JP5023920B2 - Inkjet recording device - Google Patents

Description

  The present invention relates to an inkjet recording apparatus, and more particularly to an inkjet recording apparatus that records an image by irradiating ultraviolet curable ink discharged onto a substrate with ultraviolet rays.

  Provided on one end of the recording head as an image recording device that can record images not only on ordinary substrates such as paper and fabrics but also on substrates with poor ink absorption such as resin films and metals. An ink jet recording apparatus has been developed in which ink is ejected from the nozzles and landed on a substrate, and the technology is currently applied in various technical fields.

  Above all, the UV curable inkjet recording device that cures and fixes the ink landed on the substrate by irradiating it with ultraviolet rays is actively developed as a recording device that can easily obtain high-definition images. It has been. In order to record a high-definition image, the amount of ink droplets ejected from the recording head onto the substrate becomes a very small amount, and as described in Patent Documents 1 and 2, etc., it is in the order of pl (picoliter). There is a demand for ejecting ink of a droplet amount.

In addition, it is often required to enrich the gradation expression of the recorded image. In order to meet such a demand, for example, various amounts of droplets of ink ejected from the recording head can be used. An ink jet recording apparatus that can be changed has been developed (see, for example, Patent Document 1). For example, in a multi-drop type ink jet recording apparatus, for example, 2 [pl] or 4 [pl] ink is ejected from each nozzle, or the ink ejected from the recording head is combined in the air. The amount of ink droplets that land on the material can be changed to 2, 4, 8, 16, 32 [pl], or the like.
JP 2006-346919 A JP 2005-89552 A

  By the way, as an ink used for image recording, a cation polymerization type ink or a radical polymerization type ink is generally used. However, in any ink, if the amount of ink droplets is very small, In some cases, the ink that has landed thereon does not sufficiently cure even when irradiated with ultraviolet rays. This is because when the ink spreads on the base material, the ratio of the surface area to the volume of the ink increases, and it is easy to be influenced by the surrounding environment. This is probably because the ratio of the surface area to the volume is originally large, so that it is more easily influenced by the surrounding environment.

  In other words, in the case of a cationic polymerization type ink, the viscosity of the ink changes according to the ambient temperature and humidity, the moisture evaporates from the ink, or the surrounding moisture is absorbed into the ink. Curing properties change. For example, if the surrounding environment is at a high temperature, the viscosity of the ink will decrease and it will not cure sufficiently even when irradiated with ultraviolet rays.If the surrounding environment is highly humid, the ink will absorb the surrounding moisture. Even if it is irradiated with ultraviolet rays, it will not be cured sufficiently. In particular, the effect of ink with a small amount of droplets becomes significant, and there are cases where the ink does not sufficiently cure even when irradiated with an amount of ultraviolet light that cures ink with a large amount of droplets.

  Further, in the case of radical polymerization type ink, there is a characteristic that the radical polymerization reaction of the ink is easily inhibited by oxygen in the air as described in Patent Document 2, but the ratio of the surface area to the volume is originally large. When ink with a small droplet volume lands on the substrate and spreads on the substrate and the ratio of the surface area to the volume increases, oxygen enters the ink through the large surface area with respect to the minute volume, and the unit volume The amount of mixed oxygen increases and the radical polymerization reaction is inhibited. For this reason, there is a case in which ink with a small amount of droplets is not sufficiently cured even if it is irradiated with an ultraviolet ray having a light amount that can cure the ink with a large amount of droplets.

  FIG. 6 is a graph showing an example of the results of an experiment conducted by the present inventor. Ink liquid in the case of using a radical polymerization type ink and curing in a state where the landed ink is sufficiently spread on the substrate S. It is a graph showing the relationship between the amount of droplets and the minimum amount of ultraviolet light necessary for curing ink, that is, the amount of cured light. In the figure, ● represents the value when an LED that irradiates ultraviolet rays having a wavelength of about 365 nm is used as the light source of the ultraviolet irradiation device 5, and ◆ represents irradiation of ultraviolet rays having a broad wavelength having a peak wavelength of about 365 nm. This shows the value when using a high-pressure mercury lamp. Further, in FIG. 6, the amount of curing for the same amount of ink is smaller with the high-pressure mercury lamp than with the LED because of the influence of light of wavelengths other than ultraviolet rays included in the irradiation light from the high-pressure mercury lamp, This is considered to be due to the effect of the rise in ink temperature due to the heat generated.

