JPH0226748A - Hot melt type ink jet printer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to hot melt inkjet printers, and more particularly to fixing ink to printing paper.

2. Description of the Related Art Inkjet printers record characters, figures, etc. by jetting liquid ink onto printing paper, and one type of inkjet printer is called a hot-melt printer. A hot-melt inkjet printer heats and melts ink that is solid at room temperature during printing, and prints by jetting the molten ink. , (a) a platen that supports printing paper; (b) an ink supply device that stores ink that is solid at room temperature and has an ink heater that heats and melts the ink; and (C) the ink supply device. The printer is configured to include an ink ejecting head that prints on printing paper by ejecting molten ink supplied from the printer. According to this printer, there is no ink bleeding and clear printing can be obtained.

However, in inkjet printers, the ink ejected from the ink jet head has a small heat capacity because it is scraped in a small amount, and if it adheres to the printing paper, it immediately absorbs heat and solidifies, causing a large bulge from the printing paper. It becomes a protruding ink lump. As a result, the ink blobs can get caught on other printing paper or the operator's hands, etc., and easily scrape or peel off.
There have been problems such as the printing becoming unclear or when multiple sheets of printing paper are stacked on top of each other, the back side of the printing paper stacked on top is smudged. In order to solve this problem, the printer described in the above-mentioned publication is equipped with a pressure member, which presses the printed area on the surface of the printing paper between it and the support member, and gently reduces the swelling of the ink lump. It is made to be. By doing this, the ink blobs become flat and less likely to get caught, and are less likely to be scraped or peeled off (which prevents deterioration in printing quality, and also prevents the printing paper from getting stained even if the printing paper is stacked.

Problems to be Solved by the Invention However, in the above-mentioned inkjet printer, the pressure member is made of metal, has high adhesive properties, and ink tends to adhere to it. The contact angle between the metal pressure member and the liquid ink is small and the ink has good wettability, so it easily adheres to the pressure member. Therefore, if a lump of ink is pressurized, the ink will adhere to the pressure member and the print will be thin, or if the pressure member becomes dirty and the next time the printing paper is pressurized, the ink that has adhered to the pressure member will be applied to the printing paper. There was a problem that the printing paper was smeared due to the transfer.

In addition, cracks appear around the ink lump that has been crushed by the metal pressure member, and it also rises from the printing paper.
There was also the problem that adhesion deteriorated and it became easy to peel off.

The present invention prevents ink from adhering to the pressure member, and
The object of this invention is to provide a hot-melt inkjet printer that can pressurize an ink mass without impairing its adhesion to printing paper.

Means for Solving the Problems In order to solve the above problems, the present invention provides the following: (a) platen, (b) ink supply device, (C) ink jet head, (d) pressure member, and (e) In a true-melt inkjet printer equipped with a support member, at least the contact surface of the pressure member that contacts the printing portion of the printing paper is made of a low-adhesive soft synthetic resin material.

Operation and Effects of the Invention When the printing portion of the printing paper is pressurized in the printer configured as described above, the contact surface made of a low-adhesive soft synthetic resin material comes into contact with the ink mass.

The contact angle between this contact surface and the ink is large and the wettability is poor, so even if the pressure member presses the ink mass, the ink will not adhere to the contact surface, and the contact surface is made of soft synthetic resin. When applying pressure to the ink mass, the contact surface deforms elastically along the ink mass to apply pressure evenly to the entire ink mass, which prevents cracks from forming around the ink mass. The comparatively thin peripheral portion of the ink mass is also pressurized and no longer lifts off the print paper, improving the adhesion of the ink mass to the print paper.

As described above, according to the printer according to the present invention, even if the ink lump that has hardened on the printing paper is pressurized, the ink does not adhere to the pressing member, so the printing paper is not stained, and the ink lump Since the adhesion of the ink to the printing paper is not impaired, the ink mass is difficult to peel off from the printing paper, and deterioration in printing quality is avoided.

Embodiment FIG. 1 is a diagram showing the main parts of a true melt type inkjet printer which is an embodiment of the present invention.
0 is the platen. This platen 10 has a hollow cylindrical shape made of stainless steel, is rotatably attached to a frame 13 by a shaft 12, and is driven by a motor 14. An ink jet head 15 is provided opposite the platen 10. The ink jet head 15 is placed on a carriage 18 together with an ink supply device 16. The carriage 18 is slidably supported by two guide rods 20 that are arranged parallel to the center line of the platen 10, and is connected to a timing belt 24 that is wound around a pair of boots IJ22. The carriage 18 is moved along the platen 10 by rotating the pulley 22 by the motor 23 and feeding the timing belt 24.

