Flexographic printing plate

Abstract

To provide a flexographic printing plate capable of securing uniformity of thickness of a printed film up to a periphery of a printing region.SOLUTION: A flexographic printing plate P includes plane-view shapes of a plurality of projections formed on a dot pattern. A central region 2A of a projection for printing 2 is different in terms of the dot pattern from peripheral regions 2B and 2C located on a periphery of the central region 2A.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a printing plate used in flexographic printing, and more particularly to a flexographic printing plate capable of uniformly printing all the way to the periphery. [Background technology]

[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 which applies ink to the flexographic printing plate P1, an ink supply device 53 which supplies ink to the surface of the anilox roll 52, a doctor blade 54 which 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: flexographic printing plate P1 is attached to the peripheral surface of plate cylinder 51, and while rotating plate cylinder 51, ink supplied from ink supply device 53 is applied to the printing area of ​​flexographic printing plate P1 via anilox roll 52, and the applied ink is transferred to a printing medium Q such as a glass substrate placed on printing stage 55, thereby performing printing (forming a printing film). At this time, printing stage 55 is slid in synchronization with the rotation of plate cylinder 51.

[0004] Here, the flexographic printing plate P1 generally comprises a flat base 11 and a printing convex portion 12 formed in the center of the surface of the base 11, as shown in a plan view in Fig. 15A and in an MM cross-sectional view of Fig. 15A in Fig. 15B. The printing convex portion 12 is the printing area, and the portion of the base 11 around the printing convex portion 12 is not involved in printing. As shown in Figure 15C, which is an enlarged cross-sectional view of a main portion of Figure 15B, a plurality of protrusions 13 are distributed on the top surface of the printing convex portion 12, separated by grooves 14, and ink is retained in the grooves 14. The flexographic printing plate P1 has flexibility so that it can be attached to the peripheral 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 material Q, and the ink held in the printing convex portions 12 is collected in the peripheral region (e.g., peripheral region 12B) of the printing convex portions 12 due to the pressure generated when the printing convex portions come into contact with the anilox roll 52 and the printing material Q. This may 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 a flexographic printing plate in which the distribution density of the protrusions 13 formed in the printing convex portion 12 is set higher in the peripheral region 12B than in the central region 12A of the printing convex portion 12. That is, in this plate, the distribution density of the protrusions 13 is increased in the peripheral region 12B of the printing convex portion 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 the thickness of the peripheral portion of the printing film from becoming thicker. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent No. 3376908 [Patent Document 2] JP 2002-293049 A Summary of the Invention [Problem to be solved by the invention]

[0008] On the other hand, flexographic printing is required to have various performance features other than suppressing the occurrence of marginal phenomena. For example, with recent technological developments, a high level of uniformity is required, and it is becoming necessary to guarantee the uniformity of the thickness of the printed film up to the periphery of the printing area.

[0009] The present invention has been made in consideration of the above circumstances, and has an object to provide a flexographic printing plate that can ensure uniformity in the thickness of the printing film up to the periphery of the printing area. [Means for solving the problem]

[0010] However, in light of these circumstances, the inventors conducted extensive research 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 in the end of the printing film (alignment film) to accommodate the narrowing of the frame of liquid crystal panels, thereby completing the present invention.

[0011] That is, the present invention has the following aspects. [1] A flexographic printing plate having a printing convex portion on a top surface of which a plurality of protrusions are formed, the plurality of protrusions having planar shapes formed into a halftone dot pattern, 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. [2] The flexographic printing plate according to [1], wherein the dot pattern in the peripheral region is a collection of dots arranged in rows, and an angle T between an imaginary line R connecting the centers of adjacent dots arranged in the rows and the printing progress direction S is set to 0°±10° or 45°±10°. [3] The flexographic printing plate according to [1] or [2], wherein the dot pattern in the central region is a collection of dots arranged in a row, and an angle T formed by a virtual line R connecting the centers of adjacent dots arranged in the row and the printing progress direction S is set to 11° to 34° or 56° to 79°. [4] The peripheral region has a printing direction portion along the printing direction and a perpendicular direction portion along the 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. The flexographic printing plate according to any one of [1] to [3]. [5] In the halftone dot pattern in the peripheral region, the pitch of the adjacent halftone dots arranged in the columnar shape is set to 20 μm to 300 μm. The flexographic printing plate according to any one of [1] to [4]. [6] In the halftone dot pattern in the peripheral region, the distances between the halftone dots arranged in the six surrounding directions adjacent to each other are set to be equal. The flexographic printing plate according to any one of [1] to [5]. [7] In the peripheral region, the halftone dot pattern is different between the printing direction portion and the perpendicular direction portion, 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. The flexographic printing plate according to any one of [1] to [6].

