JPH05208493A - Jet recording method - Google Patents

Abstract

PURPOSE:To obtain a recording image superior in abrasion resistance and quality by a method wherein the bubble is exposed to the outside air, and a drop has a diameter of dmum within a specific range and an average speed of vm/sec within a specific range. CONSTITUTION:A recording medium 3 which is solid at normal temperature is heated to be melted. By heating the thermally melted recording medium 3 in accordance with a recording signal, a bubble 6 is produced in the recording medium 3. A drop 7 of the recording medium 3 is delivered out of a delivery port 5 by the bubble 6 to be recorded on a recording body. At this time, the bubble 6 is exposed to the outside air, and the drop 7 has a diameter of dmum ranging 10<=d<=60 and an average speed of vm/sec ranging 7<=v<=20. In this manner, since the recording medium which is solid at normal temperature is prevented from being raised on the body to be recorded, a recording image superior in abrasion resistance and quality can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jet recording method for recording by causing a droplet of a recording medium to fly onto a recording material.

[0002]

2. Description of the Related Art A jet recording method is one in which a droplet of a recording medium (ink) is ejected and adhered to a recording material such as paper for recording. In particular, among the jet recording methods, the applicant of the present invention discloses Japanese Patent Publication No. 61-59911 and Japanese Patent Publication No. 61-599.
No. 12 and Japanese Patent Publication No. 61-59914, a method in which thermal energy is applied to ink to generate bubbles in the ink, and the bubbles generated in the ink eject droplets from an ejection port (orifice). According to this, it is possible to easily realize a high density multi-orifice of the recording head, and it is possible to record a high resolution and high quality image at high speed.

In addition to the above-mentioned methods, there are the following jet recording methods, for example.

In Japanese Unexamined Patent Publication No. 54-161935, as shown in FIG.
There is disclosed a method in which 1 is gasified and the gas 32 is ejected together with the ink droplet 33 from the ejection port. According to this method, the clogging of the orifice can be prevented by ejecting the gas 32 from the nozzle. In addition, 35 is an electrode.

Further, in Japanese Patent Laid-Open No. 61-185455, a plate member 4 having a small opening 40 as shown in FIG.
1 and the heating element head 42, the liquid ink 44 filled in the minute gap 43 is heated by the heating element head (see FIG.
2 (a) and (b), the generated bubbles 45 cause the ink droplets 46 to fly from the small openings 40, and the gas forming the bubbles is also ejected from the small openings 40 (FIG. 1).
2 (c)) There is a description regarding a recording method for forming an image on a recording paper.

In Japanese Patent Laid-Open No. 61-249768, when the liquid ink 50 is subjected to thermal energy to form bubbles as shown in FIG. 13, and ink droplets 58 are formed and fly based on the expansion force of the bubbles. At the same time, a recording method is described in which the gas forming the bubbles is also ejected into the atmosphere through the large opening 52. In addition, 51 is a heating element.

Japanese Unexamined Patent Publication No. 61-197246 discloses a plurality of holes 6 formed in a film 60 as shown in FIG.
There is described a recording method in which the ink 62 filled in 1 is heated by the recording head 64 having the heating element 63 to generate bubbles 67 in the ink 62 and the ink droplets 65 fly to the recording medium 66.

The applicant of the present invention has proposed an ejection recording method different from the conventional ejection recording methods. In this jet recording method, bubbles are generated in the recording medium by applying heat energy according to a recording signal to the recording medium, and when the recording medium is ejected from the ejection port by the bubbles, the recording is performed. Bubbles are communicated with the outside air (hereinafter referred to as a communication jet recording method). According to this communication jet recording method, splash and mist of the recording medium can be prevented, and the recording material and the inside of the apparatus are not polluted. Further, according to this continuous jet recording method, the recording medium between the generated bubble and the ejection port is entirely ejected. Therefore, the amount of the recording medium that flies is determined by the shape of the nozzle and the position of the heater, and accordingly, the flying amount is small. It is possible to perform stable recording with a constant drop amount.

The ink used in the above jet recording method is required to have contradictory characteristics that it quickly dries and fixes on the recording material, but does not easily dry in the nozzle and does not easily cause nozzle clogging.

To meet this requirement, conventional inks which are liquid at room temperature generally contain water as a main component and a water-soluble high-boiling point solvent such as glycol for the purpose of preventing drying and clogging. When recording on plain paper using such an ink, the ink does not dry and fix quickly, and if you touch the character immediately after printing with your hand, the ink may get in your hand or the character may be rubbed and the printing quality deteriorates. There was a problem such as doing.

Further, since the penetrability of the ink varies greatly depending on the type of recording paper, there is a problem that only a specific recording paper can be used when the conventional ink containing water as a main component is used. Particularly in recent years, it has been demanded that good recording can be performed even on so-called plain paper such as copy paper, report paper, notebook, and notepaper which are often used in offices.

