JP2012150107A - Evaluation method of optical anisotropic film, measuring apparatus for optical characteristics of optical anisotropic film and manufacturing method of optical anisotropic film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaluation method with which whether a traveling long optical anisotropic film can obtain desired optical characteristics can be measured in an in-line state, a measuring apparatus for enabling such an evaluation method, and a method of manufacturing the optical anisotropic film having the desired optical characteristics using a result of the evaluation.SOLUTION: An evaluation method of an optical anisotropic film is provided. The method includes a step of radiating light in a direction being vertical to the optical anisotropic film and having an azimuth angle -5° to +5° and a polar angle θ(30°≤θ≤70°) with respect to an in-plane delay phase axial direction and in a direction having an azimuth angle θ(30°≤θ≤60°) and a polar angle θ(30°≤θ≤70°) with respect to the in-plane delay phase axial direction and measuring a change in transmission polarization state, respectively, and a step of comparing the measurement with a change in transmission polarization state obtained by performing the similar measurement on an optical anisotropic film having desired optical characteristics.

Description

  The present invention relates to an optically anisotropic film evaluation method, an optical property measuring apparatus for an optically anisotropic film, and an optically anisotropic film manufacturing method. More specifically, an evaluation method that enables in-line measurement to determine whether or not a long optical anisotropic film that is running has optical characteristics, a measurement device that enables the evaluation method, The present invention also relates to a method for producing an optical anisotropic film having desired optical characteristics using the evaluation results.

  Optically anisotropic films capable of changing the polarization state of light are used in various optical devices such as liquid crystal display devices as retardation plates and viewing angle compensation plates. Depending on the optical characteristics required for the optical device, a multilayer film composed of two or more different layers may be used as the optical anisotropic film. However, it has not been easy to produce a multilayer optically anisotropic film having desired optical characteristics.

  That is, in the case where the optically anisotropic film is composed of a single layer, the in-plane retardation Re and the thickness direction retardation Rth of the optically anisotropic film are made to coincide with the desired values. An optically anisotropic film having characteristics could be obtained. However, for a multilayer optically anisotropic film, desired optical characteristics may not be obtained only by matching Re and Rth. This is presumably because the optical characteristics of each layer are different even when Re and Rth obtained as values of the entire multilayer optically anisotropic film coincide.

  As a method of measuring the retardation of each layer of the optically anisotropic film composed of two types of layers, the optically anisotropic film is regarded as one film, and the retardation value of the entire optically anisotropic film is measured. Optical anisotropy that agrees with the actual measurement value from the actual measurement value obtained by calculating the retardation value when bonding was performed assuming the retardation value of each layer and the orientation direction of the main axis. A method for determining Re of each layer by obtaining a combination of a retardation value of a film and an orientation direction is disclosed (see Non-Patent Document 1).

  In addition, the present inventors irradiate light from three directions to the optically anisotropic film and measure the change of the respective transmitted polarization states, whereby Re of each layer of the optically anisotropic film composed of two types of layers is measured. And Rth were found (see Non-Patent Document 2).

“Plastic Age”, April 2000, p. 154-156 International Display Worksshop 2010 Proceedings, LCTp3-3

  However, in these methods, it is necessary to perform an analysis called fitting that performs calculation assuming Re of each layer and matches the measured values of Re and Rth obtained as the values of the two layers as a whole. . Since fitting often involves complicated calculations and analysis, when manufacturing optically anisotropic films continuously, measurement and analysis are performed in a timely manner, and the results are reflected in manufacturing conditions for obtaining desired optical properties. That was not easy.

  In the case of producing a multilayer optically anisotropic film by multilayer extrusion, it is usual to impart optical anisotropy by stretching an unstretched film obtained by multilayer extrusion. In this method, Re and Rth for each layer cannot be individually controlled. Therefore, even if Re and Rth for each layer of the optical anisotropic film are obtained, the manufacturing conditions are adjusted to obtain desired optical characteristics. That was not easy.

  In view of the above, an object of the present invention is to provide an evaluation method that makes it possible to determine whether or not a desired long optical anisotropic film has a desired optical characteristic by in-line measurement. . It is another object of the present invention to provide a measuring apparatus that enables such an evaluation method and a method for producing an optical anisotropic film having desired optical characteristics using the evaluation result.

  As a result of intensive studies, the present inventors have determined that the change in the respective transmitted polarization states obtained by irradiating the multilayer optically anisotropic film with light from three specific directions is the optical characteristics of the optically anisotropic film. It has been found that there is a strong correlation, and the present invention has been completed based on this finding.

