Liquid crystal polarization interference element and optical filter

Abstract

Provided is a liquid crystal polarization interference element which, when used in a bandpass filter or the like, is not susceptible to wavelength shift of maximum transmittance even when light is incident from an oblique direction. The liquid crystal polarization interference element has two or more liquid crystal layer groups each comprising a first liquid crystal layer and a second liquid crystal layer, the first liquid crystal layer including a first horizontal alignment liquid crystal layer in which a horizontal alignment liquid crystal compound is fixed and a first vertical alignment liquid crystal layer in which a vertical alignment liquid crystal compound is fixed; the second liquid crystal layer includes a second horizontally oriented liquid crystal layer in which a horizontally oriented liquid crystal compound is fixed and a second vertically oriented liquid crystal layer in which a vertically oriented liquid crystal compound is fixed, and in each of the liquid crystal layers, the liquid crystal compound is a rod-like liquid crystal compound or a disc-like liquid crystal compound. The in-plane slow axes of the first liquid crystal layer and the second liquid crystal layer intersect, the in-plane retardation of the horizontal alignment liquid crystal layer is 1.33-4 times the retardation of the vertical alignment liquid crystal layer in the thickness direction, and the in-plane retardation of the first liquid crystal layer is equal to the in-plane retardation of the second liquid crystal layer.

Description

TECHNICAL FIELD

[0001] The present application relates to a liquid crystal polarization interference element and an optical filter using the same. BACKGROUND

[0002] A band-pass filter that transmits light in a specific wavelength region and blocks light of other wavelengths is used for various optical devices.

[0003] As a band-pass filter, a polarization interference filter using a dielectric multilayer film, a filter combining a polarization element and a birefringent crystal, and the like are known.

[0004] Further, a band-pass filter as described in Patent Document 1 is known, in which a birefringent plate (λ / 2 plate) having a thickness equal to that of a polarizer and an angle of a transmission axis of the polarizer and a slow axis of +p and a birefringent plate of -p are alternately stacked between polarizers arranged in an orthogonal Nicol system.

[0005] In Patent Document 1, as an optical filter (band-pass filter) having a small number of parts, an optical filter composed of a crystal having a structure in which two different polarization regions are periodically arranged, and a principal axis of a refractive index ellipsoid cut parallel to an interface between the two different polarization regions is different between the two different polarization regions is proposed.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENTS

[0008] Patent Document 1: Japanese Patent Application Publication No. 2004-101577 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In such a band-pass filter, there is a problem that, for light incident from an oblique direction, a wavelength showing the maximum transmittance is different from that for light incident from a normal (perpendicular) direction, so-called short-wave shift occurs.

[0011] The present application aims to solve the problems of the prior art and provide a liquid crystal polarization interference element that, when used in a band-pass filter or the like, does not easily cause a shift in the wavelength showing the maximum transmittance even when light is incident from an oblique direction.

[0012] MEANS FOR SOLVING THE PROBLEMS

[0013] To solve the problem, the present application has the following structure.

[0014] [1] A liquid crystal polarization interference element having two or more sets of a set of liquid crystal layers composed of a first liquid crystal layer and a second liquid crystal layer in a thickness direction,

[0015] The first liquid crystal layer includes at least one first horizontal alignment liquid crystal layer in which a first-1 liquid crystal compound that aligns an optical axis horizontally is fixed, and at least one first vertical alignment liquid crystal layer in which a first-2 liquid crystal compound that aligns an optical axis vertically is fixed,

[0016] The second liquid crystal layer includes at least one second horizontal alignment liquid crystal layer in which a second-1 liquid crystal compound that aligns an optical axis horizontally is fixed, and at least one second vertical alignment liquid crystal layer in which a second-2 liquid crystal compound that aligns an optical axis vertically is fixed,

[0017] The first-1 liquid crystal compound and the first-2 liquid crystal compound are both rod-like liquid crystal compounds, or are both discotic liquid crystal compounds,

[0018] The second-1 liquid crystal compound and the second-2 liquid crystal compound are both rod-like liquid crystal compounds, or are both discotic liquid crystal compounds,

[0019] An in-plane slow axis of the first liquid crystal layer and an in-plane slow axis of the second liquid crystal layer cross each other,

[0020] A total of in-plane retardation of the first horizontal alignment liquid crystal layer is 1.33 to 4 times a total of thickness-direction retardation of the first vertical alignment liquid crystal layer,

[0021] A total of in-plane retardation of the second horizontal alignment liquid crystal layer is 1.33 to 4 times a total of thickness-direction retardation of the second vertical alignment liquid crystal layer.

[0022] An in-plane retardation of the first liquid crystal layer is equal to an in-plane retardation of the second liquid crystal layer.

[0023] [2] The liquid crystal polarization interference element according to [1], wherein,

[0024] A total of in-plane retardation of the first horizontal alignment liquid crystal layer is twice a total of thickness-direction retardation of the first vertical alignment liquid crystal layer,

[0025] A total of in-plane retardation of the second horizontal alignment liquid crystal layer is twice a total of thickness-direction retardation of the second vertical alignment liquid crystal layer.

[0026] [3] The liquid crystal polarization interference element according to [1] or [2], having three or more sets of liquid crystal layers in a thickness direction,

[0027] In the liquid crystal layer group arranged on both sides in the thickness direction and the liquid crystal layer group arranged in the center in the thickness direction, the angle formed by the in-plane slow axis of the first liquid crystal layer and the in-plane slow axis of the second liquid crystal layer, as well as the in-plane retardation in the first liquid crystal layer and the second liquid crystal layer are different.

[0028] [4] The liquid crystal polarization interference element according to any one of [1] to [3], wherein

[0029] The first liquid crystal layer and the second liquid crystal layer contain infrared absorbing pigments.

[0030] [5] The liquid crystal polarization interference element according to any one of [1] to [4], wherein

[0031] The first liquid crystal layer and the second liquid crystal layer include liquid crystal elastomer.

[0032] [6] A filter having:

[0033] The liquid crystal polarization interference element described in any one of [1] to [5]; and

[0034] Two polarizers sandwiching the liquid crystal polarization interference element in the thickness direction,

[0035] The two polarizers are arranged so that their transmission axes are orthogonal to each other.

[0036] [7] The optical filter according to [6], wherein

[0037] A retardation layer is included between one or both of the two polarizers and the liquid crystal layer group, and the in-plane slow axis of the retardation layer is parallel to the absorption axis of one of the two polarizers.

[0038] Effects of the Invention

[0039] According to the present invention, a liquid crystal polarization interference element can be provided which, when used in a bandpass filter or the like, is less likely to experience a shift in the wavelength of maximum transmittance even when light is incident from an oblique direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a diagram conceptually showing an example of an optical filter including the liquid crystal polarization interference element of the present invention.

[0041] Figure 2 This is a graph for explaining an optical filter including the liquid crystal polarization interference element of the present invention.

[0042] Figure 3 This is a graph for explaining an optical filter including the liquid crystal polarization interference element of the present invention.

[0043] Figure 4This is a diagram conceptually showing an optical filter including a liquid crystal polarization interference element according to another example of the present invention. DETAILED DESCRIPTION

[0044] Hereinafter, the liquid crystal polarization interference element and the optical filter of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

[0045] In this specification, the numerical range expressed using "to" means a range including the numerical values ​​described before and after "to" as the lower limit and the upper limit.

[0046] In this specification, unless otherwise specified, angles such as "45°," "parallel," "perpendicular," or "orthogonal" refer to angles that differ from a strict angle by less than 5 degrees. The difference from a strict angle is preferably less than 3 degrees, and more preferably less than 1 degree.

[0047] In this specification, terms such as “same” and “equal” include an error range generally allowed in the relevant technical field.

[0048] In this specification, Re(λ) represents the in-plane retardation at a wavelength λ.

[0049] In this specification, Re(λ) is a value measured at a wavelength of λ using an AxoScan (manufactured by Axometrics). The following is calculated by inputting the average refractive index ((nx+ny+nz) / 3) and the film thickness (d (μm)) into the AxoScan.

[0050] Slow axis direction (°)

[0051] Re(λ)=R0(λ)

[0052] In addition, R0(λ) is expressed as a numerical value calculated by AxoScan and refers to Re(λ).

[0053] Furthermore, the drawings shown below are all conceptual diagrams for explaining the present invention, and the positional relationship, size, thickness, shape, etc. of each component are different from the actual ones.

[0054] [Liquid crystal polarization interference elements and filters]

[0055] The liquid crystal polarization interference element of the present invention has two or more liquid crystal layer groups consisting of a first liquid crystal layer and a second liquid crystal layer in the thickness direction.

[0056] The first liquid crystal layer includes at least one first horizontal alignment liquid crystal layer formed by fixing a 1-1 liquid crystal compound that aligns the optical axis horizontally, and at least one first vertical alignment liquid crystal layer formed by fixing a 1-2 liquid crystal compound that aligns the optical axis vertically.

[0057] The second liquid crystal layer includes at least one second-1 horizontal alignment liquid crystal layer in which a second-1 liquid crystal compound that causes optical axes to be horizontally aligned is fixed, and at least one second-2 vertical alignment liquid crystal layer in which a second-2 liquid crystal compound that causes optical axes to be vertically aligned is fixed,

[0058] The first-1 liquid crystal compound and the first-2 liquid crystal compound are both rod-like liquid crystal compounds, or are both discotic liquid crystal compounds,

[0059] The second-1 liquid crystal compound and the second-2 liquid crystal compound are both rod-like liquid crystal compounds, or are both discotic liquid crystal compounds,

[0060] The in-plane slow axis of the first liquid crystal layer and the in-plane slow axis of the second liquid crystal layer intersect,

[0061] The sum of the in-plane retardation of the first horizontal alignment liquid crystal layer is 1.33 to 4 times the sum of the thickness-direction retardation of the first vertical alignment liquid crystal layer,

[0062] The sum of the in-plane retardation of the second horizontal alignment liquid crystal layer is 1.33 to 4 times the sum of the thickness-direction retardation of the second vertical alignment liquid crystal layer,

[0063] The in-plane retardation of the first liquid crystal layer and the in-plane retardation of the second liquid crystal layer are equal.

[0064] Further, the filter of the present application has:

[0065] The liquid crystal polarization interference element described above; and

[0066] Two polarizers sandwiching the liquid crystal polarization interference element in the thickness direction,

[0067] The two polarizers are configured so that their transmission axes are orthogonal to each other.

[0068] In Figure 1 An example of the filter of the present application having the liquid crystal polarization interference element of the present application is conceptually illustrated in FIG. 1.

[0069] Figure 1 The filter 10 illustrated is a band-pass filter (narrow-band filter) that transmits light in a specific wavelength region and blocks light of wavelengths other than this. The filter 10 has a first polarizer 12 and a second polarizer 14, and a liquid crystal polarization interference element 16. The liquid crystal polarization interference element 16 is disposed between the first polarizer 12 and the second polarizer 14.

[0070] The first polarizer 12 and the second polarizer 14 are polarizers (polarizing plates) that transmit linearly polarized light in a prescribed direction, and are disposed in an orthogonal Nicol configuration in which the transmission axes are orthogonal.

[0071] The first polarizer 12 and the second polarizer 14 are not limited, and various linear polarizers known in the art, such as an iodine polarizer, a dye polarizer using dichroic dye, a polyene polarizer, and a wire grid polarizer, can be used.

[0072] In the illustrated example of the optical filter 10, a liquid crystal polarization interference element 16 is disposed between the first polarizer 12 and the second polarizer 14.

[0073] In addition, in the case where the first polarizer 12 and the second polarizer 14 are separate from the liquid crystal polarization interference element 16, Figure 1

[0074] However, the present application is not limited thereto, and the first polarizer 12 and the second polarizer 14 can be in contact with and laminated with the liquid crystal polarization interference element 16. Also, in the case where the first polarizer 12 and the second polarizer 14 are in contact with the liquid crystal polarization interference element 16, the two can be bonded with an adhesive transparent to transmitted light, such as an OCA (Optical Clear Adhesive) and an acrylic adhesive, as needed.

[0075] The liquid crystal polarization interference element 16 is an optical element that functions as a λ / 2 phase difference plate for light in a specific wavelength region (specific wavelength) and does not function as a phase difference layer for light other than that.

