JP5728904B2 - Method for measuring retardation of optically anisotropic film, and method for producing optically anisotropic film - Google Patents

Description

  The present invention relates to a method for measuring the retardation of an optically anisotropic film. More specifically, the in-plane retardation Re and the thickness direction retardation Rth of each layer of an optically anisotropic film composed of two types of layers are calculated. It relates to a measuring method.

  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 film having a two-layer structure or two-layer / three-layer structure including two different layers may be used as the optical anisotropic film. In order to control the optical characteristics more precisely, it is important to measure the optical characteristics of each layer of the optically anisotropic film composed of the two types of layers.

  A spectroscopic ellipsometry method is widely used as a method for measuring the optical characteristics of a thin film. For example, there is disclosed a method of performing structural analysis by measuring a thin film having a two-layer structure or a two-type three-layer structure on a substrate surface using a spectroscopic ellipsometer and performing a three-stage analysis (Patent Documents 1 and 2). .

  The main axis of the birefringent film includes a step of obtaining a retardation value of a composite film formed by laminating two birefringent films by detecting a change in the polarization state of transmitted light with respect to incident light using an ellipsometer. A measurement method is also disclosed (Patent Document 3).

JP 2003-302334 A JP 2004-286468 A JP 2004-294370 A

  However, a method for measuring the retardation of each layer of an optically anisotropic film composed of two types of layers has not been known so far. In particular, for optically anisotropic films obtained by multilayer extrusion, it is virtually impossible to measure each retardation by separating each layer, and the optical characteristics of each layer in the production of optically anisotropic films It was difficult to control precisely.

  An object of this invention is to provide the method of measuring the retardation of each layer of the optically anisotropic film which consists of two types of layers, without isolate | separating each layer.

  As a result of intensive studies, the present inventors determined the retardation of each layer of the optically anisotropic film by irradiating the optically anisotropic film with light from three directions and measuring the change in the respective transmitted polarization states. Based on this finding, the present invention has been completed.

Thus, according to the present invention, there is provided a method for measuring the retardation of an optically anisotropic film composed of two types of layers,
Irradiating light in a substantially perpendicular direction 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. Irradiating light in the direction of (a) and measuring the change (3) in the transmitted polarization state;
And
A step of calculating in-plane retardation Re and retardation Rth in the thickness direction of each layer constituting the optically anisotropic film using the transmitted polarization state changes (1) to (3),
A method for measuring retardation of an optically anisotropic film is provided.

In the measurement method, the measurement of the change in the transmitted 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,
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.

The step of calculating in-plane retardation Re and thickness direction retardation Rth of each layer constituting the optically anisotropic film,
Assuming Re ₁ and Rth ₁ , the step of obtaining the thickness and three-dimensional refractive index of each layer by the following equations [1] to [4]:
Using the thickness and three-dimensional refractive index of each layer, a calculated value Δ _{3c of} a change in phase difference of transmitted light when light is irradiated in the directions of azimuth angle θ ₂ and polar angle θ ₃ by the 4 × 4 matrix method, and Calculating a calculated value Ψ _3c of a change in amplitude ratio;
Calculating Re ₁ and Rth ₁ as values at which the difference between Δ _3c and ψ _3c and Δ ₃ and ψ ₃ is minimized,
A step of obtaining the thickness and three-dimensional refractive index of each layer from Re ₁ and Rth ₁ by the following equations [1] to [4];
A step of calculating Re ₂ and Rth ₂ from the three-dimensional refractive index by the following equation [5]:
It is preferable that it contains.

In the formula, n _i denotes an average refractive index of each layer of the optically anisotropic film,
n _x, n _y and n _z represent the three-dimensional refractive index of each layer of the optically anisotropic film (where subscripts x, y and z-plane slow axis direction of each of the optically anisotropic film, Represents the direction perpendicular to the in-plane slow axis of the optically anisotropic film in the plane and the thickness direction of the optically anisotropic film).
d represents the thickness of each layer of the optically anisotropic film.
The subscript 1 in Re, Rth, Δ ₁ , Δ ₂ , n _i , n _x , n _y , _nz, and d is a layer on the optically anisotropic film that is irradiated with light, and a layer of the same type 2 represents a value for a different kind of layer.

