JP6764576B2 - Flexographic printing plate and manufacturing method of liquid crystal display element using it - Google Patents

Description

The present invention relates to a flexographic printing plate and a method for manufacturing a liquid crystal display element using the flexographic printing plate.

For example, the flexographic printing method is widely used in a wide range of printing fields such as printing of packaging materials.
In the flexographic printing method, flexographic printing is made of a flexible resin sheet or the like, and the surface thereof is a plate surface, that is, a surface that comes into contact with a printing surface while carrying ink to transfer ink to the printing surface. The plate is used.
The flexographic printing method is known to have good printing characteristics, and is also used for printing a liquid crystal alignment film of a liquid crystal display element as a special application other than general purpose utilizing the flexographic printing method.

In printing a liquid crystal alignment film, the thickness of the liquid crystal alignment film formed by transferring ink from the plate surface of the flexographic printing plate to the surface to be printed can be reduced, and even if the thickness is reduced, the thickness accuracy of the liquid crystal alignment film can be reduced. It is required that the thickness is high and that uneven thickness and pinholes do not occur.
As an ink for forming a liquid crystal alignment film having such high accuracy and no uneven thickness or pinholes, an ink having low wettability to a resin or the like forming a flexographic printing plate and easily releasing from the plate surface is preferable. Used.

Further, as a flexographic printing plate, even if the ink has low wettability, it is supported on the plate surface while maintaining a uniform thickness without causing unevenness in thickness or pinholes due to repelling or the like. A plate surface having a rough surface having a constant specific surface area or the like is used (see Patent Documents 1 and 2 and the like).
In the flexographic printing plate, the surface of the layer of the photosensitive resin composition is brought into contact with the mold surface of the roughened sheet having a rough surface formed on one side corresponding to the rough surface formed on the plate surface. In this state, it is produced through a step of exposing the photosensitive resin composition to active rays such as ultraviolet rays to cure the photosensitive resin composition.

When the roughened sheet is peeled off after curing, the three-dimensional shape of the mold surface of the roughened sheet is transferred to the surface of the layer of the cured photosensitive resin composition, and the surface becomes the three-dimensional shape of the mold surface. It is a roughened plate surface having a corresponding three-dimensional shape.
The method for manufacturing such a flexographic printing plate may be abbreviated as "exposure transfer method" below.
Further, the roughened sheet has a predetermined three-dimensional shape by, for example, forming a pressure sheet using an embossed roll whose outer peripheral surface is roughened by etching or molding from etching on one side of the sheet on which it is based. It is manufactured by roughening the surface into a shape.

Japanese Unexamined Patent Publication No. 2013-119179 Japanese Unexamined Patent Publication No. 2014-133335

However, when the conventional flexographic printing plate described in Patent Documents 1 and 2 is used, the thickness of the liquid crystal alignment film formed on the surface to be printed by the flexographic printing method tends to be insufficient.
Moreover, in the conventional technique, it is necessary to change various printing conditions in order to increase the thickness of the liquid crystal alignment film.
That is, it is necessary to change the anilox roll for supporting the ink on the plate surface, change the composition of the ink, change the nip pressure, the printing speed, and the like.

However, there is a problem that it takes a lot of labor and cost to change these printing conditions.
An object of the present invention is to form a liquid crystal alignment film which is highly accurate, has no thickness unevenness, pinholes, etc., is thicker than the current state, and has a thickness suitable for a liquid crystal display element, without significantly changing printing conditions. The purpose is to provide a flexographic printing plate that can be used.

Another object of the present invention is to provide a method for manufacturing a liquid crystal display element, which comprises a step of forming a liquid crystal alignment film by a flexographic printing method using the flexographic printing plate.

The present invention is a flexographic printing plate used in a step of forming a liquid crystal alignment film by a flexographic printing method, which includes a plate surface for supporting ink, and the plate surface has a specific surface area _RS of 4.3 or more. in 6.0 or less, and the unit space volume _{S V} is 12μm ³ / μm ² or more, a flexographic printing plate is a rough surface of 29μm ³ / μm ² or less.
Further, the present invention is a method for manufacturing a liquid crystal display element, which comprises a step of forming a liquid crystal alignment film by a flexographic printing method using the flexographic printing plate.

According to the present invention, a liquid crystal alignment film having a thickness larger than the current state and a thickness suitable for a liquid crystal display element is formed with high accuracy and no thickness unevenness, pinholes, etc., and without significantly changing the printing conditions. It is possible to provide a flexographic printing plate that can be used.
Further, according to the present invention, it is possible to provide a method for manufacturing a liquid crystal display element including a step of forming a liquid crystal alignment film by a flexographic printing method using the flexographic printing plate.

It is a perspective view which shows an example of embodiment of the flexographic printing plate of this invention. It is a perspective view explaining how to obtain the specific surface area and the unit space volume on the plate surface of a flexographic printing plate. It is sectional drawing which shows an example of the three-dimensional shape of the plate surface of a flexographic printing plate. It is sectional drawing which shows the layer structure of an example of the roughening sheet used for manufacturing a flexographic printing plate. FIGS. (A) to (C) are cross-sectional views showing an example of a process of manufacturing the flexographic printing plate of the example of FIG. FIGS. (A) to (c) are cross-sectional views showing an example of the steps following the steps of FIGS. 5 (a) to 5 (c). It is a micrograph of the plate surface in the Example of this invention. It is a micrograph of the plate surface in the comparative example.

《Flexographic printing version》
FIG. 1 is a perspective view showing an example of an embodiment of the flexographic printing plate 1 of the present invention.
With reference to FIG. 1, the flexographic printing plate 1 of this example includes a flexible resin layer (resin layer) 2, and one side (upper surface in the drawing) of the resin layer 2 is the plate surface 3 and the opposite side. The reinforcing sheet 4 is laminated on (the lower surface in the figure), and the entire surface is formed in a rectangular flat plate shape.

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

Further, the grip portion 5 has chuck holes 7 for inserting fixing pins (not shown) into the grip portion 5 in a state of being gripped with a vise at a plurality of locations (5 locations in the figure) in the length direction at equal intervals. Is formed.
<Specific surface area _RS and unit space volume S _V >
As described above, the plate surface 3 of the flexographic printing plate 1 has a specific surface area R _S of 4.3 or more and 6.0 or less, and a unit space volume S _V of 12 μm ³ / μm ² or more and 29 μm ³ / μm ² or less. Must be a rough surface.

The reason is as follows.
That is, the relatively smooth plate surface 3 having a specific surface area _RS of less than 4.3 has too low wettability of the ink, so that the ink cannot be supported in a uniform thickness state.
Further, the plate surface 3 having a large unevenness having a specific surface area _RS of more than 6.0 cannot support the ink in a uniform thickness due to the influence of the unevenness.

