Microcapsule sheet for pressure-sensitive recording paper

A microcapsule sheet is disclosed. At least one surface of the base paper has a coating produced from a solution that contains microcapsules each containing an electron donating color former, a binder whose solid content is from 20 to 50 parts by weight based on 100 parts by weight of the solid content of the microcapsules, a protective agent and a surfactant having a hydrophobic atomic group of the formula: ##STR1## wherein R.sub.1 and R.sub.2 are each an aliphatic hydrocarbon having 2 to 20 carbon atoms or aromatic hydrocarbon having 6 to 20 carbon atoms.

FIELD OF THE INVENTION 
The present invention relates to a microcapsule sheet for 
pressure-sensitive recording paper having formed thereon microcapsules 
each containing a substantially colorless electron donating color former 
that is contacted by an acidic material (color developer) to form a color. 
BACKGROUND OF THE INVENTION 
Pressure-sensitive recording paper is a recording medium that uses the 
color forming mechanism due to the transfer of electrons between an 
electron donating color former and an inorganic or organic acid. The paper 
generally consists of an upper leaf having microcapsules formed on one 
surface of a base, a lower leaf having a coating of color developer formed 
on one surface of a base, and an intermediate leaf having microcapsules 
formed on one surface of a base and a coating of color developer on the 
other surface (the upper and intermediate leaves are hereunder 
collectively referred to as microcapsule sheets). The above-described 
pressure-sensitive recording papers are well known, for example, as 
described in U.S. Pat. Nos. 2,505,470; 2,505,489; 2,550,471; 2,548,366 and 
2,712,507. To reduce the cost of producing the pressure-sensitive 
recording paper, it is desired that coatings of microcapsules and color 
developer be formed on a base at maximum speed. However, as the web 
handling speed is increased, more air is entrapped by the web being 
rolled, and the resulting roll has wrinkles similar to the twisted pattern 
of a rope. This tendency is conspicuous when the web handling speed is 
greater than 300 m/min. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide a microcapsule sheet for 
pressure-sensitive recording paper that is adapted for high-speed 
production. 
This object of the present invention is achieved by applying to at least 
one surface of base paper a solution that contains microcapsules each 
containing an electron donating color former, a binder whose solid content 
is 20 to 50 parts by weight based on 100 parts by weight of the solid 
content of the microcapsules, a protective agent and a surfactant having a 
hydrophobic atomic group of the formula: 
##STR2## 
(wherein R.sub.1 and R.sub.2 are each an aliphatic hydrocarbon having 2 to 
20 carbon atoms or aromatic hydrocarbon having 6 to 20 carbon atoms). 
DETAILED DESCRIPTION OF THE INVENTION 
The term "solid" as applied to the microcapsules means oil globules which 
are the core of the microcapsule and which have a color former dissolved 
therein, the color former and the wall of the microcapsule. 
The binder coated on the base together with microcapsules has 20 to 50 
parts by weight of solid content for 100 parts by weight of the solid 
content of the microcapsule. If the solid content of the binder is less 
than 20 parts by weight, unevenness of color appears in spots on the web 
being rolled at high speed, and the roll of coated pressure-sensitive 
recording paper fouls when it is slit or cut into a form adapted for 
practical applications. If the solid content exceeds 50 parts by weight, 
only a low color density is achieved by the resulting pressure-sensitive 
recording paper that is used in combination with a lower leaf having a 
coating of color developer formed on one surface of a base. Furthermore, 
if a plurality of the microcapsule sheets are used as intermediate leaves 
that are placed alternately on plain paper sheets, a clear copy is 
obtained on the first two or three sheets but only a fuzzy copy is 
obtained on the lower sheets. However, a microcapsule solution containing 
only the binder having 20 to 50 parts by weight of solid content provides 
a coating having high gas permeability and cannot be applied onto a base 
at a web handling speed of 300 m/min or more without causing wrinkles in 
the paper roll (the wrinkles are hereunder referred to as roll wrinkles). 
To produce a microcapsule sheet having low gas permeability and which is 
adapted to high-speed production, the microcapsule solution must contain a 
surfactant having a hydrophobic atomic group of the formula: 
##STR3## 
(wherein R.sub.1 and R.sub.2 are each an aliphatic hydrocarbon having 2 to 
20 carbon atoms, or aromatic hydrocarbon having 6 to 20 carbon atoms). The 
microcapsule solution containing such surfactant as well as the binder can 
be applied onto a base at high speed without fouling the base and it 
provides a microcapsule sheet for pressure-sensitive recording paper that 
is subject to minimum fouling during the subsequent slitting or cutting 
and which gives high color density. 
