JP2015021098A - Butadiene oligomer having hydroxyl groups at both ends, flexographic printing plate, and liquid crystal alignment layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a butadiene oligomer having hydroxyl groups at both ends, in which only a low molecular weight component is favorably removed at a high percentage without varying a molecular weight, and to provide a flexographic printing plate comprising the butadiene oligomer having hydroxyl groups at both ends, and a liquid crystal alignment layer formed by flexographic printing using the above flexographic printing plate.SOLUTION: The butadiene oligomer having hydroxyl groups at both ends is obtained by removing a low molecular weight component from a raw material oligomer through steps of stirring the raw material with a solvent without heating, leaving the material to stand so as to separate a supernatant, and decanting. The flexographic printing plate is manufactured by using the butadiene oligomer having hydroxyl groups at both ends as a start material. The liquid crystal alignment layer is formed by flexographic printing using the above flexographic printing plate.

Description

  The present invention relates to a both-end hydroxyl group butadiene oligomer, a flexographic printing plate formed using the both-end hydroxyl group butadiene oligomer, and a liquid crystal alignment film formed by flexographic printing using the flexographic printing plate.

In order to form a liquid crystal alignment film on an electrode formation surface of a substrate for a liquid crystal panel, it has been studied to use a printing method, particularly a flexographic printing method.
Flexographic printing plate for liquid crystal alignment film formation is, for example, roughened after photopolymerization by irradiating ultraviolet rays in a state of being sandwiched in layers so as to have a constant thickness between a reinforcing sheet and a roughened sheet By peeling the sheet, it is formed into a sheet shape or the like with one side (printing surface) roughened (Patent Document 1 etc.).

As the photosensitive resin composition, for example, a prepolymer having a 1,2-butadiene structure and having an ethylenic double bond at the terminal and an ethylenically unsaturated monomer, a photopolymerization initiator, etc. Is used.
The prepolymer is synthesized, for example, by reacting a hydroxyl-butadiene oligomer at both terminals with tolylene diisocyanate, 2-hydroxypropyl (meth) acrylate, or the like.

The liquid crystal alignment film is required to be as thin as possible, free from pinholes, and thin.
However, with the recent demand for higher definition and higher functionality of liquid crystal panels, the ink for alignment films containing a highly soluble solvent is being developed from the conventional photosensitive resin composition described above. When the liquid crystal alignment film is formed by flexographic printing in combination with the flexographic printing plate, the thickness of the liquid crystal alignment film and pinholes may be generated, or the flexographic printing plate may be worn in a short period of time when printing is repeated. There is a problem.

According to the inventor's investigation, the cause of these problems lies in the low molecular weight component contained in the both-end hydroxyl group butadiene oligomer.
That is, when flexographic printing is performed, low molecular weight components ooze into the ink and change the composition of the ink, so that unevenness in thickness and pinholes are likely to occur in the liquid crystal alignment film.
Further, a flexographic printing plate from which a low molecular weight component has oozed out is likely to be worn out in a short period of time because it swells and decreases in strength when printing is repeated.

It is conceivable to remove such low molecular weight components by heating distillation.
However, in such a case, the molecular chain of both-end hydroxyl group butadiene oligomers may be cleaved due to the effect of heating, resulting in a decrease in molecular weight, or the substitution rate of hydroxyl groups as functional groups may vary.
And when using both-end hydroxylated butadiene oligomers that cause these problems, prepolymers cannot be synthesized, or even if they can be synthesized, their molecular weight is small, so that flexographic printing plates having predetermined printing characteristics can be formed. The problem that it does not occur.

JP 2009-34913 A

An object of the present invention is to provide a both-end hydroxyl group butadiene oligomer from which only a low molecular weight component is well removed at a high rate without changing the molecular weight or the like.
Another object of the present invention is to provide a flexographic printing plate comprising such a hydroxyl-terminated butadiene oligomer at both ends, having a predetermined printing property, and that does not affect the liquid crystal alignment film to be formed or wear itself at an early stage. is there.

  It is another object of the present invention to provide a liquid crystal alignment film formed by flexographic printing using such a flexographic printing plate and having a uniform thickness and no pinholes.

  In the present invention, a low molecular weight component and a raw material oligomer containing both-end hydroxyl butadiene oligomers are added with a solvent having a higher solubility for the low-molecular weight components than the both-end hydroxyl butadiene oligomers, and then left to stand. A butadiene oligomer having a hydroxyl group at both ends, wherein the low molecular weight component is removed by decantation of the separated supernatant.

