JP2007177202A - Antistatic polyester film and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antistatic polyester film improved in antistatic property and optical physical property. <P>SOLUTION: This antistatic polyester film is produced by laminating/coating an antistatic layer on one side surface or on both of the surfaces of the polyester film by an in-line method, and laminating/coating a light-dispersing layer on the antistatic layer by an off-line method. When the polyester film is used as a light-dispersing film of an LCD display, a uniform antistatic property is obtained and also excellent characteristics capable of reducing a peeling electric charge without deteriorating photo characteristics caused by the elution under a high temperature and a high humidity, and dissolving defects caused by the static electricity generated on peeling are obtained. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an antistatic polyester film. More specifically, one or more antistatic layers are coated and laminated on one or both sides of a polyester film by an inline method, and a light diffusion layer is formed on the antistatic layer by an off-line method. The present invention relates to a polyester film in which antistatic properties and optical properties are improved by coating and laminating and a method for producing the same.

  In recent years, with the progress of industrialization, the damage caused by the generation of static electricity has increased in various fields ranging from various electronic and electrical equipment, information and communication fields and general household goods. It has been an issue. Antistatic means that the charge accumulated on the surface of the insulator is discharged by an appropriate method. In order to prevent antistatic, an antistatic layer that can discharge the charge accumulated on the surface of the product is used. What is necessary is just to form. In particular, in the film manufacturing process to which impurities and dust adhere, discharge occurs in the process of processing the film. If an organic solvent is used in these processes, there is a risk of ignition. In addition, when this type of film is used as a material for electric / electronic parts, it causes static damage, and thus it has been an essential requirement to provide antistatic performance in the use of these films.

  On the other hand, off-line coating is conventionally used to solve problems such as discharge, contamination, and foreign matter adsorption caused by static electricity when manufacturing diffusion films and sheeting operations and assembling on BLU (backlight unit). A method of giving an antistatic function to the light diffusion layer when the light diffusion layer is laminated has been used. In order to impart an antistatic function to the light diffusion layer, a metal substance such as lithium, copper, magnesium, calcium, iron, cobalt, or nickel was added to the light diffusion layer composition. However, the method of adding a metal substance to the light diffusing layer as described above has a limitation that it is difficult to obtain sufficient antistatic properties and high luminance characteristics besides being inferior in economic efficiency.

  As another conventional method for imparting an antistatic function, there is a method of carrying out an antistatic coating between a film and a light diffusion layer. The antistatic agent used at this time is a surfactant or an anion or cation type polymer. When a diffusion coating is applied to the coating surface, the antistatic agent is charged depending on the humidity in the atmosphere. In general, it exhibits a prevention function, but the light diffusion layer laminated on the antistatic layer makes it difficult to come into contact with moisture in the air, resulting in a decrease in the antistatic function. Particularly, the surfactant type antistatic agent deteriorates the adhesion between the antistatic layer and the light diffusing layer, and acts as a factor for decreasing the brightness on the detachment of the diffusion layer or on the BLU, thereby deteriorating the light characteristics. In addition, when the antistatic agent is used in combination with the light diffusion layer composition, it dissolves into the surface under high temperature and high humidity conditions, and turns into a light foreign substance such as white spots or black spots on the surface of the diffusion layer. There was a problem to do.

  In addition, when an antistatic layer is added between the film and the light diffusion layer, an off-line coating method in which the diffusion layer and the antistatic layer are usually formed separately is used, thereby increasing the number of coating steps and manufacturing costs. In addition to increasing the diffusion layer, it is possible to reduce costs by mixing the adjustment liquid for the diffusion layer and the adjustment liquid for the antistatic layer and performing coating at the same time. The mixing process with the adjustment liquid for the prevention layer is difficult, the diffusion layer is not well cured by the antistatic agent, and elution occurs during coating.

  The present invention is for solving the above-mentioned problems, and the object thereof is to achieve high antistatic property and economical efficiency by forming an antistatic layer coating in an in-line manner between the polyester film and the light diffusion layer. It is to provide an antistatic polyester film.

  Another object of the present invention is to provide a method for producing an antistatic polyester film that achieves high antistatic properties and economy by coating an antistatic layer between the polyester film and the light diffusion layer in an in-line manner. There is.

