JPH0416380A - Pressure sensitive recording material - Google Patents

Abstract

PURPOSE:To enable a high density coloring image to be obtained by a method wherein a degradation preventive agent is contained in a microcapsule including solid wax of an under coat. CONSTITUTION:Degradation preventive agents to be used are various kinds of oxidation preventive agents, ultraviolet absorbing agents, and stabilizers, and are not especially limited. However, solubility into solid wax should be favorably considered. A mixing rate of the degradation preventive agent in the solid wax should favorably be within a range of the degradation preventive agent/the solid wax (ratio by weight)<=1. In order to mix the degradation preventive agent into the solid wax, the solid wax is liquified by heating to its melting point or higher, is joined by a specific quantity of the degradation preventive agent, which are dissolved by heating until insoluble contents disappear. Thereby, a high density coloring image can be obtained.

Description

[Detailed description of the invention] A5 Industrial application fields The present invention relates to pressure sensitive recording materials.

More specifically, the present invention relates to a pressure-sensitive recording material that provides a recorded image of high density and that is prevented from deteriorating.

B. Conventional technology A pressure-sensitive recording material is a recording material that utilizes the pressure rupture properties of microcapsules containing liquid image-forming active ingredients and the release properties of the encapsulated active ingredients when broken. Dye precursors and the like are involved in forming recorded images.

Therefore, a high-performance pressure-sensitive recording material is: 1) The microcapsules stably hold the encapsulated active ingredient, and the pressure rupture property is moderately sensitive; 2) The encapsulated active ingredient is released as much as possible when the microcapsules are ruptured. , ■It can be said that recorded images do not easily deteriorate.

The present invention particularly aims to improve the above-mentioned (1) and (2) at the same time.

In the past, carbon paper was used as a pressure-sensitive recording material that skillfully utilized a pressure-sensitive layer, but because the colored coloring material is exposed, it can stain and stain hands and other objects. It was easy.

In contrast, in recent years, for example, a combination of an electron-donating colorless dye (dye precursor) and an electron-accepting developer is used as a pair of image-forming active ingredients, and each is printed on a support sheet such as high-quality paper. Coated, carbonless paper with a colorless appearance (
Also known as carbonless paper) is predominantly used (for example, Japanese Patent Publication No. 37451/1983).

That is, one of the pair of image-forming active ingredients is made into a solution, sealed in microcapsules, and coated on a support sheet such as high-quality paper, and a set of upper paper and lower paper coated with the other. When pressure is applied, the microcapsules are destroyed and a solution of one of the image-forming active ingredients is released, which is transferred from the upper paper to the lower paper to cause a coloring reaction and form an image on the lower paper.

Colored dyes or pigments can also be used as image-forming active ingredients (for example, Japanese Patent Application Laid-Open No. 62-39844
Publication No.). In this case, a colored dye/pigment solution or dispersion is sealed in microcapsules and coated onto a support sheet such as high-quality paper to form a top paper. and,
When pressure is applied in combination with plain paper that does not require a color developer, the colored dyes and pigments that are active ingredients for image formation are transferred from the upper paper side to the lower paper, forming a colored image.

Here, in order to explain pressure-sensitive recording materials in more detail, we will talk about non-carphone paper, which is a typical example.Nor-carphone paper usually contains one of a pair of image-forming active ingredients (crystal violet sotolactone, benzoyl leucomethylene blue malachite green). lactone, rhodamine, anilinolactam, 3-diethylamino-6-methyl 7-anilinofluorane, often electron-donating colorless dyes, or electron-accepting color developers such as phenolrescine or zinc salts of salicylic acid derivatives. Alternatively, it may be one component of a redox coloring system such as a combination of a reduced dye and an oxidizing agent, or one component of a chelate forming coloring system consisting of a combination of a metal compound and an organic ligand. The upper paper is coated with a stilt material (spacer) such as starch particles dissolved in a solvent and encapsulated in microcapsules, and the other active ingredient, such as acid clay, activated clay, various phenol resins, It consists of a base paper coated with an electron-accepting color developer such as a salicylic acid derivative polyvalent metal salt, and when the coated surfaces of both papers are placed facing each other and pressure is applied using a ballpoint pen or an impact printer, the The microcapsules on the upper paper in the pressure area are destroyed, the liquid active ingredient contained therein is released, and a percentage of it is transferred to the lower paper.
A colored image appears.

