Pressure-sensitive color-developer material

Abstract

 A color-developer material for use in pressure-sensitive recording is disclosed which is capable of developing a colored image upon reactive contact with substantially colorless color-formers, and comprises a salicylic acid derivative and/or a multivalent metal salt thereof, dispersed in a petroleum resin. This combination provides enhanced intensity of the developed image and increased speed of the imaging performance.

Description

[0001] This invention relates to pressure-sensitive color-developer material, and particularly to such material for use in the form of a sheet capable of developing a colored image on reactive contact with a substantially colorless organic chromogenic material.

[0002] The art to which this invention pertains is commonly known as "carbonless copying technology" in which an electron-donative, substantially colorless, organic material (hereinafter referred to as a color-former) is brought into reactive contact with an electron-acceptive acidic material (hereinafter referred to as a color-developer) to produce a colored image corresponding to the pattern of the areas to which pressure is applied as by pen, typewriter or the like. It is this color-developer material with which the invention is particularly concerned.

[0003] Pressure-sensitive record materials are well known per se as disclosed for example in U.S. Patent Nos. 2,505,470 and 2,505,489.

[0004] Typical known materials as the color-developer for pressure-sensitive record paper includes solid acids such as active clay, acid clay, attapulgite and the like. However, record paper using these clay-type color-developer materials often produce a colored image which is unstable particularly to light and moisture.

[0005] Further color-developer materials include novolak-type phenol-formaldehyde resins and salicylic acid derivatives and/or their multivalent metal salts. These salts per se possess a color-developing ability, and salicylic acid derivatives can also serve as the color-developer when combined with oxides, hydroxides or carbonates of certain multivalent metals as disclosed in Japanese Patent Publication No. 52-20883. Such color-developer materials have been found not quite satisfactory in respect of the intensity (density) of a developed image, and to improve the image intensity, it has been proposed to combine the said color-developer materials with polystyrene resin, xylene resin or the like as disclosed in Japanese Patent Publication No. 55-1195. This proposal however has failed to contribute to the speed at which the imaging is performed.

[0006] With the foregoing drawbacks of the prior art in view, the present invention provides an electron-acceptive color-developer composition reactive with electron-donative color-formers, said color-developer composition essentially comprising a salicylic acid derivative and/or its multivalent metal salt in the form of fine particles uniformly dispersed in a petroleum resin.

[0007] In the practice of the invention, the color-developer composition is applied to a substrate such as paper web by a binder and, if desired, in the presence of additives such as clays and dispersants to improve the receptivity of the color former containing oil and the properties of the resulting liquid coating formulation.

[0008] The salicylic acid derivatives used in the inventim include those in which the benzene ring of the salicylic acid contains from 1 to 4 substituent groups, such as alkyl, cycloalkyl, aralkyl, aryl and halogen groups. Such salicylic acid derivativs can all form salts with multivalent metals such as zinc, magnesium, aluminum, titanium, calcium, cobalt, nickel, manganese, tin and copper. Alternatively, it is possible to use such derivatives in their acid form in combination with metal compounds.

[0009] The term "petroleum resin" as used herein means a thermoplastic resin having a molecular weight of 2,000 or less obtained by subjecting naphtha to pyrolysis, separating C₂-C₄ olefins such as ethylene and propylene and then polymerizing the remaining C_S-C₉ olefins as a mixture. Examples of such petroleum resins include aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, hydrogenated alicyclic hydrocarbon resins and aromatic hydrocarbon resins.

[0010] Specific examples of the aliphatic hydrocarbon resins are represented by the structural formula:

where n is a positive integer.

[0011] Specific examples of the alicyclic hydrocarbon resins are represented by the structural formula:

where n is a positive integer.

[0012] The above alicyclic hydrocarbon resins may be at least partially hydrogenated to provide hydrogenated alicyclic hydrocarbon resins.

[0013] A specific example of the aromatic hydrocarbon resins is "Toho High Resin" (trade name; product of Toho Petroleum Resin Co., Ltd.).

[0014] It has now been found that the above petroleum resins are conducive to increased color-developing or imaging efficiency beyond what is achieved by the organic polymeric materials disclosed in Japanese Patent Publication 55-1195.

[0015] There may be considered several methods for producing a particulate mixture of salicylic acid derivatives and/or their multivalent metal salts and petroleum resins according to the invention.

[0016] One such method comprises heating the petroleum resin to melt it, dissolving or dispersing therein the salicylic acid derivative (and/or its multivalent metal salt) and grinding the mixture upon cooling. Alternatively, the petroleum resin may be dissolved, with heat if necessary, in an organic solvent, followed by the dissolving or dispersing of the salicylic acid derivative (and/or its multivalent metal salt), the resulting material being immediately available as a starting color-developer ink, or being comminuted after the solvent is stripped off.

[0017] It has now been found that in order to achieve most satisfactory results, the amount of salicylic acid derivative (and/or its multivalent metal salt) should be in the range of 10% - 90% by weight of the petroleum resin.

[0018] It is believed that the salicylic acid derivative and/or its multivalent metal salt is rendered substantially amorphous in the petroleum resin and because of this, it is easily soluble in and highly reactive with co-reactive color-formers. Although it is not exactly known, it may be that the fact that the petroleum oil used in the invention is structurally different and a complex mixture of organic high molecular compounds, that provides surprisingly high imaging efficiency.

[0019] The invention will be further described by way of the following examples in which all parts are by weight.

