JP6938758B2 - Phase difference film manufacturing method and manufacturing equipment - Google Patents

Description

The present disclosure relates to a method and an apparatus for manufacturing a retardation film.

As a retardation film used for a liquid crystal display or the like, a film in which an alignment layer and a liquid crystal layer are provided on a support is known.

As an example of a method for producing a retardation film, Japanese Patent Application Laid-Open No. 2007-52049 states that "a first step of forming at least one optically anisotropic layer on a long film that runs continuously is described. A second step of winding a long film on which at least one optically anisotropic layer is formed is included, and after the first step and before the second step, at least one layer of optical heterogeneity is included. A method for producing an optical compensation sheet, characterized in that the retardation of a long film having a sex layer is continuously measured, is disclosed.

Further, in Japanese Patent Application Laid-Open No. 2014-199321, a transparent strip-shaped support having a photoreactive alignment film coated on its surface is continuously transported, and during the transport, the alignment film is alternately transported with a constant width in the width direction. A pattern position in which a series of multiple line-shaped pattern exposures are applied in the transport direction to apply a resin layer exhibiting polarization characteristics to the alignment film, and then the resin layer is irradiated with light to be cured. In the method for producing a retardation film, the support is continuously conveyed with a tension such that the shrinkage ratio in the width direction is 0.02% or less from the time when the pattern exposure is applied until the end of the curing treatment, and the curing treatment is started. To change the intensity of light irradiation during the period from time to end, and give a temperature history that suppresses the fluctuation of the linear pattern within the desired numerical range while keeping the polarization characteristics imparted to the resin layer within the desired numerical range. A method for producing a pattern retardation film, which is characterized by the above, is disclosed.

Lettering is the most important physical characteristic of retardation films. In recent years, a retardation film having a small in-plane distribution of retardation has been desired.
In order to improve productivity, the retardation film is produced by a continuous process in a roll-to-roll method using a continuous film support.
More specifically, the retardation film is a coating film obtained by applying and drying a liquid crystal layer forming material containing a liquid crystal compound on the alignment layer of a continuous film support provided with an alignment layer (hereinafter, "" It is manufactured by a method of immobilizing the orientation of a liquid crystal compound by exposing it to ultraviolet rays on a "coating film for a liquid crystal layer").
When a material for forming a liquid crystal layer containing a liquid crystal compound is applied, a slight unevenness in the coating thickness occurs in the width direction of the continuous film support. In particular, when a coating means such as a curtain coating method is used, uneven coating thickness often continues in the transport direction.
Then, the unevenness of the coating thickness mainly causes the unevenness of the retardation of the retardation film.
In Japanese Patent Application Laid-Open No. 2007-52049, fine adjustment is made under the conditions in the coating process and the heating process so as to reach the target value based on the measurement result of the retardation. However, in this method, the phase difference is obtained. It is difficult to adjust the retardation in the width direction of the film, and there is a limit to reducing the in-plane distribution of the retardation.
Further, in Japanese Patent Application Laid-Open No. 2014-199321, the retardation of the retardation film is not adjusted.

Therefore, the problem to be solved by one embodiment of the present invention has been made in view of the above circumstances, and the phase difference in which the in-plane distribution of the retardation is small while using the continuous process in the roll-to-roll method. The purpose is to provide a method for producing a film.
Another problem to be solved by another embodiment of the present invention is to provide a retardation film manufacturing apparatus having a small in-plane distribution of retardation while using a continuous process in a roll-to-roll method. be.

Means for solving the above problems include the following embodiments.
<1> The first step of forming an alignment layer having an orientation regulating force for a liquid crystal compound on a continuous film support that is continuously conveyed, and
The second step of applying and drying a liquid crystal layer forming material containing a liquid crystal compound on the alignment layer to form a coating film, and
The third step of irradiating the coating film with ultraviolet rays,
In the fourth step, the retardation is measured along the width direction of the continuous film support for the coating film irradiated with ultraviolet rays, and the distribution of the measured values of the retardation in the width direction is obtained.
When there is a measured value outside the predetermined range in the width direction distribution of the obtained retardation measurement value, ultraviolet rays to irradiate the coating film at the width direction position corresponding to the measurement position of the measured value outside the predetermined range. The fifth step of adjusting the illuminance of
A method for producing a retardation film having.

<2> In the fifth step, the coating film is irradiated with an adjustment amount obtained in advance from the relationship between the illuminance of the ultraviolet rays applied to the coating film and the retardation value of the coating film irradiated with the ultraviolet rays. The method for producing a retardation film according to <1>, which is a step of adjusting the illuminance of ultraviolet rays.

<3> The phase difference according to <1> or <2>, wherein the third step is performed by a module light source in which a plurality of units including a plurality of light emitting diode elements are arranged in parallel along the width direction of a continuous film support. Film manufacturing method.

<4> The method for producing a retardation film according to any one of <1> to <3>, wherein the application of the liquid crystal layer forming material in the second step is performed by a curtain coating method or a die coating method.

<5> The method according to any one of <1> to <4>, which comprises a sixth step of further irradiating the coating film irradiated with ultraviolet rays with ultraviolet rays by a high-pressure mercury light source or a metal halide light source after the fourth step. A method for manufacturing a retardation film.

<6> An alignment layer forming means for forming an alignment layer having an orientation regulating force for a liquid crystal compound on a continuous film support that is continuously conveyed.
A coating means for applying a liquid crystal layer forming material containing a liquid crystal compound on the alignment layer, and
A drying means for forming a coating film by drying the material for forming a liquid crystal layer after coating,
Ultraviolet irradiation means for irradiating the coating film with ultraviolet rays,
A retardation measuring means for measuring the retardation of a coating film irradiated with ultraviolet rays along the width direction of a continuous film support,
When there is a measured value outside the predetermined range in the width direction distribution of the measured value of the retardation obtained from the measured value of the measured retardation, the width corresponding to the measurement position of the measured value outside the predetermined range. A control means for controlling the illuminance of the ultraviolet rays irradiating the coating film at the directional position, and
A device for manufacturing a retardation film having.

<7> The control means irradiates the coating film with an adjustment amount obtained in advance from the relationship between the illuminance of the ultraviolet rays applied to the coating film and the retardation value of the coating film irradiated with the ultraviolet rays. The device for producing a retardation film according to <6>, which controls the adjustment of the illuminance of ultraviolet rays.

<8> The retardation film according to <6> or <7>, wherein the ultraviolet irradiation means is a module light source in which a plurality of units including a plurality of light emitting diode elements are arranged in parallel along the width direction of a continuous film support. Manufacturing equipment.

<9> The retardation film manufacturing apparatus according to any one of <6> to <8>, wherein the coating means is a means using a curtain coating method or a die coating method.

<10> In addition to the ultraviolet irradiation means, another ultraviolet irradiation means for irradiating the coating film with ultraviolet rays by a high-pressure mercury light source or a metal halide light source is provided on the downstream side in the transport direction of the continuous film support. The apparatus for producing a retardation film according to any one of 1.

According to one embodiment of the present invention, there is provided a method for producing a retardation film having a small in-plane distribution of retardation while using a continuous process in a roll-to-roll method.
According to another embodiment of the present invention, there is provided an apparatus for producing a retardation film having a small in-plane distribution of retardation while using a continuous process in a roll-to-roll system.

FIG. 1 is a schematic view showing each step of the method for producing a retardation film according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part showing an example of irradiation with polarized ultraviolet rays in the method for producing a retardation film according to an embodiment of the present invention. FIG. 3 is a plan view showing the arrangement of the wire grid of the wire grid polarizer. FIG. 4 is a diagram illustrating an irradiation angle when irradiating polarized ultraviolet rays. FIG. 5A is a schematic diagram showing an example for explaining the measurement of retardation. FIG. 5B is a schematic diagram showing another example for explaining the measurement of retardation.

Hereinafter, an embodiment of a method for manufacturing a retardation film and a manufacturing apparatus of the present invention will be described. However, the present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention.