In the measurement method, θ ₂ is preferably 40 ° ≦ θ ₂ ≦ 50 °.
Moreover, it is preferable that the optical anisotropic film which consists of two types of layers is obtained by multilayer extrusion molding.

  According to the present invention, it is possible to measure the retardation of each layer of an optically anisotropic film composed of two types of layers. Thereby, in the manufacture of the optical anisotropic film, the optical characteristics of each layer can be precisely controlled by controlling the manufacturing conditions based on the obtained retardation value.

It is a figure which shows the 1st measurement which concerns on one Embodiment of this invention. It is a figure which shows the 2nd measurement which concerns on one Embodiment of this invention. It is a figure which shows the 3rd measurement which concerns on one Embodiment of this invention.

  The measuring method of the present invention is a method for measuring the retardation of an optically anisotropic film comprising two types of layers. The optically anisotropic film to which the measurement method of the present invention can be applied is a film composed of two types of layers, and the in-plane slow axis of each layer is parallel or orthogonal. Here, “consisting of two types of layers” means having a configuration in which two types of layers having different compositions are laminated. The configuration of the optically anisotropic film may be two layers or three or more layers as long as it is composed of two types of layers, but is preferably a two-type two-layer or two-type three-layer, more Two types and two layers are preferable.

  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, amorphous polyethylene, 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. Since the optically anisotropic film is usually thin, the x axis and y axis perpendicular to each other are taken in a direction parallel to the film surface, the z axis is taken in a direction perpendicular to the film (thickness), and _nx is optically different. plane slow axis direction of the refractive index of the isotropic film, the refractive index in the direction orthogonal to n _y in a plane in the in-plane slow axis of the optically anisotropic film, the n _z of the optically anisotropic film thickness It is defined as the refractive index in the direction.

  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. A method in which two or more films are bonded together, and then the film is stretched to impart optical anisotropy; and (c) a film comprising two layers is formed by multilayer extrusion, and then the film is stretched. And a method of imparting optical anisotropy. 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. According to the measuring method of the present invention, the retardation of each layer can be measured even with the optically anisotropic film produced by the method (c) in which it is difficult to separate the layers.

  The measuring method of the present invention includes a step of irradiating the optically anisotropic film with light and measuring a change in its transmitted polarization state. Although the kind of light used by this invention is not limited, It is preferable that it is a thin parallel light beam like a laser beam. The range of light irradiated to the optically anisotropic film can be narrowed, and more accurate measurement is possible.

  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 measurement method of the present invention, as a first measurement, light is irradiated in a substantially vertical direction with respect to the optically anisotropic film, and the change (1) in the transmitted polarization state is measured. Here, the perpendicular direction to the optically anisotropic film is equal to the z-axis direction, and the substantially perpendicular direction means that the polar angle that is an angle formed by the z-axis and the light irradiation direction is 5 ° or less. Represent. When performing measurement by spectroscopic ellipsometry, a change in polarization state (1) is expressed by the change delta ₁ phase difference of the transmitted light.

In the measurement 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. When the measurement by spectroscopic ellipsometry is performed, the change (2) in the polarization state is represented by the change Δ ₂ in the phase difference of the transmitted light.

In the measurement 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 measurement method of the present invention, the in-plane retardation Re and the thickness direction retardation Rth of each layer constituting the optically anisotropic film are calculated using the transmission polarization state changes (1) to (3). Process.

The calculation method is not particularly limited, and for example, by applying crystal optical theory, the three-dimensional refractive index (nx ₁ , ny ₁ , nz ₁ , nx ₂ , ny ₂ , nz ₂ ) of each layer is changed to change Δ ₁ , Δ ₂ , Δ ₃ , Ψ ₃ can be calculated and the calculation results can be fitted to the measurement results to calculate Re and Rth of each layer. However, when the change in the transmitted polarization state is measured by spectroscopic ellipsometry, It is preferable to calculate Re and Rth using the equations [1] to [5]. This is because analysis is easy because there are few parameters to be changed.

