Visual Recording Method And Means

Abstract

An almost colorless aqueous ink containing a color coupler is used to inscribe a record on a recording sheet having a coated layer containing a fine white powder and a color developer which reacts with the color coupler to form a visual record of vivid color of highly durable nature.

Parent Case Text

This is a continuation-in-part application of our copending U.S. Pat. application Ser. No. 53,054, filed July 7, 1970 and now abandoned.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to visual recording methods and means and more particularly to a new method and means for inscribing with colorless or light-colored inks records on recording structures. The invention also concerns a process for producing the visual recording means.

Examples of aqueous inks known heretofore are inks formed by dissolving in water dyes such as ink blue and eosin, pigments such as carbon black, permeation-proofing agents such as dextrin and arabic gum, and wetting agents such as glycerine and ethylene glycol. These aqueous inks are advantageous in that they can be readily used for writing and recording on almost any kind of paper or like material.

However, since these inks contain dyes and pigments, they are colored and therefore are accompanied by the undesirable possibility of contamination or discoloration of the recording paper, hands, clothing, and nearby articles and facilities during handling thereof or during their use in recording. When such articles become thus discolored, it is not easy to wash off the adhering color or to decolor the same.

Furthermore, since an aqueous ink of the above-stated character contains a dye or pigment, the ink feed flow tends to be retarded when the writing tip of a writing instrument using the ink becomes dry, whereby grazing or abrasive scratching tends to occur. In some severe cases, the instrument becomes incapable of writing. This undesirable phenomenon is particularly observable in the case of black ink and at present is becoming a problem demanding an effective solution as the use of black ink, which is particularly effective for making photocopies, becomes increasingly advantageous.

These difficulties are serious drawbacks particularly in inks for recording, with pen-writing oscillographs, data produced by industrial instruments, medical treatment instruments, and various other measuring instruments.

Heretofore, pen-writing type recording in measuring instruments and like equipment has been accomplished in each case by feeding an ink comprising a dye, a permeation-proofing agent, a wetting agent, and other additives through a tubular writing member having a small-diameter hole at the writing end thereof, causing this end to contact lightly a recording substrate medium, such as a paper for measurements and paper for recording, and causing the substrate medium to travel at a constant speed. Frequently, there are instances wherein, when an instrument for such operation is placed in the operational state for measuring and recording, the ink drips from the writing member and adheres to the operator's hands, clothing and other objects from which the ink cannot be easily washed off. In some instances, the measuring and recording instrument becomes contaminated by the ink.

Furthermore, the ink in such instruments flows through and out of an extremely small hole of a diameter of the order of from 0.2 to 0.5 mm., which is normally open and exposed to the atmosphere. Consequently, the ink dries easily and once the ink dries, it is not redissolved by the ink subsequently flowing out because of the dye. Moreover, the ink viscosity tends to rise substantially, thereby disturbing uniform ink flow, whereby necessary data cannot be clearly and accurately recorded in some cases.

These undesirable characteristics are particularly pronounced when black ink is used. Accordingly, at present, red ink is widely used since these disadvantages are somewhat reduced therein. Records in red ink, however, cannot be reproduced by photosensitive means with full clarity and then fully satisfactory copies cannot be obtained.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a recording method wherein the above-described difficulties are overcome.

Specific objects and features of the invention will become apparent as the following disclosure proceeds.

According to the present invention, briefly summarized, there is provided a method for making visual recordings in which a record is inscribed on a recording structure comprising a base structure and a coated layer supported on the base structure and containing at least a fine white powder and a color developer with an aqueous colorless or light-colored ink containing a coupler for reacting with the color developer in the recording structure to form a visual record of strong color.

According to the present invention, there is further provided a visual recording combination comprising the above-stated ink and recording structure.

According to the present invention, there is additionally provided a process for producing a visual recording combination as stated above.

The nature, principle, details and utility of the invention will be more clearly apparent from the following detailed description beginning with general considerations and concluding with specific examples of practicce illustrating preferred embodiments of the invention and results.

