JP6045421B2 - Method for producing retardation film - Google Patents

Description

  The present invention relates to a method for producing a retardation film having an optically anisotropic layer in which liquid crystal compounds are aligned.

  In recent years, the use of liquid crystal display devices has been rapidly advanced, and is used in mobile phones, personal computer monitors, televisions, liquid crystal projectors, and the like.

  In general, in a liquid crystal display device, a TN (Twisted Nematic) mode, a VA (Vertical Alignment) mode, an IPS (In-Plane Switching) mode, an OCB (Optically Compensatory Bend) mode, an ECB (Electrically Bend mode), and the like. By operating the liquid crystal, the light passing through the liquid crystal is electrically controlled to show the difference between light and dark on the screen. As a result, the liquid crystal display device expresses characters and images.

  As such a liquid crystal display device, a TFT (Thin Film Transistor) -LCD is generally known. In recent years, with the progress of application development of liquid crystal display devices, there is an increasing demand for display devices with small changes in luminance and chromaticity depending on viewing angles. In order to meet this demand, research on an IPS mode liquid crystal display device is in progress. The IPS mode is often adopted as a display for a tablet PC or the like, and the brightness of the screen is greatly improved. For this reason, a slight light leakage in the diagonally oblique incident direction at the time of black display, which has not been regarded as a problem in the past, has become apparent as a cause of a decrease in display quality.

  For such a problem, Patent Document 1 discloses that a coating liquid in which a rod-like polymerizable liquid crystal compound is dissolved in an organic solvent is applied onto a support having an intermediate layer, and the coating liquid is dried. A method for forming an optically anisotropic layer by heating the coating solution and irradiating the heated coating solution with actinic radiation to cure it is described.

  In Patent Document 2, a blocking layer and an intermediate layer are formed on a support, a coating liquid containing a liquid crystal compound is applied thereon, and the liquid crystal layer is raised to an isotropic phase transition temperature or higher, Liquid crystal layer—A method for forming an optically anisotropic layer through a drying, heat treatment, and curing step that is maintained below an isotropic phase transition temperature is described.

JP 2010-211110 A JP 2002-277737 A

  However, in the method of Patent Document 1, since the alignment regulating force is weak and the heating time is insufficient, the occurrence of alignment defects cannot be avoided.

  Further, in the method of Patent Document 2, it is necessary to form two layers of the intermediate film, and thus the process becomes complicated, and since the solvent for dissolving the support is not used in the coating solution at the time of forming the intermediate film, the support and The problem was that the adhesion performance of the was poor.

  As described above, in order to align the liquid crystal on the support, an intermediate layer is often provided on the support and a liquid crystal layer is formed on the intermediate layer in many cases. This is because the intermediate layer has a function of aligning the liquid crystal and a function of preventing the support composition component from diffusing into the liquid crystal film.

  As a method for forming the intermediate layer, there is a coating method. In the case of the retardation film for IPS mode, the problem that the film peels off due to insufficient adhesion between the support and the intermediate layer has become apparent. It is considered that the lack of adhesion occurs because there is no factor for bonding the support and the interlayer film.

  Therefore, an attempt was made to enhance the adhesion between the support and the intermediate layer using a solvent that dissolves or swells the support in the coating solution for the intermediate layer. However, although the adhesion between the support and the intermediate layer is improved, a trade-off problem that the liquid crystal alignment defect of the liquid crystal layer occurs has become apparent.

  Therefore, as a result of extensive research by the inventors, the cause of liquid crystal alignment failure is that the components in the support are eluted and mixed in the intermediate layer, and the components in the support are further eluted in the liquid crystal layer above the intermediate film. -It was found that, as a result, the alignment at the interface between the intermediate layer and the liquid crystal layer is hindered, resulting in an alignment defect.

  The present invention has been made in consideration of such problems, and aims to provide an improved adhesion between a support and an intermediate layer and a method for producing a retardation film with little liquid crystal alignment failure. To do.

  In one embodiment of the present invention, a method for producing a retardation film includes a step of preparing a belt-like support containing a plasticizer and / or an optical property adjusting agent, and dissolving or supporting the support on a continuously running support. A first application step of applying a first raw material solution in which a resin is dissolved in a swelling solvent; a first drying step of drying the first raw material solution applied on the support to form a first coating film; A first curing step of irradiating the first coating film with actinic radiation, curing the first coating film, and forming an intermediate layer, and forming a plasticizer on a region of 10% or more of the surface of the intermediate layer And / or a second coating step in which an optical property modifier is present, and a second raw material liquid in which a rod-like polymerizable liquid crystal compound, an alignment controller, and an alignment aid are dissolved in a solvent is applied on the intermediate layer. The second raw material liquid applied on the intermediate layer is dried, the positions of the alignment control agent and the alignment aid are fixed, and the second coating liquid is Heating the second coating film for 25 seconds or more so that the internal temperature of the second coating film becomes a temperature at which the orientation control agent and the alignment aid are moved to the surface of the coating film. A heat treatment step, a cooling step for cooling the internal temperature of the second coating film to a temperature for fixing the position of the alignment control agent and the alignment aid after the heat treatment step, and a residual of less than 3% after the cooling step A curing step of irradiating the second coating film having a solvent ratio with actinic radiation, curing the second coating film, and forming an optically anisotropic layer.

Preferably, the solvent contained in the first raw material liquid has a solubility parameter SP value within a range of ± 2 (J / cm ³ ) ^1/2 with respect to the solubility parameter SP value of the support material.

  Preferably, the first raw material liquid contains a plurality of other solvents in addition to the solvent that dissolves or swells the support.

  Preferably, the resin contained in the first raw material liquid contains an organic material containing a hydrophilic group.

  According to this invention, the adhesiveness between a support body and an intermediate | middle layer is improved, and retardation film with few liquid crystal orientation defects can be manufactured.

