JP6216971B2 - Paper with watermark using cellulose microfiber - Google Patents

Description

  The present invention relates to a paper having a watermark in which significant information such as symbols and characters is formed from cellulose microfibers.

  Valuable printed matter such as banknotes, passports, and securities is required to have a function of preventing counterfeiting and unauthorized copying. Examples of the preventive measures include a technique for imparting a forgery prevention function in paper such as squeezed and mixed paper, and a technique for imparting a forgery prevention function by printing on paper such as fine image lines and intaglio image lines.

  However, in recent years, digital devices such as high-performance scanners, personal computers, and printers have become widespread, and there is a tendency that counterfeit products can be easily manufactured at an individual level. Therefore, there is a demand for a printed material that cannot be copied by a digital device and that can be differentiated from a genuine product even if it is forged.

  For example, Patent Document 1 discloses a watermarked paper in which a watermark pattern is formed by printing on a base material using ink containing titanium oxide of the same color as the paper. Since titanium oxide has the property of blocking light, when a watermarked paper is observed under transmitted light, the watermark pattern formed with titanium oxide is visible darker than the base material. Therefore, it can be confirmed as a watermark pattern. Watermarks cannot be copied on digital devices.

  Further, when printing, it is possible to obtain a watermark pattern having gradation by changing the halftone dot area ratio and the image line width of the printing plate.

  Furthermore, in recent years, technological progress has been remarkable, and it has become possible to apply not only synthetic materials but also natural materials such as cellulose when creating nanoscale products. As an example, there is cellulose nanofiber (hereinafter referred to as “cellulose microfiber”) obtained by refining a cellulose-based raw material by chemical or physical treatment to form an ultrafine fiber having a nano-order fiber width.

  Patent Document 2 discloses a paper that is difficult to replicate with a digital device by using cellulose microfibers. Cellulose microfibers having the same color as the paper are applied to the paper so that they cannot be visually identified under reflected light and transmitted light. The attached paper cannot visually recognize the cellulose microfibers, but its presence is confirmed by machine reading because the air permeability, the chemical structure, etc. are different between the place where it is given and the place where it is not given. It becomes possible.

Japanese Patent No. 3444535 JP 2012-21235 A

  According to Patent Document 1, it is possible to easily form a watermark pattern having gradation by printing. However, in Patent Document 1, a watermark pattern is formed by printing using an ink containing titanium oxide. Ordinary ink contains varnish, so even if the ink and paper are of the same color, the glossiness of the varnish solidified under reflected light may cause a difference in gloss between the paper and the watermark pattern. There is a problem that the hiding property of the stripe pattern is lowered.

  Further, according to Patent Document 2, it is possible to make a paper that makes it difficult to replicate with a digital device using cellulose fine fibers and has excellent concealability under reflected light. However, the paper of Patent Document 2 is provided with a small amount of cellulose microfiber that cannot be visually recognized under reflected light and transmitted light and can be identified only by machine reading.

  Therefore, although it has a high deterrence against copying in digital devices, it cannot be identified by a simple method under transmitted light as in the past. For example, in charge of inspection at various counter operations such as banking, immigration inspection, etc. There is a problem that a person cannot perform authenticity determination by visual inspection, and there is room for improvement.

  The present invention solves these problems, and is superior in hiding property under reflected light compared to a watermark pattern formed with watermark ink, and can be formed by printing, and is identified under transmitted light. The present invention provides a paper sheet having a watermark having a gradation that can be applied.

  In order to achieve the above-mentioned object, a first watermark portion having a higher light transmittance than the substrate and a light transmittance lower than that of the first watermark portion on a part of the light-transmitting substrate. It is a watermark pattern composed of areas, and the overlapping area is formed by laminating a second watermark part formed of cellulose microfibers of the same color as the first watermark part on a part of the first watermark part. It is a paper having a watermark using cellulose microfibers.

  In addition, the first watermark portion and the overlapping region are paper having a watermark using cellulose microfibers having a lightness difference of 5 or more.

  Further, the first watermark portion and / or the second watermark portion is a paper having a watermark using cellulose microfiber, which is different in light transmittance and has gradation.

  Further, the first watermark portion has a watermark using cellulose microfibers characterized in that the substrate is processed by either compression, watermark printing or filling, or a combination thereof. It is paper.

  As described above, on the first watermark portion that is formed on a part of the light-transmitting base material and has a light transmittance higher than that of the base material, it is the same color as the first watermark portion, By laminating the second watermark portion made of cellulose microfiber, it becomes possible to obtain a watermark pattern by printing without using a varnish, and the concealability under reflected light is excellent.

  Moreover, under transmitted light, the light transmittance of the location where only the first watermark portion and the location where the first watermark portion and the cellulose microfiber are laminated is different, so that identification can be performed under the transmitted light. The authenticity can be determined by a simple method.

The top view of paper (S). Development view of watermark pattern (2). The schematic diagram which shows the visual recognition state of a watermark pattern (2). The schematic diagram which shows the formation method of the 1st watermark part (3) by compression of a base material (1). The top view which shows an example of the shape of a 1st watermark part (3) The top view which shows an example in case a 1st watermark part (3) has a gradation. The schematic diagram which shows an example of the method of printing a cellulose microfiber by a screen printing system. The schematic diagram which shows the paper (S2) which provided the watermark pattern (2) which has a gradation. The schematic diagram which shows the paper (S3) which provided the watermark pattern (2) which has a gradation. The schematic diagram which shows the paper (S4) which provided the watermark pattern (2) which has a gradation. The schematic diagram which shows the paper (S5) which provided the watermark pattern (2) which has a gradation.

  Embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiments to be described below, and various other embodiments can be implemented within the scope of the technical idea described in the claims.

  FIG. 1 shows a plan view of a watermarked sheet (S) (hereinafter referred to as “sheet”) in the present invention. The sheet (S) has a watermark pattern (2) on at least a part of the substrate (1). The watermark pattern (2) is a transmissive pattern that is visible under transmitted light.

  FIG. 2 is a development view showing details of the watermark pattern (2). As shown to Fig.2 (a), a watermark pattern (2) consists of a 1st watermark part (3) and a superimposition area | region (W). The first watermark (3) is a transmissive pattern having a higher light transmittance than the substrate (1).

  The overlapping region (W) is a transmission pattern having a light transmittance lower than that of the first watermark portion (3), and a part of the first watermark portion (3) is shown in FIG. 1 watermark part (3) and the 2nd watermark part (4) formed with the cellulose microfiber of the same color are laminated | stacked.

  FIG. 3 is a schematic diagram showing a visually recognized state of the watermark pattern (2). In the watermark pattern (2), the first watermark portion (3) is visually recognized as a transmission pattern under transmitted light, and the first watermark portion (3) is present in the first watermark portion (3). The second watermark (4) is visually recognized as a region with lower light transmittance. Therefore, with the naked eye, the first watermark part (3) is visually recognized as a white scratch pattern, and the second watermark part (4) is visually recognized as a black crack pattern.

  Note that, under transmitted light, the overlapping region (W) formed by stacking the first watermark portion (3) and the second watermark portion (4) is visually recognized as a black scratch pattern. In the invention, it is assumed that the second watermark (4) is visible. Hereinafter, each element constituting the watermark pattern (2) will be described.

  First, the base material (1) will be described. The base material (1) in this invention needs to have the characteristic which permeate | transmits light, what is called a light transmittance. With opaque plastic or metal, the effect under transmitted light cannot be obtained. In addition, there is no restriction | limiting in particular about the color of a base material (2). The substrate (1) is not particularly limited as long as it has a light-transmitting sheet shape, such as paper, synthetic fiber paper, nonwoven fabric, and film.

  More specifically, wood fibers such as conifers and hardwoods, paper made of non-wood fibers such as kenaf, bagasse, hemp, abaca, cotton, honey, zozo, straw and bamboo, recycled fibers such as rayon, polyvinyl alcohol, polyethylene It is possible to use synthetic fiber paper or nonwoven fabric made of synthetic fibers such as polystyrene, PET, and polyolefin. A hydrophilic film or a film subjected to hydrophilic treatment can also be used.

  In particular, paper made of wood or non-wood fibers, synthetic fiber paper made of synthetic fibers having a functional group capable of forming hydrogen bonds, or nonwoven fabric are preferred. Although details will be described later, the second watermark (4) is obtained by dispersing cellulose fine fibers in water and then dispersing the cellulose fine fibers (hereinafter referred to as “microfiber dispersion”). Is formed on the substrate (1). Therefore, by forming the base material (1) with natural fibers such as wood fibers and non-wood fibers, or synthetic fibers having a functional group capable of forming hydrogen bonds, cellulose microfibers dispersed in water are formed by hydrogen bonding. It is possible to firmly fix on the substrate (1).

  Contains synthetic fiber paper, non-woven fabric, and film-like base material (1) that has a water absorption property, and plastic fibers and glass fibers that do not form hydrogen bonds. Even if it is the base material (1), if a small amount of binder components are mix | blended with a microfiber dispersion liquid and a cellulose microfiber can be fixed on a base material (1), it can be used. However, the binder to be blended at this time is a water-soluble binder, and the amount is such that the gloss of the binder solidified after drying cannot be visually recognized under reflected light.

  As a base material (1) formed from a fibrous material, use a sheet-like material composed of plant fibers such as conifers, hardwoods, kenaf, bagasse, hemp, abaca, cotton, mitsumama, groves, straw, bamboo, etc. Is possible.

  Next, the first watermark portion (3) will be described. The first watermark (3) is a transmission pattern having a higher light transmittance than the base material (1), and a part of the base material (1) having the light transmittance is compressed, watermark printed, laser processed, This is a region processed by any one of the gaps or a combination thereof.

  As described above, the light transmittance is a characteristic (ratio) through which light is transmitted. In the present invention, the difference in light transmittance means that the lightness difference (ΔL) is 5 or more. When the brightness difference (ΔL) is 5 or more, the substrate (1) and the first watermark (3) can be separated and visually recognized when observed with the naked eye under transmitted light.

  The lightness difference (ΔL) is obtained by measuring the value of lightness (L) under transmitted light with a colorimeter or by capturing the transmitted image of the paper (S) as a transmitted image with a scanner or the like. When the value of lightness (L) is measured by image processing software, it can be calculated by calculating the lightness difference (ΔL) between the base material (1) and the first watermark (3).

