阅读说明：本技术 利用喷墨印刷的涂覆钢板的制造装置 (Apparatus for manufacturing coated steel sheet by inkjet printing ) 是由 金炅锡 洪完基 刘锡填 于 2019-01-23 设计创作，主要内容包括：本发明涉及一种即使长时间生产也不会发生图像模糊或光反射导致的喷头喷嘴堵塞的利用喷墨印刷的涂覆钢板的制造装置,其特征在于,包括：印刷装置,利用喷墨印刷对钢板表面进行印刷,所述印刷装置包括：油墨喷头,将由光固化的油墨排出到钢板的印刷区；光源,设置在所述油墨喷头的下游,向印刷区的油墨照射光；以及屏蔽部件,设置在所述光源的周围,防止从所述钢板反射的光到达所述油墨喷头,所述屏蔽部件在朝向所述钢板的面上沿斜线方向形成有多个凹槽。(The present invention relates to an apparatus for manufacturing a coated steel sheet by inkjet printing, which does not cause nozzle clogging due to image blurring or light reflection even in long-term production, the apparatus comprising: a printing apparatus for printing a surface of a steel sheet by inkjet printing, the printing apparatus comprising: an ink jet head discharging ink cured by light to a printing area of the steel plate; a light source disposed downstream of the ink jet head and configured to irradiate ink in the printing region with light; and a shielding member provided around the light source to prevent light reflected from the steel plate from reaching the ink jet head, the shielding member having a plurality of grooves formed in a diagonal direction on a surface facing the steel plate.)

1. A manufacturing apparatus of a coated steel sheet, comprising:

a printing device for printing the surface of the steel plate by ink jet printing,

the printing device includes:

an ink jet head discharging ink cured by light to a printing area of the steel plate;

a light source disposed downstream of the ink jet head and configured to irradiate ink in the printing region with light; and

a shielding member disposed around the light source to prevent light reflected from the steel plate from reaching the ink jet head,

the shield member has a plurality of grooves formed in a diagonal direction on a surface facing the steel plate.

2. The apparatus for manufacturing a coated steel sheet according to claim 1,

the printing apparatus further includes a base frame for fixing the ink jet head and the light source,

the base frame is provided with an opening for the ink ejection head and an opening for the light source.

3. The apparatus for manufacturing a coated steel sheet according to claim 1,

each groove is formed with a blocking wall crossing the groove on an end opened to an upstream side.

4. The apparatus for manufacturing a coated steel sheet according to claim 1,

a plurality of the grooves have a shape curved from the middle.

5. The apparatus for manufacturing a coated steel sheet according to claim 1,

a plurality of baffles are formed in each groove across the groove.

6. The apparatus for manufacturing a coated steel sheet according to claim 5,

the groove wall or the partition board of each groove is provided with a protruding surface protruding from the wall surface, so that at least 2 spatial layers are formed in each groove.

7. The coated steel sheet manufacturing apparatus according to any one of claims 1 to 6,

the shielding member is made of a light absorbing material or coated with black paint.

8. The coated steel sheet manufacturing apparatus according to any one of claims 1 to 6,

the depth and number of the grooves are changed according to the number of internal reflections of the light reflected within the grooves,

the number of internal reflections is the number of times when the intensity of the reflected light is 0.8% or less of the initial light intensity.

Technical Field

The present invention relates to an apparatus for manufacturing a coated steel sheet by inkjet printing, which does not cause nozzle clogging due to image blurring or light reflection even in long-term production.

Background

The steel sheet with patterns printed on the surface may be classified into a printing steel sheet using a screen, a printing steel sheet using a roll printer, and the like. Screen-printed steel sheets perform a printing process on non-rolled sheet materials (sheets) using a batch type process, roll-printed steel sheets use a method of applying and coating ink or paint on a roll etched with a printing pattern, and pattern transfer paper printed steel sheets use a method of transferring pattern-printed transfer paper to a steel sheet.

There are problems in this prior art.

In the case of the screen method, although the manufacturing process is relatively simple, it is necessary to separately manufacture screens as printing plates according to patterns to be printed or the type of product, and there is a disadvantage that the number of screens increases according to the number or type of colors, and thus the productivity is lowered due to a slow operation speed.

