JP2016068346A - Flexographic printing plate for testing and method for manufacturing the same, and method for manufacturing liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexographic printing plate for testing and a method for manufacturing the flexographic printing plate, by which a flexographic printing plate with an optimal specific surface area can be selected while requiring energy, time and cost as little as possible, and a liquid crystal display element and a method for manufacturing the liquid crystal display element using the selected flexographic printing plate.SOLUTION: A flexographic printing plate 1 for testing has a plate surface 3 roughened in such a manner that a specific surface area with respect to a flat plane is continuously varied from one side of the plate surface to the other side. The method for manufacturing the flexographic printing plate for testing includes a step of forming a photosensitive resin composition layer on a mold surface that is an original of the above plate surface 3 and irradiating the composition layer with active rays to cure. The method for manufacturing a liquid crystal display element includes: selecting a flexographic printing plate on the basis of the results of test printing using the above flexographic printing plate for testing; and forming a liquid crystal alignment film by flexography using the selected flexographic printing plate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a test flexographic printing plate used for selection of a flexographic printing plate for forming, for example, a liquid crystal alignment film of a liquid crystal display element by flexographic printing, a manufacturing method thereof, and a liquid crystal display using the selected flexographic printing plate The present invention relates to a method for manufacturing an element.

In order to form a liquid crystal alignment film that requires high coating quality, that is, as thin as possible, without pinholes, etc., on the electrode forming surface of the substrate constituting the liquid crystal display element, it has good printing characteristics. The flexographic printing method is used.
The flexographic printing method consists of a flexible resin sheet, one side of which is in contact with the surface to be printed such as the electrode forming surface while carrying the ink that is the basis of the liquid crystal alignment film, etc. A flexographic printing plate having a surface to be transferred to a printing surface, that is, a plate surface is used.

The plate surface is a rough surface having a predetermined surface roughness in order to improve the affinity for the ink so as to hold the ink well and to transfer the held ink to the printing surface. It is common.
In addition, the arrangement is such that not only a rough surface but also minute protrusions having a predetermined planar shape are regularly arranged, and the arrangement interval of the protrusions is different for each print region, or the area of the protrusions is different. In some cases (see Patent Documents 1 and 2, etc.).

  However, the substrate of high-definition liquid crystal display elements, which have been particularly popular in recent years, has a highly minute surface on the surface, and the fine uneven shape is not different for each liquid crystal display device manufacturer or even in the same manufacturer. Since it is generally different for each element product, it is difficult to completely match the compatibility with the flexographic printing plate, and there is a problem that uneven printing or repellency is likely to occur if the compatibility is slightly shifted.

Therefore, every time a manufacturer of a liquid crystal display element develops a substrate having a new fine concavo-convex shape with the development of a new liquid crystal display element, for example, it is a great deal to select an optimal flexographic printing plate that matches the compatibility. The current situation is that labor and cost are paid.
That is, a flexographic printing plate having a plurality of samples having different specific surface areas with respect to a flat surface, which defines the state of the rough surface of the plate surface, is prepared, and test printing is repeated using each flexographic printing plate to have an optimal specific surface area. The version is selected,
(1) A lot of flexographic printing plates that require a great deal of energy, time and cost even if only one sheet is made.
(2) For example, if it is found that there is an appropriate value for the specific surface area between two sample flexographic printing plates, a new sample flexographic printing plate is made and retested to determine the specific surface area. More energy, time and cost,
There is a problem.

JP 2002-293049 A Japanese Patent No. 2933790

  An object of the present invention is to provide a flexographic printing plate for testing which can select a flexographic printing plate having an optimum specific surface area with as little energy, time and cost as possible, a method for producing the same, and a liquid crystal using the selected flexographic printing plate. The object is to provide a method for manufacturing a display element.

The present invention comprises a resin layer formed in a flat plate shape with one side being a plate surface, the plate surface is roughened, and the specific surface area relative to the plane is from one side of the plate surface to the other side It is a flexographic printing plate for testing that is continuously changed from side to side.
The present invention also comprises a material having transparency to actinic rays capable of curing the photosensitive resin composition on one side of the layer of the photosensitive resin composition that is the basis of the test flexographic printing plate. In a state where one surface corresponds to the plate surface of the flexographic printing plate and is in contact with the mold surface of the roughened sheet which is a rough mold surface whose specific surface area with respect to the plane is continuously changed, the layer For the test of the present invention, comprising a step of making the surface of the layer roughened by peeling off from the mold surface after curing reaction by irradiation of the actinic ray through the roughened sheet It is a manufacturing method of a flexographic printing plate.

