JP2005131957A - Surface protecting film and optical component whereon it is stuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface protecting film which can reduce the amount of static electricity generated in peeling, and an optical component whereon the surface protecting film is stuck. <P>SOLUTION: This surface protecting film A is characterized in that a pressure-sensitive adhesive layer 2, which is composed of a pressure-sensitive adhesive containing an alkyltrimethylammonium salt, an acrylic polymer with a hydroxyl group, and a polyisocyanate, is provided on one side of a transparent base film 1. The optical component is manufactured by sticking the film A on the surface of an optical film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a surface protective film that is attached to the surface of an optical film such as a polarizing plate, a retardation plate, or a lens film.

When manufacturing products using optical films such as polarizing plates, phase difference plates, and lens films, a surface protective film is attached to the surface of the optical film, and the surface becomes dirty or scratched in the subsequent process. Has been made to prevent. The appearance inspection of the optical film may be performed with the surface protective film adhered.
Conventional surface protective films typically have a configuration in which a slightly adhesive pressure-sensitive adhesive layer is provided on one side of a base film. The pressure-sensitive adhesive layer is a layer for attaching the surface protective film to the optical film. The reason why the pressure-sensitive adhesive layer is slightly tacky is that when the used surface protective film is peeled off from the surface of the optical film, it can be smoothly peeled off and no adhesive residue remains.

However, if the surface resistance value of the surface protective film is large, foreign matter is adsorbed on the optical film due to static electricity generated in the process, or when the surface protective film is peeled and removed, the circuit is destroyed due to significant peeling electrification. There is a risk of For this reason, attempts have been made to add an antistatic layer to the surface protective film to reduce the surface resistance value and to prevent the antistatic.
As the antistatic layer, a layer containing various surfactants (cationic, anionic or amphoteric surfactants), a functional group-containing polymer, or the like, or a vapor deposition layer of metal or metal oxide is used.

For example, Patent Document 1 discloses a surface protective film in which an antistatic layer containing a transparent conductive polymer is provided between a transparent base film and an adhesive layer. As the transparent conductive polymer, an acrylate monomer having a quaternary ammonium salt group is described.
Patent Document 2 discloses a surface protective film in which an antistatic layer containing a quaternary ammonium salt is provided between a transparent base film and an adhesive layer.
The base films described in the above publications are characterized in that a layer containing a quaternary ammonium salt is provided between the base film and the pressure-sensitive adhesive layer.
JP 2000-85068 A JP 2000-273417 A

Currently, in the production process of liquid crystal panels, when peeling off the surface protective film stuck on the optical film, there are few cases where circuit components such as driver ICs for liquid crystals are destroyed due to peeling charging. It is done.
In addition, in order to reduce power consumption, the driving voltage of the liquid crystal material used for the liquid crystal panel has been lowered, and along with this, the breakdown voltage of the driver IC has also been lowered. There has been a demand for peeling charge in the range of -0.7 kV.
However, in the conventional surface protective film, since the antistatic layer is provided between the base film and the pressure-sensitive adhesive, an optical film as an adherend, a liquid crystal cell to which the optical film is attached, In addition, it is impossible to prevent static electricity damage to the driver IC connected thereto. In addition, in order to provide the antistatic layer, one coating / drying step is required, which is disadvantageous in terms of cost.

  This invention is made | formed in view of the said situation, Comprising: It aims at providing the surface protection film which can reduce the quantity of the static electricity generate | occur | produced at the time of peeling, and the optical component by which this was stuck.

In order to solve the above-mentioned problems, the present invention provides an adhesive layer made of an adhesive containing an alkyltrimethylammonium salt, an acrylic polymer having a hydroxyl group, and a polyisocyanate on one side of a transparent substrate film. A surface protective film is provided.
The alkyltrimethylammonium salt preferably has an alkyl group having 8 to 18 carbon atoms.
The polyisocyanate is preferably a self-emulsifying polyisocyanate. Further, it is preferable that at least a part of the isocyanate groups are three-dimensionally protected by a hydrophobic group when dispersed in water.
Furthermore, this invention provides the optical component by which the above-mentioned surface protection film was stuck.

  Since the surface protective film of the present invention contains an alkyltrimethylammonium salt in the pressure-sensitive adhesive layer in direct contact with the surface of an optical film such as a polarizing plate, a retardation plate, and a lens film, not only the surface protective film itself, The charging of the optical component can be suppressed low. Since the polymer is crosslinked by the reaction between the acrylic polymer having a hydroxyl group and the polyisocyanate, the alkyltrimethylammonium salt can be appropriately mixed in the pressure-sensitive adhesive. Since the surface protective film of the present invention has a small peel charge amount and low surface contamination, the surface of the optical component can be reliably protected and the production yield can be improved.

