JP7124220B2 - Printing paper with hinge - Google Patents

Description

The present invention relates to printing paper having a hinge portion. The printing paper according to the present invention is used, for example, as a booklet in which a plurality of printing papers are stacked. In particular, the printing paper according to the present invention is suitable for printing a photo album or the like that is viewed in a double-page spread.

Conventionally, there is known a bookbinding method in which a plurality of pages printed with photographs or the like are stacked, aligned on the spine, and the pages are bound by a binding portion provided around the edge of the spine. . For example, when combining pages for a photo book, hot melt adhesive is applied around the spine to join each page, and multiple holes are formed through the binding part of each page. In general, screws (bookbinding screws) are inserted into the holes to connect the pages.

By the way, in the bookbinding method as described above, it is difficult to flatten the left and right pages when the booklet is opened, and there is a risk of damaging the pages and the binding if the booklet is forced to open flat. (Patent Document 1). In order to overcome such problems, in Patent Document 1, openings are formed along the binding portion of each page, and a flexible film is attached so as to cover the openings. A sheet stock has been proposed in which a hinge region is formed by a film and a hinge area for facilitating folding of each page.

Japanese Patent Publication No. 2010-520099

However, when an opening is formed in each printing paper and a flexible film is pasted thereon like the sheet stock described in Patent Document 1, there is a gap between the printing paper and the film around the opening. There will be a step. In this case, when printing is to be performed around the opening, there is a risk that the print will be disturbed due to the level difference between the printing paper and the film. Further, depending on the material of the flexible film, it may be difficult to print on it. Therefore, it is a realistic countermeasure to avoid printing around the opening of each printing paper by avoiding flexible film, but if you do so, the central part of the two-page spread ( There is an area where printing cannot be performed (around the binding), and the photos and the like printed on the left and right pages become discontinuous. If so, the significance of opening the left and right pages flat will be lost.

Therefore, the present invention provides a printing paper that has a hinge portion and can be opened flat, so that printing can be easily performed around the hinge portion, and printing on the left and right pages can be performed seamlessly when the paper is opened in a two-page spread. The purpose is to provide something that is easy to connect and see.

The inventors of the present invention have made intensive studies on means for achieving the above object. The inventors have found that printing can be performed up to just before the hinge portion (concave portion). Based on the above findings, the inventor of the present invention conceived that the problems of the prior art can be solved, and completed the present invention.

Specifically, the present invention relates to printing paper. The printing paper according to the present invention is formed by laminating a substrate layer and a printing layer. The substrate layer is made of a thermoplastic resin film including a porous layer. The printed layer is laminated on one or both surfaces of the substrate layer, and can record characters, images, and the like by printing. The printing paper according to the present invention has a linear hinge portion recessed in the thickness direction of the printing paper. The hinge portion is preferably linear, but may be curved or polygonal. The hinge portion can be formed, for example, by pressing the printing paper while heating it. The substrate layer included in the printing paper is compressed by heating and pressing to form a concave hinge portion.

As described above, the printing paper according to the present invention is a series of printing papers containing a porous thermoplastic resin film with concave hinge portions. There is no need to perforate openings in the sheet or apply a flexible film thereon. Therefore, with the printing paper of the present invention, printing can be easily performed even in the vicinity of the hinge portion. As a result, when a booklet made of each printing paper is spread open, even the central part (near the binding part) can be printed with uniform quality. are seamlessly connected and easy to see. Further, since there is no need to form an opening or attach a flexible film, according to the present invention, the material cost and manufacturing cost of the printing paper can be kept low. In addition, the printing paper of the present invention can be easily folded along the concave hinge portion, so that the double-page spread can be easily opened naturally and flatly.

In the printing paper according to the present invention, the paper thickness in the region other than the hinge portion is 80 to 600 μm, and the paper thickness in the hinge portion is preferably 10 to 85% of the paper thickness in the region other than the hinge portion. In the specification of the present application, the term "region other than the hinge portion" means a flat printed portion on which characters and images are printed. Assuming that the printing paper is used for general photobook applications, the paper thickness of the printing paper is 80 to 600 μm as described above, so that moderate rigidity is created and bending is difficult to occur. It becomes easier to form the hinge part. Further, since the paper thickness at the hinge portion is 10 to 85% of the paper thickness of the printing paper, the hinge portion has a suitable strength and is less likely to break, and the printing paper can be easily folded at the hinge portion.

