CN117021726A - Pressure-sensitive paper and application thereof in inkless printing - Google Patents

Abstract

The application relates to the technical field of inkless printing, in particular to a press-developing paper and application thereof in inkless printing. The color-pressed paper sequentially comprises a base color paper, an absorption layer and a top color pressed paper; the top color paper comprises color development microcapsules taking transparent materials as wall materials and first pigments as core materials; the absorbing layer includes a material that is reactive with the first pigment such that the first pigment changes from a colored state to a colorless state; the base color base paper includes a second pigment. According to the application, the color developing microcapsule of the pressed part of the top color paper is broken, the first pigment is released to react with the absorbing layer material, so that the color of the pressed part is irreversibly changed into transparent colorless, the color of the second pigment of the underlying color base paper is exposed, and the underlying color base paper can be prepared into various colors by the prior art, thus the ink-free printing of any color is realized, and the long-term preservation of the printed pattern is ensured based on irreversible color change.

Description

A kind of embossing paper and its application in inkless printing

Technical field

The present invention relates to the technical field of inkless printing, and in particular to an embossed paper and its application in inkless printing.

Background technique

Generally speaking, ink is a necessary raw material for printing, but as environmental protection requirements become more and more popular and strict, environmentally friendly inks and even ink-free printing have become new technological directions for research and development. Inkless printing in the prior art is mostly achieved through heat-sensitive materials or photosensitive materials.

The principle of photosensitive materials in inkless printing is to pre-coat photosensitive color-forming materials such as diacetylene on the substrate. When these photo-sensitive color-forming materials are exposed to a suitable energy source (such as laser), they will The substrate changes color to achieve ink-free printing. However, it has the following problems: first, the printed content of the paper will disappear over time, making it only suitable for temporary printed matter, such as newspapers. For products that need to be permanently preserved, this technology is useless; secondly, the photosensitive material only Being able to change between specific colors makes the print options limited, making it unsuitable for iconic packaging of goods.

The principle of heat-sensitive materials in inkless printing is similar to that of photosensitive materials: it is to coat the substrate with heat-sensitive color-changing materials. Currently, a variety of heat-sensitive color-changing materials have been developed on the market. This heat-sensitive color-changing material is used in different applications. It can change from colorless to magenta, cyan, yellow and black respectively under temperature. This type of material contains heat-sensitive and discolored organic compounds, such as trigonal methane, fluorane, spiropyran, etc. When heated, a carbon atom in the compound system is converted from sp ³ hybridization to sp ² hybridization. Titanium, the originally separated π system is transformed into a complete π system, absorbing the corresponding spectral energy, thereby changing the thermochromic material from colorless to colored. The existing problems are: first, on the substrate, when the temperature is provided to the part that needs to be printed to change color, based on the conduction of heat, the part that does not need to be printed will also heat up and change color, causing the printing edge to be unclear; Secondly, due to the fact that its color is easily affected by temperature, there are high requirements for the storage and transportation environment of printed products, which is not conducive to long-term preservation and packaging of goods; thirdly, it can only be used in specific Changes between colors make the choice of printed colors limited.

Based on this, there is an urgent need to develop an ink-free printing technology that can print in any color and is not easy to fade.

Contents of the invention

The present invention aims to solve the above problems and provide an embossed paper and its application in inkless printing.

The technical solution of the present invention to solve the problem is to first provide a pressed paper, which sequentially includes a background color base paper, an absorption layer and a top color pressing paper;

The top color pressing paper includes color-developing microcapsules with a transparent material as a wall material and a first pigment as a core material;

The absorption layer includes a material that can react with the first pigment so that the first pigment changes from a colored state to a colorless state;

The base paper includes a second pigment that is different in color from the first pigment.

The basic idea of the present application is to rupture the color-developing microcapsules in the pressed part of the top-color press paper, release the first pigment, and react with the absorbing layer material, so that the color of the pressed part irreversibly becomes transparent and colorless. The color of the second pigment of the base paper underneath is revealed, and the base paper can be prepared in various colors through existing technology, thus enabling ink-free printing of any color, and ensuring the long-lasting printing pattern based on irreversible discoloration. save.

