Optical Film

Abstract

This specification discloses a geometric phase optical element, its manufacturing method, and its uses. This specification discloses a geometric phase optical element that has no or very little wavelength dependency, its manufacturing method, and its uses. This specification discloses a geometric phase optical element that has no or little wavelength dependency by using a liquid crystal compound with a specific structure, controlling the thickness of the liquid crystal layer, and adjusting the manufacturing method, as well as a manufacturing method and its uses.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0120854, filed September 23, 2022, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to optical films and their applications. [Background technology]

[0003] Geometric phase optical elements are elements that record the wavefront of light on a recording medium using a holographic polarization interference pattern, and are flat optical elements that can be manufactured thinner than existing elements that use dynamic phase differences. Such geometric phase optical elements are also known as PBP (Pancharatnam Berry Phase) optical elements.

[0004] Such geometric phase optical elements can be applied to a variety of applications, a typical example of which is application to VR (Virtual Reality), AR (Augmented Reality), or MR (Mixed Reality) systems.

[0005] For example, the geometric phase optical element may be applied as part of an optical assembly in a Head-Mounted Display (HMD), which may be part of the VR, AR and / or MR system.

[0006] The geometric phase optical element can function as a geometric phase grating and / or a geometric phase lens in the system.

[0007] A known problem when implementing the geometric phase optical element using a liquid crystal compound (e.g., a so-called reactive mesogen) is that it is very difficult to ensure the alignment of the liquid crystal compound. To form a geometric phase optical element, the slow axis of the liquid crystal compound needs to be aligned in one or more arbitrary in-plane directions, and achieving such alignment is very difficult.

[0008] Another problem with geometric phase optical elements is that their performance is highly wavelength-dependent. When a geometric phase optical element has wavelength dependence, the diffraction angle, refraction angle, or focus distance varies depending on the wavelength of light, which can cause various problems, including an optical defect known as chromatic aberration (CA).

[0009] A conventional technique for solving this problem is a multilayer optical element constructed by stacking at least three geometric phase lenses corresponding to the respective wavelengths of RGB (for example, Non-Patent Document 1). In Non-Patent Document 1, the geometric phase lenses are realized using a so-called positive dispersion liquid crystal compound.

[0010] If a geometric phase lens can be implemented using a reverse dispersion liquid crystal compound, it is possible to provide a geometric phase optical element that has fewer layers, or even a single layer in some cases, and that solves the problem of wavelength dependency.

[0011] However, most known reverse dispersion liquid crystal compounds have poor alignment properties and are therefore unable to stably realize complex alignments such as geometric phase alignments. [Prior art documents] [Non-patent literature]

[0012] [Non-Patent Document 1] Tao Zhan et al.,Adv.Optical Mater.2019,1901360 Summary of the Invention [Problem to be solved by the invention]

[0013] This specification discloses a geometric phase optical element, a manufacturing method thereof, and uses thereof. This specification discloses a geometric phase optical element that has no or very little wavelength dependency, a manufacturing method thereof, and uses thereof. This specification discloses a geometric phase optical element that has no or very little wavelength dependency, a manufacturing method thereof, and uses thereof, by using a liquid crystal compound with a specific structure, controlling the thickness of the liquid crystal layer, and adjusting the manufacturing method. [Means for solving the problem]

[0014] This specification discloses an optical film.

[0015] The optical film includes a liquid crystal layer. In this specification, the term "liquid crystal layer" refers to a layer containing aligned liquid crystal compounds. For example, the lower limit of the content of the aligned liquid crystal compounds in the liquid crystal layer may be about 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, or 95 wt%, based on the total weight of the liquid crystal layer, and the upper limit may be about 100 wt%, 98 wt%, 96 wt%, 94 wt%, 92 wt%, or 90 wt%, based on the total weight of the liquid crystal layer. The content may be greater than or equal to any one of the lower limits; or greater than or equal to any one of the lower limits and less than or equal to any one of the upper limits.

[0016] The liquid crystal layer may be a so-called active liquid crystal layer or a passive liquid crystal layer. As used herein, the term active liquid crystal layer refers to a liquid crystal layer in which the alignment of the liquid crystal compound within the liquid crystal layer is not fixed and can be changed by external action (e.g., application of an external electric field), while the term passive liquid crystal layer refers to a liquid crystal layer in which the alignment of the liquid crystal compound is fixed and does not change by external action. For example, the passive liquid crystal layer can be formed by aligning a so-called reactive mesogen (RM) and then fixing the alignment by polymerization or the like.

[0017] The liquid crystal layer may include a so-called T-shaped liquid crystal compound as the liquid crystal compound. As is well known, the term T-shaped liquid crystal compound refers to a liquid crystal compound in which the mesogen skeleton of the liquid crystal compound is formed in a T shape. The T-shaped liquid crystal compound has excellent alignment properties, and in particular, geometric phase alignment can be effectively achieved.

[0018] The lower limit of the content of the T-type liquid crystal compound based on the total weight of the liquid crystal compound contained in the liquid crystal layer may be about 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 90 wt%, or 95 wt%, and the upper limit may be about 100 wt%, 98 wt%, 96 wt%, 94 wt%, 92 wt%, or 90 wt%. The content may be equal to or greater than any one of the lower limits; or may be equal to or greater than any one of the lower limits and equal to or less than any one of the upper limits.

[0019] As the T-type liquid crystal compound, a liquid crystal compound having so-called reverse wavelength dispersion can be used.

[0020] In this specification, reverse wavelength dispersion refers to the property of the liquid crystal compound in which R(450) / R(550) in the following formula A is within a specific range. The specific range of R(450) / R(550) is determined when the liquid crystal compound is uniaxially aligned, and is evaluated by the method described in "Test Example 1. Evaluation of R(450) / R(550)" in the Examples section of this specification. [Formula A] R(450) / R(550) In formula A, R(450) is the in-plane retardation of the liquid crystal compound at a wavelength of 450 nm, and R(550) is the in-plane retardation of the liquid crystal compound at a wavelength of 550 nm.

[0021] In this specification, the term "in-plane retardation" refers to a value determined by the following formula B. [Formula B] Rin=d×(nx-ny) In formula B, Rin is the in-plane retardation, nx and ny are the refractive indices in the x-axis direction (slow axis direction) and y-axis direction (fast axis direction) of the layer formed by the liquid crystal compound, respectively, and d is the thickness of the liquid crystal layer (unit: nm).

[0022] By substituting nx and ny according to wavelength into the above formula B, the in-plane retardation for the target wavelength can be obtained.

[0023] The lower limit of R(450) / R(550) of the liquid crystal compound of Formula A may be about 0.6, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, or 0.79, and the upper limit may be about 1, 0.99, 0.98, 0.97, 0.96, 0.95, 0.94, 0.93, 0.92, 0.91, 0.90, 0.89, 0.88, 0.87, 0.86, 0.85, 0.84, 0.83, 0.82, 0.81, 0.80, or 0.79. The R(450) / R(550) may be less than or equal to any one of the upper limits mentioned above; or may be greater than or equal to any one of the lower limits mentioned above and less than or equal to any one of the upper limits mentioned above.

[0024] The R(650) / R(550) ratio of the liquid crystal compound can also be adjusted. R(650) is the in-plane retardation of the liquid crystal compound for light with a wavelength of 650 nm, and R(550) is the in-plane retardation of the liquid crystal compound for light with a wavelength of 550 nm. The method for measuring R(650) / R(550) is essentially the same as the method for measuring R(450) / R(550), except for changing the measurement wavelength. The upper limit of R(650) / R(550) may be approximately 1.19, 1.18, 1.17, 1.16, 1.15, 1.14, 1.13, 1.12, 1.11, 1.1, or 1.08, and the lower limit may be approximately 1, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, or 1.09. The R(650) / R(550) may be greater than or equal to any one of the aforementioned lower limits; or less than or equal to any one of the aforementioned upper limits; or greater than or equal to or exceeding any one of the aforementioned lower limits and less than or equal to any one of the aforementioned upper limits.

[0025] In the liquid crystal layer, the liquid crystal compound may be in an oriented state, and such an orientation may be a so-called geometric phase orientation.

[0026] In this specification, the term "geometric phase orientation" refers to an orientation in which the liquid crystal compound causes the liquid crystal layer to function as a so-called geometric phase lens or a geometric phase grating.

[0027] The alignment form that enables a liquid crystal compound to function as the geometric phase lens or geometric phase grating is known.

[0028] When the orientation of the liquid crystal compound is an orientation that can function as the geometric phase lens, the orientation can be called a geometric phase lens orientation. When the orientation of the liquid crystal compound is an orientation that can function as the geometric phase grating, the orientation can be called a geometric phase grating orientation.

[0029] A geometric phase lens orientation can generally be defined as an orientation that has spatially varying azimuth angles.

[0030] 1 is a schematic diagram showing a liquid crystal layer 200 having a geometric phase lens orientation according to one example. The liquid crystal layer 200 generates a corresponding lens profile through the in-plane orientation of the liquid crystal compound. The in-plane orientation of the liquid crystal compound can be defined as an azimuth angle (θ), which generates an optical phase difference T, and the optical phase difference T can be defined as 2θ with respect to the azimuth angle.

[0031] 2 shows an example of the geometric phase lens orientation 210. In the geometric phase lens orientation, the azimuth angle θ of the liquid crystal compound continuously changes along a direction from the center 220 to the edge 230 of the liquid crystal layer 200, thereby generating a varying pitch Λ. The pitch Λ refers to the distance required for the azimuth angle of the liquid crystal compound to rotate 180 degrees from the initial state, and in the geometric phase lens orientation, it can be expressed as a function of the distance r from the center 220.

[0032] In one example, the azimuth angle may satisfy the relationship of the following Equation 9 depending on the distance. [Formula 9] θ(r)={π×r 2} / {2×f×λ} In Equation 9, θ(r) is the azimuthal angle of the liquid crystal compound in a region of the liquid crystal layer that is a distance r (unit: mm) from the center of the geometric phase lens orientation, where r is the distance, f is the focal length of the geometric phase lens orientation, and λ is the wavelength of the incident light.

[0033] 3 is a diagram illustrating an exemplary orientation 240 of the liquid crystal compound along the y-axis of the liquid crystal layer 200 of FIG. 1. From FIG. 3, it can be seen that the rate of change of the pitch is a function of the distance r from the center 220 of the liquid crystal layer. The rate of change of the pitch increases as the distance increases. For example, the pitches Λ0, Λ1, and Λ2 in FIG. 3 are r is Λ0>Λ1>Λ r have the following relationship.