Thus, according to the present invention, the following [1] to [3] are disclosed.
[1] A method for evaluating a multilayer optically anisotropic film,
Irradiating light in a direction perpendicular to the optically anisotropic film and measuring a change (1) in the transmitted polarization state;
Irradiating light in the direction of the azimuth angle −5 ° to + 5 ° and the polar angle θ ₁ (where 30 ° ≦ θ ₁ ≦ 70 °) with respect to the in-plane slow axis direction of the optically anisotropic film Measuring the change (2) in the transmitted polarization state;
An azimuth angle θ ₂ (where 30 ° ≦ θ ₂ ≦ 60 °) and a polar angle θ ₃ (where 30 ° ≦ θ ₃ ≦ 70 ° with respect to the in-plane slow axis direction of the optically anisotropic film. A step of irradiating light in a certain direction and measuring the change (3) of the transmitted polarization state, and the measured values of the changes (1) to (3) of the transmitted polarization state and an optical having desired optical characteristics A step of comparing the transmitted polarization state changes (1) to (3) obtained by performing the same measurement on the anisotropic film,
A method for evaluating an optically anisotropic film, comprising:

In the evaluation method according to [1], the measurement of the change (1) to (3) in the transmitted polarization state is based on spectroscopic ellipsometry,
The change in the transmitted polarization state (1) is the change delta ₁ phase difference of the transmitted light,
The change in the transmitted polarization state (2) is a change in delta ₂ of the phase difference of the transmitted light,
It is preferable that the change in the transmitted polarization state (3) is changed [psi ₃ changes delta ₃ and an amplitude ratio of the phase difference of the transmitted light.
Further, θ ₂ is preferably 40 ° ≦ θ ₂ ≦ 50 °.
The multilayer optically anisotropic film is preferably obtained by multilayer extrusion molding.

[2] A device for measuring optical characteristics of a long, multi-layered optically anisotropic film that travels,
A unit that irradiates light in a direction perpendicular to the optically anisotropic film and measures a change (1) in the transmitted polarization state;
Irradiating light in the direction of the azimuth angle −5 ° to + 5 ° and the polar angle θ ₁ (where 30 ° ≦ θ ₁ ≦ 70 °) with respect to the in-plane slow axis direction of the optically anisotropic film A unit for measuring the change (2) in the transmitted polarization state, and an azimuth angle θ ₂ (where 30 ° ≦ θ ₂ ≦ 60 °) and a pole with respect to the in-plane slow axis direction of the optically anisotropic film A unit that irradiates light in the direction of an angle θ ₃ (where 30 ° ≦ θ ₃ ≦ 70 °) and measures the change (3) in the transmitted polarization state;
An apparatus for measuring optical characteristics of an optically anisotropic film, characterized by comprising:

[3] A method for continuously producing a multilayer and long optically anisotropic film,
A step of stretching a long optical film in multiple layers to impart optical anisotropy to the optical film;
Irradiating light in the vertical direction to the optical film and measuring the change (1) in the transmitted polarization state;
With respect to the in-plane slow axis direction of the optical film, light is irradiated in the direction of azimuth angle −5 ° to + 5 ° and polar angle θ ₁ (where 30 ° ≦ θ ₁ ≦ 70 °), and the transmitted polarized light. Measuring the state change (2);
An azimuth angle θ ₂ (where 30 ° ≦ θ ₂ ≦ 60 °) and a polar angle θ ₃ (where 30 ° ≦ θ ₃ ≦ 70 °) with respect to the in-plane slow axis direction of the optical film. Irradiating light in the direction to measure the change (3) in the transmitted polarization state, and adjusting the manufacturing conditions so that the changes (1) to (3) in the transmitted polarization state have desired values,
The manufacturing method of the elongate optically anisotropic film | membrane characterized by including.

  According to the evaluation method of the present invention, it is possible to easily determine whether or not a multilayer optically anisotropic film has a desired optical characteristic without performing complicated calculation and analysis. In addition, the measuring apparatus of the present invention can easily measure in-line changes in the transmission polarization state necessary for the determination. Furthermore, according to the manufacturing method of the present invention, the determination result can be reflected in the manufacturing conditions of the optically anisotropic film in a timely manner, so that an optically anisotropic film having desired optical characteristics can be efficiently manufactured. it can.

It is the schematic which shows the measuring apparatus of the optical characteristic of the optically anisotropic film which concerns on one Embodiment of this invention.

  The evaluation method of the present invention is a method for evaluating the optical characteristics of a multilayer optically anisotropic film. The optically anisotropic film to which the evaluation method of the present invention can be applied is a multilayer film in which the in-plane slow axes of each layer are in parallel or orthogonal to each other. Here, the term “multilayer” refers to a configuration in which two or more different layers are stacked. The structure of the optically anisotropic film may be two layers or three or more layers as long as it is a multilayer, but preferably two or two layers or two or three layers, more preferably two or two layers. It is.

  The material constituting each layer of the optically anisotropic film is not particularly limited as long as it has a property of transmitting light, but a resin film is usually used. Examples of the resin used include polymethyl methacrylate, polystyrene, polycarbonate, polyether sulfone, polyester, triacetyl cellulose, and cyclic olefin resin.

The film thickness of the optically anisotropic film is usually 20 to 250 μm, preferably 40 to 180 μm. Optically anisotropic film is usually so thin, optically in a direction parallel to the film surface in the x-axis and y-axis orthogonal to each other, taken perpendicular to the z-axis membrane (thickness direction), and the n _x plane slow axis direction of the refractive index of the anisotropic layer, the refractive index in the direction orthogonal in the plane of the n _y in-plane slow axis of the optically anisotropic film, the thickness of the optically anisotropic film n _z It is defined as the refractive index in the vertical direction.