There are many specific implementation methods, based on different selections of the first pigment, different materials of the absorption layer, and different discoloration principles.

In one embodiment, the first pigment is nano-zinc oxide; the absorption layer includes polyvinyl acetate, a first microcapsule with a first solvent as a core material, and a second microcapsule with a second solvent as a core material. Microcapsules, the first solvent is a solvent that can dissolve the nano zinc oxide, and the second solvent is a solvent that can dissolve the polyvinyl acetate.

The specific principle is as follows: the top color pressed paper appears nearly white through nano-zinc oxide. When subjected to pressure, the color-developing microcapsules in the pressed part rupture, release nano-zinc oxide, and are driven close to the absorption layer under the action of pressure. , at the same time, the first microcapsule and the second microcapsule in the compressed part of the absorption layer rupture and release the first solvent and the second solvent respectively, and the nano zinc oxide and the first solvent form a nano zinc oxide sol system, polyvinyl acetate and the second The solvents form a dispersion system together, and the nano-zinc oxide sol system and the dispersion system form a colorless and transparent nano-ZnO/PVAc composite sol system. Finally, it can be dried to obtain a colorless and transparent ZnO/PVAc composite film, making the pressurized part appear colorless. Transparent, revealing the base paper underneath.

The source of nano-zinc oxide is not limited. Suitable preparation methods are: hydrothermal method: This is a method to prepare nano-zinc oxide by chemical reaction in a high-temperature and high-pressure aqueous solution, usually at appropriate temperature, pressure and reaction. Under time, an appropriate amount of zinc salt and alkali solution are reacted to generate nano zinc oxide. Sol-gel method: This is a method of gradually converting a solution into a gel or solid. When preparing nano zinc oxide, a suitable zinc salt and a sol agent are usually mixed to form a sol, and then heat treated or dried to make it The sol transforms into a gel, and ultimately nano-zinc oxide is obtained.

The source of polyvinyl acetate is not limited. It can be prepared from commercially available analytically pure materials or by common methods in the existing technology. Suitable preparation methods for polyvinyl acetate are: emulsion polymerization: vinyl acetate, surface Active agents and emulsifiers are added to water to form an emulsion system, and through heating and stirring, the emulsion is polymerized into polyvinyl acetate. During the polymerization process, it may be necessary to add an initiator or starter to initiate the polymerization reaction. Solution polymerization method: Dissolve vinyl acetate in an appropriate solvent to form a polymer solution, add an initiator or starter, and initiate the polymerization reaction through heating or the action of ultraviolet light. After the polymerization reaction is completed, the solvent is removed by distillation or other methods to obtain polyvinyl acetate.

The first solvent that can dissolve nano-zinc oxide is preferably one or both of ethanol and isopropyl alcohol.

The second solvent that can dissolve polyvinyl acetate is preferably one or more of benzene, acetone, and chloroform.

The choice of wall material in the first microcapsule and the second microcapsule is not limited, and is preferably a brittle material that is easily broken under pressure, and may optionally include polyethylene, polypropylene, polymethyl methacrylate, or polyvinyl alcohol. one or several kinds.

The preparation methods of the chromogenic microcapsules, the first microcapsules and the second microcapsules are not limited, and suitable preparation methods include known chemical and physical methods for forming polymer capsules. Representative examples of chemical methods include complex coacervation, interfacial polymerization, polymer-polymer incompatibility, plain polymerization, centrifugal force process, and submerged nozzle process. Representative implementations of physical methods include spray drying, fluid bed coating, centrifugal extrusion, and spin suspension centrifugation.

In the above embodiment, since the discoloration principle theoretically involves a three-step binding process, in order to ensure that the combination of nano zinc oxide and the first solvent is not interfered by the second solvent and polyvinyl acetate, as a preferred method of the present invention, the absorption The layer includes a first layer and a second layer along the direction of the top color pressure paper and the bottom color base paper, the first microcapsules are arranged on the first layer, and the polyvinyl acetate and the second microcapsules are arranged on the third layer. Two layers. Through the layered design, during the paper pressure process, nano-zinc oxide is combined with the first solvent to form a nano-zinc oxide sol system and then contacts the second solvent and polyvinyl acetate.