In the case of the roll printing method, unlike the screen method, the roll printing method is a continuous roll coating method, and thus productivity is high, but it is difficult to diversify product design because printing patterns are simple and it is difficult to realize various patterns. In addition, as in the screen method, the number of printing rollers is also increased together according to the number of colors, and thus there is a disadvantage in that the production efficiency is lowered due to the complexity of the production process.

For reference, there is a prior art related to the present invention, which is korean laid-open patent publication No. 2018-0021321.

Disclosure of Invention

Technical problem to be solved

Accordingly, an object of the present invention is to provide a manufacturing apparatus for a coated steel sheet capable of improving productivity and printing quality by inkjet printing.

Another object of the present invention is to provide an apparatus for manufacturing a coated steel sheet by inkjet printing, which does not cause image blurring or clogging of a head nozzle due to light reflection even in long-term production.

(II) technical scheme

An apparatus for manufacturing a coated steel sheet according to an embodiment of the present invention is characterized by comprising: a printing apparatus for printing a surface of a steel sheet by inkjet printing, the printing apparatus comprising: an ink jet head discharging ink cured by light to a printing area of the steel plate; a light source disposed downstream of the ink jet head and configured to irradiate ink in the printing region with light; and a shielding member provided around the light source to prevent light reflected from the steel plate from reaching the ink jet head, the shielding member having a plurality of grooves formed in a diagonal direction on a surface facing the steel plate.

(III) advantageous effects

As described above, according to the present invention, the continuous rolling process production is realized by the inkjet printing, and the process is simple, the production speed and efficiency are high, and various patterns and colors with high resolution can be realized, so that the effect of printing the computer digital image onto the steel plate without distortion can be obtained.

In particular, according to the present invention, even in the case of performing printing with an increased printing height to prevent damage to the heads due to the flatness of the steel plate, the printing speed can be significantly increased without reducing the image quality, and the life span can be extended because nozzle clogging of the heads does not occur, thus having an effect of enabling vivid images to be printed for a long time.

Drawings

Fig. 1 is a diagram schematically illustrating a manufacturing apparatus of a coated steel sheet according to one embodiment of the present invention.

Fig. 2 is a perspective view illustrating a main part of a printing apparatus in a manufacturing apparatus of a coated steel sheet according to one embodiment of the present invention.

Fig. 3 is a cross-sectional view of fig. 2.

Fig. 4 is a bottom view of fig. 2.

Fig. 5 is a schematic diagram for explaining a state where image blurring and nozzle clogging of the head occur.

Fig. 6 is a graph showing the intensity variation of light according to the number of reflections.

Fig. 7 is a bottom view showing another modification of the shielding member.

Fig. 8 is a bottom view showing still another modification of the shielding member.

Fig. 9 is a photograph for comparing image quality of the present invention and the prior art.

Fig. 10 is an enlarged photograph of a portion of fig. 9.

Detailed Description

The invention is explained in detail below with reference to the accompanying drawings which illustrate examples. In assigning reference numerals to components of each drawing, it is to be noted that the same components are given the same reference numerals as much as possible even if they are shown in different drawings. In addition, in explaining the present invention, when it is judged that detailed explanation of related known structures or functions may obscure the gist of the present invention, the detailed explanation thereof will be omitted.

Fig. 1 is a diagram schematically illustrating a manufacturing apparatus of a coated steel sheet according to one embodiment of the present invention.

Although not shown in the drawings, the steel sheet may be subjected to a process of forming a coating layer before entering a printing process. That is, the manufacturing apparatus of the coated steel sheet may include a step of forming a coating layer and a step of forming a printing layer on the coating layer by inkjet printing. The coated steel sheet is a steel sheet having a coating layer or a printing layer formed on the surface thereof.

The manufacturing apparatus of the coated steel sheet may include: a tension control device 10 for applying tension to keep the steel plate in a flat state without bending; a traversing control device 20 for preventing the steel plate from deviating from the center of the production line and moving left and right; speed control means 30, 40 for maintaining the moving speed of the steel plate so that the ink can be accurately dropped to a desired position when the ink is dropped onto the steel plate; and a printing device 100 for printing a pattern or color by dropping the ink onto the steel plate.

Referring to the drawings, a tension control device 10, a traverse control device 20, a guide roller (Deflector Roll)51, a Dancer Roll 53, a speed control device 30, a printing device 100, a guide roller 52, and a speed control device 40 may be continuously provided from the entering direction of a steel sheet.

