JP4879919B2 - Laminated body - Google Patents

Description

  The present invention is a building building window, machine tool window, vehicle / railway / ship / aircraft window, helmet windshield, goggles, precious metal and art showcase, financial relations, which require crime prevention, safety and disaster prevention. Windows, laminated glass such as laminated optical lenses, flat panel image devices such as liquid crystal display, PDP (plasma display) display, EL (organic electroluminescence) display, and solar cell modules that require impact resistance, lightness, and visibility The present invention relates to a hot-melt type UV-crosslinked transparent adhesive sheet that can be used for transparent protective panel laminates for sensors, gauges, and meters, and laminates.

Conventionally, glass plates were mainly used for laminated glass and protective panels, but in recent years, the demand for crime prevention, safety, disaster prevention, weight reduction, and improvement in impact resistance has increased, and acrylic is used as a material to replace glass plates. Different types of laminated glass combined with synthetic resin plates such as plates and polycarbonate (PC) plates have been widely used.
However, since the linear expansion coefficient of glass plate and synthetic resin plate is different, conventional autoclave method using thermoplastic resin or liquid adhesive as disclosed in Patent Document 1 is injected and manufactured by UV or thermosetting With the laminated glass, problems such as warpage, peeling, and cracking could not be solved.
In addition, crime prevention and safety performance of conventional window-laminated films are not enough for crimes that are becoming more and more severe year by year, so PC laminated glass, etc. for windows, showcases, etc. related to stores that handle vehicles, ordinary houses, finance and expensive goods. However, there is a problem that warping, peeling and cracking increase as the area increases, and that existing windows must be replaced.
In addition, when a protective panel is laminated on an image display device or the like, there is a problem that it is difficult to apply pressure or heat, it is difficult to laminate directly on the display panel, and the weight and thickness cannot be reduced.

JP 7-290647 A

  The present invention has been made in view of the above-mentioned problems of the prior art, and can produce a laminate at room temperature without requiring high-temperature and high-pressure treatment by an autoclave, and is less likely to cause plate displacement. An object of the present invention is to provide a hot-melt type UV-crosslinked transparent pressure-sensitive adhesive sheet having excellent quality such as the above, and a laminate obtained by using the same.

(1) For a (meth) acrylate copolymer having a melt viscosity at 130 ° C. of 150,000 to 500,000 (mPa · s), at least a hydrogen abstraction type photoradical initiator of a photoradical initiator is reduced to 0 A hot-melt type UV-crosslinking transparent adhesive containing 0.01 to 1.0% by weight is hot-melt-molded and then cross-linked by UV irradiation , and the 40 ° C. holding force is a deviation length of 1.0 mm or more and less than 13 mm. It is a laminate formed by laminating a transparent glass plate and a synthetic resin plate using an adhesive sheet as an intermediate layer .
(2) Tg of the (meth) acrylic acid ester copolymer is -20 ° C or less.

According to the present invention, a synthetic resin plate or a glass plate can be easily bonded at room temperature without requiring high-temperature and high-pressure treatment by an autoclave, and has excellent quality such as being less likely to cause plate displacement. laminate obtained by using the hot-melt UV cross transparent adhesive sheet is provided.

The hot melt type ultraviolet cross-linking transparent adhesive used in the invention according to claim 1 is a hydrogen abstraction type photo radical initiator that is at least one kind of photo radical initiator with respect to the (meth) acrylic acid ester copolymer. It is characterized by containing.
A general ultraviolet crosslinking adhesive must contain both a UV crosslinking monomer and a photoinitiator. As a result of intensive studies, the present inventor has found that the (meth) acrylate copolymer is UV crosslinked. It has been found that UV crosslinking is possible with at least a hydrogen abstraction type photo radical initiator without containing a monomer.

  Hydrogen abstraction type photo radical initiator is a photopolymerization initiator that generates radicals by extracting hydrogen from other molecules, and typical hydrogen abstraction type photo radical initiators used in the present invention are transparent and curable. From this point, benzophenone is preferable, and the content can be selected according to the thickness of the pressure-sensitive adhesive sheet and UV irradiation conditions. In addition, benzyl, methyl O-benzoylbenzoate, acrylated benzophenone, thioxanthone, 3-ketocoumarin, 2-ethylanthraquinone, camphorquinone, Michler ketone, tetra (t-butylperoxycarbonyl) benzophenone, or the like It is also possible to use a mixture of two or more kinds, a mixture with a cleavage type photo radical initiator, and the like.