In the printing paper according to the present invention, it is preferable that the width of the hinge portion is at least twice the depth of the hinge portion. This makes it easier to maintain the folded state of the printing paper at the hinge portion. Although the upper limit of the width of the hinge portion is not particularly limited, it is preferably 5 times or less or 4 times or less the depth of the hinge portion.

In the printing paper according to the present invention, the substrate layer is preferably made of polyolefin resin. Polyethylene terephthalate (PET)-based resins and styrene-based resins can also be used as thermoplastic resins, but it is particularly preferable to use polyolefin (PO)-based resins that have both strength and flexibility to withstand repeated bending of the hinge portion. .

In the printing paper according to the present invention, the porosity of the base layer in the hinge portion is preferably lower than the porosity of the base layer in the region other than the hinge portion. As described above, in the present invention, it is preferable to form a hinge portion having a predetermined shape by heating and pressurizing a portion of the printing paper. It will be done. By reducing the porosity of the porous layer in the hinge portion, the strength of the hinge portion can be increased and the opacity can be decreased.

In the printing paper according to the present invention, the porosity of the substrate layer in the region other than the hinge portion is preferably 10 to 45%. Thereby, a preferable shape of the hinge portion can be formed. That is, if the porosity of the base material layer is too low, the base material layer will not be easily crushed even if heat and pressure are applied, making it difficult to obtain a hinge portion having a desired depth. On the other hand, if the porosity of the base material layer is too high, the paper may be torn when the hinge portion is formed by heating and pressurization, or it may become difficult to maintain the strength of the hinge portion. Therefore, it is appropriate to set the porosity of the substrate layer within the above range.

In the printing paper according to the present invention, the Clark stiffness (S value) at the hinge portion is preferably 10-250, and the Clark stiffness (S value) at the region other than the hinge portion is preferably 15-500. Note that the Clark stiffness (S value) of the hinge portion is lower than that of the other regions. By setting the Clark stiffness (S value) of the hinge portion to 10 to 250 as in the above configuration, it is possible to naturally bend the hinge portion easily and to provide the strength to withstand repeated bending. In addition, by setting the Clark stiffness (S value) of the area other than the hinge part (especially the printing part) to a high value of 15 to 500, the left and right pages naturally tend to be flat when spread, and the printing paper can be used as a photo book. It becomes possible to use it suitably for the use of.

In the printing paper according to the present invention, it is preferable that the hinge portion is formed in a linear shape parallel to one side of the rectangular printing paper. In addition, it is preferable that the printing paper has an area (reinforcing portion) where the hinge portion is not formed between the other two sides perpendicular to one side of the printing paper parallel to the hinge portion and the hinge portion. . When printing on printing paper, a reinforcing part is provided between the hinge part and the edge of the printing paper to prevent the printing paper from unintentionally bending or flexing itself, so it is possible to print accurately. print processing becomes possible. Further, when the printed printing paper is bound, the printing paper can be easily folded at the hinge portion by cutting off the reinforcing portion. Thus, the reinforcing portion is provided on the printing paper on the assumption that it will be cut off eventually.

According to the present invention, printing can be easily applied around the hinge portion of the printing paper, and when the page is opened as a double-page spread, the printing on the left and right pages can be seamlessly connected and easily visible.

FIG. 1 is a plan view schematically showing printing paper according to one embodiment of the present invention. FIG. 1(a) shows the printing paper before printing processing, FIG. 1(b) shows the cut portion of the printing paper with a dashed line, and FIG. 1(c) shows the area between the hinge and the edge of the printing paper. It shows a state in which the reinforcing part of is cut off. FIG. 2 schematically shows a cross-sectional structure along line II-II shown in FIG. FIG. 2(a) shows a pattern in which concave hinge portions are formed on one side of the printing paper, and FIG. 2(b) shows a pattern in which concave hinge portions are formed on both sides of the printing paper. FIG. 2(c) shows a pattern in which the bottom surface of the hinge portion has a semicircular cross section as a modification of FIG. 2(a). FIG. 3 schematically shows a method of a suitability evaluation test for hinge portions of printing paper.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated using drawing. The present invention is not limited to the embodiments described below, and includes appropriate modifications within the scope obvious to those skilled in the art from the following embodiments.
In the specification of the present application, "A to B" means "A or more and B or less."

