JPH03284986A - Gradation expressing method and gradation expressed printed matter - Google Patents

Abstract

PURPOSE:To obtain gradation excellent in the reproducibility of density without having irregular shapes and sizes of dots by arranging main dots formed by energy which is 0-70% the energy applied to dots having the size corresponding to the size of the center-to-center interval of dots arranged on every other dot and arranging sub-dots formed by 0-30% of energy between them. CONSTITUTION:Main dots 12 are printed along the lateral direction of one thermal head and, subsequently, the thermal head is shifted by a T/2 pitch in the direction vertical to the width of the head to print sub-dots 13 and further shifted by the T/2 pitch in a sub-scanning line direction to print the main dots 12. This printing is repeated until the printing up to the end of one image is completed. After printing, the thermal head is returned to the original position and the head is shifted by the T/2 pitch in a main scanning direction and, this time, the sub-dots 13 are printed at first. Thereafter, the main dots 12 and the sub-dots 13 are alternately printed while the head is shifted by the T/2 pitch in the sub-scanning direction.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to gradation expression, and provides a gradation expression method that has excellent density and reproducibility regardless of the ink used, and a printed matter with gradation expression using this method. The present invention also relates to a novel gradation expression method that enables fine gradation expression by expressing gradation using dots of two sizes.

<Conventional technology> Conventionally, methods for expressing gradation include changing the plate depth in gravure printing to change the amount of ink transfer, and using a thermal head in which the area of the ink ribbon and heating element is always constant. , a method of expressing gradation by changing the amount of ink transferred to the printing material by changing the amount of heat generated by the heating element through energization control, and a method of expressing gradation by changing the amount of ink transferred to the printing substrate, and by changing the size of the dots as seen in gravure printing, offset printing, etc. There are known methods for expressing gradation.

<Problems to be Solved by the Invention> However, in the prior art described above, the former method is possible by gravure printing or printing using a ribbon impregnated with a sublimable dye and a thermal head; has poor light resistance and weather resistance, and printed matter printed using this dye has poor abrasion resistance and is easily peeled off.Therefore, an overcoat agent must be applied from above as a post-process. However, the process was extremely complicated. Most of the drawbacks of this method can be overcome by using an ink made of a hot-melt resin. Therefore, the latter method attempts to express gradations using ink made of thermofusible resin, but with this method, T
If an amount of energy exceeding 70% of the amount required to form a dot with a size of Adjacent dots would stick together, resulting in a loss of density reproducibility, making it impossible to express sufficient gradation.

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art. Namely, no matter what kind of ink is used, the shape and size of the dots will not be irregular, and the reproducibility of the density will be excellent. The purpose of this paper is to disclose a gradation expression method.

Yet another object is to disclose a gradation expression method that can also perform fine gradation expression.

<Means for Solving the Problems> In order to solve the above problems, the gradation expression method according to the present invention reduces the interval between the centers of every other dot to T.
If the energy to be applied when printing dots with a diameter of T is E, then main dots formed by applying an energy of 0 to 70% of E are arranged every other time, and E is applied between them. It is also characterized in that sub-dots formed by applying energy of 0 to 30% of the dots are arranged every other dot.

In the gradation expression method according to claim 2 of the present invention, the interval between the centers of every other dot is T, and the energy applied when printing dots having a diameter of T is E. Then, an energy of 0 to 70% of E is applied, and the main dots formed with ink made of a heat-melting resin are arranged every other time, and an energy of 0 to 30% of E is applied during that time, and the main dots are It is characterized in that sub-dots formed with ink made of a synthetic resin are also arranged every other dot.

In the printed matter according to claim 3 of the present invention, the interval between the centers of every other dot is T, and the energy applied when printing the dots having a diameter of T is E.
Then, the main dots formed by applying energy of 0 to 70% of E are placed every other dot, and between them, the main dots are formed by applying energy of 0 to 70% of E.
It is characterized in that gradation is expressed by a method in which sub-dots formed by applying 0% energy are arranged every other dot.

In the printed matter according to claim 4 of the present invention, the interval between the centers of every other dot is T, and the energy applied when printing the dots having a diameter of T is E.
Then, an energy of 0 to 70% of E is applied, and the main head is formed by a thermal head made of ink containing a thermofusible resin, has a constriction in the center, and has a heating element whose heating area can be changed by controlling the energization. Arrange the dots every other dot, apply energy of 0 to 30% of E between them,
It is made of ink containing a heat-melting resin, has a constriction in the center, and is characterized by the fact that sub-dots formed by a thermal head with a heat-generating element whose heat-generating area can be changed by energization control are placed every other dot. In the printed matter according to claim 5 of the present invention, the interval between the centers of every other dot is T, and the energy applied when printing the dots having a diameter of T is E.
Then, an energy of 0 to 70% of E is applied, and the head is made of ink containing a thermofusible resin, is constricted in the center, and is formed by a thermal head having a heating element whose heating area can be changed by controlling the energization. The main dots are arranged every other time, and energy of 0 to 30% of E is applied between them, and the ink contains a heat-melting resin.The central part is constricted, and the heat generating area can be changed by controlling the current flow. This method is characterized in that gradations are expressed by arranging sub-dots formed by a thermal head having a heating element every other dot.