The Tension control device 10 can adjust the speed and contact angle of the Tension rollers (Tension bridge Roll)11, 12 to maintain the steel sheet within a set Tension range. The tension range may be set to a range that can make the shape of the surface of the steel sheet flat and does not break due to excessive tension. For example, the tension range may be set to 2 to 4kgf/mm²Within the range of (1). In this case, the tension error of the steel sheet is adjusted within a range of-1 to + 1%, so that the tension of the steel sheet can be maintained.

The 2 tensioning rollers 11, 12 may be arranged adjacently. The steel plate enters along the upper surface of the tension roller 11 in the entering direction and is discharged along the lower surface of the tension roller 12 in the discharging direction. Wherein the amount of tension applied to the steel plate can be adjusted by changing the up-down position (or horizontal position) of any one of the tension rollers.

Downstream of the tensioning rollers 11, 12, a tension measuring sensor 13 for measuring the tension of the steel sheet can be provided. The tension measuring sensor measures the tension of the steel sheet and transmits a signal to the tension control gauge 14. The tension control meter transmits an operation signal for decreasing the tension of the steel plate to the tension roller when the measured tension of the steel plate is above a set range, and transmits an operation signal for increasing the tension of the steel plate to the tension roller when the measured tension of the steel plate is below the set range.

The traverse control device 20 can rotate or move the axes of the Steering rollers (Steering Roll)21, 22 according to the traverse amount notified by the traverse measurement sensor 23, which is the degree to which the center position in the width direction of the steel sheet deviates from the center of the steel sheet conveyance line. For example, the amount of the lateral movement of the steel sheet can be controlled within the range of-1 to +1 mm.

The turning rolls 21, 22 may be located downstream of the tensioning rolls 11, 12.

In addition, 2 deflecting rollers 21, 22 may be arranged adjacently. The steel sheet may be conveyed along the upper faces of the adjacent 2 rolls. Wherein the lateral movement of the steel sheet can be controlled by changing the position of any one of the steering rollers in the steel sheet width direction (or the inclination of the rotating shaft in the steel sheet width direction).

Downstream of the deflection-corrected deflecting rollers 21, 22, a lateral-movement measuring sensor 23 for measuring the lateral movement of the steel sheet may be provided. The lateral movement measuring sensor measures the lateral movement of the steel sheet and transmits a signal to the lateral movement controller 24. When the steel plate transversely moves to the right side, the transverse moving control meter transmits an operation signal for moving the steel plate to the left side to the steering roller, and when the steel plate transversely moves to the left side, the transverse moving control meter transmits an operation signal for moving the steel plate to the right side to the steering roller.

In addition, the lateral-shift-measuring sensor 23 may be connected to the printing apparatus 100. For example, when the degree of lateral movement of the steel plate exceeds the dangerous range, the printing apparatus 100 may be stopped.

The speed control devices 30 and 40 can adjust the rotational speeds of the Pinch rolls (pinc Roll)31 and 41 so as to maintain the moving direction speed of the steel sheet at a set speed. Since the ink can only be dropped onto the desired location if the speed of the steel plate is kept constant. For example, the set speed of the steel sheet may be selected within a range of 30mpm to 50 mpm. In this case, the variation of the actual moving speed of the steel sheet may be controlled within the range of-21 to +21 μm/sec.

The pinch rolls 31, 41 may be composed of 2 rolls disposed above and below the steel plate. Wherein the speed of movement of the steel sheet can be adjusted by varying the speed of rotation of at least one of the pinch rolls.

In addition, the pinch rollers 31, 41 can reduce the steel sheet from shaking in the width direction while fixing the steel sheet to move in the width direction. For example, the horizontal vibration amplitude of the pinch roll adjusting steel plate is kept within a range of-11 to +11 μm.

Also, the pinch rollers 31, 41 may be provided at least one of upstream and downstream of the printing apparatus 100. Examples of pinch rollers provided both upstream and downstream of the printing device are shown in the drawings, but not limited thereto, and for example, pinch rollers may be provided only downstream of the printing device to pull the steel sheet and control the speed, or only upstream of the printing device to push the steel sheet and control the speed.

The guide rollers 51, 52 may be used to change the moving direction and angle of the steel plate. For example, it may be disposed between the traverse control device 20 and the speed control devices 30, 40 to change the moving direction of the steel plate, and it may be disposed between the printing device 100 and the speed control devices 30, 40 to change the moving direction of the steel plate.

