WO2009060978A1

WO2009060978A1 - Multilayer film

Info

Publication number: WO2009060978A1
Application number: PCT/JP2008/070533
Authority: WO
Inventors: Taro Ooya; Jun Iguchi; Hiroshi Kusume; Atsushi Oyamatsu
Original assignee: Teijin Dupont Films Japan Limited
Priority date: 2007-11-08
Filing date: 2008-11-05
Publication date: 2009-05-14
Also published as: CN101855081A; JP4988853B2; TWI449624B; TW200936373A; JPWO2009060978A1; KR20100089850A; KR101536024B1

Abstract

Disclosed is a multilayer film composed of a polyester film and a coating layer formed thereon and containing a phosphor. The multilayer film is characterized in that the phosphor in the coating layer is composed of an inorganic material, and the phosphor content in the coating layer is within the range of 5-80% by weight. The multilayer film is suppressed in yellowing over time, while having high luminance and less color shift. The multilayer film is suitable for reflector plates.

Description

Specification Laminated Film Technical Field

The present invention relates to a polyester film and a laminated film comprising a coating layer provided thereon. Background art

In recent years, liquid crystal display devices typified by liquid crystal televisions are rapidly spreading. A liquid crystal display device usually includes a side-type or direct-type backlight unit. In the backlight unit of LCD TVs, the direct light system has been adopted. In this method, cold cathode ray tubes are installed in parallel between the liquid crystal cell and the reflector plate located behind it. Reflectors used in backlight units of liquid crystal display devices are required to have high reflection performance. Conventionally, a film containing a white pigment or a film containing fine bubbles inside has been used as the reflector. Films containing a white pigment inside are widely used because they can obtain high brightness and uniform brightness. For example, Japanese Patent Application Laid-Open No. 2 0 0 4-0 5 0 4 7 9 0 0 4-3 3 0 7 2 7 is disclosed. In addition, films containing fine bubbles inside are disclosed in, for example, Japanese Patent Application Laid-Open Nos. 6-3 2 2 1 53 and 7-1 1 8 4 3 3. As a method for improving the luminance of the backlight unit, in addition to improving the reflectance of the film itself used for the reflector, it has been proposed to apply a fluorescent whitening agent to the film (Japanese Patent Laid-Open No. 2). 0 0 2-4 0 2 1 4). However, when fluorescent whitening agent is applied, the fluorescent whitening agent deteriorates due to ultraviolet light emitted from the cold cathode ray tube, and the film turns yellow over time. Disclosure of the invention

Problems to be solved by the invention

An object of the present invention is to provide a laminated film in which yellowing over time is suppressed. Another object of the present invention is to provide a laminated film that can obtain high luminance when used as a member of a backlight unit of a liquid crystal display device. Another object of the present invention is to provide a laminated film that can suppress yellowing over time, obtain high luminance, have little color shift, and is suitable as a reflector.

Means for solving the problem

That is, the present invention relates to a laminated film comprising a polyester film and a coating layer containing a phosphor provided thereon, wherein the phosphor of the coating layer is made of an inorganic substance, and the content of the phosphor in the coating layer is 50 to 80. It is a laminated film characterized by the weight percent.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

(Coating layer)

In the present invention, it is important that the phosphor of the coating layer is made of an inorganic substance. By using a phosphor made of an inorganic substance as the phosphor, a laminated film with little color shift can be obtained. On the other hand, when a phosphor made of an organic substance is used as the phosphor, the phosphor is decomposed by ultraviolet rays, and the laminated film is yellowed by ultraviolet rays after long-term use.

The coating layer is composed of 100% by weight of the composition of the coating layer and a phosphor made of an inorganic substance. ˜80 wt%, preferably 15 to 50 wt%. If it is less than 5% by weight, a sufficiently high luminance cannot be maintained when a white film is used as a film for use in a reflector. On the other hand, if it exceeds 80% by weight, a uniform coating layer cannot be obtained, and it is difficult to suppress yellowing without spots throughout the film.

The coating layer preferably contains a compound having an ultraviolet absorbing ability from the viewpoint of effectively suppressing yellowing of the film. When the coating layer contains a compound having an ultraviolet absorbing ability, the content is 100% by weight of the composition of the coating layer, for example, 20 to 95% by weight, preferably 20 to 50% by weight. It is. The compound having ultraviolet absorbing ability may be a low molecular type or a high molecular type. As the high molecular weight type, for example, a polymer obtained by polymerizing a low molecular weight capable of absorbing ultraviolet light into a polymer main chain or side chain can be used. This polymer type compound having ultraviolet absorbing ability is preferable because it has a function as a binder.

The coating layer preferably contains a resin as a binder in addition to the compound having ultraviolet absorbing ability. When the coating layer contains a binder resin, the binder resin can occupy the portion of the coating layer composition other than the phosphor made of an inorganic substance, or the coating layer composition. Of these, it can occupy portions other than phosphors made of inorganic substances and compounds having ultraviolet absorption.

These components constituting the coating layer are dissolved or dispersed in an organic solvent and used as a coating solution.

Examples of the binder resin include polyester, polyurethane, acrylic, polyamide, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, fluororesin, and copolymers thereof, and a mixture of two or more. Etc. can be used. Further, a binder resin obtained by copolymerizing a compound having an ultraviolet absorbing ability as a copolymerization component may be used.

The thickness of the coating layer is preferably 2 to 10; Lim. The thickness in this range As a result, it is possible to obtain a laminated film in which the inorganic phosphor does not easily fall off and has good slipperiness.

(Phosphor made of inorganic material)

The phosphor made of an inorganic substance in the present invention preferably has an excitation wavelength of 400 to 450 nm. By using a phosphor made of an inorganic substance having an excitation wavelength in this range, a high luminance can be obtained when used as a reflector, and a laminated film without coloring due to absorption can be obtained. Hereinafter, “phosphor made of an inorganic substance” may be simply referred to as “inorganic phosphor”.

