JP2011252063A - Ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink for use in a reverse printing process with less safety issue, which has appropriate wettability and releasability to a surface of a silicone blanket, wherein: an ink layer having uniform thickness and causing no vertical stripes, unevenness and pinhole can be formed on the surface of the silicone blanket; and an ink pattern having uniform thickness can be formed on an object to be printed such as a substrate.SOLUTION: The ink comprises a binder resin, a colorant, and a solvent, wherein the solvent contains: ≤50 mass% of a low-tension solvent that has a surface tension at 25°C of ≤21 mN/m; and 0.01 to 10 mass% of a fluorine-based surfactant of the total quantity of the ink. The fluorine-based surfactant has solubility, at 23°C to 100g of the low-tension solvent, of ≤10g.

Description

  The present invention relates to an ink used in a so-called reverse printing method.

In order to manufacture the color filter or the like by forming a very fine ink pattern compared to the area of the substrate, such as a color filter constituting a liquid crystal display (LCD), on the almost entire surface of the substrate, a so-called photo filter is conventionally used. A forming method using a lithographic method has been adopted.
Recently, however, the printing method, particularly intaglio offset printing, is used in order to reduce the number of processes as much as possible, reduce the energy consumption, reduce the waste of materials used, and form a pattern with high productivity in a short time instead of the photolithographic method. The use of law is becoming widespread.

In the intaglio offset printing method, the ink filled in the concave portion of a plate (intaglio) having a concave portion corresponding to the ink pattern to be printed is transferred from the plate to the surface of the printing blanket, and then from the surface of the printing blanket. An ink pattern is formed on the surface of the substrate by retransferring it onto the surface of the substrate as the substrate.
However, the ink pattern formed on the surface of the substrate by the intaglio offset printing method tends to have a large variation in thickness. That is, in the intaglio offset printing method, as is apparent from the above-described process, the ink is transferred twice, and at each transfer, the ink is torn into the amount transferred to the transfer destination and the amount remaining at the transfer source. Since the ink is separated, the ink pattern that is finally transferred onto the surface of the substrate tends to have unevenness with a large difference in height as the separation trace, resulting in a large thickness variation.

Therefore, in order to form a color filter and the like that are required to be as uniform in thickness as possible in order to make the color density uniform within and between each pixel, it is reversed as a new printing method that replaces the intaglio offset printing method. A printing method has been developed (see Patent Documents 1-3).
In the reverse printing method, ink is supplied to substantially the entire surface of the printing blanket to form a solid ink layer, and the ink layer is formed on the surface of the plate having concave portions corresponding to a predetermined ink pattern on the surface. An ink layer corresponding to the recess was formed on the surface of the printing blanket by selectively removing it from the surface of the printing blanket by contacting and transferring the ink layer other than the recess to the surface of the plate. Then, the ink pattern is formed on the surface of the substrate by transferring the ink pattern to the surface of the substrate.

According to the reverse printing method, the number of times of ink transfer for forming the ink pattern can be reduced to one time at the time of transfer from the surface of the printing blanket to the surface of the substrate, so that compared with the conventional intaglio offset printing method. Thus, the height difference of the unevenness remaining on the surface of the ink pattern can be reduced, and the variation in thickness can be reduced.
As a printing blanket, a silicone blanket having at least a surface formed of silicone rubber is widely used. Since the silicone blanket is excellent in ink releasability, the transferability of the ink pattern from the surface to the surface of the substrate can be improved.

However, the surface of the silicone blanket has low ink wettability, and when the ink is applied to the entire surface of the silicone blanket at the beginning of the process to form an ink layer, the ink repellency is likely to occur. There is a problem that it is difficult to form an ink layer having a uniform thickness without unevenness or pinholes.
Therefore, it has been studied to reduce the surface tension of the ink in order to obtain an ink for reversal printing that has appropriate wettability and releasability with respect to the surface of the silicone blanket.

In addition, by reducing the surface tension of the ink, the so-called self-leveling effect is achieved between the formation of a solid ink layer on the surface of the silicone blanket and the drying and solidification of the ink pattern transferred to the surface of the substrate. Therefore, the effect of making the thickness of the ink pattern even more uniform is also expected.
In order to reduce the surface tension of the ink, for example, a solvent having a low surface tension such as n-hexane, isopropyl alcohol, or a fluorine-based solvent (hereinafter sometimes referred to as “low tension solvent”) is used alone, or It is conceivable to use in combination with other solvents or to further contain a surfactant such as a silicone-based surfactant or a fluorine-based surfactant (see Patent Documents 4 and 5, etc.).

