EP0368960A1 - Thermal transfer ribbon - Google Patents

Abstract

The invention relates to a thermal transfer ribbon (20) comprising a substrate (22) covered with a layer (24). The layer (34) comprises one or more fluorescent pigments (26) as well as one or more coloring pigments (26) in a layer of waxy material. The fluorescence of the transferred image must be greater than 10 franking units and have a peak wavelength of 625 U 25 namometers. The tape of the invention is specifically designed to produce a transfer mark or image (32) meeting the criteria and conditions of postal applications.

Description

THERMAL TRANSFER RIBBON

Technical Field

The present invention relates to nonimpact printing. More particularly, the invention provides a thermal transfer ribbon for use in imaging or encoding characters on paper or like record media documents which enable machine, human, or reflectances reading of the imaged or encoded characters. The thermal transfer ribbon enables printing in quiet and efficient manner and makes use of the advantages of thermal printing on documents with a signal inducible in .

Background of the Invention

In the printing field, the impact type printer has been the predominant apparatus for providing increased throughput of printed information. The impact printers have included the dot matrix type wherein individual print wires are driven from a home position to a printing position by individual and separate drivers. The impact printers also have included the full character type wherein individual type elements are caused to be driven against a ribbon and paper or like record media adjacent and in contact with a platen.

The typical and well-known arrangement in a printing operation provides for transfer of a portion of the ink from the ribbon to result in a mark or image on the paper. Another arrangement includes the use of carbonless paper wherein the impact from a print wire or a type element causes rupture of encapsulated material for marking the paper. Also known are printing inks which contain magnetic particles wherein certain of the particles are transferred to the record media for encoding characters in manner and fashion so as to be machine readable in a subsequent operation. One of the known encoding systems is MICR (Magnetic Ink Character Recognition) utilizing the manner of operation as just mentioned.

While the impact printing method has dominated the industry, one disadvantage of this type printing is the noise level which is attained during printing operation. Many efforts have been made to reduce the high noise levels by use of sound absorbing or cushioning materials or by isolating the printing apparatus.

More recently, the advent of thermal printing which effectively and significantly reduces the noise levels has brought about the requirements for heating of extremely precise areas of the record media by use of relatively high currents. The intense heating of the localized areas causes transfer of ink from a ribbon onto the paper. Alternatively, the paper may be of the thermal type which includes materials that are responsive to the generated heat.

The use of thermal printing with different color inks has also been proposed and applied in certain technologies.

Disclosure of the Invention

It is an object of the present invention to provide a thermal transfer ribbon suitable for postal applications.

Thus, according to the invention, there is provided a thermal transfer ribbon having a transfer coating including a fluorescent coloring material of a reddish-orange hue in a wax material, characterized in that said transfer coating contains 50 to 90% wax including about 20 to 45% hydrocarbon wax, about 35 to 65% paraffin wax, about 5 to 30% carnauba wax and about 3 to 15% acetate copolymer; about 5 to 20% fluorescent pigment and about 5 to 20% color toning pigment, wherein the fluorescence of the transferred image is greater than 10 postage meter units and has a peak wavelength of 625 +25 nanometers, and wherein the total color difference (Δ) of the transferred image does not exceed 10 on the Hunter Color Scale when using the formula

Δ = V (ΔL)² + (Δa)² + (Δb)²

in which "L" is defined as a measure of lightness and may have a variance of +5 , "a" is a measure on the red-green axis, and "b" is a measure on the blue- yellow axis.

Brief Description of the Drawings

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 illustrates a thermal element operating with a ribbon base having a transfer coating thereon incorporating the ingredients as disclosed in the present invention;

Fig. 2 shows the receiving paper with a part of the coating transferred in the form of a character onto the receiving paper;

Fig. 3 is a diagrammatic view of a ribbon base having adjacent coatings along the length thereof;

Fig. 4 is a diagrammatic view of a ribbon base having repeated coatings in a modified arrangement; and

Fig. 5 is another modified arrangement of repeated coatings. Best Mode for Carrying Out the Invention

The thermal transfer coating of the present invention is specifically designed and formulated to provide a transfer mark or image which meets specific criteria or requirements for a fluorescent red thermal transfer ribbon which is suitable and acceptable for postal applications. --

Fluorescence of the translated image should be greater than 10 pmu (postage meter unit). The peak wavelength of the fluorescence is at 625 ±25 nm (nanometers) . ^~~

The color of the transferred image is controlled to be within the coloring of a reddish- orange hue similar to the color of the postage meter indicia.

