Coating apparatus, coating method, and printing system

Abstract

The dimensionless film thickness range is wide, and even under conditions where the coating gap H fluctuates significantly, the occurrence of coating defects is prevented. [Solution] The coating apparatus (10) applies a coating liquid (5) to a blanket cylinder (1) having a metal core (1a) and a cushion layer (1b), and includes a vacuum die (2) positioned close to the blanket cylinder (1) and having a pressure reduction section. The vacuum die (2) discharges the coating liquid (5) from its tip to form a bead (5B) between itself and the blanket cylinder (1), and while reducing the atmosphere (Rv) upstream of that point so that the actual pressure P indicated by the pressure reduction section is -0.1 to -20 [kPaG], it continuously forms a coating film (50) of the coating liquid (5) on the surface of the rotating blanket cylinder (1).

Description

Technical Field

[0001] The present disclosure relates to a coating apparatus, and particularly relates to a coating apparatus used for film formation on a blanket cylinder (blanket roller) in a roll-to-roll (R2R) process and reverse offset printing, a coating method thereof, and a printing system.

Background Art

[0002] In general, anti-counterfeiting technologies such as optical technologies, physical technologies, electronic technologies, and even AI image recognition technologies are widely known. These are mainly applied to products and labels, and are intended for authenticity verification. However, these conventional techniques focus on authenticating individual products, and do not function sufficiently as a method for monitoring the entire supply chain and ensuring the transparency of distribution channels.

[0003] Accordingly, the present applicant has developed and provided "Akliteia" (registered trademark), which combines anti-counterfeiting labels, authenticity verification devices, and blockchain technology, unlike such conventional techniques. This system enables highly accurate authenticity verification by using a transparent label printed with a special metal pattern of submicron resolution. This technology not only prevents the distribution of counterfeit products, but also realizes quantity management of genuine products. In addition, this system records the scan results of products on the blockchain and visualizes the occurrence status of counterfeit products in the entire supply chain, making it easy to grasp the actual situation of damage.

[0004] For the production of such high-resolution metal pattern labels, a manufacturing process combining continuous processing using the roll-to-roll (R2R) method and high-definition pattern formation technology using reverse offset printing is effective. The R2R method is a process in which a fine pattern on a blanket cylinder is continuously transferred while a substrate such as film or metal foil is wound into a roll, and a seamless blanking roll (SBR) is preferably used as the blanket cylinder. On the other hand, in reverse offset printing, metal ink is first uniformly applied to the SBR using a vacuum die. Then, the negative pattern of a plate cylinder having a structure with fine irregularities (relief) on its surface (surface relief microstructure, SRM) is transferred to the coating film formed on the SBR (that part is removed). By finally transferring the coating film with the positive pattern thus formed to a substrate, a high-resolution metal pattern label can be obtained.

[0005] One known method for forming a coating film on a blanket cylinder, such as an SBR, involves bringing a slot die close to the rotating cylinder surface and discharging a coating liquid from the tip of the slot die to continuously form a liquid film on the blanket cylinder. For example, Patent Document 1 describes suitable process conditions for barcode coating on an iron core cylinder using a vacuum die, and Patent Document 2 describes suitable process conditions for coating an iron core cylinder with a low-viscosity liquid film using a vacuum die. However, these techniques are based on iron core cylinders, and it has been difficult to directly apply the process conditions in Patent Documents 1 and 2 to SBRs. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 7562119 [Patent Document 2] Patent No. 6027809 [Overview of the project] [Problems that the invention aims to solve]

[0007] In other words, in reverse offset printing, the SBR requires precise alignment with the plate cylinder and impression cylinder even during continuous R2R operation, thus necessitating high mechanical rigidity and dimensional accuracy. For this reason, a metal core is used in the SBR, but a metal core alone is too rigid and cannot fully absorb the impact when pressed against the plate cylinder. To solve this problem, a structure is adopted in which a urethane rubber layer with appropriate elasticity is provided around the metal core to ensure cushioning. In addition, it is common to laminate a printing layer made of, for example, polydimethylsiloxane (PDMS) onto the surface of the SBR, which enables high-precision pattern transfer to the substrate while maintaining the microstructure.

[0008] However, with SBRs having such a multilayer structure, a problem can arise where cylindricity and roundness inevitably decrease compared to iron core rolls due to the manufacturing and material properties of the urethane rubber layer. In other words, the urethane rubber layer cannot be molded as precisely as an iron core roll. For example, the roll runout of an SBR is about ±20 μm (runout width 40 μm), which is an extremely large value compared to when the coating film thickness (h: liquid film thickness) applied to the SBR is about 1 to 2 μm. In this case, in order to prevent contact or interference between the SBR and the vacuum die, the maximum clearance between the two must be set to be sufficiently larger than the total runout tolerance = 40 μm. Furthermore, within such a large clearance range, it is required to maintain a vacuum and a stable film thickness even when the distance between the SBR and the vacuum die (coating gap (H)) fluctuates greatly by the above runout width.

