JP2005279342A - Method and system of applying coating liquid, and optical functional film formed by the coating system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably perform coating of a thin film without causing coating unevenness caused by the change of a solid portion concentration of the coating liquid with time in a field requiring the coating of the thin film such as an optical film with high precise. <P>SOLUTION: In a method of applying the organic solvent based coating liquid fed to a coater 21 through a liquid feed pipe 52 on a travelling web 14, the density of the coating liquid is feed-back-controlled by in-line-measuring the density of the coating liquid flowing in the liquid feed pipe 52 by a density meter 60, computing the difference of the density between the measured density and a previously stipulated density of the coating liquid by a computing means 62 and automatically adding a density adjusting liquid into the coating liquid at the upstream side of the density measurement position of a liquid feed pipe 52 to eliminate the difference of the density. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a coating liquid coating method and coating system, and an optical functional film, and in particular, to improve unevenness of an optical functional film such as an optical compensation film, an antireflection film, and an antiglare film, and a liquid crystal layer. The present invention relates to a coating method and a coating system that can be suitably applied to the production of useful optical functional films, and an optical functional film manufactured by the coating system.

  In recent years, the demand for optical functional films is increasing. Typical examples of the optical functional film include films having various functions such as an optical compensation film used as a retardation plate in a liquid crystal cell, an antireflection film, and an antiglare film.

  As a typical method for producing such an optical functional film, an organic solvent-based coating is applied to the surface of a traveling belt-like flexible support (hereinafter referred to as “web”) using a coating apparatus. The method of apply | coating a liquid and drying this and forming the coating film of various compositions is mentioned.

  In recent years, as the performance of optical functional films has been improved, the required accuracy for thinning coating films and preventing unevenness in film thickness has become much higher than before. For this reason, it cannot be solved simply by increasing the mechanical accuracy of the coating apparatus, but it is possible to accurately manage the change over time in the solid content concentration in the coating liquid during the coating process, and always maintain a constant solid content concentration. It is becoming important. However, in general, an organic solvent-based coating solution has a problem that the solvent is more easily evaporated than a water-based coating solution, and the solid content concentration in the coating solution is easily changed. Furthermore, examples of coating devices used in the production of optical functional films include bar coating devices (bar method, Meyer bar method), gravure coating devices (direct method, kiss method), roll coating devices, and the like. Since these coating apparatuses are a system in which the coating liquid is scraped up from the liquid reservoir and applied to the support, there is a problem that the organic solvent in the coating liquid tends to evaporate. In the case of these coating apparatuses, surplus coating liquid that has not been applied to the web is collected, and the collected coating liquid is returned to the liquid feeding line that feeds the coating apparatus and reused. It is normal. When the coating solution is reused in this way, the coating solution is exposed to the atmosphere when the coating solution is collected, and the organic solvent in the coating solution evaporates, and the solid content concentration in the coating solution is more likely to change. There is.

Conventionally, as seen in Patent Document 1, a method of measuring the viscosity of a coating solution to obtain a difference from a specified concentration and feedback-controlling the viscosity of the coating solution based on the difference in viscosity is common as management of the coating solution. Is. Patent Document 2 discloses that after the viscosity of a coating liquid collected from a coating apparatus is adjusted in a tank of a viscosity adjusting chamber, the liquid is returned to the coating apparatus.
JP-A-2-131241 Japanese Patent Laid-Open No. 9-070568

  However, the conventional coating system that feedback-controls the viscosity of the coating solution cannot accurately detect the change in the solid content concentration of the coating solution, and the coating unevenness resulting from the change in the solid content concentration of the coating solution over time. There is a drawback that cannot be eliminated. In other words, in the management of coating solutions in the production of optical functional films that require strict optical performance, it is necessary to manage changes in the solid content concentration in coating solutions that do not appear as viscosity changes. A coating method and a coating system capable of managing a coating solution that can be used are required.

  The present invention has been made in view of such circumstances, and in a field where high-precision thin film coating is required, such as an optical functional film, uneven coating due to change over time in the solid content concentration of the coating liquid is eliminated. It is an object of the present invention to provide a coating method and coating system for a coating liquid and an optical functional film that can perform stable thin film coating without causing them to occur.

  In order to achieve the above object, the present invention provides a coating liquid coating method in which an organic solvent-based coating liquid fed to a coating apparatus via a liquid feeding pipe is coated on a traveling support. In-line measurement of the density of the coating liquid flowing in the liquid feeding pipe, and calculating the density difference between the measured density and the prescribed density of the coating liquid defined in advance, upstream of the density measurement position so that the density difference is eliminated. There is provided a coating liquid coating method characterized in that a density adjusting liquid is automatically added to the liquid feeding pipe on the side and the density of the coating liquid is feedback controlled.

  In order to achieve the above object, the present invention provides an application system in which an organic solvent-based coating liquid fed to a coating apparatus via a liquid feeding pipe is coated on a traveling support. A density meter that measures the density of the coating liquid flowing in the pipe in-line; a calculation means that calculates a density difference between the measured density measured and a predetermined density of the coating liquid that has been defined in advance; and the density so that the density difference is eliminated. There is provided a coating liquid coating system comprising a density feedback control mechanism provided with an adding means for automatically adding a density adjusting liquid into the liquid feeding pipe on the upstream side of the meter.

  According to the present invention, the density feedback control mechanism for stably maintaining the density of the coating liquid at the specified density is provided on the liquid feeding pipe for feeding the organic solvent-based coating liquid to the coating apparatus. This enables real-time and high-precision detection by detecting the density of the coating liquid, even if it is a small change in the solid content concentration in the coating liquid that does not appear as a viscosity change caused by a small amount of organic solvent evaporating from the coating liquid. In order to eliminate the difference in density between the measured density measured in advance and the prescribed density of the coating liquid defined in advance, the coating flowing in the liquid feed pipe from the adding means arranged upstream of the density meter. By automatically adding the density adjusting liquid to the liquid, there is no feedback delay as in the case of adding the density adjusting liquid into the tank. If there is no difference in density, no density adjusting solution is added to the coating solution. In this case, as the density adjusting liquid, an organic solvent of the coating liquid, a solution containing the same components as the coating liquid, or the like can be used. Here, the prescribed density of the coating liquid refers to the density originally prescribed when the coating liquid is prepared.

  The present invention is particularly preferable in the case of a coating solution for producing an optical functional film. This is because, as described above, the required accuracy of thinning the coating film and preventing unevenness in film thickness has become significantly higher than before due to the higher performance of the optical functional film, and the solid content concentration in the coating liquid This is because it is necessary to manage with high accuracy.

  In the present invention, the coating apparatus collects surplus coating liquid that has not been applied to the support, and again supplies the liquid to the coating apparatus via the liquid feeding pipe, gravure coating It is preferable that it is either an apparatus or a roll coating apparatus. Since such a coating apparatus is a system in which the coating liquid is scraped up from the liquid reservoir and applied to the support, the organic solvent in the coating liquid easily evaporates, and the excess coating liquid that has not been applied to the web The recovered coating liquid is usually supplied again to the coating apparatus and reused. When the coating liquid is reused in this way, the coating liquid is recovered at the time of collecting the coating liquid. This is because the organic solvent in the coating solution evaporates due to exposure to the atmosphere, and the solid content concentration in the coating solution is more likely to change.

  In the present invention, the density meter is preferably a Coriolis mass flow meter. There are various types of density meters, but the Coriolis type mass flow meter can obtain a density signal at the same time as the mass flow rate signal, and is more accurate than other methods, and it can be used as a coating solution for optical functional film production. This is because a minute change in the required solid content concentration can be detected.