  The content of the photo radical initiator is preferably in the range of 0.01 to 1.0% by weight with respect to the (meth) acrylic acid ester copolymer, taking into consideration thick film curability, transparency, and stability over time. Then, 0.05 to 0.5% by weight is suitable.

The (meth) acrylate used for forming the (meth) acrylic acid ester copolymer, that is, as the alkyl acrylate or alkyl methacrylate component, the alkyl group is n-octyl, isooctyl, 2-ethylhexyl, n-butyl, isobutyl, One of alkyl acrylate or alkyl methacrylate which is any one of methyl, ethyl and isopropyl, or a mixture of two or more selected from these may be used. As other components, an acrylate or methacrylate having an organic functional group such as a carboxyl group, a hydroxyl group, or a glycidyl group may be copolymerized.
The alkyl (meth) acrylate component and a (meth) acrylate component having an organic functional group are appropriately selected and combined to obtain a monomer component obtained by heat polymerization using as a starting material.

In order to obtain a flexible pressure-sensitive adhesive sheet that can produce a high-quality laminate at room temperature, the following requirements for melt viscosity and / or Tg are provided as characteristics of the (meth) acrylic acid ester copolymer before crosslinking: Are preferred.
(a) The melt viscosity at 130 ° C. of the (meth) acrylic acid ester copolymer is 50,000 to 500,000 (mPa · s).
(b) The Tg of the (meth) acrylic acid ester copolymer is -20 ° C or lower.

The melt viscosity and Tg of the (meth) acrylic acid ester copolymer obtained by polymerization are measured using, for example, a viscoelasticity measuring device dynamic analyzer RDA-II manufactured by Rheometrics.
In the case of melt viscosity, the viscosity (η *) value measured at a parallel plate of 25 mmφ, strain of 2%, 130 ° C. and 0.02 Hz is read.
In the case of Tg, the temperature indicating the maximum value of Tan δ when measured at a parallel plate of 25 mmφ, a strain of 2%, and a frequency of 1 Hz is read.

The melt viscosity of the (meth) acrylic ester copolymer is in the range of 50,000 to 500,000 (mPa · s), and Tg is preferably −20 ° C. or less. If the melt viscosity is less than 50,000 (mPa · s), the thickness accuracy during thick film forming cannot be obtained, and sufficient flexibility cannot be obtained for the crosslinked sheet. When the melt viscosity exceeds 500,000 (mPa · s), hot melt processability becomes difficult.
On the other hand, if Tg is higher than −20 ° C., the durability of the laminate at a low temperature is lowered.
In view of flexibility and durability, it is more preferable to prepare the melt viscosity in the range of 150,000 to 400,000 (mPa · s) and Tg in the range of −60 to −40 ° C.
The (meth) acrylic acid ester-based copolymer as described above can contain a hydrogen abstraction type photo radical initiator to obtain a hot melt type UV crosslinking adhesive.

  The transparent pressure-sensitive adhesive sheet is usually obtained by forming the pressure-sensitive adhesive into a sheet having a thickness of 0.05 to 2 mm and then irradiating it with ultraviolet rays to crosslink. Molding into a sheet is usually formed by laminating on a release film. As illustrated in the examples, a transparent adhesive in a molten state is separated into two release films (at least one of which is a transparent release film). The film is preferably formed so as to be sandwiched between the mold films). A transparent adhesive sheet is obtained by crosslinking by irradiating with ultraviolet rays through a transparent film.

  The hot-melt type UV-crosslinked transparent pressure-sensitive adhesive sheet according to the present invention has a preferable pressure-sensitive adhesive sheet holding power (cohesive force) in order to obtain adhesion durability. The pressure-sensitive adhesive is subjected to ultraviolet irradiation after hot-melt molding. The pressure-sensitive adhesive sheet is crosslinked and has a 40 ° C. holding force of a shift length of 1.0 mm or more and less than 13 mm.

Here, the holding force is an area of 20 mm × 20 mm using an SUS plate as defined in JIS Z 0237 after a pressure-sensitive adhesive sheet molded to a thickness of 0.5 mm and UV-crosslinked is attached with a 38 μm PET film. It is measured by the deviation length after applying a load of 4.9 N in a direction along the surface of the SUS plate for 2 hours in an environment of 40 ° C.
If the holding power deviation is less than 1.0 mm, the cohesive force is large, and in the case of a laminate of different plate materials, the difference in linear expansion coefficient cannot be absorbed in the cold test, causing warping, peeling, and cracking. If the displacement is 13 mm or more, the cohesive force is small, and the laminated plates may be displaced, or the adhesive sheet may foam and cause poor appearance. Preferably, adjustment within the range of 5 mm to 10 mm can most satisfy the durability after lamination.

