JP2024006925A - Photosensitive resin composition, flexographic printing original plate, flexographic printing plate, method for producing cured product, method for producing flexographic printing plate, and printing method - Google Patents

Abstract

To provide a photosensitive resin composition which enables manufacture of a flexographic printing plate that achieves both excellent solvent resistance and flexibility at high level.SOLUTION: There is provided a photosensitive resin composition in which a cured product of light including a wavelength of 360 nm satisfies the following (Condition 1) and (Condition 2). (Condition 1) Elongation at break when a tensile test is performed on a dumbbell type test piece in which a measurement part has a thickness of 1 mm, a length of 30 mm, and a width of 3 mm at a speed of 500 mm/min at 23°C is 250% or more. (Condition 2) A mass increase rate when it is immersed in N-methyl-2-pyrrolidone (NMP) or γ-butyrolactone (GBL) for 24 hours of 25 mass% is less.SELECTED DRAWING: None

Description

The present invention relates to a photosensitive resin composition, a flexographic printing original plate, a flexographic printing plate, a method for producing a cured product, a method for producing a flexographic printing plate, and a printing method.

Flexographic printing, which utilizes a flexographic printing plate made of a photosensitive resin composition, has excellent printing properties on uneven paper, nonwoven fabric, and highly smooth plastic film, so it is suitable for printing on cardboard, food packaging, etc. , are widely used in various industries (for example, see Patent Documents 1 and 2).

In addition, since flexographic printing plates have a high degree of flexibility, in recent years they have been used for printing on surfaces where scratches cannot be tolerated, such as alkali-free glass plates for liquid crystals and semiconductor wafers.
In particular, printing plates used for printing on alkali-free glass plates for liquid crystals, specifically flexographic printing plates used for alignment film printing, are increasing in size and improving plate thickness accuracy and plate surface pattern within large sizes. High definition is now required.

The alignment film formed on the alkali-free glass plate for liquid crystal uses an alignment film varnish made by dissolving polyimide or its precursor polyamic acid in a polar solvent such as N-methyl-2-pyrrolidone (NMP) or γ-butyrolactone. Obtained by printing using a flexo printing plate.
However, the polar solvent used to form the alignment film varnish swells the flexographic printing plate, and in order to achieve high printing quality (plate thickness accuracy and high definition of plate surface pattern), It is necessary to improve the solvent resistance of photosensitive resin compositions forming flexographic printing plates.

Generally, the photosensitive resin composition that forms a flexographic printing plate is a crosslinkable polymer, and thus the solvent resistance of the photosensitive resin composition has conventionally been improved by increasing the crosslinking density.
However, increasing the crosslinking density of the photosensitive resin composition impairs the flexibility of the final flexographic printing plate, and tends to reduce the elongation and toughness, which are indicators of the durability of the flexographic printing plate. , there is a problem. In the case of flexographic printing plates, damage in one place can result in total loss of the flexographic printing plate, so larger flexographic printing plates need to be more durable than small flexographic printing plates.

For example, Patent Documents 3 and 4 disclose techniques related to flexographic printing plates with improved solvent resistance.
However, the printing quality required for large flexographic printing plates, such as plate thickness accuracy, high definition of plate surface patterns, and solvent resistance, are still insufficient, and there is still room for improvement. have.

Japanese Patent Application Publication No. 11-92659 Japanese Patent Application Publication No. 2004-148309 Patent No. 3835867 Patent No. 5206434

As mentioned above, in the past, techniques have been proposed to improve solvent resistance by increasing the crosslinking density of photosensitive resin compositions in order to improve printing quality. There was a problem that the flexibility of the flexographic printing plate was lost and the durability of the flexographic printing plate was reduced.

Therefore, the purpose of the present invention is to provide a photosensitive resin composition that can produce a flexographic printing plate that has both excellent solvent resistance (low swelling) and flexibility (elongation, toughness) at a high level. shall be.

As a result of intensive studies to solve the above problems, the present inventors discovered that a photosensitive resin composition having predetermined physical properties can solve the above problems, and completed the present invention.
That is, the present invention is as follows.

[1]
A photosensitive resin composition in which a cured product of light having a wavelength of 360 nm satisfies the following <Condition 1> and <Condition 2>.
<Condition 1>
The elongation at break is 250% or more when a dumbbell-shaped test piece with a measuring part of 1 mm thick, 30 mm long, and 3 mm wide is subjected to a tensile test at 23° C. at a speed of 500 mm/min.
<Condition 2>
The mass increase rate when immersed in N-methyl-2-pyrrolidone (NMP) or γ-butyrolactone for 24 hours is 25% by mass or less.
[2]
The photosensitive resin composition according to item [1] above, wherein the photosensitive resin composition contains a polyurethane prepolymer.
[3]
The photosensitive resin composition according to [2] above, wherein the polyurethane prepolymer has a hydrogenated polybutadiene structure.
[4]
base material and
The photosensitive resin composition according to any one of [1] to [3] above,
A flexographic printing original plate having.
[5]
base material and
A cured product of light containing a wavelength of 360 nm of the photosensitive resin composition according to any one of [1] to [3] above,
has,
The cured product has a breaking elongation of 250% or more under <Condition 1>, and an increase in mass when immersed in N-methyl-2-pyrrolidone or γ-butyrolactone for 24 hours under <Condition 2>. A flexographic printing plate having a ratio of 25% by mass or less.
[6]
A method for producing a cured product, comprising a step of irradiating the photosensitive resin composition according to any one of [1] to [3] above with light having a wavelength of 360 nm.
[7]
Laminating the photosensitive resin composition according to any one of [1] to [3] above on a base material to obtain a flexographic printing original plate;
irradiating the flexographic printing original plate with light containing light with a wavelength of 360 nm to photocure the photosensitive resin composition;
a developing step of removing unexposed areas in the photocuring;
A method for producing a flexographic printing plate having the following.
[8]
A step of manufacturing a flexographic printing plate by the method for manufacturing a flexographic printing plate described in [7] above;
an ink adhesion step of adhering ink to the flexographic printing plate;
a transfer step of transferring the ink;
A printing method having.
[9]
The printing method according to [8] above, which is a method of printing a liquid crystal alignment film used for manufacturing a liquid crystal display element.
[10]
The ink contains N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone, 1,2-dimethyl-2-imidazolidinone, γ-butyrolactone (GBL), γ-butyrolactam, N,N- Dimethylformamide, N,N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, butyl lactate, butyl acetate, methylmethoxypropionate, ethyl ethoxypropionate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol selected from the group consisting of monomethyl ether acetate, diethylene glycol monoethyl ether acetate, isoamyl propionate, isoamyl isobutyrate, diisopentyl ether, ethylene carbonate, propylene carbonate, cyclohexane, 1-octanol, ethylene glycol monobutyl ether, and tetrahydrofuran , the printing method according to [8] or [9] above, comprising one or more solvents.

