Flexographic printing plate

Abstract

In order to provide a flexographic printing plate that can ensure the uniformity of the thickness of a printing film to peripheral edges of a printing region, a flexographic printing plate P has formed therein a plurality of protrusions shaped in a halftone dot pattern in a plan view, and the halftone dot pattern differs between a central region 2A of a protruding portion 2 for printing and peripheral regions 2B, 2C positioned at peripheral edges of the central region 2A.

Description

flexographic printing plates

[0001] The present invention relates to a printing plate used in flexographic printing, and more particularly to a flexographic printing plate that can perform uniform printing all the way to the periphery.

[0002] Flexographic printing is generally performed by a printing press as shown in Fig. 14. This printing press is equipped with a cylindrical plate cylinder 51 on which a flexographic printing plate P1 is mounted, an anilox roll 52 that applies ink to the flexographic printing plate P1, an ink supply device 53 that supplies ink to the surface of the anilox roll 52, a doctor blade 54 that scrapes off excess ink from the surface of the anilox roll 52, and a printing stage 55 on which a printing medium Q to be printed is placed.

[0003] Flexographic printing by the printing press is performed as follows: A flexographic printing plate P1 is attached to the circumferential surface of a plate cylinder 51, and while the plate cylinder 51 is rotating, ink supplied from an ink supply device 53 is applied to the printing area of ​​the flexographic printing plate P1 via an anilox roll 52. The applied ink is then transferred to a printing medium Q, such as a glass substrate, placed on a printing stage 55, thereby printing (forming a printing film). At this time, the printing stage 55 is slid in synchronization with the rotation of the plate cylinder 51.

[0004] Here, the flexographic printing plate P1 generally comprises a flat base 11 and a printing projection 12 formed in the center of the surface of the base 11, as shown in a plan view in Fig. 15A and in a cross-sectional view taken along line M-M in Fig. 15B. The printing projection 12 is the printing area, and the portion of the base 11 surrounding the printing projection 12 is not involved in printing. Furthermore, as shown in Fig. 15C, an enlarged cross-sectional view of a key portion of Fig. 15B, a plurality of protrusions 13 are formed on the top surface of the printing projection 12, spaced apart by grooves 14, and ink is retained in the grooves 14. The flexographic printing plate P1 is flexible enough to be mountable on the circumferential surface of the plate cylinder 51 (see Fig. 14).

[0005] However, in the flexographic printing, the printing convex portions 12 of the flexographic printing plate P1 come into contact with the anilox roll 52 and the printing medium Q, and the pressure generated when they come into contact causes the ink held in the printing convex portions 12 to gather in the peripheral regions (e.g., peripheral regions 12B) of the printing convex portions 12. This can result in a so-called "marginal phenomenon" in which the thickness of the printing film formed by the flexographic printing is thicker in the peripheral portion surrounding the central portion than in the central portion.

[0006] Therefore, various proposals have been made to suppress the occurrence of the marginal phenomenon. For example, Patent Documents 1 and 2 propose flexographic printing plates in which the distribution density of protrusions 13 formed on the printing convex portions 12 is set higher in the peripheral region 12B than in the central region 12A of the printing convex portions 12. That is, the flexographic printing plates described in Patent Documents 1 and 2 increase the distribution density of the protrusions 13 in the peripheral region 12B of the printing convex portions 12, thereby reducing the size of the grooves 14 formed between the protrusions 13 and reducing the amount of ink held in the grooves 14, thereby suppressing an increase in the thickness of the peripheral portion of the printing film.

[0007] Japanese Patent No. 3376908 Japanese Patent Laid-Open No. 2002-293049

[0008] On the other hand, flexographic printing requires various performance features in addition to suppressing marginal phenomena. For example, with recent technological developments, a high level of uniformity is required, and it is becoming necessary to ensure uniformity in the thickness of the printed film all the way to the periphery of the printed area.

