JP6089392B2 - Antireflection film, polarizing plate and image display device - Google Patents

Description

  The present invention relates to an antireflection film, a polarizing plate, and an image display device. In particular, the present invention relates to a saponification-resistant antireflection film capable of preventing performance degradation during saponification treatment with an alkaline aqueous solution, and a polarizing plate and an image display device using the same.

In an image display device such as a liquid crystal display, plasma display, electroluminescence display, touch panel, electronic paper, tablet PC, etc., an optical film for preventing scratches, dirt, light reflection, etc. on the image display surface is usually provided on the image display surface. Is provided. For example, as an antireflection film, an optical film in which a low refractive index layer is formed by applying a resin composition obtained by adding hollow silica particles as a low refractive index agent to an ionizing radiation curable resin on a transparent base film. Is known (Patent Document 1).
By using an ionizing radiation curable resin for the resin of the low refractive index layer, the antireflection film can be provided with scratch resistance and antifouling property in addition to the antireflection performance. Further, if a hard coat layer is provided between the low refractive index layer and the transparent substrate film, the scratch resistance can be further enhanced (Patent Document 1).

  In a liquid crystal display, a polarizing plate is usually provided for a liquid crystal cell. The polarizing plate usually has a structure in which both surfaces of a polarizer made of a polyvinyl alcohol film that has been adsorbed with iodine and subjected to orientation treatment are laminated with a protective film. In addition, a triacetyl cellulose film is usually used as the protective film in terms of transparency, optical non-orientation, etc., and the surface is saponified with an aqueous alkaline solution to enhance the adhesion with the polarizer and then polarized. Laminated with a child.

JP 2010-85983 A

Incidentally, thinning is an important factor in performance in an image display device, and it is desired to cope with thinning in an optical film. For this reason, instead of providing an antireflection film in addition to the polarizing plate, an antireflection film is used as the protective film for the polarizing plate, the antireflection film is laminated on the polarizer, and the polarizing plate and the antireflection film are integrated. If a polarizing plate is used, the thickness can be reduced accordingly. Moreover, the protective film laminated | stacked on a polarizer requires the saponification process by aqueous alkali solution as an easily bonding process from an adhesive viewpoint with a polarizer.
However, when the antireflective film having the low refractive index layer is saponified, the low refractive index agent in the low refractive index layer is dropped or the resin constituting the low refractive index layer is dissolved or missing, resulting in resistance to resistance. Abrasion and antifouling properties may be impaired.
In order to give this saponification resistance, a protective film for saponification is temporarily attached on the low refractive index layer, but there is a problem of cost increase.

Therefore, the object of the present invention is to prevent the function of the low refractive index layer from being impaired even if saponification treatment is performed with an alkaline aqueous solution without attaching a protective film for saponification resistance. It is to provide an antireflection film having saponification resistance capable of maintaining functions such as property and antifouling property.
Moreover, it is providing the polarizing plate and image display apparatus using such an antireflection film. In this application, maintaining the scratch resistance function not only means maintaining the surface hardness of the low refractive index layer, but also means that the interfacial adhesion between the low refractive index layer and its lower layer can be maintained well.

The present invention provides an antireflection film, a polarizing plate, and an image display device having the following configurations.
(1) On one surface of a transparent substrate film made of triacetylcellulose, it consists of a cured product layer of an ionizing radiation curable resin, contains hollow silica particles, and has a lower refractive index than the lower layer to be laminated. In an antireflection film having a low refractive index layer,
The polymerizable compound contained in the ionizing radiation curable resin is any of the following (A), (B), and (C):
(A) A polyfunctional polymerizable compound having no hydroxyl group in the molecule and comprising any of diethylene glycol di (meth) acrylate, isocyanuric acid-modified tri (meth) acrylate, and ditrimethylolpropane tetraacrylate Polymerizable compounds,
(B) a polymerizable compound having a hydroxyl group in the molecule, the hydroxyl group content defined as dividing by 100 times the value of the number of hydroxyl groups in the molecular weight contained in one molecule, 0.2 A polyfunctional polymerizable compound,
(C) In the case where one or more kinds of polymerizable compounds having a hydroxyl group in the molecule are contained, the resin composition containing the plural kinds of polymerizable compounds at an arbitrary mass ratio is contained in the resin composition. A polyfunctional polymerizable compound wherein the total polymerizable compound is regarded as one molecule, and the hydroxyl group content is 0.2 or less when the weight average molecular weight of the total polymerizable compound is used as the molecular weight of the one molecule,
The antireflection film whose number of functional groups of the polyfunctional polymerizable compound in said (A), (B), (C) is 3-9, and whose molecular weight is 300-1000.

(2) The antireflection film according to (1) above, which has a functional layer between the transparent base film and the low refractive index layer.
(3) A polarizing plate in which the antireflection film of (1) or (2) is laminated on at least one surface of the polarizer with the transparent base film side facing the polarizer.

(4) An image display device comprising the antireflection film of (1) or (2) or the polarizing plate of (3).

(1) The antireflection film according to the present invention has antireflection properties, scratch resistance (surface hardness and adhesion between the low refractive index layer and the underlying layer), antifouling properties, It has saponification resistance that does not impair whitening resistance.
(2) According to the polarizing plate of the present invention, the antireflection film provided therein provides antireflection properties, scratch resistance (surface hardness and adhesion between the low refractive index layer and the underlying layer), antifouling properties, And whitening resistance.
(3) According to the image display device of the present invention, the image display surface is provided with antireflection properties, scratch resistance (surface hardness and adhesion between the low refractive index layer and the lower layer), antifouling properties, and antiresistance properties. Whitening property can be imparted.

Sectional drawing explaining one Embodiment of the antireflection film by this invention. Sectional drawing explaining one Embodiment of the polarizing plate by this invention.

  Embodiments of the present invention will be described below.

A. Antireflective film The antireflective film according to the present invention comprises hollow silica particles composed of a cured product layer of an ionizing radiation curable resin on one surface of a transparent substrate film made of triacetylcellulose. An antireflection film having a low refractive index layer having a refractive index lower than the refractive index. Moreover, in the present invention, the ionizing radiation curable resin is composed of a resin composition containing a polyfunctional polymerizable compound having less than a predetermined amount of hydroxyl groups in the molecule.

In the antireflection film of the present invention, it is preferable that a hard coat layer is provided between the low refractive index layer and the transparent substrate film because the scratch resistance can be further enhanced.
Here, FIG. 1 is a cross-sectional view showing one embodiment of the antireflection film according to the present invention. The antireflection film 10 in the figure is an optical film in which a low refractive index layer 2 is formed on one side of a transparent substrate film 1 via a hard coat layer 3. The hard coat layer 3 is composed of a cured layer of an ionizing radiation curable resin.

  Hereinafter, each layer will be described.

  In the present specification, the (meth) acryloyl group means an acryloyl group or a methacryloyl group, the (meth) acrylate means an acrylate or a methacrylate, and a simple acrylate system includes a methacrylate system.

