Disclosure of Invention
This patent is just proposed based on the above-mentioned demand of prior art, and the technical problem that this patent will be solved provides a method that reduces ultraviolet fluorescence ink printing color colour difference to improve the color restorability of fluorescence ink printing.
In order to solve the above technical problem, the technical solution provided by this patent includes:
1. a method of reducing color variation in a printed ultraviolet fluorescent ink, the method comprising:
printing fluorescence intensity values of different colors of fluorescent ink superposed on paper according to different sequences, and determining the overprinting sequence of the different colors of ink; the method comprises the steps of printing a first color and a second color on a printing stock in sequence by using an ink-jet printing method, measuring fluorescence intensity of a superposed part of the first color and the two colors respectively, comparing the fluorescence intensity of the first color with the fluorescence intensity difference of the superposed two colors, and taking a printing color sequence with a small value of the fluorescence intensity difference as a overprinting sequence of the printing ink with different colors.
Secondly, using three primary colors of fluorescent ink and color light to print a color code document by adopting superimposed dot ink-jet according to the color sequence determined in the first step;
measuring a color block in the color code file printed in the step two under an ultraviolet light environment;
and step four, establishing a corresponding relation file between the original image and the fluorescent ink color development.
Preferably, in the second step, the color patch file is screened to form a file for printing, and the printer executes a printing action according to the driving of the file; and in the screening process, screening is performed in a mesh point overlapping mode.
Preferably, in the third step, the device for measuring color blocks comprises a box body, one surface of the box body is opened for measurement, and the inner wall of the box body is a diffuse reflection surface so as to uniformly distribute light; an ultraviolet light source is arranged at the top of the box body, an inclined plane of the object stage and a horizontal plane form an angle of 45 degrees, the object stage is arranged in the box body to bear the printed color code document, and the ultraviolet light source emits ultraviolet light downwards to irradiate on the object stage arranged below the ultraviolet light source.
Preferably, when selecting the printing stock, a white point is determined for the printing stock printed by the fluorescent ink, and a spectrogram of the fluorescent three-color overprint white color block under an ultraviolet lamp is used as white point data.
The fluorescent ink product is printed by adopting a dot superposition ink jet printing mode, the color gamut space range of the fluorescent ink printing is improved by a method for determining the color sequence through fluorescence intensity measurement, and the original color and the color of the fluorescent printing ink are reasonably mapped by a color management method, so that the color difference of the fluorescent ink printing is reduced.
Detailed Description
The following detailed description of the embodiments of the present patent refers to the accompanying drawings and is only for the purpose of illustrating preferred embodiments of the patent and is not to be construed as limiting the scope of the patent.
The specific embodiment provides a method for reducing color aberration of printing of ultraviolet fluorescent ink. In the embodiment, the method breaks through the traditional idea of improving the fluorescent ink imaging through the arrangement mode of printing dots, and starts with another idea to improve the color reducibility of the fluorescent ink and ensure the printing definition of the fluorescent ink at the same time.
The method for reducing the color difference of the printing color of the ultraviolet fluorescent ink in the embodiment comprises the following steps:
printing fluorescent intensity values of different colors of fluorescent ink superposed on paper according to different sequences,
determining overprinting order of different color inks
Although it is described in the prior art that the superposition of fluorescent ink dots can affect the color rendering of the ink of the lower color, and the effect is theoretically present, how much the effect needs to be verified through actual measurement in the actual printing process.
In fact, the fluorescent ink is transparent, the ink layer of the ink-jet printing is very thin, and the residual ultraviolet light absorbed by the ink on the upper layer is enough for the ink on the lower layer to absorb luminescence. In order to study the influence of the dot arrangement mode on color reproduction, 20-level gray scale R, G, B monochrome RG, RB, GB dual-color RGB three-color blocks with the dot percentage varying from 5% to 100% in a gradient manner were drawn, and the fluorescence intensities of different dot arrangement modes were compared when the same ink ejection amount was selected (i.e., 100% of blocks were selected when the dots were juxtaposed, and 30% of blocks were selected when the dots were superimposed to compare the fluorescence intensity values), and the results are shown in table 1.
TABLE 1 fluorescence intensity of forest paper, offset paper, wallpaper dot juxtaposition and dot superposition
As can be seen from table 1, the fluorescence intensity of the dot-parallel color blocks printed by inkjet printing on the forest paper, offset paper and wallpaper is substantially the same as the fluorescence intensity of the dot-superimposed color blocks, and it is known that the dot-parallel and dot-superimposed inkjet printing has little influence on color reproduction.
Through the verification, the fluorescent ink with different colors has different effects on the ultraviolet intensity, so that the fluorescent ink printed matter with different color sequences is reflected to have different fluorescent intensity and influence on the color rendering property. To further verify the effect of dot superposition on the color reproduction of fluorescent ink in this embodiment, two different colors are printed on the forest paper in sequence by ink-jet printing, the fluorescence intensity of the superposed part of the first color and the two colors is measured, and whether the fluorescence intensity of the first color is reduced due to the coverage of the second layer of ink is observed, and the result is shown in fig. 1.