Therefore, in any of these cases, the accuracy of the thickness of the liquid crystal alignment film formed by transferring the supported ink to the surface to be printed is lowered, and unevenness in thickness, pinholes, and the like are likely to occur.
Further, the relatively smooth plate surface 3 having a specific surface area _RS of less than 4.3 has an insufficient amount of ink that can be supported, and the liquid crystal orientation formed by transferring the supported ink to the surface to be printed. The thickness of the film is insufficient.

The unit space volume S _V also shown configured in the plate surface 3 by particular concave portions of the concavo-convex formed on the plate surface 3, the space for carrying the ink, the volume per unit area of the plate surface 3 It is an index.
In such a unit space volume S _V is less than 12 [mu] m 3 ^/ [mu] m ^2, also becomes insufficient amount of ink that can be carried on the plate surface 3, loaded with ink of the liquid crystal alignment film formed by transferring the print surface Insufficient thickness.

On the other hand, a large plate surface 3 of irregularities unit space volume S _V exceeds 29 .mu.m 3 ^/ [mu] m ² is due to the effect of the irregularities, ink and can not thickness is supported in a uniform state.
Therefore, the accuracy of the thickness of the liquid crystal alignment film formed by transferring the supported ink to the surface to be printed is lowered, and unevenness in thickness, pinholes, and the like are likely to occur.
On the other hand, by setting both the specific surface area _RS and the unit space volume S _V of the plate surface 3 of the flexographic printing plate 1 to the above ranges, the thickness is uniform even if the ink has low wettability. Can be supported on the plate surface 3 while maintaining the above.

In addition, the amount of ink that can be supported on the plate surface 3 during one printing can be increased from the current level.
Moreover, in the unit space volume S _V only be adjusted within the above range, without greatly changing the printing condition, it is also possible to adjust the amount of ink that can be carried on the plate surface 3.
Therefore, on the absence unevenness and pinholes of the thickness with high accuracy, without greatly changing the printing condition, greater thickness than present state, to form a liquid crystal alignment film having a thickness suitable as a liquid crystal display device It will be possible.

Considering that these effects are further improved, the specific surface area _RS of the plate surface 3 of the flexographic printing plate 1 is preferably 5.0 or more, preferably 5.3 or less, even in the above range. Is preferable.
The unit space volume _{S V} is preferably at 16μm ³ / μm ² or more at the above-mentioned range, preferably at 22μm ³ / μm ² or less.

(Measuring method)
The specific surface area R _S and unit space volume S _V, for example, was measured using a shape analysis laser microscope [KEYENCE manufactured VK-X160, etc.], can be obtained from the 3-dimensional data of the plate surface 3.
Figure 2 uses the shape analysis laser microscope is a perspective view illustrating a method of finding the specific surface area R _S and unit space volume S _V.

First, a rectangular measurement area A having a length W ₁ [μm], a width W ₂ [μm], and a reference area S ₀ = W ₁ × W ₂ [μm ² ] is set on the plate surface 3, and a shape analysis laser microscope is used. Is used to scan the laser in the measurement area A to obtain three-dimensional data of the plate surface 3 in the measurement area A.
Next, from the obtained three-dimensional data, the actual surface area S [μm ² ] of the plate surface 3 in the measurement area A was obtained by three-dimensional analysis, and the actual surface area S [μm ² ] and the reference area S ₀ [μm] were obtained. ² ] and formula (1):
R _S = S / S ₀ (1)
The specific surface area _RS is determined by.

Also, from the three-dimensional data obtained, to identify the lowest point P _L and the highest point P _H of the plate surface 3 in the measurement area A, the space height represented by difference between P _H -P _L H [μm] is obtained, and the convex volume V [μm ³ ] of the resin layer 2 including the plate surface 3 is obtained within the measurement area A and within the space height H [μm].
Then, from these results and the reference area S ₀ [μm ² ] of the measurement area A, the equation (2):
S _V = H × S ₀ −V (2)
The unit space volume S _V [μm ³ / μm ² ], which is the space volume per the reference area S ₀ [μm ² ], is obtained.

<Three-dimensional shape of plate surface 3>
The plate surface 3 of the flexographic printing plate 1, in order to rough surface that together satisfy the range of the specific surface area R _S and unit space volume S _V described above may be adjusted three-dimensional shape of the rough surface.
That is, the conventional rough surface formed by the above-mentioned etching or the like generally has a three-dimensional shape in which convex portions and valley portions having a substantially triangular wavy cross section are continuous, for example, as shown in FIG.

However, according to study of the inventor, conventional rough surface having such three-dimensional shape, 4.3 or more the specific surface area R _S is described above, also satisfies the range of 6.0 or less, the unit space volume S _V is 12μm The range of ³ / μm ² or more may not be satisfied.
FIG. 3 is a cross-sectional view showing an example of a three-dimensional shape of the plate surface 3 of the flexographic printing plate 1.
In order to make the unit space volume S _V larger than the current level while maintaining the specific surface area _RS of the plate surface 3 within the above range, for example, as shown in FIG. 3, the plate surface 3 has an approximately constant diameter. It is preferable that the hemispherical depressions 8 having the above are randomly and densely arranged in a three-dimensional shape.

Thus, the unit space volume S _V and 12 [mu] m 3 ^/ [mu] m ² or more, the amount of ink 9 to be carried on the plate surface 3 at a time of printing is increased than the current, larger thickness than present, liquid crystal display element It is possible to form a liquid crystal alignment film having a thickness suitable for the above.
In order to manufacture the flexographic printing plate 1 having the plate surface 3 having the above three-dimensional shape, any manufacturing method can be adopted.

For example, the flexographic printing plate 1 may be manufactured by directly forming a large number of the hemispherical dents 8 on the plate surface 3 by ultrashort pulse laser processing or the like.
However, the flexographic printing plate 1 is preferably manufactured by the above-mentioned exposure transfer method using a roughened sheet having a large number of hemispherical protrusions corresponding to the recesses 8 on the mold surface.
Specifically, the photosensitive resin composition is cured by an exposure transfer method using such a roughened sheet to form a resin layer having a roughened one side of the flexographic printing plate 1. 2 is formed.

Further, the reinforcing sheet 4 is laminated on the opposite surface of the resin layer 2 by the above curing, and the flexographic printing plate 1 having the layer structure shown in FIG. 1 is manufactured.
<Roughened sheet>
FIG. 4 is a cross-sectional view showing a layer structure of an example of the roughened sheet 10 used in the exposure transfer method.
With reference to FIG. 4, the roughened sheet 10 of this example includes a reinforcing film 11 and a surface layer 12 laminated on one side (upper surface in the drawing) of the reinforcing film 11.

The surface layer 12 contains the binder resin 13 and a large number of spherical fine particles 14 dispersed in the binder resin 13, and at least a part of the fine particles 14 protrudes from the surface of the surface layer 12 as hemispherical protrusions. , The roughened mold surface 15 corresponding to the three-dimensional shape of FIG.
In the case of the example shown in the figure, the surface of the protruding fine particles 14 is covered with a very thin film made of the binder resin 13.