  In the present invention, it is preferable to provide a static mixer between the density meter in the liquid feeding pipe and the adding means. It is necessary to stir and mix so that the density adjusting liquid is uniformly added to the coating liquid, but dynamic mixers such as mechanical stirring tend to foam and bubbles are easily formed, so the accuracy of the density meter decreases, Density meter measurement accuracy decreases. However, since a static mixer such as a static mixer does not foam, the measurement accuracy of the density meter can be maintained with high accuracy.

  In this invention, it is preferable to provide the defoaming means which defoams the bubble in a coating liquid in the upstream of the density meter in liquid feeding piping. This is because, as described above, since bubbles cause a decrease in density measurement accuracy, it is preferable that bubbles in the coating solution be defoamed before the density meter.

  In the present invention, the adding means is preferably any one of a plunger pump, a diaphragm pump, and a gear pump. Thereby, it is necessary to accurately control the addition amount of the density adjusting liquid in accordance with a minute change in density measured by the density meter, and a plunger pump, a diaphragm pump, and a gear pump are preferable.

  In the present invention, it is preferable that a thermometer for measuring the temperature of the coating solution in-line is provided on the upstream side of the density meter in the liquid feeding pipe, and the calculation means corrects the measured density with temperature. This is because the density of the coating liquid can be measured with higher accuracy by correcting the temperature.

  In the present invention, it is preferable to provide a coating liquid amount control means for controlling the amount of the coating liquid applied from the coating apparatus to the support based on the density difference. This is because by providing both the density control of the coating liquid itself by the density feedback control mechanism and the coating liquid amount control by the coating apparatus, it is possible to perform finer control to prevent the occurrence of coating unevenness. It is.

  According to the present invention, it is preferable to provide warning means for warning when the density difference becomes larger than a predetermined value. If the density difference becomes too large, it will take a long time to converge to the specified density even if it is adjusted with the density adjusting solution, and the coated product will be defective during that time. Because it is good.

  Moreover, in order to achieve the said objective, the optical functional film manufactured using the application | coating system of the any one of Claims 2-11 is provided. By using the coating system of the present invention, it is possible to produce a highly accurate optical functional film that is a thin film and has no coating unevenness.

  As described above, according to the present invention, in a field where high-precision thin film coating is required, such as an optical functional film, it is possible to prevent the occurrence of coating unevenness resulting from a change in the solid content concentration of the coating solution over time. , Stable thin film coating can be performed.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a coating liquid coating method and coating system according to the present invention and an optical functional film manufactured using the coating system will be described below in detail with reference to the accompanying drawings. FIG. 1 is an explanatory view for explaining a production line of an optical functional film to which a coating solution coating method and a coating system according to the present invention are applied. FIG. 2 is an overall configuration diagram of the coating system of the present invention, and FIG. 3 is a cross-sectional view of an ultrasonic defoaming apparatus which is an example of a defoaming apparatus arranged in the coating system.

  In the optical functional film production line 10, as shown in FIG. 1, a web 14 is sent out from a feeding machine 12, and the web 14 is guided by a guide roller 16 and fed into a dust remover 18. The dust remover 18 removes dust attached to the surface of the web 14.

  A coating device 21 in the coating system 20 of the present invention is provided downstream of the dust remover 18, and a coating liquid for producing an optical functional film is applied to the traveling web 14. Here, the coating liquid for producing an optical functional film refers to, for example, a coating liquid for producing an optical compensation film, an antireflection film, an antiglare film and the like. An initial drying zone 22, a main drying zone 24, and a heating zone 26 are sequentially provided downstream of the coating apparatus 21, and an optical layer is formed on the web 14. Further, an ultraviolet lamp 28 is provided on the downstream side, and the optical layer is crosslinked by ultraviolet irradiation to form a desired polymer. And the web 14 in which the polymer was formed is wound up by the winder 30 provided downstream.

  Next, the coating system 20 of the present invention will be described. An example in which a gravure coating apparatus is used as the coating apparatus 21 will be described.

  The coating system 20 mainly includes a gravure coating device 21, a liquid feeding line 32 that feeds the coating solution to the gravure coating device 21, and an excess coating solution that has not been applied to the web 14 by the gravure coating device 21. The recovery line 34 is configured to recover and return to the liquid feed line 32.

  The gravure coating device 21 includes a gravure roller 36, a backup roller 38, a liquid receiving pan 40 provided below the gravure roller 36, and an excessive application scraped from the liquid receiving pan 40 by the rotational drive of the gravure roller 36. A doctor blade 42 that scrapes off the liquid before coating is provided, and the lower half of the gravure roller 36 is immersed in a liquid receiving pan 40 filled with the coating liquid fed from the liquid feeding line 32.

  The upstream guide roller 44 and the downstream guide roller 46 are supported in parallel with the gravure roller 36. The upstream guide roller 44 and the downstream guide roller 46 are preferably configured such that both end portions are rotatably supported by bearing members (ball bearings or the like) and no drive mechanism is attached.

  The gravure roller 36, the backup roller 38, the upstream guide roller 44, and the downstream guide roller 46 have substantially the same length as the width of the web 14. The gravure roller 36 is rotationally driven in the same direction as the traveling direction of the web 14 as indicated by the arrow in FIG. In addition, application by reverse rotation driving reverse to that in FIG. 2 can also be adopted depending on application conditions. The driving method of the gravure roller 36 is direct driving (shaft direct connection) by an inverter motor, but a combination of various motors and a reduction gear (gear head), or a method using winding transmission means such as a timing belt from various motors. Good. The cell shape on the surface of the gravure roller 36 may be any of a known pyramid type, lattice type, diagonal line type, and the like. That is, an appropriate cell may be selected depending on the coating speed, the viscosity of the coating liquid, the coating layer thickness, and the like.

With the above-described configuration of the gravure coating apparatus 21, the web 14 that is guided by the upstream guide roller 44 and the downstream guide roller 46 and runs is sandwiched between the gravure roller 36 and the backup roller 38 that are driven to rotate. A part of the coating liquid scraped up from the liquid receiving pan 40 by the rotation is scraped off by the doctor blade 42 and then applied to the web 14. In addition, surplus coating liquid that has not been applied to the web 14 flows along with the rotation of the gravure roller 36 and flows down to the liquid receiving pan 42, and is supplied to the liquid supply tank 50 by the recovery pump 49 provided in the recovery pipe 48 of the recovery line 34. To be recovered. The recovery pump 49 adjusts the recovery amount of the coating liquid so as to keep the liquid level of the liquid receiving pan 40 constant in consideration of the amount of the coating liquid supplied from the liquid supply line 32 to the liquid receiving pan 40. Since this gravure coating device 21 is particularly effective for thin layer coating, for example, an optical functional film that performs ultra-thin layer coating with a wet coating amount of 5 ml / m ² or less (a film thickness during coating of 5 μm or less). It can be suitably applied to the production line. The tension in the running direction of the web 14 during application is preferably in the range of 100 to 300 N / m. The coating device is not limited to the gravure coating device 21, and a bar coating device (bar method, Meyer bar method), a roll coating device, and the like can also be suitably used.

  The liquid feed line 32 includes a liquid feed pump 54, a density feedback control mechanism 56, and a filter 58 in order from the liquid feed tank 50 side on a liquid feed pipe 52 that connects the liquid feed tank 50 and the gravure coating device 21. Provided and configured. As a result, the coating liquid in the liquid feeding tank 50 flows through the liquid feeding pipe 52 by the liquid feeding pump 54 and is sent to the gravure coating apparatus 21. Filter with a filter.