The schematic block diagram of the manufacturing equipment of an intermediate | middle layer. The schematic block diagram of the manufacturing equipment of an optically anisotropic layer. The schematic block diagram of the manufacturing equipment of retardation film. Explanatory drawing which shows the effect | action of a liquid crystal compound, an alignment control agent, and an alignment adjuvant. It is a table | surface figure which shows the result of an Example.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The present invention will be described with reference to the following preferred embodiments, but can be modified in many ways without departing from the scope of the present invention, and other embodiments than the present embodiment can be used. be able to. Accordingly, all modifications within the scope of the present invention are included in the claims.

  Here, in the drawing, portions indicated by the same symbols are similar elements having similar functions. In addition, in the present specification, when a numerical range is expressed using “˜”, upper and lower numerical values indicated by “˜” are also included in the numerical range.

(Method for producing retardation film)
The method for producing a retardation film according to this aspect comprises a step of preparing a belt-like support containing a plasticizer and / or an optical property adjusting agent, and a solvent that dissolves or swells the support on the continuously running support. A first application step of applying a first raw material solution in which a resin is dissolved; a first drying step of drying the first raw material solution applied on the support to form a first coating; and a first application step A first curing step of irradiating the film with actinic radiation, curing the first coating film, and forming an intermediate layer, and in a region of 10% or more of the surface of the intermediate layer, the plasticizer and / or the aforementioned A second coating step in which an optical property adjusting agent is present, and a second raw material liquid in which a rod-like polymerizable liquid crystal compound, an alignment control agent, and an alignment aid are dissolved in a solvent is applied on the intermediate layer; The second raw material liquid applied on the layer is dried, the positions of the alignment control agent and the alignment aid are fixed, and the second A second drying step for forming a film, and the second coating film so that the internal temperature of the second coating film becomes a temperature for moving the alignment control agent and the alignment aid to the surface of the second coating film. A heat treatment step for heating for 25 seconds or more, a cooling step for cooling the internal temperature of the second coating film to a temperature for fixing the positions of the alignment control agent and the alignment aid after the heat treatment step, and after the cooling step, 3 A second curing step of irradiating the second coating film having a residual solvent ratio of less than% with actinic radiation, curing the second coating film, and forming an optically anisotropic layer.

  When the intermediate layer is formed on the support by a coating method, in order to obtain close contact between the support and the intermediate layer, a resin that is a material for the intermediate layer is dissolved in a solvent that dissolves or swells the support. 1 Prepare raw material liquid. By using a solvent that dissolves or swells the material of the support as the solvent of the first raw material liquid, a region where the support and the film of the first raw material liquid are mixed is formed. In this state, after drying, irradiation with actinic radiation causes a plasticizer and / or an optical property adjusting agent to be present in a region of 10% or more of the surface of the intermediate layer. Since the adhesion performance between the support and the intermediate layer is improved, the support and the intermediate layer are firmly bonded.

  When the optically anisotropic layer is formed on the intermediate layer by a coating method, a second raw material liquid in which a rod-like polymerizable liquid crystal compound, an alignment control agent, and an alignment aid are dissolved in a solvent is prepared.

  A 2nd raw material liquid is apply | coated on an intermediate | middle layer, and it dries, and forms a 2nd coating film. Next, in the heat treatment step, the temperature of the second coating film is raised to lower the viscosity. As a result, the liquid crystal compound moves to be in a non-aligned state, and the alignment control agent and the alignment aid are diffused to the coating film / air interface. After maintaining this state for 25 seconds or more, the temperature of the second coating film is lowered and the viscosity is increased in the cooling step before irradiation with active rays. Thereby, the movement of the liquid crystal compound is gradually realigned and the diffusion of the alignment control agent and the alignment aid is stopped. It was found that an optically anisotropic layer (liquid crystal layer) free from alignment defects can be formed by curing the second coating film by irradiation with actinic radiation in that state.

  Here, the alignment control agent plays a role of vertically aligning the liquid crystal compound, and greatly contributes to the alignment on the interface side of the intermediate film. In addition, the orientation control agent contributes to the orientation on the air interface side, but the orientation regulating force is weak, and it is an additive called an orientation aid that supports it. The alignment auxiliary agent plays a role of bringing the alignment control agent to the air interface side and unevenly distributing it. The alignment control agent moved to the air interface side contributes to the vertical alignment of the liquid crystal compound at the air interface. It is desirable to use a surfactant as an alignment aid.

  In the drying step, the second coating film is dried and fixed before the alignment control agent and the alignment auxiliary agent diffuse to the air interface side. In the subsequent heat treatment step, the orientation control agent and the alignment aid diffuse again by reducing the viscosity of the coating film. As a result, there are many alignment control agents and alignment aids at the air interface, and along with this, many alignment control agents diffuse on the air interface side. Thereby, when the liquid crystal is again vertically aligned in the cooling step, the alignment regulating force on the air interface side is strengthened.

  In the second coating film after the drying step, the liquid crystal is vertically aligned due to the effect of the alignment control agent, but the alignment is partially inhibited at the interface portion between the intermediate film and the second coating film. In the subsequent heat treatment step, the alignment of the liquid crystal in the second coating film is once brought into the non-aligned state including the interface portion between the intermediate film in which the alignment inhibition has occurred and the second coating film. Thereafter, the liquid crystal is re-orientated by cooling before irradiation with actinic radiation. At that time, the alignment regulating force on the air interface side is strengthened, so that the interface portion between the intermediate film and the second coating film is aligned. It is assumed that the orientation is improved overall.

  Regarding the heat treatment step, the heat treatment temperature needs to be a temperature at which the liquid crystal becomes non-aligned and the fixed alignment control agent and alignment aid diffuse again. Also, by setting the heat treatment time to 25 seconds or longer, it is possible to secure the time necessary for breaking the alignment inhibition at the interface portion between the intermediate film and the second coating film, and the alignment control agent and the alignment auxiliary agent are sufficiently air interface. It is possible to secure time for diffusion. As a result, the alignment of the liquid crystal compound is improved.

  With respect to the cooling step, the cooling temperature needs to be a temperature at which the liquid crystal is aligned again and the alignment control agent and alignment aid are fixed again.

