JP2005077879A - Laminate and display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply a laminate having sufficient strength and having no interference fringes in a base material provided with a hard coat. <P>SOLUTION: The laminate is characterized in that it includes at least the base material and the hard coat layer, and at least the base material surface on the hard coat layer side is amorphous polyethylene terephthalate. Further, the laminate is characterized in that the base material includes denatured amorphous polyethylene terephthalate to make the surface on the hard coat layer side into amorphous polyethylene terephthalate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hard coat in which interference fringes are eliminated and visibility is improved on a polyethylene terephthalate (hereinafter referred to as PET) substrate, and a plate, sheet, and film subjected to antireflection treatment.

  In recent years, plastics are used in various industrial fields such as liquid crystal, CRT, and PDP displays and optical lenses because they are lightweight and have excellent workability. However, the surface of the plastic itself has a drawback that it is easily scratched. In order to improve this defect, a hard coat agent is applied to the surface and a hard coat layer is formed to increase the surface hardness and protect the plastic from scratches (see Patent Document 1).

  However, when a transparent plastic substrate with a hard coat is used on the surface of a member that requires visibility such as a display, interference fringes are generated due to the difference in refractive index between the substrate and the hard coat, resulting in poor visibility. There is a problem such as.

In order to solve such a problem, it is known to apply a hard coat layer using a resin containing a solvent that dissolves or swells the base material (see Patent Document 2). However, cellulose-based film base materials dissolve or swell in general-purpose solvents, but PET films do not dissolve or swell. Therefore, when PET is used as the base material, interference fringes can be reduced by this method in practice. Was impossible.
JP-A-5-179155 JP 2003-205563 A

  The object of the present invention is to compensate for the above-mentioned drawbacks, that is, to provide a laminate having a hard coat with a polyethylene terephthalate film as a base material, sufficient strength and no interference fringes. .

  The invention of claim 1 is a laminate comprising a substrate and a hard coat layer, wherein at least the surface of the substrate on the hard coat layer side is amorphous polyethylene terephthalate.

  The invention according to claim 2 is the laminate according to claim 1, wherein the substrate is composed of a plurality of layers, and at least the hard coat layer side of the substrate is a modified polyethylene terephthalate layer.

  The invention according to claim 3 is characterized in that the modified polyethylene terephthalate layer is reacted with 1,4-cyclohexanedimethanol as a part or all of ethylene glycol among terephthalic acid and ethylene glycol which are starting materials of polyethylene terephthalate. The laminate according to claim 2, wherein the obtained substance is copolymerized.

  In the invention of claim 4, the modified polyethylene terephthalate layer is reacted with a part or all of terephthalic acid being isophthalic acid among terephthalic acid and ethylene glycol which are starting materials of polyethylene terephthalate. The laminate according to claim 2 or 3, wherein the laminate is copolymerized.

  The invention according to claim 5 is the laminate according to claim 3 or 4, wherein when the obtained substance of claim 3 or 4 is copolymerized, ethylene terephthalate is further added for copolymerization. .

  A sixth aspect of the present invention is the laminate according to any one of the first to fifth aspects, wherein a functional layer is provided on the hard coat.

  The invention according to claim 7 is the laminate according to claim 6, wherein the functional layer is an antireflection layer.

  The invention of claim 8 is a display using the laminate of claims 1 to 7 as a surface protection member.

  By using amorphous polyethylene terephthalate at least on the hard coat side, the laminate of the present invention can be made into a laminate having sufficient strength and excellent effect in suppressing interference fringes.

  Hereinafter, the laminated body which consists of the base material of this invention and a hard-coat layer is demonstrated in detail.

  In the present invention, at least the side of the base material on which the hard coat layer is provided is made of amorphous PET, so that a laminate having sufficient strength and excellent visibility with reduced occurrence of interference fringes can be obtained. Is.

  Amorphous PET used in the present invention is not crystallized by stretching treatment or the like, and has a feature such as low solvent resistance. By applying a hard coat diluted with a solvent that erodes amorphous PET on the amorphous PET, the interface between the amorphous PET and the hard coat is obscured, reflection from the interface is suppressed, and interference fringes are prevented from being generated. it can.

  The interference fringe referred to here refers to a rainbow-colored striped pattern that is visible when light is reflected on a transparent substrate on which a coating film is placed. When the reflection spectrum is measured, this interference fringe draws a waveform in which peaks and valleys are continuous, and appears to be stronger as the difference between the peaks and valleys (fringe width) is larger and weaker as the difference is smaller.

