TWI579323B - White film - Google Patents

Description

White film

The present invention relates to a single-layer white film, and more particularly to a single-layer white film having excellent reflectance, brightness, and light resistance, and thus can be used as a reflective film of a backlight.

The latest uses of white films extend from industrial films such as existing labels, printed images, and reflectors and reflective films like liquid crystal displays, back reflectors for illuminated signs, or retroreflectors for recent solar cells (as an alternative to fluorofilm) ).

White films having such applications have been widely used in liquid crystal displays, ranging from conventional notebook computers and displays to mobile terminal devices, smart devices, and large-sized TVs, and the demand for such white films has also rapidly increased.

In particular, a reflective film that is closely mounted at a light source device requires optical properties such as high opacity, high reflectance, and high brightness. In addition, due to the UV light emitted by the cathode ray tube or the LED light source, the color of the film changes (yellowing), resulting in reduced whiteness and increased yellowness, thereby reducing the reflectance and brightness of the film.

In particular, since the BLU (backlight unit) module using the side-entry LED light source has recently been thinned, the reflective film is closer to the light source. Therefore, it is extremely desirable for the reflective film to have resistance to UV light and high opacity and high reflectance. The reason is that the color change caused by the UV light and its heat, the decrease in the reflectance, etc., will cause a decrease in the brightness of the reflective film.

For the known technology of other companies, in order to obtain a white film having high opacity and high reflectivity, one introduces inorganic particles or polyester, and an incompatible resin when stretching the film, and utilizes a polyester resin and inorganic particles ( For example, a method of reflecting a void on the void interface generated by an interface between a barium sulfate or the like or an incompatible resin is most representative. This technique is disclosed in Japanese Laid-Open Patent Publication No. 2004-330727 (Patent Document 1), JP-A-1992-239540 (Patent Document 2), and the like.

However, in order to use this method, the generation of voids needs to be increased by inputting a sufficient amount of inorganic particles or resin, and in order to increase the size and number of voids, the draw ratio needs to be sufficiently large. The reason is that a large amount of diffuse reflection is caused by utilizing the difference in refractive index, wherein the difference in refractive index is The voids between the polyester and the inorganic particles or the incompatible resin are initiated to sufficiently obtain the reflectance. However, in this case, a reflective interface having a high-low-high refractive index distribution (for example, a refractive index of the polyester - 1.64; a refractive index of the void - 1.0; a refractive index of -1.64 of barium sulfate) is formed, and Part of the light loss occurs in the light scattering and refraction steps. The scattered light, the light refracted and absorbed within the film is ultimately not reflected, thus reducing the reflection efficiency.

Further, in the case where the particles forming the voids are excessively used in the single film, when the film is biaxially stretched, film breakage frequently occurs, resulting in a decrease in yield. Therefore, a co-extruded A/B, A/B/A or A/B/C structure using an outer layer as a support layer is utilized to improve the mechanical strength or heat resistance of the void-containing layer. However, in the case of using coextrusion, a separate extruder is required for each layer, and further separate equipment such as a drying line and a conveying line are required, and therefore, the production cost of the film is inevitably increased.

One of the conventional techniques is to foam the inside of the polyester film by a foaming agent, and the void of the foaming unit as a reflective interface. However, the size of the foaming unit is difficult to control uniformly and its heat resistance is lowered. Further, since a white film which is usually co-extruded requires modification of a polymer, such as copolymerization induction, excessive particles are introduced into the void-forming layer, resulting in a significant deterioration in thermal stability.

[Background literature]

[Patent Literature]

(Patent Document 1) Japanese Patent Laid-Open No. 2004-330727 (2004.11.25)

(Patent Document 2) Japanese Patent Laid-Open No. 1992-239540 (1992.08.27)

Embodiments of the present invention are directed to provide a white film which is in a non-coextruded single layer form and which exhibits excellent reflectance and brightness, and which provides a white film which is a single layer and Sufficient reflectivity and brightness are obtained with a sufficient amount of inorganic material that does not affect film breakage.

Further, another embodiment of the present invention is directed to provide a white film which can be produced in a single layer form rather than a co-extruded form and which has sufficient high reflectance and high opacity without, for example, voids during the stretching step Production problems such as film breakage caused by the production, and good light resistance for UV light.

In order to achieve the above object, the present invention provides a white film, even if only a small amount of change The inorganic material used in the preparation of the white polyester film is limited, and the single-layer white film can also exhibit sufficient reflectance and brightness. Further, by suppressing copolymerization using an excessive amount of particles, the film has a feature of no voids and exhibits good thermal stability.

