KR102423970B1 - Optical member, backlight assembly and liquid crystal display including the same - Google Patents

Abstract

An optical member, a backlight assembly including the same, and a liquid crystal display are provided. The optical member includes a first reflective polarizing part and a second reflective polarizing part disposed above the first reflective polarizing part and having a wider reflective polarization wavelength range than the first reflective polarizing part.

Description

Optical member, backlight assembly and liquid crystal display including the same

The present invention relates to an optical member, a backlight assembly including the same, and a liquid crystal display device.

A liquid crystal display (LCD) is a device that displays an image by injecting liquid crystal between two glass plates, applying power to the upper and lower glass plate electrodes, and changing the arrangement of liquid crystal molecules in each pixel. Unlike a cathode ray tube display (CRT), a plasma display panel (PDP), etc., the display by the liquid crystal display itself is non-luminous, so it cannot be used in a place where there is no light. A backlight assembly irradiated uniformly on the information display surface is mounted for the purpose of compensating for this disadvantage and enabling use in a dark place.

A general liquid crystal display device mainly transmits light of a wavelength band of visible light incident from a backlight using an LED light source through a plurality of color filters of a panel to transmit only light of a different wavelength band for each pixel, thereby realizing various colors displayed on the screen. However, the wavelength of the light filtered by the color filter has a wide width, and thus color reproducibility is not good. For example, in the case of a liquid crystal display using an organic light emitting diode (OLED), which is a self-luminous device, or a quantum dot (QD), which is recently in the spotlight, the width of the wavelength emitted when expressing red, green, and blue colors It is narrow and can express red, green, and blue with excellent saturation. However, in the case of the color filter, since the transmitted wavelength is relatively wide, even if it is intended to express pure red, a significant amount of light in the adjacent green wavelength band is also leaked, so that pure red is not well expressed. Therefore, it is difficult for a general liquid crystal display using a color filter to accurately express the color of an object.

An object of the present invention is to provide an optical member exhibiting excellent color reproducibility.

Another object of the present invention is to provide a backlight assembly having excellent color reproducibility.

Another object of the present invention is to provide a liquid crystal display having excellent color reproducibility.

The problems of the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

An optical member according to an embodiment of the present invention for solving the above problems is a first reflective polarization part and a second reflective polarization light disposed above the reflective polarization part, and having a wider reflective polarization wavelength range than the first reflective polarization part includes wealth.

A backlight assembly according to an embodiment of the present invention for solving the other problem includes the optical member as described above.

A liquid crystal display device according to an exemplary embodiment of the present invention for solving the other problems includes the above-described optical member.

The details of other embodiments are included in the detailed description and drawings.

According to the optical member according to the embodiments of the present invention, since light of a specific wavelength band is relatively amplified, excellent color reproducibility may be exhibited. In addition, in the above-described optical member, since the second reflective polarizer transmits only light of a specific polarization, a polarizing plate provided in the liquid crystal display panel may be partially omitted, thereby reducing the manufacturing cost while reducing the thickness of the liquid crystal display device. .

The effect according to the present invention is not limited by the contents exemplified above, and more various effects are included in the present specification.

1 is a schematic diagram of a liquid crystal display device according to some embodiments of the present invention.
2 is a cross-sectional view of an optical member according to an embodiment of the present invention.
3 is a graph illustrating a light spectrum of a first reflective polarization layer.
4 is a graph illustrating a light spectrum of light passing through a wavelength control film.
5 is a cross-sectional view of a wavelength control film according to another embodiment of the present invention.
6 is a graph illustrating a light spectrum of a second reflective polarization layer according to an embodiment of the present invention.
7 is a graph illustrating an optical spectrum of a first reflective polarization layer and an optical spectrum of a second reflective polarization layer according to an embodiment of the present invention.
8 is a graph illustrating a light spectrum of a second reflective polarization layer according to another exemplary embodiment of the present invention.
9 is a graph illustrating a light spectrum of a light source provided to an optical member.
10 is a graph illustrating a light spectrum of light passing through an optical member according to an embodiment of the present invention.
11 is a cross-sectional view of an optical member according to another embodiment of the present invention.
12 is a cross-sectional view of a backlight assembly according to an embodiment of the present invention.
13 is a cross-sectional view of a backlight assembly according to another embodiment of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent 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, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the present invention is only defined by the scope of the claims.

Reference to an element or layer “on” another element or layer includes any intervening layer or other element directly on or in the middle of another element. On the other hand, when an element is referred to as "directly on", it is indicated that there are no intervening elements or layers. Like reference numerals refer to like elements throughout. “And/or” includes each and every combination of one or more of the recited items.

Although the first, second, etc. are used to describe various elements, these elements are not limited by these terms, of course. These terms are only used to distinguish one component from another. Therefore, it goes without saying that the first component mentioned below may be the second component within the spirit of the present invention.

