JP2011104983A - Thermosensitive ink roller and hot roller printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that satisfactory printing quality can not be obtained at such a high-speed rotation printing that the printing rotation number is 300 rpm or more because a proper ink amount necessary for printing can not be supplied due to scattering of hot melt ink and sagging of the ink accompanied by high-speed rotation of a thermosensitive ink roller in a hot roller printer using the conventional thermosensitive ink roller. <P>SOLUTION: A continuous pore foam 3a is compressed at a compression ratio of 50 to 87.5% to make the porosity 70 to 90% and make the hardness of the surface 16 to 40°, thereby, allows a proper amount of the hot melt ink to ooze on the surface of the continuous pore foam 3a and, as the result, the optimal amount of the ink can be supplied to a type set. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention provides a thermal ink roll capable of suppressing ink scattering in high-speed printing and improving printing durability and material durability, and hot printing capable of high-speed printing using the thermal ink roll. It relates to a roll printer.

  Along with the light duty packaging such as medical packaging and the obligation to display the expiration date of food packaging materials, etc., outer packaging bags for medicines, medical supplies, confectionery, snacks, processed foods, retort foods, boiled food The display from the only display to the individual packaging is now required to be used for display purposes. Conventionally, a hot roll printer has been used to print characters, symbols and the like (hereinafter referred to as “printing”) on the packaging material of these outer packaging bags and individual packaging bags.

  The hot roll printer has a printing roll that is rotated with a typeface, and a thermal type in which a roll-like open-cell foam is impregnated with hot-melt ink in order to rotate and transfer the ink to the typeface. An ink roll, an ink roll heating part that heats the heat-sensitive ink roll by being arranged face-to-face on a part of the peripheral surface of the heat-sensitive ink roll, and a substrate to be printed by a type body are conveyed in a certain direction. And a transport unit.

  Printing on packaging materials by a hot roll printer is performed by heating a thermal ink roll with an ink roll heating section to ooze the hot melt ink onto the surface of the open cell foam, while the printing roll also heats the typeface. The thermal ink roll and the printing roll are rotated with each other while the font and the open-cell foam are in contact with each other, and the hot melt ink is transferred to the printed font, and the printing roll is in contact with the thermal ink roll. Is carried out by bringing the typeface into contact with the packaging material at another rotational location.

  The hot roll printer currently has a printing roll speed at the time of printing (hereinafter referred to as “printing speed”) as fast as about 150 rpm. However, as described above, when printing is performed on individual bags, the efficiency is high. It is desired to further increase the printing speed.

  By the way, the hot roll printer having the above-described configuration has a limitation that it is not possible to appropriately transfer the hot-melt ink from the thermal ink roll only to the typeface even if the printing rotation speed is further increased. I had to keep it to a certain extent.

  A thermal ink roll currently used for a hot roll printer is composed of a roll-like continuous foam made of polyurethane or silicone sponge having a hardness of 5 to 50 degrees and a pore diameter of 70 to 300 μm, as shown in Patent Document 1, for example. .

JP 59-196290 A

  When the conventional thermal ink roll including the above-mentioned Patent Document 1 is heated to 80 to 150 ° C. which is a melting temperature suitable for printing of hot-melt ink, the continuous bubble is increased when the printing speed is increased to 300 rpm or more. The hot-melt ink that oozes out on the surface of the foam may scatter significantly, and the ink roll heating section and packaging materials may be soiled. In particular, the adhesion of hot-melt ink to packaging materials such as foods is a critical hygiene defect.

  On the other hand, increasing the printing speed to 300 rpm or more increases the consumption rate of the hot melt ink, and accordingly, the significant scattering of the hot melt ink greatly affects the amount from the surface of the thermal ink roll. The hot-melt ink cannot be supplied to the typeface, and the print density rapidly decreases before the expected number of prints is satisfied, making it difficult to interpret the print image of characters, symbols, and the like. In particular, when it becomes difficult to interpret the printing of packaging materials such as food, the expiration date display duty cannot be fulfilled.