  The density feedback control mechanism 56 mainly calculates a density meter 60 that measures the density of the coating liquid flowing in the liquid feeding pipe 52 in-line and a density difference between the measured measurement density and a predetermined density of the coating liquid defined in advance. Means 62 and an adding means 64 for automatically adding a density adjusting liquid to the coating liquid flowing in the liquid feeding pipe 52 at a position upstream of the density meter so as to eliminate the density difference. An addition tank 66 for storing the density adjusting liquid and an addition pump 68 are provided. That is, the measured density of the coating liquid sequentially measured by the density meter 60 is input to the calculating means 62 and compared with the specified density of the coating liquid input in advance to the calculating means 62, and the density between the measured density and the specified density. Difference is required. The calculation means 62 calculates the addition amount of the density adjustment liquid necessary for eliminating the density difference from the calibration curve data indicating the relationship between the density difference and the addition amount of the density adjustment liquid, and the operation time and rotation of the addition pump 68. The addition pump 68 is controlled by obtaining the number or stroke number. Thereby, when there is a density difference between the measured density and the specified density of the coating liquid, the density adjusting liquid is automatically added to the coating liquid flowing through the liquid feeding pipe 52 so as to eliminate the density difference. As the density adjusting liquid, an organic solvent for preparing the coating liquid, a solution containing the same components as the coating liquid, or the like can be used.

  In addition, the coating system 20 of the present invention can manage the change in the solid content concentration in the coating solution that does not appear as a viscosity change in the production of an optical functional film that requires strict optical performance. It is preferable to add the following configuration to the coating system 20. That is, as the density meter 60 used here, various types of density meters are possible, but a Coriolis mass flow meter is more preferable because it can measure the density with high accuracy. The Coriolis mass flow meter can obtain a density signal at the same time as the mass flow signal, and is more accurate than other types of density meters, and changes in the solid content concentration required for coating solutions for optical functional film production This is because it can also be detected. Moreover, it is preferable to provide the static mixer 70 and the defoaming means 72 in the liquid feeding pipe 52 between the density meter 60 and the adding means 64. The order of the static mixer 70 and the defoaming means 72 may be either upstream. The static mixer 70 can stir and mix the coating liquid to which the density adjusting liquid is added without foaming, and the density adjusting liquid can be uniformly added to the coating liquid. In addition, even when air bubbles are present in the coating liquid, for example, by the liquid feeding tank 50 or the liquid feeding pump 54 during the feeding of the coating liquid, the defoaming means 72 can remove the bubbles, so the measurement with the density meter 60 is possible. The accuracy can be prevented from being reduced due to bubbles. This is because in order to maintain the measurement accuracy of the Coriolis mass flow meter with high accuracy, it is important that the coating solution is uniform and that there are no bubbles in the coating solution. Therefore, the liquid feed pump 54 is also preferably a non-pulsating pump that does not generate bubbles, and for example, a gear pump can be suitably used. Further, when returning the recovered coating liquid from the recovery pipe 48 to the liquid supply tank 50, the tip of the recovery pipe 48 is extended to the vicinity of the bottom of the liquid supply tank 50 to suppress foaming when recovering the coating liquid. It is preferable to do.

  FIG. 3 shows an example of the defoaming means 72, which is an ultrasonic defoaming device. As shown in FIG. 3, the ultrasonic defoaming apparatus mainly includes a pipeline 76 disposed in the ultrasonic liquid tank 74, and an ultrasonic vibrator provided at the bottom or the peripheral part of the ultrasonic liquid tank 74. 78. The pipeline 76 is constituted by a thin circular tube having a smooth inner surface, and the inlet side and the outlet side are connected to the liquid feeding pipe 52 (see FIG. 2). The coating liquid flowing in the pipeline 76 is pressurized to a predetermined pressure level by the liquid feed pump 54 (see FIG. 2) and the pressure valve 80. As the pressure level, the pressure in the pipeline 76 is preferably about 30 to 100 kPa. In the ultrasonic liquid tank 74, the ultrasonic wave propagation liquid is continuously supplied from the supply port 82 on the side surface of the tank lower part, fills the inside of the tank, and is discharged from the discharge port 84 on the side surface of the upper part of the tank. Thereby, the ultrasonic wave emitted from the ultrasonic vibrator 78 is propagated to the pipeline 76 by the ultrasonic wave propagation liquid, and is applied to the coating liquid flowing in the pipeline 76. The ultrasonic frequency is preferably in the range of 20 kHz to 100 kHz. As a result, the ultrasonic wave vibration is applied while the coating liquid is pressurized and fed through the pipeline 76 without any gas-liquid interface, and bubbles present in the coating liquid are dissolved in the coating liquid to be defoamed. it can. Further, as shown in FIG. 2, a thermometer 86 for measuring the temperature of the coating liquid flowing through the liquid feeding pipe 52 is provided, and the measured temperature of the coating liquid is sequentially input to the calculating means 62, and the density meter 60 A temperature correction of the measured density is performed. Thereby, since the influence of a bubble and the influence of the temperature of a coating liquid can be eliminated when measuring the density of a coating liquid with a Coriolis type mass flowmeter, a highly accurate measurement can be achieved.

  In order to configure the high-accuracy density feedback control mechanism 56, it is necessary to increase the addition accuracy of the density adjusting liquid in correspondence with high-accuracy density measurement. As the addition pump 68, a plunger pump, a diaphragm pump, It is preferably one of gear pumps. As a result, a highly accurate density feedback control mechanism 56 can be configured, and in the production of an optical functional film that requires strict optical performance, a change in the solid content concentration in the coating liquid that does not appear as a viscosity change can be achieved. It becomes possible to manage.

  In addition, in the coating system 20 of the present invention, as shown in FIG. 2, it is preferable to provide a warning means 88 that warns when the density difference between the density measured by the density meter 60 and the specified density becomes larger than a predetermined value. This is because if the density difference becomes too large, it takes a long time to converge to the specified density even if it is adjusted with the density adjusting solution, and the coated product in the meantime becomes a defective product. Because. The warning means 88 may be anything that emits a warning sound, lights up a lamp, or can clearly determine an abnormality. In the coating system 20 of the present invention, it is preferable to provide a coating liquid amount control means 90 for controlling the amount of coating liquid applied from the coating device 36 to the web 14 based on the density difference. For example, when a gravure coating device is used as the coating device 21, an inverter that controls the rotation speed of the gravure roller 36 can be used as the coating liquid amount control means 90. Thus, by providing both the density control of the coating liquid by the density feedback control mechanism 56 and the coating liquid amount control by the coating apparatus 21, it is possible to perform finer control in order to prevent coating unevenness. It is.

  Next, an optical functional film manufactured using the coating system according to the present invention will be described.

  As the web 14 used in the present invention, a polymer film having a light transmittance of 80% or more is preferably used. As the polymer film, a film in which birefringence hardly occurs due to external force is preferable. Examples of the polymer include cellulose-based polymers, norbornene-based polymers (for example, Arton (manufactured by JSR Corporation), Zeonore, Zeonex (all manufactured by Nippon Zeon Corporation)), and polymethyl methacrylate. Polymers are preferred, cellulose esters are more preferred, and lower fatty acid esters of cellulose are even more preferred.

  This lower fatty acid means a fatty acid having 6 or less carbon atoms. The number of carbon atoms is preferably 2 (cellulose acetate), 3 (cellulose propionate) or 4 (cellulose butyrate). Cellulose acetate is preferred as the cellulose ester, and examples thereof include diacetyl cellulose and triacetyl cellulose. Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate may be used.

