Digital printing of acrylic fabric with cationic dyes using conventional inkjet printer

A special printing ink formulation based on cationic dyes is developed for digital printing of acrylic fabrics using a conventional inkjet printer. In order to investigate the contribution of color gamut boundary of printer colorants to printing efficiency, customized color targets containing 3164 color patches in 25 different hues were generated. The printed color patches were then fixed through steaming for 30 minutes followed by washing with hot soap and water and finally drying. To show the influence of dye fixation on colorimetric changes as well as color gamut boundary of samples, the L*a*b* values of color patches before and after fixation process were compared. Results demonstrate that color saturation of samples is enhanced dramatically after the dye fixation process. In fact, 3D color gamut of color patches has been drastically expanded as a direct consequence of adsorption to absorption transition. Additionally, dye fixation changes the structure of printed image from halftone superimposed dots to contone superimposed dyes. Strictly speaking, during fixation process, colors inside the halftone dots diffuse through the interfacial area to make the individual printed dots integrated. This is in analogy to the chromogenic photography films and dye‐sublimation thermal transfer processes by which contone images are produced. Moreover, dye fixation improves the washing fastness of digitally printed acrylic fabrics to the level comparable with the traditional screen printing method. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 244–249, 2017     

广告输出设备的颜色性能分析

围绕广告业彩色输出的硬件设备特性,通过建立的三维色域确定方法,探讨了常用广告输出设备颜色输出的物理能力。选择常用宽幅广告打印设备,针对广告色彩的常用输出模式,定量分析和比较了色域特征。结果表明,在广告行业中,针对一般的普通用户,目前市场上的Epson彩色喷绘设备具有相当的颜色输出效果;而对于高要求的专业级用户需求,则建议使用色域较大的喷绘设备,可获得一些黄、黄绿、绿,直至青颜色的高彩度色。     

不同输出设备对数字阶调再现特性的影响

为了研究不同类型输出设备对数字输出阶调再现特性的影响,选用彩色喷墨打印机Epson R250、Epson 1390、Epson 7908和Canon iPF6350,彩色激光打印机Epson C8600和Hp 4700N,热升华打印机Canon730和Sony FP97等三类输出设备对数字输出阶调再现性能进行测试和比较,得出结论:彩色喷墨打印机在图像的亮调部分再现阶调能力优于彩色激光打印机,彩色激光打印机在图像的暗调部分再现阶调能力优于彩色喷墨打印机,热升华打印机的阶调层次再现能力较好且色域相对较大。     

The effect of paper appearance on printed color of inkjet printer

Paper properties, including the chemical or optical characteristics influence the quality and colorimetric characteristics of final printed colors. In this study, the effect of gloss, texture, and whiteness of the paper on the printed colors were investigated. The study was applied on 10 coated papers with different texture, gloss or whiteness, and the same grammage using two inkjet printers. It was found that the reproducibility of the printer can be affected with the paper brand, and this effect is statistically dependent on the brand of printer. The kind of paper significantly influences the light fastness of the final printed colors, and this effect statistically depends on the printer. Although, the paper's properties such as gloss and whiteness affect the gamut volume, it is not totally possible to model this effect. The effect of paper on the colorimetric values of the final printed colors is statistically significant. However, the influence of the brand of printer on the color changes via the paper difference is not statistically provable. Edge frequency technique was introduced as an appropriate method for computing texture properties of papers. The texture difference computed by this method shows a suitable correlation with the color differences caused by changing the paper's texture; however, it depends on the printer's brand. Furthermore, there is a good correlation between the Edge frequency difference and the gamut volume variation for papers with different texture while the other parameters such as gloss and whiteness are the same. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 284–291, 2013     

不同纸张对数字输出阶调特性的影响

为了了解不同纸张对数字输出阶调特性的影响,采用CorelDraw软件制作单色色阶测试版,选择常用的普通打印纸、一般照片纸和光泽照片纸在Epson Stylus Photo R250彩色喷墨打印机上进行输出,用DS分光光度仪对输出色阶进行CIEL*a*b*色度值的测量,用色彩管理软件为不同纸张制作特性文件,对不同纸张所能达到的数字输出阶调特性进行定量分析。针对选用的纸张进行测量后得出结论,输出色彩丰富的图像优选的纸张应是光泽照片纸,输出灰度层次丰富的图像可以选择普通打印纸。     

Investigating the effect of paper properties on color reproduction of digital printing

Digital printing is affected by several parameters including printer and paper type which determine the final printed color gamut and the quality of reproduction. For investigation of those effects, tests were done on the three types of laser printer and six types of paper with different properties of whiteness, roughness, and gloss. The gamut volume was generated by Eye-One spectrophotometer, ProfileMaker, and ColorThink software. Properties of the different types of paper were measured by the atomic force microscopy, spectrophotometer and, goniophotometer. Results showed that the reproducibility was considerably dependent on the type of printer and type of paper. High whiteness and gloss increased the color gamut volume, while high roughness decreased the reproducibility of the printer. Tests on paper properties showed that whiteness had the most significant effect on color gamut volume.     