The numerical range indicated by using "~" in the present disclosure means a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.
Each element in each of the drawings presented in this disclosure is not necessarily on an exact scale, with an emphasis on clearly showing the principles of this disclosure and some emphasis.
Further, in each drawing, components having the same function are designated by the same reference numerals, and duplicate description will be omitted.
In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

≪Manufacturing method and equipment for retardation film≫
The present inventors investigated a method for producing a retardation film in a continuous process using a roll-to-roll method, and found that the phase difference was achieved by adjusting the illuminance of ultraviolet rays irradiating the coating film for a liquid crystal layer. Focusing on the change in the retardation value of the film, we found a method to suppress the unevenness of the retardation of the retardation film by the following method.
That is, first, after the liquid crystal layer coating film is irradiated with ultraviolet rays, the retardation is measured in the width direction of the continuous film support, and the distribution of the measured values of the retardation in the width direction is obtained. Then, when there is a measured value outside the predetermined range in the widthwise distribution of the measured value of the obtained retardation, the coating for the liquid crystal layer at the width direction corresponding to the measured position of the measured value deviated from the predetermined range. Adjust the illuminance of the ultraviolet rays that irradiate the film (for example, increase or decrease the illuminance of the ultraviolet rays).
Here, the "coating film for the liquid crystal layer at the width direction corresponding to the measurement position" refers to the coating film for the liquid crystal layer not irradiated with ultraviolet rays whose position in the width direction of the continuous film support corresponding to the measurement position is conveyed. means. Therefore, in the method for manufacturing a retardation film that employs the above method, the retardation measurement position is located on the downstream side with respect to the transport direction of the continuous film support, and the ultraviolet irradiation position is located on the upstream side of the measurement position. be. Then, at the ultraviolet irradiation position, as described above, it is possible to adjust the illuminance of the ultraviolet rays to irradiate the liquid crystal layer coating film at the width direction position corresponding to the measurement position of the measured value outside the predetermined range.
As described above, by using the measurement result of the retardation for adjusting the illuminance of ultraviolet rays with respect to the coating film for the liquid crystal layer, it is possible to obtain a retardation film having a small in-plane distribution of the retardation.
In the manufactured retardation film, the retardation measurement position is located on the front end side, and the ultraviolet illuminance adjusted position is located on the end side of the measurement position.
By this method, a retardation film having a small in-plane distribution of retardation can be obtained.

From the above, the method for producing a retardation film of one embodiment includes a first step of forming an alignment layer having an orientation regulating force for a liquid crystal compound on a continuous film support that is continuously conveyed, and on the alignment layer. A second step of applying and drying a liquid crystal layer forming material containing a liquid crystal compound to form a coating film (that is, a coating film for a liquid crystal layer), a third step of irradiating the coating film with ultraviolet rays, and irradiation with ultraviolet rays. The fourth step of measuring the retardation along the width direction of the continuous film support to obtain the width direction distribution of the measurement value of the retardation on the coated film, and the width direction of the obtained measurement value of the retardation. When there is a measured value outside the predetermined range in the distribution, the illuminance of ultraviolet rays irradiating the coating film (that is, the coating film for the liquid crystal layer) at the width direction corresponding to the measurement position of the measured value outside the predetermined range. It has a fifth step of adjusting the above.
The method for producing a retardation film of one embodiment is performed by, for example, the following apparatus for producing a retardation film of one embodiment.

The retardation film manufacturing apparatus of one embodiment includes an alignment layer forming means for forming an alignment layer having an orientation regulating force for a liquid crystal compound on a continuous film support that is continuously conveyed, and a liquid crystal compound on the alignment layer. The coating means for applying the liquid crystal layer forming material including the coating material, the drying means for drying the liquid crystal layer forming material after coating to form a coating film, and the coating film (that is, the coating film for the liquid crystal layer) are irradiated with ultraviolet rays. The ultraviolet irradiation means, the retardation measuring means for measuring the retardation along the width direction of the continuous film support for the liquid crystal irradiated with ultraviolet rays, and the retardation obtained from the measured values of the measured retardation. When there is a measured value outside the predetermined range in the width direction distribution of the measured value of, the coating film at the width direction corresponding to the measurement position of the measured value deviating from the predetermined range (that is, the coating film for the liquid crystal layer). It has a control means for controlling the illuminance of the ultraviolet rays irradiating the liquid crystal.
Hereinafter, the details of the method for manufacturing the retardation film of one embodiment will be described together with the apparatus for manufacturing the retardation film of one embodiment.

[First step]
The method for producing a retardation film of one embodiment includes a first step of forming an alignment layer having an orientation regulating force with respect to a liquid crystal compound on a continuous film support that is continuously conveyed.
In the first step, the method for forming the alignment layer having the orientation regulating force with respect to the liquid crystal compound is not particularly limited, and a rubbing method or a photoalignment method may be used.
Here, the rubbing method is a method in which a roll wrapped with a rubbing cloth is rotationally moved while being pushed at a constant pressure on a coating film containing a material for forming an alignment layer to give the coating film an orientation regulating force for a liquid crystal compound. be.
Further, the photo-alignment method is a method in which a coating film of a material for forming an alignment layer is irradiated with polarized light (for example, polarized ultraviolet rays) to give the coating film an orientation-regulating force for a liquid crystal compound.
In recent years, it has become a problem that fine dust is generated or static electricity is generated due to friction of the coating film. Therefore, in the first step, a photo-alignment method that does not require friction of the coating film is adopted. It is preferable to do so.
Hereinafter, the first step using the photoalignment method will be described.

An example of the first step will be described with reference to FIG.
As shown in FIG. 1, when the tip of the wound continuous film support F is sent out, the alignment layer forming material is first applied by the alignment layer forming material coating means 1, and then the alignment layer forming material is applied. The material for forming the alignment layer is dried in the drying region by the drying means 2. In this way, a coating film (hereinafter, also referred to as "coating film for alignment layer") obtained by applying and drying a material for forming an alignment layer is formed on the continuous film support.
Subsequently, in the region where the continuous film support is wound around the backup roll, the coating film for the alignment layer is irradiated with polarized ultraviolet rays to form an alignment layer having an orientation regulating force.
Specifically, as shown in FIG. 1, after the coating film for the alignment layer is formed on the continuous film support F, photoalignment occurs in the region where the continuous film support F is wound around the backup roll 3b. The apparatus 3a irradiates the coating film for the alignment layer with polarized ultraviolet rays.

-Continuous film support-
As the continuous film support, it is preferable to use a polymer film.
Examples of polymer film materials used as continuous film supports include cellulose acylate (eg, cellulose triacetate (triacetyl cellulose, refractive index 1.48), cellulose diacetate, cellulose acetate butyrate, cellulose acetate propionate. ), Polyester such as polyethylene and polypropylene, polyester such as polyethylene terephthalate and polyethylene naphthalate, acrylic resin such as polyether sulfone and polymethyl methacrylate, polyurethane, polycarbonate, polysulfone, polyether, polymethylpentene, polyether ketone, poly ( Meta) Acrylic nitrile, polymer having an alicyclic structure (for example, norbornene resin (trade name "Arton (registered trademark)", JSR), amorphous polyolefin (for example, trade name "Zeonex (registered trademark)", Japan Zeon Co., Ltd.)), etc.
Of these, from the viewpoint of low optical anisotropy and the like, triacetyl cellulose, polyethylene terephthalate (that is, PET), and a polymer having an alicyclic structure are preferable, and triacetyl cellulose is particularly preferable.

The thickness of the continuous film support is preferably in the range of 10 μm to 250 μm. The thickness of the continuous film support is more preferably 15 μm or more, further preferably 30 μm or more, from the viewpoint of high applicability to winding on a backup roll. The thickness of the continuous film support is preferably 150 μm or less, more preferably 120 μm or less, from the viewpoint of material cost.

-Material for forming an orientation layer-
Examples of the material for forming the alignment layer used for forming the alignment layer applied to the photoalignment method include JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, and JP-A. 2007-94071, 2007-121721, 2007-140465, 2007-156439, 2007-133184, 2009-109831, 3883848 , The azo compound described in Japanese Patent No. 4151746, the aromatic ester compound described in JP-A-2002-229039, and the polyfunctional maleimide derivative having a structural unit exhibiting photoorientity described in JP-A-2002-265541. An alkenyl-substituted nadiimide compound, a polymerizable monomer having a photo-oriented group and a polymerizable maleimide group described in JP-A-2002-317013, a photocrosslinkable silane derivative described in Patent No. 4205195 and Patent No. 4205198. , Japanese Patent Laid-Open No. 2003-520878, Japanese Patent Application Laid-Open No. 2004-522220, Japanese Patent Application Laid-Open No. 4162850, photocrosslinkable polyimides, polyamic acids, or esters thereof, JP-A-9-118717, JP-A-10- Photodimerizable compounds (particularly, synnamate compounds and chalcones) described in JP-A-506420, JP-A-2003-505561, International Publication No. 2010/150748, JP-A-2013-177561, and JP-A-2014-12823. Compounds, coumarin compounds) and the like.
Among these, particularly preferable examples include the azo compound described in the above publication, the photocrosslinkable polyimide, polyamide, or an ester thereof described in the above publication, the synnamate compound described in the above publication, the chalcone compound and the like.

-Applying method-
A known coating device is applied to the coating means 1 of the material for forming an oriented layer.
Specific examples of the coating device include curtain coating method, dip coating method, spin coating method, printing coating method, spray coating method, slot coating method, roll coating method, slide coating method, blade coating method, gravure coating method, and wire. An example is a device using the bar method or the like.

