JPS62243120A - Polyester film for magnetic recording card - Google Patents

Abstract

PURPOSE:To obtain a film having excellent whiteness and having non-shining gloss by incorporating titanium dioxide and barium sulfate having specific grain sizes into a polyester under specific conditions and further incorporating a fluorescent brightener at a specific ratio therein. CONSTITUTION:This film consists of the polyester contg. 6-19wt% titanium dioxide having <=0.5mum average grain size, 1-10wt% barium sulfate having 1-5mum average grain size and the fluorescent brightener having a fluorescent peak at 400-5,000nm wavelength and is the biaxially oriented film provided with an easily printable thin film layer on at least one face if desired. The average grain size of the titanium dioxide is preferably 0.05-0.4mum and the content of the titanium dioxide to be added to the polyester is preferably 8-17wt%. The average grain size of the barium sulfate is preferably 2-4mum. The film having the excellent whiteness and having the non-shining gloss is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polyester film for magnetic recording cards that has excellent whiteness and non-glossy luster.

Polyester in general, and polyethylene terephthalate in particular, is widely used as a film because of its excellent mechanical and chemical properties.

Recently, with the advancement of information and recording fields, polyester films have come to be used for magnetic recording cards such as telephone cards. Polyester films used in these applications are generally required to have light-shielding properties that do not allow light to pass through from the back side.

A method for imparting light-shielding properties to a film includes a method of incorporating inert inorganic particles into a polyester film, for example, as described in Japanese Patent Publication No. 44-2G752.

It has been proposed in JP-A No. 57-205824 and the like to incorporate a relatively large amount of titanium dioxide into a polyester film.

However, if the content of titanium dioxide in polyester exceeds about 5% by weight, 1'J
The resulting film has a yellowish tinge due to the decomposition of poly-1 stell by the titanium dioxide, the monochromatic color, or the hue of the titanium dioxide itself. For example, when a telephone card is made using such a film as a base, the white background of the printed surface of the telephone card appears yellowed. Therefore, in order to use the film in these applications, it is necessary to print or coat the film with a white paint, which is disadvantageous in terms of productivity and economy.

In addition, titanium dioxide is an excellent substance in terms of providing light-shielding properties to films, but because the particle size is small, the surface of the resulting film is relatively flat even if titanium dioxide is contained multiple times in polyester. The film becomes glossy. Phone cards that use such films as they are tend to reflect light from lighting, etc., and lack quality.
Problems arise, such as difficulty in reading characters.

In order to overcome this drawback, it is generally considered that the film surface is subjected to post-processing such as alkali treatment or sandblasting to make the surface rough, but the performance is not sufficient and it is not economically viable. There are many disadvantages. In addition, in order to eliminate this drawback, it is possible to incorporate particles with a large particle size into polyester to impart light-shielding properties to the film and to roughen the film surface, but according to the research results of the present inventors, In order for a film to have light-shielding properties, it is necessary to contain a large amount of these particles, and the amount of gold in coarse particles mixed in the particles increases dramatically compared to fine particles. Filter clogging and film tearing are likely to occur, and the resulting film has a large number of eyelids.

1.ffi In view of the above-mentioned circumstances, the present inventors have conducted extensive research on a film for biaxially oriented magnetic recording cards that has excellent whiteness and has a non-glossy luster, and as a result, has arrived at the present invention. .

Accordingly, an object of the present invention is to provide a polyester film for magnetic recording cards that has excellent whiteness and a non-glossy luster.

Structure/Effect of the Invention This object of the present invention is that, according to the present invention, the average particle size is 0.
Titanium dioxide 6-19fi 1% below 5 μm.

and polyester containing 1 to 10% by weight of Balicum sulfate with an average particle size of 1 to 5 μm and a fluorescent whitening agent having a fluorescence peak at a wavelength of 400 to 5000 nm, and if desired, it can be easily printed on at least one side of the film. This is achieved by a biaxially oriented film provided with a thin film layer.

The unique point of the present invention is that titanium dioxide and barium sulfate having a specific particle size are contained in a polyester under specific conditions, and furthermore, a specific amount of a fluorescent brightener is contained in the polyester. As a result, the biaxially oriented polyester film has properties such as excellent whiteness, light shielding properties, and matte gloss.If necessary, a thin layer of adhesive can be formed on the surface of the film to improve printability or magnetic layer adhesion. It can also be improved.

The polyester used in the present invention may be any material as long as it can be formed into a film, such as polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1
, 4-cyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate, and the like. Of course, these polyesters may be homopolyesters or copolyesters, and examples of copolymerization components include diol components such as diethyl glycol, neopentyl glycol, and polyalkylene glycol, and adipic acid.

Dicarboxylic acid components such as sebacic acid, phthalic acid, isophthalic acid, 2.6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid; trimerisolic acid biromellitic acid within a range where the polymer remains substantially linear; Examples include polyfunctional carboxylic acid components such as.

