TWI432514B - Reflective sheet polyester film and reflective plate coated polyester film - Google Patents

Description

Coated polyester film for polyester film and reflector for reflector

The present invention relates to a polyester film for a white reflecting plate having high reflectance and excellent elongation, and a coated polyester film for a reflecting plate provided on the film.

The reflecting plate used in the backlight unit of the liquid crystal display device is required to have high reflection performance. Conventionally, a thin film to which a white dye is added or a white pigment to which a white pigment is added and a fine film are formed in the inside of the film (Japanese Unexamined Patent Publication No. 2004-050479, No. 2004-330727, No. Japanese Patent Publication No. 6-322153, JP-A-7-118433).

However, in such conventional white films, since the polyester constituting the polymer of the film or the polyolefin itself is deteriorated by the ultraviolet rays contained in the light from the cold cathode tube, the white film may be changed from the original white to yellow. problem.

In order to suppress the yellowing, it is proposed to apply a UV absorber to a white film (Japanese Laid-Open Patent Publication No. 2002-120330), and to add a large amount of pigment to the surface layer facing the light source side (JP-A-2007-15315) ).

However, in the case of such a configuration, in the use environment inside the backlight unit, there is a case where the reflecting plate is warped and cannot be used for a long time.

Further, the reflecting plate or the mirror is incorporated in the backlight unit by the constituent members. However, when the workability of the assembly process is facilitated, dot printing is performed using ink on the reflecting surface. The conventional white film has insufficient adhesion to the ink.

Then, when the power of the liquid crystal display device is turned on, the temperature in the backlight unit rises rapidly due to the heat of the light source, but at this time, the reflecting plate rubs against other members to generate an unpleasant rubbing sound.

In addition, the reflector must have a high reflectance of visible light. In general, a reflector having a high reflectance of visible light has a high reflectance of ultraviolet light. The light of the cold cathode tube contains ultraviolet light in addition to the visible light. When the reflectance of the ultraviolet light is high, the visible light and the ultraviolet light are simultaneously reflected on the reflective plate, and the reflected ultraviolet light causes the vicinity of the reflecting plate constituting the liquid crystal display device. Other components produce the possibility of deterioration.

The present invention has an object of solving the technical problems of the above.

An object of the first aspect of the present invention is to provide a reflecting plate which is excellent in stretchability and which is used as a backlight unit of a liquid crystal display device, and which is excellent in flatness which is suppressed in warpage in a use environment. Use a polyester film.

An object of the second aspect of the present invention is to provide an antistatic property in addition to the above-described characteristics, and is excellent in adhesion to an ink used in dot printing, and is not generated when the reflector is assembled in a backlight unit. The sound of the friction of the other members is a coated polyester film for the reflecting plate which is suppressed by the ultraviolet rays without causing deterioration of other members disposed in the vicinity of the reflecting plate.

According to a third aspect of the present invention, an antistatic property is provided, which is excellent in adhesion to an ink used in dot printing, and is not rubbed against other members when the reflector is assembled in a backlight unit. The ultraviolet ray reflects the suppressed coated polyester film for the reflector without causing deterioration of other members disposed in the vicinity of the reflector.

In other words, the first invention of the present invention is a polyester film for a reflector, which is characterized in that the support layer is formed of a white reflective layer provided thereon, and the support layer is composed of 0.1 to 10% by weight of barium sulfate particles and 99.9. ～90% by weight of polyethylene terephthalate containing an isophthalic acid component as a copolymerization component, having a thickness of 10 to 40 per 100 total thickness of the film, and a white reflective layer of 31 to 31 60% by weight of barium sulfate particles and 69 to 40% by weight of polyethylene terephthalate containing an isophthalic acid component as a copolymerization component, and having a thickness of 90 to 60 per 100 total thickness of the film, And the ratio of the content of the isophthalic acid component contained in the polyester constituting the white reflective layer to the content ratio of the isophthalic acid component contained in the polyester constituting the support layer (in the polyester constituting the white reflective layer) The content ratio of the isophthalic acid component contained/the content of the isophthalic acid component contained in the polyester constituting the support layer is 1.5 to 3.0.

Next, a second invention of the present invention is a coated polyester film for a reflecting sheet, which is characterized in that the polyester film for a reflecting plate and a coating layer coated on the film are formed, the coating layer It is formed by 15 to 80% by weight of a (meth)acrylic resin having a benzotriazole radical, 5 to 50% by weight of a polyfluorene oxide compound, and 15 to 80% by weight of an antistatic agent, and has a thickness of 0.02 to 0.2 μm. Coating layer.

Further, a third invention of the present invention is a coated polyester film for a reflecting sheet, which is characterized in that it is formed of a white polyester film and a coating layer coated on the film, and the coating layer is composed of 15 ～80% by weight of a (meth)acrylic resin having a benzotriazole group, 5 to 50% by weight of a polyfluorene oxide compound, 15 to 80% by weight of an antistatic agent, and a coating having a thickness of 0.02 to 0.2 μm Floor.

[Best form for implementing the invention]

The invention will be described in detail below.

Polyester film for reflector

In the present invention, the polyester film for a reflecting plate is a white polyester film, and a laminated film formed of a supporting layer and a white reflecting layer provided thereon. The respective layers are explained in detail below.

Support layer

The support layer is formed of 0.1 to 10% by weight of barium sulfate particles and 99.9 to 90% by weight of a polyester composition containing polyethylene terephthalate having a copolymerization component of an isophthalic acid component. By setting the barium sulfate particles of the polyester composition of the support layer in this range, it is possible to maintain sufficient smoothness excellent in handleability and strength as a support layer supporting the white reflective layer.

