JPH0752533A - Pressure-sensitive copy paper for optical reading - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a pressure-sensitive copying paper for optical reading, which is suitable for optically reading colored images such as letters, numbers, and bar codes. [Structure] A color developer layer containing an electron-accepting color developer, a pigment and an adhesive is provided on a support, and a color-developed image resulting from a reaction between the color-developing agent and the electron-donating color-developing agent is read by an optical reading device. JIS K of the entire pigment can be read by using at least light calcium carbonate and kaolin together as the pigment.
The weighted average value of oil absorption by 5101 is 35 ml / 100
Pressure-sensitive copy paper for optical reading of g or more. Preferably,
Light calcium carbonate is aragonite type columnar calcium carbonate, 10 to 90% by weight of the total pigment, and kaolin is 10 to 50% by weight of the entire pigment. The developer is a specific salicylic acid-based developer.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to pressure sensitive copying paper.
Furthermore, the present invention relates to a pressure-sensitive copying paper for optical reading, which is suitable for optically reading a color image such as letters, numbers, and bar codes.

[0002]

2. Description of the Related Art A color-developed image is obtained by a contact reaction between an electron-donating, colorless or pale-colored dye precursor (hereinafter, referred to as a color former) and an electron-accepting solid acid (hereinafter, referred to as a developer). It has been known for a long time. Specific examples of utilizing this phenomenon include, for example, pressure-sensitive copying paper (eg, US Pat. Nos. 2,505,470 and 2,505,489).
And thermal recording paper (eg, Japanese Patent Publication No. 45-14039).

Generally, as a developer for pressure-sensitive copying paper, an inorganic developer such as activated clay, acid clay, attapulgite, zeolite, bentonite, silica, aluminum silicate, etc., a novolac type phenol resin or a salicylic acid derivative is used. Alternatively, a polyvalent metal salt of a salicylic acid derivative is used, and in particular, a polyvalent metal salt of a salicylic acid derivative has good color forming properties and is widely used in the market. In recent years, many salicylic acid resins or their polyvalent resins have been developed for the purpose of improving the conventional phenolic resin-based color developer, which has a slow color development speed, and the salicylic acid-based color developer, which has slightly poor water resistance. Metal salts have been proposed as developers.

As these developers, polyvalent metal salts of salicylic acid and a co-condensation resin such as α, α'-dialkoxy-p-xylene (Japanese Patent Laid-Open Nos. 62-176875 and 62-62875).
178387, 62-178388, 63-5
No. 3092, No. 63-159082, No. 63-160
877, etc.), a polyvalent metal salt of a resin obtained by reacting a salicylic acid derivative with a styrene derivative (Japanese Patent Laid-Open Publication No. 6-58242)
JP-A-3-186729, JP-A-1-133780), a polyvalent metal salt of a resin obtained by reacting a salicylic acid derivative with a benzyl derivative such as benzyl alcohol, benzyl ether and benzyl halide (JP-A-63-25).
No. 4124, No. 63-289017, No. 64-567.
No. 24, No. 64-77575, JP-A-4-89274.
Nos. Etc.), salicylic acid-modified terpene phenol resin polyvalent metal salts (Japanese Patent Laid-Open No. 63-147682), and other organic developers.

Generally, as a pressure-sensitive copying paper, an upper paper having a color developer layer containing microcapsules containing a color developer on a support and a lower paper having a developer layer containing a color developer on the support are used. , A separate type in which a developer layer and a color developer layer are provided on the front and back sides of the support in combination with an intermediate paper, or a developer and a color developer in one or more layers The self-type provided on the surface is used.

In recent years, there has been an increase in the use of optically mechanically reading pre-colored characters or marks on pressure-sensitive copying paper. Examples of pressure-sensitive copying papers which are used in this way are disclosed in JP-A-2-188291 and JP-A-2-23119.
No. 0, No. 4-173288, No. 4-212882,
No. 4-224991, No. 4-251785, No. 4-
It is disclosed in various publications such as No. 272889. Typical optical readers include readers for OCR, OMR, label barcodes and the like.

In order to read a colored image of pressure-sensitive copying paper with an optical reading device, it is necessary that the reading density of the colored image in the wavelength range of the light source of the device is sufficiently high. The wavelength of the light source is mainly on the high wavelength side of 600 nm or more, and the color former used in the conventional pressure-sensitive copying paper cannot provide sufficient reading density. Being developed. As an example, Japanese Patent Laid-Open No. 3-11
No. 4878, No. 3-71883, No. 2-251484
The compounds described in each of the publications such as the publication are listed.