Surfactants having a surface tension of 45 dyne/cm or more at a critical 
micelle concentration (CMC) such as naphthalenesulfonic acid formalin 
condensate, alkyl betaines, alkyl imidazolines and alkyl picolinium salts, 
provide coated paper that has high gas permeability and which hence does 
not achieve the object of the present invention. A common surfactant such 
as alkylbenzenesulfonate salt gives a capsule solution having a surface 
tension as low as that the surfactants specified herein, but perhaps due 
to the difference in the property to wet the paper, the solution forms a 
coating whose gas permeability is still high and which cannot be applied 
to the base at fast speed without causing roll wrinkles. For the purpose 
of the present invention, the microcapsule solution should form a coating 
having a gas permeability of not more than 1,000 seconds, preferably not 
more than 500 seconds. 
The essential requirements of the present invention are described below. A 
base paper sheet on which the microcapsule solution is applied preferably 
has a gas permeability of not more than 90 seconds. If the gas 
permeability is greater than 120 seconds, a coated sheet having surface 
streaks often results. There is no particular limitation on the proportion 
of soft wood (N) pulp and hard wood (L) pulp in the base paper, the 
content of filler clay, the nature of the size (whether it is neutral or 
acidic) or the type of the surface size. One example is ordinary paper 45 
to 60.mu. thick and which has an L/N ratio of 1:1, a filler clay with a 
talc content of 5 vol%, a neutral size made of long-chain dibasic acid 
tetrahydrate, and a surface size made of starch. The surface size may be 
used together with a basic inorganic pigment or a color developer. 
The color former-containing microcapsule for use in the present invention 
can be prepared by various methods: phase separation from aqueous 
solutions as described in U.S. Pat. Nos. 2,800,457 and 2,800,458; 
interfacial polymerization as described in Japanese Patent Publication 
Nos. 19574/63, 446/67, 771/67, 2882/67, 2883/67, 8693/67, 9654/67, 
11344/67, Japanese Patent Application (OPI) No. 9097/76 (the term "OPI" as 
used herein refers to a "published unexamined Japanese patent 
application"), U.S. Pat. No. 3,287,154, and British Pat. Nos. 950,443 and 
1,046,409; polymerization of a microcapsule wall in oil globules as taught 
in Japanese Patent Publication Nos. 9168/61 and 45133/74; cooling of 
molten dispersion as described in British Pat. Nos. 952,807 and 965,074; 
crystallization of polymer as taught in U.S. Pat. Nos. 3,418,250; 
3,660,304 and Japanese Patent Publication No. 23165/72; and polymerization 
of reactants from within oil globules as described in U.S. Pat. Nos. 
3,726,804 and 3,796,669. 
A urethane resin, amino resin, epoxy resin, amide resin or mixtures thereof 
are preferably used as an agent to form the wall of the microcapsules used 
in the present invention. These resins are effective for providing a dense 
wall. If the resulting microcapsule wall is not adequately dense, the 
color density is decreased with time or during storage in a hot and humid 
atmosphere perhaps due to the reaction with the surfactant. For details of 
the microencapsulation with urethane resins, see Japanese Patent 
Publication Nos. 446/67, 11344/67, 45133/74 and 22507/75; for the 
microencapsulation with amino resins, see Japanese Patent Publication Nos. 
12380/62, 12518/63, 771/67, 2883/67, 30282/71, Japanese Patent Application 
(OPI) Nos. 42380/72, 99969/74, 8780/75, 144383/76, 66878/77, U.S. Pat. 
Nos. 3,993,831 and 4,001,140; for the microcapsulation with epoxy resins, 
see Japanese Patent Publication Nos. 19574/63, 24420/63 and 27257/69; for 
the microencapsulation with amide resins, see British Pat. No. 950,443, 
U.S. Pat. Nos. 3,270,100; 3,429,827; 3,208,951 and British Pat. No. 
1,142,649. 
The surfactant used in the present invention has a hydrophobic atomic group 
of the formula: 
##STR4## 
As R.sub.1 and R.sub.2 have more carbon atoms, the effect of the 
surfactant is increased, but then if more than 20 carbon atoms are 
present, the water solubility of the surfactant is decreased to such a 
level that its use is practically impossible. If R.sub.1 and R.sub.2 have 
less than 2 carbon atoms, the surfactant hardly exhibits its effect. The 
surfactant has hydrophilic atomic groups such as sulfonate salt, 
carboxylate salt, phosphate salt, amine salt, quaternary ammonium salt and 
pyridinium salt. A sulfonate salt having higher water solubility is 
particularly preferred. Specific examples of the surfactant used in the 
present invention include di-1-dimethyl-3-methylpentylsulfosuccinate 
ester, dihexylsulfosuccinate ester, di-1-dimethyl-heptylsulfosuccinate 
ester, di-benzylsulfosuccinate ester, tetramethyl-dodecylsulfosuccinate 
ester, tetramethyldecylsulfosuccinate ester, dioctylsulfosuccinate ester, 
di-2-ethylhexylsulfosuccinate ester, di-isohexylsulfosuccinate ester, and 
tetramethyl-2-methyl-7-ethyldodecylsulfosuccinate ester. These surfactants 
may be used in combination with any of the surfactants mentioned 
previously which have a surface tension of 45 dyne/cm or more at a 
critical micelle concentration. The surfactant is used in such an amount 
that the solid content is 0.0001 to 10 parts, preferably from 0.005 to 0.5 
part, by weight for 100 parts by weight of the solid content of the 
microcapsule. 
