Process film and method for recycling process film substrate

Abstract

To provide a process film that enables a plastic film as a substrate to be easily recycled.SOLUTION: A process film has an adhesive layer on a substrate, the substrate being a plastic film, the process film having a peeling strength of 0.001 N / 10 mm or more and 0.500 N / 10 mm or less in accordance with Method 1 of JIS Z0237: 2009, and the plastic film and the adhesive layer having a water-soluble resin layer between them.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a process film and a method for recycling the substrate of the process film. [Background technology]

[0002] In the process of manufacturing electronic devices, etc., a process may be performed in which components are temporarily fixed to an adhesive film, and after predetermined processing such as punching, the components are peeled off from the adhesive film. Such adhesive films are called process films.

[0003] Furthermore, optical films such as diffusion films, prism sheets, polarizing films, retardation films, hard coat films, and transparent conductive films may have adhesive films attached to their surfaces to prevent scratches during production, distribution, storage, etc. Such adhesive films are also called process films.

[0004] The process film has a structure in which a pressure-sensitive adhesive layer is provided on a substrate such as a plastic film, etc. As the process film, for example, Patent Documents 1 to 3 have been proposed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-292959 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-254789 [Patent Document 3] Japanese Patent Application Publication No. 11-129401 Summary of the Invention [Problem to be solved by the invention]

[0006] After a predetermined process and time has passed, the process film is peeled off from the part, etc. In order to reduce the burden on the environment, it is desirable to recycle the substrate of used process film. However, as in Patent Documents 1 and 2, general process films do not take into consideration the recycling of the substrate.

[0007] In the process film of Patent Document 3, the adhesive constituting the adhesive layer is a water-dispersible adhesive, so that the adhesive can be removed from the substrate by washing with water, and the substrate can be recycled. However, the process film of Patent Document 3 is limited to adhesives that are water-dispersible, and therefore, depending on the materials of the substrate and adherend, it is not possible to achieve good adhesion between the substrate and the adhesive layer, or between the adhesive layer and the adherend, and the process film lacks versatility.

[0008] An object of the present invention is to provide a process film that allows the plastic film substrate to be easily recycled. Another object of the present invention is to provide a method for easily recycling the plastic film substrate of the process film. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention provides the following [1] and [2]. [1] A process film having a pressure-sensitive adhesive layer on a substrate, the substrate is a plastic film, The process film has a peel strength according to JIS Z0237:2009 Method 1 of 0.001 N / 10 mm or more and 0.500 N / 10 mm or less, A process film having a water-soluble resin layer between the plastic film and the pressure-sensitive adhesive layer. [2] A method for recycling a substrate of a process film, comprising the following steps 1 to 4: Step 1: A step of recovering the process film described in [1] above. Step 2: A step of immersing the recovered film in water to dissolve the water-soluble resin layer in the water. Step 3: Recovering the plastic film base material. Process 4: The collected plastic film is recycled. [Effects of the Invention]

[0010] The process film of the present invention allows the plastic film substrate to be easily recycled. Furthermore, according to the recycling method of the present invention, the plastic film substrate of the process film can be easily recycled. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing one embodiment of the process film of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the process film of the present invention and embodiments of the method for recycling the substrate of the process film of the present invention will be described.

[0013] [Processing film] The process film of the present invention is A process film having a pressure-sensitive adhesive layer on a substrate, the substrate is a plastic film, The process film has a peel strength according to JIS Z0237:2009 Method 1 of 0.001 N / 10 mm or more and 0.500 N / 10 mm or less, A water-soluble resin layer is provided between the plastic film and the pressure-sensitive adhesive layer.

[0014] Fig. 1 is a cross-sectional view showing one embodiment of the processing film of the present invention. The processing film 100 of Fig. 1 has a pressure-sensitive adhesive layer 30 on a plastic film 10 as a substrate. The processing film 100 of Fig. 1 has a water-soluble resin layer 20 between the plastic film 10 and the pressure-sensitive adhesive layer 30. The processing film 100 of Fig. 1 has a release sheet 40 on the side of the pressure-sensitive adhesive layer 30 opposite the plastic film. The process film may be in the form of a roll or a sheet.

