KR100958597B1 - White polyester film for liquid crystal reflector and surface light source using the same - Google Patents

Abstract

(Problem) This invention provides the white polyester film for liquid crystal reflectors excellent in the prevention of burr generation at the time of punching, adhesion of dust, handling property when it is made into sheet | leaf, and oligomer precipitation prevention property, and the surface light source using the same.

(Resolution) The white polyester film for liquid crystal reflector of the present invention and the surface light source using the same have an antistatic layer containing polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative, and the surface resistivity of the surface of the antistatic layer is 1 × 10 ¹³ Ω. Or less, and the amount of oligomer on the surface of the antistatic layer side after heat treatment at a temperature of 560 nm at a wavelength of 560 nm of 95% or more, total light transmittance of 10% or less and 180 ° C. for 30 minutes is 3.0 mg / m 2. It is characterized by the following.

White polyester film for liquid crystal reflector, surface light source

Description

White polyester film for liquid crystal reflector and surface light source using this {WHITE POLYESTER FILM FOR LIQUID CRYSTAL REFLECTOR AND SURFACE LIGHT SOURCE USING THE SAME}

 The present invention relates to a white polyester film for a liquid crystal reflector and a surface light source using the same.

Biaxially oriented polyester films represented by polyethylene terephthalate (PET) films have been used in a wide range of fields such as industrial materials, magnetic recording materials and packaging materials because of their good mechanical strength, thermal properties, humidity characteristics and many other excellent properties.

As display devices such as notebooks, car navigation systems and televisions, displays using liquid crystals are widely used, but white polyester films are generally used as these reflecting plates. Since these liquid crystal displays do not emit light by themselves, a surface light source called a backlight unit is provided on the back side and light is irradiated to the liquid crystal screen side from this to express the function of the display. As a light irradiation method from a backlight unit, a direct type which directly arranges a cold cathode tube which is a light source directly under a display, and a side light which uniformly irradiates light from the edge of a plate called a light guide plate by placing a cold cathode tube beside a display. The brother method is widely used. The reflecting plate is a sheet member provided on the rearmost surface of the direct type or side light type backlight unit in order to use these lights efficiently, and reflects the light leaked to the rear side to the liquid crystal screen side to improve the brightness of the liquid crystal screen. The function to improve is provided.

In recent years, the functional demand for a reflecting plate has also increased, for example, the white polyester film which added together an inorganic particle pigment and an incompatible resin in order to raise whiteness for the purpose of providing a more high quality, and at the same time raise reflectance (patent document 1). And 2), a white polyester film (see Patent Document 3) and the like, which have simultaneously achieved thinning and high reflectance, have been proposed.

However, in recent years, not only optical characteristics such as reflectance and whiteness, but also improvement in processing efficiency and handling are required. For example, when the roll-shaped product is punched out according to the size of the display, if the reflector is electrostatic, burrs may be generated or dust may be attached, causing trouble. In addition, when static electricity is applied to the reflective plate in the shape of a sheet formed by punching, and the like, the handleability at the time of conveyance is reduced. In addition, since heat is generated when used as a display, PET oligomers may be precipitated from the surface of the film when used for a long period of time, which may cause a decrease in luminance and a failure.

(Patent Document 1) Japanese Patent Application Laid-Open No. 4-153232

(Patent Document 2) Japanese Patent Application Laid-Open No. 6-322153

(Patent Document 3) Japanese Patent Application Laid-Open No. 2004-330727

In view of such a situation, this invention improves such a fault at once, and is excellent in the prevention of the generation | occurrence | production of a burr, the adhesion of dust at the time of a punching process, the handleability at the time of single sheet, the prevention of oligomer precipitation, etc. It is an object to provide an ester film and a surface light source using the same.

In order to achieve such an object, the white polyester film for liquid crystal reflecting plates of this invention, and the surface light source using the same consist of the following structures. That is, the white polyester film for liquid crystal reflectors of the present invention and the surface light source using the same have an antistatic layer containing polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative, and the surface specific resistance of the surface of the antistatic layer is 1 × 10 ¹³ Ω / □ For a liquid crystal reflector having a light reflectance of 95% or more, a total light transmittance of 10% or less, and an oligomer amount of 3.0 mg / m 2 or less on the surface of the antistatic layer after heat treatment at 180 ° C. for 30 minutes. It is a white polyester film.

And the white polyester film for liquid crystal reflecting plates of this invention, and the surface light source using the same have the following preferable forms.

(a) the antistatic layer contains polythiophene and / or polythiophene derivative, and the surface resistivity of the surface of the antistatic layer is 1 × 10 ¹³ Ω / □ or less

(b) the antistatic layer is a coating layer stretched in at least one direction

(c) The polyester film contains a thermoplastic resin which is incompatible with the polyester, and contains fine bubbles therein.

(d) apparent density of 0.9 g / cm 3 to 0.6 g / cm 3

(e) A titanium compound is used as a polymerization catalyst of the polyester constituting the polyester film.

(f) the polyester film is a simultaneous biaxially stretched film

(g) Being a surface light source using the said white polyester film for liquid crystal reflectors

ADVANTAGE OF THE INVENTION According to this invention, the white polyester film for liquid crystal reflectors excellent in the prevention of burr generation at the time of punching processing, adhesion of dust, handling property when it is made into sheet | seat, oligomer precipitation prevention, etc., and the surface light source using the same can be obtained.

Hereinafter, the white polyester film for liquid crystal reflecting plates of this invention and the surface light source using the same are demonstrated in detail. The polyester film which is a base material of the white polyester film for liquid crystal reflecting plates of this invention is comprised from polyester fundamentally.

Polyester used in this invention is a high molecular compound which makes ester bond the main bond chain of a main chain, and can be obtained by polycondensation of dicarboxylic acid and diol. Examples of the dicarboxylic acid component include aromatic dichas such as terephthalic acid, isophthalic acid, diphenylcarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, 5-sodium sulfoisophthalic acid and phthalic acid. Alicyclic dicarboxylic acids such as aliphatic dicarboxylic acids such as carboxylic acid, oxalic acid, succinic acid, eicoic acid, adipic acid, sebacic acid, dimer acid, dodecanedioic acid, maleic acid and fumaric acid, and cyclohexane dicarboxylic acid And polyfunctional acids such as acid, trimellitic acid and pyromellitic acid. As the diol component, for example, aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, neopentyl glycol and triethylene glycol, aromatic glycols such as bisphenol A and bisphenol S, diethylene glycol and polytetra Methylene glycol, and the like.

