JPS59188492A - Color developer sheet for pressure-sensitive copying paper - Google Patents

Abstract

PURPOSE:To markedly enhance color developing performance and improve surface strength and printability such as ink setting property, by incorporating starch particles in addition to ordinarily used inorganic pigment into a color developer coating material comprising an organic color developer. CONSTITUTION:An inorganic pigment and starch particles are used in combination with each other in a color developer layer comprising an organic color developer. The organic color developer is not specially restricted, and the starch particles are those produced from wheat, rice or the like and having a particle diameter of 2-20mu. On the other hand, the inorganic pigment is a natural or synthetic pigment, such as talc, kaolin or zinc hydroxide, and there is no restriction on the blending ratio of the pigment and the starch particles. As for a binder, any of those generally used in an aqueous coating material can be used. The surfaces of the starch particles in the coating material are partially converted into paste by heat in a drying step, thereby strengthening the adhesion of the inorganic pigment to the surface of a paper, and further, contraction of the particles themselves induces multiple deep cracks in the coated layer to enhance surface strength, so that a color developer sheet excellent in color developing property and ink-absorbing property can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a color developer sheet for pressure-sensitive copying paper that has improved printability and color development performance.

In general, pressure-sensitive copying paper contains an upper paper coated with fine capsules containing an electron-donating colorless or light-colored leuco dye dissolved in an organic solvent (capsule oil) K, and an electron-accepting color developer. It consists of a bottom paper with a developing layer on its surface, and these two types of coated surfaces are stacked so that they face each other,
By applying pressure with a ballpoint pen or typewriter, etc., the capsule in the pressurized part is destroyed, and the capsule oil containing leuco dye is transferred to the color developing layer and a color reaction occurs, resulting in a printed record. It is.

The color developer sheet as used in the present invention is a sheet provided with a color developer layer as described above, and includes a bottom sheet, a color developer layer on the front side, and an inner sheet having a capsule coating layer on the back side.

In recent years, demand for pressure-sensitive copying paper has shown remarkable growth due to the rationalization of office work, the development of the information industry, and the spread of computers. At the same time, its uses have diversified, and many performance requirements have been placed on its quality. has been done. In particular, the color developing sheet, which serves as the color-developing surface, is required not only to provide clear records, but also to have good ink setting properties so that it can withstand high-speed printing in general ruled line character printing and desensitized printing. There is. In order for the color developer sheet to withstand high-speed printing, K requires that the color developer layer absorb and set general printing ink or desensitized ink in a short time.

That is, by improving the color development sheet (K) with good ink setting properties, it is possible to prevent stickiness on the printing surface or transfer of ink to other paper surfaces, and high-speed printing becomes possible. In particular, when printing with desensitized ink, the amount of ink is larger than when printing regular lined characters, so in order to speed up ink setting, it is necessary to increase the amount of ink absorption in the developing layer to speed up ink setting. becomes an important issue.

Currently, there are two types of color developer sheets for pressure-sensitive copying paper on the market, the first of which uses activated clay as a color developer, which has been in practical use for a relatively long time. This activated clay is made by treating acid clay, which is a montmorillonite clay mineral, with acid to elute the alumina and other base components it contains, thereby increasing its adsorption capacity. The color developing sheet using this activated clay as a color developer has excellent adsorption ability, so it not only develops color quickly but also prints ink easily.
The ink set is good when printing with desensitized ink, etc. However, with this type of color developing sheet, the colored characters tend to discolor or fade due to the influence of light or the passage of time.
In addition, there is a drawback that the color fades temporarily due to moisture,
The fluidity of the color developer paint is required.

The second system uses synthetic organic compounds such as 7-enol resins and metal salts of salicylic acid derivatives as color developers. These organic color developers are characterized in that they dissolve in capsule oil and react to develop color, whereas activated clay-based color developers adsorb leuco dyes and develop color. Sufficient color development performance can be obtained with a small coating amount, and the light and water resistance of the colored characters are also excellent. In addition, when using the above organic color developer, it is possible to apply highly concentrated paints with good fluidity, such as kaolin.
It also has advantages such as excellent productivity of the color developer sheet.

