WO2024014843A1

WO2024014843A1 - Laminate-type optical sheet for backlight unit

Info

Publication number: WO2024014843A1
Application number: PCT/KR2023/009878
Authority: WO
Inventors: 조창희
Original assignee: 조창희
Priority date: 2022-07-12
Filing date: 2023-07-11
Publication date: 2024-01-18
Also published as: KR102557656B1

Abstract

The laminated optical sheet for a backlight unit, having excellent light-condensing efficiency and light source concealability, comprises: a prism sheet; a transparent plate which is laminated, through an adhesive layer, to the prism sheet from under the prism sheet, and which has a thickness of at least 1.0 mm; and a half mirror arranged under the transparent plate.

Description

Laminated optical sheet for backlight unit

The present invention relates to an optical sheet for a backlight unit mounted on a liquid crystal display device, lighting device, etc.

More specifically, the present invention relates to an optical sheet for a backlight unit mounted on a liquid crystal display device, lighting device, etc., which enables additional lamination of existing optical sheets and a laminated optical sheet for a backlight unit in which at least two optical sheets are laminated. It's about optical sheets.

A liquid crystal display device has a structure in which a liquid crystal material is interposed between an upper substrate on which a color filter is formed and a lower substrate on which a thin film transistor is formed, and the arrangement of liquid crystal molecules is changed in various ways. It is a device that expresses images by controlling the transmittance of light.

Liquid crystal displays are not self-luminous devices that emit light on their own. Therefore, the liquid crystal display device requires a backlight unit to provide light to the panel.

Backlight units are divided into edge type and direct type depending on the arrangement of the light source. The edge type is a structure in which light sources are placed only on one or both edges of the backlight unit, and the direct type is a structure in which light sources are arranged at regular intervals on the substrate of the backlight unit. Cold cathode fluorescent lamps (CCFLs) were widely used as light sources, but recently, LED (Light Emitting Diode) lamps have been widely used.

The backlight unit includes an optical sheet including a light diffusion plate, a lens array sheet, a prism sheet, etc. for lamp concealment and light collection.

Generally, an optical sheet has a laminated structure in which a light diffusion plate 10 containing dispersed diffusion particles 15 and a prism sheet 20 are simply stacked with an air layer interposed therebetween, as shown in the example shown in FIG. 1A. The combination of optical sheets actually applied is a structure in which two additional lens array sheets are stacked with an air layer between the light diffusion plate and the prism sheet and on top of the prism sheet as shown in Figure 1a. A typical lens array sheet is a "diffusion sheet," which, unlike a light diffuser plate, has a structure in which diffusion particles are coated at a single layer level on the surface of a PET film. This increase in the number of sheets not only hinders the slimming of the liquid crystal display device but also may cause an increase in cost.

To overcome these shortcomings, a laminated structure in which the diffusion sheet 10 and the prism sheet 20 are laminated to each other through the lamination layer 30, as shown in the example shown in FIG. 1B, has been proposed.

When the diffusion sheet and the prism sheet are laminated, the air layer disappears, unlike lamination with an air layer interposed. In this case, the light provided from the light source is totally reflected at the interface between the light diffusion plate and the laminate layer and is not recycled, and the light concentrating effect of the prism may disappear due to the incident light at a wide angle.

In addition, the light source side of the backlight unit exhibits high transmittance toward the outside, which lowers the concealment efficiency of the light source.

As described in relation to FIGS. 1A and 1B, there are various problems when combining a light diffusion plate and other sheets.

Meanwhile, KR10-2014-0069926 A (2014.06.10.) proposes a laminated optical sheet. The laminated optical sheet proposed in the above document includes a first prism sheet on which a plurality of prisms are formed, a lamination layer formed on the lower surface of the first prism sheet, and laminated on the lower surface of the laminated layer, and the first prism and the first prism It includes a second prism sheet on which two prisms are formed, wherein the first prism sheet has a prism insertion portion formed on its lower surface, and a prism with a higher height among the first and second prisms of the second prism sheet is the first prism. It is characterized in that it is inserted into the prism insertion part formed on the lower surface of the sheet. Accordingly, an optical sheet with improved adhesion without lowering brightness can be provided.

However, in the above document, a groove is formed on the lower surface of the first prism sheet, and the end of the prism of the second prism sheet is inserted into the groove, and the light diffusion plate and lens array sheet or prism serve as a support layer for the optical sheets. It is difficult to solve the above-mentioned problems that occur when sheets are combined with a laminate layer.

The problem to be solved by the present invention is to provide a laminated optical sheet for backlight units such as liquid crystal displays and lighting devices that has high light collection efficiency and excellent light source hiding effect.

An optical sheet for a backlight unit according to an embodiment of the present invention for solving the above problems is an optical sheet that processes light provided from a light source of the backlight unit, and includes a prism sheet; A transparent plate that is laminated with the prism sheet through an adhesive layer below the prism sheet and has a thickness of 1.0 mm or more; And a half mirror disposed below the transparent plate.

The half mirror may be placed directly on the lower surface of the transparent plate. Alternatively, the polymer film on which the half mirror is disposed may be laminated to the lower surface of the transparent plate through an adhesive layer.

An optical sheet for a backlight unit according to another embodiment of the present invention for solving the above problems is an optical sheet that processes light provided from a light source of the backlight unit, and includes: a prism sheet; A transparent plate disposed below the prism sheet and having a thickness of 1.0 mm or more; A half mirror is disposed between the prism sheet and the transparent plate and is laminated with at least one of the prism sheet or the transparent plate through an adhesive.