JP-A-11-58921 JP-A-11-198337 JP 2000-289320 A JP 2005-126608 A JP 2005-128346 A

  However, a general low-tension solvent has low polarity and low solubility in a high-polar binder resin used in ink.In particular, the low-tension solvent is used alone, or in a combined system with other solvents, for example, When it is contained at a high ratio exceeding 50% by mass, the binder resin cannot be dissolved satisfactorily, and the solid content such as the binder resin tends to precipitate as foreign matter in the ink.

And, due to the deposited foreign matter, there is a problem that the solid ink layer formed on the surface of the silicone blanket is likely to have vertical stripes, or the shape of the ink pattern is likely to be disturbed due to the vertical stripes. is there.
That is, in the reverse printing method, for example, a slit having a width corresponding to the width of the ink layer to be formed and an interval corresponding to the thickness in order to form a solid ink layer by supplying ink to substantially the entire surface of the silicone blanket. It is common to use a slit die coater equipped with

While the silicone blanket is rotated at a constant speed, a predetermined amount of ink is continuously supplied to the surface through the slit of the slit die coater, so that a solid having a width and thickness corresponding to the width and interval of the slit is obtained. The ink layer is formed on the surface of the silicone blanket.
However, when foreign matter is deposited in the ink as described above, the foreign matter partially blocks the slit and prevents the ink supply by a part in the width direction of the slit, resulting in formation on the surface of the silicone blanket. Longitudinal streaks occur at positions in the width direction of the ink layer corresponding to the portions blocked by the foreign matter. In addition, the ink pattern shape is disturbed based on variations in the thickness of the ink layer due to vertical stripes.

In addition, many of the low-tension solvents have low boiling points or low flash points, and there is a risk of causing problems in terms of safety, especially when they are contained in large amounts in the ink.
Furthermore, since low-tension solvents with low boiling points tend to volatilize out of the ink, such volatilization causes vertical streaks and unevenness when forming an ink layer using the slit die coater or the like. As a result, there is a problem that the shape of the ink pattern is easily disturbed.

  That is, when an ink containing a large amount of a low-tension solvent having a low boiling point and a high volatility is used, the ink layer is formed using the slit die coater, etc. While repeating, drying of the ink due to volatilization of the low-tension solvent, and the solid content of the binder resin or the like in the ink is likely to precipitate as foreign matter in the ink, the deposited foreign matter partially clogs the slit, etc. As a result of hindering the supply of ink at a part in the width direction of the slit, a vertical stripe is generated at a position corresponding to the portion blocked by the foreign matter in the width direction of the ink layer formed on the surface of the silicone blanket.

Further, even if the foreign matter does not precipitate and the vertical stripes associated therewith, the ink layer is uneven due to the increase in the viscosity of the ink, or the ink pattern is changed based on the variation in the thickness of the ink layer due to the vertical stripes or unevenness. The shape may be disturbed.
On the other hand, when a surfactant is contained, the content of the low-tension solvent can be reduced to prevent the various problems from occurring.

As the surfactant, the fluorosurfactant is superior to the silicone surfactant in terms of the effect of reducing the surface tension of the ink.
However, according to the inventor's study, it is difficult to uniformly apply a conventional ink containing a fluorosurfactant to the surface of the silicone blanket, and there are no vertical stripes, unevenness, pinholes, etc. on the surface of the silicone blanket. It is not easy to form an ink layer having a uniform thickness and to form an ink pattern having a uniform thickness on the surface of the substrate.

  An object of the present invention is to form an ink layer having uniform wettability and releasability on the surface of the silicone blanket and having a uniform thickness without vertical stripes, unevenness, pinholes, etc. on the surface of the silicone blanket. Another object of the present invention is to provide an ink for a reversal printing method that can form an ink pattern having a uniform thickness on the surface of a substrate such as a substrate and that is less likely to cause safety problems.

  In the present invention, an ink layer formed on substantially the entire surface of a silicone blanket is brought into contact with the surface of a plate having a recess corresponding to a predetermined ink pattern on the surface, so that an ink layer other than the recess is formed on the surface of the plate. A reversal printing method in which the ink pattern corresponding to the concave portion is formed on the surface of the silicone blanket after being selectively removed from the surface of the silicone blanket by transferring, and then the ink pattern is printed on the surface of the substrate. Ink used in the above, including a binder resin, a colorant, and a solvent, the solvent contains a low-tensile solvent having a surface tension of 21 mN / m or less at 25 ° C. in a proportion of 50% by mass or less, 0.01% by mass of the total amount of the ink of fluorine-based surfactant having a solubility at 23 ° C. of 10 g or less in 100 g of the low-tension solvent. Or more, an ink which is characterized by containing in a proportion of 10 mass% or less.