However, even when such a color former is used, a sufficient reading density may not be obtained, and when a slip using pressure-sensitive copying paper is passed through a reading device, reading may not be performed. However, it caused troubles such as incorrect reading. It is also attempted to increase the reading density by increasing the coating amount of the color developer or the color developer on the support, but this may cause unnecessary color stain or thick line width of the color image. Therefore, the readability of the reading device is deteriorated, and the actual situation is that pressure-sensitive copying paper for optical reading with sufficient performance has not been obtained yet.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical reading pressure-sensitive copying paper which has a sufficient reading density for an optical reading device and has excellent readability.

[0010]

Means for Solving the Problems As a result of intensive studies for solving the above problems, the present inventors have found that a developer layer containing an electron-accepting developer, a pigment and an adhesive is provided on a support. Provided,
In a pressure-sensitive copying paper for optical reading in which a color-developed image is reacted with a colorless or light-colored electron-donating color-developing agent by an optical reading device, at least light calcium carbonate and kaolin are used in combination as a pigment. Whole JIS
・ Weighted average value of oil absorption by K5101 is 35ml / 1
It has been found that the above object can be solved by setting the amount to be not less than 00 g.

As the light calcium carbonate, columnar calcium carbonate of aragonite type is used in an amount of 10 to 10 with respect to the total weight of the pigment.
It is preferable to use 90% by weight.

As kaolin, based on the total weight of the pigment, 1
It is preferable to use 0 to 50% by weight in combination.

As the color developer, a salicylic acid derivative,
Preference is given to using one or more electron-accepting organic developers selected from salicylic acid resins or their polyvalent metal salts.

If the weighted average value of the oil absorption amount of the pigment according to JIS K5101 is less than 35 ml / 100 g, it is difficult to obtain the density of the color image. There is no particular upper limit to the weighted average value of the oil absorption of the pigment, but most of the pigments generally used for coating generally have an oil absorption of 80 ml / 100 g or less,
Further, as the weighted average value of the oil absorption increases, color stains are generated when the developer layer and the color developer layer are rubbed with each other, and the readability with an optical reader is apt to decrease.
It is preferably 0 ml / 100 g or less.

As the light calcium carbonate used in the present invention, particles such as horns, columns, needles, spindles, spheres, and rice grains, or three-dimensionally intertwined regularly or irregularly. There are agglomerated particles such as iga, urchin, etc. formed as a result, and as the crystal system, there are aragonite series, calcite series, vaterite series and the like, and any of them can be used.

As the aragonite-based columnar calcium carbonate used as a preferred pigment in the present invention, one having a single particle diameter of 1 to 3 μm in long side length and 0.1 to 0.3 μm in short side length is particularly preferable. The manufacturing method is not particularly limited, but the method disclosed in JP-B-55-51852 can be exemplified. The aragonite-based columnar calcium carbonate obtained by such a method has a relatively large oil absorption amount and can efficiently absorb the oil in which the color developing agent released from the microcapsules is dissolved, so that a small amount of color developing agent or developer is used. It is possible to obtain a high reading density even with the coating amount of.

The content of aragonite type columnar calcium carbonate is preferably 10 to 90% by weight in the total pigment, and 20 to 5% by weight.
0% by weight is particularly preferred. By the way, the content is 1 in the total pigment.
If it is less than 0% by weight, the oil transfer property is small and the color density is insufficient, while if it is used in excess of 90% by weight, the abrasion resistance and the surface strength are significantly lowered. With respect to this scuff resistance, it is most effective to use kaolin together as a part of the pigment, and the addition amount thereof is preferably 10 to 50% by weight based on the total weight of the pigment, and 20 to 4
0% by weight is particularly preferred. By the way, if it is less than 10% by weight, the abrasion resistance is not sufficiently improved, and if it exceeds 50% by weight, the color density and whiteness are lowered.

It is also possible to use light calcium carbonate and a white pigment other than kaolin in combination as long as the effect of the present invention is not impaired. Examples of pigments that can be used in combination include heavy calcium carbonate, calcium sulfate, calcined kaolin, talc, aluminum hydroxide, aluminum silicate, magnesium oxide, magnesium carbonate, magnesium sulfate, zinc oxide, activated clay, finely divided silicic acid, and oxides. White pigments such as titanium, calcium silicate, urea-formaldehyde resin, etc. may be mentioned.

The reading density by the optical reading device is PC shown in the following formula 1 in the light source wavelength range of the device.
It is commonly expressed as an S value.

[0020]

## EQU1 ## PCS value = (A−B) / A A: reflectance of uncolored portion of developer coated surface B: reflectance of colored portion Here, the PCS value is preferably 0.6 or more. Furthermore, it is particularly preferable that it is 0.7 or more.

