KR20110130411A - White film for reflector - Google Patents

Abstract

It consists of the light reflection layer whose void volume ratio is 55 to 80%, and the support layer of the biaxially stretched polyester film formed in the at least one surface, The ratio of the sum total of the thickness of a light reflection layer and the thickness of a support layer is 85: 15- It is 98: 2, the reflectance of a film is 98.0% or more, the punching energy by a drop impact test is 0.10-0.30 J, and the film thickness is 150-250 micrometers, The liquid crystal display device by the white film for reflecting plates characterized by the above-mentioned. When used as a reflecting plate in the backlight unit of the present invention, high luminance can be obtained, and burrs and whiskers are hardly generated during punching, and the white film for reflecting plate used in the backlight unit of the liquid crystal display device excellent in punching property is provided.

Description

White film for reflector {WHITE FILM FOR REFLECTOR}

This invention relates to the white film for reflecting plates used as a reflecting plate of the backlight unit of a liquid crystal display device.

In the backlight unit of the liquid crystal display device, a reflecting plate is provided on the back side to prevent the light from the light source from falling back to the back side of the screen. This reflecting plate is required to have a thin and high reflectance.

As a white film for reflecting plates used for the backlight unit for liquid crystal display devices, the white polyester film containing a fine bubble inside a film is known, and is used widely.

Japanese Laid-Open Patent Publication No. 63-62104 Japanese Patent Publication Hei 8-16175 Japanese Unexamined Patent Publication No. 2000-37835 Japanese Laid-Open Patent Publication 2005-125700 Japanese Unexamined Patent Publication No. 2004-50479

The white film for reflecting plates is processed into a predetermined shape and mounted on the backlight unit. There exists a process of cutting the white film for reflecting plates to a predetermined shape for this process, but the cutting speed in this process becomes faster as mass production of a backlight unit advances.

It is easy to generate | occur | produce a beard-like thing and a burr in the cross section of a film at the time of cutting, that high brightness is obtained with the conventional reflective film. The beard is a fine protrusion generated on the cut surface by the cutting, which needs to be removed as dust, so that the occurrence of the beard is reduced in productivity. In addition, the burr is a part that protrudes in the vicinity of the cut surface caused by the cutting, and if the burr is present, the distance between the reflecting surface and the light source may change, which may adversely affect the luminance and may not be able to obtain a uniform luminance. have.

This invention is a white film for reflecting plates which has a high reflectance and can obtain a high brightness when used as a reflecting plate for the backlight unit of a liquid crystal display device, and does not generate | occur | produce burr and beard shape well at the time of a punching process, It is an object to provide a white film for reflecting plates excellent in punchability.

Secondly, the present invention further provides a white film for a reflecting plate having excellent flatness by suppressing thermal warpage in a use environment as a reflecting plate of a liquid crystal display device.

That is, this invention consists of the light reflection layer whose void volume ratio is 55 to 80%, and the support layer of the biaxially stretched polyether film formed in the at least one surface, of the sum total of the thickness of a light reflection layer, and the sum of the thickness of a support layer. The ratio is 85:15 to 98: 2, the light reflectance of the film is 98.0% or more, the punching energy by the drop impact test is 0.10 to 0.30 J, and the film thickness is 150 to 250 µm. It is a film.

ADVANTAGE OF THE INVENTION According to this invention, it is a white film for reflecting plates which has a high reflectance and can obtain a high brightness when used as a reflecting plate for the backlight unit of a liquid crystal display device, and it does not generate | occur | produce burr and beard shape at the time of punching, This excellent white film for reflecting plates can be provided.

Secondly, the present invention can further provide a white film for a reflecting plate of a backlight unit of a liquid crystal display device, in which heat warping in a use environment as a reflecting plate of a liquid crystal display device is suppressed and excellent in flatness.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

The white film for reflecting plates of this invention consists of a light reflection layer and the support layer of the biaxially stretched polyester film formed in at least one surface thereof.

Light reflection layer

The light reflection layer in the present invention is formed by forming a void at the interface between the thermoplastic resin and the void forming material by incorporating a white colorant into the thermoplastic resin to extend the layer or void forming material to be white, and forming the void in the thermoplastic resin. It is a layer of the thermoplastic resin composition made to show.

The void volume ratio of the light reflection layer in this invention is 55 to 80%, More preferably, it is 60 to 75%, Especially preferably, it is 62 to 70%. If the void volume ratio is less than 55%, high reflectance cannot be obtained, and the punching workability is also inferior. On the other hand, when void volume ratio exceeds 80%, film manufacture becomes very difficult.

