KR102486664B1 - Module of diffractive light guide plate - Google Patents

Abstract

Embodiments of the present invention include a diffraction guide plate having a light guide unit for guiding light and a plurality of diffraction optical elements disposed on a surface of the light guide unit; and disposed in an area on one side of the light guide part corresponding to an area where at least one diffractive optical element among the plurality of diffractive optical elements is located, so that external light of a reference wavelength band incident at an angle within a predetermined reference range is disposed on the diffractive optical element and a reducing layer for reducing a ratio of reaching a reference position spaced apart from one surface of the light guide unit toward the other surface through the light guide unit.

Description

Diffraction light guide plate module {MODULE OF DIFFRACTIVE LIGHT GUIDE PLATE}

The present invention relates to a diffraction light guide plate module.

Recently, as interest in display units that implement augmented reality (AR), mixed reality (MR), or virtual reality (VR) has increased, research on display units that implement them has been actively conducted. there is a trend A display unit implementing augmented reality, mixed reality, or virtual reality includes a diffraction light guide module using a diffraction phenomenon based on a wave property of light.

Such a diffraction light guide plate module may include a diffraction light guide plate having a light guide unit and a plurality of diffraction optical elements provided on one side or the other side of the light guide unit and having a plurality of grid line patterns. A plurality of diffraction light guide plates may be provided according to the wavelength of the separated light to be separated from the light incident through the light source.

1 is a schematic diagram of a diffraction light guide plate.

The diffraction light guide plate 10 is input through the input diffraction optical element 12 and the light guide part 11 to allow light output through the micro light source output element L to be input and guided onto the light guide part 11. An intermediate that is optically coupled with the diffractive optical element 12 and allows one-dimensional expansion in a first direction (y-axis direction in FIG. 1) by diffraction of the light received from the input diffractive optical element 12 It is optically coupled with the intermediate diffractive optical element 13 through the diffractive optical element 13 and the light guide part 11, and the light received from the intermediate diffractive optical element 13 is diffracted in a second direction (refer to FIG. 1) An output diffractive optical element 14 may be provided so that the light is output from the light guide unit 11 and directed toward the user's pupil while being one-dimensionally expanded in the x-axis direction.

FIG. 2 is a vertical direction of the diffraction light guide plate showing the degree to which the exit angle (θ _e ) of the third diffractive optical element is varied according to the incident angle (θ _i ) of external light (O) other than the micro light source output device. it is a cross section

FIG. 3 is a graph showing the relationship between the diffraction angle (θ _d ) and the exit angle (θ _e ) of external light (O) in an area where the third diffraction optical element is disposed according to the incident angle (θ _i ).

The results of FIGS. 2 and 3 were derived based on the refractive index of the diffraction light guide plate being 1.7, the period of the grating line pattern of the third diffractive optical element being 400 nm, and the wavelength of incident external light (O) being 530 nm.

Referring to FIGS. 2 and 3, the external light O incident at an incident angle θ _i of −24° or less with respect to the surface of the light guide unit 11 is not diffracted by the third diffraction optical element 14, and (See (a) of FIG. 3), the external light (O) incident at an incident angle (θ _i ) between -24˚ and 18˚ is diffracted and proceeds with total reflection within the light guide unit 11 ((( a) and FIG. 3 (a) and (b)), the external light (O) incident at an incident angle (θ _i ) between 18 ° and 90 ° is diffracted and the traveling direction is changed, and then the light guide unit 11 It is emitted through the light guide unit 11 without being totally reflected in (see FIGS. 2 (b) to (g) and FIG. 3 (a) and (b)).

On the other hand, the light emitted through the light guide unit 11 in the area where the third diffractive optical element 14 is disposed is less likely to reach the user's pupil as the emission angle θ _e is closer to 90 degrees. The closer to ˚, the higher the possibility of reaching the user's pupil. When the external light (O) incident on the diffraction light guide plate 10 is emitted and reaches the pupil of the user, interference occurs with the image light that is input and expanded by the micro light source output device, resulting in an image in which a rainbow pattern is formed instead of a normal image image. There is a problem that can cause distortion of .

The foregoing background art is technical information that the inventor possessed for derivation of the embodiments of the present invention or acquired during the derivation process, and is not necessarily a known technology disclosed to the general public prior to filing the application of the embodiments of the present invention. none.

KR 2016/0091402 A

An object of the present invention is to provide a diffraction light guide module capable of preventing external light incident on a diffraction light guide plate from being unintentionally emitted and reaching a pupil of a user.

Embodiments of the present invention include a diffraction guide plate having a light guide unit for guiding light and a plurality of diffraction optical elements disposed on a surface of the light guide unit; and disposed in an area on one side of the light guide part corresponding to an area where at least one diffractive optical element among the plurality of diffractive optical elements is located, so that external light of a reference wavelength band incident at an angle within a predetermined reference range is disposed on the diffractive optical element and a reducing layer for reducing a ratio of reaching a reference position spaced apart from one surface of the light guide unit toward the other surface through the light guide unit.