And, the color of the transferred image, as determinated on a 564.5 mm inch square, will have values of L=45, a=62 and b=20 on the Hunter Color Meter. L is defined as a measure of lightness, a is a measure on the red-green axis, and b is a measure on the blue-yellow axis. A variance of ±5 is allowed for the value of L with total color difference (Δ) not to exceed 10 when using the formula:

Δ = V (ΔL)² + (Δa)² + (Δb)²

The transfer ribbon 20, as illustrated in Figs. 1 and 2, comprises a base or substrate 22 of thin, smooth, tissue-type paper or polyester-type plastic or like material having a coating 24 which is thermally activated and includes nonmagnetic pigment or particles 26 as an ingredient therein for use in imaging or encoding operations to enable human or reflectance reading of characters. Each character that is imaged on a receiving paper 28 or like record media produces a unique waveform that is recognized and read by the reader. In the case of thermal transfer ribbons relying solely on the nonmagnetic thermal printing concept, the pigment or particles 26 include coloring materials such as pigments, fillers and dyes.

As alluded to above, it is noted that the use of a thermal printer having a print head element, as 30, substantially reduces noise levels in the printing operation and provides reliability in imaging or encoding of paper or like documents 28. The thermal transfer ribbon 20 provides the advantages of thermal printing while encoding or imaging the document 28 with a nonmagnetic signal inducible ink. When the heating elements 30 of a thermal print head are activated, the imaging or encoding operation requires that the pigment or particles of material 26 on the coated ribbon 20 be completely transferred from the ribbon to the document 28 in manner and form to produce the precisely defined characters 32 for recognition by the reader. In the case of nonmagnetic thermal printing, the imaging or encoding material 26 is completely transferred to the document 28 to produce the precisely defined characters 32 for recognition and machine, human, or reflectance reading thereof.

Fig. 3 is a diagrammatic view of a substrate 34 having a width occupied by a fluorescent thermal transfer coating 36 on approximately one half of the substrate and a thermal transfer coating 40 of another color on the other half of the substrate. The coating 36 includes pigment or particles 38 and the coating 40 includes pigment or particles 42. The width of the substrate 34 or of the printed area of the transfer coatings 36 and 40 is dependent upon the configuration of the thermal printer or like apparatus that is used for causing transfer of the image from the base or substrate to the paper or other document. Fig. 3 shows a distinct line of demarcation 35 between the fluorescent coating 36 and the coating 40 of another color. It is understood, of course, that minor variations of either an uncoated or clear strip along the line 35 or an overlapping of the coatings 36 and 40 may unintentionally occur.

Fig. 4 is a diagrammatic view of a substrate 44 having a portion thereof coated with a fluorescent thermal transfer coating 46 and an adjacent portion coated with a thermal transfer coating 48 of another color. The coatings 46 and 48 are repeated along the length of the substrate 44. The coating 46 has pigment or particles 50 and the coating 48 has pigment or particles 52.

Fig. 5 is a diagrammatic view of a wider substrate 54 having a narrow portion thereof coated with a fluorescent thermal transfer coating 56 and an adjacent narrow portion coated with a thermal transfer coating 58 of another color. The coatings 56 and 58 are repeated along the length of the substrate. The coating 56 contains pigment or particles 60 and the coating 58 contains pigment or particles 62. The arrows 64 indicate the direction in which the transfer ribbon is advanced or transported in a printing or imaging operation.

The thermal transfer ribbon of the present invention is produced in a two stage process wherein the first stage includes preparation of a specific wax emulsion or formulation, and the second stage includes preparation of the transfer coating or layer.