In the ink for the reverse printing method, a solvent such as a low-tension solvent mainly functions to maintain the wettability of the ink with respect to the surface of the silicone blanket. The wettability of the fluorosurfactant itself to the surface of the silicone blanket is not as good as that of the solvent or the silicone surfactant. Rather it is the worse one.
In addition, as a fluorosurfactant, conventionally, in order to improve the uniformity of the ink, a surfactant that is well dissolved in the low-tension solvent contained in the ink and is uniformly dispersed in the ink is selected and used. It is common.

Therefore, the good wettability inherent to the solvent is hindered by the fluorosurfactant uniformly dispersed in the ink, and the wettability of the entire surface of the ink to the surface of the silicone blanket tends to decrease. is there.
In addition, as the name suggests, fluorosurfactants are used at the interface of the silicone blanket or substrate surface, or on the surface of the ink layer or ink pattern (ink liquid surface, that is, the interface with air). It functions to reduce the surface tension of the ink by increasing the activity, and if it is uniformly dispersed in the ink without being unevenly distributed at the interface, the fluorine-based surfactant is added to the ink. The effects (such as the self-leveling effect described above) due to lowering the surface tension will be insufficient.

Therefore, when a conventional ink is used, an ink layer having a uniform thickness without unevenness or pinholes cannot be formed on the surface of the silicone blanket. In addition, the ink layer thickness cannot be made uniform and the self-leveling effect cannot be sufficiently obtained, so that an ink pattern having a uniform thickness cannot be formed on the surface of the substrate.
On the other hand, in the ink of the present invention, as described above, as a fluorosurfactant, the surface tension at 25 ° C. contained in the ink at 25 ° C. with respect to 100 g of a low-tensile solvent of 21 mN / m or less. Since a fluorine-based surfactant having a solubility of 10 g or less and substantially insoluble in the low-tension solvent is selected and used, the fluorine-based surfactant is not uniformly dispersed in the ink. It is unevenly distributed.

Therefore, the wettability of the ink with respect to the surface of the silicone blanket will be governed by the solvent, suppressing the decrease in the wettability of the ink as a whole despite containing a fluorosurfactant, The state which has moderate wettability and mold release property with respect to the surface of a silicone blanket can be maintained.
In addition, the content of the low-strength solvent is reduced by the amount of the fluorine-based surfactant, and specifically, the problem is caused by vertical streaks and unevenness, or safety problems when the total amount of the solvent is suppressed to 50% by mass or less. Can also be suppressed.

Therefore, it is possible to form an ink layer having a uniform thickness without vertical stripes, unevenness, pinholes, etc. on the surface of the silicone blanket.
The fluorosurfactant is based on the low wettability described above, in the ink layer formed on the surface of the silicone blanket, and in the ink pattern formed from the ink layer, from the surface of the silicone blanket. It is unevenly distributed near the surface of the separated ink layer or ink pattern. Further, after the ink pattern is transferred to the surface of the substrate, it is unevenly distributed in the vicinity of the surface of the ink pattern away from the surface of the substrate.

Therefore, the surface tension of the ink can be satisfactorily lowered by the unevenly distributed fluorine-based surfactant, and the self-leveling effect described above can be effectively exhibited, and the thickness of the ink layer is made uniform as described above. In combination with this, an ink pattern having a uniform thickness can be formed on the surface of the substrate.
As the fluorine-based surfactant, those having a weight average molecular weight Mw of 6000 or more and 80000 or less are preferable.

Further, nonionic surfactants are preferred as the fluorine-based surfactant.
The surface tension at 25 ° C. of the ink of the present invention is preferably 22 mN / m or less, and the viscosity at 25 ° C. is preferably adjusted to 5 mPa · s or less.

  According to the present invention, the surface of the silicone blanket has appropriate wettability and releasability, and an ink layer having a uniform thickness without vertical stripes, unevenness, pinholes, etc. is formed on the surface of the silicone blanket. In addition, it is possible to provide an ink for a reversal printing method that can form an ink pattern having a uniform thickness on the surface of a substrate to be printed such as a substrate and that is less likely to cause safety problems.

