KR20170040563A

KR20170040563A - Optical Film

Info

Publication number: KR20170040563A
Application number: KR1020150139698A
Authority: KR
Inventors: 김신영; 벨리아에프 세르게이; 이지연; 박문수
Original assignee: 주식회사 엘지화학
Priority date: 2015-10-05
Filing date: 2015-10-05
Publication date: 2017-04-13
Also published as: KR102034462B1

Abstract

The present invention relates to an optical film and a usage of the optical film. Provided is the optical film which can represent selective transmission and blocking properties according to a viewing angle. The optical film can be easily used for a security film of a display apparatus like LCD, a smart window, sunglasses, and so on. The optical film comprises: a first linear polarizer; and first and second liquid crystal films including a liquid crystal compound sequentially formed in an upper part of the first linear polarizer, and aligned with linear spray.

Description

Optical Film {Optical Film}

This application relates to the use of optical films and optical films.

The use of security films is increasing with the importance of information protection or personal privacy. For example, Patent Document 1 discloses a security film using micro Louver technology. The micro-louver film has a structure in which a plurality of micro-louvers are patterned at regular intervals. A plurality of micro-louvers formed in the louver film exerts an effect (direction control effect) of controlling the traveling direction of light passing through the louver film to a predetermined flow-out angle range. Therefore, it is possible to prevent unnecessary outflow of light transmitted through the liquid crystal panel in the lateral direction, and such a louver film is also referred to as a light control film. However, the aspect ratio of micro-louver film is a major factor of the security film performance. As the line width increases, the height can be reduced. However, the larger the line width, the lower the transmittance.

Patent Document 1: Korean Published Patent Application No. 2007-0090662

The present application provides uses of optical films and optical films.

The present application relates to optical films. An exemplary optical film includes a first linear polarizer, a first liquid crystal film, and a second liquid crystal film. The first liquid crystal film and the second liquid crystal film may be sequentially formed on the first linear polarizer. Further, the first liquid crystal film and the second liquid crystal film may each comprise a spray-aligned liquid crystal compound. In one example, the liquid crystal compounds in the first liquid crystal film and the second liquid crystal film may each be present in a linear spray orientation. Fig. 1 exemplarily shows an optical film having a structure in which a first linear polarizer 101, a first liquid crystal film 102 and a second liquid crystal film 103 are sequentially formed.

As used herein, the term " polarizer " means a functional layer that exhibits selective transmission and blocking characteristics, e.g., reflection or absorption characteristics, with respect to incident light. For example, the polarizer may have a function to transmit light that vibrates in one direction from incident light that vibrates in various directions, and to block light that vibrates in the other direction. In the present specification, the term " linear polarizer " means a linearly polarized light in which the light selectively transmitted is oscillated in one direction and the light selectively blocked is linearly polarized light oscillating in a direction perpendicular to the oscillation direction of the linearly polarized light. Examples of the polarizer include a dual brightness enhancement film (DBEF), a lyotropic liquid crystal (LLC layer), and a wire grid polarizer. Polarizers in which iodine is immobilized on a polymeric stretched film such as a PVA stretched film or a liquid crystal polymerized in an oriented state are used as the absorptive polarizers and anisotropic Guest-host polarizers with dyes as guest may be used, but are not limited thereto.

The term " spray orientation " as used herein means an alignment state in which the tilt angle of the liquid crystal compound present in the liquid crystal film changes gradually along the thickness direction of the liquid crystal film. In the present specification, the term " tilt angle " means the minimum angle formed by the optical axis of the liquid crystal compound and the surface of the liquid crystal film. In the present specification, the term " average tilt angle " means the tilt angle when the average value of the tilt angle of the whole liquid crystal compound or the total arrangement of liquid crystal compounds is converted into an average value. The term " optical axis " in this specification means a rod-shaped long axis in the case of a rod-shaped liquid crystal compound and an axis in the normal direction of the circular plate plane in the case where the liquid crystal compound is in a discotic form. Therefore, in the present specification, "the liquid crystal film includes a spray-aligned liquid crystal compound" means that the long axis direction gradually changes in accordance with the thickness direction of the liquid crystal film when the liquid crystal compound has a rod shape, Shape means that the normal direction of the plane of the disk gradually changes along the thickness direction of the liquid crystal film.

In one example, the spray orientation is, for example, within a range in which the minimum tilt angle of the liquid crystal compound in the liquid crystal film is within the range of about 0 to 20 degrees, and within a range of about 70 to 90 degrees of the maximum tilt angle, It may mean an alignment state that gradually changes in accordance with the thickness direction of the liquid crystal film.

The spray orientation can be divided into a linear spray orientation and a non-linear spray orientation. In the present specification, the term " linear spray orientation " refers to an orientation state in which the graph shown with the thickness of the liquid crystal film as x-axis and the local tilt angle corresponding to the thickness as y- , I.e., an orientation state in which the slope thereof is constant. In one example, the linear spray orientation is such that the ratio (z / d) of the thickness (z) to the total thickness (d) of the liquid crystal film is taken as the x axis (that is, x = 0 to 1.0) (B) of the minimum tilt angle and the maximum tilt angle in the y-axis is the same as the interval (a) in the range of x = 0 to 1.0, and the slope of the graph shown in FIG. May refer to an orientation state in which a constant orientation state, for example, an average tilt factor is in the range of about 0.95 to 1.05 (see graph A in FIG. 24).

Alternatively, the term " non-linear spray orientation " is used herein to mean an orientation state in which the graph shown by the thickness of the liquid crystal film on the x-axis and the local tilt angle corresponding to the thickness on the y- , I.e., an orientation state in which the slope thereof changes with the thickness of the liquid crystal film. In one example, the non-linear spray orientation may mean an orientation state in which the slope of the tilt angle relative to the thickness of the liquid crystal film gradually increases or gradually decreases. In one example, the non-linear spray orientation corresponds to the thickness (x = 0 to 1.0) with the ratio (z / d) of the corresponding thickness z to the total thickness d of the liquid crystal film as x axis (B) of the minimum tilt angle and the maximum tilt angle in the y-axis is the same as the interval (a) in the range of x = 0 to 1.0, and the slope of the graph shown in FIG. (See graph B in FIG. 24) or gradually increase along the x-axis, but with an average tilt factor of greater than about 1.05, meaning that the average tilt factor is less than about 0.95 (See graph C in Fig. 24).

