Printing plate

Abstract

In order to improve the uniformity of the film thickness of an alignment film formed by applying ink (alignment film material) to the surface of a transparent electrode constituting a liquid crystal panel, a printing plate (P) is provided with a printing protrusion (2) in which a plurality of protrusions (3) are distributed and formed on the top surface, the plurality of protrusions (3) are arranged in each row, and each of the protrusions (3) constituting the row has a thickness greater than that of the ink (alignment film material). And a plurality of protrusions (3) arranged parallel to and spaced apart from each of the protrusions (3) constituting the other row, and arranged so that the positions in the direction in which the protrusions (3) are arranged are offset with respect to each of the protrusions (3) constituting the other row, the protrusions (3) having a circular top surface shape, and the protrusions (3) having a circular bottom surface shape. The ratio of the shallowest depth of the gap portion (4) between the protrusions to the deepest depth of the gap portion (4) between the protrusions (the shallowest depth of the gap portion between the protrusions / the deepest depth of the gap portion between the protrusions) is 0.4 or more.

Description

Technical Field

[0001] The present invention relates to a printing plate used for printing such as flexographic printing. Background Art

[0002] A liquid crystal panel is configured to include an array substrate, a color filter substrate disposed opposite to the array substrate, and a liquid crystal layer sandwiched between the array substrate and the color filter substrate. The array substrate has, for example, a transparent substrate, a gate electrode, a gate insulating film, a semiconductor layer, a first protective film, a source electrode, a drain electrode, a second protective film, and a resin film. Further, a contact hole having a tapered shape narrower at the bottom is formed in the second protective film and the resin film formed on the surface of the drain electrode. The surface of the drain electrode is exposed due to the contact hole. A transparent electrode is formed on the resin film by a sputtering method or the like, and the transparent electrode is electrically connected to the drain electrode at the bottom of the contact hole.

[0003] By coating an alignment film material such as polyimide so as to cover the transparent electrode and the resin film and fill the contact hole, an alignment film can be formed on the entire surface of the transparent electrode and the like. As a method of coating the alignment film material, for example, printing methods such as flexography and inkjet methods can be cited.

[0004] Here, as shown in the plan view in (a) of Figure 7 and the T-T cross-sectional view in (a) of Figure 7 in (b) of Figure 7 , a printing plate P1 used for forming an alignment film in flexographic printing generally includes a flat base portion 11 and a printing convex portion 12 formed in the central portion of the surface of the base portion 11. The printing convex portion 12 is the above-mentioned printing area, and the portion of the base portion 11 around the printing convex portion 12 does not participate in printing. Further, as shown in the cross-sectional view obtained by magnifying the main part of (b) of Figure 7 in (c) of Figure 7 , on the top surface of the printing convex portion 12, a plurality of protrusions 13 are formed to be distributed with a gap portion 14 therebetween, and ink is held in the gap portion 14. Further, the printing plate P1 has flexibility so that it can be mounted along the circumferential side surface of the printing plate cylinder 51 (see Figure 6 ).

[0005] Figure 8 (a) of Figure 8 is a plan view showing the protrusions 13 formed on the printing convex portion 12,

[0006] and Figure 8 (b) of Figure 8 is a schematic diagram showing the protrusions 13 three-dimensionally. Figure 8in (a) of Figure 8 The protrusions 13 shown in (b) of

[0007] Figure 8 are minute. In this example, 400 protrusions 13 are formed per inch (160,000 per square inch) on the printing convex portion 12. The distances S11 and S12 indicated by the arrows in (a) of

[0008] Here, Figure 9 is a plan view schematically showing the arrangement of the protrusions 13 formed on the above-described printing convex portion 12. As described above, the protrusions 13 are arranged orthogonally. The rhombic region G11 indicated by a thin line and surrounded by each protrusion 13 becomes the gap portion 14 and is a portion for holding ink.

