JP2024146803A - Method for producing pressure-sensitive adhesive sheet, method for producing optical film with pressure-sensitive adhesive sheet, and method for producing image display device - Google Patents

Abstract

To provide a novel production method suitable for efficiently producing a pressure-sensitive adhesive sheet.SOLUTION: This production method for an adhesive sheet 1 includes a step of forming the adhesive sheet 1 by irradiating a coating layer 12 containing a photocurable composition with light 14 from a light-emitting diode 34. The peak wavelength of the light 14 irradiated onto the coating layer 12 is 325 nm to 350 nm. This production method for an optical film 21 with an adhesive sheet includes arranging an optical film 2 on an exposed surface 18 of the adhesive sheet 1 formed by this production method to form the optical film 21 with an adhesive sheet.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for manufacturing an adhesive sheet, a method for manufacturing an optical film with an adhesive sheet, and a method for manufacturing an image display device.

Various image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices, generally include an optical laminate that includes an optical film, such as a polarizing film, and an adhesive sheet. Adhesive sheets are usually used to bond the optical films included in the optical laminate, and to bond the optical laminate to an image display panel. A typical adhesive sheet is a sheet made by polymerizing and crosslinking monomer groups, including acrylic monomers and silicone monomers.

Patent Document 1 discloses an example of a pressure-sensitive adhesive sheet. In Patent Document 1, the pressure-sensitive adhesive sheet is produced by irradiating a coating layer of a pressure-sensitive adhesive composition disposed between two release liners with light.

Patent No. 6688054

A typical adhesive sheet is manufactured, for example, by the following thermosetting method. First, a crosslinking agent or the like is added to a polymer produced by polymerizing a polymerizable monomer in an organic solvent to prepare an adhesive composition. This adhesive composition is applied to a substrate such as a release liner, and the organic solvent is removed by heating to form a sheet. If necessary, heat aging is performed to complete crosslinking, thereby manufacturing an adhesive sheet. In this manufacturing process, a large amount of fuel such as LNG needs to be burned in order to generate the thermal energy required for the thermal removal of the solvent and the thermal aging. In addition, if the organic solvent removed by heating is directly released into the atmosphere, it may have a significant adverse effect on the surrounding environment. Therefore, the organic solvent is often burned in a deodorizing furnace or the like before being released. In this case, not only is additional fuel required for combustion in the deodorizing furnace, but the organic solvent itself is also converted into CO ₂ by combustion and released into the atmosphere, resulting in a manufacturing process with extremely large CO ₂ emissions.

In recent years, climate change caused by greenhouse gases has become an urgent issue, and governments around the world have set numerical targets to reduce _CO2 emissions. In the manufacture of pressure sensitive adhesive sheets, too, there is a demand to select manufacturing processes that do not use organic solvents and that emit less _CO2 .

According to a method for producing an adhesive sheet using light (photocuring method), the amount of energy required for forming the adhesive sheet and the amount of _CO2 emissions can be reduced compared to the above-mentioned heat curing method. In the photocuring method, for example, a black light source is used (Patent Document 1). However, according to the study by the present inventors, in the photocuring method using a black light source, the amount of photopolymerization initiator remaining in the produced adhesive sheet tends to be large, and there is room for improvement from the viewpoint of efficiently producing an adhesive sheet.

Therefore, the present invention aims to provide a new manufacturing method suitable for efficiently producing adhesive sheets.

The present invention relates to
The method includes a step of irradiating a coating layer containing a photocurable composition with light from a light emitting diode to form a pressure sensitive adhesive sheet,
The light irradiated to the coating layer has a peak wavelength of 325 nm to 350 nm.

Further, the present invention relates to
The present invention provides a method for producing an optical film with a pressure-sensitive adhesive sheet, the method comprising: forming an optical film with a pressure-sensitive adhesive sheet by disposing an optical film on an exposed surface of the pressure-sensitive adhesive sheet formed by the above-described production method.

Further, the present invention relates to
The present invention also provides a method for producing an image display device, which comprises bonding an optical film with a pressure-sensitive adhesive sheet formed by the above-mentioned production method to an image display panel to form an image display device.

The present invention provides a new manufacturing method suitable for efficiently producing adhesive sheets.

1A to 1C are schematic diagrams illustrating an example of a method for producing a pressure-sensitive adhesive sheet of the present invention. 1A to 1C are schematic diagrams illustrating an example of a method for producing a pressure-sensitive adhesive sheet of the present invention. 1A to 1C are schematic diagrams illustrating an example of a method for producing a pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a schematic diagram for explaining an example of a method for producing an optical film with a pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a schematic diagram for explaining an example of a method for producing an optical film with a pressure-sensitive adhesive sheet of the present invention. FIG. 2 is a schematic diagram for explaining an example of a method for producing an optical film with a pressure-sensitive adhesive sheet of the present invention.

A method for producing a pressure-sensitive adhesive sheet according to a first aspect of the present invention includes the steps of:
The method includes a step of irradiating a coating layer containing a photocurable composition with light from a light emitting diode to form a pressure sensitive adhesive sheet,
The light irradiated onto the coating layer has a peak wavelength of 325 nm to 350 nm.

In the second aspect of the present invention, for example, in the manufacturing method according to the first aspect, the peak wavelength is 340±10 nm.

In a third aspect of the present invention, for example, in the production method according to the first or second aspect, the illuminance of the light irradiated onto the coating layer is 2.0 to 30 mW/cm ² .

In the fourth aspect of the present invention, for example, in the manufacturing method according to any one of the first to third aspects, the light is irradiated onto a laminate including a base sheet, the coating layer, and a release liner in this order.

In a fifth aspect of the present invention, for example, in the manufacturing method according to any one of the first to fourth aspects, the time for irradiating the coating layer with the light is 10 seconds to 1000 seconds.

In a sixth aspect of the present invention, for example, in the manufacturing method according to any one of the first to fifth aspects, the temperature of the coating layer is maintained at 10°C to 30°C while the coating layer is irradiated with the light.

In the seventh aspect of the present invention, for example, in the manufacturing method according to any one of the first to sixth aspects, the coating layer is irradiated with the light in an atmosphere having an oxygen concentration of 500 vol ppm or less.

In an eighth aspect of the present invention, for example, in the manufacturing method according to any one of the first to seventh aspects, the photocurable composition contains a monomer group including a (meth)acrylic monomer and/or a partial polymer of the monomer group.

In the ninth aspect of the present invention, for example, in the manufacturing method according to the eighth aspect, the polymerization rate of the monomer group in the pressure-sensitive adhesive sheet is 80% or more.

In a tenth aspect of the present invention, for example, in the manufacturing method according to the eighth or ninth aspect, the photocurable composition contains a photopolymerization initiator, and the amount of the photopolymerization initiator is 1.0 part by weight or less per 100 parts by weight of the total of the monomer group and the partially polymerized product.

In the eleventh aspect of the present invention, for example, in the manufacturing method according to the tenth aspect, the content of the photopolymerization initiator in the pressure-sensitive adhesive sheet is 500 wtppm or less.

In the twelfth aspect of the present invention, for example, in the manufacturing method according to any one of the first to eleventh aspects, the content of the solvent in the photocurable composition is 5% by weight or less.

A method for producing an optical film with a pressure-sensitive adhesive sheet according to a thirteenth aspect of the present invention comprises the steps of:
The method includes forming an optical film with a pressure-sensitive adhesive sheet by disposing an optical film on an exposed surface of the pressure-sensitive adhesive sheet formed by the manufacturing method according to any one of the first to twelfth aspects.

In a fourteenth aspect of the present invention, for example, in the manufacturing method according to the thirteenth aspect, the optical film includes at least one film selected from the group consisting of a polarizing film and a retardation film.

A method for producing an image display device according to a fifteenth aspect of the present invention includes the steps of:
The method includes bonding an optical film with a pressure-sensitive adhesive sheet formed by the manufacturing method according to the thirteenth or fourteenth aspect to an image display panel to form an image display device.

