JP2012082318A - Ultraviolet-curable ink for stencil printing, and stencil printing method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultraviolet-curable ink for stencil printing, which is suitable for stencil printing of a rotary printing type, and can raise glossiness of a printing part; and to provide a stencil printing method using the same.SOLUTION: The ultraviolet-curable ink for stencil printing is composed as a non-aqueous base. The viscosity η (Pa s) at 20°C of the ink is in the range of 1.5-20,000 on condition that the shear rate γ (1-/s) is 0.01, and is in the range of 0.5-20 on condition that the shear rate γ (1-/s) is 100. Moreover, the viscosity η (Pa s) at 55°C of the ink is in the range of 0.5-1,500 on condition that the shear rate γ(1-/s) is 0.01, and is in the range of 0.2-8 on condition that the shear rate γ(1-/s) is 100. The stencil printing method is characterized as follows. After heating the surface where the ultraviolet-curable ink for stencil printing in a matter to be printed has been transferred in the range of 50°C-75°C, ultraviolet is emitted onto the transferred surface.

Description

  The present invention relates to an ultraviolet curable ink for stencil printing used for rotary stencil printing, and a stencil printing method using the same.

  2. Description of the Related Art Conventionally, rotary stencil printing in which ink is transferred to a printing material through a stencil sheet from a drum on which the stencil sheet is mounted is known. As inks used for rotary stencil printing, emulsion inks, solvent inks, and ultraviolet curable inks are known. For example, Patent Document 1 proposes an emulsion ink having a predetermined rheological characteristic used for rotary stencil printing.

JP 2004-244597 A

  Since the emulsion ink used in the rotary stencil printing is dried by permeation into the printing material, the printability of the emulsion ink depends on the permeability of the ink in the printing material. In this regard, the printability of the non-aqueous ultraviolet curable ink has an advantage that it is difficult to depend on the permeability of the ink in the printed material. In addition, when solvent-type ink is used in rotary stencil printing, if the stencil printing apparatus is stopped, the ink is cured on the outer surface or inside of the printing drum due to volatilization of the solvent. For this reason, it is necessary to clean the printing drum after the printing is completed. In this respect, since the non-aqueous ultraviolet curable ink is difficult to cure while the stencil printing apparatus is stopped, the frequency of cleaning the printing drum can be reduced. Further, the curing of the non-aqueous ultraviolet curable ink with ultraviolet rays has a shorter curing time than the curing through drying of the emulsion ink, for example. Therefore, printing using a non-aqueous ultraviolet curable ink has an advantage that the efficiency can be increased.

  As described above, the non-aqueous ultraviolet curable ink has advantages over the emulsion ink and the solvent ink, but has the following problems. That is, since the non-aqueous ultraviolet curable ink has a short curing time as described above, it is easy to be cured in a state where the unevenness of the stencil sheet and the pattern of the outer peripheral surface of the drum are transferred. As a result, in the printed matter, the surface smoothness is lowered, so that it is difficult to obtain the gloss of the surface of the printed portion. However, although the surface smoothness tends to be improved by reducing the viscosity of the non-aqueous UV-curable ink, the ink tends to leak through the stencil paper when printing is stopped. May not be suitable for stencil printing.

  An object of the present invention is to provide an ultraviolet curable ink for stencil printing which is suitable for rotary stencil printing and which can increase the gloss of a printed part, and a stencil printing method using the same.

  In order to achieve the above object, the ultraviolet curable ink for stencil printing according to the first aspect of the present invention is used for rotary stencil printing in which ink is transferred from a drum equipped with a stencil sheet to a printing material through the stencil sheet. It is an ultraviolet curable ink for stencil printing that is used as a non-aqueous ink and has a viscosity η (Pa · s) at 20 ° C. of 1.5 to 1.5 under the condition of shear rate γ (1 / s) = 0.01. It is in the range of 20000 and in the range of 0.5 to 20 under the condition of shear rate γ (1 / s) = 100, and the viscosity η (Pa · s) at 55 ° C. is the shear rate γ (1 / s) It is summarized that it is in the range of 0.5 to 1500 under the condition of = 0.01 and in the range of 0.2 to 8 under the condition of the shear rate γ (1 / s) = 100.

