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United States Patent 3,837,889
Hughes ,   et al. September 24, 1974

COLOUR FORMERS

Abstract

Colourless colour formers which are compounds characterised by the general formula: ##SPC1## Wherein R.sup.1, R.sup.2 and R.sup.3 each independently represents hydrogen, an optionally substituted alkyl radical having from one to five carbon atoms or forms part of a heterocyclic ring containing the attached nitrogen atom; R.sup.4 represents a halogen atom or an alkyl, aryl, aralkyl, alkoxy, nitro, optionally substituted amino, acyl, carboxy, cyano or sulphamyl radical; n represents an integer of from 0 to 4; A represents an optionally substituted aromatic ring the points of attachment being at two pairs of ortho positions; Y represents a direct link, optionally substituted methylene, oxygen, sulphur or a group of the formula --NR.sup.6 -- wherein R.sup.6 denotes hydrogen or an optionally substituted alkyl, aryl or aralkyl radical; and Z represents an optionally substituted divalent organic radical such that a five-or six-membered ring is formed with Y, --NR.sup.3 -- and A.


Inventors: Hughes; Nigel (Blackley, Manchester, EN), Renfrew; Andrew Hunter Morris (Blackley, Manchester, EN)
Assignee: Wiggins Teape Limited (London, EN)
Appl. No.: 05/333,347
Filed: February 16, 1973


Foreign Application Priority Data

Feb 21, 1972 [GB] 7848/72

Current U.S. Class: 503/222 ; 546/15; 546/18
Current International Class: B41M 5/145 (20060101); B41M 5/132 (20060101); C09B 11/26 (20060101); C09B 11/00 (20060101); B41m 005/22 ()
Field of Search: 117/36.2,36.8 260/335,279R

References Cited

U.S. Patent Documents
3501331 March 1970 Kimura et al.
3540912 November 1970 Lim
3649649 March 1972 Orita et al.
3725416 April 1973 Yamamoto
3746562 July 1973 Lin
Primary Examiner: Sofocleous; Michael
Attorney, Agent or Firm: Burns, Doane, Swecker & Mathis

Claims



We claim:

1. A pressure sensitive copying paper comprising a paper base carrying in encapsulated form a colour former of the general formula ##SPC14##

wherein R.sup.1, R.sup.2 and R.sup.3 each independently represents hydrogen, an optionally substituted alkyl radical having from one to five carbon atoms or forms part of a heterocyclic ring containing the attached nitrogen atom; R.sup.4 represents a halogen atom or an alkyl, aryl, aralkyl, alkoxy, nitro, optionally substituted amino, acyl, carboxy, cyano or sulphamyl radical; n represents an integer of from 0 to 4; A represents an optionally substituted aromatic ring the points of attachment being at two pairs of ortho positions; Y represents a direct link, optionally substituted methylene, oxygen, sulphur or a group of the formula --NR.sup.6 -- wherein R.sup.6 denotes hydrogen or an optionally substituted alkyl, aryl or aralkyl radical; and Z represents an optionally substituted divalent organic radical such that a five- or six-membered ring is formed with Y, --NR.sup.3 -- and A.

2. In combination, a pressure-sensitive copying paper as claimed in claim 1 and a copy sheet comprising a paper base having an active mineral surface coating capable of reacting with the colour former to provide a coloured image.

3. The copying paper of claim 1 wherein n is 0.

4. The copying paper of claim 1 wherein R.sup.4 is chloro.

5. The copying paper of claim 1 wherein Y represents a direct link, optionally substituted methylene, oxygen or sulphur.

6. The copying paper of claim 1 wherein n is 0 and wherein Y represents a direct link, optionally substituted methylene, oxygen or sulphur.
Description



BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to colour formers and more particularly to coulourless colour formers suitable for use in pressure-sensitive copying systems.

2. Description of the Prior Art

In known pressure-sensitive copying systems a colourless colour former, dissolved in a suitable solvent, is brought into contact with an electron-accepting substance whereupon a coloured image in the parent dyestuff is formed.

