Erasable thermo-sensitive paper with clear two colors and preparation method of erasable thermo-sensitive paper

Abstract

The invention relates to the technical field of printing supplies, in particular to two-color clear erasable thermo-sensitive paper and a preparation method thereof. A middle layer is arranged between one side of a first color thermosensitive layer and one side of a second color thermosensitive layer of the thermosensitive paper; the material of the middle layer comprises resin and a heat-conducting auxiliary agent, and the resin is at least one of PVA (polyvinyl alcohol) resin, PVB (polyvinyl butyral) resin, PVP (polyvinyl pyrrolidone) resin and EVOH (ethylene vinyl alcohol) resin. By adding the intermediate layer between the first color thermosensitive layer and the second color thermosensitive layer, color permeation during printing can be prevented; the problem that the coatings are uneven due to direct contact of the two thermosensitive layers can be avoided, so that the color development effect is improved, the heat transfer efficiency between the coatings can be enhanced, and the color development effect of the lower layer is better; the preparation method is simple in step and easy to operate, and the obtained thermo-sensitive paper is uniform in coating and good in printing effect.

Description

Technical Field

[0001] The present invention relates to the technical field of printing consumables, and in particular to erasable thermal paper with distinct two colors and a preparation method thereof. Background Art

[0002] Erasable thermal paper was first developed by Japan's Ricoh Corporation in the 1990s. The thermal layer of erasable thermal paper generally contains two substances: colorless dye and erasable long-chain colorant. The two substances develop color when heated to a certain temperature and erase color at another temperature, thereby achieving repeated recording and erasure of information.

[0003] Currently, only monochrome erasable thermal paper is available on the market, primarily black, from Japanese companies like Ricoh and Mitsubishi. This limited functionality, allowing only a single color to be displayed for recording, has gradually failed to meet market demand for thermal paper capable of displaying multiple colors simultaneously for use as labels or records.

[0004] When a color-developing layer is directly added on the color-developing layer of monochrome thermal paper to make it two-color, the contact surface between the two color-developing layers will be unevenly coated, affecting the color-developing effect. In addition, the two-color color-developing effect of current technology is not clear, and there is interpenetration between the two colors. This phenomenon is more obvious on oil-based erasable paper.

[0005] Therefore, the technical solutions for two-color and multi-color erasable thermal paper have problems such as color interpenetration and unclear single-color display, making it difficult to apply effectively. Therefore, the development of two-color or multi-color erasable thermal paper with clear color display and multiple recycling capabilities is the current market demand. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a dual-color distinct erasable thermal paper and a preparation method thereof, so as to solve the problems of color interbleeding and unclear single-color display in the prior art.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] The present invention provides a dual-color distinct erasable thermal paper, comprising a first color thermal layer and a second color thermal layer, wherein an intermediate layer is provided between one side of the first color thermal layer and one side of the second color thermal layer;

[0009] The material of the intermediate layer includes resin and a thermal conductive additive, wherein the resin is at least one of PVA resin, PVB resin, PVP resin, and EVOH resin, and the thermal conductive additive is at least one of zinc oxide, magnesium oxide, and aluminum oxide.

[0010] On the basis of the above technical solution, the present invention can also be improved as follows.

[0011] Furthermore, the mass ratio of the resin to the thermal conductive additive is 1:0.5-1.5.

[0012] Furthermore, in the material of the intermediate layer, the components and their mass fractions are 50 parts of PVA resin and 50 parts of magnesium oxide.

[0013] Furthermore, the particle size of the thermal conductive agent is 0.1-0.5 μm.

[0014] Furthermore, the materials of the first color thermosensitive layer and the second color thermosensitive layer include hydroxy acrylic resin, a developer, a dye, polyisocyanate and a solvent; and the dyes in the first color thermosensitive layer and the second color thermosensitive layer are different in color.

[0015] Furthermore, the mass ratio of the developer to the dye is 2ˉ3:1, and the mass ratios of the developer to the dye in the materials of the first color thermosensitive layer and the second color thermosensitive layer are the same or different.

[0016] Furthermore, the thickness of the intermediate layer is 1-2 μm, the thickness of the first color thermosensitive layer and the second color thermosensitive layer is 6-10 μm, and the thickness of the first color thermosensitive layer and the second color thermosensitive layer are the same or different.

[0017] Furthermore, a protective layer is provided on the other side of the first color heat-sensitive layer, and the material of the protective layer includes epoxy resin and polyamide curing agent.