  The optically anisotropic film is preferably a long film. Here, the “long” film means a film having a length of at least 5 times the width of the film, preferably a length of 10 times or more, specifically a roll. It has a length enough to be wound up into a shape and stored or transported. Such a long film can be obtained by continuously performing the production process in the length direction on the production line. According to the evaluation method of the present invention, when a long retardation film is continuously produced, part or all of each step can be simply and efficiently performed in-line.

  The manufacturing method of the optically anisotropic film which consists of a resin film is not limited. Specifically, (a) a method of bonding two or more films having optical anisotropy so that the in-plane slow axes of the respective films are parallel or orthogonal; (b) having optical anisotropy. Bonding two or more films, and then stretching the film to impart optical anisotropy; and (c) forming a multilayer film by multilayer extrusion and then stretching the film to optically anisotropic A method for imparting sex. Among these, since it is easy to make the in-plane slow axis of each layer parallel or orthogonal, the methods (b) and (c) are preferable, and the method (c) is particularly preferable. When a resin film having no optical anisotropy is stretched in one direction (uniaxial stretching) to impart optical anisotropy, the in-plane slow axis of the film is usually such that the resin constituting the film is positive. When it has intrinsic birefringence, it becomes a direction parallel to the stretching direction (orientation direction), and when the resin constituting the film has negative intrinsic birefringence, it becomes a direction perpendicular to the stretching direction (orientation direction) in the plane. According to the measuring method of the present invention, even if the optically anisotropic film is produced by the method (c) in which it is difficult to separate the layers, the optical characteristics can be evaluated.

  The evaluation method of the present invention includes a step of irradiating the optically anisotropic film with light and measuring a change in the transmitted polarization state. Although the kind of light used by this invention is not limited, It is preferable that it is visible light with a wavelength of 350-800 nm. Moreover, it is preferable that it is thin parallel rays, such as a laser beam. This is because the range of light applied to the optically anisotropic film can be narrowed and more accurate measurement can be performed.

  Examples of the method for measuring the change in the state of transmitted polarization in the present invention include spectroscopic ellipsometry and Mueller matrix, which can be measured using a spectroscopic ellipsometer and Mueller matrix polarimeter, respectively. Among them, measurement by spectroscopic ellipsometry is preferable because a sufficient amount of information can be obtained with a small number of parameters.

In the evaluation method of the present invention, as a first measurement, light is irradiated in a direction perpendicular to the optically anisotropic film, and the change (1) in the transmitted polarization state is measured. Here, the direction perpendicular to the optical anisotropic film is equal to the z-axis direction. However, the light irradiation direction may include an error with respect to the z-axis direction as long as the effects of the present invention are not significantly impaired. Specifically, the light irradiation direction is an angle formed by the light irradiation direction and the z-axis. The polar angle is 5 ° or less. Table with a transmission change in the polarization state (1) corresponds to the Re of the entire optical anisotropic film, spectroscopic ellipsometry When performing measurement by cytometry, the change in polarization state (1) is the change delta ₁ phase difference of the transmitted light Is done.

In the evaluation method of the present invention, as the second measurement, the azimuth angle is −5 ° to + 5 ° and the polar angle θ ₁ (where 30 ° ≦ θ ₁ ≦ 70 ° with respect to the alignment direction of the optically anisotropic film. ) Is irradiated with light, and the change (2) in the transmitted polarization state is measured. The range of the polar angle θ ₁ is preferably 40 ° ≦ θ ₁ ≦ 60 °. Within this range, the measurement sensitivity is excellent. The change (2) in the transmitted polarization state correlates with the Rth of the entire optically anisotropic film. When measurement is performed by spectroscopic ellipsometry, the change (2) in the polarization state is expressed by a change Δ ₂ in the phase difference of transmitted light. Is done.

In the evaluation method of the present invention, as a third measurement, an azimuth angle θ ₂ (where 30 ° ≦ θ ₂ ≦ 60 °) and a polar angle θ ₃ (wherein the orientation direction of the optically anisotropic film) Light is irradiated in the direction of 30 ° ≦ θ ₃ ≦ 70 °), and the change (3) in the transmitted polarization state is measured.

The range of the azimuth angle θ ₂ is preferably as close to 45 °, preferably 40 ° ≦ θ ₂ ≦ 50 °, more preferably 44 ° ≦ θ ₂ ≦ 46 °. Within this range, the measurement sensitivity is excellent. The range of the polar angle θ ₃ is preferably 40 ° ≦ θ ₁ ≦ 60 °. Within this range, the measurement sensitivity is excellent. When performing measurement by spectroscopic ellipsometry, a change in polarization state (3) is expressed by the change [psi ₃ changes delta ₃ and an amplitude ratio of the phase difference of the transmitted light.

  In the evaluation method of the present invention, the measured values of the transmitted polarization state changes (1) to (3) and the transmitted polarization state change obtained by performing the same measurement on the optical anisotropic film having desired optical characteristics A step of comparing (1) to (3) is included.

  According to the findings found by the present inventors, in addition to the changes (1) and (2) in the transmission polarization state, the change (3) in the transmission polarization state coincides with the optical anisotropic film having desired optical characteristics. By doing so, the same optical characteristics as the optically anisotropic film can be obtained regardless of Re and Rth for each layer of the optically anisotropic film. Therefore, it is possible to easily evaluate the optical characteristics of the optical anisotropic film only by measuring the changes (1) to (3) in the transmission polarization state without measuring the optical characteristics of each layer of the optical anisotropic film. can do.