As can be seen from fig. 1a and 1b, in the case of the ultraviolet fluorescent inkjet ink, when the red ink is jet-printed on the blue ink or the green ink, the red ink of the second layer hardly affects the light emission of the blue-green ink of the first layer; as can be seen from fig. 1c and 1d, when the blue ink or the green ink is inkjet printed on the red ink, the blue-green ink of the second layer slightly affects the light emission of the red ink of the first layer.
This is because the intensity of the red fluorescent ink is the weakest, the ultraviolet light absorption is slightly affected by the covering of the upper ink, and the emitted visible light is weakened again through the upper ink. Depending on the uv fluorescent inkjet printing technique used, if the fluorescence intensity of the trichromatic fluorescent ink is sufficiently high, dot superimposition does not affect the color reproduction.
Therefore, through these tests, it can be determined that the red fluorescent ink is finally sprayed and printed, the influence on the fluorescence intensity is small in the fluorescent ink printing for dot superimposition, and the dot superimposition fluorescent ink printing can be actually realized through the control of the color sequence, so as to improve the definition and the color rendering of the ink printing.
Step two, using three primary colors of fluorescent ink and color light to perform ink-jet printing by adopting superimposed dots according to the color sequence determined in step one
Color code document
In this step, the relevant color patch file is printed in the order determined in step one, that is, based on the measurement in step one, the influence of the fluorescence intensity of the actually superimposed dots is small in the predetermined color order, so that the presentation effect of the printing color can be greatly ensured, and in fact, the color gamut of the printing color can be ensured. And the definition of the printed image can be improved due to the imaging mode of the overlapped dots.
In this step, since the fluorescent ink is actually an ink that can emit fluorescent light of different colors under ultraviolet rays or the like, a color light three primary color imaging method is applied, that is, an RGB three-color mode is used, and thus a mode of a color patch document original image is required for printing of a color patch document, or is modified to the RGB mode. The color scale file forms a file for printing after being screened, and the printer executes a printing action according to the driving of the file, wherein in the specific embodiment, it is emphasized that the printing color sequence should be realized according to a step one manner and screened in a screen dot superposition manner in the screening process. The color patch file refers to a color patch file for color management, such as selecting the color patch file printer TC2.83RGB in the ProfileMaker software or other similar color patch files. By printing the relevant color patch file, color management can be carried out on the fluorescent ink printing process so as to improve the color reduction degree.
In the prior art, a method for performing color management on four-color subtractive color printing is very common in the printing field, and a device for forming images by a three-color additive color method in the fields of displays and the like is also a common technology for performing color management. However, in the prior art, because the color difference is too large and the fluorescent ink is printed by a chromatic light additive method, the color management usually cannot achieve the ideal effect, and the color difference after the color management is actually obvious.
In the specific embodiment, the fluorescence intensity is reduced by setting the printing color sequence, so that the color gamut space change of the fluorescent printing ink is large, and the color management has significant positive significance for improving the color development effect of the fluorescent printing ink on the basis.
Step three, measuring color blocks in the color code file printed in the step two under the environment of ultraviolet light
The measurement of the color patch file is usually realized by a spectrophotometer or a spectroradiometer, and color data of each color patch of the printed color patch is obtained by measuring color values in the color patches of the color patch. This is already common in the prior art.
However, in this patent, the measurement of fluorescent ink print colors presents unique problems. Since the fluorescent ink actually exhibits colors in a manner of superimposing color lights, but unlike the color development of a display or the like, the ink exhibits a predetermined color that can be obtained only under a specific light source, and is therefore particularly sensitive to the environment of the light source irradiated from the outside, and the light source has a great influence on the color development of the fluorescent ink in addition to the influence of the light source on the measuring instrument itself.
In addition, the fluorescent ink is different from various conventional color developing means in that the white point of the fluorescent ink is determined because the visible light is biased to violet in the illumination environment, particularly in the environment of ultraviolet light.
Therefore, in the present embodiment, the following means is employed to improve the color development accuracy for fluorescent ink printing.
The color block measurement in this step is implemented by using the apparatus shown in fig. 3:
in the device, a box 1 is included, one side of which is open 5 for measurement, and the inner wall of which is a diffuse reflection surface to facilitate uniform arrangement of light. An ultraviolet light source 4 is arranged at the top of the box body, an inclined plane of the objective table and a horizontal plane form an angle of 45 degrees, the inclined plane and the horizontal plane are arranged in the box body to bear printed color code documents, and the ultraviolet light source 4 emits ultraviolet light downwards to irradiate on the objective table arranged below. And then adjusting the spectral radiometer PR-655 to a proper focal length, and at the moment, seeing a clear color block image from the lens of the test instrument, and starting to measure. Through the setting of above-mentioned device on the one hand can guarantee that fluorescence printing ink receives external interference less, and on the other hand can provide effectual fluorescence printing ink's measurement angle, is convenient for accurately measure its color development data.