Hereinafter, the present invention will be described in detail based on embodiments.
FIG. 1 is a cross-sectional view showing an example of the surface protective film of the present invention. This surface protective film A has a pressure-sensitive adhesive layer 2 provided on one side of a transparent substrate film 1. A release film 3 for protecting the adhesive surface is overlaid on the base film 1 side of the adhesive layer 2.

As the base film 1, a transparent plastic film is used. Thereby, the appearance inspection of the optical component can be performed with the surface protective film adhered. As the plastic film for the base film 1, a polyester film such as polyethylene terephthalate, polyethylene naphthalate, polyethylene isophthalate, or polybutylene terephthalate is preferably used. In addition to the polyester film, other plastic films can be used as long as they have necessary strength and optical suitability. The base film 1 may be an unstretched film, may be uniaxially or biaxially stretched, and may be a plastic film in which the stretching ratio and the angle of the axial method formed with crystallization of stretching are controlled. .
Although the thickness of the base film 1 is not particularly limited, it is, for example, about 12 to 100 μm, particularly about 20 to 50 μm.
If necessary, the base film 1 may be provided with an antifouling layer for the purpose of preventing surface contamination, an antistatic layer, a hard coat layer for preventing scratches, or a corona on the opposite side of the adhesive layer 2. Easy adhesion treatment such as discharge treatment or anchor coating treatment may be performed.

The pressure-sensitive adhesive layer 2 is made of a pressure-sensitive adhesive containing an alkyltrimethylammonium salt, an acrylic polymer having a hydroxyl group, and polyisocyanate.
As the acrylic polymer having a hydroxyl group, a polymer obtained by copolymerizing a monomer component having a hydroxyl group such as hydroxyethyl methacrylate together with a monomer such as acrylic ester or methacrylic ester can be used.

  In the present invention, an alkyltrimethylammonium salt is mixed in the pressure-sensitive adhesive layer as a cationic antistatic agent. Alkyltrimethylammonium salt is a low molecular quaternary ammonium salt in which one alkyl group and three methyl groups are bonded to a nitrogen atom. An anion of the alkyltrimethylammonium salt is, for example, a chloride ion (alkyltrimethylammonium chloride).

The alkyltrimethylammonium salt is not particularly limited, but in particular, those in which the alkyl group has 8 to 18 carbon atoms are preferable.
Examples of the alkyl group include linear aliphatic hydrocarbon groups such as octyl group, decyl group, dodecyl group (lauryl group), tetradecyl group, hexadecyl group, octadecyl group (stearyl group), oleyl group, and the like.
More preferably, the alkyl group of the alkyltrimethylammonium salt has a carbon number in the range of 8 to 12, and specific examples include an octyl group, a decyl group, and a dodecyl group.

  When the alkyltrimethylammonium salt is used, the alkyltrimethylammonium salt contained in the pressure-sensitive adhesive can be bleed out on the adherend. Furthermore, when the carbon number of the alkyl group satisfies the above conditions, the adhesive strength of the pressure-sensitive adhesive and the antistatic performance imparted to the optical component by appropriate bleedout of the alkyltrimethylammonium salt are optimized. When the alkyl group has 7 or less carbon atoms, the alkyltrimethylammonium salt may bleed excessively from the pressure-sensitive adhesive layer, making it difficult to control the adhesive force. In addition, when the alkyl group has 19 or more carbon atoms, the alkyltrimethylammonium salt is difficult to bleed and the required performance may be difficult.

Although it does not specifically limit as said alkyl trimethyl ammonium salt, Use what quaternized the aliphatic amine derived from the fatty acid contained in natural fats and oils (vegetable fats, animal fats, etc.). Can do. Alkyltrimethylammonium salts derived from natural fats and oils usually contain a plurality of types of alkyltrimethylammonium molecules having different alkyl group lengths.
In order to suppress the total content of alkyltrimethylammonium salt, it is preferable to use an alkyltrimethylammonium salt derived from one source. As a result, the molecular weight distribution of the alkyltrimethylammonium salt can be reduced, and the time for the alkyltrimethylammonium salt to bleed out can be easily controlled. As a result, the total content of the alkyltrimethylammonium salt can be reduced. When the surface protection film is used for short-term surface protection, such as in the manufacturing process of optical components, the surface of the adherend is adhered after the surface protection film is adhered to the surface of the optical component until the surface protection film is peeled off. Since it is preferable that a sufficient amount of alkyltrimethylammonium salt for preventing antistatic is bleed out, it is preferable to select and use an alkyltrimethylammonium salt having a relatively high bleed speed.