[0009] Figure 10 is an enlarged plan view showing the protrusions 13 formed on the above-described printing convex portion 12. Figure 11 (a) of Figure 10 shows a graph of the height difference of the W1-W1 section of Figure 11 and (b) of Figure 10 shows a graph of the height difference of the W2-W2 section of Figure 10 and Figure 11 The depth of the position A between the protrusions 13 shown in (a) of Figure 10 and Figure 11 is 19.07 μm (the depth from the height of the top surface of the protrusion 13, the same applies hereinafter). The depth of the position B between the protrusions 13 shown in (b) of 3 / m 2 is 4.65 μm. In this example, since the shape of the top surface 13a of the above-described protrusion 13 is circular, the amount of ink that the gap portion 14 surrounded by these protrusions 13 can hold is larger than that in the case where the top surface shape is formed into a polygon or the like. The unit volume (indicating the capacity for holding ink) of the printing plate P1 having the printing convex portion 12 formed with the above-described protrusions 13 is 4.60 cm

[0010] Prior art documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-164979 Summary of the Invention

[0013] Problems to be Solved by the Invention

[0014] In order to coat ink (alignment film material) on a transparent electrode using such a printing plate P1, the ink is held between minute protrusions 13 arranged orthogonally (gap portion 14), and the printing plate P1 is brought into contact with an object to be printed Q (an array substrate or a color filter substrate on which an alignment film is not formed), whereby the ink is transferred to the object to be printed Q.

[0015] At this time, if the deviation in the depth between the respective protrusions 13 formed on the printing protrusions 12 provided on the printing plate P1 (gap portion 14) is large, the difference in the amount of ink held in the gap portion 14 becomes large depending on the position, and thus there is a case where, although the amount of ink held is sufficient, the film uniformity of the obtained alignment film deteriorates. For Figure 8 Regarding the depth between the conventional protrusions 13 exemplified, according to the values in the above example, the shallowest depth M1 is 4.65 μm, the deepest depth M2 is 19.07 μm, and the ratio of the shallowest depth to the deepest depth (M1 / M2) is 0.24 (≈4.65 / 19.07) (for M1 and M2, refer to Figure 11 (a) of Figure 11 (b) of

[0016] In addition, in the case where the object to be printed Q is an array substrate, there is a case where, around the contact holes formed in the array substrate, the ink is repelled due to surface tension, minute debris (residue) generated when forming the contact holes, etc., and the ink does not sufficiently enter the contact holes, and the film thickness of the alignment film at the periphery of the contact holes is different from the film thickness formed in other portions. When the liquid crystal panel is in a light-emitting state (especially halftone), the portion where the film thickness of the alignment film is uneven becomes uneven in brightness and is easily visually recognized, and thus it is desired to achieve a higher level of film thickness uniformity.

[0017] The present invention has been completed in view of such circumstances, and an object thereof is to provide a printing plate that improves the film thickness uniformity of an alignment film.

[0018] Means for Solving the Problems

[0019] In order to achieve the above object, the printing plate of the present invention has the following structure, which includes printing protrusions, and a plurality of protrusions are formed on the top surface of the printing protrusions. Among them, the plurality of protrusions are arranged in each column, and for each protrusion constituting each column, they are arranged in parallel and separated from each protrusion constituting other columns, and are arranged such that the positions in the direction in which the protrusions are arranged are shifted with respect to each protrusion constituting other columns.

[0020] Specifically, when the depth of the gaps between the protrusions varies significantly, the uniformity of the alignment film deteriorates. In view of this, suppressing the depth variation of the gaps between the protrusions can improve the uniformity of the alignment film. Furthermore, the alignment film may become thicker around the contact holes, but this can be avoided by improving ink repellency around the contact holes.

[0021] The inventors of the present invention, focusing on the above aspects, have discovered that by seeking to maintain a sufficient amount of ink in the gaps between the protrusions and the uniformity of the ink retention in each gap, the deviation in the depth of the gaps between the protrusions can be suppressed, and the ink repulsion around the contact holes can be improved, thereby improving the film uniformity of the orientation film.

[0022] In order to achieve the above-mentioned object, the present invention provides the following [1] and [2].

[0023] [1] A printing plate having a convex portion for printing, wherein the convex portion for printing has a plurality of protrusions distributed on the top surface, characterized in that the plurality of protrusions are arranged in each column, and the protrusions constituting each column are arranged in parallel and separated relative to the protrusions constituting other columns, and are arranged so that the positions of the protrusions in the direction of arrangement are staggered relative to the protrusions constituting other columns, the top surface shape of the protrusions is circular, and the ratio (M1 / M2) of the shallowest depth M1 of the gap portion between the protrusions to the deepest depth M2 of the gap portion between the protrusions is greater than 0.4.