  Drawing 4 is a mimetic diagram showing an example of the formation method of the 1st watermark part (3) which compresses substrate (1). Forming by compressing the base material (1) is to pressurize the base material (1) having a certain thickness, thereby reducing the thickness, and increasing the fiber density at the pressurization location as compared to before pressurization. That is.

  Specifically, after installing a sheet-like pattern (P) having the same shape as the first watermark (3) on one of the two metal rolls (R), the two metal rolls (R) ) Is passed through the base material (1), and the base material (1) is pressed against the pattern mold (P), so that the pressurized portion has a higher fiber density than the non-pressurized portion. .

  In general paper, there are many voids between the fibers forming the paper layer. Light incident on the paper is scattered in the gaps between the fibers. Therefore, even if the paper is held over the light source, the light is not scattered and thus becomes opaque.

  On the other hand, when the substrate (1) is pressurized, there are almost no voids between the fibers forming the paper layer, and the fiber density is increased. Therefore, when the paper is held over the light source, light scattering in the air gap is small, and the light is transmitted through the pressurization portion, so that it is viewed brighter (white) than the non-pressurization portions other than the pressurization portion. Therefore, in the base material (1) of the same material, the transmitted light amount is higher in the portion where the density is higher. Therefore, when observed under transmitted light, a watermark pattern in the shape of the pattern type (P) is visually recognized. The

  In addition, you may install two metal rolls (R) on the paper machine in preparation of a base material (1). For example, it can be replaced with a calender roll in the glossy part of the paper machine or a press roll in the press part. Moreover, it is also possible to form the completed paper using a separate press device or calendar device.

  Next, a method for forming the first watermark (3) by laser processing will be described.

  With the formation method by laser processing, a 1st watermark part (3) is formed by removing a part of base material (2) using a well-known laser processing apparatus. By removing a region having the same shape as the first watermark (3) to be formed with respect to the base material (2) by laser processing, the removed region is thinner (concave shape) than the base material (2). )Become. Therefore, since the amount of transmitted light of the first watermark portion (3) thinner than the base material (2) becomes higher when observed under transmitted light, the first watermark portion (3) is visually recognized as a transmissive pattern. Is done.

  Next, a method for forming the first watermark portion (3) by squeezing will be described.

  First, in the wire portion of the paper machine, a convex pattern having the same shape as the first watermark portion (3) to be formed is previously formed on the wire with resin or the like, or the wire itself is embossed to make the first A convex pattern having the same shape as the watermark portion (3) is formed.

  In the process in which the stock suspension supplied to the wire part is formed on the wet paper, the amount of fibers is reduced on the convex pattern part of the wire, and the pattern by white scratching (in the first watermark part of the present invention) Applicable) is formed. The wet paper on which the pattern is formed passes through the press part, the drying part, and the glossy part of the paper machine, and is wound around the reel, so that the first watermark part (3) is visible with a high amount of transmitted light and bright (white). ).

  However, in the method using a paper machine, the transmitted light quantity of the first watermark portion (3) formed by the convex pattern on the wire varies, and the smoothness becomes slightly low, so the transferability of the cellulose microfiber is poor. It tends to be difficult to visually recognize the second watermark (4). The formation method by pressurization in which the first watermark portion (3) has little variation in the amount of transmitted light and can easily form a watermark portion with high smoothness is preferred.

  Next, a method for forming the first watermark portion (3) on the base material (1) by watermark printing will be described.

  Forming on the base material (1) by watermark printing means printing the watermark ink on the base material (1) using a printing plate having the same shape as the first watermark portion (3) to be formed. By printing the watermark ink on the base material (1), the watermark ink penetrates into the voids existing between the fibers forming the paper layer as the base material (1).

  Thereby, there are almost no gaps between the fibers forming the paper layer, and the fiber density is high, and when observed under transmitted light, in the gaps, the light passes through the printed part without scattering, It is brighter (whiter) than a non-printed part other than the printed part. Therefore, in the base material (1) made of the same material, the amount of transmitted light is higher in the portion where the watermark ink is printed. Therefore, when observed under transmitted light, a watermark pattern is visually recognized.

  The watermark ink is an ink containing resin, wax, and animal and vegetable oils close to the refractive index of cellulose forming the base material (1) (trade name: Best One Watermark Ink, manufactured by T & K TOKA, Name: SMX watermark ink)) or the like, which is visually observable under transmitted light, is different in light transmittance from an overlapping region (W) described later, and is visible.

  When the first watermark portion (3) is formed of a watermark ink, it is not preferable to use the base material (1) that is difficult for ink to penetrate. As described above, the first watermark portion (3) is formed by the penetration of the watermark ink into the voids existing between the fibers forming the paper layer as the base material (1). Therefore, the base material (1) in which ink does not easily permeate has a small difference in light transmittance between the first watermark (3) and the overlapping region (W), and a clear watermark cannot be formed. It is not preferable.

  Moreover, depending on the transfer amount of the watermark ink, the transferability of the cellulose microfibers forming the second watermark (4) may deteriorate, and the visibility of the second watermark (4) may deteriorate. . This is because the watermark ink is oleophilic and inhibits the transfer of the hydrophilic microfiber suspension. In this case, the second watermark portion (4) is first formed by printing the cellulose microfibers, and then the first watermark portion by the watermark ink is formed, whereby the second watermark portion ( 4) The paper (S) of the present invention having good visibility can be produced.