[0009] The present invention has been made in view of the above circumstances, and provides a flexographic printing plate that can ensure uniformity in the thickness of the printing film up to the periphery of the printing area.

[0010] However, the inventors conducted extensive research in light of these circumstances and discovered that by forming the planar shape of the multiple protrusions formed on the top surface into a halftone dot pattern and making the halftone dot pattern different between the central region of the printing convex portion and the peripheral region located on the periphery of the central region, it is possible to improve the linearity of the array of multiple protrusions formed at the end of the peripheral region and suppress positional variation at the end of the printing film (alignment film) to accommodate the narrower frame of liquid crystal panels.

[0011] That is, the present invention has the following aspects: [1] A flexographic printing plate having a convex printing portion with a plurality of protrusions formed on a top surface, the convex printing portion having a shape in a plan view formed in a halftone dot pattern, the halftone dot pattern being different between a central region of the convex printing portion and a peripheral region located on the periphery of the central region, the halftone dot pattern being different between a printing direction portion and a perpendicular direction portion in the peripheral region, and the distribution density of the halftone dots in the printing direction portion being set higher than the distribution density of the halftone dots in the perpendicular direction portion. [2] A flexographic printing plate having a convex printing portion on whose top surface a plurality of protrusions are formed, wherein the planar shape of the plurality of protrusions is formed into a halftone dot pattern, the halftone dot pattern being different between a central region of the convex printing portion and a peripheral region located on the periphery of the central region, the halftone dot pattern in the central region being a collection of halftone dots arranged in a row, an angle T formed by an imaginary line R connecting the centers of adjacent halftone dots arranged in a row and the direction of printing progress S being set to 11° to 34° or 56° to 79°, and the halftone dot pattern in the peripheral region being a collection of halftone dots arranged in a row, an angle T formed by an imaginary line R connecting the centers of adjacent halftone dots arranged in a row and the direction of printing progress S being set to 0°±10° or 45°±10°. [3] The flexographic printing plate according to [2], wherein in the halftone dot pattern in the peripheral region, the pitch between adjacent halftone dots arranged in a row is set to 20 μm to 300 μm. [4] The flexographic printing plate according to any of [1] to [3], wherein the peripheral region has a printing direction portion along the printing direction and a perpendicular direction portion along a perpendicular direction perpendicular to the printing direction, and wherein the ratio (W / X) of the width W of the printing direction portion of the peripheral region to the width X of the printing convex portion is set to 0 < W / X < 0.05. [5] The flexographic printing plate according to any of [2] to [4], wherein in the halftone dot pattern in the peripheral region, the distances between adjacent halftone dots arranged in six directions around the periphery are set to be equal.

[0012] According to the flexographic printing plate of the present invention, the plurality of protrusions are formed in a dot pattern in plan view, and the dot pattern is different between the central region of the printing convex portion and the peripheral region located on the periphery of the central region, thereby improving the linearity of the protrusion arrangement formed at the edge of the peripheral region. Therefore, by performing printing using this flexographic printing plate, uniformity in the thickness of the printing film can be ensured all the way to the periphery of the printing region, and parts that could not be used due to uneven thickness of the printing film can be used, thereby enabling efficient production of printing films.