In the gradation expression method according to claim 6 of the present invention, where T is the interval between the centers of every other dot, 0 of T
Main dots having a diameter of ~70% are arranged every other time, and sub dots having a diameter of 0 to 30% of T are arranged between them, and are ink containing a hot melt resin. I will explain about it. The ink is a ribbon. The ribbon 2 is a base film coated with a hot-melt resin.

That is, this ribbon 2 is provided with a release layer made of a heat-melting compound mainly composed of waxes with a melting point of 60 degrees C on a heat-resistant base, and on this release layer, a colored layer and a saturated polyester are provided. A heat-melting resin layer consisting of resin and lubricant is provided. The thermofusible resin has a glass transition temperature of 50 to 70 degrees C1, a liquefaction temperature of 70 to 100 degrees C1, and a molecular weight of 2,000 to 8,000.

The substrate used is preferably a polyester film having a thickness of 2 to 10 IIm, with a layer provided on the back side thereof to prevent sticking of the thermal head. The release layer is formed so that the hot-melt resin layer can be easily peeled off from the substrate during thermal transfer, and a material with weak adhesive strength to the substrate is used. , paraffin wax, carnauba wax, montan wax,
Melting point is 60 degrees C, such as microcrystalline wax, higher fatty acids, higher alcohols, higher fatty acid amides, etc.
Waxes at ~120 degrees Celsius are used.

The saturated polyester resin constituting the heat-melting resin layer has a molecular weight of 2,000 to 8,000 in order to improve thermal transferability to the thermal head 9 and durability of the printed image after transfer.
, liquefaction temperature 70-100 degrees C1 and glass transition temperature 5
Use one with a temperature range of 0 to 70 degrees C. This is to improve thermal transfer characteristics. This saturated polyester resin is formed by condensation polymerization of a dicarboxylic acid component and a diol component. Examples of the diol component include aliphatic dicarboxylic acids such as ethylene glycol, 1.4-butanediol, diethylene glycol, neopentyl glycol, etc., which are obtained by condensation polymerization in various combinations. Note that by changing this blending ratio, a terminal hydroxyl group type polyester resin or a terminal carboxyl group type saturated polyester resin may be used.

A lubricant is a necessary part to improve the transferability during thermal transfer and the abrasion resistance of printed images. By adding this lubricant, the image will not be damaged by scratches, etc., and will be resistant to abrasion caused by erasers etc. Specific examples of lubricants include Teflon powder, natural waxes such as animal waxes, vegetable waxes, mineral waxes, petroleum waxes, synthetic hydrocarbon waxes, fatty acid alcohols and acid waxes, Synthetic waxes such as fatty acid esters and glycerin waxes, hydrogenated waxes, synthetic ketone waxes, amine and amide waxes, chlorinated hydrocarbon waxes, synthetic animal wax waxes, alpha olefin waxes, zinc stearate, etc. Examples include metal salts of higher fatty acids.

As the colorant, commonly used dyes and pigments can be used, but from the viewpoint of improving the weather resistance of the transferred and recorded printed image, it is preferable to use an inorganic or organic colorant.
Specific examples of colorants include titanium oxide, calcium carbonate, Hanzai Elo Oil Yellow 2G, carbon black, oil fluorac, pyrazolone orange, oil relad, red iron oxide, anthraquinone violet, phthalocyanine blue, phthalocyanine green, aluminum powder, bronze powder, pearl etching. Examples include sense, magnetic powder, and the like.

The composition of the composition forming the hot-melt resin layer is such that the amount of coloring is 10 to 30 parts by weight based on the total solid content of 100,
The thermoplastic resin is 50 to 80 parts by weight, the lubricant is 5 to 30 parts by weight, and various additives can be added as necessary. The amount added is desirably 10 parts by weight or less per 100 parts by weight of the composition forming the hot-melt resin layer.

This hot-melt resin layer is formed by coating a release composition on the surface of a substrate by a hot-melt method or a solvent coating method, drying to form a release layer, and applying a composition in which a resin and a lubricant are dispersed or dissolved in a solvent. , barcode coating, blade coating, air knife coating, gravure coating, roll coating, or other solvent coating methods, and drying.