In this embodiment, the plurality of diffraction optical elements include an input diffraction optical element that receives light from a light source and diffracts the received light so that the received light can be guided on the light guide unit, and the input diffraction optical element an intermediate diffraction optical element configured to receive light diffracted from the intermediate diffraction optical element and expand the received light one-dimensionally by diffraction; and an output diffraction optical element configured to be output from the light guide, and the reduction layer may be disposed on a side of at least an output diffraction optical element among the input diffraction optical element, the intermediate diffraction optical element, and the output diffraction optical element.

In this embodiment, the diffraction optical element on which the reduction layer is disposed has a grating line pattern of period d and is disposed on one surface of the light guide part, and the reference position is the position of the diffraction optical element on which the reduction layer is disposed. It is spaced apart from the lower side of the diffraction optical element by a length B in a first direction from the lower side to the upper side, and is spaced apart by a length R from one side of the light guide unit in a second direction perpendicular to the first direction and facing the other side of the light guide part It is preferable that the reduction layer reduces the rate at which external light in the reference wavelength band, which is incident at an angle greater than or equal to the reference incident angle determined by the following [Conditional Expression 1], reaches the reference position:

[conditional expression 1]

Here, θ Is the reference angle of incidence, λ is the minimum wavelength of the reference wavelength range, is the period of the grating line pattern of the diffraction optical element on which the reduction layer is disposed, and B is the distance between the lower side of the diffraction optical element on which the reduction layer is disposed and the reference position. The shortest distance based on the first direction, R is the shortest distance based on the second direction between one surface of the light guide part and the reference position.

In this embodiment, the reference wavelength range may be 400 nm to 700 nm.

In this embodiment, the diffraction guide plate module includes a first diffraction optical element separating light with a wavelength of 550 nm or more and less than 700 nm, a second diffraction optical element separating light with a wavelength of 400 nm or more and less than 550 nm, and a wavelength of 450 nm or more A plurality of diffraction guide plates having at least one of the third diffraction optical elements for separating light with a wavelength of 650 nm or less are stacked, and the reference angle of incidence is d in [Conditional Expression 1]. It may be determined based on a case in which the longest period is selected among grating line pattern periods of optical elements.

In this embodiment, the reduction layer is a film formed elongately along a direction parallel to the first direction, and includes a microtransmitting portion and a light blocking portion that are arranged to cross each other along a direction parallel to the first direction. A louver film may be included.

In this embodiment, it is preferable that the thickness of the micro louver film and the length of the light-transmitting portion satisfy the following [Conditional Expression 2]:

[conditional expression 2]

Here, a is the thickness of the micro-louver film, and b is the length of the light-emitting part.

In this embodiment, the reduction layer includes a first linear polarizer; and first and second nonlinear spray alignment liquid crystal films sequentially formed on the first linear polarizer.

In this embodiment, the tilt factor of the first or second nonlinear spray alignment liquid crystal film may be less than 0.95 or greater than 1.05.

In this embodiment, the optical film may further include a second linear polarizer disposed adjacent to the second nonlinear spray alignment liquid crystal film.

In this embodiment, the reduction layer includes a first linear polarizer; and first and second liquid crystal films sequentially formed on the first linear polarizer and each including a linear spray-aligned liquid crystal compound.

In this embodiment, the optical film may further include a second linear polarizer disposed adjacent to the second liquid crystal film.

The diffraction light guide plate module according to an embodiment of the present invention is disposed in an area on one surface of a light guide unit corresponding to an area where at least one diffractive optical element among a plurality of diffractive optical elements is located, and is incident on a reference wavelength range at an angle within a predetermined reference range. Since a reduction layer is provided to reduce the rate at which external light reaches a reference position that is spaced from one side of the light guide unit toward the other side through the diffractive optical element and the light guide unit, unintended external light is incident to the expanded image light. Distortion of the expanded image light, such as a rainbow pattern, can be prevented by causing interference and emitting together.

1 is a schematic diagram of a diffraction light guide plate.
2 is a vertical cross-sectional view of the diffraction light guide plate showing the degree of change in the angle of emission emitted from the area where the third diffraction optical element is disposed according to the angle of incidence of external light other than the micro light source output device.
3 is a graph showing a relationship between a diffraction angle and an exit angle in a region where a third diffraction optical element is disposed according to an incident angle of external light.
4 is a diagram schematically illustrating a part of a diffraction guide plate module according to an aspect of the present invention.
5 is a schematic side cross-sectional view of a diffraction optical element and a light guide unit in which a reduction layer is disposed for explaining a method of calculating an incident condition of external light capable of reaching a reference position.
6 is a schematic view of a form in which a micro-louver film is disposed on the side of a diffractive optical element as an example of a reducing layer.
7 is a schematic diagram of an optical film including a liquid crystal film as another embodiment of a reducing layer.
8 is a schematic diagram for explaining spray orientation.

