Water-based inkjet printing apparatus and water-based inkjet printing method

Abstract

To enable aqueous inkjet printing to a plastic film which copes with small lot order, is excellent in an on-demand property, and is speedy.SOLUTION: An aqueous inkjet printer includes a database of initial preset for determining an optimal dry condition that a film is not flopped by hot air, can stably travel without meandering and contraction can be minimized, and an optimal tension condition in consideration of thermal contraction of the film changed under the dry condition, with an attribute and a coverage of a film that is an object to be printed as factors, adds information on a discharge position which is registered according to expansion and contraction of the film when moving among respective discharge heads under the condition in the database, inputs information on the attribute and the coverage relating to a printing design of the film, thereby automatically calculates a printing speed, a drying temperature, tension and a discharge position with reference to the database of the initial preset, and performs printing on the basis of the above conditions.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an aqueous inkjet printing apparatus and an aqueous inkjet printing method, and particularly relates to an optimal printing method and apparatus for a packaging material made of a plastic film used for a packaging bag for accommodating food or a lid of a food container when distributing food.

Background Art

[0002] Today, in the distribution of food, instead of face-to-face sales where food prepared on-site is packaged and sold, a method of selling prepackaged foods such as processed foods, breads, and confectioneries prepared in food factories in convenience stores and supermarkets is becoming the mainstream.

[0003] In the above sales method, prepackaged foods are displayed on display shelves in stores of retail stores, and customers pick them up and examine them when purchasing. Therefore, the packaging itself is also required to have design ideas that can attract customers' purchasing desires and be easily noticeable to customers.

[0004] In the above case, since the primary purpose of the packaging material itself is to package food, it is not possible to make a shape change that would impair its function, and the role of the pattern and / or characters (hereinafter referred to as "pattern, etc.") applied to the surface becomes very important.

[0005] As a means of applying the above pattern, etc. to a packaging bag or a lid of a food container, printing is generally used. When printing on a packaging bag or a lid of a food container, there are two printing methods: printing on the back side (reverse printing) and printing on the front side (front printing). In this case, in the food packaging material, since it is prohibited by the Food Hygiene Law for the printing ink to come into contact with food, when printing on the back side, a protective plastic film must be laminated on the side of the printing layer of the plastic film.

[0006] On the other hand, when printing on the front side of the packaging material, there are no such restrictions as described above, but since the printed layer is exposed, care had to be taken to prevent the printed layer from becoming unclear due to physical friction or solvents (alcohol or oil) caused by contact with the back side of the film when it is wound up after printing on the packaging bag or lid, or by contact with other packaging materials, items, or people's hands during distribution or display.

[0007] In the aforementioned case, unlike paper and other materials, plastic film is a substrate that does not easily absorb liquids, so gravure printing, which uses gravure inks with high coating adhesion, or flexographic printing, which uses flexographic inks, were employed for printing.

[0008] Incidentally, inkjet printing, which does not require plate making and can generate printable images from digital data, is excellent for on-demand printing and should ideally be useful for food packaging materials where various designs need to be printed as needed, but it has not been adopted.

[0009] The reason is that water-based inkjet inks, which are suitable for inkjet printing, lack various physical properties such as abrasion resistance, alcohol resistance, oil resistance, and water resistance, causing the ink to easily wash off and resulting in poor film adhesion. In this case, gravure inks and flexographic inks, which have high film adhesion, are too viscous, making it impossible to smoothly spray them from the nozzles in inkjet printing, which requires the ink to be sprayed and applied to the surface, and therefore they could not be used.

[0010] Unlike durable consumer goods with fixed designs and patterns, food packaging materials are consumed over a short period and require the printing of a wide variety of designs depending on the contents. Therefore, speeding up printing is essential to improve production efficiency.

[0011] However, gravure printing and flexographic printing, which require preparing a printing plate for each new design and setting it up on the production line each time, require time for the printing process to begin, and there were limits to how much speed could be increased.

[0012] For example, in the case of food packaging materials printed with designs using gravure printing, the necessary pre-printing work (submission of artwork + plate making) and printing itself took a total of 12 days, and other post-processing (film lamination, finishing) took another 6 days, for a total of 18 days.

[0013] Furthermore, as mentioned above, gravure printing requires color separation and plate-making time, which inevitably results in a larger minimum order quantity. This forces customers to purchase more packaging materials than necessary, leading to waste.