Generally, a wax adhesive emulsion uses hydrocarbon, paraffin or ozocerite, carnauba, macrocrystalline waxes and an ethylene vinyl acetate copolymer and/or a hydrocarbon resin soluble in aliphatic solvents. The wax emulsion uses waxes plus the acetate copolymer plus the hydrocarbon resin in one formulation. In another formulation, the wax emulsion uses waxes plus the acetate copolymer or the hydrocarbon resin. A preferred wax adhesive emulsion or formulation at 20% to 50% solids to satisfy the requirements of the first stage of the process includes the specific ingredients in appropriate amounts as set forth in Table 1 of Example I.

EXAMPLE I TABLE 1

% Dry

Wax Emulsion Percent Dry Wet Amt, Range

WB-7 Wax 27 169.6 20-45%

Paraffin 162 Wax 46 289.3 35-65%

Carnauba #3 Wax 20 125.8 5-30%

Elvax 4310 7 44.3 3-15%

Mineral Spirits 1361.3

100 1990.3 (31.6% Solids)

The nonvolatile materials in the above formulation equate from 20% to 50%, and it is here noted that Lacolene, or VM and P Naptha, can be substituted in place of the mineral spirits. The wax emulsion is heated to 60°C while mixing the above solution and then is allowed to cool to room temperature at the end of the first stage.

The second stage of the process includes preparation of a preferred fluorescent color, thermal transfer coating wherein the above wax emulsion is heated to a temperature between 40-45°C and the following ingredients in appropriate amounts, as set forth in Table 2, are placed into dispersion equipment such as a ball mill, a shot mill, a sand mill, or an attritor, and then ground for a period of approximately 20-40 minutes, or for a sufficient period of time to provide a uniform fine (3-5 microns size) dispersion. TABLE 2

% Dry

Coating Percent Dry Wet Amt. Range

Wax Emulsion

(From Table 1) 79.9 1990.3 50-90% Red-Orange PM Base

(47% Solids) 6.3 49.9 5-20% Lithol Scarlet K-3700 I 12.5 98.1 5-20% Paliogen 3911HD 1.3 10.0 0-10%

100.0 2148.3

Percent Solids 25-50%

Example II provides the specific ingredients in appropriate amounts for another fluorescent coating which uses different pigments.

EXAMPLE II

TABLE 1

% Dry

Wax Emulsion Percent Dry Wet Amt. Range

Paraffin 162 Wax 50 277.4 35-65%

WB-17 Wax 30 166.4 20-45%

Carnauba #3 Wax 13 72.1 5-20%

Elvax 40W 7 38.8 3-15%

Mineral Spirits - 1313.2

100.0 1867.9

(29.7% Solids)

TABLE 2

% Dry

Coating Percent Dry Wet Amt. Range

Wax Emulsion

(From Table 1) 72.7 1867.9 50-80% Red-Orange PM Base

(47% Solids) 9.8 159.0 5-20% Red Toner #8197 7.0 53.4 5-10% Calcium Carbonate 8.4 64.1 3-10% ARC Yellow A16N 2.1 16.0 1-4%

100.0 2160.5

(35.3% Solids)

Example III provides the specific ingredients in appropriate amounts for yet another fluorescent coating which uses different pigments.

EXAMPLE III

TABLE 1

% Dry

Wax Emulsion Percent Dry Wet Amt, • Range

WB-7 Wax 30 187.6 20-45%

Paraffin 162 Wax 50 311.8 35-65%

Carnauba #3 Wax 13 80.9 5-30%

Elvax 4310 7 44.0 3-15%

Mineral Spirits 1838.5

100 2462.8 (25.3% Solids)

TABLE 2

% Dry

Coating Percent Dry Wet Amt. Range

Wax Emulsion

(From Table 1) 64.9 2462.8 50-80%

10-5C-35-A102 23.1 247.5 15-30%

White Pigment 4.6 49.5 1-10%

Fire Orange 9.2 99.0 5-15% 100.0 2858.8 (35.7% Solids)

Example IV provides the specific ingredients in appropriate amounts for still another fluorescent coating which uses a hydrocarbon resin and a different arrangement of pigments.

