TW202411375A - Optical laminate and image display device - Google Patents

Abstract

Provided is an optical laminate suitable for use in an image display device that may be exposed to a high temperature environment. The optical laminate provided comprises: an adhesive sheet that is formed of a photocurable composition which contains a monomer group and/or a partially polymerized product of the monomer group; and a phase difference film. The adhesive sheet and the phase difference film are in direct contact with each other or sandwich therebetween a layer having a thickness of not more than 10 [mu]m. The amount of residual monomer contained in the adhesive sheet is not more than 16,000 ppm (weight basis).

Description

Optical multilayer body and image display device

The present invention relates to an optical multilayer body and an image display device.

Various image display devices represented by liquid crystal display devices and electroluminescent (EL) display devices generally have an optical laminate including an optical film such as a polarizing film and an adhesive sheet. The bonding between the optical films contained in the optical laminate or the bonding between the optical laminate and the image display panel is usually performed using an adhesive sheet. Typically, a sheet formed by curing a monomer group containing an acrylic monomer or a polysilicone monomer by polymerization and crosslinking is used as the adhesive sheet. Patent document 1 discloses an adhesive sheet formed by a photocurable composition (hereinafter referred to as a "photocurable adhesive sheet"). In a different type, there is an adhesive sheet formed by curing a layer containing an adhesive composition and a solvent by heat (hereinafter referred to as a "thermocurable adhesive sheet"). Prior art documents Patent document

Patent document 1: Japanese Patent Publication No. 2016-155981

Problem to be solved by the invention When a photocurable adhesive sheet is used for an optical laminate, there is a tendency for problems to occur in the image quality of the image display device compared to the case of using a thermosetting adhesive sheet. The above problem is particularly prone to occur in image display devices that may be exposed to high temperature environments such as those for automotive use.

The present invention aims to provide an optical multilayer body suitable for use in an image display device that may be exposed to a high temperature environment.

Means for solving the problem Optical laminates generally contain residual monomers such as unreacted monomers remaining in adhesive sheets. According to the research of the inventors of this case, among the optical films that can be contained in optical laminates, phase difference films are most susceptible to the influence of residual monomers. Typically, phase difference films are prone to cracks caused by repeated changes in ambient temperature. In addition, according to research, the amount of residual monomers contained in photocuring adhesive sheets tends to be greater than that in thermosetting adhesive sheets. This may be due to the following influence: due to oxygen in the atmosphere, it is particularly easy to hinder the curing of the photocuring composition near the surface of the sheet.

In view of the above, the present invention provides an optical laminate having: an adhesive sheet formed of a photocurable composition containing a monomer group and/or a partial polymer of the monomer group; and a phase difference film; the adhesive sheet and the phase difference film are directly connected or connected via a layer with a thickness of less than 10µm; and the amount of residual monomers contained in the adhesive sheet is less than 16000ppm (weight basis).

In another aspect, the present invention provides an image display device, which has the above-mentioned optical multilayer body of the present invention.

Effect of the invention According to the present invention, an optical multilayer body can be provided, which is suitable for use in an image display device that may be exposed to a high temperature environment.

The optical laminate of the first aspect of the present invention comprises: an adhesive sheet formed of a photocurable composition containing a monomer group and/or a partial polymer of the monomer group; and a phase difference film; the adhesive sheet and the phase difference film are directly connected or connected via a layer with a thickness of less than 10µm; and the amount of residual monomers contained in the adhesive sheet is less than 16000ppm (weight basis).

Regarding the second aspect of the present invention, for example, in the optical multilayer body of the first aspect, the optical multilayer body has two adhesive sheets arranged in a manner of sandwiching the retardation film.

Regarding the third aspect of the present invention, for example, the optical laminate of the first or second aspect has two or more adhesive sheets, and the total amount of the residual monomer contained in the two or more adhesive sheets is less than 16000 ppm (weight basis).

Regarding the fourth aspect of the present invention, for example, the optical layered structure of any one of the first to third aspects is further provided with a polarizing film.

Regarding the fifth aspect of the present invention, for example, in the optical layered structure of the fourth aspect, the polarizing film and the phase difference film together hold the adhesive sheet.

In a sixth aspect of the present invention, for example, in the optical layered structure of any one of the first to fifth aspects, the monomer group includes a (meth)acrylic monomer.

Regarding the seventh aspect of the present invention, for example, in the optical layer of any one of the first to sixth aspects, the monomer group includes a carboxyl group-containing monomer.

In the eighth aspect of the present invention, for example, in the optical laminate of the seventh aspect, the content of the carboxyl group-containing monomer in the monomer group is 4.5% by weight or more.

Regarding the 9th aspect of the present invention, for example, in the optical layered structure of any one of the 1st to 8th aspects, the monomer group includes nitrogen-containing monomers.

In the tenth aspect of the present invention, for example, in the optical laminate of any one of the first to ninth aspects, the photocurable composition comprises a photopolymerization initiator, and the photopolymerization initiator is a compound having a chemical structure represented by the following formula (1) in the molecule; [Chemical Formula 1] In the above formula (1), ^R1 and ^R2 are independently: C1~C8 alkyl; C1~C4 alkyl whose hydrogen atom is substituted by -OH, C1~C4 alkoxy, -CN, ^-COOR51 , ^-OOCR52 , or ^-NR53R54 ; ^C3 ~C6 alkenyl; or, _-CH2 - _C6H4 ^-R55 _; ^R1 and ^R2 can be bonded to each other to form C2~C9 alkylene or C3~C6 oxygen alkylene or nitrogen heteroalkylene; X is ^-OR56 or ^-NR57R58 ; ^R51 is C1~C8 alkyl; ^R52 is C1~C4 alkyl; ^R53 and ^R54 are independently: hydrogen atom, C1~C12 alkyl; hydrogen atom is selected from -OH, C1~C4 alkoxy, -CN and -COOR51, ^-OOCR52 , or -NR53R54. R ⁵³ and R ⁵⁴ may be bonded to each other to form a C3~C9 alkylene group, and the C3~C9 alkylene group may be interrupted by -O- or -N(R ⁶⁰ )-; R ⁵⁵ is a C1~C4 alkyl group; R ⁵⁶ is a hydrogen atom, -SiR ⁶² ₃ , a C1~C8 alkyl group, or a C3~C6 alkenyl group; R ⁵⁷ and R 58 are: a C1~C12 alkyl group; a C2~C4 alkyl group substituted by at least one of the groups consisting of -OH, C1~C4 alkoxy, -CN and -COOR 63; a C3~C5 alkenyl group; or a cyclohexyl group; R ⁵⁷ and R ⁵⁸ are: a C1~C12 alkyl group; a C2~C4 alkyl group substituted by at least one of the groups consisting of -OH, C1~C4 alkoxy, -CN and -COOR ⁶³ ; a C3~ ^C5 alkenyl group; or a cyclohexyl group; ^{R 58} may be bonded to each other to form a C3~C9 alkylene group, and the C3~C9 alkylene group may be interrupted by -O- or -N(R ⁶⁴ )-; R ⁵⁹ is a C1~C4 alkyl group; R ⁶⁰ is a hydrogen atom, a C1~C4 alkyl group, an allyl group, a C1~C4 hydroxyalkyl group, -CH ₂ CH ₂ -COOR ⁶¹ or -CH ₂ CH ₂ CN; R ⁶¹ is a C1~C4 alkyl group; R ⁶² is a C1~C6 alkyl group; R ⁶³ is a C1~C4 alkyl group; R ⁶⁴ is a hydrogen atom, a C1~C4 alkyl group, an allyl group, a C1~C4 hydroxyalkyl group, -CH ₂ CH ₂ -COOR ⁶⁵ or -CH ₂ CH ₂ CN; R ⁶⁵ is a C1~C4 alkyl group; The aforementioned chemical structure may be bonded to a hydrogen atom or a structure substituted with a hydrogen atom via the carbon atom represented by * in the aforementioned formula (1).

In the 11th aspect of the present invention, for example, in the optical laminate of any one of the 1st to 10th aspects, the photocurable composition comprises a first photopolymerization initiator and a second photopolymerization initiator, the first photopolymerization initiator has a relatively small first reaction rate, and the second photopolymerization initiator has a relatively large second reaction rate; the ratio of the second reaction rate to the first reaction rate is expressed as a ratio of polymerization rate A of 1.1 or more, and the polymerization rate A is obtained by using each of the photopolymerization initiators alone and evaluating using the following measurement method; [Measurement method] A mixed solution of 99 parts by weight of n-butyl acrylate and 1 part by weight of 4-hydroxybutyl acrylate as monomers and 0.1 parts by weight of a photopolymerization initiator as an evaluation object was irradiated with ultraviolet light to prepare a monomer slurry in which the aforementioned monomers were partially polymerized; the aforementioned ultraviolet light irradiation was carried out until the viscosity of the aforementioned mixed solution at 30°C reached 20 Pa·s; then, a coating layer with a thickness of 20µm consisting of the aforementioned monomer slurry was formed between a pair of polyethylene terephthalate (PET) sheets each having a thickness of 75µm; then, the aforementioned coating layer was irradiated with ultraviolet light using an LED as a light source from one of the aforementioned PET sheets, the LED having a peak wavelength at 340nm±10nm; the illumination intensity and irradiation time of the aforementioned ultraviolet light were set to 4mW/cm ² and 1200 seconds; the polymerization rate of the aforementioned monomer measured by the aforementioned coating layer photocured by the aforementioned ultraviolet irradiation is specifically referred to as the aforementioned polymerization rate A.

Regarding the twelfth aspect of the present invention, for example, in the optical laminate of any one of the first to eleventh aspects, the adhesive sheet has a surface that has been subjected to a surface modification treatment.

Regarding the 13th aspect of the present invention, for example, in the optical laminate of any one of the 1st to 12th aspects, the thickness of the adhesive sheet is less than 50µm.

Regarding the 14th aspect of the present invention, for example, in the optical laminate of any one of the 1st to 13th aspects, the anchoring force of the adhesive sheet on the phase difference film is greater than 13N/25mm.

The image display device of the 15th aspect of the present invention comprises an optical multilayer body of any one of the 1st to 14th aspects.

The present invention is described in detail below, but the present invention is not limited to the following implementation forms and can be arbitrarily modified and implemented within the scope of the gist of the present invention.

