JPS6145516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a microcapsule-coated sheet, and more specifically, the present invention relates to a strip-shaped support (hereinafter referred to as " The present invention relates to a method for manufacturing a microcapsule-coated sheet by coating a microcapsule-coated sheet on a microcapsule-coated sheet. In particular, it relates to a method for producing pressure-sensitive recording sheets such as pressure-sensitive copying paper and pressure measurement sheets.

Until now, methods for applying liquids containing these microcapsules to webs have been exclusively air knife coating methods (for example, U.S. Pat. No. 3,186,851, U.S. Pat. No. 3,472,674, British Patent No. 1,176,469, etc.) or blade coating methods ( For example, Japanese Patent Publication No. 49-35330, British Patent No. 1339082, etc.) have been used. In any of these methods, after applying an excessive amount of coating liquid to the web, the excess coating liquid is scraped off using an air knife or blade, the amount of coating liquid is measured to the desired amount, and the scraped coating liquid is collected and recycled. It is what you use.

This coating method has been used exclusively because it is possible to apply a thin layer at high speeds of 300 m/min or more with relatively simple operations, and because the product itself was not required to be of such high quality. it is conceivable that.

However, such coating methods have various drawbacks due to the fact that the excess coating liquid is scraped off after the coating liquid is excessively applied to the web.

That is, when using the air knife coating method, solid particles such as microcapsules having a large particle size are selectively scraped off more than necessary due to the classification action of the air knife. In addition, when using the blade application method, a classification effect occurs between the blade and the coating film, and solid particles with a high probability of coming into contact with the blade, that is, solid particles such as large particle size microcapsules, are selectively and necessary. In any case, it was extremely difficult to apply the desired amount of solid particles.
Since the classification effect of such an air knife or blade becomes more pronounced as the coating speed increases, it has been virtually impossible to meet the recent demand for increased production.

Moreover, when manufacturing a microcapsule-coated sheet by applying a coating solution containing microcapsules, it is necessary to prevent the destruction of the microcapsules at times other than when they are used for their original purpose, such as during manufacturing or storage. A capsule reinforcing agent consisting of solid particles is often mixed into the liquid, but when using the air knife coating method,
Such capsule reinforcing agents were also selectively scraped off more than necessary, and could not serve the intended purpose.

In addition, the excess coating liquid that is scraped off is normally collected and recycled for reuse, but as mentioned above, only the large particles are selectively removed by the classification action using an air knife or blade. When scraping off, as the operation continues for a long time, the particle size distribution of the solid particles in the coating solution gradually shifts toward larger particles, and the composition of the coating solution changes over time. It is extremely difficult to apply a coating liquid of a constant composition to a web over a long period of time, and it has been virtually impossible to obtain a high-quality product with stable performance.

Furthermore, in the case of the air knife application method, the excess coating liquid scraped off by the air knife becomes a fine mist, which is not only difficult to collect;
Defects that contaminate the work environment, contaminate the blade edge of the air doctor, and cause streaks on the paint film, or air can cause unevenness on the paint film surface or remove excess dirt that has been scraped off. It also caused the flow of the coating solution and unevenness on the coating surface.

In addition, the blade coating method has a drawback in that when operated for a long time, the blade wears or becomes dirty, which easily disturbs the coating surface, making it extremely difficult to operate continuously for a long time. It had a

Furthermore, when applying a coating liquid containing microcapsules to a web with excellent surface properties, such as a plastic film, when using the air knife coating method or the blade coating method, it is difficult to coat so-called repellents, streaks, bubbles, spots, etc. Failure occurred and it was not possible to form a uniform coating film.

It is an object of the present invention to provide a method for producing a microcapsule-coated sheet that eliminates the drawbacks of the prior art, has less variation in quality, and has excellent surface quality.

This object of the present invention is achieved by applying a coating solution containing microcapsules with a viscosity of 2 to 300 centipoise and a surface tension of 20 to 50 dyn/cm using a hopper type coating device.