  The ink of the present invention is used in a reversal printing method using a silicone blanket as a printing blanket, and includes a binder resin, a colorant, and a solvent, and the solvent has a surface tension of 21 mN / m or less at 25 ° C. The low-tension solvent is contained in a proportion of 50% by mass or less, and the fluorosurfactant having a solubility at 23 ° C. in 100 g of the low-tension solvent of 10 g or less is 0.01% in the total amount of the ink. % Or more and 10% by mass or less.

The reason why the solubility of the fluorosurfactant used in the ink of the present invention at 23 ° C. in 100 g of the low-tension solvent is limited to 10 g or less is as described above.
The solubility is preferably 0.5 g or more even within the above range. Fluorosurfactants whose solubility is less than the above range tend to aggregate excessively in the ink and become pinhole nuclei, which can easily cause pinholes in the ink layer and cause vertical stripes and unevenness. .

The solubility of the fluorosurfactant further effectively suppresses the occurrence of the above-mentioned various problems, and forms an ink layer having a uniform thickness without vertical stripes, unevenness, pinholes, etc. on the surface of the silicone blanket. Considering this, it is preferably 1 g or more even within the above range, and preferably 4 g or less.
In the present invention, the solubility of the fluorosurfactant is reduced by gradually dropping the fluorosurfactant while stirring 100 g of a low-tension solvent in an environment at a temperature of 23 ° C. It shall be expressed by the mass (g) of the fluorosurfactant that can be dripped before it becomes white turbid without dissolving in the tension solvent.

In the present invention, the reason why the content of the fluorosurfactant is limited to 0.01% by mass or more and 10% by mass or less in the total amount of the ink is as follows.
That is, when the content ratio of the fluorosurfactant is less than the above range, the effect of lowering the surface tension of the ink due to the inclusion of the fluorosurfactant cannot be obtained. An ink pattern with a uniform thickness cannot be formed.

  In addition, when a low-strength solvent is contained in a large amount exceeding the range of 50% by mass or less in order to make up for the shortage of the fluorosurfactant, the surface tension of the ink becomes too low, and the ink becomes a slit die coater. This causes a phenomenon called nozzle fouling that randomly spreads from the tip of the nozzle to the upper surface. Ink with moderate surface tension adheres to a certain width at the tip of the slit die coater and does not spread further, and there is no risk of dripping. In combination with the low surface tension of itself, a part thereof tends to drip on the coating surface as a droplet. Then, the dripping ink is mixed into the ink layer, so that the ink layer is easily disturbed.

On the other hand, when the content of the fluorosurfactant exceeds the above range, the excess fluorosurfactant inhibits the good wettability inherent to the solvent, and the silicone blanket as a whole of the ink As a result of the reduced wettability with respect to the surface, there is a possibility that an ink layer having a uniform thickness without unevenness or pinholes cannot be formed on the surface of the silicone blanket.
In addition, the excess fluorosurfactant remains in the ink pattern. For example, in the case of an LCD color filter, the adhesion of the ITO film or the alignment film laminated on the color filter is reduced, resulting in peeling. As a result, there is a risk that the production yield of the LCD may be lowered.

In consideration of more effectively suppressing the occurrence of these problems, the content ratio of the fluorosurfactant is preferably 0.3% by mass or more even within the above range, and is 8% by mass or less. Preferably there is.
The said content rate is a content rate which occupies in the total amount of ink of said 1 type of fluorosurfactant, and uses 2 or more types of fluorosurfactants, when a fluorosurfactant is used individually by 1 type When used in combination, it is the content ratio of the total amount in the total amount of ink.

The weight average molecular weight Mw of the fluorosurfactant is preferably 6000 or more, particularly 20000 or more, preferably 80,000 or less, particularly 60000 or less.
Since the low molecular weight fluorosurfactant having a weight average molecular weight Mw less than the above range has high solubility in a low tension solvent, the solubility at 23 ° C. in 100 g of the low tension solvent exceeds the range of 10 g or less, There is a possibility that the various problems described above may occur due to being uniformly dispersed in the ink.

On the other hand, a high molecular weight fluorosurfactant having a weight average molecular weight exceeding the above range has low solubility in a low-tensile solvent. There is a risk of agglomerating excessively to cause the various problems described above.
Further, nonionic surfactants are preferred as the fluorine-based surfactant.
When an anionic or cationic one is used as the fluorine-based surfactant, for example, in the case of an LCD color filter, if the surfactant is mixed in the liquid crystal, the alignment of the liquid crystal is affected, resulting in poor display. However, if it is a nonionic surfactant, such a problem does not occur.

