Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/124—Duplicating or marking methods; Sheet materials for use therein using pressure to make a masked colour visible, e.g. to make a coloured support visible, to create an opaque or transparent pattern, or to form colour by uniting colour-forming components
  • B41M5/1243—Inert particulate additives, e.g. protective stilt materials

Definitions

• This invention relates to a self-contained pressure sensitive recording paper of novel construction.
• the pressure sensitive recording paper system generally comprises a combination of a top sheet coated with microcapsules enwrapping a colorless dye as color former and an undersheet coated on one side with a color developer which is an acidic substance such as, for example, activated acid clay, a phenolic resin, or a salicylic acid derivative or its metal salt.
• a color developer which is an acidic substance such as, for example, activated acid clay, a phenolic resin, or a salicylic acid derivative or its metal salt.
• a self-contained pressure sensitive recording paper comprising a supporting sheet and, coated on one side, two consecutive coatings of a color former-containing microcapsule layer and a color developer layer.
• This recording paper can be printed with letters by means of a typewriter without using an inked ribbon, or can provide a copy by writing or printing on a superposed ordinary paper sheet.
• Japanese Patent Application Laid-open No. 6,207/72 has disclosed an improved coater for applying two coating layers in manufacturing the said self-contained pressure sensitive recording paper.
• a self-contained pressure sensitive recording paper of the single layer type applied with ' a single coating composition containing the color former and the color developer has been disclosed in Japanese Patent Publication No. 16,096/72.
• this type of recording paper is improved in regard to spontaneous background staining (self-staining)
• the present inventors found that said recording paper has disadvantages of marked yellowing and insufficient density of the developed image color, because a hydrophilic film- forming polymeric substance impregnated with a phenol- aldehyde resin is used as the capsule wall material.
• Japanese Patent Application Laid-open No. 6,413/75 has proposed the addition of amines to alleviate the self-staining. Although effective to some degree, the addition of an amine in an amount required for the complete prevention of self-staining brings about an interference with the color-forming reaction and also a yellowing tendency of the sheet surface.
• a method is described in Japanese Patent Publication No. 10,780/72, in which the coating composition is incorporated into the paper web during web formation.
• the color forming reaction takes place within the paper sheet, resulting in insufficient density of the image color.
• the disclosed method is not suitable for encapsulating oil-soluble acidic color developers such as phenolic resins, salicylic acid derivatives or metal salts thereof, because active hydrogen atoms of these color developers react with isocyanate compounds used in forming the capsule membrane.
• oil-soluble acidic color developers such as phenolic resins, salicylic acid derivatives or metal salts thereof
• This invention provides a self-contained pressure sensitive recording paper of the single coating layer type which has novel construction, is resistant to spontaneous background staining and has an excellent color forming ability.
• the coating layer of the present recording paper is formed by the application of a mixture of the following five components onto a substrate sheet: (1) a colorless dye as color former, (2) a phenolic resin, a salicylic acid derivative or its metal salt as color developer, (3) starch particles, (4) a pigment, and (5) a binder; either or each of said color former (1) and color developer (2) being encapsulated in liquid form with the wall membrane material of a melamin- formaldehyde resin to prevent self-staining and to improve color-forming quality.
• the color former (1) or the color developer (2) In encapsulating the color former (1) or the color developer (2), it is used generally in the form of dispersion or solution in an oily substance, except for the case of a phenolic resin (color developer) if it is liquid at ambient temperatures.
• the color former used is a known electron donating leuco dye such as typically crystal violet lactone or a fluorane derivative.
• the color developer used is typically a substituted phenol-formaldehyde resin described in Japanese Patent Publication No ⁇ 20,144/67 and a polyvalent metal salt of a salicylic acid derivative described in Japanese Patent Publication No. 25,174/76.
• Examples of desirable color developers include p-phenylphenol- formaldehyde resin, 3,5-di-tert-butylsalicylic acid or zinc salt thereof, and 3,5-di(dimethylbenzyl)salicylic acid or zinc salt thereof.
• the high-boiling oily substances for use in combination with a color former or color developer include "SAS” (a diarylethane type oil produced by Nippon Petrochemical Co.) and "KMC” (a dialkylnaphthalene type oil produced by Kureha Chemical Industry Co.), both of which have been used in customary carbonless copy paper sheets. If necessary, these oils can be admixed with known oils of the ester type or aliphatic type.
