Image formation method

Abstract

To provide an image formation method which can realize density gradation in a wider range without using a wide variety of ink ribbons.SOLUTION: In an image formation method in which an ink ribbon is used to form an image on an object to which the image is transferred (transferred object), image information for forming the image is acquired and an upper limit concentration in the ink ribbon is acquired. When a maximum concentration in the image information exceeds the upper limit concentration, additional ink dots d1 are placed from the ink ribbon onto ink dots d disposed on the transferred object in a portion of the maximum concentration.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming method, and more particularly to an image forming method using an ink ribbon. [Background technology]

[0002] Image formation using ink ribbons of the thermal melt type or dye sublimation type (see, for example, Patent Document 1) is widely practiced. In such image formation, color density gradation is created by the density of ink dots transferred from the ink ribbon to an object such as an image receiving sheet. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-69973 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described method of creating density gradations, the range of achievable gradations is limited by the density of the ink on the ink ribbon. That is, the upper and lower limits of the achievable gradations are roughly determined by the amount of pigment or dye in the ink on the ink ribbon. At the same time, there is a growing demand to achieve a wider range of density gradations using a single type of ink ribbon.

[0005] In view of the above circumstances, an object of the present invention is to provide an image forming method that can realize a wider range of density gradations without using many types of ink ribbons. [Means for solving the problem]

[0006] The present invention is an image forming method for forming an image on a transfer target using an ink ribbon. In this image forming method, image information for forming an image is obtained, an upper limit density in the ink ribbon is obtained, and when the maximum density in the image information exceeds the upper limit density, ink dots are placed from the ink ribbon on top of the ink dots placed from the ink ribbon on the transfer object in the area of maximum density. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an image forming method that can realize a wider range of density gradation without using many types of ink ribbons. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram illustrating an example of an ink ribbon used in an image forming method according to an embodiment of the present invention. [Figure 2] 1A to 1C are diagrams showing examples of ink dot arrangements in a normal image forming method using an ink ribbon. [Figure 3] 1A and 1B are diagrams showing examples of ink dot arrangements used in the image forming method according to the present embodiment. [Figure 4] 10 is a part of a flowchart showing an example of the flow of image formation by a printer employing the image forming method. [Figure 5] 5 is the remainder of the flowchart shown in FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0009] An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the configuration of an ink ribbon 1 according to this embodiment. The ink ribbon 1 shown in FIG. 1 is a melt transfer type, and as shown in (a) and (b), transfer ink layers 12 each consisting of a yellow layer Y, a magenta layer M, a cyan layer C, and a black layer B are repeatedly formed in a surface-sequential manner on one surface of a substrate 11. The transfer ink layer 12 may not include the black layer B, or may be composed of four or more colors including other colors. Position control marks 16 are formed between the repeatedly formed transfer ink layers 12. The transfer ink layer 12 can be formed, for example, by applying and drying a coating liquid prepared by blending a dye and / or pigment, a binder, a solvent, and the like. 1 shows a melt transfer ink ribbon, the application of the image forming method according to this embodiment is not limited to image formation using a melt transfer ink ribbon, but can also be applied to image formation using a dye sublimation ink ribbon. Therefore, in the following description, when simply referring to an "ink ribbon," it includes both melt transfer and dye sublimation ink ribbons unless otherwise specified.

[0010] In normal image formation using an ink ribbon, dots of ink (hereinafter referred to as "ink dots") fly from the ink ribbon toward and adhere to a transfer target such as an image receiving sheet or intermediate transfer medium. The density of the ink dots then represents the density gradation of the color associated with the ink. For example, when the color is light, the number of ink dots d per unit area in the area where that color is printed is reduced, as shown in Figure 2(a), and as the color becomes darker, the number of ink dots d is increased, as shown in Figure 2(b).

