JP3118827B2 - Judgment method of image quality in transfer printing method - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for quantitatively determining image quality in a transfer printing method.

[Related Art] In the transfer printing method, a transfer sheet having a colorant layer and an image receiving sheet are superimposed on each other, and printing energy (for example, thermal energy) is supplied to the back surface of the transfer sheet, whereby a transfer image is formed on the image receiving sheet. What you get.

Conventionally, as a method of determining the image quality of a transferred image obtained by the transfer printing method, that is, a transferred printed material, visually observe abnormal transfer conditions such as uneven density and missing or missing dots forming an image, A method of determining image quality is used.

The image quality depends on materials such as a transfer sheet (for example, an ink transfer sheet) and an image receiving sheet (for example, photographic paper or image receiving paper) used in the transfer printing method, and a printing energy supply means for transfer, such as control of a thermal head or a laser beam. Since the quality of the hardware is greatly affected by the quality of the hardware configuration, etc., quantitatively measuring the image quality of the transferred print and judging the tendency is important in confirming the direction of material development and improvement of the hardware configuration. It is becoming an important indicator.

[Problems to be Solved by the Invention] However, in the conventional method of visually judging the image quality of a transferred print, the environment (temperature, humidity, light source condition, and the like) for observing the sample to be judged, and the physical condition of the person who visually judges. Depending on the image of the sample to be determined at that time, and the condition of the sample previously observed, the criterion for determining the image quality greatly varies. It may fluctuate for each judgment.

Furthermore, even when the judge who observes is different, the judgment made changes, and in the end, only the sample having a large difference can obtain the reliability of the judgment, which is quantitative and stable. Thus, it was impossible to determine the image quality of the transferred print.

Therefore, the present inventor has conducted intensive studies and, as a result, noticed that unevenness in density occurring in the transferred print and chipping of dots forming an image, chipping, etc., deteriorated image quality,
We arrived at the idea that quantification and judgment can be made by measuring the magnitude of the density unevenness and the degree of the missing or missing dots of the image forming dots, and quantifying it.
The present invention has been completed.

That is, an object of the present invention is to provide a method for quantitatively measuring the image quality of a transferred print, and objectively determining the quality.

Means for Solving the Problems However, the gist of the present invention is to superimpose a transfer sheet having a colorant layer and an image receiving sheet and supply printing energy to the back surface of the transfer sheet, so that the image is received on the image receiving sheet. In the transfer printing method including obtaining a transfer image, in determining the image quality of the transfer image, at least the measurement target area is supplied. (A) By supplying a printing energy of a constant density to the back surface of the transfer sheet, (B) processing the obtained transferred image with an image processing apparatus to obtain color density level data for each unit pixel in the processing; (c) obtaining the same measurement target area Statistical processing results of color density level data in a plurality of transferred images, or obtained from the complete color density standard sample with the printing energy of the above-mentioned constant density Setting the color density level to be performed as a normal level; (d) comparing the color density level data in all of the unit pixels with the normal level, and determining the area of a portion having a color density lower than the normal level as a blank area And (e) determining the image quality based on the ratio of the blank area to the area of the measurement target area. The method of determining the image quality in the transfer printing method, the method comprising: , There is.

 Hereinafter, the present invention will be described in detail.

First, the basic concept underlying the present invention will be described.

As described above, the determination of the image quality can be made by measuring the magnitude of the density unevenness of the image or the missing or missing dots of the image forming dot.However, the unevenness of the image density or the missing of the dot forming the image is possible. It is considered that the lack or the like means that there is no color of the original density at the place where it should have been, and the "white portion where the normal color density is not colored" deteriorates the image quality of the transferred print. It is thought that it is.

Therefore, by measuring this “white portion”, it is possible to quantitatively express the image quality of the transferred print.

The method of calculating the area of the “white portion where the normal color density is not colored” of the sample to be determined basically includes the following five steps (a) to (e).

(A) A fixed density printing energy is supplied to the back surface of the transfer sheet to obtain a transfer image on the image receiving sheet.

(B) The transferred image is processed by the image processing apparatus to obtain color density level data at each unit pixel in the processing.

(C) Set the normal level.

(D) The data is compared with a normal level, and an area smaller than the normal level is calculated as a blank area.

(E) Calculate the ratio of the white area in the measurement target area (hereinafter referred to as “white area ratio”). If the white area ratio is small, the image quality is high, and if it is large, the image quality is low. judge.

Although a specific procedure is not particularly limited, for example, it is as follows.