Specifically, the present invention is characterized by providing a single-layer white film having a reflectance of 95% or more at 550 nm, which comprises a polyester resin, and rutile surface-treated with at least one organic material and inorganic material Type titanium dioxide.

Preferably, in the single-layer white film, the reflectance is 96 to 99%; the relative brightness is 98 to 102%; after UV irradiation (wavelength: 310 nm, intensity: 1.23 W/m ² , temperature: 60 ° C, Time: 99 hours), the reflectance decreased by 3.00 or less; based on the CIE LAB color difference measurement measured before UV irradiation, the ΔE ^* value calculated by the following Equation 1 is 3.00 or less; the whiteness index is decreased by 10 or Smaller; and the yellowness index increases by 10 or less, [Equation 1] △ E ^* = (ΔL ^{* 2} + Δa ^{* 2} + Δb ^{* 2} ) ^1/2

Wherein, in the equation 1, L ^* is the luminance, a ^* hue (from green to red), b ^* chromaticity (from blue to yellow), △ L ^* is _{^{L 2 * -L 1 *, △}} a * a ₂ ^* - a ₁ ^* , Δb ^* is b ₂ ^* - b ₁ ^* , L ₂ ^* is the brightness after UV irradiation, L ₁ ^* is the brightness before UV irradiation, a ₂ ^* is the hue after UV irradiation, a ₁ ^* is the color before UV irradiation, b ₂ ^* is the chromaticity after UV irradiation, b ₁ ^* is the chromaticity before UV irradiation; UV irradiation is at 310 nm wavelength, 1.23 W/m ² intensity, and at 60 ° C , irradiated for 99 hours.

In order for the single-layer white film to satisfy the above optical properties, the surface-treated rutile-type titanium oxide may have an average particle diameter of 0.1 to 0.7 μm and occupy 10 to 30% by weight of the white film.

Further, the organic material may be a hydrophobic material, and the inorganic material may be a metal oxide. Preferably, the hydrophobic material may be selected from the group consisting of polyoxyalkylene oxides, polyolefins, and perfluoropolymers, and the metal oxide may be selected from the group consisting of alumina, cerium oxide, and zirconia.

Further, the organic material or inorganic material may occupy 1 to 10% by weight of the surface-treated rutile-type titanium oxide.

Further, the polyester resin is preferably polyethylene terephthalate, and the polyester resin may have an inherent viscosity of 0.6 to 1.2 d l / g of.

Thus, in the present invention, rutile-type titanium oxide surface-treated with at least one organic material and inorganic material is used, so that the operation is stable at the mixing step, and the particles are well dispersed; in the film stretching step, due to the polyester composite resin The bonding strength is good, so that it is difficult to generate voids, thereby suppressing light loss due to voids; and light resistance is obtained by the inorganic material, Thereby, the decrease in luminance due to prolonged exposure to the light source can be prevented.

Hereinafter, the white film of the present invention having the above characteristics will be described in detail.

The present invention is intended to solve the problem caused by increasing the particle content to increase the reflectance when a film is produced by co-extrusion by the prior art, and to produce a white film as a single layer film having the same coextrusion. Good reflectivity of the film as well as good brightness. As a result, in the production of a single-layer white film, the rutile-type titanium oxide is surface-treated with at least one organic material and an inorganic material by using rutile-type titanium dioxide as an inorganic particle, and the average particle diameter of the rutile-type titanium oxide is controlled and The content is within a specific range, and the inventors have demonstrated that the white film has a desired excellent reflectance, for example, 95% or more, and thus the present invention has been completed.

A first aspect of the present invention provides a single-layer white film comprising a polyester resin and rutile-type titanium dioxide surface-treated with at least one organic material and an inorganic material, which simultaneously satisfy the following optical properties: at 550 nm, The reflectance is 95% or higher; after UV irradiation (wavelength: 310 nm, intensity: 1.23 W/m ² , temperature: 60 ° C, time: 99 hours), the reflectance is reduced by 3.00 or less; measured based on UV irradiation From the CIE LAB color difference measurement value, the ΔE ^* value calculated by the following Equation 1 is 3.00 or less; the whiteness index is decreased by 10 or less; and the yellowness index is increased by 10 or less, [Equation 1] ΔE ^* =(△L ^*2 +△a ^*2 +△b ^*2 ) ^1/2

Wherein, in the equation 1, L ^* is the luminance, a ^* hue (from green to red), b ^* chromaticity (from blue to yellow), △ L ^* is _{^{L 2 * -L 1 *, △}} a * a ₂ ^* - a ₁ ^* , Δb ^* is b ₂ ^* - b ₁ ^* , L ₂ ^* is the brightness after UV irradiation, L ₁ ^* is the brightness before UV irradiation, a ₂ ^* is the hue after UV irradiation, a ₁ ^* is the color before UV irradiation, b ₂ ^* is the chromaticity after UV irradiation, b ₁ ^* is the chromaticity before UV irradiation; UV irradiation is at a wavelength of 310 nm, an intensity of 1.23 W/m ² , and at a temperature of 60 ° C, Irradiated for 99 hours.