However, the surface of the fine particles 14 may be exposed without being coated with a film, and the coated and exposed particles may be mixed.
The surface layer 12 is formed by, for example, applying a coating agent containing the binder resin 13 and the fine particles 14 to one side of the reinforcing film 11 and then drying the coating, and further curing the binder resin 13 if it has curability.

The roughened sheet 10 is produced, for example, by continuously feeding a long reinforcing film 11 and continuously applying a coating agent to one side thereof to continuously form a surface layer 12.
Further, the produced roughened sheet 10 can be used for manufacturing the flexographic printing plate 1 by the exposure transfer method by cutting it into a predetermined length and a predetermined width as needed.
As the binder resin 13 forming the surface layer 12, for example, various resins having transparency to active light such as ultraviolet rays, which are exposed when the photosensitive resin composition is cured to form the resin layer 2, may be used. it can.

Examples of the binder resin 13 include one or more of acrylic resin, polycarbonate, polyvinyl chloride, polystyrene, polyester, polyurethane and the like.
Particularly, a thermoplastic, two-component curable, active photocurable, or thermosetting acrylic resin, particularly an acrylic polyurethane two-component curable type acrylic resin is preferable.

Examples of the acrylic polyurethane two-component curing type acrylic resin include a combination of a main agent containing an acrylic polyol and a curing agent containing an isocyanate.
Since the acrylic resin generally has high affinity and wettability with the photosensitive resin composition which is the basis of the resin layer 2, the three-dimensional shape of the mold surface 15 can be satisfactorily transferred to the plate surface 3.

As the fine particles 14, one kind or two or more kinds such as resin particles or particles of an inorganic material can be used.
Examples of the resin particles include particles such as acrylic resin, silicone resin, polystyrene, and polycarbonate.
Examples of the particles of the inorganic material include particles of glass, titanium oxide, barium sulfate, talc, clay, alumina, calcium carbonate, silica and the like.

Among them, as the fine particles 14, it is preferable to use fine particles 14 made of a material having transparency to active rays such as ultraviolet rays, which is exposed when the photosensitive resin composition is cured to form the resin layer 2.
As the coating agent, for example, when an acrylic polyurethane two-component curing type acrylic resin is used as the binder resin 13, a main agent and a curing agent as a base thereof and fine particles 14 are mixed in a predetermined ratio, and further necessary. It is prepared by adding a solvent accordingly.

The reinforcing film 11 literally has a function as reinforcement for increasing the overall tensile strength of the roughened sheet 10, and the roughened sheet 10 is formed by shrinkage of the active light-curable binder resin 13 during curing. It also works to correct warping.
As the reinforcing film 11, a PET film having an excellent function as the reinforcing film 11 is preferably used.

In particular, as the PET film, a PET film having transparency to active light such as ultraviolet rays, which is exposed when the flexographic printing plate 1 is manufactured by the above-mentioned exposure transfer method, is preferable.
However, as the reinforcing film 11, for example, a film such as polyvinyl alcohol (PVA), polyamide, polyimide (PI), polycarbonate, or cellulose acetate can be used.

If necessary, a primer treatment may be applied to one side (upper surface in the drawing) of the reinforcing film 11 on which the surface layer 12 is laminated in order to improve the adhesion of the surface layer 12.
Examples of the primer treatment include one or more types such as corona discharge treatment, frame treatment, ozone treatment, ultraviolet irradiation treatment, sandblast treatment, and solvent treatment.
Further, for example, a primer layer made of various materials having excellent affinity and adhesion with the PET forming the reinforcing film 11 and the binder resin 13 forming the surface layer 12 may be formed.

The fine particles 14 forming the surface layer 12 preferably have a minimum particle size distribution (particle size distribution) of 4 μm or more, particularly 4.5 μm or more, and a maximum particle size distribution of 30 μm or less, particularly 25 μm or less. ..
The minimum and maximum values of the particle size distribution indicate the minimum and maximum values of the particle size in the measurement result of the particle size distribution obtained for the fine particles 14 to be measured.

Of fine particles 14, the minimum value is less than 4μm of particle size distribution, the fine particles 14, both satisfying the range of the specific surface area R _S and unit space volume S _V mentioned above the plate surface 3 of the flexographic printing plate 1 Particles that are too small to have a three-dimensional rough surface will be included.
On the other hand, the fine particles 14, when the maximum value of the particle size distribution is more than 30μm, the said fine particles 14, the range of the plate specific surface area of the surface 3 mentioned above R _S and unit space volume S _V satisfies both Particles that are too large to have a three-dimensional rough surface will be included.

Therefore depending on the mixing ratio or the like of the coating thickness and fine particles 14 of the coating agent, in each case, the plate surface 3 of the flexographic printing plate 1, the range of the specific surface area R _S and unit space volume S _V described above In some cases, it may not be possible to obtain a rough surface with a three-dimensional shape that satisfies both.
Then, the thickness of the liquid crystal alignment film formed by the flexographic printing method may be insufficient, or the accuracy of the thickness may be lowered, so that unevenness of thickness, pinholes, or the like may easily occur.

On the other hand, by setting the minimum value and the maximum value of the particle size distribution of the fine particles 14 within the above ranges, the above-mentioned particles having a particle size too small or too large can be excluded.
Therefore the plate surface 3 of the flexographic printing plate 1 can be a rough surface of the three-dimensional shape that together satisfy the range of the specific surface area R _S and unit space volume S _V described above.

Further, the fine particles 14 are derived from the standard deviation σ of the particle size distribution and the average particle size from the equation (3):
Coefficient of variation Cv = (standard deviation σ) / (average particle size) (3)
The coefficient of variation Cv, which indicates the variation in the particle size distribution, is preferably 0.35 or less.
When the coefficient of variation Cv exceeds 0.35, the variation in the particle size distribution becomes large, and the fine particles 14 include a large number of the above-mentioned particles having too small particle size and particles having too large particle size. become.

Therefore, although depending on again blending ratio of the coating thickness and fine particles 14 of the coating agent or the like, the plate surface 3 of the flexographic printing plate 1, together satisfactory stereoscopic range of the specific surface area R _S and unit space volume S _V described above It may not be possible to make a rough surface of the shape.
On the other hand, by setting the coefficient of variation Cv to the above range, particles having a particle size too small and particles having a particle size too large can be excluded.

Thus, the plate surface 3 of the flexographic printing plate 1 can be a rough surface of the three-dimensional shape that together satisfy the range of the specific surface area R _S and unit space volume S _V described above.
In consideration of further improving such an effect, the fluctuation coefficient Cv is preferably 0.25 or less even in the above range.
However, if the coefficient of variation Cv is too small, the particle size approaches monodispersity, so that the pitch of the unevenness formed on the mold surface 15 of the roughened sheet 10 and the plate surface 3 of the flexographic printing plate 1 is single. Get closer to.