These objects of the present invention are achieved by applying a coating liquid containing microcapsules with a viscosity of 2 to 300 centipoise and a surface tension of 20 to 50 dyne/cm onto a web using a hopper type coating device. achieved.

In the present invention, a hopper-type coating device is a device in which the supplied coating liquid fills a reservoir, loses the dynamic pressure during supply and reaches a dynamic equilibrium state, and then flows out through a slit and runs continuously. It refers to a product that has a structure that can be applied to a web, and was published in 1973.
-Bead coating device as disclosed in Japanese Patent Publication No. 8977, extrusion coating device as disclosed in Japanese Patent Publication No. 45-12390, Japanese Patent Publication No. 49-24133, Japanese Patent Publication No. 49-
A curtain coating device such as that disclosed in No. 35447 is included.

Various coating methods using these hopper-type coating devices have been proposed and have been widely used, particularly in the photographic industry.

However, the application of a coating liquid containing microcapsules using such a hopper-type coating device has not been done so far. Although the reason for this is not necessarily clear, the large difference in physical properties between coating solutions for photographic light-sensitive materials and coating solutions containing microcapsules prevents those skilled in the art from considering the adoption of a hopper-type coating device. It is thought that it was Contrary to the predictions of those skilled in the art, the present inventor has dared to repeatedly experiment and found that by adjusting the physical properties within a specific range, it is possible to use a hopper type coating device even for liquids containing microcapsules. As a result, it has been found that an extremely uniform and high quality coating film can be obtained.

Hereinafter, embodiments of the present invention will be described in detail based on the accompanying drawings.

FIG. 1 is a schematic sectional view of a coating device showing an embodiment of the present invention.

Coating liquid 1 containing microcapsules with a viscosity of 2 to 300 centipoise and a surface tension of 20 to 50 dyn/cm is supplied from a tank 2 to a metering pump 3.
The liquid is sent to the liquid supply head 4 by. Since the amount of liquid fed is proportional to the amount of coating applied to the web 5, the amount of liquid fed to the liquid supply head 4 needs to be controlled with good viscosity. In this sense, a variable type pulseless constant flow pump is suitable as the metering pump 3.

The liquid supply head 4 has a pocket 6 inside, and the supplied coating liquid 1 fills the inside of the pocket 6, while the dynamic pressure during supply is dissipated. When the coating liquid 1 reaches a dynamic equilibrium state, the flow rate of the coating liquid 1 flowing into the pocket 6 and the flow rate flowing out from the slit 7 are perfectly balanced, and a constant flow rate of the coating liquid 1 is supplied to the so-called bead 8. be done.

Here, the slit 7 needs to be machined with high precision, and its width is preferably 0.1 to 5.0 mm.
It is appropriate to set it to 0.5 to 2.0 mm. Furthermore, if the distance d between the tip of the liquid supply head 4 and the web 5 is too wide, the bead 8 will become unstable and the liquid will easily run out, while if it is too narrow, dirt and the like will get caught in this gap and damage the coating film. The spacing d is 0.05 to 1.00 mm, preferably 0.1 to 1.0 mm, because it tends to cause streaks, and scratches or protrusions on the web 5 may get stuck to the tip of the liquid supply head 4 and even cut the web 5. It is appropriate to set it to 0.3mm.

The coating film 1 containing microcapsules is supplied from the liquid supply head 4 to the bead 8, and is applied from the bead 8 to the web 5 that is continuously running.
The amount of coating liquid on the web 5 is determined by the amount of coating liquid 1 supplied to the bead 8 and the running speed of the web 5.

In this way, coating liquid 1 containing microcapsules
The web 5 provided with the coating film 9 consisting of the I am forced to do it.