The present invention will be described in detail below, but the present invention is not limited to the following embodiments, and can be modified as desired without departing from the spirit of the present invention.

[Embodiment of the method for producing the pressure-sensitive adhesive sheet]
1, the method for producing a pressure-sensitive adhesive sheet 1 of the present embodiment includes a step of irradiating a coating layer 12 containing a photocurable composition with light 14 from a light-emitting diode (LED) 34 to form a pressure-sensitive adhesive sheet 1. In this step, the peak wavelength of the light 14 irradiated to the coating layer 12 is 325 nm to 350 nm. The illuminance of this light 14 is preferably 2.0 to 30 mW/ ^cm2 .

In the manufacturing method of this embodiment, by using the light 14, the amount of remaining photopolymerization initiator in the formed adhesive sheet 1 tends to be reduced compared to when a black light source is used. Furthermore, according to the inventors' studies, when the light 14 is used, the polymerization rate of the monomer group in the adhesive sheet 1 tends to be higher compared to when, for example, an LED that emits light with a peak wavelength of about 365 nm is used. In this way, the manufacturing method of this embodiment is suitable for efficiently producing the adhesive sheet 1.

As described above, the manufacturing method of this embodiment uses light 14 from an LED. Compared to a black light source, an LED not only has an easier adjustment of illuminance, but also tends to have a longer light source life. Compared to a black light source using mercury, an LED is also superior in terms of reducing environmental impact. Furthermore, according to the inventors' study, an LED that emits light 14 with a peak wavelength of 325 nm to 350 nm tends to generate less heat and to control the temperature of the coating layer 12 more easily than an LED that emits light with a peak wavelength of about 365 nm. Light 14 with a peak wavelength of 325 nm to 350 nm also tends to be more compatible with the absorption wavelength of the photopolymerization initiator than light with a peak wavelength of about 365 nm. As far as the inventors know, there have been no reports of the production of an adhesive sheet using an LED that emits light with a peak wavelength of 325 nm to 350 nm.

In detail, the manufacturing method of this embodiment can be carried out by the following method. First, a laminate (first laminate) 10 is prepared, which includes a base sheet 11, a coating layer 12 containing a photocurable composition, and a release liner 13 in this order. The first laminate 10 is irradiated with light 14. Irradiation with light 14 is typically performed from the side of the base sheet 11. At this time, the light 14 passes through the base sheet 11 and reaches the coating layer 12, curing the coating layer 12. However, irradiation with light 14 may be performed from the side of the release liner 13, or may be performed from both the side of the release liner 13 and the side of the base sheet 11.

The formed adhesive sheet 1 is sandwiched between the base sheet 11 and the release liner 13 until the release liner 13 is peeled off, forming part of the second laminate 17. By peeling off the release liner 13 from the second laminate 17, a third laminate 15 including the base sheet 11 and the adhesive sheet 1 is obtained. In the third laminate 15, the surface of the adhesive sheet 1 is exposed to the outside.

As described above, the peak wavelength of the light 14 irradiated to the first laminate 10 (specifically, the coating layer 12) is 325 nm to 350 nm. The peak wavelength of the light 14 is preferably 340±10 nm (330 nm to 350 nm), may be 340±5 nm (335 nm to 345 nm), may be 340±2 nm (338 nm to 342 nm), or may be 340 nm. The peak wavelength means the wavelength at which the intensity is at a maximum value in the spectrum showing the relationship between the wavelength and intensity of the light 14. The light 14 may further have a peak wavelength in a wavelength range other than 325 nm to 350 nm, but preferably does not have one.

As described above, the illuminance of the light 14 irradiated to the first laminate 10 (specifically, the coating layer 12) is preferably 2.0 to 30 mW/cm ^2. When the illuminance of the light 14 is 2.0 mW/cm ² or more, the coating layer 12 tends to be uniformly cured. Furthermore, when the illuminance of the light 14 is 30 mW/cm ² or less, the cleavage rate of the photopolymerization initiator contained in the photocurable composition can be appropriately adjusted, and the polymerization rate of the monomer group tends to increase. When the illuminance of the light 14 is 30 mW/cm ² or less, rapid heat generation in the coating layer 12 is suppressed, and the adhesive sheet 1 tends to be less prone to poor appearance. When the light 14 is irradiated from both the release liner 13 and the base sheet 11 sides, it is preferable that the total value of the illuminance of the light 14 from the release liner 13 side and the illuminance of the light 14 from the base sheet 11 side is adjusted to 2.0 to 30 mW/cm ² .

The illuminance of the light 14 is preferably 2.5 mW/cm ² or more, 3.0 mW/cm ² or more, 3.5 mW/cm ² or more, 4.0 mW/cm ² or more, 5.0 mW/cm ² or more, 6.0 mW/cm ² or more, 7.0 mW/cm ² or more, 8.0 mW/cm ² or more, 9.0 mW/cm ² or more, or even 10 mW/cm ² or more. The upper limit of the illuminance of the light 14 is, for example, 25 mW/cm ² or less, 20 mW/cm ² or less, or even 15 mW/cm ² or less. The illuminance of the light 14 can be adjusted not only by controlling the LED 34 itself, but also by changing the distance between the LED 34 and the first laminate 10.

The time for which the first laminate 10 (specifically the coating layer 12) is irradiated with light 14 is not particularly limited, and may be, for example, 10 to 1000 seconds, and may be 60 seconds or more, 100 seconds or more, 150 seconds or more, 200 seconds or more, or even 250 seconds or more. The upper limit of the time for irradiating light 14 is, for example, 800 seconds or less, and in some cases may be 600 seconds or less. Irradiation of light 14 may be continuous or intermittent.

The integrated light amount of the light 14 on the first laminate 10 (specifically, the coating layer 12) is, for example, 25 mJ/cm ² or more, and may be 100 mJ/cm ² or more, 500 mJ/cm ² or more, 1000 mJ/cm ² or more, 2000 mJ/cm ² or more, or even 3000 mJ/cm ² or more. The upper limit of the integrated light amount of the light 14 is not particularly limited, and may be, for example, 30000 mJ/cm ² or less, 10000 mJ/cm ² or less, or even 5000 mJ/cm ² or less.

While the first laminate 10 (specifically the coating layer 12) is irradiated with light 14, the temperature of the coating layer 12 is maintained at, for example, 50°C or less, preferably 10°C to 30°C. In this case, the curing speed of the coating layer 12 is appropriately adjusted, and the number average molecular weight and weight average molecular weight of the polymer contained in the pressure-sensitive adhesive sheet 1 tend to increase.

In the manufacturing method of this embodiment, the first laminate 10 (specifically, the coating layer 12) may be irradiated with light 14 in an atmosphere with a reduced oxygen concentration compared to the air (oxygen concentration 20.9 vol%). In this case, the curing of the coating layer 12 is less likely to be inhibited by oxygen, and the number average molecular weight and weight average molecular weight of the polymer contained in the adhesive sheet 1 tend to increase. The irradiation with light 14 may be performed in an atmosphere with an oxygen concentration of 20 vol% or less, 10 vol% or less, 1 vol% or less, 1000 volppm or less, or even 500 volppm or less. The irradiation with light 14 may be performed in an atmosphere that is substantially free of oxygen. The atmosphere with a reduced oxygen concentration contains, for example, an inert gas such as argon or nitrogen, and is typically an inert gas atmosphere.

The manufacturing method of this embodiment may further include a heating step of heating the adhesive sheet 1 after irradiation with light 14. As an example, the heating step is performed on the third laminate 15 including the base sheet 11 and the adhesive sheet 1. The heating step promotes drying and curing of the adhesive sheet 1, and tends to further reduce the residual monomer contained in the adhesive sheet 1.

The conditions for the heating step are not particularly limited and can be adjusted as appropriate. As an example, the temperature for the heating step is preferably 40 to 200°C, more preferably 50 to 180°C, and even more preferably 70 to 170°C. The time for the heating step is, for example, 5 seconds to 20 minutes, preferably 5 seconds to 10 minutes, and more preferably 10 seconds to 5 minutes.