  The results shown in FIG. 6 are considered to quantitatively show the inhibition of polymerization by oxygen in the radical polymerization ink described above. In addition, as shown in the figure, the droplet amount is 4 [compared to the curing light amount when the ink droplet amount is 8, 16, or 32 [pl], regardless of whether the light source is an LED or a high-pressure water source lamp. pl], the amount of curing light increases rapidly. In this way, the inventors of the present application say that when the ink droplet amount is decreased, there is a droplet amount in which the curing light amount suddenly increases at a certain droplet amount than in the case of a larger droplet amount. Obtained knowledge.

  Further, although not shown in the graph, it is also known that when the droplet amount is 2 [pl], the amount of curing light is the same as or larger than when the amount of curing is 4 [pl]. It has also been confirmed that, depending on the experimental conditions, when the amount of droplets is 8 [pl], the amount of curing light may increase more rapidly than in the case of 16 [pl] or 32 [pl].

  As described above, in order to cure the ink with a small amount of droplets reliably, the large amount of ultraviolet light necessary for curing the ink with a small amount of droplets as shown in FIG. It is conceivable to cure both ink having a small droplet amount and ink having a large droplet amount. However, the amount of power consumed by the ultraviolet irradiation device becomes very large.

  Therefore, the present invention is based on the above knowledge, and in an image recording that discharges both ink having a large amount of droplets and ink having a small amount, an ink jet capable of reliably curing ink having a small amount of droplets. An object is to provide a recording apparatus. Another object of the present invention is to provide an ink jet recording apparatus capable of reducing the amount of ultraviolet light applied to the ink.

In order to solve the above problem, the ink jet recording apparatus of the present invention comprises:
In an inkjet recording apparatus that discharges ultraviolet curable ink onto a substrate, cures the ink by irradiation of ultraviolet rays, and records an image on the substrate.
A first recording head capable of discharging ink having a droplet amount equal to or less than a set threshold;
A second recording head that ejects ink having a droplet amount larger than the threshold;
An ultraviolet irradiation device for irradiating the ink landed on the substrate with ultraviolet rays,
The inks discharged from the first recording head and landed on the base material are earlier than the inks discharged from the second recording head and landed on the base material so that the ultraviolet irradiation timing by the ultraviolet irradiation device is earlier. Arranging the recording head and the ultraviolet irradiation device ,
The second recording head, the first recording head that ejects ink of the same color as the ink ejected from the second recording head, the first recording head, and the second recording head from the upstream side in the conveyance direction of the substrate Are arranged in the order of the ultraviolet irradiation devices for irradiating ultraviolet rays to the ink discharged and landed on the base material to form one group,
A plurality of the groups are provided for each ink color,
According to the curing sensitivity of the ink to be ejected, the plurality of groups are arranged on the upstream side in the transport direction of the base material in the group related to the ink with lower curing sensitivity .

  According to the ink jet recording apparatus of the present invention, ink having a droplet amount equal to or less than a threshold value landed on a base material does not spread on the base material, and the ink is irradiated with ultraviolet rays before the ratio of the surface area to the ink volume increases. Can be cured. For this reason, since ink with a droplet amount below the threshold is irradiated with ultraviolet rays before being affected by the surrounding environment, it is possible to reliably cure the ink below the threshold with irradiation with a smaller amount of ultraviolet rays. . In addition, since the amount of ultraviolet light to be irradiated can be reduced, the amount of power consumed by the ultraviolet irradiation device can be reduced.

  Embodiments of an ink jet recording apparatus according to the present invention will be described below with reference to the drawings.

[First Embodiment]
As shown in FIG. 1, the inkjet recording apparatus 1 according to the first embodiment is configured so that the base material S is transported in the transport direction indicated by an arrow Z in the drawing on the platen 2 disposed substantially horizontally. It is configured. On the upstream side and downstream side of the platen 2 in the transport direction Z, a transport roller 3 for transporting the substrate S is disposed, and the transport roller 3 is rotationally driven by a transport device including a transport motor (not shown). It has come to be. The substrate S is transported on the platen 2 at a constant speed as the transport roller 3 rotates.

  Above the platen 2, a plurality of recording heads 4 that discharge ultraviolet curable ink are arranged in parallel so as to extend in a direction perpendicular to the transport direction Z of the substrate S. In the present embodiment, two recording heads 4 are arranged side by side, and ink of the same color such as black (K) is ejected from the two recording heads 4. Note that this embodiment is not limited to the case where the color of the ejected ink is black (K). As the ink, any of radical polymerization type ink and cationic polymerization type ink can be used.