[0011] In this method, as shown in Figure 2(c), the darkest state of a color is when ink dots d are arranged with almost no gaps in the area where that color is printed, and the darkness is determined by the density of the ink dots d themselves, that is, the color and amount of pigment, dye, etc. contained in the ink dots d. Therefore, it is difficult to express density gradations that include greater darkness than this.

[0012] Therefore, in this embodiment, if the density specified at the time of printing exceeds the upper limit of the ink ribbon being used, a new ink dot d1 is placed so as to overlap the ink dot d already placed, as shown in (a) of Figure 3. This increases the number of ink dots d per unit area beyond the upper limit shown in Figure 2(c), enabling color expression beyond the density gradation achieved by the above method. Therefore, it is possible to create images with a wider range of density gradation using only one type of ink ribbon, without using a separate ink ribbon with a higher upper limit density.

[0013] The number of additional ink dots d1 does not necessarily have to be the same as the number of ink dots d placed below, but may be determined appropriately based on the difference between the upper limit density of the ink ribbon being used and the density specified at the time of printing. This makes it possible to express density gradations in finer steps even in a range exceeding the upper limit density of the ink ribbon. Furthermore, after the additional ink dots d1 are arranged with almost no gaps between them, additional ink dots (secondary additional ink dots) d2 may be arranged on top of the ink dots d1, as shown in Figure 3(b), which allows the upper limit of density gradation to be further expanded.

[0014] An example of a processing procedure on the printer side for realizing image formation according to this embodiment is shown as a flowchart in FIGS. First, in step S1, the printer stores the upper limit density of each color in the installed ink ribbon (for example, in the case of ink ribbon 1, each of the yellow layer Y, magenta layer M, cyan layer C, and black layer B). Information regarding the upper limit density can be stored, for example, in an IC chip attached to the ink ribbon cartridge, and the printer's control program or the like can be configured to retrieve this information at a desired timing after the cartridge is installed in the printer.

[0015] In step S2, the printer receives information about the image to be formed (image information) from a computer, a mobile terminal, or the like, via a wired or wireless connection. In step S3, the printer extracts density information for each color from the received image information.

[0016] In step S4, the printer compares the maximum density of each color contained in the density information with the upper limit density of each color stored, and determines whether there is a color whose maximum density exceeds the upper limit density. If the determination in step S4 is No, the process proceeds to step S51. Based on the received information, the printer performs normal image formation using an ink ribbon on the set paper or other transfer medium, and then the process ends.

[0017] If the determination in step S4 is Yes, the process proceeds to step S61, and the image forming method according to the present invention is executed from step S61 onwards. The contents of step S61 onwards are shown in FIG. In step S61, the printer obtains the difference between the maximum density of each color included in the density information and the stored upper limit density of each color. In step S62, the printer calculates the amount of ink dots required to reach the maximum density of each color included in the density information based on the difference value obtained in step S61. If the maximum density cannot be reached even when the additional ink dots d1 are placed roughly closely together, as shown in Figure 2(C), secondary additional ink dots d2 can be placed, as shown in Figure 3(b), or a third or fourth layer of ink dots can be placed using a similar procedure. The printer adds the number of additional dots and layers set based on the calculated amount of ink dots to the print data for forming an image based on the image information.

[0018] In step S63, the printer forms an image using the print data prepared in step S62. In image formation, for areas that do not contain colors exceeding the upper limit density, the ink ribbon is placed over the paper or other paper on which the image is to be formed, and the required areas are heated and transferred using a thermal head, just as in normal image formation. Meanwhile, for areas that do not contain colors exceeding the upper limit density, thermal transfer is performed two or more times to achieve the desired color development, and additional ink dots are placed as needed. The placement of the additional ink dots is performed by placing the unused portion of the ink ribbon over the paper or other paper after the first thermal transfer. When image formation is completed on all the locations, the series of processes ends.