In one known system a sheet of pressure-sensitive copying paper comprising a paper base carrying the colour former in encapsulated form is placed in contact with a copy sheet comprising a paper base having an active mineral surface coating, for example a surface coating of a so-called acid clay. When local pressure is applied to the sheets by means of, for example, hand-writing or typewriting, the capsules on the pressed portions are broken and the colour former comes into contact with the active mineral on the copy sheet and a coloured image of the original wrting is formed on the copy sheet.

Various colour formers for use in such systems are known, but a difficulty has always been that if a dark image, for example a black image, is required then a combination of different colour formers has been required. The use of combinations of colour formers can lead to difficulties in production and also difficulties in providing a copy sheet having an active surface able to react as necessary with the colour formers used.

Clearly it would be desirable to use a single colour former to provide a dark, for example a black image.

SUMMARY OF THE INVENTION

According to the invention there are provided colourless colour formers which are compounds of the general formula:- ##SPC2##

Wherein R.sup.1, R.sup.2 and each independently represents hydrogen, an optionally substituted alkyl radical having from one to five carbon atoms or forms part of a heterocyclic ring containing the attached nitrogen atom; R.sup.4 represents a halogen atom or an alkyl, aryl, aralkyl, alkoxy, nitro, optionally substituted amino, acyl, carboxy, cyano or sulphamyl radical; n represents an integer of from 0 to 4; A represents an optionally substituted aromatic ring the points of attachment being at two pairs of ortho positions; Y represents a direct link, optionally substituted methylene, oxygen, sulphur or a group of the formula --NR.sup.6--wherein R.sup.6 denotes hydrogen or an optionally substituted alkyl, aryl or aralkyl radical; and Z represents an optionally substituted divalent organic radical such that a five-or six-membered ring is formed with Y, --NR.sup.3-- and A.

Alkyl radicals which may be represented by R.sup.1 and R.sup.2 include methyl and preferably ethyl. When R.sup.1 or R.sup.2 forms part of a heterocyclic ring containing the attached nitrogen atom this may be because R.sup.1 and R.sup.2 are joined together to form a divalent chain of atoms which together with the attached nitrogen atom constitutes a heterocyclic ring such as a pyrrolidine or morpholine ring.

A is preferably a benzene ring having points of attachment in the 1, 2, and 4, 5 positions. Z may be a 1,2-phenylene radical.

The colour formers of the invention may be prepared by reacting a compound of the formula: ##SPC3##

wherein R.sup.1, R.sup.2, R.sup.4 and n have the significances already stated, with a compound of the formula: ##SPC4##

wherein A, Y, Z and R.sup.3 have the significances already stated and R.sup.7 represents hydrogen or lower slkyl, the reaction being performed in the presence of a suitable condensing agent, preferably sulphuric acie or polyphosphoric acid.

The colour formers of the invention provide darker images than the colour formers which have generally been used to date, including black images in some cases, when reacted with a suitable electron-accepting substance. Such substances include silica and attapulgite, which is a so-called acid clay, and synthetic resins containing unreacted phenolic hydroxyl groups.

DETAILED DESCRIPTION

The invention is illustrated but not limited by the following Examples in which all parts and percentages are by weight.

EXAMPLE 1

31.3 parts of 4-diethylamino-2-hydroxybenzoyl-o-benzoic acid, 21.1 parts of 2-methoxyacidan and 100 parts of 98 percent sulphuric acid are heated at 100.degree.C with stirring for 2 hours than cooled. The reaction mixture is drowned into water and the solid which separates is filtered off and then slurred in an excess of 2N ammonium hydroxide solution to give an off-white solid. Filtration and drying gives the product, 39 parts.

A toluene soltuion of the product which has the structure ##SPC5##

gives a dark-coloured image on contact with a so-called acid clay.