The copolymerization amount of the isophthalic acid component in the copolymerized polyethylene terephthalate of the support layer is preferably 2 to 10 mol%, more preferably 4 to 8 mol%. When the amount of the copolymerization of the isophthalic acid component is within this range, good film formability and excellent mechanical strength as a support layer can be obtained.

In the polyester composition of the support layer, an additive may be additionally blended as needed. The additive is, for example, a fluorescent whitening agent, an antioxidant, or an ultraviolet absorber.

White reflective layer

The white reflective layer is formed of 31 to 60% by weight of barium sulfate particles and 69 to 40% by weight of a polyester composition containing polyethylene terephthalate having a copolymerization component of an isophthalic acid component. When the barium sulfate particles of the polyester composition of the white reflective layer are in this range, it is possible to obtain excellent light resistance and excellent productivity without causing yellowing even when used as a reflecting plate for a long period of time. Membrane. The copolymerized polyethylene terephthalate is preferably contained in the polyester composition in an amount of from 59 to 40% by weight. At this time, 41 to 60% by weight of barium sulfate particles are contained in the polyester composition.

In the copolymerized polyethylene terephthalate containing the isophthalic acid component of the white reflective layer as a copolymerization component, the copolymerization amount of the isophthalic acid component is preferably 6 to 18 mol%, preferably 8 to 12% Moore is better. When the amount of the copolymerization of the isophthalic acid component is within this range, good film formability and excellent reflectivity as a white reflective layer can be obtained.

In the polyester composition of the white reflective layer, an additive may be additionally blended as needed. The additive is, for example, a fluorescent whitening agent, an antioxidant, or an ultraviolet absorber.

Proportion of isophthalic acid components

In the present invention, the ratio of the content of the isophthalic acid component contained in the polyester constituting the white reflective layer to the content ratio of the isophthalic acid component contained in the polyester constituting the support layer (constituting the white reflection) The content ratio of the isophthalic acid component (% by mole) contained in the polyester of the layer/the content (% by mole) of the isophthalic acid component contained in the polyester constituting the support layer is 1.5 to 3.0. , is extremely important. When the ratio is less than 1.5, when a reflector which is a backlight unit of a liquid crystal display device is used, the film may be warped on the side of the white reflective layer in the use environment. Further, when it is more than 3.0, there is a warpage on the side of the support layer.

thickness

The support layer has a thickness of 10 to 40 when the thickness of the entire film is 100. By making the thickness of the support layer occupied by the entire thickness of the film within this range, good film formability and sufficient mechanical strength as a support layer can be obtained.

The white reflective layer has a thickness of 90 to 60 when the thickness of the entire film is 100. By making the thickness of the support layer occupied by the entire thickness of the film within this range, it is possible to ensure good film formability and sufficient reflectance as a reflector.

The total thickness of the polyester film for a reflecting plate of the present invention is preferably 60 to 400 μm, more preferably 75 to 300 μm, and most preferably 100 to 250 μm. By the total thickness of the range, high reflectance and handleability of the entire film can be obtained.

Next, the thickness of the support layer is preferably from 10 to 100 μm. By forming the thickness of this range, good film formability and mechanical strength can be obtained. The thickness of the white reflective layer is preferably 50 to 300 μm. By making the thickness of the white reflective layer within this range, high reflectance can be ensured and good film forming properties can be obtained.

The polyester film for a reflecting plate of the present invention is preferably composed of two layers of a support layer and a white reflective layer provided on one surface thereof in order to obtain high reflectivity.

Barium sulfate particles

The average particle diameter of the barium sulfate particles used for the support layer and the white reflective layer is preferably 0.1 to 5 μm, more preferably 0.5 to 3 μm, and most preferably 0.6 to 2 μm. By using barium sulfate particles having an average particle diameter within this range, it is possible to favorably produce a film without causing agglomeration of fine particles and without causing breakage of the film.

In the polyester film for a reflecting plate of the present invention, when the white reflecting layer is stretched, the interface between the barium sulfate particles and the copolymerized polyester causes peeling and voids are formed.

Average reflectance and heat shrinkage

The polyester film for a reflecting plate of the present invention has an average reflectance of at least one of the surfaces of the polyester film having a wavelength of 400 to 700 μm of 90% or more, preferably 92% or more, and more preferably 94% or more. By having this average reflectance, high luminance can be obtained.

Further, in the polyester film for a reflecting plate of the present invention, the heat shrinkage ratio at 85 ° C is preferably 0.5% or less in both directions of the vertical direction, more preferably 0.4% or less, and most preferably 0.3% or less. By having this heat shrinkage rate, a reflector having a small number of brightness spots can be obtained even when used for a long period of time.

Coating layer

In the coated polyester film for a reflecting plate according to the second aspect of the invention, the coating layer is applied to the polyester film for a reflecting plate, and is preferably applied to a white reflective layer of a polyester film for a reflecting plate. Thereby, when a film is used as the reflection plate of the liquid crystal display device, the surface protrusion of the white layer formed by the pore-forming substance can reduce the sound generated when rubbing with other members. Moreover, the coating layer may be disposed on one side or both sides of the white polyester film.

In the coated polyester film for a reflecting plate according to the third invention of the present invention, the coating layer is provided on the white polyester film.