[0018] Furthermore, the material of the protective layer also includes at least two of the lubricants selected from silicon dioxide, talc, oleamide, erucamide, calcium stearate, and silicone.

[0019] The present invention also provides a method for preparing the above-mentioned two-color distinct erasable thermal paper, wherein the second color thermal layer, the intermediate layer, and the first color thermal layer are sequentially prepared on a substrate, and a protective layer is prepared on the first color thermal layer.

[0020] The beneficial effects of the present invention are:

[0021] (1) The dual-color erasable thermal paper of the present invention has an intermediate layer added between the first color thermal layer and the second color thermal layer to prevent color penetration during printing;

[0022] (2) The dual-color erasable thermal paper of the present invention can avoid the problem of uneven coating caused by direct contact between the two thermal layers by providing an intermediate layer, thereby improving the color development effect;

[0023] (3) The dual-color erasable thermal paper of the present invention can enhance the heat transfer efficiency between the coating layers by providing a heat-conducting auxiliary agent in the middle layer, thereby ensuring a better color development effect of the lower layer;

[0024] (4) The present invention provides a dual-color erasable thermal paper. The intermediate layer contains a heat-conducting auxiliary agent, which eliminates the need to add a heat-conducting auxiliary agent to the heat-sensitive layer. This ensures smooth thermal printing and uniformity of the heat-sensitive layer coating, thereby significantly improving the color development effect of thermal printing.

[0025] (5) The method for preparing the erasable thermal paper with distinct two colors of the present invention has simple steps and is easy to operate. The obtained thermal paper has a uniform coating and good printing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic structural diagram of the erasable thermal paper with distinct two colors according to the present invention;

[0027] Figure 2 This is the printing effect diagram of Example 1 of the erasable thermal paper with distinct two colors of the present invention;

[0028] Figure 3 This is the effect diagram after printing on the thermal paper of Comparative Example 1;

[0029] Figure 4 This is the effect diagram after printing on the thermal paper of Comparative Example 2.

[0030] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0031] 1. Protective layer; 2. First color thermal sensitive layer; 3. Intermediate layer; 4. Second color thermal sensitive layer; 5. Base material. DETAILED DESCRIPTION

[0032] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0033] like Figure 1 As shown, the two-color distinct erasable thermal paper of the present invention includes a first color thermal-sensitive layer 2 and a second color thermal-sensitive layer 4, and an intermediate layer 3 is provided between one side of the first color thermal-sensitive layer 2 and one side of the second color thermal-sensitive layer 4; the material of the intermediate layer 3 includes a resin and a thermal conductive additive, the resin is at least one of a water-soluble resin such as PVA resin, PVB resin, PVP resin, EVOH resin, etc., and the thermal conductive additive is at least one of a thermal conductive additive such as zinc oxide, magnesium oxide and aluminum oxide.

[0034] The erasable thermal paper with distinct two colors of the present invention has an intermediate layer 3 provided between the two thermal layers, so that when the two-color thermal paper is printed in two colors, there is no interbleeding between the two colors; this can significantly increase the color density of each color, and the single color is distinct, thereby effectively improving the color rendering effect of the two-color thermal paper when printing.

[0035] The present invention provides an intermediate layer, the composition of which contains a thermal conductive additive, so that there is no need to add a thermal conductive additive to the thermal layer. Since the thermal conductive additive is in the form of powder particles, adding a thermal conductive additive to the thermal layer will lead to a decrease in the coating uniformity of the thermal layer, which makes it difficult to apply a uniform coating during the preparation process. When the thermal layer is uneven, the color development effect will be very poor. However, the thermal conductive additive is an indispensable component in the thermal material. If the thermal conductive additive is simply reduced or not used, it will make thermal printing difficult. In the present invention, adding a thermal conductive additive to the material of the intermediate layer can reduce the influence of the intermediate layer 3 on heat transfer, which can not only ensure the smooth thermal printing, but also ensure the uniformity of the thermal layer coating, thereby greatly improving the color development effect of thermal printing.

[0036] Preferably, the resin and thermal conductive additive in the material of the intermediate layer 3 can ensure that the intermediate layer 3 has good thermal conductivity and prevents interlayer interpenetration.

[0037] Preferably, the mass ratio of the resin to the thermal conductive additive is 1:0.5ˉ1.5; this mass ratio can further ensure the thermal conductivity efficiency.