In the above embodiment, the pressurized part can be discolored simply by applying pressure. In order to avoid discoloration of the paper due to accidental pressure, it is preferred in the present invention that the wall material of the first microcapsule includes a pressure rupture material and a thermal rupture material, The thermal fracture material includes a phase change material, and the pressure fracture material includes a brittle material. By adding a thermal rupture material, the first microcapsule can be completely ruptured only under the dual effects of pressure and temperature to release the first solvent to disperse the nano-zinc oxide and turn it colorless. In specific use, it is preferable to embed the first solvent with the pressure rupture material and the thermal rupture material in sequence. The phase change material optionally includes paraffin, and the selection of brittle materials is as listed above for brittle materials that are easily broken after being stressed.

In another embodiment, the first pigment is a ternary compound composed of a color-developing agent, a color-developing agent, and a temperature-controlling solvent; and the absorption layer includes a photocatalyst that catalyzes the decomposition of the color-developing agent.

The specific principle is as follows: the first pigment belongs to a three-component thermochromic system, in which the color former is an electron donor compound that can provide a color-changing structure, the color developer is an electron acceptor compound, and the melting point of the temperature-controlled solvent determines the color change of the system. Temperature, in the low-temperature solid state, the chromogen with electron-donating properties can interact with the electron-acceptor chromogen to form a complex, triggering changes in the molecular structure of the chromogen, and the system appears in a colored state; as the temperature increases, the complex regenerates Dissolved in a temperature-controlled solvent, the interaction between the chromogen and the developer is destroyed by the solvent, and the system appears colorless. Therefore, by rupturing the color-developing microcapsules in the pressed part of the top-color press paper and releasing the first pigment, and at the same time applying heating, the first pigment color-forming agent and the color-developing agent can be separated and appear colorless, revealing the bottom layer below. Color-based paper; then, the photocatalyst in the absorption layer catalyzes the decomposition of the color developer, so that the color developer can no longer be discolored by the action of the color developer, achieving irreversible color change.

Among them, the chromogenic agent includes fluorane and triarylmethane phthalide, preferably one or two of thermosensitive red and thermosensitive green.

Most color developers are weakly acidic substances, such as phenolic hydroxyl compounds (bisphenol A, bisphenol AF, gallate, etc.), hydroxyl compounds (alkyl acids such as caproic acid, stearic acid), preferably bisphenol A, One or both of ethyl gallate and TGSH. The color developer can also be made of low vapor enthalpy and volatile materials to accelerate the removal of the color developer after the color microcapsules are broken. It is preferably one or more of methylphenol and nonylphenol.

The temperature control solvent can be fatty alcohols, mercaptans, ethers, ketones, phosphatidic acids, carboxylic acid esters and amides, preferably materials with a phase change temperature between 40°C and 60°C, preferably dodecanol, tetradecanol, One or more types of cetyl alcohol.

Titanium dioxide can be used as the photocatalyst.

In any embodiment, the transparent material is used to isolate the first pigment and the adhesive substance for papermaking without affecting the color of the first pigment; the transparent material is preferably a brittle material that is easily broken after being pressed, and optional options include polyethylene, polyethylene, etc. One or more of methyl methacrylate, polyvinyl alcohol, polyethylene wax, and melamine resin.

In any embodiment, as a preferred embodiment of the present invention, the absorption layer has through holes to accelerate absorption. Suitable preparation methods for the absorbent layer with through holes include adding volatile solvents, carbonate fillers, or passing gas during the dispersion process of the absorbent layer material.

In any embodiment, as a preferred embodiment of the present invention, the top color pressing paper includes a transparent fiber web and slurry filled in the fiber web, and the color-developing microcapsules are dispersed in the slurry. The fiber mesh ensures the strength of the top color press paper and avoids the problem of overall cracking of the top color press paper caused by the rupture of the color microcapsules.

The principle of preparing a transparent fiber web is to remove lignin from plant fibers as much as possible. Lignin contains a large number of unsaturated groups that produce absorption peaks for visible light, affecting transparency. Suitable preparation methods include: mechanical treatment: rupture the cell wall of plant fibers through refining or beating to obtain a cellulose fiber solution to prepare paper; chemical treatment: remove lignin through chemical reagents to extract nanocellulose fibers, and use nanocellulose fibers to Prepare paper.