The coating layer is formed by 15 to 80% by weight of a (meth)acrylic resin having a benzotriazole radical, 5 to 50% by weight of a polyfluorene oxide compound, and 15 to 80% by weight of an antistatic agent. A coating layer having a thickness of 0.02 to 0.2 μm.

The thickness of the coating layer is 0.02 to 0.2 μm after drying, preferably 0.03 to 0.1 μm. When it is less than 0.02 μm, the ultraviolet absorbing performance and the antistatic property are insufficient, and when it is more than 0.2 μm, the coating spot is noticeable, and the coating appearance is deteriorated.

(meth)acrylic resin with benzotriazolyl

The coating layer contains 15 to 80% by weight (preferably 30 to 70% by weight) of a (meth)acrylic resin having a benzotriazole group per 100% by weight of the composition of the coating layer. The (meth)acrylic resin having a benzotriazole group functions as an ultraviolet absorber. When the amount is less than 15% by weight, the ultraviolet absorbing performance is insufficient, and even if it is more than 80% by weight, the ultraviolet absorbing performance is saturated, so that it does not have any meaning, and the amount of the antistatic agent is relatively small, and the antistatic property is changed. Insufficient, resulting in easy adhesion of dust on the surface of the film.

The benzotriazole group is on the side chain of the (meth)acrylic resin, and the content thereof is in a (meth)acrylic monomer which constitutes a (meth)acrylic resin per 100 mol%, for example, 10 to 80 mol. Ear %, preferably 20 to 70 mol%.

In the coated polyester film for a reflecting plate of the present invention, by having a benzotriazole group in the range on the coating layer, the total light reflectance at 365 nm can be 80% or less, preferably 70%. the following.

Polyoxane

The coating layer contains 5 to 50% by weight of a polyfluorene oxide per 100% by weight of the composition of the coating layer, preferably 10 to 30% by weight. When the polyoxygenated compound is less than 5% by weight, the smoothness is insufficient, and when it is more than 50% by weight, good adhesion to the UV ink cannot be obtained.

In the present invention, the polyoxymethylene compound is a compound based on an organic fluorinated alkane, such as dimethyl polyfluorene oxide, methyl phenyl polyoxynium, methyl hydrogen polyoxyn oxide, or fluorinated polyoxyl , polyoxyl polyether copolymer, alkyl modified polyoxane, higher fatty acid modified polyfluorene.

When a polyfluorene oxide compound having a reactive group is used as the polyfluorene oxide compound, the coating layer can be prevented from falling off, and smoothness or antistatic property can be maintained for a long period of time, and the contamination is not caused by the dropping component. Under the circumstance, production can be carried out with high productivity.

Antistatic agent

The coating layer contains 15 to 80% by weight of an antistatic agent per 100% by weight of the composition of the coating layer, preferably 30 to 70% by weight. When the amount is less than 15% by weight, the antistatic agent becomes insufficient, and dust adheres easily on the surface of the film. When the amount is more than 80% by weight, a sufficient amount of the ultraviolet absorber cannot be contained, and the ultraviolet absorbing performance is insufficient.

The antistatic agent is an agent for imparting antistatic properties, preferably a cationic polymer, preferably a vinyl polymer, a cationic group in a side chain, and a cationic group of four. A compound of an ammonium salt.

Quaternary ammonium salts such as quaternary ammonium sulfonates, quaternary ammonium sulfates, and quaternary ammonium nitrates.

In the coated polyester film for a reflector of the present invention, by incorporating an antistatic agent into the coating film, the surface specific resistance can be 1 × 10 ¹² Ω / □ or less, preferably 1 × 10 ¹¹ Ω / □ or less. .

Surfactant

It is preferred that the coating layer be provided by using an aqueous coating liquid. In this case, in order to form a coating liquid in the case of forming a coating layer, it is preferable to mix the composition of the coating layer with a chemically inert surfactant. When the surfactant is blended, for example, it is blended in an amount of 1 to 20% by weight, preferably 10 to 20% by weight, per 100% by weight of the coating layer. When it is blended in this range, the wettability of the aqueous coating liquid to the polyester film can be promoted, and the stability of the coating liquid can be improved.

Surfactants such as polyoxyethylene-fatty acid esters, sorbitan fatty acid esters, glycerol fatty acid esters, fatty acid metal soaps, alkyl sulfates, alkyl sulfonates, alkyl sulfosuccinates, etc. Anionic, nonionic surfactant.

additive

In the coating layer, an additive may be blended in an amount that does not impair the effects of the invention. The additive is, for example, a fluorescent whitening agent or an antioxidant.

Production method

In the following, an example of a method for producing a polyester film for a reflecting plate according to the first invention of the present invention will be described.

The blending of the barium sulfate particles with the copolymerized polyester film can be carried out during the polymerization of the polyester or after the polymerization. When it is carried out during the polymerization, it may be blended before the completion of the transesterification reaction or the esterification reaction, or may be blended before the start of the polycondensation reaction.

When it is carried out after the polymerization, it is added to the polymerized polyester and subjected to melt kneading treatment. At this time, by producing a main pellet containing barium sulfate particles at a relatively high concentration and blending the same with the polyester pellets containing no barium sulfate particles, the desired content of the polyester containing barium sulfate particles is obtained. Composition.

In the present invention, a non-woven filter having an average mesh size of 10 to 100 μm (preferably an average mesh of 20 to 50 μm) formed by a stainless steel fine wire having a wire diameter of 15 μm or less is used as a filter for film formation, and a polyester composition is formed. The material is preferred. By carrying out the filtration, it is generally possible to suppress the aggregation of particles which are easily aggregated to form coarse aggregated particles, and to obtain a film having a small amount of foreign matter.

