JP2001328849A - Method for recycling display material having adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for surely separating a display substrate such as glass from used display materials having, adhesives, without remnants of the adhesives. SOLUTION: A display material having a transparent film pasted on the surface of the material with an adhesive containing a polyester resin or an acrylic resin is immersed in an alkaline solution and the transparent film and the adhesive are peeled off from the display material to obtain the display substrate for reuse.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recycling method for separating a display material such as glass from a display material having a transparent film adhered thereto via an adhesive.

[0002]

2. Description of the Related Art In recent years, functional films having various functions have been often adhered to the front surface of a display via an adhesive, as home appliances and information devices have become more sophisticated and smaller and lighter. For example, (1) a CRT (cathode ray tube) in which a transparent film having a chromaticity and transmittance adjustment, antireflection and antiglare functions is attached to the surface of a glass substrate, and (2) an infrared ray cut on the front surface of the panel And a PDP (plasma display panel) to which a transparent film having an electromagnetic wave shielding function is adhered is a typical example. As a specific example of the method (1), in the case of coloring a CRT, the glass itself is conventionally colored, but recently a film is attached to the front of the CRT via a colored adhesive to adjust the chromaticity. Therefore, a film having a function such as anti-reflection has been used as the film. In the latter method (2), an adhesive film for color correction or a film having an antireflection function is attached to a transparent resin plate or glass to form a PDP. On the other hand, recently, there has been an increasing demand for reusing parts of home appliances and electronic devices from the standpoint of resource saving and ecology, and the display material with an adhesive of the present invention is no exception.

[0003] With such recent trends, there has been an increasing demand for a technology for separating and recycling a display substrate such as glass from an adhesive film even in an electronic display material to which an adhesive film is attached. In order to separate a display substrate from a display material according to a conventional technique, it has been proposed to peel off an adhesive sheet attached to a CRT using an external force. However, this method has a problem in that the adhesive tends to remain, that is, a so-called “paste residue”. This is considered to be due to the fact that CRTs and PDPs constantly generate a small amount of electromagnetic waves, so that the pressure-sensitive adhesive is degraded and the pressure-sensitive adhesive adheres firmly from the beginning. Therefore, in order to promote the recycling of glass, a technique for easily peeling the film without causing "adhesive residue" of the adhesive has been required.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of "adhesive residue" of an adhesive, which tends to occur when a display substrate such as glass is separated from a display material with an adhesive. is there.

[0005]

According to a first recycling method of a display material with an adhesive of the present invention, a transparent film is adhered to the surface of a display substrate via an adhesive containing a polyester resin or an acrylic resin. After immersing the attached display material in an alkaline solution, the transparent film and the adhesive are separated from the display substrate and reused. The second recycling method of the display material with an adhesive of the present invention is a method for producing a transparent film from a display material in which a transparent film is adhered to the surface of a display substrate via an adhesive containing a polyester resin or an acrylic resin. After peeling, the display material is dipped in an alkaline solution to remove the adhesive adhered to the display substrate surface, and the display substrate is separated for reuse.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, display materials applied to the present invention will be described in detail. As a display substrate of the display material, an electronic display, that is,
Glass, quartz, and transparent resin plates used as components of CRTs, PDPs, liquid crystals, ELs, PLALCDs (plasma-addressed liquid crystal displays), and the like are applicable. The transparent resin plate can be used as long as the material does not dissolve in an alkaline solution, and specifically, polyethylene, polypropylene, polyetheretherketone, styrene, acrylic resin,
Polyethylene terephthalate and the like are preferable, and a thermoplastic resin which is easy to recycle is particularly preferable.