  FIG. 5 is a plan view showing an example of the shape of the first watermark (3). The shape of the first watermark (3) is not limited to a rectangular shape as shown in FIG. 2, but a desired pattern shape such as a star shape shown in FIG. 5 (b), FIG. 5 (c), and FIG. Moreover, as shown in FIG.5 (e), it is good also as a shape which consists of a some halftone dot, and there is no restriction | limiting in particular of a shape.

  In addition, the first watermark portion (3) has a uniform light transmission pattern in FIG. 2, but may have a pattern composed of a plurality of regions having different light transmission characteristics.

  FIG. 6 is a plan view showing an example in which the first watermark portion (3) has gradation. As shown in FIGS. 6 (a) to 6 (c), the first watermark portion (3) replaces the first watermark portion (3) with a plurality of different light transmitting watermark regions ( By forming in 3a), it is possible to obtain a transparent pattern having gradation.

  For example, in FIG. 4, the first watermark portion (3) having a gradation has a thickness different from that of the pattern mold (P) so that the base (1) is compressed at a thick portion and a thin portion. It is possible to form with different compressibility and different light transmittance. Note that the gradation is given by compression, but the formation method is not limited as long as the transparency can be changed.

  Each watermark region (3a) can be formed by a different processing method. For example, in FIG. 6C, the first watermark portion (3) is composed of two watermark regions (3a), and one watermark region (3a) is compressed into the base material (1). It is also possible to form the other watermark region (3a) by watermark printing.

  Furthermore, the first watermark portion (3) can be processed by a combination of different processing methods such as compression, watermark printing, squeezing or laser processing as described above. For example, FIG. 6 (a) consists of five watermark regions (3a), of which three watermark regions (3a) are formed by squeezing, and then all five watermark regions (3a) are When the first watermark portion (3) is formed by performing watermark printing, a watermark region (3a) formed by watermarking and watermark printing, and a watermark region (3a formed only by watermark printing) ) Have different transparency, it is possible to form the first watermark (3) with richer gradation.

  Next, the overlapping area (W) will be described. The overlapping region (W) is a region having a lower light transmittance than the first watermark portion (3), and the first watermark portion (3) and a portion of the first watermark portion (3) A second watermark (4) formed of cellulose microfibers of the same color is laminated. In addition, the formation method of a cellulose microfiber is mentioned later.

  As described above, the difference in light transmittance in the present invention means that the brightness difference (ΔL) is 5 or more. Low light transmittance means that when two regions (for example, A and B) are compared, the lightness of the region A is higher than the lightness of the region B and the lightness difference (ΔL) is 5 or more. In this case, the region B is said to be less light transmissive than the region A.

  When comparing two regions (for example, A and B), if the lightness of the region A is higher than the lightness of the region B and the lightness difference (ΔL) is 5 or more, it is visible to the naked eye under transmitted light. When observed, the first watermark portion (3) is visually recognized as a white scratch pattern, and the overlapping region (W) is visually recognized as a black scratch pattern. The method for measuring the lightness difference (ΔL) is the same as the method for calculating the lightness difference (ΔL) between the base material (1) and the first watermark portion (3) described above, and therefore the description thereof is omitted.

  Next, the second watermark portion (4) will be described. A 2nd watermark part (4) consists of a cellulose microfiber. Cellulose microfibers in the present invention are fibers mainly composed of cellulose, particularly those using plant-derived natural cellulose as a raw material, and those fibrillated into fine cellulose fibers having a fiber width of less than 2 nm to 10 μm. Say.

  The term “defibration” as used herein refers to unraveling cellulosic fibers up to several micro or nanofibrils. Usually, the cellulose fiber obtained from a plant is an aggregate of cellulose nanofibrils composed of 30 to 50 cellulose molecules and having a fiber width of about 2 to 5 nm. Cellulose microfibrils are firmly bonded by innumerable hydrogen bonds, but can be broken into several units of cellulose micro or nanofibrils while remaining in a fibrous state by applying physical or chemical treatment.

  When the fiber width of the cellulose fiber is 10 μm or more, it becomes the same order as 10 to 30 μm, which is the fiber width of a general pulp fiber, and characteristics specific to microfibers cannot be obtained. Therefore, the term “microfiber” as used herein refers to a fiber having a cellulose nanofibril unit of about 2 nm to less than 10 μm, particularly preferably 2 nm to less than 1 μm, and more preferably 2 nm to less than 100 nm.

  Further, the fiber means an elongated individual having an aspect ratio (fiber length / fiber width) of usually 100 to 1000 or more, but the cellulose microfiber in the present invention is basically a fiber whose aspect ratio falls within this range. It is. In particular, in the case of microfibers having a fiber width of less than 100 nm, the aspect ratio may be 10,000 or more.

  Regarding the fiber length, it is desirable that the length is included in this aspect ratio, but the maximum limit length differs depending on the printing method, and even if the aspect ratio is 100 or less, at least the fiber length is larger than the fiber width. It only needs to be large.

  However, when the aspect ratio is 1 or less, the particle shape is obtained, and the characteristics are close to those of spherical or polygonal pigment particles, and printing characteristics using fibers cannot be obtained. From this, the fiber length of the cellulose microfiber needs to be larger than the particle diameter of the coloring agent mentioned later.