In the present invention, the surface tension at 25 ° C. of the low-tensile solvent is limited to 21 mN / m or less for the following reason.
That is, when a low tension solvent having a surface tension exceeding the above range is used, the effect of reducing the surface tension of the ink and improving the wettability by the low tension solvent cannot be obtained. Therefore, when ink is applied to substantially the entire surface of the silicone blanket to form an ink layer, repellence or the like is likely to occur, and the repellency or the like tends to cause unevenness or pinholes in the ink layer.

The surface tension of the low-tension solvent is preferably 12 mN / m or more even within the above range.
If the surface tension is less than the above range, depending on the content ratio of the low-tension solvent or the type of other solvent to be combined, the ink wettability with the surface of the silicone blanket becomes too high, and the ink pattern is changed to the silicone pattern. The transfer from the blanket surface to the substrate surface cannot be performed well, and the shape of the transferred ink pattern may be disturbed.

Also, the ink wettability with respect to the slit die coater, etc. becomes high, and it becomes easy to adhere particularly near the slit. When the adhered ink dries and the binder resin or the like is deposited as a foreign substance and partially closes the slit, the ink layer There is a risk that vertical streaks will be generated, or the ink pattern may be disturbed by the vertical streaks.
In consideration of forming a good ink layer free of unevenness and pinholes on the surface of the silicone blanket and forming a good ink pattern free of shape disturbance on the surface of the substrate, the surface tension of the low tension solvent Is preferably 16 mN / m or less even within the above range.

In the present invention, the surface tension of the low-tensile solvent is represented by a value measured by the maximum bubble pressure method using a dynamic surface tension meter Theta t60 manufactured by Eihiro Seiki Co., Ltd. in an environment at a temperature of 25 ° C. .
Examples of the low-tension solvent satisfying the surface tension range include n-pentane (16.0 mN / m), n-hexane (18.4 mN / m), n-heptane (19.6 mN / m), and isopropyl alcohol. (20.8 mN / m), fluorine-based solvent, low molecular weight silicone oil (18 to 19 mN / m), and the like.

As the fluorine-based solvent, various fluorine-based solvents that contain fluorine atoms in the molecule and satisfy the above-described surface tension range can be used. Particularly, hydrofluoroethers that are excellent in the various effects and do not contain chlorine. And at least one selected from the group consisting of hydrofluorocarbons is preferred.
Examples of the hydrofluoroether satisfying such conditions include one or more of ethyl nonafluorobutyl ether (13.6 mN / m) and methyl nonafluorobutyl ether (13.6 mN / m). Examples of hydrofluoroethers include NOVEC (registered trademark) HFE-7200 (13.6 mN / m) manufactured by Sumitomo 3M Limited. HFE-7200 is a mixture of ethyl nonafluoroisobutyl ether and ethyl nonafluorobutyl ether, both of which are hydrofluoroethers.

Examples of the hydrofluorocarbons satisfying the above conditions include one or more of tridecafluoropentane (14.1 mN / m) and tridecafluorohexane (12.5 mN / m).
The reason why the content ratio of the low-tension solvent is limited to 50% by mass or less of the total amount of the solvent is as follows.

That is, when a low-tension solvent is contained in a large amount exceeding the above range, an ink layer having a uniform thickness without vertical stripes, unevenness, pinholes, etc. can be formed on the surface of the silicone blanket by the mechanism described above. Or a safety problem may occur when using a low-tension solvent other than a fluorinated solvent.
In addition, it is preferable that the content rate of a low tension solvent is 5 mass% or more also in the said range.

  When the content ratio is less than the above range, the effect of improving the wettability of the ink with respect to the surface of the silicone blanket by reducing the surface tension of the ink by containing the low-tension solvent cannot be obtained. Therefore, when ink is applied to substantially the entire surface of the silicone blanket to form an ink layer, repellence or the like is likely to occur, and the repellency or the like tends to cause unevenness or pinholes in the ink layer.

In consideration of forming a good ink layer free of vertical stripes, unevenness, pinholes, etc. on the surface of the silicone blanket and forming a good ink pattern free of shape irregularities on the surface of the substrate, a low tension solvent The content of is preferably 40% by mass or less even within the above range.
The content ratio is the content ratio of the one kind of low tension solvent in the total amount of the solvent when the low tension solvent is used alone, and when two or more kinds of the low tension solvent are used in combination, It is the content ratio of the total amount in the total amount of the solvent.

Examples of the binder resin include one or more of polyester resin, acrylic resin, ethyl cellulose, polyvinyl butyral, polyester melamine resin, melamine resin, epoxy melamine resin, phenol resin, polyimide resin, epoxy resin, and the like.
In view of improving the durability of color filters for LCDs in particular, the binder resin is preferably a binder resin having thermosetting properties, ultraviolet curable properties, photocuring properties, and the like.

