WO2006001581A1

WO2006001581A1 - The process of manufacture to be used as a white board as well as printing paper

Info

Publication number: WO2006001581A1
Application number: PCT/KR2005/000820
Authority: WO
Inventors: Kyu-Ha Son
Original assignee: Inpa Co., Ltd.
Priority date: 2004-03-23
Filing date: 2005-03-22
Publication date: 2006-01-05

Abstract

Disclosed herein are a printing paper with added white board functions and a process for manufacturing the printing paper. The printing paper comprises: a base layer composed of paper, plastic sheet or plastic film; a primer adhesive layer composed of at least one primer selected from the group consisting of polyurethane, polyacrylic, and polyurethane acrylic resins and formed on the base layer; and a water-soluble polyvinylalcohol (PVA) coating layer with a coating thickness of 1-30 gm formed on the primer adhesive layer. The printing paper has the functions to write on using a water-based board marker pen (containing no water) and to erase, like general white boards. In addition, the printing paper enables printing of digital data, including images and text, obtained from computers, digital cameras, scanners, etc., using general and color inkjet printers and large-format printers (i.e. plotters). Furthermore, adhesion functions can be imparted to the printing paper.

Description

THE PROCESS OF MANUFACTURE TO BE USED AS A WHITE BOARD AS WELL AS PRINTING PAPER

Technical Field

The present invention relates to a printing paper with added white board functions, and a process for manufacturing the printing paper. More particularly, the present invention relates to a printing paper for general and color inkjet printers and large-format printers that can also be used as a white board, enables printing of various images and text, and has the functions to write on using a water-based board marker pen and to erase, like a white board, before and after printing; and a process for manufacturing the printing paper.

Background Art

Conventional printing papers for general and color inkjet printers and large- format printers (plotters) have problems in terms of poor durability, easy tearing, short life cycle, ink spreadability rendering reproduction of fine colors impossible, and little gloss causing poor printing effects. To overcome these problems, a great deal of research has been conducted on the manufacture of high-quality printing papers on which clear colors can be produced, minute lines and colorful images can be printed without occurrence of tearing and creasing, and no scratching is observed after printing. For example, Korean Patent No. 279057 describes a process for manufacturing a printing paper for a color inkjet printer by coating soft semitransparent PVC as an anti-dust agent on the back face of a fabric paper having an interval between threads of 0.1 mm and a thickness of about 0.2 mm, and doubly coating a mixture of a vinylacetate resin solution, a white fluorescent dye and CMC as a moisture-blocking and adsorbing agent on the printing surface of the fabric paper. Since this printing paper has no coating effects, however, it has the problem that an additional paper should be coated on the printed matter upon explanation with the aid of briefing data. Consequently, conventional printing papers for general and color inkjet printers permit printing of various images and text thereupon, but have no free writing and erasing functions. Additional coating is required to gain these functions. That is, conventional printing papers simply have the printing function to print images and text using general and color inkjet printers. White board is a tool capable of being written on with a water-based board marker pen and being erased, enabling repetitive writing. In this connection, for example, Korean Patent No. 160375 describes a coating film for a blackboard manufactured by coating a polyester film capable of roll coating and continuous drying with a paint to a dry coating film thickness of 10-20 μm, heating the coated paint to dryness, coating a heat-resistant adhesive on the back face of the polyester film, drying the coated adhesive, and bonding a release paper to the dried adhesive. Advantages of this coating film are simple manufacturing processes, ^"good handling (e.g., easy transport and cutting), superior wear resistance, no gloss, and excellent writability and erasibility. In addition, the adhesive bonded to the release paper enables attachment of the coating film to anything. Korean Patent Laid-open No. 2000-8143 describes a thin, lightweight white board manufactured by forming an adhesive layer protected by a release layer on the rear of a thin board composed of paper, plastic or cloth, and forming a hardened coating layer on the front of the thin board. This white board is easy to carry and store and can be manufactured at considerably reduced costs. In addition, the white board can be attached to anything without an additional element. Furthermore, the white board can be cut to a user's desired size, thus being applicable to various applications. However, the patent publication is directed to a thin, lightweight white board and makes no consideration of printing functions.