[0076] As described above, the first polarizer 12 and the second polarizer 14 are polarizers disposed in an orthogonal Nicol configuration with the transmission axes orthogonal to each other.

[0077] Therefore, of the light incident into the optical filter 10, linearly polarized light in a prescribed direction is transmitted through the first polarizer 12. Of this linearly polarized light, light of a specific wavelength has its polarization direction rotated by 90° by the liquid crystal polarization interference element 16 and is incident into the second polarizer 14 disposed in an orthogonal Nicol configuration with the first polarizer 12 and is transmitted. In contrast, since the liquid crystal polarization interference element 16 does not function as a phase difference layer, light other than in the specific wavelength region is incident into the second polarizer 14 disposed in an orthogonal Nicol configuration with the first polarizer 12 and is blocked.

[0078] The optical filter 10 becomes a band-pass filter that transmits only light in the specific wavelength region and blocks light other than that by this optical action.

[0079] The liquid crystal polarization interference element 16 is formed by laminating liquid crystal layers in an even number of layers, the liquid crystal layers being formed by fixing liquid crystal compounds oriented in a prescribed direction.

[0080] Specifically, the liquid crystal polarization interference element 16 is formed by laminating two or more sets of liquid crystal layer groups 26 composed of a first liquid crystal layer 20 and a second liquid crystal layer 24 in the thickness direction.​

[0081] Therefore, the total number of the first liquid crystal layer 20 and the second liquid crystal layer 24 becomes even.

[0082] In Figure 1 In the example shown, the liquid crystal polarization interference element 16 has the first to nth liquid crystal layer groups.

[0083] In the one liquid crystal layer group 26, the first liquid crystal layer 20 and the second liquid crystal layer 24 each include at least one horizontal alignment liquid crystal layer in which a liquid crystal compound that aligns the optical axis horizontally is fixed, and at least one vertical alignment liquid crystal layer in which a liquid crystal compound that aligns the optical axis vertically is fixed.

[0084] In the following description, the liquid crystal layer group closest to the first polarizer 12 is referred to as the first liquid crystal layer group 26a, and the liquid crystal layer group closest to the second polarizer 14 is referred to as the nth liquid crystal layer group 26n. When the liquid crystal layer groups do not need to be distinguished, they are also referred to as the liquid crystal layer group 26. Furthermore, the first liquid crystal layer included in the first liquid crystal layer group 26a is denoted by reference numeral 20a, and the second liquid crystal layer is denoted by reference numeral 24a. The first liquid crystal layer included in the nth liquid crystal layer group 26n is denoted by reference numeral 20n, and the second liquid crystal layer is denoted by reference numeral 24n. When the first liquid crystal layers do not need to be distinguished, they are also referred to as the first liquid crystal layer 20, and when the second liquid crystal layers do not need to be distinguished, they are also referred to as the second liquid crystal layer 24. Furthermore, the horizontally aligned liquid crystal layer included in the first liquid crystal layer 20a of the first liquid crystal layer group 26a is referred to as the first horizontally aligned liquid crystal layer 20Ha, and the horizontally aligned liquid crystal layer included in the first liquid crystal layer 20n of the n-th liquid crystal layer group 26n is referred to as the first horizontally aligned liquid crystal layer 20Hn. In the absence of a need to distinguish between the first horizontally aligned liquid crystal layers, these layers are also referred to as the first horizontally aligned liquid crystal layer 20H. Furthermore, the vertically aligned liquid crystal layer included in the first liquid crystal layer 20a of the first liquid crystal layer group 26a is referred to as the first vertically aligned liquid crystal layer 20Va, and the vertically aligned liquid crystal layer included in the first liquid crystal layer 20n of the n-th liquid crystal layer group 26n is referred to as the first vertically aligned liquid crystal layer 20Vn. In the absence of a need to distinguish between the first vertically aligned liquid crystal layers, these layers are also referred to as the first vertically aligned liquid crystal layer 20V. Furthermore, the horizontally aligned liquid crystal layer included in the second liquid crystal layer 24a of the first liquid crystal layer group 26a is referred to as the second horizontally aligned liquid crystal layer 24Ha, and the horizontally aligned liquid crystal layer included in the second liquid crystal layer 24n of the n-th liquid crystal layer group 26n is referred to as the second horizontally aligned liquid crystal layer 24Hn. In the absence of a need to distinguish between the second horizontally aligned liquid crystal layers, these layers are also referred to as the second horizontally aligned liquid crystal layer 24H. Furthermore, the vertically aligned liquid crystal layer included in the second liquid crystal layer 24a of the first liquid crystal layer group 26a is referred to as the second vertically aligned liquid crystal layer 24Va, and the vertically aligned liquid crystal layer included in the second liquid crystal layer 24n of the n-th liquid crystal layer group 26n is referred to as the second vertically aligned liquid crystal layer 24Vn. In the absence of a need to distinguish between the second vertically aligned liquid crystal layers, these layers are also referred to as the second vertically aligned liquid crystal layer 20V.

[0085] Hereinafter, the first liquid crystal layer 20 a and the second liquid crystal layer 24 a of the first liquid crystal layer group 26 a will be described representatively. However, the first liquid crystal layer 20 and the second liquid crystal layer 24 of each liquid crystal layer group 26 basically have the same structure.

[0086] like Figure 1 As shown, the first horizontal alignment liquid crystal layer 20Ha of the first liquid crystal layer 20a is formed by making the first rod-shaped liquid crystal compound 18 h1aThe optical axis of the rod-shaped liquid crystal compound is aligned along its long axis. That is, the first horizontally aligned liquid crystal layer 20Ha is formed by aligning the first rod-shaped liquid crystal compound 18 horizontally and fixing the optical axis of the ... h1a The layer is aligned in such a manner that its major axis direction is parallel to the main surface of the first horizontal alignment liquid crystal layer 20Ha. Figure 1 As shown, in the first horizontal alignment liquid crystal layer 20Ha, each 1-1 rod-shaped liquid crystal compound 18 h1a The first horizontally aligned liquid crystal layer 20Ha is aligned so that its optical axis is aligned in a predetermined direction.

[0087] In addition, the main surface refers to the largest surface of the sheet-like object (each layer).

[0088] The first vertical alignment liquid crystal layer 20Va of the first liquid crystal layer 20a is formed by making the first and second rod-shaped liquid crystal compounds 18 v1a That is, the first vertically aligned liquid crystal layer 20Va is formed by fixing the optical axis of the first and second rod-shaped liquid crystal compounds 18 v1a A layer aligned so that its major axis direction is perpendicular to the main surface of the first vertically aligned liquid crystal layer 20Va. That is, the first vertically aligned liquid crystal layer 20Va is a so-called (positive) C plate.

[0089] In the present invention, the absolute value of the sum of the in-plane retardation of the first horizontal alignment liquid crystal layer 20Ha is approximately twice the absolute value of the sum of the thickness direction retardation of the first vertical alignment liquid crystal layer 20Va.

[0090] This will be described in detail later.

[0091] Likewise, if Figure 1 As shown, the second horizontal alignment liquid crystal layer 24Ha of the second liquid crystal layer 24a is formed by making the 2-1 rod-shaped liquid crystal compound 18 h2a That is, the second horizontally aligned liquid crystal layer 24Ha is formed by fixing the optical axis of the second-1 rod-shaped liquid crystal compound 18 h2a The layer is aligned in such a manner that the long axis direction thereof is parallel to the main surface of the second horizontal alignment liquid crystal layer 24Ha. Figure 1 As shown, in the second horizontal alignment liquid crystal layer 24Ha, each 2-1 rod-shaped liquid crystal compound 18 h2a The second horizontally aligned liquid crystal layer 24Ha is aligned so that its optical axis is aligned in a predetermined direction. That is, the second horizontally aligned liquid crystal layer 24Ha is a so-called (positive) A-plate. In the following description, when it is not necessary to distinguish between the rod-shaped liquid crystal compounds constituting each liquid crystal layer, they are also referred to as the rod-shaped liquid crystal compound 18.

[0092] The second vertical alignment liquid crystal layer 24Va of the second liquid crystal layer 24a is formed by making the 2-2 rod-shaped liquid crystal compound 18 v2a That is, the second vertically aligned liquid crystal layer 24Va is formed by fixing the optical axis of the second rod-shaped liquid crystal compound 18 v2a A layer aligned so that its major axis direction is perpendicular to the main surface of the second vertically aligned liquid crystal layer 24Va. That is, the second vertically aligned liquid crystal layer 24Va is a so-called (positive) C plate.

[0093] In the present invention, the absolute value of the total in-plane retardation of the second horizontal alignment liquid crystal layer 24Ha is approximately twice the absolute value of the total thickness direction retardation of the second vertical alignment liquid crystal layer 24Va.

[0094] This will be described in detail later.

[0095] In the first liquid crystal layer group 26 a , the in-plane slow axis of the first liquid crystal layer 20 a intersects the in-plane slow axis of the second liquid crystal layer 24 a .

[0096] The direction of the in-plane slow axis of the first liquid crystal layer 20a is mainly determined by the 1-1 rod-shaped liquid crystal compound 18 in the first horizontal alignment liquid crystal layer 20Ha. h1a Similarly, the direction of the in-plane slow axis of the second liquid crystal layer 24a is mainly determined by the 2-1 rod-shaped liquid crystal compound 18 in the second horizontal alignment liquid crystal layer 24Ha. h2a The orientation direction is determined by.

[0097] Therefore, if Figure 1 As shown, the first liquid crystal layer 20a and the second liquid crystal layer 24a are aligned with the first horizontal alignment liquid crystal layer 20Ha having the first rod-shaped liquid crystal compound 18. h1a The alignment direction (long axis direction) of the second horizontal alignment liquid crystal layer 24Ha is aligned with the 2-1 rod-shaped liquid crystal compound 18 h2a The layers are stacked in such a manner that the orientation directions (long axis directions) thereof intersect with each other.

[0098] Furthermore, in the first liquid crystal layer group 26 a , the in-plane retardation of the first liquid crystal layer 20 a and the in-plane retardation of the second liquid crystal layer 24 a are substantially equal.

[0099] The first liquid crystal layer group 26a is configured such that the bisector of the angle formed by the direction of the slow axis of the first liquid crystal layer 20a and the direction of the slow axis of the second liquid crystal layer 24a is parallel to the transmission axis or absorption axis of one of the polarizers (the first polarizer 12 and the second polarizer 14) arranged in the crossed Nicols. That is, in a case where, for example, the angle in the clockwise direction when viewed from the first polarizer 12 side is set to be positive and the angle in the counterclockwise direction is set to be negative, the absolute values of the angle of the slow axis of the first liquid crystal layer 20a and the angle of the slow axis of the second liquid crystal layer 24a are the same but the signs are different from the reference line of the transmission axis or absorption axis of one of the polarizers (the first polarizer 12 and the second polarizer 14).

[0100] The liquid crystal polarization interference element 16 of the present application has two or more of such liquid crystal layer groups 26. At this time, the plurality of liquid crystal layer groups 26 are configured such that the bisectors of the angles formed by the directions of the slow axes of the first liquid crystal layers 20 and the directions of the slow axes of the second liquid crystal layers 24 are parallel to each other.

[0101] In the example shown in FIG. 1, the first liquid crystal layer 20a and the second liquid crystal layer 24a are arranged in the order of the first liquid crystal layer 20a, the second liquid crystal layer 24a, the first liquid crystal layer 20b, the second liquid crystal layer 24b, the first liquid crystal layer 20c, and the second liquid crystal layer 24c. Figure 1 In the example shown in FIG. 1, all of the first liquid crystal layers 20 have the same structure, and all of the second liquid crystal layers 24 also have the same structure. That is, in the liquid crystal polarization interference element 16 shown in FIG. 1, the in-plane retardation (Δnd) and the angle of the in-plane slow axis of the first liquid crystal layer 20a are the same as those of the first liquid crystal layer 20b and the first liquid crystal layer 20c, and the in-plane retardation (Δnd) and the angle of the in-plane slow axis of the second liquid crystal layer 24a are the same as those of the second liquid crystal layer 24b and the second liquid crystal layer 24c. Figure 1 In the liquid crystal polarization interference element 16 shown in FIG. 1, the in-plane retardation (Δnd) and the angle of the in-plane slow axis of all of the first liquid crystal layers 20 are equal, and the in-plane retardation (Δnd) and the angle of the in-plane slow axis of all of the second liquid crystal layers 24 are equal.