According to the present invention, it is possible to provide a photosensitive resin composition that can produce a flexographic printing plate that has both excellent solvent resistance and flexibility at a high level.

Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail.
Note that the following embodiment is an illustration for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be implemented with appropriate modifications without departing from the gist thereof.

[Photosensitive resin composition]
The photosensitive resin composition of this embodiment is
A cured product of light having a wavelength of 360 nm satisfies <Condition 1> and <Condition 2> below.
<Condition 1>
The elongation at break is 250% or more when a dumbbell-shaped test piece with a measuring part of 1 mm thick, 30 mm long, and 3 mm wide is subjected to a tensile test at 23° C. at a speed of 500 mm/min.
<Condition 2>
The mass increase rate when immersed in N-methyl-2-pyrrolidone (NMP) or γ-butyrolactone for 24 hours is 25% by mass or less.

By having the above structure, a photosensitive resin composition can be obtained that can produce a flexographic printing plate that has both excellent solvent resistance and flexibility at a high level.

(Elongation at break of cured product of photosensitive resin composition)
The photosensitive resin composition of the present embodiment is a photocurable resin composition, and the elongation at break of the cured product by light having a wavelength of 360 nm is 250% or more under the above-mentioned <Condition 1>. Preferably it is 250% or more and 1000% or less, more preferably 300% or more and 900% or less, and even more preferably 350% or more and 800% or less.

By setting the elongation at break of the cured product to 250% or more in the above <Condition 1>, excellent flexibility can be obtained, and when handling the flexographic printing plate, specifically, the process of wrapping it around the plate cylinder during printing, They tend to have sufficient durability against mechanical external forces that can cause damage during the removal process and post-print cleaning process. In particular, when the cured product of the photosensitive resin composition of this embodiment has an area of 0.5 m ² or more, the elongation at break is preferably 300% or more from the viewpoint of ease of handling. Furthermore, when the cured product of the photosensitive resin composition of this embodiment is a large-sized product with an area of 3 m ² or more, the elongation at break is preferably 350% or more.

In the photosensitive resin composition of the present embodiment, the photoreaction progresses upon exposure, similar to a general photocuring reaction, and therefore the curing reaction can be controlled by adjusting the exposure amount. By adjusting the exposure amount, the elongation at break of the cured product can be controlled within the above numerical range. However, regarding toughness, it is necessary to always maintain it at 50 kgf×mm or more.
The elongation at break of the cured product of the photosensitive resin composition of this embodiment can be measured by the method described in the Examples below.
An effective way to increase the elongation at break is to lower the density of the chemical or physical crosslinking points of the resin, and by adjusting the resin composition and curing method used in the photosensitive resin composition of this embodiment, the above numerical range can be achieved. can be controlled.
Specifically, the resin composition of the photosensitive resin composition should include a polymer component that is liquid at a temperature of 23°C, an ethylenic monomer component having a radically reactive group, and an initiator component that starts the reaction of the ethylenic monomer. is a preferred embodiment. As the polymer component that is liquid at a temperature of 23° C., for example, a polyurethane prepolymer that is liquid at 23° C. can be used, and as the initiator component, for example, a photoradical polymerization initiator can be used. At this time, the content of the ethylenic monomer is 40 parts by mass or less and 10 parts by mass or more with respect to 100 parts by mass of the polyurethane prepolymer, and ethylene having two or more radically reactive functional groups is It is preferable that the composition contains 0 parts by mass or more and 30 parts by mass or less of a monomer. Condition 1 can be satisfied by molding this photosensitive resin composition to a thickness of 1 mm and irradiating it with light including 360 nm. As a curing method, Condition 1 can be satisfied by exposing the front and back surfaces for 0.05 to 60 minutes, respectively, with light having an illuminance of 0.5 to 500 mW/cm ² .

(Solvent resistance of cured product of photosensitive resin composition)
The photosensitive resin composition of the present embodiment is a photocurable resin composition, and a cured product of light containing a wavelength of 360 nm is immersed in N-methyl-2-pyrrolidone (NMP) or γ-butyrolactone for 24 hours. The mass increase rate when this is done is 25% by mass or less.
Specifically, the cured product of light containing a wavelength of 360 nm was cut into sample pieces of 1 cm x 5 cm x 1 mm thick, and the sample pieces were treated with N-methyl-2-pyrrolidone (NMP: 99.0+% manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.). (Capillary GC)) or γ-butyrolactone (GBL: manufactured by Tokyo Kasei >99.0% (GC)) at a temperature of 23°C (humidity 50%) for 24 hours, the mass increase rate is 25% by mass. It is as follows.
The content is preferably 1% by mass or more and 25% by mass or less, more preferably 1% by mass or more and 20% by mass or less, and still more preferably 1% by mass or more and 15% by mass or less.