The primary components of the microcapsule coating solution are 
microcapsules, binder and protective agent. The solid content of the 
binder must be 20 to 50 parts by weight for 100 parts by weight of the 
solid content of the microcapsules. The protective agent is used in such 
an amount that its solid content is 20 to 150 parts, preferably 40 to 100 
parts, by weight for 100 parts by weight of the solid content of the 
microcapsules (this amount may slightly vary with the specific type of the 
agent). 
Suitable examples of the binder used in the present invention are latices 
such as styrene/butadiene rubber latex, styrene/butadiene latex, 
acrylonitrile latex, and styrene/maleic anhydride copolymer latex; 
proteins such as gelatin, gum arabic, albumin and casein; water-soluble 
natural polymeric compounds such as cellulose (e.g., carboxymethyl 
cellulose, hydroxyethyl cellulose, etc.) and saccharose (e.g., agar, 
sodium alginate, starch, carboxymethyl starch, etc.); water-soluble 
synthetic polymeric compounds such as polyvinyl alcohol, polyvinyl 
pyrrolidone, polyacrylic acid and polyacrylamide. Among these binders, 
carboxymethyl cellulose, starch and polyvinyl alcohol are preferred. These 
polymeric compounds used as the binder generally have a molecular weight 
of from about 1,000 to 10,000,000, more advantageously from 10,000 to 
5,000,000. For ease of handling, a binder having a viscosity of 500 
centipoises (cPs) or less in aqueous solution for a solid content of 10% 
and at 25.degree. C. is preferred. Examples of such binder are a 
styrene/butadiene rubber latex, styrene/butadiene latex, acrylonitrile 
latex, styrene/maleic anhydride copolymer latex, carboxymethyl cellulose, 
starch, polyvinyl alcohol and polyacrylic acid. 
The protective agent used in the present invention is a particulate or 
fibrous material that is solid at ordinary temperatures. Specific examples 
are starch particles (as described in British Pat. No. 1,232,347), fine 
polymer particles (as described in U.S. Pat. No. 3,652,736), microcapsule 
particles containing no color former (as described in British Pat. No. 
1,235,991), inorganic particles such as those of talc, kaolin, bentonite, 
pyrophyllite, zinc oxide, titanium oxide and alumina, and fine cellulose 
particles (as described in U.S. Pat. No. 3,625,736). The particulate 
protective agent generally has a volume average size of from 3 to 50 
microns, preferably from 5 to 40 microns. It is effective for the purpose 
of the present invention that these particles are larger than the color 
former-containing microcapsules. The fibrous protective agent is generally 
from 50 to 600 microns, preferably from 100 to 400 microns, long. The 
above mentioned protective agents are those of the type which is directly 
added to the coating solution primarily made of microcapsules, and if a 
separate protective layer is formed on a coating primarily made of the 
microcapsules, the binder described above is usually employed. It is also 
possible to add the protective agent in the coating solution primarily 
made of microcapsules while simultaneously forming a separate protective 
layer. 
According to the present invention, the coating solution primarily made of 
microcapsules is applied to the base in a dry weight of 2 g/m.sup.2 or 
more, preferably 3.5 to 6 g/m.sup.2 or more. The color former is used in 
an amount of from about 0.03 to 0.5 g/m.sup.2. While there is no 
limitation on the size of the microcapsules, the preferred size is from 3 
to 20 microns. 
The color former to be microencapsulated is generally a compound which is 
substantially colorless and has a nucleus such as lactone, lactam, 
sultone, spiropyran, ester and amide and which, upon contact with a color 
developer, have these nuclei opened or cleaved. Specific examples are 
triaryl methane compounds, diphenyl methane compounds, xanthene compounds, 
thiazine compounds and spiropyran compounds. More specific examples are 
crystal violet lactone, benzoyl leucomethylene blue, malachite green 
lactone, rhodamine B lactam, 
1,3,3-trimethyl-6'-ethyl-8'-butoxyindolinobenzospiropyran. These color 
formers are usually employed as a combination of quick release type and 
slow release type. These color formers are encapsulated by dissolving them 
in a solvent selected from among those which dissolve at least 5 wt% of 
the color former, particularly at least about 10 wt% of crystal violet 
lactone. The indicated solubility is that of one or more color formers at 
23.degree. C., and it is particularly preferred that the color formers do 
not precipitate out when left for about 3 days at 23.degree. C. Specific 
examples are aliphatic and aromatic compounds such as chlorinated paraffin 
(having a chlorination degree of about 15 to 60), alkyl or aralkylbenzene 
or naphthalene (wherein the alkyl group has not more than about 5 carbon 
atoms), such as triphenylmethane, diphenyltrimethane, xylyl phenylethane, 
benzylxylene, .alpha.-methylbenzyltoluene, diisopropylnaphthalene, 
isobutylbiphenyl, tetrahydronaphthalene, hydrogenated terphenyl, 
di-.alpha.-methylbenzyl, xylene, tert-butyl-diphenyl ether, hydrogenated 
styrene dimer, edible oils and cootonseed oil. These solvents may be used 
either alone or in combination. They can also be used in combination with 
not more than about 20 wt% of a poor solvent for the color former, for 
example, low-boiling paraffin or alkylbenzene, and this is effective for 
providing an intermediate leaf that has good printability with reduced 
fog. Furthermore, the solvents may be mixed with an antioxidant and an 
agent to increase the color forming speed. 