[0024] [2] In the printing plate described in [1], the protrusions are arranged so that the distances between the protrusions and the adjacent protrusions arranged in six directions around the periphery are equal.

[0025] Effects of the Invention

[0026] In the printing plate of the present invention, multiple protrusions are arranged in each column. For each protrusion constituting each column, they are arranged in parallel and separated from each protrusion constituting other columns, and are arranged so that the positions in the direction of protrusion arrangement are staggered relative to each protrusion constituting other columns.

[0027] Therefore, compared with the case where the shape of the top surface of the protrusion is set to be circular and the protrusions are arranged orthogonally as in the past, the distance between the protrusions can be shortened, a plurality of gaps between the protrusions can be provided within the same area, and the possibility of the gaps being located on the contact holes during printing can be increased.

[0028] If the above-mentioned gap portion is located on the contact hole, a sufficient amount of ink held in the gap portion between the respective protrusions can be efficiently filled into the contact hole, and thus generation of ink repulsion at the periphery of the contact hole can be suppressed. As a result, the film uniformity of the above-mentioned alignment film can also be improved at the periphery of the above-mentioned contact hole.

[0029] In addition, when the respective protrusions are arranged such that the distances between each of the respective protrusions and the adjacent protrusions arranged in six surrounding directions are equal, since the spaces between the above-mentioned protrusions are of the same pitch and a narrow pitch, the film uniformity of the above-mentioned alignment film can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematically shows an embodiment of a printing plate of the present invention, Figure 1 FIG. (a) is a plan view of the printing plate, Figure 1 FIG. (b) is Figure 1 a main part enlarged view at the R-R cross section of FIG. (a).

[0031] Figure 2 FIG. (a) is a plan view showing protrusions formed on a printing convex portion included in a printing plate according to an embodiment of the present invention, Figure 2 FIG. (b) is a schematic diagram three-dimensionally showing the protrusion.

[0032] Figure 3 is a plan view schematically showing the arrangement of protrusions of the present invention.

[0033] Figure 4 is a plan view showing protrusions formed on a printing convex portion included in the printing plate of the present invention.

[0034] Figure 5 FIG. (a) shows, when Figure 4 the printing convex portion is observed in side cross section using the V1-V1 cross section of FIG., a graph of the height difference formed in the printing convex portion due to the above-mentioned protrusions and gap portions. Figure 5 FIG. (b) shows, when Figure 4 the printing convex portion is observed in side cross section using the V2-V2 cross section of FIG., a graph of the height difference formed in the printing convex portion due to the above-mentioned protrusions and gap portions.

[0035] Figure 6 is an explanatory view schematically showing a printing press using the printing plate.

[0036] Figure 7 Schematically shows a conventional printing plate, Figure 7 FIG. (a) is a plan view of the printing plate, Figure 7 FIG. (b) is Figure 7 a T-T cross-sectional view of FIG. (a), Figure 7 FIG. (c) is Figure 7Enlarged view of the main part of (b).

[0037] Figure 8 (a) is a top view showing the protrusions formed on the printing convex portions provided on the conventional printing plate, Figure 8 and (b) is a schematic view three-dimensionally showing the protrusions.

[0038] Figure 9 is a top view schematically showing the arrangement of the conventional protrusions.

[0039] Figure 10 is an enlarged top view showing the protrusions formed on the printing convex portions provided on the conventional printing plate.

[0040] Figure 11 (a) shows when using Figure 10 the W1-W1 section of to observe the printing convex portion in side section, a graph showing the height difference formed in the printing convex portion due to the above-mentioned protrusions and the gap portion. Figure 11 (b) shows when using Figure 10 the W2-W2 section of to observe the printing convex portion in side section, a graph showing the height difference formed in the printing convex portion due to the above-mentioned protrusions and the gap portion. Detailed implementation mode

[0041] The implementation mode of the present invention will be described in detail based on the drawings.

[0042] However, the present invention is not limited to the implementation mode described below.

