JPS61148093A - Pressure-sensitive copying paper - Google Patents

Abstract

PURPOSE:To prevent smudging, by providing a coated layer comprising a fine powder of cellulose and mono-core microcapsules comprising an amino resin as a wall material and having a volume average particle diameter in a specified range. CONSTITUTION:In a system comprising a fine bacilliform powder of cellulose, the average particle diameter of mono-core microcapsules having walls formed of an amino resin is set to be 5-10mum. The wall thickness (a) of the microcapsules as calculated by formula I, wherein D is the average particle diameter (mum) of the microcapsules, R is the amount (pts.wt.) of the core material used, M is the amount (pts.wt.) of an amino compound used as a material for the wall, (n) is the molar ratio of formaldehyde (molecular weight: m2) to the amino compound (molecular weight: m1), and m3 is the molecular weight of water, is set to be 0.08-0.30mum. In addition, the fine powder of cellulose is so prepared that a fraction thereof having a length of not larger than 100mum constitutes not less than 98% of the whole.

Description

[Detailed Description of the Invention] U) Industrial Application Field The present invention relates to pressure-sensitive copying paper, and more specifically, pressure-sensitive copying paper that has excellent color development and prevents stains (hereinafter referred to as smudges). Regarding paper.

(b) Conventional technology Pressure-sensitive copying paper uses oil-soluble colorless or light-colored dyes.
A tray/I containing an upper paper coated with microcapsules encapsulating it on one side of the paper, and an electron-accepting solid acid substance and adhesive.
#It basically consists of a bottom paper coated with gold on one side, and an inner paper coated with a microcapsule layer on one side and a layer consisting of an electron-accepting solid acid substance on the other side.

The surface of the microcapsule and the surface coated with the electron-accepting solid acid substance often come into contact with each other during the manufacturing process, printing process, or form creation.

For example, it may come into contact with it when winding up the inner paper, during the cutting process, or when it comes into contact with the collator.

At this time, a large amount of pressure or frictional force is applied to the microcapsules, which destroys a portion of the microcapsules and causes abnormal coloration or staining on the surface coated with the electron-accepting solid acid substance (these phenomena may occur). It may cause smut (also called smut). To prevent this, substances with a larger particle size than microcapsules are mixed with the capsule as a capsule protectant (hereinafter referred to as stelt), and are generally made of fine cellulose powder, starch granules, or various plastics. Beads, etc. correspond to this.

V → Problems to be solved by the invention Special Publication No. 1) No. 78 of the Patent Publication No. 48-33204,
The starch particles described in the publications have a short-lived good property for preventing smearing, but the specific gravity of starch is 1.6, which is considerably larger than that of microcapsules (approximately 1).
In addition, since particles with a particle size of 20 to 30 microns are generally used, if a coating solution containing these particles is allowed to stand still, starch granules will settle and the composition of the coating solution will change during continuous coating over a long period of time. This results in fluctuations in the quality of print color development, smearing, etc. on the capsule coated surface. In addition, due to its particle size and hardness, color development in low-pressure printing decreases, resulting in poor color development in multi-copying.

On the other hand, cellulose fine powder, for example, wood pulp t
-Mechanically and chemically crushed and refined, the size is approximately 20 microns in width, approximately 10 microns in thickness, and approximately 100 microns in length.
It is widely distributed with gold centered around micrometers, and its specific gravity is approximately 1.

Therefore, when this is used as a stilt, its specific gravity is about the same as that of microcapsules, so there is no need to worry about precipitation in the coating solution. There is no f movement, and its hardness is moderate, so it does not interfere with capsule destruction and inhibit color development when pressure is applied intentionally, such as during printing.
Therefore, the color development characteristics in low pressure printing are also good.

However, perhaps because of its rod-like shape, the anti-smudge prevention effect may not be sufficient. In particular, mononuclear microcapsules whose film material is amino resin have excellent water resistance and solvent resistance, but when used in combination with fine cellulose powder, the powder may not be sufficiently effective in preventing smudge formation. .

In addition, mononuclear microcapsules used as a membrane material in the amine resin 1 and paper sheets made of fine cellulose powder may have concerns about long-term storage stability, and improvement thereof has also been desired. □゛Furthermore, when threads using fine cellulose powder are used as upper paper, the coated surface may not have sufficient smoothness, and improvements in this have been desired.