(Photocurable composition)
In this embodiment, the photocurable composition is a pressure-sensitive adhesive composition that forms the pressure-sensitive adhesive sheet 1 from the coating layer 12 by irradiation with light 14. The photocurable composition includes, for example, a monomer group containing a (meth)acrylic monomer and/or a partial polymer of the monomer group. The content of the (meth)acrylic component in the photocurable composition, i.e., the (meth)acrylic monomer and its partial polymer, may be 50% by weight or more, 60% by weight or more, 70% by weight or more, or even 80% by weight or more. In this case, an acrylic pressure-sensitive adhesive sheet 1 containing a (meth)acrylic polymer and its crosslinked product as the main components can be formed. However, the photocurable composition is not limited to the above example. In this specification, (meth)acrylic means acrylic and methacrylic. (Meth)acrylate means acrylate and methacrylate.

An example of a (meth)acrylic monomer is a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms on the side chain. The number of carbon atoms in the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be linear or branched. Examples of (meth)acrylic acid alkyl esters are methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, n-pentyl (meth)acrylate, isopentyl (meth)acrylate, n-hexyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, n-decyl (meth)acrylate, isodecyl (meth)acrylate, n-dodecyl (meth)acrylate (lauryl (meth)acrylate), n-tridecyl (meth)acrylate, n-tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, and octadecyl (meth)acrylate. The (meth)acrylic acid alkyl ester may be n-butyl (meth)acrylate.

The content of the (meth)acrylic acid alkyl ester in the monomer group is, for example, 40% by weight or more, and may be 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or even 95% by weight or more. In calculating the content, the weight of the partially polymerized product is converted into the weight of each monomer before polymerization.

The monomer group may contain a carboxyl group-containing monomer. The carboxyl group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may contain a carboxyl group-containing monomer. Examples of the carboxyl group-containing monomer are (meth)acrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. The content of the carboxyl group-containing monomer in the monomer group may be, for example, 10% by weight or less, 9% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5.5% by weight or less, or even 5% by weight or less. The lower limit of the content may be, for example, 0.1% by weight or more, 0.5% by weight or more, or even 1% by weight or more. The monomer group may not contain a carboxyl group-containing monomer.

The monomer group may contain a hydroxy group-containing monomer. The hydroxy group-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may contain a hydroxy group-containing monomer. The hydroxy group-containing monomer may contribute to improving the cohesive strength of the adhesive sheet. Examples of the hydroxy group-containing monomer are 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)-methyl acrylate. The hydroxy group-containing monomer is preferably 2-hydroxyethyl (meth)acrylate or 4-hydroxybutyl (meth)acrylate. The content of the hydroxyl group-containing monomer in the monomer group is, for example, 10% by weight or less, and may be 5% by weight or less, 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.8% by weight or less, 0.5% by weight or less, 0.3% by weight or less, 0.2% by weight or less, or even 0.1% by weight or less. The lower limit of the content may be, for example, 0.01% by weight or more, 0.03% by weight or more, or even 0.05% by weight or more. The monomer group may not contain a hydroxyl group-containing monomer.

The monomer group may include a nitrogen atom-containing monomer. A nitrogen atom-containing monomer means a monomer that has at least one nitrogen atom in the molecule (per molecule).

As the nitrogen atom-containing monomer, from the viewpoint of improving resistance to foaming and peeling, N-vinyl cyclic amide, (meth)acrylamide, etc. are preferred. The nitrogen atom-containing monomer may be used alone or in combination of two or more kinds.

The N-vinyl cyclic amide is preferably represented by the following formula (1).

In formula (1), R ¹ is a divalent organic group, preferably a divalent saturated or unsaturated hydrocarbon group, and more preferably a divalent saturated hydrocarbon group (e.g., an alkylene group having 3 to 5 carbon atoms). Note that formula (1) shows that N and R ¹ are directly bonded to each other via a single bond to form a ring structure.

As the N-vinyl cyclic amide represented by formula (1), from the viewpoint of improving foaming and peeling resistance, N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-morpholinone, N-vinyl-1,3-oxazin-2-one, N-vinyl-3,5-morpholinedione, etc. are preferred, more preferably N-vinyl-2-pyrrolidone, N-vinyl-2-caprolactam, and even more preferably N-vinyl-2-pyrrolidone.

Examples of (meth)acrylamides include (meth)acrylamide, N-alkyl(meth)acrylamide, and N,N-dialkyl(meth)acrylamide. Examples of N-alkyl(meth)acrylamide include N-ethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N-n-butyl(meth)acrylamide, and N-octylacrylamide. N-alkyl(meth)acrylamides also include (meth)acrylamides having an amino group, such as dimethylaminoethyl(meth)acrylamide, diethylaminoethyl(meth)acrylamide, and dimethylaminopropyl(meth)acrylamide.

Examples of N,N-dialkyl(meth)acrylamides include N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N,N-dipropyl(meth)acrylamide, N,N-diisopropyl(meth)acrylamide, N,N-di(n-butyl)(meth)acrylamide, and N,N-di(t-butyl)(meth)acrylamide.

(Meth)acrylamides also include, for example, various N-hydroxyalkyl (meth)acrylamides. Examples of N-hydroxyalkyl (meth)acrylamides include N-methylol (meth)acrylamide, N-(2-hydroxyethyl) (meth)acrylamide, N-(2-hydroxypropyl) (meth)acrylamide, N-(1-hydroxypropyl) (meth)acrylamide, N-(3-hydroxypropyl) (meth)acrylamide, N-(2-hydroxybutyl) (meth)acrylamide, N-(3-hydroxybutyl) (meth)acrylamide, N-(4-hydroxybutyl) (meth)acrylamide, and N-methyl-N-2-hydroxyethyl (meth)acrylamide.

(Meth)acrylamides also include, for example, various N-alkoxyalkyl(meth)acrylamides. Examples of N-alkoxyalkyl(meth)acrylamides include N-methoxymethyl(meth)acrylamide and N-butoxymethyl(meth)acrylamide.

Examples of nitrogen atom-containing monomers other than N-vinyl cyclic amide and (meth)acrylamide include amino group-containing monomers such as aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; (meth)acryloylmorpholine, N-vinylpiperazine, N-vinylpyrrole, N-vinylimidazole, N-vinylpyrazine, N-vinylmorpholine, N-vinylpyrazole, vinylpyridine, vinylpyrimidine, vinyloxazole, vinylisoxazole, vinylthiazole, vinylisothiazole, vinylpyridazine, (meth)acryloylpyrrolidone, (meth)acryloylpyrrolidine, (meth)acryloylpiperidine, N-methyl Examples of such monomers include heterocyclic ring-containing monomers such as vinylpyrrolidone; maleimide-based monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide-based monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-laurylitaconimide, and N-cyclohexylitaconimide; imide group-containing monomers such as succinimide-based monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; and isocyanate group-containing monomers such as 2-(meth)acryloyloxyethylisocyanate.

The content of the nitrogen atom-containing monomer in the monomer group may be, for example, 40% by weight or less, 35% by weight or less, or even 30% by weight or less. The lower limit of the content may be, for example, 5% by weight or more, 7% by weight or more, or even 10% by weight or more. The monomer group may not contain a nitrogen atom-containing monomer.

In the photocurable composition, each of the above-mentioned monomers may be contained as a partial polymer. The partial polymer may be either a homopolymer or a copolymer. The partial polymer may contribute to the stable formation of the coating layer 12 by appropriately increasing the viscosity of the photocurable composition.

The photocurable composition usually contains a photopolymerization initiator. An example of the photopolymerization initiator is a photoradical generator that generates radicals by the above-mentioned light 14. The photopolymerization initiator has an absorption coefficient for light with a wavelength of 340 nm of, for example, 0.1 L/(g·cm) or more, and may be 0.5 L/(g·cm) or more, 1.0 L/(g·cm) or more, 3.0 L/(g·cm) or more, or even 5.0 L/(g·cm) or more. The upper limit of this absorption coefficient is not particularly limited, and is, for example, 50 L/(g·cm) or less. The absorption coefficient of the photopolymerization initiator is a calculated value from the absorbance of a 0.01 mg/mL methanol solution measured by a visible-ultraviolet spectrophotometer using a quartz cell with an optical path length of 1 cm.