Examples of the electron-accepting organic developer used in the developer layer of the present invention include novolac type phenol resin or its polyvalent metal salt, salicylic acid derivative or its polyvalent metal salt, salicylic acid resin or its polyvalent metal salt. Examples thereof include metal salts. The novolac type phenol resin is produced by polycondensing various phenol derivatives and a lower aldehyde represented by formaldehyde as raw materials in the presence of an acidic catalyst. At this time, examples of the phenolic raw material used include unsubstituted phenol, alkyl group-substituted phenol (eg, cresol, ethylphenol, butylphenol, octylphenol, nonylphenol, etc., mainly para-substituted), aralkyl group-substituted phenol (eg, , P
-Benzylphenol, p-cumylphenol, etc.), aryl group-substituted phenol (eg, p-phenylphenol), halogen-substituted phenol (eg, p-chlorophenol), and the like.

The salicylic acid derivative is a compound having at least one aromatic substituent, specifically, 3-phenylsalicylic acid, 5-phenylsalicylic acid, 3-benzylsalicylic acid, 5-benzylsalicylic acid, 3- (α-
Methylbenzyl) salicylic acid, 5- (α-methylbenzyl) salicylic acid, 3- (α, α-dimethylbenzyl) salicylic acid, 5- (α, α-dimethylbenzyl) salicylic acid, 3,5-diphenylsalicylic acid, 3,5- Di (α-
Methylbenzyl) salicylic acid, 3,5-dibenzylsalicylic acid, 3,5-di (α, α-dimethylbenzyl) salicylic acid, 3,5-di (4-methylbenzyl) salicylic acid and the like can be mentioned.

Further, polyvalent metal salt compounds composed of salicylic acids, rosins and polyvalent metal compounds disclosed in JP-A-2-563 can also be mentioned as preferable developers. Salicylic acids have a total carbon number of 8 or more,
In particular, a known salicylic acid compound having an alkyl group of 8 to 20 is used. As rosins, gum rosin,
Any of natural and modified rosins such as wood rosin, tall oil rosin, disproportionated rosin, hydrogenated rosin, polymerized rosin, maleated rosin, fumarized rosin, formaldehyde modified rosin and rosin phenol resin can be effectively used. The polyvalent metal salt compound is produced, for example, by the following method. Dissolving at least one of salicylic acids or rosins in a solvent such as ethers, ketones, and acetic acid esters,
40 to 1 by adding polyvalent metal compound and inorganic ammonium salt
It is obtained by heating at 00 ° C. for 1 to 6 hours, filtering and distilling the product to remove unreacted inorganic compound and solvent.

As the salicylic acid resin or its polyvalent metal salt, all of the above-mentioned compounds can be used, but as an example, the above salicylic acid derivative and styrene, o. m. p-
Examples of salicylic acid resins obtained by reacting styrene derivatives such as methylstyrene, α-methylstyrene, β-methylstyrene and the like at a molar ratio of 1: 0.5 to 10 with a Friedel-Crafts reaction in the presence of a strong acid catalyst are polyvalent metal salts. To be Examples of the polyvalent metal include Ca, Mg, Al, Zn, and Mn, but it is most preferable to use it as a zinc salt. These color developers may be used in combination of two or more kinds.

An adhesive agent is contained in the color developer layer coating liquid component, and any conventionally known adhesive agent can be used. For example, proteins such as casein and gelatin, cellulose derivatives such as carboxymethylcellulose and hydroxymethylcellulose, water-soluble natural polymer compounds such as saccharose such as oxidized starch and esterified starch, and further polyvinyl alcohol, polyacrylic acid, styrene-butadiene. Water-soluble synthetic polymer compounds and latexes such as latex, polyvinylpyrrolidone, acrylonitrile-butadiene-acrylic acid latex, and styrene-maleic anhydride copolymer can be used.

The ratio of the color developer and the pigment used in the color developer layer is preferably in the range of 5: 100 to 25: 100,
Developer coating amount is usually, 0.05 to 1.5 g / m ² preferably used in a range of 0.1~0.7g / m ^2.

These developers and pigments are coated on a support together with an adhesive. As the support, paper, synthetic paper, non-woven fabric, plastic film or the like is used.
In addition, an intermediate layer made of a pigment, an adhesive or the like may be formed on these supports, and a developer layer may be provided thereon.