  Furthermore, the present invention provides a process for selecting an optimal flexographic printing plate having a specific surface area with respect to a plane based on the result of test printing using the test flexographic printing plate of the present invention, and the selected flexographic printing It is a method for manufacturing a liquid crystal display element including a step of forming a liquid crystal alignment film by flexographic printing using a plate.

  The test flexographic printing plate of the present invention is formed by continuously changing the specific surface area with respect to the plane of the plate surface from one side to the other side as described above. Just by performing test printing using only one sheet, it is possible to immediately select a flexographic printing plate having an optimal specific surface area that matches the compatibility, and to reduce energy, time and cost required for the selection of the flexographic printing plate as much as possible. it can.

Further, according to the method for producing a test flexographic printing plate of the present invention, a roughened sheet having a rough mold surface whose specific surface area with respect to a plane is continuously changed is used, and the rest is the same as in the prior art. Thus, the test flexographic printing plate of the present invention can be efficiently produced at low cost.
Furthermore, according to the method for manufacturing a liquid crystal display element of the present invention, it is possible to manufacture a liquid crystal display element at a lower cost because energy, time and cost when selecting a flexographic printing plate can be omitted as described above. Become.

It is a perspective view which shows an example of embodiment of the flexographic printing plate for a test of this invention. It is a figure explaining an example of the preparation methods of the roughening sheet used for the manufacturing method of the said flexographic printing plate for a test. FIGS. 3A to 3C are cross-sectional views showing an example of a manufacturing process of the test flexographic printing plate. FIGS. 3A to 3C are cross-sectional views showing an example of a manufacturing process subsequent to FIGS. 3A to 3C.

<Flexographic printing plate for testing>
FIG. 1 is a perspective view showing an example of an embodiment of a test flexographic printing plate of the present invention.
Referring to FIG. 1, a test flexographic printing plate 1 of this example includes a flexible resin layer 2, and one surface (upper surface in the drawing) of the layer 2 is a plate surface 3, and the opposite surface (FIG. Then, the reinforcing film 4 is laminated on the lower surface, and the whole is formed in a rectangular flat plate shape.

The test flexographic printing plate 1 is gripped by a vise (not shown) when the test flexographic printing plate 1 is set on the flexographic printing machine in the vicinity of two parallel sides of the rectangle of the test flexographic printing plate 1 and outside the plate surface 3. A constant width gripping portion 5 is provided over the entire width of each side.
A groove 6 having a constant width is provided between the grip 5 and the plate surface 3 in parallel with the grip 5.

Further, the holding part 5 has a pin hole for inserting a fixing pin (not shown) into the holding part 5 in a state of being held with a vise at equal intervals in a plurality of places (5 places in the figure) in the length direction. 7 is formed.
Although not shown, the plate surface 3 has a specific surface area with respect to a plane (surface area is 1) as indicated by a white arrow in the drawing from the one gripping portion 5 side to the other (in the drawing). It is roughened in a state where the specific surface area is inclined so as to continuously increase toward the grip portion 5 side on the back side.

The range in which the specific surface area of the plate surface 3 is changed is not particularly limited. For example, when evaluating compatibility with the substrate for a high-definition liquid crystal display element described above, the plane is set to 1 as described above. For example, the specific surface area is preferably continuously changed from 2.8 to 4.1 from the grip portion 5 side toward the back grip portion 5 side.
As a result, the optimum ratio for printing the liquid crystal alignment film of the high-definition liquid crystal display element can be obtained simply by test printing the compatibility with the substrate in the range of the specific surface area using one test flexographic printing plate 1. A flexographic printing plate with a surface area can be selected.

In the test printing, the substrate for compatibility is set on the flexographic printing machine, the test flexographic printing plate is set on the plate cylinder of the flexographic printing machine, and the model of the liquid crystal alignment film is actually printed. What is necessary is just to obtain | require the specific surface area of the part from which the best printing was obtained by observing a printing state.
To determine which specific surface area is to be optimized, for example, it may be confirmed whether or not the printed liquid crystal alignment film has unevenness, repellency, moire fringes, or other disturbances.