[Optical laminate] FIG. 1 shows an example of an optical laminate of the present embodiment. The optical laminate 10 (10A) of FIG. 1 has an adhesive sheet 1 and a phase difference film 2. The adhesive sheet 1 and the phase difference film 2 are directly connected. However, the adhesive sheet 1 and the phase difference film 2 may be connected via a layer having a thickness of less than 10µm, preferably less than 5µm. The layer may be a single layer or multiple layers. Examples of the layer are a base coating layer, an antistatic layer, a protective layer, a coating layer, and a hard coating layer. The optical laminate 10 may be used as an optical film with an adhesive sheet attached.

(Adhesive sheet) The adhesive sheet 1 is formed of a photocurable composition containing a monomer group and/or a partial polymer of the above monomer group. The photocurable composition is a composition that forms the adhesive sheet 1 by light irradiation. The amount of residual monomers contained in the adhesive sheet 1 is 16000ppm or less. The amount of residual monomers may also be 15000ppm or less, 12000ppm or less, 10000ppm or less, 9000ppm or less, 8000ppm or less, 7000ppm or less, 6000ppm or less, 5000ppm or less, less than 5000ppm, 4500ppm or less, 4000ppm or less, 3500ppm or less, 3000ppm or less, 2500ppm or less, 2000ppm or less, and may be 1500ppm or less. For an adhesive sheet 1 having a small amount of residual monomers, its phase difference film 2 is not prone to cracks due to changes in ambient temperature. Moreover, when the amount of residual monomers is less than 16000ppm, it is also suitable for improving the anchoring force on the phase difference film 2, especially a small amount of less than 3500ppm, less than 2500ppm, and less than 2000ppm. The adhesive sheet 1 is also suitable for improving the anchoring force on the phase difference film 2. For an adhesive sheet 1 with improved anchoring force, the cohesion of the adhesive sheet 1 may be improved by reducing the amount of low molecular weight compounds contained in the adhesive sheet 1. There is no particular lower limit on the amount of residual monomers, for example, it is more than 300ppm, it can also be more than 500ppm, and it can also be more than 750ppm. The adhesive sheet 1 having the lower limit of the residual monomer amount within the above range is suitable for suppressing the degradation of the phase difference film 2 that may occur due to light irradiation or heat when the laminate containing the phase difference film 2 is irradiated with light to form the adhesive sheet 1. In this specification, "ppm" is based on weight.

The amount of residual monomers in the adhesive sheet 1 can be evaluated by gas chromatography (GC) analysis.

FIG2 shows another example of an optical laminate of the present embodiment. The optical laminate 10 (10B) of FIG2 has two adhesive sheets 1 (1A, 1B) arranged to sandwich a phase difference film 2. The optical laminate 10B has an adhesive sheet 1A, a phase difference film 2, and an adhesive sheet 1B in this order. The amount of residual monomers contained in the two adhesive sheets 1A and 1B, in other words, when the optical laminate 10B has two or more adhesive sheets 1, the total amount of residual monomers contained in the two or more adhesive sheets 1 can be 16000ppm or less, or 15000ppm or less, 12000ppm or less, 10000ppm or less, less than 10000ppm, 9000ppm or less, 8000ppm or less, 7500ppm or less, 7000ppm or less, 6000ppm or less, 5000ppm or less, 4000ppm or less, 3500ppm or less, or even 3000ppm or less. The optical laminate 10 having the above-mentioned small total amount of residual monomers has a retardation film 2 that is not easily cracked due to changes in ambient temperature. Furthermore, when the total amount of residual monomers is less than 16000ppm, it is also suitable for improving the anchoring force between the phase difference film 2 and the adhesive sheet 1. In particular, the optical laminate 10B with a small amount of less than 3500ppm, less than 2500ppm, or less than 2000ppm is also suitable for improving the anchoring force between the phase difference film 2 and the adhesive sheet 1. The total lower limit of the amount is, for example, more than 300ppm, more than 500ppm, more than 600ppm, more than 750ppm, and more than 1000ppm. The optical laminate 10B with a lower limit within the above range is suitable for suppressing the degradation of the phase difference film 2 that may occur due to light irradiation or heat when the laminate containing the phase difference film 2 is irradiated with light to form the adhesive sheet 1.

The amount of residual monomers contained in the adhesive sheet 1 varies depending on, for example, the composition of the photocurable composition used to form the adhesive sheet 1, the type and amount of photopolymerization initiator that may be contained in the photocurable composition, the forming conditions and thickness of the adhesive sheet 1, and the type and presence of post-treatment of the adhesive sheet 1. An example of post-treatment is the surface modification treatment described below.

FIG3 shows another example of the optical laminate of the present embodiment. The optical laminate 10 (10C) of FIG3 is further provided with a polarizing film 3. The polarizing film 3 holds the adhesive sheet 1 (1A) together with the phase difference film 2. The optical laminate 10C sequentially comprises a polarizing film 3, an adhesive sheet 1A, and a phase difference film 2. Furthermore, the optical laminate 10C sequentially comprises a polarizing film 3, an adhesive sheet 1A, a phase difference film 2, and an adhesive sheet 1B. However, the position of the polarizing film 3 in the optical laminate 10 is not limited to this example. The polarizing film 3 and the adhesive sheet 1A are directly connected. However, the polarizing film 3 and the adhesive sheet 1A may also be connected via a layer having a thickness of less than 10µm, preferably less than 5µm. Examples of the layer are as described above.

Polarizing film 3 has a tendency to change its size greatly due to heat among optical films. The size change of polarizing film 3 will give a force that promotes the generation of cracks in phase difference film 2 contained in the same optical laminate 10. Therefore, the present invention is particularly beneficial to the case where the optical laminate 10 is equipped with polarizing film 3.

<Photocurable composition> The photocurable composition that can form the adhesive sheet 1 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, that is, the (meth)acrylic monomer and its partial polymer, can be 50% by weight or more, 60% by weight or more, 70% by weight or more, and can be 80% by weight or more. In this case, an acrylic adhesive sheet containing (meth)acrylic polymers and their crosslinked products as main components can be formed. However, the photocurable composition is not limited to the above examples. In this specification, (meth)acrylic acid means acrylic acid and methacrylic acid. (Meth)acrylate means acrylate and methacrylate.

An example of a (meth)acrylic acid monomer is an alkyl (meth)acrylate having an alkyl group with 1 to 20 carbon atoms in the side chain. The carbon number of the alkyl group may be 7 or less, 6 or less, 5 or less, or even 4 or less. The alkyl group may be a straight chain or may have a branched chain. Examples of the alkyl (meth)acrylates are methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, dibutyl (meth)acrylate, tertiary 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, 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, heptadecanyl (meth)acrylate, and octadecyl (meth)acrylate. The alkyl (meth)acrylate may also be n-butyl (meth)acrylate.

The content of the alkyl (meth)acrylate in the monomer group is, for example, 40% by weight or more, or 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 partial polymer is converted into the weight of each monomer before polymerization.

The monomer group may also include carboxyl-containing monomers. The carboxyl-containing monomer may be a (meth) acrylic acid monomer, in other words, the (meth) acrylic acid monomer may also include carboxyl-containing monomers. Examples of carboxyl-containing monomers are (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid and crotonic acid. The content of carboxyl-containing monomers in the monomer group is, for example, 0.1 to 15% by weight. The lower limit of the content may also be 0.5% by weight or more, 1% by weight or more, 2.5% by weight or more, 4.5% by weight or more, 5% by weight or more, 7.5% by weight or more, and may be 9.5% by weight or more. The upper limit of the content may also be 13% by weight or less, 11% by weight or less, 10% by weight or less, 9.5% by weight or less, and may be 7.5% by weight or less. The monomer group including the carboxyl group-containing monomer is particularly suitable for reducing the amount of residual monomers in the adhesive sheet 1. The monomer group may not include the carboxyl group-containing monomer.

The monomer group may also include a hydroxyl-containing monomer. The hydroxyl-containing monomer may be a (meth)acrylic monomer, in other words, the (meth)acrylic monomer may also include a hydroxyl-containing monomer. The hydroxyl-containing monomer may help to enhance the cohesive force of the adhesive sheet. Examples of hydroxyl-containing monomers 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)-methacrylate. The hydroxyl-containing monomer is preferably 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate. The content of the hydroxyl-containing monomer in the monomer group is, for example, 5% by weight or less, and may also be 4% by weight or less, 3% by weight or less, 2% by weight or less, or even 1% by weight or less. The lower limit of the content is, for example, 0.01% by weight or more, and may also be 0.05% by weight or more, or even 0.1% by weight or more. The monomer group may not contain a hydroxyl-containing monomer.

The monomer group may also include nitrogen-containing monomers. According to the research of the inventors, nitrogen-containing monomers can help reduce the amount of residual monomers. Nitrogen-containing monomers refer to monomers having at least one nitrogen atom in the molecule (in one molecule). In addition, in this specification, monomers having a hydroxyl group and a nitrogen atom in the molecule are classified as nitrogen-containing monomers. Monomers having a carboxyl group and a nitrogen atom in the molecule are classified as carboxyl-containing monomers.

The nitrogen atom-containing monomer is preferably N-vinyl cycloamide, (meth)acrylamide, etc. The nitrogen atom-containing monomer may be used alone or in combination of two or more.

The N-vinyl cyclic amide is preferably represented by the following formula (A). [Chemical Formula 2]

In formula (A), ^R1 is a divalent organic group, preferably a divalent saturated alkyl group or an unsaturated alkyl group, more preferably a divalent saturated alkyl group (such as an alkylene group having 3 to 5 carbon atoms). In addition, formula (A) indicates that N and ^R1 are directly bonded via a single bond to form a ring structure.

The N-vinyl cyclic amide represented by formula (A) is preferably N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-2-caprolactam, N-vinyl-3-morpholin, N-vinyl-1,3-pyrrolidone, N-vinyl-3,5-morpholindione, etc., more preferably N-vinyl-2-pyrrolidone, N-vinyl-2-caprolactam, and more preferably N-vinyl-2-pyrrolidone.

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

Examples of the N,N-dialkyl (meth)acrylamide 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(tertiary butyl) (meth)acrylamide.

(Meth)acrylamide also includes, for example, various N-hydroxyalkyl (meth)acrylamide. Examples of N-hydroxyalkyl (meth)acrylamide include N-hydroxymethyl (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, N-methyl-N-2-hydroxyethyl (meth)acrylamide, and the like.