The terminology used herein is for the purpose of describing the embodiments and is not intended to limit the present invention. In this specification, the singular also includes the plural, unless specifically stated otherwise in the phrase. As used herein, “comprises” and/or “comprising” does not exclude the presence or addition of one or more other components in addition to the stated components.

Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with the meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly defined in particular.

Spatially relative terms "below", "beneath", "lower", "above", "upper", etc. It can be used to easily describe the correlation between a component and other components. A spatially relative term should be understood as a term that includes different directions of components during use or operation in addition to the directions shown in the drawings. For example, when a component shown in the drawing is turned over, a component described as “beneath” or “beneath” of another component may be placed “above” of the other component. can Accordingly, the exemplary term “below” may include both directions below and above. Components may also be oriented in other orientations, and thus spatially relative terms may be interpreted according to orientation.

The terms "~ sheet", "~ film", "~ plate", etc. used herein may be used interchangeably with the same meaning. In addition, the term optical member in the present specification may be used to include an optical sheet, an optical film, an optical plate, an optical film package, and the like.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a schematic diagram of a liquid crystal display device according to some embodiments of the present invention.

Referring to FIG. 1 , a liquid crystal display according to an exemplary embodiment includes an optical member 10 and a liquid crystal display panel 20 disposed thereon. The optical member 10 includes a first reflective polarizing part 11 and a second reflective polarizing part 13 disposed above the reflective polarizing part 11 .

The first reflective polarizer 11 and the second reflective polarizer 13 transmit specific polarized light and reflect specific polarized light with respect to light of at least a partial wavelength, respectively. The first reflective polarizing part 11 has a reflective polarization function for a narrow wavelength range, and the second reflective polarization part 13 has a reflective polarization function for a wider wavelength range than the first reflective polarization part.

The optical member 10 receives light from the light source 30 . The overall light propagation path of the optical member 10 is in the order of the first reflective polarization part 11 and the second reflective polarization part 13 . Since the second reflective polarizer 13 transmits light of a specific polarization, even if the light incident on the optical member 10 is unpolarized light, the optical member 10 may emit light having a specific polarization. Light having a specific polarization emitted by the optical member 10 may be effectively utilized for a display or the like.

For example, the liquid crystal display panel 20 displays an image by controlling light transmittance. In general, the liquid crystal display panel 20 controls transmittance using polarized light. The liquid crystal display panel includes polarizing elements such as polarizing plates 21 and 22 or a wire grid in order to use polarized light. The incident-side polarizing plate 21 or the like blocks light that is not polarized in a specific direction before the light passes through the liquid crystal layer, so that the polarized light is incident on the liquid crystal layer. Accordingly, light polarized in a direction different from the polarizing plate 21 of the liquid crystal display panel is blocked and thus not used in the liquid crystal display panel 20 , resulting in loss in luminance.

In this embodiment, the light reflected by the first reflective polarizer 11 and the second reflective polarizer 13 travels in a direction opposite to the emission direction of the optical member 10 . The reflected light may be refracted and reflected by the light recycling structure inside the backlight assembly and re-enter the upper side. In the recycling process, the light does not maintain the polarization when it is reflected as the phase is changed, but is converted into an unpolarized state in which various polarizations are mixed. Accordingly, the re-entered light passes through the first reflective polarizer 11 and the second reflective polarizer 13 and is transmitted or reflected again according to its polarization state. This recycling process can be repeated.

During the recycling process, the amount of light emitted through the optical member 10 having a specific polarization is amplified. If the polarization axis of the second reflective polarizer 13 is aligned in the same direction as the incident-side polarization axis of the liquid crystal display panel 20, the amount of light blocked by the incident-side polarizing plate 21 of the liquid crystal display panel 20 is reduced. It is possible to increase the overall luminance efficiency.

On the other hand, as described above, the first reflective polarizer 11 has a reflective polarization function for a narrow wavelength range, and the second reflective polarizer 13 has a wider wavelength range than the first reflective polarizer 11 . It has a reflective polarization function. The reflective polarization wavelength range of the first reflective polarization part 11 may be completely included in the reflective polarization wavelength range of the second reflective polarization part 13 .

The light of the wavelength having the reflected polarization in the first reflective polarization unit 11 will be finally amplified and emitted through recycling. The light that has passed through the first reflective polarizer 11 may be recycled again by the second reflective polarizer 13 . The second reflective polarizer 13 has a wide reflective wavelength range and contributes to an overall increase in luminance, while the first reflective polarizer 11 selectively amplifies light of a specific wavelength.

Specifically, the light of a wavelength that does not have reflected polarization in the first reflective polarization unit 11 is recycled and amplified only by the second reflective polarization unit 13, but the first reflective polarization unit 11 generates reflected polarized light. The light having the wavelength is recycled twice by the first reflective polarizing unit 11 and the second reflective polarizing unit 13 and amplified. Accordingly, the light of the wavelength having the reflected polarization may be relatively more amplified by the first reflective polarizer 11 , and thus the light of the corresponding wavelength may be emitted relatively more.