The method of coating the developer layer and the intermediate layer is not particularly limited, and examples thereof include an air knife coater, a blade coater, a roll coater, a rod coater, a gravure coater, a curtain coater, and a size press coater. Can be manufactured by on-machine or off-machine coat by various coating methods. So-called wet on wet coating of two layers simultaneously is also possible. In addition, a defoaming agent, a water retention agent, a water resistance agent, a penetrant, a dispersion stabilizer, an antioxidant, a fluorescent dye, a lubricant, etc. may be added to each of the developer layer and the intermediate coating layer, if necessary. It can be added.

Further, as a color former suitable for the pressure-sensitive copying paper for optical reading of the present invention, Japanese Patent Publications No. 49-17489, No. 58-5940, No. 58-27825 and No. 63-5.
No. 1113, Japanese Patent Publication No. 4316, No. 4-5064
No. 4, No. 4-5065, No. 4-5066, No. 4-50
68, JP-A-51-90608 and JP-A-55-1154.
48, 62-85986, 62-243652.
No. 63-9572, 63-37158, 6
3-62777, 63-2102975, 63-
No. 120760, No. 63-130667, No. 63-1
54389, 63-159384, 63-18.
9281, 63-270672, 63-295.
672, 64-29371, 64-42276.
No. 1, JP-A 1-210378 and 1-236279.
No. 1, No. 1-131280, No. 2-138368, No. 2-251484, No. 3-71883, No. 3-11.
Although those described in each publication such as 4878 can be used, the invention is not limited thereto.

Suitable color formers for optical reading are:
Conventionally known general pressure-sensitive dyes (electron-donating color formers) can be used in combination. These color formers are
Microcapsules can be formed by a generally known method, and examples thereof include a coacervation method, a monomer polymerization method, an interfacial polymerization method, and an in situ polymerization method. Preferred examples include urea-formaldehyde resin microcapsules disclosed in U.S. Pat. No. 4,001,140, JP-A-53-84881, JP-A-54-499.
Examples thereof include a method for producing melamine-formaldehyde resin microcapsules disclosed in Japanese Patent Publication No. 84 etc.

As the non-volatile solvent used in the internal phase of the microcapsules, those used in general pressure-sensitive copying paper can be used, for example, alkylated diphenylmethane,
Diarylalkanes such as alkylated diphenylethane, alkylated diphenylpropane and alkylated diphenylbutane, alkylnaphthalene such as alkylnaphthalene and dialkylnaphthalene, alkylated biphenyl,
Examples thereof include aromatic ester type, aliphatic ester type, paraffin oils such as chlorinated paraffin, n-paraffin, and isoparaffin. These can be used alone or in combination of two or more.

The dissolved concentration of the color former in the internal phase of the microcapsules is generally 2 to 20% by weight, but 3-1.
2% by weight is preferable, and 6 to 10% by weight is particularly preferable.
When the dissolved concentration of the dye is low, many non-volatile solvents are transferred to the developer layer, which causes bleeding of the color image. Further, when the dissolved concentration of the dye is high, the transfer rate of the internal phase of the microcapsule to the developer layer is lowered, and a sufficient reading concentration cannot be obtained.

The microcapsules include a tilting agent such as wheat starch, corn starch and fine cellulose powder, a water-soluble adhesive, an adhesive such as latex, and, if necessary, a surfactant, a wax, a desensitizing agent and a decolorizing agent. A foaming agent, an ultraviolet absorber, a white pigment, etc. are added, and the whole or a part of the support is coated on a support such as acidic paper, synthetic paper, film and the like.

[0034]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto.
In addition, (part) in an Example shows a weight part.

(A) Synthesis of salicylic acid resin 3,5-di (4-methylbenzyl) salicylic acid 6.9 g
(0.02 mol), 50 ml of ethyl ether, and 12 g of sulfuric acid as a catalyst were charged into a glass reactor, and the temperature was maintained at 20 to 30 ° C. with stirring. Next, at the same temperature, 6.24 g (0.06 mol) of styrene was added dropwise over 8 hours for reaction. After dropping, the mixture was aged at the same temperature for 8 hours, warm water was added, the solvent was distilled off, and the deposited precipitate was filtered. This was vacuum dried to obtain 13.0 g of a white resin. The obtained resin has a weight average molecular weight of 1380 and a softening point of J
It was 62.0 ° C. when measured by a ring and ball softening point measuring device according to IS-K-2548.

(B) Synthesis of Salicylic Acid Resin Polyvalent Metal Salt 10 g of the resin obtained in (a) and 0.65 g of caustic soda were dissolved in 200 ml of hot water and dissolved. Then, while maintaining the temperature of the solution at 30 to 35 ° C., water 30 m
3 g of an aqueous solution prepared by dissolving 2.5 g of zinc sulfate heptahydrate in 1
Dropped in 0 minutes. A white precipitate was deposited, and the mixture was stirred at the same temperature for 2 hours, filtered, washed with water, and dried.
10.5 g (yield quantitative) of white powder was obtained. This was a zinc salt of a salicylic acid resin, and the result of analyzing the zinc content was 4.82%.

