JP2015166430A - Protective adhesive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective adhesive film to be laminated for use on a surface of a display glass substrate of an organic EL, liquid crystal or plasma electro-optic device so as to prevent scratches and deposition of contamination in a grinding and polishing process and in a cleaning process.SOLUTION: The protective adhesive film includes an adhesive layer 2 having a thickness of 10 μm or less formed on one surface of a polyethylene terephthalate (PET) film substrate 1 having a thickness of 12 μm or less, with the total thickness of the PET film substrate 1 and the adhesive layer 2 being 22 μm or less. It is preferable that, in a relationship of a thickness (A) of the adhesive layer 2 and a thickness (B) of the PET film substrate 1, A/(A+B)ranges from 1.95×10to 10.3×10, and that an adhesive force of the adhesive layer 2 measured in accordance with JIS Z0237:2000, ranges from 2.0 to 7.0 N/25 mm after a lapse of 20 minutes and from 3.0 to 10.0 N/25 mm after a lapse of 24 hours.

Description

  The present invention is used by adhering to the surface of a display glass substrate of an electro-optical device for organic electroluminescence (EL) or liquid crystal or plasma, and the display glass substrate is damaged during the cutting / polishing process and the cleaning process. The present invention relates to a protective adhesive film for preventing adhesion of dirt and dirt.

A protective adhesive film for preventing scratches and contamination on the surface of an object to be protected is generally composed of a plastic film substrate and an adhesive layer provided on the surface of the substrate. It is used by sticking so as to face the surface of the protector.
In general, the characteristics of protective adhesive films used in such applications are not easily peeled off from the object to be protected when subjected to environmental changes such as temperature and humidity or small stresses. It is required that it can be peeled off.

  For example, the following Patent Document 1 discloses a protective adhesive film having a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive composition containing an acrylic copolymer and a plasticizer, and a film base material. Is an ester compound having a specific chemical structure and a specific solubility parameter, and the initial adhesive strength (180 ° peel-off adhesive strength) of the protective adhesive film described in Patent Document 1 is It is about 0.01-1N / 25mm.

  By the way, when manufacturing an electro-optical device for organic EL, liquid crystal, or plasma, a display glass substrate is cut and polished, and then a cleaning process is performed. At this time, the surface of the glass substrate may be damaged. However, when the protective adhesive film described in Patent Document 1 is used for this purpose, for example, the adhesive force (adhesive force) is weak, and the polyethylene terephthalate film of the base material is used. Since there is stiffness, there is a problem that the protective adhesive film is easily peeled off from the glass substrate during the cutting / polishing process and the cleaning process.

JP 2010-248489 A

The problem of the present invention is that no peeling occurs even when a cutting / polishing process or a cleaning process is performed when manufacturing an electro-optical device for organic EL, liquid crystal, or plasma, and the surface of the display glass substrate is not damaged. It is an object of the present invention to provide a protective adhesive film capable of effectively preventing dirt adhesion.
As a result of earnestly examining the layer structure of the protective adhesive film in which peeling does not occur, the thickness of the adhesive, the thickness of the base film, and the total thickness of the whole are controlled to be equal to or less than a certain thickness, respectively. It has been found that a protective adhesive film that has an appropriate adhesive strength, does not peel off during the cutting / polishing process and the cleaning process, and can be peeled off with an appropriate force after performing the above process. Completed the invention.

In the protective adhesive film of the present invention capable of solving the above-mentioned problems, an adhesive layer is formed on one surface of a polyethylene terephthalate (PET) film substrate having a thickness of 12 μm or less, and the thickness of the adhesive layer is In the relationship between the thickness of the pressure-sensitive adhesive layer A and the thickness B of the polyethylene terephthalate film substrate, the value of A / (A + B) ² is 1.95 × 10 ⁻² to 10 μm or less. .3 × 10 ⁻² .

Further, in the protective adhesive film having the above-described features, the present invention has a value of 2.0 to 7.0 N / 25 mm after 20 minutes of the adhesive force of the adhesive layer measured according to JIS Z0237: 2000. It is characterized by being.
Furthermore, the present invention provides the protective adhesive film having the above-described characteristics, wherein the value after 24 hours of the adhesive strength of the adhesive layer measured according to JIS Z0237: 2000 is 3.0 to 10.0 N / 25 mm. It is also characterized by being.