As such, when the relative size of a specific wavelength is amplified, color reproducibility can be improved even in the case of the liquid crystal display panel 20 employing a general color filter. More specifically, a general liquid crystal display device transmits light of a wavelength band of visible light incident from a backlight mainly using an LED light source through a plurality of color filters of the panel, thereby transmitting only light of a different wavelength band for each pixel. implement color. However, the wavelength of the light filtered by the color filter has a wide width, and thus color reproducibility is not good.

In the case of a liquid crystal display using an organic light emitting diode (OLED), which is a self-luminous device, or a quantum dot (QD), which has recently been in the spotlight, the wavelengths emitted when expressing red, green, and blue colors are narrow and thus have excellent chroma. of red, green, and blue can be expressed. However, in the case of the color filter, since the transmitted wavelength is relatively wide, even if it is intended to express pure red, a significant amount of light in the adjacent green wavelength band is also leaked, so that pure red is not well expressed. Therefore, it is difficult for a general liquid crystal display using a color filter to accurately express the color of an object.

However, the optical member 10 as described above can exhibit excellent color reproducibility when relatively amplifying light in a specific wavelength band. In addition, in the above-described optical member 10 , since the second reflective polarizer 13 transmits (exits) only light of a specific wavelength, the incident-side polarizer 21 provided in the liquid crystal display panel 13 may be partially omitted. Therefore, it is possible to reduce the manufacturing cost while reducing the thickness of the liquid crystal display device.

The liquid crystal display device according to an embodiment of the present invention may further include a wave adjustment unit 12 . The wave adjustment unit 12 may be disposed between the first reflective polarizer 11 and the second reflective polarizer 13 . The wavelength adjusting unit 12 serves to block a specific wavelength. When the cutoff wavelength band of the wavelength adjusting unit 12 is adjusted to be different from the amplification target wavelength, the corresponding wavelength is emitted relatively smaller. Since the wavelength adjusting unit 12 is located between the first reflective polarizing unit 11 and the second reflective polarizing unit 13 , the light transmitted from the first reflective polarizing unit 11 and the second reflective polarizing unit 13 . It is possible to block or reduce the corresponding wavelength in the light that is reflected and recycled. Accordingly, the relative size of a specific wavelength can be further adjusted, and thereby the color reproducibility of the emitted light can be significantly increased. In addition, when the wavelength adjusting unit 12 is provided in the light emitting part of the liquid crystal display panel, the effect of reducing the amount of light incident on the liquid crystal display panel due to the wavelength adjusting unit 12 and/or increasing the luminance by the plurality of reflective polarizing layers is reduced. Since attenuation can be prevented, it is possible to have the effect of improving the luminance relatively while improving the color reproducibility.

In addition, when the wavelength adjusting unit 12 is disposed between the second reflective polarizer 13 and the liquid crystal display panel, luminance and color reproducibility can be improved at the same time. Accordingly, the position at which the wavelength adjusting unit 12 is disposed may be adjusted above the first reflective polarizing unit 11 according to color reproducibility and luminance characteristics of a liquid crystal display including a liquid crystal display panel.

In some embodiments, the positions of the above-described first reflective polarizer 11 and the second reflective polarizer 13 may be changed. For example, the second reflective polarizer 13 having a relatively wide range of reflection wavelength bands is disposed on the incident side of the optical member, and the first reflective polarizer 11 has a narrow range of reflection wavelength bands on the exit side. ) can be placed. In this case, the main propagation path of light will be from the second reflective polarizer 13 to the first reflective polarizer 11 side. Even in this case, the light of a wavelength that does not have reflected polarization in the first reflective polarization part 11 is recycled and amplified only by the second reflective polarization part 13, but the first reflective polarization part 11 has reflected polarization The light of the wavelength is recycled twice by the second reflective polarizing unit 13 and the first reflective polarizing unit 11 and amplified. Accordingly, the light of the wavelength having the reflected polarization may be relatively more amplified by the first reflective polarizer 11 , and thus the light of the corresponding wavelength may be emitted relatively more. In the above embodiment, when the wavelength adjusting unit 12 is further included, the wavelength adjusting unit 12 may be disposed between the second reflective polarizing unit 13 and the first reflective polarizing unit 11, but is limited thereto. and may be disposed on the light output part or the light input part of the liquid crystal display panel.

Hereinafter, the above-described optical member 10 will be described in more detail. In the following embodiment, a case will be exemplified in which the first reflective polarizer 11 is disposed at the bottom, the second reflective polarizer 13 is disposed at the top, and the wavelength adjuster 12 is disposed in the middle. . However, the present invention is not limited thereto, and the positions of the first reflective polarizing part 11 and the second reflective polarizing part 13 are changed, the wavelength adjusting part 12 is omitted, or the liquid crystal display panel light output part or Of course, it may be disposed in the light incident part.

2 is a cross-sectional view of an optical member according to an embodiment of the present invention.