As described above, in this embodiment, the coating liquid is measured in the form of the amount of liquid sent to the liquid supply head 4 prior to coating, and the coating amount is determined by this and the running speed of the web 5. There is no room for subsequent classification by the air knife or blade, which not only prevents various troubles caused by such a classification action, but also prevents unevenness in the coating surface and the occurrence of mist caused by the air knife or blade itself. Nor. Moreover, according to this embodiment, uniform coating can be achieved with a sufficiently controlled coating amount, and a coating film with a sufficiently smooth surface can be obtained.
Such an effect has been recognized in the past in the production of photographic materials, but in the case of a coating solution containing microcapsules as in this embodiment, such an effect is not obvious, and Considering that it was widely recognized among those skilled in the art that microcapsule-coated sheets with commercial quality could not be obtained due to the large difference in physical properties from coating liquids for materials, this was extremely difficult. This is an amazing effect. In order to obtain such amazing effects, the surface tension and viscosity of the coating liquid containing microcapsules must be adjusted to 20 and 20, respectively.
It is necessary to adjust to 50 dyne/cm, 2 to 300 centipoise, preferably 10 to 200 centipoise. If the surface tension of the coating liquid falls outside of this range, phenomena such as difficulty in bead formation are observed, and it is recognized that it becomes extremely difficult to uniformly apply the coating liquid to the web. Furthermore, if the viscosity of the coating liquid exceeds the upper limit mentioned above, liquid shortage will occur, while if it falls below the lower limit, vertical streaks will likely occur on the coating surface, and in any case, it will not be possible to obtain a uniform coating. .

FIG. 2 is a longitudinal sectional view of a coating device showing another embodiment of the present invention. FIG. 2 shows an example in which a so-called extrusion hopper is used instead of the slide hopper of FIG. 1. The coating liquid 1 containing microcapsules adjusted to have a predetermined viscosity and surface tension is supplied from the pocket 6 of the liquid supply head 4 through the slit 7 to the surface of the continuously running web 5, and is coated. Ru.

The present invention is not limited to the above embodiments,
It goes without saying that various changes are possible.

In the present invention, the liquid containing microcapsules refers to a liquid containing 5 to 60 wt % of microcapsules and using water as the dispersion medium. The liquid containing the microcapsules may contain additives such as a binder and a capsule reinforcing agent, if necessary.

In the present invention, microcapsules are microcapsules that contain an oily liquid containing a basic colorless color former and are coated with a wall material made of a polymeric substance that is insoluble in both water and oily liquid. can be,
It refers to those with an average grain size of 0.1 to 100μ.
As the wall material, a combination of polycation and polyanion such as gelatin-gum arabic or a combination of condensation composition such as polyisocyanate-polyamine can be used.

Examples of encapsulation methods for producing such microcapsules include the coacervation method (US Pat. No. 2,800,457, US Pat. No. 2,800,458, US Pat.
3041289, 3687865, etc.), interfacial polymerization method (US Patent No. 3492380, 3577515, UK Patent No. 950433, 1046469, 1091141, etc.), internal polymerization method (UK Patent No. 1237498, French Patent No. 2060818, French Patent No. 2090862, etc.), external polymerization method (British Patent No. 989264, Japanese Patent Publication No. 37-12380)
No. 37-14327, No. 45-29483, No. 46-7313
No. 46-30282, etc.) can be used.

In the present invention, the color former is a colorless compound that has the property of developing color when it comes into contact with a solid acid, and refers to a colorless organic compound that has electron donating properties. In the present invention, the type and properties of the color former do not have a substantial effect on the present invention, so any type of color former can be used without particular limitation. For example, triarylmethane compounds, diarylmethane compounds,
A wide variety of xanthene compounds, thiazine compounds, spiropyran compounds, etc. can be used as the coloring agent in the present invention.

Specific examples of color formers include triphenylmethane compounds such as 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (i.e., crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindole-3-
yl) phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindol-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-phenylindole) -3-yl)phthalide, 3,3-bis(1,2-dimethylindol-3-yl)-5-dimethylaminophthalide, 3,3-bis-(1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis-(9-ethylcarbazole-
3-yl)-5-dimethylaminophthalide, 3,
3-bis-(2-phenylindol-3-yl)-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrole-
Examples include 2-yl)-6 dimethyl-aminophthalide.

