JP2010189504A - Polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change the color by cheap and simple laser light irradiation, without causing problems such as environmental burden and cost increase in the ink jet method, and decoration technology and laser light in daily goods and electronic parts. Provided is a polyester film that can be applied to use as a photosensitive marker.
A polyester film containing 0.025 to 0.25% by weight of a compound colored by laser light.
[Selection figure] None

Description

  The present invention relates to a polyester film that is color-changed (colored) by laser light irradiation.

  In recent years, functional polyester films have been used in a variety of fields, ranging from solar cells, electronic devices, and to 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 on which printing by an ink-jet method has been performed is known as a household goods decoration application. The ink jet method is the mainstream, but the problems with this method are that it uses a large amount of various polymers and pigments, so it has a heavy environmental impact, and the maintenance and equipment investment costs such as contamination, running, Cost, and further, there are technical difficulties such as a drying process and a change in film thickness.

  For example, a polyester film having a laser-sensitive color change performance instead of the conventional ink jet method is expected to be used because it serves as a mark in some processing in the production process.

  As a further example, there is not only the possibility of use as a laser photosensitive decoration technique in electronic parts, but also the possibility of application to beautiful daily necessities using the laser photosensitive coloring technique.

JP 2007-55110 A JP 2008-80805 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 laser irradiation, An object of the present invention is to provide a polyester film that can be applied to decoration techniques for household goods and electronic parts and uses as a laser photosensitive marker.

  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 resides in a polyester film characterized by containing 0.025 to 0.25% by weight of a compound colored by laser light.

Hereinafter, the present invention will be described in more detail.
The polyester film constituting the polyester film of the present invention may have a single-layer structure or a multilayer structure, and may have four or more layers as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. It may be a multilayer, and is not particularly limited.

  The polyester used in the present invention is preferably a homopolyester as a result of pursuing reduction of production costs and ease of process work. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like.

  In the film of the present invention, it is preferable to blend particles mainly for the purpose of imparting slipperiness and preventing the occurrence of scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, heat-resistant organic particles as described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process may be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.1-2 micrometers. When the average particle size is less than 0.01 μm, the slipperiness may not be sufficiently imparted. On the other hand, when the thickness exceeds 3 μm, transparency may be lowered due to the aggregate of the particles when the film is formed, and it is easy to cause breakage, which causes a problem in terms of productivity. There is.

  Furthermore, the content of particles in the polyester is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is a case.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film in the present invention as necessary.

  Although the thickness of the polyester film in this invention will not be specifically limited if it can be formed into a film as a film, Usually, 10-350 micrometers, Preferably it is the range of 50-250 micrometers.

  Next, although the manufacture example of the polyester film in 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 times, preferably 3.0 to 6 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 times, preferably 3.5 to 6 times. is there. 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.

  For the production of the polyester film of the present invention, a simultaneous biaxial stretching method can also be employed. 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.

  The following compounds are preferred as those usable for the laser marking pigment used in the present invention.

As a specific example of the laser marking pigment, the metal oxide is preferably at least one selected from a copper compound, a molybdenum compound, an iron compound, a nickel compound, a chromium compound, a zirconium compound and an antimony compound. More preferably, it is at least one selected from compounds. In addition, supplementary use and use of inorganic metal compounds such as titanium oxide, zinc sulfide, zinc oxide, precipitated barium sulfate, barium carbonate and precipitated calcium carbonate and dyes such as carbon black, graphite and black lake, and leuco dye It is desirable to select and use it according to the environment.

  The content of the laser marking pigment in the film is in the range of 0.025 to 0.25% by weight. When the content is less than 0.025% by weight, the discoloration effect of the film is poor. On the other hand, when it contains exceeding 0.25 weight%, a malfunction arises with the degraded material in a film.

  Next, examples of the method for incorporating the laser marking pigment into the polyester that causes color change irreversibly by laser irradiation in the present invention include a kneading method and a coating method. In the present invention, the kneading method is adopted in consideration of coloring efficiency. The kneading into the polyester 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 laser marking pigment kneading will be described for the polyester film having color change performance by laser irradiation in the present invention. The laser marking pigment may be kneaded into either the surface layer or the intermediate layer of the homopolyester 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.

  In the present invention, the color change (coloring) is a color change in the film appearance. Specifically, it can be expressed by the contrast ratio in the luminance measurement. Specifically, the relative luminance obtained from the ratio of the laser irradiated portion and the unirradiated portion is about 102 to 200, preferably 200 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 0.5 to 6.0, more preferably 6.0 or more. is there.

In carrying out the present invention, the laser light source and the irradiation method thereof are not particularly limited, and various known Nd: YAG lasers, CO ₂ lasers, various excimer lasers, and the like can be used. Among these, the effect becomes remarkable in the marking using the Nd: YAG laser.

  According to the present invention, a polyester film having a color change performance by laser irradiation provides a polyester film having an irreversible color change performance with high transparency regardless of whether the laser marking pigment is kneaded into the surface layer or the intermediate layer within an appropriate range. can do. The polyester film having color change performance by laser irradiation according to the present invention has not only a possibility of being used as a laser photosensitive marker in a mark or an electronic component in a production process, but also to a beautiful everyday product using laser photosensitive coloring technology. Because it can be expected to be applied, its industrial value is high.

  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.