[0034] As described above, in the geometric phase lens orientation, the orientation of the liquid crystal compound may be such that it has an azimuth angle that changes with distance along at least one of the in-plane directions of the liquid crystal layer (for example, any direction perpendicular to the x-axis direction, y-axis direction, or z-axis direction in Figure 1).

[0035] In this case, the change in the azimuth angle can satisfy the formula C.

[0036] The value of f in formula C can be adjusted as appropriate depending on the application of the optical film. For example, the lower limit may be about 1 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, 70 mm, 75 mm, 80 mm, 85 mm, 90 mm, or 95 mm, and the upper limit may be about 300 mm, 250 mm, 200 mm, 150 mm, 100 mm, 95 mm, 90 mm, 85 mm, 80 mm, 75 mm, 70 mm, or 65 mm. The focal length f may be greater than or equal to any one of the lower limits; or less than or equal to any one of the upper limits; or greater than or equal to any one of the lower limits and less than or equal to any one of the upper limits. In a geometric phase lens, the focal length f can be adjusted by adjusting the change in the pitch, and such an adjustment method is well known.

[0037] In the formula C, λ may be any one wavelength within the range of 400 nm to 700 nm, any one wavelength within the range of 450 nm to 650 nm, or approximately 550 nm.

[0038] As can be seen with reference to FIG. 2, the change in azimuthal angle in the geometric phase lens orientation can appear radially within the plane of the liquid crystal layer.

[0039] 4 is a schematic diagram showing a liquid crystal layer 300 having a geometric phase grating orientation according to one example of the present application. The liquid crystal layer 300 generates a corresponding grating profile through the in-plane orientation of the liquid crystal compound. The in-plane orientation of the liquid crystal compound can be defined as an azimuth angle θ, which generates an optical phase difference T, and the optical phase difference T can be defined as 2θ by the azimuth angle.

[0040] FIG. 5 is a diagram illustrating an example of an orientation 310 of a liquid crystal compound in the geometric phase grating orientation. In the orientation, the orientation of the liquid crystal compound can be defined as an azimuth angle θ that continuously changes along any specific direction (the y-axis direction in FIG. 5), and the pitch Λ is substantially fixed. The meaning of the pitch is the same as in the case of the geometric phase lens. In one example, as illustrated in FIG. 5, the azimuth angle θ of the liquid crystal compound changes along one direction (the y-axis direction in FIG. 5) and remains substantially constant along a direction perpendicular to the one direction (the x-axis direction in FIG. 5).

[0041] 6 is an exemplary diagram illustrating the orientation 340 of the liquid crystal compound along the y-axis of the liquid crystal layer 300 of FIG. 4. From FIG. 6, it can be seen that in the liquid crystal orientation of a geometric phase grating, the rate of change of pitch is substantially fixed and is not a function of the distance from the center 320 of the grating orientation. For example, in FIG. 6, pitches Λ0, Λ1, and Λ r effectively Λ0=Λ1=Λ r Satisfy the relationship.

[0042] In the geometric phase grating orientation, the liquid crystal compound may be oriented so as to have an azimuth angle that varies along at least one of the plane directions of the liquid crystal layer. As described above, the pitch of the variation of the azimuth angle along the one direction in which the azimuth angle varies may be fixed to a constant value.

[0043] In the geometric phase grating orientation, the orientation of the liquid crystal compound can maintain the azimuthal angle of the liquid crystal compound constant along a plane direction perpendicular to the one direction in which the azimuthal angle changes.

[0044] In the above, the pitch of the azimuth angle change being fixed and the azimuth angle being maintained constant means that there is substantially no change in the pitch and azimuth angle, and in this case, substantially no change may mean that even if there is a certain amount of minute change in the pitch and azimuth angle, the liquid crystal layer or optical film as a whole can effectively perform the function of the geometric phase grating.

[0045] The pitch in one direction in which the azimuth angle changes in the geometric phase grating orientation can be adjusted depending on the application of the geometric phase grating. That is, since the refraction angle of the grating satisfies the following formula D depending on the pitch and the reference wavelength, an appropriate pitch can be set taking into account the target refraction angle. [Formula D] sinθ=λ / Λ In formula D, θ is the refraction angle, λ is a reference wavelength that is any one wavelength within the range of 400 nm to 700 nm, or any one wavelength within the range of 450 nm to 650 nm, or approximately 550 nm, and Λ is the pitch (unit: nm).

[0046] In one example, the lower limit of the alignment pitch of the liquid crystal compound may be about 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, or 15 μm, and the upper limit may be about 30 μm, 28 μm, 26 μm, 24 μm, 22 μm, 20 μm, 18 μm, 16 μm, 14 μm, 12 μm, 10 μm, 8 μm, 6 μm, 4 μm, or 2 μm. The pitch in the geometric phase grating orientation may be greater than or equal to any one of the lower limits mentioned above; or less than or equal to any one of the upper limits mentioned above; or greater than or equal to or exceeding any one of the lower limits mentioned above and less than or equal to any one of the upper limits mentioned above.

[0047] Whether a liquid crystal layer has the geometric phase orientation can be confirmed using a polarizing microscope. As described above, in geometric phase orientation, the liquid crystal compound rotates to have a varying azimuth angle, and when observed through a polarizing microscope, a pattern of relatively dark and relatively light shaded lines is observed depending on the azimuth angle. Therefore, when the repetition of the line pattern is observed through a polarizing microscope, the liquid crystal layer is considered to have a geometric phase orientation. As described above, the pitch Λ of geometric phase orientation is the distance required for the azimuth angle of the liquid crystal compound to rotate 180 degrees from the initial state. The dark or light line appears when a 90-degree azimuth angle is completed. Therefore, the pitch can be approximately defined as the distance between the two outermost dark or light shaded lines among three adjacent dark or light shaded lines in the pattern observed through a polarizing microscope.

[0048] The liquid crystal layer contains a geometrically phase oriented liquid crystal compound as described above, and since this liquid crystal compound is the T-type liquid crystal compound described above and has reverse wavelength dispersion, the liquid crystal layer or the optical film containing it can function as a geometric phase lens or a geometric phase grating with little or no wavelength dependence.

[0049] The liquid crystal layer may satisfy, for example, at least one of the conditions of the following formula 1 and the conditions of the following formula 2, or may satisfy both the conditions of the following formula 1 and the conditions of the following formula 2. In this case, the liquid crystal layer satisfying the conditions of formula 1 and / or 2 means that the entire region of the liquid crystal layer satisfies the conditions of formula 1 and / or 2, or that at least a partial region of the liquid crystal layer (for example, at least the frame of the liquid crystal layer) satisfies the conditions of formula 1 and / or 2.

[0050] For example, the liquid crystal layer may satisfy the conditions of the following formulas 1 and / or 2 when it is a single layer. In this case, not only when the liquid crystal layer is substantially a single layer, but also when the liquid crystal layer includes multiple layers, the multiple layers are considered to be a single layer as a whole if the type and composition of the liquid crystal compound contained in each liquid crystal layer are the same. That is, as will be described later, multiple sub-liquid crystal layers may be formed to form the liquid crystal layer, and even in this case, if the multiple sub-liquid crystal layers are formed using liquid crystal compounds of the same type and composition, the multiple sub-liquid crystal layers can be considered to be a single layer as a whole.

[0051] The conditions of the above formula 1 are as follows: [Formula 1] T avg ≤5% and SD T ≦1.5 Equation 1 is T avg is 5% or less and SD T This means that the liquid crystal layer also satisfies the condition that the σ is 1.5 or less.

[0052] In addition, in Equation 1, T avg is T B , T G and T R is the mean and SD T is the T B , T G and T R is the standard deviation of

[0053] T B is the rectilinear light transmittance of the liquid crystal layer at a wavelength of 450 nm, and T G is the transmittance of light of 550 nm wavelength to the liquid crystal layer, and T R is the transmittance of light having a wavelength of 610 nm traveling straight through the liquid crystal layer.

[0054] The light of wavelengths 450 nm, 550 nm and 610 nm may be unpolarized or circularly polarized (left-handed or right-handed circularly polarized), and in the case of formula 1, may be unpolarized, for example.

[0055] In relation to Equation 1, the term "linear light transmittance" refers to the transmittance in any region of the liquid crystal layer. For example, referring to FIG. 7, the linear light transmittance is the transmittance of light L incident on any region 1001 of the liquid crystal layer 100 in a direction parallel to the normal to the liquid crystal layer 100. I The ratio of light transmitted through the region 1001 in the direction parallel to the normal (i.e., L in FIG. 7) I The arrows in Figure 7 indicate the light E1 The transmittance of light is indicated by the arrows.

[0056] The geometric phase optical element diffracts or refracts the incident light in a predetermined direction depending on the state of the incident light, thereby focusing, dispersing, or steering the incident light. Therefore, as shown in FIG. 7, the geometric phase optical element condenses, disperses, or steers the incident light along the normal direction of the optical element (L in FIG. 7). I The light (shown by the arrows in Fig. 7) is emitted in a direction different from the normal direction. E2 The geometric phase optical element includes a region where light is converted into light (light indicated by an arrow). Therefore, theoretically, the transmittance of the rectilinear light should be low in this region, and this characteristic is also called zero-order leakage. However, when the geometric phase optical element exhibits wavelength dependency, the transmittance of the rectilinear light does not remain constant for each wavelength, and the transmittance of the rectilinear light may be very high depending on the wavelength.

[0057] However, the liquid crystal layer has little wavelength dependence, and therefore T B , T G and T R The mean and standard deviation of the can be controlled to be low.

[0058] T in the above formula 1 B , T G and T R Average T avg is the arithmetic mean, and therefore (T B +T G +T R ) / 3. avgThe upper limit may be on the order of 5%, as described in Equation 1, or in other examples, on the order of 4.5%, 4%, 3.5%, 3%, 2.5%, or 2%, and the lower limit may be on the order of 0%, 0.5%, 1%, 1.5%, or 2%. The average may be less than or equal to any one of the upper limits; or greater than or equal to or exceeding any one of the lower limits and less than or equal to any one of the upper limits.

[0059] Standard deviation SD in Equation 1 T is (((T avg -T B ) 2 +(T avg -T G ) 2 +(T avg -T R ) 2 ) / 3) 0.5 Calculate the SD T The upper limit may be about 1.5, as described in Equation 1, and in other examples may be about 1.4, 1.3, 1.2, 1.1, 1, 0.9, 0.8, or 0.65, and the lower limit may be about 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, or 0.7. The standard deviation may be less than or equal to any one of the upper limits; or greater than or equal to or exceeding any one of the lower limits and less than or equal to any one of the upper limits.