The present invention also provides a flexographic printing plate formed using the both-end hydroxyl group butadiene oligomer of the present invention.
Furthermore, the present invention is a liquid crystal alignment film formed by flexographic printing using the flexographic printing plate of the present invention.
According to the present invention, the low molecular weight component has a high rate without changing the molecular weight or the like by going through each step of stirring with a solvent without heating, separation by standing, and decantation treatment. Thus, it is possible to obtain a hydroxyl group butadiene oligomer having both ends removed well.

That is, the low molecular weight component is selectively eluted from the raw material oligomer into the solvent through the separation process by stirring and standing, and the low molecular weight component is removed together with the solvent by decantation treatment. Can do.
Therefore, by using the hydroxylated butadiene oligomers at both ends after treatment, it is possible to obtain a flexographic printing plate that has predetermined printing characteristics, does not affect the liquid crystal alignment film to be formed, and does not wear itself at an early stage. Can do.

  Furthermore, by using such a flexographic printing plate, a liquid crystal alignment film having a uniform thickness and no pinholes can be obtained.

According to the present invention, it is possible to obtain a both-end hydroxyl group butadiene oligomer from which only a low molecular weight component is well removed at a high rate without changing the molecular weight or the like.
Further, according to the present invention, it is possible to obtain a flexographic printing plate comprising such a both-end hydroxyl group butadiene oligomer, which has a predetermined printing characteristic and does not affect the liquid crystal alignment film to be formed or wear itself at an early stage. Can do.

  Furthermore, according to the present invention, it is possible to obtain a liquid crystal alignment film which is formed by flexographic printing using such a flexographic printing plate and has a uniform thickness and no pinholes.

In Example 1 of this invention, it is a graph which shows distribution of the molecular weight of the raw material oligomer before removing a low molecular weight component. In Example 1, it is a graph which shows distribution of the molecular weight of the both-ends hydroxyl group butadiene oligomer after removing a low molecular weight component.

<Both-terminal hydroxyl butadiene oligomer>
The both-end hydroxyl butadiene oligomer of the present invention was stirred by adding a solvent having higher solubility to the low-molecular weight component than the both-end hydroxyl butadiene oligomer to the raw material oligomer containing the low-molecular weight component and both-end hydroxyl butadiene oligomer. Thereafter, the low molecular weight component is removed by decantation of the supernatant liquid which has been allowed to stand and separated.

According to the present invention, the low molecular weight component has a high rate without changing the molecular weight or the like by going through each step of stirring with a solvent without heating, separation by standing, and decantation treatment. Thus, it is possible to obtain a hydroxyl group butadiene oligomer having both ends removed well.
Considering the molecular weight of the prepolymer to be synthesized and the printing characteristics of the flexographic printing plate to be formed, it is preferable to use a raw material oligomer having a number average molecular weight Mn of 2000 or more and 4000 or less.

Further, examples of the low molecular weight component to be removed include a component having a number average molecular weight Mn of 1200 or less, which easily causes the above-described bleeding into the ink. The lower limit of the low molecular weight component is not particularly limited, and even the minimum component contained in the raw material oligomer can be removed.
In the present invention, since the difference in solubility of the solvent with respect to both-end hydroxyl group butadiene oligomers and low molecular weight components is used, the both-end hydroxyl group butadiene oligomers are partially dissolved in the solvent while the saturation concentration is low, Further, the solvent may be dissolved in the both-end hydroxyl group butadiene oligomer.

If the amount of both-end hydroxyl butadiene oligomers dissolved in the solvent is large, the yield of both-end hydroxyl butadiene oligomers after treatment decreases, resulting in a large material loss and the amount of solvent dissolved in both-end hydroxyl butadiene oligomers. If the amount is large, energy, time, cost and the like required for solvent removal may increase.
Therefore, the selection of the solvent is important. In other words, in consideration of compatibility with both-end hydroxyl group butadiene oligomers and low molecular weight components, a solvent capable of minimizing the dissolution of both-end hydroxyl group butadiene oligomers in the solvent and the solvent into the both-end hydroxyl group butadiene oligomers is minimized. It is preferable to select. Further, by selecting a solvent, it is possible to adjust the removal rate of the low molecular weight component and the recovery efficiency (time, removal rate, material loss, energy required for solvent removal, etc.) of both-end hydroxyl group butadiene oligomers.