  As shown in FIG. 2, each recording head 4 is provided with a plurality of nozzles 4 a on its bottom surface, that is, the surface facing the substrate S. Each nozzle 4a is configured such that ink is stored in an ink reservoir (not shown) formed therein, and each nozzle 4a is pressurized by deforming a piezoelectric element (not shown) to pressurize the inside of the ink reservoir. Ink is discharged from the nozzle.

  Of the two recording heads 4, the first recording head 41 on the downstream side in the transport direction Z of the substrate S can eject ink having a droplet amount equal to or less than a threshold set to a very small droplet amount. It is configured to be able to.

  As shown in FIG. 6, the threshold value of the ink droplet amount ejected from the first recording head 41 is a droplet amount at which the curing light amount increases rapidly when the ink droplet amount is decreased. Is set. That is, in the case of the same figure, the droplet amount threshold is set to 4 [pl].

  According to the experiments conducted by the inventors of the present application, the threshold value of the droplet amount to be set is determined by the material such as the ink absorbability of the substrate S in the inkjet recording apparatus 1 and its transport speed, the properties such as the ink curing sensitivity and viscosity. It has been found that it can vary depending on various conditions such as the composition, the amount of ultraviolet light emitted from the light source of the ultraviolet irradiation device 5 described later, and the environment such as the temperature and humidity around the recording head 4 that ejects ink.

  However, as illustrated in FIG. 6, in most cases, the threshold should be set to 4 [pl] regardless of whether the ink is a radical polymerization type ink or a cationic polymerization type ink. I know. In addition, a material such as a PET (polyethylene terephthalate) sheet that spreads easily is used as the substrate S, and the amount of droplets is 8 in a special environment where image recording is performed in a high temperature and high humidity environment. Even [pl] may not be cured unless the amount of ultraviolet light is increased. In such a case, the threshold is set to 8 [pl].

  In the present embodiment, the first recording head 41 ejects 4 [pl] of ink from each nozzle 4 a and lands ink of a droplet amount of 4, 8, 16 [pl] on the substrate S. And a multi-drop type recording head. The first recording head 41 can also be configured by a multi-drop type recording head that discharges 2 [pl] of ink from each nozzle 4a, and 4 [pl] without changing the droplet amount. It is also possible to provide a recording head that discharges only ink with a constant droplet amount equal to or less than the threshold value.

  On the other hand, as shown in FIG. 1, of the two recording heads 4, the second recording head 42 on the upstream side in the transport direction Z of the substrate S receives ink having a droplet amount larger than the set threshold value. It is comprised so that it may discharge. In the present embodiment, the second recording head 42 is configured to eject 16 [pl] of ink from each nozzle 4 a, but when the threshold is set to 4 [pl], the second recording head 42 is configured to discharge the second recording head 42. The recording head 42 may be configured to eject 8 [pl] of ink. In addition, the second recording head 42 can be configured by a multi-drop recording head.

  FIG. 1 shows the case where each of the first recording head 41 and the second recording head 42 is composed of one recording head, but the configuration of the recording head 4 is not limited to this. For example, FIG. As shown in FIG. 4, the first and second recording heads 41 and 42 can be configured by arranging a plurality of unit heads 411, 412, 413, 421, 422, and 423 in a staggered manner.

  As shown in FIGS. 1 and 2, an ultraviolet irradiation device 5 is provided on the downstream side in the transport direction Z of the base material S of the recording head 4 (41, 42). In the present embodiment, as shown in FIG. 2, the ultraviolet irradiation device 5 includes a plurality of LEDs (Light Emitting Diodes) 5 a on the bottom surface, that is, the side facing the base material S. The ink ejected from the one recording head 41 and the second recording head 42 is applied to the base material S and is irradiated with ultraviolet rays. Note that the light source of the ultraviolet irradiation device 5 is not limited to the LED 5a, but other than this, for example, a high-pressure mercury lamp, a metal halide lamp, a black light, a cold cathode tube, a semiconductor laser, or the like can be appropriately selected and used.

  Further, as shown in FIG. 3, when the first recording head 41 and the second recording head 42 are configured by arranging a plurality of unit heads 411, 412, 413, 421, 422, and 423 in a staggered manner, respectively. The ultraviolet irradiating device 5 is preferably configured by arranging a plurality of irradiating devices 51, 52, 53 in a staggered manner accordingly.

  Next, the operation of the ink jet recording apparatus 1 according to this embodiment will be described.