[0102] The light passing through the liquid crystal polarization interference element 16 is alternately and repeatedly affected by the slow axis of the first liquid crystal layer 20 having a certain angle and the slow axis of the second liquid crystal layer 24 having an angle that is the same in absolute value and different in sign from the angle.

[0103] Therefore, in the liquid crystal polarization interference element 16, the Δnd of the first liquid crystal layer 20 and the second liquid crystal layer 24 is set according to the wavelength region of the transmission filter 10, and the angle of the slow axis in the first liquid crystal layer 20 and the second liquid crystal layer 24 is adjusted according to the total number of layers of the first liquid crystal layer 20 and the second liquid crystal layer 24, whereby it is possible to form a liquid crystal polarization interference element 16 that functions as a λ / 2 phase difference plate for light of a specific wavelength region and does not function as a phase difference plate for light other than this, that is, does not feel a retardation.

[0104] As described above, the optical filter 10, in which the liquid crystal polarization interference element 16, which functions as a λ / 2 retardation film only for light in a specific wavelength range, is disposed between the first polarizer 12 and the second polarizer 14, which are arranged in a crossed Nicols configuration, rotates the polarization direction of linearly polarized light of a specific wavelength that passes through the first polarizer 12 by 90° via the liquid crystal polarization interference element 16, and transmits the light through the second polarizer 14, which is arranged in a crossed Nicols configuration relative to the first polarizer 12. On the other hand, for light outside the specific wavelength range, since the liquid crystal polarization interference element 16 does not function as a retardation film, linearly polarized light that has passed through the first polarizer 12 passes through the liquid crystal polarization interference element 16 and is blocked by the second polarizer 14. This optical action enables the optical filter 10 to function as a bandpass filter that transmits only light in the specific wavelength range and blocks all other light.

[0105] In this manner, the liquid crystal polarization interference element 16 functions as a λ / 2 phase difference plate only for light within a specific wavelength range. Accordingly, the in-plane retardation (Δnd) of the first liquid crystal layer 20 and the second liquid crystal layer 24 is set to half (half) the center wavelength of the wavelength range in which the liquid crystal polarization interference element 16 is assumed to function as a λ / 2 phase difference plate, i.e., the wavelength range in which the transmission filter 10 is assumed to function.

[0106] For example, assuming that the wavelength at which the liquid crystal polarization interference element 16 functions as a λ / 2 retardation plate, i.e., the center wavelength of the wavelength range transmitted by the optical filter 10, is 550 nm, the Δnd of the first liquid crystal layer 20 and the second liquid crystal layer 24 can be set to 275 nm. When the first liquid crystal layer 20 is composed of a first horizontally aligned liquid crystal layer 20H and a first vertically aligned liquid crystal layer 20V, the in-plane retardation of the first liquid crystal layer 20 is primarily determined by the first horizontally aligned liquid crystal layer 20H. Therefore, the Δnd of the first horizontally aligned liquid crystal layer 20H can be set to 275 nm. Similarly, when the second liquid crystal layer 24 is composed of a second horizontally aligned liquid crystal layer 24H and a second vertically aligned liquid crystal layer 24V, the in-plane retardation of the second liquid crystal layer 24 is primarily determined by the second horizontally aligned liquid crystal layer 24H. Therefore, the Δnd of the second horizontally aligned liquid crystal layer 24H can be set to 275 nm.

[0107] Furthermore, the Δnd of the first liquid crystal layer 20 and the second liquid crystal layer 24 may have an error of approximately ±10% with respect to half the center wavelength of the wavelength range transmitted by the optical filter 10 .

[0108] In the liquid crystal polarization interference element 16 of the present application, the absolute value of the sum of the in-plane retardation of the first horizontal alignment liquid crystal layer 20H of the first liquid crystal layer 20 is about 1.33 to 4 times, preferably about 2 times, the absolute value of the sum of the thickness direction retardation of the first vertical alignment liquid crystal layer 20V. Also, the absolute value of the sum of the in-plane retardation of the second horizontal alignment liquid crystal layer 24H of the second liquid crystal layer 24 is about 1.33 to 4 times, preferably about 2 times, the absolute value of the sum of the thickness direction retardation of the second vertical alignment liquid crystal layer 24V.

[0109] As described above, in the conventional bandpass filter, there is a problem that, when light is incident from an oblique direction, as shown from the thick solid line to the thin solid line, wavelength shift occurs in which the transmission wavelength region shifts to the short wavelength side, relative to the case where light is normally incident. Figure 2

[0110] In the liquid crystal polarization interference element 16 of the present application, the first liquid crystal layer 20 and the second liquid crystal layer 24 each have a horizontal alignment liquid crystal layer (20H, 24H) and a vertical alignment liquid crystal layer (20V, 24V), and the absolute value of the sum of the in-plane retardation of the horizontal alignment liquid crystal layer is about 1.33 to 4 times, preferably about 2 times, the absolute value of the sum of the thickness direction retardation of the vertical alignment liquid crystal layer. Thus, the first liquid crystal layer 20 and the second liquid crystal layer 24 each can reduce the difference between the phase difference acting on light when light is normally incident and the phase difference acting on light when light is incident from an oblique direction. Thus, wavelength shift when light is incident from an oblique direction to the filter 10 can be suppressed.

[0111] In addition, the in-plane retardation of the horizontal alignment liquid crystal layer (20H, 24H) can be measured using an Axo Scan (0PMF-1, manufactured by Axometrics).

[0112] Also, the thickness direction retardation of the vertical alignment liquid crystal layer (20V, 24V) can be measured using an Axo Scan (0PMF-1, manufactured by Axometrics). Even in a state where the in-plane periodic structure layer and the thickness direction periodic structure layer are stacked, the in-plane retardation and the thickness direction retardation can be separated and measured by optical analysis.

[0113] As for the liquid crystal polarization interference element 16 having several sets of liquid crystal layer groups 26, detection can be performed by oblique cutting of the liquid crystal polarization interference element 16 and analysis of the orientation direction of the liquid crystal on the surface of the section thereof. This method is described in detail in "Depth-Dependent Determination of Molecular Orientation for WV-Film" by Yohei Takahashi et al. (FMC8-3, IDW '04, 651-654).​

[0114] Also, the in-plane slow axis direction of the first liquid crystal layer 20, i.e., the first horizontally aligned liquid crystal layer, and the in-plane slow axis direction of the second liquid crystal layer 24, i.e., the second horizontally aligned liquid crystal layer, in each liquid crystal layer group can be detected by obliquely cutting the liquid crystal polarization interference element 16 and analyzing the orientation direction of the liquid crystal compound on the surface of the cross section thereof.

[0115] Also, the in-plane slow axis direction of the first liquid crystal layer 20, i.e., the first horizontally aligned liquid crystal layer, and the in-plane slow axis direction of the second liquid crystal layer 24, i.e., the second horizontally aligned liquid crystal layer, in each liquid crystal layer group can be detected by obliquely cutting the liquid crystal polarization interference element 16 and analyzing the orientation direction of the liquid crystal compound on the surface of the cross section thereof.

[0116] The in-plane retardation of each of the first liquid crystal layer 20 and the second liquid crystal layer 24 can be measured using AxoScan or the like manufactured by AxoMetrics Co.

[0117] In the in-plane retardation (Δnd) of the first liquid crystal layer 20 and the second liquid crystal layer 24, Δn is the birefringence of the rod-shaped liquid crystal compound 18 constituting the first liquid crystal layer 20 and the second liquid crystal layer 24. Also, d is the thickness of the first liquid crystal layer 20 and the second liquid crystal layer 24. Therefore, the birefringence Δn and the thickness d of the rod-shaped liquid crystal compound 18 can be measured to obtain the in-plane retardation. In addition, the birefringence Δn of the liquid crystal compound can also be measured using AxoScan or the like manufactured by AxoMetrics Co.

[0118] Regarding the angle of the slow axis in the first liquid crystal layer 20 and the second liquid crystal layer 24 constituting the liquid crystal polarization interference element 16 (the angle with respect to the transmission axis or the absorption axis of a polarizer serving as a reference), the optimal angle at which the liquid crystal polarization interference element 16 functions as a λ / 2 phase plate can be set by simulation according to the center wavelength of the wavelength region of the transmission filter 10 and the total number N of layers of the first liquid crystal layer 20 and the second liquid crystal layer 24.

[0119] Regarding this simulation, in addition to being able to use a general optical simulation mechanism, LCD Master 1D (manufactured by SHINTECH Co., Ltd., Ver 9.8.0.0) can be used for calculation.

[0120] The thickness d of each of the first liquid crystal layer 20 and the second liquid crystal layer 24 is also not limited, and according to the liquid crystal compound used, a thickness that enables the in-plane retardation (Δnd) of each of the first liquid crystal layer 20 and the second liquid crystal layer 24 to be a half wavelength of the center wavelength of the wavelength region transmitted by the filter 10 can be appropriately set.

[0121] The thickness d of each of the first liquid crystal layer 20 and the second liquid crystal layer 24 is preferably 1 to 5 μm, and more preferably 1 to 3 μm.

[0122] Also, the thickness of each of the first horizontal alignment liquid crystal layer 20H and the first vertical alignment liquid crystal layer 20V in the first liquid crystal layer 20 and the thickness of each of the second horizontal alignment liquid crystal layer 24H and the second vertical alignment liquid crystal layer 24V in the second liquid crystal layer 24 are not limited, and the absolute value of the sum of the in-plane retardation of the horizontal alignment liquid crystal layer (20H, 24H) is set to be about twice the absolute value of the sum of the thickness-direction retardation of the vertical alignment liquid crystal layer (20V, 24V) by appropriately setting the liquid crystal compound and the like used.

[0123] In the case where the same kind of liquid crystal compound is used to form the first horizontal alignment liquid crystal layer 20H and the first vertical alignment liquid crystal layer 20V in the first liquid crystal layer 20, that is, in the case where the first-1 rod-like liquid crystal compound 18 h1a and the first-2 rod-like liquid crystal compound 18 v1a are the same kind, in order to set the absolute value of the sum of the in-plane retardation of the first horizontal alignment liquid crystal layer 20H to be about twice the absolute value of the sum of the thickness-direction retardation of the first vertical alignment liquid crystal layer 20V, it is sufficient to set the thickness of the first horizontal alignment liquid crystal layer 20H to be about twice the thickness of the first vertical alignment liquid crystal layer 20V. Similarly, in the case where the same kind of liquid crystal compound is used to form the second horizontal alignment liquid crystal layer 24H and the second vertical alignment liquid crystal layer 24V in the second liquid crystal layer 20, that is, in the case where the second-1 rod-like liquid crystal compound 18 h2a and the second-2 rod-like liquid crystal compound 18 v2a are the same kind, in order to set the absolute value of the sum of the in-plane retardation of the second horizontal alignment liquid crystal layer 24H to be about twice the absolute value of the sum of the thickness-direction retardation of the second vertical alignment liquid crystal layer 24V, it is sufficient to set the thickness of the second horizontal alignment liquid crystal layer 24H to be about twice the thickness of the second vertical alignment liquid crystal layer 24V.

[0124] Also, in the case where the same kind of liquid crystal compound is used to form the first horizontal alignment liquid crystal layer 20H in the first liquid crystal layer 20 and the second horizontal alignment liquid crystal layer 24H in the second liquid crystal layer 20, that is, in the case where the first-1 rod-like liquid crystal compound 18 h1a and the second-1 rod-like liquid crystal compound 18 h2a are the same kind, in order to make the in-plane retardation of the first liquid crystal layer 20 and the in-plane retardation of the second liquid crystal layer 24 substantially equal, it is sufficient to make the thickness of the first horizontal alignment liquid crystal layer 20H and the thickness of the horizontal alignment liquid crystal layer 24H substantially equal.