A shock absorbing member may be provided between the floating roller 53 and the base so that the steel plate moves in a small range in the up-down direction. Therefore, the dancer roll can reduce the vibration of the steel plate, and further can adjust the tension of the steel plate.

Specifically, the dancer roller 53 may reduce the vibration of the steel sheet generated while passing through the tension control device 10 and the traverse control device 20. For example, the vertical vibration amplitude of the dancer roll adjustment steel plate is kept within-60 to +60 μm.

On the other hand, the printing apparatus 100 includes: a step of spreading the steel sheet in a flat manner without bending in a Jetting Zone (Jetting Zone) or a printing Zone, which is an ink drop position, in close contact with the conveying unit 120; and a position adjusting unit (not shown) of the steel plate supporting rollers 131, 132, which adjusts the up-down position of the steel plate.

The adhesion conveying unit 120 may adhere the steel plate to the conveyor belt 133 by vacuum to make the surface of the steel plate flat. As described above, although the flatness of the surface of the steel sheet can be achieved by the tension control device 10, fine residual ripples remain on the surface of the steel sheet. For example, in the case where the distance between the ink jet head 101 and the steel plate is 0.5 to 1.0mm, the printing apparatus 100 may be damaged when the steel plate moving at a speed of 30 to 50mpm collides with the ink jet head. Thus, the residual ripple is removed using a separate close-proximity conveying unit.

The position adjusting units of the steel plate supporting rollers 131, 132 are used to adjust the up-down positions of the steel plate supporting rollers that support the steel plate and control the specified up-down position of the steel plate so that the ink is dropped onto the accurate position of the steel plate. For example, the position adjusting unit of the steel plate supporting roller adjusts the up-down position of the steel plate supporting roller so that the up-down vibration amplitude of the steel plate is kept within-60 to +60 μm.

The tension control device 10, the traverse control device 20, the speed control devices 30 and 40, the contact transport unit 120 of the printing apparatus 100, and the position adjustment units of the steel plate support rollers 131 and 132 described above function to provide conditions for the steel plate on the ink jet head that can precisely form high-resolution digital images on the steel plate by ink jet printing. That is, in the ejection area or the printing area where the ink is dropped to form the image, the widthwise center position of the steel plate needs to be located at the center of the steel plate transfer line, and the distance from the ink jet head needs to be kept at a set value.

The printing apparatus 100 may eject ink onto a steel sheet moving within a printing zone to perform inkjet printing on the surface of the steel sheet.

Fig. 2 is a perspective view showing a main part of a printing apparatus in a manufacturing apparatus of a coated steel sheet according to one embodiment of the present invention, fig. 3 is a sectional view of fig. 2, and fig. 4 is a bottom view of fig. 2.

As shown in the above drawings, a manufacturing apparatus of a coated steel sheet according to one embodiment of the present invention includes a printing apparatus 100 for printing a surface of a steel sheet by inkjet printing, the printing apparatus including: an ink jet head 101 for discharging ink cured by light to a printing area of the steel sheet 1; a light source 103 disposed downstream of the ink jet head and configured to irradiate ink in the printing area with light; and a shielding member 150 disposed around the light source to prevent light reflected from the steel plate from reaching the ink jet head, the shielding member having a plurality of grooves 151 formed in an oblique direction on a surface facing the steel plate.

The ink head 101 is provided with a plurality of nozzles 102 facing downward, and the plurality of nozzles are arranged side by side at the same pitch in the width direction of the steel plate 1. Only by arranging the nozzles at a predetermined pitch, uniform print quality can be obtained.

In addition, a plurality of ink jet heads 101 may be provided in parallel in the moving direction of the steel plate. Each of the ink jet heads disposed in the moving direction of the steel plate 1 can jet ink of a different color from each other. For example, ink heads for ejecting Cyan (Cyan, C), Magenta (M), Yellow (Y), and Black (K) inks may be provided side by side from upstream along the moving direction of the steel sheet.

Meanwhile, at least one ink jet head 101 for jetting ink having a single color may be provided in the width direction of the steel sheet 1. In the case where the length of the ink jet head is long enough to cover the width of the steel plate, one ink jet head may be provided, but in the case where the length of the ink jet head is shorter than the width of the steel plate, a plurality of ink jet heads may be connected in the width direction of the steel plate for use.