Thermoplastic polyester

As the thermoplastic resin of the light reflection layer in the present invention, thermoplastic polyester is preferably used. When using a thermoplastic polyester, the polyester which consists of a dicarboxylic acid component and a diol component is used. As this dicarboxylic acid, terephthalic acid, isophthalic acid, 2, 6- naphthalenedicarboxylic acid, 4, 4'- diphenyl dicarboxylic acid, adipic acid, sebacic acid is mentioned, for example. As a diol, ethylene glycol, 1, 4- butanediol, 1, 4- cyclohexane dimethanol, 1, 6- hexanediol is mentioned, for example. Among these polyesters, thermoplastic aromatic polyesters are preferred, and polyethylene terephthalate is particularly preferred. The polyethylene terephthalate may be a homopolymer, but a copolymer polymer is preferable, and isophthalic acid copolymerized polyethylene terephthalate is particularly preferable.

When using a polyethylene terephthalate copolymer polymer, the ratio of a copolymerization component is 1-20 mol% based on all the dicarboxylic acid components, Preferably it is 2-15 mol%, More preferably, it is 3-13. Mol%. By setting the ratio of the copolymerization component in this range, excellent film manufacturability can be obtained also for the light reflection layer, and a film excellent in thermal dimensional stability can be obtained.

 When using thermoplastic polyester as a thermoplastic resin of a light reflection layer, the intrinsic viscosity of the thermoplastic polyester measured about the light reflection layer becomes like this. Preferably it is 0.40-0.53 dl / g. By being intrinsic viscosity of this range, the thermoplastic polyester composition of a light reflection layer can melt-extrude easily, even if it contains a high concentration of inorganic particle, and can manufacture a film with high productivity, without breaking a film.

White inorganic particles

As a white coloring agent of a light reflection layer, white inorganic particle is used. As the void-forming substance, white inorganic particles, organic particles or incompatible resins are used. As the white inorganic particles, for example, barium sulfate particles, titanium dioxide particles, silicon dioxide particles, and calcium carbonate particles can be used, and barium sulfate particles are particularly preferable.

The average particle diameter of white inorganic particle becomes like this. Preferably it is 0.1-3.0 micrometers, More preferably, it is 0.2-2.5 micrometers, Especially preferably, it is 0.3-2.0 micrometers. By using the white inorganic particle of the average particle diameter of this range, it can be disperse | distributed suitably in the thermoplastic resin of a light reflection layer, hardly agglomeration of white inorganic particle, the light reflection layer which has no coarse protrusion on the surface can be obtained, and simultaneously The surface of the reflective layer is not too rough, so that the glossiness in an appropriate range can be achieved. The most preferable white inorganic particles are barium sulfate particles having an average particle diameter of 0.1 to 3.0 µm, and the average particle diameter of the white inorganic particles adopts d50 (median diameter), but d10 having a small particle diameter of 10% to a small one. When represented by 90%, d90, d90 / d10 of particle size distribution becomes like this. Preferably it is 1-500, More preferably, it is 1-300, More preferably, it is 1-100, Especially preferably, it is 1-50. If it is the particle size distribution of this range, coarse particle will not be clogged by a filter and a fine particle will not reaggregate, and it can manufacture film stably.

What kind of particle shape may the white inorganic particle be, for example, may be plate shape, or spherical shape. The white inorganic particle may be surface-treated in order to improve dispersibility.

When using organic particle | grains as a void formation material, the particle | grains of a polymer can be used, for example, specifically, a crosslinked polystyrene particle and an acryl particle can be used, for example.

When incompatible resin is used as a void formation material, resin incompatible with the thermoplastic resin of a light reflection layer is used. When using thermoplastic polyester, especially polyethylene terephthalate or its copolymer polymer, as a thermoplastic resin of a light reflection layer, polyolefin and polystyrene can be used as an incompatible resin, for example.

When the light reflection layer is composed of a thermoplastic polyester composition composed of white inorganic particles and thermoplastic polyester, in this composition, the white inorganic particles preferably occupy 50 to 60% by weight, and the thermoplastic polyester is preferably 50 to Occupies 40% by weight. When the composition is within this range, good reflectance, punching property, and stable film film production can be expected. In this composition, white inorganic particle becomes like this. More preferably, it is 52 to 60 weight%, More preferably, it is 53 to 59 weight%, Especially preferably, it occupies 54 to 58 weight%.