Referring to FIG. 2 , the optical member 100 according to the present embodiment includes a first reflective polarizing film 110 , a wavelength control film 120 disposed on the first reflective polarizing film 110 , and a wavelength control film ( 120) and a second reflective polarizing film 130 disposed thereon. In the drawing, the main propagation path of light through the optical member 100 is from the bottom to the top.

The first reflective polarizing film 110 includes a first reflective polarizing layer 111 . In FIG. 2 , the first reflective polarization layer 111 is illustrated as being disposed on the outermost side where light is incident, but the present invention is not limited thereto. After that, it may be incident on the first reflective polarization layer 111 .

In an exemplary embodiment, the first reflective polarization layer 111 is a layer that transmits any one of left circularly polarized light and right circularly polarized light with respect to light of a specific wavelength band and reflects the other. An example of a material having such properties is a cholesteric liquid crystal. The wavelength band through which the cholesteric liquid crystal transmits and reflects may be controlled by the pitch of the cholesteric liquid crystal.

When the cholesteric liquid crystal included in the first reflective polarization layer 111 has a pitch of 2 or more, the first reflective polarization layer 111 may reflectively polarize two or more wavelength bands. For example, the first reflective polarizing layer 111 may include a cholesteric liquid crystal of a first pitch having a minimum transmittance in a first wavelength band of 610 nm to 630 nm, and a second cholesteric liquid crystal having a minimum transmittance in a second wavelength band of 540 nm to 560 nm. It may include a cholesteric liquid crystal having two pitches. Here, since the reflective polarization wavelength band of the cholesteric liquid crystal of the first pitch is larger than the reflective polarization wavelength band of the cholesteric liquid crystal of the second pitch, the first pitch is longer than the second pitch.

3 is a graph illustrating a light spectrum of a first reflective polarization layer. Referring to FIG. 3 , the spectrum of the first reflective polarization layer 111 has two valleys in a first wavelength band of 610 nm to 630 nm and a second wavelength band of 540 nm to 560 nm. The trough of each valley may have a light transmittance in the range of 40 to 60%, preferably in a range adjacent to 50%. The region between the two valleys or the wavelength band outside the valley may have a light transmittance of 80% or more, preferably 90% or more.

Referring back to FIG. 2 , the first pitch cholesteric liquid crystal and the second pitch cholesteric liquid crystal may be arranged in a thickness direction in a single layer. As another example, as a multi-layer structure, the cholesteric liquid crystal of the first pitch and the cholesteric liquid crystal of the second pitch may be respectively formed as different layers or films and stacked, or may be combined by a bonding layer.

In this embodiment, it is preferable that the first reflective polarization layer 111 has a narrow reflective polarization band. The width of the reflective polarization band is related to the full width at half maximum. The full width at half maximum is defined as the distance between two X-coordinates that intersect with a straight line passing through the middle of the maximum and minimum values in a graph that is convex down. Accordingly, the full width at half maximum of the light spectrum may be defined as a width between two wavelengths corresponding to an intermediate transmittance that is an intermediate value between the maximum transmittance and the minimum transmittance in the light spectrum.

The full width at half maximum of the light spectrum of the first reflective polarization layer 111 having the narrow reflective polarization band described above may be 30 nm or less. Specifically, the light spectrum of the first reflective polarizing layer 111 may have a half maximum width of 60 nm or less and 30 nm or less, respectively, at wavelengths having the minimum transmittance in the vicinity of the above-described first and second wavelength bands.

In order for the first reflective polarizing layer 111 to have a narrow full width at half maximum, it is advantageous that the refractive index anisotropy of the cholesteric liquid crystal is small. For example, when a cholesteric liquid crystal having a refractive index anisotropy of 0.16 or less is used, the full width at half maximum can be reduced to 60 nm or less, and when the refractive index anisotropy of the liquid crystal is 0.12 or less, the half maximum width can be further reduced to 30 nm or less. A narrow reflective polarization band such as a first wavelength band or a second wavelength band may be implemented.

The first reflective polarizing film 110 may further include a retardation layer 112 . The retardation layer 112 is disposed on the first reflective polarization layer 111 to change the phase of light emitted through the first reflective polarization layer 111 . The phase change value of the retardation layer 112 is preferably a value capable of converting circularly polarized light selectively transmitted by the first reflective polarization layer 111 into linearly polarized light. For example, the retardation layer 112 may have a phase delay value of λ/4.

The first reflective polarization layer 111 transmits only specific circularly polarized light with respect to the light of the first wavelength band and the second wavelength band. On the other hand, light other than the first wavelength band and the second wavelength band is transmitted regardless of whether the light is circularly polarized or not. Accordingly, the light of the first wavelength band and the second wavelength band among the light passing through the retardation layer 112 is converted into linearly polarized light, but the light of the other wavelength bands is only converted in a polarization state when emitted, so that the linearly polarized light In addition, both circularly polarized light and elliptically polarized light are included. Based on the linearly polarized light, the light passing through the retardation layer 112 includes more linearly polarized light of the first wavelength band and the second wavelength band than the linearly polarized light of another wavelength band. Accordingly, when the polarization axis of the upper second reflective polarization layer 131 is the same as the polarization directions of the linearly polarized light in the first and second wavelength bands, the corresponding light strikes the upper second reflective polarization layer 131 . can be released effectively.