Examples of the colorant include various pigments and dyes. In particular, in the case of a color filter for LCD, various organic and inorganic pigments are preferable in consideration of forming an ink pattern excellent in chemical resistance, heat resistance, weather resistance, light resistance and the like.
Examples of other solvents used in combination with the low-tensile solvent include various solvents that can dissolve the binder resin well to prevent precipitation.

  Examples of the other solvent include ethylene glycol monomethyl ether (also known as “methyl cellosolve” and “2-methoxyethanol”), ethylene glycol monoethyl ether (also known as “cellosolve” and “2-ethoxyethanol”), propylene glycol monomethyl ether acetate ( One or two or more types such as “alias“ 1-methoxy-2-propyl acetate ”, hereinafter sometimes abbreviated as“ PGMEA ”), ethylene glycol monobutyl ether (also called“ butyl cellosolve ”, 2-butoxyethanol) It is done. PGMEA is particularly preferable.

The content ratio of the other solvent in the total amount of the solvent is the balance of the low-tension solvent, that is, 50% by mass or more.
When the other solvent is used alone, the content is the content of the one other solvent in the total amount of the solvent. When two or more other solvents are used in combination, It is the content ratio of the total amount in the total amount of the solvent.

In addition, the content ratio of all the solvents including the other solvents and the low-strength solvent in the total amount of the ink is, for example, the type and molecular weight of the fluorosurfactant, the content ratio, the type and molecular weight of the binder resin, and the content. Depending on the ratio, the type and content ratio of the colorant, etc., the ink can be arbitrarily set to have a viscosity suitable for the reverse printing method.
The ink may further contain various additives such as a pigment dispersant, a leveling agent, a thixotropic viscosity imparting agent, and an antifoaming agent in an arbitrary ratio.

The ink can be prepared by blending the above components at a predetermined ratio and kneading them using a three-roll, ball mill, bead mill, attritor, sand mill or the like.
The surface tension of the ink at 25 ° C. is preferably 22 mN / m or less, particularly preferably 20 mN / m or less, more preferably 15 mN / m or more, and particularly preferably 16 mN / m or more.
If the surface tension exceeds the above range, the wettability of the ink with respect to the surface of the silicone blanket is insufficient, and the ink layer may be formed when an ink layer is formed by applying ink over substantially the entire surface of the silicone blanket. In addition, the ink layer may cause unevenness or pinholes due to the repellency or the like.

Also, if the surface tension is less than the above range, the wettability of the ink with respect to the surface of the silicone blanket becomes too high, and the ink pattern cannot be transferred well from the surface of the silicone blanket to the surface of the substrate. There is a risk of disturbing the shape of the ink pattern.
In addition, the viscosity of the ink at 25 ° C. is preferably 0.5 mPa · s or more, particularly preferably 1 mPa · s or more, considering that a good ink pattern is formed by a reversal printing method using a silicone blanket. It is preferably s or less, particularly 3 mPa · s or less.

The ink of the present invention is suitable for efficiently producing a color filter for LCD, for example, without causing the various problems described above, using the reversal printing method using the silicone blanket.
Examples of the silicone blanket include a blanket having at least a surface made of silicone rubber.

Examples of the silicone blanket include those composed entirely of a single layer of silicone rubber, and those having a laminated structure in which a layer of silicone rubber is laminated on one side of a substrate made of polyethylene terephthalate (PET) film, metal foil, or the like. Can be mentioned.
Of these, a silicone blanket composed entirely of a single layer of silicone rubber can be formed, for example, by coating a liquid silicone rubber on a flat plate, causing a crosslinking reaction, and then peeling it from the flat plate.

In addition, the silicone blanket having a laminated structure is, for example, in a state where a base material is mounted in a mold, and a liquid silicone rubber is injected into the mold to cause a crosslinking reaction, or a liquid silicone rubber is applied to the surface of the base material. After coating, it can be formed by crosslinking reaction.
The plate is made of a metal such as iron-nickel alloy (42 alloy, etc.), stainless steel, soda glass, non-alkali glass, etc., and is printed on one side by the photolithographic method as described above. What formed the recessed part corresponding to the shape of an ink pattern can be used.

In order to improve the durability of the plate, the surface of the plate including the inner surface of the recess may be subjected to, for example, hard chrome plating.
In order to form an ink layer by applying ink over substantially the entire surface of the silicone blanket, a slit die coater or the like may be used as in the conventional case.
In order to produce a color filter for LCD using the ink of the present invention, first, inks colored in three colors of red (R), green (G), and blue (B) are prepared.