[0009] In contrast, the process window for vacuum dies proposed in conventional technology is based on the premise of iron core rolls with high cylindricity and roundness, and the distance between the roll and the vacuum die is approximately constant. Therefore, it is difficult to apply it directly to SBR, where the distance variation is large, because the preconditions are completely different. If such a conventional process window were applied to SBR, as the coating gap (H) fluctuates greatly, the vacuum cannot be maintained, which may result in coating defects (such as streaky unevenness), or in some cases, the coating film may be interrupted.

[0010] Furthermore, Patent Document 2 discloses a relationship expressed by an empirical formula that includes the number of capillaries (Ca) and the dimensionless film thickness (H / h) as a "coating window" indicating the conditions under which a stable coating film can be formed in a coating process using a die. However, the conditions under which this empirical formula was derived are h=10μm, and H=90, 110, and 130μm (Examples 1 to 4 of Patent Document 2), and the dimensionless film thickness is in a small and narrow range of about H / h=9 to 13. In contrast, when using SBR, considering the above-mentioned liquid film thickness (about 1 to 5μm) and fluctuation range (40μm), the dimensionless film thickness can be in a large and wide numerical range of about H / h>20 to 40, which is significantly different from the numerical range assumed by the empirical formula in Patent Document 2.

[0011] Therefore, this disclosure has been made in view of these circumstances, and aims to provide a coating apparatus that, in R2R reverse offset printing, uses SBR, which allows for a wide range of dimensionless film thickness, for example H / h > 20 to 40, and enables high-precision and homogeneous film coating by maintaining a good vacuum even under conditions where the coating gap H fluctuates greatly, thereby preventing the occurrence of coating defects. [Means for solving the problem]

[0012] [1] To achieve the above objective, the coating apparatus according to the present disclosure is an apparatus for applying a coating liquid to a blanket cylinder having a metal core and a cushion layer, and comprises a vacuum die positioned close to the blanket cylinder and having a pressure reduction section. The vacuum die discharges the coating liquid from its tip to form a bead of the coating liquid between itself and the blanket cylinder, and while reducing the atmosphere upstream of the bead in the direction of rotation of the blanket cylinder (rear side or back side of the tip) so that the actual pressure P (gauge pressure) indicated by the pressure reduction section is -0.1 to -20 [kPaG], it continuously forms a coating film (liquid film) of the coating liquid on the surface of the rotating blanket cylinder.

[0013] In this configuration, the coating liquid bead formed between the tip of the vacuum die and the blanket cylinder is pulled upstream (opposite to the direction of coating) by the reduced pressure, thereby promoting bead stabilization and ensuring uniform coating thickness. However, blanket cylinders with a cushion layer have a large amplitude of vibration, which can cause the bead to waver and compromise stability. In contrast, in this configuration, the reduced pressure section of the vacuum die appropriately controls the ambient pressure near the surface of the blanket cylinder, maintaining the actual pressure P at -0.1 to -20 [kPaG]. As a result, sufficient bead stability is ensured, and vacuum is maintained well even under conditions where the amplitude of the blanket cylinder fluctuates significantly. This improves the uniformity of the coating film, preventing coating defects such as streaks and breaks in the coating film, and enabling the stable formation of a highly accurate and homogeneous coating film.

[0014] [2] The above configuration is particularly useful when the runout of the blanket cylinder is, for example, ±20 [μm]. Here, "runout" in this disclosure refers to the amount of runout obtained by a method conforming to the total runout tolerance measurement method specified in "JIS B 0021 (1998): Mechanical runout measurement method". As described above, according to this disclosure, vacuum can be maintained well even under conditions in which the runout of the blanket cylinder fluctuates greatly. For this reason, the coating apparatus of this disclosure is particularly effective even under fluctuating conditions that were not anticipated in conventional iron core blanket cylinders, such as a runout of ±20 μm.

[0015] [3] In this case, the linear suction flow rate Q indicated by the depressurization section when the above atmosphere is depressurized may be 200 [L / (min·m)] or more. Here, "linear suction flow rate" in this disclosure refers to the suction flow rate per unit width of the vacuum die (width along the extending axis of the blanket cylinder). With this configuration, by setting the linear suction flow rate Q to 200 [L / min / m] or more, the formation of an appropriate vacuum environment by the depressurization section is promoted, and predetermined depressurization conditions (actual pressure P = -0.1 to -20 [kPaG]) can be stably maintained. This further reduces the influence of blanket cylinder vibration and ensures the uniformity of the coating film more reliably.

[0016] [4] The pressure reduction section may also have a cover section configured to cover or surround the above-mentioned atmosphere. By configuring the vacuum die having a pressure reduction section to include a cover section, the pressure reduction region formed in the above-mentioned atmosphere upstream of the bead becomes less susceptible to the influence of the external environment, and the inflow of air from the outside is suppressed. As a result, the pressure reduction state of the atmosphere upstream of the bead becomes more stable, and the effects of pressure fluctuations caused by the swing of the blanket can be suppressed even more effectively.

