JP4077213B2 - Anti-reflective adhesive film - Google Patents

Description

【００４９】
表１から明らかなように実施例１の粘着フィルムは、評価試験前の光学特性については、オリゴマー結晶化防止層の厚みが薄く、また、プラスチックフィルムと粘着層の間にこれらと同じ程度の屈折率のオリゴマー結晶化防止層を設けたことにより、プラスチックフィルムの粘着層を設けた面とは反対側に設けた反射防止層の機能を阻害することはなく、全光線透過率は低下せずに優れた光学特性を維持することができた。また、評価試験後は粘着層にオリゴマーの結晶は生成されず、評価試験後の光学特性についても優れた評価結果となった。
【００５０】
一方、比較例１の粘着フィルムは、オリゴマー結晶化防止層を設けていないため、プラスチックフィルムから析出したオリゴマーが粘着層に移動し、粘着層の中で流動し結晶を生成した。このため評価試験後の光学特性については低い評価結果となった。
【００５１】
比較例２の粘着フィルムは、オリゴマー結晶化防止層として無機のシリカ塗膜を用いたため、オリゴマーは粘着層に移動せず、オリゴマーの結晶の生成を防止することができた。しかし、プラスチックフィルムと粘着層の間にこれらよりも屈折率の低いシリカ塗膜の層が設けられたことにより、反射防止効果を阻害してしまい全光線透過率は低下し、評価試験前、及び評価試験後の光学特性は低い評価となった。
【００５２】
比較例３の粘着フィルムは、オリゴマー結晶化防止層として熱硬化型アクリル樹脂を用い、厚みを８μｍとしたため、オリゴマーは粘着層に移動せず、オリゴマーの結晶の生成を防止することができたが、オリゴマー結晶化防止層の厚みが厚くなったため、評価試験前、及び評価試験後の光学特性は低い評価となった。
【００５３】
比較例４の粘着フィルムは、オリゴマー結晶化防止層として熱硬化型アクリル樹脂を用い、厚みを２．５μｍと薄くしたため、評価試験前の光学特性は優れた評価となったが、オリゴマーは粘着層に移動し、オリゴマーの結晶の生成を防止することはできなかった。このため評価試験後の光学特性については低い評価となった。
【００５４】
【発明の効果】
本発明によれば、ポリエチレンテレフタレート、ポリエチレンナフタレート、ポリブチレンテレフタレート、ポリカーボネートから選ばれてなるプラスチックフィルムを基材とする反射防止性粘着フィルムであって、温度、湿度の変化が激しいような環境で使用される場合でも、オリゴマーの結晶が生成されることがなく、光線透過率などの光学的性能を低下させることがない反射防止性粘着フィルムが得られる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an adhesive film based on a plastic film, such as a polyester film, on which an oligomer is deposited by high heat, and more particularly to an adhesive film used for optical applications.
[0002]
[Prior art]
In general, a liquid crystal member used in a liquid crystal display device of an in-vehicle navigation system is provided with a layer to which an optical function such as antireflection performance is added on one side of a plastic film, and the other side. An adhesive film provided with an adhesive layer is used by being bonded to a liquid crystal member. Liquid crystal materials used in applications that require extremely high optical performance, such as temperature and humidity, that are used in a car are extremely severe. There is a problem that the optical performance of the optical disc is degraded.
[0003]
As a result of intensive studies by the present inventors on such a problem, it is difficult to confirm with the naked eye on the adhesive layer of the adhesive film used in the liquid crystal member, but a small crystal is produced when viewed under a microscope, and this is the passage of time. It has been found that this crystal has grown greatly, and this crystal causes diffused reflection of light from the light source, thereby reducing optical performance such as light transmittance.
[0004]
As a result of the inventors' further research on the cause of the growth and growth of such crystals, the plastic that is the base material of the adhesive film during the molding process after the adhesive film is bonded to the liquid crystal member. By applying a high heat exceeding the glass transition temperature of the film, oligomers are precipitated from the plastic film, and the precipitated oligomers flow and crystallize in the adhesive layer due to changes in the environment such as intense temperature and humidity. I thought that.