However, the color developer sheet using this organic color developer has inferior absorption performance of the color developer layer compared to that of activated clay, so problems such as ink set-off occur, especially in desensitized printing where the printing area is large. There are many things to do. As a countermeasure, attempts have been made to use activated clay in conjunction with an organic color developer, but this increases the cost of the paint and impairs its suitability for high-concentration coating due to poor fluidity of the paint. It has its drawbacks and does not always give satisfactory results.

In particular, a color developer sheet made of a combination of a phenolic resin developer and activated clay is susceptible to yellowing when exposed to light, which poses a practical problem.

Additionally, in JP-A-55-28857, a method has been proposed in which calcium carbonate with a fine particle size is used as a filler, but since the fine filler has a large specific surface area, a large amount of binder is required, making it impractical. In order to obtain a color developer sheet that maintains a certain surface strength, it is necessary to incorporate a large amount of binder, and as a result, the absorption performance and color development performance were both as expected. - A method has also been proposed in which a formaldehyde resin pigment is added to improve the color developing ability and whiteness of the color developing layer. This pigment is made up of fine spherical particles of 0.1 to 0.15 microns that combine in a discrete manner to form aggregates of several microns to several tens of microns, and the pigment itself has a large amount of voids inside. It has high oil absorption performance. However, when using pigments in color developer paints, because these pigments are porous and their surfaces are hydrophobic, ordinary water-based binders do not have sufficient adhesion, resulting in color discoloration. The sheet does not have sufficient surface strength. In order to obtain surface strength that can withstand commercial printing such as ruled line printing and desensitization printing, it is necessary to add a fairly large amount of binder to K. As a result, the binder fills the voids inside the pigment, reducing its absorption performance. As a result, the original performance of the pigment is lost, and a color developing sheet of excellent quality is no longer obtained.

The inventors of the present invention have conducted intensive research to improve printing suitability such as ink absorption while taking advantage of the color forming properties and other excellent properties of organic color developers. By blending starch particles in addition to inorganic pigments commonly used in paints, L and K can significantly improve color development performance and produce a color developing sheet with excellent printability such as surface strength and ink setting properties. I found out. That is, the gist of the present invention is a color developer sheet for pressure-sensitive copying paper, characterized in that starch particles and inorganic pigments are used in combination in the developer layer containing an organic color developer, filler, and binder. be.

Examples of organic color developers used in the present invention include succinic acid, tannic acid, gallic acid, phenol compounds, phenol compound-formaldehyde polymers and metal modified products thereof, phenol compound-acetylene polymers, maleic acid-rosin resins, and hydrated decomposed styrene-maleic anhydride polymer,
Examples include metal salts of aromatic carboxylic acids and hiso, and metal salts of 2,2' bisulfonol sulfone compounds, but are not particularly limited.

When the surface of the color developing sheet of the present invention obtained by the above combination was observed using an electron microscope photograph, it was found that there was no 0 in the color developing layer.
．． It is observed that there are many fairly deep cracks with a width of 5 to several microns. Due to the capillary action of these many deep cracks, when copying and recording, the capsule oil containing leuco dye is efficiently transferred from the upper paper to the color developing layer, showing excellent coloring performance and improving ink absorption during printing. It is thought that this will improve. More detailed observation of the electron micrograph reveals that the surface of the starch particles has become gelatinized, and minute inorganic pigments are adhered and fixed to the gelatinized surface. This indicates that the starch particles function both as a filler and as an adhesive. Considering the mechanism by which such a surface structure is formed, the surface of starch particles swollen by water in the paint becomes partially gelatinized by the heat applied during the drying process during coating, and the inorganic pigment adheres to the paper surface. It is thought that the many deep cracks mentioned above occurred in the coating layer because the starch particles themselves contracted when the water evaporated. As a result, a color developing sheet with high surface strength and excellent color development and ink absorption properties can be obtained.