[0013] FIG. 1 is a plan view schematically illustrating a flexographic printing plate according to one embodiment of the present invention. FIG. 2 is an enlarged view of a main portion taken along the line J-J in FIG. 1 . FIG. 3 is an enlarged view of a main portion taken along the line K-K in FIG. 1 . FIG. 4 is an enlarged view of a main portion of the peripheral region of the portion enclosed by the dashed line L in FIG. 1 . FIG. 5 is a diagram illustrating a case where the angle T formed by the imaginary line R and the traveling direction S in FIG. 4 is 0°. FIG. 6 is an enlarged view of a main portion of the central region of the portion enclosed by the dashed line L in FIG. 1 . FIG. 7 is a diagram illustrating the angle T formed by the imaginary line R and the traveling direction S in FIG. 6 . FIG. 8A is a diagram illustrating the linearity of the protrusion array at the edge of the peripheral region when the angle T formed by the imaginary line R and the traveling direction S is 0°. Note that in FIG. 8A , the imaginary line R and the traveling direction S are parallel to each other, making it impossible to show the angle T, and therefore the angle T is omitted from the drawing. FIG. 8B is a diagram illustrating the linearity of the protrusion arrangement at the edge of the peripheral region when the angle T is -5°. FIG. 8C is a diagram illustrating the linearity of the protrusion arrangement at the edge of the peripheral region when the angle T is -10°. FIG. 9A is a diagram illustrating the linearity of the protrusion arrangement at the edge of the peripheral region when the angle T formed by the virtual line R and the direction of travel S is 45°. FIG. 9B is a diagram illustrating the linearity of the protrusion arrangement at the edge of the peripheral region when the angle T is 40°. FIG. 9C is a diagram illustrating the linearity of the protrusion arrangement at the edge of the peripheral region when the angle T is 35°. FIG. 10A is a partially enlarged photograph of a flexographic printing plate according to an example of the present invention. FIG. 10B is a partially enlarged photograph of a flexographic printing plate according to a comparative example of the present invention. FIG. 11A is a diagram illustrating a halftone dot pattern formed by halftone dots arranged in rows in both the vertical and horizontal directions. FIG. 11B is a diagram illustrating a halftone dot pattern set so that the distances between adjacent halftone dots arranged in six directions around the periphery are equal. Fig. 12 is a diagram illustrating the difference in dot distribution density between the printing direction portion and the perpendicular direction portion in the dot pattern of the peripheral region. Fig. 13 is a diagram illustrating the depth of grooves between multiple protrusions formed by the arrangement of the dot pattern of Fig. 12. Fig. 14 is an explanatory diagram schematically showing a printing machine using a flexographic printing plate. Fig. 15A is a plan view schematically showing a conventional flexographic printing plate. Fig. 15B is an enlarged view of a main part at the M-M cross section of Fig. 15A. Fig. 15C is an enlarged cross-sectional view of a main part of Fig. 15B.

[0014] The present invention will be described in more detail below based on embodiments of the present invention, but the present invention is not limited to the following embodiments. In the present invention, when "Y to Z" (Y and Z are any numbers) is expressed, unless otherwise specified, it means "Y or more and Z or less", and also includes the meaning of "preferably larger than Y" or "preferably smaller than Z". Furthermore, when "Y or more" (Y is any number) or "Z or less" (Z is any number) is expressed, it also includes the meaning of "preferably larger than Y" or "preferably less than Z".

[0015] <<First Embodiment>> Fig. 1 is a plan view schematically illustrating one embodiment of a flexographic printing plate of the present invention, Fig. 2 is an enlarged view of a main portion of the J-J cross section of Fig. 1, and Fig. 3 is an enlarged view of a main portion of the K-K cross section of Fig. 1. The flexographic printing plate P of this embodiment includes a flat base 1 that is rectangular in plan view and a printing protrusion 2 that is rectangular in plan view and formed in the center of the surface of the base 1. A plurality of minute truncated cone-shaped protrusions 3 are distributed on the top surface of the printing protrusion 2, with gaps (grooves 4) between them, and ink is retained in the grooves 4. The base 1, printing protrusions 2, and protrusions 3 are integrally formed. In this embodiment, the direction of the arrow along the long side of the rectangular printing protrusion 2 in plan view corresponds to the printing direction (travel direction S).

[0016] The flexographic printing plate P is used for flexographic printing and has flexibility so that it can be attached to the peripheral surface of a plate cylinder 51 of a printing press (see FIG. 14). Materials for forming the flexographic printing plate P include, for example, resin, rubber, etc. Methods for forming the flexographic printing plate P include, for example, mold molding, and when a photosensitive resin is used as the forming material, it is preferably formed by photolithography.