The retardation layer 112 may be formed of A-plate liquid crystal or C-plate liquid crystal, or may be provided in the form of a retardation film made of uniaxially or biaxially stretched plastic.

When the retardation layer 112 is formed of liquid crystal, the first reflective polarizing film 110 may further include a substrate. The first reflective polarizing film 110 may be manufactured by coating the first reflective polarizing layer 111 on one surface of the substrate and coating the retardation layer 112 on the other surface of the substrate. As another example, the first reflective polarizing film 110 may be manufactured by coating the first reflective polarizing layer 111 on one surface of the substrate and coating the retardation layer on one surface of the first reflective polarizing layer 111 . In this case, the substrate will be disposed at the bottom. Conversely, the first reflective polarizing film 110 may be formed by first coating the retardation layer 112 on one surface of the substrate and coating the first reflective polarizing layer 111 on one surface of the retardation layer 112 . In this case, the substrate is arranged to face the uppermost. In the above examples, an adhesive layer such as a primer layer may be further interposed between the substrate, the first reflective polarizing layer 111 and the retardation layer 112 .

When the retardation layer 112 is provided as a retardation film made of plastic, the retardation layer 112 itself may serve as a substrate. In this case, the first reflective polarizing film 110 may be manufactured by coating the cholesteric liquid crystal on the retardation film or by forming and laminating a separate cholesteric liquid crystal film.

In addition, it will be easily understood by those skilled in the art that various methods for forming the first reflective polarizing layer 111 and the retardation layer 112 into one integrated film may be applied.

The wavelength control film 120 includes a wavelength control layer 121 . The wavelength control layer 121 blocks at least a portion of a specific wavelength band.

4 is a graph illustrating a light spectrum of light passing through a wavelength control film. Referring to FIG. 4 , the wavelength control layer 121 may block light of, for example, a third wavelength band between the first and second wavelength bands. Here, the meaning of blocking the light is a relative meaning and does not mean only completely blocking the light. Light blocking may be achieved through methods such as absorption, reflection, and wavelength conversion. In particular, in the case of blocking by inducing reflection or wavelength conversion by including a plurality of fine particles or forming a specific pattern, it is possible to further increase the light efficiency.

The third wavelength band may be 575 nm to 595 nm. The light transmittance of the third wavelength band may be significantly lowered compared to the light transmittance of the first wavelength band and the second wavelength band by the wavelength control layer 121 . Accordingly, since the light of the third wavelength band is blocked from the light passing through the wavelength control film 120 , the light of the first wavelength band and the second wavelength band may be relatively more amplified. The full width at half maximum of the light spectrum by the wavelength control layer 121 may be 60 nm or less, preferably 30 nm or less, at a wavelength having the minimum transmittance in the third wavelength band. The minimum transmittance in the third wavelength band may be 10% or less as indicated by a solid line in FIG. 4 . However, the present invention is not limited thereto, and the minimum transmittance in the third wavelength band may be variously selected within a range of 50% or less as indicated by a dotted line, a dashed-dotted line, and a dashed-dotted line of FIG. 4 .

The wavelength control layer 121 may include a binder and a wavelength blocking material distributed in the binder. The binder may be an acrylic and/or urethane-based binder. The wavelength blocking material may be a dye or a pigment that blocks a specific wavelength band, or a phosphor or a quantum dot material that changes a specific wavelength band into another wavelength band. In addition, the wavelength control layer 121 may include at least one of hollow particles, organic particles, and inorganic particles.

The wavelength control film 120 may further include an ultraviolet absorber. For example, the wavelength control layer 121 may further include a UV absorber or an overcoat layer including a UV absorber formed on at least one surface of the wavelength control layer 121 .

The wavelength control film 120 may further include a substrate 122 . The wavelength control layer 121 may be coated on one surface of the substrate 122 . As another example, the wavelength control layer 121 may not be formed on the substrate, but may be directly formed on at least one of the first reflective polarizing film 110 , the second reflective polarizing film 130 , and the liquid crystal display panel.

5 is a cross-sectional view of a wavelength control film according to another embodiment of the present invention. Referring to FIG. 5 , the wavelength control film 120a may further include an intermediate layer 123 interposed between the substrate 122 and the wavelength control layer 121 .

The intermediate layer 123 may be an optical functional layer. In this case, the intermediate layer 123 may have a structured surface. The structured surface may be an embossed pattern such as a prism, a microlens, or a tunnel-type lenticular, or an engraved pattern having a depression having a shape similar to the embossed pattern, or a shape in which the embossed pattern and the engraved pattern are mixed. . As another example, the surface of the intermediate layer 123 may be an uneven surface having a predetermined surface roughness.