As used herein, the tilt factor may be a derived tilt factor value obtained by measuring the phase difference of the film at different angles using Axoscan (Axometrix). The tilt factor of the spray alignment liquid crystal film can be controlled by adjusting the process temperature during the production of the spray alignment liquid crystal film. In one example, a spray-aligned liquid crystal film can be prepared by curing a layer of a known spray-oriented liquid crystal composition. The curing can be performed by irradiating ultraviolet rays to the layer of the spray orientation liquid crystal composition, and the tilt factor of the spray alignment liquid crystal film can be controlled by adjusting the temperature at the time of irradiation of the ultraviolet rays. For example, the higher the temperature at the time of ultraviolet irradiation, the more the tilt factor tends to rise.

When the first and second liquid crystal films each include a linear spray-aligned liquid crystal compound, it is advantageous that the optical film exhibits a selective transmittance different from the viewing angle. The method of forming the linear spray-aligned liquid crystal film is not particularly limited and can be formed, for example, by irradiating ultraviolet rays and curing while keeping the layer of the spray-oriented liquid crystal composition known in the art at an appropriate temperature.

The thickness of the first and / or second liquid crystal films can be appropriately adjusted in consideration of the refractive index anisotropy of the spray alignment liquid crystal, the retardation value of the liquid crystal film, and the aspect of forming a uniform coating. For example, the first and second liquid crystal films may each have a thickness of from about 0.1 탆 to about 5 탆, from about 0.5 탆 to about 5 탆, from about 1 탆 to about 5 탆, from about 1.5 탆 to about 4.5 탆, 탆, about 2.5 탆 to 3.5 탆, or about 2.75 탆 to 3.25 탆, but the thickness range is not necessarily limited to the above range.

In addition, the thickness of the first and / or second liquid crystal films may be selected so that the cut-off angle, that is, the angle of the longest angle of view for which the transmittance first becomes minimum and the cut-off angle, It is related to the transmittance at an angle. In one example, as the thickness of the first and / or second liquid crystal film increases, the cut-off angle tends to decrease and the transmittance tends to decrease at the cut-off angle. Therefore, considering the blocking performance of the optical film, it may be advantageous to design the thickness of the liquid crystal film to be large. However, as the thickness of the first and / or second liquid crystal film increases, the transmittance increases relatively rapidly at an angle after the cut-off angle. Considering the tendency of selective transmission characteristics depending on the thickness of the liquid crystal film, it may be appropriate to set the thickness ranges of the first and second liquid crystal films within the respective ranges. However, as described above, the thickness of the first and / or second liquid crystal films is not limited to the above range, and the cut-off angle and the cut-off angle required for the selective transmission characteristics and the transmittance at an angle thereafter And may be adjusted to a thickness other than the above-mentioned range with proper consideration.

In one example, the liquid crystal compound contained in the first and / or second liquid crystal film may be a polymerizable liquid crystal compound. The first and / or second liquid crystal film may contain, for example, a polymerizable liquid crystal compound in a polymerized form. As used herein, the term " polymerizable liquid crystal compound " may mean a compound containing a moiety capable of exhibiting liquid crystallinity, for example, a mesogen skeleton, and further containing at least one polymerizable functional group . Further, "the polymerizable liquid crystal compound is contained in a polymerized form" may mean a state in which the liquid crystal compound is polymerized to form a skeleton such as a main chain or side chain of the liquid crystal polymer in the liquid crystal film. As the polymerizable liquid crystal compound, a rod-shaped polymerizable liquid crystal compound or a liquid crystal compound of a discotic phenomenon can be appropriately selected and used.

The optical film may exhibit a selective transmittance depending on, for example, a viewing angle. In one example, the optical film may exhibit a low transmittance when observed at a predetermined isometric angle and a tilt angle, and may exhibit a high transmittance when observed at an inclination angle other than the predetermined isometric angle. In this specification, the terms "tilt angle and longitude angle" can be described with reference to FIG. For example, in FIG. 2, when the plane (xy plane) by the x axis and the y axis is the surface of the optical film, the inclination angle is an angle formed by the normal of the xy plane, (&Amp;thetas; in Fig. 2). The coarse angle means, for example, the angle (陸 in Fig. 2) formed by the projection on the x-axis and the xy plane of the viewing direction (P). Unless otherwise specified herein, tilted light may refer to light incident at an oblique angle within a range of about 30 degrees to about 50 degrees.

The optical film can design a selective transmittance according to the viewing angle, for example, by adjusting the optical axis of the first and second liquid crystal films and the absorption axis of the first linear polarizer. Herein, the term " vertical, orthogonal, horizontal, or parallel " means substantially vertical, orthogonal, horizontal, or parallel to the extent that the desired effect is not impaired. Therefore, each of the above terms may include an error within ± 15 °, within ± 10 °, within ± 5 °, or within ± 3 °, for example.

In one example, the projection of the average optical axis of the first and / or second liquid crystal film onto the first and second liquid crystal film planes may be parallel to the absorption axis of the first line. As used herein, the term " average optical axis " may mean the sum of the vectors of the optical axes present in the liquid crystal film.

In one specific example, the projections of the average optical axis of the first and second liquid crystal films to the first and second liquid crystal film planes may be parallel to the absorption axis of the first line chart, respectively. Such an optical film can exhibit a relatively low transmittance, for example, when observed at an oblique angle of 85 to 95 degrees and at an oblique angle of 265 to 275 degrees. Such an optical film may also exhibit a relatively high transmissivity relative to a case of observing at a long-angle angle other than the above-mentioned long-angle angle, for example, an oblique angle of 355 to 5 degrees and a oblique angle of 175 to 185 degrees .

In one example, the optical film may exhibit transmittance of about 30% or less for light incident at an inclination angle of 50 degrees at a longitude angle of 85 to 95 degrees and light incident at an inclination angle of 50 degrees at an aperture angle of 265 to 275 degrees. In addition, the optical film exhibits a transmittance of about 80% or more for light incident at an inclination angle of 50 degrees at a longitude of 355 degrees to 5 degrees and for light incident at an angle of incidence of 50 degrees at an angle of 175 degrees to 185 degrees.