[Transparent substrate film]
The transparent substrate film 1 is a transparent film made of triacetyl cellulose. By using a triacetyl cellulose film (TAC film) as a transparent substrate film, excellent transparency and excellent optical isotropy suitable as a protective film for a polarizing plate for liquid crystal displays can be obtained. For this reason, by using a TAC film, preferable optical characteristics can be obtained when it is used with a polarizing plate or used as a protective film for a polarizing plate in a liquid crystal display application.
The transparency of the transparent substrate film means that the average light transmittance is at least 70% or more in the visible light region of 380 to 780 nm, preferably 85% or more, more preferably 90% or more. The refractive index of the transparent substrate film is about 1.49 in the case of a triacetyl cellulose film.
The thickness of the transparent substrate film is usually 20 μm to 300 μm, preferably 30 μm to 200 μm.

  As the triacetyl cellulose constituting the transparent substrate film 1, in addition to pure triacetyl cellulose, components other than acetic acid are used in combination as a fatty acid that forms an ester with cellulose, such as cellulose acetate propionate and cellulose acetate butyrate. Resin may be used. The transparent substrate film may contain a cellulose lower fatty acid ester-based resin other than triacetyl cellulose such as diacetyl cellulose, if necessary.

The transparent substrate film 1 may contain various additives such as a plasticizer, an antistatic agent, and an ultraviolet absorber.
The transparent base film 1 may be subjected to surface treatment for adhesion enhancement such as glow discharge treatment, corona discharge treatment, ultraviolet (UV) treatment, flame treatment, and primer layer formation, if necessary. .

(Low refractive index layer)
The low refractive index layer 2 is formed of a cured resin layer containing a low refractive index agent and prevents light reflection by having a lower refractive index than the layer directly below, on which the low refractive index layer is directly laminated. . The refractive index of the low refractive index layer is less than the refractive index of the layer immediately below, but the difference in refractive index between the low refractive index layer and the layer immediately below is 0.02 to 0.3, more preferably 0. It is preferable that it is 05-0.2.
The refractive index itself of the low refractive index layer is preferably 1.45 or less in view of obtaining sufficient antireflection properties, more preferably 1.40 or less, and further preferably 1.38 or less.

The low refractive index layer 2 is composed of a cured layer of an ionizing radiation curable resin, contains hollow silica particles as a low refractive index agent, and the ionizing radiation curable resin has a hydroxyl group in a molecule in a predetermined amount. It is a layer made of a cured product of a resin composition containing a small amount of a polyfunctional polymerizable compound. The ionizing radiation curable resin becomes a binder resin for the hollow silica particles and improves the scratch resistance of the low refractive index layer. By using a polymerizable compound having a hydroxyl group less than a predetermined amount in the molecule for this ionizing radiation curable resin, saponification resistance can be obtained, and the ionizing radiation curable resin is used for the low refractive index layer and is multifunctional. By using this polymerizable compound, the coating strength of the low refractive index layer is increased and scratch resistance is obtained. The hollow silica particles are, for example, fine particles having an outer shell and porous or hollow inside, and disclosed in JP-A-6-330606, JP-A-7-013137, JP-A-7-133105, It can be obtained by various production methods described in JP-A-2001-233611.
The thickness of the low refractive index layer is 50 to 150 nm, preferably 80 to 120 nm.

[Ionizing radiation curable resin]
The ionizing radiation curable resin is a resin that is cured by ionizing radiation typified by ultraviolet rays and electron beams, and has a polymerizable functional group that can be polymerized by ionizing radiation, such as monomers and prepolymers (including oligomers). It is a resin composition having at least one compound or two or more compounds. A representative example of a polymerizable functional group that can be polymerized by ionizing radiation is a polymerizable unsaturated group. Examples of the polymerizable unsaturated group include radically polymerizable ethylenic divalent groups such as (meth) acryloyl group, vinyl group, and allyl group. It is a double bond. Among these, a (meth) acryloyl group can be preferably used in the present invention, and various acrylate-based ionizing radiation curable resins are known.

  As the polymerizable compound, a polyfunctional polymerizable compound having 2 or more functional groups is preferable from the viewpoint of scratch resistance (surface hardness, interfacial adhesion), more preferably a polyfunctional polymerizable compound having 3 to 9 functional groups. preferable.

Among the polyfunctional polymerizable compounds, those having no hydroxyl group in the molecule can provide saponification resistance, and those having a hydroxyl group in the molecule cannot provide saponification resistance.
The reason for this is that the hydroxyl group has a good affinity with the aqueous alkali solution, and the aqueous alkaline solution attacks the hydroxyl group in the three-dimensional crosslinked structure formed after curing by ionizing radiation, thereby destroying the crosslinked structure. It is guessed. Further, it is presumed that sodium hydroxide used in the saponification solution has very small sodium ions dissociated in an aqueous solution, so that it easily penetrates into the crosslinked structure.

Here, a specific example of a polyfunctional polymerizable compound that does not have a hydroxyl group in the molecule that provides good saponification resistance, and a polyfunctional polymerizable compound that has a hydroxyl group in the molecule that does not provide saponification resistance A specific example is shown.
If the specific example of the polyfunctional polymerizable compound which does not have the hydroxyl group in a molecule | numerator from which favorable saponification resistance is obtained is shown, it has three acryloyl groups as a polymeric functional group represented by following formula [1]. An example is trimethylolpropane triacrylate (TMPTA). In the formula, Ac is an acryloyl group.

  However, the trimethylolpropane triacrylate (TMPTA) represented by the above [Formula 1] has three acryloyl groups as polymerizable functional groups, but the terminal methyl group is replaced with a hydroxyl group, so that Pentaerythritol triacrylate (PETA) represented by the following formula [2] having a hydroxyl group cannot provide saponification resistance. In the formula, Ac is an acryloyl group. This is a specific example of a polyfunctional polymerizable compound having a hydroxyl group in the molecule for which saponification resistance cannot be obtained.

As an example of a polyfunctional polymerizable compound that does not have a hydroxyl group in the molecule, which can achieve better saponification resistance, an example of a polyfunctional monomer of an acrylate ionizing radiation curable resin is as follows:
Bifunctional polymerizable compounds include hexanediol di (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) ) Acrylate and the like.

In the trifunctional polymerizable compound, in addition to the above-exemplified trimethylolpropane tri (meth) acrylate (abbreviated as TMPTA), isocyanuric acid-modified tri (meth) acrylate, and the like,
Examples of tetrafunctional polymerizable compounds include pentaerythritol tetra (meth) acrylate and ditrimethylolpropane tetraacrylate,
The hexafunctional polymerizable compound includes dipentaerythritol hexa (meth) acrylate (abbreviation DPHA),
Examples of the polymerizable compound having 7 or more functional groups include V802 (DPHA multimer, manufactured by Osaka Organic Chemical Industry Co., Ltd.).

