JP5162054B2 - Optical laminated polyester film - Google Patents

Description

  The present invention relates to a laminated polyester film for optics, and for example, a liquid crystal display (hereinafter abbreviated as LCD), a plasma display panel (hereinafter abbreviated as PDP), an organic electroluminescence (hereinafter abbreviated as organic EL). ), Etc., for a laminated polyester film suitable for optical applications such as for producing display members.

  Conventionally, an optical film having a polyester film as a substrate has been used for various optical applications including production of display members such as LCD, PDP, and organic EL. These optical films are required to have excellent transparency and visibility.

  These optical films are used by laminating surface functional layers such as a hard coat layer and an antireflection layer on a plastic film. As the plastic film, a transparent polyester film is generally used, and in order to improve the adhesion between the polyester film of the base material and the surface functional layer, an easily adhesive coating layer may be provided as an intermediate layer. It is common.

  As an antireflection film, generally, a high-refractive index layer and a low-refractive index layer are alternately laminated as a surface functional layer to prevent reflection of external light by utilizing a light interference phenomenon.

  In recent years, LCDs, PDPs, and other display materials have been required to have larger screens, higher image quality, and higher quality, and in response to this, there has been a demand for suppressing iris-like colors (interference unevenness) especially under fluorescent lamps. The level is getting higher. In addition, fluorescent lamps have become a three-wavelength type for daylight color reproducibility, and interference unevenness is more likely to occur. Furthermore, in order to achieve cost reductions and the like, the demand for simplification of the antireflection layer structure is also increasing, and in order to cope with a higher refractive index surface functional layer, a coating layer laminated on a polyester film is required. Optical design is becoming more important.

However, hard coats used for various optical applications in recent years may have a high refractive index in order to achieve high functionality, and conventional resins and coatings such as polyester resins, acrylic resins, urethane resins, etc. In the coating layer depending on the amount, since the refractive index is fixed at around 1.50, sufficient optical characteristics cannot be obtained, and when designing an antireflection film in recent years, the antireflection performance is limited, and the external light reflection In some cases, the occurrence of unevenness in interference cannot be sufficiently suppressed. When a film in which interference unevenness due to reflection of external light is remarkably generated is used as a display member for LCD, PDP, organic EL, etc., various problems due to deterioration in visibility tend to become more apparent. In addition, the remarkable occurrence of interference unevenness not only deteriorates the visibility, but may also cause eye fatigue and health problems.
JP-A-10-119215 JP 2000-246855 A

  The present invention has been made in view of the above-described circumstances, and the solution is to reduce various types of display components such as LCDs, PDPs, organic ELs, and other display members that have reduced interference unevenness due to external light reflection. An object of the present invention is to provide an optical laminated polyester film that can be suitably used for various optical applications in addition to the production of materials.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the use of a laminated polyester film having a specific configuration can easily solve the above-mentioned problems, and have completed the present invention.

That is, the gist of the present invention is stretched in at least uniaxial direction having a coating layer formed from a coating solution containing an aromatic-containing imide compound or a coating solution containing a compound having a bisphenol A structure and a melamine compound . It is a polyester film, and the average value of the absolute reflectance of light having a wavelength of 400 to 800 nm on the coating layer surface is 5.5 to 6.5%.

Hereinafter, the present invention will be described in more detail.
The polyester film constituting the laminated polyester film in the present invention may have a single layer structure or a multilayer structure, and may have four or more layers as long as it does not exceed the gist of the present invention other than a two-layer or three-layer structure. It may be a multilayer, and is not particularly limited.

  The polyester used in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, the dicarboxylic acid component of the copolyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexane dimethanol, neopentyl glycol, is mentioned.

  In the polyester layer of the film of the present invention, it is preferable to blend particles for the main purpose of imparting slipperiness. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.01-2 micrometers. When the average particle diameter is less than 0.01 μm, the particles are likely to aggregate and dispersibility may be insufficient. On the other hand, when the average particle diameter exceeds 3 μm, the surface roughness of the film becomes too rough and Problems may occur when various surface functional layers are applied in the process.

  Further, the content of particles in the polyester layer is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, ultraviolet absorbers, heat stabilizers, lubricants, dyes, pigments, etc. may be added to the polyester film in the present invention as necessary. Can do.