Color reproduction of authenticable luminescent backlit transmissive color images

We propose a method for creating authenticable color images under UV excitation backlight by printing an invisible luminescent white emissive ink layer on the verso side of a transmissive substrate and a classical cmy image on the recto side of the substrate. In order to obtain a backlit image whose colors are as close as possible to the original image colors, we map the input image sRGB color gamut into the gamut formed by the emissive white source attenuated by the classical ink halftones. The relationship between surface coverages of the classical cmy ink halftones and the resulting backlit colors is obtained by accounting for the transmission of the emissive white through the paper substrate and through the classical cmy ink halftones. The transmittance of the classical ink halftones is modeled by a new halftone absorbance prediction model. The lightness range of the luminescent backlit color gamut is expanded by printing a black and white UV‐absorbing instance of the original color image in superposition with the luminescent white emissive layer and in registration with the cmy image printed on the recto side. Luminescent backlit color images provide a high anticounterfeiting security, as they combine a verso printed invisible luminescent ink layer, a verso printed black and white instance of the original image and a matching recto printed cmy instance of the original image. The resulting luminescent backlit image colors are close to the original image colors only when observed in transmission mode under UV light. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 331–340, 2014     

Comparison of color gamuts among several types of paper with the same printing technology

In this work, we have studied the relationship among the colorimetric properties of different types of paper, having different finishing and grammage. Their color reproduction capability has also been analyzed by using the same printing technology (inkjet printing). On the one hand, we have plotted CIELAB data under the illuminant D50 into constant lightness and hue‐angle planes to be compared with MacAdam limits and with Pointer's real‐world surface color. On the other hand, we have calculated the volume gamut of the color solid associated to each color paper gamut. Analyzing the results, we have checked that there is not any clear relationship among the colorimetric properties of paper (for instance, CIE whiteness index, etc.) and the color gamut volume associated. However, the colorimetric parameters associated to the printed sample showed a quite good linear correlation between the minimum lightness (or the maximum blackness value) of the printed color chart and the color gamut volume. In particular, the greatest color gamut volume corresponds to the glossy papers taking into account this correlation for inkjet printing. © 2009 Wiley Periodicals, Inc. Col Res Appl, 34, 330–336, 2009     

Expanding display color gamut beyond the spectrum locus

Digital video and display media are at a “sweet spot” of growth with brighter and more colorful digital projectors and displays available seemingly every day. Much more is possible in achieving brighter and more vibrant colors, colors that may even transcend our typical experience in terms of dynamic range and an expanded gamut in the perceptual sense. If the full capabilities of these technologies to produce a fuller visual experience are to be realized, new processing and encoding methodologies are required. In this article, the powers of adaptation and the CIECAM02 color appearance model are exploited to define perceptual gamut. The strategy of this methodology is, simply and in effect, to “push down” the white point of the display and demonstrate, both empirically and with a limited set of images, a striking gamut expansion in the perceptions of lightness, chroma, brightness, and colorfulness beyond the locus of pure, spectral color, and the MacAdam limits as observed with traditional display configurations. © 2006 Wiley Periodicals, Inc. Col Res Appl, 31, 475–482, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20260     

Gamut mapping from below: Finding minimum perceptual distances for colors outside the gamut volume

A colorimetrically characterized computer-controlled CRT display was used to determine closest perceptual color matches of 25 colors when an exact match was not allowed. An artificial but realistic color gamut was created by intersecting the display gamut with a gamut of a Xerox 4920 color laser printer. Each of 21 observers performed color matches between out-of-gamut colors and those on the artificial gamut's edge. Each observer made color matches on 4 different images. The images represented some of the categories that business graphic images can fall into. Between the different image types, there were no multidimensional (MANOVA) statistically significant differences at the 10% confidence level in any of the 25 colors tested. The mapping vectors showed that (1) observers don't make simple matches as assumed by most gamut-mapping experiments done to date, (2) the influence of image content for simple graphical images tested does not have a large effect when the task is to make closest perceptual color matches, and (3) CIELAB hue angle is not uniform enough, especially in blue and cyan regions, to make adequate gamut-mapping transforms. A simple model for clipping type gamut mapping is proposed. Results are compared to predictions of a new gamut-mapping technique that minimizes weighted color difference between the target color and the gamut boundary. © 1997 John Wiley & Sons, Inc. Col Res Appl, 22, 402–413, 1997     