Reference can be had to any prior art publication for the additives and 
antioxidants to be used in applying the microcapsule solution on a base 
and the method for applying it. Examples are U.S. Pat. Nos. 2,711,375; 
3,625,736; 3,836,383 and 3,846,331, British Pat. No. 1,232,347, and 
Japanese Patent Application (OPI) Nos. 44012/75, 50112/75, 127718/75, 
30615/75. The drying temperature is preferably not more than about 
180.degree. C. and not less than 100.degree. C. After drying, the web is 
preferably wound at a tension between about 50 and 250 kg. A greater 
tension will rupture the capsules and often causes unevenness in color. 
Examples of the color developer are organic or inorganic acids such as clay 
minerals (e.g., acid clay, bentonite and kaolin), and organic acids or 
salts thereof (e.g., isopropenylphenol dimer, novolak, metal-treated 
novolak, 3,5-di-tert-butylsalicylic acid and zinc 
di-.alpha.-methylbenzylsalicylate salt). The organic acids include organic 
compounds having one or more acidic groups such as a carboxyl group, 
thiocarboxyl group, phenolic hydroxy group, mercapto group and sulfo 
group, or salts (particularly polyvalent metal salts) thereof. These 
organic compounds may be a polymer of materials such as acids derived from 
phenol, butylphenol, octylphenol, phenylphenol, isopropenylphenol dimer, 
etc., or novolak resins or metal salts thereof; acids such as salicylic 
acid, hydroxynaphthoic acid, tert-butylsalicylic acid, 
di-tert-butylsalicylic acid, tert-octylsalicylic acid, laurylsalicylic 
acid, dicyclohexylsalicylic acid, dibenzylsalicylic acid, 
di-.alpha.-methylbenzylsalicylic acid, di-.alpha.-dimethylbenzylsalicylic 
acid, anthranilic acid, tert-octyl-.alpha.-methylbenzylsalicylic acid, 
.alpha.-dimethylbenzyl-tert-octylsalicylic acid, 
.alpha.-methylbenzyloxynaphthoic acid and thiosalicylic acid, or metal 
salts thereof. A polyvalent metal is preferred as the metal to form salts 
with these acids, and examples of such metals include magnesium, calcium, 
zinc, aluminum and tin, and zinc and aluminum are particularly preferred. 
These metals may be used in the form of a metal salt from the beginning, 
or they may be in such a form that a metal salt is formed after a color 
developer coating is formed and dried. For forming a color developer 
coating, 10 parts by weight of the color developer (i.e., the above 
mentioned organic acid derivatives or polyvalent metal salts thereof) may 
be used in combination with about 1 to 300 parts by weight of metal 
compounds such as oxide, hydroxide, carbonate salt, acetate salt and 
phosphate salt of a polyvalent metal such as zinc, aluminum, barium, 
calcium or arsenic, or talc and clay, and this is effective in making the 
color developer exhibit its ability for an extended period (making the 
color developer remain stable over an extended period), although these 
additives have no ability to develop a color. The color developer and 
these optional components are dissolved or dispersed in an organic solvent 
or water, and the resulting solution or dispersion is applied onto a paper 
base. There is no limit on the upper limit of the amount of the color 
developer coating to be formed since this is determined by the 
capabilities of the pressure-sensitive recording paper desired and the 
cost of manufacturing it. When an organic acid is used as the color 
developer, the coating weight is generally between about 0.2 and 2 
g/m.sup.2, preferably between 0.25 and 1.3 g/m.sup.2. A better result is 
obtained when this amount of organic acid is used together with about 0.25 
to 10 g/m.sup.2, preferably from 0.5 to 3 g/m.sup.2 of zinc oxide. A color 
developer-coated paper having good printability is obtained when about 1.0 
to 6 g/m.sup.2 of a pigment such as a basic white pigment or white clay is 
also used. If the color developer is an inorganic solid acid, the coating 
weight is generally between 2 and 6 g, preferably between 3 and 5 
g/m.sup.2. The coating solution or dispersion may optionally contain a 
latex, water-soluble polymer such as carboxyl-modified styrene/butadiene 
copolymer, butadiene/butyl acrylate/styrene/maleic acid copolymer, vinyl 
acetate/styrene/methyl methacrylate copolymer or isoprene/maleic 
acid/acrylonitrile copolymer, petroleum resin, oxidized starch, polyvinyl 
alcohol or methyl cellulose. The coating solution or dispersion may also 
contain a dispersant or stabilizer as required, and it is applied to a 
paper base by any of the methods described in the previously mentioned 
patents, for example, by dip coating, air knife coating, blade coating, 
roller bead coating, curtain coating and gravure coating (see, for 
example, Japanese Patent Publication No. 35330/74, British Pat. Nos. 