Diphenylmethane compounds include 4,4'-
Bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl leukoolamine, N
-2,4,5-trichlorophenylleucoauramine, etc.

As a xanthene compound, rhodamine-B
-anilinolactam, rhodamine-(p-nitroanilino)lactam, rhodamine-B-(p-chloroanilino)lactam, 3-dimethylamino-7
-Methoxyfluorolan, 3-diethylamino-7-methoxyfluorane, 3-diethylamino-6-chloro-6-methylfluorane, 3-diethylamino-7-(acetylmethylamino)fluorane, 3-diethylamino-7-( dibenzylamino) fluorane, 3-diethylamino-7-
Examples include (methylbenzylamino)fluoran, 3-diethylamino-7-(chloroethylamino)fluoran, and 3-diethylamino-7-(dichloroethylamino)fluoran.

Examples of thiazine compounds include benzoyl leucomethylene blue and p-nitrobenzyl leucomethylene blue.

Examples of spiro-based compounds include 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-benzyl-spiro-dinaphthopyran, and 3-methyl-naphtho-( Examples include 3-methoxy-benzo)-spirolane and 3-propyl-spiro dibenzodipyran. The above coloring agent may be used alone or in combination.
They can be appropriately selected and used by mixing more than one species.

These color formers are dissolved in a solvent and encapsulated.

As a solvent, natural or synthetic oils can be used alone or in combination. Examples of solvents include cottonseed oil, kerosene, paraffin, naphthenic oil, alkylated biphenyl, alkylated terphenyl, chlorinated paraffin, alkylated terphel, chlorinated paraffin, alkylated naphthalene, and the like.

The size of the encapsulated microcapsules is usually about 0.1 to 100μ, preferably about 0.5 to 50μ.
It is.

Since the microcapsule-containing liquid thus obtained is usually a capsule dispersion, it may be coated on the support as it is, or it may be coated with the addition of a binder.

In the present invention, binders include latexes such as styrene-butadiene rubber latex, styrene-butadiene, acrylonitrile latex, styrene-maleic anhydride copolymer latex, and proteins (e.g., gelatin, gum arabic, albumin, casein, etc.). , cellulose (e.g. carboxymethylcellulose,
Water-soluble natural polymer compounds such as hydroxyethyl cellulose, sutucarose (e.g. agar, sodium alginate, starch, carboxymethyl starch, etc.) Water-soluble synthetic polymer compounds such as polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide : Examples include organic solvent-soluble polymer compounds such as nitrocellulose, ethylcellulose, polyester, polyvinyl acetate, polyvinylidene chloride, and vinyl chloride-vinylidene chloride copolymer.
Advantageously, these polymeric substances used as protective agents usually have a molecular weight of approximately 1000 to 10,000,000, in particular 10,000 to 5,000,000.

In the present invention, capsule reinforcing agents include cellulose flocs (e.g., U.S. Pat. No. 2,711,375), starch particles (e.g., U.K. Pat. No. 1,232,347), fine polymer powders (e.g., U.S. Pat.
3625736, etc.), microcapsules that do not contain coloring agents (for example, British Patent No. 1235991, etc.), and inorganic pigments such as talc, kaolin, bentonite, waxite, zinc oxide, titanium oxide, and alumina. Although these capsule reinforcing agents do not necessarily have to be added, it is convenient to add them to a coating solution containing microcapsules in order to prevent destruction of the microcapsules.

The amount of microcapsules applied is about 0.5 to 25 g/m ² , especially about 5 to 15 g/m 2 in the case of a pressure-sensitive recording sheet.
g/m ² is convenient.