Then, although the pitch range itself is different, the electrode forming surface is formed by the interaction with the electrode forming surface of the substrate constituting the liquid crystal display element, which also includes a portion where irregularities are formed at a single pitch. Moire fringes may occur on the liquid crystal alignment film.
Therefore, in consideration of suppressing the occurrence of moire fringes, the coefficient of variation Cv is preferably 0.10 or more, particularly 0.18 or more, even in the above range.

Also in this case, for the reason explained above, the minimum value of the particle size distribution of the fine particles 14 is 4 μm or more, particularly 4.5 μm or more, and the maximum value of the particle size distribution is 30 μm or less, particularly 25 μm or less. It is preferable to have it.
Further, in order to suppress the occurrence of moire fringes, mixed particles of two types of fine particles having different particle size distributions may be used in combination as the fine particles 14.

When mixed particles of two types of fine particles having different particle size distributions are used in combination, the pitch of the unevenness formed on the mold surface 15 of the roughened sheet 10 and the plate surface 3 of the flexographic printing plate 1 approaches a single size. Can be suppressed.
Therefore, for example, it is possible to suppress the occurrence of moire fringes on the liquid crystal alignment film formed on the electrode forming surface due to the interaction with the electrode forming surface of the substrate constituting the liquid crystal display element.

Also in this case, for the reason described above, the coefficient of variation Cv of the mixed particles as a whole is preferably 0.35 or less, particularly preferably 0.25 or less, and 0.10 or more, particularly 0.18. The above is preferable.
Further, it is preferable that the coefficient of variation Cv of each of the two types of fine particles constituting the mixed particles is also individually in the above range.

The range of particle size distribution of the two types of fine particles constituting the mixed particles can be arbitrarily set.
The range of particle size distribution of the two types of fine particles may be different from each other, or may partially overlap.
However, for the two types of fine particles, the minimum value of the particle size distribution is 4 μm or more, especially 4.5 μm or more, and the maximum value of the particle size distribution is 30 μm or less, especially 25 μm or less, for the reason explained above. It is preferable to have it.

The blending ratio of the two types of fine particles can be set to an arbitrary range according to the range of particle size distribution and the coefficient of variation Cv of each fine particle, the coefficient of variation Cv of the entire mixed particles, and the like. ..
However, in order to further improve the above-mentioned effect of using the mixed particles, the ratio of the fine particles having the smaller particle size distribution to the total amount of the mixed particles is preferably 10% by mass or more, preferably 90% by mass. The following is preferable.

In the present invention, the particle size distribution of the fine particles 14 and the individual fine particles constituting the mixed particles is represented by a volume distribution measured by a laser diffraction / scattering method based on the Mie scattering theory.
Further, the standard deviation σ, which is the basis of the coefficient of variation Cv, is obtained from the result of conversion to the number reference, assuming that the shape of the particles is spherical.

Further, the average particle diameter is an arithmetic mean diameter based on the number of particles, which is obtained by dividing the particles by the number of particles after converting the particles into a spherical shape and integrating them.
In the embodiment, the volume distribution of fine particles is measured using a laser diffraction / scattering type particle size distribution measuring device LA-950V2 manufactured by HORIBA, Ltd., but the measuring device is not limited to this. Absent.

The mixing ratio of the binder resin 13 and fine particles 14, the plate surface 3 of the flexographic printing plate 1 can be a rough surface of the three-dimensional shape that together satisfy the range of the specific surface area R _S and unit space volume S _V described above It can be adjusted to any range.
However, if the amount of the binder resin 13 is too small, it may not be possible to form a continuous and strong surface layer 12.

On the other hand, when the amount of the binder resin 13 is too large, the unevenness formed on the mold surface 15 which is the surface of the surface layer 12 becomes too small, and the plate surface 3 of the flexographic printing plate 1 is subjected to the above-mentioned specific surface area _RS and unit. may not be a rough surface of the three-dimensional shape that satisfies both the scope of the space volume S _V.
Considering the size of the unevenness and the like, it is ideal that in the formed surface layer 12, fine particles are buried in the binder resin 13 at a ratio of 1/2 to 1/8 on a volume basis.

Therefore, the blending ratio of both is set to 30% by volume or more and 80% by volume or less in terms of the volume ratio of the binder resin 13 (the solid content of the resin excluding the volatile components) and the binder resin 13 in the total amount of the fine particles 14. Is preferable.
The thickness of the surface layer 12, that is, the thickness from one side of the reinforcing film 11 to the tip of the convex portion of the unevenness of the mold surface 15 formed by the fine particles 14 can be arbitrarily set based on the particle size of the fine particles 14.

For example, when the particle size of the fine particles 14 is in the range of 4 μm or more and 30 μm or less, the thickness of the surface layer 12 is not limited to this, but is preferably 0.010 mm (= 10.0 μm) or more, for example. It is preferably 0.025 mm (= 25.0 μm) or less.
Further, the thickness of the reinforcing film 11 is preferably 0.050 mm or more, particularly preferably 0.075 mm or more, and preferably 0.300 mm or less, particularly 0.250 mm or less.

If the thickness is less than this range, for example, a long roughened sheet 10 before cutting may be wound into a roll, or the cut roughened sheet 10 may be used for manufacturing a flexographic printing plate, stored, or the like. The roughened sheet 10 is liable to break during handling such as wrapping around.
When the roughened sheet 10 is broken, the mold surface 15 and eventually the plate surface 3 of the flexographic printing plate 1 are broken, and for example, a problem that a continuous liquid crystal alignment film having a uniform thickness cannot be formed occurs. There is.

On the other hand, when the thickness of the reinforcing film 11 exceeds the above range, the weight of the roughened sheet 10 increases and it becomes difficult to bend or wind the roughened sheet 10. Therefore, during the above-mentioned handling or the like. Handleability may decrease.
Further, as the thickness of the reinforcing film 11 increases, the unevenness of the thickness of the reinforcing film 11 also increases, so that the coating thickness of the coating agent also tends to be uneven.

Then, in the portion where the thickness of the reinforcing film 11 is small, the thickness of the binder resin 13 becomes large, and the fine particles 14 may be buried in the binder resin 13 to form a region which is not sufficiently roughened as compared with the surroundings.
That is, the distribution of the unevenness of the mold surface 15 which is the surface of the surface layer 12, and by extension, the three-dimensional shape of the rough surface may be easily uneven.

On the other hand, by setting the thickness of the reinforcing film 11 within the above range, the handleability of the roughened sheet 10 is improved and the uneven distribution of unevenness is eliminated while suppressing the occurrence of breakage and the like as much as possible. The three-dimensional shape of the mold surface 15 can be made uniform.
Considering that the three-dimensional shape of the mold surface 15 is made more uniform, the thickness of the reinforcing film 11 is preferably smaller even in the above range.

That is, as the thickness of the reinforcing film 11 is reduced, the unevenness of the thickness of the reinforcing film 11 can be reduced, the coating thickness of the coating agent which is the basis of the surface layer 12 is made uniform, and the three-dimensional shape of the rough surface is made uniform. Can be made into.
In particular, when combined with the fine particles 14 having a particle size range of 4 μm or more and 30 μm or less as described above, the thickness of the reinforcing film 11 is preferably 0.200 mm or less even in the above range.