When the light reflection layer is composed of a thermoplastic polyester composition composed of organic particles and a thermoplastic polyester, in this composition, the organic particles preferably occupy 50 to 60% by weight and the thermoplastic polyester is preferably 50 to 40% by weight. Occupies. If it is the composition of this range, favorable reflectance, punching workability, and stable film film manufacture can be anticipated. In this composition, the organic particles are more preferably 52 to 60% by weight, still more preferably 53 to 59% by weight, particularly preferably 54 to 58% by weight.

When the light reflection layer is composed of a thermoplastic polyester composition composed of an incompatible resin and a thermoplastic polyester, in this composition, the incompatible resin preferably accounts for 50 to 60% by weight, and the thermoplastic polyester is preferably 50 to 40% by weight. Occupies%. If the composition is within this range, good reflectance, punching property, and stable film film production can be expected. In this composition, incompatible resin becomes like this. More preferably, it is 52 to 60 weight%, More preferably, it is 53 to 59 weight%, Especially preferably, it occupies 54 to 58 weight%.

Support layer

The support layer consists of a biaxially stretched polyester film. This support layer is comprised from thermoplastic polyester, The thermoplastic aromatic polyester which consists of an aromatic dicarboxylic acid component and a diol component as a thermoplastic polyester is preferable, and polyethylene terephthalate is especially preferable. The polyethylene terephthalate may be a homopolymer, but a copolymer polymer is preferable. In the case of the copolymerized polymer, the thermoplastic aromatic polyester of the support layer is preferably 95 to 99.9 mol% of terephthalic acid component and 0.1 to 5 mol% of isophthalic acid component as the dicarboxylic acid component based on the total dicarboxylic acid component. Copolymerized polyethylene terephthalate. By copolymerizing an isophthalic acid component in this range, especially favorable punching property of a support layer can be obtained. The copolymerization amount of the isophthalic acid component is more preferably 0.1 to 4 mol%, particularly preferably 0.1 to 3 mol%.

The support layer may contain white inorganic particles. When the support layer is composed of a thermoplastic polyester composition composed of thermoplastic polyester and white inorganic particles, in this composition, the white inorganic particles preferably occupy 0.1 to 10% by weight, and the thermoplastic polyester is preferably 99.9 to 90 Occupies weight%. When the support layer is a composition in this range, good light reflectance, punching workability, and stable film film production can be expected.

The intrinsic viscosity of the thermoplastic polyester measured about the support layer of the white film for reflecting plates of this invention becomes like this. Preferably it is 0.54-0.65 dl / g. By intrinsic viscosity of this range, the melted polymer can be easily extruded during film production of the film, and the film can be produced with high production efficiency without breaking the film. From the viewpoint of obtaining particularly good punchability and film manufacturability, the intrinsic viscosity of the thermoplastic polyester of the support layer is preferably higher than the intrinsic viscosity of the thermoplastic polyester of the light reflection layer.

Floor composition

It is preferable that the white film for reflecting plates of this invention manufactured by the coextrusion method. That is, it is preferable that the light reflection layer and the support layer are laminated by the coextrusion method.

The white film for reflecting plates of this invention contains a single or multiple light reflection layer, and contains a single or multiple support layer. The ratio of the sum of the thickness of the light reflection layer and the sum of the thickness of the support layer is 85:15 to 98: 2, preferably 95: 5 to 98: 2. When the ratio of the total thickness of the reflective layer to the total thickness of the film is less than 85, it is difficult to obtain a high reflectance. On the other hand, when the ratio exceeds 98, breakage of the film increases, making film production difficult.

The white film for reflecting plates of this invention is a structure in which the support layer was formed in at least one surface of the light reflection layer, and specifically, it is a 3-layered constitution of a light reflection layer / support layer, a support layer / light reflection layer / support layer, for example. 3 layers of the light reflection layer / support layer / light reflection layer, 4 layers of the support layer / light reflection layer / support layer / light reflection layer, and 5 layers of the support layer / light reflection layer / support layer / light reflection layer / support layer. Among these, the three-layer structure of a support layer / light reflection layer / support layer is preferable from a viewpoint of film | membrane manufacture stability and manufacturing cost.

The total thickness of the white film for reflecting plates of this invention is 150-250 micrometers, Preferably it is 170-230 micrometers. By the total thickness of this range, good handling property and productivity can be obtained. If it is less than 150 µm, the reflectance is insufficient. On the other hand, when it exceeds 250 micrometers, although sufficient reflectance will be obtained, punchability will be inferior.

The white film for reflecting plates of this invention is biaxially stretched. By being biaxially stretched, high mechanical strength can be obtained.

Drop impact test

The white film for reflecting plates of this invention needs to have a punching energy of 0.10-0.30 J by a drop impact test. If it is less than 0.10 J, the film itself will be easily cracked, and if it exceeds 0.30 J, a beard or burr will be generated.