Among the polyesters, various additives such as antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic stabilizers, organic and inorganic particles, pigments, dyes, fillers, optical brighteners, antistatic agents and nucleating agents impair the effects of the present invention. You may add in the range which is not performed.

Moreover, when a titanium catalyst is used as a polymerization catalyst of polyester, there are few aggregates, and it is a more preferable form. Examples of the titanium-based polymerization catalyst include titanium alkoxides such as titanium alkoxides such as titanium tetrabutoxide and titanium tetraisopropoxide, and polyesters obtained by obtaining composite oxides or titanium complexes composed of titanium and silicon whose main metal elements are titanium. It is preferable to use 0.0005 to 0.15 weight% in conversion.

The polyester used in the present invention is preferable because polyethylene terephthalate and polyethylene naphthalate are excellent in terms of water resistance, durability, chemical resistance, and the like.

Although the total thickness of the white polyester film for liquid crystal reflecting plates of this invention is suitably selected according to the use which the white polyester film for liquid crystal reflecting plates of this invention is used, it does not specifically limit, but high reflectivity, handleability, productivity, etc. Preferably it is 30-500 micrometers from a point, Most preferably, it is 75-300 micrometers.

The polyester film of this invention needs to be white in order to provide reflectivity. In order to make it white, it is preferable to add an inorganic particle, organic microparticles | fine-particles, etc. in polyester. The said component may be independent or may use 2 or more types together. Among the inorganic fine particles, for example, calcium carbonate, magnesium carbonate, zinc carbonate, titanium dioxide (ananatase type, rutile type), zinc oxide, barium sulfate, zinc sulfide, basic lead carbonate, mica titanium, antimony oxide, magnesium oxide, phosphoric acid Calcium, silica, alumina, mica, talc, kaolin and the like can be used. Among these, it is especially preferable to use calcium carbonate and barium sulfate (precipitated barium sulfate) which have little absorption in the visible light region of 400-700 nm. If there is absorption in the visible light region, problems such as a decrease in reflectance may occur. In the case of organic fine particles, it is preferable not to melt by melt extrusion, and crosslinked fine particles such as crosslinked styrene and crosslinked acrylic are particularly preferable. The said microparticles may be individual or may use 2 or more types together.

Moreover, in order to raise whiteness and provide high reflectivity, it is most preferable to add polyester and an incompatible thermoplastic resin in polyester. By containing incompatible resin with polyester, many fine bubbles generate | occur | produce in a film, and light is scattered and whitened by this bubble. Thereby, high reflectivity can be provided. In order to form this fine bubble, it is achieved by disperse | distributing a high melting point incompatible resin finely in polyester which is a film mother body, and extending | stretching this. At the time of stretching, bubbles are formed around the incompatible resin, and since this exerts a scattering effect on light, it is possible to whitenize and obtain a high reflectance. Examples of the incompatible resins include polyolefin resins such as polyethylene, polypropylene, polybutene, and polymethylpentene, cyclic polyolefins, polystyrene resins, polyacrylate resins, polycarbonate resins, polyacrylonitrile resins, polyphenylene sulfide resins, and fluorine. Resins and the like are suitably used. These may be a homopolymer or a copolymer, and may use 2 or more types together. Particularly preferred are resins having a large critical surface tension difference with polyester, which are hard to be deformed by heat treatment after stretching, and polyolefin resins and polymethylpentene are particularly preferred.

As addition amount of the said incompatible resin, 5 weight% or more and 30 weight% or less are preferable with respect to polyester which is a mother, More preferably, they are 10 weight% or more and 25 weight% or less. If less than this, the effect of whitening is weak and high reflectivity is not obtained, which is not preferable. Moreover, when more than this, mechanical properties, such as the intensity | strength of the film itself, become low, and are unpreferable.

It is preferable that the incompatible resin is more uniform in its dispersed state. By being uniformly dispersed, bubbles are formed uniformly inside the film, which increases the degree of whitening, and further, the reflectance becomes uniform. In order to disperse | distribute incompatible resin uniformly, it is effective to add a low density agent as a dispersion adjuvant. A low density agent is a compound which has the effect of improving the dispersibility of incompatible resin and making a density small by having affinity with respect to both polyester and an incompatible resin, and the effect is confirmed by a specific compound. For example, for polyester, polyalkylene glycols such as polyethylene glycol, methoxy polyethylene glycol, polytetramethylene glycol, polypropylene glycol, ethylene oxide / propylene oxide copolymers, sodium dodecylbenzenesulfonate and sodium alkylsulfonate Salt, glycerin monostearate, tetrabutylphosphonium paraaminobenzene sulfonate and the like. In the case of the film of the present invention, polyethylene glycol and polybutylene terephthalate / polyether copolymer are particularly preferred. As addition amount, 0.1 weight% or more and 5 weight% or less are preferable with respect to polyester which is a mother, More preferably, they are 0.5 weight% or more and 4 weight% or less. If the amount added is less than this, the effect of improving dispersibility is small, which is not preferable. Moreover, when more than this, film forming stability may fall. Such a low-density agent can be previously added to the film matrix polymer and adjusted as a master chip.

As for the apparent density of the white polyester film for liquid crystal reflecting plates in this invention, 0.9 g / cm <3> -0.6g / cm <3> is preferable, More preferably, it is 0.8g / cm <3> -0.7g / cm <3>. When the apparent density is larger than 0.9 g / cm 3, bubbles are insufficiently formed in the film, and the reflectance is low, which is not preferable. When the apparent density is smaller than 0.6 g / cm 3, bubbles in the film are excessively formed, and film forming stability is lowered, which is not preferable. As a method of making an apparent density into the said range, although the method of adding 5 weight% or more and 30 weight% of said incompatible resin with respect to the polyester film which is a mother can be mentioned preferably, It is not limited to this.