The inorganic phosphor in the present invention preferably has an emission peak wavelength of 500 to 600 nm. If the emission wavelength is less than 500 nm or exceeds 600 nm, the effect of improving the luminance when used as a reflector is not preferred.

As an inorganic phosphor that satisfies the requirements for the excitation wavelength and emission peak wavelength described above, an alkaline earth metal sulfide, alkaline earth metal complex oxide, or lanthanum phosphate compound having a rock salt type crystal structure is used as a matrix. An inorganic phosphor containing an activator can be used.

As alkaline earth metal sulfides, for example, zinc sulfide (Zn S), strontium sulfide (S r S), yttrium oxide (Y ₂ 0 ₂ ) can be used.

As the alkaline earth metal composite oxide, for example, barium / magnesium / aluminum composite oxide (BaMgA 1 ₁₀ ₁₇ ) can be used.

As the activator, for example, Eu, Cu, Mn, A1, Ce, Tb, Ba, Sr, Ag can be used, and further, for example, a combination of Eu, Cu and A1, Combinations of 6 and 13, 8 £ 1 and £ 1, and 8 &, 5 and Eu can be used.

Particularly preferred inorganic phosphors are based on strontium sulfide (S r S) or yttrium oxide (Y ₂ 0 ₂ ) as the activator. And inorganic phosphor containing Z or copper (Cu), barium-magnesium-aluminum composite oxide (BaMgAl ₁₀ Ο ₁₇ ) as a base material, and plutonium (Eu) and / or manganese (Mn) as activators An inorganic phosphor containing, as a base substance, lanthanum phosphate (L aP0 ₄ ) and Ce and / or Tb as activators.

If activator is E u, can be used, for example E u ₂ O ₃ as an activator. In this case, the content of the activator Eu ₂ 〇 ₃ in the inorganic phosphors, based on the total weight of the inorganic phosphors, for example 0.01 to 10 wt% Dearu.

When the activator is Mn, for example, MnO can be used as the activator. In this case, the content of the activator MnO in the inorganic phosphor is, for example, 0.01 to 1% by weight based on the total weight of the inorganic phosphor.

If activator is C e, it can be used, for example C e P0 ₄ as an activator. In this case, the content of the activator Ce P0 ₄ in the inorganic phosphors, based on the total weight of the inorganic phosphors, for example 0.01 to 35 wt% Dearu.

When the activator is Tb, for example, Tb ₄₀ ₇ can be used as the activator. In this case, the content of the activator Tb ₄ 〇 ₇ in the inorganic phosphors, based on the total weight of the inorganic phosphor, for example, 0.01 to 25 wt%.

When the activator is Cu, for example, Cu ₂ S can be used as the activator. In this case, the content of the activator Cu ₂ S in the inorganic phosphor is, for example, 0.01 to 1% by weight based on the total weight of the inorganic phosphor. .

When the activator is A1, for example, A 1 ₂ S ₃ can be used as the activator. In this case, the content of the activator A 1 ₂ S _{3 in} the inorganic phosphor is, for example, 0.01 to 1% by weight based on the total weight of the inorganic phosphor.

As the inorganic phosphor, for example, a particulate material is used, and the shape of the particles is not limited, but for example, a spherical material can be used. The average particle diameter of the particles is, for example, 2 to 10 m, preferably 3 to 7; m. Use particulate inorganic phosphors with an average particle size in this range As a result, it can be uniformly dispersed in the coating liquid, and a coating layer in which the phosphor is uniformly distributed can be obtained.

Inorganic phosphors are commercially available. For example, the following can be used.

As green light emitting inorganic phosphors, 2210 (based on Kasei Optronics ZnS as the base material, Cu as the activator), E 7031-2 (based on Nemoto Special Chemical Co., Ltd., La ₂ 0 ₂ S as the base material, E u E401 1-1 (Sr A 1 ₂ 0 ₄ manufactured by Nemoto Special Chemical Co., Ltd. and Eu as an activator) can be used.

As the red inorganic phosphor, Dl 110 (manufactured by Nemoto Special Chemical Co., Ltd., Y ₂ 0 ₃ as a base material and Eu as an activator) can be used.

As a blue inorganic phosphor, D 1230 (Sr S manufactured by Nemoto Special Chemical Co., Ltd. is used as a base material and Eu is used as an activator), E 203 1-2 (Ba Mg A 1 ₁₀ 0 ₁₇ manufactured by Nemoto Special Chemical Co., Ltd. is used as a base material) As an activator, Eu can be used.

As the green inorganic phosphor, KX 732A (manufactured by Kasei Optronics Co., Ltd., barium / magnesium'aluminum complex oxide (BaMgA 1 ₁₀ ₁₇ )) can be used as the matrix, and Eu and Mn can be used as activators. .

As yellow-green inorganic phosphors, P 22—GN4 (based on ZnS manufactured by Kasei Optonics Co., Ltd. and Cu and A 1 as activation materials), LP—G2 (based on LaP0 ₄ manufactured by Kasei Optonics Co., Ltd., Ce, Tb can be used as an activator).

(Compound with UV absorbing ability)

Examples of the compound having ultraviolet absorbing ability include organic compounds such as benzophenone, benzotriazole, cyanoacrylate, salicylic acid, triazine, benzoate, and oxalate anilide, and inorganic sol gels. Things can be used. The organic UV-absorbing compound may be used in a form copolymerized with a polymer.

The compound which has an ultraviolet absorptivity is illustrated below.