  Cellulose microfibers are mainly composed of cellulose fibers, but the fibers composed of cellulose are not particularly limited, and include chemical pulps such as KP and SP made of various kinds of wood, GP, TMP, and CTMP. Pulp such as mechanical pulp and recycled paper recycled pulp can be appropriately selected and used. Powdered cellulose obtained by pulverizing them, microcrystalline cellulose purified by chemical treatment, and the like can also be used. In addition, non-wood such as kenaf, hemp, rice, bagasse, abaca, cotton, Mitsumata, bamboo and the like can also be used.

  Cellulose microfibers are white or yellowish white (the color of the raw material pulp). When printing on the first watermark portion (3) of a different color, the first watermark portion (3) and Cellulose microfibers colored in the same color are used. Moreover, when printing on a base material (1) of the same color, it is used as it is.

  In the present invention, the cellulose microfibers have the same color as the first watermark (3). By making it the same color, when observed under transmitted light, on the first watermark portion (3), the portion to which the cellulose microfibers are added has different light transmittance, so that the second pattern as a watermark pattern. The watermark (4) is visible. Therefore, since the second watermark portion (4) having different light transmittance is visible in the first watermark portion (3) which is a watermark pattern, the watermark pattern (2) is It is visually recognized as a watermark having gradation.

  When using colored cellulose microfibers, the cellulose microfibers are produced and then colored with a colorant, or the raw material fibers are colored with a colorant and then fibrillated to produce cellulose microfibers. However, coloring non-uniformity is less when cellulose microfibers are colored after production.

  As the colorant, it is preferable to use a direct dye or a reactive dye that dyes cellulose fibers well, but other dyes or pigments may be used as long as they can color the cellulose fibers. When coloring, an auxiliary such as a fixing agent is appropriately used according to the coloring method and the type of the coloring agent.

  As a coloring method, coloring with a dye includes an immersion dyeing method in which heating is performed in water, the dye is adsorbed on a fiber, washed with water, and dried. In addition, coloring with a pigment includes a method in which a pigment and a dispersant are wet dispersed using a mill or the like to form a colorant and the colorant is colored. These methods are all known methods, and the coloring performed for producing the colored fiber in the present invention is also performed by a known method.

  Uncolored or colored cellulose microfibers are dispersed in water to prepare a microfiber dispersion. It is possible to add a dispersant, a water-soluble polymer, a water-soluble liquid that does not inhibit the dispersion state of cellulose microfibers, an organic solvent, powder, fine particles, or the like.

  The fine fiber dispersion needs to have a concentration such that the fibrillated fine fibers do not immediately recombine with hydrogen bonds, and is preferably used at a solid content concentration of about 1 to 3%. However, if the fine fibers can be re-separated by vigorously stirring the fine fiber dispersion or adding a dispersing agent, there is no problem even if it is about 3 to 35%.

  This is because, when the solid content concentration is 35% or higher, re-defining treatment may be necessary because recombination of the microfibers cannot be suppressed only by adding stirring or a dispersing agent. On the contrary, when the solid content concentration is 1% or less, there is a possibility of promoting the swelling of the paper due to excessive moisture in the application and drying stages. However, there is no particular limitation as long as these problems can be avoided by other means.

The amount of the fine fiber dispersion applied varies depending on the method of application, but it is necessary to prepare so that the solid content of the cellulose microfibers after drying is 30 g / m ² or more.

When the solid content is less than 30 g / m ^2, it is difficult to visually recognize the application portion of the fine fiber dispersion under visible light transmission, which is not preferable.

  Depending on the application method, the application limit amount at one time may be equal to or less than the amount, but in this case, application may be repeated several times to obtain a target solid content.

  The length of cellulose microfibers is usually about 0.5 to 20 mm for wood and non-wood pulp fibers, so the minimum limit length is less than this, but the maximum limit length is the application method. Varies by For example, the screen printing method needs to be shorter than the length that can pass through the screen mesh, the flexographic printing method needs to be shorter than the length that can be transferred to the cell of the roll, and the inkjet printing method needs to be shorter than the length that can be ejected from the ejection port.

  The second watermark portion (4) is obtained by dispersing the cellulose microfibers in water, printing the formed microfiber dispersion on the first watermark portion (3), and then drying. A watermark pattern (2) having gradation in the present invention is produced.

  As described above, the watermark pattern (2) of the present invention is formed by fixing cellulose fine fibers on the first watermark portion (3) by hydrogen bonding. Therefore, in order to more firmly fix the cellulose microfibers on the first watermark (3), it is preferable to print on the base material (1) made of paper or nonwoven fabric having a high water content.

  Paper made of wood or non-wood pulp, or a non-woven fabric made of a synthetic fiber having a functional group capable of forming a hydrogen bond, which is prepared by a wet process, is formed into a sheet by bonding the fibers by inter-fiber hydrogen bonding. In the hydrogen bond, the bond between the hydroxyl groups of the cellulose fiber is the strongest, and the water bonding force is reduced by the water molecules entering between the hydroxyl groups.

  Therefore, when the base material (1) made of paper or nonwoven fabric having a high water content is used, since many water molecules are present between the fibers, loose hydrogen bonds are formed. The fibers easily form new hydrogen bonds, and the hydrogen bonds between the cellulose microfibers and the substrate (1) become stronger. Hereinafter, the base material (1) made of paper or nonwoven fabric having a high water content is referred to as “wet paper”, and the base material (1) completed through the drying process of the paper machine is referred to as “dry paper”.