[0014] On the other hand, while it is easy to choose to use inkjet printing when printing on the back of the bag, this requires a process of laminating plastic film on the side of the printed layer of the plastic film, which presents problems in terms of cost and time.

[0015] In this regard, the present inventor has created the following invention. The first invention is characterized in that, when printing a design and / or text on the front surface of a plastic film that is to be made to constitute a food packaging material, the design and / or text are inkjet printed using inkjet ink, and then a transparent inkjet ink is overprinted onto the printed area by inkjet printing (Patent Document 1).

[0016] Furthermore, the second invention is characterized in that, when printing a design and / or text on the front surface of a plastic film that is to constitute a food packaging material, the design and / or text are inkjet printed using inkjet ink, and then a transparent UV ink is overprinted (Patent Document 2).

[0017] Furthermore, the third invention is characterized in that, when printing a design and / or text on the front surface of a plastic film that is to constitute a food packaging material, the design and / or text are inkjet printed using inkjet ink, and then transparent EB ink is overprinted (Patent Document 3).

[0018] According to the invention of the present inventor, when printing a design or the like on the surface located on the front side of a packaging bag or the lid of a food container, even if inkjet printing is performed using water-based inkjet ink, a transparent inkjet ink, transparent UV ink, or transparent EB ink is overprinted on the printing area to protect the printed layer of the design or the like, so that the printed layer of the design or the like is not exposed.

[0019] Therefore, friction that can cause the printed layer of the design to become blurred or generate debris when it comes into contact with the back of the film during the printing process on packaging bags and lids and when the film is wound up, or when it comes into contact with other packaging materials, items, or people's fingers during distribution or display, is prevented.

[0020] On the other hand, since printing is completed using inkjet printing, which excels in on-demand capabilities, there is no need for the time required for the process of starting printing, such as gravure printing or flexographic printing, which require preparing plates for new designs and setting them up on the production line. This allows for faster production and can dramatically improve the production efficiency of food packaging materials, which require printing a wide variety of designs on demand depending on the contents.

[0021] The aforementioned invention breaks with the conventional technical wisdom that, in printing plastic films, water-based inkjet inks lack various physical properties such as abrasion resistance, alcohol resistance, oil resistance, and water resistance, causing the ink to easily rub off and resulting in poor coating adhesion, making them unsuitable for use. [Prior art documents] [Patent Documents]

[0022] [Patent Document 1] Japanese Patent Publication No. 2021-88171 [Patent Document 2] Japanese Patent Publication No. 2021-88410 [Patent Document 3] Japanese Patent Publication No. 2021-88409 [Disclosure of the Invention]

Problems to be Solved by the Invention

[0023] However, the inventor of the present invention, who has carried out aqueous inkjet ink printing on a plastic film that no one has attempted so far, has faced new problems.

[0024] That is, in aqueous inkjet printing where the ink head part (printing part) is non-contact type, since the tension of the film running through the drying path and the printing ink head part is under the same conditions, due to the influence of the drying temperature and the tension of the drying path, thermal expansion and contraction of the film occur, making it impossible to control the registration and dimensions.

[0025] Since the printing design has different coverages depending on the individual printing density and range, the drying temperature and speed of the printing conditions are different each time. Printing is possible by fixing the drying temperature and speed within a safe range. For example, when the coverage is low, the speed can be increased according to the drying capacity of the printing machine. To confirm this, trial printing must be performed each time to confirm the drying limit. At the limit, ink adheres to the guide roll in the drying furnace, so it cannot be confirmed before printing. Therefore, even in printing where the speed can be increased, it can only be printed at the low-speed safe speed.

[0026] Furthermore, even if the optimum conditions of the drying temperature and speed are known in advance, even if the types of various films used as the printing substrate, their thicknesses, and paper widths are different, it will affect the printing registration and finished dimensions. Therefore, at the time of the first printing, it is necessary to select the optimum tension under the drying temperature and speed conditions determined in advance. Again, trial printing is required for this purpose. This trial printing requires adjusting the registration many times and stopping the printing to take samples, resulting in a large loss meter and being unsuitable for mass production printing.