If the mass increase rate in the cured product is 1% by mass or more, the wettability between the surface of the flexographic printing plate and the alignment film varnish will be sufficient and it will tend to be possible to print evenly.
In addition, by setting the mass increase rate to 25% by mass or less, excellent solvent resistance can be exhibited, and deformation of the pattern formed on the surface of the flexographic printing plate during actual alignment film printing can be suppressed, and high definition can be achieved. tend to be achievable.
In particular, when the area of the flexographic printing plate is 0.5 m ² or more, the mass increase rate is set to 15% by mass or less, and especially when the area of the flexographic printing plate is large, 3 m ² or more, the mass increase rate is set to 10%. By making the amount less than or equal to % by mass, it is possible to suppress in-plane thickness unevenness that accompanies an increase in the size of a flexographic printing plate.
The mass increase rate of the cured product of the photosensitive resin composition of this embodiment can be controlled within the above numerical range by adjusting the exposure amount when forming the cured product.
The mass increase rate of the cured product of the photosensitive resin composition of this practical embodiment can be measured by the method described in the Examples below.
The mass increase rate can be reduced by increasing the density of the chemical or physical crosslinking points of the resin, thereby improving the solvent resistance. These can be controlled by adjusting the resin composition and curing method.
Specifically, it is a preferred embodiment that the resin composition of the photosensitive resin composition contains a polymer component having a hydrophobic unit structure, an ethylenic monomer component, and an initiator component that initiates the reaction of the ethylenic monomer. As the hydrophobic unit structure, for example, a polyurethane prepolymer having hydrogenated polybutadiene can be used, and as the ethylenic monomer component, for example, one having two or more radically reactive functional groups; or a hydrophobic A saturated cyclic compound, an ethylenic monomer having only one radically reactive functional group, which has high properties and a glass transition temperature of the polymer obtained by homopolymerizing the ethylenic monomer with a glass transition temperature of 50 ° C. or higher, and further The photosensitive resin composition preferably contains a photoradical polymerization initiator. Condition 2 can be satisfied by molding this photosensitive resin composition to a thickness of 1 mm and irradiating it with light including 360 nm. As a curing method, Condition 2 can be satisfied by exposing the front and back surfaces for 0.05 to 60 minutes, respectively, with light having an illuminance of 0.5 to 500 mW/cm ² .

(Toughness of cured product of photosensitive resin composition)
In the photosensitive resin composition of the present embodiment, the toughness of the cured product when exposed to light having a wavelength of 360 nm is preferably 50 kgf x mm or more and 300 kgf x mm or less. More preferably, it is 80 kgf×mm or more and 250 kgf×mm or less, and still more preferably 100 kgf×mm or more and 220 kgf×mm or less.
By setting the toughness of the cured product to 50 kgf x mm or more, flexibility can be obtained, and the hardness can be such that it can follow the irregularities of the printing material when printing with a flexographic printing plate using the photosensitive resin composition of this embodiment. , it is possible to suppress the occurrence of defects in printed matter. In addition, damage can be prevented during the wrapping process around the plate cylinder during printing, and good work efficiency can be achieved.
In addition, by setting the toughness of the cured product to 50 kgf x mm or more, high chipping resistance can be obtained, and when printing with a flexographic printing plate using the photosensitive resin composition of this embodiment and handling, physical impact can be avoided. This prevents damage to the plate due to excessive force and allows it to remain in good condition for a long period of time.
On the other hand, excessive toughness may deteriorate handling properties during plate making operations such as plate cutting, so it is preferable to set the toughness to 300 kgf x mm or less. Can maintain balance.
In the photosensitive resin composition of this embodiment, the toughness of the cured product can be controlled by adjusting the exposure amount during photocuring. Furthermore, by adjusting the composition of the photosensitive resin composition, the toughness of the cured product can be controlled within the above numerical range.
Specifically, it is a preferred embodiment that the resin composition of the photosensitive resin composition contains a liquid polymer component, an ethylenic monomer component, and an initiator component that starts the reaction of the ethylenic monomer at a temperature of 23°C. As the polymer component that is liquid at a temperature of 23°C, for example, a polyurethane prepolymer that is liquid at 23°C can be used, and as the initiator component, for example, a photoradical polymerization initiator can be used. At this time, the content of the ethylenic monomer is preferably 40 parts by mass or less and 10 parts by mass or more based on 100 parts by mass of the polyurethane prepolymer. Furthermore, the ethylenic monomer is a monomer in which the homopolymer of the ethylenic monomer exhibits a glass transition temperature of 50°C or higher, and has a saturated cyclic structure and one radically reactive functional group as a functional group. Preferably, it includes. Furthermore, it is preferable that the photosensitive resin composition contains a photoradical polymerization initiator. By molding this photosensitive resin composition to a thickness of 1 mm and irradiating it with light including 360 nm, the toughness conditions described above can be satisfied. As a curing method, for example, the toughness described above can be achieved by exposing the front and back sides to light with an illuminance of 0.5 to 500 mW/cm ² for 0.05 to 60 minutes, respectively.
The toughness of the cured product of the photosensitive resin composition of this practical embodiment can be measured by the method described in Examples below.

(Constituent material of photosensitive resin composition)
The photosensitive resin composition of this embodiment preferably contains a polyurethane prepolymer, an ethylenic monomer, and a photopolymerization initiator.

<Polyurethane prepolymer>
The polyurethane prepolymer preferably has hydrophobicity, and specifically, preferably has a repeating structure composed only of hydrocarbons that do not have polar groups such as carbonyl groups and ether groups, for example, It is preferable to have a polyolefin structure or a hydrogenated polybutadiene structure. Specifically, the polyurethane prepolymer has at least a polymerizable ethylenic double bond at the end of a prepolymer precursor obtained by chain-extending a hydroxyl group compound at both ends having the above structure with a urethane bond using a diisocyanate. A polyurethane prepolymer obtained by introducing one is preferable.
Note that polyurethane prepolymers and elastomers such as SBS, which have polar functional groups in their unit structures, have no problems from the viewpoint of imparting mechanical properties such as elongation at break and toughness to the cured product of the photosensitive resin composition. However, since these have high polarity, they are not preferred from the viewpoint of imparting solvent resistance to the cured product of the photosensitive resin composition. Therefore, the polyurethane prepolymer preferably has a hydrophobic unit structure such as a polyolefin structure or hydrogenated polybutadiene.