The ink heads 101 disposed along the moving direction of the steel plate 1 may be disposed such that a portion of the heads overlap each other in the moving direction of the steel plate. At this time, in each ink jet head, the nozzles 102 located at the outermost side in the width direction of the steel plate may be disposed so as not to overlap in the moving direction of the steel plate. Therefore, uninterrupted and uniform printing can be achieved in the entire width direction area of the steel sheet in the printing area.

Further, the printing apparatus 100 may include an ink supply device (not shown) capable of continuously supplying ink without bubbles. The ink supply device may be provided in connection with the ink jet head 101 to supply ink to the nozzles 102, and detachably combined with the ink jet head to be replaced in the case of ink shortage.

The ink may be one that is curable by light.

The ink may be cured using Ultraviolet (UV) light as light irradiated from the light source 103.

The ink droplets (Droplet)2 ejected on the steel plate 1 may be spread continuously with the lapse of time, and the resolution of the printed image is lower as the size of the ink droplets is larger. Therefore, the light source 103 can cure the ink so that the ink does not spread more than an appropriate amount.

Such a light source 103 may be disposed downstream of the ink ejection head 101. For example, a light source may be provided downstream of an ink head that takes charge of one color, and in this case, an ink head of C color, a light source, an ink head of M color, a light source, an ink head of Y color, a light source, an ink head of K color, and a light source may be provided in this order along the moving direction of the steel sheet.

The distance between the ink heads 101 and the distance between the light sources 103 and the distance between the adjacent ink heads and the light sources may be constant. Therefore, the degree of curing of each color can be made uniform.

The printing apparatus 100 may further include a base frame 105 for fixing the ink ejection head 101 and the light source 103.

The pedestal 105 may combine a plurality of ink ejection heads 101 and a plurality of light sources 103 into one unit. For example, the base frame may extend in the moving direction of the steel plate 1 to combine a plurality of ink jet heads and a plurality of light sources.

Although one pedestal 105 may combine the ink ejection head 101 and the light source 103 into one unit, unlike this, a plurality of pedestals may be provided according to colors.

The base frame 105 may be provided with an opening 106 for receiving the ink ejection head 101 and an opening 104 for the light source 103.

The distance between the steel plate 1 and the nozzles 102 of the ink jet head 101 is adjustable, and the shorter the distance between the steel plate and the nozzles, the better the printing quality, but in practice the distance between the steel plate and the nozzles cannot be made infinitely small due to constraints such as strength and inherent flatness of the steel plate used as a printing material.

For example, when the distance between the steel plate 1 and the nozzles 102 of the ink jet head 101 is less than about 0.5mm, the steel plate may collide with the ink jet head, thereby damaging the printing apparatus 100. Since the steel plate is not completely planar but includes fine corrugations, a safety distance is required between the steel plate and the nozzle.

Fig. 5 is a schematic diagram for explaining a state where image blurring and clogging of the head nozzles occur.

For example, as shown in fig. 5, in the case of performing ink jet printing when the distance between the steel plate 1 and the nozzles 102 of the ink jet head 101 is about 3mm, light irradiated from the light source 103 is reflected and scattered from the surface of the steel plate, and the reflected light thus scattered reaches the nozzles of the ink jet head.

Wherein the average reflectivity on the surface of the steel plate is about 87%, and part of the product has a mirror-like surface, so that the reflectivity is 95%.

The intensity of light reflected from the surface of the steel plate 1 is reduced, but reaches the vicinity of the ink jet head 101, and the falling ink droplets 2 are cured in advance, thereby inhibiting the spreading of ink. Therefore, the ink dropped onto the steel sheet is cured without being sufficiently spread, resulting in printing of a blurred image.

In particular, some of the reflected light reflected and scattered from the surface of the steel sheet 1 is irradiated to the nozzles 102 of the ink jet head 101, and the ink condensed on the nozzles after the discharge is completed is solidified. Thereafter, the solidified ink causes nozzle clogging, and the ink does not smoothly flow out, thereby adversely affecting the printing quality. For example, a portion where the nozzle is clogged may not eject ink, and a streak may be formed on a printed image.

Therefore, the manufacturing apparatus of a coated steel sheet according to one embodiment of the present invention is characterized in that the printing apparatus 100 includes the shielding member 150 for preventing light reflected from the steel sheet from reaching the ink jet head so as to be able to prevent image blurring and nozzle clogging of the ink jet head from occurring at the time of printing even if the distance between the steel sheet 1 and the nozzles is about 3mm or more while securing a safe distance between the steel sheet and the nozzles 102 of the ink jet head 101.