The laminated unstretched sheet is produced by a method in which the polyester composition melted from the mold is extruded in a plurality of layers while using the supply region. In other words, the melt of the polyester composition constituting the white reflective layer and the melt of the polyester composition constituting the support layer are used in a supply region to laminate the white reflective layer/support layer, and are developed and implemented in the mold. Execution processing. At this time, the polyester composition laminated in the supply zone is maintained in a laminated form.

In the following, the glass transition temperature of the polyester is referred to as Tg, and the melting point is referred to as Tm.

The unstretched sheets extruded from the mold are cooled and solidified in a casting bucket to form an unstretched film. The unstretched film is heated by roll heating, infrared heating or the like, and is extended in the longitudinal direction to obtain a longitudinally stretched film. This extension is preferably carried out by using a peripheral speed difference of two or more rolls.

The elongation temperature is preferably a temperature higher than Tg, and more preferably a temperature in the range of Tg to (Tg + 70) °C. The stretching ratio is determined depending on the required characteristics of the application, and the longitudinal direction and the direction perpendicular to the longitudinal direction (hereinafter referred to as the lateral direction) are preferably 2.2 to 4.0 times, more preferably 2.3 to 3.9 times. When it is less than 2.2 times, the thickness of the film is deteriorated, and a good film cannot be obtained. When it is more than 4.0 times, cracking is likely to occur in the film formation, which is not desirable. The longitudinally stretched film is continuously subjected to lateral stretching, heat setting, and thermal relaxation treatment to form a biaxial alignment film, but the treatment is such that the film is walked and carried out. The cross-extension treatment begins at a higher temperature than the Tg of the polyester. Then, the temperature is raised and raised at any temperature in the range of (Tg + 5) to (Tg + 70) °C. During the horizontal extension process, the temperature can be continuously increased, and the temperature can be increased in a stepwise manner (sequentially), but the temperature is usually increased sequentially. For example, by dividing the laterally extending region of the tenter into a plurality of zones along the traveling direction of the film, a heating medium of a predetermined temperature is passed through each zone to raise the temperature. The lateral extension ratio can also be determined depending on the required characteristics of the application, preferably from 2.5 to 4.5 times, and more preferably from 2.8 to 3.9 times. When it is less than 2.5 times, the thickness of the film is deteriorated, and a good film cannot be obtained. When it is more than 4.5 times, cracking easily occurs in film formation.

The film after the transverse stretching can be heat-treated at a width of (Tm-20) ° C to (Tm - 100) ° C at a fixed width or a width of 10% or less to reduce the heat shrinkage rate. Therefore, the flatness of the film is deteriorated at a high temperature, and the thickness of the film is increased, which is not desirable. Further, when the heat treatment temperature is lower than (Tm - 100) ° C, the heat shrinkage rate is increased, so that it is not desirable.

Further, in the process of returning the film temperature to room temperature after heat setting, in order to adjust the amount of heat shrinkage, both ends of the fixed film can be cut, and the drawing speed in the longitudinal direction of the film can be adjusted to relax in the longitudinal direction. The method of slack is to adjust the speed of the roller group on the exit side of the tenter. The ratio of slack is reduced by the speed of the roll line of the tenter, preferably from 0.1 to 1.5%, more preferably from 0.2 to 1.2%, and most preferably from 0.3 to 1.0%. The treatment is lowered to relax the film and adjust the heat shrinkage in the longitudinal direction. Further, the width direction of the film can be reduced in the process of cutting both ends, and the desired heat shrinkage rate can be obtained.

Here, when the film is stretched by the sequential biaxial stretching method, it will be described in detail by way of example, but it may be extended by either the sequential biaxial stretching method or the simultaneous biaxial stretching method.

The obtained polyester film for a reflecting plate according to the second and third aspects of the present invention is composed of two layers of a support layer and a white reflective layer provided on one surface thereof, and good flatness can be obtained.

Next, an example of a method for producing a coated polyester film for a reflecting plate according to the second and third inventions of the present invention will be described. The coating liquid used in the formation of the coating layer is preferably used in the form of an aqueous coating liquid (for example, an aqueous solution, an aqueous dispersion, or an emulsion). The solid content concentration of the aqueous coating liquid is usually 20% by weight or less, preferably 1 to 10% by weight. When the amount is less than 1% by weight, the coating property to the polyester film is insufficient, so that it is not desirable. When the amount is more than 20% by weight, the stability of the coating liquid or the appearance of the coating layer is deteriorated, which is not desirable.

The application of the aqueous coating liquid to the polyester film can be carried out at any stage, but it is preferably carried out in the production process of the polyester film, and is preferably applied to the polyester film before the completion of the alignment crystallization.

Here, the polyester before the completion of the crystallization is included in the one-axis alignment film in which the unstretched film or the unstretched film is aligned in either the longitudinal direction or the transverse direction, and is subjected to a low magnification in both the longitudinal direction and the transverse direction. Extending the aligner (finally extending in the longitudinal or transverse direction to complete the biaxially stretched film before the alignment crystallization). Among them, the uncoated film or the one-axis stretch film which is oriented in one direction is preferably coated with the aqueous coating liquid of the above composition, and is preferably subjected to longitudinal stretching and/or lateral stretching and heat setting treatment.