[0019] The image forming method according to this embodiment requires slightly more time and consumes a slightly larger amount of ink ribbon than the normal image forming method, but as described above, it can achieve a much wider range of density gradations than conventional methods without changing the ink ribbon. Furthermore, it is extremely versatile, as it can be applied to conventional cartridges and printers with only minor modifications, such as changing the printer's control program.

[0020] The upper limit density of the ink ribbon used in the image forming method according to this embodiment can be set as appropriate, but by setting the upper limit density low, it is possible to improve the print quality in low density areas. As described above, printing in low-density regions is performed using a small number of ink dots, but in areas close to the minimum density, the ink dots are arranged quite sparsely, resulting in many areas where the transfer target material is exposed. This can result in a poor appearance or poor feel in the low-density areas of the printed material on which the image is formed. However, when the image forming method according to this embodiment is performed using an ink ribbon with a low maximum density, more ink dots can be arranged even near the minimum density of conventional ink ribbons, preventing the aforementioned poor appearance and poor feel of the printed material. In addition, by reducing the minimum density itself, it is possible to express even lighter colors, and by further increasing the number of additional ink dots, it is possible to maintain a high maximum density. Furthermore, because the increase in density with each additional ink dot is smaller, it is possible to achieve finer gradations. In actual image formation, a photograph of a person's face is an example of an image in which pale colors are frequently used. Therefore, the image formation method according to the above-described modified example is extremely effective in areas such as passports that include photographs of faces. For example, if a color with a saturation of 5 or less on the Munsell color scale is considered a light color, then a color close to the upper limit of density, such as lip color, can be exemplified as a lightness of 6 to 7 and a saturation of 3 to 4 on the Munsell color scale. For skin color, it can be exemplified as a lightness of 6.5 to 7.5 and a saturation of 2.0 to 4.5. For hair color, it can be exemplified as a lightness of 2.5 to 3.5 and a saturation of 1 to 4. In this way, the inherent saturation of the face falls within the light color range. On the other hand, for example, the blue of the French flag has a Munsell color scale with a brightness of 3.7 and a saturation of 12.1, which is higher than the colors found on faces. If the saturation is set to 14 or less, the vivid colors of flags and other colors can be expressed. Generally, such high-saturation areas are not very large, so they can be formed by transferring them two or more times using areas on the ink ribbon that do not form facial images. The maximum density is set for each of the three colors of the image: cyan, magenta, and yellow. The maximum density for each color is set as a density value corresponding to the color of the ribbon. In other words, the theoretical maximum density is when each color is transferred in a single color over the entire surface (no white background, only the ribbon color). If each color is not transferred over the entire surface even at the printer's maximum density (white background remains), the density is calculated by multiplying the density of each ribbon color by a coefficient. This coefficient can be between 0.6 and 0.99. The maximum density that can be produced is, for example, 1.3 or more and 2.5 or less.

[0021] The present invention has been described above using an embodiment, but the specific configuration is not limited to this embodiment, and includes modifications and combinations of configurations within the scope that does not deviate from the gist of the present invention.

[0022] For example, in step S62 described above, the number of additional dots and the number of layers that cannot reach the maximum density of each color included in the density information may be set based on the difference value acquired in step S61. This narrows the range of achievable density gradations compared to the above embodiment, but by limiting the number of additional dots to, for example, one layer, it is possible to expand the range of achievable density gradations by a certain amount while suppressing increases in the required time and consumption of ink ribbon. [Explanation of symbols]

[0023] 1 ink ribbon d ink dot d1 additional ink dots d2 Secondary additional ink dots

Claims

1. An image forming method for forming an image on a transfer target using an ink ribbon, comprising: acquiring image information for forming the image; obtaining an upper limit density of the ink ribbon; When the maximum density in the image information exceeds the upper limit density, additional ink dots are placed from the ink ribbon on the ink dots placed from the ink ribbon onto the transfer target in the area of the maximum density. Image forming method.

2. depositing a secondary additional ink dot from the ink ribbon on top of the additional ink dot; The image forming method according to claim 1 .

Images