In response to this demand, US Pat. No. 5,006,06
170, JP-A-58-108271, JP-A-6-
1-83268, JP 61-159470, JP 62-48774, or JP 5
Japanese Patent Laid-Open No. 5-54368 discloses a jet recording method in which a solid hot-melt ink is heated and melted at room temperature to fly.

[0013]

However, the hot-melt type ink which is solid at room temperature is likely to swell on the recording paper, and therefore the ink may peel off when the recording surface of the recording paper is rubbed. To prevent ink swelling, JP-A-1-242672 and JP-A-2
Japanese Patent No. 51570 discloses a hot-melt ink which is solid at room temperature and contains a supercooling agent.

However, the hot melt type ink to which the supercooling agent is added takes a long time to be fixed, and there is a problem that the hand is soiled with the recorded image or the recorded image is disturbed unless a sufficient time is taken after recording. ..

An object of the present invention is to improve the continuous jet recording method proposed by the present applicant and to provide a jet recording method capable of obtaining a recorded image excellent in scratch resistance and image quality.

[0016]

In the jet recording method of the present invention, the recording is performed by heating and melting a recording medium that is solid at room temperature, and applying heat energy according to a recording signal to the recording medium that is heated and melted. A step of generating bubbles in the medium, discharging the small droplets of the recording medium from the discharge port by the bubbles to perform recording on the recording material, and at the time of recording, the bubbles communicate with the outside air, Droplet diameter d (μm) of the droplet
Is 10 ≦ d ≦ 60, and the average velocity v (m /
sec. ) Is 7 ≦ v ≦ 20.

The present invention is an improvement of the continuous jet recording method previously proposed by the present applicant. As will be described later, a solid recording medium (ink) is heated and melted at room temperature (5 ° C. to 35 ° C.). Then, thermal energy corresponding to a recording signal is applied to the melted recording medium so that the recording medium is ejected from an ejection port (orifice) to perform recording.

The communication jet recording method previously proposed by the present applicant will be described below with reference to the drawings.

In the jet recording method, when heat energy corresponding to a recording signal is applied to a recording medium in a molten state, bubbles are generated in the recording medium, and the recording medium is ejected from an ejection port by the generation of the bubbles. Discharge energy is generated.

The apparatus shown in FIG. 1 is an apparatus for carrying out the jet recording method. The recording medium contained in the tank 21 is supplied to the recording head 23 through a supply path 22. The recording head shown in FIG. 2 can be used as the recording head 23. The recording medium in the apparatus is kept in a liquid state in the tank 21, the supply path 22 and the recording head 23 by the heat of the heating means 20 and 24. The heating means 20 and 24 are preferably set to a temperature 10 ° C. to 50 ° C. higher than the melting point of the recording medium, and further 25 ° C. to 35 ° C. higher. A print signal is sent from the drive circuit 25 to the print head 23, and ejection energy generation means (for example, a heater) of the print head 23 is driven in response to the print signal to eject a small droplet of a print medium to print on a recording medium such as paper. Recording is performed on the material 27.

The head 23, as shown in FIG.
A wall 8 arranged in parallel above and a wall 1 forming a liquid chamber 10.
And 4 are provided. Further, the top plate 4 is arranged on the walls 8 and 14. In FIG. 2A, the top plate 4 is shown away from the walls 8 and 14 in order to make the inside of the recording head easier to see. An ink supply port 11 is formed in the top plate 4, and the melted recording medium flows into the liquid chamber 10 through the ink supply port 11. A nozzle 15 through which a molten recording medium passes is provided between the walls 8 and a heater 2 for applying heat energy according to a recording signal to the recording medium on the substrate 1 in the middle of each nozzle 15. Is provided. Bubbles are generated on the recording medium by the heat energy from the heater 2, and the recording medium is ejected from the ejection port 5 of the nozzle 15.

In the continuous jet recording method, when the bubble generated on the recording medium expands to a predetermined size due to the application of thermal energy, the bubble penetrates the discharge port 5 and communicates with the outside air.
Hereinafter, this point will be described.

FIG. 3 is a cross section of one nozzle 15 provided in the recording head 23, and FIG. 3A shows a state before foaming. First, an electric current is applied to the heating means 24 to melt the solid recording medium 3 at room temperature. After the recording medium 3 is liquefied, when a current is momentarily applied to the heater 2 to heat the recording medium 3 near the heater 2 in a pulsed manner, the recording medium 3 abruptly boils and a bubble 6 is vigorously generated to expand the recording medium 3. Start (Figure 3
(B)). The bubble 6 continues to expand, grows particularly toward the discharge port 5 side having a small inertance (inertia), and further penetrates from the discharge port 5 to communicate with the outside air (FIG. 3C). The recording medium 3 on the ejection port 5 side of the bubble 6 jumps forward due to the momentum given from the bubble 6 up to this moment, and eventually becomes an independent droplet 7.
And fly to a recording material such as paper (FIG. 3D).
After the recording medium 3 is ejected, the gap created at the tip of the nozzle 15 is filled with the new recording medium 3 due to the surface tension of the recording medium 3 at the rear and the wetting of the nozzle wall, and the state before ejection is restored.