  In general, the hydroxyl groups of 2, 3, and 6 of cellulose acetate are not evenly distributed by 1/3 of the total substitution degree, and the substitution degree of the 6-position hydroxyl group tends to be small. In the present invention, it is preferable that the substitution degree of the 6-position hydroxyl group of cellulose acetate is larger than that of the 2- and 3-positions.

  The hydroxyl group at the 6-position with respect to the total substitution degree is preferably substituted with 30% or more and 40% or less acyl group, more preferably 31% or more, and particularly preferably 32% or more. Further, the substitution degree of the 6-position acyl group of cellulose acetate is preferably 0.88 or more.

  The 6-position hydroxyl group may be substituted with a propionyl group, butyroyl group, valeroyl group, benzoyl group, acryloyl group or the like, which is an acyl group having 3 or more carbon atoms, in addition to the acetyl group. The degree of substitution at each position can be determined by NMR.

  As the cellulose acetate of the present invention, Synthesis Example 1 described in Paragraph Nos. 0043 to 0044 of JP-A No. 11-5851, Synthetic Example 2 described in Paragraph Nos. 0048 to 0049, and Paragraph Nos. 0051 to 0052 The cellulose acetate obtained by the synthesis method of Synthesis Example 3 described can be used.

  In order to adjust the retardation of the polymer film, an aromatic compound having at least two aromatic rings is used as a retardation increasing agent.

  When a cellulose acetate film is used as the polymer film, the aromatic compound is used in the range of 0.01 to 20 parts by mass with respect to 100 parts by mass of cellulose acetate. The aromatic compound is preferably used in the range of 0.05 to 15 parts by mass, and more preferably in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of cellulose acetate. Two or more aromatic compounds may be used in combination. The aromatic ring of the aromatic compound includes an aromatic hetero ring in addition to the aromatic hydrocarbon ring.

  The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable.

  Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable. More preferred are a benzene ring and a 1,3,5-triazine ring. The aromatic compound particularly preferably has at least one 1,3,5-triazine ring.

  The number of aromatic rings contained in the aromatic compound is preferably 2 to 20, more preferably 2 to 12, still more preferably 2 to 8, and most preferably 2 to 6. . The bonding relationship between two aromatic rings can be classified into (a) when forming a condensed ring, (b) when directly connecting with a single bond, and (c) when connecting via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).

  Examples of the condensed ring (a condensed ring of two or more aromatic rings) include an indene ring, a naphthalene ring, an azulene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, an acenaphthylene ring, a naphthacene ring, a pyrene ring, Indole ring, isoindole ring, benzofuran ring, benzothiophene ring, indolizine ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring, purine ring, indazole ring, chromene ring, quinoline ring, isoquinoline ring, quinolidine Ring, quinazoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, pteridine ring, carbazole ring, acridine ring, phenanthridine ring, xanthene ring, phenazine ring, phenothiazine ring, phenoxathiin ring, phenoxazine ring and thianthrene ring It is. Naphthalene ring, azulene ring, indole ring, benzoxazole ring, benzothiazole ring, benzimidazole ring, benzotriazole ring and quinoline ring are preferred.

  The single bond (b) is preferably a bond between carbon atoms of two aromatic rings. Two aromatic rings may be bonded with two or more single bonds to form an aliphatic ring or a non-aromatic heterocyclic ring between the two aromatic rings.

The linking group in (c) is also preferably bonded to carbon atoms of two aromatic rings. The linking group is preferably an alkylene group, an alkenylene group, an alkynylene group, —CO—, —O—, —NH—, —S—, or a combination thereof. Examples of linking groups composed of combinations are shown below. In addition, the relationship between the left and right in the following examples of the linking group may be reversed.
c1: -CO-O-
c2: —CO—NH—
c3: -alkylene-O-
c4: —NH—CO—NH—
c5: —NH—CO—O—
c6: —O—CO—O—
c7: -O-alkylene-O-
c8: -CO-alkenylene-
c9: -CO-alkenylene-NH-
c10: -CO-alkenylene-O-
c11: -alkylene-CO-O-alkylene-O-CO-alkylene-
c12: -O-alkylene-CO-O-alkylene-O-CO-alkylene-O-c13: -O-CO-alkylene-CO-O-
c14: -NH-CO-alkenylene-
c15: -O-CO-alkenylene-
The aromatic ring and the linking group may have a substituent. Examples of the substituent include halogen atom (F, Cl, Br, I), hydroxyl, carboxyl, cyano, amino, nitro, sulfo, carbamoyl, sulfamoyl, ureido, alkyl group, alkenyl group, alkynyl group, aliphatic acyl group , Aliphatic acyloxy group, alkoxy group, alkoxycarbonyl group, alkoxycarbonylamino group, alkylthio group, alkylsulfonyl group, aliphatic amide group, aliphatic sulfonamido group, aliphatic substituted amino group, aliphatic substituted carbamoyl group, aliphatic Substituted sulfamoyl groups, aliphatic substituted ureido groups and non-aromatic heterocyclic groups are included.

  It is preferable that the alkyl group has 1 to 8 carbon atoms. A chain alkyl group is preferable to a cyclic alkyl group, and a linear alkyl group is particularly preferable. The alkyl group may further have a substituent (eg, hydroxy, carboxy, alkoxy group, alkyl-substituted amino group). Examples of alkyl groups (including substituted alkyl groups) include methyl, ethyl, n-butyl, n-hexyl, 2-hydroxyethyl, 4-carboxybutyl, 2-methoxyethyl and 2-diethylaminoethyl. The alkenyl group preferably has 2 to 8 carbon atoms. A chain alkenyl group is preferable to a cyclic alkenyl group, and a linear alkenyl group is particularly preferable. The alkenyl group may further have a substituent.

  Examples of alkenyl groups include vinyl, allyl and 1-hexenyl. The alkynyl group preferably has 2 to 8 carbon atoms. A chain alkynyl group is preferable to a cyclic alkynyl group, and a linear alkynyl group is particularly preferable. The alkynyl group may further have a substituent. Examples of alkynyl groups include ethynyl, 1-butynyl and 1-hexynyl.

  The number of carbon atoms in the aliphatic acyl group is preferably 1-10. Examples of the aliphatic acyl group include acetyl, propanoyl and butanoyl. The number of carbon atoms in the aliphatic acyloxy group is preferably 1-10. Examples of the aliphatic acyloxy group include acetoxy. The number of carbon atoms of the alkoxy group is preferably 1-8. The alkoxy group may further have a substituent (eg, an alkoxy group).

  Examples of alkoxy groups (including substituted alkoxy groups) include methoxy, ethoxy, butoxy and methoxyethoxy. The number of carbon atoms of the alkoxycarbonyl group is preferably 2-10. Examples of the alkoxycarbonyl group include methoxycarbonyl and ethoxycarbonyl. The number of carbon atoms of the alkoxycarbonylamino group is preferably 2-10. Examples of the alkoxycarbonylamino group include methoxycarbonylamino and ethoxycarbonylamino.

  The alkylthio group preferably has 1 to 12 carbon atoms. Examples of the alkylthio group include methylthio, ethylthio and octylthio.

  The alkylsulfonyl group preferably has 1 to 8 carbon atoms. Examples of the alkylsulfonyl group include methanesulfonyl and ethanesulfonyl.

  The number of carbon atoms in the aliphatic amide group is preferably 1-10. Examples of the aliphatic amide group include acetamide. The number of carbon atoms of the aliphatic sulfonamide group is preferably 1-8. Examples of the aliphatic sulfonamido group include methanesulfonamido, butanesulfonamido and n-octanesulfonamido. The number of carbon atoms of the aliphatic substituted amino group is preferably 1-10. Examples of the aliphatic substituted amino group include dimethylamino, diethylamino and 2-carboxyethylamino.