Advantages of the Invention

[0012] According to the flexographic printing plate of the present invention, a plurality of protrusions are formed in a halftone dot pattern in a plan view shape, and the halftone dot pattern is different between the central region of the printing convex portion and the peripheral region located at the periphery of the central region. Therefore, the linearity of the protrusion array formed at the end of the peripheral region can be enhanced. Therefore, by performing printing using this flexographic printing plate, the uniformity of the thickness of the printing film can be ensured up to the periphery of the printing region, and it becomes possible to use up to the parts that could not be used conventionally due to the non-uniform thickness of the printing film. Thus, the printing film can be produced efficiently.

Brief Description of the Drawings

[0013] [Figure 1] FIG. 1 is a plan view schematically showing a flexographic printing plate according to an embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of a main part taken along the J-J cross section of FIG. 1. [Diagram 3] FIG. 3 is an enlarged view of a main portion taken along line KK in FIG. [Figure 4] FIG. 4 is an enlarged view of a main portion of the peripheral region of the portion surrounded by the dashed line L in FIG. [Diagram 5] FIG. 5 is a diagram for explaining a case where the angle T formed by the virtual line R and the traveling direction S in FIG. 4 is 0°. [Figure 6] FIG. 6 is an enlarged view of a main portion of the central region of the portion surrounded by the dashed line L in FIG. [Figure 7] FIG. 7 is a diagram for explaining the angle T formed by the imaginary line R and the traveling direction S in FIG. [Figure 8] Fig. 8A is a diagram illustrating the linearity of the protrusion array at the end of the peripheral region when the angle T between the virtual line R and the traveling direction S is 0°. Fig. 8B is a diagram illustrating the linearity of the protrusion array at the end of the peripheral region when the angle T is -5°. Fig. 8C is a diagram illustrating the linearity of the protrusion array at the end of the peripheral region when the angle T is -10°. [Figure 9] Fig. 9A is a diagram illustrating the linearity of the projection array at the end of the peripheral region when the angle T between the virtual line R and the traveling direction S is 45°. Fig. 9B is a diagram illustrating the linearity of the projection array at the end of the peripheral region when the angle T is 40°. Fig. 9C is a diagram illustrating the linearity of the projection array at the end of the peripheral region when the angle T is 35°. [Figure 10] Fig. 10A is a partially enlarged photograph of a flexographic printing plate according to an embodiment of the present invention, and Fig. 10B is a partially enlarged photograph of a flexographic printing plate according to a comparative example of the present invention. [Figure 11] Fig. 11A is a diagram illustrating a halftone dot pattern formed by halftone dots arranged in rows in both the vertical and horizontal directions, and Fig. 11B is a diagram illustrating a halftone dot pattern set so that the distances between adjacent halftone dots arranged in six surrounding directions are equal. [Figure 12] FIG. 12 is a diagram illustrating the difference in dot distribution density between the printing direction portion and the perpendicular direction portion in the halftone dot pattern of the peripheral region. [Figure 13]FIG. 13 is a diagram illustrating the depth of grooves between a plurality of protrusions formed by the arrangement of the halftone dot pattern in FIG. [Figure 14] FIG. 14 is an explanatory diagram that illustrates a schematic diagram of a printing press that uses flexographic printing plates. [Figure 15] Fig. 15A is a plan view showing a schematic diagram of a conventional flexographic printing plate, Fig. 15B is an enlarged view of a main part in the MM cross section of Fig. 15A, and Fig. 15C is an enlarged cross-sectional view of a main part of Fig. 15B. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0015] <<First embodiment>> FIG. 1 is a plan view showing a schematic diagram of one embodiment of a flexographic printing plate of the present invention, FIG. 2 is an enlarged view of a main portion of the JJ cross section in FIG. 1, and FIG. 3 is an enlarged view of a main portion of the KK cross section in FIG. The flexographic printing plate P of this embodiment comprises a base 1 in the form of a flat rectangular plate when viewed from above, and a printing protrusion 2 which is rectangular when viewed from above and formed in the center of the surface of the base 1. A plurality of minute truncated cone-shaped protrusions 3 are distributed and formed with gaps (grooves 4) on the top surface of the printing protrusion 2, 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 S along the long side of the printing convex portion 2 that is rectangular in plan view is set as the printing direction (traveling direction).