  Furthermore, due to the high-speed contact between the thermal ink roll and the print roll typeface, the deformation of the material impregnated with the hot-melt ink of the thermal ink roll and the wear deterioration are accelerated, so that the hot-melt ink can be appropriately used. It is also assumed that it becomes unusable before consumption.

  In view of the above, the conventional thermal ink roll including the above-mentioned Patent Document 1 and the hot roll printer using the same are requested to further improve the printing amount and efficiency. The maximum speed was about 150 rpm due to the scattering of the hot melt ink and the printing durability and the durability of the material of the thermal ink roll.

  Therefore, if the melt viscosity of the hot melt ink is increased in order to suppress the scattering of the hot melt ink during high-speed printing and improve the printing sustainability, the hot melt ink is less likely to spread on the surface of the thermal ink roll, and the print quality In addition, a significant decrease in print density and blurring occur. In order to eliminate this state on the hot roll printer side, if the contact pressure between the thermal ink roll and the printed body is excessively increased, the thermal ink roll may be deformed.

  On the other hand, in order to improve the printing density, it is conceivable to use a hot-melt ink having a low melt viscosity or to reduce the viscosity of the hot-melt ink by increasing the heating temperature. It tends to ooze out from the roll, causing scattering or dripping of ink, resulting in a wasteful increase in consumption and a deterioration in printing sustainability. Furthermore, there is a possibility that a problem may occur in which characters are crushed so that they cannot be identified.

  In order to eliminate this state on the hot roll printer side, it is conceivable to adjust the contact pressure between the thermal ink roll and the typeface, but the contact pressure between the typeface and the thermal type ink roll is just about to contact them. If the contact pressure is too high, the hot-melt ink escapes around the typeface and the characters printed on the packaging material are only outlines. There is a problem of becoming white.

  In order to suppress the scattering of hot melt ink during high-speed printing, it may be possible to increase the viscosity of the hot melt ink by lowering the heating temperature of the ink roll heating unit. Cannot transfer properly.

  The problem to be solved by the present invention is that when a conventional thermal ink roll is used to increase the printing speed of a hot roll printer to perform high-speed printing, hot-melt ink is scattered or the consumption pace becomes inadequate. This causes a decrease in print durability, such as a sudden drop in print density, and an early deterioration of the thermal ink roll material, which can be eliminated by adjusting the melt viscosity of the hot melt ink or the hot roll printer. Attempting to do so causes another problem and cannot improve everything in a balanced manner.

  As a result of various investigations on the above problems, the present inventor has found that the thermal ink roll can be solved as follows regardless of the adjustment of the viscosity and heating temperature of the hot melt ink. That is, the heat-sensitive ink roll of the present invention is thermally melted into an open-cell foam having a porosity of 70 to 90% and a surface hardness of 16 to 40 degrees by being compressed at a compression rate of 50 to 87.5%. It is impregnated with ink.

  Furthermore, the hot roll printer of the present invention is provided with a print body, which can be rotated at an average of 300 to 1200 rpm, and the thermal ink roll of the present invention which rotates with the print roll and transfers ink to the print body. An ink roll heating unit that is arranged in a face-to-face configuration on a part of the peripheral surface of the thermal ink roll and heats the thermal ink roll, and a conveyance unit that conveys the substrate printed by the typeface in a certain direction And a substrate speed detection unit that detects the conveyance speed of the substrate to be printed, and a control unit that controls the rotation speed of the printing roll to synchronize with the conveyance speed of the substrate when printing is performed. It is.

  The heat-sensitive ink roll of the present invention adopts a conventional heat-melt ink and can perform high-speed printing at 150 rpm or more, and even when such high-speed printing is performed, scattering and ink dripping occur. In addition, an appropriate amount of hot-melt ink can be oozed out on the surface of the open-cell foam to optimize the consumption pace and improve printing sustainability. Can also be suppressed.