 Although the polyester film used as a base material in this invention may be either a single layer or a multilayer structure, when it is set as a multilayer structure, different polyester prescriptions can be taken in an inner layer and an outer layer, and it is preferable on the surface design of a film. Especially, the three-layer structure of A-layer / B-layer / A-layer is the most preferable aspect. Here, the A layer may consist of a plurality of layers, and, if the A layers on both sides existing between the B layers are the same as the basic skeleton of the polymer of 80 mol% or more, different compositions within the range not impairing the effects of the present invention. And particle addition amount. That is, the three-layer structure like A-layer / B-layer / A 'layer may be sufficient. In this case, layer B is a layer containing bubbles, and layer A is a layer containing the inorganic / organic particles and the like described above. With such a configuration, it is possible to obtain high reflectivity in the B layer, and to obtain an effect of improving mechanical strength, further improving reflectance, and improving the degree of freedom in surface design in the A layer.

It is preferable that the light reflectance of wavelength 560nm in the surface of the white polyester film for liquid crystal reflecting plates in this invention is 95% or more, More preferably, it is 98% or more. If the reflectance is lower than 95%, the reflectance at the time of use as the liquid crystal reflector is insufficient, and the brightness (luminance) of the liquid crystal screen is insufficient, which is not preferable. In addition, although the upper limit of a reflectance is not specifically limited, The state with too high reflectance is a state in which the bubble is formed excessively, It is preferable that it is 110% or less from the point of film forming stability. Although the method of making a reflectance into the said range is not specifically limited, As mentioned previously, it can achieve suitably by adding polyester, an incompatible thermoplastic resin, and inorganic fine particles which form a bubble in polyester, and generate | occur | producing a bubble in an extending process. have. The reflectance here is a relative reflectance at an incident angle of 8 ° in 560 nm visible light measured on the basis of a barium sulfate standard plate. For example, a barium sulfate (Shimadzu) was cut in a state in which a film sample was cut to 25 mm x 50 mm (orienting the long axis direction and the length direction of the film) and attached to a spectrophotometer UV-2450 manufactured by Shimadzu Corporation, with a 60 mmφ integrating sphere unit ISR-2200. Corporation designated part: 200-53627) was used as a standard plate, and the reflectance at the incident angle of 8 ° in 560 nm visible light was measured.

It is preferable that the total light transmittance of the white polyester film for liquid crystal reflecting plates in this invention is 10% or less, More preferably, it is 7% or less, Most preferably, it is 5% or less. If the total light transmittance is larger than 10%, the amount of light leakage to the reflector increases, which is not preferable because the brightness (luminance) of the liquid crystal display is insufficient. The lower limit of the total light transmittance is not particularly limited, but in the state where the transmittance is too low, bubbles are excessively formed or the film thickness is too thick, and therefore it is preferably 1% or more from the point of film forming stability. Although the method which makes total light transmittance into the said range is not specifically limited, It can achieve suitably by making an organic / inorganic particle | grain, a incompatible thermoplastic resin, etc. in a polyester film, and making film thickness about 75-250 micrometers. have. Total light transmittance here is the ratio of the light which permeate | transmitted the parallel light of wavelength 550nm to a film with the integral type light transmittance measuring apparatus, and transmitted the film with respect to incident light. The film sample is cut into 25 mm x 50 mm (align the long axis direction and the length direction of the film), and Suga Test Instruments Co., Ltd. The total light transmittance is measured according to Japanese Industrial Standards (JIS) K-7105 using the haze computer HZ-2 of the product.

 In the present invention, it is necessary to have an antistatic layer containing polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative at least on one side in order to achieve the object of the present invention. That is, by having an antistatic layer, it is possible to suppress the generation of static electricity, and thus it is effective to improve burr generation during the punching process, to prevent the adhesion of dust, and to handle the sheet. have. In addition, the antistatic layer is preferably a coating layer formed by stretching an aqueous coating liquid in at least one direction after application of an aqueous coating solution from the viewpoints of environmental pollution prevention, explosion proofing, manufacturing cost, and the like in the film production, It is preferable to form in the manufacturing process of axial orientation. In order to enable aqueous coating, it is essential to form an antistatic agent with a component having high water dispersibility. Polystyrene sulfonic acid and / or polystyrene sulfonic acid derivatives are extremely preferred as a component of the antistatic agent of the present invention because of extremely high water dispersibility and stretching followability. Although the timing of the said stretching is not specifically limited, The method of biaxial stretching after apply | coating an aqueous coating liquid, or the method of apply | coating an aqueous coating liquid after longitudinal (longitudinal direction of film) extending | stretching, and further transverse stretching are used preferably. . Various coating methods such as a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a die coating method, and a spray coating method can be preferably used as the coating method of the aqueous coating liquid, but are limited thereto. It is not.

Although the molecular weight of the polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative which can be used in the present invention is not particularly limited, the weight average molecular weight is preferably 1000 to 1000000, more preferably 5000 to 150000 in terms of stability and conductivity of the coating agent. to be.

In addition, as for the thickness of the antistatic layer in this invention, 10-1000 nm is preferable normally, More preferably, it is 15-200 nm, Most preferably, it is 30-100 nm. If the thickness of the antistatic layer is too thin, the antistatic function will be poor. In addition, when the thickness of the antistatic layer is too thick, it is not preferable because the appearance is inferior, the antistatic layer is dropped in the manufacturing process, or the manufacturing cost of the film is high.

Moreover, in the antistatic layer in this invention, in the range which does not impair the effect of this invention, for example, polyester resin, a polyurethane resin, antioxidant, a heat stabilizer, a weather stabilizer, a ultraviolet absorber, an organic lubricating agent, a pigment, You may mix | blend dye, organic or inorganic fine particles, a filler, an antistatic agent, a nucleating agent, etc. The lubricating agent and the fine particles have an effect of improving the slipperiness of the film to facilitate handling. The average particle diameter of the lubricant and the fine particles is preferably 50% to 500% of the thickness of the antistatic layer. If the average particle diameter is less than 50%, the slidability effect is insufficient, and if it exceeds 500%, the releasing agent or fine particles tend to fall off. Moreover, the effect which raises adhesiveness with the base polyester film of the polyester resin mix | blended is anticipated.