  To achieve the above object, the present invention provides a polyester film, an antistatic layer coated on one or both sides of the polyester film by an inline method, and a light diffusion layer coated and stacked on the antistatic layer by an off-line method. And an antistatic polyester film characterized by comprising a layer.

  The in-line method includes Mayer bar coating, gravure coating, reverse roll coating, extrusion die coating, knife over roll coating and kiss coating. Any one method selected from the group consisting of coating) is used.

  The antistatic layer preferably contains a conductive polymer, a binder resin and a cross-linking agent, and more preferably 200 to 2,000 parts by weight of a binder resin and 40 to 100 cross-linking agents with respect to 100 parts by weight of the conductive polymer. The solid content is 0.5 to 10% by weight.

  The conductive polymer is preferably produced by polymerizing a polyanion and polythiophene or a derivative thereof.

  The binder resin is preferably one or more functional groups selected from the group consisting of carbonyl group, hydroxyl group, acrylic group, urethane group, carboxyl group, amide group, imide group, carboxylic acid, maleic acid and maleic anhydride. Use one containing a group.

  The cross-linking agent is preferably one or more compounds selected from the group consisting of isocyanate, carbonylimide, oxazoline, epoxy and melamine.

  The light diffusion layer contains a light diffusion resin and light diffusion particles.

  According to another aspect of the present invention, there is provided a method for coating a polyester film, the method comprising: coating an antistatic layer on one or both sides of the polyester film in an in-line manner; and offline coating the coated antistatic layer. And a step of coating the light diffusion layer by a method.

  The in-line method is preferably a Mayer bar coating, gravure coating, reverse roll coating, extrusion die coating, knife over roll coating, kissing. Any one method selected from the group consisting of kiss coating is used.

  The in-line coating is preferably performed after the uniaxial stretching process of the polyester film.

  In the antistatic polyester film according to the present invention, the antistatic agent is coated on the polyester film in an inline manner, so that the off-line coating process is omitted and the cost is low, and the surrounding environment, particularly humidity and other physical influences (scratches) The effect that permanent antistatic properties can be maintained regardless of the above is obtained. Further, the effect of reducing the generation of optical foreign matters during in-line coating can be obtained. Furthermore, when the antistatic polyester film of the present invention is used for a light diffusing film of an LCD display, uniform antistatic properties can be obtained, and peeling / charging is reduced without degradation of light characteristics due to elution under high temperature and high humidity. Defects caused by static electricity generated during peeling can be eliminated.

  Therefore, the antistatic polyester film of the present invention has an excellent characteristic that the production cost is low while the antistatic property is excellent as compared with the conventional antistatic polyester film.

  Hereinafter, the present invention will be described in more detail.

  In an antistatic polyester film according to an embodiment of the present invention, an antistatic layer having an antistatic function is laminated on a polyester film as a base layer in an in-line manner, and light is diffused on the laminated antistatic layer. A light diffusion layer having a function is laminated in an off-line manner.

  Hereinafter, the polyester film which is a base material layer is demonstrated concretely.

  The polyester film used in the present invention is a polymer material with high transparency, and any material having excellent mechanical strength and durability including scratch resistance can be used. A known material known as a material film may be used.

  In the present invention, polyester resin such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate will be mainly described, but the present invention is not limited to this. The polyester constituting the film refers to a polyester obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid. Examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical examples of polyester include polyethylene terephthalate (PET) and polyethylene-2,6-naphthalenedicarboxylate (PEN). As the polyester, a copolymer containing other components can also be used.

  Examples of the dicarboxylic acid component of the copolymer polyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (for example, P-oxybenzoic acid). Examples of the glycol component include ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol, and the like. Two or more of these dicarboxylic acid components and glycol components may be used in combination. The film of the present invention uses a uniaxial or biaxially oriented film having high transparency and excellent productivity and workability.

  The polyester film must have excellent light transmission in order to prevent light loss during light transmission, and preferably should be easy to adhere to the antistatic layer. The light transmittance of the light diffusion sheet containing the polyester film is desirably 90% or more.