2, 4-Dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy _ 5-sulfobenzophenone, 2, 2, 1, 4, 4, 1 Tetrahydroxybenzophenone, 2, 2, -dihydroxy mono 4-methoxybenzophenone, 2, 2'-dihydroxy mono 4,4'-dimethoxybenzophenone, bis (2-methoxy _ 4-hydroxy-5-benzoyl phenyl) Methane can be exemplified. As benzotriazoles, 2— (2,1hydroxy-5′-methylphenyl) benzotriazole, 2— (2′-hydroxy-5, —t-butylphenyl) benzotriazole, 2_ (2′—hydroxyl 3,, 5 '—di-t-butylphenyl) benzotriapool, 2 _ (2, —hydroxy-3, 1 t-butyl-5′-methylphenyl) 1 5-clobenzobenzotriazole, 2 1 (2, hydroxy) 3 ', 5' — Di 't-Ptylphenyl) 1 5-Clo-benzotriazole, 2— (2 ′ — Hydroxy 5 ′ — Toctylphenol) Benzotria pool, 2— (2, 1 Hydroxy _ 3,, 5, 1-di-tert-milphenyl) benzotriazole, 2, 2, -methylenebis [4 1 (1, 1, 3, 3-tetramethylbutyl) —6— (2 H_benzotriazole 2 _ Gil Phenols], 2 (2, Hydroxy-1,5 Methacryloxyphenyl) _2 H-Benzotriazole, 2- [2, -Hydroxy-1,3- (3 ", 4", 5 ", 6〃-tetrahydrofurimidomethyl 1) 5'-methylphenyl] benzotriazole.

Examples of cyanoacrylate-based compounds include ethyl 2_cyano 1,3 'diphenyl acrylate.

P- t _ butylphenyl salicylate, p-o An example is cutylphenyl salicylate.

As the polyester film, a film made of thermoplastic aromatic polyester is used. Examples of the thermoplastic aromatic polyester include polyethylene terephthalate, polyethylene naphthenic dicarboxylate, and polybutylene terephthalate. These polyesters may be copolymerized with a copolymer component. In that case, the proportion of the copolymerization component is, for example, a proportion of 20 mol% or less based on the total dicarboxylic acid component.

When the laminated film of the present invention is used as a reflector, it is preferable to use a white polyester film as the polyester film.

As a white polyester film, a sheet of a composition in which particles are blended with polyester, or a composition in which a resin incompatible with polyester is blended is stretched, and at the time of stretching, the interface between the polyester and particles, or incompatible with polyester For example, a white polyester film in which peeling occurs at the interface with the resin and fine voids are formed inside the film can be used. As the particles, for example, inorganic particles, organic particles, and composite particles thereof can be used.

As the white polyester film, it is preferable to use a white laminated film comprising a reflective layer and a support layer that supports the reflective layer. In this case, the coating layer is provided on the reflective layer in order to suppress yellowing of the reflective layer.

The void volume ratio of the reflective layer in the white laminated film is preferably 30 to 80%, more preferably 35 to 75%, and particularly preferably 38 to 70%. This void volume fraction can be obtained when the interface between the polyester and the particles or the incompatible resin is peeled off during stretching to generate voids.

When using particles as a substance that forms voids, the average particle size of the particles is preferably 0.3 to 3.Ο, more preferably 0.4 to 2.5, and particularly preferably. Or 0.5 to 2.0 xm. If the average particle size is less than 0.3 / xm, aggregation is likely to occur, which is not preferable. If the average particle size exceeds 3.0 xm, the film may be broken, which is not preferable. The particles are preferably contained in 3 to 60 parts by weight, more preferably 35 to 55 parts by weight, particularly preferably 37 to 50 parts by weight per 100 parts by weight of the polyester composition of the reflective layer. . 3 If it is less than 1% by weight, the reflectivity is lowered, or the deterioration due to ultraviolet rays becomes severe. If it exceeds 60% by weight, the film is easily broken, which is not preferable. The particles are preferably inorganic particles. From the viewpoint of obtaining particularly high reflection performance, white pigments are preferably used as the inorganic particles. As the white pigment, for example, titanium oxide, barium sulfate, calcium carbonate, and silicon dioxide particles are used, and preferably barium sulfate particles are used. Particularly good reflectance can be obtained by using barium sulfate particles. The barium sulfate particles may have a plate shape or a spherical shape.

As the organic particles, for example, incompatible resin particles described below can be used.

In the case of using an incompatible resin as a substance that forms a void, for example, a polyolefin resin or a polystyrene resin can be used as the incompatible resin. Specifically, for example, poly-3-methylbutene-1, poly-4 —Methylpentene-1, Polyethylene, Polypropylene, Polyvinyl-1, t-Butane, 1,4-Trans-1, Poly-1,2,3-Dimethylbutadiene, Polyvinylcyclohexane, Polystyrene, Polyfluorostyrene, Cellulose acetate Cellulose propionate and polychloroethylene can be used. Polypropylene and polymethylpentene are particularly preferable. Polypropylene and polymethylpentene are optimal because the resin itself is highly transparent and can improve the reflectance by suppressing light absorption.

When an incompatible resin is used, it is preferably 5 to 30 parts by weight, more preferably 8 to 25 parts by weight, particularly preferably 100 parts by weight of the polyester composition of the reflective layer. Alternatively, it is used at a ratio of 10 to 20 parts by weight. If it exceeds 30 parts by weight in the reflective layer, the film will be very easy to break, and if it is less than 5 parts by weight, sufficient void formation will not be achieved, and the reflectivity of the film will be low. It is not preferable because the resistance to ultraviolet rays is inferior.