The polyurethane prepolymer can be synthesized by a known method.
For example, the above-mentioned reaction of introducing at least a polymerizable ethylenic double bond into the end of a prepolymer precursor obtained by chain-extending a hydrogenated polybutadiene compound with a urethane bond using a diisocyanate can be performed using a tertiary amine or a tin compound. It can be carried out in the presence or absence of a urethanization catalyst such as. Further, the reaction temperature at this time is preferably 40 to 100°C.

As the diisocyanate, aliphatic, alicyclic and aromatic diisocyanates are used. Examples include, but are not limited to, hexamethylene diisocyanate (HMDI), trimethylhexamethylene diisocyanate (TMDI), 2,6- and/or 2,4-tolylene diisocyanate (2,6- and/or 2,4-TDI ), paraphenylene diisocyanate, diphenylmethane diisocyanate (MDI), hydrogenated 2,6- and/or 2,4-TDI, hydrogenated MDI, dicyclohexyldimethylmethane diisocyanate, isophorone diisocyanate, and the like.

In order to obtain the polyurethane prepolymer, the method for introducing at least one ethylenic double bond at the end of the prepolymer precursor is not particularly limited, and any known method can be used. For example, a method in which the terminal hydroxyl group of a polymer precursor is reacted with a diisocyanate in advance to introduce an isocyanate group at the terminal, and then reacted with a compound having an ethylenic double bond and a functional group having an active hydrogen such as a hydroxy group; Examples include a method of esterifying with a carboxylic acid having a terminal hydroxyl group and an ethylenic double bond.

Compounds having an ethylenic double bond and a functional group having an active hydrogen such as a hydroxyl group, which are used for introducing an ethylenic double bond, include, but are not limited to, hydroxyalkyl (meth)acrylates, polyesters, etc. Examples include oxyalkylene glycol mono(meth)acrylate.
Examples of the hydroxyalkyl (meth)acrylate include, but are not limited to, hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate.
Examples of polyoxyalkylene glycol mono(meth)acrylate include, but are not limited to, polyethylene glycol mono(meth)acrylate (Mn=300 to 1,000), polypropylene glycol mono(meth)acrylate (Mn=300 to 1) , 000), a 1:1 addition reaction product of glycolic acid and glycidyl (meth)acrylate, a 1:1 addition reaction product of glyceric acid and glycidyl (meth)acrylate, glycerine di(meth)acrylate, etc. .

The content of the polyurethane prepolymer in the photosensitive resin composition is preferably 40 to 95 parts by mass based on 100 parts by mass of the entire photosensitive resin composition from the viewpoint of high solvent resistance and high flexibility of the flexographic printing plate. , more preferably 65 to 85 parts by mass.
When the content is 40 parts by mass or more, the high solvent resistance and flexibility exhibited by the polyurethane prepolymer can be fully expressed, and when the content is 95 parts by mass or less, increase in viscosity can be suppressed and good workability can be obtained. It will be done.

<Ethylenic monomer>
As the ethylenic monomer, known ones can be used, including, but not limited to, alkyl (meth)acrylates such as 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; hydroxy Hydroxyalkyl (meth)acrylates such as ethyl (meth)acrylate and hydroxypropyl (meth)acrylate; polyethylene glycol mono(meth)acrylate (Mn = 300 to 1,000) and polypropylene glycol (meth)acrylate (Mn = 300 to 1) Polyoxyalkylene glycol mono(meth)acrylates such as caprolactone (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, isobornyl (meth)acrylate, (meth)acrylamide, N-substituted or Alkylene glycol di(meth)acrylates such as N,N'-substituted (meth)acrylamides and tetraethylene glycol di(meth)acrylates; polyethylene glycol di(meth)acrylates (Mn = 300 to 1,000) and polypropylene glycol di(meth)acrylates; Polyoxyalkylene glycol di(meth)acrylates such as meth)acrylate (Mn=300 to 1,000); trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and the like.
These ethylenic monomers may be used singly or in combination of two or more depending on the purpose.

The amount of the ethylenic monomer added is preferably 5 parts by mass or more and 200 parts by mass or less based on 100 parts by mass of the polyurethane prepolymer. By adding 5 parts by mass or more of the ethylenic monomer to 100 parts by mass of the polyurethane prepolymer, the viscosity of the photosensitive resin composition can be adjusted to an appropriate level, and the mechanical properties of the resulting flexographic printing plate can be improved. The balance will be good. Furthermore, by adding the ethylenic monomer in an amount of 200 parts by mass or less based on 100 parts by mass of the polyurethane prepolymer, it is possible to prevent curing shrinkage from becoming too large during photocuring, and to obtain the desired flexographic printing plate. A flexographic printing plate with good thickness accuracy and sufficient mechanical properties can be obtained.
From the viewpoint of workability and balance of mechanical properties in the plate-making apparatus of the photosensitive resin composition, the amount of the ethylenic monomer added is 15 parts by mass or more and 100 parts by mass or less, based on 100 parts by mass of the polyurethane prepolymer. More preferably, it is 30 parts by mass or more and 70 parts by mass or less.