DETAILED DESCRIPTION

A feature of the present invention is that it provides a method of recording and reproductive printing through the use of an ink comprising a colorless or light-colored solution containing a color coupler which, upon reacting instantaneously and at room temperature with a color developer contained in a coated layer of a recording substrate medium (hereinafter referred to as a "sheet"), forms a colored compound of strong color and high stability without discoloration.

This ink according to the invention, differing from conventional inks containing dyes and pigments, is not colored and, therefore, does not have the disadvantageous possibility of soiling equipment, clothing, hands and other objects. The ink used in accordance with the invention generates a color only when it comes into contact with the color developer which is the cooperative counterpart agent contained in the coated layer of the recording sheet. With only the ccolor coupler therein, the ink is colorless or of light color and is stable. This is particularly advantageous in that it cannot generate colors upon contacting ordinary papers, hands, clothes and equipment.

The viscosity of a conventional colored ink in which a dye of non-crystalline macromolecular substances is used rises remarkably when the ink at the writing tip of the writing tool beccomes dry, and a viscous dye separates out to obstruct the outward flow of the ink, whereby in severe cases an accurate recording cannot be attained.

In contrast, the color coupler used in the ink of the invention has a remarkably high solubility in water, and the rise in viscosity is small even when the ink becomes dry at the writing tip of the writing tool. Furthermore, ink thus dried is easily redissolved in the liquid ink. Accordingly, there is no tendency whatsoever of retardation of the outward flow of the ink through the tip of the writing tool, and a visual record which is consistently uniform can be obtained. Even when the writing is temporarily stopped during the recording operation and then resumed, the writing tool can immediately begin writing. Thus there is no possibility of broken or interrupted traced inscriptions.

Since the ink used according to the invention is colorless or of light color, it cannot be used for recording on any and all kinds of recording sheets; it is necessary to select sheets from a limited group of reccording sheets.

For the counterpart color developer, a compound capable of forming a stable record of high color concentration only upon contact with the above-described ink of colorless or light-color appearance containing the color coupler is used, contained in a coated layer. In practical use, in general, it is necessary to dispose this coated layer on a suitable supporting structure, that is, to combine this layer with specific recording sheets.

Another feature of the recording materials of the invention is that, when the ink is combined with the sheet, a durable record of high color concentration and high stability is obtained. We have found that a record thus obtained undergoes no discoloration whatsoever due to sunlight, and the recorded inscription does not run when immersed in water, and it may be said that the record made according to the present invention can be permanently preserved.

Still another feature of the recording materials of the invention is the use of specific recording sheets of limited characteristics. That is, the invention becomes particularly valuable in fields wherein specific recording sheets are used. For example, the invention can be applied in fields wherein specific papers such as forms for stock certificates, standard drawing sheets, and paper sheets bearing specific inscriptions in addition to the field of recording materials for the above-mentioned various instruments and equipment. In such other fields, the invention affords the above-described advantages and is additionally advantageous in that alterations and falsifications cannot be made on the paper sheets.

An ink according to the invention is prepared, in general, by dissolving a color coupler, constituting one component, in water and further adding to the solution and dissolving therein necessary additives such as glycerine or ethylene glycol as a hygroscopic agent, dextrin or arabic gum as a permeation preventive agent, and a surface-active agent for regulating the outward flow of the ink.

The recording sheet to constitute the opposite component is prepared, in general, by a process which comprises causing a color developer which is capable of reacting with the color in the ink to form a colored compound to dissolve or disperse in water or an organic solvent, thoroughly mixing therewith reaction-assisting agents such as a white fine powder, a stabilizer, and a binder to render the process mixture into a uniform dispersion (or disperse system), applying the resulting dispersion as a coating on a suitable base sheet such as an original copy sheet or a film, and then drying the coating.

The ccolor coupler and color developer thus using in accordance with the invention are originally colorless or light-color compounds which, upon reacting with each other, instantaneously form a vividly colored and stable compound in an aqueous solution. A representative example of such compound combination is the color coupler sodium metavanadate and the color developer calcium dihydroxynaphthalenesulfonate, which when used in combination in accordance with the present invention yield a black color instantly.

