JP3306631B2 - Magnetic recording sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording sheet,
More specifically, the present invention relates to improvement of printability of visible information recording performed on a magnetic recording layer.

[0002]

2. Description of the Related Art Magnetic recording sheets coated with magnetic powder are:
For example, JP-B-47-28043 and JP-B-47-28045.
Nos. 47-31445, 48-11162, 48-21331, 48-33683, and 49-
No. 46992, U.S. Pat.
Nos. 699408, 2855156, 324062
No. 1, No. 3,526,598 and No. 3,728,262, basically containing a magnetic fine powder and a binder as main components, together with a dispersant, a lubricant, an antistatic agent, and a water retention agent. A magnetic recording layer is provided by coating, orientation, and drying on a support such as paper. Such magnetic recording sheets are often used for cashless cards used in banks, telephones, etc., transportation tickets, coupons, commuter passes, expressway pass tickets, etc., and their applications are expanding more and more. . This is probably because the information storage capacity of the magnetic recording layer, the readability of the written information, and the accuracy and the like can be processed by the vending machine, thereby saving labor.

[0003]

More recently, in bank certificates, etc., there is a case where one or two colors are printed on the surface of the magnetic recording layer and recorded as visible information. However, since the magnetic layer of the magnetic recording sheet has the color tone of the magnetic powder applied to a support such as paper as it is and has a brownish or dark black color tone, sufficient visual information recording cannot be obtained even when printing is performed.

Japanese Patent Application Laid-Open Nos. 51-4092 and 51-1
No. 40004, No. 56-159840, No. 56-16
Nos. 9225, 58-97133, 58-2157
No. 26, No. 59-68822, No. 62-129939
Japanese Patent Application Laid-Open Publication No. H11-163873 proposes to provide a protective layer on a magnetic recording layer in order to obtain running stability, weather resistance, and friction resistance of the magnetic recording sheet, but most of the protective layer is a transparent layer. Not suitable for recording information.

In order to enable printing of visible information, for example, Japanese Patent Application Laid-Open No. 61-276101 discloses gravure printing of white gravure ink. JP-A-62-99
No. 919 and JP-A-62-249991 are provided with a white pigment layer mainly composed of a white pigment such as clay and calcium carbonate and a binder such as styrene-butadiene copolymer and vinyl acetate resin. A coating layer mainly composed of a binder such as aluminum and styrene-butadiene copolymer, vinyl acetate resin, etc., which is processed into a paste as disclosed in JP-A-63-256485 is provided. JP-A-63-268121 and JP-A-63-268126 disclose that a paste-processed aluminum is provided in a first layer and a white pigment such as kaolin or calcium carbonate is provided in a second layer. When the inventors conducted confirmation experiments and evaluated the results, they found that running stability was lacking due to insufficient smoothness, and that the visible information recording was unclear due to the concealing property of the magnetic recording layer, that is, insufficient whiteness. Increasing the coating amount to compensate for the whiteness causes a decrease in magnetic output and resolution, and furthermore, a higher saturation current.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a magnetic recording sheet in which the printability of the surface of a magnetic recording layer is improved and the recording of visible information is sharpened without impairing magnetic characteristics such as magnetic output and resolution. is there.

[0007]

Means for Solving the Problems As a result of further extensive experiments and research, the present inventors have found that the whiteness is excellent without deteriorating the magnetic properties, the visible information recording by printing is clear, and the added value is high. High magnetic recording sheet was developed. That is,
An object of the present invention is to provide a white pigment layer mainly composed of a styrene copolymer emulsion and an acrylate ester having an ester group of an alkyl group having 3 to 12 carbon atoms as a binder thereof on a magnetic recording layer. Is achieved,
Further, the present invention has been made based on the finding that a remarkable effect can be obtained by forming a layer after using an aqueous aluminum paste or zinc stearate in combination.

The titanium dioxide used in the present invention may be a general one. For example, titanium dioxide is produced by digesting the raw material ilmenite with sulfuric acid or chlorine to extract and separate the titanium component, hydrolyze, calcine and pulverize. And the volume average particle diameter is preferably 1 μm or less.