The shield member 150 has a plurality of grooves 151 formed in a diagonal direction with respect to the direction of movement of the steel plate on the surface facing the steel plate 1. In addition, the shielding member may be made of a material capable of absorbing reflected light or coated with a black or black-like paint, and specifically, an anodized layer may be coated on a metal material such as aluminum, for example.

Such a shielding member 150 may be integrally formed on the base frame 105, or may be separately manufactured and then coupled or assembled to the base frame using any fixing member (e.g., a fixing screw, etc.).

The groove walls of the groove 151 formed on the shielding member 150 preferably form an angle of about 90 degrees, i.e., at a right angle with respect to the surface of the steel plate 1, but are not limited thereto, and may have any angle according to a reflection angle that varies with the irradiation angle of the light source 103 and the roughness of the material surface, for example.

As described above, the number of times of reflection of the reflected light within the shielding member 150 is maximized to be reflected inside the groove 151, so that the intensity of the light flowing out of the shielding member can be reduced.

On the other hand, since the concave groove 151 of the shielding member 150 has a structure extending in a diagonal direction, the reflected light repeats internal reflection toward the upstream side, that is, toward the ink jet head 101 side, and thus the reflected light may flow out of the concave groove. To prevent this, a blocking wall 152 may be further formed across the groove at the end of each groove that is open to the ink ejection head on the upstream side. Therefore, each groove of the shielding member can lock the reflected light inside thereof, so that more internal reflection times can be performed.

Fig. 6 is a graph showing the intensity variation of light according to the number of reflections.

As shown in the drawing, in the case where the shielding member 150 is formed of aluminum that is not coated (Bare (barrel) state), when the number of internal reflections reaches 30 times, the intensity of reflected light is reduced to about 8%, and therefore, it is preferable to design the groove 151 to a depth at which more than 30 internal reflections can occur in the groove of the shielding member.

Also, the number of the grooves 151 may be set such that the reflected light has an intensity that does not induce ink curing even if it continuously contacts the nozzles 102 of the ink jet head 101 during the printing time of the steel sheet (about 100 minutes, based on 50 mpm).

For example, in the case of considering the safety factor, the intensity of the reflected light that does not cause the nozzle of the head to be clogged even if the irradiation is performed for 300 minutes is 0.00006% of the initial intensity, and at this time, assuming that the number of times of the internal reflection is 88 times, the depth and the number of the grooves 151, which are design variables of the shielding member 150, may be changed according to the printing height and the minimum reflection angle of the steel plate surface in the case of considering the number of times of the internal reflection in the grooves.

Fig. 7 is a bottom view showing another modification of the shielding member.

The shielding member 150 shown in fig. 7 is formed with a plurality of grooves 151 in an oblique line direction with respect to the moving direction of the steel plate on the surface facing the steel plate 1, and the plurality of grooves have a shape curved from the middle. Therefore, a plurality of grooves of a substantially V-shape may be provided on both sides of the light source 103.

As described above, when the plurality of grooves 151 are formed in a shape bent from the middle, there may be an advantage that the in-groove blocking wall 152 is provided only on one side front end side of the shielding member 150.

First, the groove 151 bent from the middle allows the reflected light to be internally reflected at the maximum number of reflection times, so that the intensity of the light flowing out of the shielding member 150 can be reduced.

In particular, since the grooves 151 extend in a diagonal direction of curvature, so that the reflected light repeats internal reflection mainly toward the downstream side, that is, toward the light source 103 side or downstream thereof, even if the reflected light flows out of the grooves, the reflected light flows out toward the light source side or downstream thereof, so that the possibility of the reflected light reaching the ink jet head 101 can be significantly reduced.

Wherein the upstream side in the groove 151 blocks the discharge of the reflected light by the blocking wall 152.

Fig. 8 is a bottom view showing still another modification of the shielding member.

The shield member 150 shown in fig. 8 is formed with a plurality of grooves 151 in an oblique line direction with respect to the moving direction of the steel plate on the surface facing the steel plate 1, and a plurality of partitions 153 crossing the grooves are formed in each groove. Therefore, a plurality of grooves in a lattice shape in a substantially diagonal direction may be provided.