Spectral color reproduction minimizing spectral and perceptual color differences

In this article, we are combining minimization criteria in the colorant separation process for spectral color reproduction. The colorant separation is performed by inverting a spectral printer model: the spectral Yule‐Nielsen modified Neugebauer model. The inversion of the spectral printer model is an optimization operation in which a criterion is minimized at each iteration. The approach we proposed minimizes a criterion defined by the weighted sum of a spectral difference and a perceptual color difference. The weights can be tuned with a parameter α ∞ [0, 1]. Our goal is to decrease the spectral difference between the original data and its reproduction and also to consider perceptual color difference under different illuminant conditions. In order to find the best α value, we initially compare a pure colorimetric criterion and a pure spectral criterion for the reproduction, then we combine them. We perform four colorant separations: the first separation will minimize the 1976 CIELAB color difference where four illuminants are tested, the second separation will minimize an equally weighted summation of 1976 CIELAB color difference with the four illuminants tested independently, the third colorant separation will minimize a spectral difference, and the fourth colorant separation will combine a weighted sum of a spectral difference and one of the two first colorimetric differences previously introduced. This last colorant separation can be tuned with a parameter in order to emphasize on spectral or colorimetric difference. We use a six colorants printer with artificial inks for our experiments. The prints are simulated by the spectral Yule‐Nielsen modified Neugebauer model. Two groups of data are used for our experiments. The first group describes the data printed by our printing system, which is represented by a regular grid in colorant space of the printer and the second group describes the data which is not originally produced by our printing system but mapped to the spectral printer gamut. The Esser test chart and the Macbeth Color Checker test chart have been selected for the second group. Spectral gamut mapping of this data is carried out before performing colorant separation. Our results show improvement for the colorant separations combining a sum of 1976 CIELAB color difference for a set of illuminants and for the colorant separation combining a sum of 1976 CIELAB color difference and spectral difference, especially in the case of spectral data originally produced by the printer. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 494–504, 2008     

Gamut evaluation of an n‐colour printing process with the minimum number of measurements

The aim of this study was to use a minimum number of measured colour patches to evaluate the colour gamut of an n‐colour printing process. Traditionally, the colour gamut of a printing system has been derived by printing and then measuring a gamut target for example, a profiling chart. For an n‐colour printing (printing with more than four process inks), it is desirable to know the colour gamut of the given set of inks without having to print a large number of test patches. Different spectral printer models were used to predict the gamut of a 7‐colour printing process. The colorant space was divided into sectors each containing four inks. For each printer model, the colour gamut of the each four‐ink sector was predicted. All sector‐gamuts were then combined to predict the overall colour gamut of the n‐colour process. This predicted gamut was then compared with the gamut obtained by measurement using a gamut comparison index (GCI). The Yule–Nielsen modified spectral Neugebauer (YNSN) model gave the best accuracy, at the cost of a larger number of input measurements, than other models. A combination of the Kubelka–Munk (KM) and YNSN models performed well with the fewest input measurements. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 408–415, 2015     

纸张对喷墨打印线条质量的影响分析

实验针对普通的彩色喷墨打印机,检测了不同类型纸张上线条输出的质量特性。基于ISO 13660标准中定义的线条属性指标,实验开发了基于工业CCD捕获的数字影像进行线条属性指标求解的工具软件;其后,根据打印机的输出分辨率,设计了含有不同宽度的水平和竖直线条图标,并由7种纸张打印输出和测量分析。结果表明:喷墨打印的线条质量与纸张性能有明显的关系,而与打印技术关系不大;此外,照片打印纸在线条的密度、对比度、线宽增量和线边缘粗糙度方面较普通打印纸有较佳的表现,但线边缘的模糊度性能却不及后者。     