[0060] T in Equation 1 B , T G and T R Each can be adjusted to meet the aforementioned mean and standard deviation. R The upper limit of T may be about 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, or 1.5%, and the lower limit may be about 0%, 0.5%, 1%, 1.5%, 2%, or 2.5%. Rmay be in the range of less than or equal to any one of the aforementioned upper limits; or may be in the range of greater than or equal to any one of the aforementioned lower limits and less than or equal to any one of the aforementioned upper limits.

[0061] T in Equation 1 G The upper limit of may be about 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, or 1.5%, and the lower limit may be about 0%, 0.5%, 1%, or 1.5%. The TG may be in a range equal to or less than any one of the upper limits mentioned above; or may be equal to or greater than any one of the lower limits mentioned above and equal to or less than any one of the upper limits mentioned above.

[0062] T in Equation 1 B The upper limit of T may be about 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, or 1.5%, and the lower limit may be about 0%, 0.5%, 1%, 1.5%, 2%, or 2.5%. B may be in the range of less than or equal to any one of the aforementioned upper limits; or may be in the range of greater than or equal to any one of the aforementioned lower limits and less than or equal to any one of the aforementioned upper limits.

[0063] The conditions of the above formula 2 are as follows: [Formula 2] I avg ≦100×10 -3 CD and SD I ≦25×10 -3 Equation 2 is I avg is 0.1cd or less and SD I This means that the liquid crystal layer also satisfies the condition that the σ is 0.025 or less.

[0064] In Equation 2, I avg I B , I G and I R is the mean and SDI I B , I G and I R is the standard deviation of

[0065] Above I B is the intensity of light of 450 nm wavelength traveling straight through the liquid crystal layer, and I G is the intensity of light of 550 nm wavelength traveling straight through the liquid crystal layer, and I R is the intensity of light of 610 nm wavelength traveling straight through the liquid crystal layer.

[0066] The light of wavelengths 450 nm, 550 nm and 610 nm may be unpolarized or circularly polarized (left-handed or right-handed circularly polarized), and in the case of formula 2, for example, may be circularly polarized, i.e., left-handed or right-handed circularly polarized.

[0067] The term "intensity of the rectilinear light" in relation to Equation 2 is the intensity in any region of the liquid crystal layer. For example, referring to FIG. 7, the intensity of the rectilinear light is the intensity of the light L incident on any region 1001 of the liquid crystal layer 100 in a direction parallel to the normal to the liquid crystal layer 100. I is the intensity of light that has passed through the region 1001 in a direction parallel to the normal direction.

[0068] For the reasons described above, the geometric phase optical element theoretically needs the intensity of the linearly propagating light to be low. If the geometric phase optical element exhibits wavelength dependency, the intensity of the linearly propagating light may not be constant depending on the wavelength, and the intensity of the linearly propagating light may be very high depending on the wavelength.

[0069] However, the liquid crystal layer has little wavelength dependency, and therefore I B , I G and I R The mean and standard deviation of the can be controlled to be low.

[0070] I in the above formula 2 B , I G and I R Average I avg is the arithmetic mean, and therefore (I B+I G +I R ) / 3. The average I avg The upper limit of may be about 100 as described in Equation 2, and in another example, 95×10 -3 CD, 90×10 -3 CD, 85×10 -3 CD, 80×10 -3 CD, 75×10 -3 CD, 70×10 -3 CD, 65×10 -3 CD, 60×10 -3 CD, 55×10 -3 CD, 50×10 -3 CD, 45×10 -3 CD, 40×10 -3 CD, 35×10 -3 CD, 30×10 -3 CD, 25×10 -3 CD, 20×10 -3 CD, 15×10 -3 cd or 10x10 -3 The lower limit is 0×10 -3 CD, 2×10 -3 CD, 4×10 -3 CD, 6×10 -3 CD, 8×10 -3 CD, 10x10 -3 CD, 12×10 -3 cd or 14x10 -3 The average may be in the range of less than or equal to any one of the upper limits recited above; or greater than or equal to or exceeding any one of the lower limits recited above and less than or equal to any one of the upper limits recited above.

[0071] Standard deviation SD in Equation 2 I is (((I avg -I B ) 2 +(I avg -I G ) 2 +(I avg -I R ) 2 ) / 3) 0.5 Calculate the SDI The upper limit of is 25 × 10 as stated in Equation 2. -3 In another example, the value may be 20×10 -3 , 15×10 -3 , 10×10 -3 , 9×10 -3 , 8×10 -3 , 7×10 -3 , 6×10 -3 , 5×10 -3 , 4×10 -3 , 3×10 -3 or 2.5 x 10 -3 The lower limit is about 0×10 -3 , 0.1×10 -3 , 0.5×10 -3 , 1×10 -3 , 1.5×10 -3 , 2 × 10 -3 , 2.5×10 -3 , 3×10 -3 , 3.5×10 -3 , 4×10 -3 , 4.5×10 -3 , 5×10 -3 , 5.5×10 -3 , 6×10 -3 or 6.5 x 10 -3 The standard deviation may be in a range equal to or less than any one of the upper limits recited above; or equal to or greater than any one of the lower limits recited above and equal to or less than any one of the upper limits recited above.

[0072] I in Equation 2 B , I G and I R Each can be adjusted to meet the mean and standard deviations mentioned above.

[0073] For example, in Equation 2, I RThe upper limit of the above may be about 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, 0.01, 0.009, 0.008, 0.007, or 0.006, and the lower limit of the above may be about 0, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, or 0.02. R may be in the range of less than or equal to any one of the aforementioned upper limits; or may be in the range of greater than or equal to any one of the aforementioned lower limits and less than or equal to any one of the aforementioned upper limits.

[0074] In Equation 2, I G The upper limit of the above may be about 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, 0.01, 0.009, 0.008, 0.007, or 0.006, and the lower limit of the above may be about 0, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, or 0.02. G may be in the range of less than or equal to any one of the aforementioned upper limits; or may be in the range of greater than or equal to any one of the aforementioned lower limits and less than or equal to any one of the aforementioned upper limits.

[0075] In Equation 2, I B The upper limit of the above may be about 0.5, 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, 0.01, 0.009, 0.008, 0.007, or 0.006, and the lower limit of the above may be about 0, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, or 0.02. Bmay be in the range of less than or equal to any one of the aforementioned upper limits; or may be in the range of greater than or equal to any one of the aforementioned lower limits and less than or equal to any one of the aforementioned upper limits.

[0076] In this way, the liquid crystal layer can also exhibit a diffraction efficiency that is independent of wavelength or that has low wavelength dependency.

[0077] For example, the liquid crystal layer may satisfy the following formula 3 or may include a region that satisfies formula 3. Such a region of the liquid crystal layer may be a region that satisfies the conditions of formulas 1 and / or 2. The liquid crystal layer may satisfy formula 3 below in the state of being the above-mentioned single layer, or may include a region that satisfies formula 3. [Formula 3] △F1 and △F2≦30% In Equation 3, ΔF1 is the absolute value of F1 according to Equation 4 below, and ΔF2 is the absolute value of F2 according to Equation 5 below: [Formula 4] F1 = 100 × (θ R -θ G ) / θ G [Formula 5] F2 = 100 × (θ B -θ G ) / θ G θ in Equations 4 and 5 R is the refraction angle that satisfies the following formula 6, and θ G is the refraction angle that satisfies the following formula 7, and θ B is a refraction angle that satisfies the following formula 8. The refraction angle may be a refraction angle in the liquid crystal layer or in any region of the liquid crystal layer. [Formula 6] sinθ R =610 / Λ [Formula 7] sinθ G =550 / Λ [Formula 8] sinθ B =450 / Λ In formulas 6 to 8, Λ is the pitch (unit: nm) of the geometric phase alignment in the liquid crystal layer or in any region of the liquid crystal layer. The meaning of the pitch of the geometric phase alignment is the same as that explained for the geometric phase alignment.

[0078] The geometric phase optical element must diffract or refract incident light at a predetermined refraction angle depending on the state of the incident light. In this case, the refraction angle is the angle between the normal direction of the optical element and the outgoing direction of the refracted light. For example, referring to FIG. 7, the normal direction of the liquid crystal layer 100 and the outgoing light (L E2 The angle between the direction of the light (shown by the arrow) and the direction of the light emitted is the refraction angle.

[0079] If a geometric phase optical element has a strong wavelength dependency, the refraction angle varies depending on the wavelength in the same region, and such a difference in the refraction angle depending on the wavelength may cause optical defects.

[0080] The liquid crystal layer contains the geometrically oriented liquid crystal compound and at the same time has the reverse wavelength dispersion described above, and therefore may satisfy formula 3 or may contain a region that satisfies it.

[0081] The upper limit of ΔF1 in Equation 3 may be about 30%, as shown in Equation 3, or may be about 28%, 26%, 24%, 22%, 20%, 18%, 16%, 14%, 12%, 10%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1%, and the lower limit may be about 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 10%, or 15%. The ΔF1 may be in a range equal to or less than any one of the upper limits mentioned above; or may be in a range equal to or greater than any one of the lower limits mentioned above and equal to or less than any one of the upper limits mentioned above.

[0082] The upper limit of ΔF2 in Equation 3 may be about 30%, as shown in Equation 3, or may be about 28%, 26%, 24%, 22%, 20%, 18%, 16%, 14%, 12%, 10%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1%, and the lower limit may be about 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 10%, or 15%. The ΔF2 may be in a range equal to or less than any one of the upper limits mentioned above; or may be in a range equal to or greater than any one of the lower limits mentioned above and equal to or less than any one of the upper limits mentioned above.

[0083] As described above, the liquid crystal layer may include a T-type liquid crystal compound, which may have reverse wavelength dispersion. In one example, the T-type liquid crystal compound may be a polymerizable liquid crystal compound, which can form the passive liquid crystal layer when polymerized.

[0084] When the liquid crystal layer is a passive liquid crystal layer, it may contain a polymerized unit of the T-type liquid crystal compound, which is a polymerizable liquid crystal compound. The polymerized unit means a unit formed by polymerization or curing of the polymerizable liquid crystal compound.