Light reflectance

The light reflectance of the white film for reflecting plates of this invention is a light reflectance in wavelength 550nm, Preferably it is 98.0% or more, More preferably, it is 98.5% or more, Especially preferably, it is 99.0% or more. When the light reflectance is 98.0% or more, high luminance can be obtained when used in the backlight unit.

These punching energy and light reflectance can be achieved by the white film of the composition and layer structure of this invention.

Loss tangent tan peak temperature of δ

In the white film for reflecting plates of this invention, it is preferable that the highest peak temperature of the loss tangent tan-delta by dynamic viscoelasticity measurement is 110 degreeC or more. If the highest peak temperature of the loss tangent tan δ is less than 110 ° C., warpage of the film occurs due to the temperature rise due to heat from the cold cathode tube.

Storage modulus E ＇ _{(120 ℃)}  With 50 ℃ In  Storage modulus E ＇ _{(50 ℃)}  Rain of

The white film for reflecting _plates of this invention is the ratio of the storage elastic modulus E ' _{(120 degreeC) at 120 degreeC,} and the storage elastic modulus E' ₍₅₀ degreeC ₎ at 50 degreeC by dynamic viscoelasticity measurement (E ' _{(120 degreeC)} / E _{(50 degreeC)} becomes like this. Preferably it is 0.25-1.00, More preferably, it is 0.27-1.00. If the ratio (E ＇ _{(120 ° C.)} / E＇ _{(50 ° C.)} ) is less than 0.25, the Young's modulus of the film cannot be maintained in the temperature range where the film reaches when heat is applied from the cold cathode tube, and the curvature of the reflective film This happens. The nature of the thermoplastic polyester does not exceed 1.00. Since this ratio (E ' _{(120 degreeC)} / E' _{(50 degreeC)} ) is 0.25-1.00, favorable planarity can be maintained even if it receives heat from a light source.

Young's modulus

It is preferable that the Young's modulus of at least one direction of the white film for reflecting plates of this invention is 3000 Mpa or more. If the Young's modulus is less than 3000 MPa, thermal warpage occurs.

Heat shrinkage

As for the white film for reflecting plates of this invention, in both directions in which the 85 degreeC heat shrinkage is orthogonal, Preferably it is 0.5% or less, More preferably, it is 0.4% or less, Especially preferably, it is 0.3% or less. It is preferable to have the heat shrinkage in this range because the planarity of the film is maintained even when exposed to high temperature.

The peak peak temperature of these lost tangent tanδ _, the ratio of the storage modulus E ＇ _{(120 ° C.)} and the storage modulus E＇ _{(50 ° C.)} at _{50 ° C.} , the Young's modulus, and the heat shrinkage are to produce a white film under the following production conditions. Can be achieved.

additive

You may mix | blend a fluorescent brightener with the white film for reflecting plates of this invention. When mix | blending a fluorescent brightener, it is 0.005-0.2 weight% per 100 weight% of thermoplastic polyester compositions of the layer to mix | blend, for example, Preferably it is 0.01-0.1 weight%. If the optical brightener is less than 0.005% by weight, the reflectance in the wavelength region around 350 nm is not sufficient, and the meaning of addition is insufficient. If the optical brightener exceeds 0.2% by weight, the characteristic color of the optical brightener is not preferable. . As a fluorescent brightener, OB-1 (made by Eastman Co., Ltd.), Uvitex-MD (made by Chiba-Geigi Co., Ltd.), and JP-Conc (made by Nippon Chemical Co., Ltd.) can be used, for example.

As needed, you may add antioxidant, a ultraviolet absorber, a lubricating agent.

Manufacturing method

Hereinafter, an example of the method of manufacturing the white film for reflecting plates of this invention is demonstrated. Hereinafter, the glass transition temperature of a polymer may be called Tg and melting | fusing point may be called Tm. The mixing | blending with respect to the thermoplastic polyester composition of a white inorganic particle may be performed at the time of superposition | polymerization of a thermoplastic polyester, and may be performed after superposition | polymerization. When performing at the time of superposition | polymerization, you may mix | blend before a transesterification reaction or esterification reaction completion, and may mix | blend before a polycondensation reaction start.

When performing after superposition | polymerization, what is necessary is just to melt-kneading by adding to the thermoplastic polyester after superposition | polymerization. In this case, it is possible to obtain a thermoplastic polyester composition containing white inorganic particles at a desired content rate by preparing a master pellet containing relatively high concentrations of white inorganic particles and blending them into thermoplastic polyester pellets containing no white inorganic particles. .