FIG. 1 is a plan view schematically showing printing paper 10 according to one embodiment of the present invention. Characters and images can be printed on the front and back sides of the printing paper 10 . In particular, the printing paper 10 according to the present embodiment is assumed to be used for printing photographic images on both sides. A photo album (booklet) can be created by stacking a plurality of printing papers 10 on which photo images are printed and binding one end of each printing paper 10 together.

As shown in FIG. 1A, the printing paper 10 has a linear hinge portion 11 recessed in the thickness direction. In other words, the printing paper 10 has a smaller paper thickness only at the hinge portion 11, and the other regions have substantially the same paper thickness. As described above, the print paper 10 has a feature that the hinge portion 11 is thinner than other regions, and therefore, the print paper 10 is easily bent along the hinge portion 11 .

The hinge portion 11 extends in the vicinity of one side of the printing paper 10 and parallel to the side. Specifically, the printing paper 10 according to the present embodiment is rectangular and has two short sides 10a and 10b and two long sides 10c and 10d orthogonal to these. Since the printing paper 10 of this embodiment is intended to be used in landscape orientation, the hinge portion 11 is formed in the vicinity of one of the four sides of the printing paper 10, the short side 10b. When the printing paper 10 is used vertically, the hinge portion 11 may be formed in the vicinity of either the long side 10c or 10d.

The printing paper 10 has a binding portion 13 provided between the hinge portion 11 and one short side 10b adjacent thereto, and a printing portion 12 provided between the hinge portion 11 and the other short side 10a. The printing section 12 is an area for printing characters and images, and occupies most of the printing paper 10 . The binding portion 13 is an area used for binding each printing paper 10 when a plurality of printing papers 10 are piled up and bound. For example, an adhesive such as a hot-melt adhesive may be applied to the binding portion 13 of each printing paper 10 to bond the short sides of each printing paper 10 . Alternatively, a plurality of small holes may be bored through the binding portion 13 of each printing paper 10, and a screw (bookbinding screw) may be inserted into each small hole to join the printing papers 10 together. Alternatively, the binding portions 13 of the printing papers 10 may be bound together using thread, wire, staples, or the like. Note that the bookbinding method is not limited to the one described here, and a known method can be appropriately adopted. The width of the binding portion 13 may be appropriately adjusted according to the bookbinding method, and may be, for example, 5 to 50 mm.

In the printing paper 10 before printing processing, a reinforcing portion 14 having no depression is provided between the concave hinge portion 11 and the two long sides 10c and 10d. That is, the reinforcing portion 14 has substantially the same paper thickness as the area other than the hinge portion 11 . In other words, the paper thickness of the reinforcing portion 14 is greater than that of the hinge portion 11 . The width of the reinforcing portion 14 (the gap between the hinge portion 11 and the long sides 10, 10d) is preferably 1 to 20 mm, particularly preferably 2 to 10 mm. In this manner, by providing the reinforcing portions 14 on both longitudinal ends of the hinge portion 11 in the printing paper 10 before printing processing, the printing paper 10 is less likely to bend when the printing paper 10 is put on a printing machine. Therefore, printing can be performed accurately.

Further, the printing paper 10 after the printing process is positioned along the long sides 10c and 10d of the printing paper 10 so as to traverse the positions indicated by the dashed lines in FIG. Cut along parallel cutting lines. As a result, the reinforcing portions 14 located on both longitudinal ends of the hinge portion 11 are cut off. After the printing paper 10 has been cut, the hinge portion 11 reaches two long sides 10c and 10d, as shown in FIG. 1(c). In this way, in the cut printing paper 10, the hinge portion 11 is located near one side (10b) of the rectangular printing paper 10 between two sides (10c, 10d) perpendicular to the one side (10b). , extending parallel to the one side (10b). This makes it easier to fold the printing paper 10 along the hinge portion 11 .

