(b) Description of the Related Art Wall paper is classified into a wall paper made of paper, a joint wall paper consisting of 2 or more joined sheets of paper, a vinyl wall paper made of PVC, a wall paper made of fiber, and a wall paper made of natural substances, etc. according to its material, and is further classified into a plane wall paper, an embossed wall paper, etc. according to its structure. An embossed wall paper, in which patterns of raised and depressed engravings are provided on the surface of the wall paper to maximize reality of a product, is prepared by a method comprising an embossing process.

A conventional method for preparing an embossed wall paper comprises the steps of a) printing patterns on a plane surface, which will become a product surface, using a printing method such as gravure printing, flexo printing, rotary printing, pigment printing, etc. to prepare a semi-product, b) passing the semi-product between an embo roll (for example, a steel roll) and an opposite back-up roll to apply compression while heating to form embo patterns such that raised and depressed patterns form, and c) cooling.

Korean Patent Publication No. 1991-3890 discloses a technology for preparing a wall paper having precisely corresponded printing and embossed parts by joining a decoration paper embossed by way of gravure printing equipment and embossing equipment and a supplementary paper introduced by an adhesion roller, to correspond a printing part to an embossing part, thereby forming a space between the embossing part and the supplementary paper. However, according to such a common embossing process, all printing processes are completed on a plane surface of a product before conducting an embossing process, and thus printed patterns are provided only on the plane including the eventual raised and depressed surfaces of the embossed patterns, which cannot sufficiently express a 3-dimensional appearance.

In order to solve the problems of the plane printing and embossing process, and to express more delicate embo-patterns, a synchronous embossing method has been developed, which prints patterns on a product surface of a plane wall paper, and corresponds the printed patterns to the embo-patterns having raised and depressed parts from a steel embo roll surface, to express a somewhat 3-dimensional appearance. As an example, Japanese Patent Publication Hei 61-70100 discloses a synchronously printed synthetic resin foam wall paper. However, this method also gives printed patterning effects only on the plane and thus expression of motif (for example, a flower pattern, a set pattern) is insufficient and a 3-dimensional appearance is limitedly expressed.

Therefore, the conventional processes have problems of limited 3- dimesional appearance expression due to plane printing, because they comprise preparing the semi-product, printing, and conducting an embossing process.

In order to solve the above problems, it was suggested to conduct a post-printing process such as wiping printing, valley printing, and top printing.

However, these could not be used in combination because of the process conditions, and thus printing can be conducted only over a small area at a time.

Japanese Patent Laid-Open Patent Publication No. 06-39984 discloses a method for transcribing raised and depressed patterns by forming the patterns on PVC sheets using PVC sol and removing a release paper having raised and depressed parts. This method employs valley printing in order to print on depressed parts. However, since the wall paper is a semi- product prepared by gelling PVC sol, a substrate layer (a kind of a backing material : non-woven fabric, simili, etc. ) capable of supporting tension applied during processes is required, and repeated contraction and expansion due to consecutive heating and cooling substantially make the processing impossible.

In addition, only a piece-type product having a small area, a narrow width, and inferior quality can be obtained, and the application of the post-printing would deteriorate productivity and commerciality in practical operation.

Japanese Patent Laid-Open Publication No. 08-218298 discloses a method for giving a partial motif pattern such as lines and flowers by a post- printing method such as gravure printing, flexo printing, or rotary printing after forming embossed patterns. However, the above patent simply enumerates methods for printing a flat semi-product.

Meanwhile, according to a common wiping method, a colored PVC sol or ink is somewhat excessively introduced into raised and depressed parts of embossed patterns and then wiped using a knife, and if a high and low difference of the raised and depressed parts is large, product quality is unstable. And, if the embossed pattern is complicated, it is very difficult to employ a knife.

In addition, conventional valley printing shows bending (a phenomenon in which a rounding of a counter roll affects an embo roll and transfer rubber roll to generate a difference in the amount of transferred ink) because a depressed part of the embo pattern is printed simultaneously with embossing, and thus color deepens in the middle of the final product.

Therefore, if printing is conducted over a large area, product quality is irregular, and thus it can be applied only over a small area.

In addition, conventional gravure printing, one of the top printing methods, expresses gradation (gradual change of ink concentration) on a flat surface, and if conducted on a raised part of embossed patterns having a large high and low difference, printing is limitedly expressed such that only a partial motif can be expressed. And, conventional rotary printing has inferior operability due to tension differences from side to side of the raised part, and delicate printing cannot be expressed due to its rough appearance expression.

Also, a PVC sol-based ink that is generally used in flexo printing requires high temperature drying conditions, so it is suitable for rough image expression.

Moreover, the above methods of the prior art do not concretely mention compositions of ink used in post-printing. Up to now, an organic solvent having a high boiling point such as PVC sol, cyclohexane, toluene, xylene, etc. has been predominantly used as the ink. However, since these require high temperature heating (170-200°C, 10-20 sec) during drying and cooling processes, hardness and sharpness of the embossed patterns formed in an embossing process are lost, and the remaining solvent in the final product is harmful to a human body due to its noxious odor (TVOC: total volatile organic compound). Also, the conventionally used alcohol-based ink causes irregular product quality because ink concentration increases due to its rapid volatilization during a long-term operation, allowing only a small area of printing or partial lot operation because of mesh blocking of a GN roll and F/X roll, and it cannot be applied for stacking printing wherein two consecutive methods are applied and drying and cooling are repeated.