[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 machine (see FIG. 14). Examples of materials for forming the flexographic printing plate P include resin, rubber, etc. Examples of methods for forming the flexographic printing plate P include molding, and when a photosensitive resin is used as the forming material, it is preferable to form the plate by a photolithography method.

[0017] The dimensions of the truncated cone-shaped protrusion 3 can be set, for example, such that the top diameter is within a range of 20 to 70 μm, the bottom diameter is within a range of 185 to 300% of the top diameter, and the depth D from the top to the bottom of the groove 4 is within a range of 5 to 25 μm (see FIG. 2). Moreover, the distribution density of the protrusions 3 can be set within a range of 100 to 1300 protrusions 3 per inch (25.4 mm), for example.

[0018] The printing raised portion 2 is roughly divided into two regions (portions). That is, depending on the distribution state of the protrusions 3, the printing raised portion 2 is divided into a central region 2A of the printing raised portion 2 and peripheral regions 2B, 2C located on the periphery of the central region 2A, and the central region 2A and the peripheral regions 2B, 2C have different dot patterns (hereinafter sometimes referred to as "dot patterns") recognized as the planar shape of the protrusions 3. Here, the 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 Areas 2B, 2C> First, the peripheral regions 2B and 2C of the printing convex portion 2 will be described. FIG. 4 illustrates a halftone dot pattern in plan view of a plurality of protrusions 3 formed in peripheral regions 2B and 2C in the portion surrounded by dashed line L in FIG. In this embodiment, the dot patterns in the peripheral regions 2B and 2C are the same, and the dot patterns are formed by a combination of dots 3a arranged in a row, and the angle T between a virtual line R connecting the centers 3b of adjacent dots 3a arranged in the row and the printing progress direction S is set to 0°. In addition, the dot pattern of the protrusions 3 formed in the central region 2A is omitted in Fig. 4. Also, the imaginary line R and the traveling direction S are parallel to each other and do not intersect with each other, so the corner T is not shown.

[0020] In the halftone dot pattern, the imaginary line connecting the centers 3b of adjacent halftone dots 3a arranged in a row is not only the imaginary line R shown in Figure 4, but also the imaginary line r1 connecting the centers 3b of adjacent halftone dots 3a in the vertical direction (the up and down direction on the paper) as shown in Figure 5. There is also an imaginary line r2 that connects the centers 3b of adjacent halftone dots 3a in a diagonal direction (upward to the left on the paper). However, in the halftone dot pattern, the distance between the centers 3b of adjacent halftone dots 3a in the vertical and horizontal directions is longer than the distance between the centers 3b of adjacent halftone dots 3a in the diagonal direction (distance E2) as shown in Fig. 11A. Therefore, as for the halftone dots 3a to obtain the virtual line R, as shown in Fig. 5, the halftone dots 3a adjacent in the vertical and horizontal directions are selected, but the halftone dots 3a adjacent in the diagonal direction are not selected (the same applies to the halftone dots 3a adjacent in the upward sloping direction on the paper, not shown). In the present invention, when multiple imaginary lines can be drawn in this manner, the imaginary line is defined as the one that forms an angle between the imaginary line and the traveling direction that is equal to or greater than 0° and less than 90°. 5, in the halftone dot pattern, the angle t between the virtual line r1 and the traveling direction S is 90°, and therefore this is not adopted. Also, as described above, the virtual line r2 is not adopted because it would increase the distance between adjacent halftone dots 3a.

[0021] In this way, when the angle T between the imaginary line R of the dot pattern in the peripheral regions 2B, 2C and the printing progression direction S is 0°, the linearity of the arrangement of each protrusion 3 formed at the extreme end of the printing convex portion 2 is improved, as shown in the area surrounded by the dashed line 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 end is improved (see Figures 8B and 8C).

