JP2010202749A - White 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 2 to 40% by weight of a white pigment having an average particle size of 0.1 to 1.0 μm and 0.025 to 0.25% by weight of a compound colored by laser light, A white polyester film having a degree of 90 or more.
[Selection figure] None

Description

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

  In recent years, functional white polyester films have been used in various fields, ranging from solar cells, electronic devices, and other home decorations such as building materials. In these applications, a white polyester film that is inexpensive, environmentally friendly, and highly functional is 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 problem 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, It is an object of the present invention to provide a white polyester film that does not contain copolymerization and can be applied to decoration techniques in daily life products 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 white film having a specific configuration, and has completed the present invention.

  That is, the gist of the present invention is a polyester film containing 2 to 40% by weight of a white pigment having an average particle size of 0.1 to 1.0 μm and 0.025 to 0.25% by weight of a compound colored by laser light. There is a white polyester film characterized in that the Hunter whiteness is 90 or more.

Hereinafter, the present invention will be described in more detail.
The polyester film constituting the white polyester film having coloring performance in the present invention preferably has a multilayer structure in consideration of functionality and price, and does not exceed the gist of the present invention other than the two-layer or three-layer structure. As long as it has four or more layers, it is not particularly limited.

  The polyester referred to in the present invention refers to a polymer containing an ester group obtained by polycondensation from a dicarboxylic acid and a diol or from a hydroxycarboxylic acid. Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and diols include ethylene glycol and 1,4-butanediol. , Diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol, and the like. Examples of hydroxycarboxylic acids include p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. it can.

  Typical examples of such polymers include polyethylene terephthalate and polyethylene-2,6-naphthalate. These polymers are preferably homopolymers.

  The transmission density of the white polyester film of the present invention is preferably in the range of 0.1 to 3.0, more preferably 0.2 to 2.5, and particularly preferably 0.3 to 2.2. When the transmission density is less than 0.1, the film can be seen through depending on the use of the film. When the transmission density is more than 3.0, it is disadvantageous in terms of productivity such as cost.

  The concealability in the polyester white film is achieved by adding various white pigments to the film. As the white pigment, titanium dioxide, barium sulfate, calcium carbonate and the like can be used in combination as long as they can be used as a white pigment. Of these white pigments, titanium dioxide is preferable. Further, the surface of the pigment may be surface-treated in order to improve whiteness and the like.

  The average particle size of the white pigment used is in the range of 0.1 to 10 μm, and preferably in the range of 0.2 to 0.5 μm. If the average particle size is less than 0.1 μm, the light transmittance is increased and the white hiding effect is insufficient. On the other hand, when the average particle diameter exceeds 1.0 μm, the original whiteness of titanium dioxide is lowered in addition to the deterioration of the appearance due to foreign matters. If the shielding effect is inferior, it is necessary to increase the pigment concentration. When titanium dioxide is used, the lead content in the white polyester film increases.

  The blending amount of the white pigment is 2.0 to 40% by weight, preferably 5.0 to 20% by weight, based on the polyester. If the blending amount is less than 2.0% by weight, the light transmittance increases and the concealment effect becomes insufficient. In addition, if this amount exceeds 40% by weight, the mechanical strength of the polyester is reduced, causing problems such as film breakage during film formation. When titanium dioxide is used, the lead content in the polyester film is low. Increase.

  A white pigment can be mix | blended in the arbitrary steps of the manufacturing process of a polyester film. In the present invention, if necessary, the average particle size and content do not adversely affect weather resistance and whiteness, do not increase the number of coarse particles, and do not adversely affect the smoothness of the polyester film surface. If present, inert particles other than the white pigment may be used in combination. In addition to the above-mentioned inert particles, so-called precipitation-type fine particles which are precipitated by the reaction between the catalyst residue and the phosphorus compound in the reaction system can be used in combination.

  When anatase-type titanium dioxide is used as a white pigment, the dispersibility of titanium dioxide in polyester is improved by adjusting the amount of silicon dioxide in anatase-type titanium dioxide to 1.0% by weight or less in terms of silicon element. be able to.

  When the film of the present invention has a laminated structure, it is preferable to add a white pigment to the intermediate layer, and the polyester of the outer layer portion is preferably a homopolyester in consideration of production cost and ease of film formation. . 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, the heat-resistant organic particles 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, sufficient slipperiness cannot be imparted, and the particles are aggregated, resulting in insufficient dispersibility and may deteriorate the appearance.