It is preferable to perform a filtration of the thermoplastic polyester used for manufacture of the white film for reflecting plates using the nonwoven fabric filter of 10-100 micrometers of average scale | intervals which consists of stainless steel fine wire of 15 micrometers or less of line diameters. By performing this filtration, aggregation of the particle | grains which tend to aggregate and become coarse aggregated particle | grains is normally suppressed, and the white film with few coarse foreign substances can be obtained. Moreover, the average graduation spacing of a nonwoven fabric becomes like this. Preferably it is 20-50 micrometers, More preferably, it is 15-40 micrometers. The composition of the filtered thermoplastic polyester is extruded and unstretched laminated sheet | seat in a multilayered state from die | dye by the simultaneous multilayer extrusion method using a feed block in the molten state.

The unstretched laminated sheet extruded from the die is cooled and solidified by a casting drum to become an unstretched laminated film. This unstretched laminated film is heated by roll heating, infrared heating, or the like, stretched in the longitudinal direction to obtain a longitudinally stretched laminated film. It is preferable to perform this extending | stretching using the circumferential speed difference of two or more rolls.

It is preferable to perform extending | stretching at the temperature more than Tg of a thermoplastic polyester. The stretching ratio is 2.5 to 5.0 times, preferably 2.5 to 4.3 times, more preferably 2.7 to 4.2 times in both the longitudinal direction and the direction orthogonal to the longitudinal direction (hereinafter referred to as the horizontal direction). If it is less than 2.5 times, the thickness nonuniformity of a film will worsen and a favorable film will not be obtained, and if it exceeds 5.0 times, breakage will occur easily during film manufacture, and it is unpreferable.

The laminated film after the longitudinal stretching is subsequently subjected to horizontal stretching, heat setting, and thermal relaxation treatment to form a laminated biaxially oriented film, which is carried out while running the film. The preheating treatment of the transverse stretching starts with a temperature higher than the Tg of the thermoplastic polyester. And it is preferable to carry out, heating up from (Tg + 5 degreeC) to the temperature of (Tg + 70 degreeC). The temperature rising in the transverse stretching process may be continuous or may be stepwise (sequential), but usually the temperature is increased sequentially. For example, the lateral stretch zone of the tenter is divided into a plurality along the film running direction, and the temperature is raised by flowing a heating medium having a predetermined temperature for each zone. The magnification of the lateral stretching is, for example, 3.5 to 5.0 times, preferably 3.7 to 4.8 times, more preferably 4.0 to 4.6 times. By extending | stretching on this condition, the peak peak temperature of the loss tangent tan-delta _is a ratio of the storage elastic modulus E ' _{(120 degreeC)} at 110 degreeC or more and _{120 degreeC,} and the storage elastic modulus E' _{(50 degreeC)} at ₅₀ degreeC (E ＇ _{(120 degreeC). )} / E ' _{(50 degreeC)} ) The film of 0.25-1.00 can be obtained without breaking a film.

It is good to heat-process a film after lateral stretch at the temperature of (Tm-20 degreeC)-(Tm-100 degreeC) under fixed width or 10% or less of width reduction, holding | gripping both ends, and reducing a thermal contraction rate. . When heat processing temperature is higher than (Tm-20 degreeC), planarity of a film will worsen and thickness nonuniformity will become large and it is unpreferable. If it is lower than (Tm-100 ° C), the heat shrinkage ratio may increase, which is not preferable.

Moreover, in order to adjust the amount of thermal contraction, both ends of the film hold | gripping are cut out, the take-up speed of a film longitudinal direction can be adjusted, and it can relax in a longitudinal direction. As a means to relax, the speed of the roll group of a tenter exit side is adjusted. As a ratio to relax, the speed | rate down of a roll group is performed with respect to the film line speed of a tenter, Preferably it is 0.1 to 2.5%, More preferably, it is 0.2 to 2.3%, Especially preferably, the speed down of 0.3 to 2.0% is performed, The film is relaxed (this value is referred to as "relaxation rate"), and the thermal contraction rate in the vertical direction is adjusted by controlling the relaxation rate. Moreover, the film width direction can reduce width | variety in the process until it cuts off both ends, and a desired thermal contraction rate can be obtained.

The white film for reflecting plates of the present invention can be produced by the sequential biaxial stretching method as described above. Instead of the sequential biaxial stretching method, the white film can also be manufactured using the simultaneous biaxial stretching method. In this case, the draw ratio is, for example, 2.7 to 4.3 times, preferably 2.8 to 4.2 times in both the vertical direction and the horizontal direction.

Example

Hereinafter, an Example demonstrates this invention in detail. In addition, each characteristic value was measured with the following method.

