【作者】 钟泽辉；

【导师】 詹怀宇；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2008， 博士

【摘要】 新闻纸是一种重要的文化用纸,是传播信息、传承文化的重要载体,其的印刷适性对报纸印刷质量有重要的影响。本论文以我国二次纤维配抄的新闻纸为研究对象,结合目前彩报印刷工艺特点,进行了新闻纸的印刷适性与改进彩报印刷质量的研究。对我国目前常用的新闻纸的基本性能进行了全面的测试,分析了新闻纸贮存条件对新闻纸性能的影响,温湿度的波动对新闻纸的印刷适性影响很大,低温低湿有利于新闻纸的保管,纸张仓库保持温度在18～25℃,相对湿度在60%～70%对新闻纸较合适。新闻纸的印刷适性与胶印水墨平衡有密切的联系。在相同的时间内,新闻纸吸水量随着润版液中异丙醇含量的增加而减少,吸水速率随着异丙醇含量的增加而减小。横向抗张强度从开始平均值15.36KN/m至最终平均值18.47KN/m,润版液异丙醇体积含量每增加2%,纸张的抗张强度就增加0.62KN/m。新闻纸的伸长率在异丙醇体积含量16%的润版液中最低,为0.2%,增加润版液中异丙醇体积含量有利于套印,但过高导致印刷油墨的过度乳化。控制合适的异丙醇含量可以有效防止新闻纸的变形,并有利于保障彩报的印刷质量。比较了新闻纸Y、M、C、K(黄、品红、青、黑)四种油墨印刷的颜色密度、网点增大、印刷反差和色彩反差,研究分析了新闻纸对印品阶调和色彩再现的影响,得到了新闻纸的最佳实地密度范围,确保了阶调和色彩再现的合理性,并确定给墨量、印刷压力、墨层厚度等参数,通过实验分析了CTP(计算机直接制版技术)工艺的网点扩大规律,画出了适合彩报印刷复制工艺的系统灰平衡曲线,比较了调频加网、调幅加网在新闻纸印刷过程中的网点扩大规律,探索加网最佳实地密度的确定方法,形成彩报印刷的数字化工作流程和工艺。油墨的Tack值随乳化率的升高而缓慢下降,粘度越大,抵抗乳化的能力越强,乳化率越低。油墨粘度顺序为Y＜C＜M＜K,乳化率高低顺序为K＜M＜C＜Y,彩色报纸印刷色序应以C、M、Y、K的排列为最佳。实验测得在印刷5000份报纸过程中,润版液浓度从3.5%降到3.2%,pH值从4.98上升到5.54,电导率从1237 Ns降到675 Ns。利用先进的数码打样系统在新闻纸喷墨打样中定标及色彩校正,得出最佳技术参数。以Kubelka-Munk定律为基础,研究了油墨、新闻纸在印刷中墨层的表面反射、承印物纸张内的多重内反射、墨层内光的吸收和散射,针对其中的光散射距离的长短两种可能,修正了Clapper-Yule颜色预测模型,引入代表长短光散射距离的比例系数h,建立了新的颜色预测模型,计算得到h=0.43。利用现代化的柔性版印刷适性仪,通过实验证实了加网线数对网点增大有较大的影响,证实了柔性版版材的硬度对网点增大的影响,得出印刷压力与网点增大的关系,推导各种条件下的拟合方程,各方法的R~2都在0.95以上。为实现柔性版报纸印刷工艺的标准化、数据化和规范化提供技术依据,对彩报的柔性版印刷实际应用和推广有指导意义。更多还原

【Abstract】 The newsprint is an important culture paper and an important carrier that spreads information and culture.The newsprint printability has an important influence to the newspaper printing quality.In this thesis,the printability of newsprint using secondary fibers as a furnish of improving colorful newspaper printing quality have been researched combined with the characteristics of currently colorful newspaper printing.The basic properties of newsprint used commonly in our country have been tested,the influence of storage condition on the newsprint properties has been analyzed,The fluctuating temperature and humidity affect newsprint printability greatly,and low temperature and low humidity are good for newsprint storage,the temperature of 18℃to 25℃and humidity form 60%to 70%of warehouse are beneficial for the newsprint storage.There is close relation between newsprint printability and the water-ink balance during offset printing.The newsprint absorbs less water along with the increment of IPA content in fountain solution at the same time,and the absorption rate decreases with the increase of IPA.The average tensile strength of cross direction increases from 15.36KN/m to 18.47KN/m as IPA concentration increases,the tensile strength will increases 0.62KN/m along with per 2%increase of IPA concentration in fountain solution.The lowest stretch of newspaper at break is 0.2%as the IPA volume content in fountain solution is 16%. Increasing concentration of IPA in fountain solution will be beneficial to register but harmful to ink emulsification.A suitable IPA content in fountain solution can prevent the deforming of newsprint effectively and guarantee the printing quality of color newspaper.The color density,dot gain,printing difference and color difference of yellow,magenta, cyan and black ink printed on the newsprint have been compared,the effects of newsprint on the tone replication and color replication have been analyzed,and the optimal range of solid density of newsprint has been obtained,which will guarantee the reasonability of tone replication and color replication and set up the parameters of ink supply,printing pressure and ink thickness.By the experiment and analysis of dot gain regularity in CTP technology, the curves of system grey balance of replicating technology which is suited for color newspaper printing have been drawn,the dot gain regularities by AMS and FMS in the printing process of newsprint have been compared,the methods of optimal solid density with screening have been established,and digital working procedure and technology for color newspaper printing have been formed.The value of ink Tack descends slowly with the increase of emulsion rate,the higher the viscosity of the ink,the stronger of resisting emulsion ability,and the lower the emulsion rate.The order of the ink viscosity is Y＜C＜M＜K,and the order of emulsion rate is K＜M＜C＜Y,so the best color newspaper printing sequence is C-M-Y-K.During the printing process of 5000 scopes of newspaper,the concentration of fountain solution declines from 3.5%to 3.2%,the pH value rises from 4.98 to 5.54,the conductivity decreases from 1237Ns to 675Ns.Using the advanced digital proof system for standard establishment and color correction in ink-jet proof on newsprint,the best technique parameters have set up.Taking the Kubelka-Munk laws as foundation,the light interaction of ink and paper by existing models has been analyzed,including surface reflection of ink and multiple intemal reflection of paper,and light absorption and scattering and so on,the Clapper-Yule color prediction model has been modified aiming at the two possibilities of long and short distance of light scattering in newspaper.A new color prediction model has been established by bring in proportional coefficient ’h’ which represents the proportion of long and short distance of light scattering in newsprint.The ’h’ calculated is equal to 0.43.By using advanced flexographic printability testing instrument,it has confirmed that dot screen lines has great influence on dot gain through the experiment results,and the degree of flexographic plate hardness has great influence on dot gain,The relationship between printing pressure and dot gain has been set up,the imitate equations at various conditions have been deduced,the values of R~2 are all above 0.95,which will offer technical and theoretical support for application of flexographic printing method in color newspaper printing.更多还原