Patent GB-1105936-A (GB)
Title: Improvements in or relating to pressure-sensitive recording materials
IPC: B01J13/02
Filed: 1965-05-21
Abstract: Compositions used in pressure-sensitive recording material (see Division D2) comprise a layer of a light-scattering material that can be made transparent by contact with a clarifying agent. Disposed in or next to the layer of light-scattering material are microcapsules containing discrete quantities of a clarifying agent which can be released by the application of pressure.  The microcapsules may be in the light-scattering layer or in a separate layer. The clarifying agent may be castor oil, soyabean oil, linseed oil, dibutyl phthalate, dioctyl phthalate or tricresyl phosphate.  The light-scattering layer may be of nitrocellulose, ethylcellulose, cellulose acetate, acetate-butyrate or propionate, polyvinyl chloride, poly(vinyl chloride/vinyl acetate), polyvinylidene chloride, poly(vinyl chloride/vinylidene chloride), a polyalkyl acrylate or methacrylate, polystyrene, poly(styrene/butadiene), poly(styrene/acrylonitrile), polyvinyl butyral, a linear polyester or polycarbonate, and is deposited from solution under conditions such that it precipitates out during the later stages of drying.  This may be done by using as solvent a mixtur of a low-boiling solvent and a higher-boiling non-solvent, or by drying a solution in a water-miscible solvent, e.g. acetone, methanol or ethanol, in a current of humid air, or by dissolving the material in an organic solvent not miscible with water and adding water and a surface-active agent to form a dispersion.  The light-scattering layer may also contain a small quantity of a metallic soap, pigment, plasticizer or colouring matter.  In the Examples: (1) castor oil is emulsified in a solution of gelatin at 50 DEG  C., aqueous sodium sulphate at the same temperature is stirred in and the mixture then poured into a solution of sodium sulphate at 19 DEG  C., gelatin is coacervated round the oil droplets, the microcapsules are cooled to 5 DEG  C., filtered, washed with water, hardened with aqueous formaldehyde, again filtered, washed and dispersed in water, a coating of this dispersion is applied to a red paper and dried; nitrocellulose, barium stearate, castor oil, acetone and methanol are blended in a ball mill and diluted with more acetone and methanol, this solution is applied to the coated paper and dried in air at 40 DEG  C. and 65% R.H., (2) cellulose acetate butyrate, zinc stearate, dicyclohexyl phthalate, cyclohexane and acetone are blended in a ball mill, applied to a microcapsule-containing layer, dried at 35 DEG  C. in air of 30% R.H., and heated at 75 DEG  C., (3) black paper is coated with a dispersion of microcapsules similar to that of Example 1, but encapsulating a solution of dibutyl phthalate in xylene in place of castor oil; nitrocellulose, barium stearate, castor oil, acetone and methanol are blended in a ball mill, diluted with more acetone and methanol, applied to the microcapsule-containing layer and dried in air at 40 DEG  C. and 70% R.H.; (4) the hardened microcapsules of Example 3 are dispersed in the nitrocellulose solution of that Example, and applied to a black paper subbed with an alkyd resin; (5) the capsule dispersion of Example 3 is applied to a black paper; ethylcellulose, toluene, an emulsifying agent and water are then applied.ALSO:A pressure-sensitive recording material comprises a base material supporting a layer of a light-scattering material that can be made transparent by contact with a clarifying agent. Disposed in or next to the layer of light-scattering material are microcapsules containing discrete quantities of a clarifying agent which can be released by the application of pressure.  The microcapsules may be in the light-scattering layer or in a separate layer between the light-scattering layer and the base.  A thin protective layer may be interposed between the light-scattering and capsule-containing layers.  The clarifying agent may be castor oil, soya-bean oil, linseed oil, dibutyl phthalate, dioctyl phthalate or tricresyl phosphate.  The light-scattering layer may be of nitrocellulose, ethylcellulose, cellulose acetate, acetate-butyrate or propionate, polyvinyl chloride, poly (vinyl chloride/vinyl acetate), polyvinylidene chloride, poly(vinyl chloride/vinylidene chloride), a polyalkyl acrylate or methacrylate, polystyrene, poly(styrene/butadiene), poly/(styrene/acrylonitrile), polyvinyl butyral, a linear polyester or polycarbonate, and is deposited from solution under conditions such that it precipitates out during the later stages of drying.  This may be done by using as solvent a mixture of a low-boiling solvent and a higher-boiling non-solvent, or by drying a solution in a water-miscible solvent, e.g. acetone, methanol or ethanol, in a current of humid air, or by dissolving the material in an organic solvent not miscible with water and adding water and a surface-active agent to form a dispersion.  The base may be a coloured paper, a coloured or transparent film of, e.g. polyethylene terephthalate or metal foil supported on paper or plastics.  The light-scattering layer may also contain a small quantity of a metallic soap, pigment, plasticizer or colouring matter.  In the Examples: (1) castor oil is emulsified in a solution of gelatin at 50 DEG C., aqueous sodium sulphate at the same temperature is stirred in and the mixture then poured into a solution of sodium sulphate at 19 DEG C gelatin is coacervated round the oil droplets, the microcapsules are cooled at 5 DEG C., filtered, washed with water, hardened with aqueous formaldehyde, again filtered, washed and dispersed in water a coating of this dispersion is applied to a red paper and dried; nitrocellulose, barium stearate, castor oil, acetone and methanol are blended in a ball mill and diluted with more acetone and methanol, this solution is applied to the coated paper and dried in air at 40 DEG C and 65% R.H; (2) polyethylene terephthalate film is subbed with a linear polyester resin soluble in methylene chloride, coated with the microcapsule dispersion of Example 1 and dried; cellulose acetate butyrate, zinc stearate, dicyclohexyl phthalate, cyclohexane and acetone are blended in a ball mill, applied to the microcapsule-containing layer, dried at 35 DEG C in air of 30% RH, and heated at 75 DEG C; a trace made by a sapphire needle in clear; (3) black paper is coated with a dispersion of microcapsules similar to that of Example 1, but encapsulating a solution of dibutyl phthalate in xylene in place of castor oil; nitrocellulose, barium stearate, castor oil, acetone and methanol are blended in a ball mill, diluted with more acetone and methanol, applied to the microcapsule-containing layer and dried in air at 40 DEG C and 70% R.H; the back of the sheet is treated with water to remove curl; (4) the hardened microcapsules of Example 3 are dispersed in the nitrocellulose solution of that Example, and applied to a black paper subbed with an alkyd resin; (5) the capsule dispersion of Example 3 is applied to a black paper; ethylcellulose, toluene, an emulsifying agent and water are then applied.