<Method for producing test flexographic printing plate>
As described above, the test flexographic printing plate of the present invention uses only a roughened sheet having a roughened mold surface whose specific surface area with respect to a flat surface is continuously changed as described above. Can be manufactured.
FIG. 2 is a diagram for explaining an example of a method for producing the roughened sheet.

With reference to FIG. 2, in the manufacturing method of this example, first, the molten resin that becomes the roughened sheet 8 is extruded into a sheet shape through a nozzle 9 of an extruder (not shown), and then cooled and solidified. The precursor sheet 10 before being inserted is continuously inserted between the rubber roll 12 whose outer peripheral surface 11 is subjected to fine unevenness processing and the counter roll 13.
At this time, the rubber roll 12 is applied with a predetermined nip pressure in the direction of the opposite roll 13 as indicated by a white arrow in the drawing, and is pressed against the left side surface in the figure of the precursor sheet 10, whereby the surface is in contact with the above surface. Fine irregularities on the outer peripheral surface 11 of the rubber roll 12 are continuously transferred.

And the roughening sheet | seat 8 used as the type | mold surface 14 by which the said fine unevenness | corrugation was fixed by the subsequent cooling and the said surface was roughened is produced continuously.
The transferred fine irregularities vary in height, formation interval, and the specific surface area of the mold surface 14 based on the height and formation interval according to the nip pressure of the rubber roll 12. That is, the specific surface area increases as the nip pressure increases, and the specific surface area decreases as the nip pressure decreases.

In the case of producing a normal roughened sheet, the specific surface area of the mold surface is made constant by keeping the nip pressure constant.
However, in the case of the present invention, when the roughened sheet 8 is continuously formed in a long shape through the above steps, the nip pressure is repeated for each length of the roughened sheet, for example. After continuously changing, the specific surface area of the mold surface 14 in the one roughened sheet 8 is cut according to the change in the nip pressure, for example, by cutting it to one sheet length. It can be formed small on the side and large on the other end side.

As the resin that becomes the basis of the roughened sheet 8, extrusion molding and roughening are possible as described above, and any of various resins having transparency to actinic rays can be used.
Examples of the resin include thermoplastic resins such as polyethylene (PE), polypropylene (PP), thermoplastic polyurethane elastomer (TPU), polyethylene terephthalate (PET), and tetrafluoroethylene / hexafluoropropylene copolymer (FEP). A seed | species or 2 or more types is mentioned.

Of these, the roughened sheet 8 made of a relatively soft thermoplastic resin such as PE, PP, TPU and the like, and relatively thin (for example, about 150 μm or less) is weak in itself and difficult to handle.
In that case, a reinforcing sheet made of, for example, PET and having transparency to actinic rays may be bonded to the opposite surface 15 of the roughened sheet 8.

3 (a) to 3 (c) and 4 (a) to 4 (c) are cross-sectional views showing an example of the manufacturing process of the test flexographic printing plate of the present invention using the roughened sheet.
Referring to FIG. 3 (a), in the manufacturing method of this example, first, it is made of a hard material such as glass or a hard resin such as an acrylic resin, a polycarbonate resin, or a polyester resin, and is also transmissive to actinic rays such as ultraviolet rays. A support substrate 16 having the above is prepared.

In the figure of the support substrate 16, the roughened sheet 8 is brought into contact with the surface 17 such that the roughened sheet 8 faces the mold surface 14 and the opposite surface 15 faces downward, for example, FIG. As indicated by the one-dot chain line arrow in (a), it is fixed detachably by overlapping one on the other from the other end.
In the drawing, the unevenness constituting the mold surface 14 is drawn with a large emphasis so as to be easy to understand. However, since the actual unevenness does not affect the shape of the liquid crystal alignment film to be printed, the rough surface shown in the drawing is used. It is a minute one that cannot be determined by comparison with the size of the plasticized sheet 8. Further, in the drawing, the irregularities are drawn almost uniformly on the entire surface of the mold surface 14, but actually, as explained above, the specific surface area of the roughened sheet 8 continuously changes from the left end to the right end in the drawing, for example, It is formed by changing its height, formation interval and the like. The method for changing the specific surface area is as described above.

  The roughened sheet 8 is applied to the support substrate 16 by a shearing force when a liquid photosensitive resin composition is spread on the roughened sheet 8 or a shrinkage force when the photosensitive resin composition is cured. In order to prevent misalignment and to facilitate replacement of the roughened sheet 8 after use, it can be detachably attached to the surface 17 of the support substrate 16 by any of the following methods (i) to (iii), for example. It is preferable to fix to.