[0017] The dimensions of the truncated cone-shaped protrusions 3 can be set, for example, such that the top diameter is in the range of 20 to 70 μm, the bottom diameter is in the range of 185 to 300% of the top diameter, and the depth D from the top to the bottom of the groove 4 is in the range of 5 to 25 μm (see FIG. 2). The distribution density of the protrusions 3 can be set, for example, in the range of 100 to 1,300 protrusions 3 per inch (25.4 mm).

[0018] The printing protrusions 2 are roughly divided into two regions (portions). That is, depending on the distribution of the protrusions 3, the printing protrusions 2 are divided into a central region 2A of the printing protrusions 2 and peripheral regions 2B and 2C located on the periphery of the central region 2A, and the central region 2A and the peripheral regions 2B and 2C have different halftone dot patterns (hereinafter sometimes referred to as "halftone dot patterns") recognized as the planar shape of the protrusions 3. Here, the halftone dots recognized as the planar shape of the protrusions 3 refer to the top surfaces, not the bottom surfaces, of the protrusions 3. This is to accommodate the fact that the aperture ratio is usually calculated based on the area of ​​the top surfaces of the protrusions 3.

[0019] <Peripheral Regions 2B, 2C> First, the peripheral regions 2B, 2C of the printing protrusion 2 will be described. FIG. 4 illustrates the halftone dot pattern of the multiple protrusions 3 formed in the peripheral regions 2B, 2C in a plan view in the area surrounded by the dashed line L in FIG. 1. In this embodiment, the halftone dot patterns in the peripheral regions 2B, 2C are the same, and are formed by a collection of rows of halftone dots 3a. The angle T formed by the imaginary line R connecting the centers 3b of adjacent rows of halftone dots 3a and the direction of printing progress S is set to 0°. Note that FIG. 4 does not illustrate the halftone dot pattern of the protrusions 3 formed in the central region 2A. Furthermore, the imaginary line R and the direction of printing progress S are parallel to each other and do not intersect, so the angle T is not illustrated.

[0020] In the halftone dot pattern, the imaginary line connecting the centers 3b of adjacent halftone dots 3a arranged in a row is not limited to the imaginary line R shown in Fig. 4, but there is also an imaginary line r1 connecting the centers 3b of adjacent halftone dots 3a in the vertical direction (up and down on the paper) as shown in Fig. 5. There is also an imaginary line r2 connecting the centers 3b of adjacent halftone dots 3a in the diagonal direction (upward and downward on the paper). However, in the halftone dot pattern, as shown in Fig. 11A, the distance between the centers 3b of adjacent halftone dots 3a in the diagonal direction (distance E2) is longer than the distance between adjacent halftone dots 3a in the vertical and horizontal directions (distance E1). Therefore, as shown in Fig. 5, the halftone dots 3a used to obtain the imaginary line R are selected from those adjacent in the vertical and horizontal directions, but not those adjacent in the diagonal direction (the same applies to adjacent halftone dots 3a in the upward and downward direction on the paper, although this is not shown). In the present invention, when multiple imaginary lines can be drawn in this way, the imaginary line is defined as the one whose angle between the imaginary line and the direction of travel is equal to or greater than 0° and less than 90°. Therefore, as shown in Figure 5, in the halftone dot pattern, the angle t between the imaginary line r1 and the direction of travel S is 90°, and therefore this is not adopted. Furthermore, as mentioned above, the imaginary line r2 is not adopted because it would increase the distance between adjacent halftone dots 3a.

[0021] In this way, when the angle T formed by the imaginary line R of the dot pattern in the peripheral regions 2B, 2C and the direction of printing progress S is 0°, the linearity of the arrangement of each protrusion 3 formed at the extreme edge of the printing raised portion 2 is improved, as shown in the area surrounded by dashed lines in Figure 8A (to make the arrangement easier to see, a line (imaginary line F) tangent to the outside of the protrusions 3 (dots 3a) is drawn; the same applies below). Note that the angle T is omitted in Figure 8A. Similarly, when the angle T is set to 0°±10° or 45°±10°, the linearity of the arrangement of each protrusion 3 formed at the extreme edge is improved (see Figures 8B and 8C).