Accordingly, there is a need for a method that can be applied over a large area and that can express a delicate 3-dimensional appearance.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an embossed wall paper and the preparation thereof, wherein 2 or more kinds of post-printings selected from the group consisting of wiping, valley, and top-printing are conducted, thereby improving printing effects and enabling printing over a large area to obtain a superior 3-dimensional appearance.

It is another object of the present invention to provide a method for preparing an embossed wall paper by changing the materials of a substrate layer and the material of ink used in post-printing to enable printing over a large area and show delicate printing effects.

In order to achieve these objects, the present invention provides a method for preparing an embossed wall paper having a 3-dimensional appearance, comprising the steps of: a) forming a substrate layer ; b) forming embossed patterns on the substrate layer ; c) conducting wiping printing on depressed parts of the embossed patterns; and d) conducting top printing on raised parts of the embossed patterns.

The present invention also provides a method for preparing an embossed wall paper having a 3-dimensional appearance, comprising the step of: a) forming a substrate layer ; b) forming embossed patterns on the substrate layer, while simultaneously conducting valley printing on depressed parts of the embossed patterns ; and c) conducting top printing on raised parts of the embossed patterns.

The present invention also provides a method for preparing an embossed wall paper having a 3-dimensional appearance, comprising the steps of : a) forming a substrate layer ; b) forming embossed patterns on the substrate layer, while simultaneously conducting valley printing on depressed parts of the embossed patterns; c) conducting wiping printing on depressed parts of the embossed patterns; and d) conducting top printing on raised parts of the embossed patterns.

The present invention also provides an embossed wall paper comprising a substrate layer, at least one of a wiping layer and a valley layer, and a top print layer, wherein the wiping layer and/or valley layer is formed on depressed parts of embossed patterns, and the top print layer is formed on raised parts of embossed patterns.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view of an embossed PVC wall paper having a 3-dimensional appearance according to the present invention.

Fig. 2 is a cross-sectional view of another embossed PVC wall paper having a 3-dimensional appearance according to the present invention.

Fig. 3 is a cross-sectional view of another embossed PVC wall paper having a 3-dimensional appearance according to the present invention.

Fig. 4 is a cross-sectional view of another embossed PVC wall paper having a 3-dimensional appearance according to the present invention.

Fig. 5 is a cross-sectional view of an embossed PVC wall paper of the prior art.

Fig. 6 is a cross-sectional view of an embossed joint wall paper having a 3-dimensional appearance according to the present invention.

Fig. 7 is a cross-sectional view of another embossed joint wall paper having a 3-dimensional appearance according to the present invention.

Fig. 8 is a cross-sectional view of another embossed joint wall paper having a 3-dimensional appearance according to the present invention.

Fig. 9 is a cross-sectional view of another embossed joint wall paper having a 3-dimensional appearance according to the present invention.

Fig. 10 is a cross-sectional view of an embossed PVC wall paper having a 3-dimensional appearance according to the present invention.

Fig. 11 is a cross-sectional view of an embossed joint wall paper of the prior art.

Fig. 12 shows a flow chart for preparing an embossed PVC wall paper of Example 1 of the present invention.

Fig. 13 shows a flow chart for preparing an embossed PVC wall paper of Example 2 of the present invention.

Fig. 14 shows a flow chart for preparing an embossed PVC wall paper of Example 3 of the present invention.

Fig. 15 shows a flow chart for preparing an embossed PVC wall paper of Example 4 of the present invention.

Fig. 16 shows a flow chart for preparing an embossed PVC wall paper of Example 5 of the present invention.

10: lower paper (imitation paper) 12: non-woven fabric 20: PVC foam layer 22: PVC soft sheet 32 : transcription print layer 30: print layer 40: wiping layer 50: valley layer 60: top print layer 70: upper paper (imitation paper) 80: adhesive layer 90: PVC sol adhesive layer 100: vacuum embossed pattern layer DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in more detail.

The present inventors recognized that the conventional preparation of embossed wall paper conducts printing only on a flat paper, and wiping, valley, and top printing cannot be employed in combination, and thus the printing process is completed before an embossing process, and therefore it is insufficient for preparing a wall paper having a 3-dimensional appearance.

Additionally, they discovered that 3-dimensional patterns can be embodied over a large area by conducting 2 or more kinds of post-printing processes on a 3-dimensional surface of a wall paper on which embossed patterns are formed.

The method for preparing an embossed wall paper of the present invention comprises the steps of preparing a substrate layer, conducting an embossing process, and conducting 2 or more kinds of post-printing on the embossed patterns.

The post-printing is a method wherein patterns are printed on an embossed surface, and the present invention is characterized by employing 2 or more kinds of post-printing selected from the group consisting of wiping, valley, and top printing.