<Support>
The support is preferably a resin film that is optically transparent and has birefringence. Engineeringly transparent means having a transmittance of 60% or more, and a transmittance of 80% or more is more preferable. Birefringence is expressed by retardation Re in the film plane and retardation Rth in the film thickness direction,
_{Re = (n x -n y)} × d
(N _x : refractive index in the direction of maximum refractive index in the plane of the support, n _y : refractive index in the direction perpendicular to the x axis in the plane, d: film thickness)
_{Rth = ((n x -n y} ) / 2-n z) × d
( _Nz : refractive index in the thickness direction)
Both Re and Rth are preferably 0 to 150 nm, and particularly preferably 70 to 120 nm.

  Specifically, the support is made of cellulose ester film (cellulose diacetate, cellulose triacetate, cellulose acetate butyrate, etc.), polyester film, polycarbonate film, polyester film (polyethylene terephthalate), polyethylene film, polypropylene film, poly Examples thereof include a chloride film, a polyvinyl alcohol film, a polymethyl methacrylate film, an acrylic film, and a norbornene film. A cellulose ester film is desirable as such a material.

  The support includes a plasticizer for imparting desired physical performance and an optical property adjusting agent for imparting desired optical performance.

  The plasticizer is not particularly limited, and preferred examples thereof include phthalate ester, phosphate ester, and resin acid.

  The optical property adjusting agent is not particularly limited, and preferred examples thereof include optical compounds such as aromatic ring-containing compounds, liquid crystal compounds, and anisotropically shaped compounds including nitrogen compounds described in JP-A-2012-234094. Examples include compounds having large anisotropy.

<First raw material liquid>
(Interlayer formation material)
The intermediate layer forming material is not particularly limited, and examples thereof include phenol resin, epoxy resin, fluororesin, polyethylene resin, and polypropylene resin. Further, for example, an organic material containing a hydrophilic group such as a hydroxyl group, an amino group, a carboxyl group, a sulfonic acid group, or a phosphoric acid group is preferable. Specifically, an acrylic resin, a polyvinyl alcohol resin, a polyester resin, an amino resin, or the like can be used.

  In particular, when the support is triacetylcellulose, the resin material of the intermediate layer is preferably an acrylic resin. The reason is that the hydrophilic group on the surface of the intermediate layer and the polar group of the alignment control agent are hydrogen-bonded, so that the vertical alignment of the liquid crystal compound of the optically anisotropic layer and the adhesion between the support and the intermediate layer are good. Because it becomes.

(solvent)
The solvent has a property of dissolving a resin as an intermediate layer forming material and dissolving or swelling the support. Examples of solvents that dissolve or swell cellulose ester include methyl ethyl ketone, acetone, methyl acetate, ethyl acetate, methylene chloride, ethylene chloride, tetrachloroethane, trichloroethane, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate. A plurality of solvents that dissolve or swell the support can also be combined.

  Here, the swelling means a state in which the volume of the polymer substance such as a resin is expanded by maintaining the solid state shape of the polymer substance, and the solvent molecules having a relatively low molecular weight enter the gap between the polymer substances and penetrate. Specifically, it means that a polymer film having a thickness of 0.1 mm is immersed in a solvent for 10 minutes and the thickness is increased by 1% or more. The thickness can be measured with a film thickness tester (Anritsu KB601). Dissolution means a state in which a polymer chain surrounded by solvent molecules is separated and dispersed in a solvent. Specifically, a polymer film of 50 mm × 50 mm × 0.1 mm is immersed in a solvent for 10 minutes. It means that the phenomenon of 0.1% or more occurs before and after the weight of the film is immersed. The weight can be measured with an electronic balance (XS104 manufactured by Mettler Toledo).

  A part of the solvent that does not dissolve or swell may also be included. These solvents are preferred, for example, to control dissolution or swelling of the support. For example, there are alcohols (ethanol, methanol, n-butanol, i-propyl alcohol, n-propyl alcohol, etc.), hydrocarbons (xylene, toluene, etc.) and the like.

  As described above, the first raw material liquid may contain a plurality of other solvents in addition to the solvent that dissolves or swells the support.

The solvent contained in the first raw material liquid preferably has a solubility parameter SP value within a range of ± 2 (J / cm ³ ) ^1/2 with respect to the solubility parameter SP value of the support material. Specifically, with respect to cellulose ester (SP value: 10.9), methyl ethyl ketone (SP value: 9.3), acetone (SP value: 10.0), methyl acetate (SP value: 9.6), acetic acid The combination of ethyl (SP value: 9.0) is mentioned.

  By using the solvent in the above range, adhesion between the intermediate layer and the support can be improved.

  As long as the first raw material liquid contains a solvent that dissolves or swells the support (= a solvent having an SP value close to that of the support), it may contain a plurality of other solvents. Since the solubility of the support can be controlled by another solvent, adhesion can be improved, which is more preferable.

(Polymerization initiator)
The first raw material liquid preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is advanced by ultraviolet irradiation, the polymerization initiator to be used is preferably a photopolymerization initiator that can start the polymerization reaction by ultraviolet irradiation. 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 aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US patents) No. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850), oxadiazole compounds (US Pat. No. 4,221,970), and the like. .

  It is preferable that the usage-amount of the said photoinitiator is 0.1-20 mass% of solid content of a 1st raw material liquid, and it is further more preferable that it is 1-8 mass%.

(Preparation of the first raw material liquid)
The first raw material liquid is prepared as a coating liquid in which the intermediate layer forming material is dissolved in a solvent. In the manufacturing method of the present embodiment, it is preferable to add a photopolymerization initiator to the first raw material liquid.

  In the coating step of the present embodiment, it is preferable that the coating liquid is applied to the surface of the support. As a coating method, it can be performed by various methods such as a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method.

<Second raw material liquid>
(Polymerizable liquid crystal compound)
The rod-like liquid crystal compound contained in the optically anisotropic layer is, for example, a rod-like nematic liquid crystal compound. Examples of rod-like nematic liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used. Not only low-molecular liquid crystal compounds but also high-molecular liquid crystal compounds can be used.