Disclosure of the Invention

To solve the problems of conventional printing papers for general and color inkjet printers, the present inventor has earnestly and intensively conducted research to develop a printing paper which has repetitive writing and erasing functions without additional coating and optionally adhesive function depending on the desired application, while providing convenience and superior quality to consumers. As a result, the present inventor has developed a printing paper for general and color inkjet printers with added white board functions which is manufactured by coating a selected primer as an adhesive reinforcement on a base layer (made of a plastic sheet, film or paper) and coating selected polyvinyl alcohol (PVA) or modified PVA as a water- soluble resin thereon. Thus, it is an object of the present invention to provide a printing paper which has repetitive writing function using a water-based board marker pen and erasing function without additional coating while providing superior printing quality, and a process for manufacturing the printing paper.

Brief Description the Drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a side cross-sectional view schematically showing the structure of a printing paper for a printer with added white board functions according to one embodiment of the present invention; and Fig. 2 is a side cross-sectional view schematically showing the structure of a printing paper for a printer with added white board functions according to another embodiment of the present invention.

Best Mode for Carrying Out the Invention

In accordance with one aspect of the present invention for achieving the above object, there is provided a printing paper with added white board functions, comprising: a base layer composed of paper, plastic sheet or plastic film; a primer adhesive layer composed of at least one primer selected from the group consisting of polyurethane, polyacrylic, and polyurethane acrylic resins and formed on the base layer; and a water- soluble polyvinylalcohol (PVA) coating layer with a coating thickness of l~30 μm formed on the primer adhesive layer. The primer adhesive layer is preferably formed by coating a primer having a solid content of 1-5 wt% in a coating amount of 1-3 g/m² on the base layer. The water-soluble polyvinylalcohol (PVA) coating layer is preferably formed by coating water-soluble polyvinylalcohol (PVA) having a solid content of 5-20 wt%, a weight-average molecular weight of 800-3,000, a saponification degree of 80-99 mole% and a cation mole fraction of 0.1-10 mole% on the primer adhesive layer. The printing paper of the present invention may further comprise: a removal primer adhesive layer formed by coating at least one primer selected from the group consisting of polyurethane, polyacrylic and polyurethane acrylic resin aqueous solutions having a solid content of 1-5 wt% in a coating amount of 2~5 g/m on the back face of the base layer; and a removal paper adhered to the removal primer adhesive layer. In accordance with another aspect of the present invention for achieving the above object, there is provided a process for manufacturing the printing paper with added white board functions, comprising the steps of: coating at least one primer selected from the group consisting of polyurethane, polyacrylic and polyurethane acrylic resin aqueous solutions having a solid content of 1-5 wt% in a coating amount of 1-3 g/m² on a base layer composed of paper, plastic sheet or plastic film, and drying the coated primer to form a primer adhesive layer; and coating water-soluble polyvinylalcohol (PVA) having a solid content of 5-20 wt%, a weight-average molecular weight of 800-3,000, a saponification degree of 80-99 mole% and a cation mole fraction of 0.1-10 mole% on the primer adhesive layer to form a water-soluble polyvinylalcohol (PVA) coating layer with a coating thickness of 1-30 μm. The step of forming a water-soluble PVA coating layer preferably includes the sub-steps of: dissolving a 4-20% aqueous PVA solution containing at least one PVA selected from the group consisting of PVA, acetyl-modified PVA, carboxyl-modified PVA and silane-modified PVA, and a copolymer prepared by copolymerizing methylmethacrylate, ethylacrylate and a monomer having a cation-forming group (dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylamide, etc.) in a molar ratio of 10 : 10 : 1, in a mixed solvent of water and ethanol (1 : 1), to provide a coating agent; and coating the coating agent on the primer adhesive layer and drying the coated agent. The monomer having a cation-forming group is preferably selected from the group consisting of dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and dimethylaminoethyl methacrylamide. The process of the present invention may further comprise the steps of: coating at least one primer selected from the group consisting of polyurethane, polyacrylic and polyurethane acrylic resin aqueous solutions having a solid content of 1-5 wt% in a coating amount of 2-5 g/m² on the back face of the base layer to form a removal primer adhesive layer; and attaching a removal paper to the removal primer adhesive layer. The present invention will now be described in more detail with reference to the accompanying drawings. Fig. 1 schematically shows a printing paper according to one