JPS5835479B2 - pressure sensitive recording material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pressure-sensitive recording material that can be copied multiple times by applying pressure such as printing pressure or writing pressure, and more particularly to a pressure-sensitive recording paper having a surface coating layer with a novel structure. be.

A conventional pressure-sensitive recording material in which two coloring components are coated on separate supports is of the type shown in FIG.

That is, one of the coloring components is microencapsulated 2 and covers the lower surface of the upper support 1, and the other coloring component is present as a coating layer 3 on the upper surface of the lower support 1, and the printing pressure or writing pressure is When the microcapsules 2 are added, the liquid content of the microcapsules 2 flows out and is transferred to and absorbed by the coating layer 3. At the same time, the two coloring components react to produce a colored substance, and an image is formed on the receiving surface of the coating layer 3. be done.

However, in the case of the type shown in FIG. 1, when the upper support and the lower support are overlapped and cut or bent, colored contamination occurs in the area where pressure is applied.

In order to suppress or avoid the occurrence of such inconveniences, pressure-sensitive recording paper is known in which microcapsules 2 containing a coloring component are spot-coated on the upper and lower surfaces of a support, as shown in FIG. .

However, spot coating of microcapsules is actually difficult because it is difficult to obtain capsules that are strong enough to withstand spot coating, and because it relies on a water-based paint, wrinkles occur on the support after coating.

Therefore, by spot coating the lower surface of the upper support 1 as shown in FIG. 3 using a so-called hot melt ink in which a coloring component is dispersed in hot melt wax, the spot transfer property is improved. It is proposed to form a covering layer 4.

However, in the case of this type, although the coloring components contained in the transferable coating layer 4 and the receptive coating layer 3 are surrounded by other components (e.g. wax, binder, etc.), the upper support and the lower support When handled together with the body, colored contamination occurs due to unexpected external forces.

In addition, when printing pressure or writing pressure is applied, the transferable coating layer 4
is not only transferred to the receptive coating layer 3, but also a reverse transfer of the receptive layer 3 to the transferable coating layer 4 occurs, and an image is generated in both coating layers, resulting in an increase in the rate of color development in the receptive coating layer. and the color density is often reduced.

In order to prevent such inconveniences, if the composition of the transferable coating layer 4 is changed so that it is difficult to transfer, the coloring when printing pressure or writing pressure is applied will be poor, and a clear image will not be obtained.

In order to improve these disadvantages, according to the present invention, the transferable coating layer is a layer of a hot-melt paint containing one color-forming component, and the receptive coating layer opposite thereto is a layer of a hot-melt paint containing the other color-forming component. Provided is a pressure-sensitive recording material characterized in that it is a layer having porous fine absorption pores, which is composed of microcapsules containing microcapsules, fine powder, and a binder.

4 and 5 illustrate the present invention, in which the transferable coating layer 5 is spot-coated on the lower surface of the upper support 1, and in FIG. In this example, a transferable coating layer 5' is coated on the entire lower surface of the upper support 1.

In the figure, reference numeral 6 denotes a layer having porous fine absorption pores, which is formed on the upper surface of the lower support 1 and is made of microcapsules, fine powder, and a binder.

As mentioned above, pressure-sensitive recording paper is generally a type in which microcapsules holding one coloring component as a liquid are present in a transferable coating layer, and the liquid contained in the capsules is transferred to the opposite receiving surface to develop color. In this case, the entire amount of liquid within the capsule does not necessarily transfer to the receiving surface, and remains on the transfer surface side without contributing to color development.

In contrast, the present invention does not allow the microcapsules containing the coloring component to exist in the transferable coating layer and transfer them to the receptive coating layer, but rather allows the microcapsules to exist in the receiving layer and transfers the coloring component to the receptive coating layer. It is based on the principle of exposing and absorbing liquid within the layer, and the coloring component inside the capsule is effectively transformed into a colored substance, which directly forms an image on the receiving surface, resulting in both color development speed and density. growing.

Furthermore, for the same reason, there is no need to incorporate a large amount of a coloring component.

The first feature of the present invention is that the receptive coating layer contains microcapsules containing one of the coloring components.

The second feature of the present invention is the use of a hot-melt paint containing a coloring component in the transferable coating layer.