  Although the thickness of the polyester film in this invention will not be specifically limited if it can be formed into a film as a film, Usually, 10-300 micrometers, Preferably it is the range of 50-250 micrometers.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can be adopted for the production of the polyester film constituting the laminated polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Furthermore, what is called an in-line coating which processes the film surface during the extending | stretching process of the above-mentioned polyester film can be given. When a coating layer is provided on a polyester film by in-line coating, coating can be performed simultaneously with stretching, and the thickness of the coating layer can be changed by the stretching ratio, so that a film suitable as a polyester film can be produced. .

  Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. As for the coating layer, it may be provided on the polyester film by the above-mentioned in-line coating, a so-called off-line coating applied outside the system on the film once manufactured may be employed, or both may be used in combination. In-line coating is preferably used because it can be manufactured at low cost.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When a coating layer is provided on a polyester film by in-line coating, coating can be performed simultaneously with film formation, and the coating layer can be processed at a high temperature, and a film suitable as a polyester film can be produced.

  In the present invention, it is an essential requirement that the average value of the absolute reflectance of light rays having a wavelength in the range of 400 to 800 nm is in the range of 5.5 to 6.5% on the surface of the coating layer.

  In order to form a coating layer that satisfies the above requirements, a coating layer having a refractive index increased to the vicinity of the geometric mean of the refractive index of the polyester film of the substrate and the refractive index of the surface functional layer laminated on the coating layer. This can be realized by stacking or thinning the coating layer so that the optical characteristics of the coating layer can be ignored.

  What is used for a coating layer in order to raise the refractive index of a coating layer will not be specifically limited if a refractive index is high, For example, a metal compound, an aromatic organic compound, etc. are mentioned.

  Examples of the metal compound include titanium oxide, zinc oxide, tin oxide, antimony oxide, yttrium oxide, zirconium oxide, indium oxide, cerium oxide, ATO (antimony / tin oxide), and ITO (indium / tin oxide). Aluminum such as metal oxide, aluminum acetylacetonate, hydroxyaluminum diacetate, dihydroxyaluminum acetate; tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate, titanium acetylacetate Nato, titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamine Titanium such as iron acetate and titanium ethyl acetoacetate; Iron such as iron acetylacetonate and iron acetate; Cobalt such as cobalt acetylacetonate; Copper acetate, copper acetate monohydrate, copper acetate multihydrate, copper acetyl Coppers such as acetonate; zincs such as zinc acetate, zinc acetate dihydrate, zinc acetylacetonate hydrate; zirconium acetate, zirconium normal propylate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetate Examples thereof include organic compounds having a metal element such as zirconium and zirconium compounds such as narate and zirconium bisacetylacetonate. These may be used alone or in combination of two or more.

  Among the above metal compounds, an organic compound having a titanium element or a zirconium element is preferable in terms of particularly good coatability and transparency, and more preferably a water-soluble titanium chelate compound when considering application to in-line coating, A water-soluble zirconium chelate compound or the like is preferably used.

  Examples of the aromatic-containing organic compound include a condensed polycyclic aromatic compound exemplified by a naphthalene ring and an anthracene ring, a compound having a high benzene ring ratio such as a bisphenol A compound and a biphenyl compound, an aromatic-containing imide compound, and a benzophenone. And ultraviolet absorber-containing compounds such as benzotriazole and the like. These may be used alone or in combination of two or more.

  In the laminated polyester film of the present invention, a binder polymer is used to improve antireflection performance and transparency when various surface functional layers are laminated on the coated surface, and to improve adhesion to various surface functional layers. Can also be used.

  The “binder polymer” used in the present invention is a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) according to a polymer compound safety evaluation flow scheme (sponsored by the Chemical Substance Council in November 1985). ) Is a polymer compound having a molecular weight of 1000 or more and having a film-forming property.

  Specific examples of the binder polymer include polyester resin, acrylic resin, urethane resin, polyvinyl, polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, and starches. In terms of improving adhesion with the surface functional layer, polyester resins, acrylic resins, and urethane resins are more preferably used, and aromatics may be contained in these compounds in that the reflectance can be designed to be higher. More preferred.

  Furthermore, a crosslinking agent may be used in the coating layer as long as the gist of the present invention is not impaired, and various known resins can be used, but at least one selected from melamine compounds, epoxy compounds, oxazoline compounds, and isocyanate compounds. Preferably it is a seed. A melamine compound is more preferable in that a high reflectance can be designed.