(C) Preparation of Developer Dispersion Liquid Using the metal salt of salicylic acid resin obtained in (b) as a developer, the following composition was dispersed in a sand gliding mill to prepare a suspension. Developer 10 parts by weight 10% polyvinyl alcohol aqueous solution (Kuraray # 117) 3 parts by weight Water 22.5 parts by weight Next, a developer dispersion X having the following composition was prepared using the suspension. Further, a developer dispersion Y was obtained in the same manner by using zinc 3,5-di- (α-methylbenzyl) salicylate instead of the salicylic acid resin metal salt as the developer. Furthermore, a developer dispersion Z was obtained using p-phenylphenol resin.

Using the various pigments shown in Table 1, a developer coating solution was prepared with the following composition, and the dry coating amount was 4.5 g / m ^2.
Was coated with a blade coater and dried to obtain optical reading pressure-sensitive copy papers of Examples 1 to 10 and Comparative Examples 1 to 3. [Developer coating liquid formulation] Developer dispersion X, Y or Z 35.5 parts by weight Sodium pyrophosphate 0.5 parts by weight Pigment 100 parts by weight 10% oxidized starch aqueous solution 150 parts by weight It should be noted that the developer coating liquid The pigment ratio in the formulation is shown in Table 2.

The optical reading pressure-sensitive copying papers produced in Examples 1 to 10 and Comparative Examples 1 to 3 were evaluated as follows. Using a pressure-sensitive copying paper for optical reading (lower paper) and commercially available Mitsubishi OCR upper paper and middle paper (manufactured by Mitsubishi Paper Mills), prepare a set of 5 sheets, and use a bar code printer YL-5545 (manufactured by Yamada Kogyo). A bar code was printed. After 24 hours, the minimum white background reflectance and the maximum black background reflectance of the bar code copied on the lower sheet were measured using a bar code verifier Laser Check II (manufactured by Olympus Symbol Co., Ltd.) to determine readability. . The larger the white background density, the less the color stain, and the lower the black background density, the higher the color density. Readability is:
Good, Δ: Slightly good, ×: Bad

[0040]

[Table 1] The average particle size of Tamapearl TP-123 used as aragonite-based columnar calcium carbonate has a long side length of 2.
The length is 0 μm and the short side length is 0.15 μm. In addition, the brilliant 15 is a cubic Callite SA with a side of 0.15 μm.
Is a bulky shape in which aragonite-based acicular columnar calcium carbonate is aggregated in a sea urchin shape and has an average particle diameter of about 3 μm.

[0041]

[Table 2]

In Examples 1 to 10, pigments composed of light calcium carbonate and kaolin were used in combination, and the weighted average value of the oil absorption amount of the entire pigment was 35 ml / g or more. The color density of the part was sufficient and the readability was good. On the other hand, in Comparative Examples 1 and 2, the weighted average value of the oil absorption amount was small, it was difficult to obtain the color density of the black background portion, and the readability was not sufficient. In addition, Comparative Example 3
Although kaolin was not used, a sufficient color density was obtained in the black background, but the color stain on the white background was severe and the readability was insufficient.

[0043]

As is apparent from the results shown in Table 2, all of the pressure-sensitive copying papers for optical reading of the present invention have good color developability, little color stain, and good optical readability.

Claims (4)

[Claims] 1. A color-developed image formed by providing a color developer layer containing an electron-accepting color developer, a pigment and an adhesive on a support, and reacting the color developer with a colorless or light-colored electron-donating color developer. In a pressure-sensitive copying paper for optical reading in which an optical reading device is used, at least light calcium carbonate and kaolin are used in combination as the pigment, and JIS K5101 of the entire pigment is used.
The pressure-sensitive copying paper for optical reading, wherein the weighted average value of the oil absorption amount is 35 ml / 100 g or more. 2. As light calcium carbonate, aragonite type columnar calcium carbonate is used in an amount of 10 to 10 with respect to the total weight of the pigment.
The pressure-sensitive copying paper for optical reading according to claim 1, which contains 90% by weight. 3. The pressure-sensitive copying paper for optical reading according to claim 1, wherein kaolin is contained as a pigment in an amount of 10 to 50% by weight based on the total weight of the pigment. 4. The electron-accepting developer is one or more organic developers selected from salicylic acid derivatives, salicylic acid resins, and polyvalent metal salts thereof. The pressure-sensitive copying paper for optical reading according to the item 2 or 3.