Further, a second aspect of the present invention provides a single-layer white film comprising a polyester resin and rutile-type titanium oxide surface-treated with at least one organic material and an inorganic material, having the following optical properties: at 550 nm, reflection The rate is 96% to 99% and the relative brightness is 98% to 102%.

The first and second aspects are for explaining embodiments of the invention and are not intended to limit the invention.

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

The present invention is directed to a single-layer white film comprising a polyester resin and rutile-type titanium dioxide surface-treated with at least one organic material and an inorganic material; and simultaneously satisfying the following optical properties: at 550 nm, the reflectance is 95. % or higher; after UV irradiation (wavelength: 310 nm, intensity: 1.23 W/m ² , temperature: 60 ° C, time: 99 hours), reflectance decreased by 3.00 or less; measured from CIE LAB color difference before UV irradiation The measured value, the ΔE ^* value calculated by the following Equation 1 is 3.00 or less; the whiteness index is decreased by 10 or less; and the yellowness index is increased by 10 or less; and at the same time, the reflectance is satisfied at 550 nm. 96% to 99% and relative brightness of 98% to 102%, [Equation 1] △ E ^* = (ΔL ^{* 2} + Δa ^{* 2} + Δb ^{* 2} ) ^1/2

Wherein, in the equation 1, L ^* is the luminance, a ^* hue (from green to red), b ^* chromaticity (from blue to yellow), △ L ^* is _{^{L 2 * -L 1 *, △}} a * a ₂ ^* - a ₁ ^* , Δb ^* is b ₂ ^* - b ₁ ^* , L ₂ ^* is the brightness after UV irradiation, L ₁ ^* is the brightness before UV irradiation, a ₂ ^* is the hue after UV irradiation, a ₁ ^* is the color before UV irradiation, b ₂ ^* is the chromaticity after UV irradiation, b ₁ ^* is the chromaticity before UV irradiation; UV irradiation is at 310 nm wavelength, 1.23 W/m ² intensity, and at 60 ° C , irradiated for 99 hours.

Within the scope of satisfying such optical properties, the present invention is applicable to a vestibule of various advertisements or a pedestal of a reflection plate of a liquid crystal display, or a base film of a solar cell back sheet. However, when the reflectance is lowered, the ΔE ^* value, or the conversion range of the whiteness index or the yellowness index deviates from the above range, the light transmittance of the LED lamp or the external solar lamp of the present invention is good even if the reflectance or the whiteness is good before the UV irradiation. The property may be degraded, thereby reducing the reflectance and brightness, thereby detracting from the utility of the reflector used as a display device, or reducing the efficiency of the solar module, which may reduce the value of the product of the present invention.

More specifically, the preferred reflectance is 95 to 99.2%; after UV irradiation (wavelength: 310 nm, intensity: 1.23 W/m ² , temperature: 60 ° C, time: 99 hours), the reflectance is reduced to 0.3 to 2.0. Based on the CIE LAB color difference measurement measured before UV irradiation, the ΔE ^* value calculated by the following Equation 1 is 0.37 to 2.48; the whiteness index is decreased to 3 to 8; and the yellowness index is increased to 1 to 7. The reflectance is lowered, the ΔE ^* value, the whiteness index is decreased, and the yellowness index is increased to a value showing light resistance, and the optical characteristics show the difference between the optical characteristics after UV irradiation and the optical characteristics before UV irradiation. The UV irradiation was irradiated for 99 hours at a wavelength of 310 nm, an intensity of 1.23 W/m ² , and at a temperature of 60 °C.

Titanium dioxide used to satisfy the above optical properties may have three crystal structures depending on the preparation method thereof, including anatase type, rutile type, and brookite type. The change in the crystal structure is caused by a phase change in the preparation of titanium dioxide by a sulfuric acid method or a chlorine method. Rutile titanium dioxide There is a denser crystal structure and a relatively high refractive index, which can be confirmed by an X-ray crystal structure pattern. Further, titanium dioxide having a rutile structure is preferred because it has an adsorption ability with respect to UV light.