In the present invention, the titanium dioxide contained in the polyester may be any of the anaterpic and ruti-type crystals. Further, for the purpose of improving the dispersion of titanium dioxide into polyether, titanium dioxide whose surface is treated with oxides such as aluminum, silicon, zinc, or various organic substances can also be used.

The average particle size of titanium dioxide is 0.5 μTrL or less,
Preferably it is 0.05 to 0.4 μm. Here, the average particle size is the particle size at 50% by weight of all particles measured.
"equivalent spherical diameter". Furthermore, the term "equivalent spherical diameter" refers to an imaginary sphere having the same volume as the particle, and can be calculated from measurements using a conventional sedimentation method. If the average particle size of titanium dioxide is larger than 0.5 μm, there will generally be many coarse particles and the light-shielding property will be poor, which is not preferable. The added content of titanium dioxide polyester is 6-1
9% by weight, preferably 8 to 17% by weight. If the content of titanium dioxide is less than 61% by weight, the film will not have sufficient light-shielding properties, while if it exceeds 19% by weight, the light-shielding properties will be saturated and no improvement in effectiveness will be seen. Another problem arises in that the film is more likely to break during stretching.

The barium sulfate used in combination with titanium dioxide in the present invention may be either so-called precipitated barium sulfate or positive barium sulfate.

The average particle size of barium sulfate is 1 to 5 μm, preferably 2 to 4 μm. The average particle size is defined in the same manner as for titanium dioxide described above. When the average particle size of barium sulfate is less than 1 μm, the surface of the resulting film is flat and glossy. If it exceeds 5 μm, the surface of the film becomes too rough, causing problems such as poor magnetic recording conversion characteristics when used in a magnetic card, and poor filterability during film production.

The added content of barium sulfate is 1 to 10% by weight, preferably 2 to 8% by weight. The amount of barium sulfate added is 1% by weight.
If it is less than 51%, the film surface will be glossy, and if it exceeds 51%, there will be problems such as deterioration of magnetic recording conversion characteristics and increased film breakage during film stretching.

Further, in the present invention, the fluorescent whitening agent to be contained in the polyester can be of any type as long as it has a fluorescent peak at a wavelength of 400 to 500 nm, but a suitable one is Uvitex 08 (trade name, manufactured by Ciba Kaigy Co., Ltd.). ), 08-1
(Eastman Co.) r Commercially available products are listed.

The addition content of polyester in the fluorescent whitening agent is preferably 10 to 1000 flDl, more preferably 50 to 8
00 ppm.

It is preferable that titanium dioxide and barium sulfate in the present invention be subjected to a purification process to reduce the particle size and remove coarse particles before incorporating them into polyester. As industrial means for the purification process, examples of crushing means include jet mills and ball mills, and examples of classification means include dry or wet centrifuges.

It goes without saying that these means may be used to perform stepwise purification of two or more types.

Polyester, titanium dioxide, barium sulfate.

Various methods can be used to incorporate the fluorescent brightener. The following methods can be cited as representative methods.

(a) A method of adding it before the end of the transesterification or esterification reaction during polyester synthesis, or adding it before the polycondensation reaction.

(a) A method of adding it to polyester and melting and kneading it.

(1) In the method of (a) and (b) above, a masterbatch was produced by adding a large number of additives, or one or two types of each of titanium dioxide, barium sulfate, and a fluorescent brightener were added. A method of producing a masterbatch, kneading it with particle-free polyester and containing a predetermined amount of additives.

In addition, when using the method (a) of adding additives during polyester synthesis, it is preferable to add the additives to the reaction system as a slurry dispersed in glycol.

The polyester film forming conditions are known methods, for example, usually 280
Melt extrusion into a sheet at ~300°C, quench and solidify to form an amorphous sheet, then vertical and horizontal, or vertical, horizontal, II
A method of sequential biaxial stretching in the order of , a method of simultaneous 2@ stretching in the longitudinal and transverse directions, etc. can be adopted.

The two-wheel stretched film is preferably heat-set at a predetermined temperature to improve dimensional stability. In particular, when post-processing such as printing or coating with a magnetic layer is applied, 150
It is preferable that the shrinkage rate of the film after heat treatment at ℃ for 30 minutes is preferably 2% or less, more preferably 1% or less, since post-processability and quality of the obtained product are good.

The biaxially oriented polyester film of the present invention preferably has a surface roughness Ra of 0.1 to 0.5 μm. If the surface roughness Ra is less than 0.1 μm, gloss will occur, and if it exceeds 0.5 μm, the surface will become too rough.
Magnetic cards and the like have poor electromagnetic conversion characteristics and are not preferred.