As shown in FIG. 3, a plurality of ejection holes 30 are formed in eleven rows in the main body 28 of the ink ejection head 15. As shown in FIG. Each of these injection holes 30 is communicated with an ink reservoir 34 provided at the rear of the head through an ink chamber 32 formed on the second side of the main body. A rectangular diaphragm (not shown) is disposed on one side of each ink chamber 32 in the head movement direction, and when this diaphragm is electrically deformed, the ink is The ink in the chamber 32 is ejected from the ejection hole 30,
Printing is performed on a printing paper 36 that is supplied between the platen 10 and the ink jet head 15.

As shown in FIG. 4, the ink supply device 16 includes an ink case 40 having a cylindrical shape with a bottom.

Inside the ink case 40 is an ink block 4 that is solid at room temperature.
2 are fitted to be slidable in the axial direction, and are urged toward the opening side of the ink case 40 by a compression coil spring 46 disposed between the ink case 40 and the bottom wall 44 of the ink case 40. An ink heater 48 is attached to the open end of the ink case 40. The ink heater 48 includes a heating plate 50 and a heating resistor 52 that heats the heating plate 50, and one end of the ink block 42 is connected to the heating plate 5.
0 is being contacted. The portion of the ink block 42 that contacts the heating plate 50 is melted by the heat from the heating plate 50, and the ink passes through a passage 54 provided in the heating plate 50 and is collected in an ink reservoir 56.

A resistance heating plate 58 is attached to the ink reservoir 56 to prevent the ink from solidifying, and the liquid molten ink within the ink reservoir 56 is guided to the ink reservoir 34 of the ink jet head 15 through a conduit 60. In addition, ink reservoir 5
6 is provided with an ink amount sensor (not shown) that measures the amount of molten ink stored in the ink reservoir 56, so that the amount of ink stored in the ink reservoir 56 is kept constant and is not heated excessively. In addition, the ink block 42 is heated and melted only when necessary. 62 is an ink block sensor that detects when the remaining ink block 42 is running low.

In FIGS. 1 and 2, a pressure roller 70 as a pressure member is disposed above the platen 10. As shown in FIG. The pressure roller 70 is made of a metal such as stainless steel and has a hollow cylindrical shape, and has a base material 72 having approximately the same length as the platen 10. The pressure roller 70 has a base material 72 coated with Teflon (trade name of polytetrafluoroethylene) on the surface thereof. It is coated to form a synthetic resin layer 74, and the surface of the synthetic resin layer 74 constitutes a contact surface 75 that contacts the printed portion of the printing paper 36. This pressure roller 70 has a shaft 76
It is attached to the frame 13 so as to be rotatable about a center line parallel to the rotational center line of the platen 10, and is urged by a pair of left and right leaf springs 77 to be brought into contact with the platen 10.

Further, the rotation of the motor 14 is transmitted to the shaft 76 via a gear train 78, so that the pressure roller 70 rotates at the same circumferential speed as the platen IO. After printing, the printing paper 36 supplied between the platen 10 and the ink jet head 15 is sent between the platen 10 and the pressure roller 70,
While being supported by the platen 10, it is pressed by the pressure roller 70. The platen 10 also serves as a support member that supports the printing paper 36 during pressurization.

Teflon forming the synthetic resin layer 74 has low adhesiveness.
Moreover, it is a soft synthetic resin with low hardness, and has the following properties.

Tensile modulus: 40.8kgf/mrd Hardness (Shore hardness): HsD 50~HsD 55 Critical surface tension 18.5dyn 70m Contact angle (room temperature): 110~
120 degree static friction coefficient (relative to steel): 0.05 Further, Teflon is coated to a thickness of 0.5 mm so that the hardness of the contact surface of the pressure roller 70 is that of Teflon.