  In the protective adhesive film having the above-described features, the present invention is also characterized in that the total light transmittance of the protective adhesive film is 85% or more and the HAZE value is 5.0% or less.

  Furthermore, this invention is a protective adhesive film which has the said characteristic, The adhesive layer contains 1 mass part or less of silane coupling agents with respect to 100 mass parts of resin components which comprise the said adhesive layer. It is also a feature.

In the protective adhesive film having the above-described characteristics, the present invention is such that the surface of the PET film substrate is subjected to antistatic treatment, and the surface resistance value of the substrate surface is 10 ⁶ Ω / □ to 10 ¹¹ Ω. It is also characterized by being / □.

According to the present invention, it is possible to prevent cracks and scratches during the cutting process and the polishing process of the display glass substrate of the electro-optical device for organic EL, liquid crystal, or plasma, and the protective adhesive film during the cleaning process Can also be prevented.
In addition, since the protective adhesive film of the present invention has a high total light transmittance and a small HAZE value, it is possible to inspect as it is with the protective adhesive film attached.

It is a figure which shows the layer structure of the protective adhesive film of this invention, and the release liner 3 is laminated | stacked in order to protect the surface of the adhesive layer 2 provided in PET film base material 1. FIG. It is a figure which shows the state at the time of sticking the protective adhesive film of this invention illustrated in FIG. 1 on the glass substrate surface of an organic light emitting diode (OLED).

Hereinafter, the details of the protective adhesive film of the present invention will be described with reference to FIG.
As shown in FIG. 1, the protective adhesive film of the present invention is composed of a PET film substrate 1 excellent in transparency and an adhesive layer 2 provided on one surface side of the PET film substrate 1. The thickness of the PET film substrate 1 is 12 μm or less, the thickness of the adhesive layer 2 is 10 μm or less, and the total thickness of the PET film substrate 1 and the adhesive layer 2 is 22 μm or less. At this time, as shown in FIG. 1, the release liner 3 is generally laminated on the surface of the pressure-sensitive adhesive layer for the purpose of protecting the pressure-sensitive adhesive layer 2, and the release liner 3 is coated with a release agent on the surface. A release-treated PET film is common.

As the PET film substrate 1 in the present invention, a commercially available product having a thickness of 12 μm or less can be used. However, when the thickness is less than 2 μm, the stiffness and strength as a film are lost and the handling becomes difficult. If it exceeds 12 μm, the film end tends to warp during the cutting process, and peeling tends to occur. For this reason, the thickness of the PET film substrate 1 in the present invention is preferably in the range of 2 to 12 μm, particularly preferably in the range of 4 to 12 μm, and more preferably in the range of 4 to 6 μm. The surface of the PET film substrate 1 on the pressure-sensitive adhesive layer 2 side may be subjected to a corona treatment or an easy-adhesion coat such as acrylic for the purpose of increasing the adhesive force with the pressure-sensitive adhesive layer 2.
In the present invention, since PET having excellent transparency is used as the base material of the protective adhesive film, it is possible to carry out an optical inspection with the protective adhesive film still attached. The total light transmittance of the adhesive film is preferably 85% or more, and the HAZE value is preferably 5.0% or less. When the total light transmittance is less than 85% or the HAZE value exceeds 5.0%, it is difficult to perform optical inspection.

Further, the thickness of the pressure-sensitive adhesive layer 2 laminated on the surface of the PET film substrate 1 in the present invention is 10 μm or less, and when the thickness of the pressure-sensitive adhesive layer 2 exceeds 10 μm, it is not preferable because the adhesive force is too strong. . Conversely, when the thickness of the pressure-sensitive adhesive layer 2 is less than 4.5 μm, the adhesive strength is too weak, and the protective pressure-sensitive adhesive film is easily peeled off from the glass substrate. In addition, coating of 4.5 μm or less by a general coating method may impair production stability and cause a deterioration in quality. In the present invention, the preferable pressure-sensitive adhesive layer 2 has a thickness in the range of 4.5 to 10 μm, and particularly preferably in the range of 5 to 8 μm.
And in the protective adhesive film of this invention, the total thickness of PET film base material 1 and the adhesive layer 2 is 22 micrometers or less. This is because when the thickness of the pressure-sensitive adhesive layer 2 is within the above range and the total thickness exceeds 22 μm, a load is applied to the side surface of the end due to an increase in end area accompanying an increase in the total thickness of the pressure-sensitive adhesive film. This is because the adhesive strength to the surface is weakened and the protective adhesive film is peeled off during the cutting / polishing step and the cleaning step of the display glass substrate.