(i) Removably attached and fixed through a weak adhesive layer made of a material having transparency to actinic rays.
(ii) A suction groove is formed on the surface of the support substrate 16, and vacuum suction is performed through the suction groove to detachably adsorb and fix.
(iii) Removably press-fixed in a state of being stretched between a pair of chuck jigs spaced apart from the dimension in the surface direction of the support substrate 16.

  Among these, as the weak adhesive layer used for the adhesive fixation of (i), various adhesives having weak adhesiveness to the forming material of the support substrate 16 and the roughened sheet 8 and having transparency to actinic rays. Any of these layers can be used. The weak adhesive layer is formed by applying an adhesive to at least one of the surface 17 of the support substrate 16 and the opposite surface 15 of the roughened sheet 8 by various application methods such as spray application.

After forming such a weak adhesive layer on the surface 17 of the support substrate 16 and / or the opposite surface 15 of the roughened sheet 8, the roughened sheet 8 is supported on the support substrate as indicated by the dashed line arrow in FIG. When the layers are sequentially stacked with care so that air does not enter between one end and the other end of the surface 17 of the surface 16, the roughened sheet 8 can be fixed on the surface 17 by the adhesive force of the weak adhesive layer.
Further, in order to remove the fixed roughened sheet 8 from the surface 17, for example, the roughened sheet 8 is formed on the weak adhesive layer from the other end to the one end of the support substrate 16 opposite to the arrow in FIG. What is necessary is just to peel off in order, resisting adhesive force.

In order to perform the adsorption fixation of (ii), the surface 17 of the support substrate 16 is finished smoothly and suction grooves are formed on substantially the entire surface 17. The suction groove is connected to a vacuum system including a vacuum pump.
Then, the vacuum system is operated in a state where the roughened sheet 8 is overlapped on the surface 17 of the support substrate 16 with the opposite surface 15 facing down, or the previously operated vacuum system is connected to the suction groove, etc. The roughened sheet 8 can be fixed on the surface 17 by vacuum suction through the suction groove.

In order to remove the fixed roughened sheet 8 from the surface 17, the vacuum system may be stopped or the connection between the vacuum system and the suction groove may be interrupted.
Next, referring to FIG. 3B, in the manufacturing method of this example, a predetermined amount of liquid photosensitive resin composition is formed on the mold surface 14 of the roughened sheet 8 fixed on the surface 17 of the support substrate 16. 18 is supplied.
Then, the photosensitive resin composition 18 is sandwiched between the roughened sheet 8 and the reinforcing film 4, and from one end to the other end of the surface 17 of the support substrate 16 as shown by a dashed line arrow in FIG. A layer 19 of the photosensitive resin composition is formed by spreading on the mold surface 14 of the roughened sheet 8 in order so that air does not enter between the layers, and the reinforcing film 4 is laminated thereon. To do.

Next, referring to FIG. 3C, the facing surface 21 of the facing substrate 20 is brought into contact with the reinforcing film 4.
Then, while maintaining the opposing surface 21 of the opposing substrate 20 parallel to the surface 17 of the supporting substrate 16 with a certain distance therebetween, the opposing substrate 20 is supported by the supporting substrate 16 as indicated by a black arrow in FIG. The layer 19 is pressed against the mold surface 14 of the roughened sheet 8 by pressing in the direction of.

In this state, the layer 19 is exposed with actinic rays through the support substrate 16 and the roughened sheet 8 as indicated by solid arrows in FIG. 3C, and the photosensitive resin composition 18 forming the layer 19 is exposed. Is cured.
At this time, the distance between the surface 17 of the support substrate 16 and the facing surface 21 of the counter substrate 20 is maintained at a size obtained by adding the thickness of the roughened sheet 8 to the thickness of the test flexographic printing plate 1 to be manufactured. To.

The counter substrate 20 can be formed of any material such as metal, glass, and hard resin.
In particular, the counter substrate 20 is formed of a material having transparency to active light similar to the support substrate 16, and the reinforcing film 4 is also formed of a material having transparency to active light similar to the roughened sheet 8. The photosensitive resin composition layer 19 may be exposed to actinic rays from the side of the counter substrate 20 to cause a curing reaction.