[0027] Figure 2 is a conceptual diagram showing the flow of film F in an aqueous inkjet printing device. In an aqueous inkjet printing device, achromatic inks such as white will mix with chromatic inks such as KCMY when printed simultaneously. Therefore, after printing chromatic inks (Figure A), the ink is dried in a drying path, and then achromatic inks are printed (Figure B) and dried. As is clear from this, the film expands and contracts due to heating as it moves between each ink ejection head that prints the ink. Therefore, the position of the achromatic ink ejection head must be set taking this expansion and contraction into account, and if this is not done, misregistration of each color will occur in the printed result.

[0028] The expansion and contraction of the film as it moves between the aforementioned ejection heads varies depending on the film's properties, drying temperature, running speed, and tension. Therefore, even if the film's properties and the appropriate drying temperature, speed, and tension for the print design coverage are all pre-configured, simply starting from the head's standard position will result in misregistration of each color in the printed output. This makes it difficult to achieve accurate registration on the first try, requiring multiple test prints.

[0029] As described above, water-based inkjet printing is much more complex to operate compared to gravure printing. Specifically, the printing conditions differ for each print pattern, requiring the appropriate conditions to be set each time and a test print to be performed before starting. Similarly, different film types, brands, and thicknesses require settings to be adjusted each time. Since water-based inkjet printing is primarily intended for small-lot, short-lead-time orders, this is a fatal flaw for a small-lot mass-production machine. While it excels in on-demand capabilities, it risks compromising its original purpose of speeding up printing. [Means for solving the problem]

[0030] The present invention was created with the aim of providing an aqueous inkjet printing apparatus and an aqueous inkjet printing method that solve the aforementioned problems.

[0031] In other words, the aqueous inkjet printing apparatus of the present invention is an aqueous inkjet printing apparatus in which the film to be printed passes through the ink ejection head section and travels along a hot air drying path while being subjected to a constant tension, It features an initial preset database that allows for the determination of optimal drying conditions, consisting of a drying temperature and running speed that enable stable running without the film flapping or meandering due to the hot air during hot air drying, while minimizing shrinkage, and optimal tension conditions that take into account the thermal shrinkage of the film under those drying conditions, using the attributes of the film to be printed and the coverage related to the print design as factors. Under optimal drying and tension conditions, which consist of drying temperature and running speed obtained according to the attributes of the film to be printed and the coverage of the print design, information on the ejection position, which is aligned with the expansion and contraction of the film as it moves between each ejection head, is added to the initial preset database. When printing, by inputting information about the attributes of the film to be printed and the coverage of the print design, the system references an initial preset database. printing speed, drying temperature, tension, Discharge position The system is characterized by automatically calculating these values ​​and printing based on them.

[0032] Furthermore, the invention described in claim 2 is characterized in that, in the aqueous inkjet printing apparatus described above, the attributes of the film to be printed are defined as film type, brand name, thickness, and paper width.

[0033] Furthermore, the aqueous inkjet printing method described in claim 3 is an aqueous inkjet printing apparatus in which the film to be printed passes through the ink ejection head section and travels along a hot air drying path while being subjected to a constant tension, Under optimal drying conditions and optimal tension conditions, which consist of a drying temperature and running speed calculated according to the attributes of the film to be printed and the coverage of the print design, The database contains information on the discharge position, which is adjusted according to the expansion and contraction of the film as it moves between each discharge head. The printing process is characterized by setting the ejection position based on the aforementioned information. [Effects of the Invention]

[0034] The aqueous inkjet printing apparatus of the present invention enables on-demand inkjet printing. Furthermore, by inputting information on the attributes of the film to be printed and the coverage of the print design, the apparatus automatically calculates the printing speed, drying temperature, and tension even when the coverage, film type, brand, and thickness differ. It also automatically adjusts to ensure stable movement during hot air drying, preventing the film from flapping or meandering due to the hot air, and to prevent shrinkage. Additionally, it has a preset function that automatically adjusts the ejection position to match the expansion and contraction of the film as it moves between each ejection head. This eliminates the need to set appropriate conditions each time and perform test prints before starting, thereby increasing the printing speed. [Brief explanation of the drawing]

[0035] [Figure 1] A conceptual diagram of the aqueous inkjet printing apparatus of the present invention. [Figure 2] Conceptual diagram of a water-based inkjet printing device. [Figure 3] Graph showing the height and depth dimensions of printed pages. [Figure 4] Graph showing left and right dimensions of printed product [Best Mode for Carrying Out the Invention]