Examples of photopolymerization initiators include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzil dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkylphenones such as 1-hydroxycyclohexyl-phenyl ketone, 2-hydroxy-2-methylpropiophenone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, and 2,2'-dihydroxy-2,2'-dimethyl-1,1'-[methylenebis(4,1-phenylene)]bis(propan-1-one); and 2-methyl-2-hydroxypropiophenone. substituted alpha-ketols such as 2-naphthalenesulfonyl chloride; aromatic sulfonyl chlorides such as 2-naphthalenesulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; benzophenone compounds such as benzophenone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4-benzoyl-4'-methyldiphenyl sulfide, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone; thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and 2,4-diethylthioxanthone. thioxanthone compounds such as 2,4,6-trichloro-s-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-tolyl)-4,6-bis(trichloromethyl)-s-triazine, 2-piperonyl-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6-triazine, 2,4-tri triazine-based compounds such as chloromethyl-(4'-methoxystyryl)-6-triazine; oxime ester-based compounds such as 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O-benzoyloxime)], O-(acetyl)-N-(1-phenyl-2-oxo-2-(4'-methoxy-naphthyl)ethylidene)hydroxylamine; phosphine-based compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; quinone-based compounds such as 9,10-phenanthrenequinone, camphorquinone, and ethylanthraquinone; borate-based compounds; carbazole-based compounds; imidazole-based compounds; and titanocene-based compounds. The photocurable composition may contain one or more photopolymerization initiators. In particular, α-hydroxyalkylphenones tend to have high absorption of light with wavelengths of 325 nm to 350 nm, making them suitable for the manufacturing method of this embodiment.

The amount of the photopolymerization initiator in the photocurable composition is, for example, 20 parts by weight or less, and may be 10 parts by weight or less, 5.0 parts by weight or less, 3.0 parts by weight or less, 1.0 parts by weight or less, 0.5 parts by weight or less, or even 0.3 parts by weight or less, based on 100 parts by weight of the total of the monomer group and its partial polymer. When the amount of the photopolymerization initiator is 1.0 part by weight or less, the weight average molecular weight of the polymer contained in the adhesive sheet 1 tends to be sufficiently large. The lower limit of the amount of the photopolymerization initiator is, for example, 0.02 parts by weight or more, and may be 0.05 parts by weight or more, based on 100 parts by weight of the total of the monomer group and its partial polymer.

The photocurable composition may contain a crosslinking agent. An example of the crosslinking agent is a polyfunctional monomer having two or more polymerizable functional groups in one molecule. The polyfunctional monomer may be a (meth)acrylic monomer. An example of the polyfunctional monomer is a monomer having two or more C=C bonds in one molecule, and a monomer having one or more C=C bonds and one or more polymerizable functional groups such as epoxy groups, aziridine groups, oxazoline groups, hydrazine groups, and methylol groups in one molecule. The polyfunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

Examples of polyfunctional monomers include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol diacrylate (N DDA), 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, and other polyfunctional acrylates (such as ester compounds of polyhydric alcohols and (meth)acrylic acid); allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, and hexyl di(meth)acrylate. The polyfunctional monomer is preferably a polyfunctional acrylate, and more preferably 1,9-nonanediol diacrylate, trimethylolpropane tri(meth)acrylate, hexanediol di(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

The amount of the crosslinking agent to be blended varies depending on the molecular weight, the number of functional groups, etc., but may be, for example, 5 parts by weight or less, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, 0.5 parts by weight or less, or even 0.3 parts by weight or less, relative to 100 parts by weight of the total of the monomer group and its partial polymer. The lower limit of the blending amount may be, for example, 0.01 parts by weight or more, or even 0.05 parts by weight or more.

The photocurable composition may contain additives other than those mentioned above. Examples of additives include chain transfer agents, silane coupling agents, viscosity modifiers, tackifiers, plasticizers, softeners, antioxidants, fillers, colorants, antioxidants, surfactants, antistatic agents, and UV absorbers.

The content of the solvent in the photocurable composition is, for example, 5% by weight or less, and may be 4% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or even 0.5% by weight or less. The photocurable composition may be substantially free of solvent. "Substantially free of solvent" means that solvents derived from additives, etc. are permitted at a content of, for example, 0.1% by weight or less, preferably 0.05% by weight or less, and more preferably 0.01% by weight or less.

The viscosity of the photocurable composition is preferably 1 to 100 poise. Photocurable compositions having a viscosity in the above range are particularly suitable for forming the coating layer 12.

(Release liner)
An example of the substrate of the release liner 13 (hereinafter, "liner substrate") is a resin film. Examples of resins that can be contained in the liner substrate are polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyethersulfone, polycarbonate, polyamide, polyimide, polyolefin, (meth)acrylic resins, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylate, and polyphenylene sulfide. The resin is preferably a polyester such as polyethylene terephthalate.

The release liner 13 may be transparent to light 14. As an example, the spectral transmittance of the release liner 13 for light with a wavelength of 340 nm may be, for example, 60% or more, 70% or more, or even 80% or more. The upper limit of the spectral transmittance is not particularly limited, and may be, for example, 95% or less, or may be 90% or less. The spectral transmittance for light with a wavelength of 340 nm can be determined, for example, by measuring the total light transmittance spectrum in the wavelength range of 300 to 2000 nm for the release liner 13 using a commercially available spectrophotometer, and determining the spectral transmittance from the spectrum obtained.

The thickness of the release liner 13 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

The release liner 13 may have a layer other than the liner substrate. The release liner 13 may have a release layer. The release liner 13 may have, for example, a liner substrate and a release layer formed on one side of the liner substrate. This release liner 13 can be used so that the release layer is on the coating layer 12 side.

The release layer is typically a cured layer of a release agent composition containing a release agent. Various types of release agents can be used as the release agent, such as silicone-based release agents, fluorine-based release agents, long-chain alkyl-based release agents, fatty acid amide-based release agents, and silica powder. The release liner 13 may be provided with a cured layer of a release agent composition containing a silicone-based release agent as the main component (hereinafter, "silicone release layer"). The silicone release layer is particularly suitable for achieving both adhesion to the pressure-sensitive adhesive sheet 1 and releasability. In this specification, the main component means the component with the largest content.

Silicone-based release agents are various types of curable silicone materials, such as addition reaction type, condensation reaction type, ultraviolet curable type, electron beam curable type, and solventless type, and addition reaction curable silicone materials are preferred. Addition reaction curable silicone materials are particularly suitable for forming a release layer that has both adhesion to the adhesive sheet 1 and releasability. The curable silicone material may be a silicone-modified resin in which reactive silicone is introduced into an organic resin such as urethane, epoxy, or alkyd resin by graft polymerization or the like.

An example of the addition reaction curing silicone material is a polyorganosiloxane having a vinyl group or an alkenyl group in the molecule. The addition reaction curing silicone material may not have a hydrosilyl group. Examples of the alkenyl group are 3-butenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 10-undecenyl, and 11-dodecenyl. Examples of the polyorganosiloxane are polyalkylalkylsiloxanes such as polydimethylsiloxane, polydiethylsiloxane, and polymethylethylsiloxane, polyalkylarylsiloxane, and copolymers of multiple types of Si atom-containing monomers such as poly(dimethylsiloxane-diethylsiloxane). The polyorganosiloxane is preferably polydimethylsiloxane.

A release agent composition containing a silicone-based release agent as a main component (hereinafter referred to as "silicone release agent composition") usually contains a crosslinking agent. An example of the crosslinking agent is a polyorganosiloxane having a hydrosilyl group. The crosslinking agent may have two or more hydrosilyl groups in one molecule.