In addition, PET means polyethylene terephthalate and IPA means isophthalic acid.

(1) light reflectance

The integrating sphere was attached to the spectrophotometer (UV-3101 PC manufactured by Shimadzu Corporation), and the light reflectance of the sample film when the BaSO ₄ white plate was 100% was measured at a wavelength of 550 nm.

(2) luminance

The brightness | luminance of the display apparatus at the time of using as a reflecting plate for the liquid crystal display device was evaluated. Remove the reflective film of the backlight of Sony 32-inch TV (Bravia KDL-32 V2500), and install the sample film of evaluation object instead, using the luminance meter (Otsuka Electronics Model MC-940), The luminance was measured at a measurement distance of 500 mm from the center of the backlight.

(3) average particle diameter of inorganic particles

The particle size distribution of the particle | grains was calculated | required with the particle size distribution analyzer (LA-950 by Horiba Corporation), and the particle diameter in d50 was made into the average particle diameter.

(4) punching energy by drop impact test

It was carried out based on the DuPont Impact Test (JIS K 5600-5-3, ISO6272). The sample film (30 mm x 30 mm) prepared under 25 degreeC and 50% RH environment was set on the base, and the core (circle shape of 4 mm in diameter, material SUS) was installed on the sample film. A weight (300 g of load) was dropped over the core at an appropriate position, and it was observed whether or not a crack occurred in the sample film below the core. In the determination of the presence or absence of a crack, the thing which fell out in the circular shape by the elongation of the sample film did not determine that there was a crack, but it judged that only the thing which cracked in the sample film had a crack. The drop height was increased by 1 cm until cracking of the sample film occurred, and preliminary testing was performed until cracking occurred in the sample film. When a crack generate | occur | produced in the sample film, the drop height was made into 1 cm low, and when a crack did not generate, the fall height was repeated into 1 cm high. This test was done about 50 sample films, and the fall height which a crack generate | occur | produces in half the sample film was calculated | required. A load was applied to the drop height to set punching energy J in the drop impact test.

(5) void volume ratio

From the density of the polymer of the light reflection layer, the density of the inorganic particles, and their blending ratio in the light reflection layer, the calculated density of the light reflection layer in the case where there was no void in the light reflection layer was determined. The density used in this calculation is 1.39 g / cm <3> of polyethylene terephthalate, and 4.5 g / cm <3> of barium sulfate particles. In addition, only the light reflection layer was isolate | separated from the white film, the weight per unit volume was measured, and the true density of the light reflection layer was calculated | required. The void volume fraction was computed by the following formula.

Void Volume Ratio (%) = (1-Calculated Density Without Actual Density / Void) × 100

(6) thickness ratio of each layer

The cross section of the film was observed by 500 times the magnification using the Hitachi, Ltd. S-4700 type field emission type scanning electron microscope, and the thickness ratio of each layer of the film was calculated | required by the average of 5 points of measurement.

(7) film thickness

The film thickness was measured using the contact thickness meter (Anritsu K-402B).

(8) punchability

Using the punched jig CARL CP-5, the film was punched 50 times (the diameter of the circular hole was 6 mm, the punching speed was 50 times / 1 minute), and the punched end was observed at 25 times magnification with an optical microscope. The occurrence of burrs and burrs were observed. Regarding the beard shape, a punching hole with a beard shape protruding from the punching part by 1 mm or more in length is referred to as "occurrence", and with respect to the burr, part or all of the punching part is projected by 0.5 mm or more based on the film plane. The punching hole which was present was set as "it exists." For each of the beard and bur, the generation rate was calculated by the following equation.

Occurrence rate (%) = number of occurrences / 50

(9) intrinsic viscosity

To 0.3 g of the thermoplastic polyester peeled from each layer from each white film, 25 ml of o-chlorophenol was added, dissolved at 100 ° C, and measured at a temperature of 25 ° C after melting. In addition, the thing containing inorganic particle is melt | dissolved in o-chlorophenol, and centrifuged for 30 minutes at 12000 rpm using the centrifugal separator (Type CF-15 RXII by Hitachi Kogyo Machinery Co., Ltd.), and the inorganic particle and o After separating the thermoplastic polyester dissolved in -chlorophenol, the intrinsic viscosity was measured and calculated. Intrinsic viscosity was calculated | required by the following conversion formula.

Intrinsic viscosity = measured value / 측정 (100-inorganic particle concentration) / 100 kPa

(10) Glass transition temperature (Tg), melting point (Tm)

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

(11) extensibility

In the film film manufacture in an Example, it was observed whether film | membrane manufacture could be performed stably, and the following reference | standard evaluated. In addition, a vertical direction is a continuous film production direction of a film, and a horizontal direction is a direction orthogonal to this.