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

Examples of nitrogen-containing monomers other than N-vinyl cyclic amide and (meth)acrylamide include aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, tertiary butylaminoethyl (meth)acrylate, and the like; cyano-containing monomers such as acrylonitrile and methacrylonitrile; (meth)acryloyl pyrrolidine, N-vinyl piperidine, N-vinylpyrrole, N-vinylimidazole, N-vinylpyrrolidine, N-vinyl pyrrolidine, N-vinyl pyrrolidine, N-vinyl pyrrolidine, vinyl pyrazole, vinyl isothiazole, vinyl thiazole, vinyl isothiazole, vinyl thiazolidine, (meth)acryloyl pyrrolidone, (meth)acryloyl pyrrolidine, (meth)acryloyl piperidine, N-methylvinyl pyrrolidine, Heterocyclic monomers such as ketones; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide, N-methyliconimide, N-ethyliconimide, N-butyliconimide, N-octyliconimide, N-2-ethylhexyliconimide, N-lauryliconimide, N-cyclohexyl Iconimide-based monomers such as iconimide, succinimide-based monomers such as N-(meth)acryloxymethylenesuccinimide, N-(meth)acryl-6-oxyhexamethylenesuccinimide, and N-(meth)acryl-8-oxyoctamethylenesuccinimide, and the like; isocyanate-based monomers such as 2-(meth)acryloxyethyl isocyanate, and the like.

The content of the nitrogen atom-containing monomer in the monomer group is, for example, 40% by weight or less, and may also be 35% by weight or less, 30% by weight or less, 25% by weight or less, 20% by weight or less, 18% by weight or less, 15% by weight or less, 14% by weight or less, 13% by weight or less, 12% by weight or less, 11% by weight or less, and may further be 10% by weight or less. The lower limit of the content is, for example, 1% by weight or more, and may also be 2% by weight or more, 3% by weight or more, 4% by weight or more, 5% by weight or more, 6% by weight or more, 7% by weight or more, 8% by weight or more, 9% by weight or more, and may further be 10% by weight or more.

The monomer group may also include both carboxyl group-containing monomers and nitrogen atom-containing monomers.

In the photocurable composition, each of the above monomers may also be contained as a partial polymer. The partial polymer may be any of a homopolymer and a copolymer. The partial polymer will appropriately increase the viscosity of the photocurable composition, thereby contributing to the stable formation of the coating layer described later.

The photocurable composition usually contains a photopolymerization initiator. Examples of the photopolymerization initiator are photoradical generators that generate free radicals using visible light and/or ultraviolet light having a wavelength shorter than 450 nm.

Examples of photopolymerization initiators include benzoin ethers such as benzoin methyl ether, benzoin isopropyl ether, and benzyl dimethyl ketal; substituted benzoin ethers such as anisole methyl ether; substituted acetophenones such as 2,2-diethoxyacetophenone and 2,2-dimethoxy-2-phenylacetophenone; α-hydroxyalkyl phenones such as 1-hydroxycyclohexyl-phenyl ketone; substituted α-keto alcohols such as 2-methyl-2-hydroxypropiophenone; aromatic Sulfonyl chloride; photoactive oximes such as 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime; diphenyl ketone compounds such as diphenyl ketone, benzoylbenzoic acid, methyl benzoylbenzoate, 4-phenyldiphenyl ketone, hydroxydiphenyl ketone, acrylated diphenyl ketone, 4-benzoyl-4'-methyl diphenyl sulfide, 3,3',4,4'-tetrakis(tertiary butylperoxycarbonyl)diphenyl ketone; 9-oxysulfur , 2-chloro-9-oxysulfuron , 2-methyl 9-oxosulfuron 、Isopropyl 9-oxysulfide 、2,4-Diisopropyl 9-oxysulfide , 2,4-diethyl 9-oxysulfide 9-Oxysulfuron Series compounds; 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 (piperonyl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-bis(trichloromethyl)-6-phenylvinyl-s-triazine, 2-(naphthoyl-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4-methoxy-naphthoyl-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2,4-trichloromethyl-(piperonyl)-6 -trioxane, 2,4-trichloromethyl-(4'-methoxyphenyl)-6-trioxane and other trioxane compounds; oxime ester 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 compounds such as bis(2,4,6-trimethylbenzyl)phenylphosphine oxide and 2,4,6-trimethylbenzyldiphenylphosphine oxide; quinone compounds such as 9,10-phenanthrenequinone, camphorquinone, ethylanthraquinone; borate compounds; carbazole compounds; imidazole compounds; and, titaniumocene compounds. The photocurable composition may also contain one or more photopolymerization initiators.

Another example of a photopolymerization initiator is a compound having a chemical structure represented by the following formula (1) (hereinafter referred to as chemical structure X) in the molecule. According to the research of the inventors, the compound can help reduce the amount of residual monomers. [Chemical formula 3]

In the above formula (1), ^R1 and ^R2 are independently: C1~C8 alkyl; C1~C4 alkyl whose hydrogen atom is substituted by -OH, C1~C4 alkoxy, -CN, ^-COOR51 , ^-OOCR52 , or ^-NR53R54 ; ^C3 ~C6 alkenyl; or, _-CH2 - _{C6H4 -} ^R55 . ^R1 and ^R2 may also be bonded to each other to form C2~C9 alkylene, C3~C6 oxygen alkylene, or nitrogen heteroalkylene. ^R51 is C1~C8 alkyl. ^R52 is C1~C4 alkyl. R ⁵³ and R ⁵⁴ are independently: a hydrogen atom, a C1~C12 alkyl group; a C2~C4 alkyl group substituted by at least one group selected from the group consisting of -OH, C1~C4 alkoxy, -CN and -COOR ⁵⁹ ; a C3~C5 alkenyl group; or a cyclohexyl group. R ⁵³ and R ⁵⁴ may also be bonded to each other to form a C3~C9 alkylene group, and the C3~C9 alkylene group may be interrupted by -O- or -N(R ⁶⁰ )-. R ⁵⁵ is a C1~C4 alkyl group. R ⁵⁹ is a C1~C4 alkyl group. R ⁶⁰ is a hydrogen atom, a C1~C4 alkyl group, an allyl group, a C1~C4 hydroxyalkyl group, -CH ₂ CH ₂ -COOR ⁶¹ or -CH ₂ CH ₂ CN. R ⁶¹ is a C1~C4 alkyl group.

X is -OR ⁵⁶ or -NR ⁵⁷ R ⁵⁸ . R ⁵⁶ is a hydrogen atom, -SiR ⁶² ₃ , a C1~C8 alkyl group, or a C3~C6 alkenyl group. R ⁵⁷ and R ⁵⁸ are: a C1~C12 alkyl group; a C2~C4 alkyl group in which the hydrogen atom is substituted by at least one group selected from the group consisting of -OH, C1~C4 alkoxy, -CN, and -COOR ⁶³ ; a C3~C5 alkenyl group; or a cyclohexyl group. R ⁵⁷ and R ⁵⁸ may also be bonded to each other to form a C3~C9 alkylene group, and the C3~C9 alkylene group may be interrupted by -O- or -N(R ⁶⁴ )-. R ⁶² is a C1~C6 alkyl group. R ⁶³ is a C1~C4 alkyl group. R ⁶⁴ is a hydrogen atom, a C1-C4 alkyl group, an allyl group, a C1-C4 hydroxyalkyl group, -CH ₂ CH ₂ -COOR ⁶⁵ or -CH ₂ CH ₂ CN. R ⁶⁵ is a C1-C4 alkyl group.

The chemical structure X may be bonded to a hydrogen atom or a structure substituted with a hydrogen atom via the carbon atom represented by * in formula (1).

The alkyl, alkoxy, alkenyl, alkylene, oxyalkylene, nitrogen heteroalkylene and hydroxyalkylene described in the description of formula (1) may be unbranched or branched. In addition, together with the description of formula (1), the description of "Cn1~Cn2" in this specification (n1 and n2 are natural numbers) means that the carbon number is within the range of n1~n2.

^R1 and ^R2 can be independently C1-C8 alkyl or C3-C6 alkenyl, or C1-C8 alkyl. ^R1 and ^R2 can be independently C1-C4 alkyl, or C1-C3 alkyl, or C1-C2 alkyl. ^R1 and ^R2 can also be methyl.

^R1 and ^R2 may be the same.

X may also be -OR ⁵⁶ . R ⁵⁶ may be a hydrogen atom or a C1-C8 alkyl group, or may be a hydrogen atom. In other words, X may also be -OH.

R ¹ , R ² and X may be arbitrarily combined as the above-mentioned ideal examples.

The chemical structure X may also be a structure represented by the following formula (2). In the chemical structure X of formula (2), when a substitution structure having a hydrogen atom is bonded to the carbon atom represented by *, the substitution structure and the -COCR ¹ XR ² group in formula (2) are in a para position to the benzene ring of the chemical structure X. [Chemical formula 4]

The photopolymerization initiator may be a compound having two or more chemical structures X in one molecule.

The photopolymerization initiator may also be a compound represented by the following formula (3). The compound represented by formula (3) has two chemical structures X in one molecule. The two chemical structures X are located at both ends of the photopolymerization initiator molecule. More specifically, the two chemical structures X are bonded to each other at the carbon atom of the phenylene group represented by * through -A-. [Chemical Formula 5]

In formula (3), R ¹ ' and R ² ' are groups that can be used as R ¹ and R ² , respectively; and are groups that can be used as R ¹ and R ² independently of R ¹ and R ^2. R ¹ ' and/or R ² ' may be the same as R ¹ and/or R ^2. R ¹ , R ² , R ¹ ' and R ² ' may all be the same.

X' in formula (3) is independent of X in formula (1) and can be used as a group of X. X' and X may be the same.

A is -O-, -CYR ³ -, or -C(CH ₃ )R ⁴ .

Y is a hydrogen atom, -Cl, -Br, -OR ⁷¹ , -NR ⁷² R ⁷³ , or -SR ⁷⁴ . R ³ is a hydrogen atom, a C1-C8 alkyl group, a C3-C6 alkenyl group, a benzyl group, -CH ₂ -C ₆ H ₄ -R ⁷⁵ , or a phenyl group. R ⁴ is a C1-C6 alkyl group or an alkylene group, and the alkylene group is bonded to the carbon atom of the phenylene group of the compound of formula (3).