  The invention according to claim 2 is the ultraviolet curable ink for stencil printing according to claim 1, wherein the viscosity η (Pa · s) at 20 ° C. is a shear rate γ (1 / s) = 0.01. The range is 4 to 12000 and the shear rate γ (1 / s) = 100. The range is 0.5 to 18 and the viscosity η (Pa · s) at 55 ° C. is the shear rate γ (1 /S)=0.01 in the range of 0.8 to 500 and the range of 0.2 to 5 in the condition of shear rate γ (1 / s) = 100.

  Invention of Claim 3 is a stencil printing method which performs the said stencil printing using the ultraviolet curable ink for stencil printing of Claim 1 or Claim 2, Comprising: The ultraviolet for said stencil printing in the said to-be-printed material The gist is to irradiate the transferred surface with ultraviolet rays after heating the surface to which the curable ink has been transferred in a range of 50 ° C to 75 ° C.

  According to the present invention, there are provided an ultraviolet curable ink for stencil printing and a stencil printing method which are suitable for rotary stencil printing and can increase the gloss of a printed part.

The flowchart which shows the stencil printing method in embodiment. Schematic which shows a stencil printing apparatus.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments embodying the present invention will be described in detail.
The ultraviolet curable ink for stencil printing is used for rotary stencil printing in which ink is transferred from a drum equipped with a stencil sheet to a printing material through the stencil sheet.

  The ultraviolet curable ink for stencil printing is configured as a non-aqueous system. The viscosity η (Pa · s) at 20 ° C. of the ultraviolet curable ink for stencil printing is 1.5 to 20000 under the condition of shear rate γ (1 / s) = 0.01 (hereinafter referred to as “condition A”). And a range of 0.5 to 20 under the condition of shear rate γ (1 / s) = 100 (hereinafter referred to as “condition B”). The viscosity η (Pa · s) at 55 ° C. of the ultraviolet curable ink for stencil printing is 0.5 to 1500 under the condition of shear rate γ (1 / s) = 0.01 (hereinafter referred to as “condition C”). And a range of 0.2 to 8 under the condition of shear rate γ (1 / s) = 100 (hereinafter referred to as “condition D”).

  When the viscosity η (Pa · s) in Condition A is 1.5 or more, ink leakage from the drum can be suppressed when printing is stopped. On the other hand, when the viscosity η (Pa · s) in Condition A exceeds 20000, the resistance when ink passes through the stencil sheet from the inside of the drum increases, and printing unevenness is likely to occur.

When the viscosity η (Pa · s) in Condition B is in the range of 0.5 to 20, suitability for rotary stencil printing is easily obtained.
When the viscosity η (Pa · s) in condition C is 0.5 or more and the viscosity η (Pa · s) in condition D is 0.2 or more, the outline of the printed portion becomes unclear. This can be suppressed. On the other hand, when the viscosity η (Pa · s) under condition C is 1500 or less and the viscosity η (Pa · s) under condition D is 8 or less, the gloss of the printed surface can be increased.

  In the UV curable ink for stencil printing, the viscosity η (Pa · s) of the condition A is in the range of 4 to 12000 and the viscosity η (Pa · s) of the condition B is in the range of 0.5 to 18. The viscosity η (Pa · s) of the condition C is preferably in the range of 0.8 to 500, and the viscosity η (Pa · s) of the condition D is preferably in the range of 0.2 to 5. In this case, the gloss of the printed part is increased and suitability for rotary stencil printing is further easily obtained.

  The viscosity of the UV curable ink for stencil printing with respect to the shear rate can be measured with a stress-controlled rheometer. The viscosity with respect to the specific shear rate is obtained from the approximate equation below after obtaining the following approximate equation from the measured value of the viscosity η (Pa · s) when the shear rate γ (1 / s) is in the range of 0.01 to 100. This is a calculated value.