[0005]
[Problems to be solved by the invention]
Therefore, the present invention is an adhesive film based on a plastic film, and even when used in an environment where the temperature and humidity change drastically, oligomer crystals are not generated, and the light transmittance It aims at providing the adhesive film which does not reduce optical performance, such as.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned object, the present inventors have developed an ionizing radiation curable resin composition between a plastic film and an adhesive layer so that oligomers precipitated from the plastic film due to high heat do not flow and crystallize in the adhesive layer. It has been found that by providing a layer formed from a paint containing a product, the oligomer can be prevented from moving to the adhesive layer and the oligomer can be prevented from crystallizing. (Hereinafter, this layer is referred to as “oligomer crystallization prevention layer”.)
[0007]
That is, the antireflection adhesive film of the present invention, on one side of a plastic film provided with an adhesive layer oligomerization crystallization preventing layer in this order, it provided with an anti-reflection layer on the other surface, the plastic film is polyethylene It is selected from terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polycarbonate, and the oligomer crystallization preventing layer is formed of a paint containing at least an ionizing radiation curable resin composition. It is.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the pressure-sensitive adhesive film of the present invention will be described in detail.
[0009]
The plastic film used as a base material in the pressure-sensitive adhesive film of the present invention precipitates a crystalline oligomer by high heat, and examples thereof include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polycarbonate. Such a plastic film may contain various ultraviolet absorbers, antistatic agents, antioxidants, anti-aging agents, slip agents, and the like that are usually used depending on the use of the adhesive film.
[0010]
Since the thickness of the plastic film varies depending on the application to be used, it cannot be generally stated. However, in order not to deteriorate optical properties such as light transmittance, a film having a thickness of 50 μm to 125 μm is used.
[0011]
Next, the pressure-sensitive adhesive film of the present invention is obtained by providing an oligomer crystallization preventing layer and a pressure-sensitive adhesive layer in this order on at least one surface of the plastic film.
[0012]
The oligomer crystallization-preventing layer is formed from a paint containing an ionizing radiation curable resin composition in which one or more photopolymerizable prepolymers and / or photopolymerizable monomers are mixed, such as ultraviolet rays and electron beams. It is formed by being cured by irradiation with ionizing radiation.
[0013]
Here, the photopolymerizable prepolymer and / or the photopolymerizable monomer contained in the ionizing radiation curable resin composition undergoes radical polymerization or cationic polymerization when the functional group introduced into the skeleton is irradiated with ionizing radiation. In particular, those that are cured by radical polymerization are preferable because they have a high curing rate and a high degree of freedom in resin design.
[0014]
Examples of the prepolymer for radical polymerization include acrylic prepolymers such as polyester (meth) acrylate, epoxy (meth) acrylate, urethane (meth) acrylate, polyether (meth) acrylate, polyol (meth) acrylate, and melamine (meth) acrylate. Examples of the monomer include monofunctional acrylic monomers such as 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and butoxypropyl acrylate, 1,6-hexanediol acrylate, neopentyl glycol diacrylate, 2 such as diethylene glycol diacrylate, polyethylene glycol diacrylate, hydroxypivalate ester neopentyl glycol acrylate Ability acrylic monomer, dipentaerythritol hexaacrylate, trimethylolpropane triacrylate, such as polyfunctional acrylic monomers such as pentaerythritol acrylate.
[0015]
Examples of the prepolymer or monomer for cationic polymerization include epoxy prepolymers or monomers such as bisphenol A type epoxy, novolak type epoxy, alicyclic epoxy, phenol novolak type epoxy, aliphatic vinyl ether, urethane type vinyl ether, ester type vinyl ether, etc. Vinyl ether prepolymer or monomer, oxetane prepolymer or monomer, and the like.
[0016]
Moreover, when making it harden | cure using an ultraviolet-ray, in order to accelerate | stimulate photopolymerization, it is preferable to contain a photoinitiator and a photoinitiator in an ionizing radiation curable resin composition.
[0017]
Examples of such a photopolymerization initiator include those that undergo radical polymerization by cleavage, those that undergo radical polymerization by abstracting hydrogen, and those that undergo cationic polymerization by generating ions. Prepolymers and monomers used It chooses suitably according to.
[0018]
Examples of radical type photopolymerization initiators include benzoin ether, ketal, acetophenone, and thioxanthone. Examples of the cationic photopolymerization initiator include diazonium salts, diaryliodonium salts, triarylsulfonium salts, triarylbililium salts, benzylpyridinium thiocyanates, dialkylphenacylsulfonium salts, and dialkylhydroxyphenylphosphonium salts. These photopolymerization initiators can be used alone or in combination.