A method for calculating Re and Rth using the following formulas [1] to [5] will be described in detail below by taking an optically anisotropic film having a two-layer / two-layer structure as an example.
Incidentally wherein, n _i denotes an average refractive index of each layer of the optically anisotropic film,
n _x, n _y and n _z represent the three-dimensional refractive index of each layer of the optically anisotropic film (where subscripts x, y and z-plane slow axis direction of each of the optically anisotropic film, optical Represents the direction perpendicular to the in-plane slow axis of the anisotropic film in the plane and the thickness direction of the optically anisotropic film).
d represents the thickness of each layer of the optically anisotropic film.
Further, the subscript 1 in Re, Rth, Δ ₁ , Δ ₂ , Δ ₃ , Ψ ₃ , n _i , n _x , n _y , _nz, and d indicates the light irradiation side of the optical anisotropic film. This represents a value for a layer (hereinafter sometimes referred to as “first layer”), and 2 represents a value for a different type of layer (hereinafter sometimes referred to as “second layer”). Represents that.

First, assuming Re ₁ and Rth ₁ , the three-dimensional refractive indexes n _x1 , n _y1, and _nz1 of the first layer (average refractive index n _i1 , thickness d ₁ ) are obtained by the equation [1].

Next, using the n _x1 , n _y1, and n _z1 , the changes Δ ₁₁ and Δ ₂₁ in the first layer phase difference in the first measurement and the second measurement are obtained by the equation [2].

Using Δ ₁₁ and Δ ₂₁ obtained by the equation [2], and changes Δ ₁ and Δ ₂ of the retardation of the entire optically anisotropic film obtained by the first measurement and the second measurement, The changes Δ ₁₂ and Δ ₂₂ in the phase difference of the second layer in the first measurement and the second measurement are obtained by Equation [3].

The delta ₁₂ and the second layer using a delta ₂₂ (average refractive index _{n i2, d 2} thickness) three-dimensional refractive indexes of the _{n x2, n y2} and _{n z2} is obtained by equation [4].

Then, applying the Berreman 4 × 4 matrix method using the thickness and three-dimensional refractive index of each layer obtained, an ellipsometry representing the change in the polarization state of the optically anisotropic film in the third measurement Variables Δ _3c and ψ _3c are calculated.

  The 4 × 4 matrix method is described in Journal of Optical Society of America, vol. 62, 6, p. 502-510 (1972), which is a well-known calculation method, but since it is a complicated calculation, detailed description thereof is omitted here.

The Δ _3c and ψ _3c obtained in this way are compared with the changes Δ ₃ and ψ _{3 in} the polarization state of the optically anisotropic film obtained directly in the third measurement. When the calculations of the above equations [1] to [4] are repeated while changing the values of Re ₁ and Rth ₁ assumed first, the difference between Δ _3c and Ψ _3c and Δ ₃ and Ψ ₃ is the smallest. Re ₁ and Rth ₁ are obtained. This value becomes the true Re ₁ and Rth ₁ of the first layer.

Further, n _x2 , n _y2 and _nz2 corresponding to Re ₁ and Rth ₁ become the true refractive index of the second layer. Using these, the in-plane retardation Re ₂ and the thickness direction retardation Rth ₂ of the second layer are obtained by the equation [5].

As described above, the two-type two-layer optically anisotropic film has been described as an example. However, the retardation of each layer can be similarly obtained for an optically anisotropic film having three or more layers. In this case, each parameter used for the calculation is a value obtained by summing up the same kind of layers. For example, if it is a two-kind-three-layer optically anisotropic film having a structure in which a first layer, a second layer, and a third layer, which is the same kind of layer as the first layer, are stacked in this order, Re ₁ , Rth ₁ , Δ ₁₁ , Δ ₂₁ , n _i1 , n _x1 , n _y1 , n _z1, and d ₁ are all obtained as values obtained by combining the first layer and the third layer.