-Drying method-
A known drying means is applied to the drying means 2 of the material for forming an oriented layer.
Specific examples of the drying means include a method using an oven, a hot air blower, an infrared (IR) heater, and the like.
In drying with a warm air blower, warm air may be blown from the surface of the continuous film support opposite to the surface on which the alignment layer forming material is applied, and the surface of the applied alignment layer forming material becomes warm air. A diffuser plate may be installed so that the film does not flow.
The drying conditions may be determined according to the type of the material for forming the alignment layer used, the coating amount, the transport speed, and the like. For example, the drying conditions are preferably carried out in the range of 30 ° C. to 140 ° C. for 10 seconds to 10 minutes.

As described above, the coating film for the alignment layer is formed.
The film thickness of the formed alignment layer coating film is preferably 0.1 μm to 5 μm, more preferably 0.2 μm to 1 μm.

-Polarized UV irradiation and photo-alignment device-
Subsequently, the coating film for the alignment layer formed on the continuous film support F is irradiated with polarized ultraviolet rays.
According to FIG. 1, in the region where the continuous film support F on which the coating film for the alignment layer is formed is wound around the backup roll 3b, the coating film for the alignment layer is irradiated with polarized ultraviolet rays by the photoalignment device 3a. ..
Irradiation of polarized ultraviolet rays in the form of supporting the continuous film support F by the backup roll 3b can be performed on the continuous film support in a state of being stretched along the shape of the backup roll 3b, and This is preferable from the viewpoint that the temperature of the continuous film support F can be easily controlled by the backup roll 3b.
The irradiation of polarized ultraviolet rays in the first step is not limited to the form in which the back surface of the continuous film support F (that is, the surface opposite to the surface on which the coating film for the alignment layer is formed) is supported by the backup roll 3b. The back surface of the continuous film support F may be supported by a flat belt or a flat guide.
Further, the irradiation of the polarized ultraviolet rays in the first step does not require a flat belt or a flat guide for supporting the back surface of the continuous film support F as long as the flatness of the coating film for the alignment layer can be ensured.

Hereinafter, an example of the photoalignment apparatus used for irradiating polarized ultraviolet rays will be described with reference to FIGS. 2 to 4.
As shown in FIG. 2, the photoaligning device 3a includes a rod-shaped light source 10, a concave reflector 11 that efficiently reflects the light from the rod-shaped light source 10 in the vertical direction toward the wire grid polarizer 30, and the longitudinal length of the rod-shaped light source 10. It is composed of a louver 20 composed of a plurality of parallel plates 21 arranged in a direction, and a wire grid polarizer 30 that linearly polarizes the light parallelized by the louver 20.
Then, the polarized ultraviolet rays emitted through the wire grid polarizer 30 are applied to the coating film for the alignment layer.

-Bar-shaped light source As the bar-shaped light source 10, for example, a tungsten lamp, a halogen lamp, a xenon lamp, a xenon flash lamp, a mercury lamp, a mercury xenon lamp, a carbon arc lamp or the like, and various lasers (eg, a semiconductor laser, a helium neon laser) , Argon ion laser, helium cadmium laser, YAG (Yttrium Aluminum Garnet) laser), light emitting diode, cathode wire tube and the like.
The peak wavelength of ultraviolet rays emitted from the rod-shaped light source 10 is preferably 200 nm to 400 nm.

-Lovers As shown in FIG. 2, the parallel plates 21 of the louvers 20 are arranged at equal intervals in the longitudinal direction X of the backup roll 3b (that is, the circumferential direction of the backup roll 3b), and the rod-shaped light source 10 and the wire grid. It is arranged between the polarizer 30 and the polarizer 30. By installing the louver 20, the light from the rod-shaped light source 10 can be made into parallel light, the spread of the light incident on the wire grid polarizer 30 can be suppressed, and the light can be made directly in front of the backup roll.
Further, in FIG. 2, the parallel plates 21 are arranged at an angle orthogonal to the longitudinal direction X of the backup roll, but the parallel plates 21 may be arranged not only orthogonally but also in parallel in an oblique direction. The pitch and angle of the parallel plate 21 can be adjusted by an interlocking mechanism (not shown).

Although FIG. 2 shows a case where the louver 20 is composed of parallel plates arranged in the longitudinal direction of the backup roll 3b, the configuration of the louver 20 is not limited to this. As another configuration of the louver 20, for example, the louver 20 may be composed of a plurality of tubular portions having a polygonal or circular cross section, and the central axis of the cylinder may be arranged in a direction perpendicular to the central axis of the backup roll. A non-reflective film may be provided on the constituent surface.

Further, it is preferable that the louver 20 is installed as close as possible to the rod-shaped light source 10 so as not to leak light from the louver 20. In order to suppress light leakage, the louver 20 may be brought into contact with the rod-shaped light source 10, or the gap may be shielded by another member.
The same applies to the gap between the louver 20 and the wire grid polarizer 30.

As the material of the louver 20, a heat-resistant material such as stainless steel or aluminum can be used.
The surface of the louver 20 may be smoothed to improve the reflectance in order to increase the irradiation efficiency of the irradiation light. Further, the louver 20 may be provided with irregularities on the surface or covered with a non-reflective film to reduce the reflectance in order to enhance the straightness of the irradiation light. When reducing the reflectance of the surface of the louver 20, it is preferable that a light absorbing member is provided on the surface of the parallel plate 21 of the louver 20.

-Wire grid polarizing element As shown in FIGS. 2 and 3, the wire grid polarizing element 30 includes a plurality of wire grid polarizing elements 32 held in a frame 31.
Each wire grid polarizing element 32 has a wire grid 34 composed of a plurality of linear electric conductors arranged on the substrate 33.
The wire grid polarizing element 32 reflects the polarized (polarized) component parallel to the longitudinal direction of the wire grid 34, and passes the polarized (polarized) component orthogonal to the wire grid 34. The direction of passing through the orthogonal polarization components is called the transmission axis.
Examples of the electric conductor include metal wires such as chromium and aluminum.

As shown in FIG. 3, the arrangement angle θ of the wire grid 34 satisfies 0 ° <θ <90 ° with respect to the direction orthogonal to the longitudinal direction X of the backup roll 3b (that is, the direction indicated by the dotted line in FIG. 3). Is preferable. That is, the arrangement angle θ of the wire grid 34 is preferably an angle that is not orthogonal or parallel to the longitudinal direction X of the backup roll 3b.

-Irradiation angle of polarized ultraviolet rays by the photoaligning device Next, the irradiation angle of polarized ultraviolet rays on the backup roll 3b will be described with reference to FIG.
As shown in FIG. 4, in the plane perpendicular to the axis center O of the backup roll 3b, the line passing through the axis center O of the backup roll 3b and perpendicular to the substrate surface 38 of the wire grid polarizer 30 is defined as the reference line L1. The angle formed by the line L1 and the line L2 connecting the axial center O of the backup roll 3b and the upstream end M of the polarized light irradiation region A on the continuous film support F in the transport direction is θ1, and the reference line L1 and the backup When the angle formed by the line L3 connecting the axial center O of the roll 3b and the downstream end N in the transport direction of the polarized light irradiation region A on the continuous film support F is θ2, | It is preferable to satisfy.
More preferably, | θ1-θ2 | <7 °, and even more preferably, | θ1-θ2 | = 0 °.
By setting | θ1-θ2 | <10 °, it is possible to irradiate the curved surface of the backup roll 3b with polarized ultraviolet rays from the front, and it is possible to reduce the variation in the orientation axis of the liquid crystal compound.

-Backup roll-
As the backup roll 3b, a known one can be used without particular limitation.
As the backup roll 3b, for example, one having a hard chrome-plated surface can be preferably used.
The thickness of the plating is preferably 40 μm to 60 μm from the viewpoint of ensuring conductivity and strength.
The surface roughness of the backup roll 3b is preferably 0.1 μm or less in terms of surface roughness Ra from the viewpoint of reducing the variation in the frictional force between the continuous film support F and the backup roll 3b.

The temperature of the backup roll 3b is preferably maintained at 25 ° C to 100 ° C, more preferably 25 ° C to 50 ° C.
By maintaining the backup roll 3b at the above temperature, the temperature of the continuous film support F to be wound can be controlled.

It is preferable that the surface temperature of the backup roll 3b is maintained by the temperature control means that detects the surface temperature and controls the surface temperature based on the surface temperature.
The temperature control means of the backup roll 3b includes a heating means and a cooling means. Induction heating, water heating, oil heating and the like are used as the heating means, and cooling water is used as the cooling means.

The diameter of the backup roll 3b is preferably 100 mm to 1000 mm, more preferably 100 mm to 800 mm, from the viewpoint of easy winding of the continuous film support, easy irradiation of polarized ultraviolet rays, and the manufacturing cost of the backup roll 3b. It is preferably 200 mm to 700 mm, and more preferably 200 mm to 700 mm.