[0019]
Further, the photopolymerization accelerator can reduce the polymerization obstacle due to air at the time of curing and increase the curing speed. For example, p-dimethylaminobenzoic acid isoamyl ester, p-dimethylaminobenzoic acid ethyl ester, and the like. can give.
[0020]
Such an ionizing radiation curable resin composition may be diluted with a diluent solvent, another resin, a crosslinking agent, a filler, a colorant, a matting agent, a lubricant, an antistatic agent, a flame retardant, an antibacterial agent, and an antifungal agent as necessary. Ionizing radiation, UV absorbers, light stabilizers, antioxidants, plasticizers, leveling agents, pigment dispersants, flow regulators, antifoaming agents, etc., as long as they do not impair the performance of the oligomer crystallization prevention layer. It can be set as the coating material containing a curable resin composition. Examples of the other resins include unsaturated polyester polyol resins, polyether polyol resins, acrylic polyol resins, urethane polyol resins, melamine resins, phenol resins, amino resins, epoxy resins, and other thermosetting resins, polycarbonates, acrylic resins, Examples thereof include thermoplastic resins such as polyester resin, styrene resin, and ethylene vinyl acetate copolymer resin.
[0021]
As a paint containing such an ionizing radiation curable resin composition, an ultraviolet curable hard coat coating solution generally used for the purpose of preventing scratches can be diverted.
[0022]
Since the oligomer crystallization prevention layer formed from the coating material containing such an ionizing radiation curable resin composition is a resin layer having a very high crosslink density, the oligomer crystallization prevention layer formed from another resin is used. In contrast, even if the thickness is small, the movement of the oligomer to the adhesive layer can be sufficiently blocked, and optical performance such as light transmittance is not deteriorated. Furthermore, since such an oligomer crystallization prevention layer is a resin layer that is so hard that the hard coat performance can be obtained as described above because of its very high crosslink density, it is more than an oligomer crystallization prevention layer formed of other resins. The cushioning property of the pressure-sensitive adhesive layer can be further reduced, and a pressure-sensitive adhesive film that is not easily damaged can be obtained.
[0023]
In addition, for example, to give a function such as an antireflection effect, silica having a refractive index lower than that of the plastic film is provided on the surface opposite to the surface on which the oligomer crystallization prevention layer and the adhesive layer of the plastic film are provided. When the inorganic film layer is provided, the refractive index of the oligomer crystallization preventing layer is an intermediate refractive index between the plastic film and the adhesive layer, and therefore the adhesive film does not hinder the antireflection effect. can do.
[0024]
Such an oligomer crystallization-preventing layer is obtained by applying a paint containing the above-mentioned ionizing radiation curable resin composition to the above-described coating method, for example, a bar coater, a blade coater, a spin coater, a roll coater, a gravure coater, or the like. It can be applied to at least one surface of a plastic film, dried by heating as necessary, and cured by irradiation with ionizing radiation to form an oligomer crystallization preventing layer.
[0025]
The ionizing radiation used for curing the ionizing radiation curable resin composition includes ultraviolet rays in a wavelength region of about 100 nm to 400 nm emitted from an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a metal halide lamp, and the like. And an electron beam having a wavelength region of 100 nm or less emitted from a mold-type or curtain-type electron beam accelerator.
[0026]
The thickness of the oligomer crystallization-preventing layer cannot be generally determined depending on the type of ionizing radiation curable resin composition, but the lower limit is 1 μm or more, preferably 1.5 μm or more, and the upper limit is 7 μm or less, preferably 5 μm or less. More preferably, it is about 3 μm or less. By setting the thickness to 1 μm or more, it is possible to prevent the oligomer precipitated from the plastic film from moving to the adhesive layer, and to prevent the oligomer from crystallizing by flowing in the adhesive layer. The productivity can be increased by reducing the irradiation time of the radiation, and optical performance such as light transmittance can be maintained.
[0027]
The pressure-sensitive adhesive film of the present invention is laminated on the thus formed oligomer crystallization prevention layer to form a pressure-sensitive adhesive layer.
[0028]
As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, generally used acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, and the like are used. Moreover, you may use the adhesive which has performances, such as antistatic.
[0029]
Additives such as metal powders, inorganic pigments, organic pigments, conductive agents, crosslinking agents, antistatic agents, antifoaming agents, leveling agents, and light stabilizers may be added to the adhesive layer depending on the application. However, the addition amount of these additives is preferably in a range that does not hinder the effect of the adhesive layer.