The recording head 23 is provided at a position closer to the position of the heater 2 in the direction of the ejection port 5 than the conventional recording head. This is the most convenient configuration for communicating bubbles with the outside air. The amount of heat energy generated by the heater 2, the physical properties of the ink, the size of each part of the recording head 23 (the distance between the discharge port 5 and the heater 2, the width and height of the discharge port 5 and the nozzle 15), etc. can be selected as desired. The bubbles can be communicated with the outside air by selecting.

Although it cannot be generally stated how close the heater 2 should be to the discharge port 5 for the bubbles to communicate with the outside air, the distance from the end of the heater 2 on the discharge port 5 side to the discharge port 5 (shown in FIG. 9). In the case of a recording head, the distance from the surface of the heater 2 to the discharge port 5) is 5 μm or more and 80 μm or less,
Further, it is preferably 10 μm or more and 60 μm or less.

In order to ensure that the bubbles are in communication with the outside air, it is preferable that the height H of the discharge port (see FIG. 2A) is equal to or smaller than the nozzle width W measured at the heater.

In order to communicate the bubbles with the outside air, the width of the heater 2 is preferably 50% to 95%, more preferably 70% to 90% of the width of the nozzle. Furthermore, heating means 2
It is preferable that the viscosity of the ink in the molten state according to No. 4 is 100 cps or less. It is also possible to make the bubbles communicate with the outside air when the bubbles have a maximum volume of 70% or more, or more preferably 80% or more of the maximum volume of the bubbles that will be reached when the bubbles do not communicate with the outside air. It is preferable.

In the continuous jet recording method, bubbles generated in the recording medium communicate with the outside air, so that substantially all the recording medium between the bubbles and the discharge port 5 is discharged. Therefore, the volume of the ejected droplet is always constant. In the conventional jet recording method,
Usually, bubbles generated in the recording medium do not communicate with the outside air, and after maximum growth, shrink and disappear. When the bubbles generated in the recording medium do not communicate with the outside air as in the conventional case, the bubbles and the discharge port 5
The recording medium between and does not eject all but only partially.

Further, in the jet recording method in which the bubble contracts after reaching the maximum without communicating with the outside air, the bubble may not completely disappear even if it contracts and may remain on the heater. If the small bubbles remain on the heater in this way, there is a problem that the bubbles will not be generated and grown correctly due to the small bubbles remaining on the heater when the next small droplet is discharged. In this respect, in the continuous jet recording method in which bubbles are communicated with the outside air, all the recording medium between the bubbles and the discharge port is discharged, so that small bubbles do not remain on the heater.

In the continuous jet recording method, since the inertance from the heater 2 of the recording head 23 to the ejection port 5 is small, the momentum of the generated bubble is efficiently received by the droplet 7. Therefore, it is possible to stably eject even a high-viscosity recording medium such as a recording medium that is difficult to eject by the conventional recording method, that is, a recording medium that is solid at room temperature is heated to a temperature higher than the melting point to be liquefied. Also, in the continuous injection recording method,
Since the bubbles generated in the recording medium communicate with the outside air when the recording medium is ejected, the ejection speed of the recording medium becomes very fast. For this reason, the small droplets of the recording medium accurately adhere to the target point on the recording material, and they adhere thinly without rising on the solid recording medium or the recording material. The advantage that the solid recording medium adheres thinly on the recording material is particularly effective when the recording media are superposed on the recording material to form a multicolor color image.

In the continuous jet recording method, when the bubbles generated by the heater 2 communicate with the outside air from the discharge port 5, it is preferable that the bubbles are communicated under the condition that the internal pressure of the bubbles is equal to or lower than the outside atmospheric pressure.

FIG. 4 is a graph showing the relationship between the foam internal pressure (graph a) and the foam volume (graph b). However, FIG.
Is a graph when bubbles do not communicate with outside air. In FIG. 4, when a pulse current is passed through the heater 2 at time T = t ₀ , bubbles are generated in the recording medium and the internal pressure of the bubbles rises sharply. The bubbles start to expand as soon as they occur.

The expansion of the bubbles does not end immediately after the application of the current to the heater 2 ends, but continues for a while. As a result, the internal pressure of the bubble drops rapidly and becomes lower than the external pressure at time T = t ₁ . The bubble continues to expand to some extent, then contracts and disappears.

Therefore, as shown in FIG. 5, time T = t ₁
If the bubbles are made to communicate with the outside air at a subsequent time, for example, at time ta, the internal pressure of the bubbles immediately before they are made to be equal to or lower than the outside atmospheric pressure.

When the bubbles are communicated with the outside air to eject the small droplets under the condition that the internal pressure of the bubbles is equal to or lower than the external pressure, it is possible to prevent the mist-like recording medium unnecessary for recording from scattering, and Does not pollute the inside of the device.

Conventionally, in the jet recording method, a splashed mist-like recording medium (hereinafter referred to as splash or mist) is often ejected except for a small droplet for recording. According to the communication injection recording method, splash and mist can be prevented by lowering the internal pressure of the bubble lower than the external pressure when the bubble is communicated with the outside air.