For example, as described above, when the number average molecular weight of the raw material oligomer is 2000 or more and 4000 or less and the low molecular weight component to be removed is a component having a number average molecular weight of 1200 or less, considering compatibility with both components As the solvent, at least one kind such as isopropanol (boiling point: 82.4 ° C.), methyl ethyl ketone (boiling point: 79.5 ° C.) is preferable.
Although the addition amount of the solvent can be arbitrarily set, for example, it is preferably 200 parts by mass or more and preferably 300 parts by mass or less per 100 parts by mass of the raw material oligomer.

If the addition amount is less than this range, it is difficult to stir uniformly with the raw material oligomer, and therefore there is a possibility that the low molecular weight component cannot be efficiently eluted in the solvent. Moreover, when the addition amount exceeds the range, the energy required for removing the solvent may increase.
Stirring is preferably carried out at room temperature (5-35 ° C.), but it is carried out by heating to a temperature below the boiling point of the solvent and in the range of, for example, 60 ° C. May be.

The stirring time is preferably 0.5 hours or more and 1.5 hours or less.
If the stirring time is less than this range, the low molecular weight component may not be efficiently eluted in the solvent. In addition, even if the stirring time exceeds the range, not only the effect is not obtained, but also the productivity of the both-end hydroxyl group butadiene oligomer may be lowered.
Separation of the solvent by standing after stirring is preferably carried out at room temperature.

The standing time is preferably 1.5 hours or more and 2.5 hours or less.
If the standing time is less than this range, the solvent may not be sufficiently separated from the hydroxyl-butadiene oligomers at both ends. Moreover, even if the standing time exceeds the range, not only a further effect cannot be obtained, but the productivity of the both-end hydroxyl group butadiene oligomers may be lowered.
Next, the supernatant liquid separated by standing is removed by decantation treatment.

The decantation treatment is preferably performed at room temperature.
In the present invention, the steps of stirring with the solvent, separation by standing, and decantation treatment described above may be performed only once, but considering that the removal efficiency of low molecular weight components is improved. These steps are preferably repeated twice or more.
However, the number of repetitions is preferably 3 or less. If the number of repetitions exceeds the range, not only the effect is not obtained, but also the productivity of the hydroxyl-butadiene oligomers at both ends may be lowered.

In the present invention, the solvent remaining in the both-terminal hydroxyl butadiene oligomers may be removed by, for example, distillation under reduced pressure while stirring the both-end hydroxyl butadiene oligomers after removing the solvent by decantation treatment. . By removing under reduced pressure, it is possible to efficiently remove the solvent remaining in the both-end hydroxyl group butadiene oligomer after the treatment.
The vacuum removal may be carried out at room temperature, but considering the improvement of the removal efficiency, for example, near the boiling point of the solvent and does not cause the fluctuation of the molecular weight described above, for example, 75 ° C. or higher, 85 ° C. It is preferable to carry out the heating in the following range.

The degree of decompression at the time of removing the reduced pressure, the processing time, etc. can be arbitrarily set.
<Flexographic printing plate>
The flexographic printing plate of the present invention can be formed in the same manner as in the prior art except that the both-end hydroxyl group butadiene oligomer from which the low molecular weight component has been removed through the above-described steps is used as a starting material.
That is, using a hydroxyl-butadiene oligomer at both ends as a starting material, a prepolymer having a 1,2-butadiene structure and having an ethylenic double bond at the end is synthesized, and an ethylenically unsaturated monomer and photopolymerization are started on the prepolymer. A photosensitive resin composition is prepared by blending an agent and the like.

Next, in the case of a flexographic printing plate for forming a liquid crystal alignment film, the photosensitive resin composition is placed in a layered state so as to have a constant thickness between, for example, a reinforcing sheet and a roughened sheet, and then an ultraviolet ray. Can be formed into a sheet shape with one surface (printed surface) roughened by peeling the roughened sheet after photopolymerization.
(Prepolymer synthesis)
As a method for synthesizing a prepolymer using a hydroxyl-butadiene oligomer at both ends from which low molecular weight components have been removed, for example,
(a) A hydroxyl group at both ends of a butadiene oligomer at both ends is reacted with a diisocyanate in advance to introduce a terminal diisocyanate group, to which an ethylenic double bond and an active hydrogen group (active hydrogen is added). And a compound comprising a group containing
(b) A method in which a carboxyl group is introduced into the terminal of both-end hydroxyl group butadiene oligomer, and an epoxy compound having an ethylenic double bond is reacted therewith,
Etc. Of these, the method (a) is preferred.