[0022] In other words, when the angle T is -5°, as shown in the area surrounded by dashed lines in Figure 8B, the linearity of the arrangement (virtual line F) of each protrusion 3 formed at the extreme end is slightly disturbed (there are areas on the end edge where protrusions 3 are not formed), but the linearity is sufficient. Furthermore, when the angle T is -10°, as shown in the area surrounded by dashed lines in Figure 8C, the linearity of the arrangement (virtual line F) of each protrusion 3 formed at the extreme end is further disrupted (there are areas on the end edge where protrusions 3 are not formed), but the linearity is still acceptable. Note that Figures 8B and 8C explain patterns shifted by 5° or 10° in the - (negative) direction when angle T is 0°, but even in patterns shifted by 5° or 10° in the + (positive) direction, the arrangement of each protrusion 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 end is improved. And, similar to the case where the angle T is 0°, the linearity is also improved when the angle T is in the vicinity of 45°.

[0024] In other words, when the angle T is 40°, as shown in the area surrounded by the dashed line in Figure 9B, the linearity of the arrangement (virtual line F) of each protrusion 3 formed at the extreme end is slightly disturbed (there are areas on the end edge where protrusions 3 are not formed), but the linearity is sufficient. Also, when the angle T is 35°, as shown in the portion surrounded by the dashed line in FIG. 9C, although the linearity of the arrangement (virtual line F) of each protrusion 3 formed at the outermost end is further disrupted (there is a portion where no protrusion 3 is formed at the end side), it has an acceptable linearity. Note that FIGS. 9B and 9C illustrate patterns shifted by 5° or 10° in the -(minus) direction when the angle T is 45°. However, even for patterns shifted by 5° or 10° in the +(plus) direction, the arrangement of each protrusion 3 formed at the outermost end has a similar linearity.

[0025] And as shown in FIG. 1, the peripheral regions 2B and 2C have a printing direction portion 2B along the printing direction and a perpendicular direction portion 2C along the direction perpendicular to the printing direction. However, the ratio (W / X) of the width W of the printing direction portion 2B of the peripheral region to the width X of the printing convex portion 2 is preferably 0 < W / X < 0.05. Also, the width X is preferably 0.1 mm or more and 1 mm or less. That is, it is preferably smaller to minimize the influence on the active area. On the other hand, in order to obtain the effect of improving linearity, it is necessary to arrange a certain number of dots in the peripheral region in an arrangement different from the dot pattern in the central region. The width W of the printing direction portion 2B is the sum (W1 + W2) of the widths of the left and right edges (W1, W2) with respect to the printing direction, and the widths W1 and W2 may be the same as or different from each other. If the width W is too small, the area of the peripheral region 2B becomes too small, and it tends to be difficult to form a desired dot pattern. If the width W is too large, the area of the central region 2A becomes too small. For example, when the object to be printed is an array substrate, even if a dot pattern is set to solve the problem of regularly occurring uneven ink thickness, the obtained effect tends to decrease. Thus, when the ratio (W / X) is within the above range, it is excellent in the balance between the complexity of dot pattern design and the obtained effect.

[0026] In addition, in the dot pattern in the peripheral regions 2B and 2C, the pitch between adjacent dots 3a arranged in a row is not particularly limited, but is preferably set to 20 μm to 300 μm, and more preferably set to 30 μm to 90 μm. In other words, the shorter the pitch, the more advantageous it is in terms of linearity, but if the pitch is too short, the volume of the groove 4 cannot be secured and there is a tendency for it to be unable to hold the required amount of ink. However, if the pitch of adjacent halftone dots 3a is set within the above range, an excellent balance between linearity and ink retention amount is achieved. As shown in FIGS. 4, 11A and 11B, the pitch of adjacent halftone dots 3a refers to the distance H at which the distance between the halftone dots 3a is the shortest. <Central area> Next, the central region 2A of the printing convex portion 2 will be described. Fig. 6 illustrates the dot pattern of protrusions 3 formed in central region 2A in the portion surrounded by dashed line L in Fig. 1. In this embodiment, an angle T between an imaginary line R connecting centers 3b of adjacent dots 3a arranged in a row and the printing progress direction S is set to 68°. In FIG. 6, the dot pattern of the protrusions 3 formed in the peripheral regions 2B and 2C is omitted.