We have found that in the practice of the invention vanadium compounds as color couplers and polyphenol derivatives as color developers are particularly effective in producing good results. When a polyphenol derivative is used as the color developer, it is possible to obtain a durable black recording of especially high color concentration.

Examples of polyphenol derivatives are polyphenolic carboxylic acid esters and metallic salts. As for polyphenolic carboxylic acid derivatives for use as color developers, esters of acids which dissolve with difficulty or are insoluble in acid, such as gallic acid, tannic acid dihydroxybenzene carboxylic acid, and dihydroxynaphthalene carboxylic acid, are especially suitable. By esterifying the polyphenolic carboxylic acids, polyphenolic carboxylic acid derivatives which are colorless or light-colored, and which dissolve with difficulty, i.e. are only slightly soluble, or are insoluble in water are obtained. For example, polyphenolic carboxylic acid esters of aliphatic alcohols such as lauryl alcohol and stearyl alcohol and in general alkyl esters wherein the alkyl group has more than six carbon atoms have the necessary low solubility as well as the aromatic esters such as benzyl ester.

When an aliphatic or aromatic amine salt or a salt of a metal, such as calcium or barium, of dihydroxynaphthalene sulfonic acid or dihydroxybenzene sulfonic acid comes in contact with the ink containing the color coupler, a jet black inscription is instantaneously recorded.

Examples of some preferred color developers according to the invention include lauryl gallate stearyl dihydroxybenzoate, calcium dihydroxynaphthalenesulfonate and 2-ethylhexylammonium dihydroxynaphthalenesulfonate.

A most important feature of the invention is the admixing of a fine white powder with the color developer to form a coated layer in order to increase the color-generating speed and color concentration of the color developer. By merely causing only the color developer to be coated on or impregnate the base sheet, it is not possible to obtaine a sufficiently satisfactory color-generating speed or color concentration. Unless an extremely large quantity of the color developer is used, the desired color concentration or strength cannot be obtained.

We have found that, when a fine white powder is added to form a suspension in a solvent in which the color developer has been dissolved or dispersed, and this suspension is applied on the base sheet to form a coated layer, it is possible to produce recording materials of a color concentration and color-generating speed which are several times those obtainable without the addition of a fine white powder. In a coated layer containing a fine white powder, of course, a large quantity of the color developer is not required, and a fully satisfactory inscription can be recorded with a minimum required quantity of the developer.

One reason for this desirable phenomenon is that the addition of the fine white powder causes the coated layer to become remarkably porous, whereby its capacity to absorb the ink is greatly improved. A further reason is that the color developer is distributed uniformly over the outer surface of the ifne white powder and does not permeate into the base sheet interior, and only a small quantity of the color developer is used in a highly efficient manner.

This result, in combination with the above-mentioned porosity of the surface, produces a record without luster but with a color concentration which is several times that attainable without the fine white powder. The final result is not merely a record with an increase in the contrast due to an increase in the whiteness of the base sheet but a record of remarkable definition and high color concentration due to the above-described phenomenon.

Examples of fine white powders we have found to be suitable are calcium carbonate, silicon dioxide, talc, titanium dioxide, aluminum oxide, and clays. Such inorganic fine powders are those which can be used as white filters in papers. They must be insoluble in water and fine enough. The effectiveness of this fine white powder is indicated with respect to the recording materials of Example 1 set forth hereinafter.

For causing the color developer and fine white powder to adhere to the surface of the base sheet, a natural or synthetic high-polymer substance is used as an adhesive. Examples of suitable adhesives are water-soluble high-polymer substances such as dextrin, poly, gelatines, high-polymer substances soluble in organic solvents, such as vinyl resins, acryl resins, and styrene resins, and high-polymer latex solvents.