  Among the methods of (a), the reaction of synthesizing a prepolymer by introducing an ethylenic double bond using a urethanation reaction between a terminal diisocyanate group and a group having active hydrogen is a tertiary amine or It can be carried out in the presence of a urethanization catalyst such as a tin compound. However, the reaction can also be carried out under conditions in which no urethanization catalyst is present. Although reaction temperature is not specifically limited, It is preferable that it is 40 degreeC or more, and it is preferable that it is 100 degrees C or less. In that case, it is preferable that a suitable polymerization inhibitor is present.

Examples of the diisocyanate that forms the terminal diisocyanate group include one or more of aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates.
Specific examples of the diisocyanate include hexamethylene diisocyanate (HMDI), ω, ω′-diisocyanate-1,3-dimethylbenzole, 2,6- and / or 2,4-tolylene diisocyanate. Narate (2,6- and / or 2,4-TDI), paraphenylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate (MDI), hydrogenated 2,6- and / or 2,4-TDI , Hydrogenated MDI, dicyclohexyldimethylmethane diisocyanate, lysine isocyanate and the like.

Examples of the compound containing an ethylenic double bond and an active hydrogen group include hydroxyalkylene (meth) acrylate, polyalkylene glycol mono (meth) acrylate, secondary aminoalkylene (meth) acrylate, N-monosubstituted acrylamide, and unsaturated. 1 type, or 2 or more types, such as carboxylic acid, is mentioned.
Specific examples of such compounds include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polybutylene glycol mono ( (Meth) acrylate, trimethylolpropane di (meth) acrylate, trimethylolethane di (meth) acrylate, tetramethylolmethane tri (meth) acrylate, dibromoneopentyl glycol mono (meth) acrylate, glycerin di (meth) acrylate, hydroxy Cyclohexyl (meth) acrylate, monomethylaminoethyl (meth) acrylate, monomethylaminoethyl (meth) acrylate, N-methyl (meth) acrylami , N- octyl (meth) acrylamide, acrylic acid, methacrylic acid, itaconic acid monoester, fumaric acid monoester, maleic acid mono-esters, one or more of such glycidyl (meth) acrylate.

What is necessary is just to set the mixture ratio of a both-ends hydroxyl-butadiene oligomer and diisocyanate so that the equivalent of the hydroxyl group of a both-ends hydroxyl-butadiene oligomer and the equivalent of the diisocyanate group of a diisocyanate may be set to about 1: 2.
Moreover, what is necessary is just to set the mixture ratio of the compound containing an ethylenic double bond and an active hydrogen group so that the equivalent of the terminal isocyanate group of the previous reaction product and the equivalent of an active hydrogen group may become substantially equal.

The average molecular weight of the prepolymer to be synthesized is preferably 5000 or more and preferably 30000 or less in terms of number average molecular weight Mn.
If the number average molecular weight Mn is less than this range, the rubber elasticity of the flexographic printing plate may be insufficient. In addition, when exceeding the range, the viscosity of the photosensitive resin composition is increased, the fluidity of the liquid photosensitive resin composition, the processability is reduced, the developability is reduced, and the plate making Workability may be reduced.

(Ethylenically unsaturated monomer)
The ethylenically unsaturated monomer that forms the photosensitive resin composition together with the prepolymer functions as a crosslinking agent that crosslinks the prepolymer. Examples of the ethylenically unsaturated monomer include vinyl pyridine, N-vinylcarbazole, (meth) acrylic acid or its ester, (meth) acrylamide or its derivative, styrene, vinyl toluene, divinylbenzene, diallyl phthalate, triacryl cyanurate, vinyl acetate, acrylonitrile, itaconic acid, fumaric acid, maleic One type or two or more types such as acid anhydride, maleic acid, and mono- or dialkyl ester of these acids may be mentioned.

  Examples of the esters of (meth) acrylic acid include mono (meth) acrylates of alkyl, cycloalkyl, tetrahydrofurfuryl, allyl, glycidyl, and hydroxyalkyl, mono- or di (meth) acrylates of alkylene glycol and polyoxyalkylene glycol ( For example, polypropylene glycol dimethacrylate, etc.), trimethylolpropan mono, di or tri (meth) acrylate, pentaerythritol mono, di, tri or tetra (meth) acrylate, or the like.

Further, examples of (meth) acrylamide derivatives include one or more of N-methylol (meth) acrylamide, N, N′-alkylenebis (meth) acrylamide, diacetone (meth) acrylamide, and the like.
Further, mono (meth) acrylates of monohydric alcohols having 8 to 30 carbon atoms such as octyl, capryl, nonyl, decyl, lauryl, ceryl, etc. (for example, lauryl methacrylate), 1,3-butanediol, 1,8-octanediol, Mono- or di (meth) acrylates of dihydric alcohols having 4 to 30 carbon atoms such as 1,9-nonanediol, 1,10-decanediol, 1,18-stearlanediol (for example, 1,3-butanediol diester) Methacrylate) is particularly effective in improving the solvent resistance of flexographic printing plates.