Next, a black matrix layer for partitioning LCD pixels is formed on the surface of a substrate such as a glass substrate by an arbitrary formation method.
Then, the three color inks are sequentially printed on the surface of the substrate partitioned by the black matrix by a reverse printing method, dried to remove the solvent, and then baked as necessary to produce a color filter. .

In the following examples and comparative examples, ink preparation and tests were carried out in an environment at a temperature of 23 ± 1 ° C. and a relative humidity of 55 ± 1%, unless otherwise specified.
<Example 1>
100 parts by mass of polyester melamine resin [weight average molecular weight Mw = 10000] as binder resin, 20 parts by mass of colorant, 100 parts by mass of n-hexane as low-tension solvent, propylene glycol monomethyl ether acetate (PGMEA) as other solvent 300 parts by mass, 2.75 parts by mass of Surflon (registered trademark) S-611 (manufactured by AGC Seimi Chemical Co., Ltd., weight average molecular weight Mw = 44000) as a fluorosurfactant, and 5 parts by mass of a pigment dispersant, The ink was prepared by mixing using a planetary mixer and then kneading using a bead mill.

The solubility of Surflon S-611 at 23 ° C. with respect to 100 g of n-hexane as a low-tension solvent was 2 g, and the content ratio in the total amount of ink was 0.5% by mass.
As the colorant, a red pigment (anthraquinone pigment), a green pigment (brominated phthalocyanine), or a blue pigment (copper phthalocyanine) each having a primary particle diameter of 1 to 100 nm is used. An ink was prepared.

Moreover, as a pigment dispersant, the mixture which mix | blended Solsperse (trademark) 5000 (pigment derivative type) by Lubrizol, and Solsperse 24000GR (SC) made by the company by mass ratio 1: 1 was used.
<Examples 2 to 4, Comparative Examples 1 and 2>
The blending amount of Surflon S-611 was adjusted, and the content ratio in the total amount of the ink was 0.005 mass% (Comparative Example 1), 0.015 mass% (Example 2), 5 mass% (Example 3). Ink was prepared in the same manner as in Example 1 except that 9.5% by mass (Example 4) and 12% by mass (Comparative Example 2) were used.

<Comparative Example 3>
Example 1 except that 2.64 parts by mass of Surflon S-651 (manufactured by AGC Seimi Chemical Co., Ltd., weight average molecular weight Mw = 5400), which is a fluorochemical surfactant, was used instead of Surflon S-611. An ink was prepared in the same manner.
The solubility of Surflon S-651 with respect to 100 g of n-hexane as a low-tension solvent at 23 ° C. was 15 g, and the content ratio in the total amount of ink was 0.5% by mass.

<Comparative example 4>
Implemented except that instead of Surflon S-611, 2.64 parts by mass of a fluorosurfactant, Megafac (registered trademark) F-444 (DIC Corporation, weight average molecular weight Mw = 4800) was used. An ink was prepared as in Example 1.
The solubility of Megafac F-444 at 23 ° C. in 100 g of n-hexane as a low-tensile solvent was 20 g, and the content ratio in the total amount of ink was 0.5% by mass.

<Example 5>
An ink was prepared in the same manner as in Example 1 except that 100 parts by mass of NOVEC (registered trademark) HFE-7200 (manufactured by Sumitomo 3M Co., Ltd.) was used as the low tension solvent instead of n-hexane.
The solubility of Surflon S-611 in 23 g at 100 g of the low-tension solvent (HFE-7200) was 3 g.

<Comparative Example 5>
An ink was prepared in the same manner as in Comparative Example 3, except that 100 parts by mass of NOVEC (registered trademark) HFE-7200 (manufactured by Sumitomo 3M Limited) was used as the low-tensile solvent instead of n-hexane.
The solubility of Surflon S-651 at 23 ° C. in 100 g of the low-tension solvent (HFE-7200) was 20 g.

<Surface tension measurement>
The surface tension of the inks prepared in Examples and Comparative Examples was measured by a maximum bubble pressure method using a dynamic surface tension meter Theta t60 manufactured by Eihiro Seiki Co., Ltd. in an environment at a temperature of 25 ° C.
<Viscosity measurement>
The viscosity of the inks prepared in Examples and Comparative Examples was measured using a cone plate viscometer (digital viscometer LVDV-I manufactured by Brookfield) in an environment at a temperature of 25 ° C., using Japanese Industrial Standard JIS _Z8803-1991 “Liquid” The viscosity was measured by the “cone-viscosity measurement method using a plate-type rotational viscometer” described in The measurement conditions were a cone diameter φ = 48 mm (radius R = 24 mm), and an angle α = 3 ° between the cone and the flat disk.