The method for preparing an embossed wall paper of the present invention may further comprise the step of pre-printing.

The method for preparing a wall paper will be explained in more detail.

1) Formation of a substrate layer In the present invention, the substrate layer includes a PVC foam layer, a joint layer, and a PVC sheet.

This step comprises coating a PVC (polyvinyl chloride) foam layer on a material paper, or coating an adhesive layer on a lower paper layer and joining an upper paper layer to the adhesive layer, or coating an adhesive on one surface of a non-woven layer and joining a PVC sheet to the coated surface.

The present invention may further comprise a pre-printing step of printing on a plane part by a conventional method, after forming the substrate layer and before conducting an embossing process, as will be discussed.

Specifically, the present invention may further comprise the step of forming a printed layer on the PVC foam layer or on the upper paper layer.

The present invention may further comprise the step of forming a transcription print layer on the PVC sheet. The PVC sheet is preferably prepared by a calendaring process, for durability.

Formation of the PVC foam layer or the joint layer as a substrate layer will be explained.

First, a material paper (1) used for a base material of a wall paper is introduced. For a PVC wall paper, a PVC foam layer (2) is formed and then gelled, foamed, and cooled to obtain a semi-product. For a joint wall paper, an adhesive is coated over a material paper layer (1) to form an adhesive layer, and then an upper paper layer (7) is joined to the adhesive layer. As the adhesive, an acryl-based adhesive having a solid content of 40i5% and a viscosity of 3000500 cps can be used. In addition, various coating methods can be employed according to the properties of products, and generally gravure coater is used.

Then, a printing process for imparting patterns on the surface of the semi-product can be conducted by gravure printing, offset-printing, or a rotary screen method. Patterns are printed on the PVC foam layer (2) or on the upper paper layer (7) to form a print layer (3). The print layer (3) is then dried and heated in order to dry ink in the print product and for a subsequent embossing process. As the ink, an oil or aqueous ink can be used.

2) Embossing process An embossing process comprises forming raised and depressed patterns using an embo-roller having raised and depressed parts, and then cooling. The raised parts of the embo-roll are formed into depressed patterns of a wall paper, and the depressed parts of the embo-roll are formed into raised patterns of a wall paper.

The embossed patterns are preferably formed by vacuum embossing, because those formed by vacuum embossing are light weight, based on thickness.

Specifically, an embossing roll of a common embossing machine is made of steel and has raised and depressed patterns, and it forms embossed patterns by compressing a semi-product and cooling the same. However, in the present invention, embossed patterns are formed using a vacuum embossing machine. The surface of an embossing roll of the vacuum embossing machine is made of silica, such as Si02, and micro-holes with a size of 50 to 200 ßm are uniformly distributed over the embossing roll. The inside of the roll consists of vacuum and cooling systems. The vacuum system draws air through the micro-holes on the surface of the embossing roll, and thus when the heated (170 to 200 °C) semi-product contacts the embossing roll surface, embossed patterns are formed by adsorption through the micro-holes of the embossing roll surface. Therefore, the product has a larger thickness than those formed by common methods, on the basis of the same area and weight. In addition, the vacuum embossing machine simultaneously conducts cooling in order for curing and prevention of overheating of an embossing roll.

3) Post-printing process i) Wiping printing Wiping printing is a method wherein printing is conducted using two compression rolls. Specifically, the compression rolls consist of an upper roll and a lower roll, and ink is transferred through a lower front mesh roll to coat an excessive amount of ink on the surface of a product having raised and depressed parts. Most of the ink in the raised parts is wiped off by compression with the upper roll, and ink gathers in the depressed parts. The ink gathers differently according to depths of depressed parts to maximize printing effects. The wiping printing, which is used as a post-printing process in the present invention, is continuously or subsequently conducted after conducting an embossing process to prepare a final product having raised and depressed patterns.

Specifically, the wiping printing of the present invention is characterized in that the upper compression rubber roll rotates with completely wound by the surface of a semi-product, on the opposite surface of which embossed patterns are formed, when the lower front mesh roll transfers aqueous ink to the embo pattern-formed surface, and simultaneously the upper compression roll wipes off ink, thereby uniformly coating ink. The upper roll includes a rubber roll such as silicone, MBR, or natural rubber, and the lower mesh roll is preferably a front mesh roll made of steel and preferably has a mesh size of 40 to 150 mesh. According to this method, the problem of the prior art that paper having raised and depressed patterns of a large height is curled is prevented by complete winding, thereby facilitating uniform printing over the total area. This method can also be applied for hard embo-patterns. ii) Valley printing Valley printing expresses printing effects by a slight difference in ink transfer amount according to heights of raised parts. Specifically, during an embossing process, ink in the raised parts of an embossing roll is transferred onto a valley of a product which will be formed as depressed parts of a product by an embossing process. Thus, this method gives coloring effects to depressed parts of embossed patterns of a product.