1,339,082; 1,176,469, U.S. Pat. Nos. 3,186,851 and 3,472,674). For the 
purpose of the present invention, the color developer coating is desirably 
smoothed and to do so the paper base with a color developer coating is 
preferably calendered before drying.

The present invention is now described in greater detail by reference to 
the following examples and comparative examples which are given here for 
illustrative purposes only and are by no means intended to limit its 
scope. In the examples and comparative examples, all parts are by weight. 
(1) Preparation of Color Developer-coated Paper A 
A dispersion with a solid content of 25 wt% consisting of 90 parts of talc, 
1.0 part of naphthalenesulfonic acid/formalin condensate, 12 parts of zinc 
oxide, 9.5 parts of zinc 3,5-di-.alpha.-methylbenzylsalicylate, 3 parts of 
oxidized starch, 5.5 parts of polyvinyl alcohol, and 9 parts of 
carboxyl-modified styrene/butadiene latex was prepared with an attritor. 
The dispersion was applied to one surface of a paper base 1.8 m wide 
having a basis weight of 40 g/m.sup.2 and a gas permeability of 60 seconds 
until the coating weight of zinc di-.alpha.-methylbenzylsalicylate was 
0.36 g/m.sup.2. The dispersion particles had a volume average size of 
5.mu.. 
(2) Preparation of Color Developer-coated Paper B 
A hundred parts of acidic clay was dispersed in 400 parts of a 0.5% aqueous 
solution of sodium hydroxide. To the dispersion, 20 parts of a 
styrene/butadiene copolymer latex on a solid basis and 40 parts of a 100 
wt% aqueous starch solution were added, and the mixture was stirred 
thoroughly to provide a color developer coating solution. The solution was 
applied to one surface of a paper base 1.8 m wide having a basis weight of 
40 g/m.sup.2 and a gas permeability of 60 seconds until the coating weight 
was 5.0 g/m.sup.2 on a solid basis. 
(3) Preparation of Microcapsule Solution A 
Microcapsules each containing a color former were prepared according to 
U.S. Pat. No. 2,800,457. A mixture of 10 parts of acid-treated pigskin 
gelatin and 10 parts of gum arabic was dissolved in 400 parts of water at 
40.degree. C. To the solution, 0.2 part of sulfonated oil was added as an 
emulsifier and then 40 parts of a color former oil was dispersed. The 
color former oil was a 2% solution of crystal violet lactone in 
cyanopropylnaphthalene. When the average size of the oil globules became 5 
microns, the dispersion was stopped, and water (40.degree. C.) was added 
to make 900 parts of the emulsion which was further stirred. Then, 10% of 
acetic acid was added to adjust the pH of the emulsion to be 4.0 to 4.2 
for initiating coacervation. The stirring was continued and 20 minutes 
later, the emulsion was cooled with ice water to gel the coacervate film 
formed around the oil globules. When the temperature of the emulsion 
became 20.degree. C., 37% formalin was added. When the temperature was 
decreased to 10.degree. C., 15% aqueous caustic soda was added to adjust 
the pH to 9. The emulsion was heated for 20 more minutes under agitation 
until the temperature was 50.degree. C. The resulting emulsion was 
referred to as microcapsule solution A. 
(4) Preparation of Microcapsule Solution B 
One part of crystal violet lactone was dissolved in 22 parts of 
diisopropylnaphthalene. To the solution, 3 parts of an adduct of tolylene 
diisocyanate and trimethylolpropane and 0.1 part of an adduct of 
ethylenediamine and propylene oxide were added. The solution was put into 
a solution of 2.6 parts of polyvinyl alcohol in 29 parts of water at 
20.degree. C., and the resulting emulsion was mixed with 65 parts of water 
under stirring with heating. When the temperature was elevated to 
70.degree. C., the emulsion was further stirred for one hour to make a 
microcapsule solution B. This solution differed from the solution A in 
that it contained 2.6 parts of polyvinyl alcohol as a binder. 
(5) Preparation of Microcapsule Solution C 
Five parts of a partial sodium salt of poly(vinylbenzenesulfonic acid) 
(VERSA TL 500 of National Starch K.K., av. m.w. 500,000) was dissolved in 
95 parts of hot water (80.degree. C.) in about 30 minutes under stirring. 