  As shown in FIG. 1, when the base material S is transported on the platen 2 in the transport direction Z, first, the amount of liquid droplets larger than the threshold value from the nozzle 4a of the second recording head 42 (16 [ pl]) ink is ejected and landed on the substrate S. The ink that has landed on the base material S spreads on the base material S until it is transported to the lower side of the ultraviolet irradiation device 5 in response to the transport of the base material S and is irradiated with ultraviolet light.

  When the substrate S is further transported, ink of a droplet amount equal to or smaller than the threshold value is subsequently ejected from the nozzle 4 a of the first recording head 41 and landed on the substrate S. The ink ejected from the first recording head 41 and landed on the substrate S also spreads on the substrate S until it is transported below the ultraviolet irradiation device 5 and irradiated with ultraviolet rays.

  However, as shown in FIG. 1, the first recording head 41 is provided downstream of the second recording head 42 in the transport direction Z of the substrate S, and the distance L1 between the first recording head 41 and the ultraviolet irradiation device 5. Is shorter than the distance L2 between the second recording head 42 and the ultraviolet irradiating device 5, the ink having a droplet amount equal to or smaller than the threshold value discharged from the first recording head 41 and landed on the substrate S is used. The irradiation timing of the ultraviolet rays from the landing to the irradiation of the ultraviolet rays is earlier than that of the ink having a droplet amount larger than the threshold value discharged from the ink and landed on the substrate S.

  Therefore, the second recording head 42 discharges the degree of spread on the substrate S until the ink having a droplet amount equal to or less than the threshold value discharged from the first recording head 41 and landed on the substrate S is irradiated with ultraviolet rays. The degree of spreading of the ink having a larger droplet amount than the threshold value can be suppressed to be smaller, and the ink can be cured by irradiating with ultraviolet rays before the ratio of the surface area to the ink volume is increased.

If the ratio of the surface area to the volume of the ink with the amount of droplets below the threshold does not increase, the ink is not significantly affected by the surrounding environment, so the ink can be cured by irradiation with a smaller amount of ultraviolet light. It becomes. That is, for example, in the example of FIG. 6 described above, in order to cure 4 [pl] of ink having a droplet amount equal to or less than the threshold, the light quantity exceeding 350 [mJ / cm ² ] as shown in FIG. When the light source is a high-pressure mercury lamp, it can be sufficiently cured without irradiating with ultraviolet rays of a quantity exceeding 150 [mJ / cm ² ].

If the distance L1 between the first recording head 41 and the ultraviolet irradiation device 5 is set to be sufficiently short, the irradiation timing for irradiating the ink with the droplet amount equal to or smaller than the threshold can be made very early, which is larger than the threshold. Ultraviolet rays having a light quantity of about 230 [mJ / cm ² ] (about 120 [mJ / cm ² ] when the light source is a high-pressure mercury lamp) that is a curing light quantity of ink such as 8 [pl] or 16 [pl] of the droplet amount It is also possible to sufficiently cure ink having a droplet amount equal to or less than the threshold.

  As described above, according to the ink jet recording apparatus 1 according to the present embodiment, the ink ejected from the first recording head 41 and landed on the substrate S rather than the ink ejected from the second recording head 42 and landed on the substrate S. The ink was configured so that the irradiation timing of ultraviolet rays by the ultraviolet irradiation device 5 was advanced.

  Accordingly, the ink having a droplet amount equal to or less than the threshold value landed on the substrate S does not spread on the substrate S, and the ink is cured by irradiating with ultraviolet rays before the ratio of the surface area to the volume of the ink increases. It becomes possible. For this reason, since ink with a droplet amount below the threshold is irradiated with ultraviolet rays before being affected by the surrounding environment, it is possible to reliably cure the ink below the threshold with irradiation with a smaller amount of ultraviolet rays. .

  In addition, since the amount of ultraviolet light to be irradiated can be reduced, the amount of power consumed by the ultraviolet irradiation device can be reduced.

[Second Embodiment]
In the first embodiment, the ink of the same color can be used to eject ink having a droplet amount equal to or less than the threshold value from the first recording head 41 disposed near the ultraviolet irradiation device 5. The case has been described in which ink having a droplet amount larger than the threshold value is ejected from the second recording head 42 disposed at a position far from 5.

  In the second embodiment, as in the case of recording a color image on the substrate S, a process of a plurality of types of inks, for example, yellow (Y), magenta (M), cyan (C), and black (K) is used. An ink jet recording apparatus that performs image recording using color ink will be described.