The surface specific resistance of the surface of the antistatic layer is preferably 1 × 10 ¹³ Ω / □ or less, more preferably 1 × 10 ¹⁰ Ω / □ or less, most preferably 1 × 10 ⁸ Ω / □ or less. When the surface specific resistance exceeds 1 × 10 ¹³ Ω / □, it is difficult to improve the trouble in the machining process due to the poor antistatic performance. Although the lower limit of surface specific resistance is not specifically limited, It is preferable that it is 1 * 10 <^{5> (} ohm) / square or more from a viewpoint of manufacturing cost or film forming stability. Surface specific resistance here is an electrical resistance value ((ohm / square)) when electricity is sent to the film surface. For example, the film sample is allowed to stand for 24 hours under measurement conditions (temperature 25 ° C., relative humidity 65%), and then applied under an atmosphere using a digital ultra-high resistance / microammeter R8340A (manufactured by Advantest Corporation) for 10 seconds at an applied voltage of 100V. After the measurement is performed.

In the white polyester film for liquid crystal reflector of the present invention, in addition to the polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative, the polyaniline-based conductive agent, tin oxide-based conductive agent, polythiophene and / or polythiophene which are conjugated electron conductors in addition to the polystyrene sulfonic acid and / or polystyrene sulfonic acid derivatives It is more preferable to further include a system derivative. The conjugated electron conductor is preferable because the amount of change in the antistatic performance due to humidity is very small since the electron conductive mechanism does not depend on the moisture in the air, and by adding them, higher antistatic properties are preferable. In particular, polythiophene and / or polythiophene derivatives are particularly preferred forms because they are excellent in transparency of coating film, adhesiveness with base polyester film, and coating appearance.

The polythiophene and / or polythiophene derivatives are very difficult to disperse as a single substance, and are easily dispersed or aqueous by polymerization in the presence of polystyrene sulfonic acid and / or polystyrene sulfonic acid derivatives. Moreover, it is thought that the function as an acid also functions as a dopant of a polythiophene type compound.

The polythiophene and polythiophene derivative which is a conjugate electron conductor can be obtained by superposing | polymerizing the compound represented by following General formula (1) or following General formula (2), for example in presence of a polyanion.

In the general formula (1), R ₁ and R ₂ each independently represent a hydrogen atom, an aliphatic hydrocarbon group having 1 to 12 carbon atoms, an alicyclic hydrocarbon group or an aromatic hydrocarbon group, for example, a methyl group, an ethyl group, a propyl group, and isopropyl Group, a butyl group, a cyclohexylene group, and a phenyl group. In addition, in said General formula (2), n is an integer of 1-4.

In the white polyester film for liquid crystal reflecting plates of this invention, it is preferable to use the polythiophene or polythiophene derivative which consists of a structural formula represented by the said General formula (2), for example, n = 1 in General formula (2). (Methylene group), n = 2 (ethylene group) and n = 3 (propylene group) are preferable. Especially preferred is a compound of n = 2 ethylene group, that is, poly-3,4-ethylenedioxythiophene. As a polythiophene or a polythiophene derivative, the compound which the functional group couple | bonded with the 3-position and 4-position of a thiophene ring is illustrated, for example. As mentioned above, the compound which the oxygen atom couple | bonded with the carbon atom of 3-position and 4-position is preferable. For a compound having a structure in which a carbon atom or a hydrogen atom is directly bonded to the carbon atom, aqueous coating of the coating liquid may not be easy.

 In the present invention, a polystyrene sulfonic acid and / or a polystyrene sulfonic acid derivative is preferably present in an excessive amount in a solid weight ratio with respect to a polythiophene or a polythiophene derivative in terms of conductivity, and polythiophene or polythiophene is preferable. The polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative is preferably 1 part by weight to 5 parts by weight, and more preferably 1 part by weight to 3 parts by weight with respect to 1 part by weight of the derivative.

Further, the composition consisting of the polythiophene or polythiophene derivative and polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative is disclosed in, for example, Japanese Patent Application Laid-Open No. 6-295016, Japanese Patent Application Laid-Open No. 7-292081, and Japanese Patent Application Laid-Open. Although it can manufacture by the method as described in 1-313521, Unexamined-Japanese-Patent No. 2000-6324, the specification of European patent 602713, the specification of US Pat. No. 5391472, etc., methods other than these may be sufficient.

For example, 3,4-ethylenedioxythiophene is obtained using an alkali metal salt of 3,4-dihydroxythiophene-2,5-dicarboxyester as a starting material, and then potassium peroxodisulfate and iron sulfate in an aqueous polystyrene sulfonic acid solution. And 3,4-ethylenedioxythiophene obtained first and reacted to obtain the above-mentioned composition, in which polythiophene such as poly (3,4-ethylenedioxythiophene) and a polyanion compound such as polystyrene sulfonic acid are complexed.

It is preferable that the antistatic treatment layer in this invention contains the said polythiophene or a polythiophene derivative, a polystyrene sulfonic acid and / or a polystyrene sulfonic acid derivative, and a crosslinking agent. As a crosslinking agent, a melamine type crosslinking agent, an epoxy type crosslinking agent, an oxazoline type crosslinking agent, an isocyanate type crosslinking agent, an acrylamide type crosslinking agent, etc. can be used, for example. It is preferable that the said crosslinking agent is a crosslinking agent whose molecular weight is 1000 or less, More preferably, it is 800 or less, More preferably, it is 600 or less. In particular, by using a water-soluble crosslinking agent having a molecular weight of 1000 or less, flexibility and fluidity in the stretching process are expressed, the stretching followability after drying of the mixture forming the laminated film is increased, and the whitening phenomenon due to cracking of the coating film is suppressed to give transparency. do. When the molecular weight becomes too large, there is a tendency for transparency to decrease because cracks occur in the coating film at the time of stretching after application and drying. Moreover, it is preferable that the temperature at which the heat loss rate of an epoxy type crosslinking agent becomes 5% is 230 degreeC or more, More preferably, it is 250 degreeC or more, Especially preferably, it is 270 degreeC or more. When the temperature at which the heat loss rate is 5% is less than 230 ° C., the epoxy component may be dispersed in the manufacturing process of the polyester film, particularly in the lateral stretching to heat treatment oven, to contaminate the process.