[0017] [5] Furthermore, the cover portion may have a back plate extending along the axial direction of the blanket cylinder upstream of the tip portion, and a side plate extending along a portion of the end face of the blanket cylinder and vacuum die upstream of the tip portion. This configuration provides the advantage of being able to more effectively block or suppress the inflow of external air into the reduced pressure region formed in the atmosphere upstream of the bead, while maintaining a simple structure. In addition, by having this simple component perform the function of a reduced pressure chamber, an increase in installation space can be suppressed.

[0018] [6] More specifically, the vacuum die may be configured to satisfy at least one of the following conditions (1) to (3). D1 = 100 ± 20 [μm] …(1) D2 = 450 ± 150 [μm] …(2) D3 = 40 ± 20 [μm] …(3) Here, D1: Clearance between the surface of the blank cylinder and the back plate D2: Clearance between the end face of the blank cylinder and the side plate D3: Clearance between the surface of the blank cylinder and the tip of the vacuum die

[0019] By setting each clearance in this way, it is generally considered that the sealing performance of the atmosphere (region) that should be depressurized is lowered, and it becomes difficult to maintain a good depressurized state. However, the coating apparatus of the present disclosure targets a blank cylinder with a very large runout as described above, and it is preferable to intentionally set such a relatively wide clearance in order to avoid contact and interference between the blank cylinder and each member. Furthermore, even under these conditions, by maintaining the actual pressure P indicated by the depressurization unit at -0.1 to -20 [kPaG], the stability of the bead is sufficiently ensured, and good vacuum retention can be achieved even under conditions where the runout of the blank cylinder varies significantly.

[0020] [7] Furthermore, in the above configuration, the coating conditions represented by the following formula (4) may be satisfied. Ca / (L / L1)≦0.00253·exp(-0.026(H / h)) …(4) Where: H: Coating gap [μm] h: Coating film thickness [μm] L1: Thickness of the discharge port end of the downstream lip of the vacuum die [μm] L: Distance between the inner end of the discharge port of the upstream lip of the vacuum die and the contact position of the bead Ca: Capillary number represented by the following formula (5) Ca=μ·V / σ …(5) Where: μ: Viscosity of the coating liquid [mPa·s] σ: Static surface tension of the coating liquid [mN / m] V: Relative speed between the surface of the blank cylinder and the tip of the vacuum die [m / min]

[0021] In this way, the actual pressure P indicated by the reduced pressure section can be well maintained at -0.1 to -20 [kPaG], preventing the occurrence of coating defects and enabling high-precision and homogeneous film coating even in a different range than conventional methods, especially over a wide range of H / h (particularly H / h > 20 to 40).

[0022] [8] More specifically, the coating solution may contain a metal or a metal oxide. In this way, by using a plate cylinder with a high-resolution pattern as the SRM, a fine pattern of metal or metal oxide with submicron resolution can be formed, and a transparent label with excellent anti-counterfeiting properties can be obtained. Examples of such metals include copper, aluminum, and cobalt.

[0023] [9] Furthermore, the coating method according to the present disclosure is a method that can be effectively carried out using the printing apparatus according to the present disclosure. That is, the coating method according to the present disclosure is a method of applying a coating liquid to a blanket cylinder having a metal core and a cushion layer, wherein a vacuum die positioned close to the blanket cylinder and having a vacuum section discharges the coating liquid from its tip to form a bead of the coating liquid between itself and the blanket cylinder, and while reducing the atmosphere upstream of the bead in the direction of rotation of the blanket cylinder (rear side or back side of the tip) so that the actual pressure P indicated by the vacuum section is -0.1 to -20 [kPaG], a coating film (liquid film) of the coating liquid is continuously formed on the surface of the rotating blanket cylinder.

[0024]

[10] Furthermore, the printing system according to this disclosure comprises a blanket cylinder having a metal core and a cushion layer, a vacuum die positioned close to the blanket cylinder and having a pressure reduction section, and a plate cylinder and an impression cylinder positioned opposite the blanket cylinder so as to sandwich the vacuum die in the rotational direction of the blanket cylinder. The vacuum die discharges a coating liquid from its tip to form a bead of the coating liquid between itself and the blanket cylinder, and while reducing the atmosphere upstream of the bead in the rotational direction of the blanket cylinder (behind or behind the tip) so that the actual pressure P indicated by the pressure reduction section is -0.1 to -20 [kPaG], it continuously forms a coating film (liquid film) of the coating liquid on the surface of the rotating blanket cylinder. The plate cylinder has a negative pattern, and a positive pattern is formed by extracting a portion corresponding to the negative pattern from the coating film on the surface of the blanket cylinder, and the blanket cylinder transfers the positive pattern onto a substrate being transported on the surface of the impression cylinder. [Brief explanation of the drawing]