In the present specification, the transmittance at an oblique angle is described while it may mean a transmittance at an oblique angle of about 50 degrees unless otherwise specified. In the present specification, the transmittance for the long axis can be referred to as the transmittance for the long axis when the absorption axis of the first line segment is viewed at about 0 degrees and about 180 degrees.

In another example, the projection of the average optical axis of the first and / or second liquid crystal film onto the plane of the first and / or second liquid crystal film is arranged so as to form an angle of about 10 degrees or more with respect to the absorption axis of the first linear polarizer, . The angle may be more specifically about 10 degrees or more, about 12.5 degrees or more, about 15 degrees or more, about 17.5 degrees or more, about 20 degrees or more, but it is not limited thereto and the selective transmission characteristic of a desired viewing angle may be considered And can be appropriately selected. Such an optical film can exhibit a relatively low transmittance when observed at an oblique angle of 85 to 95 nm and at an oblique angle of 265 to 275, A relatively high transmittance can be exhibited when observed at an inclination angle of 355 degrees to 5 degrees and at an inclination angle of 175 degrees to 185 degrees.

In one example, the optical film may exhibit transmittance of about 10% or less with respect to light incident at an inclination angle of 50 to 95 degrees with respect to a light incident at an inclination angle of 50 to 265 to 275, A transmittance of about 60% or less can be exhibited. In addition, the optical film exhibits a transmittance of about 80% or more for light incident at an inclination angle of 50 degrees at a longitude of 355 degrees to 5 degrees and for light incident at an angle of incidence of 50 degrees at 175 degrees to 185 degrees.

In another example, the projection of the average optical axis of the first and / or second liquid crystal film onto the first and second liquid crystal film planes may be arranged to be parallel to the absorption axis of the first line chart. In one specific example, the projection of the average optical axis of the first and second liquid crystal films onto the first and second liquid crystal film planes may be arranged to be parallel to the absorption axis of the first line film. Such an optical film can exhibit a relatively low transmittance when observed at an inclination angle of 355 degrees to 5 degrees and at an inclination angle of 175 degrees to 185 degrees. A relatively high transmittance can be exhibited when observation is performed at a longitude angle other than the above-mentioned copper angle, for example, at an inclination angle of 85 to 95 degrees and at an inclination angle of 265 to 275 degrees.

In one example, the optical film may have a transmittance of about 30% or less for light incident at an oblique angle of 50 at an angular range of 355 to 5 degrees and for light incident at an oblique angle of 50 degrees at an angle of 175 to 185 degrees have. In addition, the optical film may exhibit transmittance of about 80% or more for light incident at an inclination angle of 50 degrees at a longitude angle of 85 to 95 degrees and for light incident at an inclination angle of 50 degrees at an aperture angle of 265 to 275 degrees.

The design of the optical axis of the first and second liquid crystal films and the absorption axis of the first linear polarizer in the present application is not limited to the above but may be appropriately changed in consideration of the selective transmittance according to the desired viewing angle.

The direction of rotation of the spray orientation of the first and / or second liquid crystal film can be appropriately selected within a range that does not impair the purpose of the present application. As used herein, the term " rotational direction of spray orientation " may refer to a direction in which the tilt angle increases. For example, when the direction in which the tilt angle increases is clockwise, it can be referred to as a right rotation spray orientation, and when the direction in which the tilt angle increases is counterclockwise, it can be referred to as a left rotation spray orientation. In one example, the rotational directions of the spray orientations of the first and second liquid crystal films may be the same as each other. For example, the first and second liquid crystal films may each have a right turn spray orientation state or a left turn spray orientation state, respectively. In another example, the first and second liquid crystal films may have different rotation directions of the spray orientation. For example, the first liquid crystal film may have a right turn spray orientation, the second liquid crystal film may have a left turn spray orientation, or the first liquid crystal film may have a left turn spray orientation and the second liquid crystal film may have a right turn spray orientation have.

The tilt angle at the interface between the first and second liquid crystal films can be appropriately adjusted within a range that does not impair the purpose of the present application. In the present specification, the "tilt angle at the interface between the first and second liquid crystal films" is the tilt angle of the region closest to the second liquid crystal film in the first liquid crystal film and the tilt angle of the region closest to the first liquid crystal film in the second liquid crystal film And the tilt angle of the tilt angle. In one example, the tilt angle at the interface between the first and second liquid crystal films is about 0 to 20 degrees, about 0 to 18 degrees, about 0 to 16 degrees, about 0 to 14 degrees, 12 degrees or about 0 degrees to 10 degrees. In another example, the tilt angle at the interface between the first and second liquid crystal films is about 70 to 90 degrees, about 72 to 90 degrees, about 74 to 90 degrees, about 76 to 90 degrees, about 78 To about 90 degrees or about 80 degrees to about 90 degrees.

Figs. 3 and 4 are exemplary views for explaining the tilt angle in the rotation direction and the interface of the spray orientation of the first and / or second liquid crystal films. In one example, as shown in Fig. 3, the optical film has the first liquid crystal film 102 and the second liquid crystal film 103 each having a right-turn spray orientation, and the tilt at the interface between the first and second liquid crystal films The angle can be about 0 degrees (- sign is the optical axis). 4, the first liquid crystal film 102 has a left-turn spray orientation, the second liquid crystal film 103 has a right-turn spray orientation, and the first and second liquid crystal films 103, The tilt angle at the interface between the films can be about 80 degrees to 90 degrees (-the sign is the optical axis)

The retardation value of the first and / or second liquid crystal film can be appropriately selected within a range not to impair the purpose of the present application. For example, the first and / or second liquid crystal films may have an in-plane retardation value (Rin) defined by the following formula A within the range of about 150 nm to about 650 nm. When the first and / or second liquid crystal film has the retardation value, it is advantageous that the optical film exhibits a selective transmittance with respect to the viewing angle, but the retardation value is not necessarily limited to the above range.

[Formula A]

Rin = d x (nx - ny)

In the formula A, d is the thickness of the liquid crystal film, nx is the refractive index in the slow axis direction in the plane of the liquid crystal film, and ny is the refractive index in the direction perpendicular to the slow axis of the liquid crystal film. The term "refractive index" in this specification can be a refractive index for light with a wavelength of 550 nm, unless otherwise specified.