[0038] Preferably, the materials of the intermediate layer 3 include the following components and their mass fractions: 50 parts of PVA resin and 50 parts of magnesium oxide.

[0039] Preferably, the particle size of the thermal conductive agent is 0.1-0.5 μm; this particle size can fully exert the efficiency of the thermal conductive agent without affecting the coating thickness of the intermediate layer 3 .

[0040] Preferably, the materials of the first color thermosensitive layer 2 and the second color thermosensitive layer 4 include hydroxy acrylic resin, color developer, dye, polyisocyanate and solvent; and the dye colors in the first color thermosensitive layer 2 and the second color thermosensitive layer 4 are different; since the present invention provides an intermediate layer 3, there is no need to add thermal additives to the components of the two thermosensitive layers, so that the two thermosensitive layers can be coated more evenly and have higher color density and color rendering effect.

[0041] Preferably, the first color thermosensitive layer 2 and the second color thermosensitive layer 4 have different thermal sensing temperatures.

[0042] In the two heat-sensitive layers of the present invention, various dyes of different colors can be selected. In actual use, the colors of the two most widely used dyes are black and red.

[0043] Preferably, the mass ratio of the developer to the dye is 2ˉ3:1, and the mass ratios of the developer to the dye in the materials of the first color thermosensitive layer 2 and the second color thermosensitive layer 4 are the same or different.

[0044] The color developer can use any commercially available color developer, or a color developer as shown in formula (1):

[0045]

[0046] Wherein P=12ˉ37, and the molecular weight exceeds 500.

[0047] Preferably, in the first color thermosensitive layer 2 and the second color thermosensitive layer 4 , the color developer and the dye are collectively referred to as a color developing component, and the mass ratio of the color developing component to the pure resin is preferably 3:1.

[0048] Preferably, in the first color thermosensitive layer 2 and the second color thermosensitive layer 4, in order to ensure coating uniformity, the solid mass percentage in the coating liquid is preferably 30%.

[0049] Preferably, the thickness of the intermediate layer 3 is 1-2 μm. This thickness range can directly ensure that the first color thermosensitive layer 2 and the second color thermosensitive layer 4 do not bleed into each other, and can also facilitate coating and drying; the thickness of the first color thermosensitive layer 2 and the second color thermosensitive layer 4 is 6-10 μm, and the thickness of the first color thermosensitive layer 2 and the second color thermosensitive layer 4 are the same or different; the above thickness can enable the intermediate layer 3 to well isolate the two thermosensitive layers, and at the same time have a good thermal conductivity effect, so that the effect of thermal printing is significantly improved.

[0050] Preferably, a protective layer 1 is provided on the other side of the first color heat-sensitive layer 2, and the material package of the protective layer 1 is a cured epoxy resin; the resin selected for the protective layer 1 is dense and transparent after film formation, and has good air isolation and organic solvent resistance.

[0051] Preferably, the thickness of the protective layer 1 is 1-2 μm.

[0052] Preferably, a substrate 5 is provided on the other side of the second color heat-sensitive layer 4. The substrate 5 can be made of various commonly used materials. More preferably, the substrate 5 is coated paper, PET, or PVC.

[0053] Preferably, the thickness of the substrate 5 is 100-140 μm.

[0054] The method for preparing the dual-color distinct erasable thermal paper of the present invention comprises sequentially preparing a second color thermal layer 4, an intermediate layer 3, and a first color thermal layer 2 on a substrate 5, and preparing a protective layer 1 on the first color thermal layer 2.

[0055] Specifically, the following steps are included:

[0056] The coating liquid for the second color heat-sensitive layer 4 , the coating liquid for the first color heat-sensitive layer 2 , the coating liquid for the intermediate layer 3 , and the coating liquid for the protective layer 1 are prepared separately.

[0057] The coating liquid for the second color heat-sensitive layer 4 is applied to the substrate 5 and cured to obtain the second color heat-sensitive layer 4. The coating liquid for the intermediate layer 3 is applied to the second color heat-sensitive layer 4 and dried to obtain the intermediate layer 3. The coating liquid for the first color heat-sensitive layer 2 is applied to the intermediate layer 3 and further cured to obtain the first color heat-sensitive layer 2. The coating liquid for the protective layer 1 is applied to the first color heat-sensitive layer 2 and cured to obtain a distinct two-color erasable thermal paper.