[0085] As used herein, the term "liquid crystal compound" refers to a compound containing a moiety capable of exhibiting liquid crystallinity, such as a mesogen skeleton, and "polymerizable liquid crystal compound" refers to a compound containing the moiety capable of exhibiting liquid crystallinity and one or more polymerizable functional groups. Such polymerizable liquid crystal compounds are variously known as reactive mesogens (RMs). The polymerizable liquid crystal compound may be in a polymerized form within the cured layer, i.e., contained in the aforementioned polymerized units, which may refer to a state in which the liquid crystal compound is polymerized to form a skeleton such as a main chain or side chain of a liquid crystal polymer within the cured layer.

[0086] The polymerizable liquid crystal compound may be a monofunctional or polyfunctional polymerizable liquid crystal compound. The monofunctional polymerizable liquid crystal compound is a compound having one polymerizable functional group, and the polyfunctional polymerizable liquid crystal compound is a compound having two or more polymerizable functional groups. In one example, the lower limit of the number of polymerizable functional groups in the polyfunctional polymerizable liquid crystal compound may be about 2 or 3, and the upper limit may be about 10, 9, 8, 7, 6, 5, 4, 3, or 2. The number of polymerizable functional groups may be greater than or exceeding any one of the lower limits mentioned above; or less than or equal to any one of the upper limits mentioned above; or greater than or exceeding any one of the lower limits and less than or equal to any one of the upper limits mentioned above.

[0087] The polymerizable liquid crystal composition is prepared by blending the polymerizable liquid crystal compound with other components such as an initiator, a stabilizer, and / or a non-polymerizable liquid crystal compound, and the polymerizable liquid crystal composition is then cured in an aligned state on an alignment film to form the cured layer (liquid crystal layer) exhibiting birefringence.

[0088] In order to ensure the desired geometric phase alignment, a reverse dispersion liquid crystal compound or a reverse dispersion polymerizable liquid crystal compound having a predetermined structure can be used.

[0089] It is known that the birefringence of liquid crystal compounds is determined mainly by the molecular conjugation structure, differential oscillator strength, and order parameter. In order for liquid crystal compounds to exhibit high birefringence, they require a large electron density in the direction of the principal axis, and therefore most liquid crystal compounds have a highly conjugated shape in the direction of the long axis.

[0090] In order for a liquid crystal compound to exhibit reverse dispersion characteristics, it is necessary to adjust the birefringence between the long axis and the axis perpendicular to it. As a result, most liquid crystal compounds designed to have reverse dispersion characteristics have an H-type molecular shape, in which the main axis (long axis) has a large retardation and a small dispersion value, and the axis perpendicular to it has a small retardation and a large dispersion value.

[0091] In the liquid crystal layer disclosed herein, a liquid crystal compound having a T-shaped molecular structure or mesogen skeleton structure (T-type liquid crystal compound) is used as the liquid crystal compound. By using such a compound, the desired alignment can be effectively achieved.

[0092] As such a liquid crystal compound, compounds known as T-type liquid crystal compounds may be used among known general liquid crystal compounds.

[0093] In order to obtain the desired liquid crystal layer more efficiently, for example, a liquid crystal compound having a structure represented by the following Chemical Formula 1 can be used as the T-type liquid crystal compound. [Chemical formula 1] [ka] In Chemical Formula 1, Q may be a carbon atom or a sulfur atom. When Q is a sulfur atom, R2 and R3 do not exist in Chemical Formula 1.

[0094] In Chemical Formula 1, R 11~R 14 and R3 to R5 may each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a cyano group, or a halogen atom. 11 ~R 14 and R3 to R5 are each independently a hydrogen atom or an alkyl group, or may be a hydrogen atom.

[0095] In Chemical Formula 1, R2 may be a substituent of Chemical Formula 2 or 3 below, for example, a substituent of Chemical Formula 3 below. [Chemical formula 2] [ka] In Chemical Formula 2, A1 and A2 may each independently be an oxygen atom or a single bond. For example, when A1 is an oxygen atom, the oxygen atom may be linked to the skeleton of Chemical Formula 1, and when A1 is a single bond, L1 may be linked to the skeleton of Chemical Formula 1.

[0096] In Chemical Formula 2, L1 and L2 may each independently be -C(=O)-O-, -OC(=O)-, an alkylene group, or an alkylidene group; Cy may be an arylene group or a cycloalkylene group; and P1 may be a hydrogen atom, an alkyl group, an aryl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group. [Chemical formula 3] [ka] In Chemical Formula 3, L3 and L4 may each independently be an alkylene group or an alkylidene group, and L3 is connected to the skeleton of Chemical Formula 1. In Chemical Formula 3, P2 may be a hydrogen atom, an alkyl group, an aryl group, an acryloyl group, or a methacryloyl group, for example, a hydrogen atom, an alkyl group, an acryloyl group, or a methacryloyl group. In Chemical Formula 3, n is any number. For example, the lower limit of n may be about 1 or 2, and its upper limit may be 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1. n may be equal to or greater than any one of the lower limits mentioned above; or equal to or greater than any one of the lower limits mentioned above and equal to or less than any one of the upper limits mentioned above. In Chemical Formula 3, when n is a number of 2 or more and a plurality of O-L4s are present, the carbon numbers of the L4s may be the same or different.

[0097] In Chemical Formula 1, R 61 ~R 65 may each independently represent a hydrogen atom, an alkyl group, an alkoxy group, a cyano group, a halogen atom, a substituent of the following chemical formula 4, or a substituent of the following chemical formula 5. For example, R 61 ~R 65 Two or more of these may be a substituent of Chemical Formula 4 below or a substituent of Chemical Formula 5 below, for example, a substituent of Chemical Formula 5 below.

[0098] For example, in Formula 1, R 61 and R 62 Any one of and R 63 ~R 65 Any one of the R in Chemical Formula 1 may be a substituent of Chemical Formula 4 or a substituent of Chemical Formula 5, for example, a substituent of Chemical Formula 5. 61 ~R 65When two of the substituents are the substituents of Chemical Formula 4 or the substituents of Chemical Formula 5, or when two of the substituents are the substituents of Chemical Formula 5, the two substituents may be in the para position relative to each other. [Chemical formula 4] [ka] In Chemical Formula 4, A3 and A4 may each independently be an oxygen atom, an alkylene group, an alkylidene group, or a single bond. For example, when A3 is an oxygen atom, an alkylene group, or an alkylidene group, A3 may be linked to the skeleton of Chemical Formula 1, and when A3 is a single bond, L5 may be linked to the skeleton of Chemical Formula 1.

[0099] In Chemical Formula 1, L5 and L6 may each independently be -C(=O)-O-, -OC(=O)-, an alkylene group, or an alkylidene group; Cy may be an arylene group or a cycloalkylene group; and P3 may be a hydrogen atom, an alkyl group, an aryl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group. P3 may be an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group in appropriate examples. [Chemical formula 5] [ka] In Chemical Formula 5, A5, A6, and A7 may each independently be an oxygen atom or a single bond. For example, when A5 is an oxygen atom, an alkylene group, or an alkylidene group, A5 may be linked to the skeleton of Chemical Formula 1, and when A5 is a single bond, L7 may be linked to the skeleton of Chemical Formula 1.

[0100] In Chemical Formula 5, L7, L8, and L9 may each independently be -C(=O)-O-, -OC(=O)-, an alkylidene group, or an alkylene group.

[0101] In Chemical Formula 5, one of Cy1 and Cy2 may be a cycloalkylene group and the other may be an arylene group. For example, Cy1 may be an arylene group and Cy2 may be a cycloalkylene group, or Cy1 may be a cycloalkylene group and Cy2 may be an arylene group.

[0102] In Chemical Formula 5, P4 may be a hydrogen atom, an alkyl group, an aryl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group, for example, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group.

[0103] In Chemical Formulas 1 to 5, the term "single bond" means that there is no additional atom at that site. For example, if A2 in Chemical Formula 2 is a single bond, there is no additional atom at A2, and a structure in which Cy is directly linked to L2 can be embodied.

[0104] In Chemical Formulas 1 to 5, the term alkyl or alkoxy group may refer to a linear or branched alkyl or alkoxy group having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms, which may be optionally substituted with one or more substituents.

[0105] In Chemical Formulas 1 to 5, the halogen atom may be fluorine, chlorine or iodine.

[0106] In Chemical Formulas 1 to 5, the alkylene group is a divalent functional group formed by the removal of two hydrogen atoms from an alkane, and refers to a functional group in which the hydrogen atoms are removed from the other carbon atoms of the alkane. Such an alkylene group may be a linear or branched alkylene group having 2 to 20, 2 to 16, 2 to 12, 2 to 8, or 2 to 4 carbon atoms, which may be optionally substituted with one or more substituents.

[0107] In Chemical Formulas 1 to 5, the alkylidene group is a divalent functional group formed by the removal of two hydrogen atoms from an alkane, and refers to a functional group in which the hydrogen atoms are removed from one carbon atom of the alkane. Such an alkylidene group may be a linear or branched alkylidene group having 1 to 20, 1 to 16, 1 to 12, 1 to 8, or 1 to 4 carbon atoms, which may be optionally substituted with one or more substituents.

[0108] In Chemical Formulas 1 to 5, the arylene group may be an arylene group having 6 to 12 carbon atoms or a phenylene group.

[0109] In the chemical formulas 1 to 5, the cycloalkylene group may be a cycloalkylene group having 3 to 12 carbon atoms or 3 to 9 carbon atoms, or may be a cyclohexylene group.

[0110] In the substituent of Chemical Formula 2, A1 may be a single bond, L1 may be -C(=O)-O- or -OC(=O)-, A2 may be an oxygen atom, and L2 may be an alkylene group having 3 or more, 4 or more, or 5 or more carbon atoms. The alkylene group of L2 may have 12 or less, or 8 or less carbon atoms.

[0111] In one example of Chemical Formula 3, L3 and L4 may each independently be an alkylene group having 1 to 4 carbon atoms, n may be a number ranging from 1 to 3 or a number ranging from 1 to 2, or may be 1 or 2, and P2 may be a polymerizable functional group (an acryloyl group or a methacryloyl group), a hydrogen atom, or an alkyl group (e.g., an alkyl group having 1 to 4 carbon atoms). In addition, in the above case, when there are two or more units of [O-L4] in Chemical Formula 3, the number of carbon atoms in the alkylene group or alkylidene group of L4 in each unit may be the same or different.

[0112] In Chemical Formula 4, A3 may be a single bond or an alkylene group having 1 to 4 carbon atoms, L5 may be -C(=O)-O- or -OC(=O)-, A4 may be an oxygen atom, and L6 may be an alkylene group having 3 or more, 4 or more, or 5 or more carbon atoms. The alkylene group of L6 may have 12 or less or 8 or less carbon atoms.