[0025] [Figure 1] This is a schematic diagram illustrating the configuration (partial process flow) of a printing system 100 equipped with a coating apparatus 10 according to one embodiment of the present disclosure. [Figure 2] Figure 1 shows an example of a cross-section perpendicular to the extension axis Ax of SBR1. [Figure 3] (A) is a schematic plan view showing the state in which the SRM is transferred to the coating film 50 in section A, which is enclosed by a dashed line in Figure 1, and (B) is a schematic plan view showing the state in which the positive pattern 50p is transferred to the film 7 in section B, which is enclosed by a dashed line in Figure 1. [Figure 4] Figure 1 is a cross-sectional view of the vacuum die 2, which includes a portion of the SBR1 shown, and Figure 5 is a cross-sectional view taken along line IV-IV. [Figure 5] Figure 1 is a longitudinal cross-sectional view of the vacuum die 2, which includes a portion of the SBR1 shown, and Figure 4 is a cross-sectional view along the VV line shown. [Figure 6] This is a magnified cross-sectional view of a portion of Figure 4, in particular, showing the state of the tip of the vacuum die 2, the surface of the SBR1, and the coating liquid 5 discharged between them. [Figure 7](A) and (B) are enlarged schematic diagrams of section C, enclosed by a dashed line in Figure 4, and section D, enclosed by a dashed line in Figure 5, respectively. [Figure 8] This graph shows an example of the results obtained in coating test 1. [Modes for carrying out the invention]

[0026] This embodiment will be described below with reference to the attached drawings. To facilitate understanding of the description, the same reference numerals are used for identical components in each drawing whenever possible, and redundant descriptions are omitted. The following embodiments are illustrative examples for illustrating the present disclosure and are not intended to limit the present disclosure to these embodiments only. Furthermore, the present disclosure can be modified in various ways without departing from its essence. Moreover, those skilled in the art can adopt embodiments in which each of the elements described below is replaced with equivalent components, and such embodiments are also included within the scope of the present disclosure.

[0027] [Examples of printing system and coating equipment configurations] Figure 1 is a schematic diagram illustrating the configuration (and part of the process flow) of a printing system 100 equipped with a coating apparatus 10 according to one embodiment of the present disclosure. The printing system 100 is a system that produces a transparent label 7' by printing, for example, a special metal pattern for anti-counterfeiting purposes onto a film 7 (corresponding to an example of a "substrate" in the present disclosure). To achieve this, the printing system 100 employs R2R (roll-to-roll) reverse offset printing. The film 7 is held between an unwinding roll R1 and a take-up roll R2, and is configured to be transported in the direction of the arrow X shown in the figure, via a plurality of rollers G11 to G16, while appropriate tension is applied and its direction is adjusted.

[0028] Furthermore, the coating apparatus 10 includes a cylindrical seamless blanket cylinder (SBR) 1, a vacuum die 2 positioned close to the SBR 1, and cylindrical or cylindrical plate cylinders 3 and impression cylinders 4 positioned opposite the SBR 1, sandwiching the vacuum die 2 in the rotation direction Y1 (clockwise) of the SBR 1. In the printing system 100, a drying and curing device 9 is installed between the impression cylinder 4 and the winding roll R2 for drying and curing the coating film 50 (and its positive pattern 50p) that has been final transferred onto the film 7.

[0029] Figure 2 shows an example of a cross-section perpendicular to the extension axis Ax (longitudinal axis, central axis) of the SBR1 shown in Figure 1. As shown in Figure 2, the SBR1 has, for example, a metal core 1a made of iron at its center, with a urethane rubber layer 1b having appropriate elasticity (corresponding to an example of a "cushion layer" in this disclosure) provided around it, and a printed layer 1c made of polydimethylsiloxane (PDMS) or the like laminated and coated on its surface.

[0030] Returning to Figure 1, the main body 20 of the vacuum die 2 is connected to a storage tank 5T via piping equipped with a precision metering pump Pm1. By operating the precision metering pump Pm1, the coating liquid 5 is accurately metered in a predetermined amount and continuously supplied to the inside of the main body 20 of the vacuum die 2. The coating liquid 5 is, for example, a thermosetting or photocurable resin composition containing a metal or metal oxide as an element, and a fine pattern of metal or metal oxide is formed on the film 7.

[0031] Furthermore, the vacuum die 2 has a die lip 21 (described later) at the tip of the main body 20 facing the SBR 1, and by discharging the coating liquid 5 from here toward the SBR 1, a bead 5B (described later) of the coating liquid 5 is formed between the SBR 1 and the vacuum die 2. At the same time, the vacuum die 2 performs a depressurization process by sucking the atmosphere Rv (described later) located behind the tip with a depressurization pump Pm2. In addition, a cover portion 22 is provided to cover or surround the atmosphere Rv in order to enhance the depressurization effect at that time.