The support layer is made of a polyester composition, and inorganic particles, preferably 0.5 to 30% by weight, more preferably 1 to 27% by weight, and particularly preferably 2 to 2%, per 100 parts by weight of the polyester composition. Contains 5% by weight. If it is less than 0.5% by weight, sufficient slipperiness cannot be obtained, which is not preferable, and if it exceeds 30% by weight, the strength as a support layer for supporting the reflective layer cannot be maintained, and the film breaks. This may lead to an unfavorable situation.

The average particle size of the inorganic particles is preferably 0.1 to 5; m, more preferably 0.5 to 3 / m, and particularly preferably 0.6 to 2 × m. If it is less than 0.1 m, particles are likely to aggregate, and if it exceeds 5 / x m, coarse protrusions are formed, which may lead to film breakage.

(Production method)

Hereinafter, the method for producing the laminated film of the present invention will be described by taking as an example a laminated film in which a coating layer is provided on a white polyester film comprising a reflective layer containing barium sulfate particles and a support layer.

The blending of the barium sulfate particles into the polyester composition may be performed during the polymerization of the polyester or after the polymerization. In the case of polymerization, it may be added before the end of the transesterification or esterification reaction, or before the start of the polycondensation reaction.

When it is performed after polymerization, it may be added to the polymerized polyester and melt-kneaded. In this case, master pellets containing barium sulfate particles at a relatively high concentration are produced and blended with polyester pellets containing no barium sulfate particles. Thus, a polyester composition containing barium sulfate particles at a desired content can be obtained.

Non-woven fabric type filter with an average opening of 10 to 100 m, preferably an average opening of 20 to 50 jm, made of stainless steel fine wire with a wire diameter of 15 // m or less. It is preferable to filter the polyester composition. By performing this filtration, it is possible to obtain a film with few coarse foreign matters by suppressing aggregation of particles that tend to agglomerate into coarse agglomerated particles.

A laminated unstretched sheet is produced by a simultaneous multilayer extrusion method using a feed block of a polyester composition melted from a die. In other words, the polyester composition melt constituting the reflective layer and the polyester composition melt constituting the support layer are laminated to form the reflective layer Z support layer using a feed block, and developed on a die. And extruding. At this time, the polyester composition laminated by the feed block maintains the laminated form.

The unstretched sheet extruded from the die is cooled and solidified with a casting drum to form an unstretched film.

The coating liquid used for coating the coating layer is preferably applied to this unstretched film or to a longitudinally stretched film that has been subjected to subsequent longitudinal stretching.

The unstretched film is heated by roll heating, infrared heating, etc., and stretched in the machine direction to obtain a stretched film. This stretching is preferably performed by utilizing the difference in peripheral speed between two or more rolls. The stretching temperature is preferably a temperature equal to or higher than the glass transition point (T g) of the polyester, and more preferably a temperature of T g to (at T g +70). Depending on the required characteristics of the application, the draw ratio is preferably from 2.2 to 4.0 times, more preferably 2 in both the machine direction and the direction perpendicular to the machine direction (hereinafter referred to as the transverse direction). 3 to 3.9 times. If it is less than 2 times, the thickness unevenness of the film is deteriorated and a good film cannot be obtained, and if it exceeds 4.0 times, breakage tends to occur during film formation, which is not preferable. The longitudinally stretched film is subsequently subjected to the processes of cocoon stretching, heat setting, and thermal relaxation to form a biaxially oriented film, which are performed while the film is running. The lateral elongation treatment starts from a temperature higher than the glass transition temperature (Tg) of the polyester and is performed while raising the temperature to a temperature of (Tg + 5) to (Tg + 70). The temperature rise in the transverse stretching process may be continuous or stepwise (sequential), but usually the temperature rises sequentially. For example, the horizontal stretching zone of Ten Ten is divided into a plurality along the film running direction, and the temperature is raised by flowing a heating medium of a predetermined temperature for each zone. The transverse stretching ratio is preferably 2.5 to 4.5 times, more preferably 2.8 to 3.9 times. 2. If it is less than 5 times, the thickness unevenness of the film deteriorates and a good film cannot be obtained, and if it exceeds 4.5 times, breakage tends to occur during film formation, which is not preferred.

The film after transverse stretching should be held at both ends (Tm-20) to (: Tm_100) to reduce the thermal shrinkage rate by heat treatment under constant width or width reduction of 10% or less. When the temperature is higher, the flatness of the film is deteriorated, and the thickness unevenness is unfavorable. If the heat treatment temperature is lower (Tm-10.0), the thermal shrinkage rate may increase.

In the process of returning the film temperature to room temperature after heat treatment, in order to adjust the thermal shrinkage of the film in the temperature range of (Tm-20) to (Tm-10 0) ° C, It may be cut off and adjusted in the longitudinal direction of the film to be relaxed in the longitudinal direction. To relax, adjust the speed of the roll group on the ten evening side. For the relaxation, the speed of the roll group is reduced with respect to the film line speed of Ten Ten, preferably 0.1 to 1.5%, more preferably 0.2 to; L. 2%, particularly preferably Can be performed by performing a speed reduction of 0.3 to 1.0%. By relaxing the film in this way, the heat shrinkage rate in the vertical direction can be adjusted. In addition, the width of the film in the horizontal direction can be reduced in the process until the both ends are cut off to obtain a desired heat shrinkage rate.

Here, the case of stretching by the sequential biaxial stretching method was explained in detail as an example, The laminated film of the present invention may be stretched by either a sequential biaxial stretching method or a simultaneous biaxial stretching method.