The ester group used in the present invention has 3 to 3 carbon atoms.
An acrylic acid ester and a styrene copolymer emulsion, which is an alkyl of 12, are, for example, styrene-acrylic acid n
-Propyl copolymer, styrene-isobutyl acrylate copolymer, styrene-tetrahydrofurfuryl acrylate copolymer, styrene-2-ethylhexyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-acrylic acid Ethyldecyl copolymer, styrene-
Examples thereof include a dodecyl acrylate copolymer emulsion, and particularly preferred is a styrene-2-ethylhexyl acrylate copolymer emulsion. If the number of carbon atoms is less than 3 or more than 12, sufficient surface strength required for whiteness and printing durability during printing cannot be obtained. The number of parts of the styrene-acrylate copolymer emulsion which is an alkyl having 3 to 12 carbon atoms is 5 to 100 parts by weight based on 100 parts by weight of titanium dioxide. Preferably 15 to 50
Parts by weight, particularly preferably 20 to 40 parts by weight.

The aqueous aluminum paste and zinc stearate obtained by pulverizing the aluminum foil pieces used in the present invention with a ball mill are used alone or in combination.
The amount is 1 to 20 parts by weight, particularly preferably 5 to 10 parts by weight, per 100 parts by weight.

Further, in the present invention, a water-soluble polymer such as starch, methylcellulose, hydroxyethylcellulose, carboxyethylcellulose, sodium alginate, polyvinyl alcohol, polyvinylpyrrolidone and polyethylene oxide is used as a surface quality improving agent (leveling agent) at the time of coating. I do. In the present invention, if desired, a dispersant such as sodium pyrophosphate and sodium polyacrylate; a binder such as a styrene-butadiene copolymer system and a vinyl acetate emulsion; and an antifoaming agent may be mixed to form a coating solution for a white pigment layer. Then, the composition is applied by an application method such as an air knife, a curtain, a roll, a blade, or the like so as to be 1 to 10 g / m ² (dry weight solid content). Preferably 2 to 8 g / m
² , particularly preferably 3 to 5 g / m ² . 1g
/ M ² , clear visible information recording cannot be obtained and 10 g
If it exceeds / m ² , the magnetic properties are impaired.

The magnetic powder of the magnetic recording sheet used in the present invention includes, for example, γ-iron oxide, γ-iron oxide modified with cobalt, chromium oxide, barium ferrite and the like.
These magnetic powders are prepared by applying a water-soluble polymer such as starch, casein, polyvinyl alcohol or the like; a hydrophobic polymer such as a styrene-butadiene copolymer system or a vinyl acetate emulsion as a binder by a coating method such as an air knife or curtain.
0-30 g / m ² (dry weight solids) is applied. The magnetic recording sheet of the present invention is used by providing a white pigment layer or a water-soluble polymer layer or a heat-sensitive recording layer containing an electron-donating dye and an electron-accepting acidic substance as main components on the other surface of the magnetic recording layer. can do.

[0013]

The preferred embodiments and excellent effects of the present invention will be specifically described below with reference to the most typical examples. In addition, the following parts are all parts by weight, and all% represent weight%.

Example 1 After adding 5 parts of a 40% aqueous solution of sodium polyacrylate (Aron T-40, manufactured by Toagosei Chemical Co., Ltd.) to 106 parts of water, barium ferrite (MC, manufactured by Toda Kogyo KK)
-127) 100 parts were mixed and finely pulverized with a ball mill so as to have a volume average particle diameter of 5 μm, and a 50% styrene-butadiene copolymer emulsion (DL-DL, manufactured by Asahi Kasei Corporation)
620) and 40 parts of a 2% carboxymethylcellulose aqueous solution (Cellogen WS-C, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were sequentially mixed to prepare a coating solution for a magnetic recording layer. This coating liquid is applied on the surface of a ^high- quality paper having a basis weight of 160 g / m ^{2 in an} amount of 30 g / m ^2.
m ² (dry weight solids) was applied by an air knife coater, and after magnetic field orientation, dried and super calendered to provide a magnetic recording layer. After adding 10 parts of a 10% aqueous sodium hexametaphosphate solution to 250 parts of water,
Titanium dioxide (Ishihara Sangyo Co., Ltd., Taipaque CR-9)
3) 100 parts were almost completely dispersed, and a 20% styrene-2-ethylhexyl acrylate copolymer emulsion 12
Five parts were mixed to obtain a coating solution for a white pigment layer. This coating solution was laminated and applied on the magnetic recording layer with an air knife coater so as to have a coating amount of 5 g / m ² (dry weight solid content), followed by super calendering to prepare a magnetic recording sheet.