<Printing test>
Striped ink patterns (line width 100 μm, pitch 300 μm) of each color of red, green and blue on a glass substrate by reversal printing using a silicone blanket using the inks of each color prepared in Examples and Comparative Examples Were sequentially printed to produce a color filter for LCD.

As the silicone blanket, one having a laminated structure in which a layer of 0.6 mm thick silicone rubber was laminated on one side of a 0.35 mm thick PET film was used.
A slit die coater was used to form an ink layer on substantially the entire surface of the silicone blanket.
The following items were evaluated through the manufacturing process of the color filter described above by the reverse printing method.

(Ink layer state)
The ink layer formed on substantially the entire surface of the silicone blanket using the slit die coater was visually observed and observed using an optical microscope, and the presence or absence of vertical stripes and the presence or absence of unevenness were evaluated according to the following criteria.
* Vertical stripes A: No vertical stripes were observed in the ink layer.

○: Although slight vertical stripes were observed in the ink layer, there was no problem in practical use.
X: Many vertical stripes were observed in the ink layer.
* Unevenness A: The ink layer was uniform with no unevenness.

A: Slight unevenness as seen by an optical microscope was observed in the ink layer, but it was practically acceptable.
X: Unevenness that can be seen visually was observed in the ink layer.
(Print shape)
The ink pattern printed on the glass substrate was observed visually and using an optical microscope, and the shape disorder was evaluated according to the following criteria.

A: No irregular shape was found in the ink pattern.
A: The ink pattern was slightly disturbed to the extent that can be seen with an optical microscope, but it was practically acceptable.
X: Disturbance to the extent that the ink layer can be visually confirmed was observed.
The above results are shown in Tables 1 and 2. Table 2 also shows the results of Example 1 for comparison. The symbols in both tables are as follows.

n-Hex: Normal hexane HFE: HFE-7200
S-611: Surflon S-611
S-651: Surflon S-651
F-444: Mega Fuck F-444

  From the results of Examples 1 to 5 and Comparative Examples 3 to 5 in Tables 1 and 2, a silicone blanket was obtained by using a substantially solvent-insoluble fluorosurfactant having a solubility in 100 g of low-tension solvent of 10 g or less. It has moderate wettability and releasability with respect to the surface of the silicone blanket, and forms an ink layer with a uniform thickness without vertical stripes, unevenness, pinholes, etc. on the surface of the silicone blanket, and a substrate such as a substrate It was found that an ink for a reversal printing method can be obtained, in which an ink pattern with a uniform thickness can be formed on the surface of the ink, and which is less likely to cause safety problems.

  Further, from the results of Examples 1 to 4 and Comparative Examples 1 and 2 in Table 1, in order to obtain the above effect, the fluorosurfactant is used in an amount of 0.01% by mass or more and 10% by mass in the total amount of ink. It has been found that it is necessary to contain it in the following proportions, in particular, it is preferably 0.3% by mass or more and 7% by mass or less.

Claims (4)

  An ink layer formed on substantially the entire surface of the silicone blanket is brought into contact with the surface of the plate having a recess corresponding to a predetermined ink pattern on the surface, and the ink layer other than the recess is transferred to the surface of the plate. The ink is selectively removed from the surface of the silicone blanket to form an ink pattern corresponding to the concave portion on the surface of the silicone blanket, and then the ink is used in a reverse printing method for printing the ink pattern on the surface of the printing medium. And a binder resin, a colorant, and a solvent, wherein the solvent contains a low-tensile solvent having a surface tension of 21 mN / m or less at 25 ° C. in a proportion of 50% by mass or less, and the low-tensile solvent A fluorine-based surfactant having a solubility at 100C of 23 ° C. of 10 g or less is 0.01% by mass or more in the total amount of the ink, 1 Ink, characterized in that are contained in a proportion of less mass%.   The ink according to claim 1, wherein the fluorosurfactant has a weight average molecular weight Mw of 6000 or more and 80,000 or less.   The ink according to claim 1, wherein the fluorosurfactant is a nonionic surfactant.   The ink according to any one of claims 1 to 3, wherein the ink has a surface tension at 25 ° C of 22 mN / m or less and a viscosity at 25 ° C of 5 mPa · s or less.