Approximate expression: η = A × γ ⁿ
(However, A is a positive constant, and n is a negative constant.)
The ultraviolet curable ink for stencil printing described above includes an ultraviolet curable resin, an ultraviolet polymerization initiator, and a gelling agent.

  As the ultraviolet curable resin, a monomer or oligomer of (meth) acrylic acid is preferably used. Specific examples of the UV curable resin include cyclohexyl acrylate, tetrahydrofurfuryl acrylate, dipentaerythritol hexaacrylate, trimethylolpropane acrylate, dimethyloltricyclodecane diacrylate, dimethylaminoethyl methacrylate, 2-hydroxy-3-phenoxypropyl acrylate. , Trimethylolpropane triacrylate, propylene glycol diacrylate, nonylphenol propylene oxide (PO) modified acrylate, ethylene oxide (EO) modified trimethylolpropane triacrylate, amine modified polyether acrylate, caprolactone modified tetrahydrofurfuryl acrylate and urethane acrylate oligomer , Vinyl ester oligomers , And a polyester acrylate oligomer.

  Only one type of ultraviolet curable resin may be used, or two or more types of ultraviolet curable resins may be used in combination. The ultraviolet curable resin is not limited to those exemplified as specific examples, and can be appropriately selected in consideration of viscosity characteristics, compatibility with a gelling agent, and the like.

  The content of the ultraviolet curable resin in the ultraviolet curable ink for stencil printing is preferably 60 to 95% by mass, more preferably 70 to 95% by mass, and still more preferably 80 to 95% by mass.

  Examples of the ultraviolet polymerization initiator include 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and 2-methyl-1- [4- (methylthio) phenyl. ] -2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2-hydroxy-1- {4- [4- (2-hydroxy-2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propan-1-one and the like.

Only one type of ultraviolet polymerization initiator may be used, or two or more types of ultraviolet polymerization initiators may be used in combination.
The content of the ultraviolet polymerization initiator in the ultraviolet curable ink for stencil printing is preferably 1 to 20% by mass.

  The gelling agent has a function of adjusting the rheological properties of the ultraviolet curable ink for stencil printing. Examples of the gelling agent include castor oil, 12-hydroxystearic acid, sebacic acid, dibenzylidene-D-sorbitol, hydroxystearic acid ester wax, and hydroxy fatty acid amide. Examples of the hydroxy stearic acid ester wax include stearyl-12-hydroxystearate and methyl-12-hydroxystearate. Examples of the hydroxy fatty acid amide include N-hydroxyethyl-12-hydroxystearylamide.

Only one type of gelling agent may be used, or two or more types of gelling agents may be used in combination.
The content of the gelling agent in the ultraviolet curable ink for stencil printing is preferably 0.1 to 5% by mass.

  The ultraviolet curable ink for stencil printing may contain a colorant as required. In the case where no colorant is contained, that is, when the ultraviolet curable ink for stencil printing is configured as a clear ink, for example, a three-dimensional effect and gloss can be imparted to the printing material.

  Known pigments and dyes can be used as the colorant. Examples of the pigment include insoluble azo pigments, azo lake pigments, condensed azo pigments, diketopyrrolopyrrole pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, isoindoline pigments, anthraquinone pigments, dioxazines. Organic pigments such as pigments, indigo pigments, thioindigo pigments, quinophthalone pigments, perinone and perylene pigments, inorganic pigments such as iron oxide, carbon black, titanium oxide, cadmium red, chrome yellow, cadmium yellow, ultramarine blue, and bitumen Is mentioned. Further, organic or inorganic fluorescent pigments may be used. Examples of the dye include acid dyes, basic dyes, metal complex dyes, salt-forming dyes, azine dyes, anthraquinone dyes, phthalocyanine dyes, and triphenylmethane dyes.

  Only one type of colorant may be used, or two or more colorants may be used in combination. In addition, it is preferable that the particle size of the colorant is 10 μm or less from the viewpoint of improving the gloss of the printed part and the passability of the stencil sheet.