The optical film may further comprise a third liquid crystal film comprising a linear spray oriented liquid crystal compound. The details of the linear spray orientation in the third liquid crystal film may be the same as those described in the items of the first liquid crystal film and the second liquid crystal film. In one example, the third liquid crystal film may exist between the first liquid crystal film 102 and the second liquid crystal film 103 as shown in Fig. In this case, the first liquid crystal film and the second liquid crystal film may have the same rotation direction of the spray orientation, and may have the same right rotation spray orientation, for example. 5, the tilt angle at the interface between the third liquid crystal film and the first liquid crystal film and / or the tilt angle at the interface between the third liquid crystal film and the first liquid crystal film are about 70 degrees to 90 degrees About 72 degrees to 90 degrees, about 74 degrees to 90 degrees, about 76 degrees to 90 degrees, about 78 degrees to 90 degrees, or about 80 degrees to 90 degrees. Such an optical film is advantageous in that it exhibits selective transmission characteristics uniformly according to the viewing angle with respect to light of a wide wavelength band, for example, light of a full wavelength band of visible light. That is, since the optical film exhibits uniform transmission characteristics in a wide wavelength band, it can exhibit excellent color characteristics.

The optical film may further include a retardation film satisfying the following general formula (1) and having a thickness direction retardation value (Rth) defined by the following equation (B) being positive. Such a retardation film can be called a so-called + C plate.

[Formula 1]

n _x ≒ n _y ≠ n _z

[Formula B]

Rth = d x (nz - ny)

In the formula (1) or (B), d is the thickness of the retardation film, nx is the refraction index in the slow axis direction in the plane of the retardation film, ny is the refraction index in the direction perpendicular to the slow axis of the retardation film, That is, the refractive index in the direction perpendicular to both the slow axis and the direction perpendicular thereto

In one example, the retardation film may comprise a liquid crystal compound present in a vertically aligned state. As used herein, the term " vertical alignment " means that the optical axis of the liquid crystal compound is in a range of from about 90 degrees to about 65 degrees, from about 90 degrees to about 75 degrees, from about 90 degrees to about 80 degrees, from about 90 degrees to about 85 degrees It may mean having an inclination angle of 90 degrees. In one example, the retardation film may exist between the first liquid crystal film and the second liquid crystal film, as shown in Fig. . In this case, the first liquid crystal film and the second liquid crystal film may have the same rotation direction of the spray orientation, and may have the same right rotation spray orientation, for example. Further, as shown in Fig. 6, the tilt angle at the interface between the retardation film and the first liquid crystal film and / or the tilt angle at the interface between the retardation film and the first liquid crystal film is about 0 to 20 degrees, About 0 degrees to about 16 degrees, about 0 degrees to about 14 degrees, about 0 degrees to about 12 degrees, or about 0 degrees to about 10 degrees. Such an optical film is advantageous in that it exhibits selective transmission characteristics uniformly according to the viewing angle with respect to light of a wide wavelength band, for example, light of a full wavelength band of visible light. That is, since the optical film exhibits uniform transmission characteristics in a wide wavelength band, it can exhibit excellent color characteristics.

The optical film may further comprise a twisted nematic liquid crystal layer or a half-wave retardation layer. The twisted nematic liquid crystal layer or the half-wave phase retardation layer 201 may exist between the first linear polarizer 101 and the first liquid crystal film 102, for example, as shown in Fig. 7 .

As used herein, the term " twisted nematic liquid crystal layer " means a layer containing a twisted nematic liquid crystal compound, and this layer may be, for example, a liquid crystal polymer layer. The liquid crystal polymer layer may mean, for example, a layer in which a polymerizable liquid crystal compound is polymerized in a twisted orientation to form a polymer. In the present specification, " the liquid crystal compound is twisted oriented " can mean a spiral alignment structure in which waveguides of liquid crystal molecules are twisted along a spiral axis and oriented in layers. Such a structure is similar to the so-called cholesteric alignment, but when the distance from the waveguide of the liquid crystal molecule to the completion of rotation of 360 degrees is referred to as " pitch ", the twisted nematic liquid crystal layer has a thickness Can be distinguished from the cholesteric orientation. That is, in the twisted nematic liquid crystal layer, the waveguide of the liquid crystal molecules may not be rotated 360 degrees. Such a twisted nematic liquid crystal layer may be formed, for example, on a suitable film or sheet.

In this specification, the "n-wavelength phase delay characteristic" may mean a characteristic that the incident light can be phase-delayed by n times the wavelength of the incident light within at least a part of the wavelength range. Therefore, the half-phase retardation layer can have a characteristic that the incident light can be retarded by a half of the wavelength of the incident light within at least a part of the wavelength range. The half-wave phase retardation layer can exhibit a phase retardation within a range of 200 nm to 290 nm or 220 nm to 280 nm, for example, at a wavelength of 550 nm. The half-wave-length phase-retarding layer is not particularly limited as long as it exhibits the phase-retarding property, and for example, a liquid crystal film or a polymeric stretched film can be used.

When the optical film further includes a twisted nematic liquid crystal layer or a half-wave retardation layer, the above-described projection of the absorption axis of the first polarizer and the average optical axis of the first and second liquid crystal films onto the plane of the liquid crystal film It is possible to reverse the tendency of the selective transmission characteristic according to the angular range at the angle formed and the inclination angle. In the following examples, specific numerical values for the transmittance and the inclination angle can be equally applied to the above-described numerical values.

For example, when the optical film includes the twisted nematic liquid crystal layer or the half-phase retardation layer between the first linear polarizer and the first liquid crystal film, the first and second retardation layers of the average optical axis of the first and second liquid crystal films, When the projections of the second liquid crystal film to the plane are parallel to the absorption axis of the first linearly polarized light beam, the light is observed at an inclination angle of 355 to 5 at an east longitude and at an inclination angle of 175 to 185, It is possible to exhibit a low transmittance and a relatively high transmissivity relative to a case of observing at a longing angle other than the above-mentioned longing angle, for example, an oblique angle of 85 to 95 degrees and a oblique angle of 265 to 275 degrees Can be represented

Alternatively, when the optical film includes the twisted nematic liquid crystal layer or the half-phase retardation layer between the first linear polarizer and the first liquid crystal film, the first and second When the projection onto the plane of the liquid crystal film is perpendicular to the absorption axis of the first linearly polarized light, respectively, when observed at an oblique angle of 85 to 95 degrees and at a oblique angle of 265 to 275, And it is possible to exhibit a relatively high transmissivity relative to a case of observation at an exceptional angle other than the above-mentioned long-angle angle, for example, an oblique angle of 355 degrees to 5 degrees and a oblique angle of 175 degrees to 185 degrees have.