Depending on the necessity, the durability of the recorded inscriptions and the stability of the base sheet can be further increased by adding stabilizers such as an agent for absorbing ultra-violet rays, an oxidation-preventive agent and acids during the formation of the caoted layer. While the color developer or the colored record itself is substantially stable with respect to sunlight and oxygen, the further addition of various stabilizers affords full resistance to the effects of sunlight and oxidation, whereby there is produced a recording material accompanied by almost no discoloration or change in characteristics and quality.

When a record is inscribed by means of an ink of the invention containing a colorless or light-colored coupler on a recording material produced in the manner disclosed above, a record of high color concentration is instantaneously formed. The record thus formed has high resistance to water and light and exhibits almost no change over a long period. The recording material itself undergoes almost no change in quality of characteristics when left standing for a long time. Accordingly, it is possible to produce a recording material in which there is no change in color and almost no reduction of its color-generating performance.

While the recording materials of the invention are particularly useful as recording materials of a large variety of industrial instruments and equipment, the invention can be applied to various other uses. For example, the ink of the invention can be used for general writing and for various writing tools such as fiber-tip pends and ball-point pens in combination with specific paper sheets according to the invention.

Another example of application is the impregnation of stamp pads with the ink of the invention, the ink thereby being used to stamp inscriptions of specific paper sheets. Still another application is the impregnation of the ink on a typewriter ribbon which is then used in conjunction with a specific paper according to the invention to form inscriptions thereon. A further application is that of printing by means of printing presses.

In order to indicate still more fully the nature and utility of the invention, the following examples of practice cconstituting preferred embodiments of the invention and results are set forth, it being understood that these examples are presented as illustrative only and that they are not intended to limit the scope of the invention.

EXAMPLE 1

A. Preparation of aqueous ink. Recipe, quantities in g. vanadium pentoxide 9 sodium hydroxide 6 sodium alkylnaphthalenesulfonate 1 polyvinyl pyrrolidone 20 water 964

The vanadium pentoxide and sodium hydroxide are added to and agitated with the water to dissolve the vanadium compound, and then the polyvinyl pyrrolidone and sodium alkylnaphthalenesulfonate are added to and dissolved in the resulting solution to prepare a colorless ink.

______________________________________ B. Preparation and application of base-sheet coating Recipe, quantities in g. lauryl gallate (ester) 1 vinyl resin 2 mineral acid 1 organic acid 2 silicic acid, fine powder 3 ethyl acetate 10 ______________________________________

The first four ingredients set forth are successively added to and dissolved in the ethyl acetate, and then the silicic acid powder is dispersed uniformly in the resulting solution to prepare a coating dispersion. This dispersion is applied as a coating on a sheet of white instrument recording paper of a weight of 50 g./square meter by means of a suitable coating device as, for example, a roll coater or a bar coater, in a quantity such that the coating thickness after drying will be from 8 to 10 microns. The ethyl acetate is dried off, whereupon a white recording sheet is obtained.

This recording sheet is useful as a recording material in medical and industrial measuring instruments. When the above-described ink is used in conjunction with this recording sheet, a jet-black recording without interrupted ink inscription or ink blotches can be obtained.

REFERENCE EXAMPLE 1

For the purpose of comparison, the ink and recording sheet of Example 1 were prepared, and a record was inscribed on the sheet with the ink and compared with that on a recording sheet ccoated with a dispersion prepared in the manner specified in Example 1 except for the omission of the fine powder of silicic acid. The results of this comparison are set forth in Table 1 and indicate the importance of the use of a white powder in accordance with the invention.

Table 1 ______________________________________ TESTED RECORDING SHEET RECORDING SHEET OF PROPERTY OF EXAMPLE 1 EXAMPLE 1 WITHOUT SILICIC ACID POWDER ______________________________________ Color jet black greyish black Intensity high low Definition remarkably high record in small type definition illegible Color-generat- instantaneous 5 to 10 seconds re- ing speed quired to develop full color ______________________________________

EXAMPLE 2

A. Preparation of aqueous ink Recipe, quantities in g. ammonium metavanadate 10 glycerine 200 dextrin 50 water 740

The ammonium metavanadate and dextrin are added to and dissolved in the water, and the glycerine is added to and mixed with the resulting solution to form a colorless ink.