In order to help the color-developing microcapsules adhere to the fiber web, as a preferred option of the present invention, the slurry further includes an adhesive. The adhesive is used to disperse the color microcapsules evenly and then adhere them together. It is preferably able to disperse and adhere to the wall material of the color microcapsules and cannot adhere to the first pigment after curing, so as to allow microscopic movement of the first pigment. Suitable adhesives include one or more of polyvinyl alcohol, polyurethane, polyimide, chitosan, and gelatin.

The embossed paper of the present application is mainly used in inkless printing technology. Therefore, another object of the present invention is to provide an application of embossed paper in inkless printing.

As a preferred method of the present invention, the application method includes the following steps:

S1. Press the printing mold onto the top color pressing paper of the developing paper, and apply pressure to cause the color microcapsules to rupture;

S2. Continue to pressurize, supplement with heating and light if necessary, until the pressurized area becomes colorless;

S3. Remove the printing mold and complete printing.

As a preferred option of the present invention, the printing mold includes an upper pressing mold and a lower receiving mold, and the pressed paper is sandwiched between the upper pressing mold and the lower receiving mold.

Further preferably, the lower receiving mold is provided with a negative pressure hole, and while applying pressure, the portion of the printed paper to be printed is adsorbed by negative pressure to avoid lateral diffusion of the core material after the microcapsules are broken.

Beneficial effects of the present invention:

In this application, the color microcapsules of the pressed part of the top color pressure paper are ruptured, releasing the first pigment and reacting with the absorbing layer material, so that the color of the pressed part irreversibly becomes transparent and colorless, thereby revealing the bottom underneath. The color base paper is the color of the second pigment, while the base color base paper can be prepared in various colors through existing technology, thus enabling ink-free printing of any color and ensuring the long-term preservation of the printed pattern based on irreversible discoloration.

Description of the drawings

Figure 1 is a rendering of the printed matter produced in Example 1.

Detailed ways

The following are specific embodiments of the present invention, and further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

Example 1

An embossed paper, prepared through the following steps:

(1) Prepare background color base paper: Mix 92 parts by mass of softwood bleached sulfate chemical pulp and 8 parts of ultramarine blue pigment, stir evenly, and then make paper to produce a light blue background color base paper.

(2) Prepare top color pressing paper:

Preparation of polymethylmethacrylate-coated nano-zinc oxide color microcapsules: mix 1 part of stearic acid, 15 parts of zinc chloride and 100 parts of ethanol according to mass parts, stir and react at 70°C for 2 hours, where During the process, 2 drops of distilled water were added every 30 minutes. After the reaction, a ZnO nanosuspension was obtained for later use. After mixing 14 parts of methyl methacrylate, 1 part of propyl methacrylate and 0.3 parts of azobisisobutyl cyanide, mix it with 0.1 part of the above-mentioned ZnO nano-suspension as an oil phase; mix 12 parts of styrene-male Dissolve the acid anhydride copolymer in 200 parts of distilled water as the water phase; add the oil phase to the water phase under stirring, and shear at a speed of 6000r/min for 10 minutes to obtain an emulsion; react the emulsion at 70°C for 6 hours to obtain microcapsules Suspension; filter and dry to obtain colored microcapsules.

Papermaking: Mix 92 parts of softwood bleached sulfate chemical pulp and 8 parts of color microcapsules according to parts by mass, stir evenly, and then make paper to produce a white top-color pressed paper.

(3) Preparation of absorption layer

Prepare the first microcapsule of polyvinyl alcohol-coated ethanol: add 1 part of ethanol and 0.3 part of glyceryl monolaurate to 10 parts of vegetable oil according to the mass part, and disperse evenly to obtain a mixture; add 1 part of the mixture and 0.3 part of 12 Sodium alkyl benzene sulfonate was added to 10 parts of polyvinyl alcohol solution, and after uniform dispersion, the mixture was filtered and dried to obtain the first microcapsule.