[0113] In Chemical Formula 5, A5 may be an oxygen atom, L7 may be an alkylene group having 1 to 4 carbon atoms, A6 may be a single bond, L8 may be -C(=O)-O- or -OC(=O)-, A7 may be an oxygen atom, and L9 may be an alkylene group having 3 or more, 4 or more, or 5 or more carbon atoms. The alkylene group of L9 may have 12 or less or 8 or less carbon atoms.

[0114] It has been confirmed that the liquid crystal compound can effectively satisfy the desired physical properties (e.g., alignment) due to its unique T-shaped structure and conjugated structure realized mainly through NN bonds.

[0115] The liquid crystal compound as described above is a known compound, and is known, for example, from Korean Patent Publication No. 10-2018-0048837.

[0116] In order to more precisely achieve the desired alignment, the T-type liquid crystal compound may be either (1) a compound within the category of Chemical Formula 1, wherein R2 in Chemical Formula 1 is a substituent of Chemical Formula 2 in which P1 is a hydrogen atom, an alkyl group, or an aryl group, or a substituent of Chemical Formula 3 in which P2 is a hydrogen atom, an alkyl group, or an aryl group (first liquid crystal compound), or (2) a compound within the category of Chemical Formula 1, wherein R2 in Chemical Formula 1 is a substituent of Chemical Formula 2 in which P1 is an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group, or a substituent of Chemical Formula 3 in which P2 is an acryloyl group or a methacryloyl group (first liquid crystal compound).

[0117] When R2 in the first liquid crystal compound is a substituent of Formula 2, P1 in Formula 2 may be a hydrogen atom, an alkyl group, or an aryl group, or a hydrogen atom, an alkyl group, or an alkyl group.

[0118] When R2 in the first liquid crystal compound is a substituent of Formula 3, P2 in Formula 3 may be a hydrogen atom, an alkyl group, or an aryl group, or a hydrogen atom, an alkyl group, or an alkyl group.

[0119] In the first and second liquid crystal compounds, the specific types of substituents and functional groups other than P1 of the substituent in Chemical Formula 2 or P2 of the substituent in Chemical Formula 3 are as described above.

[0120] In one example, Q in Chemical Formula 1 of the first liquid crystal compound may be a sulfur atom, and Q in Chemical Formula 1 of the second liquid crystal compound may be a carbon atom.

[0121] When the first and second liquid crystal compounds are used, the lower limit of the weight ratio of the second liquid crystal compound based on 100 parts by weight of the first liquid crystal compound may be about 1 part by weight, 10 parts by weight, 20 parts by weight, 30 parts by weight, 40 parts by weight, 50 parts by weight, 60 parts by weight, 70 parts by weight, 80 parts by weight, 90 parts by weight, 95 parts by weight, or 100 parts by weight, and the upper limit thereof may be about 1,000 parts by weight, 950 parts by weight, or 1,000 parts by weight. , 900 parts by weight, 850 parts by weight, 800 parts by weight, 750 parts by weight, 700 parts by weight, 650 parts by weight, 600 parts by weight, 550 parts by weight, 500 parts by weight, 450 parts by weight, 400 parts by weight, 350 parts by weight, 300 parts by weight, 250 parts by weight, 200 parts by weight, 150 parts by weight, 140 parts by weight, 130 parts by weight, 120 parts by weight, 110 parts by weight, 105 parts by weight, or 100 parts by weight. The content may be greater than or equal to any one of the lower limits mentioned above; or less than or equal to any one of the upper limits mentioned above; or greater than or equal to any one of the lower limits mentioned above and less than or equal to any one of the upper limits mentioned above.

[0122] If necessary, the liquid crystal layer may contain other types of reverse dispersion liquid crystal compounds or further contain a normal dispersion liquid crystal compound in addition to the T-type liquid crystal compound, and there is no particular limitation on the specific types of other types of liquid crystal compounds that may be contained in such cases.

[0123] Other applicable types of liquid crystal compounds include, but are not limited to, liquid crystal compounds known in the art, such as those disclosed in Korean Patent No. 1729819, Korean Patent No. 1640670, Korean Patent No. 1557202, Korean Patent No. 1472187, Korean Patent No. 1460862, Korean Patent No. 1191124, Korean Patent No. 1191125 and / or Korean Patent No. 1191129.

[0124] The proportion of the positive dispersion liquid crystal compound in the liquid crystal layer can be adjusted within a range that ensures the desired properties. For example, the liquid crystal compound other than the T-type liquid crystal compound may be contained in an amount of more than 0 to 45 parts by weight based on 100 parts by weight of the T-type liquid crystal compound.

[0125] The liquid crystal layer may contain necessary additives in addition to the liquid crystal compound, such as known additives such as initiators, UV stabilizers and / or UV absorbers.

[0126] The thickness of such a liquid crystal layer can be adjusted to exhibit the desired characteristics. For example, if the thickness of the liquid crystal layer is too low, the desired performance may not be achieved even when the liquid crystal compound is used. For example, the lower limit of the thickness of the liquid crystal layer may be about 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 3.9 μm, 4.0 μm, 4.1 μm, or 4.2 μm, and the upper limit may be about 10 μm, 9 μm, 8 μm, 7 μm, 6 μm, 5 μm, 4.9 μm, 4.8 μm, 4.7 μm, 4.6 μm, 4.5 μm, 4.4 μm, 4.3 μm, 4.2 μm, 4.1 μm, or 4 μm. The thickness may be greater than or equal to any one of the lower limits; or may be greater than or equal to any one of the lower limits and less than or equal to any one of the upper limits.

[0127] The optical film may further include other layers as needed, as long as it includes the liquid crystal layer. Examples of such other layers include, but are not limited to, an alignment layer that induces the alignment of the liquid crystal compound, a substrate layer on which the alignment layer or liquid crystal layer is formed, and / or a retardation film or circular polarizer formed to allow circularly polarized light to be incident on the liquid crystal layer.

[0128] The present specification also discloses a method for producing the optical film.

[0129] When the above-mentioned liquid crystal compounds are used to form a geometrically oriented liquid crystal layer, relatively excellent alignment can be obtained. However, it is difficult to obtain the desired alignment by using only the liquid crystal compounds, and the process conditions must be controlled, and in particular, the thickness of the liquid crystal layer must be controlled.

[0130] The liquid crystal layer can be formed by coating a material containing a liquid crystal compound (e.g., a coating liquid) on a liquid crystal alignment surface, aligning the liquid crystal compound, and then curing the liquid crystal compound as needed.

[0131] The method for forming the liquid crystal layer disclosed in this specification can also be applied to the above-mentioned methods, but the thickness of the layer containing the liquid crystal compound must be controlled during the process.

[0132] For example, the method for producing the optical film includes forming a layer of material containing a liquid crystal compound on a liquid crystal alignment surface and geometrically orienting the liquid crystal compound to form a liquid crystal layer.

[0133] In this case, at least the above-mentioned T-type liquid crystal compound is used as the liquid crystal compound.

[0134] In the manufacturing method disclosed in this specification, the thickness of the layer of the material containing the liquid crystal compound or the liquid crystal layer must be controlled in the above process so that T / P in the following formula A falls within a predetermined range. [Formula A] T / P In formula A, T is the thickness of the layer of material containing the liquid crystal compound or the liquid crystal layer, and P is the pitch of the geometric phase alignment.

[0135] In the above, P is the pitch that is maintained constant when the geometric phase orientation is an orientation in which the pitch is maintained constant (such as a geometric phase grating orientation), and is the smallest pitch among the pitches that change when the geometric phase orientation is an orientation in which the pitch changes (such as a geometric phase lens orientation).

[0136] In formula A, the same unit is applied to T and P, for example, μm.

[0137] For example, the upper limit of T / P in Formula A may be about 0.45, 0.43, 0.41, 0.39, 0.37, 0.35, 0.33, 0.31, 0.29, or 0.27, and the lower limit may be about 0.01, 0.03, 0.05, 0.07, 0.09, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, 0.24, 0.26, 0.28, 0.30, 0.32, or 0.34. The T / P may be within a range equal to or less than any one of the upper limits; or may be equal to or greater than any one of the lower limits and equal to or less than any one of the upper limits. If the T / P range is not satisfied, it may be difficult to achieve the desired appropriate orientation.

[0138] There is no particular limitation on the method for adjusting the thickness of the layer of material containing the liquid crystal compound or the liquid crystal layer. For example, when a material such as a coating liquid containing the liquid crystal compound is applied, the thickness of the applied material can be adjusted to ensure the thickness.

[0139] The liquid crystal compound formed as described above can be aligned and then cured to form a liquid crystal layer. In this case, the curing method can be a known method.

[0140] The specific type of liquid crystal alignment surface used is not particularly limited. Various alignment layers for aligning liquid crystal compounds are known, and alignment layers that induce the geometric phase alignment are also known. Therefore, in one example, the liquid crystal alignment surface can be formed by forming the alignment layer on a suitable substrate.

[0141] In some cases, for example, when the desired pitch is relatively small, it may be difficult to form the desired thickness in one step while satisfying the T / P ratio in the above formula A.

[0142] In this case, the liquid crystal layer formation process can be repeated multiple times.

[0143] For example, the method for manufacturing the optical film may include a first step of forming a layer of a material containing the liquid crystal compound on a liquid crystal alignment surface and orienting it to form a first sub-liquid crystal layer; and a second step of forming a layer of a material containing the liquid crystal compound on the first sub-liquid crystal layer and orienting it to form a second sub-liquid crystal layer.

[0144] Even in such a case, at least the T-type liquid crystal compound can be used as the liquid crystal compound.

[0145] In addition, in both the first and second steps, a layer of a material containing the liquid crystal compound or a liquid crystal layer (in this case, the sub-liquid crystal layer) can be formed so that its thickness satisfies the T / P range of the aforementioned formula A.

[0146] In this method, the coating, alignment and optional curing steps are carried out multiple times to form a liquid crystal layer of a desired thickness.

[0147] Accordingly, the method for manufacturing the optical film includes forming a layer of a material containing a liquid crystal compound on a liquid crystal alignment surface, geometrically orienting the liquid crystal compound to form the liquid crystal layer containing the geometrically orientated liquid crystal compound, and the liquid crystal layer can be formed multiple times.