  The order in which the first to third measurements are performed is not limited. Each measurement may be performed sequentially or at the same time (simultaneously). Specifically, for example, when performing measurement by spectroscopic ellipsometry, the measurement may be performed by sequentially changing the angle of the light source and the analyzer using a spectroscopic ellipsometer having one set of the light source and the analyzer. You may perform the 1st-3rd measurement at once using the spectroscopic ellipsometer which has 3 sets of photons. Since measurement can be performed with high accuracy in a short time, each measurement is preferably performed at once.

  The measuring device of the present invention is a measuring device for the optical characteristics of an optically anisotropic film, which includes the first measuring unit, the second measuring unit, and the third measuring unit. A spectroscopic ellipsometer having three sets of light sources and analyzers is preferable. Since the spectroscopic ellipsometer can perform measurement in a short time without contacting the optically anisotropic film, it is possible to perform in-line measurement on a long optically anisotropic film while traveling.

  Hereinafter, an embodiment of a measuring apparatus of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiment.

FIG. 1 is a schematic view showing a measuring apparatus of the present invention. In FIG. 1, a long and multilayer optically anisotropic film 2 having an in-plane slow axis in the width direction runs from the lower left side to the upper right side in FIG. A first light source 11 for irradiating light in a direction perpendicular to the optical anisotropic film 2 is provided above the optical anisotropic film 2, and an azimuth angle of -5 ° with respect to the in-plane slow axis direction of the optical anisotropic film. Second light source 12 that irradiates light in the direction of ˜ + 5 ° and polar angle θ ₁ (where 30 ° ≦ θ ₁ ≦ 70 °), and orientation with respect to the in-plane slow axis direction of the optically anisotropic film A third light source 13 that irradiates light in the direction of the angle θ ₂ (where 30 ° ≦ θ ₂ ≦ 60 °) and the polar angle θ ₃ (where 30 ° ≦ θ ₃ ≦ 70 °) is installed. ing.

  Below the optically anisotropic film 2, a first analyzer 21 that receives light emitted from the first light source 11, a second analyzer 22 that receives light emitted from the second light source 12, and a third A third analyzer 23 that receives light emitted from the light source 13 is provided.

The first analyzer 21 is disposed at a position facing the first light source 11 with the optical anisotropic film 2 interposed therebetween, and the first analyzer 21 changes the phase difference Δ of the light transmitted through the optical anisotropic film 2. ₁ is measured. The second analyzer 22 is disposed at a position facing the second light source 12 with the optical anisotropic film 2 interposed therebetween, and the first analyzer 22 changes the phase difference Δ of the light transmitted through the optical anisotropic film 2. ₂ is measured. The third analyzer 23 is disposed at a position facing the third light source 13 with the optical anisotropic film 2 interposed therebetween, and the third analyzer 23 changes the phase difference Δ of the light transmitted through the optical anisotropic film 3. ₃ and the change in amplitude ratio Ψ ₃ are measured. In FIG. 1, the line connecting the light source and the analyzer represents the optical axis of light used for measurement.

  That is, the first light source 11 and the first analyzer 21 constitute a unit for performing the first measurement, and the twelfth light source 12 and the second analyzer 22 constitute a unit for performing the second measurement. The light source 13 and the third analyzer 23 constitute a unit for performing the third measurement, and the respective units constitute the measuring apparatus 1 of the present invention. Since each of the light sources and each of the analyzers is installed at a position not in contact with the optical anisotropic film 2, the optical characteristics of the long optical anisotropic film 2 that is running can be measured in-line.

  The measurement apparatus of the present invention is preferably installed on the same line as the apparatus that performs the stretching process in the production of a long optically anisotropic film. This is because it is possible to easily manufacture an optical anisotropic film having desired optical characteristics by measuring the optical characteristics of the optical anisotropic film immediately after the stretching process and adjusting the conditions of the stretching process based on the result.

  The production method of the present invention is a method for continuously producing a multilayer and long optical anisotropic film, and extending the multilayer and long optical film to impart optical anisotropy to the optical film. Process.

  The method for producing a multilayer and long optical film before stretching (hereinafter sometimes referred to as a film before stretching) is not limited, and any known method can be adopted, but it is preferably produced by multilayer extrusion. . The pre-stretch film obtained by multilayer extrusion may be wound on a roll or the like to form a wound body, and then subjected to a stretching treatment, or the multilayer extrusion and the stretching treatment described later may be performed on a series of production lines. Good.

  The thickness of the pre-stretch film may be appropriately determined in consideration of the stretch ratio, and is preferably 30 to 1000 μm, more preferably 80 to 380 μm.

  The film before stretching is stretched to impart optical anisotropy to the optical film. Examples of the stretching operation include a method of uniaxial stretching in the longitudinal direction using a difference in peripheral speed between rolls (longitudinal uniaxial stretching); a method of uniaxial stretching in the width direction using a tenter (lateral uniaxial stretching); A method of performing longitudinal uniaxial stretching and lateral uniaxial stretching in order (sequential biaxial stretching); a method of stretching in an oblique direction with respect to the longitudinal direction of the film before stretching (oblique stretching); From the viewpoint that the in-plane slow axis direction of the optically anisotropic film can be made constant, longitudinal uniaxial stretching, lateral uniaxial stretching, or sequential biaxial stretching is preferable.

