JP5302756B2 - Polyester film - Google Patents

Description

  The present invention relates to a polyester film containing an organic photochromic compound that is colored (color-changed) by irradiation with ultraviolet rays (hereinafter sometimes abbreviated as UV), and has a color-changing function in the visible range after UV irradiation. Is.

  In recent years, functional polyester films have been used in a variety of fields ranging from solar cells, electronic equipment, and other home decorations such as building materials. In these applications, low-cost, environmentally friendly and highly functional polyester films are desired.

  As an existing polyester film, a polyester film that has been printed by a mainstream inkjet method is known as a building material application for household goods decoration. The problems with the inkjet method are that a large amount of various polymers and pigments are used, so the burden on the environment is large, the size of maintenance such as contamination, capital investment costs, running costs, and the drying process and And technical difficulties such as changes in film thickness.

  For example, a polyester film having UV-sensitive color change performance is not a conventional ink jet method, but can be used as a measure of ultraviolet intensity by sticking it to a window glass coated with a photocatalyst. It is expected to be used because it can be used as a standard for measuring the UV intensity of batteries.

  As a further example, there is not only the possibility of use as a UV photosensitive marker or photosensor technology in electronic components, but also the possibility of application to beautiful daily goods using UV photosensitive coloring technology.

  Therefore, if a certain UV photosensitive coloring function can be imparted to the polyester film, a new novel polyester film that can replace the ink jet method can be provided.

JP 2007-146014 A

  The present invention has been made in view of the above circumstances, and its solution is to solve problems such as environmental impact and cost due to the inkjet method, and it is possible to change the color by cheap and simple ultraviolet irradiation, An object of the present invention is to provide a polyester film that can be used for ultraviolet intensity measurement in various uses such as outdoor building materials, and can also be applied to uses as UV photosensitive markers and optical sensor technology in electronic parts.

  As a result of intensive studies in view of the above circumstances, the present inventor has found that the above problem can be easily solved by a polyester film having a specific configuration, and has completed the present invention.

That is, the gist of the present invention is that the polyester layer constituting the film surface having a surface roughness (Ra) in the range of 0.1 to 1.0 μm contains 3 to 30% by weight of particles having an average particle size of 3 to 10 μm. It is a laminated polyester film having a structure of three or more layers, and an organic photochromic compound that is colored by ultraviolet irradiation is contained in the surface layer of the laminated film, and the content of the organic photochromic compound in the polyester film is 0.05 to 1. 0 resides in a polyester film, wherein the percentages by weight.

  According to the polyester film of the present invention, an organic photochromic compound-containing polyester film having color change performance can be provided by kneading the organic photochromic compound within an appropriate amount range. In addition, the polyester film of the present invention can be used for measuring UV intensity in various applications such as outdoor building materials including solar cells, and can be used as a mark for production lines in place of ink jet methods. In addition to its potential use as a UV photosensitive marker and optical sensor technology in electronic parts, it can be expected to be applied to beautiful daily necessities using the UV photosensitive light emitting technology, so its industrial value is high.

  Hereinafter, the present invention will be described in more detail. The details of the matte polyester film having the coloring performance of the present invention will be described. The polyester film constituting the polyester film having coloring performance in the present invention preferably has a multilayer structure in consideration of functionality and price, as long as it does not exceed the gist of the present invention other than the two-layer or three-layer structure. There may be four or more layers, and there is no particular limitation.

  As the polyester constituting the polyester film of the present invention, typically, for example, polyethylene terephthalate in which 80 mol% or more of the structural unit is ethylene terephthalate, and 80 mol% or more of the structural unit is ethylene-2,6-naphthalate. Specific polyethylene-2,6-naphthalate and poly-1,4-cyclohexanedimethylene terephthalate in which 80 mol% or more of the structural unit is 1,4-cyclohexanedimethylene terephthalate. In addition to these, polyethylene isophthalate, polybutylene terephthalate, and the like can also be mentioned.

  In the polyester film of the present invention, in order to maintain the surface appearance, it is essential to provide a specific range of Ra (arithmetic mean roughness), that is, a high degree of surface unevenness.