In the present invention, the coating layer may be provided directly on the base polyester film. However, when the adhesiveness is insufficient, it is preferable to subject the surface of the polyester film to corona discharge treatment or subbing treatment. The subbing treatment may be provided in the polyester film manufacturing process (inline coating method), or may be applied separately after the polyester film is manufactured (offline coating method). The material used for the subbing treatment may be selected as appropriate, but as a suitable material, copolymer polyester, polyurethane, acrylic, and various coupling agents can be used. The coating layer containing the inorganic phosphor can be coated by any method. For example, gravure, roll, spin, reverse, bar, screen, datebing, etc. can be used. A known method can be used as a curing method after coating. For example, a method using active rays such as thermosetting, ultraviolet rays, electron beams, and radiation can be applied. The application may be performed before the completion of the crystal orientation of the film during the production of the polyester film, or after the completion of the crystal orientation of the film. Example

Hereinafter, the present invention will be described in detail by way of examples.

Measurement and evaluation were performed by the following methods.

(1) Film thickness

The film sample was measured for 10-point thickness with an electric micrometer (K-1400 B, manufactured by Anritsu), and the average value was obtained to obtain the film thickness.

(2) Coating layer thickness

Samples were cut into triangles, fixed in embedded capsules, and embedded in epoxy resin. Then, after embedding the sample with a micro I ^ 1 um (ULTRACUT-S), the section parallel to the longitudinal direction was made into a thin film slice, and then observed and photographed using an optical microscope, The thickness ratio of the coating layer to the film was measured from the photograph, and the thickness of the coating layer was determined by calculating from the thickness of the entire film.

(3) Emission and peak emission wavelength at excitation wavelength of 400 to 450 nm

Using fluorescence spectrophotometer F_4500 (manufactured by Hitachi), we collect excitation emission spectra in the excitation wavelength range of 400 to 450 nm and emission wavelength range of 300 to 800 nm and evaluate the presence or absence of fluorescence emission according to the following criteria. did. The measurement was performed on the surface provided with the phosphor-containing coating layer. For those with fluorescent emission, the emission peak wavelength was determined from the excitation emission spectrum.

◎: With fluorescence

X: No fluorescence

(4) Yellowing over time

Light irradiation was performed for 50 hours with a high-pressure mercury lamp ("Tosukia 40 1" manufactured by Harrison Toshiba Lighting) with a glass fill, and the color change before and after the light irradiation was observed. The irradiance with light irradiation was 1 SmWZcm ² . When the film was composed of two layers, a reflective layer and a support layer, measurement was performed by irradiating light from the reflective layer side.

The initial film hue (1 ^ *, a, b, and the film hue after irradiation (L ₂ *, a ₂ b ₂ *) are combined with a color difference meter (Nippon Denshoku SZ S_∑ 90 COLOR MEASUR I NG SYSTEM ), A hue change dE * represented by the following formula was calculated, and evaluated according to the following criteria.

dE * = {(L -L2 *) ² + (aa ₂ *) ² + (b ^ — b ₂ *) ² } ^1/2 ◎ dE * ≤ 5

○: 5 <dE * ≤ 10

Δ: 10 <d E * ≤ 1 5

X: 1 5 <d E *

(5) Average particle size

Scanning electron microscope (SEM) shows particles in powder before being added to polyester A double-sided tape was placed on the sample stage, and the particles were thinly deposited on it. After carbon deposition, a scanning electron microscope (SEM) was used to change the magnification appropriately according to the size of the particles and take pictures. The equivalent circle diameter of at least 100 particles or more was obtained with an image processing apparatus, and divided by the number of particles to obtain a number-based average particle diameter (/ m).

(6) Luminance and chromaticity

When the measurement object was a white polyester film (Examples 1 to 5 and Comparative Examples 1 to 3), the evaluation was performed by the method described in (6_1) to (6_5) below.

(6-1) Creating a backlight unit for evaluation

Take the direct backlight unit (20 inches) from the LCD TV (SHARP AQUOS L C-20 S 4) prepared for evaluation, and replace it with the light reflection sheet originally built in the backlight unit. A backlight unit for evaluation was created.

Divide the backlight surface of the evaluation backlight unit into 2 × 2 4 sections, and turn on the backlight and measure the brightness and chromaticity of the front one hour later using a Topcon BM _ 7 luminance meter. The angle was 1 ° and the distance between the luminance meter and the backlight was 50 cm. The measurement was performed for each of the four sections of the backlight surface, and a simple average of luminance was obtained as average luminance, and a simple average of chromaticity was obtained as average luminance.

(6-2) Brightness improvement rate

Using the film before coating of the phosphor-containing coating layer as an object of measurement, the average luminance before coating was measured by the method (6-1) above. Next, the average brightness after coating was measured by the above method (6-1) using the film after coating of the phosphor-containing coating layer as a measurement target. From the obtained average luminance, the luminance improvement rate was calculated using the following formula.

Brightness improvement rate (%)

= (Average brightness after coating) / (Average brightness before coating) X 100

(6-3) Chromaticity difference The average chromaticity (x, y) before coating was measured by the method of (6-1) above using the film before coating of the phosphor-containing coating layer as a measurement target. Next, the average chromaticity (x, y) after coating was measured by the method of (6-1) above using the film after coating of the phosphor-containing coating layer as a measurement target. From the average chromaticity (x, y) obtained, the chromaticity difference Δχγ was calculated using the following formula.

Δ X y = (Δ χ ² + Δ y ² ) ^1/2

Δχ = (χ component of average chromaticity after coating) 1 (X component of average chromaticity before coating) Δγ = (y component of average chromaticity after coating) 1 (average chromaticity before coating) Y component) Using the obtained Δ X y, the chromaticity difference Δ X y was evaluated according to the following criteria.

: Δ X y <0. 0 δ

〇: 0. 05≤Δ X y <0. 10

X: 0.10≤Δ x y

(6-4) Luminance maintenance rate in durability test

The average luminance was measured by the method described in (6-1) above using the film after coating of the phosphor-containing coating layer (the film before the durability test) as the measurement target. Next, a durability test was performed for 3000 hours with the backlight lit. The average luminance after the durability test was measured for the film after the durability test by the method (6-1) above.