Especially as said crosslinking agent, an epoxy type crosslinking agent, especially a water-soluble epoxy type crosslinking agent is especially preferable, and can form the antistatic layer excellent in transparency, antistatic property, and the appearance of a coating film. Although the kind of epoxy crosslinking agent is not specifically limited, For example, sorbitol polyglycidyl ether type, polyglycerol polyglycidyl ether type, diglycerol polyglycidyl ether type, polyethyleneglycol diglycidyl ether type, and polyethyleneglycol diglycol Cyl ether ether and the like can be used. For example, the epoxy compound "DENACOL" (trademark) from Nagase ChemteX Corporation (EX-611, EX-614, EX-512, EX-521, EX-412, EX-313, EX-810, EX-830, EX). -850 etc.), Sakamoto Yakuhin Kogyo Co., Ltd. Diepoxy polyepoxy clock compound (SR-EG, SR-8EG, SR-GLG, etc.), Dainippon Ink and Chemicals, Inc. The product epoxy crosslinking agent "EPICLON" EM-85-75W or CR-5L etc. can be used suitably.

The solid content mixing ratio of the polythiophene or polythiophene derivative and the composition consisting of polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative and the crosslinking agent is determined by the composition of the composition consisting of polythiophene or polythiophene derivative and polystyrene sulfonic acid and / or polystyrene sulfonic acid derivative. When the sum of the solid content and the solid content of the crosslinking agent is 100 parts by weight, the solid content of the crosslinking agent is preferably 30 parts by weight to 90 parts by weight, more preferably 50 parts by weight to 85 parts by weight. In the case where the solid content of the crosslinking agent is more than 90 parts by weight, antistatic properties are less likely to be expressed. In addition, when the solid content of the crosslinking agent is less than 30 parts by weight, cracks tend to occur in the antistatic layer, resulting in inferior transparency or antistatic property.

The white polyester film for liquid crystal reflecting plates in this invention has an oligomer amount of 3.0 mg / m <2> or less on the surface of an antistatic layer after heat-processing at 180 degreeC for 30 minutes, More preferably, it is 2.0 mg / m <2> or less, Most preferably, 1.0 mg / m 2 or less. When the amount of oligomer on the surface of the antistatic layer after heat treatment at 180 ° C. for 30 minutes exceeds 3.0 mg / m 2, the oligomer is precipitated on the surface of the film due to heat generation when actually used for a long time as a display, resulting in a decrease in luminance or an electronic device portion. It is not preferable because it may cause failure due to the mixing of oligomers. Although the minimum of oligomer precipitation amount is not specifically limited, It is preferable that it is 0.4 mg / m <2> or more from a viewpoint of manufacturing cost and film forming stability.

In the present invention, the amount of oligomer precipitation is a polyester film is heat-treated in an oven at 180 ° C. for 30 minutes, the antistatic treatment layer side of the polyester film is immersed in a dimethylformamide solvent for 3 minutes, and a cyclic oligomer of polyethylene terephthalate (3 Dimer Purity 89%) Measured by high performance liquid chromatography (HPLC) using a standard solution, the amount of cyclic trimers obtained. Measurement conditions are described later.

Moreover, it does not specifically limit as a method of suppressing oligomer precipitation amount, It is preferable to have a coating film layer containing a water dispersible acrylic resin. It is because precipitation of an oligomer is easy to be prevented by the surface energy difference of an acrylic resin coating film layer and a film. The water-dispersible acrylic resin is, for example, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylol acrylamide, N-butoxyacrylamide, 2-hydroxyethyl methacrylate, 2-hydroxyethyl acrylate Although copolymers of monomers, such as alkyl acrylate which has a C12-C25 alkyl group in a side chain, etc. are mentioned, It is not limited to these. In these water-dispersive acrylic resins, it is preferable that an average emulsion particle diameter is 50-200 nm, and it is preferable to use a uniform thing so that it may become a distribution. In order to give higher oligomer precipitation prevention property, it is preferable to add the component which has an oligomer precipitation prevention function to a coating film layer. Examples of the component having an oligomer precipitation preventing function include, but are not limited to, long chain alkyl acrylates, fluorine acrylates, silicone compounds, polyolefin compounds, and the like. Since these components have a larger surface energy difference from the film than the water-based acrylic resin, higher oligomer precipitation prevention properties are obtained.

It is preferable that the polyester film which comprises the white polyester film for liquid crystal reflecting plates of this invention is a biaxially oriented film. A biaxially-oriented polyester film is manufactured by extending | stretching the polyester sheet or film of a non-stretched state to a longitudinal direction and the width direction in a so-called biaxial direction, and shows the pattern of biaxial orientation by wide-angle X-ray diffraction. The method of stretching in the biaxial direction may be either a sequential biaxial stretching method or a simultaneous biaxial stretching method, but in the case of simultaneous biaxial stretching, the surface of the film is less likely to be damaged, and online coating can be performed at a low speed. There is an advantage.

The surface light source formed by using the white polyester film for liquid crystal reflector of the present invention may be in any form as long as it emits a light beam uniformly from a plane serving as an emission surface, but a surface light source generally called a backlight is preferable.

In addition, there are various means for introducing the luminous flux emitted from the light source between the reflecting surface and the emitting surface, but (A) at least a rectangular light guide plate, a point or line light emitting source, and a luminous flux emitted from the induced light source. A surface light source (edge backlight) using means for introducing from one light incident edge or two light incident edges of opposite sides to each other, (B) a plurality of linear fluorescent tubes at least parallel to the back side of the fluorescent tube It is particularly preferable to use a surface light source (direct type backlight) having a structure in which a light reflector is disposed.

As the light emitting source, a point or linear light source is preferable. LEDs, fluorescent tubes, organic or inorganic electric luminescence and the like are preferably used. The light source color is preferably close to achromatic color. The number of these light sources may be single or plural, and other light sources may be mixed.

[Measurement method of characteristics and evaluation method of effects]

The measuring method of the characteristic and the evaluation method of an effect in this invention are as follows.