Since it is difficult to directly measure the internal pressure of the bubble, the magnitude relationship between the internal pressure of the bubble and the external atmospheric pressure may be determined as follows.

That is, the volume Vb of the bubble from the time when the recording medium starts to foam until the bubble communicates with the outside air is measured, and the second derivative d ² Vb / dt ² of Vb is calculated to determine the internal pressure of the bubble. It is possible to know the magnitude relationship between and the atmospheric pressure. If d ² Vb / dt ² > 0, the internal pressure of the bubble is higher than the external pressure, and if d ² Vb / dt ² ≦ 0, the internal pressure of the bubble is the external pressure or less. Explaining in FIG. 6, foaming start T = t ₀
Until T = t _1, the internal pressure of the bubble is higher than the external pressure d ² V
b / dt ² > 0, and the internal pressure of the bubble is equal to or lower than the external atmospheric pressure until T = ta from T = t ₁ until the bubble communicates with the outside air, and d ² Vb / dt ² ≦ 0. As described above, the magnitude relationship between the internal pressure of the bubble and the external atmospheric pressure can be known by obtaining the second derivative d ² Vb / dt ² of Vb.

Instead of measuring the above Vb, the discharge port 5 is provided from the time when the bubble is generated until the droplet on the recording medium is ejected (between (a) and (c) in FIG. 3). The recording medium 3a (see FIG. 3B) protruding from the recording medium 3a (hereinafter referred to as the recording medium ejection portion 3a) is measured to obtain a second derivative d ² V of Vd.
It is also possible to know the magnitude relationship between the internal pressure and the external atmospheric pressure of the bubble by obtaining d / dt ² . That is, d ² Vd / dt ²
> 0, the internal pressure of the bubble is higher than the external pressure, and d ² Vd /
If dt ² ≦ 0, the internal pressure of the bubbles is below the atmospheric pressure.

The volume of the recording medium projecting portion 3a at each time is observed by the microscope 201 while illuminating the recording medium projecting portion 3a with pulsed light using a light source 200 such as a strobe, an LED or a laser as shown in FIG. Can be measured by That is, by causing the recording head ejecting small droplets continuously at a constant frequency to emit pulsed light in synchronization with the drive pulse and after a predetermined delay time, the recording medium is projected at a predetermined time. Part 3a
The projected shape of can be measured. At this time, the pulse width of the pulsed light can be more accurately measured if the pulse width is as small as possible within a range in which a sufficient amount of light can be secured for measurement. The volume of the recording medium projecting portion 3a can be converted from the measurement from one direction, but in order to obtain it more accurately, as shown in FIG. Moreover, it is desirable to simultaneously measure the projected shape of the recording medium protruding portion 3a from two directions y and z which are orthogonal to each other. At this time, it is desirable that either the measurement direction y or z in the microscope 201 be parallel to the direction in which the ejection ports 5 are arranged.

As shown in FIGS. 8 (a) and 8 (b), the widths a (x) and b (x) of the recording medium protrusion 3a with respect to the x-coordinate value of the images measured in the two directions as described above. To measure. The volume Vd of the recording medium protruding portion 3a at a predetermined time can be obtained by calculating from these values according to the following equation. The following formula is obtained by approximating the yz cross section of the recording medium protrusion 3a with an ellipse, and can be obtained with sufficient accuracy for calculating the volume of the recording medium protrusion 3a and the bubble 6.

Vd = (π / 4) ∫a (x) · b (x) dx In this way, by changing the lighting delay time of the pulsed light from the light source 200 sequentially from 0, recording is performed after bubbles are generated. It is possible to determine the change in Vd until the droplet of the medium flies.

The bubble volume Vb in the nozzle 15 can also be measured by applying the method shown in FIG. However, in order to measure the bubble volume Vb, it is necessary to configure a part of the recording head with a transparent member so that the bubble can be observed from the outside of the recording head.

An infrared LED is preferable as the pulse light source 200 because the time resolution of about 0.1 μsec is required to observe the behavior of the recording medium protruding portion 3a and the bubble 6, and the pulse width of the light source is 50 nsec is preferable. An infrared camera is preferably connected to the microscope 201 to take an image.

Further, ink mist and splash can be further prevented by making the bubbles communicate with the outside air through the discharge ports 5 under the condition that the first differential value of the moving speed of the bubbles toward the discharge ports 5 is negative.

Further, referring to FIG. 3B, bubbles 6 are discharged from the end of the heater 2 which is the discharge energy generating means on the discharge port 5 side.
The distance 1a from the end of the heater 2 on the side opposite to the discharge port 5 to the distance 1b from the end on the side opposite to the discharge port 5 of the heater 2 to the outside air. By setting 1a / 1b ≧ 1, preferably 1a / 1b ≧ 2, and more preferably 1a / 1b ≧ 4 immediately before, a new recording medium is filled in the void portion generated near the ejection port after the recording medium protrudes. It is possible to shorten the time until, and it becomes possible to perform higher speed recording. 1a / 1b becomes larger when the position of the heater 2 is brought closer to the discharge port 5, for example.