  A polyester film having a thickness of 25 μm to 250 μm is used. The thickness of the polyester film depends on the size of the backlight unit. In small backlight units used for mobile phones, PDAs, etc., polyester films of 100 μm or less are mainly used. In medium-sized backlight units used in notebooks, monitors, etc., polyester films of about 50 μm to 188 μm are used, and large-sized used in televisions and the like. In the backlight unit, a polyester film of 125 μm or more is preferably used. As described above, the thickness of the polyester film increases in proportion to the size of the backlight unit. This is because the larger the backlight unit, the more light sources used and the heat generated from these light sources. This is to increase the heat resistance of the polyester film.

  Next, the antistatic layer will be specifically described.

  The antistatic layer is coated in an in-line manner on the polyester film as the base material layer. This in-line method is a process in which a melt-extruded polyester sheet is uniaxially stretched in the length direction or width direction, and then coated on one or both sides of the stretched sheet. It is also possible to perform coating after stretching in both directions. Such in-line coating is a process that provides high performance under high-speed conditions, and is therefore very competitive in terms of productivity. However, it is very difficult to develop and apply coating coating solutions and coating process conditions, as it is done under high speed conditions. The in-line type coating is not particularly limited unless it is an off-line type, and is preferably a Mayer bar coating, a gravure coating, a reverse roll coating, an extrusion die coating, a knife. Any method selected from the group consisting of over roll coating and kiss coating can be used.

  As the antistatic layer, a conventional humidity-dependent antistatic composition such as a surfactant can be used as long as it can be coated on a polyester film in an in-line manner. However, in order to improve the antifouling property and antistatic ability of the antistatic layer, preferably, the antistatic layer uses an antistatic composition containing a conductive polymer, a binder resin and a crosslinking agent.

  Specifically, the conductive polymer resin contained in the antistatic layer is preferably used by mixing polythiophene or a derivative thereof with a polyanion in order to impart antistatic properties. Specifically, the conductive polymer is obtained by polymerizing compounds represented by the following general formula 1 (Chemical formula 1) and the following general formula 2 (Chemical formula 2) alone or in the presence of a polyanion. Can do.

R ₁ and R ₂ in the above general formula 1 each independently represent a hydrogen atom, a C _1-12 aliphatic hydrocarbon group, an alicyclic hydrocarbon group or an aromatic hydrocarbon group. , Methyl group, ethyl group, propyl group, isopropyl group, butyl group and benzene group.

  N in the said General formula 2 is an integer of 1-4.

  The poly anion is an acidic polymer, and includes high molecular carboxylic acid, high molecular sulfonic acid, polyvinyl sulfonic acid, and the like. Examples of the polymeric carboxylic acid include polyacrylic acid, polymethacrylic acid, and polymaleic acid. Examples of the polymeric sulfonic acid include polystyrene sulfonic acid.

  On the other hand, in the present invention, an aqueous dispersion of a polymer containing 0.5% by weight of poly (3,4-ethylenedioxythiophene) and 0.8% by weight of polystyrene sulfonic acid (molecular weight Mn = 150,000) ( Baytron P, Bayer).

  The binder resin contained in the antistatic layer is a water acid or water-soluble binder resin, which contributes to improving the adhesion between the antistatic layer and the polyester film as the base film, and is based on 100 parts by weight of the conductive polymer resin. 200 to 2000 parts by weight are added. If the binder resin content is less than 200 parts by weight, there is a problem that it is difficult to provide adhesion to the substrate, and if it exceeds 2000 parts by weight, it is difficult to provide transparency and antistatic properties.

The binder resin has one or more functional groups selected from the group consisting of carbonyl group, hydroxyl group, acrylic group, urethane group, carboxyl group, amide group, imide group, carboxylic acid, maleic acid and maleic anhydride. Including.
As the binder resin containing the functional group, any one or more of polyacrylic, polyurethane, epoxy, polyester, vinyl resin, and amide resin can be used. Each of these compounds can have a substantially complex structure by copolymerization or the like in each skeleton structure. Examples of binders having a complex structure include acrylic graft polyester, acrylic graft polyurethane, vinyl resin graft polyester, vinyl resin graft. Examples include polyurethane.