The number of carbon atoms in the aliphatic substituted carbamoyl group is preferably 2-10. Examples of the aliphatic substituted carbamoyl group include methylcarbamoyl and diethylcarbamoyl. The number of carbon atoms in the aliphatic substituted sulfamoyl group is preferably 1-8. Examples of the aliphatic substituted sulfamoyl group include methylsulfamoyl and diethylsulfamoyl. The number of carbon atoms in the aliphatic substituted ureido group is preferably 2-10. Examples of the aliphatic substituted ureido group include methylureido. Examples of non-aromatic heterocyclic groups include piperidino and morpholino. The molecular weight of the retardation increasing agent is preferably 300 to 800. Specific examples of the retardation increasing agent include JP-A Nos. 2000-1111914, 2000-275434, PCT / JP00 / 02619, etc. It is described in.

  Hereinafter, the case where a cellulose acetate film is used as the polymer film will be specifically described. It is preferable to produce a cellulose acetate film by a solvent cast method. In the solvent cast method, a film is produced using a solution (dope) in which cellulose acetate is dissolved in an organic solvent.

  The organic solvent is a solvent selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, esters having 3 to 12 carbon atoms, and halogenated hydrocarbons having 1 to 6 carbon atoms. It is preferable to contain.

  The ether, ketone and ester may have a cyclic structure. A compound having two or more functional groups of ether, ketone and ester (that is, —O—, —CO— and —COO—) can also be used as the organic solvent. The organic solvent may have another functional group such as an alcoholic hydroxyl group. In the case of an organic solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group.

  Examples of the ether having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclohexanone and methylcyclohexanone. Examples of the esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate.

  Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol. The number of carbon atoms of the halogenated hydrocarbon is preferably 1 or 2, and most preferably 1. The halogen of the halogenated hydrocarbon is preferably chlorine. The proportion of halogen atoms substituted by halogen in the halogenated hydrocarbon is preferably 25 to 75 mol%, more preferably 30 to 70 mol%, and more preferably 35 to 65 mol%. More preferably, it is most preferable that it is 40-60 mol%. Methylene chloride is a representative halogenated hydrocarbon.

  Technically, halogenated hydrocarbons such as methylene chloride can be used without problems, but from the viewpoint of the global environment and working environment, the organic solvent preferably does not substantially contain halogenated hydrocarbons. “Substantially free” means that the proportion of halogenated hydrocarbon in the organic solvent is less than 5% by mass (preferably less than 2% by mass). Moreover, it is preferable that halogenated hydrocarbons such as methylene chloride are not detected at all from the produced cellulose acylate film. Two or more organic solvents may be mixed and used.

  A cellulose acetate solution can be prepared by a general method. The general method means that the treatment is performed at a temperature of 0 ° C. or higher (normal temperature or high temperature). The solution can be prepared by using a dope preparation method and apparatus in a normal solvent cast method. In the case of a general method, it is preferable to use a halogenated hydrocarbon (particularly methylene chloride) as the organic solvent. The amount of cellulose acetate is adjusted so as to be contained in the obtained solution in an amount of 10 to 40% by mass. The amount of cellulose acetate is more preferably 10 to 30% by mass.

  Arbitrary additives described later may be added to the organic solvent (main solvent). The solution can be prepared by stirring cellulose acetate and an organic solvent at room temperature (0 to 40 ° C.). The high concentration solution may be stirred under pressure and heating conditions. Specifically, cellulose acetate and an organic solvent are placed in a pressure vessel and sealed, and stirred while heating to a temperature not lower than the boiling point of the solvent at normal temperature and in a range where the solvent does not boil. The heating temperature is usually 40 ° C or higher, preferably 60 to 200 ° C, more preferably 80 to 110 ° C.

  Each component may be coarsely mixed in advance and then placed in a container. Moreover, you may put into a container sequentially. The container needs to be configured so that it can be stirred. The container can be pressurized by injecting an inert gas such as nitrogen gas. Moreover, you may utilize the raise of the vapor pressure of the solvent by heating. Or after sealing a container, you may add each component under pressure.

  When heating, it is preferable to heat from the outside of the container. For example, a jacket type heating device can be used. The entire container can also be heated by providing a plate heater outside the container and piping to circulate the liquid. It is preferable to provide a stirring blade inside the container and stir using this. The stirring blade preferably has a length that reaches the vicinity of the wall of the container. A scraping blade is preferably provided at the end of the stirring blade in order to renew the liquid film on the vessel wall. Instruments such as a pressure gauge and a thermometer may be installed in the container. Each component is dissolved in a solvent in the container. The prepared dope is taken out of the container after cooling, or taken out and then cooled using a heat exchanger or the like.

  Preparation of the cellulose acetate solution (dope) of the present invention is carried out according to a cooling dissolution method and will be described below. First, cellulose acetate is gradually added to an organic solvent with stirring at a temperature around room temperature (-10 to 40 ° C). When a plurality of solvents are used, the order of addition is not particularly limited.

  For example, after adding cellulose acetate to the main solvent, another solvent (for example, a gelling solvent such as alcohol) may be added, or conversely, the main solvent after the gelling solvent is previously moistened in cellulose acetate. A solvent may be added, which is effective in preventing non-uniform dissolution. The amount of cellulose acetate is preferably adjusted so as to be contained in the mixture in an amount of 10 to 40% by mass. The amount of cellulose acetate is more preferably 10 to 30% by mass. Furthermore, you may add the arbitrary additive mentioned later in a mixture.

  The mixture is then cooled to -100 to -10 ° C (preferably -80 to -10 ° C, more preferably -50 to -20 ° C, most preferably -50 to -30 ° C). The cooling can be performed, for example, in a dry ice / methanol bath (−75 ° C.) or a cooled diethylene glycol solution (−30 to −20 ° C.). When cooled in this way, the mixture of cellulose acetate and organic solvent solidifies. Although the cooling rate is not particularly limited, in the case of batch-type cooling, the viscosity of the cellulose acetate solution increases with cooling, and the cooling efficiency is inferior. is necessary.

  In addition, the cellulose acetate solution of the present invention can be achieved by swelling the cellulose acetate solution and then transferring the cooling device at a predetermined cooling temperature for a short time. The faster the cooling rate, the better. However, 10,000 ° C / second is the theoretical upper limit, 1000 ° C / second is the technical upper limit, and 100 ° C / second is the practical upper limit.

  The cooling rate is a value obtained by dividing the difference between the temperature at the start of cooling and the final cooling temperature by the time from the start of cooling until the final cooling temperature is reached. Further, when this is heated to 0 to 200 ° C. (preferably 0 to 150 ° C., more preferably 0 to 120 ° C., most preferably 0 to 50 ° C.), cellulose acetate flows in the organic solvent. Become a solution. The temperature can be raised by simply leaving it at room temperature or in a warm bath.

  A uniform solution is obtained as described above. If the dissolution is insufficient, the cooling and heating operations may be repeated. Whether or not the dissolution is sufficient can be determined by merely observing the appearance of the solution with the naked eye.

  In the cooling dissolution method, it is desirable to use a sealed container in order to avoid moisture mixing due to condensation during cooling. In the cooling and heating operation, when the pressure is applied during cooling and the pressure is reduced during heating, the dissolution time can be shortened. In order to perform pressurization and decompression, it is desirable to use a pressure-resistant container.

  In addition, according to differential scanning calorimetry (DSC), a 20 mass% solution obtained by dissolving cellulose acetate (acetylation degree: 60.9%, viscosity average polymerization degree: 299) in methyl acetate by a cooling dissolution method was 33. There exists a quasi-phase transition point between the sol state and the gel state in the vicinity of ° C, and a uniform gel state is obtained below this temperature.