Example 2 After adding 15 parts of a 10% aqueous solution of sodium hexametaphosphate to 260 parts of water, titanium dioxide (Taipec CR-
93) 100 parts and 17 parts of a 60% aqueous aluminum paste (AW-7000R, manufactured by Asahi Kasei Corporation) are sequentially and almost completely dispersed, and 150 parts of a 20% styrene-2-ethylhexyl acrylate copolymer emulsion are mixed. A magnetic recording sheet was prepared in the same manner as in Example 1, except that the coating liquid for a white pigment layer was used.

Example 3 After adding 15 parts of a 10% aqueous sodium hexametaphosphate solution to 240 parts of water, titanium dioxide (Taipec CR-
93) 100 parts and 40 parts of a 25% zinc stearate dispersion (volume average particle size 0.8 μm) were sequentially and almost completely dispersed, and mixed with 150 parts of a 20% styrene-2-ethylhexyl acrylate copolymer emulsion 150 parts. A magnetic recording sheet was prepared in the same manner as in Example 1, except that the coating liquid for a white pigment layer was used.

Example 4 After adding 15 parts of a 10% aqueous sodium hexametaphosphate solution to 250 parts of water, titanium dioxide (Taipec CR-
93) 100 parts, 60% aqueous aluminum paste (A
W-7000R) 10 parts and 20 parts of a 25% zinc stearate dispersion were sequentially and almost completely dispersed to give a 20% styrene-2-ethylhexyl acrylate copolymer emulsion 15
A magnetic recording sheet was prepared in the same manner as in Example 1 except that 0 parts were mixed to obtain a coating liquid for a white pigment layer.

Example 5 125 parts of the 20% styrene-2-ethylhexyl acrylate copolymer emulsion of Example 1 was added to 20% styrene-
A magnetic recording sheet was prepared in the same manner except that the same amount was replaced with an n-propyl acrylate copolymer emulsion to obtain a coating solution for a white pigment layer.

Example 6 125 parts of the 20% styrene-2-ethylhexyl acrylate copolymer emulsion of Example 1 was added to 20% styrene-
A magnetic recording sheet was prepared in the same manner except that the same amount was replaced with a 2-ethyldecyl acrylate copolymer emulsion to obtain a coating liquid for a white pigment.

Comparative Example 1 250 parts of water and 20% styrene-acrylic acid 2 of Example 1
-125 parts of an ethylhexyl copolymer emulsion in water 3
A magnetic recording sheet was prepared in the same manner except that 25 parts and 50 parts of a 50% styrene-butadiene copolymer emulsion (DL-620) were used instead of a coating solution for a white pigment layer.

Comparative Example 2 125 parts of the 20% styrene-2-ethylhexyl acrylate copolymer emulsion of Example 1
A magnetic recording sheet was prepared in the same manner except that the same amount was replaced with an ethyl acrylate copolymer emulsion to obtain a coating solution for a white pigment layer.

Comparative Example 3 125 parts of the 20% styrene / 2-ethylhexyl acrylate copolymer emulsion of Example 1
A magnetic recording sheet was prepared in the same manner except that the same amount was replaced with an n-tetradecyl acrylate copolymer emulsion to prepare a coating solution for a white pigment layer.