  On the other hand, since the hot roll printer of the present invention can rotate the printing roll (with the thermal ink roll) at an average of 300 to 1200 rpm using the thermal ink roll of the present invention, without deteriorating the printing quality. The printing efficiency is dramatically improved compared to the conventional case.

FIG. 2 shows a hot roll printer of the present invention, in which (a) is a schematic perspective view of a main part, and (b) is a diagram showing a conveyance path for packaging materials. It is a figure which shows the thermal ink roll of this invention. It is a figure which shows the experimental result regarding the effect of this invention.

  Hereinafter, modes for carrying out the present invention will be described. As a material of the open-cell foam in the thermal ink roll of the present invention, the hardness becomes 16 to 40 degrees and the porosity becomes 70% to 90% by compressing at a compression rate of 50 to 87.5%. For example, polyurethane can be employed.

  Even if the heat-sensitive ink roll of the present invention satisfies the compression ratio, the problem cannot be solved unless both the hardness and the porosity are satisfied. For example, even if the compression is performed at the above compression ratio and the hardness is set to 16 to 40 degrees, if the porosity is lower than 70%, the hot melt ink cannot be sufficiently supplied to the typeface, and printing may be drowned. Therefore, the capacity of the hot melt ink becomes insufficient, and stable print quality cannot be maintained at a high speed and in a large amount of print, and if the porosity is higher than 90%, the hot melt ink is scattered or dripped.

  On the other hand, for example, even if the compression rate is set to 70 to 90% and the porosity is lower than 16 degrees (soft), excessively hot-melt ink oozes out due to its elasticity when contacting the typeface. Since the hot melt ink is scattered or dripped because it is supplied to the typeface, if the hardness is higher than 40 degrees (hard), the hot melt ink cannot be sufficiently supplied to the typeface. Will drown.

  Further, even if the compression ratio is satisfied, if the hardness is lower than 16 degrees and the porosity is higher than 90% under the conditions of hardness and porosity, the hot melt ink exudes excessively from the thermal ink roll. Spattering and ink dripping occur, or so-called squeezed characters appear to be blurred, resulting in a decrease in print quality.

  On the other hand, even if the compression rate is satisfied, if the hardness is higher than 40 degrees and the porosity is lower than 70%, there is little ink bleeding from the thermal ink roll, and sufficient ink cannot be supplied to the type. However, the printing is performed with the sheet being low, and printing wrapping or the like occurs in the packaging material or the like, and a preferable printing quality cannot be obtained.

Moreover, the conditions of the hardness and the porosity in the heat-sensitive ink roll of the present invention should be satisfied by compressing the hardness and the porosity of the original physical property values at a compression rate of 50 to 87.5%. Yes. In addition, the compression rate said in this application shall mean the compression ratio of a volume so that a volume may be set to 15 cm < ³ >, when the original material whose volume is 100 cm < ³ > is compressed with a compression rate of 85%.

  That is, even if the hardness and porosity of the open cell foam originally satisfy the above range, there is a large and small variation in the size of each cell, strictly speaking, on the peripheral surface of the open cell foam. There is a variation in the amount of bleeding of the hot-melt ink at each location that comes into contact with the typeface.

  Therefore, by compressing the open-cell foam at a compression rate of 50 to 87.5%, first, the physical properties of the original hardness and porosity can be made to satisfy the above range, Further, the difference in size of the bubbles is reduced by the compression, and the size of the entire bubbles is averaged. As a result, the supply amount of the hot-melt ink to the typeface can be made uniform and appropriate.

  If the compression ratio of the open-cell foam is lower than 50%, the difference in the size of the bubbles is difficult to be averaged, and the above effect cannot be obtained. On the other hand, the compression ratio is higher than 87.5%. Even if the porosity and hardness satisfy the above ranges, the properties of the material before compression appear due to the heat during printing, and the printing is insufficiently sustained due to excessive bleeding, the characters are crushed, the roll itself This results in poor durability. The compression rate is more preferably in the range of 82.5 to 87.5%.