When the aqueous coating liquid is applied to the film, in order to improve the applicability, the surface of the film is subjected to physical treatment such as electric discharge surface treatment, flame treatment, or plasma treatment, or when there is no preliminary treatment. A surfactant which is chemically inert with the composition of the coating layer in the cloth liquid is preferred.

As the coating method, any conventional coating method can be used. For example, a roll coating method, a gravure coating method, a roll brush method, a spray coating method, an air knife coating method, an impregnation method, and a curtain coating method. These can be used singly or in combination.

According to the obtained coated polyester film for a reflecting plate of the present invention, the reflectance of at least one surface can be 90% or more at a wavelength of 400 to 700 nm, preferably 92% or more. The best is more than 94%. When the reflectance of this range is used, when a reflector which is a backlight unit of a liquid crystal display device is used, high luminance can be obtained.

In the following, the invention will be described in detail by way of examples. Moreover, the measurement and evaluation were carried out in the following manner.

(1) Film thickness

The film sample was measured for thickness of 10 points by an electronic micrometer (K-402B manufactured by Anritsu), and the average value was used as the thickness of the film.

(2) Thickness of each layer

The film sample was cut into triangles, fixed in an embedding capsule, and embedded in epoxy resin. Then, the embedded thin film sample was subjected to thin film slicing in the longitudinal direction by a micro-slice device (UL-TRACUT-S), and then photographed by an optical microscope, and the thickness ratio of each layer was measured from the photograph by the film test. Calculate the thickness of each sample and determine the thickness of each layer.

(3) Reflectivity

(3-1) Reflectance (%)

An integrating sphere was placed on a spectrophotometer (UV-3101PC manufactured by Shimadzu Corporation), and when the BaSO ₄ whiteboard was 100%, the reflectance of the film was measured at 400 to 700 nm, and the reflectance was read from the obtained graph at intervals of 2 nm. . Further, a film composed of two layers of the A layer (white reflective layer) / the B layer (support layer) was measured using the A layer (white reflective layer) as a reflecting surface.

(3-2) UV reflectance (%)

An integrating sphere was placed on a spectrophotometer (UV-3101PC manufactured by Shimadzu Corporation), and when the BaSO ₄ whiteboard was 100%, the reflectance (%) of the film was measured at a wavelength of 365 nm. Further, a film composed of two layers of the A layer (white reflective layer) / the B layer (support layer) was measured using the A layer (white reflective layer) as a reflecting surface.

(4) Extensibility

The film was stretched in a direction of 2.5 to 3.4 times in the longitudinal direction and 3.5 to 3.7 times in the transverse direction to form a film, and it was observed whether or not the film was formed stably, and the evaluation was performed based on the following criteria.

○: It can be stably formed for more than 1 hour.

×: The film was cut off less than 1 hour ago, and it was impossible to form a film stably.

(5) Glass transition point (Tg), melting point (Tm)

The measurement was performed at a temperature increase rate of 20 m/min using a differential scanning calorimeter (TA Instruments 2100 DSC).

(6) Assembly of the film sample to the background light unit

The light-reflecting sheet of the original assembly was taken out from the background light (20 Å) of the liquid crystal television (AQUOS-20V manufactured by SHARP Co., Ltd.) for evaluation, and the film sample to be measured was assembled. Further, a film composed of two layers of the A layer (white reflective layer) / the B layer (support layer) is assembled with the A layer (white reflective layer) as a reflecting surface.

(7) Brightness of the reflector

The light-emitting surface of the backlight unit was divided into four regions of 2 × 2, and the front luminance after one hour of lighting was measured using BM-7 manufactured by TOPCON Corporation. The measurement angle was 1°, and the distance between the luminance meter and the backlight unit light-emitting surface was 50 cm. A simple average of the four luminances in the plane of the backlight unit light-emitting surface is obtained as the luminance.

(8) Warpage of the film

The film was cut into a rectangular shape having a length of 200 mm in the film forming direction and cut into a length of 50 mm in the width direction, and used as a film sample for measurement of warpage. Further, a direction perpendicular to the film forming direction of the film is referred to as a width direction. The film sample was placed vertically, and the short side of the film sample (hereinafter referred to as the short side of the upper end) was fixed, and the film sample was suspended. This fixing was carried out by fixing the fixing portion to a clip having a width of 50 mm and a depth of 5 mm so that the upper short side was fixed in a range of a width of 50 mm and a depth of 5 mm. At this time, the other short side of the sample (hereinafter referred to as the lower end short side) is disposed below the short side of the upper end. The film sample was subjected to heat treatment in this state. This heat treatment was carried out by holding the film sample in an oven at 85 ° C for 30 minutes in a state of no tension, and then taking it out of the oven and cooling it in an environment of 25 ° C for 10 minutes. By this heat treatment, the film sample is warped, and the short side of the lower end is moved from the original position. The degree of warpage was measured by measuring the distance from the upper side of the upper short side to the short side of the lower end. This distance is shown in the "warping" column of the table.

(9) Planarity of the film

The light-reflecting sheet of the original assembly was taken out from the background light (65 Å) of the liquid crystal television (AQUOS-65V manufactured by SHARP Co., Ltd.), and the film sample to be measured was assembled. At this time, the layer A (white reflective layer) is used as a reflecting surface.

After the power is turned on and left for 24 hours, the sample for evaluation is taken out, and the evaluation sample is distributed on a flat plate having a high plane precision and an air removal hole, so that the air on the film and the flat plate is naturally left for more than 3 minutes. After the reduction, the maximum length in the film formation direction of the floating portion of each of the produced films was measured, and the total value was obtained.