When a colorant is contained in the ultraviolet curable ink for stencil printing, it is preferable to further contain a dispersant from the viewpoint of enhancing the dispersibility.
As the dispersant, for example, known low molecular surfactants, polymer surfactants, and resin dispersants can be used. Among these dispersants, rosin resins and alkyd resins are preferably used. Only one type of dispersant may be used, or two or more types of dispersants may be used in combination.

  The ultraviolet curable ink for stencil printing may contain a polymer material, an oil component, and the rheology modifier as necessary. Examples of the polymer material include acrylic resins, cellulose resins, urethane resins, vinyl resins, and polyester resins.

  Examples of the oil component include vegetable oils and petroleum oils. Examples of vegetable oils include soybean oil, castor oil, tall oil, and rapeseed oil. Examples of petroleum oils include paraffinic oils and naphthenic oils.

  Examples of the rheology modifier include bentonite, silica, clay, white carbon, precipitated barium sulfate, aluminum silicate, and kaolin. The rheology modifier may be configured as an extender pigment.

The ultraviolet curable ink for stencil printing can further contain an antifoaming agent, a wetting agent, a leveling agent, and a repellency inhibitor.
The substrate to be printed using the ultraviolet curable ink for stencil printing is not particularly limited, and examples thereof include paper products such as coated paper and art paper, resin products, and metal products.

Next, a stencil printing method using ultraviolet curable ink for stencil printing will be described.
FIG. 1 shows the flow of the stencil printing method. In the transfer step, the ultraviolet curable ink for stencil printing is transferred from the inside of the drum to the printing material through the stencil sheet (step 1). In this transfer step, the temperature of the UV curable ink for stencil printing through the stencil sheet is preferably in the range of 5 ° C to 40 ° C, and preferably 15 ° C to 35 ° C, from the viewpoint of sufficiently exhibiting the ink characteristics. More preferably, it is the range of 20 to 30 degreeC. When the temperature is less than 5 ° C., there is a risk that uneven printing is likely to occur. On the other hand, when it exceeds 40 degreeC, there exists a possibility that the outline of a printing part may become unclear easily.

  Next, in the heating step, the surface of the substrate to which the ultraviolet curable ink for stencil printing is transferred (hereinafter referred to as a transfer surface) is heated to a range of 50 ° C. to 75 ° C. (Step 2). Here, the viscosity η at 55 ° C. of the ultraviolet curable ink for stencil printing is defined as described above. For this reason, the surface of the ultraviolet curable ink for stencil printing on the printing material becomes smooth due to the fluidity of the ink and the excessive flow is suppressed by the heating process.

  Subsequently, in the ultraviolet irradiation step, ultraviolet rays are irradiated on the surface of the printing material to which the ultraviolet curable ink for stencil printing is transferred (step 3). By this ultraviolet irradiation process, the ultraviolet curable ink for stencil printing is cured and fixed to the substrate.

  FIG. 2 shows an outline of the stencil printing apparatus. The stencil printing apparatus includes a stencil printing machine 11, a heating device 12, and an ultraviolet irradiation device 13. As the stencil printing machine 11, for example, a known rotary stencil printing machine such as an ink roller type or a squeegee blade type can be used. A rotary stencil printing machine is disclosed in, for example, Japanese Unexamined Patent Application Publication Nos. 2009-000940, 2009-018564, and 2001-030604. The outer periphery of the drum of such a stencil printing machine 11 is formed by a mesh-like support so that UV curable ink for stencil printing can flow out from the inside of the drum to the outer peripheral surface of the drum. A mesh-like sheet, that is, a screen is laminated on the outer peripheral surface of the drum as necessary.

  As the stencil paper (stencil-made base paper) to be mounted on the drum, for example, a well-known paper obtained by hand-made plate making, heat-sensitive plate making, and photosensitive plate making can be used. Such stencil paper generally has a stencil layer and a support layer that is reinforced by supporting it. For example, the stencil layer of the stencil sheet obtained by thermal plate making is composed of, for example, a polyester-based thermoplastic film, and the support layer of the stencil sheet is made of, for example, a thin paper mixed with natural fibers and synthetic fibers, or synthetic fibers And a mesh sheet of polyester or polyamide. Among these support layers, for example, a mesh-like sheet of about 120 to 300 mesh is preferable because of the good ink permeability.