In addition, the hardness said by this application is a numerical value by the measurement based on JISK7312 using an Asker C type rubber hardness meter.
The porosity is a numerical value calculated by the following formula 1.

  Furthermore, the hot-melt ink employed in the heat-sensitive ink roll of the present invention heats and impregnates an open-cell foam with a conventional existing composition. Here, as an example of the composition of the hot melt ink, the hot melt ink includes a thermoplastic resin and a colorant, and if necessary, includes a tackifier, a wax, a plasticizer, an antioxidant, a dispersant, and the like. . Then, these are heated and melted, and heated and dispersed using a dispersing machine such as a roll mill, an attritor, a vertical bead mill, a horizontal bead mill, etc. to obtain a hot melt ink.

  Examples of the thermoplastic resin include ethylene-vinyl acetate copolymer, polyester, polyamide, polyethylene, polyurethane, polyvinyl alcohol, acrylic ester, ethylene-acrylic acid copolymer, ethylene-ethyl acrylate copolymer, ionomer, Epoxy can be used.

  Examples of the colorant include pigments and dyes such as carbon black, oil black, nigrosine, titanium oxide, lake red, and cyanine blue.

  Examples of tackifiers include rosin, rosin derivatives, terpenes, modified terpene resins, petroleum resins, chroman-indene resins, and isoprene-based resins.

  Examples of the wax include, for example, paraffin wax, microcrystalline wax, Fischer-Tropsch wax, low molecular weight polyethylene wax, polypropylene wax, montan wax, candelilla wax and carnauba wax, and montan derivatives, microwax derivatives, synthetic oxidized wax, and the like. Wax can be used.

  Examples of the plasticizer include polybutene, DOP, DBP, DCHP, liquid rosin ester, low molecular weight styrene resin, chlorinated paraffin, and sulfonamide plasticizer.

  As the antioxidant, for example, phenol, sulfur, and hydrazine can be used, and various known dispersants can be used as the dispersant.

  The melt viscosity is preferably 60 rpm 4000 ± 2000 cps (B type viscometer), more preferably 4000 ± 1000 cps. The TI value (6 rpm melt viscosity / 60 rpm melt viscosity) is 1.0 to 1.5, preferably 1.0 to 1.3. If the TI value is out of the above range, printing may be lost.

  The hot roll printer of the present invention is characterized in that the thermal ink roll of the present invention is used and that the thermal ink roll can be rotated at 300 to 1200 rpm on average as a printing roller. However, in order to rotate at high speed, a motor satisfying the output of the speed band may be used.

  Naturally, if the rotation speed is lower (slower) than 300 rpm on average, the printing efficiency is low, and if the rotation speed is higher (faster) than 1200 rpm on the average, rattling and thermal inks are caused by the eccentric rotation of the print roller having the typeface. There is a possibility that the contact state with the roll or the packaging material will become unstable, and the print quality may deteriorate.

  Hereinafter, the configuration of the thermal ink roller and the hot roll printer of the present invention will be described with reference to the drawings. The hot roll printer 1 of the present invention shown in FIG. 1 has the following configuration. Reference numeral 2 denotes a printing roll. The printing roll 2 is rotated by a shaft 2A so that a typeface P such as a predetermined character protrudes from a part of the circumferential surface so as to be orthogonal to the circumferential direction, for example. Is arranged.

  Reference numeral 3 shown in FIG. 1B denotes a thermal ink roll according to the present invention which is rotated by a shaft 3A provided in parallel with the shaft 2A of the printing roll 2. The heat-sensitive ink roll 3 is composed of an open-cell foam 3a and a hot-melt ink (not shown or reference number).

  Further, the thermal ink roll 3 rotates in the direction opposite to the rotation of the printing roll 2, and the peripheral surface spacing is such that the peripheral surface of the open-cell foam 3 a is in contact with the typeface P with an appropriate pressure during this rotation. Is set.