In the first step, since the continuous film support F in a state where the irradiation of polarized ultraviolet rays is stretched is performed, for example, as shown in FIG. 1, the continuous film support F on which the backup roll 3b is wound is subjected to. It is preferable that tension is applied in the longitudinal direction.
The width of the continuous film support F (referred to as Fw2) when tension is applied is smaller than the width of the continuous film support F (referred to as Fw1) when tension is not applied.
The shrinkage ratio of the width of the continuous film support F on the backup roll 3b is obtained from the following formula (1), preferably 0.05% to 1.00%, and 0.07% to 0. More preferably, it is 30%.
Equation (1) Shrinkage rate (%) = (Fw1-Fw2) / Fw1 × 100
(Fw1 indicates the width of the continuous film support when tension is not applied, and Fw2 indicates the width of the continuous film support when tension is applied on the backup roll.)
Tension may be applied to the continuous film support F on the backup roll 3b so that the shrinkage ratio is as described above. Specifically, in order to achieve the above shrinkage ratio, the tension applied to the continuous film support F on the backup roll 3b is preferably 100 N / m to 600 N / m.

The transport speed of the continuous film support F on the backup roll 3b is preferably 10 m / min or more and 100 m / min or less from the viewpoint of ensuring productivity and improving the accuracy of irradiation with polarized ultraviolet rays. , 20 m / min or more and 60 m / min or less is preferable.

The lap angle of the continuous film support F with respect to the backup roll 3b is preferably 60 ° or more, more preferably 90 ° or more.
The lap angle is the transport direction of the continuous film support F when the continuous film support F comes into contact with the backup roll 3b, and the continuous film support F when the continuous film support F is separated from the backup roll 3b. It refers to the transport direction of and the angle consisting of.

By irradiating the coating film for the alignment layer with polarized ultraviolet rays as described above, a photoreaction is generated in the material for forming the alignment layer, and as a result, an alignment layer having an orientation regulating force for the liquid crystal compound is formed. ..

[Second step]
In the method for producing a retardation film of one embodiment, after the first step, a liquid crystal layer forming material containing a liquid crystal compound is applied and dried on an alignment layer to form a coating film (that is, a coating film for a liquid crystal layer). It has a second step.
An example of the second step will be described with reference to FIG.
As shown in FIG. 1, when the irradiation of the coating film for the alignment layer on the backup roll 3b with polarized ultraviolet rays is completed, the liquid crystal layer forming material containing the liquid crystal compound is subsequently applied by the coating means 4 of the liquid crystal layer forming material. Is applied, and then the material for forming the liquid crystal layer is dried in the drying region by the drying means 5.
In this way, a coating film for a liquid crystal layer is formed on the alignment layer of the continuous film support.

-Material for forming a liquid crystal layer-
The material for forming a liquid crystal layer contains a rod-shaped liquid crystal compound or a disk-shaped liquid crystal compound, and further known other components such as a polymerizable compound, a crosslinkable compound, a chiral agent, an orientation control agent, a polymerization initiator, and an orientation aid. May be contained.

-Stick-shaped liquid crystal compounds Examples of rod-shaped liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, and alkoxy-substituted ones. Phenylpyrimidines, phenyldioxans, trans, and alkenylcyclohexylbenzonitriles are preferably used.
In addition to the small molecule liquid crystal molecules as described above, high molecular weight liquid crystal molecules can also be used.

It is more preferable to fix the orientation of the rod-shaped liquid crystal compound by polymerization, and therefore it is preferable to use a rod-shaped liquid crystal compound having a polymerizable group.
Examples of the polymerizable rod-shaped liquid crystal compound include Makromol. Chem. , 190, 2255 (1989), Advanced Materials 5, 107 (1993), US Pat. No. 4,683,327, 5,622,648, 5770107, International Publication 95/22586, 95 / 24455, 97/00600, 98/23580, 98/52905, Japanese Patent Application Laid-Open No. 1-272551, 6-16616, 7-110469, 11- Examples thereof include compounds described in Japanese Patent Application Laid-Open No. 80081 and Japanese Patent Application Laid-Open No. 2001-328973.
Further, as the rod-shaped liquid crystal compound, for example, those described in JP-A No. 11-513019, JP-A-2007-279688, etc. can be preferably used.

-Disc-shaped liquid crystal compound As the disk-shaped liquid crystal compound, for example, those described in JP-A-2007-108732, JP-A-2010-2404038 and the like can be preferably used.

-Applying method and drying method-
Since the same method as the coating and drying in the first step can be used for coating and drying the liquid crystal layer forming material, detailed description thereof will be omitted here.
However, the application of the liquid crystal layer forming material in the second step is preferably performed by a curtain coating method or a die coating method.
Even when such a coating method is adopted, a retardation film having a small in-plane distribution of retardation can be obtained by having the fourth step and the fifth step described later.

Here, the solid content concentration of the liquid crystal layer forming material (that is, the coating liquid applied to the above-mentioned coating) containing the liquid crystal compound used in the second step is preferably 5% by mass to 40% by mass.
The viscosity of the liquid crystal layer forming material containing the liquid crystal compound (that is, the coating liquid applied to the above-mentioned coating) at 25 ° C. is preferably 0.5 mPa · s to 10 mPa · s.

-Orientation of liquid crystal compounds-
In the third step described later, it is preferable to perform the orientation treatment of the liquid crystal compound in the coating film for the liquid crystal layer before fixing the orientation of the liquid crystal compound.
The orientation treatment can be performed by drying at room temperature or the like or by heating.
In the case of a liquid crystal compound having thermotropic properties, the liquid crystal formed by the orientation treatment can generally be transferred by a change in temperature or pressure. Further, in the case of a liquid crystal compound having a lyotropic property, it can be transferred by a composition ratio such as the amount of solvent.

When the rod-shaped liquid crystal compound expresses the smectic phase, the temperature range in which the nematic phase is expressed is usually higher than the temperature range in which the rod-shaped liquid crystal compound expresses the smectic phase. Therefore, the rod-shaped liquid crystal compound is heated to the temperature range in which the rod-shaped liquid crystal compound expresses the nematic phase, and then the heating temperature is lowered to the temperature range in which the rod-shaped liquid crystal compound expresses the smectic phase, whereby the rod-shaped liquid crystal compound is brought into the nematic phase. Can be transferred to the smectic phase. By setting the smectic phase in this way, a liquid crystal in which the liquid crystal compounds are oriented with high order can be obtained.

In the temperature range in which the rod-shaped liquid crystal compound expresses the nematic phase, it is necessary to heat the rod-shaped liquid crystal compound for a certain period of time until it forms a monodomain. The heating time is preferably 10 seconds to 5 minutes, more preferably 10 seconds to 3 minutes, and most preferably 10 seconds to 2 minutes.
In the temperature range in which the rod-shaped liquid crystal compound expresses the smectic phase, it is necessary to heat for a certain period of time until the rod-shaped liquid crystal compound expresses the smectic phase. The heating time is preferably 10 seconds to 5 minutes, more preferably 10 seconds to 3 minutes, and most preferably 10 seconds to 2 minutes.

The orientation of the liquid crystal compound may be performed by drying in the second step. That is, in the drying in the second step, both the drying of the liquid crystal layer forming material coated on the alignment layer and the orientation of the liquid crystal compound may be performed.
Of course, the orientation of the liquid crystal compound may be performed separately from the drying in the second step. In that case, a drying means or a heating means for orienting the liquid crystal compound may be provided on the downstream side of the continuous film support F of the drying means 5 shown in FIG. 1 in the transport direction.

[Third step]
The method for producing a retardation film of one embodiment includes a third step of irradiating the coating film for a liquid crystal layer with ultraviolet rays after the second step.
In the third step, the liquid crystal compound in the liquid crystal layer coating film is oriented and the orientation is fixed to form the liquid crystal layer.
An example of the third step will be described with reference to FIG.
As shown in FIG. 1, after the liquid crystal layer coating film is formed on the alignment layer of the continuous film support F, the liquid crystal layer coating film is irradiated with ultraviolet rays by the ultraviolet irradiation means 6. By irradiating with this ultraviolet ray, the orientation of the liquid crystal compound in the coating film for the liquid crystal layer is fixed to form the liquid crystal layer.