It is preferable to add at least one type of ethylenic monomer among the ethylenic monomers that has high hydrophobicity and whose homopolymer of the ethylenic monomer has a glass transition temperature of 50 or higher. Examples of such ethylenic monomers include cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, 1-ethylcyclohexyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2 -Methyl adamantyl (meth)acrylate, 2-isopropyl-2-(meth)acryloyl adamantane, 2-cyclohexylpropan-2-yl methacrylate, and other saturated cyclic compounds. These are particularly preferred because they are effective in improving the solvent resistance of the flexographic printing plate and imparting flexibility, and preferably contain at least one type of the ethylenic monomer. The amount of these ethylenic monomers added is preferably 5 parts by mass or more and 80 parts by mass or less, more preferably 10 parts by mass or more and 50 parts by mass or less, based on 100 parts by mass of the polyurethane prepolymer.

<Photopolymerization initiator>
As the photopolymerization initiator, known ones can be used, including, but not limited to, benzoin (dimethyl ketanol), benzoin, benzoin ethyl ether, benzoin-n-propyl ether, benzoin-isopropyl ether, benzyl dimethyl ketanol, etc. ) Alkyl ethers; benzyl, diacetyl, diphenyl sulfide, dimethylacetophenone and the like.
The blending amount of these photopolymerization initiators is preferably 0.01 parts by mass or more and 10 parts by mass or less based on 100 parts by mass of the total amount of the polyurethane prepolymer and the ethylenic monomer.

<Other materials>
In addition to the polyurethane prepolymer, ethylenic monomer, and photopolymerization initiator, the photosensitive resin composition of the present embodiment may include, for example, a thermal polymerization inhibitor, an ultraviolet absorber, a light stabilizer, a dye and a pigment, etc., depending on the purpose. A lubricant, antioxidant, inorganic filler, surfactant, plasticizer, process oil, liquid paraffin, liquid rubber, etc. can be added.

[Flexo printing original plate]
The flexographic printing original plate of this embodiment has a base material and the photosensitive resin composition of this embodiment.
The flexographic printing original plate of this embodiment can be manufactured by laminating a layer of the photosensitive resin composition of this embodiment on a base material.
According to the flexographic printing original plate of this embodiment, it is possible to manufacture a flexographic printing plate that has both excellent solvent resistance and flexibility at a high level.

[Flexo printing plate]
The flexographic printing plate of this embodiment has a base material and a cured product of light containing a wavelength of 360 nm of the photosensitive resin composition of this embodiment. included. The cured product has a breaking elongation of 250% or more under the <condition 1>, and a mass increase when immersed in N-methyl-2-pyrrolidone or γ-butyrolactone for 24 hours under the <condition 2>. The percentage is 25% by mass or less.
According to the flexographic printing plate of this embodiment, it is possible to achieve both excellent solvent resistance and flexibility at a high level.

[Method for producing cured product]
The method for producing a cured product of this embodiment includes the step of irradiating the photosensitive resin composition of this embodiment described above with light having a wavelength of 360 nm.
In the method for producing a cured product of this embodiment, an uncured resin recovery step for removing uncured resin after curing, a washing step, and a post-exposure step can be further carried out.
A fluorescent lamp or an LED light can be used as a light source for the irradiation light having a wavelength of 360 nm.
As for the irradiation time, select a time that allows the coating to be cured by applying an exposure amount that is at least enough to produce the desired thickness. The irradiation environment can be cured without major constraints.

[Method for manufacturing flexographic printing plates]
The method for producing a flexographic printing plate of this embodiment includes a step of laminating the photosensitive resin composition of this embodiment on a base material to obtain a flexographic printing original plate;
irradiating the flexographic printing original plate with light having a wavelength of 360 nm to photocure the photosensitive resin composition;
a developing step of removing unexposed areas in the photocuring;
have.

Specifically, a negative film is placed on a glass plate, covered with a thin protective film, and the photosensitive resin composition of this embodiment is laminated thereon. With a base film (substrate) serving as a support attached, a glass plate is placed on top of the base film so that the thickness of the photosensitive resin composition layer becomes a preset constant value. Next, short-time back exposure is performed using an upper actinic light source to form a uniform thin resin layer, ie, a back exposure layer, over the entire surface of the support. Next, image-forming exposure is performed by irradiating light with a wavelength of 360 nm from the lower actinic light source to form a relief. Then, a development step is carried out in which the uncured, unexposed portions of the photosensitive resin composition are washed and removed. Next, the entire plate obtained is further irradiated with actinic rays (post-exposure) in water or air to further complete curing, followed by drying treatment to obtain a flexographic printing plate.

Examples of the active light source used for exposure in the process of manufacturing the flexographic printing plate include a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, an ultraviolet fluorescent lamp, a carbon arc lamp, and a xenon lamp. Further, as a transparent image carrier used for forming a relief image, a negative or positive film for photolithography using a silver salt image is mainly used.

As the cleaning liquid for the uncured resin, for example, water, aqueous alkaline solution, aqueous surfactant solution, solvent, etc. are used.

The photosensitive resin composition of this embodiment can also be used for plate making such as flexo printing plates and stamp plates.

In addition to glass plates, substrates used for printing such as flexo printing plates and stamp plates include wafers; polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyurethane, polylactic acid, Teflon (registered trademark), ABS resin/AS resin.・Acrylic resin, polyvinyl chloride, polyvinylidene chloride, polyimide, polyacetal, polycarbonate, modified polyphenyl ether, polyethylene terephthalate, polybutylene terephthalate, cyclic polyolefin, polyphenylene sulfide, polytetrafluoroethylene, polysulfone, polyether sulfone, liquid crystal Polymer, polyetheretherketone, methacrylic resin, polyether, polyphenylene sulfide, resin containing one or more polyarylates, steel, stainless steel, aluminum, magnesium, titanium, copper, lead, zinc, nickel, chromium, tungsten, gold, silver , platinum, and alloys containing two or more of these can be used.

[Printing method]
The printing method of this embodiment includes a step of manufacturing a flexographic printing plate by the above-described flexographic printing plate manufacturing method, an ink adhering step of adhering ink to the convex portion of the flexographic printing plate, and a step of transferring the ink. and a transfer step.
The printing method of this embodiment is suitable, for example, as a method for printing a liquid crystal alignment film used for manufacturing a liquid crystal display element on a substrate.