  The polymerizable liquid crystal compound can be obtained by introducing a polymerizable group into the liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, preferably an unsaturated polymerizable group, and particularly preferably an ethylenically unsaturated polymerizable group. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups possessed by the polymerizable liquid crystal compound is preferably 1 to 6, more preferably 1 to 3. Examples of polymerizable liquid crystal compounds are described in Makromol. Chem. 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, US Pat. No. 5,622,648, US Pat. No. 5,770,107, International Publication No. WO95 / 22586, No. 95/24455, No. 97/00600, No. 98/23580, No. 98/52905, JP-A-1-272551, No. 6-16616, No. 7-110469, The compounds described in JP-A-11-80081 and JP-A-2001-328773 are included. Two or more kinds of polymerizable liquid crystal compounds may be used in combination.

  The amount of the polymerizable liquid crystal compound contained in the second raw material liquid is preferably 10 to 50% by mass, more preferably 20 to 40% by mass, and 25 to 35% by mass. Particularly preferred.

(Orientation control agent)
The alignment control agent plays a role of vertically aligning the liquid crystal compound, and contributes to the alignment of the liquid crystal compound on the intermediate film interface side. That is, the molecules of the liquid crystal compound are substantially vertically aligned by the alignment control agent. There is no particular limitation as long as the alignment control agent can align the molecules of the liquid crystal compound substantially vertically. Preferable examples include compounds represented by the following general formula. You may contain 2 or more types selected from these.

As the alignment control agent, a material having a rod-like structure for vertically aligning the liquid crystal compound (that is, the main chain is somewhat long) and a hydrophilic group that easily binds to the intermediate film or the alignment aid is considered preferable. For example, the —N—C ₂ H ₆ moiety in Chemical Formula 1 is considered to be related to the function of the orientation control agent.

  In the general formula, R represents an alkoxy group having 1 to 30 carbon atoms, more preferably an alkoxy group having 1 to 20 carbon atoms, and still more preferably an alkoxy group having 1 to 15 carbon atoms. Provided that one or more CH2s in the alkoxy group and two or more CH2s not adjacent to each other are -O-, -S-, -OCO-, -COO-, -NRa-, -NRaCO-, -CONRa-, -NRaSO2 -Or -SO2NRa- may be substituted. Ra represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.

  Vertical alignment means that the liquid crystal molecule major axis is perpendicular to the film surface. However, it is not required to be strictly perpendicular, and in this specification, it means an orientation in which an inclination angle (= tilt angle) formed with a vertical plane is less than 30 degrees.

  The use amount of the orientation control agent is preferably 0.001 to 1% by mass, more preferably 0.005 to 0.5% by mass, and 0.01 to 0% by mass of the solid content of the second raw material liquid. It is particularly preferable that the content be 1% by mass.

(Alignment aid)
The alignment auxiliary agent plays a role of bringing the alignment control agent to the air interface side to be unevenly distributed, and contributes to the vertical alignment of the liquid crystal compound at the air interface. The above-mentioned alignment control agent contributes to the alignment on the air interface side but does not have a strong alignment regulating force. The alignment aid supports alignment on the air interface side. It is desirable to use a surfactant as an alignment aid. However, it is not particularly limited.

  Preferred examples include compounds represented by the following general formulas (I) and (II). Since the driving force for the alignment auxiliary agent itself to go to the air interface is required, the alignment auxiliary agent includes a group containing F, which has poor compatibility with the liquid crystal compound, and a hydrophilic group for bonding with the alignment control agent. It is considered preferable to have For example, in Chemical Formulas 2 and 3, the group containing F corresponds to the left group, and the hydrophilic group corresponds to the right -COOR- moiety. These are considered to be related to the function of the alignment aid.

  In the general formula, R represents an alkoxy group having 1 to 30 carbon atoms, more preferably an alkoxy group having 1 to 20 carbon atoms, and still more preferably an alkoxy group having 1 to 15 carbon atoms.

  In the above general formula, the parts marked with * are bonded to each other.

  Moreover, in the said general formula, a and b show the ratio contained in a compound.

  The amount of the alignment aid used is preferably 0.001 to 1% by mass, more preferably 0.005 to 0.5% by mass, based on the liquid crystal compound (solid content in the case of a coating liquid). Preferably, it is especially preferable that it is 0.01-0.1 mass%.

(solvent)
The solvent is not particularly limited as long as it dissolves the liquid crystal compound, the alignment controller, and the alignment aid. For example, ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and acetone, hydrocarbons such as benzene, toluene and xylene, esters such as methyl acetate, ethyl acetate, propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate , Ethers such as methoxybenzene and diethylene glycol dimethyl ether, amides such as dimethylformamide and dimethylacetamide, halogens such as methylene chloride, ethylene chloride, tetrachloroethane, and trichloroethane, alcohols such as methanol, ethanol, isopropyl alcohol, glycerin, and ethylene glycol There is a system. Also, a plurality of solvents can be combined.

(Polymerization initiator)
The second raw material liquid preferably contains a polymerization initiator. In the embodiment in which the polymerization reaction is advanced by ultraviolet irradiation, the polymerization initiator to be used is preferably a photopolymerization initiator that can start the polymerization reaction by ultraviolet irradiation. 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 aromatics. Group acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US patents) No. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850), oxadiazole compounds (US Pat. No. 4,221,970), and the like. . It is preferable that the usage-amount of the said photoinitiator is 0.1-20 mass% of solid content of a 2nd raw material liquid, and it is further more preferable that it is 1-8 mass%.

(Preparation of second raw material liquid)
The second raw material liquid is prepared as a coating liquid in which a liquid crystal compound, an alignment controller, and an alignment aid are dissolved in a solvent. In the manufacturing method of the present embodiment, it is preferable to add a photopolymerization initiator to the second raw material liquid. In the coating process of the present embodiment, it is preferable that the second raw material liquid is applied to the surface of the intermediate film. As a coating method, it can be performed by various methods such as a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, and a die coating method.