In the inkjet printer configured as described above, the printing paper 36 is sent between the platen 10 and the pressure roller 70 after printing is performed by the ink jet head 15 . The ink droplets ejected from the ink ejecting head 15 have a spherical shape with a diameter of about 30 μm, and because they have a small heat capacity, they are cooled and solidified immediately upon adhering to the printing paper 36, forming hemispherical ink as shown in FIG. It becomes a lump 79. This ink mass 79 is distributed between the platen 10 and the pressure roller 7.
When passing between 0 and 0, it is pressurized by the pressure roller 70,
A flat ink mass 79' is formed. Since the contact surface of the pressure roller 70 is made of Teflon, ink does not adhere to the pressure roller 70 and ink lumps 79
' is maintained in close contact with the printing paper 36. Printing paper 36
The ink mass 79 that has solidified after being sprayed has a spherical crown shape as shown in FIGS. 5(a) and 5(b).If this ink mass 79 is pressed by a metal roller,
Since the metal roller forcibly presses the ink mass to a substantially uniform thickness between it and the platen 10, the ink mass 8 at this time
0 cracks around the periphery as shown in FIG. 6(b), and also separates from the printing paper 36 as shown in FIG. 6(a), resulting in loss of adhesion to the printing paper 36. However, if the ink lump 79 is pressurized by the soft synthetic resin layer 74, the contact surface 75 will be appropriately elastically deformed along the ink lump 79, and the entire ink lump 79 will be evenly pressurized. As shown in (b), no cracks occur around the ink mass 79', and the peripheral part does not separate from the printing paper 36.
Maintains good adhesion.

In this way, in the printer of this embodiment, ink lumps do not adhere to the pressure roller 70, and the printing paper 3
6, the pressure roller 70 and the printing paper 36 are not stained, and there is no fear of them peeling off from the printing paper 36.

In addition, in this embodiment, the platen 10 also serves as a support member, so the number of parts can be reduced.Furthermore, the pressure member is a roller, and together with the platen 10, the printing paper 3
6, the configuration of the printing paper feeding device can be simplified.

Furthermore, since the base material 72 constituting the pressure roller 70 is formed of metal, the pressure roller 70 has high rigidity, and it is possible to increase the pressure force. However, the entire pressure roller may be made of a low-adhesive soft synthetic resin.

Another embodiment of the invention is shown in FIGS. 8 and 9. In this embodiment, a cleaning roller 82 for removing ink adhering to the pressure roller 81 is provided. The pressure roller 81 has the same structure as the pressure roller 70, and has a stainless steel base material 84 coated with Teflon to form a synthetic resin layer 86. therefore,
Although it is difficult for ink to adhere to the contact surface 87 of the pressure roller 81, the cleaning roller 82 is provided to remove ink if it adheres. The cleaning roller 82 has a heater 92 built into a cylindrical base material 90 made of a metal such as stainless steel that has higher adhesiveness than Teflon.

The cleaning roller 82 is attached to the frame by a shaft 94 so as to be rotatable around a center line parallel to the rotation center line of the pressure roller 81, and is pressed onto the platen IO via the pressure roller 81 by a spring (not shown). At the same time, the platen 10 is rotated at the same circumferential speed as the pressure roller 81 by the motor that drives the platen 10 .

The heater 92 has a longitudinal shape, and the cleaning roller 82
The surface temperature of the ink is said to have a calorific value high enough to heat and soften the ink.

The other configurations are the same as those of the previous embodiment, and corresponding parts are given the same reference numerals and detailed explanations will be omitted.

After printing, the printing paper 36 is moved between the pressure roller 81 and the platen 10.
and is pressed by a pressure roller 81. When ink 96 adheres to the pressure roller 81, the ink 96 is transferred to the cleaning roller 82, the surface of the pressure roller 81 is kept clean, and the printing paper 36 is not stained. In particular, the cleaning roller 82 is made of a metal with higher adhesiveness than Teflon, and the cleaning roller 82 has a built-in heater 90 to heat and soften the ink. It easily adheres to the pressure roller 81.
Easy to clean.

Further, the cleaning roller 82 is made of stainless steel, has high hardness, and can easily remove attached ink. Since the contact surface of the pressure roller 81 is made of Teflon, it is not easy to remove adhered ink without damaging the pressure roller 81, and the pressure roller itself may have to be replaced. Although the cost increases, if the cleaning roller 82 is provided and cleaned, there is no need to replace the pressure roller 81, and an increase in cost can be suppressed.

Yet another embodiment of the invention is shown in FIG. In this embodiment, a resin film 102 made of polyethylene, which is a low-adhesive soft synthetic resin, is interposed between the platen IO and the pressure roller 100. Pressure roller 100
has a hollow cylindrical shape made of metal such as stainless steel. Further, the resin film 102 is wound around a supply roller 104 to form a roll shape, passes between the platen 10 and the pressure roller 100, and is wound up by a take-up roller 106. The surface on the platen IO side constitutes the contact surface 108. The resin film 102 has a thickness such that the contact surface 108 has sufficient elasticity, and in this embodiment, the pressure roller 100. The resin film 102 constitutes a pressure member. The take-up roller 106 is rotated by a platen driving motor via a friction transmission device (not shown), and excess rotation is absorbed by the slip of the friction transmission device, so that the amount of take-up depends on the platen 10 and pressure roller 100. It is made to be equal to the feed amount of the printing paper 36.