As a result, the effect of making the three-dimensional shape of the rough surface uniform can be further improved.
However, the thickness of the reinforcing film 11 is preferably 0.100 mm or more, particularly 0.150 mm or more, in consideration of prevention of breakage defects and the like.
When a primer layer is formed on one side of the reinforcing film 11 as a primer treatment, the thickness of the reinforcing film 11 described above is the total thickness of the reinforcing film 11 and the primer layer.

The total thickness of the roughened sheet 10, which is the sum of the thickness of the reinforcing film 11 and the thickness of the surface layer 12, is 0.150 mm or more, particularly 0.180 mm or more, considering that the occurrence of breakage is suppressed as much as possible. It is preferable to have it.
Further, in consideration of improving the handleability of the roughened sheet 10, the overall thickness is preferably 0.240 mm or less, particularly 0.220 mm or less.

<Manufacturing method of flexographic printing plate>
5 (a) to 5 (c) are cross-sectional views showing an example of a process of manufacturing a flexographic printing plate 1 by an exposure transfer method using the roughened sheet 10 of the example of FIG.
6 (a) to 6 (c) are cross-sectional views showing an example of the steps following the steps of FIGS. 5 (a) to 5 (c).
With reference to FIG. 5A, in the manufacturing method of this example, for example, glass, a hard resin such as an acrylic resin, a polycarbonate resin, a polyester resin, etc., which is hard and transparent to active light such as ultraviolet rays A support substrate 16 made of a material to be provided is prepared.

Further, as the roughened sheet 10, for example, a reinforcing film 11, a binder resin 13 forming the surface layer 12, and fine particles 14 are all made of a material having transparency to active light rays.
Then, the roughened sheet 10 is placed on the upper surface 18 of the support substrate 16 in the drawing so that the mold surface 15 which is the surface of the surface layer 12 is on the top and the opposite surface 17 which is the exposed surface of the reinforcing film 11 is on the bottom. Overlay on.

Specifically, for example, while making one end of the opposite surface 17 of the roughened sheet 10 in contact with the surface 18 of the support substrate 16, as shown by the arrow of the alternate long and short dash line in the drawing, the roughened sheet 10 is formed. The surfaces 18 are stacked in order from one end to the other end.
The roughened sheet 10 laminated on the support substrate 16 is subjected to a shearing force when the liquid photosensitive resin composition is spread on the roughened sheet 10 and a shrinkage force when the photosensitive resin composition is cured. In addition to being less likely to shift in position, it is required to be easy to replace after use.

For that purpose, the roughened sheet 10 laminated on the support substrate 16 is detachably fixed to the surface 18 of the support substrate 16 by, for example, any of the following methods (i) to (iii). preferable.
(i) The roughened sheet 10 is detachably adhered and fixed to the surface 18 of the support substrate 16 via a weak adhesive layer made of a material having transparency to active rays.

(ii) A suction groove is formed on the surface 18 of the support substrate 16, vacuum suction is performed through the suction groove, and the roughened sheet 10 is detachably sucked and fixed to the surface 18 of the support substrate 16.
(iii) The roughened sheet 10 is detachably pressed and fixed to the surface 18 of the support substrate 16 in a state of being spread between a pair of chuck jigs separated by a distance from the surface direction dimension of the support substrate 16. ..

As the weak adhesive layer used for the adhesive fixing of (i), various adhesives having weak adhesiveness to both the support substrate 16 and the PET film as the reinforcing film 11 and having transparency to active light rays. Any layer consisting of can be adopted.
The weak adhesive layer is formed by applying an adhesive to at least one of the surface 18 of the support substrate 16 and the opposite surface 17 of the roughened sheet 10 by various coating methods such as spray coating.

After forming the weak adhesive layer, as shown by the arrow of the alternate long and short dash line in FIG. 5A, the roughened sheet 10 is placed from one end to the other end of the surface 18 of the support substrate 16 with the opposite surface 17 facing down. Stack them in order, being careful not to let air in between them.
Then, the roughened sheet 10 is fixed on the surface 18 by the adhesive force of the weak adhesive layer.

Further, in order to remove the fixed roughened sheet 10 from the surface 18, for example, the roughened sheet 10 is weakened from the other end to one end of the support substrate 16 contrary to the arrow in FIG. 5 (a). It may be peeled off in order while resisting the adhesive force of the adhesive layer.
In order to perform suction fixing in (ii), the surface 18 of the support substrate 16 is finished smoothly, a suction groove is formed on substantially the entire surface of the surface 18, and the suction groove is connected to a vacuum system including a vacuum pump or the like. To do.

Then, the vacuum system is operated with the roughened sheet 10 stacked on the surface 18 of the support substrate 16 with the opposite surface 17 facing down, or the previously operated vacuum system is connected to the suction groove. And so on.
Then, the stacked roughened sheets 10 are vacuum-sucked through the suction groove and fixed on the surface 18.

To remove the fixed roughened sheet 10 from the surface 18, the vacuum system may be stopped or the connection between the vacuum system and the suction groove may be cut off.
Next, referring to FIG. 5B, in the manufacturing method of this example, the resin layer 2 of the flexographic printing plate 1 is placed on the mold surface 15 of the roughened sheet 10 fixed on the surface 18 of the support substrate 16. A predetermined amount of the liquid photosensitive resin composition 19 which is the basis of the liquid photosensitive resin composition 19 is supplied.

The supplied photosensitive resin composition 19 is sandwiched between the roughened sheet 10 and the reinforcing sheet 4 constituting the flexo printing plate 1 together with the resin layer 2.
Then, as shown by the arrow of the one-point chain line in FIG. 5B, the roughened sheet 10 is sequentially applied from one end to the other end of the surface 18 of the support substrate 16 while being careful not to allow air to enter between them. The photosensitive resin composition 19 is spread on the mold surface 15.

Then, the layer 20 of the photosensitive resin composition 19 is formed, and the reinforcing sheet 4 is laminated on the layer 20.
Next, with reference to FIG. 5C, the facing surface 22 of the facing substrate 21 is brought into contact with the reinforcing sheet 4.
Then, while maintaining the facing surface 22 of the facing substrate 21 parallel to the surface 18 of the supporting substrate 16 at a certain interval, the facing substrate 21 is supported as shown by a black arrow in FIG. 5 (c). The layer 20 is pressed against the mold surface 15 of the roughened sheet 10 by pressing in the direction of the substrate 16.

In this state, the photosensitive resin composition forming the layer 20 by exposing the layer 20 with active rays through the support substrate 16 and the roughened sheet 10 as shown by the solid arrows in FIG. 5 (c). 19 is cured.
At this time, the distance between the surface 18 of the support substrate 16 and the facing surface 22 of the opposing substrate 21 is set to the thickness of the flexographic printing plate 1 to be manufactured (= the thickness of the resin layer 2 + the thickness of the reinforcing sheet 4). The dimensions including the thickness of the chemical sheet 10 are maintained.