Example 1

[0020] 50 Parts of Marucarez R-100B (trade name for an aliphatic petroleum resin produced by Maruzen Petrochemical Co., Ltd.) were heated to melting at ₁₅₀°C, to which 20 parts of zinc 3,5-di-tert-butylsalicylate were added. The resultant mixture was stirred thoroughly to disperse the salicylate in the melt. After cooling and solidifying, the mixture was ground in a mortar. The resultant powder was dispersed in 280 parts of a 1% aqueous solution of polyvinyl alcohol. The dispersion was finely comminuted for 2 days in a ball mill. The comminuted particles were mixed with 30 parts of calcium carbonate, 10 parts of a 5% aqueous solution of sodium pyrophosphate, 3.8 parts of 40% aqueous solution of sodium polyacrylate and 65 parts of 48% SBR latex, thereby providing a coating composition. The coating composition was applied to a high-quality paper web of 40 g/m² to give a dry coat weight of 4 g/m² and dried at 105 C to obtain color-developer sheets.

Example 2

[0021] The procedures of Example 1 were followed except that Arucon P90 (trade name for a hydrogenated alicyclic petroleum resin produced by Arakawa Chemical Co., Ltd.) was used in lieu of the aliphatic petroleum resin of Example 1.

Example 3

[0022] The procedures of Example 1 were followed except that zinc 3-phenylsalicylate was used in place of zinc 3,5-di-tert-butylsalicylate of Example 1.

Example 4

[0023] The procedures of Example 1 were followed except that zinc 3-phenylsalicylate and Arucon P90 were used in place of zinc 3,5-di-tert-butylsalicylate and aliphatic petroleum resin, respectively.

Example 5

[0024] The procedures of Example 1 were followed except that 18 parts of 3,5-di-tert-butylsalicylate and 6 parts of zinc oxide were used in place of 20 parts of zinc 3,5-di-tert-butylsalicylate.

Comparison Example 1

[0025] 20 parts of zinc 3,5-di-tert-butylsalicylate were dispersed in 280 parts of a 1% aqueous solution of polyvinyl alcohol, followed by comminution for 2 days in a ball mill. 80 parts of calcium carbonate, 10 parts of 5% sodium pyrophosphate, 3.8 parts of 40% sodium polyacrylate and 65 parts of 48% SBR latex were added to make a coating composition. The procedures of Example 1 were followed in producing color-developer sheets.

Comparison Example 2

[0026] The procedures of Example 1 were followed except that Picolastic A-75 (trade name for polystyrene produced by Exxon Corporation) was used in place of aliphatic petroleum resin.

Comparison Example 3

[0027] The procedures of Example 1 were followed except that Nicanol S-100 (trade name for xylene resin produced by Mitsubishi Gas Chemical Co., Inc.) was used in place of aliphatic petroleum resin.

Comparison Example 4

[0028] The procedures of Comparison Example 1 were followed except that zinc 3-phenylsalicylate was used in place of zinc 3,5-di-tert-butylsalicylate.

Comparison Example 5

[0029] The procedures of Example 3 were followed except that Picolastic A-75 was used in place of aliphatic petroleum resin.

Comparison Example 6

[0030] The procedures of Example 3 were followed except that Nicanol S-100 was used in place of aliphatic petroleum resin.

Comparison Example 7

[0031] The procedures of comparison Example 1 were followed except that 18 parts of 3,5-di-tert-butylsalicylic acid and 6 parts of zinc oxide were used in place of 20 parts of zinc 3,5-di-tert-butylsalicylate.

Comparison Example 8

[0032] The procedures of Example 5 were followed except that Picolastic A-75 was used in place of aliphatic petroleum resin.

[0033] In each of the above Examples and Comparison Examples, the coat weight of zinc 3,5-di-tert-butylsalicylate and of zinc 3-phenylsalicylate was 0.59 g/_m², while the coat weight of 3,5-di-tert-butylsalicy- late was 0.52 g/m .

[0034] Commercial CB-sheets of Mitsubishi-NCR paper were superposed on the color-developer sheets of the Examples and Comparison Examples with respective coated sides face to face. The combined sheets were calendered to develop entire surface coloration.

[0035] Table 1 shows the intensities of colored images produced 1 minute and 24 hours respectively after passage through calender rolls at a nip pressure of 290 kg/cm .

Claims

1. A pressure-sensitive color-developer material characterised in that it comprises a salicylic acid derivative and/or a multivalent metal salt thereof, finely dispersed in a petroleum resin.

2. A pressure-sensitive color-developer material as claimed in Claim 1, characterised in that the benzene ring of said salicylic acid derivative contains from 1 to 4 substituents.

3. A pressure-sensitive color-developer material as claimed in Claim 2, characterised in that the or each said substituent is selected from cycloalkyl, aralkyl, and aryl groups and halogen - atoms.

4. A pressure-sensitive color-developer material as claimed in any one of Claims 1 to 3, characterised in that the multivalent metal of said multivalent metal salt is selected from zinc, magnesium, aluminum, titanium, calcium, cobalt, nickel, manganese, tin and copper.

5. A pressure-sensitive color-developer material as claimed in any one of Claims 1 to 4, characterised in that said petroleum resin is a thermoplastic resin having a molecular weight of less than 2,000.

6. A pressure-sensitive color-developer as claimed in Claim 5, characterised in that said resin is an aliphatic hydrocarbon resin, alicyclic hydrocarbon resin, or aromatic hydrocarbon resin.

7. A pressure-sensitive color-developer material as claimed in any one of the preceding Claims, characterised in that said derivative and/or the multivalent metal salt thereof is present in an amount of 10% to 90% by weight of said petroleum resin.