[0032] As described above, coating liquid 5 is continuously supplied from the vacuum die 2, and as the SBR 1 rotates, the coating liquid 5 is uniformly applied to the surface of the printing layer 1c of the SBR 1, forming a coating film 50 of a constant thickness. This coating film 50 reaches the plate cylinder 3 opposite the SBR 1, and since the plate cylinder 3 is driven in the rotation direction Y2 (counterclockwise), the surface relief microstructure (SRM) formed on the plate cylinder 3 is transferred to the coating film 50. Figure 3(A) is a schematic plan view showing the state in which the SRM is transferred to the coating film 50, with the area A enclosed by the dashed line in Figure 1 enlarged. As shown in the figure, the negative pattern 3n of the SRM formed on the plate cylinder 3 is pressed against the coating film 50 on the SBR 1, and the corresponding portion is extracted as the negative pattern 50n of the coating film 50. As a result, a positive pattern 50p is formed on the coating film 50 after passing through the plate cylinder 3. Furthermore, the negative pattern 50n that has been removed and held in the plate cylinder 3 is transferred to another film 8 that is fed out from the unwinding roll R3 and changed direction by roller G3, and then recovered by the take-up roll R4 (Figure 1).

[0033] Furthermore, as the SBR1 rotates, the coating film 50 having the positive pattern 50p is positioned opposite the SBR1 and reaches the impression cylinder 4, which is driven in the rotation direction Y3 (counterclockwise). At this point, the positive pattern 50p is finally transferred to the film 7 unwound from the unwinding roll R1. Figure 3(B) is a schematic plan view showing the state in which the positive pattern 50p has been transferred to the film 7, enlarged from section B enclosed by a dashed line in Figure 1. As shown in the figure, the positive pattern 50p of the coating film 50 formed on the printed layer 1c of the SBR1 is pressed against the film 7 on the impression cylinder 4, and that portion is transferred onto the film 7. Subsequently, the film 7 having this positive pattern 50p passes through the drying and curing device 9 to obtain a transparent label 7' with a metallic pattern printed on it, which is then wound onto the winding roll R2.

[0034] [Examples of coating using coating equipment] Figure 4 is a cross-sectional view of the vacuum die 2 including a portion of the SBR1 shown in Figure 1 (a cross-sectional view perpendicular to the extension axis Ax of the SBR1), and is the cross-sectional view taken along line IV-IV shown in Figure 5. Figure 5 is also a longitudinal cross-sectional view of the vacuum die 2 (a cross-sectional view along the extension axis Ax of the SBR1), and is the cross-sectional view taken along line VV shown in Figure 4. Furthermore, Figure 6 is an enlarged transverse cross-sectional view of a portion of Figure 4, in particular showing the tip of the vacuum die 2, the surface of the SBR1, and the state of the coating liquid 5 discharged between them. Figures 4 to 6 are also schematic diagrams to explain the coating method of the coating liquid 5 by the coating apparatus 10.

[0035] The vacuum die 2's body 20 is equipped with a reservoir 23 (manifold) that communicates with a coating liquid 5 storage tank 5T, and a slit 24. The reservoir 23 is a groove-shaped structure with a larger diameter than the slit 24, and is effective in uniformly spreading and conveying the coating liquid 5 onto the SBR 1. On the other hand, the slit 24 helps to straighten the flow of the coating liquid 5 from the reservoir 23 toward the die lip 21. The aforementioned die lip 21 is installed at the tip of the body 20, facing the SBR 1, and the die lip 21 has an upstream lip 21a and a downstream lip 21b. The width S (gap) of the slit 24 is defined by these upstream lip 21a and downstream lip 21b.

[0036] Furthermore, the aforementioned cover portion 22 consists of a back plate 22a and a pair of side plates 22b, which are located upstream of the front end of the main body 20. The back plate 22a extends along the extending axis Ax of the SBR1, and the side plates 22b extend along the end face 1s of the SBR1 and a portion of the end face 20s of the main body 20. In addition, a pressure reducing pump Pm2 is connected to the cover portion 22 via piping in which a pressure gauge 61 and a flow meter 62 are installed.

[0037] With the above configuration, when the coating liquid 5 supplied through the slit 24 is discharged from the die lip 21 toward the SBR1, a bead 5B (coating bead) of the coating liquid 5 is formed to fill the space between the end face of the die lip 21 and the surface of the SBR1. In this state, when the vacuum pump Pm2 is operated, a portion of the space on the back side of the coating liquid 5 bead 5B, i.e., the atmosphere Rv surrounded by the cover portion 22, is sucked in, and the pressure inside the atmosphere Rv is reduced. As a result, the coating liquid 5 bead 5B is pulled in the direction of the arrow V shown in the figure, maintaining a shape that bulges out in a convex shape toward the back side. Thus, the vacuum pump Pm2 and the cover portion 22 correspond to an example of a "vacuum reduction section" in this disclosure and act as a vacuum reduction chamber.