Such surface roughness is basically caused by titanium dioxide and VA.
It can be adjusted by adjusting the average particle size of barium acid and the amount added, and can also be slightly adjusted by changing the stretching conditions.

In the present invention, the biaxially oriented polyester film is preferably provided with an easily printable thin film layer on at least one of its surfaces. The easily printable thin film layer can be formed in any manner. For example, there are two methods: one is formed during the production of a biaxially oriented film, and the other is formed after the production of a biaxially oriented film.A specific example of the former is, for example, after applying a thin film forming liquid to the surface of an unstretched film, the film is stretched in the biaxial direction. or -A method of applying a thin film forming liquid to the surface of a biaxially stretched film and further stretching in the perpendicular direction, and a specific example of the latter is a method of applying a thin film forming liquid to the surface of a biaxially stretched film. Can be mentioned.

Of these, the former is preferably applied in-line. A normal coating method can be used as the coating method.

The easy-printability forming agent has good adhesion to printing inks such as water-soluble inks and UV-curable inks, and magnetic recording compositions containing cretane, vinyl chloride, vinyl acetate, etc., and iron oxide, etc. There is no particular limitation as long as it improves. Examples of the four-body thin film forming agent include water-soluble polyester compositions, water-dispersible polyester compositions,
Preferred examples include water-dispersible polyurethane compositions and water-dispersible polyacrylic acid compositions. Among these, polyester-based compositions, especially water-dispersed polyester-based compositions, are difficult to discolor due to foreign matter generation due to decomposition of the thin film forming agent when using polymer recovered products (reclaim polymers) such as film edges generated during film production. Therefore, it is preferable.

The polyvinyl film for magnetic recording cards of the present invention has excellent whiteness, no gloss, and well-balanced surface roughness for telephone cards.

It is preferably used for magnetic recording cards such as ID cards.

101 The present invention will be further explained below with reference to Examples.

Note that various physical property values and characteristics relevant to the present invention were measured as follows.

(1) Film surface roughness (Ra) JIS B
Measured according to 0601. Using a stylus type surface roughness meter (StJRFCOM3B) manufactured by Tokyo Seimitsu Co., Ltd., a chart (film surface roughness curve) was drawn under conditions of a needle radius of 2 μm and a load of 0.079. A portion of measurement length L is extracted from the film surface roughness curve in the direction of its center line, the center line of this handled portion is taken as the X axis, the direction of longitudinal magnification is taken as the Y axis, and the roughness curve is expressed as Y=f When expressed as X), the value (Ra: μm) given by the following formula is defined as the film surface roughness.

Ra -1/L/, If (x) Idx In the present invention, eight measurements are taken with a reference length of 0.25 mm, and Ra is expressed as the average value of five measurements, excluding three from the largest value.

(2) Protrusion distribution Using a three-dimensional roughness meter <SE-3CK> made by Small Plate Research Institute,
Needle diameter: 3 μyl, pressure: 30IItg, measurement length: 1#
1I11. 'Nashipring pitch 2μm, cutoff 0
．． 25 RAM, vertical magnification of 20,000 times, horizontal magnification of 200 times, and number of scans of 150, the profile of the protrusions on the film surface is imaged three-dimensionally (stereoscopically).

When the profile is cut in a plane perpendicular to the thickness direction of the film, the plane where the total cross-sectional area of the profile of each protrusion is 70% of the area of the measurement area of the film is defined as the reference level (0 level). Let y be the number of protrusions that are cut when the plane is parallel to the plane of the reference level and spaced apart by a distance 111x in the height direction of the protrusions.

By sequentially increasing or decreasing X and reading the number of V at that time and plotting it on a graph, a protrusion distribution curve can be drawn. The value of y when this distance X is 1 μm is expressed as the "number of protrusions."

(3) The surface color of the color tone film was measured using a Color Machine CM-20 model (manufactured by Color Machine Co., Ltd.), and the L value was 9.

Judgment was made using a value and b value. The color tone of a film judged to have excellent whiteness is one having the following values.

88≦L value 12≦a hani≦1 15≦bl≦2 (4) Light shielding property 5EP-HUP (Boick integrating sphere type) manufactured by Nippon Seimitsu Kogaku Co., Ltd.
The measurement was made using the total transmittance (Tt) obtained.

The total transmittance (Tt) is preferably 10% or less, especially 5%
The following are preferred.

(5) Synthesis of printable and easily printable thin film layer material> Dimethyl terephthalate 159 parts by weight (0.82 mol), dimethyl terephthalate 291! ffi part (0,
15 mol), 9 parts by weight of 5-sodium isophthalate (
0,03 mol), 135 parts by weight (1,50 mol) of 1,4-butanediol, and 202 parts by weight (ω) of 2,2-bis[4-(2hydroxyethoxy)phenyl]propane (0,50 mol).
mole) and 0.34 Iffi part of tetrabutoxytitanium (
0,0005 mol) was charged into a reaction vessel and heated from 150°C to 1
The transesterification reaction was carried out at 70°C. Then 170℃
The pressure was gradually reduced while the temperature was raised from 250° C. to 250° C., and the polycondensation reaction was further carried out under high vacuum. Phenol/tetrachloroethane (6/4) of the obtained copolymerized polyester
Reduced viscosity ff(ηSt)/C) measured using a mixed solution
was 0.70 dl/g.