  However, a plurality of types of alkyltrimethylammonium salts having different origins can be used in combination. By blending multiple types of alkyltrimethylammonium salts and increasing the molecular weight distribution of the alkyltrimethylammonium salts, the alkyltrimethylammonium salts gradually bleed out over time, and bleedout continues for a longer period of time. Can be made. The type and blending ratio of the alkyltrimethylammonium salt can be selected depending on the miscibility with the pressure-sensitive adhesive.

Polyisocyanate is a compound having a plurality of isocyanate groups (NCO groups) in the molecule. In particular, self-emulsifying polyisocyanates having self-emulsifying properties are preferred. Also preferred are polyisocyanates in which the isocyanate groups are three-dimensionally protected by hydrophobic groups. More specifically, it is preferable that the polyisocyanate is mixed with about 5 to 9 times the weight ratio of water and the time until the NCO group disappears at room temperature (NCO group remaining time) is 5 to 7 hours.
Such a polyisocyanate can be produced, for example, by the method described in Japanese Patent No. 3089623. Specific examples of the polyisocyanate include Aquanate series (registered trademark of Nippon Polyurethane Co., Ltd.) manufactured by Nippon Polyurethane Industry Co., Ltd.

  The ratio of the alkyltrimethylammonium salt to the total amount of the pressure-sensitive adhesive is preferably in the range of 0.01 to 5 parts by weight with respect to 100 parts by weight of the pressure-sensitive adhesive. In particular, it is preferably 0.1 to 1.5 parts by weight, and more preferably 0.3 to 1.2 parts by weight. When the content of the alkyltrimethylammonium salt is too small, the peel charge amount cannot be made sufficiently small. On the other hand, when the proportion of the alkyltrimethylammonium salt is excessively large, the peel charge amount can be reduced. This is because, even if it is possible, the surface of the optical film as the adherend is excessively contaminated, and adverse effects such as difficulty in controlling the adhesive force occur.

  The surface protective film A can be produced by providing the pressure-sensitive adhesive layer 2 made of the above-mentioned pressure-sensitive adhesive on one side of the base film 1. That is, the present invention uses an alkyltrimethylammonium salt as an antistatic agent, further uses an acrylic polymer having a hydroxyl group as an adhesive, and includes the antistatic agent by curing the adhesive with polyisocyanate. Even if the pressure-sensitive adhesive layer is formed, the present invention has been completed based on the surprising finding that a surface protective film that exhibits excellent antistatic performance can be produced without deteriorating surface contamination.

The pressure-sensitive adhesive layer 2 containing an antistatic agent is prepared by preparing a composition in which an organic solvent is mixed as necessary with a pressure-sensitive adhesive component containing the acrylic polymer, the alkyltrimethylammonium salt, and a polyisocyanate. The composition may be applied on the base film 1 by a coating means such as gravure coating, Mayer bar coating, air knife coating, doctor knife coating, reverse coating, and then dried.
The pressure-sensitive adhesive layer 2 is preferably a slightly pressure-sensitive adhesive layer having a light adhesiveness with a peel strength with respect to the surface of the adherend of about 0.03 to 0.3 N / 25 mm.
The thickness of the pressure-sensitive adhesive layer 2 is not particularly limited, but is often about 5 to 40 μm, particularly about 10 to 30 μm.

  The peelable film 3 can be coated on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer 2 as necessary. The release film 3 is not particularly limited, and examples thereof include those obtained by subjecting the surface of a film such as a polyester film to a release treatment using a release agent such as a silicone release agent.

The surface protective film A having the above-described configuration is provided with the pressure-sensitive adhesive layer 2 containing an antistatic agent, so that the surface potential when peeling from the optical film as an adherend is +0.7 kV to −0.7 kV. It is particularly preferable that the voltage be +0.5 kV to -0.5 kV, more preferably +0.1 kV to -0.1 kV.
This surface potential can be adjusted by the type and content of the antistatic agent contained in the pressure-sensitive adhesive layer.

In the above surface protective film, an acrylic polymer having a hydroxyl group is used as an adhesive, and in addition to curing the adhesive with polyisocyanate, the adhesive contains an alkyltrimethylammonium salt as an antistatic agent. Therefore, an excellent effect is obtained that the amount of charge to be peeled when the surface protective film is peeled from the optical film is sufficiently low and the contamination of the adherend surface is small. Such an effect cannot be expected with antistatic agents other than alkyltrimethylammonium salts.
In addition, there is an advantage that the number of coatings formed on the base film can be reduced by one.