The silicone release agent composition may contain a curing catalyst. An example of the curing catalyst is a platinum-based catalyst. Examples of the platinum-based catalyst are chloroplatinic acid, platinum olefin complexes, and chloroplatinic acid olefin complexes. The amount of the platinum-based catalyst used is, for example, 10 to 1000 ppm (by weight, platinum equivalent) based on the total solid content of the composition.

The silicone release agent composition may contain additives. Examples of additives are release control agents and adhesion promoters. Examples of release control agents are unreactive silicone resins, and more specific examples are organosiloxanes such as octamethylcyclotetrasiloxane, and MQ resins. The amount of the release control agent and adhesion promoter used is, for example, 1 to 30% by weight in total based on the total solid content of the composition. Further examples of additives are fillers, antistatic agents, antioxidants, ultraviolet absorbers, plasticizers, and colorants. The amount of the further additives used is, for example, 10% by weight or less in total based on the total solid content of the composition.

The silicone release agent composition may contain an organic solvent. Examples of organic solvents are hydrocarbon solvents such as cyclohexane, n-hexane, and n-heptane; aromatic solvents such as toluene and xylene; ester solvents such as ethyl acetate and methyl acetate; ketone solvents such as acetone and methyl ethyl ketone; and alcohol solvents such as methanol, ethanol, and butanol. Two or more types of organic solvents may be contained. The amount of the organic solvent used is preferably 80 to 99.9% by weight of the silicone release agent composition.

The release layer can be formed, for example, by heating and drying a coating film containing the release agent composition formed on a liner substrate. Various coating methods such as roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating can be used for coating the release agent composition. For example, hot air drying can be used for heating and drying. The heating temperature and time vary depending on the heat resistance of the liner substrate, but are usually 80 to 150°C and about 10 seconds to 10 minutes. If necessary, irradiation with active energy rays such as ultraviolet rays may be used in combination.

The thickness of the release layer is, for example, 10 to 300 nm. The upper limit of the thickness may be 200 nm or less, 150 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, less than 100 nm, 90 nm or less, 80 nm or less, 70 nm or less, less than 70 nm, or even 65 nm or less. The lower limit of the thickness may be 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, 40 nm or more, 45 nm or more, or even 50 nm or more.

The release liner 13 may be in sheet or elongated form.

(Base sheet)
An example of the base sheet 11 is a resin film. Examples of the resin contained in the base sheet 11 are the same as the examples of the resin that can be contained in the liner base material.

The base sheet 11 preferably has excellent transmittance to light 14. As an example, the spectral transmittance of the base sheet 11 for light with a wavelength of 340 nm is, for example, 60% or more, and may be 70% or more, or even 80% or more. The higher the spectral transmittance, the more efficiently the coating layer 12 can be cured by light 14. Furthermore, the base sheet 11 can be prevented from absorbing light 14 and generating heat. The upper limit of the spectral transmittance is not particularly limited, and may be, for example, 95% or less, or may be 90% or less. The spectral transmittance for light with a wavelength of 340 nm can be determined by the method described above for the release liner 13.

The thickness of the base sheet 11 is, for example, 10 to 200 μm, and may be 25 to 150 μm.

The base sheet 11 may have a release layer on the surface on the side of the coating layer 12. Examples of the release layer that the base sheet 11 may have and the manufacturing method thereof are the same as the examples of the release layer that the release liner 13 may have and the manufacturing method thereof. Both the release liner 13 and the base sheet 11 may have a release layer. In this case, both release layers may be formed from a release agent composition containing the same release agent as a main component. In addition, the thicknesses of both release layers may be different; for example, the release layer provided on the base sheet 11 may be thicker.

For the base sheet 11, a sheet that has a greater peel strength with respect to the adhesive sheet 1 than the release liner 13 can usually be selected.

The base sheet 11 may be in the form of a sheet or a long piece.

(First Laminate and Its Formation)
The first laminate 10 may include an additional layer other than the base sheet 11, the coating layer 12, and the release liner 13. The additional layer may be disposed on the side of the base sheet 11 and/or the release liner 13 opposite to the side of the coating layer 12. It is preferable that the coating layer 12 is in contact with the base sheet 11 and the release liner 13.

The first laminate 10 can be formed, for example, by forming a coating layer 12 on a base sheet 11 (or a release liner 13) and then placing the release liner 13 (or base sheet 11) on the formed coating layer 12. Alternatively, the first laminate 10 can be formed by applying a photocurable composition in a poured manner into the space between the base sheet 11 and the release liner 13, which are held at a predetermined distance so that their main surfaces face each other.

Various coating methods can be used to form the coating layer 12, including roll coating, kiss roll coating, gravure coating, reverse coating, roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, and die coating.

The thickness of the coating layer 12 can be adjusted according to the desired thickness of the adhesive sheet 1, and may be, for example, 2 mm or less, 1 mm or less, 2 to 300 μm, 2 to 200 μm, 2 to 150 μm, 2 to 100 μm, 2 to 70 μm, 2 to 50 μm, 5 to 40 μm, 10 to 30 μm, 10 to 25 μm, or even 10 to 20 μm.

The first laminate 10 may include a long base sheet 11, a long coating layer 12, and a long release liner 13, or in other words, may be long. The long first laminate 10 can be obtained, for example, by forming the coating layer 12 between the base sheet 11 and the release liner 13 while conveying them from a roll.

(Adhesive sheet)
As described above, the adhesive sheet 1 produced by the manufacturing method of this embodiment tends to have a small amount of remaining photopolymerization initiator. The adhesive sheet 1 with a small amount of remaining photopolymerization initiator tends to be suppressed from yellowing or foaming in a high temperature environment. As an example, the content of the photopolymerization initiator in the adhesive sheet 1 is, for example, 500 wtppm or less, and may be 300 wtppm or less, 200 wtppm or less, 150 wtppm or less, 120 wtppm or less, 100 wtppm or less, 80 wtppm or less, 50 wtppm or less, or even 30 wtppm or less. The adhesive sheet 1 may not substantially contain a photopolymerization initiator.

Furthermore, the adhesive sheet 1 produced by the manufacturing method of this embodiment tends to have a high polymerization rate of the monomer group and a small amount of the remaining monomer group. An adhesive sheet 1 with a small amount of the remaining monomer group not only contributes to improving productivity, but also tends to suppress odor. This adhesive sheet 1 also has the advantage of being easy to handle and transport. The polymerization rate of the monomer group in the adhesive sheet 1 is preferably 80% or more, and may be 85% or more, 90% or more, 95% or more, 97% or more, 98% or more, or even 99% or more.

According to the manufacturing method of this embodiment, the molecular weight of the polymer contained in the adhesive sheet 1 also tends to be large. As an example, when the manufacturing method of this embodiment is carried out using a sample having the same composition as the above-mentioned photocurable composition except that it does not contain a crosslinking agent, the weight average molecular weight (Mw) of the polymer obtained by polymerization of the monomer group contained in the sample is, for example, 400,000 or more, 500,000 or more, 700,000 or more, 800,000 or more, 900,000 or more, or even 1 million or more. The larger this Mw is, the more likely it is that the adhesive sheet 1 will be prevented from peeling off in a high temperature environment. The upper limit of Mw is not particularly limited, and is, for example, 3 million or less. The number average molecular weight (Mn) of the above-mentioned polymer is, for example, 80,000 or more, and may be 100,000 or more, 150,000 or more, 180,000 or more, 200,000 or more, or even 250,000 or more. The upper limit of Mn is not particularly limited, and is, for example, 600,000 or less. The weight average molecular weight (Mw)/number average molecular weight (Mn), which indicates the molecular weight distribution, is, for example, 1.8 to 10, or may be 1.8 to 7, or even 1.8 to 5. The weight average molecular weight and number average molecular weight are measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

The gel fraction of the adhesive sheet 1 is, for example, 50% or more, and may be 75% or more, 80% or more, or even 85% or more.

The thickness of the adhesive sheet 1 is, for example, 2 mm or less, and may be 1 mm or less, 2 to 300 μm, 2 to 200 μm, 2 to 150 μm, 2 to 100 μm, 2 to 70 μm, 2 to 50 μm, 5 to 40 μm, 10 to 30 μm, 10 to 25 μm, or even 10 to 20 μm.