  As an example of a polyfunctional polymerizable compound having no hydroxyl group in the molecule, a polyfunctional prepolymer of an acrylate ionizing radiation curable resin, for example, polyester, polyether, urethane, epoxy, silicone Examples include various acrylate-based prepolymers such as those.

  Examples of polyfunctional polymerizable compounds having no hydroxyl group in the molecule include NK esters (dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, Shin-Nakamura Chemical Co., Ltd.). Made).

  Among the examples of the polyfunctional polymerizable compound having no hydroxyl group in the molecule, a compound that can be preferably used in the present invention is trimethylolpropane tri (meth) acrylate. This compound exhibits particularly excellent scratch resistance against saponification.

(Use of a polymerizable compound having a hydroxyl group in the molecule)
The resin composition of the ionizing radiation curable resin used for forming the low refractive index layer 2 is composed of only a polyfunctional polymerizable compound having no hydroxyl group in the molecule as its polymerizable compound. Most preferred in terms. However, within the range not impairing the saponification resistance, a polymerizable compound having a hydroxyl group in the molecule can be used for adjusting physical properties such as scratch resistance and coating suitability. In this case, from the viewpoint of scratch resistance, the polymerizable compound having a hydroxyl group in the molecule is preferably a polyfunctional polymerizable compound.

  As an example of a polyfunctional polymerizable compound having a hydroxyl group in the molecule, an example of a polyfunctional monomer of an acrylate ionizing radiation curable resin, a polyfunctional monomer having one hydroxyl group in the molecule is trimethylol. Examples include propanedi (meth) acrylate (abbreviation TMPDA), pentaerythritol tri (meth) acrylate (abbreviation PETA), dipentaerythritol penta (meth) acrylate (abbreviation DPPA), etc., and has two hydroxyl groups in the molecule. As the polyfunctional monomer, dipentaerythritol tetra (meth) acrylate (abbreviation DPTA) can be given.

  Thus, in the case of a polyfunctional polymerizable compound having a hydroxyl group in the molecule, a compound having a large proportion of the hydroxyl group in the molecule is not preferable in terms of saponification resistance. As much as possible, it is preferable that the proportion of hydroxyl groups in the total amount of the resin composition of the ionizing radiation curable resin forming the low refractive index layer is smaller in that the saponification resistance can be improved more reliably.

(Hydroxyl group content)
Therefore, in the present invention, in the case of a polyfunctional polymerizable compound having a hydroxyl group in the molecule, the number of hydroxyl groups (OH groups) contained in one molecule is expressed as a molecular weight as an index of the proportion of the hydroxyl group in the molecule. The value obtained by dividing by 100 is defined as “hydroxyl group content”.
Here, if a specific example of the hydroxyl group content is shown, the pentaerythritol tri (meth) acrylate (abbreviated as PETA) has an OH group number of 1 and a molecular weight of 298, 0.33, and dipentaerythritol pentaacrylate (abbreviated as DPPA) The number of OH groups is 1, and the molecular weight is about 550 and 0.18.
In general, compounds such as TMPTA, PETA, DPHA, and DPPA are not completely OH groups according to the structural formula, but are generated accurately during compound synthesis and have OH groups that cannot be removed 100%. Although molecules different from the number of structural formulas are also slightly mixed, when calculating the hydroxyl group content in the present application, it is calculated by the number of OH groups in the structural formula without considering what is slightly mixed.

  The hydroxyl group content is preferably 0.2 or less. A preferred saponification resistance can be obtained by using a compound having a hydroxyl group content of 0.2 or less as a polyfunctional polymerizable compound.

Although the hydroxyl group content is an index for one molecule, when the ionizing radiation curable resin composition is a mixture of plural kinds of polymerizable compounds, the plural kinds of polymerizable compounds as a whole contain hydroxyl groups. The rate is preferably 0.2 or less. When the molecular weight of the polymerizable compound is not single but has a molecular weight distribution, the weight average molecular weight is used as the molecular weight in the calculation formula.
That is, in the case where the resin composition of the ionizing radiation curable resin includes a plurality of types of polymerizable compounds including the case of having a molecular weight distribution, all the polymerizable compounds contained in the resin composition are regarded as one molecule. Accordingly, the weight average molecular weight of all the polymerizable compounds is used as the molecular weight of this one molecule, and the hydroxyl group content of the resin composition is calculated from the number of hydroxyl groups in this molecule. The same applies to the case where a polymerizable compound having a hydroxyl group in the molecule and a polymerizable compound having no hydroxyl group in the molecule are included. For example, in the case of a resin composition containing a polymerizable compound having a molecular weight of 500 and a polymerizable compound having a molecular weight of 1000 in a mass ratio of 50:50, one compound having one hydroxyl group and no other compound. Is calculated assuming that one hydroxyl group is present for a compound having a molecular weight of 750, and that the hydroxyl group content is (1/750) × 100 = 0.13.

  The number of functional groups of the polyfunctional polymerizable compound in the case where the resin composition of the ionizing radiation curable resin includes a plurality of types of polymerizable compounds can be calculated in the same manner as the hydroxyl group content described above.

  As an example of a compound having a hydroxyl group content of 0.2 or less and preferable saponification resistance even if it is a polyfunctional polymerizable compound having a hydroxyl group in the molecule, dipentaerythritol pentaacrylate (DPPA) and di Pentaerythritol pentamethacrylate (DPPMA) can be preferably used in the present invention.

As a resin composition of an ionizing radiation curable resin for forming a cured product layer of an ionizing radiation curable resin constituting the low refractive index layer 2, polymerization having no hydroxyl group in the molecule as the polymerizable compound As the functional compound, a polyfunctional polymerizable compound is preferable, but a monofunctional polymerizable compound may be used in combination for adjusting physical properties.
For example, as an example of a monofunctional polymerizable compound having no hydroxyl group in the molecule, a monofunctional monomer of an acrylate-based ionizing radiation curable resin, methyl (meth) acrylate, ethyl (meth) acrylate, Other ethylenically polymerizable compounds such as methylhexyl (meth) acrylate, ethylhexyl (meth) acrylate, and the like can be mentioned.

(Molecular weight)
The molecular weight of the polyfunctional polymerizable compound having no hydroxyl group and the polyfunctional polymerizable compound having a hydroxyl group is necessarily a molecular weight of 300 or more because it is a bifunctional or more, more preferably a trifunctional or more polyfunctional. Is preferred. However, if the molecular weight is too large, under the thin film condition of 50 to 150 nm, the number of crosslinkable portions per molecule in the whole layer decreases, resulting in a decrease in crosslinking density, resulting in a decrease in scratch resistance. Therefore, the molecular weight is preferably 1000 or less at the maximum. For this reason, it is preferable that the molecular weight of the polyfunctional polymerizable compound which does not have a hydroxyl group, and the polyfunctional polymerizable compound which has a hydroxyl group uses the thing of the range of 300-1000. In the case of a polymerizable compound having a molecular weight distribution, this molecular weight means a weight average molecular weight.