R ⁷¹ is a hydrogen atom, -Si(R ⁷⁶ ) ₃ , a C1~C12 alkyl group, a C2~C18 acyl group, -CO-NH-R ⁷⁷ , a C2~C20 hydroxyalkyl group, a C2~C20 methoxyalkyl group, 3-R ⁷⁸ -2-hydroxy-propyl group, 3-[1,3,3,3-tetramethyl-1-[(trimethylsilyl)oxy]disiloxyalkyl]-propyl group, 2,3-dihydroxy-propyl group, or a C2~C21 hydroxyalkyl group whose carbon chain is interrupted by 1 to 9 oxygen atoms, or a C3~C25 alkyl group. R ⁷² and R ⁷³ are independently: C1~C12 alkyl; C2~C4 alkyl substituted with at least one group selected from the group consisting of -OH, C1~C4 alkoxy, -CN and -COOR ⁷⁹ ; C3~C5 alkenyl; cyclohexyl; or C7~C9 phenylalkyl. R ⁷² and R ⁷³ may also be bonded to each other to form a C3~C9 alkylene group, and the C3~C9 alkylene group may be interrupted by -O- or -N(R ⁸⁰ )-. R ⁷⁴ is C1~C18 alkyl, hydroxyethyl, 2,3-dihydroxypropyl, cyclohexyl, benzyl, phenyl, C1~C12 alkylphenyl, -CH ₂ -COOR ⁸¹ -CH ₂ CH ₂ -COOR ⁸² , or -CH(CH ₃ )-COOR ⁸³ . R ⁷⁵ is a C1~C4 alkyl group. R ⁷⁶ is a C1~C6 alkyl group. R ⁷⁷ is a C1~C12 alkyl group. R ⁷⁸ is a C1~C18 alkoxy group. R ⁷⁹ is a C1~C4 alkyl group. R ⁸⁰ is a hydrogen atom, a C1~C4 alkyl group, an allyl group, a benzyl group, a C1~C4 hydroxyalkyl group, -CH ₂ CH ₂ -COOR ⁸⁴ , or -CH ₂ CH ₂ CN. R ⁸¹ , R ⁸² and R ⁸³ are independently a C1~C18 alkyl group. R ⁸⁴ is a C1~C4 alkyl group.

The alkyl part and alkylene group of the alkyl, alkenyl, acyl, hydroxyalkyl, methoxyalkyl, alkoxy and phenylalkyl described in the description of formula (3) may be unbranched or branched.

The preferred examples of R ¹ , R ² , R ¹ ' and R ² ' in formula (3) are the same as the preferred examples of R ¹ and R ² described previously in the description of formula (1). The preferred example of X' in formula (3) is the same as the preferred example of X described previously in the description of formula (1). A may be -CYR ³ -. Y may be a hydrogen atom. R ³ may be a hydrogen atom. When A is -CYR ³ -, Y and R ³ may both be hydrogen atoms. In other words, A may be -CH ₂ -.

R ¹ , R ² , R ¹ ′, R ² ′, X, X′, and A in formula (3) may be arbitrarily combined as in the above-mentioned ideal examples.

The photopolymerization initiator may also be a compound represented by the following formula (4). The compound of formula (4) is one of the compounds of formula (3). [Chemical Formula 6]

Specific examples of photopolymerization initiators are shown in the following formulas (5) to (9). The photopolymerization initiator may be a compound represented by at least one formula selected from the group consisting of formulas (5) to (9), a compound represented by at least one formula selected from the group consisting of formulas (5) to (8), a compound represented by at least one formula selected from the group consisting of formulas (5) to (7), or a compound represented by formula (5). In addition, the compound of formula (8) is derived from a vinyl compound having a chemical structure X in the side chain. More specifically, it is an oligomer of the vinyl compound.

[Chemical formula 7]

[Chemical formula 8]

[Chemical formula 9]

[Chemical formula 10]

[Chemical formula 11]

The photopolymerization initiators represented by formulas (5) to (9) are sold on the market as Omnirad127, Esacure KIP160, Esacure one, Esacure KIP150, and Omnirad1173 (all manufactured by IGM Resins). The photopolymerization initiator may also be at least one selected from the above groups.

Specific examples of photopolymerization initiators include 1-hydroxycyclohexyl-phenyl ketone, bis(2,4,6-trimethylbenzyl)phenylphosphine oxide, and 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one. Among them, 2-hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one is preferred. The above-mentioned photopolymerization initiators are sold on the market as Omnirad184, Omnirad819, and Omnirad127, respectively (all manufactured by IGM Resin Co., Ltd.).

The amount of the photopolymerization initiator in the photocurable composition may be, for example, 20 parts by weight or less, 10 parts by weight or less, 5.0 parts by weight or less, 4.0 parts by weight or less, 3.0 parts by weight or less, 2.5 parts by weight or less, 2.0 parts by weight or less, 1.5 parts by weight or less, 1.0 parts by weight or less, 0.5 parts by weight or less, 0.3 parts by weight or less, 0.25 parts by weight or less, or even 0.2 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 amount of the photopolymerization initiator may be, for example, 0.01 parts by weight or more, 0.03 parts by weight or more, 0.05 parts by weight or more, 0.08 parts by weight or more, 0.1 parts by weight or more, 0.13 parts by weight or more, 0.15 parts by weight or more, or even 0.18 parts by weight or more, relative to 100 parts by weight of the total of the monomer group and its partial polymer.

The photocurable composition may contain one or more photopolymerization initiators.

The photocurable composition may also include a first photopolymerization initiator and a second photopolymerization initiator, wherein the first photopolymerization initiator has a relatively small first reaction rate, and the second photopolymerization initiator has a relatively large second reaction rate. The reaction rate of each photopolymerization initiator can be specified by the polymerization rate achieved when the monomer is polymerized using only the photopolymerization initiator. The ratio of the second reaction rate to the first reaction rate is expressed as a ratio of polymerization rate A of 1.1 or more, and the polymerization rate A is obtained by using each photopolymerization initiator alone and evaluating using the following measurement method. The ratio of polymerization rate A may be 1.15 or more, or 1.2 or more, 1.2 or more, 1.22 or more, 1.25 or more, or 1.27 or more. The upper limit of the ratio is not particularly limited, and is, for example, 3 or less. In addition, the ratio of the polymerization rate A can be specified by [polymerization rate A when the second photopolymerization initiator is used alone]/[polymerization rate A when the first photopolymerization initiator is used alone]. [Measurement method] A mixed solution of 99 parts by weight of n-butyl acrylate and 1 part by weight of 4-hydroxybutyl acrylate as monomers and 0.1 parts by weight of the photopolymerization initiator to be evaluated is irradiated with ultraviolet light to prepare a monomer slurry in which the aforementioned monomers are partially polymerized. The ultraviolet irradiation is carried out until the viscosity of the mixed solution reaches 20 Pa·s at 30°C. Then, a coating layer with a thickness of 20µm consisting of the prepared monomer slurry is formed between a pair of polyethylene terephthalate (PET) sheets each having a thickness of 75µm. Next, the coating layer is irradiated with ultraviolet light from one of the PET sheets, using an LED as a light source, the LED having a peak wavelength of 340 nm ± 10 nm. The irradiation intensity and irradiation time of the ultraviolet light are set to 4 mW/cm ² and 1200 seconds, respectively. The polymerization rate of the aforementioned monomer measured for the coating layer photocured by ultraviolet irradiation is designated as polymerization rate A.

According to the research of the inventors, the combination of the first and second photopolymerization initiators affects the polymerization state when the adhesive sheet is formed, and thus helps to reduce the amount of residual monomers. In addition, the general composition used to form acrylic adhesive sheets is known to be the composition of the monomer slurry used to evaluate the polymerization rate A. In addition, the above-mentioned ultraviolet irradiation conditions are suitable for evaluating the polymerization state.

The polymerization rate A of the first photopolymerization initiator may be 80% or less, 79% or less, or 78% or less. The lower limit of the polymerization rate A is, for example, 65% or more, 66% or more, 67% or more, 68% or more, 69% or more, or 70% or more.

The polymerization rate A of the second photopolymerization initiator may be 90% or more, or 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, or even 99% or more. The upper limit of the polymerization rate A is, for example, 99.9% or less, or even 99.5% or less.

The polymerization rate A of the first photopolymerization initiator and the polymerization rate A of the second photopolymerization initiator may also satisfy the above ranges at the same time. For example, the polymerization rate A of the first photopolymerization initiator may be 80% or less, and the polymerization rate A of the second photopolymerization initiator may be 90% or more.

Examples of the first and second photopolymerization initiators include: benzyl ethers, substituted benzyl ether compounds, substituted acetophenone compounds, α-hydroxyacetophenone compounds, substituted α-ketoalcohol compounds, aromatic sulfonyl chloride compounds, photoactive oximes, diphenyl ketone compounds, 9-oxysulfuronium compounds, The invention also includes oxime ester compounds, isophosphite compounds, quinone compounds, borate compounds, carbazole compounds, imidazole compounds and titanocene compounds.

The first photopolymerization initiator is preferably an α-hydroxyacetophenone compound. The first photopolymerization initiator, which is an α-hydroxyacetophenone compound, is particularly suitable for increasing the molecular weight of the polymer in combination with the second photopolymerization initiator. The number of α-hydroxyacetophenone structures in one molecule of the first photopolymerization initiator is, for example, 1 to 3, preferably 1 or 2, and more preferably 1.

A specific example of the first photopolymerization initiator is 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methylacetone. The photopolymerization initiator is an α-hydroxyacetophenone compound and is commercially available as Omnirad 2959 (manufactured by IGM Resins).

The second photopolymerization initiator is not limited and may be an α-hydroxyacetophenone compound. The second photopolymerization initiator, which is an α-hydroxyacetophenone compound, is particularly suitable for increasing the molecular weight of the polymer in combination with the first photopolymerization initiator, especially with the first photopolymerization initiator, which is an α-hydroxyacetophenone compound. The number of α-hydroxyacetophenone structures in one molecule of the second photopolymerization initiator is, for example, 1 to 3, preferably 1 or 2, and more preferably 2.

The second polymerization initiator may also be the above-mentioned compound having a chemical structure X in the molecule, as well as a preferred example.

The photocurable composition may contain one or more first photopolymerization initiators. The photocurable composition may contain one or more second photopolymerization initiators.

The weight ratio of the blending amount X1 of the first photopolymerization initiator to the blending amount X2 of the second photopolymerization initiator is, for example, 5:1-1:5, 4:1-1:4, 3:1-1:3, 2:1-1:2, and may further be 1.5:1-1:1.5.