(Manufacturing process)
1 and 2 show an example of a retardation film manufacturing facility according to the present embodiment. A method for producing a retardation film using this production facility comprises applying a first raw material liquid on a belt-like support, drying the formed first coating film in a first drying step, A step of irradiating the first coating film with actinic radiation in the curing step to cure the first coating film to form an intermediate layer; and a second raw material liquid formed by applying a second raw material liquid on the intermediate layer. After the coating film was dried, the second coating film was heat-treated, the second coating film was cooled in the cooling step, and then the second coating film was irradiated with actinic radiation and cured in the second curing step. Forming an optically anisotropic layer. Manufacturing equipment and each process are explained.

  The retardation film manufacturing facility comprises the intermediate film manufacturing facility 10 shown in FIG. 1 and the optically anisotropic layer manufacturing facility 40 shown in FIG. The production apparatus 10 for the intermediate film includes a delivery device 12 that sends out a belt-like support W, a coating head 14 that coats the first raw material liquid, a backup roller 16 that holds the support W, and an upstream side of the coating head 14. A decompression chamber 18, a drying device 20, an active ray irradiation device 22, a temperature control roller 24, and a winding device 26 are provided.

  The optical anisotropic layer manufacturing facility 40 also includes a delivery device 42 for delivering the support W on which the intermediate layer is formed, a coating head 44 for applying the second raw material liquid, and a backup roller 46 for holding the support W. , A decompression chamber 48 upstream of the coating head 44, a drying device 50, a heat treatment device 52, a cooling device 54, an actinic radiation irradiation device 56, a temperature control roller 58, and a winding device 60.

(A) Step of preparing a belt-like support The belt-like support W has a roll shape wound around a winding core. The roll-shaped support W is continuously run using the delivery device 12. The delivery device 12 includes a roller (not shown) on which a roll-shaped support W wound around a winding core can be installed. By rotating this roller, the belt-like support W is continuously conveyed to a coating device or the like.

(B) First application step of applying the first raw material solution In the first application step, the first raw material solution is applied onto the belt-like support W that has been continuously conveyed using an application device. As a coating device, a general coating device can be used without limitation. For example, the backup roller 16 that holds the belt-like support W that is continuously conveyed, the coating head 14 that coats the first raw material liquid on the belt-like support W wrapped on the backup roller 16, and the coating head 14 In order to stabilize a bead (a pool of coating liquid) formed between the first raw material liquid and the belt-like support, there is a coating apparatus having a decompression chamber 18 on the upstream side of the coating head 14. The flow rate of the first raw material liquid supplied from the coating head 14 is adjusted by the pump so that the required film thickness is obtained. The degree of decompression of the decompression chamber 18 is adjusted by a decompression pump. The gap with the backup roller 16 is adjusted to be narrow, and the beads are stably formed.

(C) The 1st drying process which dries the 1st raw material liquid apply | coated on the support body, and uses it as a 1st coating film In the 1st drying process, it apply | coats using the drying apparatus 20 which heats a 1st raw material liquid. The 1st raw material liquid apply | coated on the strip | belt-shaped support body W at the process is dried, and a 1st coating film is formed. As the drying apparatus 20, a general drying apparatus can be used without limitation. For example, a convection drying method using hot air, a radiation drying method using radiant heat such as infrared rays, or the like can be used. When hot air is used, drying of the coating film is controlled by adjusting the temperature and air volume of the hot air. Moreover, as a method of applying hot air, a slit nozzle (a nozzle having a slit-like opening shape in the width direction of a belt-like support), a punching nozzle (a porous flat plate nozzle), or the like can be used.

(D) First curing process in which the first coating film is irradiated with actinic radiation to cure the first coating film to form an intermediate layer. In the first curing process, the active ray irradiation device 22 is used to perform the first drying process. The dried first coating film is irradiated with actinic rays to cure the first coating film. For example, an ultraviolet irradiation device or the like is used as the active ray irradiation device 22. When using an ultraviolet irradiation device, the irradiation intensity and irradiation amount of ultraviolet light are adjusted to adjust the degree of cure of the first coating film. The irradiation intensity is preferably ^{10~1000mW / cm 2, 100~400mW / cm} 2 is more preferable. Moreover, 10-1000 mJ / cm < ² > is desirable for integrated irradiation amount, and 20-200 mJ / cm < ² > is more desirable. Moreover, the oxygen concentration of the atmosphere around the 1st coating film at the time of irradiation with an active ray may be reduced as needed, and the hardening degree of a 1st coating film may be adjusted, and 50-1000 ppm is desirable.

  Moreover, the first coating film temperature before irradiation with active rays can be adjusted by an arbitrary method, and for example, it can be adjusted by wrapping a belt-like support on the temperature control roller 24. 5-80 degreeC is desirable and 20-50 degreeC is more preferable.

  After the first curing step, the belt-like support W on which the intermediate layer is formed is wound up by the winding device 26 in the winding step. The winding device 26 includes a roller (not shown) on which a winding core can be installed, and continuously winds the belt-like support W by rotating the roller. A plasticizer and / or an optical property adjusting agent is present in an area of 10% or more of the surface of the formed intermediate layer. Thereafter, the optically anisotropic layer is formed by the optically anisotropic layer manufacturing equipment 40.

(E) Second Application Step for Applying Second Raw Material Liquid A roll-like belt-like support W on which an intermediate layer is formed is installed in the delivery device 42 of the optical anisotropic layer manufacturing facility 40. The roll-shaped support W is continuously run on a coating device or the like by using a delivery device 42.

  In the second application step, the second raw material liquid is applied onto the belt-like support W that is continuously transported using an application device. As a coating device, a general coating device can be used without limitation. For example, the backup roller 46 that holds the belt-like support W that is continuously conveyed, the coating head 44 that coats the second raw material liquid on the belt-like support W wrapped by the backup roller 46, and the coating head 44 In order to stabilize a bead (a pool of coating liquid) formed between the second raw material liquid and the belt-like support W, there is a coating apparatus having a decompression chamber 48 on the upstream side of the coating head 44. The flow rate of the second raw material liquid supplied from the coating head is adjusted by the pump so that the required film thickness is obtained. The degree of decompression of the decompression chamber 48 is adjusted by a decompression pump. The gap with the backup roller 46 is adjusted to be narrow and a bead is stably formed.