  The said weight average molecular weight can be calculated | required by polystyrene conversion by a gel permeation chromatography (GPC). Tetrahydrofuran or chloroform can be used as the solvent for the GPC mobile phase. The measurement column may be used in combination with a commercially available column such as a column for tetrahydrofuran or a column for chloroform. As this commercial item column, Shodex (trademark) GPC KF-801, GPC KF-800D (all are the Showa Denko KK make) etc. can be mentioned, for example. As the detector, an RI (differential refractive index) detector and a UV detector may be used. Using such a solvent, a column, and a detector, the weight average molecular weight can be appropriately measured by a GPC system such as Shodex (registered trademark) GPC-101 (manufactured by Showa Denko KK).

(Combination with ionizing radiation non-polymerizable resin)
For ionizing radiation curable resins, in addition to polymerizable compounds that can be cured with ionizing radiation, ionizing radiation non-polymerizable resins that do not polymerize with ionizing radiation can interfere with saponification resistance when necessary, such as for adjusting physical properties. They may be used in combination as long as they do not. Ionizing radiation non-polymerizable resins other than polymerizable compounds curable by ionizing radiation are polymerizable compounds curable by energy other than ionizing radiation, for example, thermosetting resins that are not cured by ionizing radiation but can be cured by heat, ionization For example, a thermoplastic resin that is not cured by radiation or heat.
Examples of thermosetting resins include urethane resins, melamine resins, phenolic resins, silicone resins, etc., and thermoplastic resins include acrylic resins, thermoplastic urethane resins, polyamide resins, styrene resins, Cellulosic resins, polycarbonate resins, vinyl resins, silicone resins and the like. Examples of the cellulose-based resin include nitrocellulose, acetylcellulose, cellulose acetate propionate, and ethylhydroxyethylcellulose.

(Polymerization initiator)
When the ionizing radiation curable resin is cured with ultraviolet rays, it is preferable to further include a polymerization initiator in the resin composition of the ionizing radiation curable resin. As the polymerization initiator, a known one, for example, when curing by radical polymerization, an acetophenone-based, benzophenone-based, or thioxanthone-based polymerization initiator is used. The polymerization initiator is used alone or in combination. In the commercial product, for example, 1-hydroxy-cyclohexyl-phenyl-ketone is available as Irgacure (registered trademark) 184 (manufactured by BASF Japan Ltd.), Irgacure (registered trademark) 127 (manufactured by BASF Japan Ltd.), and the like. . In the case of curing by cationic polymerization, a polymerization initiator such as metallocene, aromatic sulfonium or aromatic iodonium is used. About 0.1 to 10 parts by mass of the polymerization initiator is added to 100 parts by mass of the resin content.

(solvent)
The resin composition of the ionizing radiation curable resin can contain a solvent for adjusting physical properties such as coating suitability on the transparent substrate film.
Examples of the solvent include alcohols such as isopropyl alcohol, methanol, ethanol, butanol, and isobutyl alcohol, ketones such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), and cyclohexanone, and glycols such as propylene glycol monomethyl ether (PGMEA). Ethers, esters such as methyl acetate, ethyl acetate, butyl acetate, and propyl acetate; halogenated hydrocarbons such as chloroform, methylene chloride, and tetrachloroethane; and aromatic hydrocarbons such as toluene and xylene. These solvents are used alone or as a mixture thereof. Among them, preferred are methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), propylene glycol monomethyl ether (PGME), propylene glycol monomethyl ether acetate (PGMEA), etc. in terms of coating suitability and dispersion stability. is there.

(Anti-fouling agent)
The low refractive index layer 2 preferably has an antifouling property against dirt in that it is the outermost layer of the antireflection film. In this respect, it is preferable to include an antifouling agent in the low refractive index layer. A well-known thing can be suitably employ | adopted as an antifouling agent. For example, examples of the antifouling agent include silicone compounds and fluorine compounds. Further, the antifouling agent is preferably an acrylate compound for maintaining saponification resistance and curability performance. For example, silicone acrylate compounds, fluorine-containing acrylate compounds, and acrylate compounds containing fluorine and silicone.

(Other additives)
Various known additives can be added to the resin composition of the ionizing radiation curable resin in order to adjust physical properties such as coating suitability and dispersion stability of the low refractive index agent. For example, a leveling agent, a dispersion stabilizer, an antistatic agent, an ultraviolet absorber, an antioxidant, a refractive index adjusting agent and the like.

[Hollow silica particles]
The hollow silica particles are particles having a function of lowering the refractive index while maintaining the coating strength of the low refractive index layer. The hollow silica particles used in the present invention are silica fine particles having a structure having a cavity inside. The hollow silica particles are silica fine particles having a refractive index that is inversely proportional to the occupation ratio of the internal cavity as compared with the original refractive index (refractive index n = 1.46) of the silica fine particles. For this reason, the refractive index of the hollow silica particles as a whole is 1.20 to 1.45.

  The hollow silica particle is not particularly limited as long as it is a silica fine particle having a cavity inside, and is, for example, a fine particle having an outer shell and having a porous or hollow inside. 330606, JP-A-7-013137, JP-A-7-133105, and silica fine particles prepared by using the technique disclosed in JP-A-2001-233611.

  The average particle diameter of the hollow silica particles is preferably 5 to 300 nm, more preferably 5 nm to 200 nm. When the average particle diameter is within this range, excellent transparency can be imparted to the low refractive index layer. Further, the range of the average particle diameter is more preferably a lower limit of 8 nm, a more preferable upper limit of 100 nm, a still more preferable lower limit of 10 nm, and a still more preferable upper limit of 80 nm.

  Although content of the hollow silica particle in a low-refractive-index layer is not specifically limited, Preferably, it is the range of 20-180 mass parts with respect to 100 mass parts of resin solid content. If it exceeds 180 parts by mass, the coating strength of the low refractive index layer may be insufficient, and if it is less than 20 parts by mass, the effect of lowering the refractive index by the hollow silica particles is sufficiently low. Cannot be granted.

  Further, the surface of the hollow silica particles may be treated in advance with a silane coupling agent before compounding. The silane coupling agent may be a commercially available product such as KBM-1003, KBE-1003, KBM-303, KBM-402, KBM-403, KBE-402, KBE-403, KBM-1403, manufactured by Shin-Etsu Chemical Co., Ltd. KBM-502, KBM-503, KBE-502, KBE-503, KBM-5103, KBM-602, KBM-603, KBM-903, KBE-903, KBE-9103, KBM-573, KBM-575, KBE- 585, KBM-802, KBM-803, KBE-846, KBE-9007, etc., and preferably a silane coupling agent containing a (meth) acryloyl group, KBM-502, KBM-503, KBE-502, KBE-503 and KBM-5103, most preferred is KB It is -503.