In the optical film of the present application, as described above, the projection angle of the average optical axis of the first and second liquid crystal films to the plane of the first and second liquid crystal films, with respect to the absorption axis of the first linear polarizer, Each of which can exhibit selective transmission characteristics. Particularly, when the projections of the average optical axis of the first and second liquid crystal films onto the plane of the first and second liquid crystal films are perpendicular to the absorption axis of the first linear polarizer, the uniform and sharp It is advantageous to show an elliptical transmittance. Therefore, in designing the optical film to exhibit a relatively low transmittance when observed at an oblique angle of 85 to 95 degrees and a oblique angle of 265 to 275, the first liquid crystal film and the second liquid crystal film of the optical film A twisted nematic liquid crystal layer or a half-wave phase retardation layer is disposed between the first linearly polarized light and the projection of the average optical axis of the first and second liquid crystal films onto the first and second liquid crystal film planes is It is advantageous in terms of showing a uniform elliptical transmittance reduction in the full-paraxial all-azimuth direction, but the present invention is not limited thereto.

The optical film may further include a pressure-sensitive adhesive layer. As shown in Fig. 8, the first liquid crystal film 102 and the second liquid crystal film 103 may exist in a state of being attached by the pressure-sensitive adhesive layer 301. Fig. As the pressure-sensitive adhesive layer, it is possible to appropriately select and use from among known pressure-sensitive adhesive layers within a range not to impair the purpose of the present application. For example, a cured product of a composition containing a curable compound may be used as a pressure-sensitive adhesive layer, and a heat curable or ultraviolet curable compound may be used as the curable compound, but the present invention is not limited thereto. Further, the type of the pressure-sensitive adhesive layer can be appropriately selected within a range not to impair the purpose of the present application. For example, a solid-state adhesive, a semi-solid adhesive, an elastic adhesive, or a liquid crystal adhesive can be appropriately selected and used. A solid-state adhesive, a semi-solid adhesive or an elastic adhesive may be referred to as a so-called pressure sensitive adhesive (PSA) and may be cured before the object to be bonded is adhered. The liquid adhesive can be referred to as a so-called optical clear resin (OCR) and can be cured after the objects to be bonded are cemented. According to one embodiment of the present application, PSA may be used as the pressure-sensitive adhesive, but the present invention is not limited thereto.

The optical film may further comprise a substrate layer. The substrate layer may be present adjacent to the first and / or second liquid crystal film. 9, the base layer 401A is present adjacent to the opposite side of the first liquid crystal film 102 on which the second liquid crystal film 103 is formed, that is, the first liquid crystal film 102 Or the first linear polarizer 101 or the base layer 401B may exist adjacent to the opposite side of the second liquid crystal film 103 on which the first liquid crystal film 102 is formed.

As the substrate layer, known materials can be used without any particular limitation. For example, inorganic films such as glass films, crystalline or amorphous silicon films, quartz or indium tin oxide (ITO) films, and plastic films can be used. As the base layer, an optically isotropic base layer such as an optically isotropic base layer or a retardation layer can also be used.

Examples of the plastic substrate layer include TAC (triacetyl cellulose); COE (cyclo olefin copolymer) such as COC (cyclo olefin polymer) and norbornene derivatives; Poly (methyl methacrylate), PC (polycarbonate), polyethylene (PE), polypropylene (PVP), polyvinyl alcohol (PVA), diacetyl cellulose (DAC), polyacrylate (PAC), polyether sulfone (PES) (PPS), polyarylate (PAR), amorphous fluororesin, or the like may be used as the base layer, but it is possible to use a base layer containing at least one selected from the group consisting of PPS (polyphenylsulfone), PEI (polyetherimide), PEN (polyethylenemaphthatate) A coating layer of a silicon compound such as gold, silver, silicon dioxide or silicon monoxide, or a coating layer such as an antireflection layer may be present on the base layer.

In one example, a substrate layer having a small phase retardation value may be used as the base layer. Examples of the base layer include Normal TAC in an unstretched state having an in-plane retardation value of about 10 nm or less, or NRT (no retardation TAC) having an in-plane retardation value of about 10 nm or less and a thickness retardation value of about 5 nm, Or ORT (O-retardation TAC), or COP or COC having substantially no phase retardation value. However, the present invention is not limited thereto, and the type of the substrate layer may be suitably selected depending on the use of the optical film have.

The optical film may further include one or more alignment films. The orientation film can adjust the projection of the average optical axis of the first and / or second liquid crystal film onto the liquid crystal film. The orientation film may be present adjacent to the first and / or second liquid crystal films. In one example, the alignment film may be present adjacent to the opposite side of the first liquid crystal film on which the second liquid crystal film is formed, or may be adjacent to the opposite side on which the first liquid crystal film of the second liquid crystal film is formed. 10, the alignment films 501A and 501B are provided between the base layer 401A and the first liquid crystal film 102, between the base layer 401B and the second base layer 401B, respectively, And may be disposed between the liquid crystal films 103. As the alignment film, there can be used, without limitation, an alignment film known to be capable of exhibiting alignment characteristics by, for example, a contact alignment film or a non-contact method such as irradiation of linear polarized light including a photo alignment film compound such as a rubbing alignment film.

The optical film may further include a second linear polarizer. The second line polarizer 601 may exist adjacent to the opposite side of the first liquid crystal film of the second liquid crystal film 103, for example, as shown in Fig. The definition and kind of the second linear polarizer, and the like may be applied equally to those described in the item of the first linear polarizer. In one example, the optical film may be arranged such that the absorption axis of the second linear polarizer is parallel to the absorption axis of the first linear polarizer. For example, when the optical film is observed at an inclination angle of a predetermined angular range, the first and second liquid crystal films may have a polarizing direction of the polarized light having passed through any one of the first and second linear polarizers, And the polarized light in which the oscillation direction is rotated can not pass through the other linearly polarized light, so that the transmittance can be controlled when observed at an inclination angle of a predetermined angular range.