The solution was then cooled and had a pH of 2 to 3. A 20 wt% aqueous 
solution of sodium hydroxide was added to the solution to increase its pH 
to 4.0. A hydrophobic solution was prepared by dissolving 4 parts of 
crystal violet lactone (CVL) in 100 parts of KMC-113 (an alkylnaphthalene 
of Kureha Chemical Industry Co., Ltd., mainly comprising 
diisopropylnaphthalene) under heating. The resulting hydrophobic solution 
was dispersed in 100 parts of the previously prepared 5% solution of 
partial sodium salt of poly(vinylbenzenesulfonic acid) to form an emulsion 
having particles of an average size of 4.5.mu.. A mixture of 6 parts of 
melamine, 11 parts of 37 wt% aqueous solution of formaldehyde and 83 parts 
of water was heated under stirring for 30 minutes to form a transparent 
aqueous solution which was a mixture of melamine, formaldehyde and an 
initial melamine/formaldehyde condensate. The resulting solution had a pH 
of 6 to 8. The aqueous solution which was a mixture of melamine, 
formaldehyde and initial melamine/formaldehyde condensate is hereunder 
referred to as an initial condensate solution. The initial condensate 
solution thus-prepared was mixed with the previously prepared emulsion 
under stirring while 20 wt% aqueous acetic acid was added to adjust the pH 
of the mixture to 6.0. The temperature of the mixture was elevated to 
65.degree. C., stirred for 60 more minutes, mixed with 1 N hydrochloric 
acid to adjust the pH of the system to 4.0, and further mixed with 30 g of 
a 40 wt% aqueous solution of urea. The system was further stirred at 
65.degree. C. for 40 minutes, and then, its pH was adjusted to 9.0 with 20 
wt% aqueous sodium hydroxide. The so-prepared solution was referred to as 
microcapsule solution C. 
The microcapsule coating solutions prepared in the examples and comparative 
examples contained 75 parts (based on 100 parts of the solid content of 
the microcapsules) of starch particles having a volume average size of 
12.mu. as a protective agent. 
EXAMPLE 1 
After adding a protective agent to the microcapsule solution A, the 
solution was blended with a 1:1 mixture of polyvinyl alcohol and oxidized 
starch that was added as a binder in 30 parts with respect to 100 parts of 
the solid content of the microcapsules. As a surfactant, 
di-2-ethylhexylsulfosuccinate ester was added in 0.03 part with respect to 
100 parts of the solid content of the microcapsules, to thereby prepare a 
microcapsule coating solution. The solution was then applied onto the 
uncoated surface of the color developer-coated paper A at a speed of 500 
m/min to give a dry coating weight of 5.0 g/m.sup.2. The web could be 
wound up without causing roll wrinkles and the sample obtained could form 
a desired color without fog. It had a gas permeability of 700 seconds. The 
sample was subjected to a heat resistance test wherein it was stored at 
100.degree. C. for 10 hours and the microcapsules were ruptured to form a 
color. In the test, a slight decrease in the color density was observed. 
COMATIVE EXAMPLE 1 
After adding a protective agent to the microcapsule coating A, the solution 
was blended with a 1:1 mixture of polyvinyl alcohol and oxidized starch 
that was added as a binder in 30 parts with respect to 100 parts of the 
solid content of the microcapsules, to thereby form a microcapsule coating 
solution. The solution was applied to the uncoated surface of the color 
developer-coated paper A at a speed of 500 m/min to give a dry coating 
weight of 5.0 g/m.sup.2. When the web was wound up, a roll having wrinkles 
similar to the twisted pattern of a rope resulted. The sample obtained had 
a gas permeability of 5,000 seconds. No reduction in color density 
occurred in the subsequent heat resistance test. 
EXAMPLE 2 
A microcapsule coating solution prepared as in Example 1 was applied to the 
uncoated surface of the color developer-coated paper B at a speed of 500 
m/min to give a dry coating weight of 5.0 g/m.sup.2. The web could be 
wound up without causing roll wrinkles and the sample obtained could form 
a desired color without fog. The sample had a gas permeability of 500 
seconds. A slight reduction in color density occurred in the subsequent 
heat resistance test. 
COMATIVE EXAMPLE 2 
A microcapsule coating solution prepared as in Comparative Example 1 was 
applied to the uncoated surface of the color developer-coated paper B at a 
speed of 500 m/min to give a dry coating weight of 5.0 g/m.sup.2. When the 
web was wound up, a roll having wrinkles similar to the twisted pattern of 
a rope resulted. The sample had a gas permeability of 3,500 seconds. No 
reduction in color density occurred in the subsequent heat resistance 
test. 
EXAMPLE 3 
A microcapsule coating solution was prepared as in Example 1 except that 
the microcapsule solution A was replaced by the microcapsule solution B. 
The coating solution was applied to the uncoated surface of the color 
developer-coated paper A at a speed of 500 m/min to give a dry coating 
weight of 5.0 g/m.sup.2. The web could be wound up without forming roll 
wrinkles and the sample obtained could form a desired color without fog. 