  The stretching temperature is preferably 70 to 200 ° C, more preferably 100 to 170 ° C, although it depends on the glass transition temperature of the resin constituting the film before stretching. The draw ratio can be any ratio that can express desired optical properties, but is preferably 1.1 times or more and 5 times or less, more preferably 1.3 times or more and 3 times or less. preferable.

  Next, the changes (1) to (3) in the transmission polarization state of the film stretched as described above are measured. From the viewpoint that the measurement can be performed quickly and reflected in the adjustment of the stretching conditions to be described later in a timely manner, the measurement is preferably performed in-line on the running film after the stretching treatment. The first to third measurements are preferably performed simultaneously.

  Subsequently, based on the result of the above measurement, the manufacturing conditions are adjusted so that the changes (1) to (3) in the transmitted polarization state become desired values. Here, adjusting the manufacturing conditions preferably means adjusting the stretching conditions, but the film before stretching is continuously produced by multilayer extrusion, and this is stretched on the same production line to obtain optical anisotropy. When obtaining a film, the thickness of at least one layer of the film before stretching may be adjusted. Examples of the method for adjusting the thickness of the pre-stretch film layer include a method for adjusting the amount of resin used for multilayer extrusion and a method for adjusting the speed of extrusion.

  The stretching conditions are usually adjusted by adjusting the stretching temperature or stretching ratio, but the stretching temperature is adjusted from the viewpoint that the thickness and width of the obtained optically anisotropic film can be made constant. Is preferred.

If the influence of the adjustment of the manufacturing conditions on the transmission polarization state changes (1) to (3) is grasped in advance, the manufacturing conditions are adjusted appropriately, and an optical anisotropic film having desired optical characteristics can be easily obtained. Since it is obtained, it is preferable. That is, for example, when the above measurement is spectroscopic ellipsometry, how much Δ ₁ , Δ ₂ , Δ _3, and Ψ ₃ fluctuate by adjusting the manufacturing conditions (for example, increasing the stretching temperature). By grasping in advance, the production conditions can be adjusted more appropriately, and the optically anisotropic film can be continuously produced without stopping the film running.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited to these. In the examples, subscripts A to F represent values for the optically anisotropic films A to F, respectively.

Example 1
A film forming apparatus for two-type two-layer coextrusion molding was prepared, and a pellet of polycarbonate resin (manufactured by Asahi Kasei Co., Ltd., Wonderlite PC-110, deflection temperature under load 145 ° C., average refractive index n _i1 = 1.590), It was charged into one single screw extruder equipped with a double flight type screw and melted. Pellets of styrene-maleic anhydride copolymer resin (Nova Chemicals, Dylark D332, deflection temperature under load, 135 ° C., average refractive index: n _i2 = 1.585), another uniaxial extrusion equipped with a double flight type screw The machine was charged and melted. A molten 260 ° C. polycarbonate resin is passed through a polymer filter in the form of a leaf disk having a mesh size of 10 μm to one manifold of a multi-manifold die, and a molten 260 ° C. styrene-maleic anhydride copolymer resin is leaf having a mesh size of 10 μm. Each was supplied to the other manifold through a disk-shaped polymer filter. A polycarbonate resin and a styrene-maleic anhydride copolymer resin were simultaneously extruded from the multi-manifold die at 260 ° C. to form a film. The amount of resin to be coextruded was set to a ratio of 1: 9.2 in a volume ratio of polycarbonate resin: styrene-maleic anhydride copolymer resin. The film-like molten resin was cast on a cooling roll adjusted to a surface temperature of 130 ° C., and then passed between two cooling rolls adjusted to a surface temperature of 50 ° C. to obtain a polycarbonate resin layer (first layer) and styrene- A pre-stretching film a having a width of 1350 mm composed of a maleic anhydride copolymer resin layer (second layer) was obtained. It was 150 micrometers as a result of measuring the thickness of the film a before extending | stretching using a micrometer.

The unstretched film a was supplied to a longitudinal uniaxial stretching machine and stretched in the longitudinal direction at a stretching temperature of 155 ° C. and a stretching ratio of 2 times. Subsequently, the stretched film was supplied to a tenter stretching machine, and stretched in the transverse direction at a stretching temperature of 130 ° C. and a stretching ratio of 1.15 to obtain an optical anisotropic film A. The thickness of the optically anisotropic film A was measured using a micrometer and found to be 92 μm. The film thickness of each layer calculated from the quantitative ratio of the polycarbonate resin and the styrene-maleic anhydride copolymer resin was the first layer thickness d ₁ = 9 μm and the second layer thickness d ₂ = 83 μm. .

  About this optically anisotropic film A, the change of the transmission polarization state was measured as follows using a spectroscopic ellipsometer (M-2000 manufactured by JA Woollam). In any of the following first to third measurements, light was irradiated from the surface of the optically anisotropic film A on the first layer side.