The present invention has been made in view of the above-mentioned objectives, and it is an object of the present invention to provide a well-balanced pressure-sensitive copying paper that is excellent in water resistance, solvent resistance, long-term storage stability, color development, smoothness, and smoothness.

2) Means for solving the problem As a result of intensive studies, the present inventors have found that in a system using rod-shaped cellulose fine powder, the average particle size of mononuclear microcapsules using amino resin as a membrane material is small. The surprising result was that it was better to make the thickness thicker, and by making it 5 to 10 microns, the improvement in the anti-smearing effect of the fine cellulose powder was noticeable, and the color development was also improved. It has been found that a superior quality top paper can be obtained.

Furthermore, calculation formula (1) (where D is the average particle size (diameter, μm) of the microcapsules
), the core material used! (parts by weight), M is the amount (parts by weight) of the amino compound used as the raw material for the wall film, and n is the amount of the amino compound (parts by weight) of formaldehyde (molecular weight m2) used.
m3 represents the molar ratio to the molecular weight (t), and m3 represents the molecular weight of water (t).

) The total film thickness of the microcapsule is 0.08 when calculated by
It has been found that by adjusting the thickness to 0.30 microns (μm), the balance between long-term storage stability and color development when used as top paper is excellent.

Then, on top of that, add cellulose fine powder to a length of 10
By increasing the content of 7 lacquer particles of 0 micron or less to 98% or more, the smoothness of the coated surface was improved and the viscosity of the coating solution was reduced, further increasing the usefulness of the present invention.

The fine cellulose powder has a rod-like shape with a width of about 20 microns, a thickness of about 10 microns, and a length of about 100 microns.If the capsule particle size is too small, it will most likely sit on top of the fine cellulose powder. The number of capsules increases,
Capsules whose membrane material is amino resin have a charge relationship (i.e., the capsule has a glass charge, and cellulose has a negative charge, so many capsules sit on top of the fine cellulose powder. On the other hand, if the particle size of the microcapsules becomes too large, the thickness of the microcapsules becomes larger than the thickness of the fine cellulose powder, and the capsules protrude, resulting in insufficient smudge prevention effects.

As a result of numerous experiments, the present inventors have found that only when the particle size of the mononuclear microcapsules is 5 to 10 microns, a system using fine cellulose powder has good coloring performance and the effect of preventing smudges from fusing. I found out that it can be seen. As a result, the system using cellulose micro#Song maintains its advantageous coloring properties, no precipitation in kick liquid, and therefore no compositional iodine during long-term smearing, and little variation in quality. In addition, we succeeded in obtaining the most practical pressure-sensitive copying paper that combines the water resistance and solvent resistance that are characteristic of the amino resin film in the capsule, and has a good balance of color development and smearability.

Furthermore, by setting the microcapsule film thickness to, os to 0.30 microns (μm) according to the calculation formula (1), it is possible to achieve excellent long-term storage stability and color development when used as top paper. succeeded in obtaining pressure-sensitive copying paper with good quality.

For calculation of film thickness, use the following formula in the film thickness section of Tamotsu Kondo, et al., "New technology of microencapsulation and its application development and application examples" (published by Management Development Center Publishing Department in 1978), p. 104. Fermented.

W is the weight of the microcapsule, Ww is the strength of the wall material, ρ
W is the density of the wall material, ρ is the density of the core material, and d is the particle size of the core material.

From this equation, we make the following assumptions and transform the equation.

It is assumed that the densities of the wall material and the core material are mutually equal.

That is, ρW#ρ Since the thickness of the wall film is smaller than the particle size d of the core material or the (average) particle size of the microcapsules, it is set as d#D.