The ink used in the printing method of this embodiment contains N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone, 1,2-dimethyl-2-imidazolidinone, and γ-butyrolactone (GBL) as a solvent. ), γ-butyrolactam, N,N-dimethylformamide, N,N-dimethylacetamide, and other highly polar solvents are used.In addition, 4-hydroxy-4-methyl-2-pentanone, butyl lactate, butyl acetate, Methyl methoxypropionate, ethyl ethoxypropionate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, isoamyl propionate, isoamyl isobutyrate, diisopentyl ether, ethylene carbonate, Examples include solvents containing one or more of propylene carbonate, cyclohexane, 1-octanol, ethylene glycol monobutyl ether, and tetrahydrofuran.

According to the printing method of this embodiment, since the flexographic printing plate of this embodiment has excellent flexibility and solvent resistance, high quality and long-time printing can be achieved.

Hereinafter, the present embodiment will be specifically described with reference to specific examples and comparative examples, but the present invention is not limited to the following examples and comparative examples.

[Production Example 1 of polyurethane resin (PU-1), which is the elastomer type constituting the photosensitive resin compositions of Examples 1 to 7 and Comparative Examples 1 to 2]
300 g of hydrogenated polybutadiene with terminal hydroxyl groups and 20.7 g of tolylene diisocyanate were stirred and mixed at 40°C for 30 minutes, and then reacted at 80°C for 5 hours, followed by 11 g of 2-hydroxypropyl methacrylate, 0.3 g of hydroquinone, and A mixed solution of 0.6 g of dibutyltin dilaurate was added and reacted at 80°C. The reaction was stopped when the absorption characteristic of NCO groups disappeared in the infrared absorption spectrum chart, and a polyurethane prepolymer was obtained.

[Production Example 2 of polyurethane resin (PU-2), which is an elastomer species constituting the photosensitive resin compositions of Examples 8, 9, and 11]
300 g of terminal hydroxyl group type polyolefin and 20.7 g of tolylene diisocyanate were stirred and mixed at 40°C for 30 minutes, and then reacted at 80°C for 5 hours, followed by 11 g of 2-hydroxypropyl methacrylate, 0.3 g of hydroquinone, and dibutyltin dilaurate. 0.6 g of the mixture was added and reacted at 80°C. The reaction was stopped when the characteristic absorption of NCO groups disappeared in the infrared absorption spectrum chart, and a polyurethane prepolymer was obtained.

[Examples 1 to 11], [Comparative Examples 1 to 6]
The abbreviations of the compounds used in Examples 1 to 11 and Comparative Examples 1 to 2 and the material compositions of the photosensitive resin compositions are listed in Table 1 below.
The polyurethane prepolymer produced in Production Example 1, the ethylenic monomer, photopolymerization initiator, and polymerization inhibitor listed in Table 1 were added to produce photosensitive resin compositions of Examples 1 to 11 and Comparative Examples 1 to 2. did.
The abbreviations of the compounds listed in Table 1 are explained below.
PU-1: Prepolymer produced in Production Example 1: Elastomer PU-2: Prepolymer produced in Production Example 2: Elastomer SLMA: Lauryl methacrylate: Ethylene monomer HP: 2-Hydroxypropyl methacrylate: Ethylene monomer AP-400 : Polyoxypropylene monoacrylate: Ethylene monomer KH: 2-hydroxyethyl methacrylate: Ethylene monomer GMGA: Glycerin monomethacrylate: Ethylene monomer CH: Cyclohexyl methacrylate: Ethylene monomer IBX: Isobonyl methacrylate: Ethylene monomer IBX- A: Isobonyl acrylate: Ethylene monomer MADMA: 2-methyladamantan-2-yl methacrylate FA-512M: Dicyclopentenyloxyethyl methacrylate HOP(N): 2-hydroxypropyl methacrylate: Ethylene monomer 513AS: Dicyclopenta Nyl acrylate: ethylenic monomer TMPT: trimethylolpropane trimethacrylate: ethylenic monomer 6EO: trimethylolpropane EO 6 mol modified triacrylate: ethylenic monomer A-DPH: dipentaerythritol hexaacrylate: ethylenic monomer Z4: 2-(1 -Methyl ethoxy)-1,2-diphenylethanone, benzoin isopropyl ether: Photopolymerization initiator Z7: 2,2-dimethoxy-2-phenylacetophenone: Photopolymerization initiator Z8: Benzophenone: Photopolymerization initiator I13: 2, 6-di-t-butyl-4-methylphenol: Polymerization inhibitor I14: 3,9-bis-{1,1-dimethyl-2-[3-(3-t-butyl-4-hydroxy-5-methyl) phenyl)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro(5,5)undecane: polymerization inhibitor

In Comparative Example 3, Asahi Kasei Corporation's product name "K-11" was used as the photosensitive resin composition.
Note that "polyurethane resin" in Tables 2 and 3 means not the polyurethane resin (polyurethane prepolymer) of Production Example 1, but a polyurethane resin that is a general polymer classification.

In Comparative Example 4, Asahi Kasei Corporation's product name "KS-80" was used as the photosensitive resin composition.
Note that "polyurethane resin" in Tables 2 and 3 means not the polyurethane resin (polyurethane prepolymer) of Production Example 1, but a polyurethane resin that is a general polymer classification.

In Comparative Example 5, Asahi Kasei Corporation's product name "SH" was used as the photosensitive resin composition.
As shown in Table 3, the binder polymer used in the above "SH" is an elastomer type SBS resin.

In Comparative Example 6, Asahi Kasei Corporation's product name "F-900" was used as the photosensitive resin composition.
Note that "polyurethane resin" in Tables 2 and 3 means not the polyurethane resin (polyurethane prepolymer) of Production Example 1, but a polyurethane resin that is a general polymer classification.
As shown in Table 3, the binder polymer used in the above "F-900" is a polyurethane resin as an elastomer.