[0125] Also, in the case where the same kind of liquid crystal compound is used to form the first horizontal alignment liquid crystal layer 20H in the first liquid crystal layer 20 and the second horizontal alignment liquid crystal layer 24H in the second liquid crystal layer 20, that is, in the case where the first-1 rod-like liquid crystal compound 18 h1a and the second-1 rod-like liquid crystal compound 18 h2a are the same kind, in order to make the in-plane retardation of the first liquid crystal layer 20 and the in-plane retardation of the second liquid crystal layer 24 substantially equal, it is sufficient to make the thickness of the first horizontal alignment liquid crystal layer 20H and the thickness of the horizontal alignment liquid crystal layer 24H substantially equal. Figure 1In the illustrated example, the one first liquid crystal layer 20 is provided with a structure of one first horizontally aligned liquid crystal layer 20H and one first vertically aligned liquid crystal layer 20V, but is not limited thereto. The first liquid crystal layer 20 can be provided with a structure of a plurality of first horizontally aligned liquid crystal layers 20H and / or a plurality of first vertically aligned liquid crystal layers 20V. In the structure of a plurality of first horizontally aligned liquid crystal layers 20H and / or a plurality of first vertically aligned liquid crystal layers 20V, the sum of the in-plane retardation of the plurality of first horizontally aligned liquid crystal layers 20H can be approximately twice the sum of the thickness-direction retardation of the plurality of first vertically aligned liquid crystal layers 20V.

[0126] Likewise, in the structure of a plurality of second horizontally aligned liquid crystal layers 24H and / or a plurality of second vertically aligned liquid crystal layers 24V, the sum of the in-plane retardation of the plurality of second horizontally aligned liquid crystal layers 24H can be approximately twice the sum of the thickness-direction retardation of the plurality of second vertically aligned liquid crystal layers 24V. Figure 1 In the illustrated example, the one second liquid crystal layer 24 is provided with a structure of one second horizontally aligned liquid crystal layer 24H and one second vertically aligned liquid crystal layer 24V, but is not limited thereto. The second liquid crystal layer 24 can be provided with a structure of a plurality of second horizontally aligned liquid crystal layers 24H and / or a plurality of second vertically aligned liquid crystal layers 24V. In the structure of a plurality of second horizontally aligned liquid crystal layers 24H and / or a plurality of second vertically aligned liquid crystal layers 24V, the sum of the in-plane retardation of the plurality of second horizontally aligned liquid crystal layers 24H can be approximately twice the sum of the thickness-direction retardation of the plurality of second vertically aligned liquid crystal layers 24V. At this time, in the one first liquid crystal layer and / or the one second liquid crystal layer, by further subdividing the horizontally aligned liquid crystal layer and the vertically aligned liquid crystal layer to increase the number of horizontally aligned liquid crystal layers and vertically aligned liquid crystal layers, the difference between the retardation observed from the front (normal direction) and the retardation observed from a more oblique direction (a direction of a large polar angle) can be mitigated, and thus is preferable.

[0127] As for the total number of layers of the first liquid crystal layer 20 and the second liquid crystal layer 24, as long as the liquid crystal layer group 26 is two or more, that is, four or more, and is an even number, there is no limitation other than this.

[0128] The total number of layers of the first liquid crystal layer 20 and the second liquid crystal layer 24 is preferably six to thirty layers, more preferably six to twenty layers, and further preferably six to ten layers. That is, the number of liquid crystal layer groups 26 is preferably three to fifteen groups, more preferably three to ten groups, and further preferably three to five groups.

[0129] In addition, in the present application, the more the total number of layers of the first liquid crystal layer 20 and the second liquid crystal layer 24, that is, the more the number of liquid crystal layer groups 26, the narrower the wavelength region in which the liquid crystal polarized light interference element 16 functions as a λ / 2 phase difference layer.

[0130] Therefore, in the present application, the more the total number of layers of the first liquid crystal layer 20 and the second liquid crystal layer 24, the narrower the half-width of the wavelength region of the transmitted light. In other words, the more the total number of layers of the first liquid crystal layer 20 and the second liquid crystal layer 24, the more the optical filter 10 can be a band-pass optical filter with a narrower transmission wavelength region.

[0131] Therefore, the total number of stacked layers of the first liquid crystal layer 20 and the second liquid crystal layer 24, that is, the number of liquid crystal layer groups 26, is determined according to the width of the transmission wavelength range required by the filter 10. When a broadband is preferred, a smaller number of layers is selected, and when a narrowband is required, a larger number of layers can be appropriately selected.

[0132] Figure 1 In the liquid crystal polarization interference element 16 shown, all liquid crystal layer groups have the same structure. That is, Figure 1 In the liquid crystal polarization interference element 16 shown in FIG. 1 , all first liquid crystal layers 20 have the same structure, and all second liquid crystal layers 24 also have the same structure. Figure 1 In the illustrated liquid crystal polarization interference element 16 , the in-plane retardation (Δnd) and the in-plane slow axis angle of all first liquid crystal layers 20 are equal, and the in-plane retardation (Δnd) and the in-plane slow axis angle of all second liquid crystal layers 24 are equal.

[0133] However, the present invention is not limited to this, and the in-plane retardation (Δnd) and the in-plane slow axis angle of the liquid crystal layer may be distributed in the thickness direction. That is, in the present invention, if the in-plane retardation (Δnd) of the first liquid crystal layer and the second liquid crystal layer in each liquid crystal layer group are equal, and the absolute value of the in-plane slow axis angle is equal, then the in-plane retardation (Δnd) and / or the in-plane slow axis angle of the first liquid crystal layer and the second liquid crystal layer in each liquid crystal layer group may be different.

[0134] As an example, the following structure is illustrated: there are more than three liquid crystal layer groups in the thickness direction, and in the liquid crystal layer group in the center of the thickness direction (stacking direction) and the liquid crystal layer groups on both sides of the thickness direction, the in-plane delay (Δnd) and the angle of the in-plane slow axis of the first liquid crystal layer and the second liquid crystal layer, that is, the angle formed by the in-plane slow axis of the first liquid crystal layer and the in-plane slow axis of the second liquid crystal layer are different.

[0135] Specifically, compared with the liquid crystal layer (the first liquid crystal layer and the second liquid crystal layer) of the liquid crystal layer group on both sides of the thickness direction, the in-plane delay (Δnd) of the liquid crystal layer (the first liquid crystal layer and the second liquid crystal layer) can be increased, and the absolute value of the in-plane slow axis angle can be reduced.

[0136] In the following embodiments, as an example, the following structure is shown: when the liquid crystal polarization interference element has 8 liquid crystal layers, that is, 4 groups of liquid crystal layers,

[0137] In the first liquid crystal layer group, the in-plane retardation of the first liquid crystal layer (the first layer) is set to Δnd1, the angle of the in-plane slow axis is set to θ1, the in-plane retardation of the second liquid crystal layer (the second layer) is set to Δnd1, the angle of the in-plane slow axis is set to -θ1,

[0138] In the first group of liquid crystal layer groups, the in-plane retardation of the first liquid crystal layer (the third layer) is set to be smaller than Δndl, and the angle of the in-plane slow axis is set to be larger than θl, the in-plane retardation of the second liquid crystal layer (the fourth layer) is set to be Δndl, and the angle of the in-plane slow axis is set to be -θl,

[0139] In the third group of liquid crystal layer groups, the in-plane retardation of the first liquid crystal layer (the fifth layer) is set to be Δnd2, and the angle of the in-plane slow axis is set to be θ2, the in-plane retardation of the second liquid crystal layer (the sixth layer) is set to be Δnd2, and the angle of the in-plane slow axis is set to be -θ2,

[0140] In the fourth group of liquid crystal layer groups, the in-plane retardation of the first liquid crystal layer (the seventh layer) is set to be Δndl, and the angle of the in-plane slow axis is set to be θl, the in-plane retardation of the second liquid crystal layer (the eighth layer) is set to be Δndl, and the angle of the in-plane slow axis is set to be -θl.

[0141] In a band-pass filter, as Figure 3 As conceptually shown, at positions sandwiching the target transmission wavelength region and shorter wavelengths than the target transmission wavelength region and longer wavelengths, a transmission wavelength region called a side lobe as shown by an arrow S in the figure is generated.

[0142] In this regard, as described above, by increasing the in-plane retardation of the liquid crystal layer of the liquid crystal layer group on both sides in the thickness direction and decreasing the angle of the in-plane slow axis compared to the liquid crystal layer of the liquid crystal layer group in the center in the thickness direction, it is possible to reduce the side lobe.

[0143] In addition, as an example, the in-plane retardation of the liquid crystal layer can be adjusted by changing the thickness of the liquid crystal layer, but can also be adjusted by changing the liquid crystal compound used.

[0144] In the structure in which the in-plane retardation of the liquid crystal layer of the liquid crystal layer group on both sides in the thickness direction is increased and the angle of the in-plane slow axis is decreased compared to the liquid crystal layer of the liquid crystal layer group in the center in the thickness direction, the number of layers of the liquid crystal layer in the center in the thickness direction, in which the in-plane retardation is increased and the angle of the in-plane slow axis is decreased compared to both sides, that is, the division method of the liquid crystal layer groups of both sides and the center is not limited, and can be appropriately set according to the number of liquid crystal layers (liquid crystal layer groups) possessed by the filter.

[0145] Also, as to the in-plane retardation and the angle of the in-plane slow axis of the liquid crystal layer of the liquid crystal layer group on both sides in the thickness direction and the in-plane retardation and the angle of the in-plane slow axis of the liquid crystal layer of the liquid crystal layer group in the center in the thickness direction, the optimal in-plane retardation and the angle of the in-plane slow axis at which the liquid crystal polarization interference element functions as a λ / 2 phase difference plate and the side lobe can be reduced can be set by simulation.

[0146] Further, it is preferable to control the change in the angle of the in-plane slow axis of the liquid crystal layer of the liquid crystal layer group and the distribution of the in-plane retardation of the liquid crystal layer group in the thickness direction as gently and finely as possible from both sides toward the center in the stacking direction (thickness direction).

[0147] In Figure 1 the optical filter 10b shown in FIG. 6, the liquid crystal compound constituting the first horizontal alignment liquid crystal layer 21Ha of the first liquid crystal layer 21a and the liquid crystal compound constituting the first vertical alignment liquid crystal layer 21Va of the first liquid crystal layer 21a are each set to a discotic liquid crystal compound 19, but the present application is not limited thereto.

[0148] For example, as shown in Figure 4 the optical filter 10b, the liquid crystal polarization interference element 16b, the liquid crystal compound constituting the first horizontal alignment liquid crystal layer 21Ha of the first liquid crystal layer 21a and the liquid crystal compound constituting the first vertical alignment liquid crystal layer 21Va of the first liquid crystal layer 21a can each be set to a discotic liquid crystal compound 19.

[0149] The direction of the optical axis of the discotic liquid crystal compound is a direction perpendicular to the discotic plane. Therefore, as shown in Figure 4 for example, the first-1 discotic liquid crystal compound 19 constituting the first horizontal alignment liquid crystal layer 21Ha of the first liquid crystal layer 21a of the first liquid crystal layer group 27a is oriented in such a manner that the optical axis thereof is aligned with a prescribed direction. h1a Therefore, the discotic plane is oriented perpendicularly to the major surface. Also, as shown in Figure 4 in the first horizontal alignment liquid crystal layer 21Ha, each first-1 discotic liquid crystal compound 19 h1a is oriented in such a manner that the optical axis thereof is aligned with a prescribed direction. That is, the first horizontal alignment liquid crystal layer 21Ha is a so-called (negative) A plate.

[0150] Also, the first-2 discotic liquid crystal compound 19 constituting the first vertical alignment liquid crystal layer 21Va of the first liquid crystal layer 21a is oriented in such a manner that the optical axis thereof is perpendicular to the major surface of the first vertical alignment liquid crystal layer 21Va, and therefore the discotic plane is oriented in parallel with the major surface. That is, the first vertical alignment liquid crystal layer 21Va is a so-called (negative) C plate. v1a

[0151] ​In the first liquid crystal layer 21a having a first horizontally aligned liquid crystal layer 21Ha and a first vertically aligned liquid crystal layer 21Va formed using such a disc-shaped liquid crystal compound, the absolute value of the sum of the in-plane delays of the first horizontally aligned liquid crystal layer 21Ha is 1.33 to 4 times, and preferably about 2 times, the absolute value of the sum of the thickness direction delays of the first vertically aligned liquid crystal layer 21Va.