黑版及总墨量限制对输出设备颜色表现能力的影响分析

CMYK减色成色体系中,黑版的加入及总墨量的不同会影响设备的颜色输出能力。利用自己开发的工具软件和色彩管理技术,从设备的ICC特性文件入手,求解了输出设备的三维色域体。比较了黑版产生、不同的产生方式,以及不同的总墨量限制下设备可输出的色域。结果表明,加入黑版后设备在暗色调的输出色域得到扩展;总墨量限制相同时,不同的黑版产生方式主要影响分色结果,对色域几乎没有影响;允许的总墨量大时,输出的色域则大,体现在暗色调区域颜色的增多,从380%到320%的总墨量变化,可造成暗色调2个单位的明度增加;而340%到320%的总墨量变化,色域差异则不明显。     

Color separation for improved perceived image quality in terms of graininess and gamut

Multi‐channel printing employs additional inks to improve the perceived image quality by reducing the graininess and augmenting the printer gamut. It also requires a color separation that deals with the one‐to‐many mapping problem imposed when using more than three inks. The proposed separation model incorporates a multilevel halftoning algorithm, reducing the complexity of the print characterization by grouping inks of similar hues in the same channel. In addition, a cost function is proposed that weights selected factors influencing the print and perceived image quality, namely color accuracy, graininess and ink consumption. The graininess perception is qualitatively assessed using S‐CIELAB, a spatial low‐pass filtering mimicking the human visual system. By applying it to a large set of samples, a generalized prediction quantifying the perceived graininess is carried out and incorporated as a criterion in the color separation. The results of the proposed model are compared with the separation giving the best colorimetric match, showing improvements in the perceived image quality in terms of graininess at a small cost of color accuracy and ink consumption. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 486–497, 2017     

Pretreatment effects on pigment‐based textile inkjet printing – colour gamut and crockfastness properties

The application of two commercial pretreatment agents, formulated to improve the performance of a six‐colour nano‐scale pigment ink set during the textile inkjet printing of cotton and polyester (PET) fabrics, was examined. An industrial scale printer, operating at 55 linear m/h and equipped with Kyocera printheads, was used to print on commercial fabrics (180 cm wide) prepared for digital printing. The work employed an industrial scale rather than a benchtop printer to enhance the utility of the results for a commercial environment. The colorimetric attributes of printed fabrics were recorded for the individual inks as well as for spot colour combinations generated using Dr. Wirth RIPMaster v11 software. Colour table profiles were also generated and the colorimetric values of inks were compared. Colour gamuts of inks on cotton and PET, including three‐dimensional volumes in the CIELab space, were examined to assess the role of pretreatment on the colorimetric properties of the printed substrates. It was found that the pretreatments enhanced the ink receptiveness, colour intensity and colour gamut of fabrics. Pretreatment of cotton resulted in a larger gamut and more vivid colours than on PET. However, wet and dry crockfastness results were found to be low. In this regard, Time‐of‐Flight Secondary Ion Mass Spectrometry analysis of fabrics printed in the presence and absence of pretreatment indicated that the low crockfastness arises from higher pigment levels on the surface of the pretreated fabric.     

Color reproduction on varnished cardboard packaging by using lower ink coverages due to the gray component replacement image processing

Even in these challenging times, cardboard packaging industry is increasing its revenue with stable annual increase prediction, but customers are increasing demands on the packaging with respect to environmental protection, attractiveness, and branding. This article aims to determine the influence of image processing in terms of gray component replacement and overprint varnishing on the color reproduction on a cardboard packaging material. A test chart with tertiary colors was defined and modified by different gray component replacement levels. It was printed in accordance with ISO norm on coated and uncoated cardboard and finished by overprinting water based, offset, and UV varnish. The prepared samples were evaluated by measuring surface coverage, tone value increase (dot gain) of primary colors and calculating ΔE₀₀ of defined tertiary colors. The results showed that gray component replacement application reduces ink consumption. Higher gray component replacement applied results in lower ink surface coverage, but the decrease is also dependent on the image content. The TVI (dot gain) is significantly influenced only by applying UV varnish, resulting with higher TVI. The color differences of the tertiary colors showed that increased level of the gray component replacement applied did not cause significant color differences, even decreased color difference in some cases. Additionally, applying gray component replacement decreased color differences in “reddish” part of the gamut. This research proved that lowering the ink consumption due to the gray component replacement will not cause significant differences in the color reproduction. Furthermore, varnishing with commercial offset or water-based varnish will not cause higher deviations in color reproduction, but use of the UV varnish would.     

环保型水性油墨的研制、开发与市场展望

环保型水性油墨具有无毒、无刺激气味、无腐蚀性的优良特性，可广泛应用于卫生条件要求严格的包装印刷产品，对我国柔性版印刷的配套国产化产品起到了积极推进作用。