After making the temperature environment at the time of making samples such as printing machines and receiving papers constant and stable, and keeping the pressure constant, the printing start temperature and printing temperature are stabilized (prevention of energy increase due to heat storage). To prepare a sample of the transfer print.

In particular, creating a single color of magenta is effective in capturing images with a camera or in correspondence with visual observation.However, even in the case of other colors or transfer prints formed with full color images, printing is performed inside the measurement target area. If no energy density gradient occurs, it is effective as a sample.

Only a certain area of a certain place of the sample is extracted as a measurement target area, that is, a determination place, and is taken into the image processing equipment as a video.

The captured video is recognized by unit pixels of an appropriate size, and color density level data at each unit pixel is obtained.

Based on the color density data of a plurality of samples obtained for the same measurement target area, for example, the peak level is set as a normal level. Alternatively, when a complete and ideal color density standard sample exists, the color density level is set as a normal level. Of course, other methods of setting the regular level may be adopted.

With the normal level as a boundary, the color density data in each unit pixel is binarized, and the image is displayed in two colors. At this time, so that the portion of the color density below the normal level remains black,
Negative processing is better because area measurement is easier.

The area of the white part after image processing (black part when negative processing is performed), that is, the white area is measured.

The ratio of the obtained blank area to the determination area,
That is, the blank area ratio is calculated.

The image quality is determined based on the white area ratio.
Qualitative expression of image quality (for example,
If it is necessary to correspond to “excellent”, “good”, “acceptable”, “impossible”, etc.), determine it empirically from the data on the correspondence between the numerical value of the blank area ratio and the visual judgment. Can be.

[Examples] Next, specific embodiments of the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention.

Sample 1 was prepared by using a dye sublimation type transfer sheet and changing the sublimation dye receiving type photographic paper (image receiving paper) to various types.

The preparation of the sample is a method of applying printing energy of a constant density, by controlling the printing temperature at the same time as keeping the pressing constant and controlling the printing energy after the printing is started, taking into account the thermal storage effect of the thermal head. In this case, a constant heat energy was controlled so as to be applied to the rear surface of the transfer sheet.

 The following were used as the image receiving sheet.

No.1 Printing paper based on synthetic paper No.2 Printing paper based on paper (cellulose) with medium dyeing layer thickness No.3 Printing based on paper (cellulose) Paper, thick dyeing layer No.4 Printing paper based on paper (cellulose), thin dyeing layer No.5 Printing based on foamed PET (polyethylene terephthalate) Paper No.6 Printing paper using milk white PET as a base material Each of the above-mentioned image receiving sheets is used.Magenta single color is used as the transfer sheet, and a printing energy of 0.21 W / dot is supplied to transfer the sample of the transferred printing material. Created.

Image processing equipment (MKSIPS product name, manufactured by Mitsubishi Kasei Co., Ltd.)
A particle image analysis system was used as an image processing program. ) Was captured as an image with a resolution of 1600 pixels per 1 mm ^2, binarized according to the normal color density level of each sample, the white area was calculated, and the white area ratio was further calculated.

The results are compared with the results of visual judgment by the conventional method.
It is shown in FIG.

As described above, the judgment result based on the blank area ratio obtained by the method of the present invention was in good agreement with the judgment result by visual observation.

[Effects of the Invention] The following effects were achieved by the method of the present invention.

(1) The image quality of the transferred print, which has been visually judged, can be quantitatively represented by numerical values.

(2) The determination is no longer affected by the person, date, and visual environment to be determined.

(3) Subtle differences can be objectively determined without being influenced by images.

(4) Accumulation of data, and thus analysis, became possible.

Claims (1)

(57) [Claims] In a transfer printing method, a transfer sheet having a colorant layer is superimposed on an image receiving sheet, and printing energy is supplied to the back of the transfer sheet to obtain a transfer image on the image receiving sheet. In determining the image quality of the image, at least for the measurement target area: (a) obtaining a transfer image on the image receiving sheet by supplying a constant density of printing energy to the back surface of the transfer sheet; (b) the obtained transfer Processing an image with an image processing apparatus to obtain color density level data for each unit pixel in the processing; (c) statistical processing results of color density level data in a plurality of transfer images obtained for the same measurement target area; Or, from the complete color density standard sample, the color density level to be obtained with the printing energy of the above-mentioned constant density is regarded as a normal level. (D) comparing the color density level data in all of the unit pixels with the normal level, and calculating the area of a portion having a color density lower than the normal level as a blank area; and (e) Determining the image quality based on the ratio of the blank area and the area of the measurement target area. The method of determining image quality in the transfer printing method.