The present invention will become clear with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, only these embodiments make the disclosure of the present invention complete, and common knowledge in the art to which the present invention belongs. It is provided to fully inform the holder of the scope of the invention, and the present invention is only defined by the scope of the claims. Meanwhile, terms used in this specification are for describing the embodiments and are not intended to limit the present invention. In this specification, singular forms also include plural forms unless specifically stated otherwise in a phrase. As used herein, "comprises" and/or "comprising" means that a stated component, step, operation, and/or element is present in the presence of one or more other components, steps, operations, and/or elements. or do not rule out additions. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. Terms are used only to distinguish one component from another.

In this specification, the term “light guide unit” may be defined as a structure that guides light from the inside using total internal reflection. A condition for total internal reflection is that the refractive index of the light guide part should be greater than the refractive index of the surrounding medium adjacent to the surface of the light guide part. The light guide unit may be formed of glass and/or plastic material, and may be transparent or translucent. The light guide unit may be formed in various layouts in a plate type. Here, the term "plate" means a three-dimensional structure having a predetermined thickness between one surface and the other surface opposite to it, and the one surface and the other surface may be substantially flat planes, but at least one of the one surface and the other surface is It may be formed by being curved one-dimensionally or two-dimensionally. For example, the plate-type light guide unit may be one-dimensionally curved so that one side and/or the other side thereof may have a shape corresponding to a part of the side surface of the cylinder. However, the curvature formed by the curvature preferably has a sufficiently large radius of curvature to facilitate total internal reflection in order to guide the light on the light guide unit.

In this specification, the term “diffractive optical element” may be defined as a structure for changing an optical path by diffracting light on a light guide unit. Here, the "diffraction optical element" may refer to a part in which a plurality of grating lines oriented in one direction are arranged in a predetermined direction on the light guide unit to form a predetermined area while having a pattern.

In this specification, the term “grid line” refers to a projection shape having a predetermined height on the surface of the light guide unit (ie, an embossed pattern) and/or a groove shape having a predetermined depth on the surface of the light guide unit (ie, an intaglio pattern). ) can mean. Here, the alignment direction of the grating lines can be freely designed so that the optical path can be changed in an intended direction through diffraction by the diffractive optical element.

4 is a diagram schematically illustrating a part of a diffraction guide plate module according to an aspect of the present invention.

Referring to FIG. 4 , the diffraction guide plate module 1000 may include the diffraction guide plate 100 and the reduction layer 200 . The reduction layer 200 is disposed adjacent to the diffraction guide plate 100, but is shown in a form separated from the diffraction guide plate 100 in FIG. 4 for convenience of description.

The diffraction guide plate module includes a first diffraction optical element that separates and diffracts light with a wavelength of 550 nm to 700 nm, a second diffraction optical element to separate and diffracts light with a wavelength of 400 nm to 550 nm, and 450 nm to 650 nm. It may have a structure in which a plurality of diffraction guide plates including at least one of the third diffractive optical elements for separating and diffracting light of different wavelengths are stacked. Preferably, the diffraction guide plate module has a structure capable of including all of the first diffraction optical element, the second diffraction optical element, and the third diffraction optical element by combining a plurality of diffraction light guide plates. For example, the diffraction guide plate module includes a first diffraction guide plate having a first diffraction optical element on one surface of the first light guide unit and a second diffraction guide plate having a second diffraction optical element on one surface of the second light guide unit. and a third diffraction guide plate having a third diffraction optical element on one surface of the third light guide unit may be stacked on each other. For another example, the diffraction guide plate module includes a first diffraction guide plate having a first diffraction optical element on one surface of the first light guide unit and a second diffraction optical element on the other surface of the first light guide unit; It may have a structure in which second diffraction guide plates having third diffraction optical elements are stacked on one surface of the light guide unit. Hereinafter, for convenience of description, the diffraction guide plate module includes a first diffraction guide plate having a first diffraction optical element, a second diffraction guide plate having a second diffraction optical element, and a third diffraction guide plate having a third diffraction optical element. A description will be made focusing on the fact that the structures are stacked on each other.

In addition, the drawings showing the diffraction guide plate among the drawings below in FIG. 4 show the diffraction guide plate located farthest from the user's pupil side within the diffraction guide plate module, and the remaining diffraction guide plates are not shown.

The diffraction light guide plate 100 may include a light guide unit 110 and a plurality of diffractive optical elements 120 , 130 , and 140 disposed on a surface of the light guide unit 110 .

The light guide unit 110 may guide light inside using total internal reflection.

The input diffractive optical element 120 may receive the light L1 from the light source S and diffract the received light so that the received light may be guided on the light guide unit 110 .