[0148] The second step may be repeated two or more times during the manufacturing process. In this case, the sub-liquid crystal layer may be formed on the sub-liquid crystal layer formed in the second step. In this case, each sub-liquid crystal layer is formed so that T / P in formula A falls within the above-mentioned range.

[0149] There is no particular limit to the number of times the second step may be repeated. For example, the second step may be repeated until the sum of the thicknesses of the formed sub-liquid crystal layers reaches the desired final thickness of the liquid crystal layer.

[0150] The method for forming the liquid crystal layer or sub-liquid crystal layer by coating and aligning the material containing the liquid crystal compound is not particularly limited, and the liquid crystal layer or sub-liquid crystal layer can be formed by a conventional method as long as the thickness of the liquid crystal layer or sub-liquid crystal layer is controlled as described above. In addition, if necessary, each step of forming the liquid crystal layer or sub-liquid crystal layer may be followed by a step of fixing the alignment of the liquid crystal compound through polymerization or curing.

[0151] The present application also relates to an optical device including the optical film. The specific type of the optical device is not particularly limited, and may be various types of optical devices that require a geometric phase lens and / or a geometric phase grating.

[0152] Representative examples of such optical devices include so-called VR (Virtual Reality) displays, AR (Augmented Reality) displays, and MR (Mixed Reality) displays, and therefore the optical device may be or be part of the VR (Virtual Reality) display, AR (Augmented Reality) display, or MR (Mixed Reality) display.

[0153] The method for constructing the optical device using the optical film of the present application is not particularly limited, and the optical device can be constructed by a known method as long as the optical film is applied.

[0154] Furthermore, the specific type of the optical device is not limited to the VR (Virtual Reality) display, AR (Augmented Reality) display, or MR (Mixed Reality) display, and the optical film can be applied to various types of optical devices that require a geometric phase lens and / or a geometric phase grating. [Effects of the Invention]

[0155] This specification discloses a geometric phase optical element, its manufacturing method, and its uses. This specification discloses a geometric phase optical element that has no or very little wavelength dependency, its manufacturing method, and its uses. This specification discloses a geometric phase optical element that has no or little wavelength dependency by using a liquid crystal compound with a specific structure, controlling the thickness of the liquid crystal layer, and adjusting the manufacturing method, as well as a manufacturing method and its uses. [Brief explanation of the drawings]

[0156] [Figure 1] FIG. 1 is an exemplary diagram for explaining a geometric phase lens orientation. [Figure 2] FIG. 1 is an exemplary diagram for explaining a geometric phase lens orientation. [Figure 3] FIG. 1 is an exemplary diagram for explaining a geometric phase lens orientation. [Figure 4] FIG. 1 is an exemplary diagram for explaining a geometric phase grating orientation. [Figure 5] FIG. 1 is an exemplary diagram for explaining a geometric phase grating orientation. [Figure 6] FIG. 1 is an exemplary diagram for explaining a geometric phase grating orientation. [Figure 7] 10A and 10B are exemplary diagrams for explaining rectilinear light transmittance and the like. [Figure 8] 1 is a polarizing microscope photograph of the geometric phase orientation of Example 1. [Figure 9] 1 is a polarizing microscope photograph of the geometric phase orientation of Example 2. [Figure 10] 1 is a polarizing microscope photograph of the geometric phase orientation of Example 3. [Figure 11] 1 is a polarizing microscope photograph of the geometric phase orientation of Comparative Example 1. [Figure 12] 1 is a polarizing microscope photograph of the geometric phase orientation of Comparative Example 2. [Figure 13] 1 is a polarizing microscope photograph of the geometric phase orientation of Comparative Example 3. [Figure 14] 1 is a polarizing microscope photograph of the geometric phase orientation of Comparative Example 4. [Figure 15] 1 is a polarizing microscope photograph of the geometric phase orientation of Comparative Example 5. [Figure 16] 1 is a polarizing microscope photograph of the geometric phase orientation of Comparative Example 6. [Figure 17] 1 is a polarizing microscope photograph of the geometric phase orientation of Comparative Example 7. [Figure 18] 1 is a polarizing microscope photograph of the geometric phase orientation of Comparative Example 8. [Figure 19] 1 is a polarizing microscope photograph of the geometric phase orientation of Comparative Example 9. [Figure 20] 1 is a polarizing microscope photograph of the geometric phase orientation of Comparative Example 10. [Figure 21] 1 shows the results of evaluating the diffraction efficiency of the optical film of Example 1. [Figure 22] 1 shows the results of evaluating the diffraction efficiency of the optical film of Example 2. [Figure 23] 10 shows the results of evaluating the diffraction efficiency of the optical film of Example 3. [Figure 24] 10 shows the results of evaluating the diffraction efficiency of the optical film of Comparative Example 8. [Figure 25] 10 shows the results of evaluating the diffraction efficiency of the optical film of Comparative Example 9. [Figure 26] 10 shows the results of evaluating the diffraction efficiency of the optical film of Comparative Example 10. [Figure 27] 1 shows the results of evaluating the diffraction efficiency of the optical film of Example 1. [Figure 28] 1 shows the results of evaluating the diffraction efficiency of the optical film of Example 2. [Figure 29] 10 shows the results of evaluating the diffraction efficiency of the optical film of Example 3. [Figure 30] 10 shows the results of evaluating the diffraction efficiency of the optical film of Comparative Example 8. [Figure 31] 10 shows the results of evaluating the diffraction efficiency of the optical film of Comparative Example 9. [Figure 32] 10 shows the results of evaluating the diffraction efficiency of the optical film of Comparative Example 10. DETAILED DESCRIPTION OF THE INVENTION

[0157] The present application will be described in detail below through examples and comparative examples, but the scope of the present application is not limited to the transmittance variable device described below.

[0158] Production example 1. A reactive liquid crystal compound having the structure of the following chemical formula A and a reactive liquid crystal compound having the structure of the following chemical formula B were used. [Chemical formula A] [ka] [Chemical formula B] [ka]

[0159] The reactive compound is a T-shaped reactive mesogen, as disclosed in Korean Patent Publication No. 10-2018-0048837, and can be obtained from DIC or synthesized using the method described in the publication. A mixed solvent was prepared by mixing toluene (Tol) and BC (butyl carboxylate) in a weight ratio of 8:2 (Tol:BC), and the reactive liquid crystal compounds of Formulas A and B were added to the mixed solvent. The weight ratio (A:B) of the reactive liquid crystal compounds of Formulas A and B was 1:1, and the weight ratio (solvent:liquid crystal) of the mixed solvent to the reactive liquid crystal compounds was 7:3. Next, approximately 5 parts by weight of an initiator (Irgacure 819, Ciba) was mixed with 100 parts by weight of the reactive liquid crystal compound to prepare coating solution A.

[0160] Production example 2. A coating liquid (coating liquid B) was prepared in the same manner as in Example 1, except that the weight ratio of the mixed solvent to the reactive liquid crystal compound (solvent:liquid crystal) was 91:9.

[0161] Example 1 Isotropic alkali-free glass (thickness: approximately 0.7 mm) was used as the substrate. To form an alignment layer on the substrate, an alignment layer coating solution (Nissan, Small A-LC) was bar-coated and dried at approximately 65°C for approximately 4 minutes to form a layer (thickness: approximately 180-200 nm). Next, an alignment treatment was performed on the layer of alignment layer coating solution to form an alignment layer. The alignment treatment involved laser pattern exposure to induce the alignment of a geometric phase grating. The laser pattern exposure was performed by overlapping rectilinear light and diffused light. The alignment treatment was performed using the method described in the literature (Optics Express Vol. 27, Issue 3, pp. 2632-2642 (2019)), and an alignment treatment was performed that allowed the formation of a geometric phase grating with a pitch of approximately 15 μm.

[0162] The coating solution A of Preparation Example 1 was coated on the alignment film by bar coating, and then maintained at about 100°C for about 2 minutes, followed by cooling (about 40°C) to align the liquid crystal compound. Then, ultraviolet rays of about 100 mJ / cm were applied using a Fusion UV system under a nitrogen atmosphere. 2 The liquid crystal layer was irradiated with a light intensity of 1000 uV, forming a liquid crystal layer (geometric phase grating) with a thickness of approximately 4 μm. Figure 8 shows the results of observing the orientation of the geometric phase grating of the liquid crystal compound using a polarizing microscope. The polarizing microscope images were taken at a magnification of 50x using equipment (Olympus, BX53M). Figure 8 confirms that a geometric phase grating with a pitch of approximately 15.84 μm was formed through efficient orientation.

[0163] Example 2 A geometric phase grating was formed in the same manner as in Example 1, except that the coating thickness of Coating Solution A of Preparation Example 1 was adjusted so that a liquid crystal layer (geometric phase grating) with a final thickness of approximately 4.3 μm was formed on the alignment film. Figure 9 shows the results of observing the alignment of the geometric phase grating using a polarizing microscope, as in Example 1. From Figure 9, it can be seen that a geometric phase grating with a pitch of approximately 15.40 μm was formed through efficient alignment.

[0164] Example 3 The same isotropic alkali-free glass (thickness: approximately 0.7 mm) as in Example 1 was used as the substrate. To form an alignment layer on the substrate, an alignment layer coating liquid (Nissan, Small A-LC) was bar-coated and dried at approximately 65°C for approximately 4 minutes to form a layer (thickness: approximately 180 to 200 nm). Next, an alignment treatment was performed on the layer of alignment layer coating liquid to form an alignment layer. The alignment treatment involved laser pattern exposure to induce the alignment of the geometric phase lens. The laser pattern exposure was performed by overlapping rectilinear light and diffused light. The alignment treatment was performed using the method described in the literature (Optics Express Vol. 27, Issue 3, pp. 2632-2642 (2019)), and was capable of forming geometric phase lenses with a pitch in the edge region of approximately 1.7 μm.

[0165] The coating solution B of Preparation Example 2 was coated on the alignment film to a thickness of about 0.6 μm using a spin coating method (3,000 rpm), and then maintained at about 100°C for about 2 minutes, followed by cooling (about 40°C) to align the liquid crystal compound. Then, ultraviolet rays of about 100 mJ / cm were applied using a Fusion UV system under a nitrogen atmosphere. 2 Next, coating solution B was coated on the first liquid crystal layer in the same manner as above to a thickness of about 0.6 μm, and then the coating was maintained at about 100°C for about 2 minutes, cooled (to about 40°C), and then irradiated with ultraviolet light (about 100 mJ / cm) using a Fusion UV system under a nitrogen atmosphere. 2 ) was repeated seven times to form a liquid crystal layer (geometric phase lens) with a final thickness of about 4.8 μm. FIG. 10 shows the results of observing the alignment of the edge regions of the geometric phase lens using a polarizing microscope (Olympus, BX53M) (magnification: 100x), as in Example 1. From FIG. 10, it can be seen that geometric phase lenses with an edge region pitch of about 1.67 to 1.76 μm were formed through efficient alignment.