[0058] In the above preparation process, the specific coating method, curing and drying conditions can all adopt conventional operations.

[0059] The preparation method of the present invention has simple steps, mild conditions, and each layer has good uniformity.

[0060] The present invention is described in detail below through specific examples and comparative examples.

[0061] Example 1

[0062] In this embodiment, the method of the present invention is used to prepare erasable thermal paper with distinct two colors. The layer structure of the paper is as follows from top to bottom: a protective layer 1, a first color thermal-sensitive layer 2, an intermediate layer 3, a second color thermal-sensitive layer 4, and a substrate 5. The first color thermal-sensitive layer 2 is a red thermal-sensitive layer, and the second color thermal-sensitive layer 4 is a black thermal-sensitive layer.

[0063] In this embodiment, the material of the protective layer 1 includes the following specific components in parts by weight: 75 parts of epoxy resin adhesive resin, 50 parts of curing agent, and 5 parts of lubricant. The thickness of the protective layer 1 is 1.5 μm.

[0064] In this embodiment, the material of the red heat-sensitive layer includes the following specific components by weight: 24 parts of developer, 12 parts of red heat-sensitive dye, 12 parts of hydroxy acrylic resin, and 2 parts of polyisocyanate curing agent. The thickness of the red heat-sensitive layer is controlled to be 6-8 μm; the developer is the developer shown in formula (1), and P is 28

[0065] In this embodiment, the material of the intermediate layer 3 includes the following specific components in parts by weight: 5 parts of PVA resin and 5 parts of magnesium oxide powder. The thickness of the intermediate layer 3 is 1.5 μm.

[0066] In this embodiment, the material of the black thermosensitive layer includes the following specific components in parts by weight: 24 parts of a color developer, 8 parts of a black thermosensitive dye, 11 parts of a hydroxy acrylic resin, 2 parts of a polyisocyanate curing agent, and 6 parts of a magnesium oxide filler, with a thickness of 9 μm; the color developer is the color developer shown in formula (1), and P is 28.

[0067] In this embodiment, the substrate 5 is PVC with a thickness of 120 μm.

[0068] The preparation method of this embodiment is:

[0069] Prepare the coating solutions for the red heat-sensitive layer, the black heat-sensitive layer, the intermediate layer 3, and the protective layer 1 separately. Apply the black heat-sensitive layer coating solution to substrate 5 and cure to obtain the black heat-sensitive layer. Apply the intermediate layer 3 coating solution to the black heat-sensitive layer and dry to obtain the intermediate layer 3. Apply the red heat-sensitive layer coating solution to the intermediate layer 3 and continue curing to obtain the red heat-sensitive layer. Apply the protective layer 1 coating solution to the red heat-sensitive layer and cure to obtain the dual-color erasable thermal paper of this embodiment.

[0070] Example 2

[0071] The material of the intermediate layer 3 of this embodiment includes the following specific components in parts by weight: 7.5 parts of PVA resin and 2.5 parts of magnesium oxide powder. Other components are the same as those in Example 1.

[0072] Example 3

[0073] The material of the intermediate layer 3 of this embodiment includes the following specific components in parts by weight: 8.75 parts of PVA resin and 1.25 parts of magnesium oxide powder. Other components are the same as those in Example 1.

[0074] Example 4

[0075] The thickness of the intermediate layer 3 in this embodiment is 5 μm, and the rest is the same as in the first embodiment.

[0076] Example 5

[0077] The thickness of the intermediate layer 3 in this embodiment is 9 μm, and the rest is the same as in the first embodiment.

[0078] Example 6

[0079] The material of the intermediate layer 3 of this embodiment includes the following specific components by weight: 5 parts of EVOH resin and 5 parts of aluminum oxide powder. The thickness of the intermediate layer 3 is 1 μm. Other components are the same as those of the embodiment 1.

[0080] Example 7

[0081] The materials for the intermediate layer 3 of this embodiment include the following components by weight: 2.5 parts PVP resin, 2.5 parts EVOH resin, 2.5 parts zinc oxide powder, and 2.5 parts magnesium oxide powder. The thickness of the intermediate layer 3 is 2 μm. Other components are the same as those in Example 1.

[0082] Comparative Example 1

[0083] The erasable thermal paper with distinct two colors in this comparative example is based on Example 1, but does not have the intermediate layer 3 .

[0084] Comparative Example 2

[0085] The erasable thermal paper with distinct two colors in this comparative example is based on Example 2, but does not include the intermediate layer 3 .