The sample had a gas permeability of 500 seconds. No reduction in color 
density occurred in the subsequent heat resistance test. 
COMATIVE EXAMPLE 3 
A microcapsule coating solution was prepared as in Comparative Example 1 
except that the microcapsule solution A was replaced by the microcapsule 
solution B. The coating solution was applied to the uncoated surface of 
the color developer-coated paper A at a speed of 500 m/min to give a dry 
coating weight of 5.0 g/m.sup.2. When the web was wound up, a roll having 
wrinkles similar to the twisted pattern of a rope was obtained. The sample 
had a gas permeability of 4,000 seconds. No reduction in color density 
occurred in the subsequent heat resistance test. 
EXAMPLE 4 
A microcapsule coating solution prepared as in Example 3 was applied to the 
uncoated surface of the color developer-coated paper B at a speed of 500 
m/min to give a dry coating weight of 5.0 g/m.sup.2. The web could be 
wound up without forming roll wrinkles and the sample obtained could form 
a desired color without fog. The sample had a gas permeability of 400 
seconds. No reduction in color density occurred in the subsequent heat 
resistance test. 
COMATIVE EXAMPLE 4 
A microcapsule coating solution prepared as in Comparative Example 3 was 
applied to the uncoated surface of the color developer-coated paper B at a 
speed of 500 m/min to give a dry coating weight of 5.0 g/m.sup.2. When the 
web was wound up, a roll having wrinkles similar to the twisted pattern of 
a rope was formed. The sample had a gas permeability of 3,000 seconds. No 
reduction in color density occurred in the subsequent heat resistance 
test. 
EXAMPLE 5 
A microcapsule coating solution was prepared as in Example 1 except that 
the microcapsule solution A was replaced by the microcapsule solution C. 
The coating solution was applied to the uncoated surface of the color 
developer-coated paper A at a speed of 500 m/min to give a dry coating 
weight of 5.0 g/m.sup.2. The web could be wound up without forming roll 
wrinkles, and the sample obtained could form a desired color without fog. 
The sample had a gas permeability of 350 seconds. No reduction in color 
density occurred in the subsequent heat resistance test. 
COMATIVE EXAMPLE 5 
A microcapsule coating solution was prepared as in Comparative Example 1 
except that the microcapsule solution A was replaced by the microcapsule 
solution C. The coating solution was applied to the uncoated surface of 
the color developer-coated paper A at a speed of 500 m/min to give a dry 
coating weight of 5.0 g/m.sup.2. When the web was wound up, a roll having 
wrinkles similar to the twisted pattern of a rope was formed. The sample 
had a gas permeability of 3,000 seconds. No reduction in color density 
occurred in the subsequent heat resistance test. 
EXAMPLE 6 
A microcapsule coating solution as prepared in Example 5 was applied to the 
uncoated surface of the color developer-coated paper B at a speed of 500 
m/min to give a dry coating weight of 5.0 g/m.sup.2. The web could be 
wound up without forming roll wrinkles, and the sample obtained had a gas 
permeability of 300 seconds. No reduction in color density occurred in the 
subsequent heat resistance test. 
COMATIVE EXAMPLE 6 
A microcapsule coating solution prepared as in Comparative Example 5 was 
applied to the uncoated surface of the color developer-coated paper B at a 
speed of 500 m/min to give a dry coating weight of 5.0 g/m.sup.2. When the 
web was wound up, a roll having wrinkles similar to the twisted pattern of 
a rope was formed. The sample had a gas permeability of 2300 seconds. No 
reduction in color density occurred in the subsequent heat resistance 
test. 
COMATIVE EXAMPLE 7 
To the microcapsule solution C, a protective agent was added, and a 1:1 
mixture of polyvinyl alcohol and oxidized starch was added as a binder in 
10 parts with respect to 100 parts of the solid content of the 
microcapsules, to thereby form a microcapsule coating solution. The 
solution was applied onto the uncoated surface of the color 
developer-coated paper B at a speed of 500 m/min to give a dry coating 
weight of 5.0 g/m.sup.2. The web could be wound up without forming roll 
wrinkles, but the sample obtained formed a color with fog. The sample had 
a gas permeability of 700 seconds. No reduction in color density occurred 
in the subsequent heat resistance test. 
COMATIVE EXAMPLE 8 
To the microcapsule solution C, a protective agent was added, and a 1:1 
mixture of polyvinyl alcohol and oxidized starch was added as a binder in 
60 parts with respect to 100 parts of the solid content of the 
microcapsules. As a surfactant, di-2-ethylhexylsulfosuccinate ester was 
added in 0.03 part with respect to 100 parts of the solid content of the 
microcapsules, to thereby form a microcapsule coating solution. The 
coating solution was applied to the uncoated surface of the color 
developer-coated paper B at a speed of 500 m/min to give a dry coating 
weight of 5.0 g/m.sup.2. The web could be wound up without forming roll 
wrinkles, and the sample obtained formed a desired color without fog. 