4 (a) and 4 (b), the laminate 22 of the reinforcing film 4, the layer 2 formed by the curing reaction of the photosensitive resin composition 18, and the roughened sheet 8 is opposed to the support substrate 16. The substrate is taken out from between the substrates 20, is turned upside down, and placed on the work table 23 with the reinforcing film 4 facing downward.
4B, when the roughened sheet 8 is peeled in order from one end to the other end of the laminate 22, the upper surface side of the roughened sheet 8 is the surface of the roughened sheet 8. The plate surface 24 as a precursor of the test flexographic printing plate 1 shown in FIG. 4C is completed by forming the roughened plate surface 3 by transferring the uneven shape of the mold surface 14.

Thereafter, although not shown, the four sides of the plate sheet 24 are cut to adjust the entire planar shape to a rectangle, and the layer 2 in the vicinity of the two sides parallel to each other is subjected to, for example, laser processing to hold the grip portion 5 and the groove portion. 6 and pin holes 7 are formed, and a predetermined printing pattern is formed on the plate surface 3 as necessary, whereby the test flexographic printing plate shown in FIG. 1 is completed.
The photosensitive resin composition that is the basis of the layer 2 can be cured by actinic rays such as ultraviolet rays, and after curing, it has suitable flexibility and rubber elasticity suitable for use in, for example, flexographic printing. Any of various resin compositions capable of forming a cured product having excellent solvent resistance against a solvent contained in an ink used for printing or used for cleaning a printing plate can be used.

Examples of such a photosensitive resin composition include, but are not limited to, a prepolymer having a 1,2-butadiene structure and having an ethylenic double bond at the terminal, an ethylenically unsaturated monomer, and initiation of photopolymerization. The thing containing an agent etc. are mentioned.
As the photopolymerization initiator, benzoin alkyl ether is preferable, and the content of benzoin that causes yellowing of the printing resin original plate by reacting with visible light from a fluorescent lamp or the like is the total amount of the photosensitive resin composition. What is 500 ppm or less is used suitably. As a result, it is possible to obtain a printing resin original plate excellent in light resistance that does not yellow in a short period of time.

  As the reinforcing film 4, as with the roughened sheet 8, for example, polyethylene (PE), polypropylene (PP), thermoplastic polyurethane (TPU), polyethylene terephthalate (PET), tetrafluoroethylene / hexafluoropropylene copolymer ( A sheet made of a thermoplastic resin such as FEP) and having transparency to actinic rays can be used.

<Manufacturing method of liquid crystal display element>
The present invention provides a process for selecting an optimal flexographic printing plate having a specific surface area with respect to a plane based on the result of test printing using the test flexographic printing plate, and the selected flexographic printing plate. And a method of manufacturing a liquid crystal display element including a step of forming a liquid crystal alignment film by flexographic printing.

In the process of test printing → selection, as described above, the compatible substrate is set on the flexographic printing machine, and the test flexographic printing plate is set on the plate cylinder of the flexographic printing machine to actually form a model of the liquid crystal alignment film. After printing, the specific surface area of the portion where the best printing is obtained is determined by observing the printed state on the substrate.
This makes it possible to test the compatibility with a substrate within a specified specific surface area using a single test flexographic printing plate, and the optimal specific surface area for printing a liquid crystal alignment film of a high-definition liquid crystal display element. Flexographic printing plates with can be selected.

Therefore, according to the manufacturing method of the present invention, it is possible to manufacture a liquid crystal display element at a lower cost because energy, time and cost for selecting a flexographic printing plate can be omitted.
Other steps of the production method of the present invention can be carried out in the same manner as in the prior art.
That is, after forming a transparent electrode layer corresponding to a predetermined matrix pattern on one side of a transparent substrate such as a soda lime glass substrate, a liquid crystal alignment film is formed by flexographic printing using the flexographic printing plate selected in the previous step Further, the substrate is manufactured by subjecting the surface of the liquid crystal alignment film to alignment treatment by rubbing or the like as necessary.

Then, two substrates are prepared, and the transparent electrode layers are aligned with each other, and a liquid crystal material is sandwiched between them and fixed to each other. If necessary, polarizing plates are disposed on both outer sides of the laminate. By doing so, a liquid crystal display element is manufactured.
The present invention is not limited to the examples of the drawings described above. For example, the reinforcing film 4 may be omitted in the test flexographic printing plate 1 of the present invention. Further, in the manufacturing method, instead of pressing the photosensitive resin composition layer in the direction of the support substrate by the counter substrate, the surface is roughened by spreading the surface by a roller of a roughened sheet to make the thickness constant. May be.