(10) noise

Overlay acrylic sheets on film samples in an environment where the background light level is below 20 dB (ACRYLITE L N865), on which a negative hammer is loaded, and the film is stretched at a constant speed (10 cm/min), and the generated abnormal sound is collected from a hammer and a microphone having a distance of 30 cm. When an abnormal sound of 40 dB or more is generated, it is called a noise, and when only a noise of less than 40 dB is generated, it is called no noise. Further, regarding the film of the two layers of the A layer (white reflective layer) / the B layer (support layer), the acrylic plate was superposed on the side of the A layer (white reflective layer). ○, △ has practical performance.

○: The hammer of 3 kg did not cause noise, and the hammer of 5 kg did not generate noise.

△: In the case where the hammer of 3 kg did not generate a noise, a hammer of 5 kg was used to generate a noise.

×: A noise is generated by a hammer of 3 kg.

(11) Surface specific resistance (Ω/□)

The surface specific resistance of the surface of the coating layer of the film sample was measured. The surface resistance (Ω/□) after holding for 1 minute at an applied voltage of 100 V was measured by using a natural resistance measuring instrument manufactured by Takeda Riken Co., Ltd., and measuring humidity of 23 ° C and measuring humidity of 60% for one day. In the table, a+bE means a × 10 ^b .

(12) Average particle size

The measurement was carried out using a CP-50-type Centrifugal Particle Size Analyzer manufactured by Shimadzu Corporation. From the obtained centrifugal sedimentation curve, the cumulative curve of the particles having the respective particle diameters and the amount of the particles thereof was obtained, and the particle diameter corresponding to 50% by mass was read, and this value was used as the average particle diameter.

(13) UV ink adhesion

A polyester film having a thickness of 250 μm was attached to one surface of the coating layer on which the sample film was not applied, and an ultraviolet ray was printed on one side of the coating layer by an RI tester (manufactured by Mingsho Co., Ltd.). Hardened printing ink (Flash Dry FDO Red APN made by Toyo Ink). Then, it was subjected to a hardening treatment using a medium pressure mercury lamp UV curing device (80 W/cm, one lamp type, manufactured by Nippon Battery Co., Ltd.) to form a UV ink layer having a thickness of 3.0 μm. A tape of 15 cm in length (18 mm wide, made in Japan) was attached to the UV ink layer, and a film having a load of 2 kg on a manual load roller was fixed thereon, and one end of the tape was observed to be 90°. The direction of the UV ink layer after peeling. The adhesion of the UV ink was evaluated by the following criteria. ○, △ has practical performance.

○: The UV ink layer was not peeled at all (the UV ink adhesion was good)

△: Peeling phenomenon in which the coating film and the UV ink layer are partially agglomerated and broken (the UV ink adhesion is slightly better)

×: peeling between the coating film and the UV ink layer in a layered manner (poor ink adhesion)

Example 1

132 parts by weight of dimethyl terephthalate, 18 parts by weight of dimethyl isophthalate (12 mole % of polyester for the whole carboxylic acid component), 96 parts by weight of ethylene glycol, 3.0 weight Diethylene glycol, 0.05 parts by weight of manganese acetate, and 0.012 parts by weight of lithium acetate are placed in a flask equipped with a rectification column and a distillation condenser, stirred, and heated at 150 to 235 ° C to carry out methanol distillation. The transesterification reaction. After distilling off methanol, 0.03 part by weight of trimethyl phosphate and 0.04 part by weight of cerium oxide were added to transfer the reactant to the reactor. Then, stirring was carried out, and the inside of the reactor was gradually reduced to 0.5 mmHg, and the temperature was raised to 290 ° C to carry out a polycondensation reaction. The amount of the diethylene glycol component of the obtained copolymerized polyester was 2.5% by weight, the amount of the lanthanum element was 50 ppm, and the amount of the phosphorus element was 5 ppm. The copolymerized polyester was added as shown in Table 1 and the inert particles were added as shown in Table 1 (based on the total weight of the composition) to obtain a polyester composition used as the layer A.

Further, 132 parts by weight of dimethyl terephthalate, 9 parts by weight of dimethyl isophthalate (6 mol% of polyester for all dicarboxylic acid components), and 96 parts by weight of ethylene An alcohol, 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 are placed in a flask equipped with a rectification column and a distillation condenser, stirred, and heated at 150 to 235 ° C. A transesterification reaction for distilling off methanol is carried out. After distilling off methanol, 0.03 part by weight of trimethyl phosphate and 0.04 part by weight of cerium oxide were added to transfer the reactant to the reactor. Then, stirring was carried out, and the inside of the reactor was gradually reduced to 0.5 mmHg, and the temperature was raised to 290 ° C to carry out a polycondensation reaction. The amount of the diethylene glycol component of the obtained copolymerized polyester was 2.5% by weight, the amount of the lanthanum element was 50 ppm, and the amount of the phosphorus element was 5 ppm. The copolymerized polyester was added as shown in Table 2, and the inert particles were added under the content shown in Table 2 (based on the total weight of the composition) to obtain a polyester composition used as the layer B.

The polyester composition used in the layer A was supplied to an extruder heated at 280 ° C, and the polyester composition used in the layer B was supplied to an extruder heated at 280 ° C, and the polyester composition of the layer A was made. The polyester composition of the layer B is joined by a layer 2 and a layer B in a layer 2 supply area device under A/B, and formed into a sheet shape by molding while maintaining the layered state.