The adhesive sheet 1 produced by the manufacturing method of this embodiment is particularly suitable for applications requiring high light transmittance (e.g., optical applications). However, the adhesive sheet 1 can also be used for various applications other than optical applications. The adhesive sheet 1 may be used as a double-sided tape.

Next, referring to FIG. 2, another example of a method for manufacturing an adhesive sheet will be described. In this example, a coating layer 12 of a photocurable composition is formed on one side of a long base sheet 11 unwound from a roll 31 by a coating device 32. Next, a long release liner 13 unwound from a roll 33 is placed on the coating layer 12 to form a long first laminate 10. Next, light 14 is irradiated from an LED 34 to the first laminate 10 to form a long adhesive sheet 1. Next, the release liner 13 is peeled off from a second laminate 17 including the adhesive sheet 1 and wound up on a roll 35. The above steps are performed while the base sheet 11 and the release liner 13 are being transported. The method of FIG. 2 is particularly suitable for mass production of adhesive sheets.

Next, referring to FIG. 3, another example of a method for manufacturing a pressure-sensitive adhesive sheet will be described. In this example, a coating device 32 is used to coat a photocurable composition between a long base sheet 11 unwound from a roll 31 and a long release liner 13 unwound from a roll 33. This forms a coating layer 12 containing the photocurable composition, and a long first laminate 10 is obtained.

Next, the first laminate 10 is transported so as to pass between the pair of light sources 38a and 38b. In detail, first, the first laminate 10 is caused to pass through the first region 40A near the light source 38a. Next, the first reversal mechanism (first transport roller 39a) is used to reverse the moving direction of the first laminate 10, and the first laminate 10 is moved in the opposite direction to the moving direction in the first region 40A. As a result, the first laminate 10 is caused to pass through the second region 40B, which is closer to the light source 38b than the first region 40A. Next, the second reversal mechanism (second transport roller 39b) is used to further reverse the moving direction of the first laminate 10, and the first laminate 10 is moved in the same direction as the moving direction in the first region 40A. As a result, the first laminate 10 is caused to pass through the third region 40C near the light source 38b.

Light source 38a is typically an LED that emits light L1 with a peak wavelength of 325 nm to 350 nm. Similarly, light source 38b is typically an LED that emits light L2 with a peak wavelength of 325 nm to 350 nm. The above-mentioned LED 34 can be used as light sources 38a and 38b.

In the example of FIG. 3, the total value (illuminance LA) of the illuminance of the light L1 from the release liner 13 side and the illuminance of the light L2 from the base sheet 11 side in the first region 40A, the total value (illuminance LB) of the illuminance of the light L1 from the base sheet 11 side and the illuminance of the light L2 from the release liner 13 side in the second region 40B, and the total value (illuminance LC) of the illuminance of the light L1 from the release liner 13 side and the illuminance of the light L2 from the base sheet 11 side in the third region 40C are preferably adjusted to 2.0 to 30 mW/cm ^2. The illuminances LA to LC may satisfy the relationship LA<LB<LC. The illuminances LA to LC can be adjusted by the positions and outputs of the light sources 38a and 38b. As an example, the distance between the light source 38a and the first region 40A may be adjusted to be greater than the distance between the light source 38b and the third region 40C.

By passing the light between a pair of light sources 38a and 38b, light L1 and L2 with a peak wavelength of 325 nm to 350 nm is irradiated onto the coating layer 12, forming a long adhesive sheet 1. Next, the release liner 13 is peeled off from the second laminate 17 containing the adhesive sheet 1 and wound up on a roll 35. The method of FIG. 3 allows the adhesive sheet to be formed in a small space, and is particularly suitable for mass production of adhesive sheets.

In the example of FIG. 3, it is preferable that the polymerization rate of the monomer group at the time of passing through the first region 40A is 50% or more. In this case, when the direction of movement of the first laminate 10 is reversed using the first reversal mechanism (first conveying roller 39a), the members constituting the first laminate 10 tend not to have poor appearance such as wrinkles, streaks, or lifting.

[Method of manufacturing optical film with adhesive sheet]
An example of a method for producing an optical film with a pressure-sensitive adhesive sheet according to the present embodiment will be described with reference to Fig. 4. In the example of Fig. 4, an optical film 2 is placed on an exposed surface 18 of a pressure-sensitive adhesive sheet 1 formed by peeling off a release liner 13 from a second laminate 17 produced by the above-mentioned method, to form an optical film with a pressure-sensitive adhesive sheet 21. Note that, before placing the optical film 2, a surface modification treatment may be performed on the exposed surface 18 of the pressure-sensitive adhesive sheet 1.

The optical film 21 with adhesive sheet includes a base sheet 11, an adhesive sheet 1, and an optical film 2 in this order. The optical film 21 with adhesive sheet can be used as it is or after the base sheet 11 is peeled off, for example, as an optical laminate including the adhesive sheet 1 and the optical film 2 in an image display device or the like. The optical laminate may be attached to an object (for example, an image forming panel) via the adhesive sheet 1. However, the use of the optical film 21 with adhesive sheet is not limited to the above example. An additional member such as an optical film may be disposed on the exposed surface 18 formed by peeling off the base sheet 11 from the optical film 21 with adhesive sheet. As an example, an optical film 22 with adhesive sheet including an optical film 2A, an adhesive sheet 1, and an optical film 2B in this order can be formed (see FIG. 5). The optical films 2A and 2B may be the same or different from each other.

The optical film 2 may be disposed directly or indirectly on the exposed surface 18. In other words, the optical film 2 may be disposed so as to be in contact with the exposed surface 18, or may be disposed with another layer sandwiched between the optical film 2 and the exposed surface 18.

With reference to FIG. 6, another example of the manufacturing method of the optical film with adhesive sheet of this embodiment will be described. In this example, a long optical film 2 is placed on the exposed surface 18 of the adhesive sheet 1 in the third laminate 15 formed by the method of FIG. 2 to form a long optical film with adhesive sheet 21. The optical film 2 is unwound from the roll 36 and placed on the exposed surface 18. As shown in FIG. 6, the formation of the adhesive sheet 1 and the formation of the optical film with adhesive sheet 21 may be carried out continuously. The method of FIG. 6 is particularly suitable for mass production of the optical film with adhesive sheet 21.

The optical film 2 is, for example, a film including at least one selected from the group consisting of a polarizing film and a retardation film. The optical film 2 may be a laminated film including a polarizing film and/or a retardation film. The optical film 2 may include a glass film. However, the optical film 2 is not limited to the above examples.

The polarizing film includes a polarizer. The polarizing film typically includes a polarizer and a protective film (transparent protective film). The protective film is, for example, disposed in contact with the main surface (the surface having the widest area) of the polarizer. The polarizer may be disposed between two protective films. The protective film may be disposed on at least one surface of the polarizer.

The polarizer is not particularly limited, and examples thereof include hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified ethylene-vinyl acetate copolymer films, which are uniaxially stretched after adsorbing dichroic substances such as iodine and dichroic dyes; and polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride. Polarizers are typically made of polyvinyl alcohol films (polyvinyl alcohol films include partially saponified ethylene-vinyl acetate copolymer films) and dichroic substances such as iodine.

The thickness of the polarizer is not particularly limited, and may be, for example, 80 μm or less, 50 μm or less, 30 μm or less, 25 μm or less, or even 20 μm or less. The lower limit of the thickness of the polarizer is not particularly limited, and may be, for example, 1 μm or more, 5 μm or more, 10 μm or more, or even 15 μm or more. A thin polarizer (for example, a thickness of 20 μm or less) suppresses dimensional changes and can contribute to improving the durability of the optical laminate, particularly the durability at high temperatures.

As the material of the protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture blocking property, isotropy, etc. is used. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material of the protective film may be a thermosetting resin or an ultraviolet-curing resin such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone. When the polarizing film has two protective films, the materials of the two protective films may be the same or different from each other. For example, a protective film made of a thermoplastic resin may be attached to one main surface of the polarizer via an adhesive, and a protective film made of a thermosetting resin or an ultraviolet-curing resin may be attached to the other main surface of the polarizer. The protective film may contain one or more types of additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, color inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, colorants, etc.