  In the method for producing an optically anisotropic film, in order to obtain an optically anisotropic film having desired optical properties, various conditions of the production process, such as temperature, pressure, film thickness, film forming speed, viscosity, and draw ratio The feedback control is performed automatically or manually so that the values such as the refractive index and the retardation approach a desired value. According to the measurement method of the present invention, the in-plane retardation Re and the thickness direction retardation Rth of each layer can be measured for the optically anisotropic film composed of two types of layers. It becomes possible to carry out precisely and it becomes easy to manufacture the optical anisotropic film which has a desired optical characteristic.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1
A non-stretched cyclic olefin resin film (Zeonor film ZF14; manufactured by Nippon Zeon Co., Ltd.) having a thickness of 67 μm is stretched 1.5 times in the longitudinal direction at 144 ° C., the thickness d ₂ is 55 μm, and the average refractive index n _i2 is A film having 1.535, Re of 118 nm and Rth of 61 nm was obtained as the second layer film.

A stretched cyclic olefin resin film (Zeonor film) having a thickness d ₁ of 50 μm, an average refractive index n _i1 of 1.535, Re of 52 nm, and Rth of 126 nm as a first layer film on the second layer. ZB12 (manufactured by ZEON CORPORATION) was bonded using a double-sided adhesive tape manufactured by Nitto Denko Corporation so that the slow axes of both films were orthogonal to produce an optically anisotropic film A. In addition, the optical characteristic of each film was measured based on the method as described in Unexamined-Japanese-Patent No. 2007-225426. That is, the average refractive index by the method described in JP 2007-225426 _{n i} and the three-dimensional refractive index _n x, measured _{n y} and _{n z,} was calculated Re and Rth by the formula [5]. The thickness was measured using a micrometer.

  Re and Rth of each layer were 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, as shown in FIG. 1, the light beam is to measure the change delta ₁ phase difference of the adjusted transmission light to be perpendicularly incident on the optically anisotropic film A. At this time, Δ ₁ = 65.9 nm (= 43.1 °).

As a second measurement, as shown in FIG. 2, the slow axis (orientation direction) of the optical anisotropic film A is 0 °, and the light beam has a polar angle θ ₁ of 50 ° with respect to the optical anisotropic film A. adjusted to measure the change delta ₂ of the phase difference of the transmitted light as incident. At this time, Δ ₂ = 12.0 nm (= 7.85 °).

As a third measurement, as shown in FIG. 3, the azimuth angle θ ₂ is 45 ° with respect to the slow axis (orientation direction) of the optically anisotropic film A, and the light beam has a polar angle with respect to the optically anisotropic film A. Adjustment was made so that θ ₃ was incident at 50 °, and a change Δ _{3 in} phase difference of transmitted light and a change in amplitude ratio ψ ₃ were measured. At this time, Δ ₃ = −97.7 ° and Ψ ₃ = 23.9 °.

The Re ₁ of the first layer film is changed within the range of −300 to +300 nm and the Rth ₁ is changed within the range of −300 to +300 nm, and the above equations [1] to [4] are used for the respective Re ₁ and Rth ₁ . the three-dimensional refractive indexes _{n x1, n y1, n z1} and 3-dimensional refractive index of the film of the second layer _{n x2, n y2, n z2} of the first layer film was calculated.

Using the obtained n _x1 , n _y1 , n _z1 and n _x2 , n _y2 , n _z2 , the phase difference of the transmitted light with respect to the incident condition of azimuth angle θ ₂ and polar angle θ ₃ by the 4 × 4 matrix method A change Δ _3c and an amplitude ratio change Ψ _3c were calculated. The calculated Δ _3c and Ψ _3c are compared with Δ ₃ and Ψ ₃ obtained in the third measurement, and Re ₁ and Rth ₁ when the difference is the smallest are used as the in-plane letters of the first layer. It was obtained Deshon _Re 1 = _52nm and the thickness direction retardation _Rth 1 = _122nm.