  In addition, various changes can be made without departing from the scope of the present invention.

<Example 1>
A roughened sheet 8 in which the specific surface area of the mold surface 14 is continuously changed from one end side to the other end side of the rectangle is prepared by the method of FIG. 2 described above, and the roughened sheet 8 is used to create a roughened sheet 8. 3 (a) to (c), and after passing through the steps of FIGS. 4 (a) to (c), the specific surface area of the plate surface 3 is between 2.8 and 4.1 from one side to the other side. The test flexographic printing plate 1 shown in FIG. 1, which was continuously changed, was produced.

Then, after test printing a liquid crystal alignment film model on a newly designed substrate using this test flexographic printing plate 1, are there any irregularities, repellency, moire fringes, or other disturbances in the liquid crystal alignment film? As a result, it was confirmed that the optimum specific surface area was 3.7 to 3.8.
The time required for the process so far was 12 hours, no retest was performed, only one flexographic printing plate for testing was required, and the production cost was 2 million yen.

<Comparative example 1>
Conventionally, three test flexographic printing plates having a specific surface area of 2.8, 3.4, and 4.1 are constant, and liquid crystals are formed on the substrate using the test flexographic printing plates. After test-printing the alignment film model, it was confirmed whether the liquid crystal alignment film had irregularities, repellency, moire fringes or other disturbances. The optimum specific surface area was between 3.4 and 4.1. However, no conclusion was reached.

Therefore, we made two test flexographic printing plates whose specific surface area was constant at 3.6 and 3.8 and made a follow-up test, and 3.8 was better than 3.6. I was able to confirm that there was.
However, the time required for the process so far was 60 hours, the number of test flexographic printing plates was 5, and the production cost reached 10 million yen.

  From the above results, it was confirmed that by using the test flexographic printing plate of the present invention, a flexographic printing plate having an optimal specific surface area can be reliably selected with as little energy, time and cost as possible compared with the conventional one. It was.

DESCRIPTION OF SYMBOLS 1 Test flexographic printing plate 2 Layer 3 Plate surface 4 Reinforcing film 5 Holding part 6 Groove part 7 Pin hole 8 Roughening sheet 9 Nozzle 10 Precursor sheet 11 Outer peripheral surface 12 Rubber roll 13 Pair roll 14 Mold surface 15 Opposite surface 16 Support substrate 17 Surface 18 Photosensitive resin composition 19 Layer 20 Counter substrate 21 Counter surface 22 Laminate 23 Work table 24 Plate sheet

Claims (5)

  It comprises a resin layer formed in a plate shape with one side being a plate surface, the plate surface is roughened, and the specific surface area relative to the plane is from one side of the plate surface to the other side Flexographic printing plates for testing that are continuously changing.   2. The test flexographic printing plate according to claim 1, wherein the specific surface area is changed between 2.8 and 4.1, with the plane being 1. 3.   One side of the layer of the photosensitive resin composition that is the basis of the test flexographic printing plate is made of a material having transparency to actinic rays that can cure the photosensitive resin composition, and one side of the layer is the flexographic printing The layer is roughened in a state in which the surface of the roughened sheet corresponding to the plate surface of the plate is in contact with the die surface of the roughened sheet whose surface area is continuously changed. The test flexo according to claim 1, further comprising a step of forming a roughened plate surface on one side of the layer by causing a curing reaction by irradiation of the actinic ray through a sheet and then peeling from the mold surface. A method for producing a printing plate.   The roughened sheet is a mold surface whose one surface is roughened by pressing a rubber roll having fine irregularities on its outer peripheral surface against one surface of a resin sheet formed by extruding a molten resin. The method for producing a flexographic printing plate according to claim 3, wherein the specific surface area of the mold surface is continuously changed by continuously changing the pressure contact force of the rubber roll.   A step of selecting an optimum flexographic printing plate having a constant specific surface area with respect to a plane based on the result of test printing using the test flexographic printing plate according to claim 1 or 2, and the selected flexographic printing plate The manufacturing method of the liquid crystal display element including the process of forming a liquid crystal aligning film by flexographic printing using.

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