As is well known, hot-melt paints are so-called hot-melt inks and hot-melt waxes, and they are easy to spot coat, only need to be cooled after coating, and do not require drying, and the equipment is simple and easy to apply. Although this is advantageous in that the processing speed can be improved, as mentioned above, there are many disadvantages when using this in the configuration shown in FIG. 3.

However, according to the present invention, when a transferable coating layer made of such a heat-melting paint containing a coloring component is combined with the first feature, that is, a structure in which microcapsules are contained in a receptive coating layer, the advantages of both can be obtained. S works together to bring about good results.

However, there are still disadvantages in combining only these first and second features.

In other words, if the microcapsules are ruptured just before the printing pressure is applied and the heat-melting paint of the transferable coating layer is transferred onto the surface of the microcapsules of the receptive coating layer, the liquid will be exposed and the transferable coating layer will be transferred to the surface of the transferable coating layer. The liquid may transfer and color develops, or the hot-melt paint may not be able to transfer, resulting in poor image development and undesirable results.

Therefore, in the present invention, the receptive coating layer has a structure having porous fine absorption pores composed of microcapsules, fine powder, and a binder, so that the liquid exposed during pressurization is instantaneously and completely absorbed into the pores. .

By doing this, the hot-melt paint will be completely transferred and no back-transfer of the liquid will occur.

This porous structure with fine absorption pores also serves to protect the microcapsules from external forces.

When creating the receptive coating layer, the size of the capsule is adjusted so that the pore volume is larger than the total volume of liquid within the capsule, in order to form porous microscopic absorption pores having the above-mentioned functions. Appropriate conditions must be selected depending on the amount of binder, particle shape, particle size, particle size distribution, etc. of the fine powder.

The table below is an experimental example showing the relationship between the blending ratio of capsules, fine powder, and binder and their functions when creating a receptive coating layer.

In this experiment, a hot melt paint containing 30% Jilton clay (manufactured by Mizusawa Chemical Co., Ltd.) was used as the transferable coating layer.

Here, the formation of porous fine absorption pores and its effects will be further explained.

Generally, in order for liquid to permeate the capillary and reach a long distance, the smaller the diameter of the capillary, the better.

However, in order to absorb a large amount of liquid within a short period of time, the larger the diameter of the capillary, the better.

In the receptive coating layer of the present invention, it is desired that the liquid flowing out from the microcapsules is instantaneously and completely absorbed within the coating layer.

Therefore, it is desirable that the diameter of the porous fine absorption pores present in the layer is large.

However, the size of a microcapsule is usually about 1 to 10 microns, and the liquid content is small, so if the nearby pores are too large, it will not move at all through the pores.

That is, it is not in an absorbed state.

Therefore, the diameter of the porous fine absorption pores must be smaller than about 10 microns.

Furthermore, in order to increase the liquid absorption capacity, it is necessary that the total volume of the pores be approximately the same.

Generally, microcapsules have a spherical shape when dispersed in a liquid, but when dried as a coating layer, they become nearly a continuous phase, leaving few gaps between the microcapsules.

Therefore, powder or fine fiber powder is used in between to leave fine spaces after drying.

Generally, when a box is filled with spheres and the diameters of the spheres are the same, 26% of the space remains for the densest spheres and 50% for the bulkier spheres.

A cylindrical filament similarly leaves 22% space.

Therefore, if a coating layer made of various fine powders and microcapsules is applied to a support and dried, the above-mentioned spaces should remain.

However, if a binder is added to the dry coating layer to prevent it from falling off, the amount of space will be reduced according to the amount of binder blended, and if a larger amount of binder is filled than this amount of space, no porous fine absorption pores will remain. It disappears.

The above is an estimate based on calculated values, but since the fine powder actually used is irregular rather than spherical or cylindrical, and the powder size distribution is continuous, there is a considerable deviation from the calculated values.

The table above shows some of these aspects.

When printing is performed with the receiving layer and the transfer layer facing each other, the image appears on the transfer layer because the color component in the microcapsules migrates to the color component in the transfer layer, and the liquid content of the destroyed microcapsules This indicates that the liquid was not completely absorbed by the receiving layer and the excess liquid was transferred to the transfer surface.

This experiment shows that when the amount of microcapsules in the receptive coating layer is less than 20%, the liquid in the microcapsules is completely absorbed into the receptive coating layer, and no coloring occurs in the transferable coating layer. has been done.

However, the total spatial volume of the porous fine absorption pores that give this effect is not only related to the amount of fine powder blended, but also directly related to the amount of binder blended, and decreases when a large amount is blended, and decreases when a small amount is blended. Increases when blended.