FIG. 2 is a schematic configuration diagram showing an example of the optical component C of the present invention.
This optical component C is obtained by sticking the surface protective film A to the surface of the optical film B using the pressure-sensitive adhesive layer 2. Examples of the optical film B include a polarizing plate, a retardation plate, a lens film, a polarizing plate that also serves as a retardation plate, and a polarizing plate that also serves as a lens film. Such an optical component C can be used for manufacturing a liquid crystal display device such as a liquid crystal display panel, an optical system device of various instruments, and the like.
According to the optical component C of the present invention, the peeling charge of the optical film B when the surface protective film A is used up and removed is suppressed sufficiently small, so that the driver IC, TFT element, gate line drive There is no risk of damaging circuit components such as circuits, and the reliability of devices such as liquid crystal display panels can be maintained.

The following examples further illustrate the invention.
(Preparation of the surface protective film of Example 1)
As an antistatic agent, alkyltrimethylammonium chloride (trade name: Electro Stripper QN, manufactured by Kao Corporation), which is an alkyltrimethylammonium salt, and acrylic adhesive (trade name: SZ-2242, developed by Nippon Carbide Industries Co., Ltd.) And polyisocyanate-based curing agent (trade name: Aquanate AQ-200, manufactured by Nippon Polyurethane Industry Co., Ltd.), the weight ratio of the antistatic agent, the adhesive and the curing agent is 1: 100: 3. The resulting mixture was diluted with an organic solvent (toluene) to prepare an adhesive diluted solution. The NCO group remaining time of the polyisocyanate (AQ-200) is about 7 hours.
An antistatic agent is applied to one side of a biaxially stretched polyester film (biaxially stretched polyethylene terephthalate film) with a thickness of 38 μm as a base film, and the antistatic agent is applied and dried to a thickness of 15 μm on a dry basis. A pressure-sensitive adhesive layer was formed. Furthermore, a release film made of a polyester film subjected to silicone treatment was coated on the pressure-sensitive adhesive layer. Thus, a surface protective film of Example 1 having a layer structure of “base film / adhesive layer / release film” was obtained.

(Preparation of surface protective film of Example 2)
Other than using polyisocyanate-based curing agent instead of the above-mentioned Aquanate AQ-200, an isocyanate-based curing agent of the type that does not protect the isocyanate group with a hydrophobic group (trade name: Coronate HX, manufactured by Nippon Polyurethane Industry Co., Ltd.) Obtained the surface protection film of Comparative Example 4 by the same procedure as in Example 1.

(Production of surface protective film of Comparative Example 1)
A surface protective film of Comparative Example 1 was obtained by the same procedure as in Example 1 except that the alkyltrimethylammonium salt was not added to the adhesive diluent.

(Production of surface protective film of Comparative Example 2)
Example 1 except that instead of alkyltrimethylammonium salt, alkylbenzenesulfonic acid sodium salt (Nippon Emulsifier Co., Ltd., trade name: New col-210), which is an anionic antistatic agent, was used as the antistatic agent. A surface protective film of Comparative Example 2 was obtained by the same procedure as in Example 1.

(Production of surface protective film of Comparative Example 3)
As an antistatic agent, instead of the alkyltrimethylammonium salt, a lithium ion type antistatic agent (manufactured by Nippon Carlit Co., Ltd., trade name: PEL-20) was used in the same procedure as in Example 1, A surface protective film of Comparative Example 3 was obtained.

(Production of surface protective film of Comparative Example 4)
As an antistatic agent, benzyltrimethylammonium chloride (trade name: SANISOL B-50, manufactured by Kao Corporation) is used in place of the alkyltrimethylammonium salt, and the weight ratio of the antistatic agent, the adhesive, and the curing agent is solid. The surface protective film of Comparative Example 4 was obtained by the same procedure as in Example 1 except that the pressure-sensitive adhesive was prepared by blending so as to be 3: 100: 3.

(Production of surface protective film of Comparative Example 5)
As the antistatic agent, dialkyldimethylammonium chloride (trade name: Cotamine D2345P, manufactured by Kao Corporation) is used in place of the alkyltrimethylammonium salt, and the weight ratio of the solids of the antistatic agent, the adhesive and the curing agent is 3 : A surface protective film of Comparative Example 5 was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive was prepared by blending to be 100: 3.

<Production of optical components>
The release film was peeled and removed from the surface protective film A obtained in Examples 1 and 2 and Comparative Examples 1 to 5, and attached to the surface of the optical film to produce an optical component with a surface protective film. .