The transparent adhesive sheet as described above is used as an intermediate layer to form a laminate formed by laminating a transparent glass plate or synthetic resin plate on at least one side.
A conventional transparent laminated body such as laminated glass uses two glass plates and a thermoplastic resin or a liquid adhesive, whereas the present invention uses a flexible adhesive sheet that can be bonded in a room temperature environment. To do.
For example, it can be configured as a transparent laminate formed by laminating at least two glass plates, glass plates and synthetic resin plates, or synthetic resin plates using the transparent adhesive sheet. Two or more laminated structures may be laminated alternately such as glass plate / synthetic resin plate / glass plate, synthetic resin plate / glass plate / synthetic resin plate. A transparent laminate or a laminate which is a transparent plate only on one side has good transparency. For example, if one side is a transparent plate, the other side may be an opaque metal plate, a design plate, or the like. In addition, when it is not necessary to provide a transparent board on one side, it can also comprise as laminated bodies, such as a metal plate / metal plate, using the transparent adhesive which concerns on this invention.

Although there are various methods for producing the laminate, examples of a method that can be laminated without using an autoclave include the following methods.
First, there is a method in which the transparent adhesive sheet of the present invention is previously applied to one plate-like body constituting the laminate, and then the other plate-like body is evacuated and then laminated by pressing through the pressure-sensitive adhesive surface. .
First, the transparent adhesive sheet of the present invention is applied in advance to one plate-like body constituting the laminate, and then the other plate-like body is contacted for the first time between the nip rolls via the adhesive surface. There is a method of laminating both plates continuously while extruding bubbles with the pressure of a roll.
In this way, a laminate having good quality can be obtained.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and additions are possible within the scope of the present invention.

Hereinafter, although an example is described, the present invention is not limited to this.
Example 1
Acrylic ester copolymer: 0.1 parts by weight of benzophenone as a hydrogen abstraction type photoinitiator is added to 100 parts by weight, and the mixture is melted and stirred to form a transparent adhesive, which has a thickness of 75 μm and 100 μm. The sheet was hot-melt molded into a 0.5 mm thick sheet sandwiched between molds PET, and a single-sided integrated light amount of 3600 mJ / cm ² was irradiated through the release PET using a high-pressure mercury lamp to obtain a transparent adhesive sheet. The integrated light quantity was measured by attaching an X19 filter to a UV-M10 UV3t sensor manufactured by Oak Manufacturing Co., Ltd.
The composition of the acrylic ester copolymer used was obtained by copolymerizing n-butyl acrylate: 78.4% by weight, 2-ethylhexyl acrylate: 19.6% by weight, and acrylic acid: 2.0% by weight. The melt viscosity was -40 ° C. and 130 ° C. 250,000 (mPa · s).

Using the pressure-sensitive adhesive sheet as an intermediate film-forming sheet, a transparent laminate was produced by the following method. The temperature conditions during the production were performed at room temperature (20 ° C.).
The production method was as follows. An adhesive sheet for an intermediate film, in which a release film on one side was peeled off from one of commercially available polycarbonate (PC) plates (thickness 5 mm, width 300 mm, length 600 m) previously dried at 80 ° C., and nip roll It was carried in between the rolls so that it contacted for the first time between the drive rolls, and after sticking at a linear pressure: 9.8 N / cm and speed: 5 m / min, the remaining release film was peeled off.
Next, the PC plate with the adhesive sheet attached is faced to the commercial float glass plate (thickness 3 mm, width 300 mm, length 600 mm) through the adhesive sheet, and the ends of the two plates are nip-rolled. And a driving roll were fed so as to be in contact with each other for the first time, and sandwiched between nip rolls (linear pressure: 294 N / cm, speed: 0.5 m / min) to obtain a transparent laminate.