In addition, when the support is absorbent, it absorbs the binder contained in the coating layer paint and changes the amount of binder remaining in the dry coating layer.
The absorbency of the support also affects the total volume of space.

Therefore, the paint formulation examples in the table above have a US weight of 43 mm as a support.
This is an example in which precipitated calcium carbonate and polyvinyl alcohol are blended into microcapsules using high-quality paper of g. It does not necessarily indicate the results.

Usually, the weight ratio of each component in the coating layer is Good results can be obtained by adjusting the amount.

Of course, the ratio of the fine powder to the binder must be appropriately selected within the above range so that a desired volume of porous fine absorption pores is formed.

In short, in the present invention, the amounts of fine powder and binder used are appropriately selected so that the total amount of liquid in the microcapsules does not exceed the total volume of the porous fine absorption pores generated in the receptive coating layer. It is necessary to

The support in the present invention is mainly paper.

However, in the present invention, since the receptive coating layer is provided with liquid absorbing properties, non-absorbing materials such as films, metal foils, etc. can also be used in some cases, and there are no particular limitations on the support material.

As the coloring components, various pairs can be used as long as they react with each other to form colored substances.

However, in the case of the present invention, since one of the pairs is used in the form of a hot melt type paint, substances that are highly volatile at around 100°C or liquid at room temperature are not preferred.

For triphenylmethane phthalide series, fluoran series, phenothiazine series, indolyl phthalide series, leucoauramine series, spiropyran series, triphenylmethane series, triazenes, naphtolactam series, benzopyran series, azomethine series, hydroxyphthalane series, etc. Pairs of colorless dyes belonging to the above group and inorganic color developers such as activated clay, colloidal silica, zeolite, etc. and various organic color developers can be used.

These pairs can be used interchangeably for transferable and receptive coating layers.

In addition, a combination of a ferric fatty acid salt and a higher alcohol ester of gallic acid, a combination of a vanadium compound such as stearyltrimethylammonium vanadate and a higher alcohol ester of gallic acid, etc. are also used.

Optionally, a mixture of these pairs can also be used.

The fine powder in the present invention refers to various inorganic and organic white pigments, starch particles, wood cellulose powder, etc., but it must not develop color upon contact with coexisting coloring component-containing microcapsules.

This is because even if the coloring component is inside the microcapsule, it does not necessarily adhere to the outer wall of the capsule at all.

For example, for capsules such as crystal violet ratatone, it is desirable to incorporate substances that do not exhibit coloration, such as calcium carbonate and aluminum hydroxide.

For fine powders, particle shape, particle size, and particle size distribution are also related to the formation of porous microabsorption pores and are factors that determine the rate and amount of liquid absorbed in the capsule.

-Although it is difficult to express numerically, the particle shape is close to a sphere, the particle size is in the range of 0.5 to 20 microns, and the particle size distribution is concentrated at one point as much as possible. Good.

It is desirable that the wood cellulose powder passes through 300 meshes or less.

As binders, coloring components and non-coloring natural and synthetic polymers are used.

Since the amount of binder blended is an important factor in the formation of porous fine absorption pores, the calculated value of the remaining space when the spheres mentioned above are packed in a box, the particle shape and diameter of the fine powder used,
The amount is determined by taking into consideration the particle size distribution, etc., and maintaining a balance with the amount of capsules blended.

Since hot-melt paints must be transferable, it is desirable to prime them before application.

As this undercoat, the polymer used as the binder as described above is used, and one with good sealing effect is selected.

Materials other than the coloring components of hot-melt paints include high-melting natural waxes such as carnauba wax, candelilla wax, and montan wax, oils and fats, hydrogenated oils, higher fatty acids, their polyvalent metal salts, and petroleum-based Waxes, non-volatile high melting point substances, etc. are used.

Optionally, small amounts of non-volatile solvents are added, and stabilizers such as antioxidants, ultraviolet light inhibitors, etc. are included as necessary.

Example 1 Microcapsules containing a colorless dye are prepared as follows.

50 g of crystal violet lactone and 30 g of penzoyl leucomethylene blue were mixed with alkylnaphthalene (
Dissolve in KMC-113 (Kugyo Kagaku) to obtain 1001.