[0022] That is, when the angle T is -5°, as shown in the area surrounded by the dashed line in FIG. 8B , the linearity of the arrangement (imaginary line F) of the protrusions 3 formed at the extreme end is slightly disrupted (there are portions at the end where the protrusions 3 are not formed), but the linearity is sufficient. When the angle T is -10°, as shown in the area surrounded by the dashed line in FIG. 8C , the linearity of the arrangement (imaginary line F) of the protrusions 3 formed at the extreme end is further disrupted (there are portions at the end where the protrusions 3 are not formed), but the linearity is acceptable. Note that FIGS. 8B and 8C illustrate patterns in which the angle T is shifted by 5° or 10° in the negative (negative) direction when the angle T is 0°. However, even in patterns in which the angle T is shifted by 5° or 10° in the positive (positive) direction, the arrangement of the protrusions 3 formed at the extreme end has similar linearity.

[0023] On the other hand, as shown in the area surrounded by the dashed line in Fig. 9A, even when the angle T is 45°, the linearity of the arrangement (imaginary line F) of the protrusions 3 formed at the extreme end is improved. As in the case when the angle T is 0°, the linearity is also improved when the angle T is in the vicinity of 45°.

[0024] That is, when the angle T is 40°, as shown in the area surrounded by the dashed line in FIG. 9B , the linearity of the arrangement (imaginary line F) of the protrusions 3 formed at the extreme end is slightly disrupted (there are portions at the end where the protrusions 3 are not formed), but the linearity is sufficient. When the angle T is 35°, as shown in the area surrounded by the dashed line in FIG. 9C , the linearity of the arrangement (imaginary line F) of the protrusions 3 formed at the extreme end is further disrupted (there are portions at the end where the protrusions 3 are not formed), but the linearity is acceptable. Note that FIGS. 9B and 9C illustrate patterns in which the angle T is 45° and is shifted by 5° or 10° in the negative (negative) direction. However, even in patterns in which the angle T is shifted by 5° or 10° in the positive (positive) direction, the arrangement of the protrusions 3 formed at the extreme end has similar linearity.

[0025] As shown in FIG. 1 , the peripheral regions 2B and 2C consist of a peripheral region 2B that is aligned with the printing direction and a peripheral region 2C that is aligned with the perpendicular direction perpendicular to the printing direction. The ratio (W / X) of the width W of the peripheral region 2B to the width X of the printing protrusion 2 is preferably 0 < W / X < 0.05. Furthermore, the width W of the peripheral region 2B is preferably 0.1 mm or more and 1 mm or less. That is, a narrower width is preferable to minimize the impact on the active area. On the other hand, to achieve the effect of improving linearity, it is necessary to arrange a certain number of halftone dots in the peripheral region in an arrangement different from the halftone dot pattern in the central region. The width W of the peripheral region 2B is the sum (W + W) of the widths W1 and W2 of the left and right edges in the printing direction. The widths W1 and W2 may be the same or different. If the width W is too small, the area of ​​the peripheral region 2B becomes too small, making it difficult to form the desired halftone dot pattern, while if the width W is too large, the area of ​​the central region 2A becomes too small, and even if a halftone dot pattern is set to solve the problem of regular unevenness in ink thickness when the printing target is an array substrate, the effect obtained tends to be reduced. Thus, when the ratio (W / X) is within the above range, an excellent balance is achieved between the complexity of halftone dot pattern design and the effect obtained.