In the valley printing of the present invention, transfer rubber rolls are located and aqueous ink is used, thereby preventing bending. According to the present invention, transfer rubber rolls for transferring ink are located in a direction perpendicular to a part to which bending force is applied through a counter roll and an embo roll. Specifically, the transfer rolls are located perpendicularly on or below the embo roll to prevent bending and thereby securing stable quality. As the ink, a water-based aqueous ink comprising acryl-based resin is used, thereby securing operability and stable quality. As an example, in order to transfer ink in the raised parts of an embo roll, three rubber rolls are closely adhered and engaged with each other. If ink is coated on a first rubber roll, a specific amount of ink is transferred onto a second roll by controlling close adherence between the first and second rolls, and the transferred ink is transferred onto a third roll by controlling close adherence between the second and third rolls, and then ink is transferred onto raised parts of the embo roll by skin touch through a specific separation because the third roll and the embo roll are not closely adhered to each other.

The embo roll supplies power to the third roll to cause operation. The embo roll has a similar circumference and gears of a similar size with those of the third roll, which are engaged with each other. The first and second rolls are rotated using the power supplied to the third roll, and the circumferences are set to 90 to 50% of that of the third roll to control the ink transfer amount and adherence degree between rubber rolls. iii) Top printing A top printing is a method of printing on raised parts of the product after an embossing process.

The top printing is preferably conducted by flexo or gravure printing.

More preferably, it is conducted by flexo printing using an aqueous ink.

According to the top printing of the present invention, printing is conducted only on raised parts of a product partially or wholly to clearly express embossed patterns on raised parts, thereby maximizing embossed pattern expressing effects. The present invention can conduct printing on a 3- dimensional surface by a minute pressure of skin touch, unlike conventional flexo and gravure printing. The present invention applies flexo printing that is favorable for printing of raised patterns, thereby enabling uniform printing over the total area.

Specifically, the flexo printing of the present invention is conducted using an ink transfer rubber roll, high mesh steel roll, flexo rubber roll, and counter steel roll, in this order. Ink is transferred from an ink plate to the ink transfer rubber roll, which transfers ink to the high mesh front steel roll in a regular amount. The amount of ink is controlled by the number of mesh lines of the steel roll, thereby transferring a regular amount of ink to the flexo rubber roll, which prints on the paper.

The flexo printing rolls enable uniform printing along with the raised and depressed patterns of embossed paper, or the roll itself can be raise- carved to express uniform printed patterns.

In addition, the present invention preferably employs acryl-based aqueous ink in the wiping, valley, and top printing. The acryl-based aqueous ink can prevent mesh blocking of the high mesh steel roll, thereby enabling printing over a large area and also enabling successive applications of 2 or more kinds of printing. And, the aqueous ink allows maximum expression of delicate embossed patterns because the embossed patterns are formed by evaporation of water, and it also allows good productivity due to maintenance of uniform product quality during total area printing and lot operation over a long period. Such acryl-based aqueous ink can be used for the raised part and/or depressed part.

The acryl-based aqueous ink preferably comprises, on the basis of 100 parts by weight of a water base, 15 to 30 parts by weight of an acrylic copolymer, 5 to 10 parts by weight of propylene glycol, 1 to 5 parts by weight of a surfactant, 0.1 to 2 parts by weight of a defoamer, and 3 to 5 parts by weight of additives.

The acrylic copolymer is an emulsion type having printing competence, a self-crosslinking property, and heat resistance, and the weight average molecular weight is preferably 180,000 to 200,000. The content of the acrylic copolymer is 15 to 30 parts by weight, based on 100 parts by weight of the water base, and if the content goes beyond this range, cracks form or the surface becomes tacky.

The content of the propylene glycol is preferably 5 to 10 parts by weight, based on 100 parts by weight of the water base.

As the surfactant, commonly used cationic, anionic, or non-ionic surfactants can be used, and the non-ionic surfactant is preferable in terms of safe arrival of pigment, storage properties, etc. The content of the surfactant is 1 to 2 parts by weight, based on 100 parts by weight of the water base, and if the content goes beyond this range, layer separation of the aqueous ink occurs, pigment coloring or dispersibility decreases or coloring is not sufficient, and wash resistance of the surface of the final product decreases.

The defoamer includes a mineral oil type, a mineral oil free type, etc., and in order to prevent layer separation and foster printing competence, a polyether siloxane copolymer of a mineral oil free type is used, and the content is 0.5 to 2 parts by weight, based on 100 parts by weight of the water base.

As the additives, an antibacterial (antiseptic) can be used in order to prevent deterioration of physical properties during long-term storage, and polyethylene powder can be used in order to impart scratch resistance and slip properties to the surface. One or more kinds of additives can also be used.

The content of the additive is 0.5 to 1 parts by weight, based on 100 parts by weight of the water base.

Referring to the figures, the method of the present invention for preparing a wall paper having a superior 3-dimensional appearance will be explained.

According to the method of the present invention, valley printing during an embossing process or wiping printing is conducted, drying and cooling is conducted, and then flexo or gravure printing is conducted followed by drying and cooling.

Fig. 1 and Fig. 2 show embossed PVC wall papers of the present invention, and Fig. 6 and Fig. 7 show embossed joint wall papers of the present invention. Therein, wiping or valley printing is conducted to naturally express the amount of coated ink according to depths of the depressed parts, thereby expressing a 3-dimensional appearance, and simultaneously top printing is conducted on raised parts to give 3-dimensional effects of floating at the product surface.