[0038] Here, as shown in Figure 6, the die lip 21 provided at the tip of the main body 20 of the vacuum die 2 is positioned at a distance of coating gap H from the surface of the printed layer 1c of the SBR 1 (non-contact state). As mentioned above, the coating gap H is determined considering the runout of the SBR 1 (±20 μm in this disclosure as an example), and is a larger value than when using a conventional iron core roll. Also, the coating gap H is not constant but fluctuates greatly depending on the runout. The coating liquid 5 discharged from the die lip 21, which is the discharge port of the coating liquid 5 of the vacuum die 2, is continuously applied to the surface of the printed layer 1c of the SBR 1, which is driven in the rotation direction Y1, with a coating film thickness h (liquid film thickness, wet film thickness) while maintaining the bead 5B.

[0039] In this embodiment, when the atmospheric pressure Rv is reduced by the depressurization section of the vacuum die 2, the actual pressure P indicated by the depressurization pump Pm2 is adjusted to be between -0.1 and -20 [kPaG]. In this case, it is desirable that the linear suction flow rate Q be maintained at 200 [L / (min·m)] or higher. Note that the "linear suction flow rate Q" is the value obtained by dividing the measured flow rate, which is the indicated value of the flow meter 62, by the width Dw of the vacuum die 2 (Figure 5).

[0040] Furthermore, Figures 7(A) and 7(B) are enlarged schematic diagrams of section C, enclosed by a dashed line in Figure 4, and section D, enclosed by a dashed line in Figure 5, respectively. In this embodiment, it is preferable that the dimensions D1 to D3 shown in the figures satisfy at least one of the following conditions (1) to (3). D1 = 100 ± 20 [μm] …(1) D2 = 450 ± 150 [μm] …(2) D3 = 40 ± 20 [μm] …(3) D1: Clearance between the surface of SBR1 and the back panel 22a D2: Clearance between the end face 1s of SBR1 and the side plate 22b D3: Clearance between the surface of SBR1 and the die lip 21 of vacuum die 2

[0041] [Coating Test 1] Next, using the coating apparatus 10 prototyped based on the configuration shown in Figures 1 to 7, coating tests were conducted for various combinations of the following parameters. H: Coating gap (50 and 120 [μm]) h: Coating film (liquid film) thickness (each measured value in μm) L1: Thickness of the discharge end of the downstream lip 21b of the vacuum die 2 (0.1 [μm]) L: Distance (0.3 [μm]) between the inner end of the discharge port of the upstream lip 21a of the vacuum die 2 and the contact position with the bead 5B. μ: Viscosity of coating solution 5 (2 m [Pa·s]) σ: Static surface tension of the coating solution (15.5 [mN / m]) V: Relative velocity between the surface of SBR1 and the tip of vacuum die 2 (0.50~5.00 [m / min])

[0042] The 50 coating films obtained for each combination of parameters were visually observed, and test cases without streaky unevenness were evaluated as "good," while test cases with streaky unevenness were evaluated as "poor." Furthermore, the H / h[-] calculated from the parameter combination of each test case was plotted on the horizontal axis, and the Ca[-] obtained by the following formula (5) was plotted on the vertical axis (logarithmic axis). The results obtained were plotted as symbols ("good" as "○" or "●" and "poor" as "×"), and the graph is shown in Figure 8. Ca = μ·V / σ …(5)

[0043] The results confirmed that, across a wide range of H / h, regions of "good" and "poor" Ca(L / L1) were observed. Therefore, in the graph of Figure 8, a fitting (regression) was performed using the Ca(L / L1) values ​​represented by the black circle ("●") symbols that were deemed to be located at the boundary between the "good" and "poor" regions in the range of H / h > 20, and coating conditions based on the following equation (4) were obtained. Ca / (L / L1)≦0.00253·exp(-0.026(H / h))…(4),

[0044] This result indicates that even under conditions where the coating gap H fluctuates significantly, such as a wide range of H / h (especially H / h > 20 to 40), satisfying the coating conditions shown in equation (4) above ensures that the vacuum is well maintained, preventing the occurrence of coating defects and enabling high-precision and homogeneous film coating.

[0045] Furthermore, for the above test example with V (relative velocity between the surface of SBR1 and the tip of the vacuum die 2) = 5.00 [m / min], which is assumed to be prone to streaky unevenness as a coating defect, the results regarding the actual pressure P indicated by the reduced pressure section and the presence or absence of coating defects (streaky unevenness) are summarized in Table 1 below. From these results, it can be understood that applying the coating liquid 5 while reducing the atmospheric pressure Rv upstream of the bead 5B is advantageous when the actual pressure P indicated by the reduced pressure section is greater than -0.1 [kPaG].