The obtained sheet was cooled and hardened in a cooling barrel having a surface temperature of 25 ° C to form an unstretched film, and the unstretched film was stretched 3.0 times in the longitudinal direction (longitudinal direction) at 90 ° C to a roll group of 25 ° C. Cool down. Then, both ends of the longitudinally stretched film were fixed by a clip and introduced into a tenter, and extended 3.6 times in the vertical direction (lateral direction) in a gas atmosphere heated at 120 °C. Then, the film was thermally hardened in a tenter at a temperature of 200 ° C for 3 seconds, and then subjected to a relaxation treatment of 0.5% in the longitudinal direction, a relaxation treatment of 2.0% in the lateral direction, and cooling to room temperature to obtain A polyester film for a reflecting plate having a film thickness of 153 μm, an A layer of 116 μm, and a B layer of 37 μm of a biaxially stretched film. The evaluation results of the obtained film are shown in Table 5.

In the table, PET means polyethylene terephthalate, IPA means isophthalic acid, Tg means a glass transition temperature of a copolymerized polymer, and Tm means a melting point.

Examples 2 to 10

The polyester composition of the layer A was changed to the copolymerized polyester and inert particles as shown in Table 1, and the content of the inert particles shown in Table 1 (based on the total weight of the composition) of the polyester composition Things. Further, the polyester composition of the layer B was changed to a copolymerized polyester and inert particles as shown in Table 2, and the content of the inert particles shown in Table 2 (based on the total weight of the composition) was aggregated. Ester composition.

The biaxially stretched film was obtained in the same manner as in Example 1 except that the thickness of the film after the biaxial stretching and the thickness of the layer A and the thickness of the layer B were as shown in Table 3. The evaluation results of the obtained biaxially stretched film are shown in Table 5.

Comparative Examples 1 to 9

The polyester composition of the layer A was changed to the copolymerized polyester and inert particles as shown in Table 1, and the content of the inert particles shown in Table 1 (based on the total weight of the composition) of the polyester composition Things. Further, the polyester composition of the layer B was changed to a copolymerized polyester and inert particles as shown in Table 2, and the content of the inert particles shown in Table 2 (based on the total weight of the composition) was aggregated. Ester composition.

The biaxially stretched film was obtained in the same manner as in Example 1 except that the thickness of the film after the biaxial stretching and the thickness of the layer A and the thickness of the layer B were as shown in Table 3. The evaluation results of the obtained biaxially stretched film are shown in Table 5.

Examples 11 to 21

132 parts by weight of dimethyl terephthalate, 18 parts by weight of dimethyl isophthalate (12 mol% of polyester for all dicarboxylic acid components), 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 placed in a flask equipped with a rectification column and a distillation condenser, stirred, and heated at 150 to 235 ° C to cause Transesterification of methanol distillation. After distilling off methanol, 0.03 part by weight of trimethyl phosphate and 0.04 part by weight of cerium oxide were added to transfer the reactant to the reactor. Then, stirring was carried out, and the inside of the reactor was gradually reduced to 0.5 mmHg, and the temperature was raised to 290 ° C to carry out a polycondensation reaction. The amount of the diethylene glycol component of the obtained copolymerized polyester was 2.5% by weight, the amount of the lanthanum element was 50 ppm, and the amount of the phosphorus element was 5 ppm. The copolymerized polyester was added as shown in Table 1 and the inert particles were added as shown in Table 1 (based on the total weight of the composition) to obtain a polyester composition used as the layer A.

132 parts by weight of dimethyl terephthalate, 9 parts by weight of dimethyl isophthalate (6 mol% of polyester for all dicarboxylic acid components), 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 placed in a flask equipped with a rectification column and a distillation condenser, stirred, and heated at 150 to 235 ° C to cause Transesterification of methanol distillation. After distilling off methanol, 0.03 part by weight of trimethyl phosphate and 0.04 part by weight of cerium oxide were added to transfer the reactant to the reactor. Then, stirring was carried out, and the inside of the reactor was gradually reduced to 0.5 mmHg, and the temperature was raised to 290 ° C to carry out a polycondensation reaction. The amount of the diethylene glycol component of the obtained copolymerized polyester was 2.5% by weight, the amount of the lanthanum element was 50 ppm, and the amount of the phosphorus element was 5 ppm. The copolymerized polyester was added as shown in Table 2, and the inert particles were added under the content shown in Table 2 (based on the total weight of the composition) to obtain a polyester composition used as the layer B.

The polyester composition used in the layer A was supplied to an extruder heated at 280 ° C, and the polyester composition used in the layer B was supplied to an extruder heated at 280 ° C, and the polyester composition of the layer A was made. The polyester composition of the layer B is joined by a layer 2 and a layer B in a layer 2 supply area device under A/B, and formed into a sheet shape by molding while maintaining the layered state.