A pair of image-forming active ingredients, e.g., a colorless dye and a color developer, are each separately dissolved into solutions, encapsulated in separate microcapsules, and then mixed into a single coating solution, which is then applied onto a support sheet. Coated colorless pressure-sensitive copying paper that can record copies on plain paper, etc.
121790゜Japanese Unexamined Patent Publication No. 57-203588, etc.)
. In this case, both microcapsules are destroyed by the application of pressure, and both internal phase liquids are released and transferred to plain paper or the like while reacting, and a colored image appears.

C1 Problem to be solved by the invention In such a pressure-sensitive recording material, the obtained image density is
It depends on the ability to release the active ingredient when the pressure-sensitive microcapsule containing the active ingredient is ruptured under pressure. This is evaluated by the transfer rate of the image forming active ingredient from the upper paper to the lower paper.

It is known that the value of this transfer rate is surprisingly small in the prior art, and most of the active ingredients remain on the upper paper without transferring (eg, Japanese Patent Publication No. 1-14037).

Furthermore, the image formed on the lower paper tends to fade or change color over time due to the effects of light, heat, moisture, oxygen, nitrogen oxides, and the like.

As described above, pressure-sensitive recording materials have the problems of a low transfer rate of image-forming active ingredients and instability of images, and these are the problems to be solved by the present invention.

01 Means for Solving the Problems Regarding the means for improving the low transfer rate of image-forming active ingredients, for example, the above-mentioned Japanese Patent Publication No. 1-14037 describes that it is good to mix wax into the upper paper microcapsule coating layer. The proposed method is not only ineffective but also has the major drawback that the coating layer becomes water repellent and the glue becomes ineffective.

Regarding the problem of image instability, it is possible to mix various deterioration inhibitors into the microcapsules containing image-forming active ingredients or into the bottom paper coating layer, but this may have a negative effect on the color reaction and reduce the image density. or decrease.

The present inventors have already reported in Japanese Patent Application No. 1-311118 that when a solid wax-containing microcapsule layer is provided between the support sheet and the image-forming active ingredient-containing microcapsule layer, the transfer rate is significantly improved. Moreover, it is stated that the hydrophilicity of the coating layer is not impaired.

Specifically, when pressure-sensitive recording paper is printed on the top paper/bottom paper set, a character image with extremely high density is given to the bottom paper,
Moreover, gluing does not impair suitability.

As a result, the image-forming active ingredient transfer rate has been improved to an unprecedented degree, but there has been no particular improvement in the instability of the obtained images.

The present invention is a further development of Japanese Patent Application No. 1-311118, in which a microcapsule layer containing a solid wax containing an anti-deterioration agent is formed between a support sheet and a microcapsule layer containing an image-forming active ingredient. The purpose is to intervene in between.

When the new upper paper created in this way is set with the lower paper and pressurized, a high-density colored image can be obtained as in Japanese Patent Application No. 1-311118, and the stability of the obtained image is significantly improved. It was discovered that it could be done.

At the time of filing Japanese Patent Application No. 1-311118, the solid wax in the solid wax-containing microcapsules interposed between the support sheet and the image-forming active ingredient-containing microcapsule layer was transferred to the lower paper side when pressurized. Perhaps they did not see this happening, but as a result of subsequent research, they surprisingly came to believe that some of it was transferred onto the image.

In the present invention, in short, the anti-deterioration agent is contained in the solid wax-encapsulated microcapsules of the undercoat layer. As a result, a pressure-sensitive image with high density can be obtained, and at the same time, its durability has been improved. Moreover, it does not actually inhibit the color reaction.

The deterioration inhibitors used in the present invention include various antioxidants, ultraviolet absorbers, and stabilizers, and are not particularly limited. However, of course, consideration should be given to solubility in solid wax.