The ethylenically unsaturated monomers are preferably used in combination of two or more depending on the printing characteristics required for the flexographic printing plate.
An ethylenically unsaturated monomer can be mix | blended in the ratio of 5 to 100 mass parts with respect to 100 mass parts of prepolymers. In particular, considering the workability of the plate making and the printing characteristics of the flexographic printing plate, etc., it is preferably blended at a ratio of 40 parts by mass or more and 60 parts by mass or less. This blending ratio is the ratio of the total amount to 100 parts by mass of the prepolymer when two or more ethylenically unsaturated monomers are used in combination.

(Photopolymerization initiator)
As the photopolymerization initiator, benzoin alkyl ether is used. Examples of the benzoin alkyl ether include one or more of benzoin ethyl ether, benzoin-n-propyl ether, benzoin isobutyl ether, and the like.
A photoinitiator can be mix | blended in the ratio of 0.001 mass% or more and 10 mass% or less of the total amount of a prepolymer and an ethylenically unsaturated monomer. In particular, in order to obtain an optimum photosensitivity for making a flexographic printing plate, it is preferable to blend at a ratio of 0.01% by mass or more and 5% by mass or less even within this range.

(Thermal polymerization inhibitor)
You may mix | blend a thermal-polymerization inhibitor with the photosensitive resin composition.
The thermal polymerization inhibitor may be blended at the same time when the components constituting the photosensitive resin composition are mixed, but it is blended in advance with each component before mixing, in particular with the prepolymer or the ethylenically unsaturated monomer. You may keep it.

Examples of thermal polymerization inhibitors include hydroquinone or derivatives thereof, benzoquinone, 2,5-diphenyl-p-benzoquinone, picric acid, di-p-fluorophenylamine, p-methoxyphenol, 2,6-di-tert-butyl. 1 type, or 2 or more types, such as -p-cresol, is mentioned.
These thermal polymerization inhibitors are desirably those that prevent the thermal polymerization reaction (dark reaction) without affecting the photocrosslinking reaction. Hydroquinone or a derivative thereof is preferably used as the thermal polymerization inhibitor having excellent effects.

Examples of hydroquinone derivatives include compounds in which 1 to 4 alkyl groups are substituted on the six-membered ring that is the central skeleton of hydroquinone, such as methylhydroquinone and mono-tert-butylhydroquinone.
However, such hydroquinone or a derivative thereof is easily yellowed by reaction with visible light from a fluorescent lamp or the like, and can cause yellowing of a flexographic printing plate in a short period of time.

Therefore, when hydroquinone or a derivative thereof is blended as the thermal polymerization inhibitor, the blending ratio is preferably set to 10 ppm or more and 40 ppm or less of the total amount of the photosensitive resin composition.
If the blending ratio is less than this range, there is a possibility that the effect of preventing the start of the thermal polymerization reaction due to the thermal history and improving the storage stability by blending the thermal polymerization inhibitor may not be sufficiently obtained, and exceeds the range. In some cases, the flexographic printing plate may easily turn yellow in a short period of time.

(Other)
Various additives may be added to the photosensitive resin composition in order to adjust its viscosity, rubber elasticity, strength, solvent resistance, weather resistance, etc. of the flexographic printing plate.
Examples of the additive include softeners such as dioctyl phthalate, process oil, liquid paraffin, liquid rubbers (butyl rubber, butadiene rubber, styrene butadiene rubber, nitrile rubber, etc.), antioxidants, and the like.

The photosensitive resin composition can be cured by light having a wavelength of 200 nm to 700 nm. The photosensitive resin composition is supplied in various states such as liquid, sheet, or plate.
(Formation of flexographic printing plates)
In order to form a flexographic printing plate for forming a liquid crystal alignment film using a liquid photosensitive resin composition, the same process as in the prior art can be employed.

That is, as described above, the liquid photosensitive resin composition is photopolymerized by irradiating with ultraviolet rays in a state where it is sandwiched between the reinforcing sheet and the roughened sheet so as to have a constant thickness, for example. After the roughening sheet is peeled off, a sheet-like flexographic printing plate having one surface (printing surface) roughened is formed.
In addition, when forming a flexographic printing plate with a predetermined printing pattern on the printing surface, the negative or positive film corresponding to the printing pattern is irradiated with ultraviolet rays, or the printing pattern is directly supported by scanning with laser light. Then, the image area is selectively cured by irradiating with ultraviolet rays.