  Hereinafter, a method for imparting a high degree of surface irregularities to the polyester film of the present invention will be described. In providing unevenness on the film surface, a method of blending inactive inorganic particles or organic particles into the polyester layer constituting the surface can be employed.

  The inert particles include mainly known inorganic particles such as silicon oxide (silica), titanium oxide, calcium carbonate, barium sulfate, aluminum oxide, kaolin, clay, carbon black, acrylic resin, polystyrene, and organic silicone resin. And organic particles such as an acrylic-styrene copolymer, and any one or more of them may be blended. Among these, silicon oxide (silica) is preferable from the viewpoints of particle size distribution and film formability. In addition to the silicon oxide particles, it is also one of preferred embodiments that other particles such as titanium oxide are blended.

  In the film of the present invention, the average particle diameter of the inert particles in the polyester layer constituting the film surface having a surface roughness (Ra) in the range of 0.10 to 1.0 μm is 3 to 10 μm, preferably 3 It is in the range of 5-9 μm, more preferably 4-8 μm. When the average particle size is less than 3 μm, sufficient unevenness is not formed on the film surface, and a desired Ra, that is, an appearance peculiar to a so-called mat film cannot be expressed. On the other hand, if the average particle diameter exceeds 10 μm, the unevenness of the film surface becomes too high, causing problems such as dropout of particles and deterioration of film forming continuity.

  In the present invention, the content of the inert particles in the polyester layer constituting the film surface having a surface roughness (Ra) in the range of 0.1 to 1.0 μm is 3 to 30% by weight, preferably 4 to 20% by weight, more preferably 5 to 15% by weight. When the content of the inert particles is less than 3% by weight, sufficient unevenness is not formed on the film surface, and desired Ra, that is, an appearance peculiar to the mat film cannot be expressed. On the other hand, when the content exceeds 30% by weight, the unevenness of the film surface becomes too large, causing problems such as dropout of particles and deterioration of film forming continuity.

  The intrinsic viscosity of the polyester film of the present invention is preferably 0.60 dl / g or more, more preferably 0.65 dl / g or more. When the intrinsic viscosity is less than 0.60 dl / g, a film having sufficient mechanical strength may not be obtained.

  The arithmetic average roughness (Ra) of at least one surface of the polyester film of the present invention needs to be 0.1 to 1.0 μm, preferably 0.4 to 0.9 μm, more preferably 0.5. It is in the range of ~ 0.8 μm. When Ra is less than 0.1 μm, the appearance unique to the mat film cannot be expressed. On the other hand, when Ra exceeds 1.0 μm, breakage or the like is likely to occur during film formation, which causes a problem in terms of productivity.

  The ten-point average roughness (Rz) of at least one surface of the polyester film of the present invention is preferably 1.0 to 5.0 μm, more preferably 1.3 to 4.0 μm, still more preferably 1. It is in the range of 0 to 3.0 μm. When Rz is less than 1.0 μm, sufficient unevenness is not formed on the film surface, and there is a tendency that the appearance specific to the mat film cannot be expressed. On the other hand, when Rz exceeds 5.0 μm, the unevenness of the film surface tends to be too large, and because of the excessively large particles, breakage or the like tends to occur during film formation, which causes a problem in terms of productivity. There is.

  Although the total thickness of the polyester film of the present invention is not particularly limited, it may be used for general purposes as a decorative item such as an electronic device or a car interior. Therefore, considering the productivity and cost, the thickness of the base film Is usually in the range of 20 to 100 μm, preferably 25 to 75 μm, and more preferably 30 to 50 μm from the viewpoint of moderate waist strength and avoiding the occurrence of wrinkles.

  The polyester film of the present invention is preferably composed of two or more layers, but may be a single-layer film as long as the above conditions are satisfied.

  Since at least one outermost surface needs to maintain a high degree of unevenness (matte tone), it is necessary to contain a considerable amount (3 to 30% by weight) of inorganic particles or organic particles having a specific particle size (3 to 10 μm), A film having such a composition often has a risk of not being able to maintain the strength to withstand biaxial stretching in a single-layer structure, and may not be able to maintain film forming continuity. Therefore, a structure having at least one particle reducing layer (a layer for contributing to maintaining the film strength) different from the surface layer is preferable. As long as the gist of the present invention is not exceeded, the particle reduction layer may be composed of two or more layers.