Antioxidants that are examples of deterioration inhibitors include phenolic antioxidants (monophenolic 2,6-di-t),
-Butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, stearyl-β(3,5-di-t-butyl-4-hydroxyphenyl)propionate, etc., bisphenol-based 2,2'-methylene-bis-(4-methyl-6-
t-butylphenol), 2.2=-methylenebis-(
4-ethyl-6-t-butylphenol), 4.4--
Thiobis-(3-methyl-6-t-butylphenol)
, 4.4-butylidenebis-(3-methyl-6-t-
butylphenol), etc., polymeric phenol type 1
, 1. 3-Tris-(2-methyl-4-hydroxy-5t-butylphenyl)butane, 1,3.5-hlymethyl-2,4,6-tris(3,5-di-butyl-
4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3-5--di-t-butyl-4'-hydroxyphenyl)propionate)methane, tocopherols, etc.), sulfur-based antioxidants (dilauryl thiodipropionate), pionate, simiristyl thiodipropionate,
distearyl thiodipropionate, etc.), phosphorus antioxidants (triphenyl phosphite, diphenylisodecyl phosphite, 4.4-butylidene-bis(3-
Methyl-6-t-butylphenyl-di-tridecyl) phosphite, cyclic neopentanetetrylbis(octadecyl phosphite), tris(nonyl phenyl) phosphite, diisodecyl pentaerythritol siphosphite, 10-decyloxy-9 ,10-
(dihydro-9-oxa-10-phosphaphenanthrene, etc.), salicylic acid-based UV absorbers (p-t-butylphenyl salicylate, p-octylphenyl salicylate, etc.), benzophenone-based UV absorbers (2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2,2'-dihydroxy-4,4-1dimethoxybenzophenone, etc.), henctriazole UV stabilizers (2-(2'-hydroxy-5'-methylphenyl)
Henctriazole, 2-(2-hydroxy-5-t
-butylphenyl)benzotriazole, 2-(2″-
Hydroxy-3'5'-di-t-butylphenyl)benzotriazole, 2-(i-hydroxy-3-,5--
di-t-amylphenyl)benzotriazole, 2-(
2'-hydroxy-4'-t-octoxyphenyl)benzotriazole, etc.), cyanoacrylate ultraviolet absorbers (2-ethylhexyl-2-cyano-3,3'-diphenylacrylate, ethyl-2-cyano- Examples of UV stabilizers include nickel bis(octylphenyl) sulfide,
2゜2'-thiobis(4-t-octylferulate)
Quenchers such as E-n-butylamine nickel, nickel complex-3,5-sheet t-butyl-4-hydroxybenzyl-phosphate monoethylate, nickel-dibutyldithiocarbamate, and hindered amine light stabilizers (HALS) include: A group of compounds having a 2,2,6,6-titramethyl-piperidine ring include [bis(2,2゜6.6-tetramethyl-4-piperidyl)sebake-1-) (trade name Tinuvin-700, Ciba Geigy), product name Sanol LS-770 (Sankyo), product name Himatsurubu 944LD (Geigy), product name Tinuvin-765, Tinuvin-622LD1 Tinuvin-144 (Ciba-Geigy), product name mark LA-5
7 (ADEKA ARGUS CHEMICAL), trade name Gutudrite U
V-3034 (Gutudrich) and the like are examples of deterioration inhibitors useful in the present invention.

These may be mixed into the solid wax alone or in combination. The higher the mixing rate in the solid wax, the greater the deterioration prevention effect, but it must be in a range where the deterioration inhibitor/solid wax compatible solution solidifies at room temperature, and it is experimentally necessary to consider the transition rate and deterioration prevention effect. It is a strange thing as defined in . However, it can be said that a range of anti-deterioration agent/'solid wax (weight ratio)≦1 is preferable.

To mix an anti-aging agent into a solid wax, the solid wax is heated above its melting point to liquefy, a predetermined amount of an anti-aging agent is added, and the wax is heated until all insoluble matter is removed, and then dissolved. If undissolved matter remains, problems such as generation of coarse particles will occur during microencapsulation.

(The amount of the anti-deterioration agent to be mixed is such that the anti-deterioration agent/solid wax compatible solution will completely solidify when cooled to 40°C.

) The microencapsulation method of the anti-deterioration agent/solid wax compatible solution used in the present invention includes, for example, the coacervation method as described in U.S. Pat. .001,140, 4,100,103 or 4,233,178
An in-situ polymerization method such as that described in Japanese Patent Publication No. 42-446, or an interfacial polymerization method such as that described in Japanese Patent Publication No. 42-446 can be used, but the present invention is not limited to these methods.

Microencapsulation is performed under heat so that the anti-deterioration agent/solid wax compatible solution remains in a liquid state. but,
When cooled to near room temperature, the internal phase of the capsule solidifies.

As mentioned above, solid wax is used in the present invention.

As stated in the ``Chemistry Dictionary'' (published by Imori Publishing), in a strict chemical sense, wax (English name: wax) is composed of fatty acids and higher or dihydric alcohols that are insoluble in water. Based on its properties, it is classified into solid wax and liquid wax (e.g. Matsukora whale oil, Tsuchijiraura), and depending on its source, it is classified into vegetable wax (e.g. carnauba wax, cotton wax) and animal wax (e.g. beeswax, wool wax). However, wax does not follow the above chemical composition; for example, fats with a high melting point, such as wooden wax, are called wax, and montan wax, osikelite, which is mainly composed of hydrocarbons and occurs naturally, and crude oil. There is petroleum wax that is produced by melting. Petroleum wax is classified into paraffin wax, microcrystalline wax, and petrolatum, depending on the manufacturing route and properties. These waxes have different chemical components from the animal and vegetable waxes mentioned above.