Fig. 12 is a flow chart showing an embossed PVC wall paper preparation process according to the present invention. Therein, a) a material paper (10) is introduced, and a PVC foam layer (20) is formed thereon and then gelled, foamed, and cooled ; b) pre-printing is conducted on the plane to form a print layer (30), and the layer is dried and heated; c) an embossing process is conducted; d) a wiping process (40) is conducted and dried; and e) top printing is conducted to form a top print layer (60), which is dried to prepare a wall paper of Fig. 1. In addition, during the process as shown in Fig. 12, instead of the wiping process (40), valley printing (50) can be conducted during the embossing process (30) as shown in Fig. 13 to prepare a wall paper of Fig. 2. Also, a wiping process (40) can be conducted after conducting valley printing (50) during an embossing process.

Referring to Figs. 14 and 15, one example of a process for preparing an embossed joint wall paper is explained. First, a) a lower paper (10) is introduced and an adhesive layer (80) is formed, and an upper paper (70) is introduced to join the lower and upper papers; b) a print layer is formed; c) embossing is conducted and the embossed layer is heated and dried; d) wiping printing (40) is conducted and the wiping layer is dried; and e) top printing (60) is conducted followed by drying to prepare a final product (a wall paper of Fig. 6). During the process as shown in Fig. 14, instead of the wiping printing (40), valley printing (50) can be conducted during the embossing process as shown in Fig. 15 to prepare a wall paper of Fig. 7. In addition, after valley printing, wiping printing can be conducted. Each of the above process except the process of printing on a 3-dimensional surface can be conducted by common methods known to ordinarily skilled persons in the art.

One example of a wall paper preparation method using a PVC soft sheet is as shown in Fig. 16.

Referring to Fig. 16, the wall paper of the present invention comprises a non-woven fabric layer (12) that is a back sheet to be adhered to a wall surface, an adhesive layer (90), a PVC sheet layer (22), a transcription print layer (32), a wiping print layer (40), and a top print layer (60), and it is prepared according to the following process.

A polyvinyl chloride soft sheet prepared by a calendaring method is, if necessary, manufactured to a predetermined thickness, and then a transcription print layer (32) is formed on one surface of the sheet. On one surface of a back sheet comprising a non-woven fabric or plain fabric, an adhesive (90) is coated, and then the back side of the polyvinyl chloride sheet is joined to the adhesive-coated surface. Thereby, a semi-product is obtained, wherein a transcription print layer (32) is formed on the PVC sheet, and an adhesive layer (90) and a back sheet layer (12) are formed under the PVC sheet. On the semi-product, an embossed pattern layer (100) is formed, a wiping print layer (40) is formed on the depressed parts of the embossed pattern layer (100), and a top print layer (60) is formed on the raised parts of the embossed pattern layer.

The PVC sheet can be prepared by calendaring a composition comprising 100 parts by weight of straight PVC resin, 30 to 50 parts by weight of a plasticizer, 1 to 5 parts by weight of a stabilizer, 1 to 10 parts by weight of a flame retarding plasticizer, 1 to 5 parts by weight of a flame retardant, and 80 to 100 parts by weight of filler. The back sheet is a non-woven fabric or plain fabric comprising one or more kinds selected from the group consisting of polyethylene, polypropylene, and viscose rayon.

After forming embossed patterns using a vacuum embossing machine, a cooling process is conducted in order to completely cool the embossed patterns. Then, wiping printing (40) is conducted followed by drying with hot air and cooling, and then top printing (60) is conducted.

The transcription print layer (32) is formed on a PVC sheet before joining of a PVC sheet and back sheet. It is formed by transcribing print patterns on a PVC sheet by a laminate method using a transcription film of polyethyleneterephthalate to which print patterns are given by gravure printing.

After joining, an embossing process is conducted, and then wiping printing for depressed parts of the embossed patterns and top printing for raised parts of the embossed patterns are conducted to prepare a wall paper of the present invention having superior durability and appearance.

The embossed wall paper of the present invention includes a PVC vinyl wall paper, a joint wall paper, and a PVC sheet wall paper.

In addition, the wall paper of the present invention comprises a substrate layer, a wiping print layer, and a top print layer, wherein the wiping print layer is formed on depressed parts of embossed patterns, and the top print layer is formed on raised parts of embossed patterns. The wall paper of the present invention also comprises a substrate layer, a valley layer, and a top print layer, wherein the valley layer is formed on depressed parts of embossed patterns, and the top print layer is formed on raised parts of embossed patterns. In addition, the wall paper of the present invention comprises a substrate layer, a valley layer, a wiping layer, and a top print layer.

In the present invention, a PVC wall paper comprises a lower paper layer and a PVC foam layer as a substrate layer, on which gravure, flexo, and rotary screen printing are conducted. And, a joint wall paper comprises a lower paper layer, an adhesive layer, and an upper paper layer as a substrate layer, on which gravure and flexo printings are conducted.