At the same time, conventional white films have the disadvantage of degradation of reflectance performance due to the formation of voids, light scattering at the void interface, and light refracting into the film. However, titanium dioxide having a rutile structure has a high refractive index of 2.7, and in the case of void-free formation, strong scattering properties can be obtained by difference from polyethylene terephthalate (refractive index: 1.6).

Here, the particles need to be well dispersed in the film, thereby effectively increasing the amount of the refractive interface between the polyester and the particles, and at the same time, the affinity between the particles and the polyester matrix needs to be enhanced, thereby suppressing The generation of voids. The reason is that during the stretching step, as the affinity is lowered, voids are generated, and the resulting voids may cause a decrease in the efficiency of reflection of light. In order to achieve the above object, titanium oxide which is surface-treated with an organic material is preferred.

The organic material is preferably a hydrophobic material, and the hydrophobic material is preferably a polyoxyalkylene polymer, a polyolefin-based polymer, a perfluoropolymer or the like, but is not limited thereto.

Further, the content of the surface-treated hydrophobic material is preferably from 1 to 10% by weight based on the total amount of the surface-treated rutile-type titanium oxide, 100 wt%. If the content is less than 1% by weight, the effect of reducing voids is not remarkable, and if the content is more than 10% by weight, the amount of titanium oxide is relatively small, so that it is difficult to control the improvement of reflectance and brightness.

When a rutile-type titanium dioxide surface treatment is performed using a hydrophobic material, a film having stable workability can be obtained during the mixing step; the particles are well dispersed; the bonding strength between the polyester substrate and the resin is moderate during the film stretching process, It is difficult to generate voids, and water resistance and weather resistance are good. Further, according to the Fresnel reflection formula, since the refractive index difference between the rutile-type titanium oxide and the polyester film is large, a film having a high reflectance can be obtained; since there is no defect due to void generation, the light resistance is good. The phenomenon that the reflectance is lowered due to UV light, moisture, etc., and the whiteness index is not reduced, and the running ability is excellent.

However, when the rutile type titanium dioxide is coated with a hydrophilic material, the particles are susceptible to moisture, and the preparation performance is seriously deteriorated because the moisture in the mixing process causes the particles to be generated when the master batch and the master batch are pyrolyzed. The convergence of the acceleration. If the master batch is used for the film, the water resistance and weather resistance of the film will be severely deteriorated, and yellowness will be severely caused.

In addition, the white film requires good reflectance and good light resistance for use as a BLU (back) Optical base film of the light unit). Titanium dioxide particles exposed to CCFL or LED light sources release electrons due to high activation energy and form -OH groups from surrounding moisture, thereby promoting decomposition of the polyester film. As a result, since the film is exposed to the light source for a long time, the yellowness index rises and the reflection efficiency decreases, resulting in a decrease in brightness. Therefore, in order to suppress photocatalysis of titanium dioxide, the surface of the titanium oxide may preferably be coated with an inorganic material such as cerium oxide, aluminum oxide, zirconium oxide or the like.

The average particle diameter of the inorganic material is preferably smaller than the average particle diameter of the surface-treated titanium oxide, and more preferably 0.001 to 0.2 μm, but is not limited thereto.

The content of the rutile-type titanium oxide based on the surface treatment is 100 wt%, and the content of the inorganic material for surface treatment is preferably from 1 to 10% by weight. If the content is less than 1% by weight, the photocatalytic inhibition function is lowered, so that the reflectance and the brightness are lowered. If the content is more than 10% by weight, the amount of titanium oxide is relatively small, so that it is difficult to control the improvement in reflectance and brightness.

In particular, in order to achieve the above optical properties, rutile-type titanium dioxide surface-treated with at least one organic material and inorganic material is characterized by having an average particle diameter of 0.1 to 0.7 μm and occupying 10 to 30 wt% in the film. .

More specifically, the average particle diameter of the rutile-type titanium oxide surface-treated with at least one organic material and inorganic material is suitably from 0.1 to 0.7 μm, and preferably from 0.15 to 0.59 μm. In particular, the size of the titanium dioxide particles which produce the maximum light reflection corresponds to half the wavelength of visible light (400 to 800 nm). Therefore, the particle size of the titanium dioxide is preferably 0.2 to 0.4 μm, which can effectively improve the reflectance.