  In addition to the above-mentioned process colors, for example, dark and light inks such as light magenta (LM) and light cyan (LC), special color inks such as orange and violet, white (W) and transparent inks (multiple types of ink) It is also possible to use background image ink such as CL). Hereinafter, among the ink jet recording apparatus according to this embodiment, members having the same functions as those of the members of the ink jet recording apparatus 1 according to the first embodiment will be described with the same reference numerals.

  As shown in FIG. 4, the ink jet recording apparatus 10 according to the present embodiment includes a platen 2 on which the base material S is placed, a transport roller 3 for transporting the base material S, and the recording head above the platen 2. 4 and the ultraviolet irradiation device 5 are the same as the inkjet recording device 1 according to the first embodiment described above.

  Further, among the recording heads 4, a first recording head 41 capable of ejecting ink having a droplet amount equal to or less than the above-described threshold is provided on the downstream side in the transport direction Z of the substrate S, that is, on the side close to the ultraviolet irradiation device 5. The ink jet recording apparatus according to the first embodiment is also provided in that the second recording head 42 that ejects ink having a droplet amount larger than the threshold is provided on the upstream side in the transport direction Z of the substrate S, that is, on the side far from the ultraviolet irradiation device 5. Same as 1.

  Therefore, also in the present embodiment, the ink ejected from the plurality of first recording heads 41 and landed on the substrate S has an irradiation timing earlier than the ink ejected from the second recording head 42 and landed on the substrate S. Become.

  In the inkjet recording apparatus 10 according to the present embodiment, attention is paid to the curing sensitivity of various inks, and the irradiation timing of the first recording head that discharges the ink with lower curing sensitivity is at least between the plurality of first recording heads 41. Is arranged to be faster. Specifically, the first recording head that discharges ink with low curing sensitivity is arranged on the downstream side in the transport direction Z of the substrate S and is arranged closer to the ultraviolet irradiation device 5.

  As described above, when the ink lands on the substrate S and spreads, the ratio of the surface area to the volume of the ink increases, and it becomes difficult to cure under the influence of the surrounding environment. This is because the ink is discharged on the side closer to the ultraviolet irradiation device 5 so that it is cured by being irradiated with ultraviolet rays before being affected by the surrounding environment. In this way, it is possible to cure even ink that originally has low curing sensitivity.

  The curing sensitivity of the ink differs depending on the ink depending on the composition and the like, but in general process colors, there is a tendency that magenta (M) and cyan (C) are high and black (K) is low. In the present embodiment, the case where the magenta (M) ink has the highest curing sensitivity and then the order of cyan (C), yellow (Y), and black (K) will be described. It is determined based on the curing sensitivity of each ink determined in advance by measurement.

  From the above relationship, in the present embodiment, as shown in FIG. 4, the first recording head 41 </ b> M that discharges magenta (M) ink having the highest curing sensitivity among the plurality of first recording heads 41 is the base material. The first recording heads 41C and 41Y that are disposed on the most upstream side in the transport direction Z of S and then discharge cyan (C) and yellow (Y) inks are disposed on the downstream side in the transport direction Z and are most cured. A first recording head 41 </ b> K that discharges black (K) ink with low sensitivity is disposed on the most downstream side in the transport direction Z and is disposed at a position closest to the ultraviolet irradiation device 5.

  In the present embodiment, similarly, between the plurality of second recording heads 42 that discharge a droplet amount larger than the threshold value, the first recording head that discharges ink with low curing sensitivity is arranged so that the irradiation timing is earlier. The magenta (M), cyan (C), yellow (Y), and black (K) are arranged on the downstream side in this order from the most upstream side in the transport direction Z of the substrate S.

  Also in this embodiment, the threshold value of the amount of ink droplets ejected from the first recording head 41 is equal to the amount of curing light when the amount of ink droplets is decreased as shown in FIG. The droplet amount is set to be rapidly increased, and is set to 4 [pl], for example. The threshold value of the droplet amount to be set can be changed according to various conditions such as the material such as the ink absorbability of the substrate S as described above. Although not shown, the first recording head 41, the second recording head 42, and the ultraviolet irradiation device 5 may be arranged in a staggered manner as shown in FIG.

  The ink jet recording apparatus 10 configured as described above also operates in the same manner as the ink jet recording apparatus 1 according to the first embodiment described above.