  The heating device 12 heats the transfer surface of the printing material in a range of 50 ° C to 75 ° C. Examples of the heating source of the heating device 12 include an infrared lamp, a steam pipe, and hot air. However, it is easy to maintain the cleanliness of the surface to which the ultraviolet curable ink for stencil printing is transferred. An infrared lamp is preferable. The heating device 12 can be provided with a conveyance unit for carrying in and carrying out the printing material.

  The ultraviolet irradiation device 13 includes an ultraviolet lamp, and irradiates the transfer surface with ultraviolet rays generated by the ultraviolet lamp. Examples of the ultraviolet lamp include a high-pressure mercury lamp and a metal halide lamp. The ultraviolet irradiation device 13 can be provided with a transport unit that carries in the printed material and carries out the printed material. As a conveyance part of the said heating apparatus 12, and a conveyance part of the ultraviolet irradiation device 13, a belt conveyor and a roller for conveyance are mentioned, for example.

According to the embodiment described in detail above, the following effects are exhibited.
(1) The viscosity η (Pa · s) of the condition A of the ultraviolet curable ink for stencil printing is in the range of 1.5 to 20000, and the viscosity η (Pa · s) of the condition B is 0.5 to A range of 20. Further, the viscosity η (Pa · s) of the condition C of the ultraviolet curable ink for stencil printing is in the range of 0.5 to 1500, and the viscosity η (Pa · s) of the condition D is 0.2 to 8 Range. Thereby, the gloss of a printing part can be improved. Further, ink leakage from the drum can be suppressed when printing is stopped. Further, for example, it is possible to suppress the occurrence of printing unevenness and blurring and the blurring of the outline of the printed portion. Thus, according to the above configuration, an ultraviolet curable ink for stencil printing that is suitable for rotary stencil printing and can increase the gloss of the printed portion is provided.

  (2) The viscosity η (Pa · s) of the condition A of the ultraviolet curable ink for stencil printing is in the range of 4 to 12000 and the viscosity η (Pa · s) of the condition B is in the range of 0.5 to 18. The viscosity η (Pa · s) of the condition C is preferably in the range of 0.8 to 500, and the viscosity η (Pa · s) of the condition D is preferably in the range of 0.2 to 5. In this case, the gloss and printability of the printed part can be further enhanced.

  (3) In the stencil printing method, the transfer surface is heated in the range of 50 ° C to 75 ° C. Next, the transfer surface is irradiated with ultraviolet rays. According to this method, the performance of the ultraviolet curable ink for stencil printing can be exhibited sufficiently.

Next, the technical idea that can be grasped from the above embodiment will be described below.
(A) The stencil printing method according to claim 3, wherein the temperature of the ultraviolet curable ink for stencil printing through the stencil sheet is in the range of 5 ° C to 40 ° C.

  (B) The stencil printing method according to claim 3 or (a), wherein the transferred surface is heated by an infrared lamp.

Next, the embodiment will be specifically described with reference to examples, comparative examples, and test examples.
In each example and each comparative example, an ultraviolet curable ink for stencil printing having the viscosity values shown in Table 1 under conditions A to D was prepared.

インクの粘度の測定の詳細は、以下のとおりである。

Details of the measurement of the viscosity of the ink are as follows.

Measuring device: Stress-controlled rheometer (CSL100: manufactured by Carri-Med)
Measurement conditions: Flow curve Cone: φ40mm, Gap 49μm
In the measurement of the viscosity, the pre-shear was added to the ink before the measurement at 50 Pa for 1 minute, and then left for 5 minutes, and then the measurement was started. The shear rate was 0.01 to 100 (1 / s), and the viscosity at 20 ° C. and 55 ° C. was measured while increasing the shear stress from 1 Pa to 300 Pa under the condition of 100 Pa / min. And the viscosity of conditions AD was computed from the approximate formula mentioned above.

  Table 2 shows the composition of the ultraviolet curable ink for stencil printing in each example.

表２中に示される“モノマー”の詳細は以下のとおりである。

Details of the “monomer” shown in Table 2 are as follows.