The intermediate diffraction optical element 130 may be configured to receive the diffracted light L2 from the input diffractive optical element 120 and expand the received light one-dimensionally by diffraction. As the diffracted light received from the input diffraction optical element 120 passes through the intermediate diffractive optical element 130, some of it is diffracted and the optical path is changed, and the rest can be totally reflected into the existing optical path. Since the initially received light can be split into a plurality of beams L3 while being diffracted multiple times at points spaced apart in a specific direction, one-dimensional expansion can be achieved.

The output diffractive optical element 140 may be configured to receive the light L3 expanded from the intermediate diffractive optical element 130 and output the received light from the light guide unit 110 by diffraction. Meanwhile, the output diffraction optical element 140 may also one-dimensionally expand the light received from the intermediate diffraction optical element 130 by diffraction. At this time, with respect to the light-receiving side 140a of the output diffractive optical element 140, the direction in which the plurality of beams L3 formed by the light expanded by the intermediate diffractive optical element 130 are spaced apart, and the single beam L3 Since the directions in which the plurality of beams L4 expanded by the reference output diffractive optical element 140 are spaced apart intersect (eg, orthogonal) to each other, eventually the input diffractive optical element 120 from the light source S A two-dimensional expansion is performed as a standard for receiving light.

The reduction layer 200 is disposed in an area corresponding to the area where at least one diffractive optical element among the plurality of diffractive optical elements 120, 130, and 140 is located on one surface 110a side of the light guide unit 110 in advance. External light (O) of the reference wavelength range incident at an angle of a predetermined reference range is spaced apart from one surface (110a) of the light guide part (110) toward the other surface (110b) side through the diffraction optical element and the light guide part (110) The ratio of reaching the reference position P can be reduced. It is preferable that the reduction layer 200 is disposed on the side of at least the output diffraction optical element 140 among the input diffraction optical element 120, the intermediate diffraction optical element 130, and the output diffraction optical element 140. The video light output from the light source S is diffracted by the plurality of diffraction optical elements 120, 130, and 140 and guided through the light guide unit 110, and finally the expanded video light is output from the light guide unit 110. This area is the area where the output diffractive optical element 140 is located, and when unintentional external light other than the expanded image light is incident and emitted through the light guide unit 110, interference with the expanded image light causes distortion that creates a rainbow pattern. because it can cause

5 is a schematic side cross-sectional view of a diffractive optical element and a light guide unit in which a reduction layer is disposed for explaining a method of calculating an incident condition of external light O that can reach a reference position P.

5(a) shows the reference critical angle θ of the horizontal line H of the optical path that can reach the reference position P through the area of the light guide unit 110 occupied by the diffractive optical element 140 when there is no reduction layer. _e ) is a drawing.

Here, the diffraction optical element 140 may have a grating line pattern of period d and may be disposed on one surface 110a of the light guide part 110 .

Here, the reference position P is spaced apart from the lower side 140b of the diffractive optical element 140 by a length B in a first direction D1 toward the upper side 140c from the lower side 140b of the diffractive optical element 140. , It may be a position spaced apart from one surface 110a of the light guide unit 110 by a length R in a second direction perpendicular to the first direction D1 and directed toward the other surface 110b. The reference position P may be determined as a position corresponding to a position where a user's pupil may be located when manufacturing a display device including a diffraction guide plate module.

On the other hand, referring to FIG. 5, when there is no reduction layer, the horizontal line H of the optical path that can reach the reference position P through the area of the light guide unit 110 occupied by the diffractive optical element 140 is the reference critical angle ( θ _e ) may be defined by Equation 1 below.

[Equation 1]

Here, θ _e Is the critical angle (θ _e ) based on the horizontal line (H) of the optical path that can reach the reference position (P), B is the shortest distance between the lower side of the diffractive optical element on which the reduction layer is disposed and the reference position in the first direction, R may be defined as the shortest distance between one surface of the light guide unit and the reference position in the second direction. Here, it is assumed that the thickness (t) of the light guide part 110 is significantly thinner than R.

5(b) shows a case in which external light O is incident and diffracted by the diffractive optical element 130 and then emitted through the light guide unit 110 to reach the reference position P when there is no reduction layer. It is a drawing showing an example of an optical path.

The condition of the emission angle (θ _o ) at which the diffracted light diffracted by the diffractive optical element 130 can reach the reference position P is as follows Conditional Expression A.

[conditional expression A]

That is, diffracted light diffracted by the diffraction optical element 130 when the emission angle θ _o is smaller than the reference critical angle θ _e of the horizontal line H of the optical path that can reach the reference position P. This reference position (P) is reached.

On the other hand, light having a wavelength of λ is incident on the diffractive optical element 140 having a refractive index of n and a period of a grating line pattern of d at an angle of incidence θ based on a horizontal line H, and diffracting in the light guide unit 110. The diffraction angle (θ _d ) formed by the diffracted light and the horizontal line (H) is in the relationship of Equation 2 below.