  Specifically, the first recording head 41 (41M, 41C, 41Y, 41K) is provided downstream of the second recording head 42 (42M, 42C, 42Y, 42K) in the transport direction Z of the substrate S, and the ultraviolet ray Since the ink is provided at a position close to the irradiation device 5, the amount of ink having a droplet amount equal to or smaller than the threshold discharged from each first recording head 41 is larger than the threshold discharged from each second recording head 42. The irradiation timing of ultraviolet rays from landing to irradiation with ultraviolet rays is earlier than the amount of ink.

  Therefore, the degree of spread on the substrate S until the ink having a droplet amount equal to or smaller than the threshold value discharged from each first recording head 41 and landed on the substrate S is irradiated with the ultraviolet rays is determined for each second recording head 42. It is possible to suppress the degree of spreading of the ink having a droplet amount larger than the threshold value discharged from the ink, and to cure the ink by irradiating ultraviolet rays before the ratio of the surface area to the ink volume is increased. .

For example, in the example of FIG. 6, the amount of light exceeding 350 [mJ / cm ² ] necessary for curing the ink of 4 [pl], which is the droplet amount below the threshold (if the light source is a high-pressure mercury lamp, 150 [ mJ / cm ² ], which can be cured sufficiently without being irradiated with ultraviolet rays, and if the distance between each first recording head 41 and the ultraviolet irradiation device 5 is set sufficiently short, the threshold value is exceeded. About 230 [mJ / cm ² ] (about 120 [mJ / cm ² ] when the light source is a high-pressure mercury lamp), which is the curing light amount of ink such as 8 [pl] or 16 [pl] with a large droplet amount It is also possible to sufficiently cure the ink having a droplet amount equal to or less than the threshold by irradiating with ultraviolet rays.

  Further, between the plurality of first recording heads 41 that discharge ink having a droplet amount equal to or less than the threshold value, the first recording head that discharges ink with lower curing sensitivity is arranged so that the irradiation timing is earlier, thereby curing. Ink with low sensitivity does not spread on the substrate S and can be cured by irradiation with ultraviolet rays before being affected by the surrounding environment.

  As described above, according to the ink jet recording apparatus 10 according to the present embodiment, the same effects as those of the ink jet recording apparatus 1 according to the first embodiment described above can be achieved.

  In addition, the first recording head that discharges ink with lower curing sensitivity between the plurality of first recording heads 41 that discharge ink having a droplet amount equal to or less than the threshold value is arranged so that the irradiation timing is earlier. Ink that has low sensitivity and is difficult to cure spreads on the base material S, is prevented from being hardened further by the influence of the surrounding environment, and spread of the ink having low curing sensitivity on the base material S is suppressed. The ink can be cured by being irradiated with ultraviolet rays without being affected by the surrounding environment, and the ink having low curing sensitivity can be cured accurately.

[Third Embodiment]
In the second embodiment described above, the plurality of first recording heads 41 that discharge a plurality of types of inks having a droplet amount equal to or less than the threshold value are arranged so that the ink curing sensitivity is closer to the ultraviolet irradiation device 5. In addition, a case has been described in which a plurality of second recording heads 42 that eject a plurality of types of ink having a droplet amount larger than the threshold value are provided upstream of each first recording head 41 in the transport direction Z of the substrate S.

  However, when ejecting a plurality of types of ink, in addition to the second embodiment, for example, a set of the second recording head 42, the first recording head 41, and the ultraviolet irradiation device 5 as shown in FIG. It is also possible to configure so that each color ink group is arranged in the transport direction Z of the substrate S. In the third embodiment, an ink jet recording apparatus configured as described above will be described.

  In the following, among the inkjet recording apparatuses according to the present embodiment, members having the same functions as those in the inkjet recording apparatuses 1 and 10 according to the first and second embodiments are denoted by the same reference numerals and described. To do.

  The configuration of the inkjet recording apparatus 20 according to the present embodiment will be described in detail. The inkjet recording apparatus 20 has the same color as the ink ejected from the second recording head 42 and the second recording head 42 as shown in FIG. The first recording head 41 that discharges ink, and the ultraviolet irradiation device 5 that irradiates ultraviolet rays to the ink discharged from the first recording head 41 and the second recording head 42 and landed on the substrate S, respectively, in the transport direction of the substrate S Arranged in this order from the upstream side of Z to form one group G, a group Gm for each of a plurality of types of inks, for example, magenta (M), cyan (C), yellow (Y), and black (K) inks. , Gc, Gy, Gk are arranged in parallel in the transport direction Z.