The elastomer types and unit structures of the photosensitive resin compositions of Examples 1 to 11 and Comparative Examples 1 to 6 are shown in Tables 2 to 3 below.
In addition, regarding the elastomer type, the case where the elastomer was a polyurethane resin was indicated as "○", and the case where it was an SBS resin was indicated as "x".
In addition, regarding the unit structure of the elastomer species, the case where the unit structure is butadiene is indicated as "〇", and the case where the unit structure is an ester or ether unit structure, or a unit structure containing styrene is indicated as "x".

[Measurement method and evaluation method of characteristics]
((1) Method for measuring swelling rate (mass increase rate))
The photosensitive resin compositions of Examples 1 to 11 and Comparative Examples 1 to 6 were placed between two 4 mm thick transparent resin plates covered with a thin protective film with a spacer so that the thickness was 1 mm. A sample plate with a thickness of 1 mm was prepared by sandwiching the transparent resin plate and exposing the front and back sides to light using an irradiation lamp at a light source intensity of 2.0 mW/cm ² .
This sample plate was cut into sample pieces of 1 cm x 5 cm and immersed in N-methyl-2-pyrrolidone (NMP) or γ-butyrolactone (GBL) for 24 hours.
The mass of each sample piece before and after immersion was measured, and the mass increase rate (swelling rate (mass %)) was calculated.
The swelling rate was evaluated according to the following criteria.
〇: 25% by mass or less.
×: Exceeds 25% by mass.

((2) Measuring method of elongation at break and toughness)
A sample plate with a thickness of 1 mm was prepared in the same manner as the swelling rate measurement method described above.
A dumbbell-shaped sample with a measurement portion measuring 30 mm in length x 3 mm in width was prepared using the sample plate, and was used as a test piece for measuring tensile elongation.
The tensile elongation was measured using a tensile tester (AUTOGRAPH AG-AGS-X type: manufactured by Shimadzu Corporation) by pulling the test piece at 23°C at a tensile speed of 500 mm/min until it broke, and elongation at break (%), Toughness (kgf×mm) was obtained and evaluated according to the following criteria.
<Elongation at break>
○: 250% or more.
×: Less than 250%.
<Toughness>
〇: 50kgf×mm or more ×: Less than 50kgf×mm

((3) Method for measuring the rate of change in 500 μm independent line width before and after swelling)
Using a negative that forms independent lines of 500 μm, the exposure of Examples 1 to 11 and Comparative Examples 1 to 6 was carried out by sequentially going through the molding/exposure process, development process, post-exposure process, and drying process as shown below. A flexographic printing plate was prepared using a flexible resin composition.
<1: Molding/exposure process>
Using an ALF-213E type plate making machine (manufactured by Asahi Kasei Corporation), a plate with a thickness of 2.84 mm and an R. Curing was performed using a mask exposure amount and a relief exposure amount such that D=1.5 mm, and a flexographic printing plate having independent lines of 500 μm was obtained.
<2: Development process>
After recovering the uncured photosensitive resin composition by a conventional method, it was treated with an AL-400W type developing machine (drum rotation spray type, manufactured by Asahi Kasei Corporation, drum rotation speed: 20 rotations/min, spray pressure: 0.15 Pa). APR (registered trademark) cleaning agent type W-6 (manufactured by Asahi Kasei Corporation) capable of emulsifying a photosensitive resin composition: 4.5% by mass, antifoaming agent SH-4 (silicone mixture, Asahi Kasei Corporation) ): 0.18% by mass was prepared as a developer, and development was performed at a solution temperature of 40° C. and a development time of 20 minutes.
After development, the film was washed with tap water to the extent that bubbles caused by the developer were removed.
<3: Post-exposure process>
Exposure was performed using an underwater exposure method using an AL-200UP model post-exposure machine (manufactured by Asahi Kasei Corporation) equipped with both an ultraviolet fluorescent lamp and a germicidal lamp. Exposure was carried out at an exposure time such that the amount of light irradiated from each light source was 960 mJ/cm ² for an ultraviolet fluorescent lamp and 1920 mJ/cm ² for a germicidal lamp on the surface of the cured product of the photosensitive resin composition.
<4: Drying process>
Using ALF-DRYER (manufactured by Asahi Kasei Corporation), the cured plate after post-exposure was dried for about 30 minutes or more until the moisture on the surface disappeared, to obtain a flexographic printing plate.
<5: Measurement of change rate of independent line width of 500 μm>
A 500 μm independent line made from a plate was immersed under the same conditions as described above ((1) Method for measuring swelling ratio).
Thereafter, the sample was taken out, and the rate of change in line width before and after dipping was calculated.

Regarding the value of the change rate of 500 μm width before and after swelling, it is practically preferable that it is less than 20% because if it changes by more than 20%, it will adversely affect printing quality such as thickening and deformation of the pattern during printing. Evaluated by.
〇: Rate of change is less than 20% ×: Rate of change is 20% or more

((4) Hardness (Shore A hardness) measurement method)
A flexographic printing plate (thickness: 2.84 mm) having a solid surface was prepared in the same manner as described above ((3) Method for measuring change rate of 500 μm independent line width before and after swelling).
After leaving the prepared flexographic printing plate in a constant temperature and humidity chamber at a temperature of 23°C and a relative humidity of 50% for one day, it was placed in a JIS constant pressure loader GS-710 (manufactured by Techlock Co., Ltd., durometer GS-719G ASTM: D2240A, JIS :K6253A, ISO:7619A), Shore A hardness was measured. The value after 15 seconds of applying a load (mass 1 kg) to the solid surface was defined as Shore A hardness.
If the flexographic printing plate is too hard, a printed matter with a uniform solid surface cannot be obtained. Therefore, it is practically preferable that the Shore A hardness of the flexographic printing plate is 50° or less, and the evaluation was made according to the following criteria.
<Evaluation criteria>
〇: 50° or less ×: More than 50°