Comparative Example 4 Titanium dioxide (Typek CR-93) 10 of Example 1
0 parts are light calcium carbonate (PC, manufactured by Shiraishi Industry Co., Ltd.)
A magnetic recording sheet was prepared in the same manner except that the same amount was used as a coating liquid for a white pigment layer.

Comparative Example 5 Titanium dioxide of Example 1 (Typek CR-93) 10
0 parts was replaced with the same amount of light calcium carbonate (PC) to obtain a coating solution for a white pigment layer, and the coating amount of 5 g / m ² was changed to 10 g / m ^2.
A magnetic recording sheet was prepared in the same manner except that the number was ² .

Test Methods The magnetic recording sheets prepared in Examples 1 to 6 and Comparative Examples 1 to 5 were measured by the following test methods, and the results are shown in Tables 1 and 2. Magnetic output decrease rate (%) An average output value read by a magnetic writer was determined by the following equation. The smaller the value is, the smaller the reduction rate is and the more excellent it is. A: Sheet output value of only magnetic recording layer of Example 1 (V) B: Sheet output value of white recording layer provided on magnetic recording layer (V) Output reduction rate (%) = (AB) / A × 100

Resolution (%) Two types of magnetic writing densities (420FRPI, 210F
The output (V) was measured with RPI change set, and the resolution was determined by the following equation. The higher the numerical value, the better and better the resolution.
(Where FRPI is the flux reversal density) Resolution (%) = V (420FRPI) / V (210F
RPI) × 100

Saturation current (mA) Writing was performed while varying the magnetic writing current, the output was measured until the output reached a saturation region, and the current value at 90% of the saturation output was defined as the saturation current. The smaller the value, the better.

Whiteness (%) The whiteness was measured using a Hunter whiteness meter (manufactured by Toyo Seiki Co., Ltd.). The higher the value, the higher the whiteness and the better.

Surface strength Black ink (SMX-NO1 manufactured by Toyo Ink Mfg. Co., Ltd.)
Using 5), the surface strength was visually observed with an IGT tester (manufactured by Kumagai Riki Co., Ltd.), and evaluated by ○, Δ, and ×. ○ mark: strong △ mark: slightly peeled × mark: almost peeled

Clarity of Visible Information Recording A PS plate was prepared and the ink was Newprous G (DI
C) (ink). It is printed with an offset printing machine (Miyakoshi Seisakusho's “Miyastar 18 type”), and the printing (recording) part is visually observed and observed with a loupe (× 30 magnifier).
The inking property and sharpness of the black ink were evaluated. ○ Mark: high printing ink density, excellent in-coating property, printed area is clear △ Mark: printed area is slightly unclear × mark: printed area is unclear

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

As is apparent from the present invention, in a magnetic recording sheet having a white pigment layer provided on a magnetic recording layer, titanium dioxide and an alkyl group having an ester group having 3 to 12 carbon atoms are used as a binder. By providing a white pigment layer containing an acrylic ester and styrene copolymer emulsion, it is possible to achieve clear visible information recording by printing without impairing magnetic properties, and to use an aqueous aluminum paste and zinc stearate in combination. As a result, a remarkable effect was exhibited, and a practically excellent magnetic recording sheet could be provided.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-1-176325 (JP, A) JP-A-3-128246 (JP, A) JP-A-54-158905 (JP, A) JP-A-57- 133523 (JP, A) JP-A-4-201398 (JP, A) JP-A-1-171898 (JP, A) JP-A-63-256485 (JP, A) JP-A-5-8571 (JP, A) JP-A-3-297699 (JP, A)

Claims (3)

(57) [Claims] 1. A magnetic recording sheet comprising a paper support having a magnetic recording layer on one side and then a white pigment layer, wherein the pigment layer comprises titanium dioxide and an ester group as a binder having 3 to 12 carbon atoms. A magnetic recording sheet comprising, as a main component, a copolymer of an acrylate ester of alkyl and styrene. 2. The magnetic recording sheet according to claim 1, wherein the pigment layer contains an aqueous aluminum paste. 3. The magnetic recording sheet according to claim 1, wherein the pigment layer contains zinc stearate.