  In addition, it is possible to use inks other than the above process colors as a plurality of types of inks, as in the case of the first and second embodiments. However, any type of ink is used. In each group G, the second recording head 42, the first recording head 41, and the ultraviolet irradiation device 5 are arranged in this order from the upstream side in the transport direction Z of the base material S. The first recording head 41 can eject ink having a droplet amount equal to or smaller than a threshold value, and the second recording head 42 is configured to eject ink having a droplet amount larger than the threshold value. This is the same as in the case of the second embodiment.

  In the inkjet recording apparatus 20 according to the present embodiment, the groups Gm, Gc, Gy, and Gk are further divided in the transport direction Z of the base material S in accordance with the curing sensitivity of the ink to be ejected, as the group has a lower curing sensitivity. It is arranged on the upstream side.

  Specifically, when the ink curing sensitivity is, for example, in the order of magenta (M)> cyan (C)> yellow (Y)> black (K) as in the case described above, the second embodiment is illustrated in FIG. As shown in FIG. 4, the first recording head 41m that discharges magenta (M) ink having the highest curing sensitivity is arranged on the upstream side in the transport direction Z farthest from the ultraviolet irradiation device 5, but in the present embodiment, the reverse In addition, the group Gk including the first recording head 41k for discharging the black (K) ink having the lowest curing sensitivity is arranged on the upstream side in the transport direction Z.

  Then, the groups Gk, Gy, Gc, and Gm related to the respective inks of black (K), yellow (Y), cyan (C), and magenta (M) in order of increasing curing sensitivity from the upstream side in the transport direction Z of the substrate S. Are arranged in this order.

  In this embodiment, the case where the ink curing sensitivity is in the order of magenta (M)> cyan (C)> yellow (Y)> black (K) is shown, but the order of ink curing sensitivity is measured in advance. Needless to say, it is determined based on the curing sensitivity of each ink determined by, for example.

  Also in the present embodiment, the threshold value for the amount of ink droplets ejected from the first recording head 41 is such that the amount of curing light is reduced when the ink droplet amount is decreased, as shown in FIG. The droplet amount is set to be rapidly increased, and is set to 4 [pl], for example. The threshold value of the droplet amount to be set can be changed according to various conditions such as the material such as the ink absorbability of the substrate S as described above. Although not shown, each group may be configured by staggering the first recording head 41, the second recording head 42, and the ultraviolet irradiation device 5 as shown in FIG.

  In the inkjet recording apparatus 20 configured as described above, the configuration for each group Gk, Gy, Gc, and Gm is exactly the same as that of the inkjet recording apparatus 1 according to the first embodiment shown in FIG. Therefore, each group acts in the same manner as the ink jet recording apparatus 1.

  That is, as shown in FIG. 5, the ink ejected from the first recording head 41 and landed on the substrate S is more suitable for the ultraviolet irradiation device 5 than the ink ejected from the second recording head 42 and landed on the substrate S. The irradiation timing of ultraviolet rays by will be accelerated. Therefore, it is possible to cure the ink by irradiating it with ultraviolet rays before the ink having a droplet amount equal to or less than the threshold value landed on the substrate S does not spread on the substrate S and the ratio of the surface area to the volume of the ink does not increase. It becomes.

  For this reason, since the ink with the droplet amount below the threshold is not significantly affected by the surrounding environment, it is possible to reliably cure the ink below the threshold by irradiation with a smaller amount of ultraviolet light. In addition, since the amount of ultraviolet light to be irradiated can be reduced, the amount of power consumed by the ultraviolet irradiation device can be reduced.

  Further, in the inkjet recording apparatus 20 according to the present embodiment, the recording operation on the substrate S is completed for each group.

  That is, when the substrate S is conveyed under the black (K) group Gk, ink is ejected from the second recording head 42k and the first recording head 41k of the group Gk, and immediately after that, the ultraviolet irradiation of the group Gk is performed. The ink is cured by irradiating ultraviolet rays from the device 5k, and the recording operation in the group Gk is completed. When the substrate S is further conveyed, ink is subsequently ejected from the group Gy, and the ink is cured by irradiation with ultraviolet rays, and the recording operation in the group Gy is completed. Further, the recording operation is performed in the groups Gc and Gm.

  However, at that time, the black (K) ink is cured by being irradiated with ultraviolet rays from the ultraviolet irradiation device 5k of the group Gk, and then passes below the groups Gy, Gc, and Gm as the substrate S is conveyed. In this case, each group of ultraviolet irradiation devices 5y, 5c, and 5m is irradiated with ultraviolet rays, and the ultraviolet rays are irradiated a total of four times.