  Reference numeral 4 denotes an ink roll heating unit disposed in a face-to-face manner on a part of the peripheral surface of the thermal ink roll 3, in the drawing, the peripheral surface area of the rotating peripheral surface of the open-cell foam 3 a excluding the contact portion with the type P Yes, this ink roll heating unit 4 melts the hot-melt ink of the thermal ink roll 3.

  5 is a transport unit that transports the packaging material H printed by the typeface P of the printing roll 2 to the printing position by the printing roll 2 in the fixed direction between the typeface P and the printing position of the packaging material H. .

  The transport unit 5 includes a print receiving roll 5a pivotally supported by a shaft 5A so as to send the packaging material H to a printing position by the printing roll 2, and an arrangement position and a radial direction of the printing roll 2 of the print receiving roll 5a. The guide rolls 5b and 5c are pivotally supported on the shafts 5B and 5C arranged in the conveying direction of the packaging material H at positions opposite to each other.

  As shown in FIG. 1B, the packaging material H is conveyed linearly from upstream and passes between the guide roller 5b and the print receiving roll 5a and between the print receiving roll 5a and the printing roll 2 here. And is conveyed linearly downstream between the print receiving roll 5a and the guide roll 5c.

  The hot roll printer 1 of the present invention shown in FIG. 1 is normally installed in a packaging line (not shown), and the conveyance speed of the packaging material H is controlled (determined) on the packaging line side. The hot roll printer 1 reads the conveyance speed with an encoder 6 to be described later in order to make the printing clear, and when the printing is performed, the rotation speed of the printing roll 2 is synchronized with the conveyance speed of the packaging material H. As described above, it is controlled by the control unit 8 described later.

  The synchronization at the time of printing in the present invention refers to the printing position of the type P in the rotation angle of the printing roll 2 on the hot roll printer 1 side with respect to the conveyance speed of the packaging material H in order to make the printing clear. This means that the rotational speeds (circumferential speeds) in a predetermined angle θ range (hereinafter referred to as angle θ) immediately before and immediately after the center are matched.

  Reference numeral 6 denotes an encoder (base material speed detection unit) provided to detect the rotation amount of the print receiving roll 5a in order to detect the conveyance speed of the packaging material H of the conveyance unit 5. The encoder 6 may be a rotary encoder of FIG. 1 or an appropriate one of known conveyance speed detection means. The output of the encoder 6 is output to the control unit 8 described later.

  Reference numeral 7 denotes a mark sensor that detects a mark 7 a provided on the packaging material H. The mark sensor 7 is output to the control unit 8 so that printing can be accurately performed at a predetermined position from the predetermined position of the packaging material H, that is, the position where the mark 7a is detected.

  A control unit 8 controls the rotational speed of the printing roll 2 at the angle θ based on the output of the encoder 6. That is, the controller 8 rotates the printing roll 2 outside the angle θ with respect to the conveyance speed of the packaging material H so that the rotation speed at the angle θ matches the conveyance speed of the packaging material H according to the printing pitch. Control is performed such as stopping at a predetermined position before rotating to the same speed, fast, slow, or angle θ range.

  Therefore, the expression “average” per rotation is used in the rotation speed (rpm) of the hot roll printer 1 of the present invention. And since the control part 8 performs synchronous control of the printing roll 2 with respect to the conveyance speed of the packaging material H in this way, even if it prints at high speed, clear printing can be performed reliably.

  Then, the experimental result regarding the hot roll printer of this invention of the said structure and the thermal ink roll of this invention is shown.

(experimental method)
Experiments were conducted using hot roll printers (present invention) equipped with the thermal ink rolls of the present invention in Examples 1 to 4, while those produced using hot roll printers fitted with other thermal ink rolls were compared with Comparative Examples 1 to 6. At a temperature of 25 ° C., 50,000 times of continuous printing is performed on the packaging material H made of OPP at a temperature of 25 ° C. with a conveyance speed of 40 m / min for each packaging material H, a printing interval of 50 mm pitch, and an average rotation speed of the printing roll of 800 rpm. That's it. Note that the rotation control of the printing rolls of Comparative Examples 1 to 6 in this experiment was performed by the control of the hot roll printer of the present invention as in Examples 1 to 4. The conditions and evaluation of this experiment are shown in FIG.