(Example 2)
Acrylate ester copolymer used in Example 1: 100 parts by weight of Irgacure 500 (hydrogen abstraction type benzophenone / cleavable photoinitiator Irgacure 184 manufactured by Ciba Specialty Chemicals Co., Ltd.) as a photoinitiator = 50/50 blended product): 0.15 parts by weight is added and melted and stirred to form a transparent adhesive, which is sandwiched between 75 μm and 100 μm release PET and hot into a 0.5 mm thick sheet. Using a high-pressure mercury lamp, melt-molding was performed, and a single-sided integrated light amount of 3600 mJ / cm ² was irradiated front and back through the release PET to obtain a transparent adhesive sheet. Other conditions were the same as in Example 1.
A transparent laminate was obtained in the same manner as in Example 1 using the transparent adhesive sheet thus obtained.

(Example 3)
The composition ratio of the acrylate ester was the same as in Example 1. The acrylate copolymer prepared at a melt viscosity of 400,000 (mPa · s): 100 parts by weight, benzophenone: 0.1 part by weight was melted and stirred. After that, a transparent adhesive sheet and a transparent laminate were obtained in the same manner as in Example 1.

(Comparative Example 1)
Acrylic ester copolymer used in Example 1: 100 parts by weight of melt-stirred irgacure 184: Ciba Specialty Chemicals Irgacure 184 as a photoinitiator was used as a photoinitiator. Then, the transparent adhesive sheet and the transparent laminated body were obtained by the method similar to Example 1.

(Comparative Example 2)
Acrylic acid ester copolymer used in Example 1: 100 parts by weight, Ivacure 500: 1.2 parts by weight manufactured by Ciba Specialty Chemicals as a photoinitiator was melted and stirred, and then the same as in Example 1 A transparent adhesive sheet and a transparent laminate were obtained by the method.

(Comparative Example 3)
After melting and stirring Irgacure 500: 0.008 parts by weight as a photoinitiator with respect to 100 parts by weight of the acrylic ester copolymer used in Example 1, the transparent adhesive sheet and the transparent were prepared in the same manner as in Example 1. A laminate was obtained.

(Comparative Example 4)
The composition ratio of the acrylic ester is copolymerization of n-butyl acrylate: 70% by weight, 2-ethylhexyl acrylate: 5% by weight, acrylic acid: 25% by weight, Tg is −10 ° C., 130 ° C. melt viscosity is 100,000 ( mPa · s) Acrylate ester copolymer: 100 parts by weight, Irgacure 500: 0.8 parts by weight as a photoinitiator was melted and stirred, and then the transparent adhesive sheet and A transparent laminate was obtained.

(Comparative Example 5)
The composition ratio of the acrylate ester was the same as in Example 1, and the acrylate ester copolymer prepared at a melt viscosity of 40,000 (mPa · s): 100 parts by weight, Irgacure 500: 1.0 parts by weight was melted. After stirring, a transparent adhesive sheet and a transparent laminate were obtained in the same manner as in Example 1.

(Test and evaluation)
About the produced adhesive sheet, 40 degreeC retention strength is measured with the said measuring method, and about a transparent laminated body, it is an external appearance about a laminated body after a 2 week test by -20-80 degreeC heat (4 cycles / day) cycle. The observation results are shown in Table 1. In the evaluation by appearance observation, a sample satisfying all of no foaming, no peeling, and no plate displacement was evaluated as ◯.

  As is apparent from the results in Table 1, when each of the transparent adhesive sheets of Examples 1 to 3 is used, a laminate that can be laminated at room temperature and is satisfactory in appearance and excellent in durability is obtained. In contrast, in each of the transparent adhesive sheets of Comparative Examples 1 to 3 using an adhesive that does not satisfy the structure of claim 1 of the present invention, good results were obtained for both the holding power and the appearance observation. I couldn't. In Comparative Examples 4 and 5, although the holding power was good, peeling occurred in appearance observation.

Claims (2)

For a (meth) acrylic acid ester copolymer having a melt viscosity at 130 ° C. of 150,000 to 500,000 (mPa · s), at least a hydrogen abstraction type photoradical initiator of the photoradical initiator is 0.01 to A pressure-sensitive adhesive sheet having a shift length of 40 ° C. holding force of 1.0 mm or more and less than 13 mm after hot-melt molding of a hot-melt type UV-crosslinked transparent pressure-sensitive adhesive containing 1.0% by weight , followed by UV irradiation. A laminate formed by laminating between a transparent glass plate and a synthetic resin plate as an intermediate layer. The laminate according to claim 1, wherein Tg of the (meth) acrylic acid ester copolymer is −20 ° C. or lower.