The intermediate layer 123 may be made of a material having a refractive index different from that of the wavelength control layer 121 and the substrate 122 . Although the present invention is not limited thereto, the refractive index of the intermediate layer 123 may be the largest among them. The difference between the refractive indices of the intermediate layer 123 with respect to the refractive indices of the wavelength control layer 121 and the substrate 122 may be at least 0.01. When the refractive index difference is 0.01 or more, light refraction characteristics are high, so that light collection performance and viewing angle characteristics can be improved.

The wavelength control film 120a may further include an anti-reflection layer 124 formed on the lower surface of the substrate 122 . The anti-reflection layer 124 lowers the reflectance of light entering the wavelength control film 120a, and helps a greater amount of light to enter the wavelength control film 120a.

Referring back to FIG. 2 , the second reflective polarizing film 130 includes a second reflective polarizing layer 131 . The second reflective polarization layer 131 has a reflective polarization characteristic in a wavelength band wider than that of the first reflective polarization layer 111 . The second reflective polarizing layer 131 may be a liquid crystal type reflective polarizing layer applied in the same manner as the first reflective polarizing layer 111 , but may also be a layer that reflectively polarizes linearly polarized light. As described above, when the liquid crystal type reflective polarizing layer is applied to the second reflective polarizing layer 131 in the same manner as the first reflective polarizing layer 111 , the retardation layer 112 is a second reflective polarizing layer that is not the first reflective polarizing layer 111 . 2 may be provided on the reflective polarization layer 131 . When the second reflective polarizing layer 131 is a linearly polarizing reflective polarizing layer, for example, the second reflective polarizing layer 131 is a multilayered reflective polarizing layer or stretched reflective layer in which a high refractive layer and a low refractive layer are stretched and alternately stacked. It may be a polarizing layer. In addition, the second reflective polarizing layer 131 is a polymer dispersed type having a plurality of second polymers having different refractive indices in the first polymer layer, or a polymer type reflective polarizing layer having fibers instead of the second polymer, or a plurality of microscopic It may be a wire grid type reflective polarizing layer having a nanopattern.

The second reflective polarization layer 131 may have broadband reflective polarization characteristics. For example, it may have uniform or similar light transmittance over the entire wavelength band of visible light. The polarization axis of the second reflective polarization layer 131 is a polarization direction of the linearly polarized light of the first and second wavelength bands of the first and second wavelength bands, which are reflected and transmitted by the first reflective polarization layer 111 and converted into linearly polarized light by the retardation layer 112 . may be the same as

6 is a graph illustrating a light spectrum of a second reflective polarization layer according to an embodiment of the present invention. Referring to FIG. 6 , the light transmittance of the second reflective polarization layer 131 may be 40 to 60% over the entire visible light wavelength range of 400 nm to 700 nm.

7 is a graph illustrating an optical spectrum of a first reflective polarization layer and an optical spectrum of a second reflective polarization layer according to an embodiment of the present invention.

Referring to FIG. 7 , the minimum transmittance of the first reflective polarization layer may be equal to or smaller than the minimum transmittance of the second reflective polarization layer. In addition, the light spectrum of the first reflective polarization layer and the light spectrum of the second reflective polarization layer may cross each other. The intersection point is in the vicinity of the first wavelength band and the second wavelength band. In the vicinity of the first wavelength band and the second wavelength band, the minimum transmittance of the first reflective polarizing layer may be smaller than the transmittance of the second reflective polarizing layer in the corresponding wavelength band. In this case, since the light spectrum of the first reflective polarization layer has a downward convex shape in the vicinity of the first wavelength band and the second wavelength band, it may have two intersection points in the vicinity of each wavelength band.

When the minimum transmittance of the first reflective polarizing layer in the vicinity of the first and second wavelength bands is lower than the minimum transmittance of the second reflective polarizing layer, the amplification of wavelengths in the vicinity of the first and second wavelength bands may be sufficient . However, it goes without saying that the present invention is not limited to the above examples.

8 is a graph illustrating a light spectrum of a second reflective polarization layer according to another exemplary embodiment of the present invention. 8 illustrates that the second reflective polarizing layer may have different light transmittances in a wavelength band of 400 nm to 500 nm and a wavelength band of 500 nm to 700 nm. That is, in FIG. 8 , the maximum light transmittance is 90% or more in the wavelength band of 400 nm to 500 nm, and the light transmittance is at least 50% or more in the wavelength band. It shows that the reflective polarization is well made in this 40 to 60% range. When the light emitted from the light source has a maximum peak in the 450 nm wavelength band and a lower peak in the 540 nm wavelength band, as will be described later, the luminance of the light near the 450 nm wavelength band having a originally high peak is not amplified by the overall wavelength band. It may be more advantageous for exhibiting luminance uniformity.

Hereinafter, the light spectrum in the above-mentioned optical member is demonstrated.

9 is a graph illustrating a light spectrum of a light source provided to an optical member.