FIG. 2 schematically shows a cross-sectional structure along line II-II shown in FIG. 2 shows a pattern in which the hinge portion 11 is formed by providing recesses on one side of the printing paper 10 (FIG. 2A) and a pattern in which the hinge portions 11 are formed by providing recesses on both sides of the printing paper 10 (FIG. 2A). FIG. 2(b)) is shown. A feature common to both patterns is that the printing paper 10 has a structure in which a substrate layer A including a porous layer and printing layers B1 and B2 provided on both sides of the substrate layer A are laminated in the thickness direction. ing. In this embodiment, since it is assumed that both sides of the printing paper 10 are printed, the printing layers B1 and B1 are laminated on both the front and back sides of the base material layer A. FIG. However, if printing is to be performed only on one side of the printing paper 10, the printing layer may be laminated only on one side of the base material layer A. Further, as shown in FIG. 2(c), the bottom surface of the hinge portion 11 can be formed in a semicircular cross section.

In the present invention, the base material layer A is made of a thermoplastic resin film. By using a thermoplastic resin film as the base material layer A, the printing paper 10 can be provided with mechanical strength such as stiffness, water resistance, chemical resistance, and opacity if necessary.

The thermoplastic resin used for the substrate layer A is not particularly limited, and examples thereof include polyolefin resins such as polyethylene resins and polypropylene resins; polyester resins such as polyethylene terephthalate and polylactic acid; nylon-6, nylon-6, 6, polyamide resins such as nylon-6, 12; styrene resins such as polystyrene, acrylonitrile-styrene (AS) copolymer, styrene-butadiene (SBR) copolymer; polyvinyl chloride resin; polycarbonate resin; polyphenylene sulfide etc. These resins can be used in combination of two or more. Among them, the thermoplastic resin constituting the base layer A is preferably a polyolefin-based resin because it has both strength and flexibility to withstand repeated bending of the hinge portion. In particular, from the viewpoint of film moldability, it is more preferable to use a polypropylene-based resin among polyolefin-based resins. Examples of polypropylene-based resins include isotactic homopolypropylene and syndiotactic homopolypropylene obtained by homopolymerizing propylene, and ethylene, 1-butene, 1-pentene, 1-hexene, 4-methyl- Polypropylene-based copolymers having various stereoregularities obtained by copolymerizing α-olefins such as 1-pentene, 1-heptene, and 1-octene can be used. The polypropylene-based copolymer may be a two-component system or a multi-component system of three or more components, and may be a random copolymer or a block copolymer.

The base material layer A can contain a filler for adjusting stiffness, whiteness and opacity. Examples of fillers include inorganic fillers such as calcium carbonate and organic fillers such as resin particles, and these can be used alone or in combination. When a thermoplastic resin film containing a filler is stretched, a large number of fine pores are formed inside the base material layer A with the filler as the nucleus. As a result, the base material layer A can be whitened, made opaque, and lightened. By including the filler in the base material layer A in this manner, a porous layer is formed therein.

The average particle size of the filler is preferably large from the viewpoint of ease of mixing with the thermoplastic resin. From the viewpoint of making it difficult for troubles such as deterioration to occur, a smaller value is preferable. Specifically, it is preferably 0.01 μm or more, more preferably 0.1 μm or more, and still more preferably 0.5 μm or more. Also, it is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less. The average particle size of the filler is obtained by observing the cut surface of the base material layer A with an electron microscope and measuring the maximum size of at least 10 particles. It can be obtained as the average dispersed particle diameter at the time.

From the viewpoint of obtaining a desired porosity, the content of the filler in the substrate layer A is preferably 1% by mass or more, more preferably 3% by mass or more, and still more preferably 5% by mass or more, and It is preferably 45% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

In addition, the base material layer A can optionally contain known additives as needed. Further, the base material layer A may have a single layer structure or a multilayer structure. In the case of multiple layers, by providing a solid print layer or a pigment-containing layer on the inside as a concealing layer, when viewed from one side, the printing on the other side does not show through, and visibility is improved during double-sided printing. It is also possible to obtain recording paper suitable for printing photographic images and the like.

The porosity, which indicates the percentage of pores in the base material layer A, is preferably 10% or more, more preferably 12% or more, in the portion where the hinge portion 11 is not formed (especially the printed portion 12). It is more preferably 15% or more, and particularly preferably 20% or more. The porosity of the printed portion 12 is preferably 45% or less, more preferably 44% or less, even more preferably 42% or less, and particularly preferably 40% or less.