While stirring this at high speed with a homomixer, disperse it in a solution of 200 g of gelatin dissolved in 1500 g of water, then add a solution of 40 g of carboxymethyl cellulose dissolved in 3000 g of water, then add 2000 g of water, and then add 90 g of 10% acetic acid. Add to adjust pH to 4.0.

Subsequently, the temperature was cooled to 7°C on ice, and 37% formaldehyde 15
0g, then add 300g of 4% caustic soda and p
Let it be H9,0.

Then, the mixture was kept at 50° C. for 1 hour, and 200 g of wood cellulose powder (Sanyo Kokusaku Pulp, KC Flock-300) was added thereto, and then stored at room temperature.

Alternatively, if necessary, a small amount of an ultraviolet inhibitor may be added to the alkylnaphthalene.

The formulation (parts by weight) of the paint for the receptive coating layer is as follows.

Microcapsule liquid mentioned above (solid content) 15 Precipitated calcium carbonate (Shiraishi calcium) 45 Polyvinyl alcohol (electrochemistry) 15 Solid content concentration of the above formulation 18
LBKP70% by air knife coating of aqueous dispersion,
A coating amount of 3.5 g/n on high-quality paper with a rice weight of 40.9 and a composition of 30% NBKP. coat.

An 8% polyvinyl alcohol solution was previously applied to the back side of the paper using a Mayer bar to provide curl prevention and barrier properties as an undercoat for the transferable coating layer.

3. Apply the following hot-melt paint for a transferable coating layer to the surface provided with barrier properties using a hot-melt transfer gravure method.
Spot coat at a rate of 0.097m.

The composition of the paint (parts by weight) is as follows.

The above components were melt-mixed at 80° C. using a Ni-Goo, and used for coating as a hot-melt type paint.

A pressure-sensitive recording form as shown in Fig. 6 was made by stacking 10 sheets of the thus obtained front and back coated papers (however, the middle six sheets were omitted), and when printed with an electric typewriter, the results showed that Even on the lower leaf portion (10th sheet), clear blue characters were quickly printed.

In addition, when letterpress printing was applied to the surface of the receptive coating layer,
As with printing on high-quality paper, no problems were observed.

When a pressure-sensitive recording form was prepared in the same manner as above using the receptive coating layer obtained in Experiment No. 7 in the above table, good results similar to those described above were obtained.

Example 2 In the same manner as in Example 1, the following iron-based microcapsules were created.

That is, 80 g of ferric coconut oil mixed fatty acid was dissolved in oxyethylene lauryl ether (Matsumoto Kosan, Actinol) to make 1000 g, and the solution was microencapsulated.

A paint for the receptive coating layer was also prepared according to Example 1.

The composition (parts by weight) of the heat-melting paint for the transferable coating layer on the other hand was as follows.

Hereinafter, when 10 sheets of coated paper obtained according to Example 1 were stacked and printed, a black image with good light resistance was obtained, although the coloring speed was slightly inferior to that of Example 1.

[Brief explanation of the drawing]

Figures 1 to 3 show two pressure-sensitive recording materials according to the prior art.
An example in which two color-forming components are coated on the support surface facing each other, Figures 4 and 5 are examples showing the coating layer in the present invention, and Figure 6 is a spot-type recording material using the pressure-sensitive recording material of the present invention. These are examples of pressure recording forms, and all are cross-sectional views. In the figure, 1 is a support, 2 is a layer of microcapsules containing a liquid containing a coloring agent, 3 is a solid layer containing a coloring agent, and 4 and 5 are hot-melt paints containing a coloring agent. A layer 5' is a layer in which this is spot-coated only on required parts, a layer 5' is a layer in which this is coated on the entire surface, and a layer 6 is a layer having porous fine absorption pores composed of microcapsules, fine powder, and a binder.

Claims (1)

[Claims] 1. In a pressure-sensitive recording material in which two color-forming components that react with each other to form a colored substance are separately applied to the surface of a support as a transferable coating layer and a receptive coating layer, the transferable coating layer is applied to one side of the support. The receptive coating layer is a layer of a hot-melt paint containing a coloring component, and the receptive coating layer contains 10 to 35% by weight of microcapsules containing the other coloring component, an inorganic white pigment, an organic white pigment, starch particles, and wood cellulose powder. 70 to 50% by weight of a fine powder selected from the group consisting of: and 20 to 1% of a binder
A pressure-sensitive recording material characterized in that it is a layer having porous fine absorption pores composed of 5% by weight.