[0043] In addition, in this specification, when expressed as "F or more" (F is an arbitrary number), it also includes the meaning of "preferably greater than F".

[0044] And, in this specification, when expressed as "X to Y" (X and Y are arbitrary numbers), unless otherwise specifically stated, it means: including the meaning of "X or more and Y or less", and also includes the meaning of "preferably greater than X" or "preferably less than Y".

[0045] Figure 1 (a) is a top view showing the printing plate P as an embodiment of the present invention, Figure 1 (b) is Figure 1 an enlarged view of the main part of the R-R section of (a).

[0046] The printing plate P of an embodiment of the present invention includes a base portion 1 having a rectangular flat plate shape when viewed from above, and a printing convex portion 2 having a rectangular shape when viewed from above formed at the central portion of the surface of the base portion 1. A plurality of protrusions 3 are formed and distributed on the top surface of the printing convex portion 2 (refer to Figure 2)。The printing plate P is used for flexographic printing. As Figure 6 shown, the printing plate P is flexible so that it can be mounted on the circumferential side surface of the plate cylinder 51 of the printing press. The forming material of such a printing plate P is, for example, a photosensitive resin, rubber, etc.

[0047] The above-mentioned base portion 1, the printing convex portion 2, and the protrusion 3 are integrally formed. And, in this embodiment, the direction of the arrow along the long side of the above-mentioned printing convex portion 2 that is rectangular in plan view is set as the printing direction. As shown below, on the top surface of the above-mentioned printing convex portion 12, a plurality of protrusions 3 are formed so as to be distributed with a gap portion 4 therebetween, and ink is held in the gap portion 4.

[0048] Figure 2 (a) is a plan view showing the protrusions 3 formed on the printing convex portion 2, Figure 2 (b) is a schematic view three-dimensionally showing the protrusion 3 portion. As Figure 2 (a), Figure 2 (b) shown, on the printing convex portion 2, a plurality of protrusions 3 having a circular top surface 3a are arranged and disposed in each of a plurality of columns. For each of the protrusions 3 constituting each of these columns, they are arranged parallel to the protrusions 3 constituting other columns and are arranged and disposed separated from the protrusions 3 constituting other columns. Furthermore, for each of the protrusions 3 constituting each of these columns, they are arranged such that the positions in the direction in which the protrusions 3 are arranged are shifted with respect to the protrusions 3 constituting other columns.

[0049] And, the above-mentioned protrusions 3 are arranged such that the distances between the protrusions 3 in the six adjacent surrounding directions are equal to each other (honeycomb arrangement).

[0050] In addition, Figure 2 (a), Figure 2 (b) shown protrusions 3 are minute. For example, 184,752 protrusions 3 are formed per square inch of the printing convex portion 2. In comparison with the conventional protrusions 13 exemplified by Figure 8 etc., it is 1.15 (≒184,752 / 160,000) times that of the conventional protrusions 13.

[0051] Figure 2 (a) The distance S (S1 to S3) indicated by the arrow represents the pitch (center-to-center distance) between adjacent protrusions 3. The distances S1 to S3 are all the same. The distance S (S1 to S3) is, for example, 63.5 μm. In addition, the diameter C of the top surface 3a of the protrusion 3 is, for example, 44.7 μm, and the ratio (S / C) of the above-mentioned distance S to the diameter C is 1.42.

[0052] Figure 3It is a top view schematically showing the arrangement of the protrusions 3. As described above, the plurality of protrusions 3 are formed in the printing convex portion 2 arranged in each column. For each protrusion 3 constituting each column, they are arranged parallel to and separated from the protrusions 3 constituting other columns, and are arranged with a position shift in the direction in which the protrusions 3 are arranged with respect to the protrusions 3 constituting other columns. The triangular region G1 represented by a thin line surrounded by the protrusions 3 is a portion (gap portion 4) for holding ink.

[0053] Figure 4 It is a magnified top view showing the protrusions 3 formed in the printing convex portion 2. Figure 5 (a) of [X] is showing when Figure 4 observing the printing convex portion 2 in a side cross-section with the V1-V1 cross-section of [X], it is a graph showing the height difference formed in the printing convex portion 2 due to the above-mentioned protrusions 3 and the gap portion 4. Figure 5 (b) of [X] is showing when Figure 4 observing the printing convex portion 2 in a side cross-section with the V2-V2 cross-section of [X], it is a graph showing the height difference formed in the printing convex portion 2 due to the above-mentioned protrusions 3 and the gap portion 4.