Monomer 1 is dimethylol tricyclodecane diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: Light acrylate DCP-A).
Monomer 2 is tripropylene glycol diacrylate (manufactured by Toagosei Co., Ltd., trade name: Aronix M-220).

Monomer 3 is trimethylolpropane triacrylate (manufactured by Toagosei Co., Ltd., trade name: Aronix M-309).
Monomer 4 is dipentaerythritol hexaacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: Light acrylate DPE-6A).

“Oligomer” shown in Table 2 is a non-yellowing type oligourethane acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: urethane acrylate UF8001G).
“Polymer” shown in Table 2 is a thermoplastic acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd., trade name: Dianar BR105).

The “gelling agent” shown in Table 2 is 12-hydroxystearic acid.
The “extreme pigment” shown in Table 2 is finely divided silica.
The “additive” shown in Table 2 is an antifoaming agent.

Details of the “photopolymerization initiator” shown in Table 2 are as follows.
Photopolymerization initiator 1 is IRGACURE 184 (trade name) manufactured by BASF Japan.

Photopolymerization initiator 2 is IRGACURE907 (trade name) manufactured by BASF Japan.
<Evaluation of UV curable ink for stencil printing>
(Printing conditions)
Printing was performed using the ultraviolet curable ink for stencil printing of each example. As a stencil printing machine used in the transfer process, Duploter DP-440 (trade name) manufactured by Duplo Co., Ltd. was used. The screen mounted on the drum of the stencil printing machine was removed, and the stencil paper was mounted on the drum. As the stencil paper, a thermal screen base paper (manufactured by Asia Base Paper Co., Ltd., a base paper with a 120 mesh mesh-like sheet as a supporting layer) made by Duplo DP-440 (trade name) made by Duplo Corporation is used. It was. Coated paper was used as the substrate. The temperature of the ink in the transfer process is room temperature (25 ° C.).

  In the heating step, the transfer surface was heated to 55 ° C. with warm air using a dryer (power consumption: 1200 W). The temperature of the transfer surface was measured with a non-contact handy type surface thermometer manufactured by TASCO JAPAN.

As an ultraviolet irradiation device, a UV irradiation device using a 1.5 kW mercury lamp (UV device “model UE 0151-225.04C” manufactured by Eye Graphics Co., Ltd.) and a power supply device “UBX01. 51-3L1 ") was used. In this ultraviolet irradiation step, the ink was cured by adjusting the integrated irradiation amount to 90 mJ / cm ² .

(Evaluation of ink leakage)
The presence or absence of ink leakage from the drum was visually confirmed before starting printing immediately after the ink was supplied to the drum and after leaving the stencil printing machine in a room temperature (25 ° C.) environment for 24 hours. In Table 3, a case where ink did not leak from the drum was judged good (◯), and a case where ink leak was confirmed from the drum was judged as impossible (×). The results are shown in Table 3.

(Evaluation of uneven printing and fading)
Regarding the printed matter at the start of printing, the printing unevenness and faint state of the solid printing portion were visually confirmed. Furthermore, after leaving the stencil printing machine in a room temperature (25 ° C.) environment for 24 hours, printing was performed in the same manner, and the printing unevenness and faint state of the solid printing portion were visually confirmed. Based on the confirmed results, printing unevenness and fading were evaluated according to the following evaluation criteria.

The evaluation criteria are as follows.
Excellent (◎): There is no printing unevenness and fading, and printing can be performed uniformly.
Good (O): Although there is some printing unevenness, there is no fading and printing is almost uniform.

Inferior (Δ): There is printing unevenness and part of printing is faint.
Impossible (x): printing unevenness is large, and the whole printing is faint.
The evaluation results are shown in Table 3.

(Evaluation of print definition)
Regarding the printed matter at the start of printing, the gloss of the printed surface and the sharpness of the stroke were visually confirmed. Further, after leaving the stencil printing machine for 24 hours in an environment of room temperature 25 ° C., printing was performed in the same manner, and the gloss of the printed surface and the sharpness of the characters were visually confirmed. Based on the confirmed results, the print definition was evaluated according to the following evaluation criteria.