In addition, since the fluorescence proof needs to be imaged under an ultraviolet lamp, introducing a white point under corresponding viewing conditions is more beneficial for accurate mapping of colors. On the basis, in the embodiment, the influence of the fluorescent three-color overprint white and the white point on the display on different printing stocks is different, so that the white point needs to be determined for the printing stock printed by the fluorescent ink when the printing stock is selected, and a spectrogram of the fluorescent three-color overprint white color block under an ultraviolet lamp is used as white point data.
Step four, establishing a corresponding relation file between the original image and the fluorescent ink color development
In practice, the correspondence file is a color management file, and the correspondence between the colors of the original image and the printed image, that is, the correspondence between the color data a of the color patch (which may be in units of pixels) of the image in the original image and the color data B of the printed image, is mainly recorded in the file. Because the color space of the original image and the color space of the fluorescent printing ink are different, the original image can be better restored through the mapping.
The corresponding relation files can be established by the existing color management software, for example, by using the ProfileMaker software to establish an ICC file, and then various parameters are determined and obtained.
Specifically, the color management process of the above steps can be realized by the following specific operations by way of example and not limitation
S1, performing channel division processing on the image, outputting the image by using an ink-jet printer, and forming the image in a dot superposition mode.
Which comprises
And performing image processing by using Photoshop software, firstly changing the color mode into RGB, then setting the resolution and the screening parameters, and then saving the files R.GIF, G.GIF and B.GIF by channels.
Any three channels in the EPSON7600 printer are selected to be respectively filled with RGB three-color fluorescent ink-jet ink, a small program EPSON7600TEST capable of controlling EPSON sub-channel output is used for controlling the channel for placing R color ink to output R.GIF, the channel for placing G color ink to output G.GIF and the channel for placing B color ink to output B.GIF. The output proof is shown in fig. 2.
S2, information acquisition method for determining color block color value of fluorescence
Which comprises
A bracket with an angle of 45 degrees is placed in a lamp box, a fluorescent ink-jet sample is placed on the bracket, then a spectral radiometer PR-655 is adjusted to a proper focal length, a clear color block image can be seen from a lens of a testing instrument at the moment, the measurement can be started, and a measurement scene is shown in figure 3. It should be noted that the standard white is selected: because the fluorescent sample needs to be imaged under an ultraviolet lamp, a white point under corresponding observation conditions needs to be introduced, the influence of the three-color overprint white of the fluorescent sample and the white point on a display on different printing stocks is different, and therefore, the selection research of the white point needs to be carried out when the printing stocks are selected. The white point embedding method is to store the spectrogram of the fluorescent white color block under an ultraviolet lamp or the spectrogram of a white point of a display into C \ Photo research \ SpectraWin2\ Sources. Then, the Measurement-Source-Save \ Load is executed on the SpectraWin2 software, and the fluorescence white point data can be loaded.
And S3, establishing an ICC file by using Profilemaker software, and determining various parameters.
Which comprises
The color patch file printer TC2.83RGB in the ProfileMaker software was selected, and color patch output and measurement were performed using S1 and S2.
And comparing the influence of each parameter in the ProfileMeker software on the ICC profile accuracy through multiple experiments to obtain the optimal parameters for the fluorescent inkjet ink as follows: file size default; the perceptual chroma transforms Paper-colored Gray and logo classic.
And generating an ICC profile.
In addition to performing the above-described steps of S1, S2, and S3 at a single time, it is preferable that the steps of S1, S2, and S3 be repeated a plurality of times for the optimization of the ICC file.
In the specific application process, the following examples are also given in the present embodiment to facilitate understanding of the inventive concept of the present patent:
example 1
Using dow paper (without fluorescent whitening agent), the reference white point was fluorescent trichrome white, the steps S1, S2 and S3 were performed to generate ICC1, and representative color patches were selected for direct output and color difference comparison with the output after Photoshop loading into profile ICC1, as shown in table 2.
TABLE 2 color management vs. non-color management color difference comparison
As can be seen from Table 2, the color difference after color management is much smaller than that without color management, the maximum color difference is reduced from 80.15 to 33.41, the minimum color difference is reduced from 3.73 to 0.66, the average color difference is reduced from 39.92 to 16.34, and the effect is remarkable.
It should be noted that while this patent presents numerous embodiments and implementations of the inventive concepts of this patent in a detailed description, these embodiments are not to be construed as limiting the scope of the patent. Rather, those skilled in the art can make modifications, deletions, or substitutions to related elements based on the inventive concept of this patent. Such modifications, omissions, and substitutions do not depart from the gist of the patent and are intended to be within the scope of the patent.