[Equation 2]

In addition, the emission angle (θ _o ) emitted through the light guide unit 110 out of the condition that can be totally reflected within the light guide unit 110 is related to the diffraction angle (θ _d ) according to Snell's law It can be defined by Equation 3 below.

[Equation 3]

Therefore, the angle of incidence θ Can be defined as the following Equation 4 by a combination of Equations 2 and 3.

[Equation 4]

On the other hand, combining Equation 4 and conditional expression A, the following conditional expression B can be derived.

[conditional expression B]

클 때일 수 있다.That is, light with a wavelength of λ is incident on the diffraction optical element 140 having a refractive index of n and a period of a grating line pattern of d at an angle of incidence θ based on a horizontal line H, and is emitted through the diffraction and light guide unit 110. After reaching the reference position (P), the incident angle θ based on the horizontal line (H) this

may be when it is large.

Therefore, it is preferable that the reduction layer 200 reduces the rate at which external light in the standard wavelength range, which is incident at an angle equal to or greater than the standard incident angle determined by the following [Conditional Expression 1], reaches the reference position. Here, the term “reduce” may mean further reducing the transmittance of light incident at an angle greater than or equal to the reference incident angle compared to the transmittance of light incident at an angle less than the reference incident angle.

[conditional expression 1]

Here, θ is the reference angle of incidence, λ is the minimum wavelength of the reference wavelength range, is the period of the grating line pattern of the diffraction optical element on which the reduction layer is disposed, B is the reference position in the first direction between the lower side of the diffraction optical element on which the reduction layer is disposed and the reference position The shortest distance, R, may be defined as the shortest distance between one surface of the light guide unit and the reference position in the second direction.

Meanwhile, the reference wavelength range may be 400 nm to 700 nm, which is a wavelength range in the visible light region. In addition, the reference angle of incidence (θ) is preferably determined based on a case in which d in [Conditional Expression 1] is selected as the longest period among grating line pattern periods of output diffraction optical elements provided in a plurality of diffraction guide plates. If d in [Condition 1] is not selected as the longest period among grating line pattern periods of the output diffraction optical elements provided in the plurality of diffraction light guide plates, the reduction layer 200 is incident on the reference wavelength range at an angle greater than or equal to the reference incident angle. Even if the transmittance of external light is designed to be below a predetermined standard, the transmittance of external light in the standard wavelength band incident at an angle greater than the standard incident angle is below the predetermined standard in the diffraction guide plate on which the output diffraction optical element having the longest period grating line pattern is disposed. because it may not be That is, the transmittance of external light in a reference wavelength band incident at an angle greater than or equal to the reference incident angle may not be less than or equal to the predetermined criterion based on the entire standard of the diffraction guide plate module.

For example, the minimum wavelength λ of the reference wavelength range is 400 nm, the period of the grating line pattern of the diffraction optical element on which the reduction layer is disposed is 408 nm, and the first When the shortest distance B in the direction is 10 mm and the shortest distance R in the second direction between one surface of the light guide part and the reference position is 30 mm and substituted into [Conditional Expression 1], the reference angle of incidence θ can be derived as about 41.6 degrees, and accordingly, the reduction layer needs to reduce the transmittance of external light incident at an angle of 41.6 degrees or more.

6 is a schematic diagram of a micro louver film as an example of a reducing layer.

One embodiment of the reduction layer is a film that is formed long in a direction parallel to the first direction D1, and is different from the light transmitting parts 210a that are arranged to cross each other along a direction parallel to the first direction D1. It may include a micro louver film (200a) having a miner (220a).

Since the length (b) of the light transmitting portion 210a in the first direction D1 is longer than the length (c) of the light blocking portion 210b, the overall light transmittance of the microlouver film 200a is not significantly reduced. The length (b) of the light transmitting portion 210a is preferably 50 to 500 μm, more preferably 70 to 200 μm. The length (c) of the light blocking portion 220a is 1 to 100 μm, preferably 10 to 50 μm. The angle of the light blocking portion 220a is approximately 40° to 90°. The angle of the light blocking portion 210b means an angle between the surface of the microlouver film 200a and the longitudinal direction of the light blocking portion 220a. In this embodiment, the angle of the light blocking portion 210b is 90 degrees.

The light transmitting portion 210a may be preferably made of a polymer having high light transmittance. As such polymers, thermoplastic resins, thermosetting resins, resins curable by actinic radiation such as UV rays, and the like can be used. Examples of such resins include cellulose resins (eg, cellulose acetate butyrate, triacetylcellulose, etc.), polyolefin resins (eg, polyethylene, polypropylene, etc.), polyester resins (eg, polyethylene terephthalate, etc.), polystyrene, polyurethane, polyvinyl chloride, acrylic resins, polycarbonate resins and the like.

The light-blocking portion 220a may be formed of a light-shielding material that absorbs or reflects light. Examples of such materials include (1) dark colored pigments or dyes, such as black or gray pigments or dyes, (2) metals, such as aluminum, silver, (3) dark colored metal oxides, and (4) dark colored pigments. or the aforementioned polymers containing dyes.