As a first measurement, adjustment was made so that a light beam with a wavelength of 550 nm was perpendicularly incident on the optical anisotropic film A, and a change Δ _1A in the phase difference of transmitted light was measured. At this time, Δ _1A = 157.4 nm.

As a second measurement, adjustment was made so that the slow axis (orientation direction) of the optically anisotropic film A was 0 ° and the light beam was incident on the optically anisotropic film A at a polar angle θ ₁ of 50 °. the change delta _2A of the phase difference of the transmitted light was measured. At this time, Δ _2A = 158.0 nm.

As a third measurement, the azimuth angle θ ₂ is 45 ° with respect to the slow axis (orientation direction) of the optical anisotropic film A, and the light beam is incident on the optical anisotropic film A with the polar angle θ ₃ being 50 °. Thus, the phase difference change Δ _3A of transmitted light and the amplitude ratio change Ψ _3A were measured.
At this time, Δ _3A = 76.1 ° and Ψ _3A = 53.0 °.

(Examples 2 and 3)
By adjusting the temperature at which the film a before stretching and the stretching ratio are adjusted, Δ ₁ and Δ ₂ are almost equal to the optical anisotropic film A, and Δ ₃ and Ψ ₃ are different from the optical anisotropic film A. Film B and optically anisotropic film C were obtained. When the change of the phase difference of transmitted light and the change of the amplitude ratio of the optically anisotropic film B were measured, Δ _1B = 157.5 nm, Δ _2B = 158.1 nm, Δ _3B = 72.5 °, Ψ _3B = 52 It was 6 °. Moreover, when the change of the phase difference of the transmitted light and the change of the amplitude ratio of the optically anisotropic film C were measured, Δ _1C = 157.2 nm, Δ _2C = 158.2 nm, Δ _3C = 69.1 °, Ψ _3C = It was 52.3 °.

Example 4
A cyclic olefin resin film (Zeonor film ZF14; manufactured by Nippon Zeon Co., Ltd., average refractive index n _i1 = 1.535) having a thickness of 67 μm was prepared as a film before stretching for the first layer. Separately from this, a styrene-maleic anhydride copolymer resin (manufactured by Nova Chemicals, Dylark D332, deflection temperature under load of 135 ° C., average refractive index: n _i2 = 1.585) is used as a film before stretching for the second layer. By melt extrusion, a styrene-maleic anhydride copolymer resin film having a thickness of 150 μm was obtained.

The conditions for obtaining the optically anisotropic film D in which the change in the retardation of the transmitted light and the change in the amplitude ratio are the same as those of the optically anisotropic film A were obtained by calculation. Specifically, based on the calculation method disclosed in Non-Patent Document 2, the in-plane retardation Re and the thickness direction retardation Rth required for forming the optically anisotropic film D are calculated. As a result, Re ₁ = 39 nm, Rth ₁ = 121 nm, Re ₂ = 118 nm, and Rth ₂ = -127 nm were obtained. Here, the subscripts 1 and 2 represent values for the first layer and the second layer, respectively.

Stretching conditions were adjusted so that Re ₁ and Rth ₁ were the above values, and the cyclic olefin resin film was stretched to obtain stretched film d1. Separately from this, the styrene-maleic anhydride copolymer resin film was stretched by adjusting the stretching conditions so that Re ₂ and Rth ₂ had the above values, to obtain a stretched film d2.

Subsequently, the stretched film d1 and the stretched film d2 were bonded using a double-sided adhesive tape manufactured by Nitto Denko Corporation so that the slow axes thereof were parallel to prepare an optically anisotropic film D. When the change of the phase difference of transmitted light and the change of the amplitude ratio of the optically anisotropic film D were measured, Δ _1D = 157.4 nm, Δ _2D = 158.0 nm, Δ _3D = 76.1 °, Ψ _3D = 53 It was confirmed to be equal to the value of the optically anisotropic film A.

(Example 5)
The optical anisotropic film E in which the change in retardation of the transmitted light and the change in the amplitude ratio are the same as those in the optical anisotropic film B were calculated in the same manner as in Example 4 using the above-mentioned film before stretching. Re ₁ = 54 nm, Rth ₁ = 161 nm, Re ₂ = 103 nm and Rth ₂ = −171 nm were obtained.

Stretching conditions were adjusted so that Re ₁ and Rth ₁ were the above values, and the cyclic olefin resin film was stretched to obtain stretched film e1. Separately from this, the styrene-maleic anhydride copolymer resin film was stretched by adjusting the stretching conditions so that Re ₂ and Rth ₂ had the above values, to obtain a stretched film e2.

Next, using a double-sided adhesive tape manufactured by Nitto Denko Corporation, the stretched film e1 and the stretched film e2 were bonded to each other so that their slow axes were parallel to produce an optically anisotropic film E. When the change of the phase difference of transmitted light and the change of the amplitude ratio of the optically anisotropic film E were measured, Δ _1E = 157.3 nm, Δ _2E = 158.1 nm, Δ _3E = 72.4 °, Ψ _3E = 52 .6 °, which was confirmed to be substantially equal to the value of the optically anisotropic film B.

(Example 6)
The conditions obtained by using the pre-stretch film for the optical anisotropic film F in which the change in retardation of the transmitted light and the change in the amplitude ratio are equal to the optical anisotropic film C are calculated in the same manner as in Example 4. Re ₁ = 67 nm, Rth ₁ = 201 nm, Re ₂ = 91 nm and Rth ₂ = −214 nm were obtained.