The photocurable composition may also contain a crosslinking agent. An example of a crosslinking agent is a multifunctional monomer having two or more polymerizable functional groups in one molecule. The multifunctional monomer may also be a (meth)acrylic monomer. Examples of multifunctional monomers are: 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, azoxy, oxazolinyl, hydrazine, hydroxymethyl, etc. in one molecule. The multifunctional monomer is preferably a monomer having two or more C=C bonds in one molecule.

Examples of the multifunctional monomer 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 (NDDA), 1,12-dodecanediol di(meth)acrylate, trihydroxymethylpropane tri(meth)acrylate, tetrahydroxymethylmethane tri(meth)acrylate and other multifunctional acrylates (ester compounds of polyols and (meth)acrylic acid, etc.); allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl di(meth)acrylate, hexyl di(meth)acrylate. The multifunctional monomer is preferably a multifunctional acrylate, more preferably trihydroxymethylenepropane tri(meth)acrylate, hexanediol di(meth)acrylate, or dipentatriol hexa(meth)acrylate.

The amount of the crosslinking agent to be mixed varies depending on the molecular weight or the number of functional groups, but is, 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, or even 0.5 parts by weight or less per 100 parts by weight of the total of the monomer group and its partial polymer. The lower limit of the mixing amount is, for example, 0.01 parts by weight or more, and even 0.05 parts by weight or more.

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

The blending amount of the silane coupling agent is, for example, 3 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or even 0.5 parts by weight or less, based on 100 parts by weight of the total of the monomer group and its partial polymer. The lower limit of the blending amount is, for example, 0.1 parts by weight or more, or 0.2 parts by weight or more. The photocurable composition may not contain a silane coupling agent.

The content of the solvent in the photocurable composition is, for example, 5 wt % or less, and may also be 4 wt % or less, 3 wt % or less, 2 wt % or less, 1 wt % or less, or even 0.5 wt % or less. The photocurable composition may be substantially free of solvent. The term "substantially free of solvent" means that the content of solvent derived from additives, etc., is allowed to be, for example, 0.1 wt % or less, preferably 0.05 wt % or less, and more preferably 0.01 wt % or less.

The viscosity of the photocurable composition is preferably 5 to 100 poise. The photocurable composition having a viscosity within the above range is particularly suitable for forming the coating layer described below.

The polymerization rate of the monomer group in the adhesive sheet 1 is preferably 95% or more. The polymerization rate may also be 96% or more, 97% or more, 98% or more, or even 99% or more.

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

The thickness of the adhesive sheet 1 is, for example, 70 µm or less, and may be 50 µm or less, 40 µm or less, 30 µm or less, 25 µm or less, or 20 µm or less. The lower limit of the thickness is, for example, 2 µm or more, and may be 5 µm or more, or 10 µm or more.

The adhesive sheet 1 may also have a surface that has been subjected to a surface modification treatment (hereinafter referred to as a "modified surface") 4. The surface modification treatment is typically a treatment using active energy rays. The surface modification treatment is, for example, at least one selected from the group consisting of a corona treatment, a plasma treatment, an excimer UV light treatment, and a flame treatment, and may be a corona treatment and/or a plasma treatment, or may be a corona treatment. Each surface modification treatment may be performed by a corresponding known treatment device.

The conditions of the surface modification treatment of the corona treatment are expressed by the discharge amount, for example, 0.6~100kJ/ ^m2 . The lower limit of the discharge amount may be 1kJ/ ^m2 or more, 2kJ/ ^m2 or more, 5kJ/ ^m2 or more, 7kJ/ ^m2 or more, 10kJ/ ^m2 or more, 13kJ/ ^m2 or more, 15kJ/ ^m2 or more, 20kJ/ ^m2 or more, 25kJ/ ^m2 or more, 30kJ/ ^m2 or more, and may be 35kJ/ ^m2 or more. The upper limit of the discharge amount may be 70 kJ/m ² or less, 60 kJ/m ² or less, 50 kJ/m ² or less, 45 kJ/m ² or less, 40 kJ/m ² or less, 30 kJ/m ² or less, 20 kJ/m ² or less, and may further be 18 kJ/m ² or less.

The adhesive sheet 1 of FIG. 1 has a modified surface 4 on the side of the phase difference film 2. This aspect is particularly suitable for improving the anchoring force of the adhesive sheet 1 on the phase difference film 2. The adhesive sheet 1 may have the modified surface 4 on the side opposite to the phase difference film 2, or may have the modified surface 4 on both the side of the phase difference film 2 and the opposite side.

The anchoring force of the adhesive sheet 1 on the phase difference film 2 may be 10N/25mm or more, 12N/25mm or more, 13N/25mm or more, 14N/25mm or more, 15N/25mm or more, 16N/25mm or more, 17N/25mm or more, or even 18N/25mm or more. The upper limit of the anchoring force may be 50N/25mm or less, or 30N/25mm or less.

Improving the anchoring force of the adhesive sheet 1 on the phase difference film 2 can help, for example, suppress peeling between the adhesive sheet 1 and the phase difference film 2. The above-mentioned optical laminate with suppressed peeling is suitable for suppressing image quality degradation in image display devices that can be used in harsh environments for a long time.

The anchoring force of the adhesive sheet 1 on the phase difference film 2 can be measured by the following method. Cut the laminate including the phase difference film 2 and the adhesive sheet 1 into a width of 25 mm × a length of 150 mm to make a test piece. Then, the surface of the phase difference film 2 of the test piece is entirely overlapped on a stainless steel test plate through a double-sided tape, and a 2 kg roller is passed back and forth once to press them together. Then, the adhesive sheet 1 of the test piece is overlapped on the evaluation sheet, and a 2 kg roller is passed back and forth once to press them together. There is no special limitation on the evaluation sheet as long as it has a size of 30 mm wide × 150 mm long and does not peel off from the adhesive sheet 1 during the test. The evaluation sheet can be, for example, an ITO film (125 TETOLIGHT OES (manufactured by Oike Industries)). Next, using a commercially available tensile testing machine, the adhesive sheet 1 is peeled off from the phase difference film 2 at a peeling angle of 180° and a tensile speed of 300 mm/min while holding the evaluation sheet, and the average value of the peeling force at this time is determined as the anchoring force of the adhesive sheet 1 on the phase difference film 2. The above test is conducted in a gas environment of 23°C ± 5°C.

(Phase difference film) The phase difference film 2 can be made of a stretched polymer film or a film that has been oriented and fixed with a liquid crystal material. The phase difference film 2 has birefringence in the plane and/or thickness direction, for example.

The phase difference film 2 includes: an anti-reflection phase difference film (refer to Japanese Patent Publication No. 2012-133303 [0221], [0222], [0228]), a viewing angle compensation phase difference film (refer to Japanese Patent Publication No. 2012-133303 [0225], [0226]), a viewing angle compensation tilt-oriented phase difference film (refer to Japanese Patent Publication No. 2012-133303 [0227]), etc.

The specific structure of the phase difference film 2, such as phase difference value, configuration angle, three-dimensional birefringence, single layer or multilayer, etc. is not particularly limited, and a known phase difference film can be used.

The thickness of the phase difference film 2 is, for example, 30 to 200 μm, preferably 40 to 150 μm.

The phase difference film 2 may also include, for example, a quarter wavelength plate and/or a half wavelength plate in which the liquid crystal material is oriented and fixed.

The phase difference film 2 containing a cycloolefin polymer is particularly prone to cracking. Moreover, regarding the phase difference film 2 that is a stretched film, it is more likely to crack when it is a uniaxial stretched film than when it is a biaxial stretched film. Therefore, the present invention is particularly advantageous when the phase difference film 2 contains a cycloolefin polymer and when it is a uniaxial stretched film.

The phase difference film 2 may also have a modified surface. The phase difference film 2 of FIG. 1 has a modified surface 5 on the adhesive sheet 1 side. This aspect is particularly suitable for improving the anchoring force between the phase difference film 2 and the adhesive sheet 1. Examples of surface modification treatment and ideal examples are as described above.

An example of a residual monomer that can be contained in the phase difference film 2 and the optical laminate 10 is a (meth)acrylic monomer. The example of the (meth)acrylic monomer is the same as the example of the (meth)acrylic monomer contained in the photocurable composition that can form the adhesive sheet 1.

(Polarizing film) The polarizing film 3 includes a polarizing element. The polarizing film 3 typically includes a polarizing element and a protective film (transparent protective film). The protective film is, for example, arranged to be in contact with the main surface (surface with the widest area) of the polarizing element. The polarizing element may also be arranged between two protective films. The protective film may also be arranged on at least one side of the polarizing element.

The polarizer is not particularly limited, and examples thereof include those obtained by adsorbing dichroic substances such as iodine and dichroic dyes on hydrophilic polymer films such as polyvinyl alcohol films, partially formalized polyvinyl alcohol films, and partially saponified films of ethylene-vinyl acetate copolymers and then uniaxially stretching them; polyene-based oriented films such as dehydrated polyvinyl alcohol films and dehydrogenated polyvinyl chloride films, etc. The polarizer is typically composed of a polyvinyl alcohol film (polyvinyl alcohol films include partially saponified films of ethylene-vinyl acetate copolymers) and dichroic substances such as iodine.

There is no particular limitation on the thickness of the polarizer, for example, it is less than 80µm, and it can also be less than 50µm, less than 30µm, less than 28µm, less than 25µm, less than 20µm, and can also be less than 18µm. There is no particular limitation on the lower limit of the thickness of the polarizer, for example, it is more than 1µm, and it can also be more than 5µm, more than 10µm, and can also be more than 15µm. Thin polarizers (for example, thickness less than 20µm) can suppress dimensional changes caused by heat, and can help improve the durability of the optical laminate, especially durability under high temperatures. In addition, the greater the thickness of the polarizer, the greater the dimensional changes caused by heat. Therefore, the present invention is particularly beneficial, for example, when the thickness of the polarizer is greater than 20µm, especially when it is greater than 25µm.