(Common items: Hot melt ink)
In each example and each comparative example, the common matter is that 10 parts of carbon black and 90 parts of polyamide resin are heated and dispersed at 140 ° C. using an attritor and measured with a B-type viscometer after heating to 140 ° C. This is to use a hot-melt ink having a value of 4,000 cPs at 60 rpm and a TI value of 1.0, and impregnating 30 g of each open-cell foam of each thermal ink roll.

(Evaluation: Printing durability)
The print density of the obtained printed matter was confirmed by continuous printing of 50,000 times.
○: Even after printing 50,000 times, an appropriate amount of ink oozes from the thermal ink roll, and the printing density is maintained at the same level as the initial printing.
(Triangle | delta): The printing density after printing 50,000 times falls a little.
X: Printing cannot be performed 50,000 times and printing cannot be performed. The print density is very low from the beginning, or the print density drops significantly due to a large amount of ink scattering and ink dripping from the thermal ink roll.

(Evaluation: Print quality and print clarity)
The printed matter obtained by continuous printing of 50,000 times was checked for the presence or absence of crushing or wrinkling and chipping.
○: There is no crushing, curling or chipping.
Δ: Can be read, but some characters have slight crushing or curling and chipping.
X: Some or all of the characters are crushed or curled and missing, regardless of whether they are legible.

  In the heat-sensitive ink roll of Example 1, a polyurethane foam made from polyurethane having a true density of 1.3 was compressed at a compression rate of 87.5%, and this compression resulted in a hardness of 35 degrees and a porosity of 82%. Use what you did.

  In the heat-sensitive ink roll of Example 2, a polyurethane foam made from polyurethane having a true density of 1.3 was compressed at a compression rate of 82.5%, and this compression resulted in a hardness of 20 degrees and a porosity of 88%. Use what you did.

  In the heat-sensitive ink roll of Example 3, a polyurethane foam made from polyurethane having a true density of 1.3 was compressed at a compression rate of 85%, and this compression resulted in a hardness of 30 degrees and a porosity of 86%. Is used.

  The heat-sensitive ink roll of Example 4 was obtained by compressing a polyurethane foam made of polyurethane having a true density of 2.6 at a compression rate of 50%, and by this compression, the hardness was 32 degrees and the porosity was 90%. Is used.

(Comparative Example 1)
The heat-sensitive ink roll of Comparative Example 1 was obtained by compressing a polyurethane foam made from polyurethane having a true density of 1.3 at a compression rate of 80%, and by this compression, the hardness was 15 degrees and the porosity was 90%. It is.

(Comparative Example 2)
In the heat-sensitive ink roll of Comparative Example 2, a polyurethane foam made from polyurethane having a true density of 2.6 was compressed at a compression rate of 82.5%, and this compression resulted in a hardness of 43 degrees and a porosity of 70%. It is a thing.

(Comparative Example 3)
In the heat-sensitive ink roll of Comparative Example 3, a polyurethane foam made from polyurethane having a true density of 1.6 was compressed at a compression rate of 87.5%, and this compression resulted in a hardness of 25 degrees and a porosity of 56%. It is a thing.

(Comparative Example 4)
The heat-sensitive ink roll of Comparative Example 4 was obtained by compressing a polyurethane foam made from polyurethane having a true density of 2.6 at a compression rate of 55%, and by this compression, the hardness was 35 degrees and the porosity was 92%. It is.

(Comparative Example 5)
The heat-sensitive ink roll of Comparative Example 5 is a polyurethane foam made from polyurethane having a true density of 1.3 as a raw material, compressed at a compression rate of 90%, and this compression gives a hardness of 40 degrees and a porosity of 79%. It is.

(Comparative Example 6)
The heat-sensitive ink roll of Comparative Example 6 was obtained by compressing a polyurethane foam made from polyurethane having a true density of 2.6 at a compression rate of 45%, and by this compression, the hardness was 28 degrees and the porosity was 88%. It is.