The thermofusible resin has colors such as yellow, magenta, and cyan, and a yellow portion, a magenta portion, and a cyan portion are provided on the base film so as to be divided in the longitudinal direction of the transfer ribbon. Positioning the yellow, magenta, cyan, etc. of the transfer IJ Pon between the thermal head and the card is performed by controlling the forward and reverse rotation of the reel.

Printed matter that can be expressed in gradations by the method of the present invention include postcards, envelopes, various cards such as ID cards, and the like.

<Operation> According to the gradation expression method of the present invention, let T be the interval between the centers of every other dot, and let E be the energy applied when printing dots having a diameter of T. Then, since the main dot was first formed by applying energy of 0 to 70% of E, the resin forming the main dot would not ooze out and the shape of the main dot would be irregular, and the main dot would not be formed. Since the sub-dots are formed by applying energy of 0 to 30% of E in between, the resin forming the sub-dots does not ooze out, and the shape of the sub-dots does not become irregular and the gradation decreases. In addition, the main dot size of the dots formed in this way is approximately 70% of T at maximum.
diameter, and the maximum size of the sub-dot is about 30% of T.
When the size of the dot is maximized, it completely fills the space and provides excellent gradation expression.

<Example 1> Next, an example of the present invention will be described in which a ribbon containing ink made of a heat-melting resin and a heating element (hereinafter referred to as a heat concentrating type heating element)
A case will be described in which gradation is expressed using a thermal head having a thermal head as shown in FIG.

FIG. 4 is an explanatory diagram of one aspect of the printing device used in this embodiment. The printing apparatus used in this embodiment includes a printing section 1, an ink ribbon supply/winding section 2, and a printing medium conveying section 3. The printing section 1 includes a thermal head 10 having a shape as shown in FIG. 2, and a platen roller 7 arranged below the thermal head 10. A heating element 11 having a shape as shown in FIG. 3(a) is fixed to the tip of the short side of the thermal head 10. As shown in FIG. The printing unit 1 is arranged with the heating element 11 facing downward.

The spacing (pitch) between the heating elements 11 of the thermal head 10 used in this embodiment is 125μ, which is equal to the spacing between every other dot, that is, T=125μ. In the printing unit 1, the size of the dots is controlled by controlling the applied energy. One way to control the applied energy is to apply heating pulses at a constant cycle, the number of which corresponds to the recording density. There are a number modulation method and a pulse time modulation method in which a heating pulse is applied once for a time corresponding to each portion. As the applied energy, current, voltage, and time for applying these are used. When energy is applied to the thermal head 10, the heating element 11 shows a temperature distribution as shown in FIG. 3(b). By changing the amount of applied energy, the size of the temperature distribution curve changes, and The size of the printed dots can also be changed.

The ink ribbon supply/winding unit 2 has a delivery cylinder 5 and a take-up cylinder 6. The delivery cylinder 5 has a ribbon 4 containing a hot-melt resin wound around a roll cane. The ribbon 2 pulled out from the cylinder 5 passes under the printing section 1 and is wound around the winding cylinder 6. The ink ribbon supply/winding section 2 is driven by a transmission means consisting of a pulse motor and gears (not shown).

The printing material conveyance section 3 includes two sets of rollers 8, 9, . These rollers consist of 8
．． It is a zelkova that can be fed by sandwiching the material to be printed between 9. The printing material conveying section 3 also uses the above-described printing device and the heat-fusible ribbon 2 from a pulse motor and gears (not shown), and the method of forming an image using only one thermal head 10 is performed. and a case where two thermal heads 1O are used are considered.

The case where only one thermal head 10 is used will be described below with reference to FIG.

First, the first method is to print the main dots 12 along the width direction (hereinafter referred to as the main scanning line direction) of one thermal head, as shown in FIG. In this example, the sub-dot 1 is shifted in the vertical direction (hereinafter referred to as the sub-scanning line direction) with respect to the width of the thermal head (approximately 63u in this example).
3 is printed, and then the main dot 12 is printed by shifting the thermal head by T/2 pitch in the sub-scanning line direction. This is 1
Repeat until printing is completed to the edge of the image. When printing is completed, return the thermal head to the original position, and then shift the thermal head by T/2 pitch in the main scanning line direction.
This time, the sub dot 13 is printed first. After that, as before, the main dots 12 and sub-dots 13 are printed alternately while shifting the thermal head by T/2 pitch in the sub-scanning line direction, and 1i! Printing ends when the end of the image is printed.