The porosity can be measured by cross-sectional observation of the substrate layer with an electron microscope, as described in JP-A-2019-48433. Specifically, the porosity can be determined from the ratio of the area occupied by the pores in a certain region of the cross section of the printing paper observed with an electron microscope. Specifically, an arbitrary part of the printing paper is cut, embedded in epoxy resin and solidified, then cut perpendicular to the surface direction of the substrate using a microtome so that the cut surface becomes the observation surface. Attach it to the observation sample table. Gold or gold-palladium is vapor-deposited on the observation surface, and the pores are observed at an arbitrary magnification that is easy to observe with an electron microscope (for example, magnification of 500 to 3000 times), and the observed area is captured as image data. . The obtained image data is subjected to image processing by an image analysis device, and the area ratio of the pore portions is obtained to obtain the porosity. In this case, the porosity can be obtained by averaging the measured values obtained by observation at arbitrary 10 or more points.

The print layers B1 and B2 are layers on which characters, images, and the like can be recorded by printing. The printed layer can be formed by corona treatment, flame treatment, plasma treatment, application drying of paint, extrusion lamination of molten resin, etc. on the surface of the substrate layer A. Various printing methods such as offset printing, ink jet method, electrophotographic (laser) method, thermal recording method, and thermal transfer method can be used as printing methods for printing layers B1 and B2. In addition, the printed layer B1 or B2 is provided in advance by the above-described method on one surface of the support film, which is extremely thin and flexible compared to the base layer A and which follows the base layer A when forming the hinge portion to be described later. may be laminated on the substrate layer A via an adhesive layer. For example, a layer made of an adhesive such as a water-based adhesive, a solvent-based adhesive, or a hot-melt adhesive is formed on the side opposite to the printed layers B1 and B2 of the support film by a method such as coating, spraying, or melt extrusion molding. After forming an adhesive layer on the surface of the base material layer A, the substrate layer A may be laminated on the adhesive layer. Alternatively, after providing an adhesive layer on the base material layer A, a support film having printed layers B1 and B2 provided on one surface thereof may be laminated. Moreover, it is also possible to melt-extrude an adhesive between the substrate layer A and the support film on which the printed layers B1 and B2 are provided and press-bond them for lamination.
In still another embodiment, at least one of the printed layers B1 and B2 formed on one surface of the above-described support film is printed in advance, and then laminated on the base material layer A via an adhesive layer. good too.

In the pattern shown in FIG. 2A, recesses for forming hinge portions 11 are provided only on one side (front side) of the printing paper 10 having the laminated structure. In order to form such recesses, it is preferable to heat and press the printing paper 10 in the thickness direction using a pressing machine having protrusions having shapes corresponding to the recesses. The configuration of the press is not particularly limited, and a known one can be used as appropriate. For example, the printing paper 10 may be introduced between a press roller having a heatable peripheral surface formed with projections of a predetermined shape and an anvil roller having a flat peripheral surface. Also, a flat plate may be used instead of the anvil roller. As described above, the base layer A of the printing paper 10 is made of a thermoplastic resin film including a porous layer. Therefore, by locally heating and pressurizing the printing paper 10, the base material layer A is partially melted and the pores in the porous layer are crushed, thereby reducing the volume of the pressurized portion. Decrease. As a result, a concave portion is formed in the pressurized portion, and the concave portion functions as the hinge portion 11 .

Moreover, in the pattern shown in FIG. 2A, the width W of the recess functioning as the hinge portion 11 is preferably twice or more the depth D of the recess. Specifically, the lateral width W of the recess is preferably 2 to 5 times the depth D of the recess, particularly preferably 2.1 to 4 times or 2.2 to 3 times. By setting the width W of the recess to be at least twice the depth D, it is possible to prevent the side walls of the recess from interfering with each other when the printing paper 10 is folded at the center of the recess. The paper 10 can be naturally folded easily at the hinge portion 11 . Moreover, the width W of the recess may be 0.5 to 40 mm, preferably 1 to 30 mm, and particularly preferably 2 to 20 mm. Moreover, the depth D of the concave portion may be 40 to 400 μm, preferably 60 to 350 μm, particularly preferably 100 to 300 μm. As shown in FIG. 2C, when the bottom surface of the recess has a semicircular cross section, the depth D of the recess means the depth of the deepest part of the recess.