The solid wax used in the present invention is a wax in a broad sense as exemplified above, excluding liquid wax. In Japan, wax is also called wax, so the so-called wax is the wax referred to in the present invention. Both waxes have a long-chain aliphatic hydrocarbon chemical structure,
It imparts a high degree of crystallinity and a distinct melting point.

As mentioned above, in order to encapsulate a mixture of one or more of these solid waxes and one or more anti-deterioration agents in microcapsules, it must be heated above its melting point to become a liquid. It is preferable to emulsify the droplets in warm water using a suitable emulsifier to form droplets of a desired particle size, and then perform a microencapsulation operation. This operation is also normally carried out under heating, but after the operation is completed, if the mixture is cooled to near room temperature, the compatible solution of wax and deterioration inhibitor will solidify within the microcapsules.

Therefore, the melting point of the compatible solution must be higher than the normal environmental temperature, and m, p, 40° C. or higher is suitable.

In addition, especially when solid wax has a high melting point, when heating the solid wax to make it into a liquid, it is easier to encapsulate if the melting point is below the boiling point of water, so other types of wax or foreign substances may be added. It is better to lower the melting point. For example, adding a small amount of a high boiling point solvent facilitates liquefaction. The amount of solvent to be added must be within a range in which the compatible solution consisting of anti-deterioration agent/solid wax/solvent solidifies when cooled to room temperature. Experiments have shown that a suitable amount of solvent to be added is generally less than or equal to the weight of the solid wax. If you add more solvent than necessary,
Care must be taken because the pressure resistance, which is a characteristic of solid wax-filled capsules, will be reduced. The type of solvent is not particularly limited as long as it is water-immiscible, but aromatic, aralkyl, alicyclic, or aliphatic solvents with a boiling point of about 200°C or higher are preferred, and are used in the carbonless paper industry. High boiling point solvents for capsules can be used as is.

In order to actually produce the pressure-sensitive recording material of the present invention, first, microcapsules encapsulating at least an anti-deterioration agent/solid wax compatible solution are placed on a sheet-like support such as paper, nonwoven fabric, woven fabric, film, etc. Apply a coating solution containing adhesive. There is no limit to the amount applied, as the greater the effect, the greater the effect, but the total solid content is 10
It is sufficient to use less than g/rl, and it can be said that even about 2 to 3 g/rd can have a great effect.

On top of the thus obtained undercoat layer, follow the usual method.
A coating liquid for upper paper containing microcapsules containing image-forming active ingredients, an adhesive, a stilt agent (spacer), etc. is applied.

E1 action: If strong pressure or strong impact is applied to a sheet coated with solid wax-containing microcapsules and image-forming active ingredient-containing microcapsules in multiple layers, both will be destroyed and both internal phase substances will be exposed together. This was confirmed by electron microscopy observation. Therefore, it is considered that at this time, the solid wax exhibits a mold release effect, and more of the liquid containing the image-forming active ingredient is ejected to the lower sheet, thereby significantly increasing the transfer rate. Furthermore, since the solid wax is placed on the side of the support sheet, the -layer transition may proceed advantageously.

It is believed that at least a portion of the deterioration inhibitor contained in the solid wax is transferred together with the image-forming active ingredient to prevent image deterioration.

In addition, since the solid wax containing the deterioration inhibitor is covered with a capsule film, the surface maintains hydrophilicity when it is not destroyed.

Therefore, the undercoat layer can be topcoated uniformly (no repelling of the topcoat layer), and has high wettability with water-based glue.

F. Examples Typical examples of the present invention are shown below, but the present invention is not limited thereto.

In addition, "parts" in the examples are "parts by weight" unless otherwise specified.
represents.

Example 1. (Creation of microcapsules) (a) Microcapsules containing image-forming active ingredients 5 parts of crystal violet lactone (electron-donating colorless dye) as an image-forming active ingredient and SAS N-296, which is an aromatic solvent.
(Product name: High boiling point oil manufactured by Nippon Petrochemical Co., Ltd.) 95
Using a homogenizer, the mixture was emulsified in 100 parts of a 5% aqueous solution at pH 4.0 in which the styrene-maleic anhydride copolymer was dissolved together with a small amount of sodium hydroxide.