A: It can manufacture film | membrane stably for 2 hours or more.

B: 1 hour or more can be manufactured stably for less than 2 hours.

C: Cutting | disconnection generate | occur | produces in less than 1 hour, and cannot manufacture film | membrane stably.

(12) Young's modulus

The test piece which cut the film into 150 mm length x 10 mm width using Tensilon UCT-100 type made by Orientec Co., Ltd., was adjusted to temperature 20 degreeC, and 50% of humidity, and was made into 100 mm between rods, and tension | tensile_strength. The Young's modulus is calculated from the tangent of the granular part of the load-extension curve obtained by tensioning at a speed of 10 mm / min and a chart speed of 500 mm / min. In addition, the Young's modulus of a vertical direction made the longitudinal direction (MD direction) of a film the measurement direction, and the Young's modulus of the horizontal direction made the horizontal direction (width direction) of a film the measurement direction. Each Young's modulus is measured 10 times, respectively, and uses the average value.

(13) Ratio of peak peak temperature of loss tangent tanδ and storage modulus by dynamic viscoelasticity measurement

Using a dynamic viscoelasticity measuring device, the maximum peak temperature of the loss tangent tanδ is obtained at a measurement frequency of 11 Hz and a dynamic displacement of ± 2.5 × 10 ^-4 cm, and the storage modulus E ＇ _{(120 ° C) at 120 ° C} and at 50 ° C. The ratio (E ' _{(120 degreeC)} / E' _{(50 degreeC)} ) of the storage elastic modulus shown by the ratio of the storage elastic modulus E ' _{(50 degreeC)} of was calculated | required.

(14) thermal warpage

From the direct type backlight (65 inch) unit of the liquid crystal television (AQUOS-65V by SHARP company) prepared for evaluation, the light reflection sheet originally attached was removed, and the film sample made into the measurement object was mounted. After the power was turned on and left for 24 hours in an environment with a temperature of 40 ° C. and a humidity of 50%, the sample for evaluation was taken out, and the sample for evaluation was extended on a flat plate having high planar accuracy, in particular, to evaluate the degree of warpage of the film. Judgment was made based on the following criteria. The case where only A judgment is attached to the backlight can withstand use.

A: Most warpage was not seen

B: Some warpage is seen

C: Large warpage is seen

Example 1

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), 98 parts by weight of ethylene glycol, 1.0 part by weight of diethylene glycol, 0.05 part by weight of manganese acetate, acetic acid 0.012 parts by weight of lithium was injected into a flask equipped with a rectifying column and an outflow condenser, heated to 150 to 235 ° C. while stirring to distill methanol to carry out the transesterification reaction. After methanol was distilled off, 0.03 part by weight of trimethyl phosphate and 0.04 part by weight of germanium dioxide were added, and the reaction was transferred to a reactor. Subsequently, the inside of the reactor was gradually reduced to 0.5 mmHg while stirring, the temperature was raised to 290 ° C, and a polycondensation reaction was performed to obtain a thermoplastic polyester. Using the obtained thermoplastic polyester as the thermoplastic polyester of the support layer and the light reflection layer, a master batch of barium sulfate having an average particle diameter of 1.2 µm was produced, and 4 wt% of the thermoplastic polyester composition of the support layer was used as the thermoplastic polyester composition of the light reflection layer. The addition amount was adjusted so that it might become 55 weight% of content.

Using these raw materials, it is supplied to two extruders heated at 275 degreeC, respectively, The 3-layer feed block apparatus used as the support layer / light reflection layer / support layer is used for the thermoplastic polyester composition of a support layer, and the thermoplastic polyester composition of a light reflection layer. To form a sheet shape from a die while maintaining the lamination state. It was adjusted by the discharge amount of each extruder so that the thickness ratio of a support layer / light reflection layer / support layer might become 4/92/4 after biaxial stretching. Furthermore, the unstretched film which cooled and solidified this sheet | seat by the cooling drum of surface temperature of 23 degreeC is heated at the temperature of the preheating 1 (73 degreeC) and the preheating 2 (77 degreeC) shown in Table 1, and is lengthwise (a vertical direction). It extended | stretched by the magnification of 3.0 times at 92 degreeC by extending | stretching rate 1000% second, and cooled by the roll group of 25 degreeC. Subsequently, the both ends of the longitudinally stretched film were guided by a tenter while being held with a clip, preheated at 115 ° C, and 3.7 times in a direction perpendicular to the longitudinal direction (horizontal direction) in an atmosphere heated at 125 ° C. It extended | stretched by magnification. Thereafter, heat setting is carried out at a temperature of 195 ° C. in the tenter, and in the tenter, the film is relaxed in the longitudinal direction at a relaxation rate of 2%, and at a temperature of 145 ° C., the width is reduced in the transverse direction at a temperature of 2%. It carried out and cooled to room temperature and obtained the white film. The obtained white film was 225 micrometers in thickness, and the reflectance was 98.7%. The evaluation results are summarized in Table 3.