[0015] <Plastic film (base material)> The process film of the present disclosure uses a plastic film as a substrate. The water-soluble resin layer and the pressure-sensitive adhesive layer do not easily penetrate into the plastic film. Therefore, using a plastic film as the substrate makes it easier to recycle the substrate. On the other hand, if the substrate is paper or fiber, the pressure-sensitive adhesive layer and the like easily penetrate into the paper or fiber, making it difficult to recycle the substrate. Furthermore, by using a plastic film as the substrate, the process film can be made easier to handle and more durable.

[0016] Resins constituting plastic films include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polycarbonate; polyolefins such as polyethylene and polypropylene; polystyrene; triacetyl cellulose; poly(meth)acrylate; polyvinyl chloride; and the like. Among these resins, polyester is preferred. That is, polyester films are preferred as plastic films. Polyester films are preferred because of their excellent mechanical strength, dimensional stability, and transparency. Furthermore, among polyester films, biaxially oriented polyester films are preferred, and biaxially oriented polyethylene terephthalate films are more preferred. The surface of the plastic film may be corona discharge treated.

[0017] From the viewpoint of handling and strength, the thickness of the plastic film is preferably 10 μm or more and 500 μm or less, more preferably 15 μm or more and 250 μm or less, and even more preferably 20 μm or more and 100 μm or less.

[0018] <Peel strength> The film for use in processes of the present invention must have a peel strength according to Method 1 of JIS Z0237:2009 of 0.001 N / 10 mm or more and 0.500 N / 10 mm or less. If the peel strength is less than 0.001 N / 10 mm, the adhesion between the process film and the adherend cannot be made good. If the peel strength exceeds 0.500 N / 10 mm, a force is applied when peeling the process film from the adherend, which reduces the workability of peeling. In addition, used process film is sometimes rolled up and collected. When recycling the substrate of used process film rolled up, it is necessary to unwind the used process film from the roll. If the peel strength exceeds 0.500 N / 10 mm, the aforementioned unwinding becomes difficult, reducing the workability of recycling.

[0019] Method 1 of JIS Z0237:2009 refers to the peel strength of 180° peeling from a stainless steel test plate. The peel strength can be measured, for example, as follows (1) to (2). (1) The process film is cut into a test sample having a width of 25 mm and a length of 100 mm. (2) The adhesive layer side of the sample is attached to a stainless steel test plate, and the sample is peeled off in a direction of 180° using a peel strength measuring device. The peeling speed during the peel test is preferably 300 mm / min.

[0020] The stainless steel test plate is preferably one that has been subjected to a BA surface finish as specified in JIS G4305:2021. Furthermore, the stainless steel test plate preferably has a surface shape with an arithmetic mean roughness of 50 nm±25 nm as specified in JIS B0601:2013. Furthermore, the stainless steel test plate is preferably a SUS304 stainless steel plate.

[0021] The peel strength can be adjusted by the composition of the pressure-sensitive adhesive layer, etc. For example, increasing the degree of crosslinking of the base agent tends to decrease the peel strength, while decreasing the degree of crosslinking of the base agent tends to increase the peel strength. Furthermore, increasing the content of tackifier tends to increase the peel strength, while decreasing the content of tackifier tends to decrease the peel strength.

[0022] <Adhesive layer> The pressure-sensitive adhesive layer is preferably formed from a pressure-sensitive adhesive composition containing a base agent and a curing agent. By using such a configuration, the peel strength of the process film can be easily adjusted to the above range by adjusting the blending ratio of the base agent and the curing agent.

[0023] The base resin can be a resin for general-purpose adhesives, and specific examples include acrylic resins, polyester resins, urethane resins, rubber resins, silicone resins, etc. Among these, acrylic resins are preferred from the viewpoints of heat resistance, non-contamination properties, and cost.

[0024] As the curing agent, a general-purpose curing agent can be used, and specific examples thereof include an isocyanate-based curing agent and an amine-based curing agent.

[0025] The PSA composition may contain a tackifier. However, a PSA layer formed from a PSA composition containing a tackifier tends to have a high peel strength. For this reason, the tackifier must be carefully blended into the PSA composition so that the peel strength falls within the above range.