• capsule membrane The properties of capsule membrane are important particularly when a self-contained pressure sensitive recording paper is to be prepared with a single coating composition. It is necessary to encapsulate at least one of the color former and color developer with a wall material comprising substantially a melamine-formaldehyde resin. A satisfactory self-contained pressure sensitive recording paper is not obtained if encapsulation is performed by conventionally used or proposed coacervation of gelatin or interfacial polymerization of a polyamide, presumably because of unsatisfactory properties of the capsule wall.
• One of the features of this invention is the amount of starch particles in the coating layer.
• the amount of starch should be 1.5 times or more the weight of capsules in terms of solids.
• granular starch in carbonless copy sheets has been known (Japanese Patent Publication Nos. 1,178/72 and 33,204/73), it is used, according to the description, in an amount of at most 50% of the weight of capsules in the capsule-containing coatings of a top sheet and an intermediate sheet.
• starch is used in such an amount, the resulting copy sheet is still susceptible to self-staining or causes smudging on other paper sheets.
• a suitable size of starch particles is in the range from about 10 to about 30
• the pigments use is made of those well known to the art such as clays, kaolin, calcined clays, calcium carbonate, titanium oxide, zinc oxide, and plastic pigments.
• the pigment is used to improve the brightness of paper, printability and color forming performance.
• the amount to be used is preferably in the range of from about 10 to about 100 parts for 100 parts of capsules, depending on the type of pigment used.
• binders used in this invention are the same as those generally used in usual copying paper, such as hydroxyethylcellulose, modified starches, carboxymethylcellulose, acrylic latices, SBR latices, and polyvinyl alcohol.
• the microcapsules with the wall phase of a melamine-formaldehyde resin are most suitable not only for entrapping the color developer for use in the above-said self-contained pressure sensitive recording paper of the-single coating type having each of the color-forming reactants encapsulated, but also for entrapping either of the color former or the color developer, preferably the latter, in preparing a self-contained pressure sensitive recording paper of the single coating type having either one of the reactants encapsulated.
• a self-contained pressure sensitive recording paper of the single coating type having one of the reactants encapsulated is most preferable in view of not only production cost but also product quality, particularly the initial speed of image color formation.
• commercialization of such a type of recording paper has been hindered by lack of proper micrcencapsulacion techniques. For instance, if microcapsules having the wall phase of gelatin as major component produced by complex coacervation are used, coloration of the recording paper will occur all over the coated side.
• microcapsules having the wall phase of urea-formaldehyde resin as described in Japanese Patent Application Laid-open No.
• the present recording paper it is possible to use, as usual, other known additives such as, for example, ultraviolet absorbers, antioxidants, dispersants, water-proofing agents, lubricants, defoamers, etc.
• the coating composition is applied by known methods such as air-knife coating, roll coating, blade coating, etc.
• Microencapsulation of a color developer was carried out in a manner similar to that in Example 1 using an internal phase oil comprising 20 parts of zinc 3,5-di-tert-butylsalicylate, 40 parts of KMC-113 (an oil produced by Kureha Chemical Industry Co.) and 40 parts of a high-boiling aliphatic hydrocarbon oil (No. 3 ink solvent).
• the resulting microcapsule.s had an average particle size of 3.5 ⁇ .
• Microencapsulation of a color former was carried out in a manner similar to that in Example 1 using an internal phase oll comprising 5 parts of crystal violet lactone (CVL) and 95 parts of KMC-113 to obtain microencapsulated color former having an average particle size of 4 ⁇ .
• an internal phase oll comprising 5 parts of crystal violet lactone (CVL) and 95 parts of KMC-113 to obtain microencapsulated color former having an average particle size of 4 ⁇ .
• a uniform fluid composition was prepared by thorough mixing of the following components:
• the above composition was applied by means of a metering bar onto a paper sheet to prepare a self-contained pressure sensitive sheet of single coating layer type having one of the color-forming reactants microencapsulated.
• the application rate was 6 g/m 2 .
• the above 20-% CVL dispersion was an aqueous dispersion of finely ground CVL crystals, said CVL being in solid state and not encapsulated.
• a coating composition of the following formulation was prepared.
• the above coating composition was applied by means of an air-knife coater onto a sheet of fine paper at an application rate of 7.5 g/m2 in terms of solids to prepare a self-contained recording sheet of the single coating layer type having color-forming reactants each encapsulated.
• This white self-conrained pressure sensitive recording sheet showed no self-staining tendency. Upon impression by means of a typewriter, there was instantly formed a sharp image, bright deep blue in color.

Applications Claiming Priority (2)

Publications (2)

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Citations (4)

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• 1979
  • 1979-03-28 JP JP54036688A patent/JPS5833116B2/ja not_active Expired
• 1980
  • 1980-03-19 EP EP19800300838 patent/EP0017386B1/de not_active Expired
  • 1980-03-19 DE DE8080300838T patent/DE3069782D1/de not_active Expired

Patent Citations (6)

Non-Patent Citations (1)

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