  Examples of the melamine compound in the present invention include methoxymethylated melamine and butoxymethylated melamine which are alkylol or alkoxyalkylolated melamine compounds, and those obtained by co-condensing urea or the like with a part of melamine can also be used. .

  Further, for the purpose of improving the adhesion and slipperiness of the coating layer, inert particles may be contained, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, organic particles, and the like.

  Furthermore, as long as it does not impair the gist of the present invention, an antifoaming agent, a coating property improving agent, a thickener, an organic lubricant, an antistatic agent, an antioxidant, a foaming agent, a dye, and the like are contained as necessary. Also good.

  It is preferable to produce a laminated polyester film by coating the above-mentioned series of compounds as a solution or dispersion on a polyester film with a coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight. .

  Furthermore, in the case of in-line coating, the above-described series of compounds is used as an aqueous solution or water dispersion, and the coating solution adjusted with a solid content concentration of about 0.1 to 50% by weight as a guide is laminated on the polyester film. It is preferred to produce a polyester film. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

Regarding the laminated polyester film in the present invention, the coating amount of the coating layer provided on the polyester film (after drying) is determined by the surface function of the coating layer and the refractive index of the coating layer of the polyester film of the base material and the coating layer. When the refractive index of the layer is increased to near the geometric mean, there is no particular limitation, but it is usually in the range of 0.001 to 0.3 g / m ² , preferably 0.005 to 0.2 g / m ² . When the coating amount is less than 0.001 g / m ² , the uniformity of the coating thickness may be insufficient. On the other hand, when the coating amount exceeds 0.3 g / m ² , the slipperiness decreases. It may cause problems. If the refractive index of the coating layer is low, 0.001~0.05g / ^{m 2,} preferably in the range of 0.005~0.03g / ^{m 2.} In this case, if it exceeds 0.05 g / m ² , sufficient performance may not be exhibited depending on the surface functional layer to be laminated.

  The average absolute reflectance of light having a wavelength of 400 to 800 nm on the surface of the coating layer is in the range of 5.5 to 6.5%, more preferably 5.7 to 6.3%. When the average value of the absolute reflectance is out of this range, reflection from the interface between the coating layer and the polyester film increases, and depending on the surface functional layer to be laminated, sufficient performance may not be exhibited.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yoji Harasaki in 1979.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 280 ° C. for 3 to 200 seconds as a guide.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  According to the laminated polyester film for optics of the present invention, it is possible to provide an optical film excellent in antireflection performance when various surface functional layers are laminated, and its industrial value is high.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows.

(1) Measurement of intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. It was dissolved and measured at 30 ° C.

(2) Measurement of average particle diameter (d ₅₀ : μm) Integration (weight basis) 50% in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) Was the average particle size.

(3) Measuring method of absolute reflectance average value from one layer surface in polyester film In advance, a black tape (vinyl tape VT-50 manufactured by Nichiban Co., Ltd.) is pasted on the measurement back surface of the polyester film, and a spectrophotometer (Inc. Shimadzu Corporation UV-3100PC type) was used to measure the absolute reflectance of the coating layer surface at an incident angle of 5 °, a wavelength range of 400 to 800 nm, a sampling pitch of 1 nm, a slit width of 2 nm, and a low scanning speed. The average value was calculated from the obtained absolute reflectance values for each wavelength of 1 nm.

(4) Evaluation method of anti-reflective ability Purple light (trademark) by Nippon Synthetic Chemical Industry Co., Ltd. was apply | coated to the application layer side of a laminated polyester film, and it dried at 80 degreeC for 1 minute, and removed the solvent. Next, while the film was run at a feeding speed of 10 m / min, ultraviolet rays were irradiated using a mercury lamp under the conditions of irradiation energy of 120 W / cm and irradiation distance of 10 cm to obtain a film having a surface functional layer having a thickness of 5 μm. . The obtained film was visually observed under a three-wavelength light region type fluorescent lamp, and interference unevenness was observed.