It is preferable that the thickness (a) of the microlouver film 200a and the length of the light transmitting portion 210a satisfy the following [Conditional Expression 2].

[conditional expression 2]

Here, a is the thickness of the microlouver film, and b is the length of the light-transmitting part.

Hereinafter, the process of deriving [Conditional Expression 2] will be described.

Through the structure in which the micro-louver film shown in FIG. 6 is disposed on the side of the diffractive optical element, the area where light transmission is possible is the area where the light transmission unit 210a is located, and the critical incident angle where light transmission is possible through the light transmission unit 210a. (θ _i ) is equal to Equation 3 below.

[Equation 3]

On the other hand, as described above, since it is desirable for the reduction layer 200 to reduce the rate at which external light in the reference wavelength range that is incident at an angle greater than the reference incident angle determined by [Conditional Expression 1] reaches the reference position, [Chosun Equation 1 ] and [Equation 3], the conditions for the thickness (a) of the micro louver film 200a and the length (b) of the light transmitting part 210a may be derived as in [Conditional Expression 2].

In addition, the reference angle of incidence θ derived as an example The ratio condition of the length (b) of the light emitting part 210a to the thickness (a) of the micro louver film 200a for reducing the transmittance of external light incident at an angle of about 41.6 degrees or more is such that b / a is 0.66 or less. this is preferable

7 is a schematic diagram of an optical film including a liquid crystal film as another embodiment of a reducing layer.

Another embodiment of the reduction layer includes a first linear polarizer 210b, a second linear polarizer 220b, and a liquid crystal film 230b disposed between the first linear polarizer 210b and the second linear polarizer 220b. It may be an optical film (200b) to do.

In this specification, the term “polarizer” refers to a functional layer exhibiting selective transmission and blocking characteristics, for example, reflection or absorption characteristics, with respect to incident light. The polarizer may have, for example, a function of transmitting light vibrating in one direction from incident light vibrating in several directions and blocking light vibrating in the other direction. In this specification, "linear polarizer" means a case in which light selectively transmitted is linearly polarized light oscillating in one direction and selectively blocked light is linearly polarized light oscillating in a direction perpendicular to the oscillation direction of the linearly polarized light. The type of linear polarizer is not particularly limited, and, for example, as a reflective polarizer, for example, DBEF (Dual Brightness Enhancement Film), LLC layer (Lyotropic Liquid Crystal), or wire grid polarizer. etc. can be used, and as an absorption type polarizer, for example, a polarizer in which iodine is dyed on a polymer stretched film such as a PVA stretched film or the like, or an anisotropic polarizer in which a liquid crystal polymerized in an aligned state is used as a host and arranged according to the orientation of the liquid crystal. A guest-host type polarizer using a dye as a guest may be used, but is not limited thereto.

Absorption axes of the first linear polarizer 210b and the second linear polarizer 220b may be parallel to each other.

The liquid crystal film 230b may have a structure in which a difference in the degree of phase retardation is generated according to a propagation angle of light with respect to the surface. As a result, the light incident through the second linear polarizer 220b passes through the liquid crystal film 230b in a linearly polarized state. direction of vibration of linearly polarized light) is also changed, and transmittance may vary according to the direction of vibration of linearly polarized light reaching the first linear polarizer 210b, so that transmittance control according to the angle of incidence of light incident through the second polarizer 220b becomes possible. .

An example of the liquid crystal film 230b may be first and second nonlinear spray alignment liquid crystal films 231b and 232b sequentially formed on the first linear polarizer 210b.

Another example of the liquid crystal film 230b may be first and second liquid crystal films 233b and 234b that are sequentially formed on the first linear polarizer 210b and each include a linear spray-aligned liquid crystal compound. .

In this specification, the term “spray alignment” refers to an alignment state in which a tilt angle of a liquid crystal compound present in a liquid crystal film gradually changes along the thickness direction of the liquid crystal film. In this specification, the term "tilt angle" refers to the minimum angle between 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” refers to a tilt angle obtained by converting an average value of tilt angles of all liquid crystal compounds or an average value of arrangements of all liquid crystal compounds. In the present specification, the term “optical axis” refers to an axis in the direction of the long axis of the rod shape when the liquid crystal compound is rod-shaped, and refers to an axis in the normal direction of the plane of the disk when the liquid crystal compound is discotic. Therefore, in the present specification, "the liquid crystal film includes a spray-aligned liquid crystal compound" means that when the liquid crystal compound is rod-shaped, the long axis direction gradually changes along the thickness direction of the liquid crystal film, or the liquid crystal compound is the original plate. In the case of shape, it means that the normal direction of the plane of the original plate gradually changes along the thickness direction of the liquid crystal film.