In conventional techniques, surface strength and ink absorbency have an incompatible relationship, and when the amount of binder is increased in order to improve surface strength, ink absorbency deteriorates. Particularly in high-concentration coating using a roll coater, a blade coater, etc., the coated surface becomes dense, so it is unavoidable that the ink absorbency deteriorates significantly. The present invention solves the above problems by using an inorganic pigment and starch particles in combination. In addition, conventionally, in order to improve the absorption of printing ink, it has been proposed to mix and use pigments with high oil absorption as described above, but the present invention uses starch particles that originally have low oil absorption. It is characterized by its excellent printability and color development performance.

The starch particles used in the present invention are those manufactured from raw materials such as wheat, rice, corn, potatoes, tapioca, and sweet potatoes, or oxidized starch and acetyl starch obtained by oxidizing these with sodium hypochlorite etc. These are fine powders of starch derivatives such as esterified starch represented by , etherified starch represented by methyl starch, dialdehyde starch, and aminated starch.

The particle size of the starch particles is not particularly limited, but is preferably in the range of 2 to 20 microns. If the particle size is too small, the absorption performance of the color developing layer tends to decrease, and if it is too large, the smoothness of the coated surface will be lost, resulting in poor commercial value, such as the printed text and colored text becoming unclear. Therefore, it is necessary to select the particle size appropriately according to quality requirements. To this end, in addition to selecting starch varieties, the desired particle size can be obtained by classification.

This developer paint can be applied using various coating methods ranging from low to high concentrations, but changing the particle size of starch particles depending on the type of coating machine maintains the performance of the resulting developer sheet. It is important to do so. For example, in coating machines such as blade coaters that control the amount of paint and make the coated surface uniform by mechanically scraping off paint, there is a probability that many particles with large particle sizes will be easily scraped off, and the paint will be scraped off easily. The problem is that the composition of the paint changes over time as it accumulates inside the paint. Therefore, in such a coating method, if starch particles having an average particle size of 10 μm or less are used, a color developing sheet with little change in product quality during the coating process can be obtained.

As an example of the application of starch particles to pressure-sensitive copying paper,
Japanese Patent Publication No. 47-1178 and Japanese Patent Publication No. 10-48-33204 disclose that starch particles having a particle size of 1.5 to 2 times the size of the capsule are blended into a capsule paint containing a leuco dye. However, a method has been proposed in which the capsule is used as a so-called stilt material to protect it from external pressure. In addition, in the field of thermal paper,
Publication No. 9-1238 proposes a method of using waxes and starch particles in combination in a heat-sensitive paint for the purpose of preventing pressure color development due to scratches, etc. However, in either case, the ink absorption and color development of the color developer sheet are affected. This is clearly distinguished from the present invention, which is designed for the purpose of improving performance.

On the other hand, the inorganic pigment used in the present invention can be a natural or synthetic pigment such as talc, kaolin, calcium carbonate, aluminum oxide, aluminum hydroxide, zinc oxide, zinc hydroxide, or magnesium carbonate, or a combination of two or more kinds. It's okay.

The blending ratio of starch particles and inorganic pigment of the present invention is not particularly limited, but in paints for low concentration coating such as air knife coaters, the ratio (weight ratio) of starch particles to inorganic pigment is 1. By setting the ratio between 99 and 90 to 10, a color developing sheet with excellent performance can be obtained. On the other hand, in paints for high-concentration coating such as roll coaters, blade coaters, and roll bar coaters, the viscosity of the paint tends to increase as the blending ratio of starch particles increases, and the ratio of starch particles to inorganic pigments ( Weight ratio) is 60:4
A range of 0 to 10:90 is preferred.