[0054] Figure 4 The depth of the position A between the protrusions 3 shown in [X] is Figure 5 as shown in (a) of [X] is 14.91 μm, and it is the deepest depth M2 in the gap portion 4. In addition, Figure 4 The depth of the position B between the protrusions 3 shown in [X] is Figure 5 as shown in (b) of [X] is 11.03 μm, and it is the shallowest depth M1 in the gap portion 4.

[0055] Therefore, in this example, the ratio (M1 / M2) of the shallowest depth M1 to the deepest depth M2 becomes 0.74 (≒11.03 / 14.91). In addition, the unit volume of the printing plate P formed with the above-mentioned protrusions 3 is 4.54 cm 3 / m 2 . In addition, the above-mentioned values are just an example.

[0056] As a method for forming such a printing plate P, for example, a photolithography method can be cited. The photolithography method has: a process of manufacturing a negative film formed with a predetermined pattern, a process of placing the above-mentioned negative film on a photosensitive resin that becomes the printing plate P, and a process of irradiating light to the above-mentioned photosensitive resin on which the above-mentioned negative film is placed and curing the above-mentioned photosensitive resin at the position where the light passes through the above-mentioned negative film. The photosensitive resin portion where the light passes through the above-mentioned negative film and is irradiated with light solidifies, and the solidified portion becomes the above-mentioned protrusions 3. The photosensitive resin portion where the light does not pass through the above-mentioned negative film and is not irradiated with light becomes the above-mentioned gap portion 4.

[0057] That is, in order to produce protrusions 3 having circular top surfaces 3a, it is sufficient to form a pattern having a plurality of circles on the negative film. Furthermore, since the top surfaces 3a of the resulting protrusions 3 only need to be circular in shape, the circles in the pattern include not only true circles but also circles that take into account the precision errors of the photolithography method.

[0058] Flexographic printing applications Figure 6 The printing press is performed as shown. The printing press comprises a cylindrical plate cylinder 51 on which a printing plate P is mounted, an anilox roller 52 for applying ink to the printing plate P, an ink supply device 53 for supplying ink to the surface of the anilox roller 52, a scraper 54 for scraping excess ink off the surface of the anilox roller 52, and a printing table 55 on which a printed object Q is placed.

[0059] Flexographic printing using the above-described printing press is performed as follows. Specifically, a printing plate P is mounted on the circumferential side of a plate cylinder 51. This plate cylinder 51 is rotated, and ink supplied from an ink supply device 53 is deposited on the printing area of the printing plate P via an anilox roller 52. This deposited ink is then transferred to a printed object Q, such as a glass substrate, placed on a printing table 55, thereby performing printing. At this time, the printing table 55 slides in synchronization with the rotation of the plate cylinder 51.

[0060] Here, in printed version P, as Figure 2 As shown in (b), on the top surface of the printing convex portion 2, a plurality of protrusions 3 are distributed and formed with gaps 4 therebetween, and ink is retained in the gaps 4.

[0061] When using a printing plate P, for example, to apply ink (orientation film material) to a printed object Q (such as a transparent electrode, etc.) in order to form an orientation film for a liquid crystal panel, the ink is caused to flow into a plurality of gap portions 4 formed on the printing protrusions 2, and the ink is transferred to the printed object Q from the printing plate P in this state.

[0062] In the above-mentioned printing plate P, as mentioned above, the above-mentioned multiple protrusions 3 are formed on the printing convex portion 2 in an arranged manner in each column. For each protrusion 3 constituting each column, they are arranged in parallel and separated from each protrusion 3 constituting other columns, and are arranged so that the positions of the protrusions 3 in the arrangement direction are staggered relative to each protrusion 3 constituting other columns.

[0063] Therefore, with the use of Figure 7 and Figure 8 Compared to the conventional printing plate P1 in which the protrusions 13 are arranged orthogonally as shown, the pitch between the protrusions 3 is shortened, and variations in the depth of the gaps 4 between the protrusions 3 can be suppressed.