Stretching conditions were adjusted so that Re ₁ and Rth ₁ were the above values, and the cyclic olefin resin film was stretched to obtain stretched film f1. Separately from this, the styrene-maleic anhydride copolymer resin film was stretched by adjusting the stretching conditions so that Re ₂ and Rth ₂ had the above values, to obtain a stretched film f2.

Subsequently, the stretched film f1 and the stretched film f2 were bonded together using a double-sided adhesive tape manufactured by Nitto Denko Corporation so that the slow axes thereof were parallel to prepare an optically anisotropic film F. When the change of the phase difference of the transmitted light and the change of the amplitude ratio of the optically anisotropic film F were measured, Δ _1F = 157.2 nm, Δ _2F = 158.2 nm, Δ _3F = 69.1 °, Ψ _3F = 52 It was confirmed that the angle was .2 ° and was substantially equal to the value of the optically anisotropic film C.

(Example 7)
The optically anisotropic film A was bonded to a polarizing film NPF-G1029DU manufactured by Nitto Denko Corporation using a double-sided adhesive tape manufactured by Nitto Denko Corporation to prepare a polarizing plate A having a size of 5 cm × 5 cm. However, they were bonded so that the transmission axis of the polarizing plate and the slow axis of the optically anisotropic film were parallel. Next, a liquid crystal monitor FlexScan S2410W manufactured by Nanao Co., Ltd. was disassembled, and the rare-side polarizing plate of the liquid crystal panel was peeled off, and a polarizing plate A was placed side by side, and a liquid crystal monitor sample A was produced. However, the lamination was performed so that the transmission axis of the polarizing plate A was perpendicular to the transmission axis of the front-side polarizing plate, and the optically anisotropic film was on the liquid crystal cell side. The liquid crystal monitor was reassembled, turned on, and the dark display brightness was measured using a viewing angle measuring device IMAGEING SPHERE manufactured by RADIUS IMAGEING.

(Examples 8 to 12)
Liquid crystal monitor samples B to F were produced in the same manner as in Example 7 except that the optical anisotropic films B to F were used in place of the optical anisotropic film A. Using these samples, dark display luminance was measured in the same manner as in Example 7.

  Table 1 shows the results of measuring the dark display luminance (transmission luminance) in the polar angle of 60 ° and the azimuth angle of 45 °. However, the value is a relative value when the transmission luminance is set to 1 when the sample D having the smallest transmission luminance is used (Example 10).

From the above results, it can be seen that the three combinations of sample A and sample D, sample B and sample E, sample C and sample F have the same transmission luminance, and the other combinations have greatly different transmission luminance. . As a result, the optical characteristics of the multilayer optically anisotropic film cannot be matched only by making Δ ₁ and Δ ₂ equal, but in addition to Δ ₁ and Δ ₂ , Δ ₃ and Ψ ₃ should have the same value. Thus, it can be seen that the optical characteristics of the optical anisotropic film can be made equal. Therefore, it can be seen that the performance of the multilayer optically anisotropic film can be appropriately evaluated by measuring Δ ₁ , Δ ₂ , Δ ₃ , and ψ ₃ .

(Example 13)
A film was formed by coextrusion in the same manner as in Example 1, and the length consisting of a polycarbonate resin layer (first layer) and a styrene-maleic anhydride copolymer resin layer (second layer) was 158 μm long and 1350 mm wide. A film g before stretching was obtained.

  The unstretched film g was supplied to a longitudinal uniaxial stretching machine and stretched in the longitudinal direction at a stretching temperature of 155 ° C. and a stretching ratio of 2 times. Subsequently, the stretched film was continuously supplied to a tenter stretching machine, and stretched in the transverse direction at a stretching temperature of 130 ° C. and a stretching ratio of 1.15 to obtain an optical anisotropic film G. A part of the optically anisotropic film G manufactured continuously was sampled, and the thickness was measured using a micrometer. As a result, it was 99 μm. The film thickness of each layer calculated from the quantitative ratio of the polycarbonate resin and the styrene-maleic anhydride copolymer resin was the first layer thickness d1 = 10 μm and the second layer thickness d2 = 89 μm.

  The change in the transmission polarization state of the continuously manufactured optically anisotropic film G was measured in-line. The measurement was performed under the same conditions as in Example 1 except that the first to third measurements were simultaneously performed using a spectroscopic ellipsometer having three sets of light sources and analyzers as shown in FIG.

The change Δ _{1G in} the phase difference of the transmitted light obtained in the first measurement was 157.4 nm. The change Δ _{2G in} the phase difference of transmitted light obtained in the second measurement was 158.0 nm. The change Δ _3G in transmitted light phase difference obtained in the third measurement was 77.5 °, and the change in amplitude ratio Ψ _3G was 53.3 °. A liquid crystal monitor sample G was prepared using the optically anisotropic film G in the same manner as in Example 7, and the dark display luminance was measured. The transmission luminance was 1.30 as a relative value when the transmission luminance when Sample D was used (Example 10) was 1. The results are shown in Table 1.