In general, due to the difference between the refractive index of titanium dioxide and the refractive index of the polyester resin, the refraction of the interface between the particles and the polymer resin results in the film having a high whiteness index. If the particle size is less than 0.1 μm, the particle size is advantageous from the viewpoint of the same content and having a relatively large amount of reflective interface. However, the titanium dioxide particles are well aggregated and therefore difficult to disperse, and the number of reflective interfaces is no longer increased due to the agglomeration of the particles. In addition, the filter may be clogged frequently during the mixing process and film making process. If the particle diameter is larger than 0.7 μm, light reflection in the visible light region may be reduced. Further, the surface roughness of the film is increased, and therefore, the rutile-type titanium oxide particles having high hardness during the film forming and stretching process may cause surface damage of the stretching roll, and the film may be thick due to an increase in surface roughness. The gloss will also decrease.

In addition, rutile in the film using at least one organic material and inorganic material for surface treatment The type of titanium dioxide is suitably 10 to 30% by weight, preferably 12 to 28% by weight, and more preferably 14 to 25% by weight. If the content is less than 10% by weight, sufficient opacity and reflectance cannot be obtained despite being rutile-type titanium oxide. If the content is more than 30% by weight, sufficient opacity can be obtained, but strong scattered light can affect light loss, so that the reflectance cannot be increased or partially reduced. Moreover, although the particles do not form voids, their running ability is still deteriorated, resulting in a decrease in productivity.

In the present invention, it can be used as polyethylene terephthalate polyester, preferably having 0.6 ~ 1.2 d l / g inherent viscosity poly ethylene terephthalate. If the viscosity of the resin is lower than the range, the viscosity may be further reduced due to the pyrolysis generated during the mixing step, and the elongation of the film may not be increased, and therefore, it is impossible to produce sufficient surface smoothness and Mechanical properties of the film. If the viscosity of the resin is larger than the range, the mixing process is difficult and the film pressure of the film production line is increased when the film is formed, so that the workability is remarkably deteriorated.

When making the white film of the present invention, the particles can be placed during the preparation of the masterbatch or added during the polymerization of the polyester, similar to the production of common white films.

As shown in the first aspect and the second aspect, it can be seen that the rutile-type titanium dioxide surface-treated with at least one organic material and inorganic material can be applied to a single-layer white film to achieve a reflectance of 96 to 99%, and The relative brightness is 98 to 102%, showing a significant improvement. The single-layer white film of the present invention is suitable for a BLU (backlight unit) reflecting plate within a range satisfying the above optical properties.

Hereinafter, the detailed description of the present invention will be provided by the examples, but the present invention is not limited to the following examples.

Hereinafter, the optical properties were measured by the following measurement methods.

1. Reflectance (%)

This is the relative reflectance through a spectrophotometer (Varian Company, UV Spectrophotometers Cary 5000) when the barium sulfate standard whiteboard is 100%, and is a value measured under visible light at 550 nm. Here, the measurement angle is 3°20 " ; the average time of the detector detection signal is 0.1 second; the analysis data interval is 1 nm; and the scanning rate is 600 nm/min.

2. Brightness (cd/m ² )

The diffusion sheet and the cymbal sheet are detached from the side rod side light 17-inch backlight unit, and then a reflective film is provided at the lowest end thereof and the light guide plate is placed thereon. The brightness value at 13 o'clock in the 17-inch backlight unit was obtained by the brightness measuring instrument BM-7 while maintaining the environment at 25 ° C for 1 hour or longer after illumination, and then taking the average value.

3. Relative brightness (%)

When the UXSP is 100, a relative value (%) is used in the evaluation, wherein the UXSP is a co-extruded reflective film of the company Teijin-Dupont.

Relative brightness (%) = brightness of the film measured (cd/m ² ) / brightness of UXSP of Teijin-Dupont Company (1720 cd/m ² ) × 100.

◎ indicates: very good; relative brightness: 100% or higher.

○ indicates: good; relative brightness: 98% or higher, but lower than 100%.

△ means: poor; relative brightness: 96% or higher, but less than 98%.

X means: poor; relative brightness: less than 96%.

4. Reduced reflectivity

This decrease in reflectance is expressed as the degree of change (decrease) between the measured value after UV irradiation and the measured value before UV irradiation. UV irradiation refers to irradiation at 99 nm for a period of 99 hours at a wavelength of 1.23 W/m ² and a temperature of 60 ° C. That is, the decrease in the reflectance indicates the difference in reflectance between the measured UV irradiation and the UV irradiation before the above-described 1 reflectance measurement method.

5. Whiteness index decreases

The decrease in the whiteness index is expressed as the degree of change (decrease) between the measured value after the UV irradiation and the measured value before the UV irradiation. UV irradiation refers to irradiation at 99 nm for a period of 99 hours at a wavelength of 1.23 W/m ² and a temperature of 60 ° C. That is, the decrease in the whiteness index indicates the difference between the whiteness index measured by the following measurement method after the UV irradiation and the whiteness measured by the following measurement method before the UV irradiation.