Excellent (◎): Excellent print surface gloss, sharp print, no difference from the original.
Good (O): The printed surface is glossy, the print is sharp, and no significant difference from the original is recognized.

Inferior (Δ): The glossiness of the printed surface is low, and the characters are slightly broken and inferior to the original.
Impossible (×): There is no gloss on the printed surface, and the strokes are distorted and cannot be read.

  The results are shown in Table 3.

各実施例では、２４時間後であっても、インクの漏れ、印刷ムラ及びかすれ、並びに印刷鮮明度の評価のいずれも優れる又は良好であった。

In each Example, even after 24 hours, ink leakage, uneven printing and blurring, and evaluation of print definition were all excellent or good.

In Comparative Examples 1 to 3, the evaluation of ink leakage was good, but the printing unevenness and blurring, and the evaluation of printing definition were not possible.
In Comparative Examples 4 and 5, the ink leakage and the evaluation of printing unevenness and blurring were all good, but the evaluation of printing definition was not possible.

  In Comparative Examples 6 to 8, although ink leakage evaluation before the start of printing was good, ink leakage occurred when the stencil printing machine was left for 1 hour. Further, in Comparative Examples 6 to 8, the printing unevenness and blurring, and the evaluation of the print definition were inferior to each example or impossible.

In Comparative Examples 9 and 10, ink leakage and evaluation of printing unevenness and blurring are all good, but the print definition is inferior to each example.
<Change of heating process>
As shown in Table 4, in Test Examples 1 to 15, using the ultraviolet curable ink for stencil printing of Examples 1 to 15, the heating temperature in the heating step was 40 ° C., 50 ° C., and 75 ° C. Changed to temperature. Other than that, it printed similarly to said printing conditions, and evaluated said print definition. The results are shown in Table 4.

表４に示される各試験例の結果から、各実施例の孔版印刷用紫外線硬化型インクは、加熱工程において転写面を５０℃〜７５℃に加熱することで、印刷鮮明度、すなわち、印刷面の光沢、及び字画の鮮明度合いのいずれも良好な印刷物が得られることが分かる。

From the results of each test example shown in Table 4, the UV curable ink for stencil printing of each example is printed with a sharpness, that is, a printing surface by heating the transfer surface to 50 ° C. to 75 ° C. in the heating step. It can be seen that a good printed matter can be obtained in both the glossiness of the image and the sharpness of the stroke.

Claims (3)

An ultraviolet curable ink for stencil printing used in rotary stencil printing for transferring ink from a drum equipped with a stencil sheet to a printing material through the stencil sheet,
Configured as non-aqueous,
The viscosity η (Pa · s) at 20 ° C. is in the range of 1.5 to 20000 under the condition of shear rate γ (1 / s) = 0.01, and the condition of shear rate γ (1 / s) = 100. In the range of 0.5-20,
The viscosity η (Pa · s) at 55 ° C. is in the range of 0.5 to 1500 under the condition of shear rate γ (1 / s) = 0.01, and the condition of shear rate γ (1 / s) = 100. An ultraviolet curable ink for stencil printing, characterized by being in the range of 0.2-8. The viscosity η (Pa · s) at 20 ° C. is in the range of 4 to 12000 under the condition of shear rate γ (1 / s) = 0.01 and 0 under the condition of shear rate γ (1 / s) = 100. In the range of 5-18,
The viscosity η (Pa · s) at 55 ° C. is in the range of 0.8 to 500 under the condition of shear rate γ (1 / s) = 0.01 and at the condition of shear rate γ (1 / s) = 100. The ultraviolet curable ink for stencil printing according to claim 1, wherein the ultraviolet curable ink is in a range of 0.2 to 5. A stencil printing method for performing the stencil printing using the ultraviolet curable ink for stencil printing according to claim 1 or 2,
A stencil printing method, comprising: heating a surface of the substrate to which the ultraviolet curable ink for stencil printing has been transferred in a range of 50 ° C to 75 ° C, and then irradiating the transferred surface with ultraviolet rays.

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