On the other hand, in the pattern shown in FIG. 2B, concave portions for forming the hinge portions 11 are provided on both the front and back surfaces of the printing paper 10 having the laminated structure. The two recesses are formed at the same position when viewed in the thickness direction of the printing paper 10 . In order to form such recesses, it is possible to heat and press the printing paper 10 in the thickness direction by using a pressing machine having protrusions having shapes corresponding to the recesses, as in the case of the pattern shown in FIG. 2(a). preferable. The configuration of the press is not particularly limited, and a known one can be used as appropriate. For example, the printing paper 10 may be introduced between two press rollers having heatable projections of a predetermined shape on their peripheral surfaces, and the printing paper 10 may be sandwiched between the projections of the press rollers. As a result, a concave portion is formed in the pressurized portion, and the concave portion functions as the hinge portion 11 .

In the pattern shown in FIG. 2B, the width W1 of the recess formed on the front surface and the width W2 of the recess formed on the back surface are preferably the same value, but may be different values. For example, the width W1 of the concave portion on the front surface is preferably 90 to 110% or 95 to 105% of the width W2 of the concave portion on the back surface, but it may be, for example, 10 to 95% or 50 to 90%. . By making the lateral widths W1 and W2 of the recesses on the front and back surfaces different, the printing paper 10 can be easily bent in a certain direction. Similarly, the depth D1 of the recess formed on the front surface and the depth D2 of the recess formed on the back surface are preferably the same value, but may be different values. For example, the depth D1 of the concave portion on the front surface is preferably 90 to 110% or 95 to 105% of the depth D2 of the concave portion on the back surface. can also By making the depths D1 and D2 of the recesses on the front and back surfaces different, the printing paper 10 can be easily bent in a certain direction.

Also in the pattern shown in FIG. 2(b), it is preferable that the widths W1 and W2 of the recess functioning as the hinge portion 11 are twice or more the depth D1 and D2 of the recess. Specifically, the lateral widths W1 and W2 of the recesses are preferably 2 to 5 times, respectively, 2.1 to 4 times or 2.2 to 3 times the depths D1 and D2 of the recesses. is particularly preferred. Further, the lateral widths W1 and W2 of the recess may be 0.5 to 40 mm, preferably 1 to 30 mm, particularly preferably 2 to 20 mm.

2(a) and 2(b), the paper thickness T of the portion where the hinge portion 11 is formed is the same as that of other regions (especially the printing portion 12) where the hinge portion 11 is not formed. It is naturally smaller than the paper thickness P. The paper thickness T of the hinge portion 11 is preferably 10 to 85%, more preferably 40 to 80%, and particularly preferably 50 to 75% of the paper thickness P of the other regions. . By setting the paper thickness T of the hinge portion 11 within the above range, both the ease of folding the printing paper 10 and the strength of the printing paper at the hinge portion 11 can be achieved. Further, when it is assumed that the printing paper 10 is used for a photo album, a certain amount of thickness is required in order to suppress bending of the paper. Therefore, it is preferable that the thickness P of the printing paper is 80 to 600 μm. Moreover, the paper thickness P is more preferably 100 to 500 μm, particularly preferably 150 to 450 μm. As shown in FIG. 2(c), when the bottom surface of the recess has a semicircular cross-section, the paper thickness T at the portion where the hinge portion 11 is formed means the paper thickness at the deepest part of the recess.

The stiffness of the printing portion 12 of the printing paper 10 is defined as Clark stiffness (S value) (hereinafter simply referred to as "Clark stiffness") measured in accordance with JIS-P-8143, MD (machine direction), TD ( It is preferably in the range of 15 to 500, more preferably in the range of 40 to 400, and particularly preferably in the range of 80 to 300 in both directions (width direction). If the Clark stiffness of the printing paper 10 is within the above range, it is possible to obtain stable running performance on the printing press without causing troubles. If the Clark stiffness is less than 15 in either the MD or TD direction, there is a possibility that the paper will bend in the paper feed section of the printing machine, and paper feeding failure such as double running will occur. In addition, printing paper tends to wrinkle easily. Conversely, if it exceeds 500, the paper does not follow the running part of the printing machine and may become unstable, making it difficult to print at high speed. There is also Regardless of the grain direction of the printing paper 10, if the Clark stiffness is within the above ranges for both MD and TD, the degree of freedom in printing imposition is improved, which is more preferable in practice during printing processing.