The facing substrate 21 can be formed of any material such as metal, glass, and hard resin.
However, the opposed substrate 21 is formed of the same material as the support substrate 16 which has transparency to active rays, and the reinforcing sheet 4 is formed of the same material which has transparency to active rays as the roughened sheet 10. You may.
In this case, for example, the photosensitive resin composition 19 can be cured by exposing the layer 20 with active rays not only from the side of the support substrate 16 but also from the side of the opposing substrate 21.

Further, in this case, since the photosensitive resin composition 19 can be cured by exposing the layer 20 to the active light rays only from the side of the facing substrate 21, for example, the roughened sheet 10 has a transparency to the active light rays. It can also be formed from materials that it does not have.
Next, with reference to FIGS. 6A and 6B, a laminate 23 of the reinforcing sheet 4, the resin layer 2 formed by curing the photosensitive resin composition 19, and the roughened sheet 10 is formed. It is taken out from between the support substrate 16 and the facing substrate 21, and placed on the workbench 24 with the reinforcing sheet 4 facing down.

Then, as shown by the arrow of the alternate long and short dash line in FIG. 6B, the roughened sheet 10 is peeled off in order from one end to the other end of the laminated body 23.
Then, the upper surface side of the resin layer 2 in the drawing is the plate surface 3 which is roughened by transferring the rough surface shape of the mold surface 15 of the roughened sheet 10, and the printing resin shown in FIG. 6 (c). The original plate 25 is produced.

After that, although not shown, the four sides of the printing resin original plate 25 are cut to arrange the entire planar shape into a rectangular shape.
Next, as shown in FIG. 1, the resin layer 2 in the vicinity of the two parallel sides is thermally cut by, for example, laser processing or the like to form the grip portion 5, the groove portion 6, and the chuck hole 7.
Then, when a predetermined printing pattern is further formed on the plate surface 3 as needed, the flexo printing plate 1 is completed.

As the photosensitive resin composition 19, various resin compositions satisfying the following conditions can be used.
It can be cured by exposure to active rays such as ultraviolet rays.
After curing, it has appropriate flexibility and rubber elasticity suitable for use in flexographic printing.
It is possible to form a cured product having excellent resistance (solvent resistance) to a solvent contained in ink used for printing or used for cleaning a printing plate.

The photosensitive resin composition satisfying these conditions is not limited to this, and is, for example, a prepolymer having a 1,2-butadiene structure and an ethylenically double bond at the terminal, and an ethylenically unsaturated single amount. Examples include the body and those containing a photopolymerization initiator.
Benzoin alkyl ether is preferable as the photopolymerization initiator.
Further, as the reinforcing sheet 4, for example, a sheet made of various thermoplastic resins such as polyethylene (PE), polypropylene (PP), PET, tetrafluoroethylene / hexafluoropropylene copolymer (FEP), etc. can be used. ..

As described above, the reinforcing sheet 4 preferably has transparency to active light rays.
<< Manufacturing method of liquid crystal display element >>
The present invention is a method for manufacturing a liquid crystal display element, which comprises a step of forming a liquid crystal alignment film by a flexographic printing method using the flexographic printing plate of the present invention.

The other steps of the method for manufacturing the liquid crystal display element can be carried out in the same manner as before.
That is, a transparent electrode layer corresponding to a predetermined matrix pattern or the like is formed on the surface of a transparent substrate such as a glass substrate, a liquid crystal alignment film is formed through the above steps, and the surface of the liquid crystal alignment film is further formed as needed. The substrate is prepared by orientation treatment by rubbing or the like.
Next, two substrates are prepared, and in a state where the transparent electrode layers are aligned with each other, a liquid crystal material is sandwiched between them to form a laminated body, and further on both outer sides of the laminated body. A liquid crystal display element is manufactured by disposing a polarizing plate as needed.

The configuration of the present invention is not limited to the example of the figure described above.
For example, in the flexographic printing plate 1, the reinforcing sheet 4 may be omitted.
Further, in the method for producing the flexographic printing plate 1, instead of pressing the layer 20 of the photosensitive resin composition in the direction of the support substrate 16 by the opposing substrate 21, the roughened sheet 10 is coated with a roller-shaped one or the like. The surface may be roughened at the same time as it is expanded to make the thickness constant.

In addition, various modifications can be made without departing from the gist of the present invention.

Hereinafter, the present invention will be further described based on Examples and Comparative Examples, but the configuration of the present invention is not necessarily limited to these examples.
<Example 1>
(Preparation of roughened sheet 10)
As the binder resin 13, an acrylic polyurethane two-component curing type acrylic resin in which a main agent containing an acrylic polyol (solid content 50% by mass) and a curing agent containing isocyanate (solid content 60% by mass) were combined was used.

Acrylic resin particles (fine particles 14) were blended with this binder resin, and methyl ethyl ketone and butyl acetate as solvents were further added to adjust the viscosity to prepare a coating agent for the surface layer 12.
As the acrylic resin particles, the minimum value of the particle size distribution was 4.5 μm and the maximum value was 14 measured using the laser diffraction / scattering type particle size distribution measuring device LA-950V2 manufactured by Horiba Seisakusho Co., Ltd. The ones having a 0.0 μm, an average particle diameter of 8.0 μm, a standard deviation σ of 1.6 μm, and a coefficient of variation Cv of 0.20 were used.

As the reinforcing film 11, a long PET film having a thickness of 0.188 mm and having a primer treatment on one side was used.
While continuously feeding the PET film, a coating agent is continuously applied to one side thereof, and then a surface layer 12 is continuously formed through a warm air drying step to roughen the layer structure shown in FIG. Sheet 10 was continuously produced.

The cured binder resin 13 constituting the roughened sheet 10, the acrylic resin particles as the fine particles 14, and the PET film all have transparency to active light for producing a resin original plate for printing. Was selected.
The overall thickness of the roughened sheet 10 was 0.200 mm, and the average thickness of the surface layer 12 was 0.012 mm.

(Manufacturing of flexographic printing plate 1)
Using the roughened sheet 10, the flexographic printing plate 1 shown in FIG. 1 was manufactured through the steps of FIGS. 5 (a) to 5 (c) and 6 (a) to 6 (c).
As the photosensitive resin composition that forms the basis of the resin layer 2, NK resin manufactured by Sumitomo Rubber Industries, Ltd. is used, and as the reinforcing sheet 4, PET sheet [BF / CF manufactured by Sumitomo Rubber Industries, Ltd.] is used. Using.

The specific surface area _RS and unit space volume S _V of the plate surface 3 of the manufactured flexo printing plate 1 were measured using a shape analysis laser microscope [VK-X160 manufactured by KEYENCE CORPORATION mentioned above], and the ratios were measured. The surface area R _S was 4.3, and the unit space volume S _V was 12.22 μm ³ / μm ² .
Further, when the plate surface 3 was observed using the shape analysis laser microscope, it was confirmed that hemispherical depressions having an approximately constant diameter had a three-dimensional shape in which hemispherical depressions were randomly and precisely arranged.