  Therefore, the intensity of the interference fringes can be quantitatively expressed from the difference between the peaks and valleys. When there is no interference fringe by visual observation, it is when the difference between the peaks and valleys is less than about 0.015.

  The base material in which at least the side on which the hard coat layer is provided is made of amorphous PET according to the present invention may be composed of an amorphous PET single layer, or is composed of a plurality of layers including a support, and at least the side on which the hard coat layer is provided is made of amorphous PET. It may be a layer.

  Amorphized PET has low heat resistance, so when it is used as a substrate with a single layer, it will be difficult to handle due to problems such as shrinkage in the process of drying and solidifying the hard coat provided on it, so it preferably consists of multiple layers Is more preferable.

  When the base material is made of a plurality of layers, it is a multilayer base material provided with amorphous pets on one side or both sides of a support body having heat resistance and strength capable of supporting amorphous PET when it is softened by heat. be able to.

  The support is not particularly limited as long as it has heat resistance and strength against stress. For example, stretched PET, polyethylene naphthalate (hereinafter referred to as PEN), polyethylene sulfonate (hereinafter referred to as PES) or the like is used. I can do it. These supports are preferable because they have crystallinity and have sufficient heat resistance and strength. More preferably, biaxially stretched PET is preferable because of its adhesion to amorphous PET.

  For laminating amorphous PET on a support, amorphous PET and a support may be prepared separately and bonded together.

  As a method for producing amorphous PET, a known method can be used, which can be produced by a germanium catalyst method or by controlling the crystallization speed without changing the raw material composition. Moreover, crystallization can be suppressed by setting it as modified | denatured PET which substituted a part of PET.

  Moreover, in order to skip a bonding process, you may extrude and perform integral molding. At this time, it becomes difficult to control the crystallinity of the support layer and the amorphous PET.

  Therefore, by using modified PET for amorphous PET, it is possible to easily coextrude amorphous PET and a support with suppressed crystallization.

  Usually, PET can obtain polyethylene terephthalate by copolymerizing ethylene terephthalate obtained by reacting terephthalic acid with ethylene glycol.

  The modified PET of the present invention can be obtained by copolymerizing a part of or all of terephthalic acid and / or ethylene glycol with other substances among terephthalic acid and ethylene glycol, which are the starting materials for PET. it can.

  By doing so, the part derived from terephthalic acid and / or the part derived from ethylene glycol in PET is replaced with a group derived from another substance, and crystallization can be suppressed.

  As a substance that replaces terephthalic acid, dicarboxylic acids such as isophthalic acid, adipic acid, diphenyl carboxylic acid, diphenyl ether carboxylic acid, and sebacic acid can be used. Of these, isophthalic acid is preferred.

  As a substance that substitutes ethylene glycol, glycol compounds such as 1,4-cyclohexanedimethanol (CHDM), diethylene glycol, hexamethylene glycol, trimethylene glycol, butylene glycol, and the like can be used. Of these, 1,4-cyclohexanedimethanol and diethylene glycol are preferred.

  Further, at the time of copolymerization, ethylene terephthalate may be further added for copolymerization.

  In addition, silica, talc, or the like that is generally used for the purpose of preventing fusion of the layer itself may be added to the obtained amorphous PET layer within a range that does not impair visibility, and PET may be further added. Further, in film type molding, both ends may be embossed or a tape may be inserted.

  Although the thickness of the amorphous PET layer with respect to the support is not particularly limited, it is in the range of support: amorphous layer = 100: 1 to 100: 200 on one side, and extrusion molding is difficult at 100: 1 or less. : When it is 200 or more, the support cannot completely suppress the thermal deformation of the amorphous layer.

  Although total thickness is not specifically limited, It is 10-2000 micrometers, More preferably, it is 30-300 micrometers.

  When the substrate is made into a film, melt lamination extrusion is performed using a T-die or the like, and it is cast on a cast drum in the same manner as in ordinary PET film production and quickly cooled. Thereafter, longitudinal and lateral stretching is performed and heat treatment is performed as necessary.

  The base material having the amorphous PET layer formed on the surface can withstand the deformation of heat applied when the hard coat layer is applied and dried and solidified, and also when the antireflection layer is installed. Have.