embodiment of the present invention which comprises a base layer 1, a primer adhesive layer 2, and a water-soluble PVA coating layer 3. Fig. 2 shows a printing paper according to another embodiment of the present invention which comprises a base layer 1, a primer adhesive layer 2, a water-soluble PVA coating layer 3, a removal adhesive layer 4, and a removal paper 5. The base layer 1 can be composed of a material selected from papers, plastic sheets and plastic films. The papers usable in the present invention refer collectively to tissue papers, high-gloss papers, base papers, and the like. The plastic sheets include those of polyethyleneterephthalate (PET), polyethylene, polypropylene, polystyrene and nylon having a thickness of 300 μm or greater. The plastic films include those of polyethyleneterephthalate (PET), polyethylene, polypropylene, polystyrene and nylon having a thickness of less than 300 μm. Transparent or white plastic sheets and films may be used in the present invention. PET is commonly obtained by polycondensation of ethylene glycol and terephthalic acid. PET film is produced by extruding PET in a T-die extruder and biaxially stretching the extrudate. PET film or sheet is very suitable as a material for inkjet printing papers due to its superior heat resistance, dimensional stability and durability. Since general PET has superior mechanical (high tensile strength and elastic modulus), chemical, electrical and optical properties, it is widely used in various application fields, such as food packaging materials and industrial materials. PP film is produced by extruding PP in a T-die extruder and biaxially stretching the extrudate based on high crystallinity of PP. PP films and sheets are suitably used as base materials for inkjet printing papers in terms of their stiffness, strength, heat resistance, chemical resistance and oil resistance. Nylon film is produced by extruding nylon in a T-die or blown extruder and biaxially stretching the extrudate. Nylon film is suitable as a base material for inkjet printing papers due to its superior heat resistance, stiffness and dimensional stability. In addition to these films and sheets, polyethylene, polystyrene, polyvinyl chloride, and other plastics are suitable as base materials for inkjet printing papers. White plastic sheet or film is produced by the addition of titanium dioxide (TiO₂) to corresponding sheet or film materials. The thickness of the base layer 1 is preferably within the range of 0.03-0.2 mm, but is not especially limited to this range. Since the base layer is not adhered to the water-soluble PVA coating layer by heating, the primer adhesive layer is used to enhance adhesion of the base layer to the PVA coating layer. The primer adhesive layer 2 formed on the base layer 1 is composed of a primer resin. The primer resin is at least one resin selected from the group consisting of polyurethane, polyacrylic, and polyurethane acrylic resins. Specifically, the primer adhesive layer 2 is formed by coating the primer having a solid content of 1-5 wt% in a coating amount of 1-3 g/m² on the base layer and passing the resulting structure through a drying hood to evaporate water contained therein. The solid content of the primer resin is preferably in the range of 1-5 wt%. When the solid content is less than 1 wt%, the adhesive force between the base layer and the coating layer is poor. On the other hand, when the solid content exceeds 5 wt%, the viscosity is extremely increased and thus the adhesive force is likely to excessively increase. The coating of the primer layer 2 on the base layer 1 is carried out by means of, but not particularly limited to, gravure coater, kiss coater, dip coater, spray coater, comma coater, die coater, slide coater, etc. The primer resin is preferably coated in an amount of 1-3 g/m². If the coating amount is less than 1 g/m² or greater than 3 g/m², there is the problem that the adhesive force between the base layer and the coating layer is poor. The drying hood commonly has a 5~50m long drying chamber with an increasing temperature gradient from an inlet, for example, 5O⁰C, 7O⁰C, 9O⁰C, 12O⁰C and 14O⁰C. If the primer layer 2 formed on the base layer 1 is heated to too high a temperature from the initial stage, the outer surface is well dried but the inside of the primer layer is not readily dried, making the adhesive layer non-uniform. Accordingly, the temperature of the drying hood is adjusted to have an increasing gradient from about 5O⁰C to about 14O⁰C. The water-soluble PVA coating layer 3 having a solid content of 5-20 wt% is formed to a coating thickness of 1-30 μm on the primer adhesive layer 2. Coating and drying of the water-soluble PVA coating layer 3 can be carried out in the same manner as those of the primer adhesive layer 2. When the thickness of the water-soluble PVA coating layer 3 is less than 1 μm, the printability, writability and erasibility of the printing paper drop. Meanwhile, when the thickness exceeds 30 μm, the coating layer 3 adsorbs a large amount of moisture after long-term use, causing poor strength of the printing paper. The water-soluble PVA coating layer 3 is formed by the following procedure: 1) At least one PVA resin is selected from the group consisting of PVA, acetyl- modified PVA, carboxyl-modified PVA and silane-modified PVA to prepare a 4-20% aqueous PVA solution. 