  Further, the content of particles in the polyester layer 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 dispersibility in 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 210 ° 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.

  In the present invention, the white polyester film refers to a polyester film having a white gloss appearance. Specifically, it can be expressed by Hunter whiteness, specifically, Hunter whiteness is 90 or more. What is necessary is just to adjust the particle size and content material of the white pigment to be used so that it may become the value.

  Examples of the compound used in the present invention that is colored by laser light (hereinafter sometimes referred to as a laser marking pigment) include the following compounds.

  That is, the metal oxide is preferably one or more selected from a copper compound, a molybdenum compound, an iron compound, a nickel compound, a chromium compound, a zirconium compound and an antimony compound, and one or more selected from a zirconium compound and an antimony compound. More preferably. 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 coloring effect of the film is inferior. On the other hand, when it contains exceeding 0.25 weight%, a malfunction arises with the degraded material in a film.

  Examples of the method of blending the laser marking pigment into the white polyester film 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, when the white polyester film in the present invention has a laminated structure, the laser marking pigment-containing layer may be either a surface layer or an intermediate layer. 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, color change (coloring) is a color change in the appearance of a white polyester film. Specifically, it can be expressed by ΔE obtained from L * a * b * color difference evaluation. Specifically, the ΔE value is preferably about 0.5 to 3.0, more preferably 3.0. That's it.

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 laser marking pigment-containing white polyester film of the present invention, it is possible to provide a white polyester film having irreversible color change performance regardless of whether the laser marking pigment is kneaded into the surface layer or the intermediate layer within an appropriate amount range. The laser marking pigment-containing white polyester film of the present invention is not only used as a mark in the production process or as a laser photosensitive marker in electronic parts, but also expected to be applied to beautiful household goods using laser photosensitive coloring technology. Because it can, 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. 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.

(1) Hunter whiteness Five films stacked according to the method of JIS P813-1961, using a colorimeter NDH-1001DP (C light source, 2 ° visual field) manufactured by Nippon Denshoku Industries Co., Ltd. The whiteness (Wb) having a thickness of about 200 μm was measured. The back of the film was pressed with a black plate.
○: 90 or more ×: lower than 90

(2) Transmission density Using a Macbeth densitometer (TD-904 type), the transmission light density under the G filter was measured. The larger this value, the higher the hiding power.
○: 0.1 to 3.0 or more ×: lower than 0.1 or larger than 3.0

(3) Visual Evaluation of Appearance of Laser Marking Pigment-Containing White Polyester Film The appearance of the obtained polyester film was visually judged. Judgment was made based on the following criteria.
○: Appearance is good △: Appearance is not bad ×: Appearance is bad

(4) Evaluation of polyester white film after laser irradiation 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

・ L * a * b * color difference evaluation of white polyester film after laser irradiation 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 Evaluation of L * a * b * color difference of the colored portion was performed. 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.
A: More than 3.0 (strong coloring)
○: 1.5 to 3.0 (colored)
Δ: 0.5 to 1.5 (light color)
X: Less than 0.5 (almost not colored)

-Visual evaluation of the coloring strength after laser irradiation of a white polyester film About the polyester film after laser irradiation, judgment of the intensity | strength by visual observation was performed according to the following reference | standard.
○: Strong coloring △: Colored ×: Not colored

  In the following examples and comparative examples, the polyester used was prepared as follows.

<Manufacturing method of polyester chip>
100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.07 part of calcium acetate-hydrate are heated in a reactor and heated to a temperature while methanol is distilled off to carry out a transesterification reaction. About 4 and a half hours are required after starting the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, 0.04 part of phosphoric acid and 0.035 part of antimony trioxide were added and polymerized in accordance with a conventional method. That is, the reaction temperature was gradually raised to finally 280 ° C., while the pressure was gradually reduced to finally 0.05 mmHg. After 4 hours, the reaction was completed, and chipped into a polyester (A) according to a conventional method. The solution viscosity IV of the obtained polyester chip was 0.66.

<Manufacture of master batch chips>
60 parts of the polyester (A) obtained and 40 parts of rutile titanium dioxide having an average particle size of 0.3 μm and a lead atom concentration of 1 ppm produced according to a conventional method were melt-mixed in a twin-screw extruder, A master batch chip (B) was obtained.