[0027] FIG. 7 illustrates a method for selecting a 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 one whose angle T between the virtual line and the traveling direction is 0° or more and less than 90°. For this reason, the halftone dot pattern shown in FIG. 6 uses a virtual line R that slopes leftward relative to the paper surface, rather than a virtual line r1 that slopes rightward relative to the paper surface. This is because, as shown in FIG. 7, the angle t1 between the virtual line r1 and the traveling direction S is 158°, or the angle t2 is -22°. Also, 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 between an imaginary line R connecting the centers 3b of adjacent dots 3a arranged in a row and the printing progress direction S is 56° to 79°.

[0029] In other words, around the contact holes formed on the array substrate of the 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, and the ink does not penetrate sufficiently into the contact holes, which can result in uneven thickness of the alignment film around the contact holes and uneven film thickness. Generally, contact holes formed on an array substrate are arranged in a regular pattern in rows, so when a groove holding ink comes into contact with a location around a contact hole where ink repellency occurs, unevenness in the thickness of the film becomes noticeable in the vicinity of that location. If this noticeable unevenness in the thickness of the film occurs regularly, the unevenness in the thickness of the film becomes even more noticeable.

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

[0031] In this way, in the flexographic printing plate P of the first embodiment, the dot pattern in the peripheral regions 2B, 2C is set so that the angle T between the imaginary line R connecting the centers 3b of adjacent dots 3a arranged in the row and the printing progress direction S is set to 0°±10° or 45°±10°. As a result, the linearity of the arrangement of protrusions 3 formed at the very edge of peripheral region 2B is improved, and the amount of ink that can be held in grooves 4 formed between protrusions 3 can be made uniform all the way to the periphery of peripheral region 2B. Furthermore, if the angle T between the imaginary line R connecting the centers 3b of adjacent dots 3a arranged in the row and the printing proceeding direction S of the dot pattern in the central region 2A is set to 11° to 34° or 56° to 79°, for example, when an array substrate is used as the printing substrate, film thickness unevenness can be made less noticeable in most of the printing region. 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 electroluminescence (EL) displays, and electrode films in electronic devices with improved thickness uniformity throughout the entire surface.

[0032] <<Second embodiment>> In the second embodiment, the halftone dot pattern of the peripheral areas 2B, 2C in the first embodiment (see FIG. 11A) is changed so that the distances between adjacent halftone dots 3a arranged in six surrounding directions are equal, as shown in FIG. 11B. 11A, the distance between the centers 3b of adjacent halftone dots 3a in the vertical and horizontal directions is longer than the distance between the centers 3b of adjacent halftone dots 3a in the diagonal direction (distance E2) as compared with the distance between the centers 3b of adjacent halftone dots 3a in the vertical and horizontal directions (distance E1). Therefore, the halftone dots 3a for obtaining the virtual line R are selected from the halftone dots 3a adjacent in the vertical and horizontal directions, but not from the halftone dots 3a adjacent in the diagonal direction. 11B, the second embodiment makes it possible to reduce the variation in the depth and length of the grooves 4 by making the distance (distance E3) between adjacent halftone dots 3a arranged in six peripheral directions equal. Reducing the variation in the depth and length of the grooves 4 reduces the variation in the amount of ink held by each portion, and makes it possible to further improve the uniformity of the thickness of the printed film. In addition, if the halftone dot pattern is designed so that the distance between each of the halftone dots 3a arranged in six adjacent directions is equal, the same result will be obtained whether the adjacent halftone dots 3a are in the vertical, horizontal, or diagonal direction and a virtual line R is connected, so any halftone dots 3a used to obtain the virtual line R can be selected, and in Figure 11B, the angle T between the virtual line R and the traveling direction S is 55°.

[0033] When a dot pattern in which the distance between each of the dots 3a arranged in six adjacent directions around the peripheral region 2B, 2C is equal is adopted, the angle T between the virtual line R and the traveling direction S is not particularly limited, but when the angle T between the selected virtual line R and the traveling direction 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, 2C in the first embodiment (see Figure 4) are made different between the print direction portion 2B and the perpendicular direction portion 2C of the peripheral regions 2B, 2C, as shown in Figure 12, and the distribution density of the halftone dots 3a in the print direction portion 2B is set higher than the distribution density of the halftone dots 3a in the perpendicular direction portion 2C. As the distribution density, for example, the distribution density of the halftone dots 3a in the printing direction portion 2B is set within the range of 200 to 400 pieces / inch, and the distribution density of the halftone dots 3a in the perpendicular direction portion 2C is set within the range of 400 to 600 pieces / inch, which is a value higher than the distribution density of the halftone dots 3a in the printing direction portion 2B.