In the present invention, the web to which the liquid containing microcapsules is applied includes polyesters such as polyethylene terephthalate and polyethylene naphthalate, cellulose derivatives such as cellulose triacetate and cellulose diacetate, plastic films such as polystyrene, metal foil, paper, and resin. Includes coated paper, synthetic paper, etc. The thickness of these webs is usually about 10 to 350 μm. Among these webs, plastic film, resin coated paper (synthetic paper, metal foil)
The present invention is particularly effective when coating on webs with low water absorption, such as webs with low water absorption.

In the present invention, when the surface of the web to be coated is hydrophobic, it is desirable to carry out the coating after surface treatment in order to improve the adhesion after coating. Surface treatment methods include (1) chemical treatment, mechanical treatment, corona discharge treatment, flame treatment,
(2) A method of applying microcapsules directly to obtain adhesive strength after surface activation treatment such as ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, laser treatment, mixed acid treatment, ozone oxidation treatment, etc. There are two methods: once these surface treatments have been carried out, an undercoat layer is provided and microcapsules are applied thereon.

(For example, U.S. Patent Nos. 2,698,241, 2,764,520,
No. 2864755, No. 3462335, No. 3475193, British Patent No.
No. 788365, No. 804005, No. 891469, etc.).

Among these methods, method (2) is more effective and widely used. All of these surface treatments are
By creating some polar groups on the web surface, which was originally hydrophobic, by removing the thin layer that is a negative factor for the adhesion of the extreme surface, and by increasing the crosslinking density on the surface and increasing the adhesive strength. It is thought that the adhesion force on the surface is increased by raising the surface.
In addition, various methods have been used to apply the undercoat layer, such as providing a layer that adheres well to the web as the first layer, and then applying a hydrophilic resin layer as the second layer on top of it. There is a multilayer method and a single layer method in which only one resin layer containing both a hydrophobic group and a hydrophilic group is applied.

In the present invention, as a method for adjusting the viscosity of the liquid containing microcapsules, commonly used viscosity adjustment methods such as dilution and addition of a thickener can be widely used. Thickening agents include proteins (e.g., gelatin, gum arabic, albumin, casein, etc.), cellulose (e.g., carboxymethyl cellulose, hydroxyethyl cellulose, etc.), satucrose (e.g., agar, sodium alginate, starch, carboxymethyl starch, etc.). Water-soluble natural polymer compounds such as: water-soluble synthetic polymer compounds such as polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, and polyacrylamide can be used. The appropriate amount of the thickener to be added is 0.1wt% to 20wt%.

In the present invention, coating aids for adjusting the surface tension of the liquid containing microcapsules include various anionic, cationic, nonionic, and amphoteric surfactants and various water-soluble polymers having surface activity. substance can be used. Examples of anionic surfactants include fatty acid soap, metal soap, sulfated oil, funnel oil, alkyl sulfate salt, polyoxyethylene alkyl ether sulfate salt, polyoxyethylene alkyl allyl ether sulfate salt, and higher fatty acid alkanolamide sulfate. Ester salts, alkyl sulfonates, alkylbenzene sulfonates, alkylaryl sulfonates, dialkyl sulfosuccinates,
Higher fatty acid alkylolamide sulfonate,
Alkyl phosphates and the like are used. As the cationic surfactant, alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, etc. are used. Examples of nonionic surfactants include fatty acid glycerides, polyoxyethylene fatty acid esters, polyoxyethylene alkyl ethers, polyoxyethylene alkylaryl ethers, sorbitan fatty acid esters, sucrose fatty acid esters, polyoxyethylene sorbitanic acid esters, and polyoxyethylene alkyl amines. , polyoxyethylene fatty acid amide, polyoxyethylene polypropylene glycol ether, etc. are used. As the amphoteric surfactant, alkyl betaine, imidazoline derivative, etc. are used. As for the water-soluble polymeric substance containing a surfactant, starch, carboxymethyl cellulose, polyvinyl alcohol, gum arabic, gelatin, rosin-modified alkyd resin, and other latexes are used.
The amount of these coating aids to be added can be adjusted until the desired surface tension is achieved, but the solid content
It is appropriate to add 0.001wt% to 10wt%.