  The cross-linking agent contained in the antistatic layer is used to improve the adhesion with the polyester film as the antistatic layer base film, and preferably from isocyanate-based, carbonylimide-based, oxazoline-based and melamine-based compounds. Any one or more selected from the group consisting of: Further, 40 to 400 parts by weight of the crosslinking agent is added to 100 parts by weight of the conductive polymer resin. Here, if the addition is less than 40 parts by weight, it is difficult to obtain adhesiveness because sufficient curing is not achieved, and if it exceeds 400 parts by weight, transparency is impaired.

  The antistatic layer is coated with a polyester film after being diluted with a solvent so that the solid content is 0.5 to 10.0% based on the total weight. As the solvent, any solvent can be used as long as it dissolves the solid content of the present invention and can be coated on the polyester film, and preferably water is used. On the other hand, if the solid content is less than 0.5% by weight, film formation and antistatic function expression of the coating layer are insufficient, and if it exceeds 10.0% by weight, the transparency of the film decreases. There's a problem.

  On the other hand, in order to improve the safety, wettability and leveling of the antistatic layer, alcohols such as ethanol and isopropanol, ethers such as ethyl cellosolve and t-butyl cellosolve, One or more kinds of ketones such as methyl ethyl ketone and acetone, amines such as dimethylethanolamine or ionic / nonionic surfactants can be mixed and used in the antistatic layer. On the other hand, the preferable thickness of the antistatic layer is 0.5 to 0.2 μm, but is not limited thereto.

  Next, the light diffusion layer will be described.

  The light diffusing layer is formed in a direction in which light incident on the polyester film is emitted, and is also referred to as a “front light-diffusing layer”. The light diffusion layer diffuses light by refracting and scattering incident light.

  On the other hand, the light diffusing layer of the present invention is composed of a light diffusing resin and light diffusing particles dispersed in the resin. As the light diffusing resin, either a thermosetting resin or a photocuring resin can be used as long as it is a curable resin. Examples of the thermosetting resin include urea resin, melamine resin, phenol resin, epoxy resin, unsaturated polyester resin, alkyd resin, urethane resin, acrylic resin, polyurethane, fluorine resin, silicon resin and polyamideimide. It is desirable to use one selected from the group consisting of the following groups, but the invention is not limited to this, and a colorless and transparent one is preferred because it must transmit light. As the photocurable resin, any of acrylic, urethane, or epoxy resins or a resin having a composite structure of these resins can be used. On the other hand, the light diffusing resin can contain a dispersant, a smoothing agent, an antifoaming agent, or the like for applicability.

  The light diffusion layer particles of the present invention can be used with either organic particles or inorganic particles, and can be used alone or in combination. For the organic particles, polymethyl methacrylate is mainly used, and other polystyrenes and copolymers thereof can also be used. For inorganic particles, polysilicon and silicon oxide, titanium oxide, zirconium oxide, magnesium fluoride, etc. are used. The size of the particles can be varied, usually using a mixture of particles having a size of 2 or more, but this can be used to fill gaps that can arise from using single size particles. Because it is useful. On the other hand, the size of the particles used and the ratio of the particles to the resin can be various combinations, which are determined based on the optical properties of the polyester film. If the particle content is high, the light transmittance decreases due to the protrusion of the particles, and the particles are likely to fall off, which may cause problems in workability. It becomes difficult to ensure the light diffusibility.

  Meanwhile, in one embodiment of the present invention, the coating thickness of the light diffusion layer can be varied depending on the light diffusion particles used.

  In another embodiment of the present invention, when the light diffusion layer is laminated only on one side of the antistatic layer, an antiblocking layer may be laminated on the opposite side of the light diffusion layer on which the antistatic layer is laminated. It is.

  The method for producing an antistatic polyester film according to the present invention includes a step of coating an antistatic layer in an inline manner on one or both sides of the polyester film, and offline coating on the coated antistatic layer. Coating the light diffusing layer in a manner.