The luminance maintenance rate was calculated by the following formula.

Luminance maintenance rate (%)

= (Average brightness after endurance test) / (Average brightness before endurance test) X 100 (6-5) Change in chromaticity in endurance test

The average chromaticity (x, y) was measured by the method described in (6-1) above using the film after coating of the phosphor-containing coating layer (the film before the durability test) as the measurement target. Next, a durability test was performed for 3000 hours with the backlight on. For films that have undergone a durability test, use the method described in (6-3) above. Average chromaticity (x, y) was measured. From the average chromaticity (x, y) obtained, Axy was calculated using the following formula.

Δ X y = (Δ X ² + Δ y ² ) ^{1 2}

Δχ = (x component of average chromaticity after durability test)-(X component of average chromaticity before durability test)

Δγ = (y component of average chromaticity after durability test)-(y component of average chromaticity before durability test)

Using the obtained Δ X y, the chromaticity change Δ X y was evaluated according to the following criteria.

: Δ X y <0. 05

○: 0. 0 δ≤Δχγ <0. 10

X: 0.10≤Δ χ y

(7) Luminance and chromaticity

When the measurement object was a transparent polyester film (Example 6 and Comparative Example 4), the evaluation was performed by the methods described in (7-1) to (7-5) below.

(7 _ 1) Creating a backlight unit for evaluation

Take the direct backlight unit (20 inches) from the LCD TV (SHARP AQUOS LC-20 S 4) prepared for evaluation, and replace it with the light diffusion sheet that was originally built into the Knock Tune. An evaluation backlight unit was created by incorporating the film to be measured.

Divide the backlight surface of the backlight unit for evaluation into 2 × 2 4 sections, and turn on the backlight and measure the luminance and chromaticity of the front one hour later using a Topcon BM-7 luminance meter. Was measured at 1 °, and the distance between the luminance meter and the backlight was 50 cm. The measurement was performed for each of the four sections of the backlight surface, and a simple average of luminance was obtained as average luminance, and a simple average of chromaticity was obtained as average luminance.

(7-2) Brightness improvement rate

Using the film before coating of the phosphor-containing coating layer as the measurement target, the above (7-1) The average brightness before coating was measured by this method. Next, the average luminance after coating was measured by the above method (7-1) using the film after coating of the phosphor-containing coating layer as a measurement target. From the obtained average luminance, the luminance improvement rate was calculated using the following formula.

Brightness improvement rate (%)

(7-3) Chromaticity difference

The average chromaticity (x, y) before coating was measured by the method of (7-1) above using the film before coating of the phosphor-containing coating layer as a measurement target. Next, the average chromaticity (x, y) after coating was measured by the above method (7-1) using the film after coating of the phosphor-containing coating layer as a measurement target. From the average chromaticity (x, y) obtained, the chromaticity difference Δχγ was calculated using the following formula.

Δ X y = (Δ χ ² + Δ y ² ) ^1/2

Δχ = (χ component of average chromaticity after coating) 1 (X component of average chromaticity before coating) Δγ = (y component of average chromaticity after coating) 1 (average chromaticity before coating) Y component) Using the obtained Δχγ, the chromaticity difference Δχγ was evaluated according to the following criteria.

◎: Δ X y <0. 05

○: 0. 0 δ≤Δχγ <0. 10

X: 0.10≤Δ X y

(7-4) Luminance maintenance rate in durability test

The average luminance was measured by the above method (7_1), using the film after the coating of the phosphor-containing coating layer (the film before the durability test) as the measurement target. Next, a durability test was performed for 3000 hours with the backlight turned on. The average luminance after the durability test was measured for the film that had undergone the durability test by the method (7-1) above.

The luminance maintenance rate was calculated by the following formula.

Luminance maintenance rate (%) = (Average brightness after endurance test) / (Average brightness before endurance test) X 100

(7-5) Change in chromaticity during durability test

The average chromaticity (x, y) was measured by the method described in (7-1) above using the film after coating of the phosphor-containing coating layer (film before the durability test) as the measurement target. Next, a durability test was performed for 3000 hours with the back light lit. About the film which passed the durability test, the average chromaticity (x, y) after a durability test was measured by the method of said (7-3). From the average chromaticity (x, y) obtained, Axy was calculated using the following formula.

Δ X y = (Δ χ ² + Δ y ² ) ^1/2

Δχ = (χ component of average chromaticity after durability test) 1 (X component of average chromaticity before durability test)

◎: Δ X y <0. 05

◯: 0. 05≤Δχγ <0. 10

X: 0.10≤Δ χ y Reference Example 1 (Production of white polyester film)

132 parts by weight of dimethyl terephthalate, 18 parts by weight of dimethyl isophthalate (12 mol% based on the total dicarboxylic acid component of the polyester), 96 parts by weight of ethylene glycol, 3.0 parts by weight of diethylene glycol, 0.05 parts by weight of manganese acetate And 0.012 parts by weight of lithium acetate were charged into a flask equipped with a rectifying column and a distillation condenser, and heated to 150 to 235 with stirring to distill methanol to carry out an ester exchange reaction. After methanol is distilled, 0.03 parts by weight of trimethyl phosphate and 0.04 parts by weight of germanium dioxide are added, and the reaction product is transferred to the reactor. did. Then, while stirring, the pressure in the reactor was gradually reduced to 0.5 mmHg, and the temperature was raised to 290 to conduct a polycondensation reaction. The obtained copolymer polyester had a diethylene glycol component content of 2.5% by weight, a germanium element content of 50 ppm, and a lithium element content of 5 ppm.