  The thickness of the particle multi-layer constituting at least one outermost surface is usually 3 μm or more, preferably 5 μm or more, more preferably 7 μm or more. When the thickness of the outermost surface layer is less than 3 μm, sufficient unevenness is not formed on the film surface, and the appearance peculiar to the target mat film tends not to be expressed.

  The upper limit of the thickness of the particle multi-layer is limited by the total thickness of the film. However, in consideration of the problem of strength reduction and cost increase due to the reduction of the ratio of the particle reduction layer, the total thickness is preferable. 1/3 or less, more preferably 1/4 or less.

  The polyester film of the present invention may be provided with a surface coating layer in order to improve antistatic properties, slip properties, and peelability. The coated surface is not limited to one side or both sides of the polyester film, and in the case of both sides, either the same coating layer or different coating layers may be used.

  Next, although the manufacturing method of the film of this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7.0 times, preferably 3.0 to 6.0 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7.0 times, preferably 3.5 to 6 times. .0 times. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, a simultaneous biaxial stretching method may be employed for producing a polyester film constituting the organic photochromic compound-containing polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Examples of organic photochromic compounds that can be used in the present invention include organic photochromic substances such as naphthopyran compounds, spirooxazine compounds, 1,4-2H-oxazine, and benzopyran compounds. Among these, spirooxazine compounds And benzopyran compounds are preferred.

  Specific examples of the organic photochromic compound include 1,3,3-trimethylspiro [indoline-2,3 ′-(3H) -naphtho- (2,1-b) (1,4) -oxazine], 6′- Indolino-1,3,3-trimethylspiro [indoline-2,3 ′-(3H) -naphtho- (2,1-b) (1,4) -oxazine], 5-chloro-1,3,3- Trimethylspiro [indoline-2,3 ′-(3H) -naphtho- (2,1-b) (1,4) -oxazine], 6′-piperidino-1,3,3-trimethylspiro [indoline-2, 3 ′-(3H) -naphtho- (2,1-b) (1,4) -oxazine], 1-benzyl-3,3-dimethylspiro [indoline-2,3 ′-(3H) -naphtho- ( 2,1-b) (1,4) -oxazine], 1,3,5,6- Tramethyl-3-ethylspiro [indoline-2,3 ′-(3H) -naphtho- (2,1-b) (1,4) -oxazine], 1,3,3,5,6-pentamethylspiro [indoline] -2,3 '-(3H) -naphtho- (2,1-b) (1,4) -oxazine], 1,3,5,6-tetramethyl-3-ethylspiro [indoline-2,3'- (3H) -pyrido- (3,2-f) (1,4) -benzoxazine], 1,3 ′, 3′-trimethylspiro (2H-1-benzopyran-2,2′-indoline), spiro [ 2H-chromene-2,2′-tricyclo [3.3.1.13.7] decane], 5,7-dimethyl-spiro [2H-chromene-2,2′-tricyclo [3.3.1.13]. .7] decane], and the like.

  Organic photochromic compounds can be used alone, but they have high boiling point solvents, plasticizers, synthetic resins, hindered amine compounds, hinders for the purpose of improving the discoloring function and improving light resistance. It is preferable to use an auxiliary such as a dophenol compound. These compounds are known as materials used in combination with organic photochromic compounds. Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalenedicarboxylic acid. Examples of aliphatic glycols include ethylene glycol, Examples include diethylene glycol and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, the dicarboxylic acid component of the copolyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol, is mentioned.

  The content of the organic photochromic compound in the film is in the range of 0.05 to 1.0% by weight. When the content is less than 0.05% by weight, the discoloration effect of the film is inferior. On the other hand, when it contains exceeding 1.0 weight%, a malfunction arises with the degraded material in a film.

  Next, the kneading of polyester with an organic photochromic compound that causes color change by UV irradiation in the present invention will be described. These compounds are preferably used as a masterbatch kneaded into a polyester resin, but may be directly added to the polyester resin.