((5) Measuring method of notch crack resistance)
A flexographic printing plate (thickness: 2.84 mm) having a solid surface was prepared in the same manner as described above ((3) Method for measuring change rate of 500 μm independent line width before and after swelling).
Three strip-shaped sample plates with a width of 2 cm and a length of 5 cm were cut out from the solid surface area, and a cut line (notch) with a depth of 1.0 mm was made in the center portion in the length direction using a cutter to prepare the sample plates.
The sample plate was left in a constant temperature and humidity chamber at a temperature of 23° C. and a relative humidity of 50% for one day, and measurements were carried out in the same chamber by the following operations.
Curve both lengthwise ends of the sample plate slightly so that the notches are on the outside, and lightly pinch them with the fingers of one hand. The sample plate was supported by placing the fingers of the other hand on the support so that the body was bent directly below the notch, and quickly folding the sample plate to maintain the shape in which the supports were in close contact with each other. The time from the moment the sample plate was bent until the crack generated from the notch reached the support was measured in seconds.
Flexographic printing plates are sometimes bent when attached to a plate cylinder or when packaged. If there are minute scratches at that time, there is a risk that the flexographic printing plate will crack and the resin will completely break. In order to prevent this, it is practically preferable that the notch cracking resistance is 5 seconds or more, and was evaluated based on the following criteria.
<Evaluation criteria>
〇: More than 5 seconds ×: Less than 5 seconds

((6) Print quality evaluation)
A flexographic printing plate having 500 μm independent lines was prepared in the same manner as (3) Method for measuring the rate of change in the width of 500 μm independent lines before and after swelling, and printing was performed using this flexographic printing plate, Print quality was evaluated.
The printing machine used was "FlexPress 16S" (manufactured by Fischer & Krecke, Germany, trademark).
As the ink, an alignment film "SE-130" (manufactured by Nissan Chemical Co., Ltd.) was used.
A milky white polyethylene film with a thickness of 45 μm was used as the printing medium.
The number of lines of the anilox roll was 900 (lpi), and the cell volume of the anilox roll was 4 cc.
The printing speed was 200 m/min.

Printing evaluations were performed with the flexographic printing plate not immersed in NMP and with the flexographic printing plate immersed in N-methyl-2-pyrrolidone (NMP) for 24 hours. Obtained.
The rate of change in line width of printed matter printed using the flexographic printing plate at the initial stage and after dipping was measured using a microscope, and the rate of change was calculated.

When printing an alignment film for a liquid crystal display device using a flexographic printing plate, if the printing quality of the alignment film varies, it will lead to defects in the liquid crystal display device. The value of the 500 μm width change rate was evaluated as follows, assuming that it is practically preferable to be within ±30%.
〇: Within ±30% ×: Over ±30%.

The measurement results and evaluation results described above are shown in Tables 2 to 5.

In Examples 1 to 11, flexographic printing plates showing high flexibility were obtained.
In Examples 1 to 11, excellent solvent resistance was obtained.

The photosensitive resin composition of the present invention has industrial applicability in the field of flexographic printing plate production.

Claims (10)

A photosensitive resin composition in which a cured product of light having a wavelength of 360 nm satisfies the following <Condition 1> and <Condition 2>.
<Condition 1>
The elongation at break is 250% or more when a dumbbell-shaped test piece with a measuring part of 1 mm thick, 30 mm long, and 3 mm wide is subjected to a tensile test at 23° C. at a speed of 500 mm/min.
<Condition 2>
The mass increase rate when immersed in N-methyl-2-pyrrolidone (NMP) or γ-butyrolactone for 24 hours is 25% by mass or less. The photosensitive resin composition contains a polyurethane prepolymer.
The photosensitive resin composition according to claim 1. the polyurethane prepolymer has a hydrogenated polybutadiene structure;
The photosensitive resin composition according to claim 2. base material and
The photosensitive resin composition according to claim 1,
A flexographic printing original plate having. base material and
A cured product of light containing a wavelength of 360 nm of the photosensitive resin composition according to claim 1,
has,
The cured product has a breaking elongation of 250% or more under <Condition 1>, and an increase in mass when immersed in N-methyl-2-pyrrolidone or γ-butyrolactone for 24 hours under <Condition 2>. A flexographic printing plate having a ratio of 25% by mass or less. A step of irradiating the photosensitive resin composition according to claim 1 with light having a wavelength of 360 nm,
Method for producing cured product. Laminating the photosensitive resin composition according to claim 1 on a base material to obtain a flexographic printing original plate;
irradiating the flexographic printing original plate with light containing light with a wavelength of 360 nm to photocure the photosensitive resin composition;
a developing step of removing unexposed areas in the photocuring;
A method for producing a flexographic printing plate having the following. A step of manufacturing a flexographic printing plate by the method for manufacturing a flexographic printing plate according to claim 7;
an ink adhesion step of adhering ink to the flexographic printing plate;
a transfer step of transferring the ink;
A printing method having. A method of printing a liquid crystal alignment film used in the manufacture of liquid crystal display elements,
The printing method according to claim 8. The ink contains N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone, 1,2-dimethyl-2-imidazolidinone, γ-butyrolactone (GBL), γ-butyrolactam, N,N- Dimethylformamide, N,N-dimethylacetamide, 4-hydroxy-4-methyl-2-pentanone, butyl lactate, butyl acetate, methylmethoxypropionate, ethyl ethoxypropionate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol selected from the group consisting of monomethyl ether acetate, diethylene glycol monoethyl ether acetate, isoamyl propionate, isoamyl isobutyrate, diisopentyl ether, ethylene carbonate, propylene carbonate, cyclohexane, 1-octanol, ethylene glycol monobutyl ether, and tetrahydrofuran , containing one or more solvents,
The printing method according to claim 8.