[0035] In this way, by setting the distribution density of the halftone dots 3a in the perpendicular direction portion 2C and the printing direction portion 2B to be different, the ink held in the grooves 4 of the printing convex portion 2 is more likely to spread to a uniform thickness on the top surface of the printing convex portion 2 due to the pressure applied when the printing convex portion 2 comes into contact with the anilox roll 52 of the printing press and the material to be printed Q. In addition, of the peripheral regions 2B, 2C adjacent to the periphery of the central region 2A, the printing direction portion 2B along the printing direction and the perpendicular direction portion 2C along the perpendicular direction perpendicular to the printing direction overlap at four corners, and these four corners are included in the perpendicular direction portion 2C.

[0036] In this third embodiment, as shown in FIG. 13, the depth D1 from the surface of the protrusion 3 in the printing direction portion 2B is different from the depth D2 from the surface of the protrusion 3 in the perpendicular direction portion 2C, and it is preferable that the depths are set such that D1>D2. The depth can be set, for example, to a value smaller than the depth D1, such as a depth D1 in the printing direction portion 2B within a range of 15 to 25 μm, and a depth D2 in the perpendicular direction portion 2C within a range of 5 to 15 μm. By setting D2 to a smaller value, the amount of ink held in the grooves 4 decreases, and there is a tendency to prevent deterioration of the linearity of the printed film edge due to the spreading of excess ink during printing.

[0037] [Example] Figure 10A is a partially enlarged photograph of a flexographic printing plate P in which the dot pattern in the central region 2A is set so that the angle T is 72°, and the dot pattern in the peripheral region 2B is set so that the angle T is 45°. For example, when printing a resin (ink) for forming an alignment film on an array substrate, unevenness in film thickness is 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 protrusion arrangement at the outermost end is increased (see the boundary between the peripheral region 2B and the base 1 in Figure 10A), so that the amount of ink that can be held in the grooves 4 formed between the protrusions 3 can be made uniform all the way to the periphery of the peripheral region 2B.

[0038] [Comparative Example] Figure 10B is a partially enlarged photograph of a flexographic printing plate P1 in which the dot pattern in the central region 2A and the dot pattern in the peripheral region 2B are identical, and both are set so that the angle T is 72°. This eliminates the need for a single halftone dot pattern setting, thus reducing the time and effort required for setting it up; however, the arrangement of protrusions at the very edge of the peripheral region 2B of the printing convex portion 2 is irregular (less linear) (see the boundary between the peripheral region 2B and the base 1 in Figure 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. [Industrial Applicability]

[0039] INDUSTRIAL APPLICABILITY The present invention is useful as a flexographic printing plate capable of uniformly printing even to the periphery. [Explanation of symbols]

[0040] 2. Printing convex part 2A central area 2B Peripheral area (printing direction) 2C Peripheral area (perpendicular direction) P Flexographic printing plate S Direction of travel

Claims

1. A flexographic printing plate having a printing convex portion on a top surface of which a plurality of protrusions are formed, The plurality of protrusions are formed in a halftone dot pattern in a plan view, A flexographic printing plate, characterized in that the halftone dot pattern is different between a central region of the printing convex portion and a peripheral region located on the periphery of the central region.

2. 2. The flexographic printing plate according to claim 1, wherein the halftone dot pattern in the peripheral region is a collection of halftone dots arranged in a row, and an angle T between an imaginary line R connecting the centers of adjacent halftone dots arranged in the row and a printing progress direction S is set to 0°±10° or 45°±10°.

3. 3. The flexographic printing plate according to claim 1, wherein the halftone dot pattern in the central region is a collection of halftone dots arranged in a row, and an angle T formed by an imaginary line R connecting centers of adjacent halftone dots arranged in the row and a printing progress direction S is set to 11° to 34° or 56° to 79°.

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

05.

5. 3. The flexographic printing plate according to claim 1, 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.

6. 3. The flexographic printing plate according to claim 1, wherein the halftone dot pattern in the peripheral region is set so that the distances between adjacent halftone dots arranged in six directions around the periphery are equal.

7. 3. The flexographic printing plate according to claim 1, wherein the halftone dot patterns in the printing direction portion and the perpendicular direction portion in the peripheral region are different, 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.

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