In the examples and comparative examples, the polyester used for the outermost layer is prepared as follows.
<Production method of polyester (C)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, adding tetrabutoxy titanate as a catalyst to the reactor, setting the reaction start temperature to 150 ° C., and gradually increasing the reaction temperature as methanol is distilled off. It was 230 degreeC after 3 hours. After 4 hours, the transesterification reaction was substantially completed, and then a polycondensation reaction was performed for 4 hours.
That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (C) having an intrinsic viscosity of 0.63.

<Method for producing polyester (D)>
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate / tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is set to 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. Was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank, orthophosphoric acid was added, and germanium dioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.65 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester (D) having an intrinsic viscosity of 0.65.

<Production method of polyester (E)>
In the production method of polyester (C), 0.2 part of silica particles having an average particle size of 2.0 μm dispersed in ethylene glycol was added, and the polycondensation reaction was stopped at a time corresponding to an intrinsic viscosity of 0.66. Using a method similar to the method for producing polyester (C), polyester (E) having an intrinsic viscosity of 0.66 was obtained.

Example 1:
A material obtained by blending polyethylene terephthalate chip (B) having an intrinsic viscosity of 0.65 with polyester A so that the content of titanium dioxide was 13% was used as a raw material for the intermediate layer. In addition, mixed raw materials in which polyesters (C), (D), and (E) are mixed at a ratio of 85%, 5%, and 10%, respectively, and a composite oxide of copper and molybdenum that are laser marking pigments (CuO.xMoO ₃ : Toyo Material Technology Co., Ltd.) was mixed at a ratio of 99.87: 0.13 as the outermost layer raw material, and the surface polyester and intermediate layer mixed raw material were extruded at a ratio of 1: 4. Each is supplied to a machine, melted at 290 ° C., then coextruded in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer) on a cooling roll set at 40 ° C., and solidified by cooling and unstretched sheet Got. 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 beautiful glossy white polyester film. The white polyester film was irradiated with YVO ₄ laser (Keyence Co., Ltd .: MD-V9900) (1064 nm) to evaluate the color change performance. As a result, the change to the gray colored state was satisfactory. ΔE of the obtained film was 3.30 (L * = 93.00, a * = − 0.28, b * = 1.08).

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 98.80: 1.20 was used as the outermost layer raw material. The obtained polyester film was a beautiful glossy white polyester film. The white 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 satisfactory. ΔE of the obtained film was 3.50 (L * = 93.20, a * = − 0.21, b * = 1.38).

Comparative Example 1:
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 98.00: 2.00 was used as the outermost layer raw material. The obtained polyester film was a yellow film with poor appearance. 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 ΔE of the obtained film was 4.2 (L * = 92.60, a * = − 0.18, b * = 1.58).

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 99.90: 0.10 as the raw material of the outermost layer. Got. The obtained polyester film was a beautiful glossy white polyester film. The white 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 barely confirmed. ΔE of the obtained film was 0.20 (L * = 96.05, a * = − 0.35, b * = − 0.20).

Comparative Example 3:
A comparative study was conducted on the appearance of the white polyester film provided by MB containing rutile titanium dioxide. A polyester film was obtained in the same manner as in Example 1 except that a master batch (B) containing 1.5% by weight of rutile titanium dioxide was used.
The obtained polyester film lacked whiteness.

Comparative Example 4:
A polyester film was obtained in the same manner as in Example 1 except that a master batch (B) containing 45% by weight of rutile titanium dioxide was used.
The obtained polyester film had spots derived from aggregates in appearance.

Comparative Example 5:
A polyester film was obtained in the same manner as in Example 1 except that a master batch (B) containing rutile-type titanium dioxide having a particle size of 0.07 μm was used.
The obtained polyester film lacked whiteness.

Comparative Example 6:
A polyester film was obtained in the same manner as in Example 1 except that a master batch (B) containing rutile-type titanium dioxide having a particle size of 1.2 μm was used.
The obtained polyester film had spots derived from aggregates in appearance.

  The white 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 2 to 40% by weight of a white pigment having an average particle size of 0.1 to 1.0 μm and 0.025 to 0.25% by weight of a compound colored by laser light, and has a Hunter whiteness of 90 or more The white polyester film characterized by being.