FIG. 9 shows another example of the recording head, in which the ejection port 5 is provided in the lateral direction of the nozzle 15.
Even when the recording head of FIG. 9 is used, the bubbles 6 communicate with the outside air as in the recording head of FIG. That is, when the recording medium 3 is melted by the heating means 24 from the state before foaming shown in FIG. 9A and the heater 2 is energized, bubbles 6 are generated on the heater 2 (FIG. 9B). Thereafter, the bubble 6 continues to expand (FIG. 9 (c)), the bubble 6 communicates with the outside air, and the droplet 7 is ejected from the ejection port 5 (FIG. 9 (d)).

According to the present invention, the droplet diameter d (μm) of the small droplet discharged from the discharge port is 10 ≦ d ≦ in the above continuous jet recording method.
60 and the average velocity v (m / sec.) Of droplets is 7
≦ v ≦ 20.

If the droplet diameter d is too small, the trajectory of the droplet flight is not constant and stable ejection is impossible. vice versa,
If the small droplet size is too large, the recording medium rises on the recording material, resulting in a recorded image with poor scratch resistance.

The rise of the recording medium on the recording material is
The smaller the average droplet velocity, the more pronounced. On the other hand, if the average velocity of the droplets is too fast, the recording medium will be scattered on the recording material and stains will occur around the recording dots.

The small droplet diameter d (μm) is further defined as 15 ≦ d ≦ 60.
Is preferable, and 15 ≦ d ≦ 40 is particularly preferable. Further, the average velocity v (m / sec.) Of the droplets is 7 ≦ v ≦ 15.
Is preferred.

In the present invention, the droplet size d (μm) means the diameter calculated from the droplet volume V ₀ (μm ³ ) by the following formula (A). d = (6V ₀ / π) ^1/3 (A)

The volume V ₀ (μm ³ ) of the small droplet is determined by discharging a predetermined number of small droplets of the recording medium from one discharge port and measuring the total weight of the small droplets of the recording medium discharged by a precision balance. The number of
It is calculated from the total weight and the density of the recording medium in the molten state. In order to obtain the droplet size d, the number of droplets to be ejected is on the order of 10 ⁶ .

The number of recording medium droplets ejected from one ejection port by one ejection signal is not always one, and a satellite-like extremely small droplet is generated around one main droplet. There is. In such a case, in the present invention, attention is focused only on the largest droplet, and satellite-like extremely small droplets generated around the largest droplet are ignored.

In the present invention, the average velocity of droplets v (m /
sec. ), A small droplet is ejected from the ejection port using the device shown in FIG. The distance moved during the period is measured with a display (not shown) connected to the microscope 201, and the time is 50 μsec. And calculated from the travel distance.

The recording medium which is solid at room temperature contains at least a heat-fusible solid substance and a colorant, and further contains an additive for adjusting the physical properties as necessary or an organic solvent such as alcohol which is liquid at room temperature. To do.

A recording medium which is solid at room temperature has a melting point of 36 ° C.
Those in the range of to 200 ° C are desirable. If the temperature is lower than 36 ° C, the recording medium may melt depending on the change in room temperature to stain hands, and if the temperature exceeds 200 ° C,
A large amount of energy is required to liquefy the recording medium. More preferably, the melting point is desirably in the range of 36 ° C to 150 ° C.

Examples of the heat-fusible solid substance contained in the recording medium which is solid at room temperature include acetamide, p-vanillin,
o-vanillin, dibenzyl, m-acetotoluidine, phenyl benzoate, 2,6-dimethylquinoline, 2,6-
Dimethoxyphenol, p-methylbenzyl alcohol, p-bromoacetophenone, homocatechol, 2,
3-dimethoxybenzaldehyde, 2,4-dichloroaniline, dichloroxylylene, 3,4-dichloroaniline, 4-chloro-m-cresol, p-bromophenol, dimethyl oxalate, 1-naphthol, dibutylhydroxytoluene, 1 , 3,5-trichlorobenzene, p
-Tert-pentylphenol, durene, dimethyl p-phenylenediamine, tolan, styrene glycol,
Propionamide, diphenyl carbonate, 2-chloronaphthalene, acenaphthene, 2-bromonaphthalene, indole, 2-acetylpyrrole, dibenzofuran, p-chlorobenzyl alcohol, 2-methoxynaphthalene, tiglic acid, p-dibromobenzene, 9-heptadecane,
1-tetradecanamin, 1,8-octanediamine, glutaric acid, 2,3-dimethylnaphthalene, imidazole, 2-methyl-8-hydroxyquinoline, 2-methylindole, 4-methylbiphenyl, 3,6-dimethyl- 4-octyne-diol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,5-dimethyl-2,5
-Hexanediol, ethylene carbonate, 1,8-
Octanediol, 1,1-diethylurea, butyl p-hydroxybenzoate, methyl 2-hydroxy-naphthoate, 8-quinolinol, stearylamine acetate,
1,3-diphenyl-1,3-propanedione, methyl m-nitrobenzoate, dimethyl oxalate, phthalide,
2,2-diethyl-1,3-propanediol, 8-quinolinol, N-tert-butylethanolamine,
Glycolic acid, diacetyl monooxime, acetoxime and the like can be used alone or in combination of two or more.