[Formation of low refractive index layer]
The low refractive index layer 2 can be formed by applying the ionizing radiation curable resin resin composition described above as a paint or ink on a transparent substrate film, and then irradiating the ionizing radiation to cure the resin. . A coating method is not particularly limited, and a known coating method may be appropriately employed. Examples of the coating method include a roll coating method, a gravure coating method, a dip method, a spray method, a dye coating method, a bar coating method, a spin coating method, and a meniscus coating method. Alternatively, it may be formed by a printing method such as a flexographic printing method or a screen printing method. Typical examples of the ionizing radiation include ultraviolet rays and electron beams.

[Functional layer]
In the antireflection film 10, other functional layers 3 can be provided between the transparent base film 1 and the low refractive index layer 2 as necessary without departing from the gist of the present invention. For example, a transparent layer known as an optical film such as a hard coat layer, an antiglare layer, an antistatic layer, a high refractive index layer, and a primer layer. By providing the functional layer 3, a function corresponding to the provided functional layer 3 can be added. For example, the functional layer 3 has a scratch resistance function in the hard coat layer, an antiglare function in the antiglare layer, an antistatic function in the antistatic layer, an enhanced antireflection function in the high refractive index layer, and an antireflection function in the primer layer. An adhesion strengthening function can be imparted. Among these, the hard coat layer will be described below.

[Hard coat layer]
In the present specification, the “hard coat layer” refers to a layer having a hardness of “H” or higher in a pencil hardness test (load 500 g) defined by JIS K5600-5-4 (1999).
Providing the hard coat layer 3 as a layer immediately below the low refractive index layer 2 between the low refractive index layer 2 and the transparent base film 1 is capable of further enhancing the scratch resistance as the antireflection film 10. preferable.
The hard coat layer is formed as a cured product layer of an ionizing radiation curable resin using a curable resin, more preferably an ionizing radiation curable resin.
The thickness of the hard coat layer is 0.1 to 100 μm, preferably 0.8 to 20 μm.

  For the ionizing radiation curable resin of the hard coat layer 3, various known polymerizable compounds can be used as the ionizing radiation curable resin. For example, ionizing radiation curable resins listed in the above-described low refractive index layer can be preferably used. Therefore, it is desirable that the ionizing radiation curable resin used for the hard coat layer is formed of a resin composition containing a polymerizable compound having a hydroxyl group less than a predetermined amount in the molecule, similarly to the low refractive index layer. Preferably, all of the polymerizable compound in the resin composition is a polymerizable compound having no hydroxyl group in the molecule. In addition, the polymerizable compound is preferably a polymerizable compound having a functional group curable with ionizing radiation having at least two functions or more, more preferably three functions or more, from the viewpoint of improving the scratch resistance.

  Among the polyfunctional polymerizable compounds, those having no hydroxyl group in the molecule can provide saponification resistance, and those having a hydroxyl group in the molecule are preferable in the low refractive index layer. In severe conditions such as high saponification temperature or prolonged saponification, the saponification resistance may be weakened. This is due to the same reason as discussed in the column of the low refractive index layer.

  The polyfunctional polymerizable compound used for the low refractive index layer 2 preferably has a molecular weight of 300 to 1000 from the viewpoint of scratch resistance, but the polyfunctional polymerizable compound used for the hard coat layer 3 has a molecular weight of 1000. Excess polymerizable compounds may be used.

  However, since the hard coat layer 3 is not the outermost layer like the low refractive index layer, it does not come into direct contact with the alkaline aqueous solution during the saponification treatment. Therefore, the ionizing radiation curable resin of the hard coat layer has hydroxyl groups in the molecule. The use of the polymerizable compound is not as severe as the low refractive index layer. In this respect, as the ionizing radiation curable resin used for the hard coat layer, there are more polymerizable compounds having hydroxyl groups in the molecule in the resin than the ionizing radiation curable resin used for the low refractive index layer. Also good. However, since the low refractive index layer is as thin as 50 to 150 nm, it is preferable to use a polymerizable compound that does not have a hydroxyl group in the molecule as much as possible in consideration of the penetration of the alkaline aqueous solution.

  When a polymerizable compound having a hydroxyl group in the molecule is used for the hard coat layer, a preferred example that can be used for the hard coat layer is pentaerythritol tri (meth) acrylate (abbreviated as PETA, hydroxyl group content 0.33). And dipentaerythritol pentaacrylate (abbreviation DPPA, hydroxyl group content 0.18).

  The hard coat layer 3 may contain various known additives. For example, antistatic agents, antiglare agents, ultraviolet absorbers, silica having reactive groups, and the like. For example, by adding an antiglare agent, the hard coat layer can also be used as an antiglare layer, and the antireflection film can be used as an antiglare antireflection film. As the antiglare agent, an organic or inorganic diffusing agent can be used.

  The hard coat layer 3 impregnates the transparent substrate film with at least a part of the composition of the coating liquid used for the hard coat layer in order to prevent interference spots generated at the interface between the hard coat layer and the transparent substrate film 1. It is preferable.

  Since the hard coat layer 3 is formed as a cured product layer of an ionizing radiation curable resin in the same manner as the low refractive index layer, the resin composition of the hard coat layer 3 is the same as the low refractive index layer. Can be formed by applying ionizing radiation to the resin after being applied as a paint or ink on a transparent substrate film. The coating method is not particularly limited, and a known coating method such as listed in the low refractive index layer may be adopted as appropriate.

  When the hard coat layer 3 is provided, the low refractive index layer is formed on the hard coat layer. When the low refractive index layer is formed, the hard coat layer is not completely cured, and the resin of the low refractive index layer is formed. It is preferable from the viewpoint of adhesion between these two layers that the resin of the hard coat layer is completely cured simultaneously with the curing. By improving the adhesion between the interface of the hard coat layer and the low refractive index layer, the hardness and scratch resistance of the antireflection film outermost surface can also be improved.

B. Polarizing plate The polarizing plate according to the present invention is a polarizing plate having a structure in which the above-described antireflection film of the present invention is laminated on at least one surface of the polarizer with the transparent base film side facing the polarizer. is there.
Here, FIG. 2 is a cross-sectional view showing one embodiment of a polarizing plate. In the polarizing plate 20 shown in the figure, the antireflection film 10 of the present invention is laminated on the polarizer 4 on the surface of the transparent base film 1 so that the low refractive index layer surface 2s is the outermost surface. The antireflection film 10 is laminated on one surface of the polarizer 4, and the other surface of the polarizer 4 is a configuration example in which a protective film 5 other than the antireflection film 10 of the present invention is laminated.
The surface of the polarizing plate 20 on the antireflection film 10 side is exposed to air and prevents reflection of light entering the polarizing plate. On the other hand, the surface on the protective film 5 side of the polarizing plate is usually adhered and laminated to another optical member such as a liquid crystal cell with an adhesive layer or the like, so the surface on the protective film side is antireflection treated like an antireflection film. There is no need for.
However, as the polarizing plate of the present invention, the antireflection film of the present invention described above may be laminated on both sides of the polarizer with the transparent base film side facing the polarizer.

