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
  • B41M5/132—Chemical colour-forming components; Additives or binders therefor
  • B41M5/155—Colour-developing components, e.g. acidic compounds; Additives or binders therefor; Layers containing such colour-developing components, additives or binders

Definitions

• This invention relates to pressure-sensitive record systems comprising a donor composition and an acceptor composition, said compositions reacting on pressure contact to develop a coloured image or print, and more particularly to such systems in which improved properties have been obtained by the use of combinations of specific donor and acceptor compositions.
• a pressure-sensitive record system is an image- or print-forming system which develops a coloured image on reactive contact between a donor composition and an acceptor composition.
• the record system may be a so-called separate or transfer system having separate donor and acceptor sides.
• the donor side is usually formed by a so-called CB-sheet, obtained by coating microcapsules enclosing a chromogenic solution in the form of an electron-donating colourless dye in a high-boiling point solvent, on a sheet-like substrate, while the acceptor composition is generally in the form of a so-called CF-sheet obtained by coating an electron-accepting solid acid material (which is often referred to as a "colour developer”) toqether with other auxiliary materials also onto a sheet-like substrate.
• colour developer electron-accepting solid acid material
• both a CB- and a CF-sheet are brought into contiguous relationship at their respective coated surfaces and pressure is applied to the manifold set so produced by means of a pen, typewriter, impact printer or like means, in order to generate a coloured image or print, the microcapsules which are provided at the donor side are ruptured at each area to which pressure has been.applied, thereby releasing the solution of the electron-donating colourless dye. The solution so released is then transferred to the acceptor side, where it comes into reactive contact with the colour developer of the acceptor composition.
• more than two record sheets may be combined to form a manifold set by interposing between a CB- and a CF-sheet, one or more so-called CFB-sheets, each obtained by coating a donor composition onto one surface of a sheet and an acceptor composition onto the other surface thereof, and the sheets being arranged in the manifold set so that each donor composition coating is in contiguous relationship with an acceptor composition coating.
• Examples of electron-donating colourless dyes which can be used as chromogenic materials in the donor compositions of pressure sensitive record systems include dyes of the triphenylmethane lactone type typified by 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (so-called Crystal Violet Lactone); fluoran-type dyes typified by 3-diethylamino-6-methyl-7-anilinofluoran; dyes of the acylated leucothiazine type; dyes of the acylated leucooxazine type; lactams and spiropyrans. All of these dyes may be employed in the present invention.
• high-boiling point solvents which may be used in the donor compositions include aromatic hydrocarbons, such as alkyl-naphthalenes, typified by diisopropyl-haphthalene, diarylalkanes, typified by 1-phenyl-l-xylylethane; alkyl biphenyls typified by isopropyl biphenyl; triaryldimethanes; alkylbenzenes; benzylnaphthalenes; diarylalkylenes; arylindanes; carboxylic acid esters typified by dibutyl phthalate and dioctyl maleate; phosphoric acid esters typified by tricresyl phosphate; naturally-occurring animal and vegetable oils and fats, such as castor oil, soybean oil, and cotton oil; and natural high-boiling point fractions, consisting of aliphatic hydrocarbons, such as mineral oil.
• An aromatic hydrocarbon solvent is, however,
• colour developers Many electron-accepting solid acid materials have been previously proposed for use as colour developers. These include naturally-occurring minerals, such as acid clay, attapulgite, clay and the like, and activated clay obtained by treating an acid clay (a clay mineral of the montmorrilonite series) with a mineral acid, as inorganic colour developers; and a variety of phenolic compounds, novolak phenolic resins, multivalent metal salts of aromatic carboxylic acids and the like as colour developers of the organic acid type.
• naturally-occurring minerals such as acid clay, attapulgite, clay and the like
• activated clay obtained by treating an acid clay (a clay mineral of the montmorrilonite series) with a mineral acid, as inorganic colour developers
• phenolic compounds, novolak phenolic resins, multivalent metal salts of aromatic carboxylic acids and the like as colour developers of the organic acid type.
• the above-mentioned inorganic colour developers have serious disadvantages in that the developed colour images or prints lack stability (i.e., are susceptible to fading of the colour on exposure to light and may vanish completely if exposed to water or steam) and their colour developing capability is reduced, due to the adsorption of substances contained in the air thereon, in other words, they have a reduced storage life.
• the colour developers of the organic acid type also have disadvantages in that the rate of colour development is slow and developed colour images or prints may disappear when brought into contact with plasticizers for plastics materials or with oils, and unprinted background areas of the sheet material undergo discolouration when exposed to sunlight or to oxidizing gases present in the atmosphere, such as nitrogen oxides.
• a pressure-sensitive record system which comprises a donor composition and an acceptor composition which react under pressure contact to develop a colour image or print, characterised in that said donor composition comprises microcapsules containing a solution of an electron-donating colourless dye in a high-boiling point solvent, and said acceptor composition comprises an activated clay in combination with a para-hydroxybenzoic acid ester of the formula (1) :- where R is an aryl or aralkyl group.
• the electron-donating colourless dye used as a chromogenic material may be any of the examples listed above, or a mixture thereof.