2) Methylmethacrylate, ethylacrylate and a monomer having a cation-forming group are copolymerized in a molar ratio of 10 : 10 : 1 to prepare a copolymer. 3) The PVA solution prepared in 1) and the copolymer prepared in 2) are dissolved in a mixed solvent of water and ethanol (1 : 1) to provide a coating agent. The water-soluble PVA coating layer preferably has a solid content of 5~20 wt%. To this end, the amounts of the aqueous PVA solution and the copolymer are adjusted. When the solid content is less than 5 wt%, the coating amount of PVA is too small. On the other hand, when the solid content exceeds 20 wt%, the PVA is excessively coated. The acrylic copolymer prepared in 2) is a water-insoluble soft polymer resin having high water absorption. In addition, the acrylic copolymer is preferably cationic and contributes to antistatic properties of the surface. Further, the acrylic copolymer preferably has a cation mole fraction of 0.1~10 mole%. When the cation mole fraction is less than 0.1 mole%, the antistatic effects are small. Meanwhile, when the cation mole fraction exceeds 10 mole%, adhesiveness of the polymer and performance of the film are deteriorated. Examples of the monomer having a cation-forming group include dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylamide, and so on. It is preferred that the PVA has a weight-average molecular weight of 800-3,000 and a saponification degree of 80-99 mole%. When the PVA has a weight-average molecular weight lower than 800, the strength of the PVA coating layer is poor. On the other hand, when the PVA has a weight-average molecular weight higher than 3,000, the water solubility of the PVA drops. When the PVA has a saponification degree of less than 80 mole%, the solubility is good, but the water resistance, solvent resistance and blocking resistance are poor. Meanwhile, when the PVA has a saponification degree of more than 99 mole%, the hydrophilicity drops and thus drying time of the coating layer is extended. Since the PVA coating layer exhibits superior solvent resistance and poor water resistance, no dissolution and swelling take place when writing on the inkjet printing paper with a water-based board marker pen (containing no water), thus permitting writing on the printing paper. In addition, since the PVA coating layer exhibits weak wet tension, the written marks can be erased without difficulty. The removal primer adhesive layer is formed by coating at least one primer selected from the group consisting of polyurethane, polyacrylic and polyurethane acrylic resin aqueous solutions having a solid content of 1-5 wt% in a coating amount of 2-5 g/m² on the back face of the base layer. When the solid content is less than 1 wt%, the adhesive force between the base layer and the coating layer is poor. Meanwhile, when the solid content exceeds 5 wt%, the adhesive layer is extremely viscous and thus the adhesive force is likely to excessively increase. The coating amount of the removal primer adhesive layer 4 is preferably in the range of 2~5 g/m². When the coating amount is less than 2 g/m or exceeds 5 g/m , there is the disadvantage that the adhesive force between the base layer 1 and the removal paper 5 described below is poor. The coating of the removal primer coating layer 4 on the base layer 1 is carried out by means of, but not particularly limited to, gravure coater, kiss coater, dip coater, spray coater, comma coater, die coater, slide coater, etc. The removal paper 5 is uniformly attached on the removal primer adhesive layer 4. The printing paper of the present invention can replace conventional white boards used in situation rooms, meeting rooms, seminar rooms and lecture halls. In addition, the printing paper of the present invention enables free writing using a water- based board marker pen on it and erasing without the necessity of additional coating. The printing paper of the present invention is a paper for exclusive use in black- and-white, color and photograph inkjet printers. Since the printing paper of the present invention is glossy and prevents ink spreading, it enables production of fine colors and uniform printing. Moreover, the printing paper of the present invention can be manufactured and sold in the form of a roll, A4, A3 paper size, etc. Consequently, since the printing paper of the present invention is a white board easy to transport, handle and carry and at the same time a paper for general and color inkjet printers and large-format printers (plotters), it is suitable for use in numerous applications. For example, after military operation areas are printed on the printing paper of the present invention using a plotter, an explanation of the operation can be freely made using a water-based board marker pen. Also, Chinese or English words, arithmetical problems or the rules of multiplication are printed on the printing paper of the present invention, and then they can be explained while freely writing on the printed paper and erasing. Accordingly, the printing paper of the present invention is useful as an auxiliary learning material. Moreover, since the printing paper of the present invention made of a non-tear material has superior durability, it is advantageous in storing printed documents, photographs and text for a long period of time.