EXAMPLE 2

6.23 Parts of o-(4-diethylamino-2-hydroxy)benzoyl benzoic acid, 4.87 parts of 2-methoxy-9-chloroacridine and 50 parts of polyphosphoric acid are heated at 100.degree.C with stirring for 6 hours then cooled. The reaction mixture is drowned into ice and the suspension made alkaline with ammonia. The solid which separates is collected, washed well with water and dried to give 4.7 parts of the product of structure: ##SPC6##

A toluene solution of the above fluoran gives a dark reddishbrown image on contact with paper treated with a resin containing uncombined phenolic hydroxyl groups.

EXAMPLE 3

3.13 Parts of o-(4-diethylamine-2-hydroxy)benzoyl benzoic acid, 2.25 parts of 2-methoxy acridone and 20 parts of sulphuric acid are heated at 100.degree.C for 14 hours then cooled. The reaction misture is drowned into water and the solution made alkaline with ammonia. The solid which separates is filtered off, washed with water and dried to give 1.4 parts of the product of structure: ##SPC7##

A toluene solution of the above fluoran gives a dark blue image on contact with electron accepting surfaces.

EXAMPLE 4

3.11 Parts of o-(4-pyrrolidin-1-yl-2-hydroxy)benzoyl benzoic acid, 2.01 parts of 3-methoxy-5,6,7,8-tetrahydrocarbazole and 30 parts of sulphuric acid are heated at 80.degree.C for 6 hours then cooled. The reaction mixture is drowned into water and made alkaline with ammonia. The solid which is formed is collected, washed with water and dried to give 1.8 parts of the product of structure: ##SPC8##

A toluene solution of the above colour former gives a dark bluish-red image on contact with electron accepting surfaces.

EXAMPLE 6

6.26 parts of o-(4-diethylamino-2-hydroxy benzoyl) benzoic acid, 4.94 parts of 1-ethyl-2-methyl-3-carboethoxy-5hydroxy indole and 22 parts of 98 percent sulphuric acid are heated at 70.degree.-75.degree.C for 12 hours. The reaction mixture is drowned into water and the precipitated tar is extracted into chloroform. After drying over magnesium sulphate, the chloroform solution is evaporated to dryness and the residue is recrystallised from petroleum ether.

3.3 parts of a white solid melting at 218.degree.C and having the structure: ##SPC9##

are obtained. A toluene solution of the above colour former gives a dark ruby-red colour on contact with electron accepting surfaces.

EXAMPLE 7

The preparation of Example 6 is repeated except that the reaction temperature is 0.degree.-5.degree.C. 9.3 parts of a white solid, melting point 252.degree.C and having the structure: ##SPC10##

are obtained. A toluene solution of the above colour former gives a scarlet colour on contact with electron accepting surfaces .

EXAMPLE 8

In place of the 6.26 parts of o-(4-diethylamino-2-hydroxy benzoyl)benzoic acid used in Example 6 there are used 6.22 parts of o-[4-pyrrolidin-1-yl)-2-hydroxybenzoyl]benzoic acid. 3.5 parts of a white solid having melting point 232.degree.C and the structure: ##SPC11##

are obtained. A toluene solution of the colour former gives a dark ruby-red colour on electron accepting surfaces. EXAMPLE 10

6.26 parts of o-(4-diethylamino-2-hydroxybenzoyl)-benzoic acid, 3.3 parts of 1-methyl-6-hydroxy py-tetra-hydroquenoline and 22 parts of 98 percent sulphuric acid are heated at 50.degree.-55.degree.C for 12 hours. The reaction mixture is drowned into water and neutralised by addition of concentrated ammonia hydroxide solution. The white precipitate is collected by filtration, washed with water and recrystallised from n-propanol. 7.3 parts of a white solid having the structure: ##SPC12##

are obtained. A toluene solution of the colour former gives a green colour on electron accepting surfaces.

EXAMPLE 11

In place of the o-(4-diethylamino-2-hydroxybenzoyl) benzoic acid used in Example 10 there are used 6.54 parts of o-[4-(morpholin-1-yl)-2-hydroxybenzoyl]-benzoic acid. The product which has the structure: ##SPC13##

is obtained as a white solid. A toluene solution gives a greenish-black colour on electron accepting surfaces.

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