[0036] The aqueous inkjet printing apparatus of the present invention is In an aqueous inkjet printing apparatus in which the film to be printed passes through the ink ejection head section and travels along a hot air drying path while being subjected to a constant tension, It features an initial preset database that allows for the determination of optimal drying conditions, consisting of a drying temperature and running speed that enable stable running without the film flapping or meandering due to the hot air during hot air drying, while minimizing shrinkage, and optimal tension conditions that take into account the thermal shrinkage of the film under those drying conditions, using the attributes of the film to be printed and the coverage related to the print design as factors. Under optimal drying and tension conditions, which consist of drying temperature and running speed obtained according to the attributes of the film to be printed and the coverage of the print design, information on the ejection position, which is aligned with the expansion and contraction of the film as it moves between each ejection head, is added to the initial preset database. When printing, by inputting information about the attributes of the film to be printed and the coverage of the print design, the system refers to an initial preset database. printing speed, drying temperature, tension, Discharge position The system automatically calculates these values ​​and prints based on them.

[0037] Figure 1 is a conceptual diagram illustrating the premise of the aqueous inkjet printing apparatus of the present invention. In the figure, the symbol F represents the film to be printed on, which passes through the ink head unit 10 and travels through the hot air drying path 20 while being subjected to a constant tension. Since the ink head unit 10 is a non-contact type, the tension conditions are the same as those in the drying path 20. In the drying path 20, hot air is blown from a nozzle onto the ink surface inside a drying oven to dry it.

[0038] In the present invention, the printing speed, drying temperature, and tension are automatically calculated according to the attributes of the film, and these are automatically adjusted to ensure stable movement during hot air drying so that the film does not flap or meander due to the hot air, and also to prevent shrinkage. The following has been found to be the optimal printing conditions for automatic adjustment.

[0039] In other words, when using water-based inkjet printing on OPP (biaxially oriented polypropylene), a film that generally has low heat resistance, the heat generated during the drying of the water-based ink causes the printed dimensions to expand and contract, resulting in misregistration and product dimensions that deviate significantly from the standard, making printing impossible.

[0040] Since the ink head (printing section) is a non-contact type, it is subject to the same tension conditions as inside a drying oven. However, in general, hot air drying dries the ink surface by applying hot air from a nozzle, so a tension is required that allows the film to run stably without flapping or meandering due to the wind.

[0041] In other words, in water-based inkjet printing, where the film to be printed passes through the inkhead and travels along a hot air drying path while being subjected to a constant tension, it is necessary to consider the heat resistance and other attributes of the film and apply a tension to the film that allows for stable travel so that the film does not flap or meander due to the hot air during hot air drying. Furthermore, it is necessary to adjust the tension and drying temperature to a range in which the film to be printed does not shrink due to the tension and temperature.

[0042] In relation to the above, the inventors of this application have found optimal conditions for water-based inkjet printing even on OPP (biaxially oriented polypropylene), a general-purpose film with low heat resistance, which is used in water-based inkjet printing. By reproducing these optimal conditions, it is possible to maintain a temperature condition that allows the water-based ink to dry sufficiently, while also ensuring a stable running state without fluttering or meandering caused by the hot air in the drying oven. This prevents the OPP (biaxially oriented polypropylene) film with low heat resistance from thermally expanding or contracting, allowing for registration control during printing and ensuring that the product dimensions are within the standard range.

[0043] In this case, the goal is to suppress the thermal expansion and contraction that becomes a problem when using general-purpose film OPP (biaxially oriented polypropylene): heat shrinkage rate at 150°C for 5 minutes: MD (vertical) 8-30%, TD (horizontal) 5-35%, thereby enabling accurate print registration and dimensional reproduction.

[0044] For general-purpose OPP (biaxially oriented polypropylene) film: under the conditions of a heat shrinkage rate of 150°C for 5 minutes, when using MD (vertical) 8-30% and TD (horizontal) 5-35%, and using a drying apparatus with a length of 5.5 m in which the specified water-based ink can be sufficiently dried, by reducing the tension inside the drying oven to 20 N (10 N to 30 N for a width of 760 mm) under the conditions of a drying temperature of 85°C and a speed of 80 m / min, the printed dimensions of the printed film will be within the standard (vertical ±0.2%, horizontal ±0.2%).