Also, the total amount of starch particles and inorganic pigments is 5% relative to the color developer.
It is desirable that the amount be 20 times as large, and 30% by weight or more based on the total solid content of the color developer coating.

There are no particular restrictions on the binder for the color developer paint of the present invention, and any binder that is added to ordinary water-based coating paints can be used. For example, water-soluble binders include proteins (gelatin, albumin, casein, etc.), starches (cereal starch, pregelatinized starch, oxidized starch, etherified starch, esterified starch, etc.), and cellulose derivatives (carboxymethyl cellulose, hydroxyl starch, etc.). Water-soluble natural polymer compounds such as propyl cellulose, methyl cellulose (nato), water-soluble synthetic polymer compounds such as polyvinyl alcohol, acrylamide-modified polyvinyl alcohol, polyvinyl vinylidene, polyacrylic acid, polyacrylamide, maleic acid copolymers, etc. be. In addition, as a latex binder, styrene-butadiene latex, acrylonitrile-butadiene latex, acrylic ester latex, vinyl acetate latex, methyl methacrylate-butadiene latex,
There are latexes and carboxy-modified (eg acrylic acid) latexes thereof.

By using these binders alone or in combination of two or more, colors are developed to satisfy physical properties such as paint density, viscosity, water retention, and product properties such as color development, adhesive strength, and water resistance suitable for the coating method. Prepare the paint.

It is not an effective method to use a latex-based binder and a water-soluble binder in combination, taking into consideration the fluidity and water retention of the paint, its suitability for coating, and the strength and water resistance of the casing surface. When only a water-soluble binder is used, it is desirable to add a small amount of aldehydes such as formalin, glyoxal, and glutaraldehyde, or other water-resistant agents.

In addition, if necessary, add a pH adjuster, viscosity adjuster, etc. to prepare a color developing paint, and apply it on base paper at a solid content of 4 to 10
Apply to about f/cd and dry.

The color developing sheet obtained as described above has a uniform coating surface, and when it is layered with the upper paper to type color, the color development speed is fast.
Furthermore, the achieved density of the recorded image was high and clear. Furthermore, after pre-printing ruled line characters using offset printing on the developer sheet of the present invention, printing with desensitized ink was performed, and there were no problems such as blanket stains or plate jams, and since the ink set quickly, pre-printing ink could be used. Also, set-off of the desensitized ink did not occur, indicating excellent printability.

The present invention will be explained below with reference to Examples. In addition, in the examples, "1 part" indicates part by weight.

[Example 1] While stirring with a lab mixer, 100 parts of Kaolin 14- (Kaobrite, manufactured by Schiele, Inc., USA) was added to 100 parts of an aqueous solution of 0.5 sodium thihexametaphosphate, and 50
Prepare a kaolin slurry with a concentration of Next, the above slurry was mixed with wheat starch particles classified to an average particle size of 5μ so that the solid content was as shown in Table 1 below, a 50% dispersion of P-phenylphenol resin, and SBR latex (solid content 48%).
) and an aqueous solution of 10 g of steamed oxidized starch were added, stirred thoroughly, and then water was added to prepare a color developing paint with a solid content of 30 g.

Table 1 The above 10 types of paint were applied at 4of/lr so that the Mayer coating amount was 5 to 6f/m'K fk.
? It was applied onto base paper and dried to obtain a color developing sheet.

The color developer sheets obtained by cutting out the developer paints a-1 to a-10 are referred to as A-1 to A-10, respectively.

The following tests were carried out with these color-developing sheets.

■Color development: color development sheet on top paper (W40T manufactured by Jujo Paper Industries)
The color density after 10 seconds (color rise ) and the color density (achieved density) after 1 hour were examined. The degree of color development was calculated by measuring the whiteness (using an amber filter) of the color development sheet before and after color development using a Hunter whiteness meter, and using the following method.

Whiteness before calendar color development (%) = I.