The present invention will be explained in more detail with reference to the following Examples. However, these are only to illustrate the present invention and the present invention is not limited to them.

EXAMPLES Comparative Example 1: Preparation of conventional embossed PVC wall paper (Fig. 5) A conventional embossed PVC wall paper was prepared as follows : Structure and preparation method of conventional embossed PVC wall paper will be explained After knife-coating a liquid composition on a material sheet (10) to a thickness of 0.3 mm, the coated composition was heated at 210°C at a speed of 40 m/min for 40 seconds to gel, and then it was foamed to form a PVC foam layer (20) of a solid state composition. The liquid composition in the PVC foam layer (20) is a sol having viscosity of 5000 500 cps prepared by mixing 100 parts by weight of polyvinyl chloride resin having a polymerization degree of 500 to 1500,65 to 70 parts by weight of a primary plasticizer of dioctyl phthalate, 1 to 5 parts by weight of a foaming agent of azodicarbon diamide, 1 to 5 parts by weight of a foaming promoter of zinc, 1 to 5 parts by weight of a foam stabilizer of a barium-zinc-based compound, 6 to 8 parts by weight of a pigment of titan oxide, and 50 to 100 parts by weight of calcium bicarbonate filler.

On the PVC foam layer (20), patterns were printed by gravure printing, offset-printing, or screen printing to form a print layer (30), and then the print layer was heated at 200 °C for 10 to 20 seconds and passed through embossing and cooling processes to prepare a final product.

Comparative Example 2: Embossed joint wall paper (Fig. 11) The structure and preparation process of a conventional embossed joint wall paper will be explained.

Before operation, a paper embo roll was compressed with a steel embo roll having raised and depressed patterns and repeatedly rotated for 1 to 2 hours to form raised and depressed patterns on the paper embo roll. Then, a lower paper (10) was untied from a braider roller to move to an adhesive roller, thus coating the adhesive on the lower paper layer (10) to form an adhesive layer (80). As the adhesive, an acryl-based adhesive having a solid content of 40 5% and a viscosity of 3000 500 cps was used. On the adhesive layer (80), an upper paper layer (70) was joined, and then a print layer (30) was formed on the upper paper layer (70).

Continuously, a semi product having a print layer (30) formed thereon was passed between a steel embo roll and a paper embo roll to conduct the embossing treatment. The embossing treated product was dried by hot air at 100 °C for 10 to 15 seconds to prepare an embossed joint wall paper.

Example 1: Preparation of PVC embossed wall paper (Fig. 1) A PVC vinyl embossed wall paper having a 3-dimensional appearance was prepared by applying wiping printing and top printing.

On the semi-product having passed through a printing process and embossing process in Comparative Example 1, a wiping print layer (40) was formed. Specifically, an aqueous ink was transferred through a steel front mesh roll (mesh size: 40 to 150) to coat an excessive amount of ink on the surface of a product having raised and depressed parts, wherein most of the ink in the raised parts was wiped off by the compression between the upper rubber roll, and the ink gathered in depressed parts. Then, the product was dried with hot air at 100 °C for 10 to 30 seconds, and cooled.

Continuously, gravure or flexo printing was conducted on a product surface having raised and depressed parts, wherein printing was conducted on the raised parts of embossed patterns by slight pressure of skin touch, to form a top print layer.

After forming the top print layer (60), the product was heated and dried with hot air at 100°C for 10 to 20 seconds, and then cooled to complete a final product having a 3-dimensional appearance.

Therein, as the ink, an acryl-based aqueous ink which comprised, on the basis of 100 parts by weight of a water base, 25 parts by weight of an acrylic copolymer having a molecular weight of 200,000, 7 parts by weight of propylene glycol, 3 parts by weight of a surfactant, 1 part by weight of a defoamer, and 3 parts by weight of other additives.

Example 2: Embossed PVC wall paper (Fig. 2) An embossed PVC wall paper was prepared by applying valley printing and top printing.

The valley printing was conducted on a product having passed though a printing process in Comparative Example 1 as follows. In order to transfer ink on the raised parts of the embo roll, among the three rubber rolls that are closely adhered and engaged with each other, a first roll was coated with ink.

Since the surface temperatures of the PVC layer (20) and print layer (30) before conducting the embossing process were about 140 to 170 °C, which is very high, a cooling system using cooling water can be installed in a third rubber roll that transfers ink to an embo roll, thereby preventing overheating and drying of ink to maintain clear printing.

The product having passed though valley printing was dried with hot air at 100 °C for 10 to 30 seconds. Continuously, a top print layer (60) was formed on raised parts of embossed patterns by flexo or gravure printing, and then the product was dried with hot air at 100 °C for 10 to 20 seconds, and cooled to complete a final product having a 3-dimensional appearance.

Therein, as the ink, an acryl-based aqueous ink which comprised, on the basis of 100 parts by weight of a water base, 25 parts by weight of an acrylic copolymer having a molecular weight of 200,000, 7 parts by weight of propylene glycol, 3 parts by weight of a surfactant, 1 part by weight of a defoamer, and 3 parts by weight of other additives.