The protective film may be made of thermoplastic resins having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. Specific examples of the thermoplastic resins include cellulose resins such as cellulose triacetate, polyester resins, polyether resins, polyester resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth)acrylic resins, cyclic polyolefin resins (northene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The material of the protective film may also be a thermosetting resin or UV-curing resin such as (meth) acrylic acid, urethane, acrylic urethane, epoxy, silicone, etc. When the polarizing film has two protective films, the materials of the two protective films may be the same or different. For example, a protective film made of a thermoplastic resin may be bonded to one main surface of the polarizer through an adhesive, and a protective film made of a thermosetting resin or a UV-curing resin may be bonded to the other main surface of the polarizer. The protective film may also contain one or more arbitrary additives. Examples of additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, colorants, etc.

The thickness of the protective film can be appropriately determined, but is generally considered from aspects such as strength or operability, film properties, etc., for example, 5~200µm, preferably 10~80µm.

Polarizers and protective films are usually bonded together through water-based adhesives. Examples of water-based adhesives include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latex, water-based polyurethane, and water-based polyester. Other adhesives besides the above adhesives include UV-curable adhesives and electron beam-curable adhesives. Electron beam-curable adhesives for polarizing plates exhibit suitable adhesion to various protective films. Adhesives may also contain metal compound fillers.

Regarding the protective film, a hard coating layer may be provided on the surface opposite to the surface in contact with the polarizer, and treatments such as anti-reflection, anti-sticking, diffusion, and anti-glare may also be performed.

The polarizing film 3 may also be a circularly polarizing film.

The thickness of the polarizing film 3 is, for example, 500 μm or less, and may be 300 μm or less, 200 μm or less, 100 μm or less, or 60 μm or less. The lower limit of the thickness is, for example, 10 μm or more, 25 μm or more, or 40 μm or more.

The optical laminate 10 may also have layers other than the adhesive sheet 1, the phase difference film 2, and the polarizing film 3. Examples of such layers include optical films other than the phase difference film 2 and the polarizing film 3, a primer layer, an antistatic layer, a protective layer, a coating layer, a hard coating layer, a cover glass, an adhesive sheet other than the adhesive sheet 1, and a base sheet that can be used to form the adhesive sheet 1.

[Manufacturing method of optical laminate] The optical laminate 10 can be formed by laminating, for example, an adhesive sheet 1, a phase difference film 2, and other layers such as a polarizing film 3 as required. The adhesive sheet 1 can be formed by irradiating light 14 to a first laminate 15, which sequentially includes a base sheet 21, a coating layer 22 containing a photocurable composition, and a release liner 23 (see FIG. 4A to FIG. 4C). The coating layer 22 is irradiated with light 14 and hardened to become an adhesive sheet 1.

In the example of FIG. 4A , the light 14 is irradiated from the side of the substrate sheet 21. At this time, the light 14 will penetrate the substrate sheet 21 and reach the coating layer 22. However, the light 14 can be irradiated from the side of the peeling liner 23, or from both the peeling liner 23 and the substrate sheet 21 ( FIG. 4B ). The formed adhesive sheet 1 is sandwiched by the substrate sheet 21 and the peeling liner 23 before the peeling liner 23 is peeled off, and constitutes a part of the second laminate 16.

An example of the substrate of the release substrate 23 (hereinafter referred to as "substrate substrate") is a resin film. Examples of resins that may be contained in the substrate substrate are polyesters such as polyethylene terephthalate and polyethylene naphthalate, acetate resins, polyether sulphates, polycarbonates, polyamides, polyimides, polyolefins, (meth) acrylic resins, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl alcohol, polyarylates, and polyphenylene sulfide. The resin is preferably a polyester such as polyethylene terephthalate.

The release liner 23 may have a light 14 transmittance, or may have a light 14 transmittance to the same degree as that of the base sheet 21 .

The thickness of the release liner 23 is, for example, 10-200 μm, or 25-150 μm.

The release liner 23 may have a layer other than the liner base material. The release liner 23 may also have a release layer. The release liner 23 may have, for example, a liner base material and a release layer formed on one surface of the liner base material. The release liner 23 may be used in a manner such that the release layer is on the coating layer 22 side.

The release layer is typically a hardened layer of a release agent composition containing a release agent. For the release agent, various release agents such as polysilicone release agents, fluorine release agents, long-chain alkyl release agents, fatty acid amide release agents, and silicon powder can be used. The release liner 23 may also have a hardened layer of a release agent composition containing a polysilicone release agent as a main component (hereinafter referred to as "polysilicone release layer"). The polysilicone release layer is particularly suitable for taking into account both adhesion and releasability to the adhesive sheet 1. In addition, in this specification, the main component means the component with the largest content rate.

The silicone-based mold release agent includes various curing silicone materials such as addition reaction type, condensation reaction type, ultraviolet curing type, electron beam curing type, solvent-free type, etc., preferably addition reaction curing silicone materials. Addition reaction curing silicone materials are particularly suitable for forming a mold release layer that takes into account both adhesion to the adhesive sheet 1 and peelability. The curing silicone material can also be a silicone modified resin in which reactive silicone is introduced into organic resins such as urethane, epoxy, and alkyd resins by graft polymerization.

Examples of addition reaction curing polysiloxane materials are polyorganosiloxanes having vinyl or alkenyl groups in the molecule. Addition reaction curing polysiloxane materials may not have hydrosilyl groups. Examples of alkenyl groups are: 3-butenyl, 4-pentenyl, 5-hexenyl, 6-heptenyl, 7-octenyl, 8-nonenyl, 9-decenyl, 10-undecenyl and 11-dodecenyl. Examples of polyorganosiloxanes are: polyalkyl alkyl siloxanes such as polydimethylsiloxane, polydiethylsiloxane and polymethylethylsiloxane, polyalkylaryl siloxane, and copolymers of multiple Si atom-containing monomers such as poly(dimethylsiloxane-diethylsiloxane). The polyorganosiloxane is preferably polydimethylsiloxane.

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

The silicone release agent composition may also contain a hardening catalyst. An example of a hardening catalyst is a platinum-based catalyst. Examples of platinum-based catalysts are platinum chloride, platinum olefin complexes, and platinum chloride olefin complexes. The amount of the platinum-based catalyst used is, for example, 10 to 1000 ppm (weight basis, converted to platinum) relative to the total solid content of the composition.

The silicone release agent composition may also contain additives. Examples of additives are peeling control agents and adhesion promoters. Examples of peeling control agents are unreactive silicone resins, and more specifically, organic silicones such as octamethylcyclotetrasiloxane and MQ resins. The total amount of peeling control agents and adhesion promoters used is, for example, 1 to 30% by weight relative to the total solid content of the composition. Other examples of additives are fillers, antistatic agents, antioxidants, ultraviolet absorbers, plasticizers, and colorants. The total amount of other additives used is, for example, less than 10% by weight relative to the total solid content of the composition.

The silicone mold release agent composition may also contain an organic solvent. Examples of organic solvents include 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 organic solvents may also be included. The amount of organic solvent used is preferably 80 to 99.9% by weight of the silicone mold release agent composition.

The release layer can be formed, for example, by heating and drying a coating film containing a release agent composition formed on a liner substrate. The release agent composition can be applied by various coating methods such as roller coating, contact roller coating, gravure coating, reverse coating, roller brush, spray coating, dip roller coating, rod coating, doctor blade coating, air knife coating, curtain coating, lip coating, and mold coating. Heating and drying can be applied by, for example, hot air drying. The heating temperature and time vary depending on the heat resistance of the substrate, but are usually 80~150℃ and 10 seconds~10 minutes. Active energy rays such as ultraviolet rays can also be used as needed.

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 less than 65 nm. 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 50 nm or more.

The release liner 23 can be in the form of a single sheet or a long strip.

An example of the base sheet 21 is a resin film. Examples of the resin contained in the base sheet 21 are the same as the examples of the resin that can be contained in the backing substrate.

The base sheet 21 preferably has excellent transmittance of the light 14 .

The thickness of the base sheet 21 is, for example, 10 to 200 μm, or 25 to 150 μm.

The substrate sheet 21 may also be provided with a release layer on the surface of the coating layer 22. The examples of the release layer that the substrate sheet 21 may have and the method of making the same are the same as the examples of the release layer that the release liner 23 may have and the method of making the same. Both the release liner 23 and the substrate sheet 21 may also be provided with a release layer. In this case, the two release layers may also be formed of a release agent composition containing the same release agent as a main component. In addition, the thickness of the two release layers may be different, for example, the release layer provided by the substrate sheet 21 may also be thicker.

For the base sheet 21, a sheet having a greater peeling force with the adhesive sheet 1 than the peeling liner 23 can usually be selected.

The base sheet 21 may be in a single sheet or in a long strip.

The first laminate 15 can be formed, for example, by forming a coating layer 22 on a base sheet 21 (or a release liner 23), and disposing a release liner 23 (or a base sheet 21) on the formed coating layer 22. Alternatively, the first laminate 15 can be formed by flowing a photocurable composition into a space formed by the base sheet 21 and the release liner 23 with their main surfaces facing each other with a predetermined interval.

The coating layer 22 may be formed by various coating methods such as roller coating, contact roller coating, gravure coating, reverse coating, roller brush, spray coating, dip roller coating, rod coating, scraper coating, air knife coating, curtain coating, lip coating, and mold coating.

The thickness of the coating layer 22 can be adjusted according to the desired thickness of the adhesive sheet 1 .

The light 14 irradiated to the first laminate 15 is, for example, visible light or ultraviolet light having a wavelength shorter than 450 nm. The light 14 may also include light having a wavelength in the same region as the absorption wavelength of the photopolymerization initiator contained in the photocurable composition. The light 14 may also be short-wavelength light having a cutoff wavelength of 300 nm or less through a filter or the like, and the cutoff short-wavelength light is suitable for suppressing the degradation of the substrate sheet 21 and/or the release liner 23 caused by the light 14. The light source of the light 14 is, for example, a light irradiation device having an ultraviolet irradiation lamp. Examples of ultraviolet irradiation lamps include ultraviolet LED, low-pressure mercury lamp, medium-pressure mercury lamp, high-pressure mercury lamp, ultra-high-pressure mercury lamp, metal halogen lamp, xenon lamp, microwave-excited mercury lamp, black light lamp, chemical lamp, sterilization lamp, low-pressure discharge mercury lamp, and excimer laser. Two or more ultraviolet irradiation lamps may also be combined.

The irradiation of the light 14 may be continuous or intermittent.

The irradiation intensity of the light 14 is, for example, 1 to 20 mW/cm ² . The irradiation time of the light 14 is, for example, 5 minutes to 5 hours. The accumulated light quantity of the light 14 on the first layer 15 is, for example, 100 to 5000 mJ/cm ² .