-Fixing the orientation of liquid crystal compounds-
In the third step, the orientation of the liquid crystal compound in the coating film for the liquid crystal layer is fixed.
The orientation of the liquid crystal compound can be fixed by thermal polymerization or polymerization by active energy rays, and can be carried out by appropriately selecting a polymerizable group or a polymerization initiator of the liquid crystal compound suitable for the polymerization.
Considering the production suitability and the like, the polymerization reaction by the ultraviolet rays irradiated from the ultraviolet irradiation means 6 as shown in FIG. 1 can be preferably used.
When a polymerizable liquid crystal compound is used, if the irradiation amount of ultraviolet rays is small, the unpolymerized liquid crystal compound remains, which causes temperature changes in optical characteristics, deterioration over time, and the like. Therefore, it is preferable to determine the irradiation conditions so that the proportion of the remaining unpolymerized liquid crystal compound is 5% or less.
The irradiation conditions, the formulation of the liquid crystal layer forming material, and depending on the thickness of the liquid crystal layer coating film, the amount of ultraviolet irradiation is ^{preferably 50mJ / cm 2 ~1000mJ / cm 2} , 100mJ / cm 2 ~500mJ / cm ² is more preferable.

In addition, for details of the liquid crystal layer and the method for forming the liquid crystal layer, the description of JP-A-2008-225281 and JP-A-2008-026730 can be referred to.

[Fourth step]
In the method for producing a retardation film of one embodiment, a letter is formed along the width direction of the continuous film support with respect to the liquid crystal layer coating film (that is, the formed liquid crystal layer) irradiated with ultraviolet rays in the third step. It has a fourth step of measuring the liquid crystal and obtaining the distribution of the measured value of the liquid crystal in the width direction.
An example of the fourth step will be described with reference to FIG.
As shown in FIG. 1, the coating film (liquid crystal layer) for the liquid crystal layer irradiated with ultraviolet rays by the ultraviolet irradiation means 6 is lettered along the width direction of the continuous film support F by the retardation measuring device 7. Measure the radiation. Then, based on the measured value measured by the retardation measuring device 7, the control unit (that is, the control means) 8 obtains the distribution of the measured value of the retardation in the width direction.
Here, the width direction distribution of the measured values of the retardation refers to a set of the measured values of the retardation measured along the width direction of the continuous film support.

The retardation measuring device 7 which is a retardation measuring means is not particularly limited, and the retardation of the liquid crystal layer coating film (liquid crystal layer) on the continuous film support F during transportation is set to the width of the continuous film support F. Anything that can be measured along the direction is sufficient.
Specifically, as the retardation measuring device 7, an automatic birefringence meter (KOBRA-21ADH) manufactured by Oji Measuring Instruments Co., Ltd., AxoScan manufactured by Axometrics, or the like can be used.

As shown in FIG. 5A, the retardation may be measured by a plurality of (10 in FIG. 5A) parallel retardation measuring devices 7a along the width direction Z of the continuous film support F. Further, as shown in FIG. 5B, the retardation measurement may be performed while moving one retardation measuring device 7b along the width direction Z of the continuous film support F.
In the case of the retardation measuring device 7a, a plurality of measurement points of the retardation (P in FIG. 5A) are arranged in parallel along the width direction Z of the continuous film support F.
Further, in the case of the retardation measuring device 7b, the plurality of retardation measurement points (P in FIG. 5B) have an angle with respect to the transport direction Y of the continuous film support F when the continuous film support F is viewed from above. , The continuous film supports F are lined up in the width direction Z at regular intervals.
Here, in FIGS. 5A and 5B, P refers to a measurement point measured by the retardation measuring device, and Q refers to a measurement target point that will be measured by the retardation measuring device.
The measurement target point Q may be determined by the measurement interval (that is, Da in FIG. 5A or Db in FIG. 5B). For example, in FIG. 5A, the measurement target point Q corresponds to a position where a distance Da is provided on the upstream side of the continuous film support F in the transport direction Y with respect to the measurement point P of the retardation. Therefore, the measurement target points Q in FIG. 5A are parallel to each other along the width direction Z of the continuous film support F. Further, in FIG. 5B, the measurement target point Q corresponds to a position where a distance Db is provided on the upstream side of the continuous film support F in the transport direction Y with respect to the measurement point P of the retardation. Therefore, the measurement target point Q in FIG. 5B is also the width direction of the continuous film support F at regular intervals at an angle with respect to the transport direction Y of the continuous film support F when the continuous film support F is viewed from above. It will be lined up in Z.

In FIGS. 5A and 5B, the number of measurement points of the retardation in the width direction Z of the continuous film support F is set to 10, but the number is not limited to this. The number of retardation measurement points in the width direction of the continuous film support F depends on the size of the retardation measuring device, the width of the continuous film support F, the adjustable width of the ultraviolet illuminance described later, and the like. It should be decided.
Further, the number of measurement points of the retardation in the longitudinal direction of the continuous film support F may be one or a plurality as shown in FIGS. 5A and 5B. When the number of measurement points of the retardation in the longitudinal direction of the continuous film support F is a plurality, for example, five, the average value of the five values is used to determine the distribution of the measurement values of the retardation in the width direction. Just ask.

The measured measured value is stored in the control unit 8. Then, the control unit 8 obtains the widthwise distribution of the measured value of the retardation using the measured measured value.

The measurement of the retardation in the fourth step is preferably performed at a constant interval (for example, Da in FIG. 5A or Db in FIG. 5B) with respect to the transport distance of the continuous film support F.
The shorter the spacing, the easier it is to reduce the in-plane distribution of the retardation of the retardation film.
For example, the transport distance of the continuous film support F (that is, Da in FIG. 5A or Db in FIG. 5B) is preferably performed every time within the range of 10 m to 100 m from the viewpoint of productivity and the like, and is 0. It is more preferable to carry out every time within the range of 1 m to 1 m.
The retardation measurement may be an automatic measurement controlled by the control unit 8, or may be a manual measurement by a manufacturer, an operator, or the like.

[Fifth step]
In the method for producing a retardation film of one embodiment, when there is a measured value out of a predetermined range in the widthwise distribution of the measured value of the retardation obtained in the fourth step, the measurement deviates from the predetermined range. It has a fifth step of adjusting the illuminance of the ultraviolet rays irradiating the coating film for the liquid crystal layer at the position in the width direction corresponding to the measurement position of the value.
That is, in the fifth step, the illuminance of ultraviolet rays is not adjusted unless there is a measured value outside the predetermined range in the widthwise distribution of the measured value of the retardation obtained in the fourth step.
The illuminance (unit: mW / cm ² ) is preferably adjusted by controlling the amount of ultraviolet irradiation (unit: mJ / cm ^{2) on the coating film for the liquid crystal layer.}

An example of the fifth step will be described with reference to FIG.
As shown in FIG. 1, when the control unit 8 obtains the width direction distribution of the measured values of the retardation, the control unit 8 also has the measurement values out of the predetermined range in the width direction distribution. Whether or not it is judged. Then, when the control unit 8 determines that there is a measured value out of the predetermined range in the widthwise distribution of the measured value of the retardation, the ultraviolet irradiation means 6 moves the measured value out of the predetermined range to the measurement position. The illuminance of the ultraviolet rays irradiating the coating film for the liquid crystal layer at the corresponding width direction is adjusted.
In this way, the illuminance in the irradiation of the ultraviolet rays in the third step is adjusted by the fifth step. Then, the adjusted illuminance in the third step is maintained until the illuminance is adjusted in the fifth step.

Here, the "predetermined range" may be determined according to the allowable value of retardation unevenness required for the retardation film and the productivity.
Specifically, the predetermined range preferably means ± 1.5% or less from the target value, and more preferably ± 0.5% or less from the target value in the widthwise distribution of the measured value of the retardation. It is said that it is more preferably ± 0.25% or less from the target value.
That is, in the fifth step, for example, in the width direction distribution of the measured value of the retardation, it is determined whether or not there is a measured value exceeding ± 1.5% from the target value.
Here, the target value corresponds to the retardation value required for the produced retardation film.

When the control unit 8 determines that there is a measured value out of the predetermined range in the widthwise distribution of the measured value of the retardation, the control unit 8 controls the ultraviolet irradiation means 6 to control the measurement position of the measured value out of the predetermined range. Adjust the illuminance of the ultraviolet rays that irradiate the coating film for the liquid crystal layer.

The light source used for the ultraviolet irradiation means 6 is not limited as long as the amount of ultraviolet irradiation described in the third step can be achieved. For example, a light emitting diode (LED), a xenon lamp, an ultrahigh pressure mercury lamp, a metal halide lamp, or the like. Short arc lamps are preferred. Above all, it is preferable to use a light emitting diode because it is easy to adjust the illuminance of ultraviolet rays.
In order to enable finer adjustment of the illuminance, the light source used for the ultraviolet irradiation means 6 is a module light source in which a plurality of units including a plurality of light emitting diode elements are arranged in parallel along the width direction of the continuous film support (hereinafter referred to as a module light source). , Also referred to as “LED module”).