  Next, for example, development is performed using an organic solvent such as n-hexane, kerosene, benzene, toluene, trichrene, parkrene, chlorocene, acetone, methyl ethyl ketone, ethyl acetate, or an aqueous surfactant as a developer to remove non-image areas. Then, after drying and further post-exposure as necessary, a flexographic printing plate having a predetermined printing pattern formed on the printing surface is formed.

<Liquid crystal alignment film>
The liquid crystal alignment film of the present invention is formed by flexographic printing using the flexographic printing plate of the present invention.
For example, a transparent electrode layer corresponding to a predetermined matrix pattern or the like is formed on one surface of a transparent substrate such as a soda lime glass substrate, and a liquid crystal alignment film is formed by flexographic printing using the flexographic printing plate of the present invention.

  Next, two transparent substrates on which such a liquid crystal alignment film is formed are prepared, the respective surfaces on which the liquid crystal alignment film is formed face each other, and the liquid crystal material is sandwiched between the transparent electrode layers in alignment. A liquid crystal panel is configured by forming a laminated body by being fixed to each other and further disposing polarizing plates on both outer sides of the laminated body as necessary.

The following examples and comparative examples were processed and measured under conditions of a temperature of 23 ° C. unless otherwise specified.
<Example 1>
250 parts by mass of isopropanol (IPA) is added to 100 parts by mass of a raw material oligomer (number average molecular weight Mn = 3000) containing both-end hydroxyl butadiene oligomers and low molecular weight components, and the mixture is stirred for 1 hour, and then allowed to stand for 2 hours. After separating the supernatant, a series of operations for removing the separated supernatant by decantation was repeated twice to obtain a both-end hydroxyl group butadiene oligomer from which low molecular weight components were removed.

Next, the both-end hydroxyl group butadiene oligomer after removing the supernatant was decompressed while being heated to 80 ° C. with stirring to remove the remaining solvent.
From the mass difference before and after the pressure reduction treatment, the amount of the solvent remaining in the both-end hydroxyl group butadiene oligomer before the pressure reduction treatment was determined to be 12% by mass.
Subsequently, the molecular weight distribution of the both-end hydroxyl group butadiene oligomer after the pressure reduction treatment was measured using a high-speed GPC apparatus [HLC (registered trademark) -8320 GPC manufactured by Tosoh Corporation]. The molecular weight distribution of untreated raw material oligomer was also measured under the same conditions. The measurement conditions were as follows: column: TSKgel H _HR , mobile phase: THF, standard material: polystyrene.

FIG. 1 shows the measurement result of the raw material oligomer, and FIG. 2 shows the measurement result of the both-end hydroxyl group butadiene oligomer after the treatment.
From FIG. 1 and FIG. 2, without changing the molecular weight of both-end hydroxyl butadiene oligomers through the steps of stirring with a solvent without heating, separation by standing, and decantation treatment. It was confirmed that only the low molecular weight component can be removed well at a high rate.

That is, from FIG. 1 and FIG. 2, the peak area ratio of the low molecular weight component having a number average molecular weight Mn of 1200 or less was determined, and the removal rate of the low molecular weight component was determined from both peak area ratios, and was 100%.
Further, when the peak area ratio between the low molecular weight component and the both-end hydroxyl group butadiene oligomer was determined from FIG. 2, the low molecular weight component was 0% and the both-end hydroxyl group butadiene oligomer (main component) was 100%.

Further, comparing the peaks of both-end hydroxyl group butadiene oligomers in FIGS. 1 and 2, it is confirmed that there is no change in both peaks, and that the molecular weight of the both-end hydroxyl group butadiene oligomer is not changed by the treatment for removing low molecular weight components. It was.
<Example 2>
Except having used the same amount of methyl ethyl ketone (MEK) as a solvent, the raw material oligomer was processed through the same process as Example 1, and the hydroxyl-butadiene oligomer of the both terminal was obtained.

From the difference in mass before and after the reduced pressure treatment in each step, the amount of the solvent remaining in the both-end hydroxyl butadiene oligomer before the reduced pressure treatment was 28% by mass.
Moreover, when the removal rate of the low molecular weight component was obtained from the result of measuring the molecular weight distribution under the same conditions as in Example 1 using a high-speed GPC apparatus, it was 83%, and the peak area ratio of the low molecular weight component and both-end hydroxyl group butadiene oligomers Had a low molecular weight component of 1% and a hydroxyl group butadiene oligomer (main component) at both ends of 99%.