The thickness of the protective film can be determined as appropriate, but is generally about 10 to 200 μm, taking into consideration strength, ease of handling, thinness, etc.

The polarizer and the protective film are usually adhered to each other via a water-based adhesive or the like. Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex, water-based polyurethane, water-based polyester, and the like. Examples of adhesives other than the above-mentioned adhesives include ultraviolet-curable adhesives and electron beam-curable adhesives. Electron beam-curable polarizing plate adhesives exhibit suitable adhesion to various protective films. The adhesive may contain a metal compound filler.

In polarizing films, instead of a protective film, a retardation film or the like can be formed on the polarizer. Another protective film can be further provided on the protective film, or a retardation film or the like can be provided.

The protective film may have a hard coat layer on the surface opposite to the surface attached to the polarizer, and may also be treated for the purposes of anti-reflection, anti-sticking, diffusion, anti-glare, etc.

The polarizing film may be a circular polarizing film.

The retardation film may be one obtained by stretching a polymer film or one obtained by aligning and fixing a liquid crystal material. The retardation film has birefringence, for example, in the in-plane and/or thickness direction.

Retardation films include anti-reflection retardation films (see JP 2012-133303 A [0221], [0222], [0228]), viewing angle compensation retardation films (see JP 2012-133303 A [0225], [0226]), and tilted orientation retardation films for viewing angle compensation (see JP 2012-133303 A [0227]).

The specific configuration of the retardation film, such as the retardation value, arrangement angle, three-dimensional birefringence, whether it is a single layer or a multilayer, is not particularly limited, and any known retardation film can be used.

The thickness of the retardation film is preferably 20 μm or less, more preferably 10 μm or less, even more preferably 1 to 9 μm, and particularly preferably 3 to 8 μm.

The retardation film may include, for example, a quarter-wave plate and/or a half-wave plate in which liquid crystal material is oriented and fixed.

[Manufacturing method of image display device]
An image display device may be formed using the optical film with adhesive sheet formed by the above manufacturing method. The image display device may be formed, for example, by bonding the optical film with adhesive sheet 21, 22 to an image display panel. The bonding may be performed by the adhesive sheet 1. The image display device may be an organic EL display or a liquid crystal display. However, the image display device is not limited to the above examples. The image display device may be an electroluminescence (EL) display, a plasma display (PD), a field emission display (FED: Field Emission Display), or the like. The image display device may be used for home appliances, in-vehicle applications, public information displays (PID), and the like.

The present invention will be described in more detail below with reference to examples. The present invention is not limited to the examples shown below.

[Monomer syrup A1]
99 parts by weight of n-butyl acrylate (BA), 1 part by weight of 4-hydroxybutyl acrylate (HBA), 0.05 parts by weight of 1-hydroxycyclohexyl-phenyl ketone (Omnirad 184, manufactured by IGM Resins BV) as a photopolymerization initiator, and 0.05 parts by weight of 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651, manufactured by IGM Resins BV) were placed in a four-neck flask and irradiated with ultraviolet light under a nitrogen atmosphere to obtain a partially photopolymerized monomer syrup A1. The ultraviolet light irradiation was continued until the viscosity of the liquid in the flask (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) became about 20 Pa·s.

[Monomer syrups A2 to A9]
Monomer syrups A2 to A9 were prepared in the same manner as for the monomer syrup A1, except that the monomers used were changed as shown in Table 1.

The abbreviations in Table 1 are as follows.
BA: n-butyl acrylate AA: acrylic acid HBA: 4-hydroxybutyl acrylate Omnirad 184: 1-hydroxycyclohexyl-phenyl ketone (Omnirad 184, manufactured by IGM Resins BV)
Omnirad 651: 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651, manufactured by IGM Resins BV)
Omnirad 819: bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (Omnirad 819, manufactured by IGM Resins BV)
Omnirad 127: 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one (Omnirad 127, IGM Resins BV)
Omnirad 2959: 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone (Omnirad 2959, manufactured by IGM Resins BV)

[Photocurable compositions C1 to C13]
Next, the monomer syrup, the monomer and the crosslinking agent were mixed so as to have the composition shown in Table 2 below, thereby obtaining photocurable compositions C1 to C13.

The abbreviations in Table 2 are as follows.
AA: Acrylic acid NVP: N-vinyl-2-pyrrolidone NDDA: 1,9-nonanediol diacrylate

The final compositions of the monomers contained in photocurable compositions C3 and C4 are shown in Table 3 below.

The abbreviations in Table 3 are as follows.
BA: n-butyl acrylate AA: acrylic acid HBA: 4-hydroxybutyl acrylate NVP: N-vinyl-2-pyrrolidone

Example 1
[Preparation of release liner L1]
Addition reaction curing type silicone (LTC761 containing hexenyl group-containing polyorganosiloxane, 30 wt% toluene solution, manufactured by Toray Dow Corning) 30 parts by weight, release control agent (BY24-850 containing unreactive silicone resin, manufactured by Toray Dow Corning) 0.9 parts by weight, and curing catalyst (SRX212 containing platinum catalyst, manufactured by Toray Dow Corning) 2 parts by weight, and toluene / hexane mixed solvent (volume ratio 1: 1) as a dilution solvent were mixed to obtain a silicone-based release agent composition. The concentration of silicone solids in the release agent composition was 1.0 wt%. Next, the release agent composition was applied to one side of a liner substrate (Lumirror XD500P, a polyester film, thickness 75 μm) with a wire bar, and heated at 130 ° C. for 1 minute to produce a release liner L1 having a release layer (thickness 60 nm) on one side.

[Preparation of adhesive sheet]
The photocurable composition C1 was applied to one side of a base sheet (Lumirror XD500P, a polyester film without a release layer, thickness 75 μm) with an applicator to form a coating layer (thickness 20 μm). Next, a release liner L1 was placed on the formed coating layer to obtain a first laminate. The release liner L1 was placed so that the release layer was in contact with the coating layer. Next, light from an LED was irradiated from the base sheet side of the first laminate under conditions of an illuminance of 4 mW/cm ² and an irradiation time of 640 seconds. The peak wavelength of this light was 340 nm. The light irradiation was performed at room temperature (23° C.). As a result, the coating layer was photocured, and the pressure-sensitive adhesive sheet (thickness 20 μm) of Example 1 sandwiched between the base sheet and the release liner L1 was obtained. The illuminance of the light was measured using an illuminometer (UD-T3040T2, manufactured by Topcon Technohouse Co., Ltd.).

(Examples 2 to 13 and Comparative Examples 1 to 3)
Except for changing the photocurable composition, light source, and light irradiation conditions used as shown in Table 4, pressure-sensitive adhesive sheets of Examples 2 to 13 and Comparative Examples 1 to 3 sandwiched between a base sheet and a release liner L1 were obtained in the same manner as in Example 1. In Examples 10 to 13, an LED with a peak wavelength of 330 nm was used as the light source. In Comparative Examples 1 to 3, a black light source (B/L) was used as the light source.

[Remaining amount of photopolymerization initiator]
The compositions of the pressure-sensitive adhesive sheets produced in Examples 1 to 13 and Comparative Examples 1 to 3 were analyzed, and the remaining amount (content) of the photopolymerization initiator was calculated based on the results obtained. The composition analysis was performed using liquid chromatography (LC) under the following conditions.
・Equipment used: 1290 Infinity II (Agilent Technologies)
Column: Acquity UPLC BEH C18 (Waters, 2.1 mmφ×100 mm, 1.7 μm)
Eluent composition: ultrapure water/acetonitrile gradient conditions Column temperature: 40°C
Column flow rate: 0.2 mL/min
Injection volume: 2 μL
Detector: Photodiode array detector (PDA)
Measurement wavelength: 190 to 400 nm
・Extraction wavelength: Omnirad184=246nm, Omnirad651=253nm, Omnirad819=296nm, Omnirad127=262nm, Omnirad2959=278nm
Sample preparation method: Approximately 0.5 g of sample (adhesive sheet) was weighed, 2 mL of chloroform was added, and the mixture was shaken overnight. 8 mL of methanol was added to the resulting solution, and the supernatant was filtered through a 0.45 μm membrane filter. The resulting filtrate was injected into an LC for analysis.