[0045] On the other hand, when using high heat-resistant OPP (biaxially oriented polypropylene) with a heat shrinkage rate of 150°C for 5 minutes, MD (vertical) 3-8% and TD (horizontal) 2-6%, the tension inside the drying oven should be reduced to 50N (40N-60N for a width of 760mm).

[0046] With the aforementioned water-based inkjet printer, when using high heat-resistant OPP (biaxially oriented polypropylene) with a heat shrinkage rate of 150°C for 5 minutes, the printed finished dimensions will be within the standard range (vertical ±0.2%, horizontal ±0.2%).

[0047] Based on the above premise, the inventor of the present invention conducted experiments using typical films used in water-based inkjet printing, combining temperature, tension, and heating time. Through these experiments, the inventor discovered the optimal conditions for water-based inkjet printing, considering the temperature required for drying, the tension necessary for stable operation in the drying oven, and the heating time corresponding to the printing speed. By reproducing these optimal conditions, a mass-producible water-based inkjet printing machine can be designed. The details of these experiments are described below.

[0048] <Experiment details> ·Constant temperature and humidifier Yamato Scientific Co., Ltd. Model IG401 Equilibrium Temperature and Humidity Control System (GTHC System) (performance) Temperature and humidity range: +5℃ to +85℃ (87℃ possible) / 40% to 95% Temperature fluctuation: ±1.0℃, Temperature gradient: 5℃, Ambient temperature deviation: 5℃ Humidity fluctuation: ±596 rh, Humidity gradient: 10% rh, Ambient humidity deviation: 1096 rh ·Base material used OPP: Tosei Cello (U-1, 20μm), Futamura Chemical (FOR-AQ, 20μm) Special OPP: Toyobo (P2161, 20μm) PET: Toyobo (E5100, 12μm) ·jig Hanging clip (145mm wide) Weight clips (width 145mm): 350g, 950g, 1,500g Water-based inkjet printing machine: Experimental results with a 760mm width, converted to a sample size of 140mm. *Actual machine 20N = 350g, actual machine 50N = 950g, actual machine 80N = 1,500g specimen Size: Height (film TD direction) 200mm, Width (film MD direction) 140mm ·measurement 300mm JLS1 Grade Metal Ruler + Tokai Sangyo PEAK10x Magnifying Glass (0.1mm increments) • Temperature (each temperature setting + constant humidity of 40%) and heating time 75℃ (4 seconds = 76℃, 11 seconds = 76.5℃, 18 seconds = 77℃) 80℃ (4 seconds = 81℃, 11 seconds = 81.5℃, 18 seconds = 82℃) 85℃ (4 seconds = 86℃, 11 seconds = 86.5℃, 18 seconds = 87℃) The set temperature is adjusted for each heating time to account for the temperature drop in the constant temperature bath. Actual water-based inkjet printing machine: Heating time calculated from speed and drying oven. Drying oven 5.5m, speed 80m / min = 4 seconds, 30m / min = 11 seconds, 0.3m / min = 18 seconds The heating temperature is determined by combining the conditions under which water-based ink dries in the actual machine. *Actual machine speeds of 30m / min = 75℃, 80m / min = 85℃, no actual machine experiments were conducted for 0.3m / min.

[0049] ◎Experimental Method Samples were taken from three locations on the film substrate: both sides and the center, from the horizontal direction (film MD direction). Cut to a size of 200mm (height) x 140mm (width). Make holes with a needle at 100mm intervals both vertically and horizontally in the center of the sample. Before heating, measure both the length and width by 100mm using a metal ruler and magnifying glass (to one decimal place) and record the result. Choose the specified weight for the weight clip. Attach a hanging clip to the top of the specimen and a weight clip to the bottom. Confirm that the constant temperature bath is at the specified temperature (±1°C) and then suspend the specimen in the bath. Close the door of the constant temperature bath and heat for the specified time. After the designated time has elapsed, open the door and remove the sample. Remove the clips from the top and bottom. After heating, measure both the length and width by 100mm using a metal ruler and magnifying glass (to one decimal place) and record. Subtract the difference between the dimensions before heating and the dimensions after heating and record. The graph plots the net dimensions (+ indicates expansion, 1 indicates contraction). Confirm the thermal expansion of each sample.