  Therefore, this solution needs to be stored at a temperature equal to or higher than the pseudo phase transition temperature, preferably about the gel phase transition temperature plus 10 ° C. However, this pseudo phase transition temperature varies depending on the degree of acetylation of cellulose acetate, the degree of viscosity average polymerization, the concentration of the solution, and the organic solvent used.

  A cellulose acetate film is produced from the prepared cellulose acetate solution (dope) by a solvent cast method. Moreover, it is preferable to add the above-mentioned retardation increasing agent to the dope. The dope is cast on a drum or band and the solvent is evaporated to form a film. The dope before casting is preferably adjusted to have a solid content of 10 to 40%, more preferably 18 to 35%. The surface of the drum or band is preferably finished in a mirror state.

  Regarding casting and drying methods in the solvent casting method, U.S. Pat. Nos. 2,336,310, 2,367,603, 2,429,078, 2,429,297, 2,429,978, 2,607,704, 2,37,069, 2,273,070, British Patent 6,407,331, No. 736892, JP-B Nos. 45-4554, 49-5614, JP-A-60-176834, No. 60-203430, and No. 62-1115035.

  The dope is preferably cast on a drum or band having a surface temperature of 10 ° C. or less. After casting, it is preferable to dry it by applying air for 2 seconds or more. The obtained film can be peeled off from the drum or band and further dried with high-temperature air whose temperature is changed successively from 100 to 160 ° C. to evaporate the residual solvent. The above method is described in Japanese Patent Publication No. 5-17844. According to this method, it is possible to shorten the time from casting to stripping. In order to carry out this method, it is necessary for the dope to gel at the surface temperature of the drum or band during casting.

  In the present invention, the obtained cellulose acetate solution may be cast as a single layer liquid on a smooth band or drum as the web 14, or a plurality of cellulose acetate liquids of two or more layers may be cast. Good. When casting a plurality of cellulose acetate solutions, a film may be prepared while casting and laminating a solution containing cellulose acetate from a plurality of casting openings provided at intervals in the traveling direction of the web 14. For example, methods described in JP-A-61-158414, JP-A-1-122419, JP-A-11-198285, etc. can be applied.

  Further, it may be formed into a film by casting a cellulose acetate solution from two casting ports. For example, JP-B-60-27562, JP-A-61-94724, JP-A-61-947245, It can be carried out by the methods described in Japanese Utility Model Laid-Open Nos. 61-104413, 61-158413, and 6-134933. Alternatively, a cellulose acetate film casting method in which a flow of a high-viscosity cellulose acetate solution described in JP-A-56-162617 is wrapped with a low-viscosity cellulose acetate solution and the high- and low-viscosity cellulose acetate solution is simultaneously extruded. .

  Alternatively, using two casting ports, the film cast on the web 14 is peeled off by the first casting port, and the second casting is performed on the side that is in contact with the surface of the web 14 to thereby remove the film. For example, it is a method described in Japanese Patent Publication No. 44-20235. The cellulose acetate solution to be cast may be the same solution or different cellulose acetate solutions, and is not particularly limited. In order to give a function to a plurality of cellulose acetate layers, a cellulose acylate solution corresponding to the function may be extruded from each casting port.

  Furthermore, the cellulose acetate solution of the present invention can be cast simultaneously with other functional layers (for example, an adhesive layer, a dye layer, an antistatic layer, an antihalation layer, a UV absorbing layer, a polarizing layer). In conventional single-layer liquids, it is necessary to extrude a high-concentration and high-viscosity cellulose acetate solution to obtain the required film thickness. In this case, the stability of the cellulose acetate solution is poor and solids are generated. In many cases, however, it becomes a problem due to a failure or poor flatness. As a solution to this, by casting a plurality of cellulose acetate solutions from the casting port, it is possible to extrude a highly viscous solution onto the web 14 at the same time, thereby improving the flatness and producing an excellent planar film. In addition, by using a concentrated cellulose acetate solution, it was possible to reduce the drying load and increase the film production speed.

  A plasticizer can be added to the cellulose acetate film in order to improve mechanical properties or increase the drying speed. As the plasticizer, phosphoric acid ester or carboxylic acid ester is used. Examples of phosphate esters include triphenyl phosphate (TPP) and tricresyl phosphate (TCP). Representative examples of the carboxylic acid ester include phthalic acid esters and citric acid esters.

  Examples of phthalic acid esters include dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), dioctyl phthalate (DOP), diphenyl phthalate (DPP) and diethyl hexyl phthalate (DEHP). Examples of citrate esters include triethyl O-acetylcitrate (OACTE) and tributyl O-acetylcitrate (OACTB).

  Examples of other carboxylic acid esters include butyl oleate, methylacetyl ricinoleate, dibutyl sebacate, and various trimellitic acid esters. Phthalate plasticizers (DMP, DEP, DBP, DOP, DPP, DEHP) are preferably used. DEP and DPP are particularly preferred. The addition amount of the plasticizer is preferably 0.1 to 25% by mass of the amount of the cellulose ester, more preferably 1 to 20% by mass, and most preferably 3 to 15% by mass.

  Degradation inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines) may be added to the cellulose acetate film. The deterioration preventing agents are described in JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, and JP-A-6-107854. The addition amount of the deterioration preventing agent is preferably 0.01 to 1% by mass of the solution (dope) to be prepared, and more preferably 0.01 to 0.2% by mass. When the addition amount is less than 0.01% by mass, the effect of the deterioration preventing agent is hardly recognized. When the addition amount exceeds 1% by mass, bleed-out (bleeding) of the deterioration preventing agent to the film surface may be observed. Examples of particularly preferred deterioration inhibitors include butylated hydroxytoluene (BHT) and tribenzylamine (TBA).

  Next, the stretching process of the polymer film will be described. The produced cellulose acetate film (polymer film) can be further adjusted in retardation by a stretching treatment. The draw ratio is preferably 3 to 100%. The thickness of the polymer film is preferably 40 to 140 μm, and more preferably 70 to 120 μm. Further, by adjusting the conditions for the stretching treatment, the standard deviation of the slow axis angle of the optical compensation sheet can be reduced.

  There is no particular limitation on the stretching method, but examples thereof include a stretching method using a tenter. When the film produced by the above solvent cast method is subjected to transverse stretching using a tenter, the standard deviation of the film slow axis angle can be reduced by controlling the state of the film after stretching. Specifically, by performing a stretching process to adjust the retardation value using a tenter, and maintaining the polymer film immediately after stretching in the state in the vicinity of the glass transition temperature of the film, the standard of the slow axis angle Deviation can be reduced.

  If the film temperature during this holding is lower than the glass transition temperature, the standard deviation will increase. As another example, the standard deviation of the slow axis can be reduced by increasing the distance between the rolls when longitudinally stretching between the rolls.

  Next, the surface treatment of the polymer film will be described. When using a polymer film as a transparent protective film of a polarizing plate, it is preferable to surface-treat the polymer film. As the surface treatment, corona discharge treatment, glow discharge treatment, flame treatment, acid treatment, alkali treatment or ultraviolet irradiation treatment is performed. It is particularly preferred to carry out an acid treatment or an alkali treatment, ie a saponification treatment on the polymer film.

  Next, the alignment film will be described. The alignment film has a function of defining the alignment direction of the discotic liquid crystalline molecules of the optically anisotropic layer. The alignment film is an organic compound (eg, ω-tricosanoic acid) formed by rubbing treatment of an organic compound (preferably polymer), oblique deposition of an inorganic compound, formation of a layer having a microgroove, or Langmuir-Blodgett method (LB film). , Dioctadecylmethylammonium chloride, methyl stearylate). Furthermore, an alignment film in which an alignment function is generated by application of an electric field, application of a magnetic field, or light irradiation is also known.