The above-mentioned heat-fusible solid substance has various characteristics such as a substance having particularly excellent ejection characteristics, a substance having particularly excellent storability, and a substance having extremely little bleeding on the recording material, depending on the type. .. Therefore, it is advisable to appropriately select from the above-mentioned heat-fusible solid substances according to the purpose of use and use it for the recording medium.

The melting point of the heat-fusible solid substance is Tm, and the boiling point (1
Boiling point at atmospheric pressure. The same applies hereinafter), when Tb is used, when a heat-meltable solid substance satisfying the following formulas (A) and (B) is used among the above-mentioned heat-meltable solid substances, the fixability of a recorded image is excellent and the heat energy is high. It is possible to obtain a recording medium that is solid at room temperature and can be efficiently converted into discharge energy.

36 ° C. ≦ Tm ≦ 150 ° C. (A) 150 ° C. ≦ Tb ≦ 370 ° C. (B) The boiling point Tb is preferably 200 ° C. ≦ Tb ≦ 340 ° C.

As the colorant contained in the recording medium which is solid at room temperature, various dyes and pigments such as direct dyes, acid dyes, basic dyes, disperse dyes, vat dyes, sulfur dyes, oil-soluble dyes and the like which are conventionally known are effective. Is. Particularly preferred dyes that can be used include the oil-soluble dyes described in the following Color Index.

C. I. Solvent Yellow
1,2,3,4,6,7,8,10,12,13,1
4,16,18,19,21,25,25: 1,28,
29 etc. C.I. I. Solvent Orange 1, 2, 3,
4,4: 1,5,6,7,11,16,17,19,2
0, 23, 25, 31, 32, 37, 37: 1 etc. C.I. I. Solvent Red 1, 2, 3, 4,
7,8,13,14,17,18,19,23,24,
25, 26, 27, 29, 30, 33, 35, etc. C.I. I. Solvent Violet 2, 3, 8,
9, 10, 11, 13, 14, 21, 21, 1: 1, 24
31, 32, 33, 34, 36, 37, 38, etc. C.I. I. Solvent Blue 2, 4, 5, 7,
10, 11, 12, 22, 25, 26, 35, 36, 3
7, 38, 43, 44, 45, 48, 49, etc. C.I. I. Solvent Green 1, 3, 4,
5,7,8,9,20,26,28,29,30,3
2, 33 etc. C.I. I. Solvent Brown 1,1: 1,
2, 3, 4, 5, 6, 12, 19, 20, 22, 25,
28, 29, 31, 37, 38, 42, 43, etc. C.I. I. Solvent Black 3, 5, 6,
7,8,13,22,22: 1,23,26,27,2
8, 29, 33, 34, 35, 39, 40, 41 etc.

Furthermore, calcium carbonate, barium sulfate, zinc oxide, lithobon, titanium oxide, chromium yellow, cadmium yellow, nickel titanium yellow, navel yellow, yellow iron oxide, red iron oxide, cadmium red, mercury cadmium sulfide, navy blue, ultramarine blue, etc. Organic pigments such as inorganic pigments, carbon black, azo pigments, phthalocyanine pigments, triphenylmethane pigments and bad pigments are also preferably used.

If necessary, an organic solvent which is liquid at room temperature, such as 1-hexanol, may be added to the solid recording medium at room temperature.
It may contain alcohols such as 1-heptanol and 1-octanol, alkylene glycols such as ethylene glycol, propylene glycol and triethylene glycol, and other ketones, keto alcohols, amides and ethers. .. These organic solvents greatly grow bubbles generated in the recording medium.

The boiling point of the organic solvent is preferably 150 ° C. or higher.

In addition to the above, the recording medium which is solid at room temperature may contain various additives such as an antioxidant, a dispersant and a rust preventive.

In the recording medium which is solid at room temperature, the content of the heat-fusible solid substance is 50 to 99% by weight, further 60 to 95% by weight, and the content of the colorant is based on the recording medium. 1 to 20% by weight, more preferably 3 to 15% by weight, and if necessary, the organic solvent is preferably contained in the recording medium in an amount of 0 to 10% by weight.

The recording medium used in the recording method of the present invention is
The surface tension γ (dyne / cm) at the heating temperature by the heating means 24 (FIG. 1) is γ ≧ 20, further 20 ≦ γ.
It is preferable that ≦ 40. If the surface tension γ is too small, the recording medium easily penetrates when landed on the recording material, and it becomes difficult to obtain a clear recorded image. If the surface tension γ is too large, the recording medium tends to rise on the recording material.