[0152] Likewise, if Figure 4 As shown, the 2-1 discotic liquid crystal compound 19 of the first horizontal alignment liquid crystal layer 25Ha constituting the second liquid crystal layer 25a of the first liquid crystal layer group 27a is h2a The optical axis is aligned in parallel with the main surface of the second horizontal alignment liquid crystal layer 25Ha, so that the disc plane is aligned perpendicular to the main surface. Figure 4 As shown, in the second horizontal alignment liquid crystal layer 25Ha, each 2-1 discotic liquid crystal compound 19 h2a The second horizontally aligned liquid crystal layer 25Ha is aligned so that its optical axis is aligned in a predetermined direction.

[0153] Furthermore, the 2-2 discotic liquid crystal compound 19 of the second vertical alignment liquid crystal layer 25Va constituting the second liquid crystal layer 25a v2a Since the optical axis is aligned perpendicular to the main surface of the second vertically aligned liquid crystal layer 25Va, the disc plane is aligned parallel to the main surface. That is, the second vertically aligned liquid crystal layer 25Va is a so-called (negative) C plate.

[0154] In the second liquid crystal layer 25a having a second horizontally aligned liquid crystal layer 25Ha and a second vertically aligned liquid crystal layer 25Va formed using such a disc-shaped liquid crystal compound, the absolute value of the sum of the in-plane delays of the second horizontally aligned liquid crystal layer 25Ha is 1.33 to 4 times, and preferably about 2 times, the absolute value of the sum of the thickness direction delays of the second vertically aligned liquid crystal layer 25Va.

[0155] In the first liquid crystal layer group 27 a , the in-plane slow axis of the first liquid crystal layer 21 a intersects the in-plane slow axis of the second liquid crystal layer 25 a .

[0156] The direction of the in-plane slow axis of the first liquid crystal layer 21a is mainly determined by the 1-1 discotic liquid crystal compound 19 in the first horizontal alignment liquid crystal layer 21Ha. h1a Similarly, the direction of the in-plane slow axis of the second liquid crystal layer 25a is mainly determined by the 2-1 discotic liquid crystal compound 19 in the second horizontally aligned liquid crystal layer 25Ha. h2a The orientation direction is determined by.

[0157] Therefore, if Figure 4As shown, the first liquid crystal layer 21a and the second liquid crystal layer 25a are stacked in a manner that the orientation direction (optical axis) of the first-1 discotic liquid crystal compound 19 in the first horizontal alignment liquid crystal layer 21Ha crosses the orientation direction (optical axis) of the second-1 discotic liquid crystal compound 19 in the second horizontal alignment liquid crystal layer 25Ha. h1a h2a As shown, the first liquid crystal layer 21a and the second liquid crystal layer 25a are stacked in a manner that the orientation direction (optical axis) of the first-1 discotic liquid crystal compound 19 in the first horizontal alignment liquid crystal layer 21Ha crosses the orientation direction (optical axis) of the second-1 discotic liquid crystal compound 19 in the second horizontal alignment liquid crystal layer 25Ha.

[0158] As shown, the first liquid crystal layer 21a and the second liquid crystal layer 25a are stacked in a manner that the orientation direction (optical axis) of the first-1 discotic liquid crystal compound 19 in the first horizontal alignment liquid crystal layer 21Ha crosses the orientation direction (optical axis) of the second-1 discotic liquid crystal compound 19 in the second horizontal alignment liquid crystal layer 25Ha.

[0159] As shown, the first liquid crystal layer 21a and the second liquid crystal layer 25a are stacked in a manner that the orientation direction (optical axis) of the first-1 discotic liquid crystal compound 19 in the first horizontal alignment liquid crystal layer 21Ha crosses the orientation direction (optical axis) of the second-1 discotic liquid crystal compound 19 in the second horizontal alignment liquid crystal layer 25Ha.

[0160] As shown, the first liquid crystal layer 21a and the second liquid crystal layer 25a are stacked in a manner that the orientation direction (optical axis) of the first-1 discotic liquid crystal compound 19 in the first horizontal alignment liquid crystal layer 21Ha crosses the orientation direction (optical axis) of the second-1 discotic liquid crystal compound 19 in the second horizontal alignment liquid crystal layer 25Ha.

[0161] As shown, the first liquid crystal layer 21a and the second liquid crystal layer 25a are stacked in a manner that the orientation direction (optical axis) of the first-1 discotic liquid crystal compound 19 in the first horizontal alignment liquid crystal layer 21Ha crosses the orientation direction (optical axis) of the second-1 discotic liquid crystal compound 19 in the second horizontal alignment liquid crystal layer 25Ha.

[0162] As shown, the first liquid crystal layer 21a and the second liquid crystal layer 25a are stacked in a manner that the orientation direction (optical axis) of the first-1 discotic liquid crystal compound 19 in the first horizontal alignment liquid crystal layer 21Ha crosses the orientation direction (optical axis) of the second-1 discotic liquid crystal compound 19 in the second horizontal alignment liquid crystal layer 25Ha. Figure 1 Figure 4 As shown, the first liquid crystal layer 21a and the second liquid crystal layer 25a are stacked in a manner that the orientation direction (optical axis) of the first-1 discotic liquid crystal compound 19 in the first horizontal alignment liquid crystal layer 21Ha crosses the orientation direction (optical axis) of the second-1 discotic liquid crystal compound 19 in the second horizontal alignment liquid crystal layer 25Ha.

[0163] ​​For example, the liquid crystal compounds of the first horizontal alignment liquid crystal layer 20H and the first vertical alignment liquid crystal layer 20V constituting the first liquid crystal layer 20 may both be rod-shaped liquid crystal compounds, and the liquid crystal compounds of the second horizontal alignment liquid crystal layer 25H and the second vertical alignment liquid crystal layer 25V constituting the second liquid crystal layer 25 may both be discotic liquid crystal compounds. Alternatively, the liquid crystal compounds of the first horizontal alignment liquid crystal layer 21H and the first vertical alignment liquid crystal layer 21V constituting the first liquid crystal layer 21 may both be discotic liquid crystal compounds, and the liquid crystal compounds of the second horizontal alignment liquid crystal layer 24H and the second vertical alignment liquid crystal layer 24V constituting the second liquid crystal layer 24 may both be rod-shaped liquid crystal compounds.

[0164] Furthermore, the liquid crystal compounds constituting the first horizontal alignment liquid crystal layer and the first vertical alignment liquid crystal layer of all liquid crystal layer groups are not limited to being rod-shaped liquid crystal compounds or disc-shaped liquid crystal compounds. Alternatively, the first horizontal alignment liquid crystal layer and the first vertical alignment liquid crystal layer of the first liquid crystal layer of one liquid crystal layer group may be formed using rod-shaped liquid crystal compounds, while the first horizontal alignment liquid crystal layer and the first vertical alignment liquid crystal layer of the first liquid crystal layer of another liquid crystal layer group may be formed using disc-shaped liquid crystal compounds. Similarly, the liquid crystal compounds constituting the second horizontal alignment liquid crystal layer and the second vertical alignment liquid crystal layer of the second liquid crystal layer of all liquid crystal layer groups are not limited to being rod-shaped liquid crystal compounds or disc-shaped liquid crystal compounds. Alternatively, the second horizontal alignment liquid crystal layer and the second vertical alignment liquid crystal layer of the second liquid crystal layer of one liquid crystal layer group may be formed using rod-shaped liquid crystal compounds, while the second horizontal alignment liquid crystal layer and the second vertical alignment liquid crystal layer of the second liquid crystal layer of another liquid crystal layer group may be formed using disc-shaped liquid crystal compounds.

[0165] And, in Figure 1 and Figure 4 In the example shown, the structure in which any first liquid crystal layer and second liquid crystal layer are stacked in sequence from the first polarizer 12 side with a vertically aligned liquid crystal layer and a horizontally aligned liquid crystal layer is set, but it is not limited to this. The structure in which a horizontally aligned liquid crystal layer and a vertically aligned liquid crystal layer are stacked in sequence from the first polarizer 12 side may also be set.

[0166] In addition, in the liquid crystal polarization interference element of the present application, the first liquid crystal layer and the second liquid crystal layer can be formed by a coating method and directly laminated, or the first liquid crystal layer and the second liquid crystal layer can be made into sheet shapes and alternately laminated and bonded by an optical bonding layer transparent to transmitted light such as an OCA (Optical Clear Adhesive), an acrylic adhesive, an adhesive, a high molecular layer, and the like. At this time, from the viewpoint of improving the transmittance, the refractive index of the optical bonding layer is preferably close to the refractive index of the liquid crystal layer. Specifically, the difference in the refractive index is preferably 0.3 or less. Also, the refractive index of the optical bonding layer is preferably a value between the two birefringences possessed by the liquid crystal layer, because the difference in the refractive index is small compared to either of the two refractive indices. From the viewpoint of the transmittance of the transmitted light, direct lamination based on the coating method without an adhesive layer or the like is preferred.

[0167] Such a liquid crystal polarization interference element can be produced by a publicly known method.

[0168] As an example, it is produced by using a coating method for forming the liquid crystal composition of the first liquid crystal layer and the second liquid crystal layer.

[0169] Also, the first liquid crystal layer and the second liquid crystal layer can be laminated and bonded by an adhesive such as an OCA (Optical Clear Adhesive) and an acrylic adhesive, which are transparent to transmitted light, after the horizontal alignment liquid crystal layer and the vertical alignment liquid crystal layer are formed, respectively. Alternatively, the vertical alignment liquid crystal layer can be formed on the horizontal alignment liquid crystal layer after the horizontal alignment liquid crystal layer is formed, or the horizontal alignment liquid crystal layer can be formed on the vertical alignment liquid crystal layer after the vertical alignment liquid crystal layer is formed. As to these methods, they are described in detail in Japanese Patent No. 6276393.

[0170] The horizontal alignment liquid crystal layer can be produced by a publicly known method for forming a horizontal alignment liquid crystal layer.

[0171] As an example, first, an alignment film oriented in one direction is formed on a support appropriately selected.

[0172] The alignment film can be a publicly known alignment film such as a rubbing treatment film composed of an organic compound such as a polymer, an oblique vapor deposition film of an inorganic compound, a film having microgrooves, and a film made of an LB (Langmuir-Blodgett) film based on the Langmuir-Blodgett method using an organic compound such as ω-tricosanoic acid, dioctadecylmethylammonium chloride, and methyl stearate, and a film formed by coating an alignment film forming coating liquid containing a photoalignment material on the surface of a support, drying, and exposing the coated film to light using a polarizer such as a wire grid polarizer.

[0173] On the other hand, a composition for forming a horizontally aligned liquid crystal layer (liquid crystal composition) containing a liquid crystal compound is prepared.

[0174] The solvent used to prepare the composition is not limited and can be appropriately selected according to the purpose, but is preferably an organic solvent. The organic solvent is not limited and can be appropriately selected according to the purpose, and examples thereof include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. These can be used alone or in combination of two or more. Among these, ketones are preferred when considering the burden on the environment.

[0175] A composition for forming a horizontally aligned liquid crystal layer is applied to the surface of the formed alignment film, the liquid crystal compound is aligned, and the composition is dried and cured by ultraviolet irradiation or the like as needed to form a horizontally aligned liquid crystal layer.

[0176] The vertically aligned liquid crystal layer can be produced by a conventionally known method for forming a vertically aligned liquid crystal layer.

[0177] Details of the method for producing a vertically aligned liquid crystal layer (positive C plate) that vertically aligns rod-shaped liquid crystal compounds can be found in, for example, Japanese Patent Application Publication Nos. 2017-187732, 2016-053709, and 2015-200861. Details of the method for producing a vertically aligned layer (negative C plate) that vertically aligns disc-shaped liquid crystal compounds can be found in, for example, Japanese Patent Application No. 6001505.

[0178] The horizontal alignment liquid crystal layer and the vertical alignment liquid crystal layer produced as described above can be bonded together using OCA or the like to produce the first liquid crystal layer and the second liquid crystal layer, respectively.

[0179] Next, the first and second liquid crystal layers are bonded together using an OCA or other method so that the in-plane slow axis angle is a predetermined angle, thereby forming a liquid crystal layer group. Multiple such liquid crystal layer groups are produced and further stacked to produce a liquid crystal polarization interference element. The liquid crystal layer groups can also be stacked using an OCA or other method. Furthermore, when stacking the liquid crystal layer groups, the layers are stacked so that the bisector of the angle between the in-plane slow axis of the first liquid crystal layer and the in-plane slow axis of the second liquid crystal layer of each liquid crystal layer group is parallel.