  For printing, both wet paper and dry paper are composed of printing means for transferring the fine fiber dispersion to paper and forming significant information, and supply means for supplying the fine fiber dispersion to the printing means. The printing apparatus that can perform the above-described printing method is used. For example, the printing is performed using a printing apparatus such as a screen printing machine, a flexographic printing machine, a gravure printing machine, an inkjet printing machine, an offset printing machine, a relief printing machine, an intaglio printing machine.

  The printing means is a printing plate surface in the form of significant information or a spout in an ink jet printing machine, and is appropriately selected according to the printing apparatus to be used. The supply means is means for supplying the fine fiber dispersion to the printing means, and is an ink supply unit or an ink tank in the printing apparatus. It should be noted that other printing methods are not particularly limited as long as microfibers can be printed on paper and a pattern can be formed.

  In each printing method, printing is performed by supplying a fine fiber dispersion to a portion (usually referred to as “supplying unit”) in the printing apparatus where normal ink is supplied. When it is necessary to increase the viscosity of the fine fiber dispersion liquid by a printing method, a water-soluble polymer or the like may be appropriately added as a thickener. In addition, when it is necessary to improve the plate surface transferability and the drying property of the fine fiber dispersion by the printing method, an organic solvent such as ethers or alcohols may be appropriately added or replaced with water. good.

  The amount of printing the fine fiber dispersion needs to be such that the film thickness of the dried cellulose fine fiber is about 2 to 60 μm. Preferably, it shall be about 10-60 micrometers.

  When the film thickness is less than 10 μm, the second watermark (4) due to cellulose microfibers is difficult to visually recognize under transmitted light, and when the film thickness is less than 2 μm, it is almost impossible to visually recognize. Therefore, it is not preferable.

  On the other hand, if the film thickness exceeds 60 μm, the second watermark (4) can be clearly seen even under reflected light, which is not preferable.

  Depending on the printing method, the application limit amount at one time may be equal to or less than the amount, but in this case, printing may be repeated several times to obtain a target film thickness.

  The process of printing cellulose microfibers on paper by a printing device is a step of printing using a printing machine, as well as a step of printing using a printing device installed on a paper machine, and a printing using ordinary ink. There are two ways.

  First, the process of printing using the printing apparatus installed on the paper machine will be described. A wire that forms a paper stock suspension on a paper machine into a sheet of a printing device such as a screen printing device, flexographic printing device, inkjet printing device, gravure printing device, offset printing device, letterpress printing device, etc. Then, the fine fiber dispersion is supplied to the supplying means of each printing apparatus.

  Next, the fine fiber dispersion is supplied from the supply means to the printing means. Finally, the fine fiber dispersion is printed on the paper on the paper machine that has been dehydrated to a moisture content of less than 9 to 85% from the printing means.

  When the water content is 85% or more, the stock suspension is not in the form of a sheet on the paper machine, and the printed microfiber dispersion and the stock suspension are mixed together, making it impossible to print significant information. .

  Using a printing device such as a printing plate, anilox roll, and ink pan installed in the press section on the paper machine, the ink in the ink pan (in the present invention, the fine fiber dispersion) is applied to the wet paper on the paper machine. The details of the printing method are described in Japanese Patent No. 2740765 “Wet paper printed matter, manufacturing method thereof and wet paper printing apparatus” previously filed by the present applicant.

  Next, the process of printing using a printing machine in the same way as printing using ordinary ink will be described. In the case of dry paper, a screen printer, which is a printing device of various methods, on paper having a moisture content of less than 9%, such as paper, synthetic fiber paper, non-woven fabric, and film, which has been completed through a paper machine drying process Cellulose microfibers are printed using a flexographic printing machine, an inkjet printing machine, a gravure printing machine, an offset printing machine, a letterpress printing machine, and an intaglio printing machine.

  There are two methods for wet paper: a method performed on a paper machine and a method performed by wetting a dry paper. This is a method of printing the fine fiber dispersion by providing the above-described various types of printing devices at locations where the water content is less than 9%.

  In addition, the wet paper is wetted by impregnating or spraying water (less than 9% water content) such as paper, synthetic fiber paper, and non-woven fabric that has been completed through the paper machine drying process. Thus, after the moisture content is set to less than 9 to 85%, the fine fiber dispersion is printed using the above-described various types of printing apparatuses.

  The fine fiber dispersion is transferred to paper by various printing methods and then dried. When moisture evaporates during drying, the cellulose microfibers are fixed on the paper and form a pattern by hydrogen bonding between the cellulose microfibers and the paper fibers. There is no need to add a binder component as in normal ink, and a strong bond is formed.

  Drying of the printed fine fiber dispersion is evaporation-penetration-type drying by evaporation of moisture in the fine fiber dispersion and permeation into the paper. Heat drying is preferably a non-contact drying method such as hot air drying. However, even with a contact-type drying method using a cylinder or the like, there is no problem as long as cellulose fine fibers can be prevented from transferring to the cylinder surface. If heat drying is not performed, penetration into the paper becomes excessive rather than evaporation of water, and deformation such as curling of the paper is likely to occur. The drying method is not necessarily limited to heat drying, and any method can be used as long as the printed fine fiber dispersion can be dried.