[0026] The pressure-sensitive adhesive layer is preferably water-insoluble. By making the pressure-sensitive adhesive layer water-insoluble, it is possible to prevent the pressure-sensitive adhesive layer from dissolving in water along with the water-soluble resin layer when recycling the processing film, thereby preventing multiple resins from being mixed into the waste liquid and facilitating waste liquid disposal. Furthermore, by making the pressure-sensitive adhesive layer water-insoluble, it is possible to recover the film-like pressure-sensitive adhesive layer peeled off from the plastic film when recycling the processing film, thereby reducing the environmental impact. Furthermore, by making the pressure-sensitive adhesive layer water-insoluble, it is possible to prevent the cohesive strength of the pressure-sensitive adhesive layer from decreasing due to moisture, and it is possible to easily prevent the pressure-sensitive adhesive layer from undergoing cohesive failure when peeling off the processing film. Furthermore, by making the pressure-sensitive adhesive layer water-insoluble, it is possible to easily improve the interlayer adhesion of the processing film. Furthermore, since many adherends are water-insoluble, making the pressure-sensitive adhesive layer water-insoluble can easily improve adhesion to the adherend. Furthermore, by making the pressure-sensitive adhesive layer water-insoluble, it is possible to prevent the pressure-sensitive adhesive layer from becoming sticky due to moisture.

[0027] In this specification, a water-insoluble pressure-sensitive adhesive layer means one in which the amount of the pressure-sensitive adhesive layer that dissolves in water is less than 1.0% by mass when immersed in water at 23° C. for 120 minutes. The amount that dissolves is preferably less than 0.5% by mass, and more preferably less than 0.1% by mass.

[0028] The thickness of the pressure-sensitive adhesive layer is preferably from 1 μm to 50 μm, more preferably from 2 μm to 20 μm, and even more preferably from 3 μm to 10 μm. By making the thickness of the adhesive layer 1 μm or more, it is possible to easily achieve a peel strength of 0.001 N / 10 mm or more, and by making the thickness of the adhesive layer 50 μm or less, it is possible to reduce costs.

[0029] The pressure-sensitive adhesive layer may contain additives such as an ultraviolet absorber and an antioxidant. The pressure-sensitive adhesive layer can be formed, for example, by applying a pressure-sensitive adhesive composition onto a water-soluble resin layer and drying the applied composition. A general-purpose application method can be used as the application method.

[0030] <Release sheet> A release sheet may be provided on the side of the pressure-sensitive adhesive layer opposite the plastic film. By providing a release sheet, the process film can be easily handled during storage and distribution. When the process film is used, the release sheet is peeled off.

[0031] Examples of the release sheet include plastic films, paper, etc. The release sheet may be a plastic film, paper, etc. whose surface has been treated with a release agent such as silicone to improve releasability.

[0032] <Water-soluble resin layer> The processing film of the present invention has a water-soluble resin layer between the plastic film and the pressure-sensitive adhesive layer. The water-soluble resin layer dissolves in water when the processing film is immersed in water. When the water-soluble resin layer dissolves in water, separation of the plastic film from the water-soluble resin layer and the pressure-sensitive adhesive layer progresses, allowing the plastic film to be recovered from the processing film. In this way, the processing film of the present invention can be easily separated from the processing film by immersing it in water after use, allowing the plastic film to be recovered.

[0033] The water-soluble resin layer preferably contains a water-soluble resin. The water-soluble resin may be a general-purpose water-soluble resin. Examples of the water-soluble resin include polyester, polyurethane, acrylic resin, epoxy resin, polyvinyl alcohol, and polyvinylpyrrolidone. Among these, water-soluble polyester is preferred because it easily provides good adhesion to the polyester film. Furthermore, among water-soluble polyester resins, water-soluble polyester resins having a highly polar functional group such as a polycarboxylic acid residue, a polyhydric alcohol residue, and a polyamine residue are preferred.

[0034] In this specification, the water-soluble resin layer refers to a resin layer having a property such that, when a 3 g sample is taken from the water-soluble resin layer, the sample is placed in 97 g of water at 23° C., and stirred for 60 minutes at 300 rpm using a magnetic stirrer, 50% by mass or more of the sample dissolves. As the magnetic stirrer, for example, Yamato Scientific's "Mag Mixer MG600H" can be used.

[0035] The thickness of the water-soluble resin layer is preferably 0.1 μm or more and 10.0 μm or less, more preferably 0.3 μm or more and 5.0 μm or less, and even more preferably 0.5 μm or more and 3.0 μm or less. By making the thickness of the water-soluble resin layer 0.1 μm or more, it becomes easier to separate the plastic film from the processing film when the processing film is immersed in water. By making the thickness of the water-soluble resin layer 10.0 μm or less, it becomes possible to reduce costs.