As described above, the results shown in FIG.
In Comparative Example 1, only the surface hardness deviates from the provisions of the present application. Therefore, when the hot melt ink exudes too much from the thermal ink roll, ink scattering and character collapse occur, and the print quality is evaluated as “x”. It was. Further, since the hot melt ink was consumed excessively at the initial stage of printing, the printing durability was evaluated as “x”.

  In Comparative Example 2, since only the surface hardness deviates from the provision of the present application, the bleeding of the hot melt ink from the thermal ink roll is suppressed excessively, so that the print fading occurs and the print quality is evaluated as “×”. became. Further, since the print density remained significantly lower than the initial printing, the print durability was evaluated as “x”.

  In Comparative Example 3, since only the porosity deviates from the specification of the present application, the bleeding of the hot melt ink from the thermal ink roll is suppressed excessively, print fading occurs, and the print quality is evaluated as “x”. became. Further, since the print density remained significantly lower than the initial printing, the print durability was evaluated as “x”.

  In Comparative Example 4, only the porosity deviates from the provisions of the present application, so that the hot melt ink exudes excessively from the thermal ink roll, causing ink scattering and character collapse, and the print quality is evaluated as “x”. It was. Further, since the hot melt ink was consumed excessively at the initial stage of printing, the printing durability was evaluated as “x”.

  In Comparative Example 5, since only the compression rate is far from the provisions of the present application, the properties of the material before compression appear due to the heat at the time of printing, and the ink oozes out from the thermal ink roll, causing ink scattering and character collapse. The print quality was evaluated as “x”. Further, since the hot melt ink was consumed excessively at the initial stage of printing, the printing durability was evaluated as “x”.

  In Comparative Example 6, since only the compression rate deviates from the provisions of the present application, there is a large variation in the size of the bubbles, the amount of bleeding of the hot melt ink from the thermal ink roll is not stable, and both the print quality and the print durability are both The evaluation was “x”.

  On the other hand, in Examples 1 to 4 in which the compression ratio, porosity, and surface hardness are all within the specified range of the present application, the evaluation results of “◯” or “Δ” were obtained for both print durability and print quality. .

  Moreover, in Examples 1-4, durability was improved by compressing at a compression rate within the scope of the present application, and there was no physical wear such as wear marks due to contact of the typeface. From the above results, only in Examples 1 to 3, an additional experiment was performed in which the rotation speed of the printing roll was 1200 rpm and continuous printing was performed 500,000 times. Good results were obtained that “◯” and the print quality were “◯” in the above evaluation.

  From the above experiment, the hot roll printer of the present invention is capable of high-speed printing at 800 to 1200 rpm, and the thermal ink roll of the present invention is good for being used in such a printer for high-speed printing. It has been found that print durability and print quality can be obtained.

DESCRIPTION OF SYMBOLS 1 Hot roll printer 2 Printing roll 3 Thermal ink roll 3a Open-cell foam 4 Ink roll heating part 5 Conveying part 6 Encoder 7 Mark sensor 8 Control part

Claims (2)

  It consists of an open-cell foam and a hot-melt ink impregnated in the open-cell foam, and is compressed at a compression rate of 50 to 87.5%, so that the porosity is 70 to 90% and the surface hardness is 16 to 40 degrees. A heat-sensitive ink roll using the open-cell foam described above.   A printing roll provided with a typeface and capable of rotating at an average of 300 to 1200 rpm, the thermal ink roll according to claim 1 which rotates together with the printing roll to transfer ink to the typeface, and a peripheral surface of the thermal ink roll An ink roll heating unit that is arranged in a face-to-face configuration to heat the thermosensitive ink roll, a conveyance unit that conveys the substrate printed by the typeface in a certain direction, and conveyance of the substrate to be printed A hot roll printer comprising: a base material speed detection unit that detects a speed; and a control unit that controls the rotation speed of a printing roll to synchronize with the conveyance speed of the base material when printing.

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