[Polarizer]
The polarizer 4 is not particularly limited, and may be a conventionally known polarizer in a polarizing plate. For example, the polyvinyl alcohol film dye | stained with iodine etc. and extended | stretched is mentioned. In addition to the polyvinyl alcohol film, examples of the film to be dyed / stretched include a polyvinyl formal film, a polyvinyl acetal film, and an ethylene-vinyl acetate copolymer saponified film.

〔Protective film〕
The protective film 5 is laminated | stacked on the polarizer of the surface on the opposite side to the surface where the antireflection film is laminated | stacked. A film similar to the transparent base film in the antireflection film can be used. Therefore, it is preferable to use a transparent film made of triacetyl cellulose as the protective film. Moreover, the same kind of film is preferable from the viewpoint of curling prevention. Therefore, further explanation is omitted.
This protective film is a film that is permanently bonded and laminated, unlike the protective film for saponification that is temporarily bonded as described in the section of the prior art.

[Lamination of polarizer, antireflection film and protective film]
When laminating the polarizer 4, the antireflection film 10 and the protective film 5, it is preferable to perform a so-called saponification treatment with an alkaline aqueous solution in terms of enhancing the adhesion between the polarizer and these films. In particular, since the antireflection film according to the present invention has saponification resistance, it is also preferable in that its advantages can be exhibited.

C. Image Display Device An image display device according to the present invention is an image display device having a configuration including the above-described antireflection film of the present invention or the above-described polarizing plate of the present invention. For example, the antireflection film or the polarizing plate may be provided on the viewer side of the display panel. The antireflection film or polarizing plate may be a display panel that is closely laminated and integrated with the display panel, or may be disposed on the viewer side of the display panel via an air layer.

The display panel is not particularly limited and may be a known display panel. For example, in addition to various display panels such as a liquid crystal panel, a plasma display panel, an electroluminescence panel, a touch panel, electronic paper, and a tablet PC, a cathode ray tube (CRT) may be used. .
When the display panel provided in the image display device is a liquid crystal panel, the antireflection film and the polarizing plate usually include a polarizing plate. In the case of a display panel that basically does not require a polarizing plate, such as a plasma display panel, an electroluminescence panel, a cathode ray tube (CRT), a touch panel, electronic paper, or a tablet PC, the image display device includes an antireflection film.
In addition to this, the image display apparatus of the present invention may include known components such as a display driving circuit, wiring, chassis, frame, input / output components, cabinet, and the like depending on the application.

[Use]
The application of the image display device according to the present invention is not particularly limited, and examples thereof include a television receiver, a monitor display, an electronic signboard, a portable information terminal, a digital photo frame, and a medical device.

  Hereinafter, the present invention will be further described by way of examples, comparative examples and reference examples. In the following, the materials used or their abbreviations are as follows. Further, “part” means all parts by mass.

[Polymerizable compound (both polyfunctional polymerizable compounds)]
Hereinafter, the abbreviations of the materials used, the number of functional groups of the polymerizable functional group (acryloyl group), the molecular weight, the presence or absence of a hydroxyl group (OH group), and the like are described.

<Compound not containing hydroxyl group>
TMPTA: trifunctional, molecular weight 296, trimethylolpropane triacrylate (solid content 100%)
NK ester: hexafunctional, Mw578, dipentaerythritol hexaacrylate; DPHA (manufactured by Shin-Nakamura Chemical Co., Ltd.) (solid content 100%)
UV1700B: 10-functional oligomer having a molecular weight of about 2000, a bifunctional IPDI (isophorone diisocyanate), and a 10-functional oligomer obtained by reacting DPPA with an isocyanate group (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., solid content 100%)

<Compound containing hydroxyl group>
PETA: trifunctional, Mw298, OH group number 1, OH content 0.33, pentaerythritol triacrylate (containing one hydroxyl group)
DPPA: pentafunctional, molecular weight of about 550, OH group number 1, OH content 0.18, dipentaerythritol pentaacrylate (product name “Kayarad (registered trademark) DPHA”, manufactured by Nippon Kayaku Co., Ltd., solid content 100%)
DPPMA: 6 functional, Mw about 550, a mixture of dipentaerythritol pentaacrylate and dipentaerythritol pentamethacrylate V802: 7-9 functional, molecular weight 700-1000, OH group number 1, OH content 0.10-0.14 , DPPA multimer (Osaka Organic Chemical Co., Ltd., solid content 100%)

[solvent]
MIBK: methyl isobutyl ketone PGMEA: propylene glycol monomethyl ether acetate PGME: propylene glycol monomethyl ether [hollow silica particles treated with hydrophobic surface]
・ (Silica particles having an average particle diameter of 55 nm and voids inside and having a hydrophobic surface, solid content 20%, MIBK dispersion)
[Photopolymerization initiator]
・ Irgacure (registered trademark) 127 (manufactured by BASF Japan Ltd.):
2-Hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] phenyl} -2-methyl-propan-1-one [antifouling agent]
TU2225 (fluorine-containing silicone antifouling agent, manufactured by JSR Corporation, solid content 15%)

  Measurement of the molecular weight of the above compound is as described in the column of (Molecular weight) of [Ionizing radiation curable resin]. For those having a molecular weight exceeding 1000, as a column to be used, for example, Shodex (registered trademark) ) GPC KF-801, GPC KF-802, GPC KF-803, GPC KF-804, GPC KF-805 GPC KF-800D (all manufactured by Showa Denko KK) and the like.

[Test evaluation method]
Regarding the saponification resistance, the performance before and after the saponification treatment was measured and evaluated for the four performances of scratch resistance, antifouling property, antireflection property, whitening resistance and appearance.

[Abrasion resistance]
The scratch resistance was evaluated by steel wool resistance. By this evaluation, it is possible to evaluate not only the surface hardness but also the adhesion between the low refractive index layer and the underlying layer and the peeling of the coating film at the same time.
Specifically, the surface of the low refractive index layer was rubbed back and forth 10 times with a predetermined friction load of 300 g / cm ² using # 0000 steel wool, and then the presence or absence of peeling of the coating film was visually observed. Evaluation was made according to the following criteria.
○: No scratch (There was no peeling of the coating film)
×: Scratched (There was peeling of the coating film)

[Anti-fouling]
The antifouling property was evaluated based on the following criteria by writing on the surface of the low refractive index layer with an oil-based marking pen, then wiping with a cellulose-based nonwoven wiper 20 times.
○: Can be wiped off ×: Can not be wiped off

[Antireflection]
Anti-reflective properties are measured by applying a black tape to prevent back reflection on the transparent substrate film side on which the low refractive index layer is not formed, and measuring the spectral reflectance with the low refractive index layer surface facing the light source. Using a machine (manufactured by Shimadzu Corporation, PC-3100), the minimum reflectance in the wavelength range of 380 to 780 nm was measured as light reflectance, and evaluated according to the following criteria.
○: Light reflectance is 1.0 to 2.0%
X: The light reflectivity deteriorates from the above range after saponification treatment (exceeds 2.0%), or exceeds 2.0% even before saponification treatment.