A unit including a plurality of LED elements refers to a unit in which a plurality of (for example, 10 to 20) LED elements are grouped together.
The illuminance of the module light source in which a plurality of units (for example, 5 to 15) including the plurality of LED elements are arranged in parallel can be adjusted for each unit.

A specific method for adjusting the illuminance will be described below.
The retardation (Re) of the retardation film satisfies the relationship of Re = Δn × film thickness of the liquid crystal layer coating film (Δn is birefringence).
Therefore, since the retardation value tends to be large in the portion where the film thickness of the liquid crystal layer coating film is large, the illuminance of ultraviolet rays should be increased (that is, the temperature of the liquid crystal layer coating film should be increased) to reduce Δn. Just do it.
Further, since the retardation value tends to be small in the portion where the film thickness of the liquid crystal layer coating film is small, the illuminance of ultraviolet rays may be lowered (the temperature may be lowered) to increase Δn.

The reason why Δn (birefringence) changes with temperature is due to the fluctuation of the orientation of the liquid crystal compound.
As described above, in the liquid crystal layer coating film, after the liquid crystal compounds are oriented, the orientation of the liquid crystal compounds is fixed by irradiation with ultraviolet rays in the third step. At this time, if the orientation of the liquid crystal compound is fixed by irradiation with ultraviolet rays while the orientation of the liquid crystal compound is high, uneven retardation occurs due to the variation in the film thickness of the liquid crystal layer coating film.
Therefore, in this step, the liquid crystal compound is slightly fluctuated by adjusting the illuminance of ultraviolet rays, Δn is changed to fix the orientation of the liquid crystal compound, and the retardation value is controlled.

As for the adjustment of the illuminance, when there is a measured value deviating from the predetermined range in the positive direction in the width direction distribution of the measured value of the retardation, the liquid crystal layer at the width direction corresponding to the measured position of the measured value is used. Increase the illuminance of the ultraviolet rays that irradiate the coating film.
On the other hand, when there is a measured value deviating from a predetermined range in the negative direction in the widthwise distribution of the measured value of the retardation, the coating film for the liquid crystal layer at the width direction corresponding to the measured position of the measured value is irradiated. Reduce the illuminance of ultraviolet rays.

The illuminance adjustment amount may be a predetermined adjustment amount, for example, ^{increasing or decreasing the ultraviolet irradiation amount by 1.0 mJ / cm 2,} or deviates from the predetermined range of the measured value of the retardation. The adjustment amount may be adjusted according to the value.
In the former case, the predetermined adjustment amount includes an adjustment amount based on the experience of the manufacturer, the operator, etc., a minimum adjustment amount of the ultraviolet irradiation means 6, and the like.

In order to reduce the in-plane distribution of the retardation, it is preferable that the adjustment amount of the illuminance is an adjustment amount according to a value outside the predetermined range of the measured value of the retardation.
That is, in the fifth step, the coating film is irradiated with an adjustment amount obtained in advance from the relationship between the illuminance of the ultraviolet rays applied to the coating film and the retardation value of the coating film irradiated with the ultraviolet rays. It is preferable that the step is to adjust the illuminance of ultraviolet rays.
Specifically, the relationship between the illuminance of the ultraviolet rays irradiating the liquid crystal layer coating film and the retardation value of the ultraviolet-irradiated coating film is acquired in advance. Then, based on this relationship, the adjustment amount of the illuminance determined according to the value outside the predetermined range of the measured value of the retardation is adopted.
A more specific method for determining the amount of illuminance adjustment will be described in Examples.

The above-mentioned illuminance adjustment is performed by the control unit 8.
The control unit 8 has a ROM (Read Only Memory) that stores various programs required for performing the fourth and fifth steps, and a RAM (Random Access Memory, rewritable memory) that temporarily stores data. ), And a CPU (Central Processing Unit) that executes various programs necessary for performing the fourth and fifth steps.
The control unit 8 may control the operation of a part of the retardation film manufacturing apparatus, or may control the operation of the entire retardation film manufacturing apparatus.
However, the adjustment of the illuminance does not necessarily have to be performed by the control unit 8, and the manufacturer, the operator, or the like may manually adjust the illuminance.

In the method for producing a retardation film of one embodiment, in the fourth step and the fifth step, "it is determined whether or not there is a measured value out of a predetermined range in the widthwise distribution of the measured value of the retardation". The treatment is carried out sequentially or continuously during the continuous transfer of the continuous film support until the termination of the continuous film support passes through the third step. Then, when it is determined that there is a measured value outside the predetermined range in the widthwise distribution of the measured value of the retardation, the illuminance of the ultraviolet ray irradiating the coating film for the liquid crystal layer at the measurement position of the measured value outside the predetermined range. Is adjusted.
In this way, the unevenness of the retardation caused by the uneven coating thickness of the liquid crystal layer coating film can be reduced. Therefore, according to the method for producing the retardation film of one embodiment, the in-plane distribution of the retardation is small. A retardation film is obtained.

[Sixth step]
In the method for producing a retardation film of one embodiment, it is preferable to have a sixth step of further irradiating the liquid crystal layer coating film irradiated with ultraviolet rays with ultraviolet rays by a high-pressure mercury light source or a metal halide light source in the fourth step.
An example of the sixth step will be described with reference to FIG.
As shown in FIG. 1, the ultraviolet irradiation means 6 further irradiates the liquid crystal layer coating film irradiated with the ultraviolet rays with the ultraviolet irradiation means 9.
By performing the sixth step, sufficient film strength as a retardation film can be obtained.

The irradiation condition of the ultraviolet ray in the sixth step, the formulation of the liquid crystal layer forming material, and depending on the thickness of the liquid crystal layer coating film, the amount of UV ^{irradiation, 100mJ / cm 2 ~1000mJ / cm} 2 is preferred, 200 mJ / Cm ^{2 to} 500 mJ / cm ² is more preferable.

The liquid crystal layer is formed through the fifth step or the sixth step.
The film thickness of the formed liquid crystal layer is, for example, preferably 1 μm to 4 μm, more preferably 2 μm to 3 μm.

[Phase difference film]
As described above, the retardation film is manufactured by the method for manufacturing the retardation film and the manufacturing apparatus of one embodiment.
As the produced retardation film, the in-plane distribution of the retardation is preferably less than 3%, more preferably less than 0.5%.
Here, the in-plane distribution of the retardation is obtained as follows.
Any part of the retardation film in the longitudinal direction is cut out at 1000 mm × 1000 mm so as to include the center in the width direction.
The cut sample is divided into 11 at equal intervals in the longitudinal direction and 11 at equal intervals in the width direction. The retardation is measured at 100 intersections of the division points. An automatic birefringence meter (KOBRA-21ADH, Oji Measuring Instruments Co., Ltd.) is used for the measurement of the retardation.
For the 100 measured points, the maximum value Re _max , the minimum value Re _min , and the average value Re _ave are obtained, and the in-plane distribution of the retardation is calculated using the following formula.
In-plane distribution of lettering (%) = (Re _max − Re _min ) / Re _ave × 100

The retardation of the produced retardation film is preferably 50 nm to 300 nm, more preferably 100 nm to 200 nm.
As a method for producing a retardation film having a retardation value as described above, the method for producing a retardation film and the manufacturing apparatus according to the above-described embodiment are suitable.

Hereinafter, the present invention will be described in more detail with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

[Example 1]
(First step: Formation of coating film for alignment layer)
An orientation layer forming material having the following composition was applied to one side of a continuous film support made of a cellulose triacetate film TD80UL (Fujifilm) having a length of 1000 m and a width of 1000 mm with a wire bar. Then, the applied alignment layer forming material was dried with warm air at 60 ° C. for 60 seconds and further dried with warm air at 100 ° C. for 120 seconds to form a coating film for an alignment layer having a film thickness of 0.5 μm.

-Composition of material for forming alignment layer-
Material for photoalignment P-1 1.0 part by mass Butoxyethanol 33 part by mass Propylene glycol monomethyl ether 33 part by mass Water 33 part by mass

(First step: Irradiation of polarized ultraviolet rays)
Next, the continuous film support on which the coating film for the alignment layer was formed was wrapped around a backup roll (diameter 600 mm, material stainless steel) (see Fig. 2), and an air-cooled metal halide lamp (Igraphics) was installed in the atmosphere. Polarized ultraviolet rays were irradiated by the photoaligning apparatus used (similar configuration as in FIG. 2). At this time, the arrangement angle θ of the wire grid in the wire grid polarizer (ProFlux UVT300A, Inc., Inc.) was set to 45 °, and polarized ultraviolet rays were irradiated with | θ1-θ2 | = 0 ° to form an alignment layer. ..
^{At this time, the illuminance of ultraviolet rays was 100 mW / cm 2} in the UV (ultra-violet) -A region (integration of wavelengths of 380 nm to 320 nm), ^{and the irradiation amount was 1000 mJ / cm 2} in the UV-A region.
The shrinkage rate of the width of the continuous film support on the backup roll was 0.10%.