If the weight of the core substance is R, then R = W - Ww The weight of the amino compound that is the raw material for the wall film t - M (molecular weight m1
), the formaldehyde molecule ttm2, the molar ratio of formaldehyde (t) to the amino compound (5) used (F/A) as n%, and the molecular weight of the water dehydrated during shadow formation as m3, the weight of the wall material = The weight of the amine/compound + the weight of the formaldehyde and the weight of the water added, that is, the formula (1) for calculating the film thickness can be modified as follows. At the same time, the fine cellulose powder can be obtained by is made by mechanically and chemically crushing and refining wood valves, and the length ranges from several tens of microns to more than 100 microns, and when used as paper, its smoothness is poor, reducing the product value. In some cases, as a result of consideration, we found that simply reducing the average size is not sufficient), and the length is 100 mm.
It has been discovered that the smoothness can be greatly improved by removing particles of micron size or larger, and that an even better pressure-sensitive copying paper can be obtained by combining it with microcapsules made of amino resin t-m material. We were able to further increase its usefulness.

As the amino resin used in the present invention, for example, urea-
Examples include formaldehyde resin, melamine-formaldehyde resin, polyurea, polyurethane, etc. Encapsulation methods include interfacial polymerization and in-5-itu polymerization, but interfacial polymerization has the disadvantage of being limited by the core material. ) The in 5 situ polymerization method is more general.

Regarding this method, please refer to Japanese Patent Publication No. 37-12380, Japanese Patent Publication No. 38-12518, Japanese Patent Publication No. 54-16949, Japanese Patent Application Publication No. 52-66878, Japanese Patent Publication No. 51-14438.
It is stated in No. 3, etc.

The fine cellulose powder used in the present invention includes commercially available fine cellulose powder, such as KC Flock W manufactured by Desumu Kunisue.
-200, W-250, and W-300, but 98% of them are 100 microns or less in length.
The above-mentioned cellulose fine powder is commercially available as KC Flock W-400 manufactured by Desumikokusaku. In addition, a suitable product can be obtained by dry or wet pulverization and classification if necessary.

In the present invention, a well-known pressure-sensitive recording leuco dye can be used as the dye, as is the case with ordinary pressure-sensitive copying paper! , fLt,
There are triphenylmethane-based, diphenylmethane-based, xanthine-based, thiazine-based, and spiropyran-based compounds.

These dyes are dissolved or dispersed in a suitable oily solvent, emulsified into microdroplets in water or a hydrophilic heating medium, and microencapsulated by a suitable microforce, encapsulation method as described above.

Examples of oily solvents include alkylnaphthalenes, diallylethanes, alkyl biphenyls, hydrogenated terphenyls,
Nonvolatile solvents such as esters are used.

Further, as the electron-accepting substance that forms a colored image when combined with the dye, inorganic coloring agents such as acid clay, activated clay, attapulgide, and zeolite, phenols, phenolaldehyde polymers, phenol-acetylene polymers, Aromatic carboxylic acids such as maleic rosin resin, salicylic acid, and derivatives thereof, or metal salts thereof are known.

These applications can also be done using air knives, blades, rolls,
It is coated at high speed with a coater such as a bar and a coater with a spatula.

To further specifically explain the present invention, Example 6 parts of crystal violet lactone (CVL) was added to KMC-1).
3 (pressure-sensitive copying paper oil manufactured by Kureha Chemical Co., Ltd.) was dissolved in 100 parts and emulsified at 60°C with 220 parts of a 5% aqueous solution of styrene-maleic anhydride copolymer (PH 4,5), followed by 10 parts of melamine, A melamine-formalin initial condensate was obtained by heating and dissolving 19 parts of formalin and 70 parts of water with caustic soda to a pH of 9. Form a melemine-formalin resin wall film on the cellulose, and adjust the pH to 1 with caustic soda! -9,5
A mononuclear colorless dye-containing microcapsule dispersion using amino resin as a membrane material was obtained.

The volume average particle size of the microcapsules at this time was 6 microns.

Further, the film thickness of the micro force/pcel according to the previous 6d calculation formula at this time was 0.15 microns (μm).

KC to 100 parts (solid content) of the above microcapsule dispersion
Flock W-250 (fine cellulose powder manufactured by Dezumi Kokusaku ■)
25 parts and 100 parts of a 15% polyvinyl alcohol water bath solution were added and mixed to prepare a microcapsule coating liquid with a solid content of 20 cm. Is this 'g 4°? The coating amount was 5 fβ on high-quality β paper using an air knife coater at a speed of 100 m/decoy to obtain a top paper. On the other hand, as the lower paper, a pressure-sensitive copying paper (Mitsubishi NCR Paper "Bottom J") coated with a novolac-type oil-bath phenolic resin containing a single-child receptive substance was prepared and the coated side was placed opposite to Other characteristics were investigated.The results are shown in Table 1.