  The alignment film is preferably formed by polymer rubbing treatment. Polyvinyl alcohol is a preferred polymer. Particularly preferred is a modified polyvinyl alcohol to which a hydrophobic group is bonded. Since the hydrophobic group has an affinity with the discotic liquid crystalline molecule of the optically anisotropic layer, the discotic liquid crystalline molecule can be uniformly aligned by introducing the hydrophobic group into polyvinyl alcohol.

The hydrophobic group is bonded to the main chain terminal or side chain of polyvinyl alcohol. The hydrophobic group is preferably an aliphatic group having 6 or more carbon atoms (preferably an alkyl group or an alkenyl group) or an aromatic group. When a hydrophobic group is bonded to the main chain terminal of polyvinyl alcohol, it is preferable to introduce a linking group between the hydrophobic group and the main chain terminal. Examples of the linking group include —S—, —C (CN) R ₁ —, —NR ₂ —, —CS—, and combinations thereof. The R1 and R ₂ are each (preferably, carbon atoms an alkyl group having 1 to 6) a hydrogen atom or a carbon atoms an alkyl group having 1 to 6 is.

When a hydrophobic group is introduced into the side chain of polyvinyl alcohol, a part of the acetyl group (—CO—CH ₃ ) of the vinyl acetate unit of polyvinyl alcohol is substituted with an acyl group having 7 or more carbon atoms (—CO—R). ₃ ). R ₃ is an aliphatic group or an aromatic group having 6 or more carbon atoms. Commercially available modified polyvinyl alcohol (eg, MP103, MP203, R1130, manufactured by Kuraray Co., Ltd.) may be used. The saponification degree of the (modified) polyvinyl alcohol used for the alignment film is preferably 80% or more. The degree of polymerization of (modified) polyvinyl alcohol is preferably 200 or more.

  The rubbing process is performed by rubbing the surface of the alignment film several times in a certain direction with paper or cloth. It is preferable to use a cloth in which fibers having uniform length and thickness are uniformly planted. Even if the discotic liquid crystalline molecules in the optically anisotropic layer are aligned using the alignment film, the alignment state of the discotic liquid crystalline molecules can be maintained even if the alignment film is removed. That is, the alignment film is essential in the production of the elliptically polarizing plate in order to align the discotic liquid crystal molecules, but is not essential in the produced optical compensation sheet.

  When providing the alignment film between the transparent web 14 and the optically anisotropic layer, it is preferable to further provide an undercoat layer (adhesive layer) between the transparent web 14 and the alignment film. Moreover, you may add a citrate ester as needed for planar stabilization.

  Next, the optical anisotropic layer will be described. The optically anisotropic layer is formed from discotic liquid crystalline molecules. Discotic liquid crystal molecules generally have an optically negative uniaxial property. In the optical compensation sheet of the present invention, in the discotic liquid crystalline molecule, the angle formed by the disk surface and the transparent web 14 surface changes in the depth direction of the optically anisotropic layer (hybrid alignment). It is preferable. The optical axis of the discotic liquid crystalline molecule exists in the normal direction of the disk surface.

  The discotic liquid crystalline molecule has birefringence in which the refractive index in the disc surface direction is larger than the refractive index in the optical axis direction. The optically anisotropic layer is preferably formed by aligning the discotic liquid crystalline molecules with the alignment film and fixing the discotic liquid crystalline molecules in the aligned state. The discotic liquid crystalline molecules are preferably fixed by a polymerization reaction.

In the optically anisotropic layer, there is no direction in which the retardation value becomes 0. In other words, the minimum retardation value of the optically anisotropic layer is a value exceeding 0. Specifically, the optically anisotropic layer has a Re retardation value defined by the following formula (I) of 10 to 100.
Rth retardation value defined by the following formula (II) is in the range of 40 nm to 25 nm.
The average tilt angle of the discotic liquid crystal molecules is preferably 20 to 50 ° in the range of 0 nm.
(I) Re = (nx−ny) × d
(II) Rth = {(n2 + n3) / 2−n1} × d
In the formula (I), nx is a refractive index in the slow axis direction in the optically anisotropic layer surface, and ny is
The refractive index in the fast axis direction in the plane of the optically anisotropic layer, and d is the thickness of the optically anisotropic layer. In Formula (II), n1 is the minimum value of the refractive index principal value when the optically anisotropic layer is approximated by a refractive index ellipsoid, and n2 and n3 are other refractive index principal values of the optically anisotropic layer. And d is the thickness of the optically anisotropic layer.

  Discotic liquid crystalline molecules are described in various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by the Chemical Society of Japan, Quarterly Chemical Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J. Am. Chem. Soc., Vol. 116, page 2655 (1994)). The polymerization of discotic liquid crystalline molecules is described in JP-A-8-27284.

In order to fix the discotic liquid crystalline molecules by polymerization, it is necessary to bond a polymerizable group as a substituent to the discotic core of the discotic liquid crystalline molecules. However, when the polymerizable group is directly connected to the disc-shaped core, it becomes difficult to maintain the orientation state in the polymerization reaction. Therefore, a linking group is introduced between the discotic core and the polymerizable group. Therefore, the discotic liquid crystalline molecule having a polymerizable group is preferably a compound represented by the following formula (III).
(III) D (-LQ) n
In the formula (III), D is a discotic core, L is a divalent linking group, Q is a polymerizable group, and n is an integer of 4 to 12.

  An example of the disk-shaped core (D) is shown below. In each of the following examples, LQ (or QL) means a combination of a divalent linking group (L) and a polymerizable group (Q).

  In the formula (III), the divalent linking group (L) is selected from the group consisting of an alkylene group, an alkenylene group, an arylene group, —CO—, —NH—, —O—, —S—, and combinations thereof. A divalent linking group is preferred. The divalent linking group (L) is a divalent group in which at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, —CO—, —NH—, —O—, and —S— are combined. More preferably, it is a linking group. The divalent linking group (L) is most preferably a divalent linking group in which at least two divalent groups selected from the group consisting of an alkylene group, an arylene group, -CO- and -O- are combined. . The alkylene group preferably has 1 to 12 carbon atoms. The alkenylene group preferably has 2 to 12 carbon atoms. The number of carbon atoms in the arylene group is preferably 6-10.

Examples of the divalent linking group (L) are shown below. The left side is bonded to the discotic core (D), and the right side is bonded to the polymerizable group (Q). AL represents an alkylene group or an alkenylene group, and AR represents an arylene group. The alkylene group, alkenylene group and arylene group may have a substituent (eg, an alkyl group).
L1: -AL-CO-O-AL-
L2: -AL-CO-O-AL-O-
L3: -AL-CO-O-AL-O-AL-
L4: -AL-CO-O-AL-O-CO-
L5: -CO-AR-O-AL-
L6: -CO-AR-O-AL-O-
L7: -CO-AR-O-AL-O-CO-
L8: -CO-NH-AL-
L9: -NH-AL-O-
L10: -NH-AL-O-CO-
L11: -O-AL-
L12: -O-AL-O-
L13: -O-AL-O-CO-
L14: -O-AL-O-CO-NH-AL-
L15: -O-AL-S-AL-
L16: -O-CO-AR-O-AL-CO-
L17: -O-CO-AR-O-AL-O-CO-
L18: -O-CO-AR-O-AL-O-AL-O-CO-
L19: -O-CO-AR-O-AL-O-AL-O-AL-O-CO-
L20: -S-AL-
L21: -S-AL-O-
L22: -S-AL-O-CO-
L23: -S-AL-S-AL-
L24: -S-AR-AL-
The polymerizable group (Q) of the formula (I) is determined according to the type of polymerization reaction.