50% by weight of barium sulfate particles having an average particle diameter of 1.5 m was added to this polyester to obtain a polyester composition for a reflective layer. Further, 5% by weight of barium sulfate particles having an average particle size of 1.5 / m was added to this polyester to obtain a polyester composition for a support layer. Each composition is supplied to two extruders heated to 280, and the two layers are laminated by using a two-layer feedblock device so that the thickness ratio of the reflective layer and the support layer is 31. Then, while maintaining this laminated state, it was extruded from a die and formed into a two-layer sheet. This was cooled and solidified with a cooling drum having a surface temperature of 25 to form an unstretched film, further heated to 95, stretched in the longitudinal direction (longitudinal direction), and cooled with a roll group of 25. Next, the film was stretched in the direction perpendicular to the longitudinal direction (lateral direction) in an atmosphere heated to 120 while being held at both ends of the film that had been stretched longitudinally and held in clips. After that, heat setting is performed at a temperature of 200 in the evening, and longitudinal relaxation and lateral width adjustment are performed at 0.5% and 1% respectively at a temperature of 130, and cooled to room temperature. A biaxially stretched polyester film having a total thickness of 188 m was obtained. Reference Example 2 (Production of transparent polyester film)

96 parts by weight of dimethyl terephthalate, 58 parts by weight of ethylene glycol and 0.03 part by weight of manganese acetate were charged into the reactor, respectively, and the ester exchange was carried out while distilling the methanol until the internal temperature reached 24 Ot under stirring. After completion of the ester exchange reaction, 0.097 part by weight of trimethyl phosphate and 0.041 part by weight of antimony trioxide were added. Bow I Then, the reaction product is heated up, and finally polycondensation is carried out under high vacuum at 280 ° C to obtain the intrinsic viscosity ([]) 0. 6 4 polyester pellets were obtained.

The obtained polyester pellets were dried at 1600 for 3 hours, melt-extruded at 2800, and cooled and solidified with a cooling drum at a surface temperature of 20 to obtain an unstretched film. Subsequently, the film was heated at 95, stretched in the longitudinal direction (longitudinal direction) by a factor of 3.2, cooled by a roll group at 25, and then stretched while holding both ends of the longitudinally stretched film with clips. In the atmosphere heated at 120, the film was stretched 3.6 times in the direction perpendicular to the longitudinal direction (lateral direction) and then heat-fixed at a temperature of 220. Thereafter, at a temperature of 1130 in Tenyuichi, longitudinal relaxation and lateral width insertion were carried out by 0.5% and 1.0%, respectively, and cooled to room temperature to obtain a biaxially stretched film. Example 1 (Example of white polyester film)

The following composition was dissolved in a toluene / butyl acetate mixed solution to prepare a coating solution having a solid content concentration of 45% by weight. A 1: 1 mixture of toluene and butyl acetate was used.

(Coating liquid solid content composition)

• Green light emitting inorganic phosphor 22 10 (made by Kasei Optronics) 30 parts by weight • Ultraviolet absorbing material Ueburu UV60 10 (manufactured by Nippon Shokubai Co., Ltd.) 1 5 parts by weight The white color obtained in Reference Example 1 On the reflective layer of the polyester film, it was applied so that the thickness after drying was 5 // m, and dried with hot air at 150 for 2 minutes to obtain a coated film.

The brightness increase rate of the obtained coated film was 104%. The other evaluation results are shown in Table 1.

The green light-emitting inorganic phosphor 22 10 (manufactured by Kasei Optronics) is an inorganic phosphor made of Zn S as a base material and Cu as an activator. Example 2 (Example of white polyester film)

A coated film was obtained in the same manner as in Example 1 except that the fluorescent material of the coating liquid was changed to red inorganic phosphor D 1 110 (manufactured by Nemoto Special Chemical Co., Ltd.). Table 1 shows the evaluation results. The red inorganic phosphor D 1110 (manufactured by Nemoto Special Chemical Co., Ltd.) is an inorganic phosphor having Y ₂ 0 ₃ as a base material and Eu as an activator. Example 3 (Example of white polyester film)

A coated film was obtained in the same manner as in Example 1 except that the fluorescent material of the coating liquid was changed to blue inorganic phosphor D 1230 (manufactured by Nemoto Special Chemical Co., Ltd.). Table 1 shows the evaluation results. The blue inorganic phosphor D 1230 (manufactured by Nemoto Special Chemical Co., Ltd.) is an inorganic phosphor having SrS as a base and Eu as an activator. Example 4 (Example of white polyester film)

A coated film was obtained in the same manner as in Example 1 except that the fluorescent material of the coating liquid was changed to green inorganic phosphor KX 732 A (manufactured by Kasei Optronics). Table 1 shows the evaluation results.

The green inorganic phosphor KX 732 A (manufactured by Kasei Optronics Co., Ltd.) uses Eu / Mn as an activator based on a barium / magnesium / aluminum composite oxide (BaMgA 1 ₁₀ O ₁₇ ). It is an inorganic phosphor. Example 5 (Example of white polyester film)

A coated film was obtained in the same manner as in Example 1 except that the ultraviolet absorbing material was changed to acrylic binder Uyuburu S-2840 (manufactured by Nippon Shokubai Co., Ltd.). The brightness improvement rate was 104%. Table 1 shows the evaluation results. Comparative Example 1 (Example of white polyester film) The following composition was dissolved in a toluene-butyl acetate mixed solution to prepare a coating solution having a solid content concentration of 45% by weight. The toluene / butyl acetate mixed solution having a weight ratio of 1: 1 was used.