[Example] 5 wt% of a polyurethane resin primer was coated in a coating amount of 1 g/m² on a 30-200 μm thick PP (including OPP) sheet, and was passed through a drying hood having a constant temperature gradient to dryness to form a primer adhesive layer. A water-soluble PVA coating layer having a solid content of 10 wt% was formed to a coating thickness of 5~20 μm on the primer adhesive layer. A map was printed on the printing paper using a color inkjet printer. As a result, writing was possible on the printed paper using a water-based board maker pen (containing no water), and erasing was possible using a tissue, cloth or white board eraser. The printed map remained unchanged despite repetitive writing and erasing. In addition, clear lines and colors of the printed map could be realized, which indicates that the printing paper had superior printability. The water-soluble PVA resin having a solid content of 10 wt% was prepared by mixing 1) 90Og of an aqueous PVA solution (10 wt%) and 2) lOOg of a copolymer prepared by copolymerizing methylmethacrylate, ethylacrylate, and a monomer having a cation-forming group (dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylamide in a molar ratio of 10 : 10 : 1 by a common process, in 3) a mixed solvent of water and ethanol (1 : 1 (w/w)) at 1,000 rpm using an exchanger for 30 minutes.

Industrial Applicability

As described above, the printing paper of the present invention can also be used as a white board. In addition, the printing paper of the present invention enables printing of various images and text and has superior printability. Furthermore, since the printing paper of the present invention is easy to transport and handle while enabling free writing and erasing, it can be conveniently used as a substitute for a white board. Further, since the printing paper of the present invention has combined writing and erasing functions even without using additional coating or adhesive, it can be easily and conveniently used in any form as consumers desire in the fields of education, training, situation delivery, presentation, exhibition, image printing, and the like. Accordingly, the printing paper of the present invention can easily meet the needs of consumers. Since conventional printing papers made of paper are combined with ink after printing, they are difficult to recycle and tend to tear. In contrast, since the printing paper of the present invention can be made of plastic sheet and film, it can be recycled and is thus environmentally friendly. Further, the printing paper of the present invention does not tear and is thus convenient to store and use. Conventional printing papers having an adhesive-treated back face are likely to tear upon repetitive attachment and detachment, which makes it impossible to process and use them. In contrast, since the printing paper of the present invention uses highly durable plastic sheets and films, it is easy to impart adhesion functions and shows superior tear resistance even when repetitively attached and detached. Further, since the printing paper of the present invention is composed of compositions adapted for various manufacturing equipment, complex manufacturing procedure and excessive manufacturing costs can be avoided. Decoloration and discoloration of conventional printing papers tend to take place after long-term storage. In contrast, since the printing paper of the present invention can prevent occurrence of decoloration and discoloration, it can be stored for a long period of time.