EXAMPLE IV TABLE 1

% Dry

Wax Emulsion Percent Dry Wet Amt. Range

WB-7 Wax 30 158.1 20-45%

Paraffin 162 Wax 40 210.5 35-65%

Carnauba #3 Wax 13 68.2 5-20%

Elvax 40W 7 37.1 3-15%

Piccotex-75 10 52.9 1-25%

Mineral Spirits — 1397.0 —

100 1923.8 TABLE 2

% Dry

Coating Percent Dry Wet Amt. Range

Wax Emulsion 69.9 1923.8 50-80% (From Table 1)

Red-Orange PM Base 6.3 47.3 3-10%

Paliogen 3911 HD 1.3 9.7 1-10%

Lithol Scarlet L-3700 12.5 94.1 5-20%

Fire Orange 10.0 75.1 5-20%

100 2150.0

Percent Solids 20 - 50%

Paraffin 162 wax is a mixture of solid crystalline hydrocarbons chiefly of the methane series derived from the paraffin distillate portion of crude petroleum and is soluble in benzene, ligroine, warm alcohol, chloroform, turpentine, carbon disulfide and olive oil. WB-7 and WB-17 are oxidized, isocyanated hydrocarbon waxes. Carnauba #3 is a hard, amorphous wax derived by exudation from leaves of the wax palm and is soluble in ether, boiling alcohol and alkalies. Ozocerite is a natural paraffin wax occurring in irregular veins, consists principally of hydrocarbons, is soluble in water and has a variable melting point. Elvax 40W and 4310 are ethylene vinyl acetate copolymers. Piccotex-75 is one of the series of hydrocarbon resins and defined as a hard, color stable, substituted styrene coploymer resin.

The class or group of microcrystalline waxes may also be used in the wax emulsion and essentially consist of petroleum waxes having a higher molecular weight, a higher melting point, and a higher viscosity than paraffin wax.

In the fluorescent color coating portion of the invention, the Lithol Scarlet K-3700 and L-3700, the Paliogen 3911 HD and 10-5C-35-A102 ingredients are toning pigments, and the White Pigment and the Fire Orange are fluorescent pigments. The Red-Orange PM Base is a fluorescent pigment. Red Toner #8197 is a toning pigment, and ARC Yellow A16N is a fluorescent pigment. It is noted that a pigment is defined as a solid that reflects light of certain wavelengths while absorbing light of other wavelengths, without producing appreciable luminescence; in effect, pigments are used to impart color to other materials.

The nonvolatile materials of the fluorescent dispersion are controlled at 25% to 55% for proper viscosity. It should be noted that all ingredients are carefully weighed and solubilized in the mineral spirits using appropriate heat and agitation. After the solution is complete, it is slowly cooled to form a viscous wax dispersion to prepare a thermally active, transfer coating.

The substrate or base 22, which may be 30-40 gauge capacitor tissue, manufactured by Glatz, or 14- 35 gauge polyester film as manufactured by duPont under the trademark Mylar, should have a high tensile strength to provide for ease in handling and coating of the substrate. Additionally, the substrate should have properties of minimum thickness and low heat resistance to prolong the life of the heating elements 30 of the thermal print head by reason of reduced print head actuating voltage and the resultant reduction in burn time.

The coating 24 is applied to the substrate 22 by means of conventional coating techniques such as a Meyer rod or like wire-wound doctor bar set up on a typical solvent coating machine to provide a coating thickness in a range of 2.54 to 10.16 microns. This coating thickness equates to a coating weight of between 9 and 16 milligrams per 25.5 square centimetres. The coating is made up of approximately 25% to 55% nonvolatile material and is maintained at a desired temperature and viscosity throughout the coating process. A temperature of approximately 40- 45°C is maintained during the entire coating process. After the coating is applied to the substrate, the web of ribbon is passed through a dryer at an elevated temperature in the range between 93 and 120°C for approximately 5-10 seconds to ensure good drying and adherence of the coating 24 onto the substrate 22 in making the transfer ribbon 20. The above-mentioned coating weight, as applied by the Meyer rod onto a preferred 9-12 microns thick substrate, overall translates to a total thickness of 12-15 microns. The coating 24 can be fully transferred onto the receiving substrate or paper 28 in the range of 50-120°C by changing the ranges of the waxes used in the first step of the process.