  For example, an example of a method for printing cellulose microfibers by a screen printing method is shown in FIG. As shown to Fig.7 (a), a microfiber dispersion liquid is supplied to the ink supply location (5) of a screen printer, and a microfiber dispersion liquid is made into a screen by operating a squeegee (6) or a plate surface (7). The pattern passes through the pattern-shaped opening (8) of the printing plate, and is transferred onto the first watermark (3) to form a pattern.

  Then, as shown in FIG.7 (b), it heat-drys using a dryer (9), the water | moisture content in a microfiber dispersion liquid is evaporated, and it dries. Due to hydrogen bonding between the cellulose microfibers and the fibers of the substrate (1), the cellulose microfibers are fixed on the paper, and the second watermark (4) is produced.

  Note that the shape of the second watermark portion (4) is not limited to the symbol shape such as the double circle shape as shown in FIG. 2, but is particularly similar to the shape of the first watermark portion (3) described above. There is no limit.

  Further, the second watermark portion (4) has a uniform light transmission pattern in FIG. 5, but the second watermark portion is the same as the first watermark portion (3) described above. Within (4), you may have several area | regions from which light transmittance differs. By forming the second watermark portion (4) from a plurality of regions having different light transmittances, the overlapping region (W) in the watermark pattern (2) is composed of a plurality of regions having different light transmittances.

  As described above, the watermark pattern (2) of the present invention is formed by forming the second watermark part (4) on the first watermark part (3).

  Example 1 of the present invention will be described with reference to FIG. FIG. 8A shows a plan view of a sheet (S2) provided with a watermark pattern (2) having gradation in the present invention.

  The watermark pattern (2) is composed of the first watermark portion (3) and the overlapping region (W), and the overlapping region (W) is the first watermark portion (3) shown in FIG. It was formed by printing the second watermark (4) shown in FIG.

As the base material (1), high-quality paper (“New NPi fine quality (basis weight 81.4 (g / m ² )” manufactured by Nippon Paper Industries Co., Ltd.)) was used.

  In addition, the first watermark (3) is formed by placing the rectangular pattern (P) shown in FIG. 4 on the calender roll installed on the glossy part on the paper machine, and then the substrate (1). Formed by compression. In addition, the 1st watermark part (3) was formed as an area | region where the amount of transmitted light of a rectangular shape was uniform.

  Moreover, the 2nd watermark part (4) was formed by printing a microfiber dispersion liquid.

  As the cellulose microfiber, “Cerish KY100G” manufactured by Daicel Chemical Industries, Ltd. was used. This was stirred and diluted to prepare a fine fiber dispersion having a solid content of 2% and used for printing. Cellulose microfibers were printed by a screen printing method using a flat bed type screen printer (MF-250, manufactured by RNAS) to form a second watermark (4) having a character shape “OK”. As the screen printing plate, an 80 mesh lacquer printing plate (opening 247 μm, wire diameter 71 μm, plate thickness 119 μm, manufactured by Nippon Special Textile Co., Ltd.) was used. The film thickness of the second watermark (4) was about 15 μm.

  The authenticity of the sheet (S2) produced in this way is determined. When the sheet (S2) was observed with transmitted light, the first watermark (3) and the second watermark (4) were visible. Further, the first watermark portion (3) and the second watermark portion (4) were visually recognized as a watermark pattern having gradation due to a difference in light transmittance. Thereby, it was determined that the sheet (S2) is a genuine product.

  A second embodiment of the present invention will be described with reference to FIG. FIG. 9A shows a plan view of a sheet (S3) provided with a watermark pattern (2) having gradation in the present invention.

  The watermark pattern (2) includes a first watermark portion (3) having a gradation and an overlapping region (W), and the overlapping region (W) has a first gradation having a gradation shown in FIG. 9B. It formed by printing the 2nd watermark part (4) shown in FIG.9 (c) on the watermark part (3).

As the substrate (1), high-quality paper (“New NPi fine quality (basis weight 81.4 (g / m ² )” manufactured by Nippon Paper Industries Co., Ltd.) was used.

  In addition, the first watermark part (3) is arranged on the calendar roll installed in the glossy part on the paper machine after the double circular pattern mold (P) having different thicknesses in the central circle and the peripheral circle is installed. It formed by compressing a base material (1). The first watermark portion (3) was formed as a double circular region having a gradation and a different amount of transmitted light in a pattern shape.

  The second watermark (4) was formed by printing a fine fiber dispersion.

As the cellulose microfiber, “Cerish KY100G” manufactured by Daicel Chemical Industries, Ltd. was used. This was stirred and diluted to prepare a fine fiber dispersion having a solid content of 2% and used for printing. Using a flexographic printing aptitude tester (FLEXIPROOF100, manufactured by RK Print Coat Instruments), cellulose microfibers were printed by a flexographic printing method to form a second watermark (4) having a character shape “OK”. The anilox roll was 40 lines / cm and the cell volume was 28 cm ³ / m ² , and a photosensitive resin plate was used for the plate surface. The film thickness of the second watermark (4) was 50 to 60 μm.