[0007] The pressure-sensitive adhesive constituting the display material contains a polyester resin or an acrylic resin. The pressure-sensitive adhesive develops tackiness at any temperature of -40 ° C to 80 ° C, and may contain a polyester resin or an acrylic resin in the pressure-sensitive adhesive composition as a resin component in an amount of 50% by weight or more. More preferably, the content is 80% by weight or more. The polyester resin is a resin having an ester bond obtained by condensation of an acid component and an alcohol component, and the acrylic resin is a resin obtained by radical polymerization of a monomer having an acryl group.
If the content of the polyester-based resin or the acrylic-based resin is less than 50% by weight, it takes a long time to immerse the adhesive in an alkaline solution because the releasability of the adhesive from the display substrate is reduced. As the pressure-sensitive adhesive, (meth) acrylate resins and copolymers thereof are preferable among polyester-based resins and acrylic-based resins because of their excellent releasability. The (meth) acrylate (monomer) used for the (meth) acrylate resin and the copolymer thereof has an alkyl group having 1 to 12 carbon atoms, and includes methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n- Octyl (meth) acrylate, isooctyl (meth) acrylate, lauryl (meth) acrylate and the like can be mentioned, and these can be used alone or in combination of two or more as a copolymer. A monomer having an unsaturated double bond other than the (meth) acrylate, for example, an olefin-based or vinyl-based monomer may be used as the copolymerization component. Further, the (meth) acrylate monomer and a monomer having the following functional group may be copolymerized and cross-linked using a cross-linking agent that reacts with the functional group. Examples of the monomer having a functional group include monomers having a carboxyl group such as (meth) acrylic acid, maleic acid, itaconic acid, and crotonic acid, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl acrylate. Monomers having a hydroxyl group such as vinyl ether, N-N-dimethylaminoethyl acrylate, N
Examples include monomers having an amino group such as -t-butylaminoethyl acrylate, and monomers having an epoxy group such as glycidyl acrylate and glycidyl methacrylate.

Examples of the crosslinking agent which reacts with the functional group include polyfunctional isocyanate crosslinking agents such as tolylene diisocyanate, hexamethylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate, ethylene glycol diglycidyl ether, propylene. N, N'-hexamethylene-1,6-bis (1--polyfunctional epoxy crosslinking agent such as glycol diglycidyl ether
Polyfunctional aziridine-based crosslinking agents such as aziridinecarboxamide) and trimethylolpropane-tri-β-aziridinylpropionate; metal chelate-based crosslinking agents such as aluminum acetylacetone complex; and peroxide-based crosslinking such as benzoyl peroxide. And melamine-based cross-linking agents. These can be used alone or in combination of two or more.

The resin constituting the pressure-sensitive adhesive has a weight average molecular weight of 1 to 5,000,000, preferably 100 to 2,000,000.
The weight average molecular weight was measured by gel permeation chromatography using styrene as a standard. The glass transition temperature of the resin constituting the adhesive is 10
C. or lower, more preferably -100 to 0C, and most preferably -80 to -15C. The pressure-sensitive adhesive may contain a component other than the resin. Components other than the resin include plasticizers, tackifiers, adhesive property modifiers such as silane coupling agents, colorants such as carbon, pigments, dyes, silica, titanium dioxide, alumina, metal powder, and metal oxide powder. Such as inorganic filler, resin fine particles, ultraviolet absorber,
Infrared absorbers and the like can be mentioned, and each is used according to the purpose. For example, an adhesive containing carbon and / or a pigment is used in some of the CRTs for color correction and the like.

The transparent film constituting the display material preferably has a thickness of 10 to 500 μm, more preferably 30 to 200 μm.
If the thickness is less than 10 μm, the handleability of the film is poor,
When the thickness exceeds 500 μm, the film has poor light transmittance and poor flexibility. Preferred materials for the transparent film include polyolefin films such as polyethylene and polypropylene, polyester films such as polyethylene terephthalate (PET), polyetheretherketone, triacetylcellulose, and polyparabanic acid. And polyester films are preferably used. Preferably, one surface of the transparent film is subjected to an optical treatment such as an anti-reflection treatment and an anti-glare treatment.
The transparent film has a haze value of 30% or less, preferably 20% or less, and more preferably 10% or less, and is determined by the following equation. Haze (%) = (scattered light intensity / total light transmission intensity) × 100 The display material used in the recycling method of the present invention is, for example, a pressure-sensitive adhesive layer laminated on one surface of the transparent film and adhered to the display substrate. Then, if necessary, a curing process such as heating is performed to form the film.