(F) The second drying process in which the second raw material liquid formed on the intermediate layer is dried, the positions of the alignment control agent and the alignment aid are fixed, and the second coating film is formed. In the second drying process, Using the drying device 50 that heats the two raw material liquids, the second raw material liquid coated on the belt-like support in the coating process is dried to form a second coating film. The drying device 50 can use a general heating device without limitation. For example, a convection drying method using hot air or a radiation drying method using radiant heat such as infrared rays is used. When hot air is used, drying of the coating film is controlled by adjusting the temperature and air volume of the hot air. Moreover, as a method of applying hot air, a slit nozzle (a nozzle having a slit-like opening shape in the width direction of a belt-like support), a punching nozzle (a porous flat plate nozzle), or the like can be used.

  In the second drying step, the coating film is dried until the coating film reaches a drying point. Here, the drying point refers to a point in the drying process in which the film surface temperature of the second coating film is the same as the temperature of the drying air in the vicinity of the second coating film. This means that the solvent is evaporated until the equilibrium state is reached and the endothermic reaction associated with the evaporation disappears (= the place where the solvent in the coating film decreases and evaporation hardly occurs). The coating film viscosity at this time is 5000 mPa · s or more. The viscosity of the coating film can be measured with a vibration viscometer (SV-10, manufactured by A & D Co., Ltd.) after quickly scraping off the coating film on the support that has reached the drying point.

(G) A heat treatment step for heating the second coating film so that the internal temperature of the second coating film becomes a temperature for moving the alignment control agent and the alignment aid to the surface of the coating film. In the heat treatment step, the second drying step In order to heat-treat the second coating film of the belt-like support W having the second coating film dried in (1), a heat treatment device 52 is provided. Heat for at least 25 seconds to reach a temperature at which the alignment control agent and alignment aid move to the surface of the second coating. The temperature of the second coating film is preferably in the range of 90 to 120 ° C.

  As the heat treatment apparatus 52, a general heating apparatus can be used without limitation. For example, a convection drying method using hot air or a radiation drying method using radiant heat such as infrared rays is used. When hot air is used, the temperature and amount of hot air are adjusted to control the drying of the second coating film. Moreover, as a method of applying hot air, a slit nozzle (a nozzle having a slit-like opening shape in the width direction of a belt-like support), a punching nozzle (a porous flat plate nozzle), or the like can be used. Also, the heat treatment step can be continuously provided without any gap with the second drying step.

(H) Second curing step in which the second coating film is irradiated with actinic radiation to form an optically anisotropic layer The belt-like support W having the second coating film heat-treated in the heat treatment step is cooled in the cooling step. The apparatus 54 adjusts the temperature to be appropriate for the irradiation of active radiation in the second curing step. As the cooling device 54, a convection cooling method using cooling air is generally used. When the cooling air is used, the temperature and the air volume of the cooling air are adjusted to control the temperature of the second coating film. Moreover, as a method of applying cooling air, a slit nozzle (a nozzle having a slit-like opening shape in the width direction of a belt-like support), a punching nozzle (a porous plate nozzle), or the like can be used. In addition, a cooling device may not be installed when an appropriate coating film temperature is obtained without providing a cooling step. The cooling temperature is set so as to fix the positions of the alignment control agent and the alignment aid.

In the second curing step, the active film irradiation device 56 is used to irradiate the second coating film cooled in the cooling process with active rays to cure the coating film. For example, an ultraviolet irradiation device or the like is used as the active ray irradiation device 56. When using an ultraviolet irradiation device, the irradiation intensity and irradiation amount of ultraviolet rays are adjusted to adjust the degree of curing of the coating film. The irradiation intensity is preferably ^{10~1000mW / cm 2, 100~400mW / cm} 2 is more preferable. Moreover, 10-1000 mJ / cm < ² > is desirable for integrated irradiation amount, and 20-200 mJ / cm < ² > is more desirable. If necessary, the oxygen concentration in the atmosphere around the coating film when irradiated with actinic radiation may be reduced to adjust the degree of curing of the coating film, preferably 50 to 1000 ppm. Before the active ray irradiation by the active ray irradiation device 56, the residual solvent ratio of the coating film is set to less than 3%.

  When the residual solvent ratio in the film is 3% or more, the residual solvent in the film inhibits the alignment and the subsequent crosslinking reaction by irradiation with active rays, resulting in poor alignment and a decrease in film strength.

  Moreover, the coating film temperature before active ray irradiation can be adjusted by arbitrary methods, for example, can be adjusted by wrapping a belt-like support on the temperature control roller 58. 5-80 degreeC is desirable and 20-50 degreeC is more preferable.

  After the second curing step, the belt-like support W on which the intermediate layer is formed is wound up by the winding device 60 in the winding step. The winding device 60 includes a roller (not shown) on which a winding core can be installed, and continuously winds the belt-like support W by rotating the roller.

  1 and 2, the belt-like support W on which the intermediate layer is formed is wound into a roll, and then the roll-like support W is fed out to form an optically anisotropic layer. However, the present invention is not limited to this, and as shown in FIG. 3, the support W is transferred from the intermediate layer manufacturing facility 10 to the optical anisotropic layer manufacturing facility 40 via the guide roller 70 without being wound once. It can also be transported.

Next, operations of the liquid crystal compound, the alignment control agent, and the alignment aid will be described with reference to FIG.
FIG. 4A shows a state in which a second raw material liquid containing a liquid crystal compound, an alignment control agent, and an alignment aid is applied on the intermediate layer in the second application step. All the materials of the liquid crystal compound, the alignment control agent, and the alignment aid are arranged non-oriented.