[Whitening resistance]
As the whitening resistance before and after the saponification treatment, the saponification durability at which the prepared antireflection film did not appear white was evaluated. The whitening resistance was 1 m from the surface of the surface of the low refractive index layer in the dark room by applying a black tape for preventing back reflection on the transparent base film surface on which the low refractive index layer was not formed. Whether or not whitening occurred by reflecting the light of the fluorescent lamp at the position was visually observed from a position of 45 degrees from the surface and evaluated according to the following criteria.
○: No whitening.
X: There is whitening.

[appearance]
Appearance is a three-wavelength type fluorescence from the side of the surface where the low refractive index layer is formed by applying black tape to the surface of the transparent substrate film on the side where the low refractive index layer is not formed. The coated surface was visually observed under the light of a lamp and evaluated according to the following criteria.
○: No change in color before and after saponification treatment ×: Change in color before and after saponification treatment

[Saponification]
The saponification treatment was performed under the following two conditions. Usually, the saponification treatment is slowly immersed in a low-concentration low-temperature alkaline solution or quickly immersed in a high-concentration high-temperature alkaline solution.
Although the immersion time is shorter under the latter condition, since the antireflection film is a harsh treatment, those having better condition B below are better than those having better condition A.
Condition A: It was immersed in a 2N NaOH aqueous solution at a temperature of 50 ° C. for 3 minutes.
Condition B: It was immersed in a 4N NaOH aqueous solution at a temperature of 60 ° C. for 30 seconds.

[Example 1]
After applying the composition for hard coat layer (A) containing the following ionizing radiation curable resin to one side of a transparent triacetyl cellulose film (TAC film, refractive index: 1.48) having a thickness of 80 μm as a transparent substrate film The resin was (semi) cured by ultraviolet irradiation to form a hard coat layer having a thickness of 10 μm.
Next, after applying the following composition for low refractive index layer (1) on the formed hard coat layer, the resin is cured by ultraviolet irradiation to form a low refractive index layer having a thickness of 100 nm, The hard coat layer was also completely cured to produce an antireflection film. Next, saponification treatment was performed under saponification treatment condition A.

[Composition for hard coat layer (A)]
Dipentaerythritol hexaacrylate (DPHA, hexafunctional) 100 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Photopolymerization initiator 0.4 parts

[Composition for low refractive index layer (1)]
TMPTA 100 parts Hollow silica particles (Solid content, hereinafter the same) 100 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[Example 2]
The antireflection film produced in Example 1 was saponified under saponification condition B.

Example 3
In Example 1, an antireflection film was prepared in the same manner as in Example 1 except that the following low refractive index layer composition (2) having a different resin component was used to form the low refractive index layer. Saponification was performed under the same conditions as in Example 1.
[Composition for low refractive index layer (2)]
DPPA 100 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

Example 4
In Example 1, an antireflection film was prepared in the same manner as in Example 1 except that the following low refractive index layer composition (3) having a different resin component was used to form the low refractive index layer. Saponification was performed under the same conditions as in Example 1.
[Composition for low refractive index layer (3)]
NK ester (hexafunctional DPHA) 100 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

Example 5
In Example 1, an antireflection film was prepared in the same manner as in Example 1 except that the following low refractive index layer composition (4) having a different resin component was used to form the low refractive index layer. Saponification was performed under the same conditions as in Example 1.
[Composition for low refractive index layer (4)]
V802 100 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

Example 6
In Example 1, an antireflection film was prepared in the same manner as in Example 1 except that the following low refractive index layer composition (5) having a different resin component was used to form the low refractive index layer. Saponification was performed under the same conditions as in Example 1.
[Composition for low refractive index layer (5)]
DPPMA 100 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[ Reference Example 1 ]
In Example 1, an antireflection film was produced in the same manner as in Example 1 except that the low refractive index layer was formed by using the following low refractive index layer composition (6) having a different resin component mixed resin. The saponification treatment was performed under the same conditions as in Example 1.
[Composition for low refractive index layer (6)]
TMPTA 75 parts DPPA 25 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[ Reference Example 2 ]
In Example 1, an antireflection film was produced in the same manner as in Example 1 except that the low refractive index layer was formed by using the following low refractive index layer composition (7) in which the resin component was a mixed resin. The saponification treatment was performed under the same conditions as in Example 1.
[Composition for low refractive index layer (7)]
V802 75 parts DPPA 25 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[ Reference Example 3 ]
In Example 1, an antireflection film was produced in the same manner as in Example 1 except that the following low refractive index layer composition (8) having a different resin and solvent was used to form the low refractive index layer. The saponification treatment was performed under the same conditions as in Example 1.
[Composition for low refractive index layer (8)]
TMPTA 75 parts DPPA 25 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGME 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[Example 7 ]
In Example 1, an antireflection film was formed in the same manner as in Example 1 except that the low refractive index layer was formed using the following composition (9) for a low refractive index layer in which the amount of hollow silica particles was different. And saponified under the same conditions as in Example 1.
[Composition for low refractive index layer (9)]
TMPTA 100 parts Hollow silica particles 120 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[Comparative Example 1]
In Example 1, except that the following composition for low refractive index layer (10) containing a polyfunctional polymerizable compound having a hydroxyl group content of more than 0.2 was used for forming the low refractive index layer, Example 1, an antireflection film was prepared and saponified under the same conditions as in Example 1.
[Composition for low refractive index layer (10)]
PETA 100 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[Comparative Example 2]
The antireflection film produced in Comparative Example 1 was saponified under saponification condition B.