[0026] Furthermore, in the halftone dot pattern in the peripheral regions 2B and 2C, the pitch between adjacent halftone dots 3a arranged in a row is not particularly limited, but is preferably set to 20 μm to 300 μm, and more preferably 30 μm to 90 μm. That is, while a shorter pitch is advantageous in terms of linearity, a pitch that is too short tends to result in insufficient volume for the grooves 4 and inability to retain the necessary amount of ink. However, setting the pitch between adjacent halftone dots 3a within the above range achieves an excellent balance between linearity and ink retention. As shown in FIGS. 4, 11A, and 11B, the pitch between adjacent halftone dots 3a refers to the distance H at which the distance between halftone dots 3a is shortest. <Central Region> Next, the central region 2A of the printing convex portion 2 will be described. FIG. 6 illustrates the halftone dot pattern of the protrusions 3 formed in the central region 2A in the area surrounded by the dashed line L in FIG. 1. In this embodiment, the angle T formed by the imaginary line R connecting the centers 3b of adjacent halftone dots 3a arranged in a row and the direction S of printing progress is set to 68°. Note that in Figure 6, the halftone dot pattern of the protrusions 3 formed in the peripheral regions 2B and 2C is not shown.

[0027] FIG. 7 illustrates a method for selecting the virtual line R to be used in the present invention when multiple virtual lines can be drawn in the halftone dot pattern of FIG. 6 . As described above, when multiple virtual lines can be drawn, the virtual line in the present invention is defined as the virtual line whose angle T between the virtual line and the direction of travel is greater than or equal to 0° and less than 90°. For this reason, the halftone dot pattern shown in FIG. 6 uses the virtual line R that slopes upward to the left relative to the paper surface, rather than the virtual line r1 that slopes upward to the right relative to the paper surface. This is because, as shown in FIG. 7 , the angle t1 between the virtual line r1 and the direction of travel S is 158°, or the angle t2 is −22°. Furthermore, the virtual line r2 is not used because it would increase the distance between adjacent halftone dots 3a.

[0028] There are no particular limitations on the dot pattern in the central region 2A, but when an array substrate is used as the printing substrate, it is preferable that the angle T formed by the imaginary line R connecting the centers 3b of adjacent dots 3a arranged in a row and the printing direction S is 56° to 79°.

[0029] That is, around the contact holes formed on the array substrate of a liquid crystal panel, the ink transferred by flexographic printing is repelled by surface tension and fine debris (residue) generated during the formation of the contact holes, preventing the ink from fully penetrating the contact holes, resulting in uneven thickness of the alignment film around the contact holes and resulting in thickness irregularities. Typically, contact holes formed on an array substrate are arranged in a regular row. Therefore, when a groove holding ink abuts on a location around the contact hole where ink repellency occurs, thickness irregularities become noticeable in that area. If this noticeable thickness irregularity occurs regularly, the thickness irregularities become even more noticeable.

[0030] To address this problem, if the halftone dot pattern in the central region 2A has an angle T of 56° to 79° between the imaginary line R connecting the centers 3b of adjacent halftone dots 3a arranged in a row and the direction S of printing, the grooves 4 holding the ink tend to be less likely to come into regular contact with the arrangement of contact holes formed in the array substrate, and film thickness unevenness can be prevented from becoming more noticeable. Similarly, if the angle T is 11° to 34°, this is also preferable because it can prevent film thickness unevenness from becoming more noticeable.

[0031] As described above, in the flexographic printing plate P of the first embodiment, the halftone dot pattern in the peripheral regions 2B, 2C has an angle T formed by the imaginary line R connecting the centers 3b of adjacent halftone dots 3a in the row and the direction of printing progress S set to 0°±10° or 45°±10°. This improves the linearity of the arrangement of the protrusions 3 formed at the outermost edge of the peripheral region 2B, and makes it possible to uniformize the amount of ink that can be retained in the grooves 4 formed between the protrusions 3 all the way to the periphery of the peripheral region 2B. Furthermore, if the halftone dot pattern in the central region 2A has an angle T formed by the imaginary line R connecting the centers 3b of adjacent halftone dots 3a in the row and the direction of printing progress S set to 11° to 34° or 56° to 79°, it is possible to make film thickness unevenness less noticeable in most of the printing region when, for example, an array substrate is used as the printing substrate. Therefore, by using this flexographic printing plate P for flexographic printing, it is possible to form printed films such as alignment films in liquid crystal display units, organic light-emitting films in organic EL displays, and electrode films in electronic devices, all the way to the corners with improved thickness uniformity.