[0166] Comparative Example 1 An alignment film was formed in the same manner as in Example 3 on the same isotropic alkali-free glass substrate (thickness: about 0.7 mm) as in Example 1.

[0167] Next, a liquid crystal layer was formed on the alignment film. The coating solution used to form the liquid crystal layer was a coating solution (Merck, M2032) containing an H-shaped reactive mesogen obtained from Merck. The coating solution was coated onto the alignment film to a thickness of approximately 0.9 μm using a bar coating method, maintained at approximately 100°C for approximately 2 minutes, and then cooled (to approximately 40°C) to align the liquid crystal compound. Figure 11 shows the alignment observed using a polarizing microscope (Olympus, BX53M) (magnification: 100x). Figure 11 shows that alignment was not effective when an H-shaped reactive mesogen was used.

[0168] Comparative Example 2 The same process as in Comparative Example 1 was carried out, except that the coating thickness was adjusted to about 0.6 μm. Figure 12 shows the alignment observed through a polarizing microscope. From Figure 12, it can be seen that when an H-shaped reactive mesogen is used, alignment is not effectively achieved even when the thickness is further reduced.

[0169] Comparative Example 3 The substrate used was the same isotropic alkali-free glass (thickness: approximately 0.7 mm) as in Example 1. An alignment film was formed on the substrate in the same manner as in Example 1, so that a geometric phase grating with a pitch of approximately 2.5 μm could be formed.

[0170] The coating solution used in Comparative Example 1 was coated on the alignment film to a thickness of about 0.6 μm using a bar coating method, and then the liquid crystal compound was aligned by maintaining the temperature at about 100°C for about 2 minutes and then cooling (to about 40°C). Then, ultraviolet rays of about 100 mJ / cm were applied using a fusion UV system under a nitrogen atmosphere. 2 A primary liquid crystal layer was formed by irradiating the liquid crystal layer with a light intensity of 1000 nm (first process). The alignment of the liquid crystal compound was confirmed during the first process, and it was confirmed that the alignment of the liquid crystal compound was achieved in the first process. Next, a coating liquid was further coated on the primary liquid crystal layer in the same manner as the first process to a thickness of about 0.6 μm, and the alignment was confirmed after the alignment process. Figure 13 shows the result, and it can be confirmed that the alignment of the liquid crystal compound was not achieved effectively in this case.

[0171] Comparative Example 4 The same isotropic alkali-free glass (thickness: about 0.7 mm) as in Example 1 was used as the substrate, and an alignment film was formed in the same manner as in Comparative Example 3.

[0172] The coating solution used in Comparative Example 1 was coated on the alignment film to a thickness of about 1.2 μm using a bar coating method, and then maintained at about 100°C for about 2 minutes, followed by cooling (about 40°C) to align the liquid crystal compound. Then, ultraviolet rays of about 100 mJ / cm were applied using a fusion UV system under a nitrogen atmosphere. 2 The alignment of the liquid crystal compound was confirmed in the above process, as shown in Figure 14. In this case, it was confirmed that the alignment of the liquid crystal compound was not performed effectively.

[0173] Comparative Example 5 The same isotropic alkali-free glass (thickness: about 0.7 mm) as in Example 1 was used as the substrate, and an alignment film was formed in the same manner as in Example 1.

[0174] The coating solution used in Comparative Example 1 was coated on the alignment film to a thickness of about 1.6 μm using a bar coating method, and then the coating was maintained at about 100°C for about 2 minutes, followed by cooling (about 40°C) to align the liquid crystal compound. Then, ultraviolet rays of about 100 mJ / cm were applied using a fusion UV system under a nitrogen atmosphere. 2 The alignment of the liquid crystal compound was confirmed in the above process, as shown in Figure 15. In this case, it was confirmed that the alignment of the liquid crystal compound was not performed effectively.

[0175] Comparative Example 6 The same isotropic alkali-free glass (thickness: about 0.7 mm) as in Example 1 was used as the substrate, and an alignment film was formed in the same manner as in Example 1.

[0176] The coating solution used in Comparative Example 1 was coated on the alignment film to a thickness of about 1.2 μm using a bar coating method, and then maintained at about 100°C for about 2 minutes, followed by cooling (about 40°C) to align the liquid crystal compound. Then, ultraviolet rays of about 100 mJ / cm were applied using a fusion UV system under a nitrogen atmosphere. 2 The alignment of the liquid crystal compound was confirmed in the above process, as shown in Figure 16. In this case, it was confirmed that the alignment of the liquid crystal compound was not performed effectively.

[0177] Comparative Example 7 The substrate was the same isotropic alkali-free glass (thickness: about 0.7 mm) as in Example 1. An alignment layer was formed on the substrate in the same manner as in Example 1, so that a geometric phase grating with a pitch of about 2.5 μm could be formed. Coating solution B of Preparation Example 2 was coated on the alignment layer in the same manner as in Example 3 to a thickness of about 1.2 μm, and then maintained at about 100°C for about 2 minutes, followed by cooling (about 40°C) to align the liquid crystal compound. UV rays of about 100 mJ / cm were applied using a Fusion UV system in a nitrogen atmosphere. 2The alignment of the liquid crystal compound was confirmed in the above process, as shown in Figure 17. In this case, it was confirmed that the alignment of the liquid crystal compound was not performed effectively.

[0178] Comparative Example 8 An alignment layer was formed on a substrate in the same manner as in Example 1. Coating solution A of Preparation Example 1 was coated on the alignment layer in the same manner as in Example 1, and then the coating solution was maintained at about 100°C for about 2 minutes, followed by cooling (to about 40°C) to align the liquid crystal compound. After that, ultraviolet light of about 100 mJ / cm was applied using a Fusion UV system in a nitrogen atmosphere. 2 A liquid crystal layer (geometric phase grating) with a thickness of about 1.6 μm was formed by irradiating the liquid crystal compound with a light intensity of about 14.96 μm. Figure 18 shows the results of confirming the alignment of the liquid crystal compound, and it can be seen from Figure 18 that a geometric phase grating with a pitch of about 14.96 μm was formed through efficient alignment.

[0179] Comparative Example 9 An alignment layer was formed on a substrate in the same manner as in Example 1. Coating solution A of Preparation Example 1 was coated on the alignment layer in the same manner as in Example 1, and then the coating solution was maintained at about 100°C for about 2 minutes, followed by cooling (to about 40°C) to align the liquid crystal compound. After that, ultraviolet light of about 100 mJ / cm was applied using a Fusion UV system in a nitrogen atmosphere. 2 A liquid crystal layer (geometric phase grating) with a thickness of about 2.4 μm was formed by irradiating the liquid crystal compound with a light intensity of about 15.40 μm. Figure 19 shows the alignment of the liquid crystal compound, and it can be seen from Figure 19 that a geometric phase grating with a pitch of about 15.40 μm was formed through efficient alignment.

[0180] Comparative Example 10 An alignment layer was formed on a substrate in the same manner as in Example 1. Coating solution A of Preparation Example 1 was coated on the alignment layer in the same manner as in Example 1, and then the coating solution was maintained at about 100°C for about 2 minutes, followed by cooling (to about 40°C) to align the liquid crystal compound. After that, ultraviolet light of about 100 mJ / cm was applied using a Fusion UV system in a nitrogen atmosphere.2 A liquid crystal layer (geometric phase grating) with a thickness of about 3.1 μm was formed by irradiating the liquid crystal compound with a light intensity of about 15.40 μm. Figure 20 shows the alignment of the liquid crystal compound, and it can be seen from Figure 20 that a geometric phase grating with a pitch of about 15.40 μm was formed through efficient alignment.

[0181] Test Example 1. Evaluation of R(450) / R(550) The sample for evaluation of R(450) / R(550) was prepared as follows. An alignment film coating solution (Nissan, Small A-LC) was bar-coated onto isotropic alkali-free glass (thickness: about 0.7 mm) and dried at about 65°C for about 4 minutes to form a layer with a thickness of about 2 μm. Next, linearly polarized ultraviolet light was irradiated onto the layer using a WGP (Wire Grid Polarizer) (Fusion UV System, 100 mJ / cm). 2 ) to form an alignment film.

[0182] The coating solutions of Preparation Examples 1 and 2 were applied to the alignment film in the same manner as in Example 1 to form a liquid crystal layer.

[0183] The liquid crystal layer was measured for R(450) and R(550) using an in-plane retardation measuring device (Axoscan device) to evaluate R(450) / R(550).

[0184] As a result of checking using the above method, the R(450) / R(550) of the liquid crystal layer formed with Coating Solution A of Preparation Example 1 was approximately 0.79, and the R(450) / R(550) of the liquid crystal layer formed with Coating Solution B of Preparation Example 3 was approximately 0.79. Furthermore, when a coating solution containing an H-type reactive liquid crystal compound obtained from Merck was used in the comparative example, the R(450) / R(550) was approximately 0.73.

[0185] Test Example 2: Evaluation of Straight Light Transmittance Spectrum The transmittance spectrum of unpolarized light in the optical films of the examples and comparative examples was evaluated as follows: Unpolarized light was irradiated onto the liquid crystal layer of the optical film using an Ocean Optics spectrometer (HR4000), and the transmittance of unpolarized light was evaluated to confirm the spectrum.

[0186] As shown in FIG. 7, the liquid crystal layer 100 is irradiated with non-polarized light L1 according to wavelength in a direction parallel to the normal direction thereof, and the linear light L E1 When evaluating the transmittance, the distance between the light source irradiating the light L1 and the liquid crystal layer 100 was about 20 mm, and the transmittance of the linear light LE1 was measured at a distance of 100 mm from the liquid crystal layer 100 using a detector with a light receiving portion having a diameter of 1 mm.

[0187] 21 to 23 show the evaluation results for Examples 1 to 3, respectively, and Figs. 24 to 26 show the results for Comparative Examples 8 to 10, respectively. The evaluation was not carried out for Comparative Examples 1 to 7, in which the liquid crystal compound was not properly aligned. In Figs. 21 to 26, the x-axis represents wavelength, and the y-axis represents rectilinear light transmittance.