  As the resin constituting the hard coat layer, either an active energy ray curable resin or a thermosetting resin can be used, but an active energy ray curable resin is particularly preferable.

  The type of the active energy ray curable resin is not particularly limited, but more preferably a compound having a (meth) acryloyl group in the molecule, and more preferably 1 to 20 (meth) acryloyl groups.

  Specific examples include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like.

  Examples of the solvent to be used include aromatic and acetate solvents such as toluene and ethyl acetate that erode the amorphous PET layer of the substrate.

  The concentration can be appropriately adjusted. For example, it may be dissolved in these solvents so as to be about 50 wt% and used as a coating solution.

  Further, the solid content concentration may be appropriately adjusted in consideration of the interference fringe suppressing effect and the coating suitability.

  It is preferable to mix a photopolymerization initiator in the hard coat layer. The photopolymerization initiator is not particularly limited, and a compound that generates radicals when irradiated with ultraviolet rays or the like can be used.

  Specifically, 1-hydroxycyclophenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2,2-dimethoxy-1,2-diphenylethane-1-one, benzophenone, 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1-propan-1-one, 2 -Benzyl-2-dimethylamino-1- (4-morpholinophenyl) butan-1-one, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and the like can be used.

  In this invention, the compounding quantity of a photoinitiator shall be 0.1-10 weight part with respect to 100 weight part of energy-beam curable components, More preferably, it is 4-7 weight part. If the amount is less than 0.1 parts by weight, curing is insufficient and the strength as a film is insufficient or the function as a binder is lowered. On the other hand, if the amount exceeds 10 parts by weight, the film may crack, which is not preferable.

  In addition, the interface between the hard coat layer and the amorphous PET layer is obscured, and at the same time, the occurrence of interference fringes is further suppressed by adjusting the refractive index of the hard coat layer.

  The refractive index of amorphous PET is 1.49 to 1.65 depending on the degree of amorphization when PET is amorphized, for example, depending on the degree of amorphization in the case of PET modified using cyclohexanedimethanol or isophthalic acid. It becomes the range of 1.55-1.65.

  Therefore, in accordance with the refractive index of the amorphous layer, a fluorine-containing compound having a (meth) acryloyl group as a refractive index lowering agent is good for the hard coat component, and more preferably trifluoroacrylate having three fluorine atoms in the molecule. good. Further, an organic solvent dispersion of silica sol may be used. As the refractive index improver, generally known metal oxides are used.

Examples of the fine particles having a high refractive index include ZnO, TiO ₂ having a refractive index of 1.7 to 2.2, and Al ₂ O ₃ having a refractive index of 1.6. Is used. Particularly preferably, the use of conductive fine particles such as indium tin oxide, antimony-doped tin oxide, and antimony oxide having anti-electrical resistance action reduces dust adhesion when used in a display, and improves visibility and product. Usefulness is improved. By blending these in the hard coat, interference fringes are further suppressed and visibility is enhanced.

  In the present invention, additives such as antistatic agents, ultraviolet absorbers, leveling agents, and antifoaming agents can be appropriately used in the hard coat layer as long as the effects of the hard coat are not impaired.

  The hard coat layer can be applied to the surface of the substrate by a known method such as a roll coater method, a blade coater method, a micro gravure method, or a spin coater method. Then, it can be hardened by performing hot air drying etc. as needed and irradiating an active energy ray.

  The active energy rays used here are not particularly limited, and examples thereof include ultraviolet rays and electron beams.

  When ultraviolet rays are used, a conventionally known ultraviolet irradiation device using, for example, a high-pressure mercury lamp, a xenon lamp, a metal halide lamp, or the like can be used.

  Moreover, when using an electron beam, there is no restriction | limiting in particular in an apparatus, A well-known apparatus can be used. The acceleration voltage at this time is generally in the range of 80 to 300 kV.

  In the present invention, various functional layers can be further provided on the hard coat layer according to the purpose. Examples of the functional layer include an antireflection layer, an antistatic layer, an electromagnetic wave shielding layer, a contamination prevention layer, a color correction layer, and the like, and a plurality of these can be combined depending on the purpose. These functional layers can be provided by a known method.

  The laminate of the present invention thus obtained can be applied to various uses such as surface protective optical films for various displays such as liquid crystal displays, plasma displays, CRTs, and EL displays.