[0050] <Experimental Results> [Table 1] This indicates the hanging weight that results in a print control range of 0.296 or less. (1) OPP: Tosei Cello: U-1 passes when the vertical temperature is 85° in 4 seconds and the vertical temperature is 75°, 80°, 85°, and horizontal temperature is 85° in 11 seconds, with a tension of 350g. Since printing is done vertically and horizontally simultaneously, low tension is required so that all sides are 350g. (2) OPP: Futamura Chemical: FOR-AQ, like Tosei Cello, requires low tension to be 350g in all cases. (3) Special OPP: Toyobo: P2171 is a film with higher heat resistance than general OPP, so it can be printed in 11 seconds at a vertical temperature of 80°C or 85°C with a tension of 950g. (4) PET: Unlike OPP, Toyobo E5100 is a high heat-resistant film, so it can be printed even at a normal tension of 1,500g.

[0051] <Detailed graph of experimental results> (1) 75℃: OPP vertical heat shrink liner <Tohsero U-1#20> [Table 2]

[0052] (1) 75℃: OPP lateral heat shrinkage <Tohsero U-1#20> [Table 3] (1) At 75℃, water-based ink dries in 11 seconds at a speed of 30m / min on the actual machine, so the printable range is: vertical and horizontal expansion of 0.2% or less. With a tension of 950g for 11 seconds, the vertical tension slightly exceeds the limit; 350g would be acceptable.

[0053] (1) 80℃: OPP vertical heat shrink liner <Tohsero U-1#20> [Table 4]

[0054] (1) 80℃: OPP lateral heat shrinkage <Tohsero U-1#20> [Table 5] (1) At 80℃, the drying limit for water-based ink in the actual machine is 80m / min = 4 seconds, but Printable range: Vertical and horizontal stretching of 0.2% or less With a tension of 950g for 4 seconds, both vertical and horizontal measurements passed.

[0055] (1) 85℃: OPP vertical heat shrink liner <Tohsero U-1#20> [Table 6]

[0056] (1) 85℃: OPP lateral heat shrinkage <Tohsero U-1#20> [Table 7] (1) At 85℃, water-based ink dries in 4 seconds at a speed of 80 m / min in the actual machine. Printable range: Vertical and horizontal stretching of 0.2% or less A tension of 950g over 4 seconds slightly exceeds the limit vertically; 350g would be acceptable.

[0057] (2) 75℃: OPP vertical heat shrinkage <Futamura Chemical FOR-AQ#20> [Table 8]

[0058] (2) 75℃: OPP lateral thermal expansion <Futamura Chemical FOR-AQ#20> [Table 9] (2) At 75℃, the water-based ink dries in 11 seconds at a speed of 30m / min in the actual machine. Printable range: Vertical and horizontal stretching of 0.2% or less With a tension of 950g for 11 seconds, the vertical tension exceeds the limit; 350g would be acceptable.

[0059] (2) 80℃: OPP vertical heat shrinkage <Futamura Chemical: FOR-AQ#20> [Table 10]

[0060] (2) 80℃: OPP lateral thermal expansion <Futamura Chemical: FOR-AQ#20> [Table 11] (2) At 80℃, the drying limit for water-based ink in the actual machine is 80m / min = 4 seconds, but Printable range: Vertical and horizontal stretching of 0.2% or less With a tension of 950g for 4 seconds, the vertical tension slightly exceeds the limit; 350g would be acceptable.

[0061] (2) 85℃: OPP vertical heat shrinkage <Futamura Chemical: FOR-AQ#20> [Table 12]

[0062] (2) 85℃: OPP lateral thermal expansion <Futamura Chemical: FOR-AQ#20> [Table 13] (2) At 85℃, the water-based ink dries in 4 seconds at a speed of 80 m / min in the actual machine. Printable range: Vertical and horizontal stretching of 0.296 or less With a tension of 950g for 4 seconds, the vertical tension slightly exceeds the limit; 350g would be acceptable.