  In this invention, the polyester film which is the said base film can be manufactured by a well-known method. In the present invention, the polyester resin is melted in an extruder after being vacuum-dried, formed into a sheet with a tee die (T-DIE), this sheet is brought into close contact with a cooling roll by an electrostatic application method (pinning), and is cooled and solidified. A stretched polyester sheet is obtained. In a roll heated to a temperature higher than the glass transition temperature of the polyester resin, the film was stretched in the longitudinal direction by 2.5 to 4.5 times depending on the difference in the peripheral speed ratio between the rolls. Then, a uniaxially stretched oriented film was obtained by stretching 3.0-7.0 times and heat-setting in a transverse stretching apparatus that mechanically stretches the film continuously fixed to the clip. The produced uniaxially oriented film may be subjected to a corona discharge treatment in order to facilitate lamination with an antistatic layer and improve coatability.

  The above-mentioned polyester film is coated with the above-mentioned antistatic agent in an in-line manner to form an antistatic layer. This in-line method is preferably a Mayer bar coating, gravure coating, reverse roll coating, extrusion die coating, knife over roll coating, kissing. Any method selected from the group consisting of kiss coating is used.

  Thereafter, the above-described light diffusing agent is coated on the antistatic layer by an off-line method to form a light diffusing layer.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, these Examples are illustrated in order to demonstrate this invention more concretely, The scope of the present invention is limited to these Examples. Not.

[Production Example; Production of Polyester Fill]
After the polyester raw material resin is vacuum-dried, it is melted and extruded using an extruder, and the molten high-temperature polyester resin is formed into a sheet shape with a rotating cooling roll through a die, and then the sheet is cooled by an electrostatic application method. An unstretched polyester sheet was obtained by bringing it into close contact. The unstretched polyester sheet was stretched 3 times in the length direction while passing on a roll preheated to 70 to 120 ° C. to obtain a uniaxially stretched polyester film. Thereafter, a corona discharge treatment was performed on one side of the obtained uniaxially stretched polyester film.

[Example 1]
On the corona-treated surface of the polyester film produced in the above production example, 100 parts by weight of a conductive polymer resin (Bayer, Baytron P) and 400 parts by weight of an acrylic binder resin (Nippon Carbide, Y8003B) are used as solid components. An antistatic coating solution prepared by mixing 100 parts by weight of an epoxy crosslinking agent (Nagase Chemtech, DENACOL EX-313) with water was applied. That is, the solid content was 2.0% by weight with respect to the total antistatic coating solution, and this antistatic coating solution was applied using a # 8 Mayer bar which is one of in-line coating devices. After coating, in the 100-130 ° C tender section, the applied coating solution is dried, stretched 3.5 times in the direction perpendicular to the traveling direction of the film, and heat treated at 240 ° C for 4 seconds, thereby biaxial stretching of 25 µm thickness An antistatic polyester film was obtained.

  The composition having the composition shown in Table 1 below was applied to the surface of the manufactured antistatic polyester film on which the antistatic layer was laminated by an off-line method, and then dried at 110 ° C. for 60 seconds to obtain a thickness of 15 μm. A light diffusion layer was formed.

  By applying an anti-blocking layer coating solution having the composition shown in Table 2 below on the back surface of the polyester film on which the light diffusion layer is formed, drying at 110 ° C. for 40 seconds to form an anti-blocking layer having a thickness of 5 μm. A final antistatic polyester film was produced.

[Example 2]
In the production stage of the antistatic coating liquid, based on solid content, 100 parts by weight of conductive polymer resin (Bayer, Baytron P), 500 parts by weight of urethane binder resin (Dainippon Ink Chemical, AP-40F), melamine crosslinking agent (Cytech, CYMEL385) 150 parts by weight were mixed with water to produce an antistatic coating solution. At this time, a film was produced in the same manner as in Example 1 except that the solid content was 2.0% by weight based on the total antistatic coating solution.

[Example 3]
In the production stage of the antistatic coating solution, 100 parts by weight of conductive polymer resin (Bayer, Baytron P), 400 parts by weight of polyester resin (Nippon Gosei, WOO30), epoxy cross-linking agent (Nagase Chemtech) , DENACOL EX-313) 100 parts by weight were mixed with water to produce an antistatic coating solution. At this time, a film was produced in the same manner as in Example 1 except that the solid content was 2.0% by weight based on the total antistatic coating solution.