[0180] For example, the liquid crystal polarization interference element thus produced is arranged so that the transmission axis of the first polarizer is parallel to the bisector of the angle formed by the in-plane slow axis of the first liquid crystal layer and the in-plane slow axis of the second liquid crystal layer of each liquid crystal layer group, and the second polarizer is further arranged in a crossed Nicols arrangement with the first polarizer, thereby producing the following: Figure 1 or Figure 4 Filter shown.

[0181] In the liquid crystal polarization interference element 16 of the present application, the rod-shaped liquid crystal compound 18 is not limited and various known liquid crystal compounds can be used.

[0182] As the rod-shaped liquid crystal compound, imidazoline, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexane carboxylic acid phenyl esters, cyanophenyl cyclohexanes, cyano-substituted phenyl pyrimidines, alkoxy-substituted phenyl pyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles are preferably used. Not only low-molecular liquid crystal molecules as described above but also high-molecular liquid crystal molecules can be used.

[0183] More preferably, the rod-shaped liquid crystal compound is fixed in alignment by polymerization, and as the polymerizable rod-shaped liquid crystal compound, the compounds described in Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials, Vol. 5, p. 107 (1993), U.S. Patent No. 4683327, U.S. Patent No. 5622648, U.S. Patent No. 5770107, International Publication No. 95 / 22586, International Publication No. 95 / 24455, International Publication No. 97 / 00600, International Publication No. 98 / 23580, International Publication No. 98 / 52905, Japanese Patent Application Publication No. H1-272551, Japanese Patent Application Publication No. H6-16616, Japanese Patent Application Publication No. H7-110469, Japanese Patent Application Publication No. H11-80081, and Japanese Patent Application No. 2001-64627 can be used. In addition, as the rod-shaped liquid crystal compound, for example, the rod-shaped liquid crystal compounds described in Japanese Patent Application Publication No. H11-513019 and Japanese Patent Application Publication No. 2007-279688 can be preferably used.

[0184] Also, in the liquid crystal polarization interference element 16 of the present application, the discotic liquid crystal compound 19 is not limited and various known liquid crystal compounds can be used.

[0185] As the discotic liquid crystal compound, for example, the discotic liquid crystal compounds described in Japanese Patent Application Publication No. 2007-108732 and Japanese Patent Application Publication No. 2010-244038 can be preferably used.

[0186] In the composition used for forming the first liquid crystal layer 20 and the second liquid crystal layer 24, in addition to the liquid crystal compound, a polymerization initiator, a leveling agent, a crosslinking agent, a surfactant, and the like can be added as necessary.

[0187] In the present application, the first liquid crystal layer and the second liquid crystal layer can contain an infrared-absorbing pigment.

[0188] By including the infrared-absorbing colorant in the first liquid crystal layer and the second liquid crystal layer, the wavelength dispersion of the liquid crystal in the liquid crystal layer can be made strong positive. As a result, the wavelength region of light in which the liquid crystal polarization interference element functions as a λ / 2 plate can be narrowed. That is, by adding the infrared-absorbing colorant to the first liquid crystal layer and the second liquid crystal layer to make the wavelength dispersion of the liquid crystal in the liquid crystal layer strong positive, a band-pass filter having a narrower transmission wavelength region can be obtained. In addition, positive dispersion (positive wavelength dispersion) means that the larger the measurement wavelength, the smaller the phase difference.

[0189] As the infrared-absorbing colorant, various infrared-absorbing colorants that can reduce the difference between the refractive indices in the x direction and the y direction by being oriented in the same direction as the liquid crystal compound can be used.

[0190] The infrared-absorbing colorant is not particularly limited as long as it is a colorant that absorbs infrared rays (for example, light having a wavelength of 700 to 900 nm). Among others, the infrared-absorbing colorant is preferably a dichroic colorant. In addition, a dichroic colorant is a colorant in which the absorbance in the long axis direction of the molecule and the absorbance in the short axis direction of the molecule have different properties.

[0191] As the infrared-absorbing colorant, diketopyrrolopyrrole-based colorants, diimmonium-based colorants, phthalocyanine-based colorants, naphthalocyanine-based colorants, azo-based colorants, polymethine-based colorants, anthraquinone-based colorants, pyrilium-based colorants, squarylium-based colorants, triphenylmethane-based colorants, cyanine-based colorants, and ammonium-based colorants, etc. can be used.

[0192] Also, as the infrared-absorbing colorant, metal complex-based colorants and boron complex-based colorants can be used.

[0193] Regarding the infrared-absorbing colorant, detailed descriptions are given in International Publication No. 2019 / 044859.

[0194] The amount of the infrared-absorbing colorant added to the first liquid crystal layer and the second liquid crystal layer is not limited, and can be appropriately set according to the width of the transmission wavelength region required for the band-pass filter, etc.

[0195] In the present application, the first liquid crystal layer and the second liquid crystal layer can include a liquid crystal elastomer.

[0196] Regarding the first liquid crystal layer and the second liquid crystal layer that include a liquid crystal elastomer, the liquid crystal layer can be formed using a liquid crystal elastomer, or the liquid crystal layer formed of a general liquid crystal compound that is not an elastomer can include a liquid crystal elastomer.

[0197] In this way, by including a liquid crystal elastomer in the first liquid crystal layer and the second liquid crystal layer, the first liquid crystal layer and the second liquid crystal layer can be made elastic, and by stretching or contracting the filter in the planar direction, the thickness of the liquid crystal layer can be changed.

[0198] By changing the thickness of the liquid crystal layer, Δnd of the liquid crystal layer can be changed. As a result, in the bandpass filter, the wavelength region of the transmitted light can be changed. That is, by causing the first liquid crystal layer and the second liquid crystal layer to include a liquid crystal elastomer, the wavelength region can be made variable by stretching and contraction of the liquid crystal layer, that is, the filter, and in the bandpass filter, active wavelength control can be performed.

[0199] The liquid crystal elastomer is not limited, and various publicly known liquid crystal elastomers can be used.

[0200] As the liquid crystal elastomer, as an example, a liquid crystal elastomer prepared by a liquid crystal monomer, a chiral reagent, a cross-linking agent, and a plasticizer described in Japanese Patent Application Publication No. 2020-131638 can be used. Thereby, the liquid crystal elastomer is imparted with mechanical properties and has rubber elasticity, and thus deformation corresponding to an external force required for active wavelength control can be performed.

[0201] In addition, when the first liquid crystal layer and the second liquid crystal layer are formed of a general liquid crystal compound that is not an elastomer and an elastomer is added to impart elasticity, the amount of the liquid crystal elastomer to be added is not limited, and can be appropriately set according to the required elasticity, that is, the control range of the transmission wavelength region.

[0202] Such a liquid crystal polarization interference element and a filter of the present application can be used at an arbitrary wavelength. That is, the liquid crystal polarization interference element and the filter of the present application can be used for arbitrary electromagnetic waves such as ultraviolet rays, visible light, infrared rays, terahertz waves, and millimeter waves.

[0203] In the filter of the present application, in order to preferably obtain the desired bandpass characteristics, the transmission axis of the polarizer disposed in the crossed-Nicol manner is set to an appropriate angle. In particular, the size of the sidelobes generated in the wavelengths on both sides of the main bandpass wavelength (the long-wavelength side and the short-wavelength side) can be reduced, and adjustment to make the sizes of the sidelobes on the long-wavelength side and the short-wavelength side equal can be performed.

[0204] In the filter of the present application, a phase difference layer can be imparted to one side or both sides of the polarizer arranged in the cross-Nicol manner. The phase difference layer functions to maintain the orthogonal relationship of the polarization directions based on the linear polarizer arranged in the cross-Nicol manner not only in the normal direction but also in the oblique direction from the normal direction to the oblique direction tilted at an azimuth different by 45 degrees from the transmission axis and / or the absorption axis of the polarizer. Thus, even in the tilted state, the same good band-pass characteristics as in the normal state can be obtained. By making the in-plane slow axis of the phase difference layer parallel to the absorption axis of any one of the polarizer set arranged in the cross-Nicol manner, it is possible to compensate for the polarization state in such a manner that the orthogonal relationship of the polarization directions in the oblique direction is maintained without producing an effect in the normal direction. As the phase difference layer, a positive C-plate in which a rod-like liquid crystal compound is vertically aligned and a positive A-plate in which a rod-like liquid crystal compound is horizontally aligned, or a negative C-plate based on a discotic liquid crystal and a negative A-plate based on a discotic liquid crystal, or a combination thereof, are used. Alternatively, a B-plate (Nz coefficient: 0.1 to 0.9) which is a biaxial refractive index body can also be used.

[0205] Also, the structure of the filter using the liquid crystal polarization interference element of the present application is not limited to the structure in which the liquid crystal polarization interference element is arranged between two polarizers arranged in the cross-Nicol manner. For example, the filter of the present application can be a structure in which the liquid crystal polarization interference element of the present application is arranged between two polarizers arranged in the parallel-Nicol manner. That is, the filter of the present application can be a structure in which the liquid crystal polarization interference element is arranged between two polarizers arranged such that the transmission axes thereof are parallel to each other. In this case, the liquid crystal polarization interference element is preferably provided in a structure in which liquid crystal layers having the same thickness and in which the angle formed by the transmission axis of the polarizer and the slow axis becomes p, 3p, 5p,.... Such a structure of the liquid crystal polarization interference element is also referred to as a Solc filter (fan-shaped Solc filter).

[0206] The liquid crystal polarization interference element and the filter of the present application have been described in detail above, but the present application is not limited to the above-described examples, and various modifications or changes can of course be made within the scope of the present application without departing from the gist thereof.

[0207] Examples

[0208] The features of the present application are further specifically described below by citing examples. The materials, reagents, amounts used, amounts, proportions, contents of treatment, and treatment steps and the like shown in the following examples can be appropriately changed as long as the gist of the present application is not deviated. Therefore, the scope of the present application should not be interpreted limitatively by the specific examples shown below.

[0209] [Comparative Example 1]

[0210] (Formation of alignment film)

[0211] A glass substrate was prepared as a support. The following coating liquid for orientation film formation was applied to the support by spin coating. The support on which the coating film of the coating liquid for orientation film formation was formed was dried on a hot plate at 60°C for 60 seconds, thereby forming an orientation film P-1.

[0212] Coating liquid for orientation film formation

[0213]

[0214] Material for photo-orientation

[0215] [Chemical Formula 1]

[0216]

[0217] (Exposure of orientation film)

[0218] Next, the photo-orientation film P-1 was irradiated with ultraviolet rays as linearly polarized light using a wire grid polarizer (manufactured by MOXTEK, Inc., ProFlux PPL02) set so that the angle of the absorption axis was Φ1 (= 0°) using an ultraviolet exposure device, as an orientation film P-2. The illuminance of the ultraviolet rays was 4.5 mW / cm 2 , and the cumulative exposure amount was 300 mJ / cm 2 .

[0219] In addition, the angle of the absorption axis refers to the angle with respect to the length direction of the substrate, and is positive in the clockwise direction.

[0220] (Formation of horizontally oriented liquid crystal layer using rod-shaped liquid crystal compound)

[0221] As a liquid crystal composition for forming a horizontally oriented liquid crystal layer, the following composition B-1 was prepared.

[0222] Composition B-1

[0223]

[0224] Rod-shaped liquid crystal compound L-1

[0225] [Chemical Formula 2]

[0226]

[0227] [Chemical Formula 3]

[0228]

[0229] [Chemical Formula 4]

[0230]

[0231] [Chemical Formula 5]

[0232]

[0233] Leveling agent T-1

[0234] [Chemical Formula 6]

[0235]

[0236] A horizontal alignment liquid crystal layer was formed by coating the composition B-1 on the alignment film P-2. That is, after the composition B-1 was coated on the alignment film P-2, heating was performed, and then ultraviolet curing was performed, thereby producing a liquid crystal immobilization layer.

[0237] More specifically, a coating film was obtained by coating the composition B-1 on the alignment film P-2, the coating film was heated to 80°C on a hot plate, and then, at 80°C, the coating film was irradiated with ultraviolet rays of wavelength 365 nm using a high-pressure mercury lamp under a nitrogen atmosphere at an irradiation amount of 300 mJ / cm 2 to immobilize the alignment of the liquid crystal compound, thereby producing a liquid crystal immobilization layer. The thickness of the immobilized horizontal alignment liquid crystal layer was 1.72 μm.