The Clark stiffness of the hinge portion 11 of the printing paper 10 is preferably in the range of 10 to 250, more preferably in the range of 20 to 200, and more preferably in the range of 50 to 150 in the MD and TD directions. It is particularly preferred to have The Clark stiffness of the hinge portion 11 is naturally lower than that of the printing portion 12, but by keeping it within the above range, the strength to withstand repeated bending is maintained, and when the hinge portion 11 is bound into a booklet and opened into a double-page spread. This makes it easier to maintain the left and right pages naturally flat. That is, when the Clark stiffness of the hinge portion 11 is less than 10, the strength of the paper surface is weakened, and there is concern that the paper surface will break while being repeatedly folded. On the other hand, when the Clark stiffness of the hinge portion 11 exceeds 250, it becomes difficult to fold the printing paper 10 at the hinge portion 11, and it becomes difficult to maintain the double-spread state after the booklet is bound. Therefore, by adjusting the Clark stiffness of the hinge portion 11 within the above range, the usability of the booklet created using the printing paper 10 can be improved.

In the printing paper 10, the porosity of the base layer A in the hinge portion 11 is lower than the porosity of the base layer A in other regions (especially the printing portion 12). For example, the porosity of the hinge portion 11 is preferably 0 to 90%, more preferably 5 to 60%, and more preferably 10 to 50% when the porosity of the printing portion 12 is 100%. It is particularly preferred to have Specifically, the porosity of the hinge portion 11 measured by the method described above is preferably 0 to 20%, preferably 1 to 10% or 1 to 5%. Since the porosity of the hinge portion 11 is lower than that of other portions, the density of the base material layer A in the hinge portion 11 is increased, so that the strength of the hinge portion 11 can be maintained accordingly. That is, since the paper thickness of the hinge portion 11 is smaller than that of other portions, the reduction in strength is unavoidable. By increasing the density of the paper, it is possible to alleviate the tendency of the strength to decrease as the thickness of the paper decreases.

The opacity of the hinge portion 11 of the printing paper 10 is preferably lower than the opacity of other regions (especially the printing portion 12). In other words, the printing unit 12 needs to have a high degree of opacity in order to clearly display characters and images and prevent the printing on the opposite side from being seen through. On the other hand, the opacity of the hinge portion 11 is relatively low (that is, the hinge portion 11 is translucent), so that the hinge portion of each printing paper 11 can be seen when the printing papers 10 are stacked. Alignment of 11 is facilitated. It is also conceivable to distinguish between the hinge portion 11 of the printing paper 10 and the printing portion 12 in the printing machine and print an image or the like on the printing portion 12 when the printing paper 10 is put through the printing machine. In this case, by lowering the opacity of the hinge portion 11 to make a difference from the opacity of the printing portion 12, the hinge portion 11 and the printing portion 12 can be easily distinguished by an image sensor in the printing machine, for example. For example, the opacity of the hinge portion 11 is preferably 10 to 95%, more preferably 20 to 90%, and more preferably 30 to 80% when the opacity of the printing portion 12 is 100%. It is particularly preferred to have Specifically, the opacity of the hinge portion 11 is preferably 80% or less, preferably 75% or less, or 70% or less when measured by the opacity measurement method specified in JIS-P-8149. is particularly preferred. On the other hand, when measured by the same measuring method, the opacity of the printed portion 12 is preferably 85% or more, and particularly preferably 87% or more or 89% or more.

Regarding the printing paper according to the present invention, the following verification was performed in order to obtain an appropriate ratio of the paper thickness T of the hinge portion to the paper thickness P of the printing paper (see FIG. 2 for each symbol).

Specifically, as the printing paper, in Examples 1 to 3 and Comparative Example 1, polyolefin synthetic paper “YPI 250” manufactured by Yupo Corporation (paper thickness 250 μm, Clark stiffness (S value) MD: 180, TD :370) was used. In Examples 4 to 9 and Comparative Example 2, polyolefin-based synthetic paper “Ultrayupo (R) FEB 250” manufactured by Yupo Corporation (thickness 250 μm, Clark stiffness (S value) MD: 210, TD: 439) was used. used. A rectangle of 21 cm in the TD direction and 30 cm in the MD direction was cut out from the above printing paper, sandwiched between silicone release papers, and subjected to a heat press at 140° C. and 0.1 MPa to form a hinge portion with a width of 5 mm parallel to the TD direction. formed from end to end on one side of the The width of the binding portion was 10 mm, and the depth of the hinge portion was adjusted so that the ratio of the paper thickness of the hinge portion to the paper thickness of the printing paper was the value shown in Table 1. For the printing paper with the hinge portion thus obtained, the paper thickness T of the hinge portion, the ratio of the paper thickness T of the hinge portion to the paper thickness P of the printing paper, and the Clark stiffness (S value) in the TD direction were measured. In addition, each example and each comparative example was evaluated for hinge suitability by the following method. Table 1 shows the results.