Film samples were taken at intervals of 500 mm in the width direction of the finished product and prepared to a size of 100 mm × 100 mm. Measurements were made according to the ASTM E313 standard using the Datacolor 600 Model. The whiteness index measurement method is in accordance with CIE STM1979.

WI is whiteness index, WI=Y-a(x-xn)-b(y-yn)

Here, Y means: brightness factor

x, y means: the chromaticity coordinates of the object to be measured

Xn,yn means: the chromaticity coordinates of the complete reflector (reflectance = 100%)

a, b means: normal, a=800, b=1700

(For reference, in the case of treatment with a fluorescent whitening agent, the WI value can be increased from 100 in the case of a completely white object to 150. The whiteness index (WI) is an accurate standard for evaluating whitening, and When the WI value is higher, the object changes white.)

6. Yellowness index rises

The increase in the yellowness index is expressed as the degree of change (rise) between the measured value after the UV irradiation and the measured value before the UV irradiation. UV irradiation refers to irradiation at 99 nm for a period of 99 hours at a wavelength of 1.23 W/m ² and a temperature of 60 ° C. That is, the increase in the yellowness index indicates the difference between the yellowness index measured by the following measurement method after UV irradiation and the yellowness index measured by the following measurement method before UV irradiation.

<Measurement method of yellowness index>

Film samples were taken at intervals of 500 mm in the width direction of the finished product and prepared to a size of 100 mm × 100 mm. Measurements were made according to the ASTM E313 standard using the Datacolor 600 Model. The yellowness index measurement method is in accordance with ASTM E 313.

YI is the yellowness index, YI=100 (1-B/G)

G represents greenness, G=(Y/Yn) ^* 100

B represents blueness, B = (Z/Zn) ^* 100

Y, Z means: the chromaticity coordinates of the object to be measured

Yn, Zn means: chromaticity coordinates of the complete reflector (reflectance = 100%)

7.△E ^*

This value was measured using the same equipment as the whiteness index and the yellowness index, and was calculated by the CIE 1976 L ^* a ^* b ^* color difference system. This value is calculated by the following Equation 1.

[Equation 1] △ E ^* = (ΔL ^{* 2} + Δa ^{* 2} + Δb ^{* 2} ) ^1/2

(In Equation 1, L ^* is luminance, a ^* is hue (from red to green), b ^* is chromaticity (from blue to yellow), ΔL ^* is L ₂ ^* -L ₁ ^* , Δa ^* is a ₂ ^* - a ₁ ^* , Δb ^* is b ₂ ^* - b ₁ ^* , L ₂ ^* is the brightness after UV irradiation, L ₁ ^* is the brightness before UV irradiation, a ₂ ^* is the hue after UV irradiation, a ₁ ^* For the hue before UV irradiation, b ₂ ^* is the chromaticity after UV irradiation, b ₁ ^* is the chromaticity before UV irradiation; UV irradiation refers to the intensity at the wavelength of 310 nm, the intensity of 1.23 W/m ² and the temperature at 60 ° C 99 hours.)

8. Operational ability

The molten resin extruded by T-die was cooled by a casting roll at 30 ° C, then stretched 3.0 times in the machine direction at a preheating temperature of 95 ° C, and then stretched 3.0 in the transverse direction at a stretching temperature of 135 ° C. Times. The final line speed of the film was 35.1 m/min.

Here, the running ability was evaluated regardless of whether the film was stably manufactured, and evaluated according to the following criteria.

O indicates that the film was stably produced, and there was no film breakage for 12 hours or more.

△ indicates that the film was stably produced, and there was no film breakage of 8 hours or longer but less than 12 hours.

X indicates that the film was not stably produced, and film breakage occurred within 8 hours.

[Example 1]

50 wt% of polyethylene terephthalate having an intrinsic viscosity of 0.65 d l /g and 50 wt% of rutile-type titanium dioxide having an average particle diameter of 0.15 μm were mixed at 280 ° C to prepare a master batch, wherein The rutile-type titanium dioxide is surface-treated with a hydrophobic material (weight average molecular weight: 50,000, polyoxyalkylene, 2 wt% based on the total weight of the particles).

The masterbatch and 50 wt% of polyethylene terephthalate having an intrinsic viscosity of 0.68 d l /g were mixed so that the content of the particles in the film was 12 wt%, as shown in Table 1, and then the mixture was put into extrusion. The machine was melt extruded into sheets at 285 ° C to thereby produce a film having a thickness of 188 μm. The optical properties of the film thus produced are shown in Table 3.