[0238] After the horizontal alignment liquid crystal layer was formed by the above method, the horizontal alignment liquid crystal layer was peeled off from the photo-alignment film. With respect to the formed horizontal alignment liquid crystal layer, it was confirmed using AxoScan (manufactured by Axometrics) to have the properties shown in Table 1 below. In Table 1, Re is in-plane retardation.

[0239] Eight pieces of such a horizontal alignment liquid crystal layer were produced.

[0240] [Table 1]

[0241]

[0242] One piece of the horizontal alignment liquid crystal layer produced as described above was used as a first liquid crystal layer and a second liquid crystal layer, and two pieces of the horizontal alignment liquid crystal layer were adhered using an adhesive (manufactured by Soken Chemical & Engineering Co., Ltd., SK Dyne 2057) in such a manner that the angle formed by the in-plane slow axes of the two pieces of the horizontal alignment liquid crystal layer was 11.25°, that is, in such a manner that the angle of the bisector of the angle formed by the in-plane slow axes of the two pieces of the horizontal alignment liquid crystal layer was +5.625° and -5.625°, respectively, thereby producing a liquid crystal layer group. Four liquid crystal layer groups were formed in the same manner.

[0243] The liquid crystal polarization interference element was produced by laminating 4 liquid crystal layer groups using an adhesive (manufactured by Soken Chemical & Engineering Co., Ltd., SK Dyne 2057). At this time, the bisector of the angle formed by the in-plane slow axes of each liquid crystal layer group was made parallel.

[0244] The optical filter was produced by laminating 2 polarizers arranged in a crossed-Nicol manner with the produced liquid crystal polarization interference element interposed therebetween. At this time, the bisector of the angle formed by the transmission axis of one polarizer and the in-plane slow axis of each liquid crystal layer group was made parallel.

[0245] (Evaluation)

[0246] With respect to the produced optical filter, the wavelength shift value and the side lobe value were measured using a spectroradiometer "SR-3" manufactured by TOPCON TECHNOHOUSE CORPORATION. First, the peak wavelength (center wavelength) and the half-peak width of the transmitted light when the incident light was at a polar angle of 0° (a direction perpendicular to the optical filter) were measured. Next, in the measurement of the wavelength shift, the reference of the azimuthal angle was set to the angle bisecting the intersection angle of the in-plane slow axis of the first liquid crystal layer and the in-plane slow axis of the second liquid crystal layer, and the average value of the wavelength shift values when the incident light was at a polar angle of 60° in the directions of the azimuthal angles of 0° and 90° was calculated. Also, the side lobe value was calculated as the average value of the ratio of the transmittance at the wavelength of the side lobe on both sides to the transmittance at the peak wavelength.

[0247] The results are shown in Table 2 below.

[0248] [Table 2]

[0249]

[0250] [Example 1]

[0251] The 8 horizontal alignment liquid crystal layers were produced in the same manner as in Comparative Example 1.

[0252] (Formation of vertical alignment liquid crystal layer using rod-shaped liquid crystal compound)

[0253] Next, in order to produce the vertical alignment liquid crystal layer using the rod-shaped liquid crystal compound, Composition E-1 was prepared as follows.

[0254] Composition E-1

[0255]

[0256] Polymerizable monomer (M-4)

[0257] [Chemical Formula 7]

[0258]

[0259] fluorine-based polymer (M-5)

[0260] [Chemical Formula 8]

[0261]

[0262] fluorine-based polymer (M-6)

[0263] [Chemical Formula 9]

[0264]

[0265] onium salt compound S01

[0266] [Chemical Formula 10]

[0267]

[0268] high-molecular compound A107

[0269] [Chemical Formula 11]

[0270]

[0271] A composition E-1 was coated on a support, followed by ultraviolet irradiation (300 mJ / cm2) at 40°C under nitrogen purge at an oxygen concentration of 100 ppm, to form an alignment-fixed layer of liquid crystal compound (thickness 0.86 μm). Thereafter, the liquid crystal layer was peeled from the support, to obtain a vertically aligned liquid crystal layer. 2

[0272] The optical properties of the vertically aligned liquid crystal layer were confirmed to be the properties shown in Table 3 below. In Table 3, Rth is the retardation in the thickness direction.

[0273] Eight pieces of the vertically aligned liquid crystal layer were produced.

[0274] [Table 3]

[0275]

[0276] The produced vertically aligned liquid crystal layer was adhered to the horizontally aligned liquid crystal layer using an adhesive (manufactured by Soken Chemical & Engineering Co., Ltd., SK Dyne 2057), to produce eight pieces of liquid crystal layer (first liquid crystal layer and second liquid crystal layer).

[0277] The sum of the in-plane retardation of the horizontally aligned liquid crystal layer of the produced liquid crystal layer was twice the sum of the retardation in the thickness direction of the vertically aligned liquid crystal layer.

[0278] ​Two pieces of liquid crystal layer were laminated in such a manner that the angle of the in-plane slow axis (in-plane slow axis of the horizontally aligned liquid crystal layer) of each other became 11.25°, that is, in such a manner that the angle of the bisector of the angle of the in-plane slow axis of each other became +5.625°, -5.625°, respectively, using an adhesive (manufactured by Soken Chemical & Engineering Co., Ltd., SK Dyne 2057), thereby a liquid crystal layer group was produced. Four liquid crystal layer groups were formed in the same manner.

[0279] Four liquid crystal layer groups were laminated using an adhesive (manufactured by Soken Chemical & Engineering Co., Ltd., SK Dyne 2057), thereby a liquid crystal polarization interference element was produced. At this time, the bisector of the angle of the in-plane slow axis of each liquid crystal layer group was laminated in parallel.

[0280] Two polarizers arranged in a crossed-Nicol manner were laminated in such a manner that the liquid crystal polarization interference element produced was interposed therebetween, thereby a filter was produced. At this time, the transmission axis of one polarizer was laminated in parallel with the bisector of the angle of the in-plane slow axis of each liquid crystal layer group.

[0281] (Evaluation)

[0282] With respect to the filter produced, the wavelength shift value and the side lobe value were measured in the same manner as described above using a spectroradiometer "SR-3" manufactured by TOPCON TECHNOHOUSE CORPORATION.

[0283] The results are shown in Table 4 below.

[0284] [Table 4]

[0285]

[0286] [Example 2]

[0287] In Example 1, the optical properties of the vertically aligned liquid crystal layer were set to the properties shown in Table 5 below, and a liquid crystal polarization interference element was produced in the same manner as in Example 1, and a filter was produced, except for this. In this case, the sum of the in-plane retardation of the horizontally aligned liquid crystal layer was 1.4 times the sum of the thickness direction retardation of the vertically aligned liquid crystal layer.

[0288] [Table 5]

[0289]

[0290] (Evaluation)

[0291] As for the produced optical filter, in the same manner as described above, wavelength shift value and side lobe value were measured using a spectroradiometer "SR-3" manufactured by TOPCON TECHNOHOUSE CORPORATION.

[0292] The results are shown in Table 6 below.

[0293] [Table 6]

[0294]

[0295] [Example 3]

[0296] In Example 1, the optical properties of the vertically aligned liquid crystal layer were set to the properties shown in Table 7 below, and a liquid crystal polarization interference element was produced in the same manner as in Example 1, and an optical filter was produced. In this case, the sum of the in-plane retardation of the horizontally aligned liquid crystal layer was 3.1 times the sum of the retardation in the thickness direction of the vertically aligned liquid crystal layer.

[0297] [Table 7]

[0298]

[0299] (Evaluation)

[0300] As for the produced optical filter, in the same manner as described above, wavelength shift value and side lobe value were measured using a spectroradiometer "SR-3" manufactured by TOPCON TECHNOHOUSE CORPORATION.

[0301] The results are shown in Table 8 below.

[0302] [Table 8]

[0303]

[0304] [Example 4]

[0305] (Formation of horizontally aligned liquid crystal layer using discotic liquid crystal compound)

[0306] Composition D-1 composed of a discotic compound was prepared as follows.

[0307] Composition D-1

[0308]

[0309]

[0310] Discotic liquid crystal compound L-2

[0311] [Chemical Formula 12]

[0312]

[0313] Discotic liquid crystal compound L-3

[0314] [Chemical Formula 13]

[0315]

[0316] After the composition D-1 was applied to the alignment film P-2, heating was performed, followed by ultraviolet curing, thereby producing a fixed layer (thickness 1.72 μm) containing the discotic liquid crystal compound. Thereafter, the liquid crystal layer was peeled from the photo-alignment film, and a horizontal alignment liquid crystal layer in which the optical axis of the discotic liquid crystal compound was horizontally aligned was obtained.

[0317] It was confirmed that the optical properties of the horizontal alignment liquid crystal layer produced using the discotic liquid crystal compound became the properties shown in Table 9 below.

[0318] [Table 9]

[0319]

[0320] (Formation of a vertical alignment liquid crystal layer using a discotic liquid crystal compound)

[0321] Next, a vertical alignment liquid crystal layer in which the optical axis of the discotic liquid crystal compound was vertically aligned was produced. First, the coating solution for alignment film formation of Comparative Example 1 was changed to the following for use in the vertical alignment liquid crystal layer.

[0322] Coating solution for alignment film formation

[0323]

[0324] [Chemical Formula 14]

[0325]

[0326] [Chemical Formula 15]

[0327]

[0328] The coating solution for alignment film formation was spin-coated on a support. Thereafter, drying was performed on a hot plate at 60°C for 60 seconds, and an alignment film P-3 was formed.

[0329] The following liquid crystal composition was applied to the alignment film P-3.

[0330] Composition D-2

[0331]

[0332]

[0333] After the composition D-2 was applied on the alignment film, ultraviolet irradiation was performed, and an alignment-fixed layer of the discotic liquid crystal compound in vertical alignment was formed (thickness 0.86 μm). Thereafter, the liquid crystal layer was peeled from the support, and a liquid crystal layer in vertical alignment was obtained.

[0334] It was confirmed that the optical characteristics of the liquid crystal layer in vertical alignment made using the discotic liquid crystal compound became the characteristics shown in Table 10 below.

[0335] [Table 10]

[0336]

[0337] The liquid crystal layer was made by adhering the liquid crystal layer in vertical alignment made as described above to the liquid crystal layer in horizontal alignment using an adhesive (manufactured by Soken Chemical & Engineering Co., Ltd., SK Dyne 2057). Eight pieces of such liquid crystal layers were made.

[0338] The absolute value of the sum of the in-plane retardation of the liquid crystal layer in horizontal alignment of the liquid crystal layer made was twice the absolute value of the sum of the thickness-direction retardation of the liquid crystal layer in vertical alignment.

[0339] The liquid crystal layer made was used as the first liquid crystal layer and the second liquid crystal layer, and two pieces of the liquid crystal layers were adhered using an adhesive (manufactured by Soken Chemical & Engineering Co., Ltd., SK Dyne 2057) in such a manner that the angle formed by the in-plane slow axes (the in-plane slow axes of the liquid crystal layer in horizontal alignment) of the two pieces of the liquid crystal layers became 11.25°, that is, in such a manner that the angle of the bisector of the angle formed by the in-plane slow axes became +5.625° and -5.625°, respectively, and thereby a liquid crystal layer group was made. Four liquid crystal layer groups were formed in the same manner.

[0340] The four liquid crystal layer groups were adhered using an adhesive (manufactured by Soken Chemical & Engineering Co., Ltd., SK Dyne 2057), and thereby a liquid crystal polarization interference element was made. At this time, the liquid crystal layer groups were laminated in such a manner that the bisectors of the angles formed by the in-plane slow axes of the liquid crystal layer groups were parallel to each other.

[0341] The two polarizers arranged in the crossed-Nicol manner were laminated in such a manner that the liquid crystal polarization interference element made was interposed therebetween, and thereby a light filter was made. At this time, the polarizer was laminated in such a manner that the transmission axis of the polarizer and the bisectors of the angles formed by the in-plane slow axes of the liquid crystal layer groups were parallel to each other.

[0342] (Evaluation)

[0343] As for the produced optical filter, in the same manner as described above, a spectroradiometer "SR-3" manufactured by TOPCON TECHNOHOUSE CORPORATION was used to measure the wavelength shift value and the side lobe value.

[0344] The results are shown in Table 11 below.