[0032] Second Embodiment In the second embodiment, the halftone dot patterns (see FIG. 11A ) of the peripheral regions 2B and 2C in the first embodiment are modified so that the distances between adjacent halftone dots 3 a arranged in six directions are equal, as shown in FIG. 11B . That is, in the first embodiment, as shown in FIG. 11A , the distance between the centers 3 b of adjacent halftone dots 3 a in the vertical and horizontal directions (distance E1) is longer than the distance between adjacent halftone dots 3 a in the diagonal direction (distance E2). Therefore, halftone dots 3 a used to obtain the virtual line R are selected from halftone dots 3 a adjacent in the vertical and horizontal directions, but not from halftone dots 3 a adjacent in the diagonal direction. In contrast, in the second embodiment, the distances between adjacent halftone dots 3 a arranged in six directions are equal, as shown in FIG. 11B , which reduces variations in the depth and length of the grooves 4. 11B, the angle T between the imaginary line R and the moving direction S is 55°.

[0033] When a dot pattern in which the distances between adjacent dots 3a arranged in six directions around the periphery are equal is adopted as the dot pattern for the peripheral regions 2B and 2C, the angle T between the virtual line R and the direction of travel S is not particularly limited, but in particular, if the angle T between the selected virtual line R and the direction of travel S is set to any of 0°±10°, 30°±10°, or 60°±10°, there is a tendency for the linearity of the arrangement of protrusions 3 formed at the outermost edge of the peripheral region 2B to be further improved.

[0034] <<Third Embodiment>> In the third embodiment, the halftone dot patterns of the peripheral regions 2B and 2C in the first embodiment (see FIG. 4) are changed to different halftone dot patterns in the peripheral regions 2B and 2C, as shown in FIG. 12, and the distribution density of the halftone dots 3a in the peripheral region 2C is set higher than the distribution density of the halftone dots 3a in the peripheral region 2B. For example, the distribution density of the halftone dots 3a in the peripheral region 2B may be set within a range of 200 to 400 dots per inch, and the distribution density of the halftone dots 3a in the peripheral region 2C may be set within a range of 400 to 600 dots per inch, which is higher than the distribution density of the halftone dots 3a in the peripheral region 2B.

[0035] In this way, when the distribution densities of the halftone dots 3a are set differently in the peripheral region 2C (perpendicular direction portion) and the peripheral region 2B (printing direction portion), the ink held in the grooves 4 of the printing convex portions 2 is more likely to spread to a uniform thickness on the top surfaces of the printing convex portions 2 due to the pressure applied when the printing convex portions 2 come into contact with the anilox roll 52 of the printing press and the material to be printed Q. Of the peripheral regions 2B, 2C located on the periphery of the central region 2A, the peripheral region 2B (printing direction portion along the printing direction) and the peripheral region 2C (perpendicular direction portion along a direction perpendicular to the printing direction) overlap at four corners, and these four corners are included in the peripheral region 2C (perpendicular direction portion).

[0036] In this third embodiment, as shown in Figure 13, the depth D1 from the surface of the protrusion 3 in the peripheral region 2B (printing direction portion) is different from the depth D2 from the surface of the protrusion 3 in the peripheral region 2C (perpendicular direction portion), and it is preferable that these depths be set such that D1 > D2. For example, the depth D1 in the peripheral region 2B (printing direction portion) is set to a value within the range of 15 to 25 μm, and the depth D2 in the peripheral region 2C (perpendicular direction portion) is set to a value within the range of 5 to 15 μm, both of which are smaller than the depth D1. Setting D2 to a smaller value reduces the amount of ink held in the grooves 4, which tends to prevent deterioration of the linearity of the printed film edge due to excess ink spreading during printing.