  Furthermore, the layer structure of the kneading of the organic photochromic compound will be described for the polyester film having color change performance by UV in the present invention. The organic photochromic compound may be kneaded into either the surface layer or the intermediate layer of the polyester film. What is necessary is just to adjust content of a surface layer or an intermediate | middle layer so that it may become said content as the whole film.

  The color change (coloring) in the matte polyester film of the present invention is a color change in the appearance of the polyester film. Specifically, it can be expressed by a contrast ratio in the luminance measurement. Specifically, the relative luminance obtained from the ratio of the UV irradiated portion to the unirradiated portion is a value of about 101 to 104, preferably 104 or more. Further, coloring can also be expressed by ΔE obtained from L * a * b * color difference evaluation, and the ΔE value is preferably about 5.0 to 20.0, more preferably 20.0 or more. is there.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows. In addition, the various physical property in this invention, its measuring method, and a definition are as follows. In the following, “parts” and “%” mean “parts by weight” and “% by weight”, respectively.

Examples and comparative examples of the matte polyester film will be described.

(1) Average particle size of additive (μm)
The size of the particles was measured by a sedimentation method based on Stokes' resistance law using a centrifugal sedimentation type particle size distribution analyzer SA-CP3 manufactured by Shimadzu Corporation. The average particle diameter was determined by using a value of 50% of integration (volume basis) in the equivalent spherical distribution of particles obtained by measurement.

(2) Intrinsic viscosity of polyester (dl / g)
A mixed solvent of phenol / tetrachloroethane: 50/50 (weight ratio) was added to 1 g of polyester at a ratio of 100 ml, and the mixture was measured at 30 ° C.

(3) Arithmetic average roughness (Ra) and ten-point average roughness (Rz)
Ra and Rz were measured using a surf coder SE3500 manufactured by Kosaka Laboratory. Measurement was performed 12 times on one side (cast surface) of the sample under the following conditions, and an average value of ten points excluding the maximum and minimum two points was taken.
Stylus tip diameter: 5μm
Measuring power: 30mgf
Measurement length: 2.5mm
Cut-off value: 0.08mm
In the examples and comparative examples of the present invention, the obtained polyester films were judged by Ra. Judgment is based on the following criteria.
○: 0.10 to 1.0 or more ×: lower than 0.10 or larger than 1.0

(4) Visual Evaluation of Appearance of Organic Photochromic Compound-Containing Polyester Film In the polyester film having reversible color change (coloring) performance by UV, the present invention is aimed at industrial production in the future. Since the first condition is that the film is a film, the appearance of the obtained polyester film was visually determined. Judgment is based on the following criteria.
○: Appearance is good △: Appearance is not bad ×: Appearance is bad

(5) Contrast evaluation of coloring strength after UV irradiation of polyester film Using a luminance meter, the contrast ratio between the non-colored portion of the film before UV irradiation and the colored portion after UV irradiation was evaluated. Specifically, a sample is placed on a flat illuminator manufactured by Dentsu Sangyo Co., Ltd .: HF-SL-A48LCF, and further, using Konica Minolta Sensing Co., Ltd. CS-200, the measurement viewing angle is 1 °, and the distance between the sample and the luminance meter is measured. The luminance value (cd / m ² ) was measured at 500 mm. The relative luminance (%) was obtained from the following formula.

Relative luminance = (measured value of UV non-irradiated part) ÷ (measured value of UV irradiated part) × 100
The relative luminance was evaluated according to the following criteria from the obtained relative luminance value.

A: More than 104 (strong coloring)
○: 102 to 104 (colored)
Δ: 101-102 (lightly colored)
X: Less than 101 (almost not colored)

(6) ΔE Evaluation of Coloring Strength after UV Irradiation of Polyester Film About the obtained polyester film after UV irradiation, using a color difference meter, L of the uncolored part of the film before UV irradiation and the colored part after UV irradiation * A * b * Color difference was evaluated. Specifically, according to JIS Z 8729, the L * a * b * color difference values of the UV irradiated portion and the non-irradiated portion were measured using a color difference meter CR-410 (sample diameter 50 mm) manufactured by Konica Minolta. At this time, the light source was C / D65, the back surface was white, and measurement was performed by a reflection method. The measurement was performed three times, and an average value was adopted. ΔL * (irradiated portion L * value−non-irradiated portion L * value), Δa * (irradiated portion a * value−non-irradiated portion a * value), Δb * (irradiated portion b * value−non-irradiated portion) (Part b * value) was calculated, and ΔE value was calculated and evaluated.
The ΔE value was determined from the following formula.