[0046] [Table 1]

[0047] [Effects of the Embodiment] According to the coating apparatus 10 and coating method using the same, as well as the printing system 100 configured as described above, the bead 5B of the coating liquid 5 formed between the die lip 21 of the vacuum die 2 and the SBR1 is pulled upstream (in the opposite direction to the direction in which coating is progressing) by reduced pressure. This promotes the stabilization of the bead 5B and makes the liquid film thickness of the coating film 50 uniform. However, the SBR1 having the urethane rubber layer 1b has a large amplitude of vibration, which can cause the bead 5B to waver and impair its stability. In contrast, in this configuration, the pressure of the atmosphere Rv near the surface of the SBR1 is appropriately controlled by the reduced pressure section of the vacuum die 2, and the actual pressure P is maintained at -0.1 to -20 [kPaG]. As a result, the stability of the bead 5B is sufficiently ensured, and the vacuum is maintained well even under conditions in which the amplitude of vibration of the SBR1 fluctuates greatly. This improves the uniformity of the coating film 50, preventing coating defects such as streaky unevenness and breaks in the coating film 50, while enabling the stable formation of a highly accurate and uniform coating film 50.

[0048] Furthermore, the coating apparatus 10 ensures that vacuum is maintained even under conditions where the amplitude of the SBR1 fluctuates significantly. Therefore, the coating apparatus 10, the coating method using it, and the printing system 100 are particularly effective even under fluctuating conditions that were not anticipated with conventional iron core blankets, such as when the amplitude is ±20 μm.

[0049] At this time, by setting the linear suction flow rate Q to 200 [L / min / m] or higher, the formation of an appropriate vacuum environment by the depressurization section of the vacuum die 2 is promoted, and the predetermined depressurization conditions (actual pressure P = -0.1 to -20 [kPaG]) can be stably maintained. This further reduces the influence of the vibration of the SRM 1 and ensures the uniformity of the coating film 50 more reliably.

[0050] Furthermore, by configuring the vacuum die 2 to have a cover portion 22 that covers or surrounds the atmosphere Rv as part of the reduced pressure section, the reduced pressure region formed in the atmosphere Rv upstream of the bead 5B becomes less susceptible to the influence of the external environment, and the inflow of air from the outside is suppressed. As a result, the reduced pressure state of the atmosphere Rv is more stable, and the effects of pressure fluctuations caused by the amplitude of the SBR 1 can be suppressed even more effectively.

[0051] Furthermore, the cover portion 22 has a back plate 22a that extends along the extending axis Ax of the SBR1 upstream of the die lip 21, and a side plate 22b that extends along a portion of the end face 1s of the SBR1 and the end face 20s of the main body 20 upstream of the die lip 21. Despite this simple structure, it can more effectively block or suppress the inflow of external air into the reduced pressure region formed in the atmosphere Rv upstream of the bead 5B. In addition, by performing the function of a reduced pressure chamber with such simple components, it is also possible to suppress an increase in installation space.

[0052] Furthermore, if the vacuum die 2 sets clearances D1, D2, and D3 that satisfy at least one of the conditions shown in equations (1) to (3) above, conventionally, the airtightness of the atmosphere Rv to be depressurized will decrease, making it difficult to maintain a good depressurized state. However, as mentioned above, the coating apparatus 10 is designed for SBR1 with a very large amplitude, and it is preferable to intentionally set wide clearances as defined in D1 to D3 to avoid contact or interference between SBR1 and each component. Moreover, even under these conditions, by maintaining the actual pressure P shown by the depressurization section at -0.1 to -20 [kPaG], the stability of the bead 5B is sufficiently ensured, and good vacuum maintenance is achieved even under conditions where the amplitude of SBR1 fluctuates greatly.

[0053] In addition, by satisfying the coating conditions shown in equation (4) above, the actual pressure P shown in the reduced pressure section can be well maintained at -0.1 to -20 [kPaG], preventing the occurrence of coating defects and enabling high-precision and homogeneous film coating even in a range different from conventional methods, especially over a wide range of H / h (particularly H / h > 20 to 40).

[0054] More specifically, if the coating solution 5 contains a metal or metal oxide as an element, then by using a plate cylinder 3 with a high-resolution pattern as an SRM, a fine pattern of metal or metal oxide with submicron resolution can be formed, resulting in a transparent label that is excellent as an anti-counterfeiting label.

[0055] The embodiments described above with reference to specific examples are provided to facilitate understanding of this disclosure and are not intended to limit its interpretation. In other words, this disclosure is not limited to these specific examples, and modifications made to these examples by those skilled in the art are also included within the technical scope of this disclosure, as long as they retain the features of this disclosure. Furthermore, the elements, arrangements, materials, conditions, shapes, dimensions, scales, etc., of each of the aforementioned specific examples are not limited to those exemplified unless otherwise specified and can be modified as appropriate. Moreover, the elements of each of the aforementioned specific examples can be combined in different ways as appropriate, as long as no technical inconsistencies arise. [Explanation of Symbols]