Prepare the second microcapsule of polyvinyl alcohol-coated acetone: add 1 part of acetone and 0.3 part of glyceryl monolaurate to 10 parts of palm oil according to the mass part, and disperse evenly to obtain a mixture; add 1 part of the mixture and 0.3 part of ten Sodium dialkyl benzene sulfonate was added to 10 parts of polyvinyl alcohol solution, and after uniform dispersion, the mixture was filtered and dried to obtain the second microcapsule.

Mixing: Dissolve 15 parts of polyvinyl acetate into 100 parts of acetone according to parts by mass, then add 8 parts of the first microcapsule and 20 parts of the second microcapsule to disperse evenly and set aside.

(4) Preparation of pressed paper:

Place the base paper of the background color on the negative pressure adsorption device, then apply an absorption layer, let it stand for 10 minutes, then stack the top color pressing paper, and press it with a pressure of 20Kpa, and then dry it at room temperature to obtain the pressed paper.

(5) A method for applying embossed paper, including the following steps:

S1. Press the printing mold onto the top color pressing paper of the prepared pressed paper, and pressurize it to 80Kpa to rupture the colored microcapsules.

S2. Continue to pressurize until the pressurized area becomes colorless.

S3. Remove the printing mold, dry at room temperature, and complete printing.

As shown in Figure 1, the resulting print exhibits a light blue pattern on the top color press paper.

Example 2

This embodiment is basically the same as Embodiment 1, and the only difference lies in:

(3) During the preparation of the absorption layer, when mixing:

Mixing: According to parts by mass, add 7 parts of polyvinyl acetate to 50 parts of acetone and dissolve it, then add 8 parts of the first microcapsules to disperse evenly to obtain the first coating; add 8 parts of polyvinyl acetate to 50 parts of acetone and dissolve it. , add 20 parts of the second microcapsules and disperse them evenly to obtain the second coating.

(4) In the process of preparing pressed paper:

Place the base color base paper on the negative pressure adsorption device, apply a layer of second paint and let it sit for 5 minutes; then apply a layer of first paint and let it stand for 5 minutes; then overlap the top color pressing paper and press it with a pressure of 20Kpa Press and then dry at room temperature to obtain embossed paper.

Example 3

This embodiment is basically the same as Embodiment 1, and the only difference lies in:

(3) During the preparation of the absorption layer, when preparing the first microcapsule:

Prepare the first microcapsule of polyvinyl alcohol-coated ethanol: add 1 part of ethanol and 0.3 part of glyceryl monolaurate to 10 parts of paraffin according to the mass part, and disperse evenly to obtain a mixture; add 1 part of the mixture and 0.3 part of 12 Sodium alkyl benzene sulfonate was added to 10 parts of polyvinyl alcohol solution, and after uniform dispersion, the mixture was filtered and dried to obtain the first microcapsule.

Example 4

This embodiment is basically the same as Embodiment 1, and the only difference lies in:

(3) During the preparation of the absorption layer, when mixing:

Mixing: According to parts by mass, add 15 parts of polyvinyl acetate to 100 parts of acetone to dissolve, then add 8 parts of the first microcapsule, 20 parts of the second microcapsule and 5 parts of sodium bicarbonate to disperse evenly and set aside.

(4) Preparation of pressed paper:

Place the base color base paper on the negative pressure adsorption device, then apply an absorption layer, let it stand for 10 minutes in an environment of 50°C, then stack the top color base paper, press it with a pressure of 20Kpa, and then dry it at room temperature. Obtain embossed paper.

Example 5

This embodiment is basically the same as Embodiment 1, and the only difference lies in:

(2) In the process of preparing top color pressing paper:

Prepare a transparent fiber web: mix 2.5 parts of sodium hydroxide, 0.4 parts of sodium sulfite, and 50 parts of water according to parts by mass to obtain a solution; after crushing the plant raw materials into chips, add 5 parts of the plant chips into 50 parts of the solution, and Cook at 80°C for 5 hours and then transfer to distilled water to clean; then continue to treat the product with hydrogen peroxide in a water bath until the product turns white; take it out; clean and disperse with distilled water to obtain a solution with a cellulose solid content of 50%; then use a vacuum The cellulose solution is dried by suction filtration to obtain a fiber web.