Example 2 The same procedure as in Example 1 was conducted except that the volume average particle size of the capsules was 8 microns and the amount of melamine stool i was 1 part.

Table 1 shows the results.

Example-3 KC71: 1 pcs W-250 (8.7% of 7 lacs over 100 microns in length) was mixed with KC flock W-40.
0 (Hooks longer than 100 microns are 1.0
%) was carried out in the same manner as in Example-2. Table 1 shows the results.

Example 4 KC floc W-250 was treated with a jet pulverizer manufactured by Nippon Gu Neematic@ (the fraction exceeding 100 microns was 1.5 inches). Example-2 using it
I did the same thing. Table 1 shows the results.

Example-5 The volume average particle size of the capsule was 5 microns, and melamine was used i'1! -6.4 parts, 12.4 parts of 37% formalin, and Example 1 except that KC floc W-40 (l) was used.
I did the same thing. The results are shown in Table-1.

Example-6 The volume average particle size of the capsules was 10 microns, the amount of melamine used was 12 parts, 37% formalin was 23°2 parts, and K.
The same procedure as in Example 1 was conducted except that C flock W-400 was used. Table 1 shows the results.

Comparative Example-1 Capsule particle size T4 Old Kuron, Melami 7! The same procedure as in Example 1 was carried out except that 6 parts of kf was used. The results are shown in Table-1.

Comparative Example 2 The same procedure as Example 1 was carried out except that the capsule particle size was 15 microns and the amount of melamine was 12 parts.

The results are shown in Table-1.

Comparative Example 3 The same procedure as Example 2 was carried out except that wheat starch was used instead of KC70TSKUW-250. The results are shown in Table-1.

Comparative Example-4 Table 1 shows the results of the same procedure as in Example-1 except that the capsule particle size was 6 microns, the amount of melamine was 3 parts, and the amount of 37-thiformin was 6.8 parts.

Comparative Example-5 The same procedure as in Example-1 was performed except that the capsule particle size was 8 microns and 5 parts of melamine@1H22° was used.The results are shown in Table-
Shown in 1.

(E) Invention 6 @ As is clear from Table 1, smut occurs only when the particle size of mononuclear microcapsules using amine resin as a membrane material is 5 to 10 microns in a system using fine cellulose powder. A fine cellulose powder that prevents this, has good print color development, has little sedimentation in the coating liquid, and therefore has little change in composition during long-term smearing! It is possible to obtain the most practical pressure-sensitive copying paper that maintains the superiority of water resistance and solvent resistance of microcapsules whose film materials are mold and amino resin, and furthermore, the capsule film thickness is 0.08 to 0. By adjusting the thickness to .30 microns (μm), it was possible to obtain a pressure-sensitive copying paper with excellent long-term storage stability and a better balance between color development and smearing when used as top paper.

Furthermore, by making the cellulose fine powder have a weight ratio of 98 or more flax grains of 100 microns or less, a pressure-sensitive copying paper with even better smoothness can be obtained.

Claims (1)

[Scope of Claims] 1. A coating layer comprising (a) cellulose fine powder and (b) mononuclear microcapsules having a volume average particle diameter of 5 to 10 microns (μm) and made of amino resin as a film material. Pressure-sensitive copying paper with 2. The pressure-sensitive copying paper according to claim 1, wherein the cellulose fine powder has a fraction with a length of 100 microns (μm) or less that accounts for 98 percent by weight or more. 3. Pressure-sensitive copying paper according to claim 1, wherein the film thickness of the microcapsules is 0.08 to 0.3 microns (μm) when calculated by the following formula (1); Film thickness (μm) =(DM/6R){1+[(2m_2-m
_3)n]/(2m_1)}...(1) (where D is the average particle size (diameter, μm) of the microcapsules, R is the amount of the core material used (parts by weight), and M is the wall membrane The amount (parts by weight) of the amino compound used as a raw material, n is the amino compound (molecular weight m_2) of the formaldehyde (molecular weight m_2) used.
1), m_3 represents the molecular weight of water. ).