In general, a light source used in a liquid crystal display is mainly a white light source. 9 exemplarily shows the light spectrum of a typical white LED. Referring to FIG. 9 , the light spectrum of the white LED has two peaks. Specifically, it has a highest peak in a 450 nm wavelength band representing blue, and a low peak in a 540 nm wavelength band representing green. The light emitted from the light source is incident on the liquid crystal display panel through one or more optical sheets or optical members via a light guide for inducing surface light emission, such as a light guide plate or a diffusion plate, and is emitted by a color filter of the liquid crystal display panel. The light will have a spectrum with three peaks.

However, in the above light spectrum, the relative peak value in the wavelength band of 540 nm or higher representing green is not so high, and the light transmittance in the wavelength band of 580 nm to 590 nm is high, so that the distinction between green, yellow, and orange is vague, and accurate color reproduction is difficult. Not easy to do.

10 is a graph illustrating a light spectrum of light passing through an optical member according to an embodiment of the present invention. For convenience of explanation, the light spectrum passing through the optical member and the light spectrum of the light source of FIG. 9 are shown together. In FIG. 10 , a solid line indicates a light spectrum that does not pass through the optical member, and a dotted line indicates a light spectrum of light that has passed through the optical member.

In addition, for better understanding, the maximum luminance of the light spectrum of the light source and the light spectrum passing through the optical member is the same.

9 and 10, while the light provided from the light source passes through the first reflective polarizing film, the wavelength control film, and the second reflective polarizing film, the wavelength bands of 550 nm and 620 nm are relatively significantly amplified, and the 590 nm wavelength band It can be seen that the light transmittance is relatively low. Accordingly, while light in the green and red wavelength bands is amplified, the light in the green and red wavelength band is reduced, thereby improving color reproducibility of the liquid crystal display panel. That is, the color reproducibility of the liquid crystal display panel is improved by using an optical member in which the first reflective polarization layer, the second reflective polarization layer, and the wavelength control layer provided on the upper part of the first reflective polarization layer or on one surface of the liquid crystal display panel are configured as an optical package. can do.

11 is a cross-sectional view of an optical member according to another embodiment of the present invention. Referring to FIG. 11 , the optical member 101 according to the present embodiment is shown in FIG. 2 in that the first reflective polarizing film 110 , the wavelength control film 120 , and the second reflective polarizing film 130 are integrated. It is different from the Example. Since the first reflective polarizing film 110 , the wavelength control film 120 , and the second reflective polarizing film 130 are integrated, assembly of the backlight assembly may be simplified and the thickness may be reduced.

Their integration may be implemented by coating each film on an adjacent film, or by laminating using an adhesive or pressure-sensitive adhesives 141 and 142 . A more specific integration method will be readily apparent to those skilled in the art, and thus a description thereof will be omitted.

Hereinafter, a backlight assembly according to embodiments of the present invention using the above-described optical member will be described.

12 is a cross-sectional view of a liquid crystal display according to an exemplary embodiment. 12 illustrates a case in which an optical member according to embodiments of the present invention is employed in an edge-type backlight assembly.

Referring to FIG. 12 , the liquid crystal display 700 according to the present exemplary embodiment includes a backlight assembly 400 and a liquid crystal display panel 500 .

The backlight assembly 400 includes a light source 410 , a light guide plate 415 for guiding light emitted from the light source 410 , a reflective film 420 disposed below the light guide plate 415 , and an upper side of the light guide plate 415 . and the disposed optical member 100 .

The light sources 410 are disposed on both sides of the light guide plate 415 . The light source 410 may be, for example, a Light Emitting Diode (LED), a Cold Cathode Fluorescent Lamp (CCFL), a Hot Cathode Fluorescent Lamp (HCFL), or an External Electrode Fluorescent Lamp (EEFL). In another embodiment, the light source 410 may be disposed on only one side of the light guide plate 415 .

The light guide plate 415 moves the light emitted from the light source 410 through total internal reflection and emits it upward through a scattering pattern formed on the lower surface of the light guide plate 415 . A reflective film 420 is disposed under the light guide plate 415 to reflect light emitted downward from the light guide plate 415 upward.

The optical member 100 is disposed on the light guide plate 415 . Since the optical member 100 has been described in detail above, a redundant description thereof will be omitted. Other optical sheets may be further disposed above or below the optical member 100 . For example, a diffusion film for diffusing the incident light, a prism sheet for condensing the incident light, a micro lens, and/or a protective film may be further installed.

The light source 410 , the light guide plate 415 , the reflective film 420 , and the optical member 100 may be accommodated by the bottom chassis 440 .

The liquid crystal display panel 500 includes a first display panel 511 , a second display panel 512 , and a liquid crystal layer (not shown) interposed therebetween. It may further include a polarizing plate (not shown) respectively attached to the surface.

The liquid crystal display device 700 may further include a top chassis 600 covering the edges of the liquid crystal display panel 500 and surrounding side surfaces of the liquid crystal display panel 500 and the backlight assembly 400 .