Example 3: Embossed PVC wall paper (Fig. 3) An embossed PVC wall paper was prepared by applying valley printing, wiping printing, and top printing.

The valley printing was conducted on a product having passed though a printing process in Comparative Example 1 as follows. In order to transfer ink on the raised parts of an embo roll, among the three rubber rolls that are closely adhered and engaged with each other, a first roll was coated with ink.

Since the surface temperatures of the PVC layer (20) and print layer (30) before conducting the embossing process were about 140 to 170 °C, which is very high, a cooling system using cooling water can be installed in a third rubber roll that transfers ink to an embo roll, thereby preventing overheating and drying of ink to maintain clear printing.

The product having passed through the valley printing was dried with hot air at 100 °C for 10 to 30 seconds and cooled, and a wiping print layer was continuously formed thereon. Specifically, an aqueous ink was transferred through a steel front mesh roll (mesh size : 40 to 150) to coat an excessive amount of ink on the surface of a product having raised and depressed parts, wherein most of the ink in the raised parts was wiped off by the compression with the upper rubber roll, and the ink gathered in depressed parts. Then, the product was dried with hot air at 100 °C for 10 to 30 seconds, and cooled.

Continuously, a top print layer (60) was formed on raised parts of embossed patterns of the product by flexo or gravure printing, and then the product was dried with hot air at 100 °C for 10 to 20 seconds and cooled to complete a final product having a 3-dimensional appearance.

Therein, as the ink, an acryl-based aqueous ink which comprises, on the basis of 100 parts by weight of water base, 25 parts by weight of an acrylic copolymer having molecular weight of 200,000, 7 parts by weight of propylene glycol, 3 parts by weight of a surfactant, 1 part by weight of a defoamer, and 3 parts by weight of other additives.

Example 4: Embossed PVC wall paper (Fia. 4) An embossed PVC wall paper was prepared by applying valley printing and wiping printing by the same process as in Example 3, except that the top printing was not conducted.

Example 5 : Preparation of embossed joint wall paper (Fig. 6) A joint wall paper consisting of 2 sheets of imitation paper was prepared by applying wiping printing and top printing.

On the embossed semi-product having elastic embossed patterns that had passed through the processes of Comparative Example 2, an aqueous ink was transferred through a steel front mesh roll. Thereby, an excessive amount of ink coated the surface of the product having raised and depressed parts, wherein most of the ink in the raised parts was wiped off by compression between the upper rubber roll, and ink gathered in the depressed parts of the product, thus forming a wiping print layer (40), which was dried with hot wind at 100 °C for 10 to 30 seconds.

Continuously, a top print layer was formed on the raised parts of the product by flexo or gravure printing, wherein printing was conducted on a 3- dimensional surface by slight pressure of skin touch.

After forming a top print layer (60), the product was dried with hot air at 100 °C for 10 to 20 seconds and cooled to complete a final product having a 3-dimensional appearance.

Therein, as the ink, an acryl-based aqueous ink which comprises, on the basis of 100 parts by weight of a water base, 25 parts by weight of an acrylic copolymer having a molecular weight of 200,000, 7 parts by weight of propylene glycol, 3 parts by weight of a surfactant, 1 part by weight of a defoamer, and 3 parts by weight of other additives.

Example 6: Preparation of embossed 6oint wall paper (Fig. 7) A joint wall paper consisting of 2 sheets of imitation paper and having a 3-dimensional appearance was prepared by applying valley printing and top printing.

The valley printing was conducted on the product having passed through the printing process of Comparative Example 2. Among the three rubber rolls which are closely adhered and engaged with each other, a first rubber roll was coated with ink to transfer ink to a third rubber roll, which transfers ink to an embo roll by skin touch. Thus, ink was transferred to the raised parts of the embo roll to conduct the embossing process. The product having passed through the valley printing (50) was dried with hot air at 100 °C for 10 to 30 seconds. Continuously, a top print layer (60) was formed on the raised parts of the embossed patterns by flexo or gravure printing, and then dried with hot air at 100 °C for 10 to 20 seconds and cooled to complete a final product having a 3-dimensional appearance.

The final product consists of, from the bottom, a lower paper layer (10), an aqueous acrylic adhesive layer (80), an upper paper layer (70), a print layer (30), a valley print layer (50), and a top print layer (60). After conducting the embossing process together with valley printing, the embossed patterns become elastic by drying with a hot wind at 100 °C for 10 to 15 seconds, and continuously delicate embossed patterns are clearly expressed on the raised parts of the product through flexo or gravure printing, thereby maximizing expression of embossed patterns.

Therein, as the ink, an acryl-based aqueous ink which comprises, on the basis of 100 parts by weight of a water base, 25 parts by weight of an acrylic copolymer having a molecular weight of 200,000, 7 parts by weight of propylene glycol, 3 parts by weight of a surfactant, 1 part by weight of a defoamer, and 3 parts by weight of other additives.

Example 7: Preparation of embossed joint wall paper (Fig. 8) A joint wall paper consisting of 2 sheets of imitation paper and having a 3-dimensional appearance was prepared by applying valley printing, wiping printing, and top printing.