Next, the second method is as shown in FIG. 5(b),
The main dot 12 is printed on one main scanning line, then the sub dot 13 is printed by shifting the thermal head by T/2 in the main scanning line direction, and the main dot 12 is printed by further shifting the thermal head by T/2 in the sub scanning line direction. is printed, then the excitation dot 13 is printed with a shift of -T/2 in the main scanning direction, and finally the excitation dot 13 is printed by T/2.
12 in the sub-scanning line direction.

This operation is repeated several times as a basic unit, and printing ends when the end of the image is printed.

Furthermore, the third method, as shown in FIG. 5(C), is to print the main ton) 12 on one main scanning line, and then thermally print 7 dots by T/'2 in the main scanning line direction. Print the sub dots 13 with a shift, then print the main dots 12 with a shift of T/2 in the sub-scanning line direction, then print the sub dots 13 with a shift of -T/2 in the main scan line direction, -DanT/
The main dot 12 is returned by 2 in the main scanning line direction and finally shifted by T/2 in the sub-scanning direction to print the main dot 12, thereby completing the basic operation. After this, this basic operation is repeated several times, and printing ends when the end of the image is printed.

Next, a case where two thermal heads 10 are used will be described with reference to FIG. First, the thermal head 10 (a
) on one main scanning line, and another thermal head 10
The thermal head 10 (b) is installed at a position shifted from (a) by T/2 pitch in the main scanning direction and an integral multiple of T/2 pitch in the sub-scanning direction.
(a) and thermal head 10(b) alternately, T/2
Print while moving in pitch increments in the sub-scanning line direction. The thermal head 10(b) may be installed at the front or rear of the thermal head 10(a) as long as it can form an image completely during printing.

In this example, an image was formed on paper using the pulse number modulation method and the first method as the image forming method. The resulting image had a uniform dot shape as shown in FIG. 7(a), and was clear and rich in gradation. The density reproducibility was also measured using a transmission type density needle, and it was found that the density was reproduced smoothly as shown in FIG.

<Example 2> The same printing device and ribbon containing ink made of the same thermofusible resin as used in Example 1 were used, the same pulse number modulation method was used as in Example 1, and the first method was used to print a ribbon made of vinyl chloride. An image was formed on the card. As in Example 1, the image obtained was clear and rich in gradation, expressing fine gradation, and was printed with ink made of hot-melting resin, so it had good weather resistance. It had excellent light resistance, scratch resistance, etc.

<Effects of the Invention> By expressing gradations using the gradation expression method of the present invention, the shape of the dots will not be irregular, so density reproducibility is ensured, and gradation can be expressed smoothly. It became so. In particular, even when an ink made of a heat-soluble resin is used, the above effects can be obtained, and at the same time, the printed matter formed by this method has excellent light resistance, weather resistance, and scratch resistance. In addition, since this gradation expression method attempts to express gradation using dots of two sizes, it is possible to express subtle gradations, and when the size of both dots is maximized, the image becomes perfect. Since the area is filled with dots, it has become possible to disclose an extremely excellent gradation expression method, such as the gradation in areas with high density being well expressed.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of an image expressed in gradation by the gradation expression method of the present invention and a heating element, FIG. An enlarged view of the heating element attached to the thermal head and the temperature distribution when energy is applied, Figure 4 is an explanatory diagram of the printing device used in this example, and Figures 5 and 6 are the printing of Figure 4. An explanatory diagram illustrating the image forming method when forming an image using the apparatus, FIG. 7 shows the compression of dot shapes formed by the present method and the conventional method, and FIG. 8 shows the application of the image formed by the present method. Explanatory diagram explaining the relationship between energy and concentration, No. 9
The figure is an explanatory diagram illustrating the relationship between applied energy and density of an image formed by a conventional method.

Claims (6)

[Claims] (1) The interval between the centers of every other dot is T
If the energy applied when printing a dot with a diameter of T is E, then main dots formed by applying an energy of 0 to 70% of E are placed every other A gradation expression method characterized in that sub-dots formed by applying energy of 0 to 30% of the above are also arranged every other dot. (2) The gradation expression method according to claim (1), wherein the main dots and the sub-dots are formed with ink made of a thermofusible resin. (3) A printed matter expressed in gradation by the method according to claim (I). (4) The gradation expression method according to claim (2), wherein the main dots and the sub-dots are formed by a thermal head having a heating element whose central portion is constricted and whose heating area can be changed by controlling energization. (5) A printed matter expressed in gradation by the method according to claim (4). (6) The interval between the centers of every other dot is T
Then, main dots with diameters ranging from 0 to 70% of T are placed every other time, and subdots with diameters ranging from 0 to 30% of T are arranged every other time. A gradation expression method characterized by placement.