[Polymerization rate of monomer group]
For the pressure-sensitive adhesive sheets produced in Examples 1 to 13 and Comparative Examples 1 to 3, the polymerization rate of the monomer group was determined by the following method. First, the base sheet and release liner were peeled off from the pressure-sensitive adhesive sheet, and the weight W ₀ of the pressure-sensitive adhesive sheet (weight before drying) was measured. Next, the pressure-sensitive adhesive sheet was dried by heating at 130°C for 2 hours, and then cooled at room temperature (23°C) for about 20 minutes, and the weight W ₁ of the pressure-sensitive adhesive sheet (weight after drying) was measured. Based on the weight W ₀ (g) and the weight W ₁ (g), the polymerization rate of the monomer group was calculated by the following formula.
Polymerization rate (%) = W ₁ /W ₀ ×100

[Number average molecular weight (Mn) and weight average molecular weight (Mw) of the polymer]
First, samples were prepared that had the same composition as the photocurable compositions used in Examples 1 to 13 and Comparative Examples 1 to 3, except that they did not contain a crosslinking agent. The samples were irradiated with light under the conditions of the corresponding Examples and Comparative Examples. As a result, the monomer groups contained in the samples were polymerized to form polymers. The number average molecular weight (Mn) and weight average molecular weight (Mw) of the polymers were measured.

The above Mn and Mw were measured by GPC (gel permeation chromatography). The measurement device and measurement conditions were as follows. The measurement device and measurement conditions were different for the NVP-containing composition and the NVP-free composition.

(NVP-free composition)
Analytical equipment: Tosoh Corporation, HLC-8120GPC
Column: Tosoh Corporation, G7000H _XL + GMH _XL + GMH _XL
Column size: 7.8 mm diameter x 30 cm, total 90 cm
Column temperature: 40°C
・Flow rate: 0.8mL/min
Injection volume: 100 μL
Eluent: Tetrahydrofuran Detector: Differential refractometer (RI)
・Standard sample: polystyrene

(NVP-containing composition)
Analytical equipment: Agilent Technologies, Agilent 1200
Column: Tosoh Corporation, TSKgel SuperAWM-H + superAW4000 + superAW2500
Column size: 6.0 mm diameter x 15 cm, total 45 cm
Column temperature: 40°C
・Flow rate: 0.4mL/min
Injection volume: 40 μL
Eluent: N,N-dimethylformamide (DMF)
Detector: differential refractometer (RI)
・Standard sample: polystyrene

As can be seen from Table 4, when Example 2 and Comparative Example 2, which use the same photocurable composition (C2) and the same illuminance (4 mW/cm ² ) of light irradiated to the coating layer, are compared, the adhesive sheet of Example 2, which was prepared by irradiating light using an LED under conditions of a peak wavelength of 325 nm to 350 nm, had a smaller amount of remaining photopolymerization initiator than Comparative Example 2. Similarly, the adhesive sheets of Examples 1 and 3 to 13 also had a smaller amount of remaining photopolymerization initiator. Furthermore, the adhesive sheets of Examples 1 to 13 had sufficiently high polymerization rates of the monomer groups. From this, it can be said that the manufacturing method of this embodiment is suitable for efficiently producing adhesive sheets.

(Examples 14 to 16 and Comparative Examples 4 to 6)
Pressure-sensitive adhesive sheets of Examples 14 to 16 and Comparative Examples 4 to 6 sandwiched between a base sheet and a release liner L1 were obtained in the same manner as in Example 1, except that the photocurable composition, light source, and light irradiation conditions used were changed as shown in Table 5. In Comparative Examples 4 to 6, an LED emitting light with a peak wavelength of 365 nm was used as the light source.

[Residual amount of photopolymerization initiator, polymerization rate of monomer group]
For the pressure-sensitive adhesive sheets produced in Examples 14 to 16 and Comparative Examples 4 to 6, the remaining amount of photopolymerization initiator and the polymerization rate of the monomer group were calculated by the above-mentioned method.

[Number average molecular weight (Mn) and weight average molecular weight (Mw) of the polymer]
Samples having the same composition as the photocurable compositions used in Examples 14 to 16 and Comparative Examples 4 to 6, except that they did not contain a crosslinking agent, were prepared, and the number average molecular weight (Mn) and weight average molecular weight (Mw) of the polymer were measured by the above-mentioned method.

As can be seen from Table 5, when Example 16 and Comparative Example 6, which use the same photocurable composition (C11) and the same illuminance (14 mW/cm ² ) of light irradiated to the coating layer, are compared, the pressure-sensitive adhesive sheet of Example 16, which was prepared by irradiating light using an LED under conditions of a peak wavelength of 325 nm to 350 nm, had a smaller amount of remaining photopolymerization initiator and a higher polymerization rate of the monomer group than Comparative Example 6. Similarly, the pressure-sensitive adhesive sheets of Examples 14 and 15 also had a smaller amount of remaining photopolymerization initiator and a higher polymerization rate of the monomer group. From this, it can be said that the manufacturing method of this embodiment is suitable for efficiently producing pressure-sensitive adhesive sheets.

The adhesive sheet produced by the manufacturing method of the present invention can be used, for example, in optical laminates and image display devices.

Reference Signs List 1: Adhesive sheet 2: Optical film 10: First laminate 11: Base sheet 12: Coating layer 13: Release liner 14: Light 18: Exposed surfaces 21, 22: Optical film with adhesive sheet 34: Light-emitting diode

Claims (15)

The method includes a step of irradiating a coating layer containing a photocurable composition with light from a light emitting diode to form a pressure sensitive adhesive sheet,
The method for producing a pressure-sensitive adhesive sheet, wherein the light irradiated to the coating layer has a peak wavelength of 325 nm to 350 nm. The manufacturing method according to claim 1, wherein the peak wavelength is 340±10 nm. The method according to claim 1, wherein the illuminance of the light irradiated to the coating layer is 2.0 to 30 mW/ ^cm2 . The manufacturing method according to claim 1, in which the light is irradiated onto a laminate including a base sheet, the coating layer, and a release liner in this order. The manufacturing method according to claim 1, wherein the coating layer is irradiated with the light for a period of 10 to 1000 seconds. The manufacturing method according to claim 1, wherein the temperature of the coating layer is maintained at 10°C to 30°C while the coating layer is irradiated with the light. The manufacturing method according to claim 1, in which the coating layer is irradiated with the light in an atmosphere having an oxygen concentration of 500 vol ppm or less. The method according to claim 1, wherein the photocurable composition contains a monomer group including a (meth)acrylic monomer and/or a partial polymer of the monomer group. The manufacturing method according to claim 8, wherein the polymerization rate of the monomer group in the adhesive sheet is 80% or more. The photocurable composition includes a photopolymerization initiator,
The method according to claim 8 , wherein the amount of the photopolymerization initiator is 1.0 part by weight or less with respect to 100 parts by weight of the total of the monomer group and the partially polymerized product. The manufacturing method according to claim 10, wherein the content of the photopolymerization initiator in the adhesive sheet is 500 wtppm or less. The method according to claim 1, wherein the content of the solvent in the photocurable composition is 5% by weight or less. A method for producing an optical film with an adhesive sheet, comprising forming an optical film with an adhesive sheet by disposing an optical film on the exposed surface of the adhesive sheet formed by the manufacturing method according to any one of claims 1 to 12. The manufacturing method according to claim 13, wherein the optical film includes at least one film selected from the group consisting of a polarizing film and a retardation film. A method for producing an image display device, comprising bonding an optical film with a pressure-sensitive adhesive sheet formed by the method according to claim 13 to an image display panel to form an image display device.

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