The pH of the alkaline solution used in the method for recycling a display material with a pressure-sensitive adhesive of the present invention is preferably 8 or more, and more preferably 10 or more. More preferred pH is 11 or higher, optimally 1
2 or more. It is more preferable to set the pH to a higher value because the peeling becomes easier and the time for immersion in the alkaline solution is reduced. The alkaline solution can be easily prepared by dissolving an alkaline salt in water in an aqueous solution. Examples of the salt include sodium hydroxide, potassium hydroxide, sodium phosphate, ammonium hydroxide, sodium carbonate / sodium hydrogencarbonate and the like. Among them, sodium hydroxide and / or potassium hydroxide are inexpensive and are used for the pressure-sensitive adhesive composition. It is preferably used because of good releasability.

First of Display Materials with Adhesive of the Present Invention
The recycling method, the display material, a transparent film adhered to the surface of the display substrate via an adhesive containing a polyester resin or an acrylic resin,
After dipping in an alkaline solution, the transparent film and the adhesive are separated from the display substrate, and the display substrate is separated for reuse. First, the display material is placed in an alkaline solution for several minutes to 4 hours.
Soak for 8 hours. At this time, the temperature of the alkaline solution is 1
5-100 ° C. is preferred, and more preferably 20-95 ° C.
C., preferably 25-85C, most preferably 30-80C. If the temperature is lower than 15 ° C., it takes a long time for immersion,
If it exceeds ℃, there is a risk of bumping. The solution can be used under a pressure of 100 ° C. or more.
It is preferable that the alkaline solution flows slowly in the tank. Specifically, it is preferable to flow the solution with a stirring blade or the like because the pressure-sensitive adhesive is easily peeled off. It is also effective and preferable to directly spray the alkaline solution onto the adhesive and the transparent film in a shower manner.

Next, the display material is taken out of the alkaline solution, the transparent film and the adhesive are peeled off, and the display base material for reuse is separated. At this time, it is preferable to apply a weak external force, that is, an external force that grasps one end of the film and peels off, because even a weak force can easily peel off without causing cohesive failure of the adhesive layer. At this time, if necessary, the display material may be taken out of the alkaline solution and then washed with water. It is also preferable to neutralize with a weakly acidic solution as a pretreatment for washing with water.

Second Embodiment of the Display Material with Adhesive of the Present Invention
The method of recycling is, after the transparent film is peeled off from the display material in which the transparent film is adhered to the surface of the display substrate via an adhesive containing a polyester resin or an acrylic resin, the display material is converted into an alkaline solution. The method is characterized in that the pressure-sensitive adhesive adhered to the surface of the display substrate is removed by immersion, and the display substrate is separated for reuse. When peeling the transparent film from the display material, a certain external force is applied to peel the transparent film. At this time, the adhesive "glue remains" on the display substrate. The adhesive material can be easily removed by immersing the display substrate with “adhesive residue” in an alkaline solution. The preferred immersion time, immersion temperature, and alkaline solution in the tank in each step are as described in the first recycling method. The display base material such as glass separated from the display material by the recycling method of the present invention is returned to a glass factory and reused in principle, or a functional transparent film is stuck as it is via an adhesive, and the display material is It is also possible to reuse as.

[0015]

The present invention will be described below with reference to examples. [Synthesis of (meth) acrylate copolymer adhesive] 94 parts by weight of n-butyl acrylate, acrylic acid 5 in a flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet tube
Parts by weight, 1 part by weight of 2-hydroxyethyl acrylate,
0.3 parts by weight of benzoyl peroxide, 40 parts by weight of ethyl acetate, and 60 parts by weight of toluene were charged, nitrogen was introduced from a nitrogen introduction tube, the flask was set to a nitrogen atmosphere, and then heated to 65 ° C. for polymerization for 10 hours. The reaction was carried out to obtain a weight average molecular weight of about 12
An acrylic polymer solution having a Tg of about -49 ° C. was obtained.
Ethyl acetate was added to this acrylic polymer solution so that the solid content was 20%, and 1 part by weight of polyisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name: Coronate L) was added to 100 parts by weight of the solid content. Agent coating liquid. (Preparation of First Sample for Peeling Test) One side of a 38 μm-thick PET film subjected to a peeling treatment was coated with a pressure-sensitive adhesive coating solution having the above composition so that the thickness after drying was 25 μm, and then 100 ° C. For 3 minutes to produce an adhesive film, and the film was aged at 23 ° C. for 1 week. Next, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive film (25 mm width) was attached to a 2 mm-thick soda glass plate (manufactured by Nippon Sheet Glass Co., Ltd., trade name: FT2.0) as a display substrate with a laminator. The sample was put into a thermostat for 500 hours to cure the pressure-sensitive adhesive layer, thereby obtaining a first sample for a peeling test.