The availability of the various ingredients used in the present invention is provided by the following list of companies.

Material Supplier

WB-7 and WB-17 Bareco

Paraffin 162 Wax Boler

Carnauba #3 Wax Baldini & Co., Inc.

Elvax 40W and 4310 Wax E. I. duPont

Piccotex-75 Hercules

Mineral Spirits Ashland Chemical Co.

Red Orange PM Base Day-Glo

Red Toner #8197 Paul Uhlich

Calcium Carbonate Omya

ARC Yellow A16N Day-Glo

Lithol Scarlet K-3700 BASF

Paliogen 3911 HD BASF

10-5C-35-A102 Hilton-Davis

White Pigment Day-Glo

Fire Orange Day-Glo The method of thermal transfer of the images by use of a dry ribbon enables the creation of the fluorescent mark or image which is recognized for postage recognition applications. The fluorescent mark or image is produced by suitable software control of a thermal transfer printer to create a bar code or other postal indicia which can be recognized by reading of the mark.

In the case where a dual color ribbon is desired, the arrangement of Fig. 3 can be used wherein a portion of the ribbon width comprises the fluorescent color and the other portion of the ribbon comprises a red, black, blue, yellow color or a mixture of colors. Figs. 4 and 5 illustrate a sequential arrangement of the fluorescent color and any other color or mixture of colors in repeated manner.

Claims

CLAIMS :

1. A thermal transfer ribbon having a transfer coating including a fluorescent coloring material of a reddish-orange hue in a wax material, characterized in that said transfer coating contains 50 to 90% wax including about 20 to 45% hydrocarbon wax, about 35 to 65% paraffin wax, about 5 to 30% carnauba wax and about 3 to 15% acetate copolymer; about 5 to 20% fluorescent pigment and about 5 to 20% color toning pigment, wherein the fluorescence of the transferred image is greater than 10 postage meter units and has a peak wavelength of 625 +25 nanometers, and wherein the total color difference (Δ) of the transferred image does not exceed 10 on the Hunter Color Scale when using the formula

Δ = (ΔL)² + (Δa)² + (Δb)²

in which "L" is defined as a measure of lightness and may have a variance of +5, "a" is a^"measure on the red-green axis, and "b" is a measure on the blue- yellow axis.

2. A thermal transfer ribbon according to claim 1, characterized in that the color of the transferred image, as determined on a 564.5 mm- area, will have the value of L=45, a=62 and b=20 on the Hunter Color Meter.

3. A thermal transfer ribbon according to claim 1, characterized in that said color toning pigment is a red pigment.

4. A thermal transfer ribbon according to claim 1, characterized in that said color toning pigment is a scarlet pigment.

5. A thermal transfer ribbon according to claim 1, characterized in that said fluorescent pigment is a mixture of reddish-orange and fire orange pigments.

6. A thermal transfer ribbon according to claim 1, characterized in that said fluorescent pigment is a mixture or orange and white or yellow pigments.

7. A thermal transfer ribbon according to claim 1, characterized in that said hydrocarbon wax is an oxidized isocyanated wax.

8. A thermal transfer ribbon according to claim 1, characterized in that said paraffin wax is a mixture of solid crystalline hydrocarbons chiefly of the methane series.

9. A thermal transfer ribbon according to claim 1, characterized in that said acetate copolymer is at least one of a series of ethylene vinyl acetate copolymers that are compatible with waxes.

10. A thermal transfer ribbon according to claim 1, characterized in that said transfer coating includes about 3 to 10% calcium carbonate.