[0063] (3) 75℃: Special OPP vertical heat shrinkage <Toyobo P2171 20μ> [Table 14]

[0064] (3) 75℃: Special OPP transverse heat shrinkage <Toyobo P2171 20μ > [Table 15] (3) At 75℃, the water-based ink dries in 11 seconds at a speed of 30m / min in the actual machine. Printable range: Vertical and horizontal stretching of 0.296 or less Because it's a heat-resistant type, it passed both the vertical and horizontal tests even with a tension of 1,500g for 11 seconds.

[0065] (3) 80℃: Special OPP vertical heat shrinkage <Toyobo P2171 20μ> [Table 16]

[0066] (3) 80℃: Special OPP transverse heat shrinkage <Toyobo P2171 20μ> [Table 17]

[0067] (3) At 80℃, the drying limit for water-based ink in the actual machine is 80m / min = 4 seconds, but Printable range: Vertical and horizontal stretching of 0.2% or less Because it's a heat-resistant type, it passed both the vertical and horizontal tests even with a tension of 1,500g for 4 seconds.

[0068] (3) 85℃: Special OPP vertical heat shrinkage <Toyobo P2171 20μ> [Table 18]

[0069] (3) 85℃: Special OPP transverse heat shrinkage <Toyobo P2171 20μ> [Table 19] (3) At 85℃, the water-based ink dries in 4 seconds at a speed of 80 m / min in the actual machine. Printable range: Vertical and horizontal stretching of 0.2% or less Because it's a heat-resistant type, it passed both the vertical and horizontal tests even with a tension of 1,500g for 4 seconds.

[0070] (4) 75℃: PET vertical heat shrinkage <Toyobo E5100 12μ> [Table 20]

[0071] (4) 75℃: PET transverse heat shrinkage <Toyobo E5100 12μ> [Table 21]

[0072] (4) At 75℃, the water-based ink dries in 11 seconds at a speed of 30m / min in the actual machine. Printable range: Vertical and horizontal stretching of 0.2% or less Because it's a heat-resistant type, it passed both the vertical and horizontal tests even with a tension of 1,500g for 11 seconds.

[0073] (4) 80℃: PET vertical heat shrinkage <Toyobo E5100 12μ> [Table 22]

[0074] (4) 80℃: PET transverse thermal expansion <Toyobo E5100 12μ> [Table 23] (4) At 80℃, the drying limit for water-based ink in the actual machine is 80m / min = 4 seconds, but Printable range: Vertical and horizontal stretching of 0.2% or less Because it's a heat-resistant type, it passed both the vertical and horizontal tests even with a tension of 1,500g for 4 seconds.

[0075] (4) 85℃: PET vertical heat shrinkage <Toyobo E510012μ> [Table 24]

[0076] (4) 85℃: PET transverse thermal expansion <Toyobo E510012μ> [Table 25] (4) At 85℃, the water-based ink dries in 4 seconds at a speed of 80 m / min in the actual machine. Printable range: Vertical and horizontal stretching of 0.2% or less Because it's a heat-resistant type, it passed both the vertical and horizontal tests even with a tension of 1,500g for 4 seconds.

[0077] The key feature of this invention is its initial preset function, which allows users to easily set optimal printing conditions by inputting the attributes of the film to be used (film type, brand, thickness, paper width) and the coverage related to the design just before printing. This function automatically sets the optimal drying conditions for water-based ink (drying temperature and speed) and the optimal tension conditions for the substrate being used (the pull ratio of each drive roll for various conditions).

[0078] In other words, a database is created of optimal drying conditions (drying temperature, speed) obtained from drying condition factors (film type, brand, thickness, paper width, and design coverage) obtained in pre-tests, and optimal tension conditions (the tension of each drive roll that corresponds to each condition) that take into account the thermal shrinkage of the film under those drying conditions. Just before printing, by selecting the film type, brand, thickness, and paper width from the initial preset settings screen and entering the percentage value for design coverage, the optimal drying temperature and speed, as well as the optimal tension conditions (the tension of each drive roll that corresponds to each condition) that take into account the thermal shrinkage of the film under those drying conditions, can be automatically and simultaneously set from the first edition without test printing.

[0079] Next, for print registration, the four chromatic colors and the achromatic white are aligned under the optimal printing conditions automatically set by the initial preset during the first printing. In this case, since the initial preset automatically sets the optimal drying and tension conditions, the position where the film is registered when it has heat-shrinkn under those conditions is determined through prior testing and added to the initial preset database.