Whiteness (%) after calendar color development 10 seconds or 1 hour = I
Degree of color development (%) = Dt ■Ink absorption; &N ink (
(manufactured by AndN Laboratories, USA) was applied uniformly, the ink was wiped off with a cloth after 2 minutes, and the degree of ink absorption was examined.

The absorbency of K&N ink was calculated by measuring the whiteness before applying the ink and after wiping it off, and using the following method.

Whiteness before ink application (%) = Whiteness after IO ink wiping (%) =! kK&N ink absorption (ch)
= Dk I OI k to6 Dk = X4 = 16 ■Surface strength: Using an R1 printing aptitude tester (Mei Seisakusho F11), apply Toyo Ink's tack value 10 offset printing ink to the coated surface of the color developer sheet. Print 3 times,
The state of powder falling off was sensory evaluated.

The test results of Example 1 are shown in Table 5), and A-2 to A-1 are the color developer sheets of the present invention in which kaolin and wheat starch particles are combined as fillers.
-1 and color developing sheet using wheat starch particles alone) A-1
Compared to 01C, it has excellent color development, high density, and 4N ink absorption, and has strong surface strength.

[Example 2] Light calcium carbonate (MP) was used instead of kaolin in Example 1.
5558. Color developing sheet B-
1 to B-9 were obtained.

As the test results of Example 2 are shown in Table 5, the color developer sheets B-2 to B-8 of the present invention are the color developer sheet B-1 using calcium carbonate alone and the color developer sheet B-1 using wheat starch alone. ) Compared to B-'a, color development rise, final density and &
High N ink absorption. In addition, the lack of surface strength of the calcium carbonate-only sheet was improved by the combination of wheat starch, demonstrating the superiority of the color-developing sheet of the present invention.

[Example 3] Aluminum hydroxide (Hisilite H-32, manufactured by Showa Light Metal) was used in place of the kaolin in Example 1, and wheat starch classified to an average particle size of 15 μm was used in place of the 5 μm wheat starch. Except for this, color developer sheets) C-1 to C-9 were obtained in the same manner as in Example 1.

The test results of Example 3 are as shown in Table 5.
C-2 to C-S show excellent performance similar to Examples 1 and 2.

[Example 4] Color developer paint d-
1 to d-3, e-1 to e-3, f-1 to f-3, g-1
~g-3, h-1~h-3 and i-1~1-3 were prepared.

Table 2 -1%J - Color developer sheet D-1~ obtained by applying the above color developer paint
D-3, E-1 to E-3, F-1 to F-3, H-1 to)
The test results of I-3 and I-1 to I-3 are as shown in Table 6. C,
Excellent results are shown for all qualities of coloring performance, K&N ink absorption and surface strength.

[Example 5] The P-phenylphenol resin of Example 1 was 2.2'-
Developing paints "-1 to j-4" were prepared in the same manner except that bisphenol sulfone zinc salt was used.

Table 3 21- 20- Color-developing sheets obtained by applying the above-mentioned color-developing paint) J-1 to J-J
The test results of -4 are shown in Table 6, and the effects of the present invention are clear even when 2,2'-bisphenolsulfone zinc salt is used as the organic 54 coloring agent.

[Example 6] In the same manner as in Example 1 except that the P-phenylphenol resin in fll [1 was replaced with 3.5 di-tert-butylsalicylic acid zinc salt, -1 to -4 was added to the developer paint. Prepared.

Table 4 =22- The test results of -1 to -4 on the color developer sheet obtained by applying the above color developer paint are consistent with those shown in Table 6, and 3,5 di-tertiary was used as an organic color developer. - When zinc butylsalicylate is used, the effect of the combination of inorganic pigment and starch particles is also noticeable.

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Claims (1)

[Claims] (1) A color developer sheet for pressure-sensitive copying paper, characterized in that a color developer layer containing an organic color developer contains a combination of an inorganic pigment and starch particles.