Example 1 The PET film of the first sample for peel test was peeled off, and the sample was immersed in a potassium hydroxide solution of pH 14 (solution temperature: 25 ° C., the solution was stirred by a stirrer). After 8 hours, the pressure-sensitive adhesive layer was completely peeled off from the glass plate in its original shape.

[Example 2] A sample was immersed in a liquid in the same manner as in Example 1 except that the temperature of the solution was set to 60 ° C.
After 1.5 hours, the pressure-sensitive adhesive layer was completely peeled off from the glass plate as it was.

Example 3 A sample was immersed in a liquid in the same manner as in Example 1 except that the temperature of the solution was 80 ° C.
After one hour, the pressure-sensitive adhesive layer was completely peeled off from the glass plate in its original shape.

Example 4 A sample was immersed in a solution in the same manner as in Example 3 except that the alkaline solution was changed to a potassium hydroxide solution having a pH of 12 (solution temperature: 80 ° C.). After 3 hours, the pressure-sensitive adhesive layer was completely peeled off from the glass plate in its original shape.

Example 5 A sample was immersed in a solution in the same manner as in Example 3 except that the alkaline solution was changed to a sodium hydroxide solution having a pH of 10 (solution temperature: 80 ° C.). After 6 hours, the pressure-sensitive adhesive layer was completely peeled off from the glass plate in its original shape.

(Preparation of Sample for Second Peeling Test) On one surface of a PET film having a thickness of 188 μm, the above-mentioned pressure-sensitive adhesive coating liquid was applied so as to have a thickness of 25 μm after drying.
The film was dried at 3 ° C. for 3 minutes to prepare a film with an adhesive layer, and the film was aged at 23 ° C. for 1 week. Next, the film with an adhesive layer was attached to the glass plate used in Example 1 with a laminator, and was put into a constant temperature bath at 80 ° C. for 500 hours.
The adhesive layer was cured to obtain a second sample for a peel test.

Example 6 The sample for the second peel test was immersed in a potassium hydroxide solution having a pH of 14 (solution temperature: 25 ° C., stirred by a stirrer). After taking out from the liquid after 12 hours and washing with water, one end of the PET film was gripped and peeled off (300 mm / min, 180 ° peel test), and peeled off with a force of 2.9 N / 25 mm. The layer could be completely removed from the glass with the PET film.

Example 7 A sample was immersed in a potassium hydroxide solution in the same manner as in Example 6 except that the temperature of the solution was 60 ° C. After taking out from the liquid after 6 hours and washing with water, one end of the PET film was gripped and peeled off (300 mm / min, 180 ° peel test).
It could be peeled off with a force of 7 N / 25 mm, and the adhesive layer could be completely peeled off the glass together with the PET film.

Example 8 A sample was immersed in a solution in the same manner as in Example 6 except that the alkaline solution was changed to a potassium hydroxide solution having a pH of 12 (solution temperature: 80 ° C.). After 6 hours, the PET film was taken out of the liquid and washed with water, and then one end of the PET film was gripped and peeled off (300 mm / min,
180 ° peel test) The film could be peeled off with a force of 2.7 N / 25 mm, and the pressure-sensitive adhesive layer could be completely peeled off the glass together with the PET film.

Comparative Example 1 A first sample for a peel test was immersed in the same manner as in Example 1 except that the aqueous potassium hydroxide solution was changed to pure water (pH 7, liquid temperature 25 ° C.). Even after immersion for 2 weeks, the pressure-sensitive adhesive layer did not peel off from the glass plate.