<Example 2>
Acrylic resin particles (fine particles 14) having a minimum particle size distribution of 6.0 μm, a maximum value of 18.0 μm, an average particle size of 10.0 μm, a standard deviation σ of 1.9 μm, and a coefficient of variation of Cv of 0.19. ) Was used, and the roughened sheet 10 was produced in the same manner as in Example 1.
The overall thickness of the roughened sheet 10 was 0.203 mm, and the average thickness of the surface layer 12 was 0.015 mm.

Next, the flexographic printing plate 1 was manufactured in the same manner as in Example 1 except that the roughened sheet 10 was used.
When the specific surface area _RS and the unit space volume S _V of the plate surface of the produced flexographic printing plate 1 were measured in the same manner as in Example 1, the specific surface area _RS was 5.0 and the unit space volume S _V was 16.19 μm. It was ³ / μm ² .

Further, when the plate surface 3 was observed using a shape analysis laser microscope, as shown in FIG. 7, hemispherical depressions having a substantially constant diameter were randomly and precisely arranged in a three-dimensional shape. Was confirmed.
<Example 3>
Acrylic resin particles (fine particles 14) having a minimum particle size distribution of 6.0 μm, a maximum value of 25.0 μm, an average particle size of 13.0 μm, a standard deviation σ of 3.2 μm, and a coefficient of variation of 0.25. ) Was used, and the roughened sheet 10 was produced in the same manner as in Example 1.

The overall thickness of the roughened sheet 10 was 0.207 mm, and the average thickness of the surface layer 12 was 0.019 mm.
Next, the flexographic printing plate 1 was manufactured in the same manner as in Example 1 except that the roughened sheet 10 was used.
When the specific surface area _RS and the unit space volume S _V of the plate surface of the manufactured flexographic printing plate 1 were measured in the same manner as in Example 1, the specific surface area _RS was 5.3 and the unit space volume S _V was 21.47 μm. It was ³ / μm ² .

Further, when the plate surface 3 was observed using a shape analysis laser microscope, it was confirmed that hemispherical depressions having a substantially constant diameter had a three-dimensional shape in which hemispherical depressions were randomly and precisely arranged.
<Example 4>
Acrylic resin particles (fine particles 14) having a minimum particle size distribution of 9.0 μm, a maximum value of 25.0 μm, an average particle size of 15.0 μm, a standard deviation σ of 1.5 μm, and a coefficient of variation of Cv of 0.10. ) Was used, and the roughened sheet 10 was produced in the same manner as in Example 1.

The overall thickness of the roughened sheet 10 was 0.212 mm, and the average thickness of the surface layer 12 was 0.024 mm.
Next, the flexographic printing plate 1 was manufactured in the same manner as in Example 1 except that the roughened sheet 10 was used.
When the specific surface area _RS and the unit space volume S _V of the plate surface of the produced flexographic printing plate 1 were measured in the same manner as in Example 1, the specific surface area _RS was 6.0 and the unit space volume S _V was 28.08 μm. It was ³ / μm ² .

Further, when the plate surface 3 was observed using a shape analysis laser microscope, it was confirmed that hemispherical depressions having a substantially constant diameter had a three-dimensional shape in which hemispherical depressions were randomly and precisely arranged.
<Comparative example 1>
The conventional method of forming a mold surface by continuously inserting a urethane-based thermoplastic elastomer (TPU) sheet and a reinforcing film between a roughened roll and a pair of rolls is reproduced. A PET film having a thickness of 0.100 mm was used.

Moreover, as the TPU for the surface layer, an ester type TPU was used.
The TPU is continuously extruded into a sheet through the die of the extruder to form a surface layer, and the roughened roll is combined with a long, continuously supplied reinforcing film before the surface layer is cooled and solidified. It was integrally laminated by continuously inserting it between the roll and the roll.
At the same time, the rough surface shape of the prototype surface of the roughened roll was continuously transferred to the surface of the surface layer to continuously produce a roughened sheet having the roughened surface as the mold surface. ..

As the roughened roll, a roll having an outermost layer made of silicone rubber and having a specific surface area of 3.4 was used.
The overall thickness of the roughened sheet was 0.200 mm, and the thickness of the surface layer was 0.100 mm.
Next, a flexographic printing plate was produced in the same manner as in Example 1 except that the roughened sheet was used.

When the specific surface area _RS and the unit space volume S _V of the plate surface of the produced flexographic printing plate were measured in the same manner as in Example 1, the specific surface area _RS was 3.0 and the unit space volume S _V was 9.41 μm ^3. It was / μm ² .
Further, when the surface of the plate was observed using a shape analysis laser microscope, it was confirmed that the convex portion and the valley portion having a substantially triangular wavy cross section had a continuous three-dimensional shape.

<Comparative example 2>
As the roughened roll, a roughened sheet was prepared in the same manner as in Comparative Example 1 except that the outer layer was made of silicone rubber and the outermost layer had a specific surface area of 3.9.
The overall thickness of the roughened sheet was 0.200 mm, and the thickness of the surface layer was 0.100 mm.

Next, a flexographic printing plate was produced in the same manner as in Example 1 except that the roughened sheet was used.
When the specific surface area _RS and the unit space volume S _V of the plate surface of the produced flexographic printing plate were measured in the same manner as in Example 1, the specific surface area _RS was 3.4 and the unit space volume S _V was 11.40 μm ^3. It was / μm ² .

Further, when the surface of the plate was observed using a shape analysis laser microscope, it was confirmed that, as shown in FIG. 8, the convex portion and the valley portion having a substantially triangular wavy cross section had a continuous three-dimensional shape.
<Comparative example 3>
As the roughened roll, a roughened sheet was produced in the same manner as in Comparative Example 1 except that the outer layer was made of silicone rubber and the outermost layer had a specific surface area of 4.5.

The overall thickness of the roughened sheet was 0.200 mm, and the thickness of the surface layer was 0.100 mm.
Next, a flexo printing plate was manufactured in the same manner as in Example 1 except that the roughened sheet was used.
When the specific surface area _RS and the unit space volume S _V of the plate surface of the produced flexographic printing plate were measured in the same manner as in Example 1, the specific surface area _RS was 4.1 and the unit space volume S _V was 12.06 μm ^3. It was / μm ² .

Further, when the surface of the plate was observed using a shape analysis laser microscope, it was confirmed that the convex portion and the valley portion having a substantially triangular wavy cross section had a continuous three-dimensional shape.
<Comparative Example 4>
Acrylic resin particles (fine particles 14) having a minimum particle size distribution of 2.5 μm, a maximum value of 10.0 μm, an average particle size of 5.0 μm, a standard deviation σ of 2.0 μm, and a coefficient of variation Cv of 0.40. ) Was used, and the roughened sheet 10 was produced in the same manner as in Example 1.