(Example 14)
In order to obtain an optically anisotropic film in which the change in retardation of transmitted light and the change in amplitude ratio are equal to those of the optically anisotropic film A using the unstretched film g, continuous production of the optically anisotropic film G is performed. On the way, the stretching conditions were changed while performing the first to third measurements in-line. When the draw ratio in the machine direction was 1.98 times and the draw temperature in the transverse direction was 131 ° C., Δ _1H = 157.4 nm, Δ _2H = 158.0 nm, Δ _3H = 76.1 °, Ψ _3H = 53. Since it became 1 degree, it manufactured continuously on this extending | stretching condition, and obtained the optically anisotropic film H. A liquid crystal monitor sample H was prepared using this optically anisotropic film H in the same manner as in Example 7, and the dark display luminance was measured. The transmission luminance was 1.03 as a relative value when the transmission luminance when Sample D was used (Example 10) was 1. The results are shown in Table 1.

These results, in the continuous production of optically anisotropic _{films, Δ 1, Δ 2, Δ} 3, and [psi ₃ while continuously measuring inline, optically anisotropic these values with desired optical properties It can be seen that the optical characteristics of the obtained optically anisotropic film can be made to match the desired one by adjusting the manufacturing conditions so as to be equal to the property film.

DESCRIPTION OF SYMBOLS 1 Optical characteristic measuring apparatus 2 Optical anisotropic film 11 1st light source 12 2nd light source 13 3rd light source 21 1st analyzer 22 2nd analyzer 23 3rd analyzer

Claims (6)

A method for evaluating a multilayer optically anisotropic film,
Irradiating light in a direction perpendicular to the optically anisotropic film and measuring a change (1) in the transmitted polarization state;
Irradiating light in the direction of the azimuth angle −5 ° to + 5 ° and the polar angle θ ₁ (where 30 ° ≦ θ ₁ ≦ 70 °) with respect to the in-plane slow axis direction of the optically anisotropic film Measuring the change (2) in the transmitted polarization state;
An azimuth angle θ ₂ (where 30 ° ≦ θ ₂ ≦ 60 °) and a polar angle θ ₃ (where 30 ° ≦ θ ₃ ≦ 70 ° with respect to the in-plane slow axis direction of the optically anisotropic film. A step of irradiating light in a certain direction and measuring the change (3) of the transmitted polarization state, and the measured values of the changes (1) to (3) of the transmitted polarization state and an optical having desired optical characteristics A step of comparing the transmitted polarization state changes (1) to (3) obtained by performing the same measurement on the anisotropic film,
A method for evaluating an optically anisotropic film, comprising: A device for measuring the optical properties of a long, multi-layer optically anisotropic film that is running,
A unit that irradiates light in a direction perpendicular to the optically anisotropic film and measures a change (1) in the transmitted polarization state;
Irradiating light in the direction of the azimuth angle −5 ° to + 5 ° and the polar angle θ ₁ (where 30 ° ≦ θ ₁ ≦ 70 °) with respect to the in-plane slow axis direction of the optically anisotropic film A unit for measuring the change (2) in the transmitted polarization state, and an azimuth angle θ ₂ (where 30 ° ≦ θ ₂ ≦ 60 °) and a pole with respect to the in-plane slow axis direction of the optically anisotropic film A unit that irradiates light in the direction of an angle θ ₃ (where 30 ° ≦ θ ₃ ≦ 70 °) and measures the change (3) in the transmitted polarization state;
An apparatus for measuring optical characteristics of an optically anisotropic film, characterized by comprising: A method for continuously producing a multilayer and long optical anisotropic film,
A step of stretching a long optical film in multiple layers to impart optical anisotropy to the optical film;
Irradiating light in the vertical direction to the optical film and measuring the change (1) in the transmitted polarization state;
With respect to the in-plane slow axis direction of the optical film, light is irradiated in the direction of azimuth angle −5 ° to + 5 ° and polar angle θ ₁ (where 30 ° ≦ θ ₁ ≦ 70 °), and the transmitted polarized light. Measuring the state change (2);
An azimuth angle θ ₂ (where 30 ° ≦ θ ₂ ≦ 60 °) and a polar angle θ ₃ (where 30 ° ≦ θ ₃ ≦ 70 °) with respect to the in-plane slow axis direction of the optical film. Irradiating light in the direction to measure the change (3) in the transmitted polarization state, and adjusting the manufacturing conditions so that the changes (1) to (3) in the transmitted polarization state have desired values,
The manufacturing method of the elongate optically anisotropic film | membrane characterized by including. The measurement of the change in the transmission polarization state (1) to (3) is based on spectroscopic ellipsometry,
The change in the transmitted polarization state (1) is the change delta ₁ phase difference of the transmitted light,
The change in the transmitted polarization state (2) is a change in delta ₂ of the phase difference of the transmitted light,
The transmitted polarization state change (3) is a transmitted light phase difference change Δ ₃ and an amplitude ratio change ψ ₃ .
The evaluation method according to claim 1. The measurement method according to claim 1, wherein θ ₂ is 40 ° ≦ θ ₂ ≦ 50 °.   The evaluation method according to claim 1, 4, or 5, wherein the multilayer optically anisotropic film is obtained by multilayer extrusion molding.

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