Papermaking: Mix 20 parts of polyvinyl alcohol and 8 parts of color-developing microcapsules according to parts by mass, stir evenly, apply on fiber web, and dry to obtain top-color pressed paper.

Example 6

This embodiment is basically the same as Embodiment 1, and the only difference lies in:

(5) A method for applying embossed paper, including the following steps:

S1. The printing mold includes an upper pressing mold and a lower receiving mold. The lower receiving mold is equipped with a negative pressure hole; the pressure display paper is sandwiched between the upper pressing mold and the lower receiving mold. The upper pressing mold is pressurized to 80Kpa while the lower receiving mold is pressed. The mold provides 10 Kpa negative pressure adsorption.

S2. Continue pressurization and negative pressure adsorption until the pressurized area becomes colorless.

S3. Remove the printing mold, dry at room temperature, and complete printing.

Example 7

An embossed paper, prepared through the following steps:

(1) Prepare background color base paper: Mix 92 parts by mass of softwood bleached sulfate chemical pulp and 8 parts of ultramarine blue pigment, stir evenly, and then make paper to produce a light blue background color base paper.

(2) Prepare top color pressing paper:

Preparation of polymethylmethacrylate-coated nano-zinc oxide color microcapsules: mix 1 part of stearic acid, 15 parts of zinc chloride and 100 parts of ethanol according to mass parts, stir and react at 70°C for 2 hours, where During the process, 2 drops of distilled water were added every 30 minutes. After the reaction, a ZnO nanosuspension was obtained for later use. After mixing 14 parts of methyl methacrylate, 1 part of propyl methacrylate and 0.3 parts of azobisisobutyl cyanide, mix it with 0.1 part of the above-mentioned ZnO nano-suspension as an oil phase; mix 12 parts of styrene-male Dissolve the acid anhydride copolymer in 200 parts of distilled water as the water phase; add the oil phase to the water phase under stirring, and shear at a speed of 6000r/min for 10 minutes to obtain an emulsion; react the emulsion at 70°C for 6 hours to obtain microcapsules The suspension is filtered and dried to obtain colored microcapsules.

Prepare a transparent fiber web: mix 2.5 parts of sodium hydroxide, 0.4 parts of sodium sulfite, and 50 parts of water according to parts by mass to obtain a solution; after crushing the plant raw materials into chips, add 5 parts of the plant chips into 50 parts of the solution, and Cook at 80°C for 5 hours and then transfer to distilled water to clean; then continue to treat the product with hydrogen peroxide in a water bath until the product turns white; take it out; clean and disperse with distilled water to obtain a solution with a cellulose solid content of 50%; then use a vacuum The cellulose solution is dried by suction filtration to obtain a fiber web.

Papermaking: Mix 20 parts of polyvinyl alcohol and 8 parts of color-developing microcapsules according to parts by mass, stir evenly, apply on fiber web, and dry to obtain top-color pressed paper.

(3) Preparation of absorption layer

Prepare the first microcapsule of polyvinyl alcohol-coated ethanol: add 1 part of ethanol and 0.3 part of glyceryl monolaurate to 10 parts of paraffin according to the mass part, and disperse evenly to obtain a mixture; add 1 part of the mixture and 0.3 part of 12 Sodium alkyl benzene sulfonate was added to 10 parts of polyvinyl alcohol solution, and after uniform dispersion, the mixture was filtered and dried to obtain the first microcapsule.

Prepare the second microcapsule of polyvinyl alcohol-coated acetone: add 1 part of acetone and 0.3 part of glyceryl monolaurate to 10 parts of palm oil according to the mass part, and disperse evenly to obtain a mixture; add 1 part of the mixture and 0.3 part of ten Sodium dialkyl benzene sulfonate was added to 10 parts of polyvinyl alcohol solution, and after uniform dispersion, the mixture was filtered and dried to obtain the second microcapsule.

Mixing: According to parts by mass, add 7 parts of polyvinyl acetate into 50 parts of acetone to dissolve, then add 8 parts of the first microcapsules and 3 parts of sodium bicarbonate to disperse evenly to obtain the first coating; add 8 parts of polyvinyl acetate. After dissolving 50 parts in acetone, add 20 parts of the second microcapsule and 2 parts of sodium bicarbonate to disperse evenly to obtain the second coating.