Example 2

Example 1 except having changed the addition amount of the barium sulfate particle | grains of a support layer and a light reflection layer into 6 weight% and 60 weight%, respectively, and changed the average particle diameter (d50) of barium sulfate particle | grains as shown in Table 1. In the same manner as 1, a white film was prepared. The evaluation results are summarized in Table 3.

Example 3

In Example 1, the polyester of the support layer was polymerized using only dimethyl terephthalate without using dimethyl isophthalate as the dicarboxylic acid component in the step of polymerization, to prepare a master batch of barium sulfate thereof. White film was manufactured on extending | stretching conditions of Table 2 so that it might become the ratio of 1st. The evaluation results are summarized in Table 3.

Example 4

Example 3 WHEREIN: Except having changed the inorganic particle of the support layer into the rutile titanium dioxide particle of 0.2 micrometer of average particle diameters (d50), and using the thing of average particle diameter (d50) of 1.2 micrometers as a barium sulfate particle of a light reflection layer. In the same manner as 3, a white film was prepared. The evaluation results are summarized in Table 3.

Examples 5-9

Except changing to the conditions of Table 1, it carried out similarly to Example 1, and obtained the white film. Moreover, although Example 9 produced the 2-layer laminated | multilayer film, all evaluated from the light reflection layer side. The evaluation results are summarized in Table 3.

Comparative Examples 1 to 7

Except changing to the conditions of Table 1, it carried out similarly to Example 1, and obtained the white film. In addition, in Comparative Example 5, the film manufacturability was so bad that no sample was obtained due to film breaking. The evaluation results are summarized in Table 3.

The white film for reflecting plates of this invention can be used suitably as a reflecting film of a liquid crystal display device.

Claims (11)

It consists of the light reflection layer whose void volume ratio is 55 to 80%, and the support layer of the biaxially stretched polyester film formed in the at least one surface, The ratio of the sum total of the thickness of a light reflection layer and the thickness of a support layer is 85: 15- It is 98: 2, the light reflectance of a film is 98.0% or more, the punching energy by a drop impact test is 0.10 to 0.30 J, and the film thickness is 150-250 micrometers, The white film for reflecting plates characterized by the above-mentioned. The method of claim 1,
The film for reflecting plates which a light reflection layer consists of a composition which consists of 40-48 weight% of thermoplastic polyesters, and 52-60 weight% of white inorganic particles. The method of claim 2,
The film for reflecting plates whose intrinsic viscosity of the thermoplastic polyester of a light reflection layer is 0.40 to 0.53 dl / g. The method of claim 2,
The film for reflecting plates whose thermoplastic polyester of a light reflection layer is isophthalic acid copolymerization polyethylene terephthalate. The method of claim 2,
The reflector film whose white inorganic particle of a light reflection layer is particle | grains of 0.1-3.0 micrometers of average particle diameters which consist of at least 1 sort (s) chosen from the group which consists of barium sulfate, titanium dioxide, calcium carbonate, and silicon dioxide. The method of claim 1,
The biaxially stretched polyester film of a support layer is a film for reflecting plates which consists of 99.9 to 90 weight% of thermoplastic polyester, and 0.1 to 10 weight% of inorganic particles. The method according to claim 6,
The film for reflecting plates whose intrinsic viscosity of the thermoplastic polyester measured about the support layer is 0.54-0.65 dl / g. The method of claim 1,
Film for reflecting plates whose peak peak temperature of loss tangent tan-delta of a film is 110 degreeC or more. The method of claim 1,
The reflecting plate whose ratio (E ＇ _{(120 degreeC)} / E＇ _{(50 degreeC)} ) of the storage elastic modulus E ' _{(120 degreeC) at 120 degreeC,} and the storage elastic modulus E' _{(50 degreeC)} at ₅₀ degreeC of film is 0.25-1.00. Dragon film. The method of claim 1,
The film for reflecting plates whose Young's modulus of at least one direction of a film is 3000 Mpa or more. The method of claim 1,
The film for reflecting plates used as a reflecting film of the backlight unit of a liquid crystal display device.