[0345] [Table 11]

[0346]

[0347] [Example 5]

[0348] In Example 1, the in-plane retardation Re was set to the values shown in Table 12 below by appropriately changing the thickness of the horizontally oriented liquid crystal layer in each liquid crystal layer, the thickness-direction retardation Rth was set to the values shown in Table 12 by appropriately changing the thickness of the vertically oriented liquid crystal layer, and the angle of the in-plane slow axis of each liquid crystal layer was set to the values shown in Table 12 below, and the optical filter was produced in the same manner as in Example 1 except for this.

[0349] [Table 12]

[0350]

[0351] Using this liquid crystal polarization interference element, the optical filter was produced in the same manner as in Example 1, and the wavelength shift value and the side lobe value were measured in the same manner as in Example 1.

[0352] The results are shown in Table 13 below.

[0353] [Table 13]

[0354]

[0355] From the above results, it was found that the wavelength shift value was smaller in the examples of the present application than in the comparative examples.

[0356] Further, from the comparison of Examples 1 to 3, it was found that the closer the sum of the in-plane retardations of the horizontally oriented liquid crystal layers to about twice the sum of the thickness-direction retardations of the vertically oriented liquid crystal layers, the more preferable.

[0357] Further, from the comparison of Example 1 and Example 5, it was found that by reducing the in-plane retardation of the liquid crystal layer of the liquid crystal layer group on both sides in the thickness direction and increasing the absolute value of the slow axis θ of the liquid crystal layer compared to the liquid crystal layer of the liquid crystal layer group at the center in the thickness direction, it was possible to reduce the side lobe of the band-pass optical filter.

[0358] [Example 6]

[0359] By optical simulation (Optical Waves in Layered Media 2nd Edition, Pochi Yeh, Wiley-Interscience, March 3, 2005) for evaluating optical performance of a laminate of a birefringent medium, in Example 5, a liquid crystal polarization interference element in which an infrared absorbing dye was added to a liquid crystal layer was modeled, and a filter was modeled. In addition, the conditions of the infrared absorbing dye were set as follows: having dichroic absorption to near infrared, and being oriented as a guest dye in a liquid crystal compound that is a host.

[0360] By the simulation, the center wavelength, the half peak width, the wavelength shift value, and the side lobe value were calculated. Further, the ratio of the birefringence Δn (450) at a wavelength of 450 nm to the birefringence Δn (650) at a wavelength of 650 nm was calculated, and the result was Δn (450) / Δn (650) = 1.4. If Δn (450) / Δn (650) exceeds 1.3, it can be said that it is strong positive dispersion.

[0361] The results are shown in Table 14 below.

[0362] [Table 14]

[0363]

[0364] As described above, the center wavelength of the transmitted light of the band pass filter of Example 5 was 550 nm, and the half peak width of the transmitted light was 120 nm. In contrast to this, in Example 6 in which an infrared absorbing dye was added to a liquid crystal layer, it was possible to narrow the half peak width of the transmitted light, and a band pass filter having a narrower wavelength region of the transmitted light could be obtained.

[0365] [Example 7]

[0366] By the aforementioned simulation, in Example 5, a filter was produced in the same manner as in Example 5 using a liquid crystal elastomer as a liquid crystal compound forming a liquid crystal layer. In addition, the conditions of the liquid crystal elastomer were set as follows: using a liquid crystal elastomer prepared from a liquid crystal monomer, a crosslinking agent, and a plasticizer described in Japanese Patent Application Publication No. 2020-131638.

[0367] The liquid crystal polarization interference element of the produced filter could be stretched by a uniaxial and biaxial stretching device, and stretching of 10% and 20% was performed, and the center wavelength was calculated.

[0368] The results are shown in Table 15 below.

[0369] [Table 15]

[0370]

[0371] From the above results, it was found that by using a liquid crystal elastomer for the liquid crystal layer, the wavelength region can be made variable by stretching and shrinking of the liquid crystal layer, i.e., the optical filter.

[0372] [Example 7]

[0373] In Example 1, eight pieces of liquid crystal layers (first and second liquid crystal layers) were prepared to form four groups of liquid crystal layer groups, and in relation thereto, twelve pieces of liquid crystal layers (first and second liquid crystal layers) were prepared to form six groups of liquid crystal layer groups. Two pieces of liquid crystal layers were bonded using an adhesive (manufactured by Soken Chemical & Engineering Co., Ltd., SK Dyne 2057) so that the angle between the in-plane slow axes (in-plane slow axis of the horizontally oriented liquid crystal layer) of the two pieces of liquid crystal layers became 7.5°, i.e., so that the angle of the bisector of the angle between the in-plane slow axes became +3.75° and -3.75°, respectively, thereby preparing the liquid crystal layer groups. Other than this, the optical filter was prepared in the same manner as in Example 1, and the wavelength shift value and the side lobe value were measured. The results are shown in Table 16 below.

[0374] [Table 16]

[0375]

[0376] From the results of Example 7, it was found that even in the case where the total number of liquid crystal layers is different, the wavelength shift value is smaller compared to the comparative example.

[0377] [Example 8]

[0378] In Example 1, a phase difference layer was disposed between the one side of the polarizer disposed in the crossed-Nicol manner and the liquid crystal polarization interference element. The phase difference layer functions to maintain the orthogonal relationship of the polarization directions based on the linear polarizer disposed in the crossed-Nicol manner not only in the front but also in the oblique direction. A positive C-plate (thickness direction retardation Rth of -90 nm) that vertically aligns the rod-shaped liquid crystal compound, and a positive A-plate (in-plane direction retardation Re of 140 nm) that horizontally aligns the rod-shaped liquid crystal compound were sequentially disposed adjacent to the first polarizer and bonded. At this time, the in-plane slow axis of the positive A-plate was set to be parallel to the absorption axis of the one side of the polarizer. In this way, the optical filter was prepared, and the wavelength shift value and the side lobe value were measured in the same manner as in Example 1. The results are shown in Table 17 below.

[0379] [Table 17]

[0380]

[0381] From the results of Example 8, in the structure in which the phase difference layer is disposed between the polarizer and the liquid crystal polarization interference element, the wavelength shift value is also smaller compared to the comparative example. Also, from the comparison with Example 1, by disposing the phase difference layer, the wavelength shift value at the oblique incidence can be further reduced.

[0382] [Example 9]

[0383] In Example 1, the liquid crystal polarization interference element was produced by disposing 8 pieces of liquid crystal layer in a manner that the angle of the in-plane slow axis becomes the relationship shown in Table 18 below, and the filter was produced by changing the disposition of the polarizer from the crossed Nicols to the parallel Nicols. The disposition of the liquid crystal layer in Example 9 corresponds to a bandpass filter made of a Solc filter (fan-shaped Solc filter) made of a birefringent plate (λ / 2 phase difference plate) in which the angle of the transmission axis of the polarizer and the slow axis becomes p, 3p, 5p,..., disposed between the polarizer disposed in the parallel Nicols.

[0384] [Table 18]

[0385]

[0386] Regarding the produced filter, the wavelength shift value and the side lobe value were measured in the same manner as in Example 1. The results are shown in Table 19 below.

[0387] [Table 19]

[0388]

[0389] From the results of Example 9, in the structure in which the angle of the transmission axis of the polarizer and the direction of the slow axis becomes p, 3p, 5p,..., the wavelength shift value is also smaller compared to the comparative example.

[0390] From the above results, the effects of the present application are obvious.

[0391] Industrial Applicability

[0392] The filter of the present application can be preferably used for various optical devices as a bandpass filter or the like.

[0393] Explanation of Symbols

[0394] 10, 10b - filter, 12 - first polarizer, 14 - second polarizer, 16, 16b - liquid crystal polarization interference element, 18 - rod-like liquid crystal compound, 18 h1a , 18 h1n - first-1 rod-like liquid crystal compound, 18 v1a , 18 v1n - first-2 rod-like liquid crystal compound, 18h2a , 18 h2n - No. 2-1 rod-shaped liquid crystal compound, 18 v2a , 18 v2n - No. 2-2 rod-shaped liquid crystal compound, 19- disc-shaped liquid crystal compound, 19 h1a 、19 h1n -1-1 discotic liquid crystal compound, 19 v1a 、19 v1n -1-2 discotic liquid crystal compounds, 19 h2a 、19 h2n - No. 2-1 discotic liquid crystal compound, 19 v2a 、19 v2n - the 2nd discotic liquid crystal compound, 20, 20a, 20n, 21, 21a, 21n- the 1st liquid crystal layer, 20H, 20Ha, 20Hn, 21H, 21Ha, 21Hn- the 1st horizontally aligned liquid crystal layer, 20V, 20Va, 20Vn, 21V, 21Va, 21Vn- the 1st vertically aligned liquid crystal layer, 24, 24a, 24n, 25, 25a, 25n- the 2nd liquid crystal layer, 24H, 24Ha, 24Hn, 25H, 25Ha, 25Hn- the 2nd horizontally aligned liquid crystal layer, 24V, 24Va, 24Vn, 25V, 25Va, 25Vn- the 2nd vertically aligned liquid crystal layer, 26, 27- liquid crystal layer group, 26a, 27a- the 1st liquid crystal layer group, 26n, 27n- the nth liquid crystal layer group.

Claims

1. A liquid crystal polarization interference element comprising two or more liquid crystal layer groups consisting of a first liquid crystal layer and a second liquid crystal layer in a thickness direction, The first liquid crystal layer includes at least one first horizontal alignment liquid crystal layer formed by fixing a 1-1 liquid crystal compound that aligns the optical axis horizontally, and at least one first vertical alignment liquid crystal layer formed by fixing a 1-2 liquid crystal compound that aligns the optical axis vertically. The second liquid crystal layer includes at least one second horizontal alignment liquid crystal layer formed by fixing a 2-1 liquid crystal compound that aligns the optical axis horizontally, and at least one second vertical alignment liquid crystal layer formed by fixing a 2-2 liquid crystal compound that aligns the optical axis vertically. The 1-1 liquid crystal compound and the 1-2 liquid crystal compound are both rod-shaped liquid crystal compounds, or both are disc-shaped liquid crystal compounds, The 2-1 liquid crystal compound and the 2-2 liquid crystal compound are both rod-shaped liquid crystal compounds, or both are disc-shaped liquid crystal compounds, The in-plane slow axis of the first liquid crystal layer intersects the in-plane slow axis of the second liquid crystal layer. The total in-plane retardation of the first horizontal alignment liquid crystal layer is 1.33 to 4 times the total thickness-direction retardation of the first vertical alignment liquid crystal layer. The total in-plane retardation of the second horizontal alignment liquid crystal layer is 1.33 to 4 times the total retardation in the thickness direction of the second vertical alignment liquid crystal layer. The in-plane retardation of the first liquid crystal layer is equal to the in-plane retardation of the second liquid crystal layer.

2. The liquid crystal polarization interference element according to claim 1, wherein: The total in-plane retardation of the first horizontal alignment liquid crystal layer is twice the total retardation in the thickness direction of the first vertical alignment liquid crystal layer. The total in-plane retardation of the second horizontal alignment liquid crystal layer is twice the total retardation in the thickness direction of the second vertical alignment liquid crystal layer.

3. The liquid crystal polarization interference element according to claim 1 , comprising three or more liquid crystal layer groups in the thickness direction. In the liquid crystal layer group arranged on both sides in the thickness direction and the liquid crystal layer group arranged in the center in the thickness direction, the angle formed by the in-plane slow axis of the first liquid crystal layer and the in-plane slow axis of the second liquid crystal layer, and the in-plane retardation in the first liquid crystal layer and the second liquid crystal layer are different.

4. The liquid crystal polarization interference element according to claim 1, wherein: The first liquid crystal layer and the second liquid crystal layer include infrared absorbing pigments.

5. The liquid crystal polarization interference element according to claim 1, wherein: The first liquid crystal layer and the second liquid crystal layer include liquid crystal elastomer.

6. A filter comprising: The liquid crystal polarization interference element according to any one of claims 1 to 5; and Two polarizers sandwiching the liquid crystal polarization interference element in the thickness direction, The two polarizers are arranged so that their transmission axes are orthogonal to each other.

7. The optical filter according to claim 6, wherein: A phase difference layer is included between one or both of the two polarizers and the liquid crystal layer group, and the in-plane slow axis of the phase difference layer is parallel to the absorption axis of one of the two polarizers.

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