[0030]
Such an adhesive layer is prepared as a coating solution prepared by dissolving or dispersing the above-described adhesive and additives that are added as necessary in a diluent solvent. It can form by apply | coating and drying on an oligomer crystallization prevention layer by a method.
[0031]
The thickness of the adhesive layer is not particularly limited because it varies depending on the application, but is preferably about 0.1 to 50 μm, more preferably about 5 to 25 μm.
[0032]
As described above, according to the present invention, an oligomer is precipitated by high heat, and is an antireflection adhesive film based on a plastic film selected from polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polycarbonate. The oligomer crystallization prevention layer and the adhesive layer are provided in this order on one side of such a plastic film, and the antireflection layer is provided on the other side. The oligomer crystallization prevention layer is at least an ionizing radiation curable type. the Rukoto such is formed by paint containing the resin composition, without crystal oligomer is produced, and the antireflection adhesive film does not degrade the optical performance, such as light transmittance.
[0033]
【Example】
Hereinafter, the present invention will be described in more detail based on examples. In this example, “parts” and “%” are based on weight unless otherwise specified.
[0034]
[Example 1]
A paint containing an ionizing radiation curable resin composition of the following formulation was applied to one side of a transparent polyester film (Melenex 709: Teijin DuPont) with a thickness of 50 μm, dried, and then cured by ultraviolet irradiation with a high-pressure mercury lamp. An oligomer crystallization preventing layer having a thickness of about 2.5 μm was formed.
[0035]
<Prescription of paint containing ionizing radiation curable resin composition>
・ Ionizing radiation curable resin composition 10.0 parts (Unidic 17-806: Dainippon Ink & Chemicals, Inc.)
・ Photopolymerization initiator 0.3 parts (Irgacure 184: Ciba Specialty Chemicals)
・ Toluene 5.0 parts ・ Methyl ethyl ketone 5.0 parts ・ Ethyl cellosolve 2.0 parts 【0036】
Next, an acrylic pressure-sensitive adhesive (SK Dyne 1811-L: Soken Chemical Co., Ltd.) and an isocyanate cross-linking agent (L-45: Soken Chemical Co., Ltd.) are diluted with ethyl acetate and laminated on the oligomer crystallization preventing layer. After drying, an adhesive layer having a thickness of 10 μm was formed and bonded to a separator (Diafoil MRF, 25 μm: Mitsubishi Chemical Polyester Film), and then allowed to stand at room temperature for 7 days to produce an adhesive film of the present invention.
[0037]
Next, the surface of the pressure-sensitive adhesive film opposite to the side where the pressure-sensitive adhesive layer is provided is coated and dried with a tetraethoxysilane hydrolyzed solution to form an antireflection layer having a thickness of about 0.1 μm. The adhesive film of Example 1 was obtained.
[0038]
[Comparative Example 1]
A pressure-sensitive adhesive film of Comparative Example 1 was produced in the same manner as Example 1 except that the oligomer crystallization preventing layer was not provided.
[0039]
[Comparative Example 2]
In the adhesive film of Example 1, instead of the oligomer crystallization prevention layer, the antireflection layer of Example 1 was provided, and this was changed to the oligomer crystallization prevention layer. An adhesive film was prepared.
[0040]
[Comparative Example 3]
In the same manner as in Example 1 except that the pressure-sensitive adhesive film of Example 1 was coated with an application liquid having the following formulation instead of the oligomer crystallization prevention layer and dried to obtain an oligomer crystallization prevention layer (thickness 8 μm). Thus, an adhesive film of Comparative Example 3 was produced.
[0041]
<Formulation of coating liquid for oligomer crystallization preventing layer of Comparative Example 3>
Acrylic polyol resin (solid content 50%) 4.0 parts (Acridic A814: Dainippon Ink & Chemicals, Inc.)
・ Isocyanate-based crosslinking agent (solid content 60%) 0.3 parts (Takenate D110N: Mitsui Takeda Chemical Company)
・ Toluene 5.0 parts ・ Methyl ethyl ketone 5.0 parts ・ Butyl acetate 5.0 parts ・ Cyclohexanone 1.0 part
[Comparative Example 4]
The pressure-sensitive adhesive film of Comparative Example 4 was prepared in the same manner as in Comparative Example 3 except that the thickness of the oligomer crystallization preventing layer was 2.5 μm.