[0064] As a result, the deviation in the ink holding amount and the ink transfer amount in each gap portion becomes smaller, and the film uniformity of the alignment film is improved.

[0065] In addition, in the printing plate P according to an embodiment of the present invention, the distance between the above-mentioned protrusions 3 is short, and a plurality of gap portions 4 are formed in a dense state (refer to Figure 3 ). This can also be understood by comparing with the protrusions 13 and the gap portions 14 formed in the conventional printing plate P1 (refer to Figure 9 ).

[0066] In this way, in the printing plate P according to an embodiment of the present invention, since minute irregularities are formed on the printing convex portion 2, there is a high possibility that the gap portion 4 is disposed at a position overlapping the contact hole during printing, and the ink does not repel near the contact hole, and the contact hole can be filled with the ink. Therefore, the film uniformity of the alignment film around the contact hole is also improved.

[0067] Moreover, in the above-mentioned printing plate P, the protrusions 3 are arranged in a state where the distances between the protrusions 3 adjacent to each other in the six surrounding directions are equal. Therefore, the distances between the above-mentioned protrusions 3 are the same and narrow, and the film uniformity of the alignment film around the contact hole is further improved.

[0068] In addition, in the present embodiment, since the protrusions 3 are formed by photolithography, the shape of the top surface 3a of the protrusions 3, that is, a circle, of course includes a perfect circle, and also includes a circle having a shape deformed, shifted, etc. caused by the above-mentioned manufacturing method. As the shape having the above-mentioned deformation, shift, etc., for example, an ellipse with an aspect ratio exceeding 0 and up to 0.2 can be cited.

[0069] In addition, in the above-mentioned printing plate P, for each of the protrusions 3, the ratio (M1 / M2) of the shallowest depth M2 to the deepest depth M1 of the depth of the gap portion 4 between the adjacent protrusions 3 is formed to be 0.74, but it can also be set to any other ratio.

[0070] However, from the aspect of further improving the film uniformity of the alignment film, for the depth of the gap portion 4 between the adjacent protrusions 3, the ratio (M1 / M2) of the shallowest depth M1 to the deepest depth M2 is preferably 0.4 or more, more preferably 0.5 or more, further preferably 0.6 or more, and still further preferably 0.7 or more.

[0071] Furthermore, in the above-mentioned printing plate P, the diameter C of the top surface 3a of the protrusion 3 is formed to be 44.7 μm, but the diameter C is not limited thereto. However, from the viewpoints of the ink holding amount and fluidity, the diameter C is preferably 10 μm to 70 μm, more preferably 15 μm to 60 μm.

[0072] Also, in the above-described printing plate P, the ratio (S / C) of the distance S between the respective protrusions 3 to the diameter C of the top surface 3a is set to 1.42, but the ratio (S / C) is not limited thereto. However, from the aspect of being able to effectively control the flow of the ink held in the gap portion 4 during printing, the ratio (S / C) is preferably 1.15 to 3, more preferably 1.25 to 2.5.

[0073] In the above embodiment, a specific mode in the present invention is shown, but the above embodiment is merely illustrative and is not to be construed in a limiting sense. What can be achieved is that various modifications known to those skilled in the art are within the scope of the present invention.

[0074] Industrial Applicability

[0075] The printing plate of the present invention is useful as a printing plate for improving the uniformity of the film thickness of the alignment film.

[0076] Explanation of Reference Numerals

[0077] P, printing plate; 2, printing convex portion; 3, protrusion; 3a, top surface.

Claims

1. A printing plate having printing convex portions on which a plurality of protrusions are formed on the top surface, characterized in that the plurality of protrusions are arranged in each column, and for each protrusion constituting each column, they are arranged in parallel and separated from the protrusions constituting other columns, and are arranged with a position shift in the direction of protrusion arrangement with respect to the protrusions constituting other columns; the top surface shape of the protrusions is circular; the ratio M1 / M2 of the shallowest depth M1 to the deepest depth M2 of the gap portion between the protrusions is 0.4 or more.

2. The printing plate according to claim 1, characterized in that the protrusions are arranged to have equal distances from each of the adjacent protrusions arranged in six surrounding directions.

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