The valley printing was conducted on the product having passed through the printing process in Comparative Example 2. Among three rubber rolls which are closely adhered and engaged with each other, a first rubber roll was coated with ink to transfer ink to a third rubber roll, which transfers ink to the raised parts of an embo roll by skin touch, thereby conducting an embossing process. The product having passed through the valley printing (50) was dried with hot air at 100 °C for 10 to 30 seconds and cooled to an embossed semi-product having elastic embossed patterns and valley printing.

Continuously, an aqueous ink was transferred to the product through a steel front mesh roll to coat an excessive amount of ink on the product surface having raised and depressed parts, wherein most of the ink in the raised parts was wiped off by compression with the rubber roll, and ink gathered in the depressed parts, thus forming a wiping print layer (4). Then, the product was dried with hot air at 100 °C for 10 to 30 seconds and cooled.

Continuously, on the raised parts of the embossed patterns, a top print layer (60) was formed by flexo or gravure printing, and then heated and dried with hot wind at 100 °C for 10 to 20 seconds and cooled to complete a final product having a 3-dimensional appearance.

The final product consists of, from the bottom, a lower paper layer (10), an aqueous acrylic adhesive layer (80), an upper paper layer (70), a print layer (30), a valley print layer (50), and a top print layer (60). After conducting the embossing process together with valley printing, the embossed patterns become elastic by drying with hot air at 100 °C for 10 to 15 seconds, and continuously delicate embossed patterns are clearly expressed on the raised parts of the product through flexo or gravure printing, thereby maximizing expression of embossed patterns.

Therein, as the ink, an acryl-based aqueous ink which comprises, on the basis of 100 parts by weight of a water base, 25 parts by weight of an acrylic copolymer having a molecular weight of 200,000, 7 parts by weight of propylene glycol, 3 parts by weight of a surfactant, 1 part by weight of a defoamer, and 3 parts by weight of other additives.

Example 8: Preparation of embossed joint wall paper (Fig. 9) An embossed joint wall paper was prepared by applying valley printing and wiping printing by the same process as in Example 7, except that the top printing was not conducted.

Example 9: Preparation of a wall paper using a PVC sheet (Fig. 10) Preparation of PVC sheet> A PVC soft sheet with a thickness of 0.3 mm was prepared by calendaring a composition which comprises 100 parts by weight of straight PVC resin, 40 parts by weight of a plasticizer of dioctyl phthalate (DOP), 40 parts by weight of a Ba-Zn type stabilizer, 4 parts by weight of ZnB, Mg (OH) 2 type complex flame retardant, and 90 parts by weight of CaC03.

Formation of a transcription print layer> The prepared PVC soft sheet was passed through a heating drum by skin touch to manufacture it to a thickness of 0.3 mm, and then predetermined patterns were transcription-printed on the PVC sheet by a laminate method using a transcription film made of polyethylene terephthalate on which patterns were printed by common gravure printing.

<Joint> Separately from the above process, on one surface of a non-woven fabric with a density of 60 g/m2 consisting of polyethylene, a PVC sol adhesive was coated to a thickness of 0.1 mm by gravure coating to prepare a back sheet, and the PVC sheet was then joined to the adhesive-coated surface of the back sheet. Thus, around the PVC sheet, a transcription print layer (32) was formed thereon, and an adhesive layer (90) and a non-woven fabric layer (12) were formed thereunder.

Formation of embossed patterns> The semi-product was pre-heated to 180 °C, and the surface of the transcription print layer (32) was contacted with an embossing roll of a vacuum embossing machine, on which minute holes with a size of 50 to 200 um were uniformly formed to form predetermined embossed patterns, and then cooled.

Formation of print layer on raised and depressed parts> On the depressed parts of the embossed patterns, a wiping print layer (40) was formed by compression of two compression rolls, and dried and cooled. Continuously, a top print layer (60) was formed on the raised parts by gravure printing to obtain a commercial wall paper having superior durability and appearance.

As explained, the conventional valley printing, wiping printing, and top printing could be applied to only a small area such as a flower pattern and they could not be simultaneously applied, while according to the present invention, they can be used in combination over a large area.

The present invention uses an acryl-based aqueous ink, unlike to the conventional alcohol-based ink, to solve mesh-blocking of a mesh steel roll or expansion of a rubber roll during lot operation over a long time, thereby enabling combined use of post-printing methods and printing over a large area.

In addition, the present invention uses a polyvinyl chloride soft sheet prepared by a calendaring method, thus fostering durability, and forms embossed patterns with a vacuum embossing machine, thereby reducing the weight of the product compared to its thickness to improve construction properties. Therefore, the best. grade wall paper having a superior appearance in terms of interior design can be obtained. According to the present invention, superior surface durability is obtained because a calendar- processed PVC sheet is used, construction properties are superior due to light weight and high thickness (high thickness of 145% is obtained in Example on the basis of the same area and weight as Comparative Example) because a vacuum embossing process is employed, and appearance after construction is superior due to transcription printing and separate printing of raised and depressed parts of the embossed patterns.