Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-10-22
2002-08-20
Hess, Bruce H. (Department: 1774)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S328000, C428S331000, C428S688000
Reexamination Certificate
active
06436514
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording sheet having high gloss and used for printers which utilize the ink jet recording system. Particularly, it relates to an ink jet recording sheet of high gloss which is improved in running property during being carried in printers and color forming property.
Ink jet recording system performs recording of images or letters by ejecting ink droplets according to various principles and absorbing them into recording sheets such as paper. The recording system has the features that it is carried out at high speed, produces little noise, is easy to perform multicolor printing, is great in versatility of patterns to be recorded, and requires no development and fixation step, and recently rapidly spreads in various uses for recording various figures and color images including Chinese characters. Furthermore, the color images obtained by multicolor ink jetting systems are not inferior in the resulting color images to multicolor prints obtained by platemaking methods or images obtained by color photographic systems. Moreover, when a small number of prints are to be produced, they can produce the prints more cheaply than the photographic techniques. Thus, ink jet recording system is being applied to the field of full-color image recording.
Furthermore, owing to demand by the market for further improvement in image quality, it is attempted for the printers utilizing the ink jet recording system to enhance the resolution and enlarge the scope of color reproduction. Thus, it becomes essential that ink jet recording sheets which are recording media have high ink receiving capacity and have a coat excellent in color forming property for attaining high image quality. In addition, it is also desired that appearance such as gloss, stiffness and hue are similar to those of the silver salt photographs and those of printing papers.
Hitherto, for giving gloss, it is generally known to smoothen the surface of the coat by passing the sheet between rolls to which pressure and temperature are applied using calendering apparatuses such as super calender and gloss calender. However, if an ink jet recording sheet is subjected to calendering treatment under a high linear pressure for the purpose of giving gloss to the sheet, gloss is improved, but voids of the coat decrease to cause slow absorption of ink and overflow of ink due to insufficient absorption capacity. Therefore, it is difficult to obtain high gloss by calendering treatment.
In order to give high gloss to a coat without lowering ink absorbability, for example, JP-A-63-265680, JP-A-2-274587 and JP-A-5-59694 disclose to produce ink jet recording sheets by cast coating method. According to this method, since the specular configuration of the casting drum is transferred to the ink jet recording sheet, the smoothness of the surface becomes very high and a strong gloss can be obtained. Moreover, the linear pressure at which the sheet is pressed to the casting drum is lower than when a calendering apparatus is used, and, therefore, good ink absorbability is obtained.
When printers utilizing the ink jet system are used, in some cases, one figure is printed on a plurality of ink jet recording sheets and, in some cases, a plurality of figures are continuously printed. In these cases, the ink jet recording sheets can be fed one by one, but, in general, a large number of the ink jet recording sheets are set and continuously fed. In this case, if feeding property or running property of the sheets is inferior, such troubles are caused that the sheets cannot be fed to printers or a plurality of the sheets are fed at one time and clog the printers to stop them. In case a plurality of the sheets are fed with slipping from each other, printing of the figure is carried out over a plurality of the sheets.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an ink jet recording sheet of high gloss which has high color forming property and causes no troubles in carrying of them in printers, thereby to solve the above problems.
As a result of intensive research conducted by the inventors in an attempt to solve the above problems, the present invention has been, accomplished.
That is, the present invention is an ink jet recording sheet having at least one ink receiving layer and a gloss developing layer laminated in succession on one side of a support and a back-coat layer comprising a pigment and a binder on another side of the support, said gloss developing layer having been coated by a cast coating method, wherein a static friction coefficient between the gloss developing layer and the back-coat layer is 0.9 or lower under the conditions of 20° C. and 65%RH. The static friction coefficient in the present invention is a value measured in accordance with JIS P8147, except that the moving speed is 250 mm/min.
Moreover, the effect of the present invention is greater when the gloss developing layer is provided by coating a coating composition comprising an alumina hydrate and then subjecting the coat to casting treatment.
Furthermore, the pigment used in the back-coat layer is preferably at least one selected from the group consisting of kaolin, talc, calcium carbonate and synthetic amorphous silica because the static friction coefficient between the back-coat layer and the gloss developing layer can be easily adjusted to the smaller level.
Preferably, the coating composition forming the back-coat layer contains a lubricant because the static friction coefficient between the back-coat layer and the gloss developing layer becomes further smaller.
The present invention further provides a method for producing an ink jet recording sheet which comprises providing at east one ink receiving layer on one side of a support, then providing a gloss developing layer thereon by a cast coating method comprising coating a coating composition for the gloss developing layer, pressing the coat still in wet state to a heated specular roll and drying the coat, and, thereafter, providing a back-coat layer comprising a pigment and a binder on another side (back side) of the support.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be explained in detail below.
The present invention is an ink jet recording sheet which has a high color forming property and causes no troubles when being carried in printers.
The inventors have considered that the troubles which occur when the ink jet recording sheets are carried in a printer are caused by the too high friction coefficient between the superposed ink jet recording sheets. Especially, ink jet recording sheets obtained by cast coating method are very high in smoothness of the side having gloss surface and, hence, the friction coefficient between the side having gloss surface and the another side (the back side) is apt to be very high. In case the side having gloss surface is subjected to a treatment to lower the smoothness, the gloss is also lowered. It is effective to previously add materials such as lubricants which lower frictional force to the gloss developing layer. However, fatty acid metallic salts generally have a large particle size and cannot inhibit decrease of gloss, and, besides, they sometimes deteriorate image quality. Similarly, when an overcoat layer is provided on the side having gloss to lower the frictional force, the gloss lowers and the image quality deteriorates. Thus, it has been difficult to sufficiently lower the frictional force with keeping the high gloss thereby securing the feeding property of the sheets and the running property of the sheets when carried in the printers.
Furthermore, JP-A-9-39376 discloses a method of coating a composition containing alumina hydrate on a support by cast coating method to enhance color forming property. In this case, although the cause is not clear, the friction coefficient of the gloss surface is apt to increase than when using other pigments such as colloidal silica, and the sheet feeding property and running property in printers are deteriorated. When an overcoat lay
Ishiyama Kenyuki
Yamamoto Hirokazu
Armstrong Westerman & Hattori, LLP
Mitsubishi Paper Mills Limited
Shewareged B.
LandOfFree
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