(Second step: formation of coating film for liquid crystal layer)
Subsequently, a material for forming a liquid crystal layer having the following composition was prepared.
The solid content concentration of the liquid crystal layer forming material was 15% by mass, and the viscosity of the liquid crystal layer forming material at 25 ° C. was 2.0 mPa · s.

-Composition of material for forming liquid crystal layer-
Reverse wavelength dispersion liquid crystal compound R-3 100 parts by mass Photopolymerization initiator 3.0 parts by mass (Irgacure 819, BASF)
Fluorine-containing compound A 0.8 parts by mass Crosslinkable polymer O-2 0.3 parts by mass Chloroform 588 parts by mass

A liquid crystal layer forming material was applied onto the oriented layer using a curtain coating method.
The applied liquid crystal layer forming material was heated at a film surface temperature of 100 ° C. for 60 seconds to form a liquid crystal layer coating film, and cooled to 70 ° C.

(Third step: UV irradiation)
Subsequently, under air, an LED module manufactured by Acroedge was used ^{to irradiate ultraviolet rays of 100 mJ / cm 2} to fix the orientation state and form a liquid crystal layer.
The LED module used was a unit consisting of 10 elements with a peak wavelength of 365 nm from Nichia Corporation arranged in the width direction of the continuous film support, and 10 of these units were arranged in the width direction of the continuous film support. It was a parallel one.

(4th and 5th steps: measurement of retardation and adjustment of illuminance)
Subsequently, after irradiation with ultraviolet rays by a light source including the LED module, the retardation of the coating film for the liquid crystal layer is measured along the width direction of the continuous film support, and the distribution of the measured values of the retardation in the width direction is obtained. (4th step). Then, when there was a measured value out of the predetermined range in the widthwise distribution of the obtained measured value of the retardation, the illuminance of the ultraviolet ray was adjusted (step 5).

The details of the fourth step and the fifth step are as follows.
An automatic birefringence meter KOBRA-21ADH (Oji Measuring Instruments Co., Ltd.) was used for the measurement of the retardation (hereinafter referred to as a measuring instrument).
The width of the continuous film support was divided by the number of units of the LED module (that is, divided into 10), and the measuring instrument was sequentially moved in the width direction of the continuous film support at the center of the divided region to measure the retardation. .. That is, the retardation was measured by moving the measuring instrument at intervals of 100 mm in the width direction of the continuous film support.
The first retardation measurement was performed on the central portion of the split region at one end in the width direction of the continuous film support. The measurement time of the retardation at one point was 2 seconds, and the measured values during this period (measured repeatedly 5 times in the transport direction of the continuous film support while the measuring instrument was stationary) were averaged to calculate the measured values of the retardation. .. It took 1 second to move to the next measurement position (that is, the center of the adjacent divided region), and the same measurement time was applied after the movement to obtain the measurement value of the retardation. By repeating this measurement operation, a total of 10 points were measured from one end to the other end of the continuous film support in the width direction (this is defined as one cycle). After measuring the retardation at a total of 10 points, the measuring instrument was moved to the measurement position of the retardation at the first point and put into a standby state for the second cycle.
As a result of the measurement in the first cycle, there was a measured value having a deviation of more than ± 0.5% from the target value (target retardation value). The illuminance of ultraviolet rays to the coating film for the liquid crystal layer was adjusted by the LED module of. For example, for the liquid crystal layer coating film at the width direction corresponding to the position where the retardation is displaced by 2%, the output of the unit in the LED module is 10% so that ^{the ultraviolet irradiation amount is 90 mJ / cm 2.} I made it smaller.
After changing the illuminance of ultraviolet rays, it takes more than the time required for the continuous film support that has passed through the third step to reach the measurement position of the retardation in the fourth step (here, 1 minute, the transport distance is 20 m). After the elapse of (corresponding to), the retardation was measured again in the fourth step (second cycle).
As a result of the second cycle, all of the 10 measured values were within the range of ± 0.5% or less from the target value, so the adjustment of the ultraviolet illuminance in the fifth step was not performed.
Subsequently, the measuring instrument was moved to the measurement position of the first retardation again, left for 1 minute, and then the measurement of the third cycle was performed.
After that, since the measured values of the retardation were all within the range of ± 0.5% or less from the target value, the illuminance of the ultraviolet rays in the fifth step was not adjusted.
The retardation measurement in the fourth step was continued at regular intervals, and it was repeatedly determined whether or not the measured value of the retardation was within the predetermined range.
The above operation was repeated for the length of the continuous film support.

(Sixth step: UV irradiation)
After the exposure with the LED module, an ultraviolet ray of ^{300 mJ / cm 2} was irradiated with a high-pressure mercury light source (Igraphics Co., Ltd.).

As described above, a retardation film having a liquid crystal layer having a film thickness of 2.5 μm was obtained. The obtained retardation film was wound into a roll.
In the obtained retardation film, the liquid crystal layer was orthogonal to the polarization irradiation direction in the slow axis direction (that is, also orthogonal to the absorption axis of the polarizing plate) (the inverse wavelength dispersed liquid crystal compound was orthogonal to the polarization irradiation direction). Was oriented orthogonally).

[Example 2]
A light source (short arc lamp, Ushio, Inc.) in which 10 high-pressure mercury lamps (Short Arc Lamp, Ushio, Inc.) are arranged in parallel along the width direction of the continuous film support to irradiate the coating film for the liquid crystal layer with ultraviolet rays from "Acroedge LED module". Hereinafter, a retardation film was produced in the same manner as in Example 1 except that it was replaced with a high-pressure mercury module).
In Example 2, after irradiation with ultraviolet rays by the above light source, the retardation of the coating film for the liquid crystal layer is measured along the width direction of the continuous film support, and the distribution of the measured values of the retardation in the width direction is obtained. (4th step). Then, when there was a measured value out of the predetermined range in the widthwise distribution of the obtained measured value of the retardation, the illuminance of the ultraviolet ray was adjusted (step 5).

The details of the fourth step and the fifth step are as follows.
An automatic birefringence meter KOBRA-21ADH (Oji Measuring Instruments Co., Ltd.) was used for the measurement of the retardation (hereinafter referred to as a measuring instrument).
The width of the continuous film support is divided by the number of high-pressure mercury lamps arranged in parallel (that is, 10 divisions), and the measuring instrument is sequentially moved in the width direction of the continuous film support at the center of the divided region to measure the retardation. went. That is, the retardation was measured by moving the measuring instrument at intervals of 100 mm in the width direction of the continuous film support.
The first retardation measurement was performed on the central portion of the split region at one end in the width direction of the continuous film support. The measurement time of the retardation at one point was 2 seconds, and the measured values during this period (measured repeatedly 5 times in the transport direction of the continuous film support while the measuring instrument was stationary) were averaged to calculate the measured values of the retardation. .. It took 1 second to move to the next measurement position (that is, the center of the adjacent divided region), and the same measurement time was applied after the movement to obtain the measurement value of the retardation. By repeating this measurement operation, a total of 10 points were measured from one end to the other end of the continuous film support in the width direction (this is defined as one cycle). After measuring the retardation at a total of 10 points, the measuring instrument was moved to the measurement position of the retardation at the first point and put into a standby state for the second cycle.
As a result of the measurement in the first cycle, there was a measured value having a deviation of more than ± 0.5% from the target value (target retardation value). The illuminance of ultraviolet rays to the coating film for the liquid crystal layer was adjusted by the high-pressure mercury module of. For example, for the liquid crystal layer coating film at the width direction corresponding to the position where the retardation is displaced by 2%, the output of the high-pressure mercury lamp in the high-pressure mercury module is increased so that ^{the ultraviolet irradiation amount is 90 mJ / cm 2.} It was reduced by 10%.
After changing the illuminance of ultraviolet rays, it takes more than the time required for the continuous film support that has passed through the third step to reach the measurement position of the retardation in the fourth step (here, 1 minute, the transport distance is 20 m). After the elapse of (corresponding to), the retardation was measured again in the fourth step (second cycle).
As a result of the second cycle, there was a measured value having a deviation of more than ± 0.5% from the target value, so in the fifth step, the illuminance of ultraviolet rays was adjusted again according to the amount of deviation.
Subsequently, the measuring instrument was moved to the measurement position of the first retardation again, left for 1 minute, and then the measurement of the third cycle was performed.
After that, since the measured values of the retardation were all within the range of ± 0.5% or less from the target value, the illuminance of the ultraviolet rays in the fifth step was not adjusted.
The retardation measurement in the fourth step was continued at regular intervals, and it was repeatedly determined whether or not the measured value of the retardation was within the predetermined range.
The above operation was repeated for the length of the continuous film support.