Claims

Claims:

1. A printing paper with added white board functions, comprising: a base layer composed of paper, plastic sheet or plastic film; a primer adhesive layer composed of at least one primer selected from the group consisting of polyurethane, polyacrylic, and polyurethane acrylic resins and formed on the base layer; and a water-soluble polyvinylalcohol (PVA) coating layer with a coating thickness of 1-30 μm formed on the primer adhesive layer.

2. The printing paper according to claim 1, wherein the primer adhesive layer is formed by coating a primer having a solid content of 1~5 wt% in a coating amount of 1-3 g/m² on the base layer.

3. The printing paper according to claim 1, wherein the water-soluble polyvinylalcohol (PVA) coating layer is formed by coating water-soluble polyvinylalcohol (PVA) having a solid content of 5-20 wt%, a weight-average molecular weight of 800-3,000, a saponification degree of 80-99 mole% and a cation mole fraction of 0.1-10 mole% on the primer adhesive layer.

4. The printing paper according to any one of claims 1 to 3, further comprising: a removal primer adhesive layer formed by coating at least one primer selected from the group consisting of polyurethane, polyacrylic and polyurethane acrylic resin aqueous solutions having a solid content of 1-5 wt% in a coating amount of 2-5 g/m² on the back face of the base layer; and a removal paper adhered to the removal primer adhesive layer.

5. A process for manufacturing a printing paper with added white board functions, comprising the steps of: coating at least one primer selected from the group consisting of polyurethane, polyacrylic and polyurethane acrylic resin aqueous solutions having a solid content of 1-5 wt% in a coating amount of 1-3 g/m² on a base layer composed of paper, plastic sheet or plastic film, and drying the coated primer to form a primer adhesive layer; and coating water-soluble polyvinylalcohol (PVA) having a solid content of 5-20 wt%, a weight-average molecular weight of 800-3,000, a saponification degree of 80-99 mole% and a cation mole fraction of 0.1-10 mole% on the primer adhesive layer to form a water-soluble polyvinylalcohol (PVA) coating layer with a coating thickness of 1-30 μm.

6. The process according to claim 5, wherein the step of forming a water- soluble PVA coating layer includes the sub-steps of: dissolving a 4-20% aqueous PVA solution containing at least one PVA selected from the group consisting of PVA, acetyl-modified PVA, carboxyl-modified PVA and silane-modified PVA, and a copolymer prepared by copolymerizing methylmethacrylate, ethylacrylate and a monomer having a cation-forming group (dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylamide, etc.) in a molar ratio of 10 : 10 : 1, in a mixed solvent of water and ethanol (1 : 1), to provide a coating agent; and coating the coating agent on the primer adhesive layer and drying the coated agent.

7. The process according to claim 6, wherein the monomer having a cation- forming group is selected from the group consisting of dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and dimethylaminoethyl methacrylamide.

8. The process according to any one of claims 5 to 7, further comprising the steps of: coating at least one primer selected from the group consisting of polyurethane, polyacrylic and polyurethane acrylic resin aqueous solutions having a solid content of 1-5 wt% in a coating amount of 2-5 g/m² on the back face of the base layer to form a removal primer adhesive layer; and attaching a removal paper to the removal primer adhesive layer.