As described above, when the plurality of grooves 151 are formed in a lattice shape in an oblique line direction, it is not necessary to form a separate blocking wall in the groove.

In addition, the groove walls or partitions 153 of each groove 151 are provided with protruding surfaces 154 protruding from the wall surface, so that at least 2 spatial layers can be formed in each groove. Fig. 8 illustrates an enlarged cross-sectional view of an example in which three spatial layers are formed.

Such a groove 151 having a plurality of space layers may be formed at the time of manufacturing the shielding member 150 or formed by machining. Alternatively, a plurality of thin plate members having holes or grooves corresponding to the grooves may be stacked, thereby forming a groove having a plurality of spatial layers.

As described above, in the groove 151 having a plurality of spatial layers inside, the reflected light is internally reflected by the maximum number of reflections, so that the intensity of the light flowing out of the shielding member can be reduced.

In particular, since the concave groove 151 has an internal structure in which a plurality of space layers and the protruding surface 154 are formed, reflected light can be locked inside the concave groove and a larger number of times of internal reflection can be performed, and therefore, reflected light cannot flow out of the concave groove, and the possibility of reaching the ink jet head 101 can be remarkably reduced.

In order to confirm the influence of the shielding member 150 on the image quality in the printing apparatus 100 of the manufacturing apparatus of the coated steel sheet according to one embodiment of the present invention, the embodiment of the present invention mounted with the shielding member and the comparative example of the related art without the shielding member were tested by changing the printing height.

Printing was performed under printing conditions of a steel plate speed of 50mpm, an ink ejection speed of 20Khz, and a resolution of 600dpi, and the printing heights, i.e., the distances between the steel plate and the nozzles 102 of the ink jet head 101 were classified into 0.5mm, 1mm, 2mm, and 3 mm.

[ Table 1]

In the case of printing on a steel plate according to the related art, nozzle clogging of the head does not occur when the recommended printing height, i.e., the distance between the steel plate 1 and the nozzles 102 of the ink head 101 is within 1mm, but nozzle clogging occurs when it exceeds 1mm, resulting in poor image quality.

On the other hand, such as the manufacturing apparatus of the coated steel sheet according to one embodiment of the present invention, when the shielding member 150 is installed on the printing apparatus 100 to perform printing, nozzle clogging of the head does not occur during printing even at a printing height of 3 mm.

Therefore, it was confirmed that even in the case where the printing height, i.e., the distance between the steel plate 1 and the nozzles 102 of the ink jet head 101 had to be increased due to the constraint conditions such as flatness of the steel plate itself, nozzle clogging of the head did not occur at the time of printing according to the present invention, and vivid images could be printed for a long time while preventing the head from being damaged by poor flatness of the steel plate.

Fig. 9 is a photograph for comparing image quality of the present invention and the prior art, and fig. 10 is an enlarged photograph of a portion of fig. 9.

Fig. 9 and 10 show the image quality in the coated steel sheet using inkjet printing according to the present invention and the prior art when the printing height, i.e., the distance between the steel sheet 1 and the nozzles 102 of the ink jet head 101 is 3 mm.

It was confirmed that in the embodiment of the present invention in which the shielding member 150 was mounted, a vivid and dark image was realized even when the printing height was 3mm, whereas in the comparative example of the related art in which the shielding member was not provided, a blurred image was printed when the printing height was 3 mm. In particular, the comparative example of the related art shows an example in which the ink droplets being dropped are cured in advance by the reflected light, thereby blocking the spreading of the ink and printing a blurred image.

As described above, according to the present invention, it is possible to continuously print digital images on a steel sheet by inkjet printing, thereby realizing continuous wrap process production, and also to remarkably increase the printing speed without reducing the image quality in the case of performing printing at an increased printing height to prevent damage of a head due to flatness of the steel sheet, and to extend the service life due to no occurrence of nozzle clogging of the head, thereby having an effect of printing vivid images for a long time.

The above description is merely exemplary of the technical idea of the present invention, and various modifications and variations can be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments shown in the present specification and the drawings are not intended to limit the technical idea of the present invention but to illustrate, and the scope of the technical idea of the present invention is not limited to these embodiments. The scope of the invention should be construed by the appended claims, and all technical ideas within the equivalent scope thereof should be construed as being included in the scope of the claims.

Industrial applicability

The invention is suitable for the manufacture of coated steel sheets by means of inkjet printing.