 (1) surface resistivity

The film sample was allowed to stand for 24 hours under measurement conditions (temperature 25 ° C, 65% relative humidity), and then applied with 100 V of applied voltage for 10 seconds using a digital ultra-high resistance / microammeter R8340A (manufactured by Advantest Corporation) under the atmosphere. Was performed.

 (2) light reflectance of wavelength 560nm

 The film sample is cut into 25 mm x 50 mm (align the long axis direction and the length direction of the film), and barium sulfate (Shimadzu Corporation-designated parts) with a 60 mm φ integrating sphere unit ISR-2200 mounted on a spectrophotometer UV-2450 from Shimadzu Corporation. (200-53627) as a standard plate, the reflectance at 8 ° inclination at 560 nm was measured.

 (3) apparent density

 Ten pieces of film samples were cut into 100 mm x 100 mm sizes using an SD-type lever type sample cutting machine SDL-100 (manufactured by DUMBBELL CO., LTD.), And each was named an electronic scale. Next, a thickness of 8 points per sheet was measured with a calibrated digital micrometer (M-30, manufactured by Sony Precision Technology Inc.), and the average thickness was calculated for each sample and calculated by the following equation.

Apparent density (g / cm 3) = nominal weight (g) ÷ {average thickness (μm) x 100 (mm) x 100 (mm) ÷ 10 ⁶ }.

(4) total light transmittance

The film sample is cut into 25 mm x 50 mm (align the long axis direction and the length direction of the film), and Suga Test Instruments Co., Ltd. The total light transmittance was measured according to Japanese Industrial Standard (JIS) K-7105 using the haze computer HZ-2 of the product.

 (5) Evaluation of Burr Whiskers

 50 sheets of test samples are prepared by punching the film into a size of 100 mm x 100 mm using the SD-type lever type sample cutting machine SDL-100 (manufactured by DUMBBELL CO., LTD.). The end surface was confirmed with a handy microscope (x50-x200 times), and it determined as follows. △ or more is a pass. Defective product is defined as "one or more burr whiskers 0.5mm or more per inspection sample".

○: 2 or less defective products occur in 50 sheets

△: 3 or more and 5 or less defective products occur in 50 sheets

×: 6 or more defective products occur in 50 sheets

(6) handleability at the time of sheetfed (conveyance test)

50 sheets of film samples cut to A4 size were prepared, and left to stand in an oven at 45 ° C. for 2 hours in order to remove the winding marks. After curing for 1 hour at room temperature, the sample was provided to a digital multifunction device (manufactured by Matsushita Graphic Communication Systems, Inc., Workio DP-4510) and subjected to a transfer test using a copy mode. By this test, it confirmed whether there were no conveyance defects, such as a bending and shrinking, and made it the evaluation of the handleability of a polyester film. Judgment is as follows, and (triangle | delta) or more is a pass.

○: No return defects out of 50 sheets

(Triangle | delta): The conveyance defect generate | occur | produces once or three times in 50 sheets.

X: 4 or more conveyance defects generate | occur | produce in 50 sheets.

(7) adhesion of dust (ash test)

The white polyester film cut | disconnected to A4 size was humidified for 24 hours in 23 degreeC and the measurement atmosphere of 50% RH. The wet film surface was rubbed 10 times with a friction cloth (100% wool). 1.5 g of the tobacco material preliminarily dried at 70 ° C. for 1 hour was gradually brought into close contact with the tabletop in a range of 10 cm × 10 cm. Adhesion of the tobacco material was visually determined. △ or more is a pass.

○: not attached even if the film is in contact with the ash

△: adhered when the film is in contact with the ash

×: adhered only to the film close to the ash

(8) Quantification of oligomer precipitation

The polyester film was heat-processed for 30 minutes in 180 degreeC oven. Thereafter, the film was bonded to a 50 mm x 50 mm surface of a 50 mm x 50 mm x 30 mm rectangular aluminum jig with the antistatic treatment layer on the outside, and the end was bent and fixed along the jig. The jig was immersed in a dimethylformamide solvent for 3 minutes to a position having a depth of 5 mm with the film face down, and the surface precipitation oligomer was extracted.

Next, 11.2 mg of a cyclic oligomer (89% of trimer purity) of polyethylene terephthalate was added to a 100 mL volumetric flask as a standard solution, and a mixed solvent of 1,1,1,3,3,3-hexafluoro-2-propanol / chloroform After dissolving in 2 mL of (= 1/1), it was diluted to 100 mL with chloroform as a standard stock solution (trimer concentration of 100 µg / mL). This solution was diluted sequentially with dimethylformamide, and the standard solution of trimer concentration of 10 microgram / mL, 1 microgram / mL, and 0.1 microgram / mL was adjusted.

The surface oligomer extraction solvent and the standard solution were analyzed by high performance liquid chromatography (HPLC) under the following conditions, and the amount of cyclic trimers was measured to obtain an oligomer amount.

Device: Shimazu LC-10A

Column ： Inertsil ODS-3

Mobile phase: acetonitrile / water = 70/30

Flow rate: 1.5 mL / min

Detector: UV242nm

Injection volume: 10 μl

Example

Although an Example is given to the following and this invention is demonstrated in more detail, this invention is not limited to a following example, unless the summary is exceeded.

(Example 1)

Using the composite film forming apparatus which has an extruder (a), an extruder (b), and a T-die die compounding | diffusion, it was set as the 3-layer laminated polyester film which consists of the following A layer and B layer. The laminated structure is A / B / A.

First, resin which forms A layer is demonstrated. 28% by weight of PET pellets containing calcium carbonate particles (CaCO ₃ (50)) containing 50% by weight of calcium carbonate particles having an average particle diameter of 1.0 μm, 5% by weight of the optical brightener “OB-1” (Eastman Kodak Company) Polyethylene terephthalate pellets containing 1% by weight of a fluorescent brightener master PET pellet (OB (5)) containing and an ethylene glycol slurry of a citrate chelate titanium compound as a polymerization catalyst so as to be 0.01% by weight in terms of titanium atoms. PET, melting point 255 ° C.) 72% by weight of the mixture was vacuum dried at a temperature of 160 ° C. for 5 hours, then fed to the extruder (a), and melt-extruded at a temperature of 280 ° C., followed by foreign material filtration by a 30 μm cut filter. After performing, it was introduce | transduced into T-shaped die complex detention.