[Comparative Example 1]
Phase difference in the same manner as in Example 1 except that the irradiation of ultraviolet rays to the coating film for the liquid crystal layer was changed from "LED module of Acroedge" to "air-cooled metal halide lamp (eye graphics) with a length of 1500 mm". A film was made.
In Comparative Example 1, after irradiation with ultraviolet rays by an air-cooled metal halide lamp, the retardation was measured along the width direction of the continuous film support with respect to the coating film for the liquid crystal layer, and the distribution of the measured values of the retardation in the width direction was measured. Obtained (4th step). Then, when there is a measured value outside the predetermined range in the width direction distribution of the obtained retardation measurement value, the illuminance is collectively adjusted in the width direction of the continuous film support by changing the output of the entire lamp. And adjusted the retardation (also called step A).

Details of the measurement of the retardation and the adjustment of the illuminance of ultraviolet rays are as follows.
An automatic birefringence meter KOBRA-21ADH (Oji Measuring Instruments Co., Ltd.) was used for the measurement of the retardation (hereinafter referred to as a measuring instrument).
The width of the continuous film support was divided into 10 equal parts, and the measuring instrument was sequentially moved in the width direction of the continuous film support at the center of the divided region to measure the retardation. That is, the retardation was measured by moving the measuring instrument at intervals of 100 mm in the width direction of the continuous film support.
The first retardation measurement was performed on the central portion of the split region at one end in the width direction of the continuous film support. The measurement time of the retardation at one point was 2 seconds, and the measured values during this period (measured repeatedly 5 times in the transport direction of the continuous film support while the measuring instrument was stationary) were averaged to calculate the measured values of the retardation. .. It took 1 second to move to the next measurement position (that is, the center of the adjacent divided region), and the same measurement time was applied after the movement to obtain the measurement value of the retardation. By repeating this measurement operation, a total of 10 points were measured from one end to the other end of the continuous film support in the width direction (this is defined as one cycle). After measuring the retardation at a total of 10 points, the measuring instrument was moved to the measurement position of the retardation at the first point and put into a standby state for the second cycle.
As a result of the measurement in the first cycle, the average value of the measured values deviated from the target value (target retardation value) by more than ± 0.25%. The illuminance of ultraviolet rays to the film was adjusted. For example, when the average value of the retardation deviates by 1% from the target value, the output of the air-cooled metal halide lamp is reduced by 5% so that ^{the ultraviolet irradiation amount to the liquid crystal layer coating film is 95 mJ / cm 2.} bottom.
After changing the illuminance of ultraviolet rays, it takes more than the time required for the continuous film support that has passed through the third step to reach the measurement position of the retardation in the fourth step (here, 1 minute, the transport distance is 20 m). After the elapse of (corresponding to), the retardation was measured again in the fourth step (second cycle).
As a result of the second cycle, the average value of the retardation deviated from the target value by more than ± 0.25%. Therefore, in the step A, the illuminance of the ultraviolet rays was adjusted again according to the amount of the deviation.
Subsequently, the measuring instrument was moved to the measurement position of the first retardation again, left for 1 minute, and then the measurement of the third cycle was performed.
Even after the measurement in the third cycle, the average value of the retardation had a deviation of more than ± 0.25% from the target value. Therefore, in the step A, the illuminance of the ultraviolet rays was adjusted again according to the amount of the deviation.
The above operation was repeated for the length of the continuous film support.

[Comparative Example 2]
A retardation film was produced in the same manner as in Example 1 except that "measurement of retardation and adjustment of illuminance" were not performed.

[Measurement of in-plane distribution of retardation]
The in-plane distribution of the retardation of the retardation films produced in the above Examples and Comparative Examples was evaluated based on the following methods and evaluation criteria. The results are shown in Table 1.

A portion 1 m from the end (that is, the end on the winding end side) of the obtained retardation film was cut out at a size of 1000 mm × 1000 mm so as to include the center in the width direction of the retardation film.
The cut sample is divided into 11 at equal intervals in the longitudinal direction and 11 at equal intervals in the width direction. Letterings were measured at 100 intersections at the divisions. An automatic birefringence meter (KOBRA-21ADH, Oji Measuring Instruments Co., Ltd.) was used for the measurement of the retardation.
For the 100 measured points, the maximum value Re _max , the minimum value Re _min , and the average value Re _ave were obtained, and the in-plane distribution of the retardation was calculated using the following formula.
In-plane distribution of lettering (%) = (Re _max − Re _min ) / Re _ave × 100

-Evaluation criteria-
A: In-plane distribution of retardation is less than 0.5% B: In-plane distribution of retardation is 0.5% or more and less than 3% C: In-plane distribution of retardation is 3% or more and less than 5% D: The in-plane distribution of the retardation is 5% or more.

As is clear from Table 1, it can be seen that the in-plane distribution of the retardation of the retardation films obtained in Examples 1 and 2 was suppressed to less than 3%.
According to Comparative Example 1, it can be seen that when the method for adjusting the retardation is a batch in the width direction using a metal halide lamp, the reduction of the in-plane distribution of the retardation is insufficient.
According to Comparative Example 2, it can be seen that the in-plane distribution of the retardation is large unless the retardation is measured and adjusted.

The disclosure of Japanese application 2018-032153 filed on February 26, 2018 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated herein by reference.

Claims (7)

The first step of forming an alignment layer having an orientation regulating force for a liquid crystal compound on a continuous film support that is continuously conveyed, and
The second step of applying and drying a liquid crystal layer forming material containing a liquid crystal compound on the alignment layer to form a coating film, and
The third step of irradiating the coating film with ultraviolet rays,
In the fourth step, the retardation is measured along the width direction of the continuous film support for the coating film irradiated with ultraviolet rays, and the distribution of the measured values of the retardation in the width direction is obtained.
When there is a measured value outside the predetermined range in the width direction distribution of the obtained retardation measurement value, ultraviolet rays to irradiate the coating film at the width direction position corresponding to the measurement position of the measured value outside the predetermined range. The fifth step of adjusting the illuminance of
Have,
The fifth step is applied in the third step with an adjustment amount obtained in advance from the relationship between the illuminance of the ultraviolet rays irradiating the coating film and the retardation value of the coating film irradiated with the ultraviolet rays. This is the process of adjusting the illuminance of the ultraviolet rays that irradiate the film.
A method for manufacturing a retardation film, wherein the third step is performed by a module light source in which a plurality of units including a plurality of light emitting diode elements are arranged in parallel along the width direction of a continuous film support. The method for producing a retardation film according to claim 1, wherein the application of the liquid crystal layer forming material in the second step is performed by a curtain coating method or a die coating method. The method for producing a retardation film according to claim 1 or 2, further comprising a sixth step of irradiating the coating film irradiated with ultraviolet rays with ultraviolet rays by a high-pressure mercury light source or a metal halide light source after the fourth step. .. An alignment layer forming means for forming an alignment layer having an orientation regulating force for a liquid crystal compound on a continuous film support that is continuously conveyed.
A coating means for applying a liquid crystal layer forming material containing a liquid crystal compound on the alignment layer, and
A drying means for forming a coating film by drying the material for forming a liquid crystal layer after coating,
Ultraviolet irradiation means for irradiating the coating film with ultraviolet rays,
A retardation measuring means for measuring the retardation of a coating film irradiated with ultraviolet rays along the width direction of a continuous film support,
When there is a measured value outside the predetermined range in the widthwise distribution of the measured value of the retardation obtained from the measured value of the measured retardation, the measurement of the measured value outside the predetermined range by the ultraviolet irradiation means. A control means for controlling the illuminance of ultraviolet rays in the ultraviolet irradiation means for irradiating the coating film at a position in the width direction corresponding to the position, and a control means for adjusting the illuminance of the ultraviolet rays.
Have,
A retardation film manufacturing apparatus in which the ultraviolet irradiation means is a module light source in which a plurality of units including a plurality of light emitting diode elements are arranged in parallel along the width direction of a continuous film support. The control means adjusts the amount of the ultraviolet rays to be applied to the coating film by the adjustment amount obtained in advance from the relationship between the illuminance of the ultraviolet rays to be applied to the coating film and the retardation value of the coating film irradiated with the ultraviolet rays. The apparatus for producing a retardation film according to claim 4, wherein the control for adjusting the illuminance is performed. The apparatus for producing a retardation film according to claim 4 or 5, wherein the coating means is a means using a curtain coating method or a die coating method. Any of claims 4 to 6, wherein the ultraviolet irradiation means has another ultraviolet irradiation means for irradiating the coating film with ultraviolet rays by a high-pressure mercury light source or a metal halide light source on the downstream side in the transport direction of the continuous film support. The apparatus for producing a retardation film according to item 1.

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