The present application also relates to the use of said optical film. The optical film may exhibit selective transmittance and shielding characteristics according to a long axis angle at a predetermined tilt angle. Such an optical film can be usefully used as a security film or an anti-reflection film of a display device. The optical film may be disposed on the observer side of the display device.

In one example, the observer can observe the image of the display device relatively well when observing the display device at a long angle showing the transmission characteristic, and when the observer observes the display device at a large angle indicating the shielding characteristic, The optical film can function as a security film of the display device.

In another example, when the display device is used in an external environment having a reflection function, the reflection of the image of the display device to the external environment having the reflection function can be reduced, so that it can be used as an anti-reflection film. The external environment having the reflection function may exemplify a window of the vehicle. For example, when a display device is disposed so that the observer can observe the display device at a long angle indicating the transmission characteristic, and the display device is disposed so that the external environment having a reflection function is positioned at a long angle indicating the shielding characteristic, It is possible to observe the image of the display device, and the phenomenon that the image of the display device is reflected by the reflective external environment can be reduced. For example, when the external environment having the reflection function is the window of the vehicle, when the display device is arranged to be observable from the side of the driver's seat of the vehicle, the image of the display device is reflected on the vehicle front window, The phenomenon can be reduced.

In one example, the display device may be a liquid crystal display device. The liquid crystal display device may include a light source, a liquid crystal panel, and an optical film of the present application sequentially.

As the light source, for example, a direct type or an edge type backlight unit (BLU) commonly used in a liquid crystal display (LCD) can be used. Various kinds of light sources other than the above can be used without limitation.

The liquid crystal panel may include, for example, a first substrate, a pixel electrode, a first alignment film, a liquid crystal layer, a second alignment film, a common electrode, and a second substrate sequentially formed from the light source side. In the first substrate on the light source side, for example, an active driving circuit including TFT (Thin Film Transistor), wiring and the like may be formed as a driving element electrically connected to the transparent pixel electrode. The pixel electrode includes, for example, ITO (Indium Tin Oxide) or the like and can function as an electrode for each pixel. In addition, the first or second alignment film may include a material such as polyimide.

The liquid crystal layer may include an appropriate type of liquid crystal depending on the mode of the liquid crystal display device to be driven. For example, the optical film of the present invention can be applied to the IPS (In Plane Switching) or TN (Twisted Nematic) mode liquid crystal display device to adjust the transmission characteristics according to the viewing angle. However, But can be applied to liquid crystal display devices of various modes.

In one example, when the optical film of the present invention is applied to an IPS mode liquid crystal display device, it is advantageous to exhibit selective transmission and blocking characteristics according to viewing angles. In another example, in the case where the optical film of the present invention is applied to a liquid crystal display device of a TN mode, if a separate optical film is additionally disposed as required, Can be more advantageous. As the separate optical film, a half-wave phase retardation layer or a twisted nematic liquid crystal layer or the like can be exemplified. When the half-wave phase retardation layer is used as the separate optical film, the optical axis of the half-wave phase retardation layer and the absorption axis of the first linearly polarized light are about 20 to 25 degrees, specifically about 22 to about 23 degrees , More specifically about 22.5 degrees. The liquid crystal layer may have a function of transmitting or blocking the light from the light source for each pixel by the voltage applied from the driving circuit. The common electrode includes, for example, ITO or the like, and can serve as a common counter electrode.

The liquid crystal display may further include upper and lower polarizers present in upper and lower portions of the liquid crystal panel. The lower polarizer plate may be arranged adjacent to the light source side, for example, as compared with the upper polarizer plate. In one example, the upper polarizer plate may play a role corresponding to the second linear polarizer described in the item of optical film. For example, the optical film may be disposed so that the second liquid crystal film and the upper polarizer of the liquid crystal panel adhere to each other. In one example, the optical film may be arranged such that the absorption axis of the first linear polarizer and the absorption axis of the upper polarizer of the liquid crystal panel are parallel. 12 exemplarily shows a liquid crystal display element including a first linear polarizer 101, a first liquid crystal film 102, a second liquid crystal film 103, and an upper polarizer 701 in sequence. In such a liquid crystal display element, for example, when the liquid crystal display device is observed at an inclination angle of a predetermined greatest angle in a state where the first linearly polarized light is adjacent to the observer, the first and second liquid crystal films are moved from the light source to the upper polarizer plate The polarization direction of the polarized light can be rotated about 80 to 90 degrees, and the polarized light having the rotated direction of the polarized light can not pass through the first linear polarizer of the optical film, so that the transmittance can be reduced.

As long as the liquid crystal display device includes the optical film of the present application, the other components, structures, and the like are not particularly limited, and all contents well known in the art can be appropriately applied.

The optical film of the present application can also be usefully used in smart windows or sunglasses. As used herein, the term " Smart Window " refers to a window having a function of controlling incident light, for example, transmittance of sunlight, and is called a smart blind, an electronic curtain, a variable transmittance glass, Is a concept encompassing functional devices called " functional devices " As used herein, the term " Sun Glass " may refer to a functional element for protecting the eye from sunlight. For example, as shown in Fig. 13, the smart window or the sunglass including the optical film of the present application can lower the transmittance particularly for the light incident at an inclination angle of a predetermined greatest angle, The transmittance for light incident at an angle of incidence can be increased. Therefore, the optical film of the present application can be usefully used in a smart window or a sunglass which is intended to exhibit a selective transmittance according to a viewing angle. As long as the smart window or sunglass includes the optical film of the present application, the other parts, structures, and the like are not particularly limited, and all contents well known in the art can be appropriately applied.

The present application can provide an optical film showing selective transmission and blocking characteristics according to viewing angles, and such an optical film can be usefully used for a security film, a smart window and a sunglass of a display device such as an LCD.

1 is a schematic view of an optical film of the present application.
2 is a schematic view for explaining the inclination angle and the longing angle.
Figs. 3 to 6 are schematic views of the spray alignment of the first and second liquid crystal films. Fig.
Figs. 7 to 11 are schematic views of the optical film of the present application. Fig.
12 is a schematic diagram of a liquid crystal display device of the present application.
13 is a schematic view for explaining selective transmission and shielding characteristics according to the viewing angle of the smart window or sunglass of the present application.
14 shows the structure of the optical film of Example 1. Fig.
15 shows the structure of the optical film of Example 4. Fig.
Figs. 16 to 23 show the evaluation of permeability and the results.
24 is a schematic diagram for explaining the spray orientation.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the scope of the present application is not limited to the following examples.