[0080] In other words, the optimal drying conditions (drying temperature, speed) obtained from the drying condition factors (film type, brand, thickness, paper width, and design coverage) acquired in preliminary tests, and the optimal tension conditions (pull ratio of each drive roll under various conditions) that take into account the thermal shrinkage of the film under those drying conditions, are added to the initial preset database, along with information on the head ejection position that is properly registered under those conditions. This ensures that the first print run is properly registered without the need for multiple test prints. Since registration can be achieved from the very first print run in the first edition, losses are virtually eliminated, enabling mass production printing. The following is a specific example.

[0081] The initial preset function allows you to easily set optimal printing conditions by first inputting the factors of the substrate to be used (film type, brand, thickness, paper width = example: OPP, Tosei Cello, U-1, #20, 760mm) and the coverage related to the design (example: 4-color coverage = 100%, white 2-color coverage = 140%) just before printing. The function then automatically sets the optimal drying conditions for water-based inks (drying temperature 88℃, speed 80m / min) and the optimal tension conditions for the substrate being used (pull ratio of each drive roll for various conditions: ultra-low pattern = tension 20~25N).

[0082] Figures 3 and 4 are graphs related to print-finished dimensions and print registration. Based on the initial preset database determined through pre-testing, under the conditions shown in Figure 3, for example, the print-finished dimensions would be 0.00 ± 0.1% vertically and 0.30 ± 0.1% horizontally, as shown in the graph in Figure 3 and Figure 4. If the horizontal dimensions are not within the standard, the design dimensions are enlarged before printing to bring them within the standard. In other words, this can be addressed with pre-adjustment work, ensuring that the print is completed correctly from the very first print run.

[0083] Print registration is affected by the optimal drying conditions shown in Figure 3 (drying temperature 88°C, speed 80m / min) and the optimal tension conditions for the substrate used (pull ratio of each drive roll for various conditions: ultra-weak pattern = tension 20~25N). During drying, the film undergoes thermal shrinkage, which causes misregistration, especially for the four CMYK colors and the two white colors printed afterward. A database of initial preset registration, determined through prior testing, is necessary. This database contains head position information data for all four colors and two white colors (e.g., CMYK 4 colors x 7 heads, white x 2 = position information for all 7 heads) when the registration is correct (e.g., the difference in deviation from the K (black) position (top, bottom, left, right) is within ±0.2mm of the standard).

[0084] The aqueous inkjet printing apparatus of the present invention, when printing, inputs information on the attributes of the film to be printed and coverage information related to the print design, and refers to an initial preset database. printing speed, drying temperature, tension, Discharge position The system automatically calculates these values ​​and performs printing based on them. The database of the initial presets and the print control device for automatic calculation are integrated with the printing device. Alternatively, the printing orderer may integrate the print original creation device, which creates the print original data and attribute specification data for the film to be printed, with a separate printing device that exchanges data via wired or wireless connections. [Explanation of Symbols]

[0085] F Film 10. Inkhead section 20 Hot air drying path

Claims

1. In an aqueous inkjet printing apparatus in which a film to be printed passes through multiple ink ejection heads while being subjected to a constant tension, and is transported while being dried by a drying means provided between each of the ejection heads, Based on the coverage of the print design and the attributes of the film to be printed on, including film type, brand, thickness, and paper width, A storage means for storing drying conditions consisting of drying temperature and running speed, and tension conditions corresponding to the thermal shrinkage of the film under those drying conditions, The system includes means for storing correction information, associated with the attributes and coverage of the film, for correcting the discharge position at each discharge head based on the expansion and contraction of the film after drying by the drying means, A water-based inkjet printing apparatus characterized by, during printing, referring to the storage means based on the input film attributes and coverage, setting drying conditions, tension conditions, and ejection position correction information, and then performing printing.

2. The aqueous inkjet printing apparatus according to Claim 1, wherein the attributes of the film include film type, brand name, thickness and paper width.

3. In the aqueous inkjet printing apparatus according to claim 1, Information on the discharge position, adjusted according to the expansion and contraction of the film after drying by the drying means provided between each discharge head, is stored in the storage means in association with the coverage related to the film attributes and print design. A water-based inkjet printing apparatus characterized by setting the ejection position by referring to the storage means based on the attributes and coverage of the input film during printing.

Images