[Hinge Adequacy Evaluation Criteria]
Fig. 3 shows the method of the suitability evaluation test for the hinge part. The end of the printing paper with the hinged part on the binding side was fixed with a fixture, the printing paper was set up vertically, and then the angle formed by the binding part and the printing part was measured when the hand was released ( Test 1). In addition, when the angle formed by the bound portion and the printed portion was 180°, the bending force was repeated 50 times so that the angle formed by the printed portion became 0°. Based on the results of Tests 1 and 2, the adequacy of the hinge portion was evaluated as follows.
A: The angle formed by the bound portion and the printed portion is 90° or less, and the sheet does not break even after repeated folding.
B: The angle formed by the bound portion and the printed portion is greater than 90° and 135° or less, and does not break even after repeated folding.
C: The angle formed by the bound portion and the printed portion was larger than 90° and 135° or less, and the hinge portion was slightly cracked after repeated bending.
D: The angle between the bound portion and the printed portion is greater than 135°. Alternatively, although the angle formed by the bound portion and the printed portion was 90° or less, cracks occurred in the hinge portion after repeated bending.

As shown in the above test results, when the paper thickness P of the printing paper is 250 μm, the ratio of the paper thickness T of the hinge portion to the paper thickness P of the printing paper is in the range of about 10 to 85%, specifically It has been found that the folding performance of the printing paper at the hinge portion reaches a practical level by setting it to about 38 to 80%. In particular, by setting the same ratio in the range of about 40 to 80%, specifically about 44 to 80%, the hinge portion of the printing paper is provided with strength that can withstand repeated folding, and when it is in a double-page spread state. The effect of naturally flattening the left and right pages was confirmed. Above all, the effect became more remarkable when the same ratio was in the range of about 50 to 75%, specifically about 52 to 72%.

In the specification of the present application, the embodiments and examples of the present invention have been described with reference to the drawings in order to express the content of the present invention. However, the present invention is not limited to the above embodiments and examples, and includes modifications and improvements that are obvious to those skilled in the art based on the matters described in the specification of the present application.

The present invention relates to printing paper having a hinge portion. By using the printing paper according to the present invention, it is possible to produce a booklet (photo album, etc.) in which the printing on the left and right pages is seamlessly connected when opened in double-page spread and is easy to see. Therefore, the present invention can be suitably used in, for example, the printing industry and the paper industry.

DESCRIPTION OF SYMBOLS 10... Printing paper 10a, 10b... Short side 10c, 10d... Long side 11... Hinge part 12... Printing part 13... Binding part 14... Reinforcing part A... Base material layer B (B1, B2)... Printing layer

Claims (8)

A printing paper in which a printing layer is laminated on at least one surface of a substrate layer that is a thermoplastic resin film containing a porous layer,
Having a linear hinge part recessed in the thickness direction of the printing paper ,
The hinge portion is formed by pressing the printing paper while heating it.
printing paper. The paper thickness in the region other than the hinge portion is 80 to 600 μm,
The printing paper according to claim 1, wherein the paper thickness at the hinge portion is 10 to 85% of the paper thickness at the area other than the hinge portion. The printing paper according to claim 1, wherein the width of the hinge portion is at least twice the depth of the hinge portion. The printing paper according to claim 1, wherein the base material layer is made of polyolefin resin. The printing paper according to claim 1, wherein the porosity of the base layer in the hinge portion is lower than the porosity of the base layer in a region other than the hinge portion. The printing paper according to claim 5, wherein the base material layer has a porosity of 10 to 45% in a region other than the hinge portion. Clark stiffness (S value) at the hinge portion is 10 to 250,
The printing paper according to claim 1, wherein the Clark stiffness (S value) in the region other than the hinge portion is 15-500. The hinge portion is formed in a straight line parallel to one side of the rectangular printing paper,
2. The printing paper according to claim 1, wherein there is an area in which the hinge portion is not formed between the other two sides orthogonal to the one side and the hinge portion.

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