(Coating liquid solid content composition)

· Organic optical brightener O B— 1 (Eastman) 5 parts by weight

• UV absorbing material U-Uvable UV 6 0 1 0 (manufactured by Nippon Shokubai Co., Ltd.) 1 5 parts by weight This coating solution is applied on the reflective layer of the white polyester film obtained in Reference Example 1, and the thickness after drying is 5 / m, and dried with hot air at 1550 for 2 minutes to obtain a coated film.

Although the brightness increase rate of the obtained coated film was 105%, the difference in chromaticity due to coloring was large, and the decrease in brightness after the durability test was large, and it was a film and was difficult to use practically. It was. Table 1 shows the evaluation results. Comparative Example 2 (Example of white polyester film)

Coating was performed in the same manner as in Example 1 except that the fluorescent substance shown in Table 1 was changed to the organic fluorescent brightener UVITEX-OB (manufactured by Ciba Specialty Company) and the addition amount was 5 parts by weight. A film was obtained. The luminance increase rate at this time was about 100%, and no improvement in luminance was confirmed. This film had a large difference in chromaticity due to coloring, and had a large decrease in luminance after the durability test, so that it was difficult to use practically. Table 1 shows the evaluation results. Comparative Example 3 (Example of white polyester film)

A coated film was obtained in the same manner as in Comparative Example 1, except that the amount of the organic fluorescent brightener OB-1 added was changed to 30 parts by weight. Table 1 shows the evaluation results. Example 6 (Example of transparent polyester film) The following composition was dissolved in butyl acetate to prepare a coating solution having a solid content of 45% by weight.

(Coating liquid solid content composition)

• Inorganic phosphor (22 10 made by Kasei Optonics) 10 parts by weightAcrylic beads (MBX-1 δ made by Sekisui Plastics) 60 parts by weight

• (manufactured Yudaburu S 2740 Shokubai Co., Ltd.) Acrylic Binder 25 parts by weight • crosslinking agent (Coronate HL manufactured by Nippon Urethane Kogyo) This coating solution as 5 parts by weight coating solution is applied so that the solidified after 8 gZm ² Otherwise, a coated film was obtained in the same manner as in Example 1. Table 1 shows the evaluation results.

The green light emitting inorganic phosphor 22 10 (manufactured by Kasei Obtronics) is an inorganic phosphor using Zn S as a base material and Cu as an activator. MB X—15 is an acrylic particle having an average particle size of 15 / m.

This coating liquid was applied onto the transparent polyester film obtained in Reference Example 2 so that the thickness after drying was 5 zxm, and dried with hot air at 150 for 2 minutes to obtain a coated film. Table 1 shows the evaluation results. Comparative Example 4 (Example of transparent polyester film)

The following composition was dissolved in butyl acetate to prepare a coating solution having a solid content of 45% by weight.

(Coating liquid solid content composition)

• Acrylic beads (MBX— 1 5 Sekisui Plastics Co., Ltd.) 60 parts by weight

• Acrylic binder (Udouble S 2740, Nippon Shokubai Co., Ltd.) 32 parts by weight • Cross-linking agent (Coronate HL, Nippon Urethane Kogyo Co., Ltd.) 8 parts by weight Apply this coating solution to 8 gZm ² after solidification Otherwise, a coated film was obtained in the same manner as in Example 6. Table 1 shows the evaluation results. Phosphor Coating Layer Excitation Wave Emission Time Luminance Chromaticity Durability Durability Length 400 ~ Peak Improvement Test Type Test Phosphor Wavelength at 450nm Yellowing Rate Luminance Content Emission Retention Rate Chromaticity

(Wt%), nm) (%) (%) Change Implementation Inorganic

Example Phosphor 30 ◎ 535 ◎ 104.0 o 99.6 6 ◎

1 2210

Inorganic

Example Phosphor 40 ◎ 650 ◎ 101. 8 ◎ 99.5 o

2 D1110

Inorganic

Example Phosphor 40 ◎ 440 ◎ 101.1 ◎ 99.5 ◎ 3 D1230

Inorganic

Implementation

Phosphor

Example 30 ◎ 510 ◎ 101.2 ◎ 99.5 ◎ KX732

Four

A

Inorganic

Example Phosphor 30 ◎ 535 o 104.0 o 96.4 o 5 2210

Comparison ¾ machine

Example Phosphor 5 ◎ 550 X 105.2 X 94.3 X 1 OB-1

Organic fireflies

Comparison

Light body

Example 5 ◎ 440 X 100.0 o 95.2 X UVITEX

2

-OB

Compare Organic Firefly

Example Light 30 ◎ 550 X 108.2 X 94.2 X 3 OB-1

Inorganic firefly

Example Light 10 ◎ 535 O 103.8 8 o 99. 1 O 6 2210

Comparison

Example 0 XO 100.0 ◎ 99.0 O 4 The invention's effect

According to the present invention, it is possible to provide a laminated film in which yellowing with time is suppressed, and a laminated film that can obtain high luminance when used as a member of a backlight unit of a liquid crystal display device. Can be provided. Further, according to the present invention, it is possible to provide a laminated film suitable for a reflecting plate, in which yellowing over time can be suppressed, high luminance can be obtained, color misregistration is small. Industrial applicability

The laminated film of the present invention can be widely used for optical applications. For example, the laminated film can be suitably used as a backlight unit member of a liquid crystal display device, particularly as a reflection plate of a back light unit of a liquid crystal display device.

Claims

The scope of the claims

1. In a laminated film comprising a polyester film and a coating layer containing a phosphor provided thereon, the phosphor of the coating layer is made of an inorganic substance, and the content of the phosphor in the coating layer is 5 to 80% by weight. A laminated film characterized by being:

2. The laminated film according to claim 1, which is used as a backlight unit member of a liquid crystal display device.

3. The laminated film according to claim 1, wherein the polyester film is a white polyester film, and is used as a reflector of a backlight unit of a liquid crystal display device.