In the protective adhesive film of the present invention, the A / (A + B) ² value of the thickness (A) of the pressure-sensitive adhesive layer 2 and the thickness (B) of the PET film substrate 1 is 1.95 × 10 ^{−. 2 to} 10.3 × 10 ⁻² , preferably 2.00 × 10 ^{−2 to} 10.2 × 10 ⁻² , wherein the ratio is less than 1.95 × 10 ⁻² If it becomes, it will become easy to produce peeling between the glass substrate surface and an adhesive layer at the time of a cutting | disconnection at the edge part of a base material at the time of cutting, or a cutting / polishing process and a washing | cleaning process. When the above ratio exceeds 10.3 × 10 ⁻² , the relative balance between the strength and rigidity of the PET base material and the weight of the pressure-sensitive adhesive is lost, and the workability of the protective pressure-sensitive adhesive film is impaired. When the protective adhesive film is peeled off after the washing step, the material tends to break, which is not preferable.

Furthermore, in this invention, it is preferable that the value after 20 minutes of adhesive force of the adhesive layer 2 is 2.0-7.0N / 25mm, More preferably, it is 2.2-5.1N / 25mm. . The value after 24 hours of adhesive strength is preferably in the range of 3.0 to 10.0 N / 25 mm, more preferably 3.2 to 7.3 N / 25 mm. By setting it as such adhesive force, peeling does not arise in a protective adhesive film at the time of a cutting and grinding | polishing process or a washing | cleaning process, but it can peel with moderate force after performing the said process. At this time, when the adhesive strength after 20 minutes is less than 2.0 N / 25 mm, when temporarily attaching the protective adhesive film, it becomes easy to peel off due to poor adhesion, and the workability is lowered, and conversely to 7.0 N / 25 mm or more. Then, the adhesive force is too strong, and it becomes difficult to reattach the protective adhesive film. When the adhesive strength after 24 hours is less than 3.0 N / 25 mm, sufficient adhesive strength cannot be obtained when pasted to the glass substrate, and the surface of the glass substrate and the pressure-sensitive adhesive layer during the cutting / polishing process or cleaning process are not obtained. Peeling is likely to occur in the meantime, and conversely if it exceeds 10.0 N / 25 mm, the adhesive strength is too great, and when the protective adhesive film is peeled off from the glass substrate after performing the above steps, the PET film base material is destroyed. Sometimes, it is not preferable.
The adhesive strength of the pressure-sensitive adhesive layer 2 in the present invention is a value measured according to JIS Z0237: 2000. When measuring the adhesive strength, first, the sample is cut into a size of 25 mm × 150 mm, Affixed to an adherend (stainless steel plate whose surface was polished with water-resistant abrasive paper # 360), pressed once with a 2 kg rubber roller, and measured for adhesion using a tensile tester (unit: N / 25 mm). The measurement conditions at this time are 180 ° peeling, 23 ° C./50% RH, and a peeling speed of 300 mm / min.

The pressure-sensitive adhesive layer 2 in the protective pressure-sensitive adhesive film of the present invention is formed by applying a pressure-sensitive adhesive to the surface of the PET film substrate, and is commercially available as a pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer 2. Various pressure-sensitive adhesives such as (meth) acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, and polyester-based pressure-sensitive adhesives can be used. Among them, it is preferable to use an acrylic pressure-sensitive adhesive in terms of transparency and durability. As the acrylic pressure-sensitive adhesive suitable for the present invention, any acrylate copolymer having an alkyl group having 1 to 18 carbon atoms can be used, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n- Examples include propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and these may be used alone or in admixture of two or more. May be.
The coating method for forming the pressure-sensitive adhesive layer 2 is not particularly limited, and various known coating methods can be used. For example, a die coater, a comma coater, a knife coater, a gravure coater, a roll coater, etc. are used. it can.