(1) Transmittance measurement of a polyester film As a reference | standard of transparency, evaluation of transparency by visual observation and transmittance | permeability measurement are mentioned. Judgment is based on the following criteria.
・ Regarding visual observation ○: Almost transparent Δ: Transparent, but slightly colored yellow ×: Yellow is strong and cloudy ・ Transmission measurement Integration according to JIS-K7105, manufactured by Nippon Denshoku Industries Co., Ltd. The total light transmittance of the film was measured with a spherical turbidimeter NDH-300A. The transmittance decrease in the range of 0.5 to 1% with respect to the transmittance of a general polyester film is ◎, the transmittance decrease in the range of 1-2% is ○, and the range of 2 to 4% The decrease in transmittance was evaluated as Δ, and the decrease in transmittance exceeding 4% was evaluated as x.

(2) Evaluation of polyester film after laser irradiation The laser marking conditions are as follows.
Laser marking device: Keyence Co., Ltd. laser marker MD-V9900
Laser type: YVO ₄ laser (wavelength 1064 nm)
Irradiation method: XYZ 3-axis simultaneous scanning method (CW (continuous oscillation), Q switch frequency 1 to 400 kHz)
Marking power: 13W
Scanning speed: 1500mm / s

-Contrast evaluation of the coloring intensity after laser irradiation of the polyester film Using a luminance meter, the contrast ratio between the non-colored portion of the film before laser irradiation and the colored portion after laser 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 the laser unirradiated part) ÷ (measured value of the laser irradiated part) × 100
The relative luminance was evaluated according to the following criteria from the obtained relative luminance value.
○: More than 200 (strong coloring)
Δ: 102 to 200 (colored)
X: Less than 102 (almost not colored)

・ L * a * b * Color Difference Evaluation of Coloring Strength after Laser Irradiation of Polyester Film About the obtained polyester film after laser irradiation, using a color difference meter, uncolored portions of the film before laser irradiation and after laser irradiation The L * a * b * color difference of the colored portion was evaluated. Specifically, according to JIS Z 8729, L * a * b * color difference values of the laser 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.
○: More than 6.0 (strong coloring)
Δ: 0.5 to 6.0 (colored)
X: Less than 0.5 (almost not colored)

-Visual evaluation of coloring strength after laser irradiation of polyester film The polyester film after laser irradiation was visually evaluated for strength according to the following criteria.
○: Strong coloring △: Colored ×: Not colored

Example 1:
As a raw material for the intermediate layer, a mixed raw material obtained by mixing polyester and laser oxide pigment copper and molybdenum composite oxide (CuO.xMoO ₃ : Toago Material Technology Co., Ltd.) in a ratio of 99.97: 0.03 is used. The mixed raw materials of the surface layer polyester and the intermediate layer were respectively supplied to two extruders at a ratio of 1: 9, melted at 290 ° C., respectively, and then on the cooling roll set at 40 ° C. Coextruded with a layer structure of (surface layer / intermediate layer / surface layer) and cooled and solidified 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 film was relaxed by 2% in the lateral direction to obtain a transparent polyester film having a thickness of 100 μm (surface layer: 5 μm, intermediate layer: 90 μm). The obtained polyester film was a colorless and transparent film. The polyester film was irradiated with YVO ₄ laser (Keyence Corporation: MD-V9900) (1064 nm) and evaluated for color change performance. As a result, the change to the gray colored state was satisfactory. The obtained film had a relative luminance of 210% and ΔE of 5.73 (L * = 82.81, a * = 1.86, b * = 2.04).

Example 2:
A film was obtained in the same manner as in Example 1 except that a mixed raw material in which the ratio of the raw material and CuO.xMoO ₃ was mixed at a ratio of 99.75: 0.25 was used as the intermediate layer raw material. The obtained polyester film was a colorless and transparent film. The polyester film was irradiated with laser in the same manner as in Example 1 to evaluate the color change (coloring) performance. As a result, the change to the gray colored state was good. The obtained film had a relative luminance of 210% and ΔE of 6.40 (L * = 82.17, a * = 1.82, b * = 2.14).

Comparative Example 1:
A film is produced in the same manner as in Example 1 except that a polyester film is obtained using a mixed raw material in which the ratio of the raw material and CuO.xMoO ₃ is mixed at a ratio of 99.98: 0.02 as a raw material for the intermediate layer. Got. The obtained polyester film was a transparent film. The polyester film was irradiated with laser in the same manner as in Example 1 and the color change (coloring) performance was evaluated. As a result, a change to a gray colored state could not be confirmed. The relative luminance of the obtained film was less than 110%, and ΔE was 0.03 (L * = 88.13, a * = 2.00, b * = − 0.14).

Comparative Example 2:
A film is produced in the same manner as in Example 1 except that a polyester film is obtained by using a mixed raw material in which the ratio of the raw material and CuO.xMoO ₃ is mixed at a ratio of 99.6: 0.4 as the raw material of the intermediate layer. Got. The obtained polyester film was a yellow film that lost transparency. The polyester film was irradiated with laser in the same manner as in Example 1 to evaluate the color change (coloring) performance. As a result, the change to the gray colored state was remarkable. The relative luminance of the obtained film was 240%, and ΔE was 7.73 (L * = 81.71, a * = 1.46, b * = 2.54).

Comparative Example 3:
A general transparent polyester film not containing the laser marking pigment CuO.xMoO ₃ was irradiated with laser in the same manner as in Example 1 and the color change performance was evaluated. The laser was transmitted and absorbed. There wasn't. That is, as expected, the general transparent polyester film was not colored, and the results showed that the effect of the laser marking pigment was remarkable.

  The polyester film of the present invention can be used not only as a mark in the production process and as a laser photosensitive marker in electronic parts, but also to be applied to beautiful daily goods using laser photosensitive coloring technology.

Claims (1)

A polyester film containing 0.025 to 0.25% by weight of a compound colored by laser light.