  A co-extruded film was prepared by the T-die method so that the ethylene glycol part of polyethylene terephthalate was introduced with a ratio of 1: 1 of ethylene glycol and cyclohexanedimethanol in a molar ratio of 10 μm and polyethylene terephthalate was 90 μm. At this time, the refractive index of the amorphous PET layer was 1.58.

  As a hard coat layer, 50 g of KAYARAD TMPTA (manufactured by Nippon Kayaku Co., Ltd.) and 50 g of MEK in which 2.5 g of a polymerization initiator (IRGACURE-184) were dissolved were added and stirred uniformly to prepare a coating solution. This coating solution was applied to the amorphous PET surface of the film with a wire bar so that the dry coating thickness was 10 μm, dried in an oven at 70 ° C. for 1 minute, and then irradiated with ultraviolet rays to obtain a sample. The refractive index of the hard coat layer was 1.52.

  A sample was obtained in the same manner as in Example 1 except that OSCAL suluria: MIBK dispersion (manufactured by Catalyst Kasei Kogyo Co., Ltd.) was added to the hard coat coating solution shown in Example 1 so that the solid content was 70 g. The refractive index of the hard coat layer at this time was 1.58.

  A co-extruded film was prepared by the T-die method so that the PET resin in which the terephthalic acid portion of polyethylene terephthalate was introduced so that the molar ratio of terephthalic acid and isophthalic acid was 2: 1 was 10 μm, and the polyethylene terephthalate was 90 μm. At this time, the refractive index of the amorphous PET layer was 1.61. A hard coat layer was provided thereon as in Example 1 to obtain a sample.

A SiO ₂ sol solution: DTP-1 (manufactured by Sumitomo Osaka Cement) was applied on the hard coat layer prepared in Example 2 so that the dry film thickness was 100 nm, dried and cured, and an antireflection layer was installed. Got.
<Comparative Example 1>
A sample was obtained in the same manner as in Example 1 except that the untreated surface of a 100 μm A4100 (Toyobo) PET film was used as the coating surface.
<Comparative example 2>
A sample was obtained in the same manner as in Example 1 except that the easy adhesion treated surface of an A4100 (Toyobo) 100 μm PET film was used as the coating surface.
<Evaluation>
The sample of an Example and a comparative example was evaluated by the method shown below.
(Fringe width)
Using an automatic spectrophotometer U-4000 manufactured by Hitachi, Ltd., the reflection spectrum was measured at 5 ° regular reflection. From this spectrum data, the absolute value of the difference between the maximum value and the minimum value of the reflectance was defined as the fringe width. In the measurement, the surface opposite to the coated surface was roughened with sandpaper, and measures were taken to prevent back surface reflection.
(Visual evaluation)
Interference fringes were visually evaluated from a distance of 20 cm closest to the 20 W fluorescent lamp.

At the time of evaluation, the surface opposite to the coated surface was roughened with sandpaper, and antireflection measures were taken.
(Adhesiveness)
The test and evaluation were performed by the cross-cut tape method described in JIS K5400-8,5 and a 1 mm cross cut.

  These evaluation results are shown in Table 1.

Claims (8)

  A laminate comprising a substrate and a hard coat layer, wherein at least the surface of the substrate on the hard coat layer side is amorphous polyethylene terephthalate.   The laminate according to claim 1, wherein the substrate comprises a plurality of layers, and at least the hard coat layer side of the substrate is a modified polyethylene terephthalate layer.   The modified polyethylene terephthalate layer reacts with terephthalic acid, which is a starting material for polyethylene terephthalate, and ethylene glycol, with a part or all of ethylene glycol being reacted with 1,4-cyclohexanedimethanol, and the resulting material is co-produced. The laminate according to claim 2, wherein the laminate is polymerized.   The modified polyethylene terephthalate layer is formed by copolymerizing a substance obtained by reacting a part or all of terephthalic acid with isophthalic acid among terephthalic acid and ethylene glycol which are polyethylene terephthalate starting materials. The laminate according to claim 2 or 3, characterized in that   5. The laminate according to claim 3, wherein, when the obtained substance of claim 3 or 4 is copolymerized, ethylene terephthalate is further added for copolymerization.   The laminated body according to claim 1, wherein a functional layer is provided on the hard coat.   The laminate according to claim 6, wherein the functional layer is an antireflection layer. A display using the laminate according to claim 1 as a surface protective member.