The viscosity η of the recording medium at 100 ° C.
(Cp) is 1.5 ≦ η ≦ 10, and further 1.5 ≦ η ≦
It is preferably 5.0. If the viscosity η is too small, the discharged recording medium tends to splash and become mist-like, and if too large, the recording medium tends to rise on the recording medium.

In the present invention, the surface tension γ is Wilhe
It is a value measured using an lmy-type surface tensiometer. The recording medium is measured with a water bath or an oil bath at a predetermined temperature. In addition, the viscosity η is Book fi
It is a value measured using an eld type rotational viscometer.

[0072]

【Example】

 (Examples 1 to 7) Ink 1 • C.I. I. Solvent Black3 6% by weight-Ethylene carbonate 41% by weight-1,12-Dodecanediol 53% by weight

Ink 2 C. I. Solvent Yellow 162 4% by weight-acetamide 40% by weight-stearic acid 56% by weight

Ink 3 C. I. Solvent Blue 38 3% by weight-acetamide 30% by weight-cetyl alcohol 45% by weight-behenic acid 22% by weight

Ink 4 C. I. Solvent Black3 3% by weight-acetamide 50% by weight-Carnauba wax (Carnauba No. 1, Noda Wax Co., Ltd.) 30% by weight-Stearic acid 17% by weight

Ink 5 C. I. Solvent Red49 2% by weight Ethylene carbonate 30% by weight 1,12-Dodecanediol 30% by weight 1,10-Decanediol 38% by weight

Ink 6 C. I. Solvent Black3 6% by weight-paraffin wax 84% by weight-stearic acid 10% by weight

Ink 7 C. I. Solvent Red 49 11% by weight 12-hydroxystearic acid 71% by weight 1,10-decanediol 18% by weight

The above ink components were stirred at 100 ° C.,
After filtering insolubles using a filter while heating,
Upon cooling, solid inks 1 to 7 were obtained. Using the inks 1 to 7 thus obtained, recording was performed on a commercially available copy paper with the apparatus shown in FIG. 1 equipped with the recording head shown in FIG. 2, and the rubbing property and quality of the recorded image were evaluated. The evaluation results are shown in Table 1.

The recorded image has a checkered pattern in which a recording portion of 5 mm square is repeated. The temperature at which the ink was melted was 100 ° C. for all inks.

The size of the nozzle 15 of the recording head used was 26 μm in height H and 38 μm in width W. The size of the heater 2 was 30 μm in width and 42 μm in length. The position of the heater 2 is the orifice 5 of the heater 2.
The distance from the side end to the orifice 5 was 20 μm. Nozzle 15 has a density of 400 per inch,
Forty eight are arranged.

The drive conditions for the recording head are as follows:
18V (voltage changed by ink), pulse width 2.5
μsec. The driving frequency was 1 KHz.

The scratch resistance of the recorded image was determined by rubbing the recorded image three times with a filter paper (made by Toyo Roshi Co., Ltd., rank No. 2).

The quality of the recorded image was evaluated by visually observing the degree of ink bleeding and the degree of ink splattering around the dots by leaving for 5 minutes after recording.

The viscosity η of each ink at 100 ° C.
(Cp), surface tension γ (dyne / c at operating temperature
m), small droplet diameter d (μm) and average velocity v (m / se
c. ) Was measured by the method described above. Table 1 shows the measurement results
It was shown to.

Recording and evaluation were carried out in an environment of (20 ± 5) ° C. and (50 ± 10)% RH (the same applies to Comparative Examples 1 and 2 shown below).

In addition to the above recording, the state of ejection of each ink was observed using the apparatus shown in FIG. The solid ink used is the same as the solid ink used for the above recording except that it does not contain a colorant. The colorant was not included in order to make the bubbles easier to observe.

The recording head 23 used in the apparatus of FIG.
The same as that used in the above recording, but with the recording head 2
The top plate 4 (FIG. 2A) is made transparent so that the inside of 3 can be observed. Above the recording head 23, the inside of the nozzle 15 can be observed through a transparent top plate.
A microscope 16 is arranged. A strobe 17 is attached to the microscope 16 so that the ink bubbling and ejection state can be observed only when the strobe 17 emits light. The strobe 17 is configured to emit light after a lapse of a delay time that can be arbitrarily set after the heater 2 starts applying heat by the strobe drive circuit 18 and the delay circuit 19. The recording head 23 is provided with a heating unit 24, which heats the recording head 23 to 100 ° C. to keep the ink in a molten state. Reference numeral 100 is a head drive circuit, and 101 is an external power supply. In this way, the liquid chamber 10 of the recording head 23 was filled with the melted ink, and the heater 2 was pulse-energized to observe bubbles generated on the heater 2 while changing the delay time of strobe light emission.

As a result, it was confirmed that, for each of the inks, the bubbles communicated with the outside air about 3 μsec after the start of foaming, and stable ejection was performed.