[0086] Comparative Example 3

[0087] The erasable thermal paper with distinct two colors in this comparative example is based on Example 1. In the material of the intermediate layer 3, the particle size of the thermal conductive additive is 1 μm, and the rest is the same as Example 1.

[0088] The thermal papers obtained in the above examples and comparative examples were subjected to printing and erasure tests. Specifically, the steps were as follows: printing on a Zebra printer with a red print density of 10 and a black print density of 30; after printing, the colors were observed for bleeding. The color densities before and after erasure are shown in Table 1 below:

[0089] Table 1 Printing color density and erasure efficiency of erasable thermal paper of embodiment and comparative example

[0090]

[0091] The bleeding phenomenon of each thermal paper obtained in the above examples and comparative examples was observed after printing. The situation of the erasable thermal paper of Example 1 after printing was as follows: Figure 2 As shown, the thermal paper of Comparative Examples 1 and 2 is printed as shown in FIG. Figure 3 and 4 shown.

[0092] according to Figure 2 As can be seen in Figure 4, the pattern printed on the thermal paper of Example 1 exhibits no bleeding, with distinct red and black colors and a moderately improved color density. The thermal paper of Examples 2 and 5 achieves similar results (not shown). The thermal papers of Comparative Examples 1 and 2 both exhibit color bleeding after printing, with the red and black colors appearing similar and unclear.

[0093] In summary, by adding the intermediate layer 3 between the red and black heat-sensitive coatings, the color interpenetration phenomenon can be effectively solved and the color density of the color can be improved.

[0094] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0095] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0096] In the present invention, unless otherwise expressly specified or limited, when a first feature is "above" or "below" a second feature, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. Furthermore, when a first feature is "above," "above," or "above" a second feature, it may mean that the first feature is directly above or diagonally above the second feature, or simply means that the first feature is at a higher level than the second feature. When a first feature is "below," "below," or "below" a second feature, it may mean that the first feature is directly below or diagonally below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0097] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A two-color distinct erasable thermal paper, comprising a first color thermal layer (2) and a second color thermal layer (4), characterized in that: An intermediate layer (3) is provided between one side of the first color heat-sensitive layer (2) and one side of the second color heat-sensitive layer (4); The material of the intermediate layer (3) includes resin and a thermal conductive additive, and the resin is at least one of PVA resin, PVB resin, PVP resin, and EVOH resin.

2. The dual-color erasable thermal paper according to claim 1, characterized in that: The thermal conductive additive is at least one of zinc oxide, magnesium oxide and aluminum oxide.

3. The erasable thermal paper with distinct two colors according to claim 2, characterized in that: The mass ratio of the resin to the thermal conductive additive is 1:0.5-1.

5.

4. The erasable thermal paper with distinct two colors according to claim 1, characterized in that: The particle size of the thermal conductive agent is 0.1-0.5 μm.

5. The erasable thermal paper with distinct two colors according to claim 1, characterized in that: The materials of the first color thermosensitive layer (2) and the second color thermosensitive layer (4) include polyurethane, a color developer, and a dye; and the colors of the dyes in the first color thermosensitive layer (2) and the second color thermosensitive layer (4) are different.

6. The erasable thermal paper with distinct two colors according to claim 5, characterized in that: The mass ratio of the developer to the dye is 2ˉ3:

1.

7. The dual-color erasable thermal paper according to any one of claims 1 to 6, characterized in that: The thickness of the intermediate layer (3) is 1-2 μm, and the thickness of the first color thermosensitive layer (2) and the second color thermosensitive layer (4) are respectively 6-10 μm.

8. The dual-color erasable thermal paper according to any one of claims 1 to 6, characterized in that: A protective layer (1) is provided on the other side of the first color heat-sensitive layer (2), and the material of the protective layer (1) includes epoxy resin and polyamide curing agent.

9. The erasable thermal paper with distinct two colors according to claim 8, characterized in that: The material of the protective layer (1) further comprises at least two of the lubricants silicon dioxide, talc, oleamide, erucamide, calcium stearate, and silicone.

10. A method for preparing the dual-color erasable thermal paper according to any one of claims 1 to 9, characterized in that: The second color heat-sensitive layer (4), the intermediate layer (3), and the first color heat-sensitive layer (2) are sequentially prepared on a substrate (5), and a protective layer (1) is prepared on the first color heat-sensitive layer (2).

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