Comparative Example 2 A first sample for a peeling test was immersed in the same manner as in Example 1 except that the aqueous solution of potassium hydroxide was changed to ethyl acetate. Even after immersion for 2 weeks, the pressure-sensitive adhesive layer did not peel off from the glass plate.

Comparative Example 3 A first peel test sample was immersed in the same manner as in Example 1 except that the aqueous potassium hydroxide solution was changed to methyl ethyl ketone. Even after immersion for 2 weeks, the pressure-sensitive adhesive layer did not peel off from the glass plate.

Comparative Example 4 A first peel test sample was immersed in the same manner as in Example 1 except that the aqueous potassium hydroxide solution was replaced with methanol. Even after immersion for 2 weeks, the pressure-sensitive adhesive layer did not peel off from the glass plate.

[Comparative Example 5] pH of aqueous potassium hydroxide solution
A first peel test sample was immersed in the same manner as in Example 1 except that the acetic acid solution of 5.5 was used. Even after immersion for 2 weeks, the pressure-sensitive adhesive layer did not peel off from the glass plate.

Comparative Example 6 A first peel test sample was immersed in the same manner as in Example 3 except that the aqueous potassium hydroxide solution was changed to pure water. Even after immersion for 2 weeks, the pressure-sensitive adhesive layer did not peel off from the glass plate.

Comparative Example 7 Comparative Example 1 was repeated except that the peel test sample of Comparative Example 1 was replaced with a second peel test sample.
The sample was immersed for 2 weeks in the same manner as described above. When the PET film was gripped at one end and peeled off (300 mm / m
In, 180 ° peel test) At 21.6 N / 25 mm, the pressure-sensitive adhesive layer caused cohesive failure, and the PET film was peeled off with a large amount of the pressure-sensitive adhesive adhered to the glass.

As is clear from the above results, in the peeling tests of Examples 1 to 8 using the recycling method of the present invention, the pressure-sensitive adhesive could be easily peeled without remaining on the glass surface. On the other hand, in the methods of Comparative Examples 1 to 7, the pressure-sensitive adhesive layer could not be peeled off from the glass even after two weeks. Examples 6 to
In Comparative Example 7, the PET film could be peeled off with "peel strength" of 2.9 N / 25 mm or less without "glue remaining", whereas in Comparative Example 7, the PET film was peeled off with a force of 21.6 N / 25 mm. However, "adhesive residue" in which a large amount of the adhesive adhered to the glass surface occurred.

[0033]

According to the method for recycling a display material with a pressure-sensitive adhesive of the present invention, the pressure-sensitive adhesive and the transparent film can be easily peeled off from the display substrate, so that the display substrate such as glass for reuse can be reliably obtained. It has become possible to separate. Further, by increasing the pH of the immersion liquid and / or increasing the solution temperature, it is possible to shorten the time required for peeling. The present invention relates to CRT, P
The present invention can be easily applied to peeling a functional film such as a colored adhesive film, an antireflection film, an antiglare film, an electromagnetic wave shielding film, and an infrared shielding film attached to an electronic display such as DP and liquid crystal.

Claims (4)

[Claims] 1. A display material having a transparent film adhered to the surface of a display substrate via a pressure-sensitive adhesive containing a polyester resin or an acrylic resin is immersed in an alkaline solution, and then the display material is removed from the display substrate. And separating the display substrate for reuse. 2. After peeling off a transparent film from a display material in which a transparent film is adhered to the surface of a display substrate via an adhesive containing a polyester resin or an acrylic resin, the display material is converted into an alkaline solution. A method for recycling a display material with a pressure-sensitive adhesive, characterized by removing the pressure-sensitive adhesive adhered to the surface of the display substrate by immersion, and separating the display substrate for reuse. 3. The method according to claim 1, wherein the temperature of the alkaline solution for immersing the display material is 15 to 100 ° C. 4. The method for recycling a display material with an adhesive according to claim 1, wherein the alkaline solution for immersing the display material is flowing.