Next, the release liner 23 is peeled off from the second laminate 16 to expose the surface of the adhesive sheet 1. By disposing the retardation film 2 on the exposed surface of the adhesive sheet 1, the optical laminate 10 can be formed. Before disposing the retardation film 2, the exposed surface of the adhesive sheet 1 may be subjected to a surface modification treatment.

The optical multilayer of the present embodiment can be distributed and stored in the form of a rolled body formed by rolling a strip-shaped optical multilayer or in the form of a single-sheet optical multilayer.

The optical multilayer body of this embodiment can typically be used in an image display device. The image display device can be formed by, for example, joining the optical multilayer body 10 and the image display panel. The joining is performed by, for example, an adhesive sheet 1. The image display device can 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 can also be an electroluminescent (EL) display, a plasma display (PD), a field emission display (FED: Field Emission Display), etc. The image display device can also be used for purposes that may be exposed to a high temperature environment, typically for vehicle use. However, the use of the image display device is not limited. The image display device can be used for various purposes such as home appliance use or public information display (PID) use.

Implementation Examples The present invention is further described in detail below through implementation examples. The present invention is not limited to the implementation examples shown below.

[Preparation of polarizing film] (Polarizing film A) A polyvinyl alcohol film with a thickness of 80µm was dyed in an iodine solution with a concentration of 0.3% at a temperature of 30°C for 1 minute between rollers with different speed ratios and stretched to 3 times. Then, it was immersed in an aqueous solution containing boric acid at a concentration of 4% and potassium iodide at a concentration of 10% at a temperature of 60°C for 0.5 minutes, and stretched to a total stretching ratio of 6 times. Then, it was immersed in an aqueous solution containing potassium iodide at a concentration of 1.5% at a temperature of 30°C for 10 seconds, washed, and dried at 50°C for 4 minutes to obtain a polarizer with a thickness of 18µm. A transparent protective film with a thickness of 30µm made of a modified acrylic polymer having a lactone ring structure was bonded to one side of the polarizer using a polyvinyl alcohol adhesive. Furthermore, a transparent protective film with a thickness of 47µm formed on a cellulose triacetate film (manufactured by Konica Minolta, trade name "KC4UY") was bonded to the other side of the polarizer using a polyvinyl alcohol adhesive. The film was heated and dried in an oven set at 70°C for 5 minutes to produce a polarizing film A. Furthermore, the surface of the polarizing film A on the transparent protective film side made of a modified acrylic polymer was subjected to a corona treatment with a discharge amount of 63W/( ^m2 ·min).

(Polarizing film B) A polarizing element with a thickness of 28 µm was obtained in the same manner as the preparation of polarizing film A except that the stretching conditions were changed. A transparent protective film with a thickness of 30 µm composed of a modified acrylic polymer having a lactone ring structure was bonded to one side of the polarizing element using a polyvinyl alcohol-based adhesive. Furthermore, a transparent protective film with a thickness of 40 µm formed on a cellulose triacetate film (manufactured by Konica Minolta, trade name "KC4UY") was bonded to the other side of the polarizing element using a polyvinyl alcohol-based adhesive. It was heated and dried in an oven set at 70°C for 5 minutes to produce polarizing film B. Furthermore, the surface of the polarizing film B on the transparent protective film side made of a modified acrylic polymer was subjected to a corona treatment at a discharge amount of 63 W/(m ² ·min).

[Preparation of phase difference film] A biaxially oriented polypropylene film (Toray, trade name "TORAYFAN" BO 2570A-5, thickness 60µm) was attached to both sides of a polymer film (ZEON Corporation, Japan, trade name "ZEONOR ZF14-100", thickness 100µm) containing a resin obtained by hydrogenating a ring-opening polymer of a nor-butylene monomer through an acrylic adhesive layer (thickness 15µm). After that, the film was stretched 1.38 times in an air circulation constant temperature oven at 146℃±1℃ while maintaining the long side direction of the film using a roll stretching machine, and a phase difference film with a thickness of 108µm was produced.

[Preparation of monomer slurry] (Synthesis Example 1) 99 parts by weight of n-butyl acrylate (BA), 1 part by weight of 4-hydroxybutyl acrylate (HBA), 10 parts by weight of acrylic acid (AA), and 0.1 parts by weight of Omnirad184 (1-hydroxycyclohexyl-phenyl ketone, manufactured by IGM RESINS) as a photopolymerization initiator were placed in a four-necked flask and irradiated with ultraviolet light in a nitrogen environment to obtain partially photopolymerized monomer slurry A1. Ultraviolet light irradiation was performed until the viscosity of the liquid in the flask (measurement conditions: BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30°C) reached about 20 Pa·s.

(Synthesis Example 2) Except that the monomers to be used are changed as shown in Table 1, monomer slurries A2 to A14 are prepared in the same manner as monomer slurry A1.

[Table 1]

The abbreviations in Table 1 are as follows. In addition, Omnirad2959 and Omnirad127 are preferably α-hydroxyacetophenone compounds. BA: n-butyl acrylate HBA: 4-hydroxybutyl acrylate AA: acrylic acid NVP: N-vinyl-2-pyrrolidone Omnirad184: 1-Hydroxycyclohexyl-phenyl ketone (Omnirad184, manufactured by IGM Resins) Omnirad651: 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad651, manufactured by IGM Resin) Omnirad127: 2-Hydroxy-1-(4-(4-(2-hydroxy-2-methylpropionyl)benzyl)phenyl)2-methylpropan-1-one (Omnirad127, manufactured by IGM Resin) Omnirad2959: 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methylpropanone (Omnirad2959, manufactured by IGM Resin)

[Preparation of photocurable composition] The monomer slurry, crosslinking agent and silane coupling agent were mixed in a manner as shown in Table 2 below to obtain photocurable compositions C1 to C14. 1,9-nonanediol diacrylate (NDDA) was used as the crosslinking agent. An epoxy-containing silane coupling agent (manufactured by Shin-Etsu Silicone, KBM-403) was used as the silane coupling agent.

[Table 2]

[Preparation of Adhesive Sheet] (Preparation Example 1: Preparation of Release Backing Material A) 30 parts by weight of addition reaction curing type silicone (LTC761 containing hexene-containing polyorganosiloxane, 30% by weight toluene solution, manufactured by Dow Corning Toray Co., Ltd.), 0.9 parts by weight of stripping control agent (BY24-856 containing unreacted silicone resin, manufactured by Dow Corning Toray Co., Ltd.), 2 parts by weight of curing catalyst (SRX212 containing platinum catalyst, manufactured by Dow Corning Toray Co., Ltd.), and a toluene/hexane mixed solvent (volume ratio 1:1) as a diluent were mixed to obtain a silicone-based release agent composition. The concentration of the polysilicone solid component in the release agent composition is 1.0 wt%. Then, the release agent composition is coated on one side of the liner substrate (polyester film Lumirror XD500P, thickness 75µm) using a wire rod and heated at 130°C for 1 minute to produce a release liner A with a release layer (thickness 60nm) prepared on one side.

(Manufacturing Example 2: Preparation of Release Liner B) Except for changing the coating thickness of the release agent composition on the liner substrate, a release liner B with a release layer (thickness 120nm) on one side was prepared in the same manner as in Manufacturing Example 1.

(Example 1) A photocurable composition C1 was applied to one side of the release liner A produced in Production Example 1 by a sprayer to form a coating layer. Then, the release liner B produced in Production Example 2 was arranged on the formed coating layer to obtain a first laminate. The release liners A and B were arranged so that the release layer was in contact with the coating layer. Next, the coating layer was photocured by irradiating ultraviolet light (black light source) from the release liner A side of the first laminate at an irradiation intensity of 2.5 mW/cm ² and an irradiation time of 640 seconds, thereby forming a second laminate consisting of the release liner A, the adhesive sheet (thickness 20 µm) and the release liner B. Next, the release liner B was peeled off from the second laminate, and the above-mentioned retardation film, both surfaces of which had been previously subjected to a corona treatment, was bonded to the exposed surface of the adhesive sheet formed by peeling. Next, another adhesive sheet formed in the same manner as above is bonded to the exposed surface of the phase difference film, thereby obtaining an optical laminate having a laminate structure of release liner A/adhesive sheet/phase difference film/adhesive sheet/release liner A. Next, one of the release liner A is peeled off from the optical laminate, and the prepared polarizing film A or polarizing film B is bonded to the exposed adhesive sheet. The bonding is performed in such a manner that the adhesive sheet is bonded to the transparent protective film made of modified acrylic polymer in the polarizing films A and B. Thus, an optical laminate A having a laminate structure of polarizing film A/adhesive sheet/phase difference film/adhesive sheet/peeling liner A (the thickness of the polarizer is 18µm) and an optical laminate B having a laminate structure of polarizing film B/adhesive sheet/phase difference film/adhesive sheet/peeling liner A (the thickness of the polarizer is 28µm) were obtained.

(Example 2) Optical laminates A and B of Example 2 were obtained in the same manner as in Example 1 except that photocurable composition C2 was used instead of photocurable composition C1 and the surface of the phase difference film side of each adhesive sheet was subjected to a corona treatment (discharge amount 61 W/(m ² ·min)) before bonding with the phase difference film.

(Examples 3 to 10) Except that the photocurable compositions C3 to C11 are used instead of the photocurable composition C1, the optical laminates A and B of Examples 3 to 10 are obtained in the same manner as in Example 1.

(Example 11) Except that the photocurable composition C11 is used instead of the photocurable composition C2, the optical laminate A and the optical laminate B of Example 11 are obtained in the same manner as Example 2.

(Comparative Examples 1-4) Except that the photocurable compositions C5, C12-14 are used instead of the photocurable composition C1, the optical laminates A and B of Comparative Examples 1-4 are obtained in the same manner as in Example 1.

[Polymerization rate] The polymerization rate of each adhesive sheet formed in the Examples and Comparative Examples was calculated from the change in weight of the adhesive sheet before and after heating and drying at 130°C for 2 hours. Specifically, the weight of the adhesive sheet just after peeling off the peeling liner A and the peeling liner B from the second laminate was set as W ₀ (weight before drying), and the weight of the adhesive sheet at the time point of cooling at room temperature (23°C) for about 20 minutes after the above heating was set as W ₁ (weight after drying), and the polymerization rate was calculated by the formula: polymerization rate (%) = W ₁ /W ₀ × 100.