Example One

The optical film of Example 1 having the structure of Fig. 14 was produced. Specifically, after a photo alignment film is formed on NRT base film (fuji yarns) 301A and 301B, cyanobiphenyl-based acrylate, cyanophenylcyclohexane-based acrylate, and cyanophenyl ester based (25% by weight of the total solution) of 95% by weight of a polymerizable liquid crystal compound (made by Merck) and 5% by weight of a photo-initiator, IGACURE 907 (manufactured by Ciba-Geigy Switzerland) Dissolved in a toluene solvent to prepare a spray alignment liquid crystal composition. The spray alignment liquid crystal composition was coated by bar coating to a thickness of about 2 탆 after drying, and then the coating layer was left to stand in an oven at about 80 캜 for 2 minutes and dried.

Next, the dried coating layer was irradiated with ultraviolet rays (300 mW / cm ² ) for about 10 seconds while maintaining the temperature at about 80 ° C to form a liquid crystal layer, thereby preparing a first spray alignment liquid crystal film 102. Next, a second spray aligned liquid crystal film 103 was prepared in the same manner as the first linear spray aligned liquid crystal film. The lowest tilt angle of the substrate surface of the first and second spray alignment liquid crystal films is about 16 degrees, the upper tilt angle of the air surface is about 73 degrees, the average tilt angle is about 45 degrees, Was in the range of about 0.95 to 1.05.

Next, the two liquid crystal films produced by the above method were bonded to each other through the adhesive 201 such that the air surfaces faced each other and the tilt angles at the interface were the same. Next, the first absorption type linearly polarized light 101 is disposed on the opposite side of the base film 301A where the liquid crystal film 102 is formed, and on the opposite side of the base film 301B on which the liquid crystal film 103 is formed, A second absorption type linear polarizer 601 functioning as an upper polarizing plate of the second absorption type linear polarizer. The optical film of Example 1 is arranged so that the projection of the average optical axis of the first and second liquid crystal films 102 and 103 onto the plane of the liquid crystal film is parallel to the absorption axis P ₁ of the first linear polarizer, And the absorption axis P ₂ of the second linear polarizer is also arranged parallel to the absorption axis P ₁ of the first linear polarizer.

Example 2

An optical film was prepared in the same manner as in Example 1 except that the thicknesses of the first and second liquid crystal films were respectively set to 3.5 탆. The lowest tilt angle of the substrate surface of the first and second spray aligned liquid crystal films of Example 2 is about 3 degrees, the highest tilt angle of the air plane is about 85 degrees, the average tilt angle is about 50 degrees, and the tilt factor tilt factor in the range of about 0.95 to 1.05.

Example 3

An optical film was produced in the same manner as in Example 1 except that the thickness of the first and second liquid crystal films was 4.5 mu m, respectively. The lowest tilt angle of the substrate surface of the first and second spray aligned liquid crystal films of Example 3 was about 2 degrees, the highest tilt angle of the air surface was about 86 degrees, the average tilt angle was about 51 degrees, and the tilt factor tilt factor is in the range of about 0.95 to 1.05.

Example 4

The optical film of Example 4 having the continuous (cascade) structure of Fig. 15 was produced. Specifically, in the optical film of Example 2, structures other than the second linear polarizer 601 were further laminated on the side of the first linear polarizer 101 of the optical film of Example 2 to obtain the optical film of Example 4 .

Example 5

An optical film was prepared in the same manner as in Example 1, except that the projection of the average optical axis of the first liquid crystal film onto the plane of the liquid crystal film was arranged at about 5 degrees with the absorption axis of the first polarizer.

Example 6

An optical film was produced in the same manner as in Example 1, except that the projection of the average optical axis of the first and second liquid crystal films onto the plane of the liquid crystal film was arranged to be about 10 degrees with the absorption axis of the first polarizer.

Example 7

An optical film was prepared in the same manner as in Example 1, except that the projection of the average optical axis of the first and second liquid crystal films onto the plane of the liquid crystal film was arranged to be about 15 degrees with the absorption axis of the first polarizer.

Comparative Example One

Comparative Example 1 was prepared in the same manner as in Example 1, except that a micro-louver film of 3M was used instead of the laminate of the first and second linear spray aligned liquid crystal films in Example 1.

Evaluation example 1 Evaluation of permeability

The optical films prepared in Example 1 were evaluated for transmittance according to their angular ranges of 0 degree to 360 degrees at 30 degree, 40 degree, and 50 degree inclination angles respectively using Axoscan (Axometrix). The results are shown in Fig. 16 and Table 1 Respectively.

Permeability (%) according to the diameter 0 degrees (360 degrees) 90 degrees 180 degrees 270 degrees Inclination angle 30 degrees 91.68 60.99 83.2 24.8 40 degrees 91.91 42.39 80.7 5.8 50 degrees 91.72 23.47 90.58 27.68

The optical films prepared in Examples 1 to 3 were evaluated for transmittance at an angle of inclination of about 50 degrees from 0 degrees to 360 degrees using Axoscan (Axometrix). The results are shown in FIG. 17 and Table 2. The optical films prepared in Examples 1 to 3 were evaluated for the transmittance according to the inclination angles at the top and bottom (long-angle 80 degrees and 270 degrees) and left and right (longitudes 0 degrees (360 degrees) and 180 degrees) Are shown in Figs. 18 to 20.

Permeability (%) according to the diameter 0 degrees (360 degrees) 90 degrees 180 degrees 270 degrees Example 1 (thickness 2 탆 ) 91.72 23.47 90.58 27.68 Example 2 (thickness: 3.5 탆 ) 95.32 4.62 94.01 7.63 Example 3 (thickness 4.5 占 퐉 ) 94.33 14.49 91.87 25.12

Transmission ratios of the greenhouse films prepared in Example 2 and Example 4 were measured at an angle of inclination of about 50 degrees from 0 to 360 degrees using Axoscan (Axometrix), and the results are shown in Table 3.