The overall thickness of the roughened sheet 10 was 0.196 mm, and the average thickness of the surface layer 12 was 0.008 mm.
Next, the flexographic printing plate 1 was manufactured in the same manner as in Example 1 except that the roughened sheet 10 was used.
When the specific surface area _RS and the unit space volume S _V of the plate surface of the manufactured flexographic printing plate 1 were measured in the same manner as in Example 1, the specific surface area _RS was 4.0 and the unit space volume S _V was 10.57 μm. It was ³ / μm ² .

Further, when the plate surface 3 was observed using a shape analysis laser microscope, it was confirmed that hemispherical depressions having a substantially constant diameter had a three-dimensional shape in which hemispherical depressions were randomly and precisely arranged.
<Comparative Example 5>
Acrylic resin particles (fine particles 14) having a minimum particle size distribution of 8.0 μm, a maximum value of 40.0 μm, an average particle size of 20.0 μm, a standard deviation σ of 7.0 μm, and a coefficient of variation of 0.35. ) Was used, and the roughened sheet 10 was produced in the same manner as in Example 1.

The overall thickness of the roughened sheet 10 was 0.222 mm, and the average thickness of the surface layer 12 was 0.034 mm.
Next, the flexographic printing plate 1 was manufactured in the same manner as in Example 1 except that the roughened sheet 10 was used.
When the specific surface area _RS and the unit space volume S _V of the plate surface of the manufactured flexographic printing plate 1 were measured in the same manner as in Example 1, the specific surface area _RS was 6.2 and the unit space volume S _V was 30.56 μm. It was ³ / μm ² .

Further, when the plate surface 3 was observed using a shape analysis laser microscope, it was confirmed that hemispherical depressions having a substantially constant diameter had a three-dimensional shape in which hemispherical depressions were randomly and precisely arranged.
<Actual machine test>
(Flexographic printing)
The flexographic printing plate produced in Examples and Comparative Examples was applied to a flexographic printing machine [A45 manufactured by Nakan Co., Ltd.] prepared for forming a liquid crystal alignment film, and Anilox Roll # 220 [cell volume: 6.5 cc / m ² ]. Incorporated with.

Then, an ink for a liquid crystal alignment film [Optomer (registered trademark) AL17901 manufactured by JSR Co., Ltd.] is supplied to a flexographic printing machine, printed on the electrode-forming surface of a simulated substrate for a liquid crystal display element, and then printed at 120 ° C. for 30. It was pre-dried for a minute to form a liquid crystal alignment film.
The printing conditions were set so that the set thickness of the liquid crystal alignment film after pre-drying was 1000 Å when the flexographic printing plate of Comparative Example 3 was used.

As the simulated substrate, a substrate in which dots were constructed with a density of 420 ppi pixels in a 5-inch square area was used, and the uneven pitch was 3 to 15 μm and the height was 0.3 to 1 μm.
<Thickness evaluation of liquid crystal alignment film>
The thickness of the liquid crystal alignment film formed above was measured using a film thickness meter.
In addition, the reproducibility of the thickness of the liquid crystal alignment film was evaluated based on the following criteria from the measurement results of the thickness when printing was repeated.

(Thickness reproducibility)
◯: Even after repeated printing, the thickness stably exceeded 1050 Å and was in the range of 1350 Å or less.
Δ: When printing was repeated, the thickness was generally within the above range, but there were cases where the thickness was more than 1000 Å and less than 1050 Å, or more than 1350 Å and less than 1400 Å.

X: When printing was repeated, the thickness was stably 1000 Å or less or more than 1400 Å.
Furthermore, the liquid crystal alignment film was observed, and the presence or absence of uneven thickness and pinholes was evaluated according to the following criteria.
(Uneven thickness, pinhole)
◯: No uneven thickness or pinhole was observed.

Δ: There was slight unevenness in thickness or pinholes, but it was at a practical level.
X: Uneven thickness and pinholes were noticeably observed.
<Comprehensive evaluation>
Both the evaluation of the reproducibility of the above thickness and the evaluation of the presence or absence of unevenness and pinholes were ○, one that was △, one that was △, and one that was ×. It was evaluated as ×.

The above results are shown in Tables 1 and 2.

From the results of Examples 1 to 4 and Comparative Examples 1 to 5 in the table, the plate surface of the flexographic printing plate has a specific surface area R _S of 4.3 or more and 6.0 or less, and a unit space volume S _V of 12 μm ^3. By using a rough surface of / μm ² or more and 29 μm ³ / μm ² or less, the surface area is highly accurate and has no thickness unevenness or pinholes, and the thickness is larger than the current state without major changes in printing conditions. It was found that a liquid crystal alignment film having a thickness suitable for a liquid crystal display element can be formed.

Further, from the results of Examples 1 to 4 and Comparative Examples 1 to 3, in order to obtain the above effect with the specific surface area _RS and the unit space volume S _V of the plate surface as the above ranges, the plate surface is made approximately constant. It has been found that it is preferable to form a three-dimensional shape in which hemispherical depressions having a diameter are randomly and densely arranged.
Further, from the results of Examples 1 to 4, considering that the above effect is further improved, the specific surface area _RS of the plate surface is preferably 5.0 or more and 5.3 or less even in the above range. , the unit space volume _{S V} is, 16μm ³ / ^{μm 2} or more at the above-mentioned range, it was found that preferably is 22μm ³ / μm ² or less.

1 Flexographic printing plate 2 Resin layer 3 Plate surface 4 Reinforcing sheet 5 Grip part 6 Groove part 7 Chuck hole 8 Depression 9 Ink 10 Roughened sheet 11 Reinforcing film 12 Surface layer 13 Binder resin 14 Fine particles 15 Mold surface 16 Support substrate 17 Opposite surface 18 surface 19 a photosensitive resin composition 20 layer 21 opposite the substrate 22 facing surface 23 laminates 24 workbench 25 printing resin precursor A measuring area _{P H} highest point _{P L} nadir _{R S} specific surface area _{S V} unit space volume V convex volume

Claims (4)

A flexographic printing plate used in a step of forming a liquid crystal alignment film by a flexographic printing method, which includes a plate surface for supporting ink, and the plate surface has a specific surface area _RS of 4.3 or more and 6.0 or less. in, and the unit space volume _{S V} is 12μm ³ / μm ² or more, 29μm ³ / ^{μm 2} or less of a flexographic printing plate is roughened. The flexographic printing plate according to claim 1, wherein the specific surface area _RS of the plate surface is 5.0 or more and 5.3 or less. Unit space volume _{S V} of the plate surface, 16μm ³ / μm ² or more, 22μm ³ / μm ² or less flexographic printing plate according to claim 1 or 2. A method for manufacturing a liquid crystal display element, which comprises a step of forming a liquid crystal alignment film by a flexographic printing method using the flexographic printing plate according to any one of claims 1 to 3.