In the present invention, the pressure-sensitive recording sheet produced is generally used in combination with a sheet provided with a coating film made of a so-called color developer, but a layer containing microcapsules and a layer containing a developer are used in the same web. It is also possible to provide a coloring function with only one sheet by providing a layer containing a coloring agent. (So-called self-coloring pressure-sensitive recording sheet) The color developer herein refers to an electron-accepting solid acid that has the property of developing a color when it comes into contact with a color former encapsulated in microcapsules. In the present invention, the type of color developer is not important, and a wide variety of conventionally known color developers can be used without particular limitation.

Specific examples include clays (e.g. acid clay, activated clay, attabulgite, etc.), organic acids (e.g. aromatic carboxyl compounds such as salicylic acid, P-t-butylphenol, P-t-amylphenol, o-chloro Aromatic hydroxy compounds such as phenol, m-chlorophenol, and P-chlorophenol or their metal salts (e.g., zinc salts), mixtures of organic acids and metal compounds (e.g., zinc oxide), acidic polymers (e.g.,
phenol-formaldehyde resin, phenol-acetylene resin), etc. Regarding color developers, see US Patent No. 3501331, US Patent No. 3669711, US Patent No.
No. 3427180, No. 3455721, No. 3516845, No. 3634121, No. 3672935, No. 3732120,
Special Publication No. 45-48545, No. 45-49339, No. 45-
No. 93245, No. 45-92246, No. 45-93247, No. 45
-94874, 45-109872, 45-112038,
No. 45-112039, No. 45-112040, No. 45-112753
No. 45-122754, No. 45-118978, No. 45-
It is also described in No. 118979 and No. 46-86950.

In the present invention, the running speed of the web, that is, the coating speed, is suitably 5 to 150 m/min.
Preferably it is 10 to 30 m/min. The amount of coating liquid supplied to the web varies depending on the desired coating amount and web speed, but is usually between 1.0 and 220 mm.
cc/m ² is suitable, and 20 to 80 c.c./m ² is particularly preferred.

Examples and comparative examples will be given below in order to make the effects of the present invention more clear.

All "parts" below refer to parts by weight.

Example 1. 1 part of 3-6-bisdiethylaminofluorane-P-nitroanilinolactam and 1.4 parts of 1,3-dimethyl-6-diethylaminofluorane were dissolved in 22 parts of diisopropylnaphthalene, and tolylene diisocyanate was added to the solution. 3 parts of methylolpropane adduct and 0.1 part of propylene oxide adduct of ethylenediamine were added and dissolved. This solution was emulsified and dispersed in a solution of 2.6 parts of polyvinyl alcohol dissolved in 29 parts of water at 20°C, and after emulsification, 65 parts of water was added and heated to 70°C with stirring. After stirring for 1 hour, it was cooled to form microcapsules. A coating liquid containing the following was obtained.

When the surface tension of the coating solution containing the microcapsules thus obtained was measured, it was found that 60dyne/
cm, so 0.5 part of sodium diethylhexylsulfosuccinate was added and the surface tension was measured in the same manner, and it was found to be 40 dyne/cm. The viscosity of this coating liquid was measured at room temperature and was found to be 15 centipoise.

A coating solution containing microcapsules whose surface tension and viscosity have been adjusted in this way is coated onto corona discharge-treated polyethylene-coated paper using a slide-type hopper coating device shown in Figure 1.
The coating was applied at 20 m/min at a coating amount of 10 g/m ² and dried to obtain a microcapsule-coated sheet.

When the coating film of the obtained microcapsule-coated sheet was observed, it was confirmed that the coating film was highly uniform without defects such as repelling, streaks, bubbles, and spots.

When this microcapsule-coated sheet was developed by spraying a color developer solution containing zinc salicylate salt dissolved in acetone, it was found that
Uniform coloring can be seen in both length directions,
It was found that the coating was carried out very well.