Using the three-dimensional refractive index n _x2 = 1.5362, n _y2 = 1.5344, n _z2 = 1.5343 of the second layer corresponding to this Re ₁ = 52 nm and Rth ₁ = 122 nm, the equation [5] Based on the calculation of Re ₂ and Rth ₂ of the second layer, Re ₂ = 119 nm and Rth ₂ = 67 nm. Re ₁ , Rth ₁ , Re ₂ and Rth ₂ thus obtained are in good agreement with the values measured individually before the first layer film and the second layer film are bonded together. It was found that the retardation of the optically anisotropic film having the seed two-layer structure can be accurately measured.

(Example 2)
On the second layer side of the optically anisotropic film A used in Example 1, the same film as the first layer is used as the third layer, and a double-sided adhesive tape manufactured by Nitto Denko Corporation is used, and the first layer and the third layer are formed. Bonding was performed so that the slow axes were parallel to each other, so that a two-type three-layer optically anisotropic film B was produced. The optical anisotropic film was measured in the same manner as in Example 1 to obtain Δ ₁ = 15.0 nm, Δ ₂ = −74.3 nm, Δ ₃ = −63.2 °, and Ψ ₃ = 6.87 °. It was.

Here, it is assumed that a layer having a refractive index equal to that of the first layer and the third layer and having a thickness equal to the sum of the thickness of the first layer and the thickness of the third layer is the fourth layer. The above-described two-type three-layer optically anisotropic film B is regarded as a two-type two-layer optically anisotropic film having the configuration of the second layer to the fourth layer, and the same method as in Example 1 is applied. ₂ is changed in the range of −300 nm to +300 nm, Rth ₂ is changed in the range of −300 nm to +300 nm, and the above-mentioned formulas [1] to [4] are used for Re ₂ and Rth ₂ , respectively. the rate _{n x2, n y2,} 3-dimensional refractive index of the film of _{n z2} and the fourth layer _{n x4, n y4, n z4} was calculated.

_{N x4,} n y4 from the _{assumption, n z4} is the three-dimensional refractive index _{n x3, n y3, n z3} film of three-dimensional refractive index _{n x1, n y1, n z1} and a third layer of the film of the first layer Equal to each. Therefore, with respect to the two-type three-layer optically anisotropic film, the transmitted light is transmitted with respect to the incident conditions of the azimuth angle θ ₂ and polar angle θ ₃ by the 4 × 4 matrix method using the obtained three-dimensional refractive index of each layer. A phase difference change Δ _3c and an amplitude ratio change ψ _3c were calculated. The calculated Δ _3c and ψ _3c are compared with Δ ₃ and ψ ₃ obtained in the third measurement, and Re ₂ and Rth ₂ when the difference is smallest are used as the in-plane letters of the second layer. The retardation Re ₂ = 119 nm and the thickness direction retardation Rth ₂ = 65 nm were obtained.

Using the three-dimensional refractive indexes n _x1 = 1.53634, n _y1 = 1.5353 and n _z1 = 1.53336 of the first layer when Re ₂ = 119 nm and Rth ₂ = 65 nm are determined, the equation [ 5], Re ₁ and Rth ₁ of the first layer were calculated to be Re ₁ = 52 nm and Rth ₂ = 123 nm. Re ₁ , Rth ₁ , Re ₂ and Rth ₂ thus obtained are in good agreement with the values measured individually for each layer, and the retardation of the optically anisotropic film having a two-layer / three-layer structure is accurately measured by the measurement method of the present invention. It turns out that it can measure well.

(Example 3)
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. Melted 260 ° C. styrene-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 (die slip surface roughness Ra: 0.1 μm). The maleic anhydride copolymer resin was supplied to the other manifold through a leaf disk-shaped polymer filter having an opening of 10 μm. 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 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 laminated film having a width of 1350 mm composed of a maleic anhydride copolymer resin layer (second layer) was obtained.

The laminated film 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 C. The thickness of the optically anisotropic film was measured using a micrometer and found to be 92 μm. Since the polycarbonate resin: styrene-maleic anhydride copolymer resin was coextruded at a ratio of 1: 9.2, the first layer thickness d ₁ = 9 μm and the second layer thickness d ₂ = 83 μm were calculated. It was.