[Examples 2 to 5]

A film was produced in the same manner as in the above Example 1, except that the average particle diameter of the rutile-type titanium oxide surface-treated with a hydrophobic material (weight average molecular weight: 50,000, polyoxyalkylene, 2 wt% based on the total weight of the particles) was changed and The content is shown in Table 1. The optical properties of the film thus produced are shown in Table 3.

[Embodiment 6]

50 wt% of polyethylene terephthalate having an intrinsic viscosity of 0.65 d l /g and 50 wt% of rutile-type titanium dioxide (average particle diameter: 0.12 μm) were mixed at 280 ° C to prepare a master batch, wherein The rutile-type titanium dioxide is a hydrophobic material (weight average molecular weight: 50,000, polyoxyalkylene, 2 wt% based on the total weight of the particles) and an inorganic material (0.05 μm average particle size zirconia, 2 wt% particle-based) Total weight) surface treatment.

The masterbatch and polyethylene terephthalate having an intrinsic viscosity of 0.68 d l /g were mixed so that the content of the particles in the film was 28 wt%, as shown in Table 1, and then the mixture was put into an extruder. The sheet was melt-extruded at 285 ° C to thereby produce a film having a thickness of 188 μm. The optical properties of the film thus produced are shown in Table 3.

[Examples 7 to 11]

A film was produced in the same manner as in the above Example 1, except that the use of a hydrophobic material (weight average molecular weight: 50,000, polyoxyalkylene, 2 wt% based on the total weight of the particles) and inorganic material (oxidation of an average particle diameter of 0.05 μm) were used. Zirconium, 2 wt% based on the total weight of the particles) The average particle size and content of the surface treated rutile-type titanium dioxide, as shown in Table 1. The optical properties of the film thus produced are shown in Table 3.

[Comparative Example 1]

A film was produced in the same manner as in the above Example 1, while barium sulfate having an average particle diameter of 0.3 μm was used as the inorganic particles, and it was made to be 20 wt% of the film. The optical properties of the film thus produced are shown in Table 4.

[Comparative Example 2]

A film was produced in the same manner as in the above Example 1, while barium sulfate having an average particle diameter of 1.68 μm was used as the inorganic particles, and it was made to be 20 wt% of the film. The optical properties of the film thus produced are shown in Table 4.

[Comparative Example 3]

A film was produced in the same manner as in the above Example 1, while calcium carbonate having an average particle diameter of 0.5 μm was used as the inorganic particles, and made 20 wt% of the film. The optical properties of the film thus produced are shown in Table 4.

[Comparative Example 4]

A film was produced in the same manner as in the above Example 1, while calcium carbonate having an average particle diameter of 1.26 μm was used as the inorganic particles, and made 15 wt% of the film. The optical properties of the film thus produced are shown in Table 4.

[Comparative Example 5]

A film was produced in the same manner as in the above Example 1, while using anatase-type titanium oxide surface-treated with a hydrophobic material (weight average molecular weight: 50,000, polyoxyalkylene, 2 wt% based on the total weight of the particles), and It accounts for 12% by weight of the film, as shown in Table 2 below. The optical properties of the film thus produced are shown in Table 4.

[Comparative Example 6]

A film was produced in the same manner as in the above Example 1, while using rutile-type titanium oxide which was not surface-treated and had an average particle diameter of 0.12 μm, and made it 28 wt% of the film. The optical properties of the film thus produced are shown in Table 4.

[Comparative Example 7]

50 wt% of polyethylene terephthalate having an intrinsic viscosity of 0.65 d l /g and 50 wt% of rutile-type titanium dioxide having an average particle diameter of 0.3 μm were mixed at 280 ° C to prepare a master batch, wherein The rutile-type titanium dioxide is surface-treated with a hydrophilic material (weight average molecular weight: 60,000, polyvinyl alcohol, 2 wt% based on the total weight of the particles). The masterbatch was mixed with polyethylene terephthalate having an intrinsic viscosity of 0.65 d l /g so that the content of the particles in the film was 15 wt%, as shown in Table 2, and then the mixture was put into an extruder. The film was melt-extruded at 285 ° C to thereby produce a film having a thickness of 188 μm. The optical properties of the film thus produced are shown in Table 4.

[Comparative Example 8]

A film was produced in the same manner as in the above Example 1, while using an anatase type titanium oxide surface-treated with a hydrophilic material (weight average molecular weight: 60,000, polyvinyl alcohol, 2 wt% based on the total weight of the particles), and 15 wt% of the film, as shown in Table 2 below. The optical properties of the film thus produced are shown in Table 4.