[Comparative Example 1]
In the antistatic coating solution, 100 parts by weight of a quaternary ammonium antistatic agent (Cytech, CYSTAT09), 300 parts by weight of a urethane binder resin (Dainippon Ink Chemical, AP-40F), 50 parts by weight of a melamine crosslinking agent (Cytech, CYMEL385) The part was mixed with water to produce an antistatic coating solution. At this time, a film was produced in the same manner as in Example 1 except that the solid content was 2.0% by weight based on the total antistatic coating solution.

[Comparative Example 2]
In the antistatic coating solution, 100 parts by weight of a quaternary ammonium antistatic agent (Nippon Yushi Co., Ltd., Elegan 264-A), 200 parts by weight of an acrylic resin (Nippon Carbide, Y8003B), an epoxy cross-linking agent (Nagase Chemtech, DENACOLLEX- 313) An antistatic coating solution was prepared by mixing 50 parts by weight with water. At this time, a film was produced in the same manner as in Example 1 except that the solid content was 2.0% by weight based on the total antistatic coating solution.

[Comparative Example 3]
One side or both sides of the polyester film produced in the production example is not subjected to any antistatic treatment, stretched 3.5 times in the direction perpendicular to the film traveling direction, and heat treated at 240 ° C. for 4 seconds to be 125 μm thick biaxial A stretched antistatic polyester film was obtained.

  A light diffusion solution having the composition shown in Table 1 was applied to one side of the produced antistatic untreated polyester film by an off-line method, and then dried at 110 ° C. for 60 seconds to form a light diffusion layer having a thickness of 15 μm. After that, an anti-blocking layer coating solution to which an antistatic agent as shown in Table 3 below was added was applied in an off-line manner and then dried at 110 ° C. for 40 seconds to form a 5 μm thick anti-blocking layer. A final antistatic light diffusion film was produced.

[Comparative Example 4]
Without any antistatic treatment on one or both sides of the polyester film produced in the production example, the polyester film is stretched 3.5 times in the direction perpendicular to the traveling direction of the film and heat treated at 240 ° C. for 4 seconds. A biaxially stretched antistatic polyester film was obtained.

  After applying the composition comprising the composition shown in Table 1 on one side of the prepared antistatic untreated polyester film by an off-line method, drying at 110 ° C. for 60 seconds to form a light diffusion layer having a thickness of 15 μm Subsequently, a solution having the same composition as in Table 3 except for the antistatic agent was applied by an off-line method and dried at 110 ° C. for 40 seconds to form an antiblocking layer having a thickness of 5 μm. Then, the antistatic coating liquid which consists of a composition of following Table 4 was apply | coated by the off-line system on the antiblocking layer, and the final antistatic light-diffusion film was manufactured by drying at 110 degreeC for 40 second.

  The physical properties of the biaxially stretched films produced in Examples 1 to 3 and Comparative Examples 1 to 4 were evaluated by the following method. The results are shown in Table 5.

<1. Antistatic property>
After installing a sample in an environment of a temperature of 23 ° C. and a humidity of 50% RH using an antistatic measuring machine (Mitsubishi Corporation, model name: MCP-T600), surface resistance (Ω / □, Alternatively, Ω / cm ² ) was measured.

<2. Dissolution test>
The antistatic polyester film produced in the above examples and comparative examples was placed between two glass plates, and the elution test was performed for 300 hours with a constant temperature and humidity dryer under conditions of temperature 85 ° C. and humidity 85% RH. The presence or absence of the generation of a light foreign substance (eluent) generated between the diffusion film and the diffusion film was examined.

<3. Transparency (Haze)>
A sample sampled to a size of 10 cm × 10 cm is placed vertically on a haze measuring machine (AUTOMATIC DIGITAL HAZEMETER, manufactured by Nippon Denso Co., Ltd.), and light having a wavelength of 400 to 700 μm in the direction perpendicular to the vertically placed sample. The value at the time of transmitting was measured.

  At this time, the haze value is obtained by the following mathematical formula 1.