The data was measured in the same manner as in Example 1 with Re and Rth of the first layer being Re ₁ and Rth ₁ and Re and Rth of the second layer being Re ₂ and Rth ₂ , and Δ ₁ = 157.4 nm.
Δ ₂ = 158.0 nm
Δ ₃ = 76.1 °
Ψ ₃ = 53.0 °
Met.
As a result of obtaining Re ₁ , Rth ₁ , Re ₂ , Rth ₂ in the same manner as in Example 1, Re ₁ = 40 [nm]
Rth ₁ = 130 [nm]
Re ₂ = 117 [nm]
Rth ₂ = −127 [nm]
Met.

  As described above, according to the measurement method of the present invention, the in-plane retardation Re and the thickness direction retardation Rth of each layer of the optically anisotropic film composed of two types of layers can be accurately measured without separating the layers. It turned out that it can measure.

1, 2, 3: Incident light 100: Optical anisotropic film 101: First layer 102: Second layer

Claims (6)

A method for measuring the retardation of an optically anisotropic film comprising two layers,
Irradiating light in a substantially perpendicular direction 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. Irradiating light in the direction of (a) and measuring the change (3) in the transmitted polarization state;
And
A step of calculating in-plane retardation Re and retardation Rth in the thickness direction of each layer constituting the optically anisotropic film using the changes (1) to (3) of the transmitted polarization state. For measuring retardation of conductive film. 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 measurement method according to claim 1, wherein the change (3) of the transmitted polarization state is a change Δ _{3 in} phase difference of transmitted light and a change Ψ ₃ in amplitude ratio. Measuring the thickness of each layer of the optically anisotropic film,
The step of calculating in-plane retardation Re and thickness direction retardation Rth of each layer constituting the optically anisotropic film,
Assuming Re ₁ and Rth ₁ , the step of obtaining the three- dimensional refractive index of each layer by the following equations [1] to [4]:
Using the thickness and three-dimensional refractive index of each layer, a calculated value Δ _{3c of} a change in phase difference of transmitted light when light is irradiated in the directions of azimuth angle θ ₂ and polar angle θ ₃ by the 4 × 4 matrix method, and Calculating a calculated value Ψ _3c of a change in amplitude ratio;
Calculating Re ₁ and Rth ₁ as values at which the difference between Δ _3c and ψ _3c and Δ ₃ and ψ ₃ is minimized,
A step of obtaining a three- dimensional refractive index of each layer from Re ₁ and Rth ₁ by the following equations [1] to [4]:
A step of calculating Re ₂ and Rth ₂ from the three-dimensional refractive index by the following equation [5]:
The measurement method according to claim 2, comprising:
(Where n _i represents the average refractive index of each layer of the optically anisotropic film,
n _x, n _y and n _z represent the three-dimensional refractive index of each layer of the optically anisotropic film (where subscripts x, y and z-plane slow axis direction of each of the optically anisotropic film, Represents the direction perpendicular to the in-plane slow axis of the optically anisotropic film in the plane and the thickness direction of the optically anisotropic film).
d represents the thickness of each layer of the optically anisotropic film.
The subscript 1 in Re, Rth, Δ ₁ , Δ ₂ , n _i , n _x , n _y , _nz, and d is a layer on the optically anisotropic film that is irradiated with light, and a layer of the same type 2 represents a value for a different kind of layer. ) theta ₂ is _{40 ° ≦ θ 2 ≦ 50 °} , the measuring method according to any one of claims 1 to 3. The measurement method according to any one of claims 1 to 4, wherein the optically anisotropic film composed of two kinds of layers is obtained by multilayer extrusion molding. A method for producing an optically anisotropic film comprising two layers,
The manufacturing method of the optically anisotropic film | membrane including the said manufacturing method including measuring the retardation of the said optically anisotropic film | membrane by the measuring method as described in any one of Claims 1-5.