate (A), an acrylic ester resin having a weight average molecular weight of 500,000 to 1,500,000 measured as a polystyrene-equivalent molecular weight by the GPC method, and a crosslinking agent A pressure-sensitive adhesive tape for protecting a photomask provided with a pressure-sensitive adhesive layer (B),
The acrylic ester resin is obtained by copolymerizing a vinyl monomer having a hydroxyl group or a carboxyl group, the main component of which is a (meth) acrylic ester monomer having 4 to 12 carbon atoms in the alkyl group. And
The pressure-sensitive adhesive layer (B) is a pressure-sensitive adhesive tape for protecting a photomask, wherein the thickness of the pressure-sensitive adhesive layer is 4 μm and the tensile shear displacement is 8 to 25 μm at a load of 200 g.   The pressure-sensitive adhesive tape for photomask protection according to claim 1, wherein the (meth) acrylic acid ester monomer is butyl acrylate and / or 2-ethylhexyl acrylate.   The pressure-sensitive adhesive tape for protecting a photomask according to claim 1 or 2, wherein the vinyl monomer is 2-hydroxyethyl (meth) acrylate and / or (meth) acrylic acid.   The pressure-sensitive adhesive tape for photomask protection according to any one of claims 1 to 3, wherein the crosslinking agent is an isocyanate compound. The pressure-sensitive adhesive was measured by previously immersing the pressure-sensitive adhesive in ethyl acetate at 23 ° C. for 24 hours, and then removing the residue from the ethyl acetate and filtering the residue with a 200-mesh wire mesh at 110 ° C. for 1 hour. 5. The pressure-sensitive adhesive tape for photomask protection according to any one of claims 1 to 4, wherein when dried, the gel fraction (Y) represented by the following formula is 50 to 75% by weight. .
Y = 100 × W2 / W1
(W1 means the initial weight of the pressure-sensitive adhesive measured before dipping, and W2 means the remaining weight of the pressure-sensitive adhesive after dipping and drying.) The pressure-sensitive adhesive layer (B) has a thickness of 2 to 9 µm, and the pressure-sensitive adhesive tape for protecting a photomask according to any one of claims 1 to 5.