Haze (%) = (1− (amount of scattered light / total amount of transmitted light)) × 100 (1)
<4. Light transmittance measurement>
One light diffusing sheet sampled to a size of 10 cm × 10 cm using a Nippon Denso Co., Ltd. haze measuring machine (AUTOMATIC DIGITAL HAZEMETER) is placed vertically, and has a wavelength of 550 nm in the direction perpendicular to the sample placed vertically. The value when light was transmitted was measured. At this time, the haze value and the light transmittance are obtained by the following mathematical formulas 2 and 3.

Haze (%) = (1− (P / TT)) × 100 (2)
Light transmittance (%) = (TT / IT) × 100 (3)
However, P represents the amount of light traveling straight, TT represents the total amount of transmitted light, and IT represents the amount of incident light.

<5. Luminance measurement>
Luminance was measured using a 32 "direct-type backlight unit. First, after the diffusion film was cut, it was mounted on a light diffusion plate and measured at a measurement angle of 0 using a Topcon BM-7 measuring machine. .2 °, the distance between BM-7 and the backlight unit is 25 cm, and the brightness of the lamps at the 12 positions of the lamps and the 12 points of the space between the lamps is measured The difference between the value and the average brightness value of the part without the lamp was measured.

  As can be seen from Table 5, in the humidity-dependent antistatic resin, the antistatic function is lowered due to the presence of the diffusion coating, but it is confirmed that the conductive resin can have a stable and excellent antistatic function together with the diffusion characteristics. It was.

  Moreover, the antistatic product manufactured by the in-line method did not generate a light foreign matter after the elution test, but in Comparative Examples 3 to 4 where the antistatic function was given by the off-line method, between the glass plate and the diffusion plate. The photo foreign material was generated in

  Although the present invention has been described above with reference to specific embodiments, it is obvious to those skilled in the art that various changes and modifications can be made within the scope of the technical idea of the present invention. Such variations and modifications are to be understood as belonging to the appended claims.

Claims (12)

Polyester film,
An antistatic layer coated in an inline manner on one or both sides of the polyester film;
A light diffusion layer that is coated and stacked on the antistatic layer in an off-line manner;
An antistatic polyester film comprising:   The in-line method is any one method selected from the group consisting of Mayer bar coating, gravure coating, reverse roll coating, extrusion die coating, knife over roll coating, and kiss coating. The antistatic polyester film as described.   The antistatic polyester film according to claim 1, wherein the antistatic layer contains a conductive polymer, a binder resin, and a crosslinking agent.   The antistatic polyester film according to claim 3, wherein the antistatic layer contains 200 to 2,000 parts by weight of a binder resin and 40 to 100 parts by weight of a crosslinking agent with respect to 100 parts by weight of the conductive polymer. .   5. The antistatic polyester film according to claim 2, wherein the conductive polymer is produced by polymerizing a polyanion and polythiophene or a derivative thereof. 6.   The binder resin contains at least one functional group selected from the group consisting of carbonyl group, hydroxyl group, acrylic group, urethane group, carboxyl group, amide group, imide group, carboxylic acid, maleic acid and maleic anhydride. The antistatic polyester film according to claim 3 or 4, wherein the antistatic polyester film is used.   The antistatic agent according to claim 3 or 4, wherein the crosslinking agent is any one or more compounds selected from the group consisting of isocyanate, carbonylimide, oxazoline, epoxy, and melamine. Polyester film.   The antistatic polyester film according to claim 2, wherein the antistatic layer contains a solid content of 0.5 to 10% by weight.   The antistatic polyester film according to claim 1, wherein the light diffusion layer contains a light diffusion resin and light diffusion particles. In a method of coating a polyester film,
Coating an antistatic layer in-line on one or both sides of the polyester film;
Coating the coated antistatic layer with a light diffusing layer in an off-line manner;
A process for producing an antistatic polyester film, comprising:   The in-line method is any one method selected from the group consisting of Meyer bar coating, gravure coating, reverse roll coating, extrusion die coating, knife over roll coating, and kiss coating. The manufacturing method of the antistatic polyester film of description.   The method for producing an antistatic polyester film according to claim 10, wherein the in-line coating is performed after a uniaxial stretching process of the polyester film.