[Comparative Example 3]
In Example 1, the following low refractive index layer composition (11) containing a polyfunctional polymerizable compound having a hydroxyl group content of more than 0.2 and having a different solvent component was used to form the low refractive index layer. Otherwise, an antireflection film was produced in the same manner as in Example 1, and saponified under the same conditions as in Example 1.
[Composition for low refractive index layer (11)]
PETA 100 parts Hollow silica particles 100 parts Solvent; MIBK 85 parts Solvent; PGME 15 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[Comparative Example 4]
In Example 1, the formation of the low refractive index layer includes a polyfunctional polymerizable compound having a hydroxyl group content of more than 0.2 and a polyfunctional polymerizable compound having a hydroxyl group content of 0.2 or less. An antireflection film was prepared in the same manner as in Example 1 except that the following composition for low refractive index layer (12) having a resin content of 50% by mass or more was used, and saponified under the same conditions as in Example 1. Processed.
[Composition for low refractive index layer (12)]
PETA 75 parts DPPA 25 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGME 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[Comparative Example 5]
In Example 1, the formation of the low refractive index layer includes a polyfunctional polymerizable compound having a hydroxyl group content of more than 0.2 and a polyfunctional polymerizable compound having a hydroxyl group content of 0.2 or less. An antireflection film was prepared in the same manner as in Example 1 except that the following composition for low refractive index layer (13) having a resin content of 50% by mass or more was used, and saponified under the same conditions as in Example 1. Processed.
[Composition for low refractive index layer (13)]
PETA 75 parts V802 25 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGME 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[Comparative Example 6]
In Example 1, the low refractive index layer was formed using the following low refractive index layer composition (14) containing a polyfunctional polymerizable compound having a different resin component and a molecular weight exceeding 1000. 1, an antireflection film was prepared and saponified under the same conditions as in Example 1.
[Composition for low refractive index layer (14)]
UV1700B 100 parts Hollow silica particles 100 parts Solvent; MIBK 70 parts Solvent; PGMEA 30 parts Antifouling agent 4 parts Photopolymerization initiator 7 parts

[Performance evaluation results]
The contents of the polymerizable compounds used in the above Examples and Comparative Examples are shown in Tables 1 and 2, and the performance evaluation results are shown in Tables 2 and 3.

As shown in Table 1, a polyfunctional polymerizable compound which does not contain a hydroxyl group in its entirety without using a polyfunctional polymerizable compound having a hydroxyl group as a polymerizable compound constituting an ionizing radiation curable resin of a low refractive index layer Example 1 to Example 2 and Example 7 using trifunctional TMPTA as Example 4 and Example 4 using hexafunctional NK ester (DPHA) as a polyfunctional polymerizable compound not containing a hydroxyl group as a whole In all cases, the scratch resistance, antifouling property, antireflection property, whitening resistance and appearance were all good, and the saponification resistance was satisfactory. In addition, Example 2 which was performed under the condition B by changing the saponification treatment was also satisfactory in saponification resistance.

A polyfunctional polymerizable compound having a hydroxyl group was used as the polymerizable compound constituting the ionizing radiation curable resin of the low refractive index layer, but the number of hydroxyl groups in one molecule was 1 or less and the hydroxyl group content was 0.00. In DPPA Example 3, V802 Example 4, and DPPMA Example 6 using the following two, all of scratch resistance, antifouling property, antireflection property, whitening resistance and appearance are all exhibited. ○, saponification resistance was satisfactory.
A polyfunctional polymerizable compound having a hydroxyl group was used, but a polyfunctional polymerizable compound having a hydroxyl group number of 1 or less and a hydroxyl group content of 0.2 or less in one molecule and having no hydroxyl group In each of Reference Examples 1 to 3 used in combination with the compound, all of scratch resistance, antifouling property, antireflection property, whitening resistance and appearance were good, and the saponification resistance was satisfactory.
As described above, Examples 1 to 7 and Reference Examples 1 to 3 are satisfactory in all evaluations with saponification resistance being good, and the resin of the low refractive index layer remains without being dissolved or dropped by the saponification treatment. It seems to be because.

  On the other hand, Comparative Examples 1 to 1 using PETA, which is a polyfunctional polymerizable compound having a hydroxyl group and a hydroxyl group content exceeding 0.2, as the polymerizable compound constituting the ionizing radiation curable resin of the low refractive index layer. In Comparative Example 5, the antireflection property, the whitening resistance, and the appearance were all good after the saponification treatment, and the saponification resistance was satisfactory. However, in Comparative Examples 1 to 5, the scratch resistance, antifouling property and appearance were x after the saponification treatment, and the saponification resistance was not satisfactory. Comparative Example 4 and Comparative Example 5 in which a polyfunctional polymerizable compound having no hydroxyl group is used together with a polyfunctional polymerizable compound having a hydroxyl group in the range of subcomponents (less than 50% by mass of the total resin content) Since the amount of the polymerizable compound having no group was small and the amount of hydroxyl groups as a whole in the resin composition was large, the scratch resistance, antifouling property and appearance became x after the saponification treatment.

  Although the polyfunctional polymerizable compound has no hydroxyl group and the hydroxyl group content is 0, Comparative Example 6 using a urethane-based oligomer type compound having a hydroxyl group has 10 and 9 functional groups of acryloyl group. In addition, the (weight average) molecular weight was over 2000 and was over 1000, so the antifouling property was ○ even after saponification treatment, but scratch resistance, antireflection, whitening resistance and appearance Was x after saponification treatment, and was not satisfactory.

When scratch resistance is evaluated by increasing the friction load from 300 g / cm ² to 600 g / cm ² , Examples 1 to 2 are good as before load increase after saponification. Examples 3 to 7 and Reference Example 1 Although -3 is within an allowable range, it is slightly lowered. Therefore, the resin was best when TMPTA was 100%.

  Although not described in Table 1, the adhesion between the transparent substrate film and the hard coat layer was good in each Example and each Comparative Example. This adhesion was performed according to the cross-cut tape method of JIS K5400, and all the cross-cut grids were not peeled off.

DESCRIPTION OF SYMBOLS 1 Transparent base film 2 Low refractive index layer 2s Low refractive index layer surface 3 Hard-coat layer (functional layer)
4 Polarizer 5 Protective film 10 Antireflection film 20 Polarizing plate

Claims (3)

On one surface of a transparent substrate film made of triacetyl cellulose, is composed of a cured product layer of a first ionizing radiation curable resin, contains hollow silica particles, and has a lower refractive index than the lower layer to be laminated. have a low refractive index layer, and between the transparent substrate film and the low refractive index layer to have a functional layer, anti-reflection film,
The functional layer is a hard coat layer made of a cured layer of a second ionizing radiation curable resin,
The polymerizable compound contained in the first ionizing radiation-curable resin is any of the following (A) and (B ) :
(A) A polyfunctional polymerizable compound having no hydroxyl group in the molecule and comprising any of diethylene glycol di (meth) acrylate, isocyanuric acid-modified tri (meth) acrylate, and ditrimethylolpropane tetraacrylate Polymerizable compounds,
(B) A polymerizable compound having a hydroxyl group in the molecule, the hydroxyl group content defined as a value obtained by dividing the number of hydroxyl groups contained in one molecule by the molecular weight and multiplying by 100, is 0.2 or less A polyfunctional polymerizable compound,
Before SL (A), a functional group number of 3-9 of the polyfunctional polymerizable compound definitive (B), the molecular weight of Ri der 300-1000,
The antireflection film , wherein the polymerizable compound contained in the second ionizing radiation curable resin is a polyfunctional polymerizable compound having no hydroxyl group in the molecule . A polarizing plate in which the antireflection film according to claim 1 is laminated on at least one surface of a polarizer with the transparent base film side facing the polarizer. The antireflection film according to claim 1, or, with a polarizing plate according to claim 2, the image display device.

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