(4) Preparation of pressed paper:

Place the base paper on the negative pressure adsorption device, apply a layer of the second paint, and let it sit for 5 minutes; apply another layer of the first paint and let it stand for 5 minutes; let it stand for 10 minutes in a 50°C environment, and then overlap it. The paper is pressed with top color and pressed at a pressure of 20Kpa, and then dried at room temperature to obtain embossed paper.

(5) A method for applying embossed paper, including the following steps:

S1. The printing mold includes an upper pressing mold and a lower receiving mold. The lower receiving mold is equipped with a negative pressure hole; the pressure display paper is sandwiched between the upper pressing mold and the lower receiving mold. The upper pressing mold is pressurized to 80Kpa while the lower receiving mold is pressed. The mold provides 10 Kpa negative pressure adsorption.

S2. Continue pressurization and negative pressure adsorption until the pressurized area becomes colorless.

S3. Remove the printing mold, dry at room temperature, and complete printing.

Example 8

This embodiment is basically the same as Embodiment 1, and the only difference lies in:

(1) In the process of preparing the background base paper: mix 92 parts of softwood bleached sulfate chemical pulp and 8 parts of carbon black pigment according to parts by mass, stir evenly, and then make paper to obtain a black background base paper.

Example 9

An embossed paper, prepared through the following steps:

(1) Prepare background color base paper: Mix 92 parts by mass of softwood bleached sulfate chemical pulp and 8 parts of ultramarine blue pigment, stir evenly, and then make paper to produce a light blue background color base paper.

(2) Prepare top color pressing paper:

Preparation of color-developing microcapsules: According to the molar ratio, mix 1 part of thermosensitive red, 3 parts of bisphenol A, and 80 parts of tetradecanol, mix evenly in a 50°C water bath, and then cool at room temperature to obtain a ternary compound. The ternary compound, Tween 20, and deionized water were mixed and emulsified under heating in a 50°C water bath at a speed of 8000 rpm for 1 hour to obtain an emulsion. After mixing formaldehyde, melamine, and deionized water and adjusting the pH to 8.5, the mixture was heated in a water bath at 70°C and stirred at a speed of 600 rpm for 1 hour to obtain a prepolymer. Put 1 part of the emulsion into a water bath at 70°C, and add 4 parts of the prepolymer while stirring. After the addition is completed, adjust the pH of the mixture to 6.5, then stir at 70°C and 600rpm, and adjust the pH to 6.5 every 1 hour. , 5.5, 4.5, and 3.5 in order, adjust downward to 3.5 and continue stirring for 1 hour. After the reaction, filter and wash with absolute ethanol to obtain colored microcapsules.

Papermaking: Mix 92 parts of softwood bleached sulfate chemical pulp and 8 parts of color-developing microcapsules according to parts by mass, stir evenly, and then make paper to produce red top-color pressed paper.

(3) Preparation of absorption layer:

Add tetrabutyl titanate dropwise to deionized water at room temperature, stir magnetically to obtain a white precipitate; filter and wash the white precipitate, mix it with 30% hydrogen peroxide, stir magnetically, and dissolve the precipitate to obtain a sol. After cooling to room temperature, use Dilute the sol with polyvinyl alcohol and set aside.

(4) Preparation of pressed paper:

Place the base paper of the background color on the negative pressure adsorption device, then apply an absorption layer, let it stand for 10 minutes, then stack the top color pressing paper, and press it with a pressure of 20Kpa, and then dry it at room temperature to obtain the pressed paper.

(5) A method for applying embossed paper, including the following steps:

S1. Press the printing mold onto the top color pressing paper of the produced pressed paper, and pressurize it to 80Kpa to rupture the colored microcapsules;

S2. Continue to pressurize and heat to 50°C until the pressurized area becomes colorless; then apply UV light to the pressurized area at 50°C for 10 minutes.

S3. Remove the printing mold, then dry at room temperature to complete printing.

Comparative example 1

This comparative example is basically the same as Example 1, and the only difference is that the first pigment is not microencapsulated.

(2) In the process of preparing top color pressing paper:

Papermaking: According to parts by mass, mix 92 parts of softwood bleached sulfate chemical pulp and 8 parts of nano zinc oxide, stir evenly, and then make paper to produce a white top-color pressed paper.