The polyester used in the examples and comparative examples was prepared as follows.
<Manufacture of polyester>
100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, the temperature is raised by heating, methanol is distilled off, transesterification is performed, and 4 hours are required from the start of the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, 0.04 part of ethyl acid phosphate, 0.03 part of antimony trioxide and 0.01 part of silica particles having an average particle diameter of 1.5 μm were added, and then the temperature reached 280 ° C. and the pressure reached 15 mmHg in 100 minutes. After that, the pressure was gradually reduced after that to finally reach 0.3 mmHg. After 4 hours, the system was returned to normal pressure to obtain polyethylene terephthalate having an intrinsic viscosity of 0.61.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
・ Polyester resin: (A)
Water dispersion monomer composition of polyester resin copolymerized with the following composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1,4-butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)
・ Acrylic resin: (B)
Emulsion polymer of methyl methacrylate / ethyl acrylate / acrylonitrile / N-methylol methacrylamide = 45/45/5/5 (molar ratio) (emulsifier: anionic surfactant)
-Urethane resin: (C)
An aqueous polyurethane resin aqueous paint obtained by the following method was used. That is, first, a polyester polyol comprising 664 parts of terephthalic acid, 631 parts of isophthalic acid, 472 parts of 1,4-butanediol, and 447 parts of neopentyl glycol was obtained. Next, 321 parts of adipic acid and 268 parts of dimethylolpropionic acid were added to the obtained polyester polyol to obtain a pendant carboxyl group-containing polyester polyol A. Further, 160 parts of hexamethylene diisocyanate was added to 1880 parts of the above polyester polyol A to obtain an aqueous polyurethane resin aqueous paint.
Organic compounds having metal elements: ( D ) Titanium triethanolamate Alkenyl substituted nadiimide ( E ):
A compound represented by the following formula (1) was used.

・ビスフェノールＡ構造を有するエポキシ化合物：（Ｆ）
ビスフェノールＡとエピクロロヒドリンを水酸化ナトリウム存在下で反応させて得られた、平均分子量が約４００のエポキシ化合物
・ヘキサメトキシメチルメラミン：（Ｇ）
・粒子：（Ｈ） 平均粒径６５ｎｍのシリカゾル

-Epoxy compound having bisphenol A structure: ( F )
Epoxy compound with an average molecular weight of about 400, obtained by reacting bisphenol A and epichlorohydrin in the presence of sodium hydroxide: hexamethoxymethylmelamine: ( G )
-Particles: ( H ) Silica sol having an average particle size of 65 nm

Example 1:
The produced polyethylene terephthalate was dried at 180 ° C. for 4 hours in an inert gas atmosphere, melted at 290 ° C. by a melt extruder, extruded from a die, and cooled by setting the surface temperature to 40 ° C. using an electrostatic application adhesion method. It cooled and solidified on the roll and the unstretched sheet was obtained. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the roll peripheral speed difference, and then the coating solution 2 shown in Table 1 below was applied to the longitudinally stretched film. The film was stretched 3.7 times at 120 ° C, heat-treated at 225 ° C, then relaxed by 2% in the lateral direction, and the coating layer was laminated so that the coating amount (after drying) was 0.01 g / m ^2. A polyester film having a thickness of 100 μm was obtained.

  The average value of the absolute reflectance of the finished laminated polyester film was 6.0%. When the antireflection ability after laminating the surface functional layer was observed, the visibility was good. The properties of this film are shown in Table 2 below.

Example 2
In Example 1, it manufactured like Example 1 except having changed the coating composition into the coating amount and coating composition which are shown to Table 1, 2, and obtained the laminated polyester film. The finished polyester film was as shown in Table 2.

Comparative Examples 1 and 2:
In Example 1, it manufactured like Example 1 except having changed the coating agent composition into the coating amount and coating agent composition which are shown to Table 1, 2, and obtained the laminated polyester film. When the finished laminated polyester film was evaluated, as shown in Table 2, the antireflection ability was deteriorated.

  The film of the present invention can be suitably used for, for example, LCDs, PDPs, organic ELs, and other optical applications for producing display members, and applications that place importance on visibility.

Claims (1)

A coating film containing an aromatic-containing imide compound or a polyester film stretched in at least uniaxial direction having a coating layer formed from a coating liquid containing a compound having a bisphenol A structure and a melamine compound, and the coating layer surface An optically laminated polyester film, wherein the average absolute reflectance of light having a wavelength of 400 to 800 nm is 5.5 to 6.5%.