  In addition, in this invention, 1 mass part or less with respect to 100 mass parts of resin components which comprise the said adhesive layer as needed, Preferably it is 0.01-1 mass part silane coupling agent, for example, an epoxy-type silane. A compound may be added. In this case, the wettability with respect to the glass substrate is improved and the adhesion is increased. At this time, if the addition amount of the silane coupling agent exceeds 1 part by mass, bleeding occurs on the surface and the adhesion is reduced, which is not preferable.

In the present invention, the surface of the PET film substrate 1 is preferably subjected to an antistatic treatment and an antistatic layer is provided, and a commercially available antistatic agent is coated to provide the antistatic layer. Therefore, it is possible to prevent dust and foreign matters from being attached due to static electricity during the process. At this time, the surface resistance value of the substrate surface is preferably 10 ⁶ Ω / □ to 10 ¹¹ Ω / □ (when not treated, 10 ¹² Ω / □ or more). You may give the antistatic effect to the adhesive itself used when forming.

FIG. 2 is a view showing a state when the protective adhesive film of the present invention is attached to the surface of a glass substrate of an organic light emitting diode (OLED). In such a laminated state, a cutting / polishing step and a cleaning step are performed. The inspection (inspection) can be performed in the laminated state after the process is completed.
In FIG. 2, reference numeral 4 denotes an OLED glass substrate to which the protective adhesive film of the present invention is attached, reference numeral 5 denotes a TFT / EL array substrate, reference numeral 6 denotes a polarizing plate, reference numeral 7 denotes an OLED element, and reference numeral 8 denotes This is a pixel circuit.

Example 1: Production Example of Protective Adhesive Film of the Invention First, as an adhesive for forming an adhesive layer, a commercially available acrylic adhesive (KP-2254 manufactured by Nippon Carbide Industries Co., Ltd.) was prepared. After adding 0.4 parts by mass of a cross-linking agent (CK-117 manufactured by Nippon Carbide Industries Co., Ltd.) to 100 parts by mass of the adhesive coating solution, it is diluted with a solvent such as ethyl acetate or toluene, and sufficiently stirred to adhere. A coating solution for forming an agent layer was obtained. On the other hand, a commercially available PET film having a thickness of 6 μm was prepared as a PET film substrate. Then, the coating solution is coated so that the thickness of the pressure-sensitive adhesive layer after drying is 7 μm, and is dried at 90 to 110 ° C. for 30 to 120 seconds to form a pressure-sensitive adhesive layer. A film was obtained.
The protective adhesive film of the present invention thus obtained has a total light transmittance (measured according to JIS K7361-1) of 89.5% and a HAZE value (measured according to JIS K7136) of 2.8. %Met.
Similarly, on the PET film substrate having the thickness described in Table 1 below (2 μm, 4 μm, 6 μm, 12 μm), the above-mentioned adhesion at the coating thickness described in Table 1 (5 μm, 7 μm, 8 μm, 10 μm). The protective adhesive film of the present invention was prepared by coating the agent.
Furthermore, as a comparative example, using the same method, the coating thickness (5 μm to 20 μm) described in Table 1 on the PET film substrate (12 to 50 μm) having the thickness described in Table 1 below. A comparative product was prepared by coating the pressure-sensitive adhesive.

The adhesive strength (value after 20 minutes and value after 24 hours) was measured in accordance with JIS Z0237: 2000 for the product of the present invention and the comparative product obtained above. Moreover, after pasting the product of the present invention and the comparative product obtained above on the surface of the glass substrate of the organic light emitting diode, the cutting / polishing step and the cleaning step are performed, and the separation between the glass substrate and the protective adhesive film occurs. It was visually evaluated whether or not it occurred.
The results are shown in Table 1 below.

As shown in Table 1 above, the protective adhesive film of the present invention has an adhesive strength of 2.0 to 7.0 N / 25 mm after 20 minutes with respect to the stainless steel plate, and 3.0 to 10 after 24 hours. A / (A + B) ² of the thickness (A) of the pressure-sensitive adhesive layer 2 and the thickness (B) of the PET film substrate 1 is 1.95 × 10 ⁻² to 10 in a range of 0.0 N / 25 mm. .3 × 10 ⁻² , the thickness of each layer of the PET base material and the pressure-sensitive adhesive is adjusted to an appropriate range, and the side surface of the edge is increased due to the increase in the edge area with the increase in the total thickness of the pressure-sensitive adhesive film Even when the cutting / polishing process and cleaning process are performed after the load is suppressed and adhered to the glass substrate surface of the organic light emitting diode, peeling does not occur between the glass substrate and the protective adhesive film. It was confirmed that there was no problem with gender. In contrast, in the case of the comparative protective protective film, peeling occurred when the cutting / polishing process and the cleaning process were performed.