[0043]
For these adhesive films, the following substitution evaluation test is conducted to determine whether oligomers are precipitated by the heat applied during molding after bonding to the liquid crystal member, and crystals are generated and grown due to changes in temperature and humidity. The anti-crystallization property and optical properties of the oligomer were evaluated.
[0044]
[Method of substitute evaluation test]
These adhesive films were cut into a size of width × length = 50 mm × 120 mm, attached to a glass plate having a thickness of 3 mm as an adherend, and allowed to stand at 150 ° C. for 90 minutes. (1) 60 ° C., 90% R . H. (2) 20 ° C., 65% R.D. H. For 24 hours. (1) and (2) were repeated 10 times, and the anti-crystallization property and optical properties of the oligomer were evaluated. The results are shown in Table 1.
[0045]
[Evaluation of anticrystallization property of oligomer]
These pressure-sensitive adhesive films were observed using an optical microscope. “X” indicates that an oligomer crystal of 10 μm or more was generated in the pressure-sensitive adhesive layer, and “◯” indicates that the crystal was not generated.
[0046]
[Evaluation of optical properties]
Using Haze MeterNDH2000 (Nippon Electric Decoration Co., Ltd.), the total light transmittance and HAZE before and after the evaluation test were measured. Using the total light transmittance before the evaluation test of Comparative Example 1 as a reference, the case where the decrease in the total light transmittance was 0.5% or more was designated as “X”, and the case where the decrease was less than 0.5% was designated as “◯”.
[0047]
Similarly, for HAZE, the HAZE before the evaluation test of Comparative Example 1 was used as a reference, and the increase in HAZE was 0.5% or more as “X”, and less than 0.5% as “◯”.
[0048]
[Table 1]

[0049]
As is clear from Table 1, the adhesive film of Example 1 has a thin oligomer crystallization prevention layer with respect to the optical properties before the evaluation test, and the same degree of refraction between the plastic film and the adhesive layer. By providing an oligomer crystallization prevention layer with a high rate, the function of the antireflection layer provided on the side opposite to the surface provided with the adhesive layer of the plastic film is not hindered, and the total light transmittance is not reduced. Excellent optical properties could be maintained. Moreover, after the evaluation test, oligomer crystals were not formed in the adhesive layer, and the optical characteristics after the evaluation test were excellent.
[0050]
On the other hand, the pressure-sensitive adhesive film of Comparative Example 1 was not provided with an oligomer crystallization preventing layer, so that the oligomer deposited from the plastic film moved to the pressure-sensitive adhesive layer and flowed in the pressure-sensitive adhesive layer to generate crystals. For this reason, the optical property after the evaluation test was a low evaluation result.
[0051]
Since the adhesive film of Comparative Example 2 used an inorganic silica coating film as the oligomer crystallization preventing layer, the oligomer did not move to the adhesive layer, and generation of oligomer crystals could be prevented. However, by providing a silica coating layer having a refractive index lower than these between the plastic film and the adhesive layer, the antireflection effect is inhibited and the total light transmittance is lowered, before the evaluation test, and The optical properties after the evaluation test were evaluated as low.
[0052]
Since the adhesive film of Comparative Example 3 used a thermosetting acrylic resin as the oligomer crystallization preventing layer and had a thickness of 8 μm, the oligomer did not move to the adhesive layer, and the formation of oligomer crystals could be prevented. Since the thickness of the oligomer crystallization preventing layer was increased, the optical properties before and after the evaluation test were evaluated as low.
[0053]
The adhesive film of Comparative Example 4 uses a thermosetting acrylic resin as an oligomer crystallization-preventing layer and has a thickness as thin as 2.5 μm. Therefore, the optical properties before the evaluation test were excellent, but the oligomer was an adhesive layer. It was not possible to prevent the formation of oligomer crystals. For this reason, the optical properties after the evaluation test were evaluated as low.
[0054]
【The invention's effect】
According to the present invention, there is provided an anti-reflective adhesive film based on a plastic film selected from polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polycarbonate , in an environment in which changes in temperature and humidity are severe. Even when used, an antireflection pressure-sensitive adhesive film is obtained in which oligomer crystals are not generated and optical performance such as light transmittance is not deteriorated.

Claims (1)

An oligomer crystallization prevention layer and an adhesive layer are provided in this order on one side of the plastic film, and an antireflection layer is provided on the other side. The plastic film is made of polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polycarbonate. An antireflective pressure-sensitive adhesive film which is selected and formed by a paint containing at least an ionizing radiation curable resin composition.