[0056] 1…Seamless Blank Cylinder (SBR), 1a…Metal Core, 1b…Urethane Rubber Layer (Cushion Layer), 1c…Printing Layer, 1s…End Face, 2…Vacuum Die, 3…Plate Cylinder, 3n…Negative Pattern, 4…Impact Cylinder, 5…Coating Liquid, 5B…Bead, 5T…Storage Tank, 7…Film, 7'…Transparent Label, 9…Drying and Curing Equipment, 10…Coating Equipment, 20…Main Body, 20s…End Face, 21…Die Lip, 21a…Upstream Lip, 21b…Downstream Lip, 22…Cover Section (Reduced Pressure Section), 22a…Back Plate, 22b ...side panel, 23...accumulation area, 24...slit, 50...coating film, 50n...negative pattern, 50p...positive pattern, 61...pressure gauge, 62...flow meter, 100...printing system, Ax...extension axis, D1, D2, D3...clearance, G3, G11~G16...roller, h...coating film thickness, H...coating gap, Pm1...precision metering pump, Pm2...pressure pump (pressure reduction section), R1, R3...unwinding roll, R2, R4...winding roll, Rv...atmosphere, S...width, V, X...arrow, Y1, Y2, Y3...direction of rotation

Claims

1. A coating apparatus for applying a coating liquid to a blanket cylinder having a metal core and a cushion layer, The vacuum die is provided, which is located in close proximity to the aforementioned blanket cylinder and has a depressurization section. The vacuum die discharges a coating liquid from its tip to form a bead of the coating liquid between itself and the blanket cylinder, and while reducing the atmosphere upstream of the bead in the direction of rotation of the blanket cylinder, the vacuum die continuously forms a coating film of the coating liquid on the surface of the rotating blanket cylinder, while reducing the pressure P indicated by the depressurization unit to -0.1 to -20 [kPaG]. Coating equipment.

2. The coating apparatus according to claim 1, wherein the swing amplitude of the blanket cylinder is ±20 [μm].

3. The coating apparatus according to claim 1 or 2, wherein the linear suction flow rate Q indicated by the depressurization section when the atmosphere is depressurized is 200 [L / (min·m)] or more.

4. The coating apparatus according to claim 1 or 2, wherein the reduced pressure section has a cover section configured to cover or surround the atmosphere.

5. The coating apparatus according to claim 4, wherein the cover portion comprises a back plate extending along the axial direction of the blanket cylinder upstream of the tip portion, and a side plate extending along a portion of the end faces of the blanket cylinder and the vacuum die upstream of the tip portion.

6. The vacuum die satisfies at least one of the following conditions (1) to (3): D1=100±20[μm]...(1), D2=450±150 [μm]...(2), D3=40±20[μm]...(3), Here, D1: Clearance between the surface of the blanket cylinder and the back plate, D2: Clearance between the end face of the blanket body and the side plate, D3: Clearance between the surface of the blanket cylinder and the tip of the vacuum die, The coating apparatus according to claim 5.

7. The coating conditions shown in the following formula (4) are satisfied: Ca / (L / L1)≦0.00253・exp(−0.026(H / h))…(4), Here, H: Coating gap [μm] h: Coating film thickness [μm], L1: Thickness [μm] of the discharge end of the downstream lip of the vacuum die, L: Distance between the inner end of the discharge port of the upstream lip of the vacuum die and the contact position of the bead. Ca: Capillary number expressed by the following formula (5), Ca=μ・V / σ...(5), Here, μ: viscosity of the coating liquid [mPa·s], σ: Static surface tension of the coating liquid [mN / m], V: Relative velocity [m / min] between the surface of the blanket cylinder and the tip of the vacuum die. The coating apparatus according to claim 1 or 2.

8. The coating apparatus according to claim 1 or 2, wherein the coating liquid contains a metal or a metal oxide.

9. A coating method for applying a coating liquid to a blanket cylinder having a metal core and a cushion layer, A vacuum die positioned close to the blanket cylinder and having a pressure reduction section discharges a coating liquid from its tip to form a bead of the coating liquid between itself and the blanket cylinder, and while reducing the atmosphere upstream of the bead in the direction of rotation of the blanket cylinder (the rear or back side of the tip) so that the actual pressure P indicated by the pressure reduction section is -0.1 to -20 [kPaG], a coating film of the coating liquid is continuously formed on the surface of the rotating blanket cylinder. Coating method.

10. A blanket body having a metal core and a cushioning layer, A vacuum die positioned in close proximity to the aforementioned barrel and having a depressurization section, A plate cylinder and an impression cylinder are positioned opposite the blanket cylinder so as to sandwich the vacuum die in the direction of rotation of the blanket cylinder, Equipped with, The vacuum die discharges the coating liquid from its tip to form a bead of the coating liquid between itself and the blanket cylinder, and while reducing the atmosphere upstream of the bead in the direction of rotation of the blanket cylinder, so that the actual pressure P indicated by the depressurization unit is -0.1 to -20 [kPaG], it continuously forms a coating film (liquid film) of the coating liquid on the surface of the rotating blanket cylinder. The plate cylinder has a negative pattern, and a positive pattern is formed by removing a portion corresponding to the negative pattern from the coating on the surface of the blanket cylinder. The blanket cylinder transfers the positive pattern onto the substrate being transported on the surface of the impression cylinder. Printing system.

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