Example 2: Effect of improving wettability when a silane coupling agent is added In the coating liquid for forming an adhesive layer described in Example 1, 0.1 part by mass of a commercially available 0.1 part by mass of acrylate component A silane coupling agent (epoxy silane compound) was added to prepare a coating solution.
Then, using this coating solution, as in Example 1, the surface of the PET film substrate having a thickness of 6 μm was coated such that the thickness of the pressure-sensitive adhesive layer after drying was 7 μm, respectively. The layer was formed and the protective adhesive film of this invention was produced.
The protective adhesive film obtained in this way is equivalent in terms of adhesive strength and optical properties (total light transmittance, HAZE value) compared to the case where no silane coupling agent is added. It was confirmed that the wettability when adhering to the surface of the substrate was excellent, and the adhesion with the glass substrate was improved.

Example 3: Dust adhesion preventing effect by providing an antistatic layer On the surface of the PET film substrate of the protective adhesive film of the present invention obtained in Example 1 (the surface on which the adhesive layer is not provided) The surface resistance value on the surface of the PET film substrate was measured for the antistatic treatment coated with a commercially available antistatic agent (ion conduction type antistatic coating agent) (thickness of about 2 μm) and for the antistatic treatment. It was measured. In the measurement of the surface resistance value, a SM-8200 super insulation meter manufactured by Toa DKK Corporation was used as a measuring device, and the measurement was performed in an atmosphere at a temperature of 23 ° C. and a relative humidity of 50% RH.
As a result, the surface resistance value of the protective adhesive film not subjected to the antistatic treatment is 10 ¹² Ω / □ or more, whereas the surface resistance value of the protective adhesive film subjected to the antistatic treatment is 10 ⁸ Ω / □. ~10 ⁹ Ω / □ and is, that dust, foreign matter or the like due to static electricity is one that is difficult to adhere has been confirmed.

  The protective adhesive film of the present invention hardly peels off during the cutting / polishing step and the cleaning step when manufacturing the display glass substrate of the electro-optical device for organic EL, liquid crystal, or plasma, and when performing each step Can be prevented and can be inspected with the protective adhesive film adhered, and is useful in the field of manufacturing display glass substrates for these electro-optical devices.

DESCRIPTION OF SYMBOLS 1 PET film base material 2 Adhesive layer 3 Release liner 4 Glass substrate 5 TFT / EL array substrate 6 Polarizing plate 7 Organic substance (OLED element)
8 Pixel circuit (poly-Si TFT)

Claims (6)

An adhesive film for protecting the surface of a glass substrate, wherein an adhesive layer is formed on one surface of a polyethylene terephthalate film substrate having a thickness of 12 μm or less, and the thickness of the adhesive layer is 10 μm or less In the relationship between the thickness A of the pressure-sensitive adhesive layer and the thickness B of the polyethylene terephthalate film substrate, the value of A / (A + B) ² is 1.95 × 10 ^{−2 to} 10.3 ×. protective adhesive film, characterized in that is between 10 ^-2.   The protective adhesive film according to claim 1, wherein a value after 20 minutes of the adhesive force of the adhesive layer measured according to JIS Z0237: 2000 is 2.0 to 7.0 N / 25 mm. .   The protection according to claim 1 or 2, wherein a value after 24 hours of the adhesive force of the pressure-sensitive adhesive layer measured according to JIS Z0237: 2000 is 3.0 to 10.0 N / 25 mm. Adhesive film.   The protective adhesive film according to any one of claims 1 to 3, wherein the protective adhesive film has a total light transmittance of 85% or more and an HAZE value of 5.0% or less.   The said adhesive layer contains 1 mass part or less of silane coupling agents with respect to 100 mass parts of resin components which comprise the said adhesive layer, The any one of Claims 1-4 characterized by the above-mentioned. The protective adhesive film as described in 2. The surface of the polyethylene terephthalate film substrate is subjected to antistatic treatment, and the surface resistance value of the substrate surface is 10 ⁶ Ω / □ to 10 ¹¹ Ω / □. The protective adhesive film of any one of these.

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