• the high-boiling point solvent used which preferably has a boiling point greater than 200°C, is preferably an aromatic hydrocarbon, and may be any of the aromatic hydrocarbon type solvents listed above. (The use of the word "colourless" herein with reference to the electron-donating dye is not intended to exclude the possibility that the dye may itself be coloured, provided that the colour developed in contact with the colour developer is in strong contrast to the original colour of the dye).
• the pressure-sensitive record systems of the invention (which may be either separate transfer record systems or self-contained systems) have been found to have significantly improved properties as compared with known record systems, as regards the speed of colour development, fastness of the coloured images or prints produced, particularly as regards stability to exposure to light, water or moisture, and to plasticizers and oxidizing gases contained in the atmosphere, and stability of the unprinted background areas of the sheet, i.e. resistance to discolouration of these areas on exposure to sunlight or oxidizing gases.
• the activated clay suitable for use in the present invention, may be obtained by subjecting acid clay (i.e. a clay mineral of the montmorrilonite series) to a mild to medium treatment with a mineral acid, so as to extract and remove therefrom acid-soluble cations, such as iron, magnesium, calcium and aluminium, to a certain extent.
• acid clay i.e. a clay mineral of the montmorrilonite series
• the activated clay is a silicic acid.anhydride still containing such cations, at substantial concentration levels.
• the activated clay has acid values pKa ⁇ -3.0, -3.0 ⁇ pKa ⁇ +0.8, and +0.8 ⁇ pKa ⁇ +4.8. (These acid values are associated with the presence of cations of mixed metals).
• an electron-donating colourless dye such as Crystal Violet Lactone or Benzoyl Leuco Methylene Blue
• activated clay produced from a domestic acid clay as starting material, e.g. that produced and sold under the Trade Mark "Shilton” by Mizusawa Chemical Industries Ltd.
• para-hydroxybenzoic acid esters which may be used together with the activated clay, include the following compounds: Benzyl p-hydroxybenzoate o-Methylbenzyl p-hydroxybenzoate p-Methylbenzyl p-hydroxybenzoate p-Chlorobenzyl p-hydroxybenzoate Phenyl p-hydroxybenzoate p-Methylphenyl p-hydroxybenzoate
• para-hydroxybenzoates may be synthesized by esterification reactions between p-hydroxybenzoic acid and the corresponding alcohols and are available commercially from various sources.
• the microcapsules provided at the donor side may be prepared by any known micro-encapsulation technique. It is possible to use, for example, the coacervation method relying on a combination of gelatin and high molecular anions; the in-situ polymerization method making use of the polycondensation reaction between urea and formaldehyde or melamine and formaldehyde; or the interfacial polymerization method making use of the interfacial polymerization reaction between an activated hydrogen compound and an isocyanate compound.
• the present invention is not, of course, limited to the use of any specific micro-encapsulation method.
• Japanese Patent Specification No. 16969/1975 discloses, as a colour-developing paper for pressure-sensitive copying (CF-paper), a paper sheet coated with an alkyl p- or o-hydroxybenzoate and activated clay.
• CF-paper colour-developing paper for pressure-sensitive copying
• the matching CB-sheet there is used a CB-sheet obtained by dissolving Crystal Violet Lactone and Benzoyl Leuco Methylene Blue in a partially-hydrogenated triphenyl (which is believed to be a partially-hydrogenated triphenyl, the aromatic nature of which has been lost to a considerable extent), forming the thus-obtained solution into microcapsules and then coating the microcapsules onto a paper sheet.
• Japanese Patent Application No. 33209/1973 discloses the use of acid clay and p-phenylphenol or p,p'-isopropylidene diphenol (usually referred to as bisphenol A) in combination as a colour developer.
• bisphenol A p-phenylphenol or p,p'-isopropylidene diphenol
• the present inventors have found that a CF-sheet even using bisphenol A, let alone p-phenylphenol, in combination with activated clay developed discolouration of unprinted background areas on exposure to light (e.g. yellowing of white background areas) and, especially, severe discolouration of such background areas on exposure to oxidizing gases generally present in the atmosphere (confirmed by the results of an NO gas exposure test).
• Such a CF-sheet is thus impractical and unsuitable for actual use.
• CF-sheet three other types were also prepared in the same manner, except that in one sheet (Sample A) benzyl p-hydroxybenzoate was not used at all (i.e. activated clay was used as a sole colour developer), in another sheet (Sample C),methyl p-hydroxybenzoate was used in place of benzyl p-hydroxybenzoate, and in a third sheet (Sample D), bisphenol A was also used in the necessary amount.
• the corresponding CB-sheets were each prepared by adding 25 parts of wheat starch and 150 parts of a 10% aqueous solution of oxidized starch to 100 parts (in terms of dry weight) of microcapsules having a melamine resin base which had been obtained by micro-encapsulating, in accordance with the teachings of U.S. Patent Specification No. 4,233,178, a solution of an electron-donating colourless dye consisting of: in a high-boiling point solvent of the aromatic hydrocarbon group, and then coating the composition so obtained onto a base paper sheet of 40 g/m 2 to give a dry coating weight of 5 g/m 2 .
• the combination of specific donor and acceptor compositions according to this invention has been found to provide an excellent pressure-sensitive record system which features a fast rate of colour development, high stability to fading of the colour images produced, substantially no discolouration of the CF-sheets (e.g. yellowing of white sheets) and a long shelf life.
• the combination of donor and acceptor compositions of the present invention may equally be applied to self-contained record systems.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Color Printing (AREA)

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Cited By (8)

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Citations (4)

• 1982
  • 1982-02-13 JP JP57021825A patent/JPS58138689A/ja active Pending
• 1983
  • 1983-02-11 DE DE8383300687T patent/DE3360745D1/de not_active Expired
  • 1983-02-11 EP EP19830300687 patent/EP0086636B1/de not_active Expired

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