[Amount of residual monomers] The amount of residual monomers in each adhesive sheet formed in the embodiment and the comparative example was evaluated by GC analysis. The apparatus and measurement conditions used for GC analysis are listed below. ・ Apparatus used: GC7890A (manufactured by Agilent Technologies) ・ Column: HP-1 (manufactured by Agilent Technologies) ・ Detector: Flame ionization detector hydrogen energy ionization detector (FID) ・ Injection port temperature: 250°C ・ Measurement temperature conditions: The following (1) to (4) were implemented in order. (1) Maintain at 0℃ for 3 minutes; (2) Increase the temperature at a rate of 10℃/min; (3) After reaching 120℃, increase the temperature at a rate of 20℃/min; (4) Maintain at 300℃ ・Sample preparation method: Take 0.05g of the sample (adhesive sheet) into a screw-cap bottle, add 2.5mL of ethyl acetate and shake overnight. Filter the resulting solution with a 0.45µm membrane filter, and inject 1µL of the filtered solution into the GC for analysis.

[Anchoring force] Using each optical laminate A produced in the embodiment and the comparative example, the anchoring force of the adhesive sheet on the phase difference film was evaluated by the above method. The double-sided adhesive tape used was the product name "No.531" manufactured by Nitto Denko Corporation. The stainless steel test material used was a SUS304 plate (width 40mm×length 120mm). The evaluation sheet used was an ITO film (125 TETOLIGHT OES, manufactured by Oike Industries). The tensile testing machine used was Autograph SHIMAZU AG-I 10KN (manufactured by Shimadzu Corporation).

[Crack Proneness] For each optical laminate A and optical laminate B of the embodiment and comparative example, the crack proneness of the phase difference film was evaluated in the following manner. The optical laminate was cut into a 300 mm × 210 mm rectangle to make a test piece. Then, the peeling backing material A was peeled off, and the test piece was attached to the surface of the glass plate through the adhesive sheet exposed by the peeling. Then, it was heated in an autoclave at 50°C for 15 minutes to stabilize the bond between the test piece and the glass plate, and an evaluation sample was obtained. The obtained samples were subjected to repeated thermal shock tests at -40℃ and 85℃, and the presence or absence of cracks in the retardation film after 100, 200 and 300 thermal cycles was confirmed by an optical microscope. Three samples were prepared for each optical laminate, and the crack susceptibility of the retardation film was evaluated by the number of samples with cracks. The thermal cycle conditions are as follows. 1 cycle: After being placed in a gas environment at -40℃ for 30 minutes, it was placed in a gas environment at 85℃ for 30 minutes.

The evaluation results are shown in Table 3 below. In addition, "corona treatment" in Table 3 means the corona treatment of the adhesive sheet. The amount of residual monomers shown in Table 3 is the total amount of residual monomers in all adhesive sheets included in the optical laminate to be evaluated. In the "crack formation susceptibility" column, when the number of samples that have cracks among the three samples evaluated is n, it is recorded as "n/3".

[table 3]

Industrial Applicability The optical multilayer body of the present invention can be used in, for example, image display devices.

1,1A,1B: Adhesive sheet 2: Retardation film 3: Polarizing film 4: Modified surface 5: Modified surface 10,10A,10B,10C: Optical laminate 14: Light 15: First laminate 16: Second laminate 21: Base sheet 22: Coating layer 23: Release liner

FIG. 1 is a cross-sectional view schematically showing an example of the optical multilayer body of the present invention. FIG. 2 is a cross-sectional view schematically showing an example of the optical multilayer body of the present invention. FIG. 3 is a cross-sectional view schematically showing an example of the optical multilayer body of the present invention. FIG. 4A is a schematic view for illustrating an example of a method for forming an adhesive sheet provided by the optical multilayer body of the present invention. FIG. 4B is a schematic view for illustrating an example of a method for forming an adhesive sheet provided by the optical multilayer body of the present invention. FIG. 4C is a schematic view for illustrating an example of a method for forming an adhesive sheet provided by the optical multilayer body of the present invention.

1: Adhesive sheet

2: Phase difference film

4: Modified surface

5: Modified surface

10,10A: Optical laminates

Claims (15)

An optical laminate, comprising: an adhesive sheet formed of a photocurable composition containing a monomer group and/or a partial polymer of the monomer group; and a phase difference film; the adhesive sheet and the phase difference film are directly connected or connected via a layer with a thickness of less than 10µm; and the amount of residual monomers contained in the adhesive sheet is less than 16000ppm (weight basis). The optical multilayer body of claim 1, wherein the optical multilayer body comprises two adhesive sheets arranged in a manner of sandwiching the phase difference film. As in claim 1, the optical laminate comprises two or more adhesive sheets, and the total amount of the residual monomers contained in the two or more adhesive sheets is less than 16000 ppm (weight basis). As in claim 1, the optical laminate further comprises a polarizing film. As in claim 4, the optical laminate, wherein the polarizing film and the phase difference film together clamp the adhesive sheet. The optical laminate of claim 1, wherein the monomer group comprises a (meth)acrylic monomer. The optical layered product of claim 1, wherein the monomer group comprises carboxyl-containing monomers. The optical laminate of claim 7, wherein the content of the carboxyl group-containing monomer in the monomer group is 4.5% by weight or more. The optical layered structure of claim 1, wherein the monomer group comprises nitrogen-containing monomers. The optical laminate of claim 1, wherein the photocurable composition comprises a photopolymerization initiator, and the photopolymerization initiator is a compound having a chemical structure represented by the following formula (1) in the molecule; [Chemical Formula 1] In the above formula (1), ^R1 and ^R2 are independently: C1~C8 alkyl; C1~C4 alkyl whose hydrogen atom is substituted by -OH, C1~C4 alkoxy, -CN, ^-COOR51 , ^-OOCR52 , or ^-NR53R54 ; ^C3 ~C6 alkenyl; or, _-CH2 - _C6H4 ^-R55 _; ^R1 and ^R2 can be bonded to each other to form C2~C9 alkylene or C3~C6 oxygen alkylene or nitrogen heteroalkylene; X is ^-OR56 or ^-NR57R58 ; ^R51 is C1~C8 alkyl; ^R52 is C1~C4 alkyl; ^R53 and ^R54 are independently: hydrogen atom, C1~C12 alkyl; hydrogen atom is selected from -OH, C1~C4 alkoxy, -CN and -COOR51, ^-OOCR52 , or -NR53R54. R ⁵³ and R ⁵⁴ may be bonded to each other to form a C3~C9 alkylene group, and the C3~C9 alkylene group may be interrupted by -O- or -N(R ⁶⁰ )-; R ⁵⁵ is a C1~C4 alkyl group; R ⁵⁶ is a hydrogen atom, -SiR ⁶² ₃ , a C1~C8 alkyl group, or a C3~C6 alkenyl group; R ⁵⁷ and R 58 are: a C1~C12 alkyl group; a C2~C4 alkyl group substituted by at least one of the groups consisting of -OH, C1~C4 alkoxy, -CN and -COOR 63; a C3~C5 alkenyl group; or a cyclohexyl group; R ⁵⁷ and R ⁵⁸ are: a C1~C12 alkyl group; a C2~C4 alkyl group substituted by at least one of the groups consisting of -OH, C1~C4 alkoxy, -CN and -COOR ⁶³ ; a C3~ ^C5 alkenyl group; or a cyclohexyl group; ^{R 58} may be bonded to each other to form a C3~C9 alkylene group, and the C3~C9 alkylene group may be interrupted by -O- or -N(R ⁶⁴ )-; R ⁵⁹ is a C1~C4 alkyl group; R ⁶⁰ is a hydrogen atom, a C1~C4 alkyl group, an allyl group, a C1~C4 hydroxyalkyl group, -CH ₂ CH ₂ -COOR ⁶¹ or -CH ₂ CH ₂ CN; R ⁶¹ is a C1~C4 alkyl group; R ⁶² is a C1~C6 alkyl group; R ⁶³ is a C1~C4 alkyl group; R ⁶⁴ is a hydrogen atom, a C1~C4 alkyl group, an allyl group, a C1~C4 hydroxyalkyl group, -CH ₂ CH ₂ -COOR ⁶⁵ or -CH ₂ CH ₂ CN; R ⁶⁵ is a C1~C4 alkyl group; The aforementioned chemical structure may be bonded to a hydrogen atom or a structure substituted with a hydrogen atom via the carbon atom represented by * in the aforementioned formula (1). The optical laminate of claim 1, wherein the photocurable composition comprises a first photopolymerization initiator and a second photopolymerization initiator, the first photopolymerization initiator having a relatively small first reaction rate, and the second photopolymerization initiator having a relatively large second reaction rate; the ratio of the second reaction rate to the first reaction rate is expressed as a ratio of polymerization rate A of 1.1 or more, and the polymerization rate A is obtained by using each of the photopolymerization initiators alone and evaluating using the following measurement method; [Measurement method] A mixed solution of 99 parts by weight of n-butyl acrylate and 1 part by weight of 4-hydroxybutyl acrylate as monomers and 0.1 parts by weight of a photopolymerization initiator as an evaluation object was irradiated with ultraviolet light to prepare a monomer slurry in which the aforementioned monomers were partially polymerized; the aforementioned ultraviolet light irradiation was carried out until the viscosity of the aforementioned mixed solution at 30°C reached 20 Pa·s; then, a coating layer with a thickness of 20µm consisting of the aforementioned monomer slurry was formed between a pair of polyethylene terephthalate (PET) sheets each having a thickness of 75µm; then, the aforementioned coating layer was irradiated with ultraviolet light using an LED as a light source from one of the aforementioned PET sheets, the LED having a peak wavelength at 340nm±10nm; the illumination intensity and irradiation time of the aforementioned ultraviolet light were set to 4mW/cm ² and 1200 seconds; the polymerization rate of the aforementioned monomer measured by the aforementioned coating layer photocured by the aforementioned ultraviolet irradiation is specifically referred to as the aforementioned polymerization rate A. The optical laminate of claim 1, wherein the adhesive sheet has a surface that has been subjected to surface modification treatment. The optical laminate of claim 1, wherein the thickness of the adhesive sheet is less than 50 µm. The optical multilayer body of claim 1, wherein the anchoring force of the adhesive sheet on the phase difference film is greater than 13N/25mm. An image display device comprises an optical multilayer body as described in any one of claims 1 to 14.

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