10 parts of melamine, 25 parts of 37% formalin, and 65 parts of water were adjusted to pH 9.0 with sodium hydroxide and heated to 80°C to obtain a transparent aqueous melamine-formaldehyde initial condensate solution. This was added to the above emulsion, the temperature of the liquid was raised to 80°C, stirring was continued for 1 hour, and then allowed to cool to room temperature.

In this way, microcapsules containing a 5% crystal violet lactone solution and having an average particle size of 7 μm were prepared.

(b) Solid wax-containing microcapsules containing a light stabilizer, which is an anti-deterioration agent.As a solid wax, 90 parts of paraffin wax (melting point 68-70°C) is heated to 80°C or higher to melt it, and the anti-deterioration agent is poured onto the solid wax. Hindered amine light stabilizer Sanol LS-770
(trade name, manufactured by Sankyo) was added to form a --like liquid (this liquid solidified as it was allowed to cool, and was completely solidified at 50°C).

This compatible solution was liquefied at 80° C. and encapsulated in microcapsules in the same manner as in (a) above.

The average particle size of the solid substance-containing microcapsules obtained after cooling was 3 μm.

(c) Solid wax-encapsulated microcapsules containing antioxidants as deterioration inhibitors 2 and 6 that are phenolic antioxidants as deterioration inhibitors
- Using di-t-butyl-p-cresol, microcapsules encapsulating a solid substance (average particle size,
3 μm).

(d) Solid wax-encapsulated microcapsules containing an ultraviolet absorber, which is a deterioration inhibitor.A solid material Encapsulated microcapsules (average particle size, 3 μm) were made.

Example 2. (Preparation of top sheet) Consisting of 66 parts (solid content) of the crystal violet lactone solution-encapsulating microcapsules prepared in Example 1, 22 parts of wheat starch granules, 12 parts of styrene-butadiene latex (solid content), and 100 parts of water. A coating liquid was prepared.

This coating liquid was made into capsules by using a coating liquid consisting of 66 parts (solid content) of the solid wax-encapsulated microcapsules containing a deterioration inhibitor prepared in Example 1, 12 parts (solid content) of styrene-butadiene latex, and 100 parts of water. High-quality paper (basis weight 40
g/i) on the coated surface, solid content coating amount 5g/rr
! Apply multiple layers using a wire rod so that
Dry.

As blanks for comparison, a top sheet was prepared by applying a single layer to unprimed high-quality paper, and a top sheet was prepared by subbing solid wax-encapsulated microcapsules containing no deterioration inhibitor.

Example 3. (Method for measuring transfer rate) Layer the top sheet so that the coated surface of the top sheet and the coated surface of Super CF N-40 (trade name, Mitsubishi Paper Mills Co., Ltd.'s non-carphone bottom paper, basis weight 40 g/rr?) are in contact with each other. Then, pressure was applied through a calender with a nip pressure of 250 kg/cnf to develop color on the lower paper.

The dye transfer rate was determined by calculating the total dye application amount (mg/'rd) for a fresh sample of each soil sheet, and then calculating the dye amount (mg/m) of the corresponding color-forming paper strip.
was calculated and expressed as a ratio (%) of the latter to the former. The amount of dye was determined by solvent extraction-acid color absorption spectrophotometry.

Example 4. (Test results) The test results are summarized in Table 1.

Sun exposure in Table 1 represents the image density after exposure of the colored paper strips to direct sunlight for 5 hours.

Nitrogen oxide exposure refers to the image density after exposing the colored paper strip to a 200 ppm nitrogen oxide (NOx) gas atmosphere for 1 hour.

(Margins below) From the test data in Table 1, using a top sheet that is undercoated with a solid wax-encapsulated microcapsule layer containing a deterioration inhibitor not only significantly increases the color density of the bottom paper, but also provides a more stable image. I understand that.

G1 Effects of the Invention As detailed above, in a pressure-sensitive recording material, an upper sheet is provided in which a solid wax-encapsulating microcapsule layer containing a deterioration inhibitor is provided between a support sheet and a microcapsule layer containing an image-forming active ingredient. (Image-forming active ingredient-donating sheet) not only provides a colored image with significantly improved density to the underlying sheet (image-forming active ingredient-receiving sheet), but also improves its stability. .

Claims (1)

[Claims] A pressure-sensitive recording material characterized in that a solid wax-encapsulating microcapsule layer containing a deterioration inhibitor is provided between a support sheet and a microcapsule layer containing an image-forming active ingredient.