Print inspection

Use a color difference detector to detect the printed matter obtained in the Examples and Comparative Examples to detect the color difference between the color of the base paper and the printed pattern. The test results are as follows in Table 1.

Detection of tensile strength of pressed paper

According to the detection method in "GB-T 12914-2008 Determination of tensile strength of paper and cardboard", the tensile strength of the pressed paper prepared in the examples and comparative examples, as well as the printed paper after printing, was tested. The test results are as follows: 1.

Table 1.

As shown in Table 1, it can be seen that the pressed paper produced in this application has good tensile strength before and after printing, and the pressed reaction process has little impact on the tensile strength of the paper; at the same time, the printed pattern The color is not much different from the color of the base paper, indicating that the color of the top-color pressing paper can be better transformed into transparent and colorless, ensuring the clarity of the printed pattern.

It can be further seen from the comparison between Example 1 and Comparative Example 1 that coating the first pigment can effectively ensure the transformation of the color state of the first pigment, and avoid printing by always bonding the wall material in the top color pressing paper. Excessive reduction in post-tensile strength. It can be seen from the comparison between Example 1 and Examples 2 and 4 that the color state conversion effect can be further improved by arranging two absorption layers and arranging through holes on the absorption layer. It can be seen from the comparison between Example 1 and Example 5 that by adding a fiber mesh, the tensile strength of the paper before and after printing can be effectively improved. It can be seen from the comparison between Example 1 and Example 6 that adding a negative pressure adsorption step during the printing pressurization process can further improve the color state conversion effect of the pressed color.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which the present invention belongs can make various modifications or additions to the described specific embodiments or substitute them in similar ways, but this will not deviate from the spirit of the present invention or exceed the definition of the appended claims. range.

Claims (10)

1. A pressed paper, characterized in that: it includes a background color base paper, an absorbing layer and a top color pressing paper in sequence; The top color pressing paper includes color-developing microcapsules with a transparent material as a wall material and a first pigment as a core material; The absorption layer includes a material that can react with the first pigment so that the first pigment changes from a colored state to a colorless state; The base paper includes a second pigment that is different in color from the first pigment. 2. A kind of embossed paper according to claim 1, characterized in that: The first pigment is nano zinc oxide; The absorption layer includes polyvinyl acetate, a first microcapsule with a first solvent as a core material, and a second microcapsule with a second solvent as a core material. The first solvent is a solvent that can dissolve the nano-zinc oxide. The second solvent is a solvent that can dissolve the polyvinyl acetate. 3. A kind of embossed paper according to claim 2, characterized in that: the absorption layer includes a first layer and a second layer along the direction of the top color embossing paper and the bottom color base paper, and the first micro layer The capsule is arranged in the first layer, and the polyvinyl acetate and the second microcapsule are arranged in the second layer. 4. The pressed paper according to claim 2, wherein the wall material of the first microcapsule includes brittle material and phase change material. 5. A kind of embossed paper according to claim 1, characterized in that: The first pigment is a ternary compound composed of a color-forming agent, a color developer and a temperature-controlling solvent; The absorbing layer includes a photocatalyst for catalyzing the decomposition of the developer. 6. A pressed paper according to claim 1, characterized in that: the top color pressed paper includes a transparent fiber web and slurry filled in the fiber web, and the color-developing microcapsules are dispersed in the fiber web. in the slurry. 7. The pressed paper according to claim 1, characterized in that the absorption layer has through holes. 8. An application of the embossed paper according to any one of claims 1 to 7 in inkless printing. 9. The application of a kind of embossed paper in inkless printing according to claim 8, characterized in that: it includes the following steps: S1. Press the printing mold onto the top color pressing paper of the developing paper, and apply pressure to cause the color microcapsules to rupture; S2. Continue to pressurize, supplement with heating and light if necessary, until the pressurized area becomes colorless; S3. Remove the printing mold and complete printing. 10. The application of pressed paper in inkless printing according to claim 9, characterized in that: in steps S1 and S2, while applying pressure, the portion of the pressed paper to be printed is subjected to negative pressure adsorption.