Permeability (%) according to the diameter Example 2 Example 4 0 degrees (360 degrees) 90 degrees 0 degrees (360 degrees) 90 degrees Inclination angle 30 degrees 94.67 44.25 82.22 17.5 40 degrees 93.53 20.48 82.92 4.16 50 degrees 95.32 4.62 83.37 1.48

The transmittances of the optical films prepared in Examples 1 and 5 to 7 were evaluated at a tilt angle of about 50 degrees with respect to a range of 0 to 360 degrees from the simulation. The results are shown in Fig. 21 (Examples 1 and 5 to 7) 22 (shown in Example 7) and Table 4

Permeability (%) according to the diameter Contrast ratio 0 degrees (360 degrees) 90 degrees 180 degrees 270 degrees Example 1 (α = 0 °) 92 17.8 90 17.8 5.1: 1 Example 5 ([alpha] = 5 [deg.]) 90 9 90 29 10: 1 Example 6 (α = 10 °) 87 3.7 90 42 24: 1 Example 7 ([alpha] = 15 [deg.]) 86 2 90 55 44: 1

The optical film of Example 1 and the micro-louver film of Comparative Example 1 were measured by using an Axoscan (Axometrix Co.) at the top and bottom (longitude 80 degrees and 270 degrees) and left and right (longitudes 0 degrees (360 degrees) and 180 degrees) And the results are shown in FIG. 23. FIG. As shown in Fig. 24, it can be seen that the optical film of Example 1 has a greater effect of increasing the front transmittance as a whole compared to the micro-louver film of Comparative Example 1. [

101: first line polarizer
102: first liquid crystal film
103: second liquid crystal film
104: third liquid crystal film
105: retardation film
201: a twisted nematic liquid crystal layer or a half-wave phase retardation layer
301: pressure-sensitive adhesive layer
401A, 401B: substrate layer
501A and 501B: alignment films
601: Second polarizer
701: Upper polarizer

Claims

A first line polarizer; And first and second liquid crystal films sequentially formed on the first linearly polarized light and including linearly spray-aligned liquid crystal compounds, respectively.

The optical film according to claim 1, wherein the projections of the average optical axis of the first and second liquid crystal films to the plane of the first and second liquid crystal films are parallel to the absorption axis of the first linear polarizer, respectively.

The optical film according to claim 2, wherein an optical film exhibiting a transmittance of 30% or less with respect to light incident at an inclination angle of 50 degrees at a longitude of 85 to 95 degrees and light incident at an inclination angle of 50 degrees at an angle of 265 to 275 degrees 0 degrees and 180 degrees are the angles of the absorption axes of the first linear polarizer).

The optical film according to claim 1, wherein the projections of the average optical axis of the first and second liquid crystal films onto the plane of the first and second liquid crystal films respectively form an angle of 10 degrees or more with the absorption axis of the first linear polarizer.

5. The optical element according to claim 4, wherein a transmittance of 10% or less for light incident at an inclination angle of 50 degrees at a longitude angle of 85 to 95 degrees, and a transmittance of 60% or less for light incident at an inclination angle of 50 degrees at a longitude angle of 265 to 275 degrees (Provided that the angle between the long axis of 0 degrees and the angle of 180 degrees is the angle of the absorption axis of the first linear polarizer).

The optical film according to claim 1, wherein the projections of the average optical axis of the first and second liquid crystal films onto the plane of the first and second liquid crystal films are orthogonal to the absorption axis of the first linear polarizer, respectively.

The optical film according to claim 6, wherein the optical film exhibits a transmittance of 30% or less with respect to light incident at an inclination angle of 50 degrees at a longitude of 355 to 5 degrees and light incident at an angle of inclination of 50 degrees from 175 degrees to 185 degrees And 180 degrees is the angle of the absorption axis of the first linear polarizer).

The optical film according to claim 1, wherein the first and second liquid crystal films have the same rotation direction of the spray orientation.

The optical film according to claim 1, wherein the tilt angle at the interface between the first liquid crystal film and the second liquid crystal film is 0 deg. To 10 deg.

The optical film according to claim 1, wherein the rotational directions of the first and second liquid crystal film spray orientations are different from each other.

The optical film according to claim 1, wherein the tilt angle at the interface between the first liquid crystal film and the second liquid crystal film is 80 to 90 degrees relative to each other.

The optical film according to claim 1, further comprising a third liquid crystal film comprising a linear spray-aligned liquid crystal compound.

The liquid crystal display device according to claim 12, wherein the third liquid crystal film is present between the first and second liquid crystal films whose rotational directions are equal to each other, and the tilt angle at the interface between the third liquid crystal film and the first liquid crystal film, And the tilt angle at the interface between the second liquid crystal films is within the range of 80 to 90 degrees.

The optical film according to claim 1, further comprising a retardation film satisfying the following general formula (1) and having a thickness retardation value defined by the following equation (B)
[Formula 1]
n _x ≒ n _y ≠ n _z
[Formula B]
Rth = d x (nz - ny)
In the formula (1) or (B), d is the thickness of the retardation film, nx is the refractive index in the slow axis direction in the plane of the retardation film, ny is the refractive index in the direction perpendicular to the slow axis of the retardation film, I.e., the refractive index in a direction perpendicular to both the slow axis and the direction perpendicular thereto.

The liquid crystal display according to claim 14, wherein the retardation film is present between the first and second liquid crystal films in which the spray directions of rotation are the same, and the tilt angle and the retardation film at the interface between the retardation film and the first liquid crystal film, Wherein the tilt angle at the interface between the optical films is within the range of 0 to 10 degrees.

The optical film according to claim 1, further comprising a twisted nematic liquid crystal layer or a half-retardation layer existing between the first linear polarizer and the first liquid crystal film.

The optical film according to claim 1, further comprising a base layer present between the first linear polarizer and the first liquid crystal film or adjacent to the top of the second liquid crystal film.

The optical film according to claim 1, further comprising a second linear polarizer adjacent to the second liquid crystal film.

19. The optical film according to claim 18, wherein the absorption axes of the second linear polarizer and the first linear polarizer are parallel to each other.

A liquid crystal display comprising a liquid crystal panel and the optical film of claim 1.

The liquid crystal display of claim 20, further comprising an upper polarizer adjacent to one side of the liquid crystal panel, wherein the optical film of claim 1 is disposed so that the upper polarizer and the second liquid crystal film are attached.

The liquid crystal display of claim 21, wherein the absorption axis of the upper polarizer and the absorption axis of the first linear polarizer are parallel to each other.

A smart window comprising the optical film of claim 1.

A sunglass comprising the optical film of claim 1.