[Comparative Examples 9 and 10]

A film was produced in the same manner as in the above Example 1, except that the average particle diameter of the rutile-type titanium oxide surface-treated using a hydrophobic material (weight average molecular weight: 50,000, polyoxyalkylene, 2 wt% based on the total weight of the particles) was changed. The content is shown in Table 2. The optical properties of the film thus produced are shown in Table 4.

[Comparative Examples 11 to 14]

A film was produced in the same manner as in the above Example 1, except that the use of a hydrophobic material (weight average molecular weight: 50,000, polyoxyalkylene, 2 wt% based on the total weight of the particles) and inorganic material (oxidation of an average particle diameter of 0.05 μm) were used. Zirconium, 2 wt% based on the total weight of the particles) The average particle size and content of the surface treated rutile-type titanium dioxide, as shown in Table 2. The optical properties of the film thus produced are shown in Table 4.

[Table 1]

As shown in Tables 3 and 4, it can be found that Examples 1 to 11 using titanium oxide surface-treated with at least one organic material and inorganic material are used with respect to the case of using rutile-type titanium oxide or other inorganic particles which are not surface-treated. 95% or higher reflectance. Further, it can be seen that the relative brightness and light resistance after UV irradiation are within a desired range, and the running ability is excellent.

The white film of the present invention, when it is a single layer film, can satisfy a reflectance of 95% or more and excellent relative brightness and light resistance, and has good optical properties for use as an optical film.

While the invention has been described by the foregoing embodiments, it will be understood that It is apparent that the present invention can be applied in the same manner as appropriate by changing the embodiment.

This application claims the Korean Patent Application No. 10-2011-0064789 filed on June 30, 2011, in the Korean Intellectual Property Office, and the Japanese Patent Application No. 10-2011-0145355, filed on December 29, 2011 The priority of the Japanese Patent Application No. 10-2012-0070180, filed on Jun. 28, 2012, the entire disclosure of which is incorporated herein by reference.

Claims (6)

A single-layer white film having a reflectance of 95% or higher at 550 nm, comprising a polyester resin, and rutile-type titanium dioxide surface-treated with at least one organic material and an inorganic material, wherein the surface-treated rutile type Titanium dioxide has an average particle diameter of 0.1 to 0.7 μm and occupies 10 to 28% by weight of the white film, wherein the organic material is a hydrophobic material, and the inorganic material is a metal oxide; wherein the single-layer white film is irradiated with UV (wavelength: 310 nm, intensity: 1.23 W/m ² , temperature: 60 ° C, time: 99 hours), reflectance decreased by 3.00 or less; measured from CIE LAB color difference measurement before UV irradiation, calculated by Equation 1 below The ΔE ^* value is 3.00 or less; the whiteness index is decreased by 10 or less; and the yellowness index is increased by 10 or less, [Equation 1] ΔE ^* = (ΔL ^*2 + Δa ^*2 + Δb ^*2 ) ^1/2 where, in Equation 1, L ^* is luminance, a ^* is a hue (from red to green), b ^* is chromaticity (from blue to yellow), and ΔL ^* is L ₂ ^* -L ₁ ^*, △ a ^* is _{^{a 2 * -a 1 *, △}} b * of _{^{b 2 * -b 1 *, L}} 2 * brightness after UV irradiation, L ₁ ^* is the luminance prior to UV exposure a ₂ ^* hue after UV irradiation, a ₁ ^* is hue before UV irradiation, b ₂ ^* color after UV irradiation, b ₁ ^* chromaticity before the UV irradiation; UV irradiation at 310nm wavelength lines, 1.23W / m ² Irradiation for 99 hours at a temperature of 60 ° C. A single-layer white film according to claim 1, wherein the single-layer white film has a reflectance of 96 to 99% and a relative brightness of 98 to 102%. The single-layer white film according to claim 1, wherein the hydrophobic material is selected from the group consisting of polysiloxanes, polyolefins, and perfluoropolymers, and the metal oxide is selected from the group consisting of alumina, cerium oxide, and oxidation. zirconium. A single-layer white film according to claim 3, wherein the organic material or the inorganic material contains 1 to 10% by weight based on the total amount of the surface-treated rutile-type titanium oxide. A single-layer white film according to claim 2, wherein the polyester resin is polyethylene terephthalate. A single-layer white film according to claim 5, wherein the polyester resin has a thickness of 0.6 to 1.2d / g inherent viscosity of polyethylene terephthalate.