[0037] 10A is a partially enlarged photograph of a flexographic printing plate P in which the halftone dot pattern in the central region 2A is set so that the angle T is 72° and the halftone dot pattern in the peripheral region 2B is set so that the angle T is 45°. When printing a resin (ink) for forming an alignment film on an array substrate, for example, the flexographic printing plate P has a structure in which film thickness variations are less noticeable in the central region 2A, which occupies most of the surface of the printing convex portion 2 of the flexographic printing plate P, and in the peripheral region 2B, the regularity (linearity) of the projection arrangement at the outermost edge is increased (see the boundary between the peripheral region 2B and the base 1 in FIG. 10A ), so that the amount of ink that can be held in the grooves 4 formed between the projections 3 can be made uniform all the way to the periphery of the peripheral region 2B.

[0038] 10B is a partially enlarged photograph of a flexographic printing plate P1 in which the halftone dot pattern in the central region 2A and the halftone dot pattern in the peripheral region 2B are the same, and both are set so that the angle T is 72°. Flexographic printing plate P1 requires only one halftone dot pattern setting, which reduces the effort required for setting, but the protrusion arrangement at the outermost edge of the peripheral region 2B of the printing raised portion 2 is irregular (poor linearity) (see the boundary between the peripheral region 2B and the base 1 in FIG. 10B ), and there is variation in the amount of ink that can be held in the grooves 4 formed between the protrusions 3 at the periphery of the peripheral region 2B.

[0039] Although the above examples show specific embodiments of the present invention, the examples are merely illustrative and should not be construed as limiting. Various modifications that are obvious to those skilled in the art are intended to fall within the scope of the present invention.

[0040] The present invention is useful as a flexographic printing plate that can perform uniform printing even to the periphery.

[0041] 2 Convex portion for printing 2A Central region 2B Peripheral region (printing direction portion) 2C Peripheral region (perpendicular direction portion) P Flexo printing plate S Traveling direction

Claims

1. A flexographic printing plate having a printing convex portion with multiple protrusions formed on its top surface, wherein the multiple protrusions have a planar shape formed into a halftone dot pattern, the halftone dot pattern is different in a central region of the printing convex portion and a peripheral region located on the periphery of the central region, the halftone dot pattern is different in a printing direction portion and a perpendicular direction portion of the peripheral region, and the distribution density of the halftone dots in the printing direction portion is set higher than the distribution density of the halftone dots in the perpendicular direction portion.

2. A flexographic printing plate having a printing convex portion having a plurality of protrusions formed on a top surface, the plurality of protrusions being formed into a halftone dot pattern in a plan view, the halftone dot pattern being different between a central region of the printing convex portion and a peripheral region located on the periphery of the central region, the halftone dot pattern in the central region being a collection of halftone dots arranged in a row, and an angle T formed by an imaginary line R connecting the centers of adjacent halftone dots arranged in the row and the direction of printing progress S being set to 11° to 34° or 56° to 79°, and the halftone dot pattern in the peripheral region being a collection of halftone dots arranged in a row, and an angle T formed by an imaginary line R connecting the centers of adjacent halftone dots arranged in the row and the direction of printing progress S being set to 0°±10° or 45°±10°.

3. The flexographic printing plate according to claim 2, wherein in the halftone dot pattern in the peripheral region, the pitch between adjacent halftone dots arranged in a row is set to 20 μm to 300 μm.

4. The flexographic printing plate according to any one of claims 1 to 3, wherein the peripheral region has a printing direction portion along the printing direction and a perpendicular direction portion along a perpendicular direction perpendicular to the printing direction, and the ratio (W / X) of the width W of the printing direction portion of the peripheral region to the width X of the printing convex portion is set to 0<W / X<0.

05.

5. A flexographic printing plate according to any one of claims 2 to 4, wherein in the halftone dot pattern in the peripheral region, the distances between adjacent halftone dots arranged in six directions around the periphery are set to be equal.

Images