[0188] Table 1 below summarizes the transmittance and intensity of the straight light when the above method is applied. In Table 1 below, transmittance is the transmittance of the straight light for each reference wavelength, and the unit is %, and intensity is the intensity of the straight light for each reference wavelength.

[0189] [Table 1]

[0190] Test Example 3: Evaluation of the intensity spectrum of straight light The intensity spectrum of straight-traveling right-circularly polarized light for the optical films of the Examples and Comparative Examples was evaluated using the following method. Right-circularly polarized light was irradiated onto the liquid crystal layer of the optical film using a spectrometer from AxoScan, and the intensity of the straight-traveling light (unit: cd) was measured to confirm the spectrum. This method was the same as in Test Example 1, except that the irradiated light was changed from unpolarized to right-circularly polarized.

[0191] 27 to 29 show the evaluation results for Examples 1 to 3, respectively, and Figs. 30 to 32 show the results for Comparative Examples 8 to 10, respectively. The evaluation was not carried out for Comparative Examples 1 to 7, in which the liquid crystal compound was not properly aligned. In Figs. 27 to 32, the x-axis represents the wavelength, and the y-axis represents the intensity of the rectilinear light.

[0192] Table 2 below summarizes the transmittance and intensity of the straight light when the above method is applied. In Table 2 below, transmittance is the transmittance of the straight light for each reference wavelength, and the unit is %, and intensity is the intensity of the straight light for each reference wavelength.

[0193] [Table 2]

Claims

1. A liquid crystal layer including a T-type liquid crystal compound aligned in a geometric phase, The liquid crystal layer is an optical film that satisfies at least one of the conditions of the following formula 1 and the conditions of the following formula 2: [Formula 1] T ａｖｇ ≤ 5% and S.D. Ｔ ≦1.5 [Formula 2] I ａｖｇ ≦0.1 cd and SD Ｉ ≦0.025 T in Equation 1 ａｖｇ Is T Ｂ , T Ｇ and T Ｒ is the mean and SD Ｔ is the T Ｂ , T Ｇ and T Ｒ is the standard deviation of the T Ｂ is the transmittance of unpolarized light of 450 nm wavelength traveling straight through the liquid crystal layer, and T Ｇ is the transmittance of unpolarized light of 550 nm wavelength traveling straight through the liquid crystal layer, and T Ｒ is the transmittance of unpolarized light of 610 nm wavelength traveling straight through the liquid crystal layer, and I ａｖｇ I Ｂ , I Ｇ and I Ｒ is the mean and SD Ｉ is the above I Ｂ , I Ｇ and I Ｒ is the standard deviation of I Ｂ is the intensity of 450 nm wavelength circularly polarized light traveling straight through the liquid crystal layer, and I Ｇ is the intensity of circularly polarized light of 550 nm wavelength traveling straight through the liquid crystal layer, and I Ｒ is the intensity of circularly polarized light of 610 nm wavelength traveling straight through the liquid crystal layer.

2. The optical film according to claim 1 , wherein the liquid crystal layer satisfies both the conditions of formula 1 and formula 2.

3. The optical film according to claim 1 , wherein the liquid crystal layer satisfies the following formula 3: [Formula 3] ΔF1 and ΔF2≦30% In Equation 3, ΔF1 is the absolute value of F1 according to Equation 4 below, and ΔF2 is the absolute value of F2 according to Equation 5 below: [Formula 4] F1=100×(θ) Ｒ -θ Ｇ ) / θ Ｇ [Formula 5] F2 = 100 × (θ) Ｂ -θ Ｇ ) / θ Ｇ In Equations 4 and 5, θ Ｒ is the refraction angle in the region that satisfies the following formula 6, and θ Ｇ is the refraction angle in the region that satisfies the following formula 7, and θ Ｂ is the refraction angle in the region that satisfies the following formula 8, [Formula 6] synth Ｒ =610 / L [Formula 7] synth Ｇ =550 / L [Formula 8] sinθB=450 / Λ In Equations 6 to 8, Λ is the pitch (unit: nm) of the geometric phase orientation of the region.

4. 2. The optical film according to claim 1, wherein the T-type liquid crystal compound is oriented in a geometric phase lens orientation having an azimuth angle that changes along at least one of the plane directions of the liquid crystal layer so as to satisfy the following formula 9: [Formula 9] θ(r)={π×r ２ } / {2×f×λ} In Equation 9, θ(r) is the azimuthal angle of the T-type liquid crystal compound in a region of the liquid crystal layer spaced a distance r (unit: mm) from the center of the geometric phase lens orientation, where r is the distance, f is the focal length of the geometric phase lens orientation, and λ is the wavelength of the incident light.

5. The optical film of claim 4 , wherein the azimuthal variation in the geometric phase lens orientation appears radial.

6. 2. The optical film according to claim 1, wherein the orientation of the T-type liquid crystal compound is such that the orientation has an azimuth angle that varies along any one of the plane directions of the liquid crystal layer, and the pitch defined by the varying azimuth angle is a geometric phase grating orientation in which the pitch is constant.

7. The optical film according to claim 6 , wherein the azimuthal angle is maintained along a plane direction perpendicular to one direction in which the azimuthal angle changes in the geometric phase grating orientation.

8. 7. The optical film of claim 6, wherein the pitch defined by the varying azimuthal angles is in the range of 0.1 μm to 20 μm.

9. The optical film according to claim 1 , wherein the liquid crystal layer has a thickness of 3.5 μm or more.

10. 2. The optical film according to claim 1, wherein the T-type liquid crystal compound has an in-plane retardation (R(450)) for light with a wavelength of 450 nm to an in-plane retardation (R(550)) for light with a wavelength of 550 nm, such that the ratio (R(450) / R(550)) is in the range of 0.6 to 0.

99.

11. 2. The optical film of claim 1, wherein the T-type liquid crystal compound is represented by the following chemical formula 1: [Chemical formula 1] 【Chemical 1】 In Chemical Formula 1, Q is a carbon atom or a sulfur atom, and when Q is a sulfur atom, R ２ and R ３ does not exist, R １１ ~R １４ and R ３ ~R ５ are each independently a hydrogen atom, an alkyl group, an alkoxy group, a cyano group, or a halogen atom, R ２ is a substituent of the following chemical formula 2 or 3, R ６１ ~R ６５ are each independently a hydrogen atom, an alkyl group, an alkoxy group, a cyano group, a halogen atom, a substituent of the following chemical formula 4, or a substituent of the following chemical formula 5, and R ６１ ~R ６５ At least two of the groups are substituents of the following Chemical Formula 4 or the following Chemical Formula 5: [Chemical formula 2] 【Chemistry 2】 In Chemical Formula 2, A １ and A ２ are each independently an oxygen atom or a single bond, and L １ and L ２ are each independently —C(═O)—O—, —O—C(═O)—, an alkylene group or an alkylidene group, Cy is an arylene group or a cycloalkylene group, P １ is a hydrogen atom, an alkyl group, an aryl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group: [Chemical formula 3] 【Chemistry 3】 In Chemical Formula 3, L ３ and L ４ are each independently an alkylene group or an alkylidene group, and P ２ is a hydrogen atom, an alkyl group, an aryl group, an acryloyl group, or a methacryloyl group, and n is a number in the range of 1 to 10: [Chemical formula 4] 【Chemistry 4】 In Chemical Formula 4, A ３ and A ４ are each independently an oxygen atom, an alkylene group, an alkylidene group, or a single bond; L ５ and L ６ are each independently —C(═O)—O—, —O—C(═O)—, an alkylene group or an alkylidene group, Cy is an arylene group or a cycloalkylene group, P ３ is a hydrogen atom, an alkyl group, an aryl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group: [Chemical formula 5] 【Chemistry 5】 In Chemical Formula 5, A ５ , A ６ and A ７ are each independently an oxygen atom or a single bond, and L ７ , L ８ and L ９ are each independently —C(═O)—O—, —O—C(═O)—, an alkylidene group, or an alkylene group; one of Cy1 and Cy2 is a cycloalkylene group, and the other is an arylene group; P ４ is a hydrogen atom, an alkyl group, an aryl group, an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group.

12. The T-type liquid crystal compound is In Chemical Formula 1, R ２ But, P １ is a hydrogen atom, an alkyl group, or an aryl group; or P ２ is a hydrogen atom, an alkyl group, or an aryl group; In Chemical Formula 1, R ２ But, P １ is a substituent of Chemical Formula 2 which is an acryloyl group, a methacryloyl group, an acryloyloxy group, or a methacryloyloxy group, or P ２ and a compound of Chemical Formula 3, wherein is an acryloyl group or a methacryloyl group.

13. 1. A method for manufacturing an optical film, comprising the steps of forming a layer of a material containing a liquid crystal compound on a liquid crystal alignment surface, and geometrically orienting the liquid crystal compound to form a liquid crystal layer, the liquid crystal compound is a T-type liquid crystal compound, A method for producing an optical film, wherein the layer of the material containing the liquid crystal compound or the liquid crystal layer is formed so that the thickness satisfies the following formula 10: [Formula 10] T / P≦0.45 In Equation 10, T is the thickness of the layer of material containing the liquid crystal compound or the liquid crystal layer, and P is the pitch of the geometric phase alignment.

14. 1. A method for manufacturing an optical film, comprising the steps of forming a layer of a material containing a liquid crystal compound on a liquid crystal alignment surface, and geometrically orienting the liquid crystal compound to form a liquid crystal layer, a first step of forming a layer of a material containing the liquid crystal compound on the liquid crystal alignment surface and aligning the layer to form a first sub-liquid crystal layer; and a second step of forming a layer of a material containing the liquid crystal compound on the first sub-liquid crystal layer and aligning the layer to form a second sub-liquid crystal layer; the liquid crystal compound is a T-type liquid crystal compound, a method for manufacturing an optical film, wherein the layer of the material containing the liquid crystal compound, the first sub-liquid crystal layer, or the second sub-liquid crystal layer is formed in the first and second steps so that the thickness satisfies the following formula 10: [Formula 10] T / P≦0.45 In Equation 10, T is the thickness of the layer of the material containing the liquid crystal compound, the first sub-liquid crystal layer, or the second sub-liquid crystal layer, and P is the pitch of the geometric phase alignment.

15. The method of claim 14, wherein the second step is repeated two or more times.

16. An optical device comprising the optical film of any one of claims 1 to 12.

17. 17. The optical device of claim 16, which is or is part of a virtual reality display, an augmented reality display or a mixed reality display.

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