Comparative Example 1. An example was prepared in which the coating liquid containing microcapsules obtained by the method of Example 1 was picked up by a coating roll rotating in the opposite direction to the web.
Coating speed 20m/on the same polyethylene coated paper as in 1.
After that, the excess coating solution was scraped off with an air knife, the coating amount was measured to be 10 g/m ² , and the coating was dried to obtain a microcapsule-coated sheet.

When the coating surface of the thus obtained microcapsule-coated sheet was observed, the occurrence of vertical streaks and streaks caused by uneven flow of the scraped coating liquid was observed.

Comparative Example 2. A coating liquid containing microcapsules obtained by the method of Example 1 (surface tension: 60 dyne/cm, viscosity: 15 centipoise) was applied to the same polyethylene coating as in Example 1 using the same equipment as in Example 1. The coating was applied to the surface of paper at a coating speed of 20 m/min in an amount of 10 g/m ² .

When the coating film was observed after drying, it was found that the coating solution did not spread over the entire surface of the web, and so-called liquid breakage occurred, and uniform coating was not possible.

Example 2 6 parts of pork skin acid-treated gelatin and 6 parts of gum arabic
Dissolved in 30 parts of water at 40°C. To this was added 0.2 parts of sodium nonylbenzenesulfonate as an emulsifier, and 30 parts of diisopropylnaphthalene oil in which 2.5% crystal violet lactone and 2% benzene leucomethylene blue were dissolved was added to the above solution and emulsified. Add 200 parts of water at 40℃ to this, and while stirring, add 20% hydrochloric acid dropwise to adjust the pH.
Adjusted to 4.4. The solution was cooled to 40°C and 37%
Add 2.0 parts of a formaldehyde solution of 20% of a 7% solution of carboxymethylcellulose sodium salt.
of cellulose fibers (average length
A coating liquid containing microcapsules was obtained by adding 10 parts of arrowroot starch (200μ, average width: 30μ) and 4 parts of arrowroot starch (average particle size: 40μ).

When the surface tension of the coating solution containing the microcapsules thus obtained was measured, it was found that 60dyne/
It was cm.

Add 0.5% of rosin-modified alkyd resin to this coating solution.
The surface tension was 45 dyne/cm and the viscosity was 20 centipoise at room temperature.

The coating solution with the surface tension and viscosity adjusted in this way was applied to the surface of polyethylene-coated paper that had been subjected to corona discharge treatment using an extrusion-type hopper coating device shown in Fig. 2, and the coating amount was applied at a coating speed of 20 m/min.
A microcapsule-coated sheet was obtained by coating at a concentration of 10 g/m ² .

When the coating film of the obtained microcapsule-coated sheet was observed, it was confirmed that the coating film was highly uniform without defects such as repelling, streaks, bubbles, and spots.

When this microcapsule-coated sheet was developed by spraying a color developer solution containing zinc salicylate salt dissolved in acetone, it was found that
Uniform coloring can be seen in both length directions,
It was found that the coating was carried out very well.

Comparative Example 3 A coating solution containing microcapsules obtained by the method of Example 2 was coated onto the same polyethylene-coated paper as in Example 2 using an air knife coating device in the same manner as in Comparative Example 1 at a coating speed of 20 m/min. is 10
g/m ² and dried to obtain a microcapsule-coated sheet.

When the coating surface of the thus obtained microcapsule-coated sheet was observed, the occurrence of vertical streaks and streaks caused by uneven flow of the scraped coating liquid was observed.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are both schematic cross-sectional views of a coating device showing an embodiment of the present invention. 1... Coating liquid, 4... Liquid supply head, 5... Web, 6... Pocket, 9... Coating film.

Claims (1)

[Claims] 1 In a method of manufacturing a microcapsule-coated sheet by applying a coating liquid containing microcapsules to a continuously running web, the viscosity is 2 or more.
300 centipoise, surface tension 20 to 50 dyne/cm
A method for producing a microcapsule-coated sheet, characterized in that a coating liquid containing microcapsules is applied using a hopper-type coating device.