Seven sheets of the sample were placed respectively under plain sheets, 
set on a typewriter (olympia SGE/50) and struck with a light key stroke. 
The 7th copy was illegible. The sample had a gas permeability of 900 
seconds and no reduction in color density occurred in the subsequent heat 
resistance test. 
COMATIVE EXAMPLE 9 
To the microcapsule solution C, a protective agent was added, and a 1:1 
mixture of polyvinyl alcohol and oxidized starch was added as a binder in 
30 parts with respect to 100 parts of the solid content of the 
microcapsules. As a surfactant, sodium dodecylbenzenesulfonate was added 
in 0.03 part with respect to 100 parts of the solid content of the 
microcapsules, to thereby form a microcapsule coating solution. The 
coating solution was applied to the uncoated surface of the color 
developer-coated paper B at a speed of 500 m/min to give a dry coating 
weight of 5.0 g/m.sup.2. When the web was wound up, roll wrinkles 
resulted. The sample had a gas permeability of 1,800 seconds, and no 
reduction in color density occurred in the subsequent heat resistance 
test. 
EXAMPLE 7 
To the microcapsule solution B, a protective agent was added, and a 1:1 
mixture of polyvinyl alcohol and oxidized starch was added as a binder in 
30 parts with respect to 100 parts of the solid content of the 
microcapsules. As a surfactant, a dihexylsulfosuccinate ester was added in 
0.03 part with respect to 100 parts of the solid content of the 
microcapsules. The resulting coating solution was applied to the uncoated 
surface of the color developer-coated paper A at a speed of 700 m/min to 
give a dry coating weight of 5.0 g/m.sup.2. The web could be wound up 
without forming roll wrinkles, and the sample obtained could form a color 
without fog. The sample had a gas permeability of 350 seconds. No 
reduction in color density occurred in the subsequent heat resistance 
test. 
EXAMPLE 8 
To the microcapsule solution B, a protective agent was added, and a 1:1 
mixture of polyvinyl alcohol and oxidized starch was added as a binder in 
30 parts with respect to 100 parts of the solid content of the 
microcapsules. As a surfactant, a tetramethyl-tetradecasulfosuccinate 
ester was added in 0.03 part with respect to 100 parts of the solid 
content of the microcapsules, to thereby form a microcapsule coating 
solution. The coating solution thus-obtained was applied onto the uncoated 
surface of the color developer-coated paper A at a speed of 700 m/min to 
give a dry coating weight of 5.0 g/m.sup.2. The web could be wound up 
without forming roll wrinkles, and the sample could form a desired color 
without fog. The sample had a gas permeability of 400 seconds, and no 
reduction in color density was observed in the subsequent heat resistance 
test. 
As shown by the foregoing examples and comparative examples, the 
microcapsule sheet of the present invention has high color density with 
little fog and is adapted to high-speed production. 
For quick reference, the results of the examples and comparative examples 
are listed in Table 1 below. 
TABLE 1 
__________________________________________________________________________ 
Binder 
(in parts) 
per 100 
Parts of Color 
Color the Solid Gas Heat 
Fog in 
Density 
Developer- Content Perme- 
Resist- 
Color 
after 
Coated 
Capsule 
Surfac- 
of Micro- 
Roll ability 
ance 
Forma- 
Typewriter 
Run No. 
Paper Solution 
tant 
capsules 
Wrinkles 
(sec) Test 
tion 
Key Impact 
__________________________________________________________________________ 
Example 1 
A A A 30 o 700 .DELTA. 
o o 
Comp.Ex.1 
A A -- 30 x 5,000 o o o 
Example 2 
B A A 30 o 500 .DELTA. 
o o 
Comp.Ex.2 
B A -- 30 x 3,500 o o o 
Example 3 
A B A 40 o 500 o o o 
Comp.Ex.3 
A B -- 40 x 4,000 o o o 
Example 4 
B B A 40 o 400 o o o 
Comp.Ex.4 
B B -- 40 x 3,000 o o o 
Example 5 
A C A 34 o 350 o o o 
Comp.Ex.5 
A C -- 34 x 3,000 o o o 
Example 6 
B C A 34 o 300 o o o 
Comp.Ex.6 
B C -- 34 x 2,300 o o o 
Comp.Ex.7 
B C -- 14 o 700 o x o 
Comp.Ex.8 
B C A 64 o 900 o o x 
Comp.Ex.9 
B C B 34 x 1,800 o o o 
Example 7 
A B C 30 o 350 o o o 
Example 8 
A B D 30 o 400 o o o 
__________________________________________________________________________ 
In Table 1, the symbols A, B, C and D in the column "surfactant" 
respectively stand for a di-2-ethylhexylsulfosuccinate ester, sodium 
dodecylbenzenesulfonate, dihexylsulfosuccinate ester and 
tetramethyltetradecasulfosuccinate ester. The signs .circle., .DELTA., and 
.times. respectively mean that the sample was good, slightly poor and poor 
in the indicated properties. 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.