[0036] The water-soluble resin layer may contain additives such as an ultraviolet absorber and an antioxidant. The water-soluble resin layer can be formed, for example, by applying a coating liquid containing components constituting the water-soluble resin layer onto a plastic film, followed by drying. As the coating method, a general-purpose coating method can be used.

[0037] [Recycling method for process film substrate] The method for recycling the substrate of a processing film of the present invention includes the following steps 1 to 4. Step 1: A step of recovering the above-mentioned process film of the present invention. Step 2: A step of immersing the recovered film in water to dissolve the water-soluble resin layer in the water. Step 3: Recovering the plastic film base material. Process 4: The collected plastic film is recycled.

[0038] <Process 1> Step 1 is a step of recovering the process film of the present invention described above. The process film to be recovered is a used process film. Therefore, the recovered process film does not have a release film. It is preferable to recycle the release film via a separate route.

[0039] The process film collected in step 1 may be in the form of a roll or sheets.

[0040] <Process 2> Step 2 is a step of immersing the recovered process film in water to dissolve the water-soluble resin layer in water.

[0041] In step 2, by dissolving the water-soluble resin layer in water, the plastic film can be easily recovered in step 3. The more the water-soluble resin layer dissolves in water, the more the plastic film separates from the water-soluble resin layer and the pressure-sensitive adhesive layer, making it easier to recover the plastic film from the processing film. Therefore, in step 2, it is preferable to allow the water-soluble resin layer to dissolve in water. However, the plastic film can be separated from the water-soluble resin layer and the pressure-sensitive adhesive layer even if the water-soluble resin layer is not completely dissolved in water. Therefore, it is not necessary to completely dissolve the water-soluble resin layer in water in step 2. However, if the water-soluble resin layer is not completely dissolved in water in step 2, there is a possibility that part of the water-soluble resin layer will adhere to the plastic film. Therefore, if the water-soluble resin layer is not completely dissolved in water in step 2, it is preferable to include a water-washing step in the recycling process.

[0042] If the pressure-sensitive adhesive layer is water-insoluble, the pressure-sensitive adhesive layer will gradually peel off from the water-soluble resin layer while remaining in a film form during step 2. Therefore, the method for recycling the substrate of a processing film of the present invention may include a step of recovering the pressure-sensitive adhesive layer in a film form. By including a step of recovering the pressure-sensitive adhesive layer, the environmental load can be further reduced.

[0043] The process film may be immersed in water while being unwound from a roll, or may be immersed in water in the form of a sheet.

[0044] The temperature of the water in which the casting film is immersed is preferably 20°C or higher and 90°C or lower, and more preferably 20°C or higher and 60°C or lower. By setting the water temperature at 20°C or higher, the water-soluble resin layer can be dissolved in water more quickly, improving the workability of recycling. By setting the water temperature at 90°C or lower, excessive power consumption can be suppressed, reducing the environmental impact.

[0045] The time for which the process film is immersed in water cannot be generalized because it varies depending on the water temperature and the water solubility of the water-soluble resin layer. When the water temperature is 23°C, the immersion time is preferably 60 to 240 minutes. When the water temperature is 60°C, the immersion time is preferably 10 to 40 minutes.

[0046] The pH of the water is preferably 5.8 or more and 8.6 or less, which are the water quality standards for tap water, and more preferably 6.8 or more and 8.1 or less. By using water with a pH in this range, the environmental load can be further reduced.

[0047] <Process 3> Step 3 is a step of recovering the plastic film substrate. Since a portion of the water-soluble resin layer and the pressure-sensitive adhesive layer may remain on the plastic film, step 3 may include a water washing step.

[0048] To improve the workability of recycling, steps 1 to 3 are preferably carried out in the form of a roll as follows. In step 1, the process film is collected in the form of a roll. In step 2, the rolled process film is immersed in water while being fed from the roll, and the water-soluble resin layer is dissolved in water. In step 3, the plastic film is collected in roll form.

[0049] <Step 4> Step 4 is the process of recycling the collected plastic film.

[0050] Recycling methods include material recycling, chemical recycling, and thermal recycling, with material recycling being preferred. [Example]

[0051] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples.