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

Spray orientation can be divided into linear spray orientation and non-linear spray orientation. In this specification, the term “linear spray orientation” refers to an alignment state in which the graph shown with the thickness of the liquid crystal film as the x-axis and the local tilt angle corresponding to the thickness as the y-axis represents a linear graph , that is, an alignment state in which the slope is constant. In one example, the linear spray orientation is the ratio (z / d) of the corresponding thickness (z) to the total thickness (d) of the liquid crystal film as the x-axis (ie, x = 0 to 1.0), corresponding to the corresponding thickness The local tilt angle to be the y-axis, but the distance (b) of the minimum tilt angle and the maximum tilt angle on the y-axis is equal to the distance (a) within the range of x = 0 to 1.0, so that the slope of the graph shown is on the x-axis Accordingly, it may mean a constant orientation state, for example, an orientation state in which an average tilt factor is in the range of about 0.95 to 1.05 (see graph A of FIG. 8).

In contrast, the term “non-linear spray orientation” in this specification refers to an alignment state in which the graph shown with the thickness of the liquid crystal film as the x-axis and the local tilt angle corresponding to the thickness as the y-axis represents a non-linear graph. , that is, an alignment state in which the slope changes according to the thickness of the liquid crystal film. In one example, the non-linear spray alignment may refer to an alignment state in which the slope of a tilt angle with respect to the thickness of the liquid crystal film gradually increases or decreases. In one example, the non-linear spray orientation takes the ratio (z / d) of the corresponding thickness (z) to the total thickness (d) of the liquid crystal film as the x-axis (ie, x = 0 to 1.0), corresponding to the corresponding thickness The local tilt angle to be the y-axis, but the distance (b) of the minimum tilt angle and the maximum tilt angle on the y-axis is equal to the distance (a) within the range of x = 0 to 1.0, so that the slope of the graph shown is on the x-axis It means an orientation state in which the average tilt factor is less than about 0.95 (refer to graph B of FIG. 8) or gradually increases along the x-axis but the average tilt factor is greater than about 1.05. Yes (see graph C in FIG. 8).

In one specific example, the slope of the graph gradually decreases along the x-axis in terms of effectively implementing selective transmission and blocking characteristics according to the viewing angle, but the average slope (tilt factor) is less than about 0.95, such as about 0.9 or less, about 0.8 or less, about 0.7 or less. In this case, the lower limit of the average slope may be about 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, or 0.6 or more.

In this specification, unless otherwise specified, the tilt factor may refer to a tilt factor value derived by measuring the phase difference of the film for each angle using Axoscan (Axometrix Co., Ltd.). The tilt factor of the spray alignment liquid crystal film may be adjusted by adjusting the process temperature during manufacture of the spray alignment liquid crystal film. In one example, the spray alignment liquid crystal film may be prepared by curing a layer of a known spray alignment liquid crystal composition. In the above, curing may be performed by irradiating the layer of the spray alignment liquid crystal composition with ultraviolet rays, and the tilt factor of the spray alignment liquid crystal film may be adjusted by adjusting the temperature during the irradiation of the ultraviolet rays. For example, the tilt factor tends to increase as the temperature at the time of ultraviolet irradiation increases.

In an optical film, when the first and second liquid crystal films are non-linear spray orientation liquid crystal films, the optical film is advantageous in exhibiting selective transmission and blocking characteristics different from viewing angles. In this case, the average tilt angle of the first and/or second liquid crystal film may be in the range of 45 degrees to 55 degrees, for example. When the first and second liquid crystal films implement non-linear spray orientation from the front side, they can function as a linear twisted nematic film at an inclination angle, so it is advantageous to exhibit selective transmission characteristics according to the viewing angle. Therefore, when the average tilt angle of the first and/or second liquid crystal film is within the above range, it is advantageous to exhibit selective transmission characteristics according to the viewing angle.

Meanwhile, the first and second liquid crystal films 231b, 232b, 233b, and 234b are adjacent to the interface with the first linear polarizer 210b and/or the second linear polarizer 220b based on [Conditional Expression 1]. The tilt angle is 0 to 30 degrees in the region (left and right sides of (b) of FIG. 7), and the tilt angle is 0 to 30 degrees in the region adjacent to the interface with both liquid crystal films (231b, 232b, 233b, 234b) (center of reference of (b) of FIG. 7). An angle of 60 to 90 degrees, a tilt factor of 0.7 to 1.3, and a thickness of the liquid crystal film may be selectively determined and designed between 0.5 and 5 μm. As a result, the blocking layer 200b is disposed on the side of the diffractive optical element 140 and can reduce the rate at which external light in the reference wavelength range reaching the reference position incident at an angle equal to or greater than the reference incident angle determined by [Conditional Equation 1] can be reduced.