Next, resin which forms B layer is demonstrated. 20% by weight of polymethylpentene (Mitsui Chemicals, Inc., TPX DX820 (hereinafter referred to as PMP)), polybutylene terephthalate / polyether copolymer (Du Pont-Toray CO., LTD., Hytrel Incompatible resin-containing PET pellets (PMP (20) -H) containing 4.0% by weight of 7247 (hereinafter referred to as Hytrel)) and 0.7% by weight of polyethylene glycol (hereinafter referred to as PEG) having a molecular weight of 4000 The mixture adjusted to 75% by weight and 25% by weight of PET pellets was vacuum dried at a temperature of 180 ° C. for 3 hours, then supplied to the extruder side, and melt-extruded at a temperature of 280 ° C., followed by a 30 μm cut filter. After filtration, the mixture was introduced into a T-die die complex.

Subsequently, the polyester layer (A) is joined to both surface layers of the polyester layer (B) so as to be laminated (A / B / A) in the T-shaped die composite mold, and then co-extruded into a sheet to form a molten laminated sheet. Then, the molten laminated sheet was tightly cooled and solidified by an electrostatic charge method on a drum maintained at a surface temperature of 18 ° C to obtain an unstretched laminated film. Subsequently, after preheating the said unstretched laminated | multilayer film by the roll group heated to the temperature of 80 degreeC in accordance with a conventional method, 3.3 times extending | stretching is performed in the longitudinal direction (lateral direction) using the heating roll of 86 degreeC temperature, It cooled by the roll group of 25 degreeC temperature, and obtained the uniaxial stretched film.

Subsequently, the corona discharge treatment was given to both surfaces of the obtained uniaxial stretched film in air, and the surface tension was 50 mN / m or more, and the antistatic layer coating liquid of the following composition was apply | coated on both sides homogeneously by the bar coat method.

<Antistatic layer coating liquid>

The aqueous solution which mixed the following antistatic layer coating liquid A1, antistatic layer coating liquid B1, and antistatic layer coating liquid C1 by 20 weight part / 80 weight part / 20 weight part by active ingredient ratio was used.

Antistatic layer coating liquid A1

A composite consisting of polyethylenedioxythiophene / polystyrene sulfonic acid and an aqueous coating liquid ("Denatron" (R) 5002RZ from Nagase ChemteX Corporation) in which a polyester resin was dispersed in water were used.

Antistatic layer coating liquid B1

An aqueous solution in which a polyglycerol polyglycidyl ether-based epoxy crosslinker (Nagase ChemteX Corporation "DENACOL" (R) EX-512) was dissolved in water was used.

Antistatic layer coating liquid C1

An aqueous solution in which 10% by weight of a long chain alkyl acrylate having the following copolymerization composition was dissolved in water containing 10% by weight of isopropyl alcohol and 5% by weight of butyl cellosolve was used.

(Copolymerization component)

Methacrylic acid 40 parts by weight

Stearyl methacrylate 60 parts by weight

2 parts by weight of N-methylol acrylamide

2 parts by weight of anionic reactive emulsifier

As the anionic reactive emulsifier, "Eleminol" JS-2 (manufactured by Sanyo Kasei Kogyo K.K.) was used.

Both ends of the uniaxial stretched film coated on both sides are guided to the preheating zone at 95 ° C in the tenter while holding the clip with a clip, and then continuously perpendicular to the longitudinal direction in the heating zone at a temperature of 100 ° C continuously (horizontal direction). It was extended by 3.4 times. Subsequently, heat treatment was performed for 10 seconds at a temperature of 210 ° C. in the heat treatment zone in the tenter, and further subjected to a 4% transverse direction at a temperature of 200 ° C., followed by a relaxation treatment at a temperature of 150 ° C. in a 1% direction. Was further performed. Subsequently, after refrigerating uniformly, it wound up and made the three-layer composite structure of A-layer / B-layer / A-layer whose thickness of a polyester layer (A) and a polyester layer (B) is 15/220/15 (micrometer). The white polyester film for liquid crystal reflectors of 250 micrometers was obtained. The results are shown in Table 1 and Table 2. Stable antistatic property and reflectivity were shown, and moldability was also favorable. The amount of oligomer precipitation was also small.

(Examples 2-5, Comparative Examples 1-6)

The white polyester film for liquid crystal reflecting plates was obtained according to Example 1 except having used the conditions shown in Table 1 and Table 2 using resin which comprises following A layer and B layer and an antistatic agent.

PET pellets containing titanium dioxide particles TiO ₂ (50)

Titanium dioxide particle-containing PET pellets (TiO ₂ (50)) containing 50% by weight of titanium dioxide particles having a number average particle diameter of 0.3 µm were used.

PET pellet PMP (20) -P containing incompatible resin

Incompatible resin-containing PET pellets containing 20% by weight of PMP, 2% by weight of PEG, and 0.05% by weight of hindered phenolic antioxidant "IRUGANOX" (registered trademark) 1010 (manufactured by Ciba Specialty Chemicals KK) (PMP (20 ) -P) was used.

Barium sulfate-isophthalic acid copolymer PET pellets BaSO ₄ (50)

A barium sulfate-isophthalic acid copolymerized PET pellet (BaSO ₄ (50)) containing 50% by weight of barium sulfate particles having a number average particle diameter of 1 µm was used.

Antistatic layer coating liquid D1

Polydiallyldimethylammonium chloride (average molecular weight: about 30000) was used.

Antistatic layer coating liquid E1

Melamine crosslinker, Dainippon Ink and Chemicals, Inc. Product, "Beckamine" J101 was used.

Antistatic layer coating liquid C2

An aqueous solution in which 10% by weight of a long chain alkyl acrylate having the following copolymerization composition was dissolved in water containing 10% by weight of isopropyl alcohol and 5% by weight of butyl cellosolve was used.