[0052] 1. Measurement and evaluation 1-1. Peel strength The release film was peeled from the process film of each of the examples and comparative examples, and the film was cut to a width of 25 mm and a length of 150 mm to prepare a test sample. Using the test sample, the peel strength was measured according to Method 1 of JIS Z0237:2009, as described in the specification. The measurement device used was Shimadzu Corporation's Autograph AGS-5NJ. The stainless steel test plate used had a BA surface finish as specified in JIS G4305:2021. The measurement environment was a temperature of 23°C ± 5°C and a relative humidity of 40 to 65%.

[0053] 1-2. Water immersion test (1) The release film was peeled off from the processing films of the Examples and Comparative Examples. Next, the processing films from which the release film had been peeled off were immersed in water at 23°C for 120 minutes. Next, the processing films were removed from the water, and the state of the coating film was visually evaluated. (2) The release film was peeled off from the processing films of the Examples and Comparative Examples. The processing films from which the release film had been peeled off were then immersed in water at 60°C for 20 minutes. The processing films were then removed from the water, and the state of the coating was visually evaluated.

[0054] 2. Preparation of process film [Example 1] The following water-soluble resin layer coating liquid was applied to one side of a 25 μm-thick transparent polyester film (Lumirror 25S10, manufactured by Toray Industries, Inc.), and dried at 100° C. for 120 seconds to form a 1 μm-thick water-soluble resin layer. Next, the following pressure-sensitive adhesive layer coating liquid was applied to the water-soluble resin layer, and dried at 100° C. for 120 seconds to form a 5 μm-thick pressure-sensitive adhesive layer, thereby obtaining the process film of Example 1. <Coating liquid for water-soluble resin layer> Water-soluble polyester 100 parts by weight (Goo Chemical Industry Co., Ltd., product name: Plus Coat, solid content 20% by mass) Dilution solvent (appropriate amount)

[0055] <Coating liquid for adhesive layer> Main ingredient 100 parts by weight (acrylic resin) (Soken Chemical & Engineering Co., Ltd., product name: SK Dyne 1499M, solid content 30% by mass) Hardener 1 part by mass (Isocyanate compounds) (Soken Chemical & Engineering Co., Ltd., product name: Hardener D-90, solid content 90% by mass) Dilution solvent (appropriate amount)

[0056] [Comparative Example 1] The above adhesive layer coating liquid was applied to one side of a 25 μm thick transparent polyester film (Lumirror 25S10, manufactured by Toray Industries, Inc.), and dried at 100°C for 120 seconds to form a 5 μm thick adhesive layer, thereby obtaining a process film for Comparative Example 1.

[0057] [Table 1]

[0058] From the results in Table 1, it can be confirmed that the process films of the examples have excellent recyclability, allowing the plastic film substrate to be easily recovered. [Explanation of symbols]

[0059] 10: Plastic film 20: Water-soluble resin layer 30: Adhesive layer 40: Release sheet 100: Processing film

Claims

1. A process film having a pressure-sensitive adhesive layer on a substrate, the substrate is a plastic film, The process film has a peel strength according to Method 1 of JIS Z0237:2009 of 0.001 N / 10 mm or more and 0.500 N / 10 mm or less, A process film having a water-soluble resin layer between the plastic film and the pressure-sensitive adhesive layer.

2. The process film according to claim 1 , wherein the water-soluble resin layer has a thickness of 0.1 μm or more and 10.0 μm or less.

3. The process film according to claim 1 or 2, wherein the pressure-sensitive adhesive layer is water-insoluble.

4. The process film according to any one of claims 1 to 3, wherein the plastic film is a polyester film.

5. The process film according to any one of claims 1 to 4, further comprising a release sheet on the side of the pressure-sensitive adhesive layer opposite to the plastic film.

6. A method for recycling a substrate of a process film, comprising the following steps 1 to 4: Step 1: A step of recovering the process film according to any one of claims 1 to 5. Step 2: A step of immersing the recovered film in water to dissolve the water-soluble resin layer in the water. Step 3: A step of recovering the plastic film substrate. Step 4: Recycle the collected plastic film.

7. 7. The method for recycling a substrate of a processing film according to claim 6, wherein in step 2, the temperature of the water in which the processing film is immersed is 20°C or higher and 90°C or lower.

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