ΔE = {(ΔL *) ² + (Δa *) ² + (Δb *) ² } ^1/2
Evaluation was performed based on the following criteria from the obtained ΔE value.
A: Over 10.0 (strong coloring)
○: 5.0 to 10.0 (colored)
Δ: 2.5 to 5.0 (light color)
X: Less than 2.5 (almost not colored)

(7) Visual Evaluation of Coloring Strength after UV Irradiation of Polyester Film In the polyester film having reversible color change (coloring) performance by UV, the present invention aims at industrial production in the future and changes visually. Since the first condition is that it can be seen, the obtained polyester film after UV irradiation was visually evaluated for strength. Judgment is based on the following criteria.
◎: Strong coloring ○: Colored △: Light color ×: Not colored

Example 1:
A polyethylene terephthalate chip having an intrinsic viscosity of 0.71 containing 9.0% of amorphous silica particles having an average particle diameter of 4.5 μm and a spirooxazine compound as an organic photochromic compound, 1,3,3-trimethylspiro [indoline- 2,3 ′-(3H) -naphtho- (2,1-b) (1,4) -oxazine] in a ratio of 99.72: 0.28, respectively, was used as a surface layer material, and the average particle size A polyethylene terephthalate chip having an intrinsic viscosity of 0.71 containing 2.5 μm of amorphous silica particles and having an intrinsic viscosity of 0.71 is used as an intermediate layer raw material. Each is supplied, melted at 290 ° C, and then coextruded in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer) on a cooling roll set to 40 ° C and solidified by cooling. Not to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 4.0 times at 120 ° C. in the transverse direction, and heat-treated at 225 ° C. Thereafter, the polyester film was relaxed by 2% in the lateral direction to obtain a polyester film having a thickness of 50 μm (surface layer: 5 μm, intermediate layer: 40 μm). The obtained polyester film was a white polyester film. The polyester film is irradiated with UV light (181 mW / cm ² , 10 m / min, d = 100 mm) using a high-pressure mercury lamp (Ushio Electric Co., Ltd .: UVC-402 / 1HN: 302 / 1MN: JC01) to provide color change performance. As a result of evaluation, the change to the yellow colored state was satisfactory. The relative luminance of the obtained film was 105%, and ΔE was 8.4 (L * = 87.01, a * = − 0.97, b * = 9.76).

Example 2:
The ratio of the raw material of Example 1 to 1,3,3-trimethylspiro [indoline-2,3 ′-(3H) -naphtho- (2,1-b) (1,4) -oxazine] was 95.2 respectively. A film was obtained in the same manner except that a polyester film was obtained using the mixed raw material mixed at a ratio of 4.8 as a raw material for the surface layer. The obtained polyester film was a white polyester film. The polyester film was subjected to UV irradiation in the same manner as in Example 1 and the color change (coloring) performance was evaluated. As a result, the change to a yellow colored state was satisfactory. The relative luminance of the obtained film was 105%, and ΔE was 24.2 (L * = 85.15, a * = − 2.18, b * 22.54).

Example 3:
A polyester film was obtained in the same manner as in Example 1 except that a polyester chip containing 4.0% by weight of amorphous silica particles having an average particle diameter of 4.5 μm was used. The obtained polyester film was a white polyester film. The polyester film was subjected to UV irradiation in the same manner as in Example 1 and the color change (coloring) performance was evaluated. As a result, the change to a yellow colored state was satisfactory.

Example 4:
A polyester film was obtained in the same manner as in Example 1 except that a polyester chip containing 3.5% by weight of amorphous silica particles having an average particle size of 9.0 μm was used. The obtained polyester film was a white polyester film. The polyester film was subjected to UV irradiation in the same manner as in Example 1 and the color change (coloring) performance was evaluated. As a result, the change to a yellow colored state was satisfactory.