Furthermore, when the peaks of both-end hydroxyl group butadiene oligomers were compared, it was confirmed that there was no change in both peaks, and that the molecular weight of the both-end hydroxyl group butadiene oligomers did not change due to the removal of the low molecular weight component.
<Comparative example 1>
Except that the same amount of tetrahydrofuran (THF) was used as a solvent, the raw material oligomer was processed through the same steps as in Example 1 to obtain a both-end hydroxyl group butadiene oligomer. As a result, separation by standing could not be performed, so the subsequent test was abandoned.

<Comparative example 2>
Untreated raw material oligomer was used as it was.
The removal rate of the low molecular weight component was determined from the result of measuring the molecular weight distribution under the same conditions as in Example 1 using a high-speed GPC apparatus. The peak area ratio of the low molecular weight component and the hydroxyl group butadiene oligomer at both ends was 0%. The low molecular weight component was 6%, and both terminal hydroxyl butadiene oligomers (main component) were 94%.

<Synthesis of prepolymer>
The both-end hydroxyl group butadiene oligomers of Examples 1 and 2 or the raw material oligomer of Comparative Example 2 are first reacted with TDI (a mixture of 2,6-TDI and 2,4-TDI), and then 2-hydroxypropyl methacrylate is added. Thus, a prepolymer having a 1,2-butadiene structure and having an ethylenic double bond at the terminal and having a number average molecular weight Mn = 15000 was synthesized.

  The blending ratio of each component was set so that the equivalent of the hydroxyl group of both-end hydroxyl group butadiene oligomer and the equivalent of the diisocyanate group of diisocyanate was 1: 2. In addition, the compounding ratio of the compound containing an ethylenic double bond and an active hydrogen group is such that the equivalent of the terminal isocyanate group of the reaction product of the both-end hydroxyl group butadiene oligomer and diisocyanate is approximately equal to the equivalent of the active hydrogen group. Was set to be.

<Preparation of photosensitive resin composition>
50 parts by mass of lauryl methacrylate, 1,3-butanediol dimethacrylate and polypropylene glycol dimethacrylate as ethylenically unsaturated monomers, and benzoin isobutyl ether as a photopolymerization initiator in 100 parts by mass of the synthesized prepolymer A photosensitive resin composition was prepared by blending 2.3 parts by mass.

<Curing sample>
The prepared photosensitive resin composition is sandwiched between two transparent flat plates held in parallel at an interval of 2 mm, and the photosensitive resin composition is photopolymerized by irradiation with ultraviolet rays through the transparent flat plate to obtain a thickness. A 2 mm flat cured sample was prepared, and the following characteristics were measured.
(50% modulus)
The produced cured sample is punched out to prepare a dumbbell-shaped test piece, and measurement using the dumbbell-shaped test piece is performed according to Japanese Industrial Standards JIS K6251: 2010 "Vulcanized rubber and thermoplastic rubber-Determination of tensile properties". A 50% modulus (MPa) was obtained by performing a tensile test according to the method.

(Shore A hardness)
The Shore A hardness (type A durometer hardness) of the prepared cured sample was determined using the Japanese Industrial Standard JIS K6253-3: 2006 "vulcanized rubber and thermoplastic rubber-Determination of hardness-Part 3: Durometer hardness" Measured according to the measurement method described.
(Swell rate)
After measuring the mass of the prepared cured sample, it was immersed in N-methyl-2-pyrrolidone maintained at a liquid temperature of 23 ° C. for 24 hours, pulled up and measured again. And formula (1):

The swelling rate (%) was determined by It can be said that the flexographic printing plate produced using the same photosensitive resin composition has a smaller decrease in strength due to swelling and is less likely to be worn in a short period as the swell ratio of the cured sample is smaller.
(Leakage of low molecular weight components)
The prepared cured sample was immersed in n-hexane as a liquid crystal alignment film ink model maintained at a liquid temperature of 23 ° C. for 4 hours, and then pulled up, and the concentration of the low molecular weight component exuded into n-hexane. (%) Was measured using a gas chromatograph mass spectrometer [GCMS-QP2010 SE manufactured by Shimadzu Corporation].