The diffraction light guide plate module 1000 according to an embodiment of the present invention is a light guide unit 110 corresponding to an area where at least one diffractive optical element 140 among a plurality of diffractive optical elements 120, 130, and 140 is located. External light of the reference wavelength band disposed in the area on one surface 110a and incident at an angle within a predetermined reference range is emitted from one surface 110a of the light guide part 110 through the diffraction optical element 140 and the light guide part 110. Since the reduction layer 200 is provided to reduce the ratio of reaching the reference position P, which is spaced toward the other surface 110b, unintentional external light is incident and interferes with the expanded image light, so that a rainbow is emitted together. There is an advantage in preventing distortion of the expanded image light, such as a pattern.

Although the present invention has been described with respect to the preferred embodiments mentioned above, various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the scope of the appended claims will include such modifications and variations as long as they fall within the gist of the present invention.

100: diffraction light guide plate
110: light guide unit
120: input diffractive optical element
131: main intermediate diffractive optical element
132: auxiliary intermediate diffraction optical element
140: output diffraction optical element
200: reduction layer

Claims (12)

a diffraction guide plate having a light guide unit for guiding light and a plurality of diffraction optical elements disposed on a surface of the light guide unit; and
It is disposed in an area on one side of the light guide part corresponding to the area where at least one diffractive optical element among the plurality of diffractive optical elements is located, and external light of a reference wavelength band incident at an angle within a predetermined reference range is disposed on the diffractive optical element and A reducing layer for reducing a ratio reached to a reference position spaced apart from one surface of the light guide part toward the other surface through the light guide part,
The diffractive optical element on which the reduction layer is disposed has a grating line pattern having a period d and is disposed on one surface of the light guide unit,
The reference position is spaced apart from the lower side of the diffractive optical element by a length B in a first direction from the lower side to the upper side of the diffractive optical element on which the reduction layer is disposed, and is perpendicular to the first direction from one side of the light guide unit and is perpendicular to the first direction from the other side. It is a position spaced apart by the length R from the one surface in the second direction toward,
The reduction layer is for reducing the rate at which external light in the reference wavelength band, which is incident at an angle equal to or greater than the reference incident angle determined by the following [Conditional Expression 1], reaches the reference position.
[conditional expression 1]

Here, θ is the reference angle of incidence, λ is the minimum wavelength of the reference wavelength band, is the period of the grating line pattern of the diffraction optical element on which the reduction layer is disposed, and B is the lower side of the diffraction optical element on which the reduction layer is disposed and the reference The shortest distance between positions in the first direction, R is the shortest distance between one surface of the light guide part and the reference position in the second direction. According to claim 1,
The plurality of diffraction optical elements include an input diffraction optical element that receives light from a light source and diffracts the received light so that the received light can be guided on the light guide unit, and receives the light diffracted from the input diffraction optical element. and an intermediate diffraction optical element configured to expand the received light one-dimensionally by diffraction, and configured to receive the expanded light from the intermediate diffraction optical element and output the received light from the light guide by diffraction. Including an output diffractive optical element that is,
wherein the reduction layer is disposed on a side of at least an output diffraction optical element among the input diffraction optical element, the intermediate diffraction optical element, and the output diffraction optical element. delete According to claim 1,
The reference wavelength range is 400 nm to 700 nm, the diffraction guide plate module. According to claim 1,
The diffraction guide plate module includes a first diffraction optical element separating light with a wavelength of 550 nm to 700 nm, a second diffraction optical element to separate light with a wavelength of 400 nm to 550 nm, and light with a wavelength of 450 nm to 650 nm. A plurality of diffraction guide plates having at least one of the third diffractive optical elements separating the ? are stacked,
The reference incident angle is determined based on a case where d in [Conditional Expression 1] is selected as the longest period among grating line pattern periods of output diffraction optical elements provided in the plurality of diffraction light guide plates. According to claim 1,
The reducing layer,
A diffraction guide plate module comprising a microlouver film formed elongately along a direction parallel to the first direction, and having a light transmitting part and a light blocking part which are arranged to cross each other along a direction parallel to the first direction. According to claim 6,
In the microlouver film, the thickness and the length of the light-transmitting portion satisfy the following [Conditional Expression 2], a diffraction guide plate module:
[conditional expression 2]

Here, a is the thickness of the micro-louver film, and b is the length of the light-emitting part. According to claim 1,
The reduction layer may include a first linear polarizer; and first and second nonlinear spray alignment liquid crystal films sequentially formed on the first linear polarizer. According to claim 8,
The first or second nonlinear spray orientation liquid crystal film has a tilt factor of less than 0.95 or greater than 1.05, the diffraction light guide plate module. According to claim 8,
The optical film further comprises a second linear polarizer disposed adjacent to the second non-linear spray alignment liquid crystal film, the diffractive light guide plate module. According to claim 1,
The reduction layer may include a first linear polarizer; and first and second liquid crystal films sequentially formed on the first linear polarizer and each including a linear spray-aligned liquid crystal compound. According to claim 11,
The optical film further comprises a second linear polarizer disposed adjacent to the second liquid crystal film, the diffraction light guide plate module.

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