20 tons of this copolyester! Part ffi was dissolved in 80 parts by weight of dioxane, and 180 parts by weight of water was added dropwise to the resulting solution under stirring at a rotational speed of 10,000 rpm to obtain a bluish milky white dispersion. This dispersion was then added to 20a
Distillation was performed under reduced pressure of wgHg to remove dioxane. In this way, a polyester aqueous dispersion having a solid content of 11,110 wt% was obtained.

Furthermore, 2 parts by weight of a nonionic surfactant: polyoxyethylene nonylphenyl ether (HL B-12,8) was added to 180 parts by weight of the aqueous polyester dispersion, and 618 parts by weight of water was further added to prepare a coating liquid. .

Ku gravure n9 ink! Made by I > Commercially available gravure ink for cellophane printing whose main binders are Nido O cellulose and rosin oil: CLS-
2 parts by weight of a stock solution of 709 White (manufactured by Dainippon Ink@) was diluted with 1 part by weight of a mixed solvent of toluene/ethyl acetate/methyl ethyl ketone-1/1/1 to prepare a paint for evaluation.

Evaluation of printability> After coating a gravure ink having the above composition on a polyester film on which an easily printable thin film was formed using the above easily printable thin WA layer forming coating solution, Scotch tape No.
no (manufactured by Three M Company) width 19.4M.

Glue the length 8c11 so that there are no air bubbles, and
fJ ISC2701 (1975) 1iK (
7) Peel one character of this sample between the laminated parts 51 of the label with a manual load of 10 mm using a Tensilon UM- manufactured by Toyo Baldwin Co., Ltd. at a head speed of 300 am+/min, and check the peel strength at this time. Calculate and divide this by the tape width to get 9/am
I asked for it as. In addition, in the T-shaped peeling, the laminate was placed with the curved side facing down, and the distance between the pull-off chips was 5 eM.

Examples 1 to 3 and Comparative Examples 1 to 5 Polyethylene terephthalate pellets (PET) with an intrinsic viscosity of 0.65 and additives were mixed in the proportions shown in the table, and then melted and mixed in a twin-screw extruder. death,
It was extruded onto a cooling drum to obtain an unstretched sheet. followed by 9
Longitudinal stretching ratio: 3.3 times at 0°C.

After stretching at a transverse stretching ratio of 3.5 times, heat treatment was performed at 210° C. for 4 seconds to obtain a stretched film with a thickness of 75 μm.

The quality of the obtained film is shown in Table-1. Example 1~
Sample No. 3 had good white skin, anti-glossy properties, and light shielding properties. On the other hand, all of Comparative Examples 1 to 5, which did not satisfy the requirements of the present invention, had some kind of drawback.

Examples 4 to 6 In Examples 1 to 3, after stretching the unstretched sheets at 90°C to a longitudinal stretching ratio of 3.3 times, the printability 111 was exactly recorded.
The same procedure as in Examples 1 to 3 was carried out, except that the Mm material coating solution was applied to one side of the uniaxially stretched film by the kiss coating method, and then further stretched at a transverse stretching ratio of 3.5 mm.
A film on which an easily printable thin film layer was formed was obtained.

The surface roughness, number of protrusions (1), and transmittance of this film showed the same values as Examples 1 to 3.

The printability of the obtained film was evaluated by the method described in (5) above. Peel strength is shown below.

Claims (1)

[Scope of Claims] 1. 6-19% by weight of titanium dioxide with an average particle size of 0.5 μm or less, 1-10% by weight of barium sulfate with an average particle size of 1-5 μm, and a fluorescent material having a fluorescence peak at a wavelength of 400-500 nm. A polyester film for biaxially oriented magnetic recording cards, which is made of polyester containing an optical brightener and has a non-glare luster. 2. The polyester film according to claim 1, wherein the content of the fluorescent whitening agent is 10 to 1000 ppm. 3. The polyester film according to claim 1, wherein the polyester film has a shrinkage rate of 1.5% or less when heat treated at 150° C. for 30 minutes. 4. The surface roughness (Ra) of the polyester film is 0.1
The polyester film according to claim 1, which has a thickness of 0.5 μm. 5. The polyester film according to any one of claims 1 to 4, wherein an easily printable thin film layer is provided on at least one side of the polyester film. 6. The polyester film according to claim 5, wherein the easily printable thin film layer is made of water-dispersible polyester.