The evaluation test methods and results are shown below.
<Peeling charge amount of surface protective film>
The peeling charge amount when peeling the surface protective film from the optical component with the surface protective film was measured as follows.
After the surface protective film cut to a width of 25 mm is attached to the optical film, the surface protective film is peeled off at a speed of 40 m / min using a high-speed peel tester (manufactured by Tester Sangyo). The maximum value of the absolute value of the surface potential when the surface potential of the film surface was measured every 10 ms using a surface potential meter (manufactured by Keyence Corporation) was defined as the peel charge amount.

<Surface contamination of surface protective film>
In a clean room, a surface protective film was stuck on a 6-inch Si wafer so that no air bubbles or foreign matter entered, and left in a temperature-controlled room at 23 ° C. and 50% RH for 24 ± 2 hours. Thereafter, the number of particles of 0.2 to 0.5 μm on the surface of the Si wafer was counted with a laser surface inspection device (manufactured by Hitachi, Ltd.), and the measured values were used as the surface contamination shown in Table 1.

(Adhesive strength of surface protective film)
Using the test plate described in JIS Z 0237 and the SUS prepared according to the cleaning method of the test plate as an adherend, the surface protective film is attached to the SUS by using a 2 kg roller and reciprocating once so that no air bubbles enter. After pasting, heat at 70 ° C. for 1 hour. When the test specimen after heating is left at room temperature and allowed to cool for about 0.5 to 1 hour, the surface protective film is peeled in the direction of 180 ° at a peeling speed of 300 mm / min using a tensile tester. The strength was measured and used as the adhesive strength.

(Surface protective film adhesive transparency)
The pressure-sensitive adhesive layer of the surface protective film was visually observed, and the presence or absence of cloudiness of the pressure-sensitive adhesive layer was examined.

  The results of the above test are shown in Table 1. In Table 1, the compounding ratio represents the weight ratio of the solids of the antistatic agent, the pressure-sensitive adhesive, and the curing agent.

From Table 1, the following can be understood.
In Example 1 using an alkyltrimethylammonium salt as an antistatic agent, the peel charge amount was small and the surface contamination of the adherend was also small.
In Example 2 using a curing agent that does not protect the isocyanate group with a hydrophobic group as the curing agent, the peel charge amount was small and the surface contamination of the adherend was also small. However, the moisture contained in the quaternary ammonium salt and the isocyanate group reacted, resulting in poor compatibility with the acrylic pressure-sensitive adhesive and white turbidity.
In Comparative Example 1 in which the adhesive layer did not contain anything as an antistatic agent, the surface chargeability was excellent, but the peel charge amount was large.
In Comparative Example 2 using an anionic antistatic agent as the antistatic agent, the peel charge amount was large and the surface contamination was not good.
In Comparative Example 3 using a lithium ion system as the antistatic agent, although the peel charge amount was small, the surface contamination property was remarkably deteriorated.
In Comparative Example 4 using benzyltrimethylammonium salt as an antistatic agent, the peel charge amount was small, but the surface contamination was significantly deteriorated. Moreover, the pressure-sensitive adhesive became cloudy because the blending ratio of the antistatic agent was large.
In Comparative Example 5 using a dialkyldimethylammonium salt as an antistatic agent, the peel charge amount was small, but the surface contamination was significantly deteriorated. Moreover, the pressure-sensitive adhesive became cloudy because the blending ratio of the antistatic agent was large.

  The present invention can be used to protect a surface by sticking to the surface of the optical component or the like in a production process of an optical film such as a polarizing plate, a retardation plate or a lens film, or an optical component, for example. it can.

It is sectional drawing which shows the schematic structural example of the surface protection film of this invention. It is sectional drawing which shows one embodiment of the optical component of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base film, 2 ... Adhesive layer, A ... Surface protection film, C ... Optical component.

Claims (5)

  A surface protective film, wherein a pressure-sensitive adhesive layer comprising a pressure-sensitive adhesive containing an alkyltrimethylammonium salt, an acrylic polymer having a hydroxyl group, and polyisocyanate is provided on one side of a transparent substrate film.   The surface protective film according to claim 1, wherein the alkyltrimethylammonium salt has an alkyl group having 8 to 18 carbon atoms.   The surface protection film according to claim 1, wherein the polyisocyanate is a self-emulsifying type polyisocyanate.   The surface protection according to any one of claims 1 to 3, wherein the polyisocyanate is one in which at least a part of the isocyanate group is three-dimensionally protected by a hydrophobic group when dispersed in water. the film.   An optical component comprising the surface protective film according to claim 1 attached thereto.

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