  FIG. 4B shows a state in which the second coating film has been dried in the second drying step. At the interface between the intermediate layer and the second coating film, some liquid crystal compounds are aligned in the vertical direction by the alignment control agent. At the interface between the second coating film and air, the liquid crystal compound is vertically aligned by the alignment control agent diffused to the air interface side by the alignment aid. When drying of the second coating film proceeds, the diffusion of the alignment control agent and the alignment aid stops. As a result, some liquid crystal compounds are not aligned in the vertical direction.

  FIG. 4C shows a state where the second coating film is heated in the heat treatment step. The viscosity of the second coating film is lowered, and the alignment control agent and the alignment aid move to the air interface side. In addition, the alignment of the liquid crystal compound is lost, and the liquid crystal compound is non-oriented.

  FIG. 4D shows a state in which the active ray is irradiated through the cooling process. By cooling before actinic ray irradiation, the liquid crystal compound is aligned again. In addition, since the alignment control agent and the alignment aid are moved to the air interface side at that time, the alignment regulating force for the liquid crystal compound on the air interface side is strengthened. As a result, it is presumed that the orientation of the interface portion of the intermediate film / optically anisotropic layer is supported, and the orientation of the liquid crystal compound of the optically anisotropic layer is improved overall.

  Hereinafter, the present invention will be described in more detail with reference to examples of the present invention. However, the present invention is not limited to these examples.

<Preparation of support>
Fujitac TD40UZ, which is a commercially available cellulose triacetate film (TAC) manufactured by FUJIFILM Corporation, was prepared. When this film was analyzed for components using a time-of-flight secondary ion mass spectrometer TOF-SIMS (TOF SIMS 5 manufactured by ION-TOF), molecular ions derived from the support and additives (support component: C ₅ H ₅ O ₂ ⁺ , a plasticizer component; C ₁₄ H ₁₅ O ₆ (derived from a phthalate ester), an optical developer component: C ₂₄ H ₂₅ N ₆ (derived from a nitrogen compound)) were detected.

<Preparation of the first raw material liquid>
PETA (pentaerythritol triacrylate) and PVA (polyvinyl alcohol) were used as the intermediate layer forming material. As the solvent, methyl acetate, MIBK (methyl isobutyl ketone), methanol, and water were used alone or in combination. Methyl acetate is a solvent that soaks into the support.

  In PETA, a first raw material liquid was prepared with a solid content concentration of 20 mass% and a photopolymerization initiator Irgacure 127 (manufactured by BASF) at 0.3 mass%. In PVA, a first raw material liquid was prepared with a solid content concentration of 5 mass% and a photopolymerization initiator Irgacure 127 (manufactured by BASF) at 0.3 mass%. As PETA, a compound represented by the following chemical formula (Chemical Formula 4)) pentaerythritol triacrylate (PET-30) manufactured by Nippon Kayaku Co., Ltd.) was used. Moreover, linear alkyl-modified polyvinyl alcohol (MP203): manufactured by Kuraray was used as PVA.

<Formation of intermediate layer>
The prepared 1st raw material liquid was supplied to the slit die of the manufacturing equipment shown in FIG. 1, and it apply | coated so that the dry film thickness might be set to 1.5 micrometers on a cellulose triacetate film. After coating, the solvent of the film was dried in a drying process to form a coating film. Thereafter, the coating film was cured by irradiating ultraviolet rays with an integrated light amount of 500 mJ / cm 2 with a high-pressure mercury lamp in an atmosphere having an oxygen concentration of 300 ppm to form an intermediate layer having a thickness of 1.5 μm.

  Here, the drying speed was controlled by adjusting the temperature of the drying process and the solvent gas concentration. Specifically, it was dried with a hot air of 80 ° C. until it reached the drying point to form a coating film. The drying point is determined by measuring the coating film temperature in the drying process and the film surface temperature of the belt-like support without the coating film after coating (= the temperature of the drying air in the vicinity of the coating film). I confirmed that. Here, the coating film temperature and the film surface temperature of the belt-like support were measured by installing a non-contact thermometer (IT2-80, manufactured by Keyence Corporation).

The composition of the surface of the intermediate layer is obtained by sampling the film after forming the intermediate layer, and adding the support using two-dimensional mapping with a time-of-flight secondary ion mass spectrometer TOF-SIMS (TOF SIMS 5 manufactured by ION-TOF). Molecular ions (support component: C ₅ H ₅ O ₂ ⁺ , plasticizer component; C ₁₄ H ₁₅ O ₆ ⁺ , optical enhancer component: C ₂₄ H ₂₅ N ₆ ) caused by the product on the film surface of the intermediate layer The ratio of existence was calculated as the area ratio of each signal component (= area where each signal exists / analysis area).

<Preparation of second raw material liquid>
A polymerizable liquid crystal compound composed of 80% by mass of a compound represented by the following chemical formula (Chemical Formula 5) and 20% by mass of the following compound represented by the following Chemical Formula (Chemical Formula 6) (the transition temperature is differential scanning calorimetry DCS (Q20 manufactured by TA Instrument) ), A photopolymerization initiator Irgacure 907 (made by BASF) represented by the following chemical formula (Chemical Formula 7), 3% by mass, an orientation control agent represented by the following chemical formula (Chemical Formula 8), 1% by mass, and the following: A second raw material liquid was prepared by dissolving an alignment aid represented by the chemical formula (Chemical Formula 9): 0.4% by mass in a solvent in which methyl ethyl ketone and cyclohexanone were mixed at a ratio of 80:20.