The flexographic printing plate produced using the same photosensitive resin composition has a smaller concentration of the low molecular weight component leached into the n-hexane from the cured sample. It can be said that changes are less likely to occur.
<Flexographic printing plate>
Reinforcing sheet [PET sheet, thickness 0.35 mm] and a roughened sheet [made by Okura Kogyo Co., Ltd.], which were held in parallel with an interval of 2 mm between the same photosensitive resin compositions used for the preparation of the cured sample In the state of being sandwiched in a layered form between CIRRON® (registered trademark) and arithmetic average roughness Ra: 1.0 to 1.5 μm], the surface-roughened sheet is peeled off after being photopolymerized by irradiating ultraviolet rays. Thus, a sheet-like flexographic printing plate for printing a liquid crystal alignment film having one surface (printing surface) roughened was prepared.

<Print quality>
The prepared flexographic printing plate is incorporated into a flexographic printing machine [model G2 manufactured by Nakan Techno Co., Ltd.] together with anilox roll # 400, and using this flexographic printing machine, a transparent electrode layer corresponding to a predetermined matrix pattern or the like on one side After the flexographic printing of the ink for the liquid crystal alignment film on the one surface of the glass substrate on which the (chromium vapor deposition film) was formed, the operation of drying and forming the liquid crystal alignment film was continuously performed 10,000 times.

The formed liquid crystal alignment film was visually observed as to whether or not thickness unevenness and pinholes were generated, and the print quality was evaluated according to the following criteria.
A: From the first sheet to the 10,000th sheet, there was no uneven thickness or pinholes in the liquid crystal alignment film.
○: Thickness unevenness and pinholes were observed in the liquid crystal alignment film from the first sheet, but they were resolved before the 150th sheet.

X: Thickness unevenness and pinholes were observed in the liquid crystal alignment film from the first sheet, and were not eliminated even after the 150th sheet.
<Abrasion of flexographic printing plates>
The ink remaining from the flexographic printing plate after 10,000 continuous printing was removed and dried to determine the mass. And equation (2):

Thus, the reduction rate (%) of the mass due to abrasion from the mass before continuous printing was determined, and the abrasion resistance of the flexographic printing plate was evaluated according to the following criteria.
A: The reduction rate was 0.05% or less.
◯: The reduction rate exceeded 0.05% and was 0.10% or less.
X: The reduction rate exceeded 0.10%.

<Comprehensive evaluation>
Based on the two evaluation results of the print quality test and the abrasion resistance of the flexographic printing plate, the flexographic printing plate was comprehensively evaluated according to the following criteria.
A: Both were A.
○: ○ and ◎, or both were ○.

X: Either one was x or both were x.
The results are shown in Table 1.

From the results of Examples 1 and 2 and Comparative Example 2 in Table 1, both of which are the main components by going through the steps of stirring with a solvent without heating, separation by standing, and decantation treatment. It has been found that only the low molecular weight component contained in the raw material oligomer can be satisfactorily removed at a high rate without changing the molecular weight or the like of the terminal hydroxyl butadiene oligomer.
However, from the results of Examples 1 and 2 and Comparative Example 1, in order to remove only the low molecular weight component from the both-end hydroxyl group butadiene oligomer through the above steps, the both-end hydroxyl group butadiene oligomer and the low molecular weight component On the other hand, it has been found preferable to select a solvent having an appropriate solubility difference.

  Furthermore, by using a hydroxyl-butadiene oligomer at both ends from which low molecular weight components have been removed, a flexographic printing plate that has the prescribed printing characteristics and does not affect the liquid crystal alignment film that is formed or wears itself at an early stage is formed. I found that I can do it.

Claims (7)

  A supernatant obtained by adding a solvent having a higher solubility for the low molecular weight component than the both-end hydroxyl group butadiene oligomer to the raw material oligomer containing the low-molecular weight component and the both-end hydroxyl group butadiene oligomer, stirring, and then allowing to stand and separate. A butadiene oligomer having a hydroxyl group at both ends, wherein the low molecular weight component is removed by decantation.   The both-end hydroxyl group butadiene oligomer according to claim 1, wherein the solvent remaining after the decantation treatment is removed under reduced pressure.   The both-end hydroxyl group butadiene oligomer according to claim 1, wherein the raw material oligomer has a number average molecular weight Mn of 2000 or more and 4000 or less.   4. The hydroxyl group-butadiene oligomer at both ends according to claim 1, wherein the low molecular weight component is a component having a number average molecular weight Mn of 1200 or less.   5. The both-terminal hydroxyl butadiene oligomer according to claim 1, wherein the solvent is at least one selected from the group consisting of isopropanol and methyl ethyl ketone.   A flexographic printing plate formed using the both-end hydroxyl group butadiene oligomer according to any one of claims 1 to 5.   A liquid crystal alignment film formed by flexographic printing using the flexographic printing plate according to claim 6.

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