Example 5:
A polyester film was obtained in the same manner as in Example 1 except that a polyester chip containing 9.0% by weight of amorphous silica particles having an average particle size of 9.0 μm was used. The obtained polyester film was a white polyester film. The polyester film was subjected to UV irradiation in the same manner as in Example 1 and the color change (coloring) performance was evaluated. As a result, the change to a yellow colored state was satisfactory.

Example 6:
A polyester film was obtained in the same manner as in Example 1 except that a polyester chip containing 25% by weight of amorphous silica particles having an average particle size of 4.5 μm was used. The obtained polyester film was a white polyester film. The polyester film was subjected to UV irradiation in the same manner as in Example 1 and the color change (coloring) performance was evaluated. As a result, the change to a yellow colored state was satisfactory.

Comparative Example 1:
The ratio of the raw material of Example 1 to 1,3,3-trimethylspiro [indoline-2,3 ′-(3H) -naphtho- (2,1-b) (1,4) -oxazine] was 90.0, respectively. A film was obtained by the same method except that a polyester film was obtained using a mixed raw material mixed at a ratio of 10.0 as a raw material for the surface layer. The obtained polyester film was a yellow polyester film with poor appearance. The polyester film was irradiated with UV in the same manner as in Example 1, and the color change (coloring) performance was evaluated. As a result, the yellow coloring state was considerably strong in appearance.

Comparative Example 2:
The ratio of the raw material of Example 1 to 1,3,3-trimethylspiro [indoline-2,3 ′-(3H) -naphtho- (2,1-b) (1,4) -oxazine] was 99.8, respectively. : A film was obtained in the same manner except that a polyester film was obtained using a mixed raw material mixed at a ratio of 0.2 as a raw material for the surface layer. The obtained polyester film was a white polyester film. The polyester film was irradiated with UV in the same manner as in Example 1 and the color change (coloring) performance was evaluated. As a result, almost no change to a yellow colored state was observed. The relative luminance of the obtained film was 101%, and ΔE was 1.4 (L * = 88.30, a * = 1.91, b * = 0.89).

Comparative Example 3:
A comparative study was conducted on the appearance of the polyester film brought about by the particle size and content of the amorphous silica particles. A polyester film was obtained in the same manner as in Example 1 except that a polyester chip containing 2.0% by weight of amorphous silica particles having an average particle size of 4.5 μm was used. The obtained polyester film resulted in lack of surface roughness.

Comparative Example 4:
A polyester film was obtained in the same manner as in Example 1 except that a polyester chip containing 32% by weight of amorphous silica particles having an average particle diameter of 4.5 μm was used. The obtained polyester film had spots derived from aggregates in appearance, and the reduction in productivity such as breakage was remarkable.

Comparative Example 5:
A polyester film was obtained in the same manner as in Example 1 except that a polyester chip containing amorphous silica particles having an average particle size of 2.0 μm was used. The obtained polyester film resulted in lack of surface roughness.

Comparative Example 6:
A polyester film was obtained in the same manner as in Example 1 except that a polyester chip containing amorphous silica particles having an average particle diameter of 12 μm was used. It was difficult to obtain a polyester film due to breakage derived from aggregates.

  The polyester film having the color change performance by UV of the present invention can be used not only for measuring ultraviolet intensity in various applications such as solar cells and building materials for outdoor use, but also for any production line in place of an inkjet method. It can be used as a landmark, and can be used as a UV photosensitive marker and optical sensor technology in electronic parts, and can be expected to be applied to beautiful daily necessities using UV photosensitive light emitting technology.

Claims (1)

A laminated polyester having three or more layers, wherein the polyester layer constituting the film surface having a surface roughness (Ra) in the range of 0.1 to 1.0 μm contains 3 to 30% by weight of particles having an average particle diameter of 3 to 10 μm. An organic photochromic compound that is a film and is colored by ultraviolet irradiation in the surface layer of the laminated film, and the content of the organic photochromic compound in the polyester film is 0.05 to 1.0% by weight. A polyester film.