  Similarly, yellow (Y) ink is measured three times from the ultraviolet irradiation devices 5y, 5c, and 5m of the groups Gy, Gc, and Gm, and cyan (C) ink is measured from the ultraviolet irradiation devices 5c and 5m of the groups Gc, Gm. The magenta (M) ink is irradiated with ultraviolet rays only once from the ultraviolet irradiation device 5m of the group Gm twice.

  As described above, according to the inkjet recording apparatus 20 according to the present embodiment, the configurations of the first recording head 41, the second recording head 42, and the ultraviolet irradiation apparatus 5 for each group Gk, Gy, Gc, Gm are described above. Since the configuration is exactly the same as that of the inkjet recording apparatus 1 according to the first embodiment, each group Gk, Gy, Gc, Gm has the same effect as that of the inkjet recording apparatus 1 according to the first embodiment. be able to.

  Further, the group G related to the ink having lower curing sensitivity according to the curing sensitivity of the ink ejected from the first and second recording heads 41 and 42 of each group G is arranged on the upstream side in the transport direction Z of the substrate S. Accordingly, the ink having low curing sensitivity that has landed on the substrate S is not only irradiated with the ultraviolet irradiation device 5 of the group G, but also irradiated with ultraviolet rays of other groups G arranged on the downstream side in the transport direction Z of the substrate S. The apparatus 5 also receives ultraviolet rays, and the ink with lower curing sensitivity can receive more ultraviolet rays.

  Therefore, according to the ink jet recording apparatus 20 according to the present embodiment, the ink discharged onto the substrate S is sufficiently cured in each group G by the same action as the action of the ink jet recording apparatus 1 according to the first embodiment. However, since the ink with lower curing sensitivity is irradiated with ultraviolet rays from the ultraviolet irradiation device 5 of the other group G downstream in the transport direction Z of the substrate S, the ink with lower curing sensitivity is included. Thus, it is possible to reliably cure all the inks.

  In the first to third embodiments, line head type inkjet recording heads are used for the first recording head 41 and the second recording head 42, and the inkjet recording apparatuses 1, 10, and 20 are line heads. Although the case of the system has been described, an ink jet recording apparatus using a serial head type recording head can be configured in the same manner, and the same operational effects as the above-described embodiment can be obtained.

1 is a plan view illustrating a configuration of an ink jet recording apparatus according to a first embodiment. It is the perspective view which looked at the recording head and the ultraviolet irradiation device from the lower side. FIG. 2 is a plan view illustrating a configuration example in which recording heads and ultraviolet irradiation devices are arranged in a staggered manner in the ink jet recording apparatus of FIG. 1. It is a top view which shows the structure of the inkjet recording device which concerns on 2nd Embodiment. It is a top view which shows the structure of the inkjet recording device which concerns on 3rd Embodiment. It is a graph which shows an example of the experimental result which calculates | requires the relationship between the amount of ink droplets, and hardening light quantity.

Explanation of symbols

1, 10, 20 Inkjet recording devices 41, 41m, 41c, 41y, 41k First recording heads 42, 42m, 42c, 42y, 42k Second recording heads 5, 5m, 5c, 5y, 5k Ultraviolet irradiation devices G, Gm, Gc, Gy, Gk Group S Substrate Z Transport direction

Claims (2)

In an inkjet recording apparatus that discharges ultraviolet curable ink onto a substrate, cures the ink by irradiation of ultraviolet rays, and records an image on the substrate.
A first recording head capable of discharging ink having a droplet amount equal to or less than a set threshold;
A second recording head that ejects ink having a droplet amount larger than the threshold;
An ultraviolet irradiation device for irradiating the ink landed on the substrate with ultraviolet rays,
The inks discharged from the first recording head and landed on the base material are earlier than the inks discharged from the second recording head and landed on the base material so that the ultraviolet irradiation timing by the ultraviolet irradiation device is earlier. Arranging the recording head and the ultraviolet irradiation device ,
The second recording head, the first recording head that ejects ink of the same color as the ink ejected from the second recording head, the first recording head, and the second recording head from the upstream side in the conveyance direction of the substrate Are arranged in the order of the ultraviolet irradiation devices for irradiating ultraviolet rays to the ink discharged and landed on the base material to form one group,
A plurality of the groups are provided for each ink color,
According to the curing sensitivity of the ink to be ejected, the plurality of groups are arranged on the upstream side in the transport direction of the base material in the group related to the ink with lower curing sensitivity . 2. The ink jet recording apparatus according to claim 1, wherein the first recording head and the second recording head are line head type ink jet recording heads .

Images