  The polymerizable group (Q) is preferably an unsaturated polymerizable group (Q1 to Q7) or an epoxy group (Q8), more preferably an unsaturated polymerizable group, and an ethylenically unsaturated polymerizable group ( Most preferably, it is Q1-Q6). In the formula (III), n is an integer of 4 to 12. A specific number is determined according to the type of the disk-shaped core (D). In addition, although the combination of several L and Q may differ, it is preferable that it is the same.

  The optically anisotropic layer can be formed by applying a coating liquid containing discotic liquid crystalline molecules and, if necessary, a polymerizable initiator and optional components on the alignment film. The thickness of the optically anisotropic layer is preferably 0.5 to 100 μm, and more preferably 0.5 to 30 μm.

  The aligned discotic liquid crystal molecules are fixed while maintaining the alignment state. The immobilization is preferably performed by a polymerization reaction. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator. A photopolymerization reaction is preferred. Examples of the photopolymerization initiator include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substituted aromatic acyloin. Compound (described in US Pat. No. 2,722,512), polynuclear quinone compound (described in US Pat. Nos. 3,046,127 and 2,951,758), a combination of triarylimidazole dimer and p-aminophenyl ketone (US Pat. No. 3,549,367) Description), acridine and phenazine compounds (JP-A-60-105667, U.S. Pat. No. 4,239,850) and oxadiazole compounds (U.S. Pat. No. 4,212,970).

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. Light irradiation for polymerization of discotic liquid crystalline molecules is preferably performed using ultraviolet rays. Irradiation energy is preferably 20~5000mJ / cm ^2, further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. A protective layer may be provided on the optically anisotropic layer. Moreover, you may add a citrate ester as needed for planar stabilization.

  In the coating system 20 shown in FIG. 2, the density feedback control mechanism 56 is compared (Example) and not (Comparative Example), and the change in the density of the coating solution over time after the start of coating is examined. It was. Therefore, also in the comparative example, only the density meter 60 was installed in the liquid feeding pipe 52. The coating liquid used contained 50% by weight of solid content as a coating material, used an organic solvent of MEK (methyl ethyl ketone) as a solvent, and adjusted the density to 1.050 (this is defined as the specified density). In FIG. 2, the gravure coating device 21 is shown as the coating device. However, in this example, a bar coating device was used and applied to the web 14 traveling at 10 m / min.

  As a result, in the comparative example that does not have the density feedback control mechanism 56, the density of the coating liquid increased to 1.090 one hour after the start of coating, and the specified density could not be maintained. Further, the film thickness of the coating liquid applied to the web 14 when the density was 1.090 was 20% thicker than the specified film thickness.

  From this, every 20 minutes from the start of coating, 300 g of MEK was added to the liquid feeding tank 50 with respect to 10 kg of the coating solution. However, the density of the coating solution increased to 1.060 one hour after the start of coating. The density could not be maintained stably. Further, the film thickness of the coating liquid applied to the web 14 when the density was 1.060 was 5% thicker than the specified film thickness.

  Next, in the embodiment having the density feedback control mechanism 56, the density of the coating liquid can be maintained at the specified density of 1.050 even after 1 hour from the start of coating, and the film thickness at that time The fluctuation could be suppressed to within 1%. Also, the display of the density meter 60 during the coating test was constantly stable at 1.050, and the film thickness was also stable.

Explanatory drawing explaining the production line of the optical functional film to which the coating method and coating system of the coating liquid concerning this invention are applied Sectional drawing explaining the whole structure of a coating system Sectional drawing explaining an example of a defoaming means

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Optical functional film production line, 12 ... Delivery machine, 14 ... Web, 16 ... Guide roller, 18 ... Dust remover, 20 ... Coating system, 21 ... Coating device (gravure coating device), 22 ... Initial drying Zone, 24 ... Main drying zone, 26 ... Heating zone, 28 ... Ultraviolet lamp, 30 ... Winder, 32 ... Liquid feed line, 34 ... Collection line, 36 ... Gravure roller, 38 ... Backup roller, 40 ... Liquid receiving pan 42 ... Doctor blade, 44 ... Upstream guide roller, 46 ... Downstream guide roller, 48 ... Recovery pipe, 50 ... Liquid feed tank, 52 ... Liquid feed pipe, 54 ... Liquid feed pump, 56 ... Density feedback control mechanism, 58 ... Filter, 60 ... Density meter, 62 ... Calculation means, 64 ... Addition means, 66 ... Addition tank, 68 ... Addition pump, 70 ... Static mixer, 72 Defoaming means, 74 ... ultrasonic bath, 76 ... pipeline, 78 ... ultrasonic vibrator, 80 ... pressurizing valve, 82 ... supply port, 84 ... discharge port, 86 ... thermometer, 88 ... warning means, 90 ... Coating liquid amount control means

Claims (12)

In the coating method of the coating liquid for coating the organic solvent-based coating liquid fed to the coating apparatus via the liquid feeding pipe on the traveling support,
The density of the coating liquid flowing in the liquid feeding pipe is measured in-line, the density difference between the measured density measured and the prescribed density of the coating liquid defined in advance is calculated, and the density measurement position is adjusted so that the density difference is eliminated. A coating liquid coating method comprising: automatically adding a density adjusting liquid into the upstream liquid feeding pipe and feedback controlling the density of the coating liquid. In a coating system for coating an organic solvent-based coating liquid fed to a coating apparatus via a liquid feeding pipe on a traveling support,
A density meter for measuring in-line the density of the coating liquid flowing in the liquid feeding pipe;
A calculation means for calculating a density difference between the measured measurement density and a predetermined density of the coating liquid defined in advance;
An adding means for automatically adding a density adjusting liquid into the liquid feeding pipe upstream of the density meter so as to eliminate the density difference;
A coating system for coating liquid, comprising: a density feedback control mechanism comprising:   3. The coating liquid coating system according to claim 2, wherein the coating liquid is a coating liquid for manufacturing an optical film.   The coating apparatus collects an excess coating liquid that has not been applied to the support and supplies the coating apparatus again to the coating apparatus via the liquid supply pipe. The bar coating apparatus, the gravure coating apparatus, and the roll coating apparatus 4. The coating liquid coating system according to claim 2, wherein the coating liquid coating system is any one of a construction apparatus.   5. The coating liquid application system according to claim 2, wherein the density meter is a Coriolis mass flow meter.   6. The coating liquid coating system according to claim 2, wherein a static mixer is provided between the density meter and the adding unit in the liquid feeding pipe.   The coating liquid application system according to any one of claims 2 to 6, wherein a defoaming means for defoaming bubbles in the coating liquid is provided on the upstream side of the density meter in the liquid feeding pipe.   8. The coating liquid coating system according to claim 2, wherein the adding means is a plunger pump, a diaphragm pump, or a gear pump.   The thermometer which measures the temperature of a coating liquid in-line is provided in the upstream of the density meter in the liquid feeding pipe, and the calculation means corrects the temperature of the measured density. Application system of 1 application liquid.   The coating liquid application unit according to claim 2, further comprising: a coating liquid amount control unit that controls a coating liquid amount to be applied from the coating apparatus to the support based on the density difference. system.   The coating system for coating liquid according to any one of claims 2 to 10, further comprising warning means for warning when the density difference becomes larger than a predetermined value.   An optical functional film manufactured using the coating system according to any one of claims 2 to 11.

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