  The authenticity of the sheet (S3) produced in this way is determined. When the sheet (S3) was observed with transmitted light, the first watermark (3) and the second watermark (4) were visible. Further, the first watermark portion (3) and the second watermark portion (4) were visually recognized as a watermark pattern having gradation due to a difference in light transmittance. Thereby, it was determined that the sheet (S3) is a genuine product.

  A third embodiment of the present invention will be described with reference to FIG. FIG. 10A shows a plan view of a sheet (S4) provided with a watermark pattern (2) having gradation in the present invention.

  The watermark pattern (2) includes the first watermark portion (3) and the overlapping region (W), and the overlapping region (W) is the first watermark portion (3) shown in FIG. It was formed by printing the second watermark (4) shown in FIG. The paper (S4) in this example was produced by making the base material (1) and the first watermark part (3) with a paper machine and making paper.

  A rectangular convex pattern was previously formed of resin on the paper machine wire. In the process of supplying the abaca fiber suspension to the wire part and forming it on the wet paper, the amount of fibers was reduced on the convex pattern part of the wire, and a rectangular pattern part was formed by white squeezing.

  The wet paper on which the pattern is formed passes through the press section, the drying section, and the gloss section of the paper machine, and is wound around a reel to produce a paper that forms a rectangular first watermark section (3) on abaca paper. did.

  The second watermark (4) was formed by printing a fine fiber dispersion.

As the cellulose microfiber, “Cerish KY100G” manufactured by Daicel Chemical Industries, Ltd. was used. This was stirred and diluted to prepare a fine fiber dispersion having a solid content of 2% and used for printing. Using a flexographic printing aptitude tester (FLEXIPROOF100, manufactured by RK Print Coat Instruments), cellulose microfibers were printed by a flexographic printing method to form a second wrinkle portion (4) having a “鳳凰” pattern. The anilox roll was 40 lines / cm and the cell volume was 28 cm ³ / m ² , and a photosensitive resin plate was used for the plate surface. The film thickness of the second watermark (4) was 20 to 30 μm.

  The authenticity of the sheet (S4) produced in this way is determined. When the paper (S4) was observed with transmitted light, the first watermark (3) and the second watermark (4) were visible. Further, the first watermark portion (3) and the second watermark portion (4) were visually recognized as a watermark pattern having gradation due to a difference in light transmittance. As a result, it was determined that the sheet (S4) was genuine.

  A fourth embodiment of the present invention will be described with reference to FIG. Fig.11 (a) shows the top view of the paper (S5) which provided the watermark pattern (2) which has a gradation in this invention.

  The watermark pattern (2) is composed of a first watermark portion (3) and an overlapping region (W), and the overlapping region (W) is the first watermark portion (3) shown in FIG. It was formed by printing the second watermark (4) shown in FIG. In the paper (S5) in this example, the first watermark (3) was produced by printing with watermark ink.

As the substrate (1), high-quality paper (“New NPi fine quality (basis weight 81.4 (g / m ² )” manufactured by Nippon Paper Industries Co., Ltd.) was used.

  First, the 2nd watermark part (4) was formed previously by printing a microfiber dispersion liquid on a base material (1).

Cellulose microfibers used “Serish KY100G” manufactured by Daicel Chemical Industries, Ltd. This was stirred and diluted to prepare a fine fiber dispersion having a solid content of 2% and used for printing. Using a flexographic printing aptitude tester (FLEXIPROOF100, manufactured by RK Print Coat Instruments), cellulose microfibers were printed by a flexographic printing method to form a second wrinkle portion (4) having a “鳳凰” pattern. The anilox roll was 40 lines / cm and the cell volume was 28 cm ³ / m ² , and a photosensitive resin plate was used for the plate surface. The film thickness of the second watermark (4) was 50 to 60 μm.

  The watermark ink (“Best One Watermark Ink” manufactured by T & K TOKA) is printed by the offset printing method so as to overlap the second watermark portion (4), and the first elliptical watermark portion (3) Formed.

  The authenticity of the sheet (S5) produced in this way is determined. When the paper (S) was observed with transmitted light, the first watermark (3) and the second watermark (4) were visible. Further, the first watermark portion (3) and the second watermark portion (4) were visually recognized as a watermark pattern having gradation due to a difference in light transmittance. As a result, it was determined that the sheet (S5) was genuine.

DESCRIPTION OF SYMBOLS 1 Base material 2 Watermark pattern 3 1st watermark part 3a Watermark area | region 4 2nd watermark part 5 Ink supply location 6 Squeegee 7 Plate surface 8 Opening part 9 Dryer S, S2, S3, S4, S5 Paper W Overlapping area

Claims (4)

  In a part of the base material having light transmittance, a watermark pattern including a first watermark portion having higher light transmittance than the base material and an overlapping region having light transmittance lower than that of the first watermark portion. And the overlap region is formed by laminating a second watermark portion formed of cellulose microfibers having the same color as the first watermark portion on a part of the first watermark portion. Paper having a watermark using the characteristic cellulose microfiber.   The paper having a watermark using cellulose microfiber according to claim 1, wherein the first watermark and the overlapping region have a brightness difference of 5 or more.   The cellulose microfiber according to claim 1 or 2, wherein the first watermark portion and / or the second watermark portion has different light transmission and has gradation. A sheet of paper.   The first watermark portion is formed by processing the base material by compression, laser processing, watermark printing, or insertion, or a combination thereof. A paper having a watermark using the cellulose microfiber according to one item.

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