13 is a cross-sectional view of a liquid crystal display according to another exemplary embodiment. 13 illustrates a case in which the optical member according to embodiments of the present invention is employed in a direct type backlight assembly.

Referring to FIG. 13 , the liquid crystal display 701 according to the present exemplary embodiment includes a backlight assembly 401 and a liquid crystal display panel 500 .

Since the liquid crystal display panel 500 and the top chassis 600 are substantially the same as in the embodiment of FIG. 11 , a redundant description will be omitted.

The backlight assembly 701 includes a storage container 441 , at least one light source 411 accommodated in the storage container 441 , and optically disposed in the storage container 441 and disposed on the light-emitting side of the at least one light source 411 . member 100 is included.

A support plate 416 may be further disposed under the optical member 100 . The support plate 416 may be a separate shielding layer or a shielding structure such as a diffusion plate, a diffusion plate, or a composite sheet in which a light diffusion layer is combined.

The storage container 441 accommodates at least one light source 411 and the optical member 100 . The storage container 441 may include a bottom surface formed in a substantially rectangular shape, and sidewalls formed perpendicular to each side of the bottom surface. A seating end on which the optical member 100 is mounted may be provided on a sidewall of the storage container 441 . The side wall of the storage container 441 may be partially extended upward from the seating end and then bent downward.

A reflective sheet 421 may be disposed on the bottom surface of the storage container 441 . In addition, a sheet support protrusion 450 may be disposed on the bottom surface of the storage container 441 . The sheet support protrusion 450 serves to prevent the optical member 100 and/or the support plate 450 from being convexly bent or deflected.

At least one light source 411 may be disposed on the bottom surface of the storage container 441 . The light source 411 may be, for example, a Light Emitting Diode (LED), a Cold Cathode Fluorescent Lamp (CCFL), a Hot Cathode Fluorescent Lamp (HCFL), or an External Electrode Fluorescent Lamp (EEFL).

The plurality of light sources 411 may be spaced apart from each other. When the plurality of light sources 411 are LEDs that are point light sources, each LED may be arranged according to a predetermined arrangement rule in the matrix direction. For example, each LED may be arranged at equal intervals in the row direction, and arranged in 3 rows, but the number is different for each row, such as 5 in 1 row, 7 in 2nd row, 6 in row 3, etc. can be arranged. It goes without saying, however, that the present invention is not limited to the arrangement illustrated above.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those of ordinary skill in the art to which the present invention pertains may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. you will be able to understand Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

100: optical member
110: first reflective polarizing film
120: wavelength control film
130: second reflective polarizing film

Claims (13)

a first reflective polarizer for reflectively polarizing a first wavelength band and a second wavelength band different from the first wavelength band;
a second reflective polarizer that reflectively polarizes a wavelength in a wider range than that of the first reflective polarizer; and
A wavelength adjusting unit positioned between the first reflective polarizer and the second reflective polarizer to block light of a third wavelength band different from the first wavelength band and the second wavelength band,
and the wavelength adjusting unit includes a wavelength blocking material that converts the light of the third wavelength band into light of the first wavelength band or the second wavelength band. delete The method of claim 1,
The wavelength blocking material is an optical member including a plurality of phosphors or quantum dots. The method of claim 1,
The first wavelength band is 610nm to 630nm,
The second wavelength band is 540nm to 560nm,
The third wavelength band is 575 nm to 595 nm of the optical member. The method of claim 1,
In the optical spectrum of the first reflective polarizer, a half width at a wavelength having a minimum transmittance of the first wavelength band and a wavelength having a minimum transmittance of the second wavelength band is 30 nm or less, respectively. The method of claim 1,
The first reflective polarizing unit includes a first reflective polarizing layer and a retardation layer,
The first reflective polarization layer reflectively polarizes circularly polarized light,
The first reflective polarizing layer includes a cholesteric liquid crystal having a first pitch, and a cholesteric liquid crystal having a second pitch greater than the first pitch,
The retardation layer is an optical member for converting circularly polarized light selectively transmitted by the first reflective polarizing layer into linearly polarized light. 7. The method of claim 6,
The refractive index anisotropy of the cholesteric liquid crystal of the first pitch and the cholesteric liquid crystal of the second pitch is 0.16 or less. The method of claim 1,
The second reflective polarizing unit includes a second reflective polarizing layer that reflectively polarizes the linearly polarized light;
The wavelength band in which the second reflective polarization layer reflectively polarizes the optical member includes the first wavelength band and the second wavelength band. 9. The method of claim 8,
An optical member having a light transmittance of 40 to 60% for light of 400 nm to 700 nm of the second reflective polarizing layer. 10. The method of claim 9,
In the vicinity of the first wavelength band and the second wavelength band, the minimum transmittance of the first reflective polarizing portion is less than the minimum transmittance of the second reflective polarizing layer. 11. The method of claim 10,
An optical member having at least two intersection points between the light spectrum of the second reflective polarization layer and the light spectrum of the first reflective polarization portion, which shows transmittance according to wavelength.
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