______________________________________ B. Preparation and application of base-sheet coating. Recipe, quantities in g. calcium dihydroxynaphthalenesulfonate 1.0 polyethylene glycol-600 0.4 4-tertiary-butylphenyl salicylate 1.0 mineral acid 0.3 styrene-maleic anhydride copolymer resin 7.5 silicic acid, fine powder 3 methyl alcohol 2 methylethyl ketone 4 ______________________________________

The above ingredients are dissolved or dispersed in the solvent to prepare a coating dispersion, which is applied as a coating on a sheet of white paper of a weight of 35 g./square meter by means of a suitable coating device in a quantity such that the coating thickness after drying will be from 7 to 9 microns. The solvent is then dried off, whereupon a white recording sheet is obtained. This recording sheet is useful as a recording medium for medical measuring instruments and for use in conjunction with a stamp pad and fiber-tip pens.

Claims

What we claim and desire to protect by Letters Patent is:

1. A visual recording method which comprises inscribing a record with an aqueous ink containing a color coupler having a chromatic appearance in the range of from colorless to lightly colored which is selected from the group consisting of ammonium metavanadate, sodium metavanadate, and vanadium pentoxide on a recording structure comprising a base structure provided over a surface thereof with a coated layer containing at least a dispersion of a fine white powder selected from the group consisting of calcium carbonate, silicon dioxide, talc, titanium dioxide, aluminum oxide and clay and a color developer which is at most only slightly soluble in water and is selected from the group consisting of lauryl gallate, stearyl dihydroxybenzoate, calcium dihydroxynaphthalenesulfonate, and 2-ethylhexylammonium dihydroxynapthalenesulfonate, which developer thereby reacts with said color coupler to form a visual record of strong color.

2. A visual recording combination comprising a recording structure comprising a base structure supporting over a surface thereof a coated layer containing at least a white powder selected from the group consisting of calcium carbonate, silicon dioxide, talc, titanium dioxide, aluminum oxide and clay and a color developer which is at most only slightly soluble in water and is selected from the group consisting of lauryl gallate, stearyl dihydroxybenzoate, calcium dihydroxynaphthalenesulfonate, and 2-ethylhexylammonium dihydroxynaphthalenesulfonate and an aqueous ink having a chromatic appearance in the range of from colorless to lightly colored and containing a water soluble color coupler which is a compound selected from the group consisting of ammonium metavanadate, sodium metavanadate, and vanadium pentoxide, said coupler being capable of reacting with said color developer to form a visual record of strong color on said recording structure when a record is inscribed thereon with said ink.

3. A visual recording combination as claimed in claim 2, in which said base structure is a sheet material.

4. A visual recording combination as claimed in claim 3, which is used in a writing machine.

5. A visual recording combination as claimed in claim 3 which is used in a printing press.

6. A visual recording combination as claimed in claim 3 in which said ink is used in a stamp pad, and said visual record is formed on said recording sheet material by being transferred thereto from said stamp pad by a stamp.

7. A process for producing a visual recording combination comprising a recording structure and an ink for inscribing visual records thereon, which process comprises

dissolving at least a water soluble color coupler which selected from the group consisting of ammonium metavanadate, sodium metavandate, and vanadium pentoxide in water to prepare said ink of a chromatic appearance in the range from colorless to lightly-colored,

combining a color developer which is at most only slightly soluble in water and is selected from the group consisting of lauryl gallate, stearyl dihydroxybenzoate, calcium dihydroxynaphthalenesulfonate, and 2-ethylhexylammonium dihydroxynaphthalenesulfonate, a fine white powder selected from the group consisting of calcium carbonate, silicon dioxide, talc, titanium dioxide, aluminum oxide and clay and a solvent to form a coating dispersion,

applying said dispersion as a uniform coating on a surface of a base structure, and

drying said coating thereby to prepare a recording structure, said color coupler and color developer being capable of reacting with each other to form a visual record of strong color on said recording structure when a record is inscribed thereon with said ink.