(Copolymerization component)

Methacrylic acid 40 parts by weight

Behenyl methacrylate 60 parts by weight

2 parts by weight of N-methylol acrylamide

2 parts by weight of anionic reactive emulsifier

In addition, anionic reactive emulsifiers were used as "Eleminol" JS-2 (manufactured by Sanyo Kasei Kogyo K.K.).

Antistatic coating liquid D2

An aqueous dispersion in which particulate matter of an acrylic resin (glass transition point 40 ° C.) having the following copolymerization composition was dispersed in water was used.

(Copolymerization component)

65 parts by weight of methyl methacrylate

35 parts by weight of ethyl acrylate

1 part by weight of acrylic acid

2 parts by weight of N-methylol acrylamide

Antistatic coating solution F1

The aqueous solution which melt | dissolved polystyrene sulfonate ammonium salt (weight average molecular weight: 10000) in water was used.

Antistatic coating solution D3

The aqueous dispersion which disperse | distributed the particulate matter of hydrophilic acrylic resin (glass transition point: 40 degreeC) in water was used.

Antistatic coating solution F2

The aqueous solution which melt | dissolved the polystyrene sulfonate lithium salt (weight average molecular weight: 10000) in water was used.

Antistatic coating solution D4

Copolymerized polyester resin consisting of 70 mol% of terephthalic acid, 23 mol% of isophthalic acid and 7 mol% of 5-sodium sulfoisophthalic acid as an acid component, and 70 mol% of ethylene glycol and 30 mol% of diethylene glycol as a diol component (glass Transition point: 55 ° C.).

In addition, in Example 2, only one side was apply | coated, and in Example 4, it extended | stretched using the simultaneous biaxial stretching method. In addition, the comparative example 1 was set as the single film using the T-shaped die mold | die for a single layer.

Example 2: The reflectance was slightly inferior but usable. The antistatic property was also good. Although only one side was apply | coated, there was no problem in moldability. Significantly high oligomer precipitation protection.

Example 3: Both reflectance and antistatic property were slightly inferior but usable. Although the incidence rate of burr whisker was slightly high, it was an acceptable range level. The oligomer precipitation amount was also no problem.

Example 4: Both reflectance and antistatic properties were slightly inferior but usable. The handling at the time of sheetfighting also had no problem practically. Although cracks generate | occur | produced at the time of film forming whether the density was a little low, it was a level which can form film stably. The amount of oligomer precipitation was slightly high but was acceptable.

Example 5 Although reflectance and antistatic property were all slightly inferior, it was a usable level. Although the density was slightly high because there were many inorganic particles in B layer, there was no problem in reflectance. The amount of oligomer precipitation was slightly high but was acceptable.

Comparative example 1: Although the value of the transmittance | permeability is appropriate, it is inferior to reflectance, density, and an antistatic property, and the level was not enough to exhibit a desired function. Moreover, the amount of oligomer precipitation was also large.

Comparative Example 2: Although the density value was appropriate, the reflectance, the transmittance, and the antistatic property were all inferior, and the level was insufficient for the desired function.

Comparative example 3: Although the transmittance | permeability value was appropriate, it was inferior to reflectance, a density, and antistatic property, and the level was not enough to exhibit a desired function. In addition, since the antistatic layer was a polyester resin, the amount of oligomer precipitation was also large.

Comparative example 4: Although it was excellent in antistatic property, there was no problem in generation | occurrence | production of a burr, etc., but it was inferior in reflectance, a transmittance | permeability, and a density, and the liquid crystal reflector lacked optical characteristics.

Comparative example 5: Although the reflectance was excellent and the transmittance | permeability and the density value were also suitable, since the problem of moldability, such as generation | occurrence | production of burr, was inferior to antistatic property, the solution of this subject was not reached. Moreover, the amount of oligomer precipitation was also large.

Comparative Example 6: Although the reflectance and the transmittance were excellent, it was not suitable for practical use because the density was small and the film cracks were inferior, resulting in inferior film forming stability. In addition, the amount of oligomer precipitation was small, but the antistatic property was insufficient.

The white polyester film for a liquid crystal reflector of the present invention and the surface light source using the same are excellent in moldability during punching processing and handling when used as a single sheet for large-sized televisions requiring high processing efficiency and yield, and liquid crystal reflector for notebooks. The oligomer precipitation prevention property can improve the problem in each process, and can improve productivity and the quality of a product remarkably, and it is useful.

Claims (8)

Having an antistatic layer containing at least one of polystyrene sulfonic acid and at least one of polystyrene sulfonic acid derivatives on one side, Further, the surface specific resistance of the surface of the antistatic layer is 1 × 10 ⁵ Ω / □ or more and 1 × 10 ¹³ Ω / □ or less, Moreover, the light reflectance of wavelength 560nm in the said surface is 95% or more, Total light transmittance is 10% or less, The amount of oligomer on the antistatic layer side surface after heat processing at 180 degreeC for 30 minutes is 3.0 mg / m <2> or less, The white polyester film for liquid crystal reflecting plates characterized by the above-mentioned. The antistatic layer according to claim 1, wherein the antistatic layer contains at least one of a polythiophene and a polythiophene derivative, and the surface specific resistance of the surface of the antistatic layer is 1 × 10 ⁵ Ω / □ or more and 1 × 10 ¹⁰ Ω / □ or less. The white polyester film for liquid crystal reflectors characterized by the above-mentioned. The white polyester film for liquid crystal reflecting plate according to claim 1 or 2, wherein the antistatic layer is a coating layer stretched in at least one direction. The white polyester film for liquid crystal reflecting plates according to claim 1 or 2, wherein the white polyester film contains a thermoplastic resin which is incompatible with the polyester, and contains fine bubbles therein. The apparent polyester is 0.9g / cm <3> -0.6g / cm <3>, The white polyester film for liquid crystal reflection plates of Claim 1 or 2 characterized by the above-mentioned. The white polyester film for liquid crystal reflecting plate according to claim 1 or 2, wherein a titanium compound is used as a polymerization catalyst of the polyester constituting the white polyester film. The said white polyester film is a simultaneous biaxially stretched film, The white polyester film for liquid crystal reflecting plates of Claim 1 or 2 characterized by the above-mentioned. The surface light source which consists of using the white polyester film for liquid crystal reflection plates of Claim 1 or 2.