The polyethylene constituting the resin film 102 is of a high density type and has the following properties.

Tensile modulus: 42.2-127kgf/mrrf Hardness (Shore hardness): D60-D70 Critical surface tension crab 31 dyn 7cm contact angle (room temperature)
Near 0-80 degree static friction coefficient (relative to steel): 0.08-0.12 The resin film 102 may be made of low-density polyethylene. Low-density polyethylene has the following properties.

Tensile modulus: 9.84-26.7kgf 7m% Hardness (Shore hardness): D41-D50 Critical surface tension crab 31 dyn 7cm contact angle 270-
80 degree static friction coefficient (against steel): 0.26 In the printer of this embodiment, the printing paper 36 is fed between the resin film 102 and the platen 10, and is pressed through the resin film 102 by the pressure roller 100. Ru. Therefore, the ink does not adhere to the pressure roller 100, and the ink mass is pressurized without impairing the adhesion of the ink to the printing paper 36.

Although the pressure roller 100 is made of metal, it may also be made of a soft synthetic resin. In that case, the contact surface 108 will have elasticity even if the resin film 102 is thin. It costs less.

Further, if ink is transferred during pressurization, the resin film can be replaced, and the pressure roller does not need to be replaced, so an increase in cost can be suppressed.

Incidentally, the resin film may be made endless and may be used in circulation.

In each of the above embodiments, the contact surfaces 75, 88, 108 were made of Teflon, high-density polyethylene, and low-density polyethylene, but other low-adhesive soft synthetic resins may also be used. In that case, the tensile modulus is 10-130k
gf/mn (40~100kgf/mn is fine)
mnr is desirable, and 60 to 80 kgf/m is optimal. Further, the hardness may be about D40 to D70, preferably D50 to D70, and D60 to D70.
~D70 is optimal. Furthermore, the critical surface tension is 15~
35 dyn/cm is enough, 15 to 3 Qdyn
Desirably 7 cm, 15-20 dyn/cm
is optimal. Furthermore, the contact angle may be 70 to 120 degrees, preferably 80 to 120 degrees, and 1
10-120 degrees is optimal.

Further, in each of the above embodiments, the platen 10 also serves as a support member, but a support member may be provided separately from the platen 10.

Furthermore, the pressure member is not limited to a roller, and various other members such as a block-shaped member that approaches and separates from the support member can be used.

Although not illustrated in detail, the present invention can be implemented in various modifications and improvements based on the knowledge of those skilled in the art.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the main parts of a true melt inkjet printer which is an embodiment of the present invention, and FIG. 2 is a side view. FIG. 3 is a side view (partially) showing the ink jet head of the printer, and FIG. 4 is a side sectional view showing the ink supply device. FIG. 5(a) is a front view showing the state of the ink lump adhering to the printing paper before being pressurized, and FIG. 5(b) is a plan view. FIG. 6(a) is a front view showing an ink mass when the ink mass ejected onto printing paper is pressed by a metal roller, and FIG. 6(b) is a plan view. FIG. 7(a) is a front view showing the case where the ink mass jetted onto printing paper is pressed by a pressure roller whose contact surface is made of a low-adhesive soft synthetic resin, and FIG. ) is a plan view. FIG. 8 is a perspective view showing the main parts of a hot melt inkjet printer according to another embodiment of the present invention, and FIG. 9 is a side view. FIG. 1O is a perspective view showing the main parts of a hot melt inkjet printer which is still another embodiment of the present invention. 10 Nibraten 15: Ink jet head 16: Ink supply device 36: Print paper 70: Pressure roller
74: Synthetic resin layer 75: Contact surface 81: Pressure roller 82: Cleaning roller 87: Contact surface 100: Pressure roller 108: Contact surface 86: Synthetic resin layer 92: Heater 102: Resin film FIG.

Claims (1)

[Claims] A platen that supports printing paper; an ink supply device that stores ink that is solid at room temperature and has an ink heater that heats and melts the ink; and an ink supply device that is supplied from the ink supply device. an ink jetting head that prints on the printing paper by jetting molten ink; a pressure member that presses a printed portion of the printing paper; and a pressure member that supports the printing paper when pressurized by the pressure member. A hot-melt inkjet printer comprising a support member, characterized in that at least a contact surface of the pressure member that contacts the printing portion of the printing paper is made of a low-adhesive soft synthetic resin material.