(Comparative Examples 1 and 2) Ink 8 C.I. I. Solvent Yellow 56 5% by weight ・ Candelilla wax (Candelilla special issue, Noda Wax Co., Ltd.) 40% by weight ・ 1,12-Dodecanediol 55% by weight

The above ink components were stirred at 100 ° C., insolubles were filtered using a filter while heating, and then cooled to obtain solid ink 8. Using the ink 8 thus obtained, and further the ink 3 used in Example 3, recording was performed on a commercially available copy sheet with the apparatus of FIG. 1 equipped with a recording head PJ1080A manufactured by Canon Inc. The scratch resistance and quality of the recorded image were evaluated in the same manner as in. The evaluation results are shown in Table 1.

The recording head PJ1080A is a recording head which uses a piezo-vibrator as an ink ejection energy source. The recording head PJ1080A is modified by providing a heating means to the head, and the ink is heated and melted at 100 ° C. for recording.

The recording head PJ1080A has a circular ejection port with a diameter of 65 μm and has four nozzles. The drive condition of the recording head PJ1080A is an applied voltage of 40 to 8
5V (voltage changed by ink), drive frequency 3.1
It was set to KHz.

[0094]

[Table 1]

In Table 1, the evaluation of scratch resistance and quality is as follows. Scratchability ◎ ... No peeling of recorded image ○ ... Slightly peeling of recorded image occurs, but practically no problem. Or there will be some scattering, but there is virtually no problem.

As described above, according to the jet recording method of the present invention, the recording medium which is solid at room temperature does not rise on the recording material and does not scatter. Therefore, according to the present invention, a recorded image excellent in scratch resistance and quality can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a recording apparatus used in a recording method of the present invention.

FIG. 2 is a schematic view showing an example of a recording head used in the recording apparatus shown in FIG.

FIG. 3 is a cross-sectional view showing an example of a recording head supplied with a recording medium to show the principle of the recording method of the present invention.

FIG. 4 is a graph showing an example of changes in the internal pressure of the foam and changes in the volume of the foam when the foam does not communicate with the outside air.

FIG. 5 is a graph showing an example of changes in the internal pressure of the foam and changes in the volume of the foam when the foam communicates with the outside air.

FIG. 6 is a graph showing examples of changes in the internal pressure of the foam, changes in the volume of the foam, and the rate of change in the volume of the foam when the foam communicates with the outside air.

FIG. 7 is a perspective view showing an example of a method for measuring the volume of the recording medium protruding from the ejection port.

FIG. 8 is a diagram showing an example of a measurement result by the measuring method shown in FIG.

FIG. 9 is a cross-sectional view showing another example of a recording head supplied with a recording medium in order to show the principle of the recording method of the present invention.

FIG. 10 is a schematic view showing an example of a recording apparatus that enables observation of a foaming state and a discharging state of a recording medium.

FIG. 11 is a cross-sectional view showing an example of a conventional recording method.

FIG. 12 is a cross-sectional view showing another example of a conventional recording method.

FIG. 13 is a sectional view showing another example of a conventional recording method.

FIG. 14 is a cross-sectional view showing another example of a conventional recording method.

[Explanation of symbols]

 1 Substrate 2 Heater 3 Ink 4 Top Plate 5 Orifice 6 Bubble 7 Droplet 8 Wall 10 Liquid Chamber 11 Ink Supply Port 14 Wall 15 Nozzle 16, 201 Microscope 17 Strobe 18 Strobe Drive Circuit 19 Delay Circuit 20, 24 Heating Means 21 Tank 22 Supply path 23 Recording head 25 Drive circuit 26 Temperature control means

Claims (8)

[Claims] 1. A step of heating and melting a recording medium that is solid at room temperature, and applying heat energy according to a recording signal to the recording medium that has been heated and melted causes bubbles to be generated in the recording medium. A step of ejecting a small droplet of the recording medium from an ejection port to perform recording on a recording material, and at the time of recording, the bubble communicates with the outside air, and a small droplet diameter d (μm) of the small droplet. Is 10 ≦ d ≦ 60, and the average velocity v (m / sec.) Of the droplets is 7 ≦ v ≦ 20. 2. When the internal pressure of the foam is below atmospheric pressure,
The jet recording method according to claim 1, wherein the bubbles communicate with outside air. 3. The droplet size d (μm) is 15 ≦ d ≦ 60.
The jet recording method according to claim 1, wherein 4. The average velocity v (m / sec.) Is 7
The jet recording method according to claim 1, wherein ≦ v ≦ 15. 5. A surface tension γ (dyne / of the recording medium.
2. The jet recording method according to claim 1, wherein (cm) is γ ≧ 20 in a molten state. 6. The surface tension γ (dyne / cm) is
The jet recording method according to claim 5, wherein 20 ≦ γ ≦ 40. 7. The viscosity η of the recording medium at 100 ° C.
The jet recording method according to claim 1, wherein (cp) is 1.5 ≦ η ≦ 10. 8. The viscosity η (cp) is 1.5 ≦ η ≦
The jet recording method according to claim 7, wherein the jet recording method is 5.0.