The obtained sheet was cooled and hardened in a cooling barrel having a surface temperature of 20 ° C to form an unstretched film, and the unstretched film was stretched 3.0 times in the longitudinal direction (longitudinal direction) at 95 ° C to a roll group of 25 ° C. Cool down. The coating liquid shown in Table 4 (solid content concentration: 2% by weight) was uniformly coated on the surface of the white layer by a roll coater under the conditions. Then, both ends of the longitudinally stretched film were fixed by a clip and introduced into a tenter, and extended 3.6 times in the vertical direction (lateral direction) in a gas atmosphere heated at 120 °C. Then, the film was thermally hardened in a tenter at a temperature of 200 ° C for 3 seconds, and then subjected to a relaxation treatment of 0.5% in the longitudinal direction, a relaxation treatment of 2.0% in the lateral direction, and cooling to room temperature to obtain The thickness of the film and the thickness of the layer A and the thickness of the layer B are as shown in Table 3 for the coated polyester film for the reflector of the biaxially stretched film. The heat shrinkage rate of the obtained film at 85 ° C for 30 minutes was 0.1% in the longitudinal direction and 0.1% in the width direction. The evaluation results of the obtained film are shown in Table 5.

Further, the components of the coating liquid in Table 4 are as follows.

UV absorber 1:

A copolymer formed of 50 mol% of a structure represented by the following formula / 45 mol % of methyl methacrylate / 5 mol % of 2-hydroxyethyl methacrylate.

The ultraviolet absorber 1 is a methacrylate resin having a benzotriazole group in a side chain.

Antistatic agent 1:

A copolymer of /10 mol% of methacrylate/10 mol% of N-methylol acrylamide as shown by the following formula of 80 mol%.

(wherein R ¹ and R ² are each H, R ³ is an alkylene group having 3 carbon atoms, R ⁴ and R ⁵ are each a saturated hydrocarbon group having 1 carbon number, and R ⁶ is a hydroxyl group having 2 carbon atoms; Alkylene, Y ^- line is a methylsulfonate ion)

Antistatic agent 2:

a copolymer of 80 mol% dimethylaminoethyl sulfonate methacrylate/10 mol% methacrylate/10 mol% N-methylol acrylamide .

Polyoxane 1:

Carboxyl modified polyfluorene (trade name X22-3701E, manufactured by Shin-Etsu Chemical Co., Ltd.)

Polyoxane 2:

Epoxy modified polyxanthine (trade name KF-101 manufactured by Shin-Etsu Chemical Co., Ltd.)

Polyoxane 3:

Amine-modified polyfluorene (trade name KF-8012, manufactured by Shin-Etsu Chemical Co., Ltd.)

Polyoxane 4:

Hydrophilic special modified polyfluorene (trade name X22-904, manufactured by Shin-Etsu Chemical Co., Ltd.)

Further, the polyoxo compounds 1 to 4 are mixed with a surfactant in advance and then added to the coating liquid.

Surfactant:

Polyethylene oxide (n=8.5) lauryl ether (Sanyo Chemical Co., Ltd., trade name Nairon Yagudi (transliteration) N-85)

Crosslinker:

Oxazoline (trade name EPOCROS, manufactured by Nippon Shokubai Co., Ltd.) WS-700)

[Effect of the invention]

According to the first invention of the present invention, it is possible to provide a polyester film for a reflecting sheet which is excellent in stretchability and which is excellent in planarity in which the reflecting plate used as the backlight unit of the liquid crystal display device is warped in the use environment. .

According to the second aspect of the present invention, it is possible to provide an antistatic property in addition to the above-described characteristics, and excellent adhesion to ink used in dot printing, and when the reflector is assembled in a backlight unit, it does not cause friction with other members. The sound is a coating film for a reflector for suppressing ultraviolet rays from being caused by deterioration of other members disposed in the vicinity of the reflector.

According to the third aspect of the present invention, it is possible to provide an antistatic property and excellent adhesion to an ink used for dot printing, and when it is incorporated as a backlight unit as a reflector, it does not cause frictional sound with other members, and does not cause The other member disposed near the reflector has a coated polyester film for the reflector for suppressing ultraviolet light reflection.

[Industry use value]

The polyester film for a reflecting plate and the coated polyester film for a reflecting plate of the present invention can be used as a reflecting plate when a white reflecting layer is used as a reflecting surface, and is particularly suitable as a surface light reflecting plate of a backlight unit of a liquid crystal display device. use.

Claims (3)

A polyester film for a reflector, characterized by a support layer and a white reflective layer disposed thereon, the support layer being composed of 0.1 to 10% by weight of barium sulfate particles and 99.9 to 90% by weight of isophthalic acid The composition is formed as a polyethylene terephthalate having a copolymerization component, and has a thickness of 10 to 40 in a total thickness of 100 films, and the white reflective layer is composed of 31 to 60% by weight of barium sulfate particles and 69 to 40. The weight % is formed by polyethylene terephthalate, wherein the copolymerization amount of the isophthalic acid component as a copolymerization component is 6 to 18 mol%; and the total thickness of the film per 100 is 90 to 60 The ratio of the content of the isophthalic acid component contained in the polyester constituting the white reflective layer to the content ratio of the isophthalic acid component contained in the polyester constituting the support layer (constituting the white reflective layer) The content ratio of the isophthalic acid component contained in the polyester/the content of the isophthalic acid component contained in the polyester constituting the support layer is 1.5 to 3.0. The polyester film for a reflecting plate according to claim 1, wherein the support layer and the white reflective layer provided on one surface thereof are composed of two layers. A coated polyester film for a reflecting plate, which is characterized in that the polyester film for a reflecting plate according to the first application of the patent application and the coating layer coated on the film are formed by a coating layer of 15~ 80% by weight of a (meth)acrylic resin having a benzotriazolyl group, 5 to 50% by weight of a polyfluorene oxide compound, 15 to 80% by weight of an antistatic agent, and a coating layer having a thickness of 0.02 to 0.2 μm .