<Formation of optically anisotropic layer>
The prepared 2nd raw material liquid was supplied to the slit die of the manufacturing equipment shown in FIG. 2, and it apply | coated on the film in which the intermediate | middle layer was formed. After coating, the solvent of the film was dried at an ambient temperature of 55 ° C. in a drying process to form a coating film. The coating film was heated by changing the temperature and time in the heat treatment step. The film surface temperature was measured with a non-contact thermometer. Thereafter, through a cooling step in which the temperature of the coating film is set to be lower than the phase transition temperature of the polymerizable liquid crystal compound, the temperature before ultraviolet irradiation is set to the temperature described in the table, and 300 mJ / cm with a high-pressure mercury lamp in an atmosphere with an oxygen concentration of 300 ppm. Irradiation with an integrated light amount of ² was performed to form an optically anisotropic layer having a thickness of 1.5 μm. The film thickness was measured using an interference type film thickness meter FE3000 (manufactured by Otsuka Electronics). Further, the residual solvent ratio in the coating film is calculated from the solid content concentration immediately after the heat treatment step, and the solid content concentration after the heat treatment step is obtained by sampling the film after the heat treatment step and vacuum drying apparatus (DP22 manufactured by Yamato Scientific) Was calculated from the mass before and after removing the solvent. The mass was measured with an electronic balance (XS104 manufactured by Mettler Toledo).

  For the alignment control agent and alignment aid, as in the evaluation of the support component amount of the interlayer film, two-dimensional mapping by TOF-SIMS (TOF SIMS 5 made by ION-TOF) is used after the drying process and after the heat treatment. The proportion of fluorine on the surface of the sample was measured, and when the amount of fluorine was large, it was determined that the alignment control agent and the alignment aid were diffused on the surface.

<Evaluation of orientation defects>
The obtained film was sandwiched between crossed Nicol polarizers, and the presence or absence of a cloudy portion observed due to alignment defects was visually observed.
A: No cloudy part B: Some cloudy part is visible, but there is no practical problem C: The cloudy part is clearly visible and practically harmful <Evaluation of adhesion>
Evaluation was performed by a cross-cut method based on JIS K5600-5-6.
A: 0% peeling (no peeling)
B: Peeling within 5% C: Peeling within 10% D: Peeling over 10% <Evaluation result>
In Examples 1-8 , evaluation of C or more was performed with respect to adhesion, and evaluation of alignment defects was B or more. In Example 5 , since the support component was 30 (%), the evaluation for the adhesion was A. On the other hand, in Examples 4 and 6 , since the support component was 10 (%), the evaluation for adhesion was C.

In Examples 1, 2, and 4-6 , which satisfy the conditions of 100 ° C. and 60 seconds in the heat treatment step, the evaluation is A regarding the alignment defect, and the alignment control agent and the alignment auxiliary agent diffuse to the surface of the coating film. I think. On the other hand, in the heat treatment step, Example in 3 times 25 seconds, actual施例7 in the liquid crystal phase - since a slightly higher 86 ° C. than the isotropic phase transition temperature, respectively evaluation was B. Movement of the alignment controlling agent and the alignment aid is considered was small compared to Example 1, 2,4-6. In the cooling step, Example 8 was 84 ° C. lower than the liquid crystal phase-isotropic phase transition temperature. Evaluation was B.

  In Comparative Example 1, the temperature was 80 ° C. in the heat treatment step. Diffusion between the alignment controller and the alignment aid was not sufficient, and the evaluation for the alignment defect was C.

  In Comparative Example 2, the heat treatment step was 100 ° C. for 20 seconds. Diffusion between the alignment controller and the alignment aid was not sufficient, and the evaluation for the alignment defect was C.

  In Comparative Example 3, the residual solvent ratio was 3 (%). The evaluation was C regarding the alignment defect.

  In Comparative Example 4-7, the evaluation was D for the adhesiveness in which the support component was less than 10%. In Comparative Example 8-10, since either one or both of the alignment controller and the alignment aid was not included, the evaluation for the alignment defect was C.

  DESCRIPTION OF SYMBOLS 10 ... Manufacturing equipment of an intermediate | middle layer, 12, 42 ... Sending-out apparatus, 14, 44 ... Coating head, 16, 46 ... Backup roller, 18, 48 ... Decompression chamber, 20, 50 ... Drying apparatus, 22, 56 ... Actinic radiation irradiation Device, 24, 58 ... Temperature control roller, 26, 60 ... Winding device, 40 ... Optical anisotropic layer manufacturing equipment, 52 ... Heat treatment device, 54 ... Cooling device, 70 ... Guide roller

Claims (4)

Preparing a belt-like support containing a plasticizer and / or an optical property modifier;
A first application step of applying a first raw material solution in which a resin is dissolved in a solvent that dissolves or swells the support on the support that continuously runs;
A first drying step of drying the first raw material liquid coated on the support to form a first coating film;
A first curing step of irradiating the first coating film with actinic radiation, curing the first coating film and forming an intermediate layer, and in a region of 10% or more of the surface of the intermediate layer The presence of the plasticizer and / or the optical property modifier,
A second coating step of coating a second raw material solution in which a rod-like polymerizable liquid crystal compound, an alignment control agent, and an alignment aid are dissolved in a solvent on the intermediate layer;
Drying the second raw material liquid applied on the intermediate layer, fixing the position of the alignment control agent and the alignment aid, and forming a second coating film; and
The second coating film is heated for 25 seconds or more so that the internal temperature of the second coating film becomes a temperature for moving the alignment control agent and the alignment aid to the surface of the second coating film. A heat treatment step;
After pre-Symbol heat treatment step, a cooling step of cooling to be the internal temperature of the second coating film to a temperature for fixing the position of the alignment aid and the alignment controlling agent,
After the cooling step, a second curing step of irradiating the second coating film having a residual solvent ratio of less than 3% with active radiation, curing the second coating film, and forming an optically anisotropic layer;
A method for producing a retardation film comprising: The said solvent contained in a said 1st raw material liquid has the solubility parameter SP value in the range of +/- 2 (J / cm < ³ >) ^<1/2 > with respect to the solubility parameter SP value of the raw material of the said support body. The method for producing a retardation film.   The method for producing a retardation film according to claim 1, wherein the first raw material liquid contains a plurality of other solvents in addition to the solvent that dissolves or swells the support.   The said resin contained in a said 1st raw material liquid is a manufacturing method of the phase difference film of any one of Claim 1 to 3 containing the organic material which has a hydrophilic group.