The half mirror may be directly placed on one of the prism sheet and the transparent plate and laminated to the other one of the prism sheet and the transparent plate through an adhesive. Alternatively, the polymer film on which the half mirror is disposed may be laminated to the prism sheet and the transparent plate through an adhesive layer.

The transparent plate may include one or more of glass, polycarbonate, polystyrene, polyolefin, poly methyl methacrylate (PMMA), and MS resin.

The transparent plate may not contain a diffusing agent or may contain less than 0.5% by weight.

The half mirror may exhibit a light reflectance of 10 to 80% and a light transmittance of 20 to 90%.

The half mirror may be selected from i) to vi) below.

i) metal compound multilayer thin film,

ii) a metal thin film containing one or more of chromium, nickel, copper, gold, silver, aluminum, tin, stainless steel alloy and titanium,

iii) dispersed metal powders or flakes containing one or more of chromium, nickel, copper, gold, silver, aluminum, tin, stainless steel alloys and titanium, for example, poly(methyl methacrylate) (PMMA), polystyrene, poly Polymer thin films containing carbonate, polyethylene terephthalate (PET), polyurethane, polypropylene, polyolefin, or derivatives or copolymers thereof,

iv) A thin film of glass in which metal powder or flakes are dispersed, containing one or more of chromium, nickel, copper, gold, silver, aluminum, tin, stainless steel alloy and titanium.

v) a low refractive index layer containing one or more of Al ₂ O ₃ , AlF ₃ , NaF, MgF ₂ , SiO ₂ , TiO ₂ , Ti ₂ O ₃ , Nb ₂ O ₅ , Ta ₂ O _{3 ,} ZnS, and AlN A multilayer thin film provided alternately with high refractive index layers containing one or more of the following.

It may further include one or more intermediate sheets disposed between the transparent plate and the prism sheet or one or more upper sheets disposed on top of the prism sheet.

It may further include an upper sheet laminated with the prism sheet through an adhesive layer on top of the prism sheet, and may include an air layer between the upper sheet and the prism sheet. The top sheet can be, for example, a lens array sheet or a prism sheet.

The adhesive layer may include one or more of an acrylic adhesive, a urethane adhesive, an epoxy adhesive, and a silicone adhesive.

Specific details of non-described embodiments of the laminated optical sheet for a backlight unit according to the present invention are included or implied in the detailed description and drawings.

The laminated optical sheet for a backlight unit according to the present invention includes a half mirror on the top or bottom of the transparent plate, thereby solving problems such as reduced light collection efficiency due to the absence of an air gap between the transparent plate and the prism sheet.

In addition, the laminated optical sheet for a backlight unit according to the present invention can contribute to cost reduction by reducing the thickness of the optical sheet through lamination of optical sheets.

The laminated optical sheet according to the present invention, which has the above effects, can be applied to the backlight unit of a liquid crystal display device, and can also be applied to the backlight unit of various lighting devices.

The effect of the laminated optical sheet according to the present invention is not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the detailed description below.

Figure 1a shows an example of an optical sheet according to the prior art, showing a laminated structure with an air layer between the light diffusion plate and the prism sheet.

Figure 1b shows another example of an optical sheet according to the prior art, showing a structure in which a light diffusion plate and a prism sheet are laminated by a laminate layer.

Figure 2 schematically shows an optical sheet according to an embodiment of the present invention, in which a half mirror is disposed below the transparent plate.

Figure 3 schematically shows an optical sheet according to another embodiment of the present invention, in which a polymer film including a half mirror is disposed below the transparent plate.

Figure 4 schematically shows an optical sheet according to another embodiment of the present invention, in which a half mirror is disposed between the prism sheet and the transparent plate.

Figure 5 schematically shows an optical sheet according to another embodiment of the present invention, in which a half mirror is disposed between the prism sheet and the transparent plate.

Figure 6 schematically shows an optical sheet according to another embodiment of the present invention, in which a polymer film including a half mirror is disposed between a prism sheet and a transparent plate.

Figure 7 schematically shows an optical sheet according to another embodiment of the present invention, in which an additional prism sheet is disposed on the prism sheet.

Figure 8 schematically shows that there is an air layer between the prism sheet and the top sheet.

Figure 9a is a comparison of the vertical viewing angle evaluation results of optical sheets having the structures of Figures 1a and 1b.

Figure 9b is a comparison of the vertical viewing angle evaluation results of the optical sheets having the structures of Figures 1a and 2.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and will be implemented in various different forms, and the following embodiments only serve to ensure that the disclosure of the present invention is complete, and that the present invention is not limited to the embodiments disclosed below and will be implemented in various different forms. It is provided to fully inform those with knowledge of the scope of the invention, and the present invention is only defined by the scope of the claims.

Throughout the specification, including the drawings, the same reference signs are used to indicate the same or similar elements. Additionally, the sizes and relative sizes of parts and regions in the drawings may be exaggerated for clarity of explanation.

Referring to an element or layer being “on” or “on” another element or layer includes not only cases where it is directly on top of another element or layer, but also cases where another layer or other element is interposed. On the other hand, when an element or layer is referred to as “directly on” or “directly on” it indicates that there is no intervening other element or layer. Additionally, when a component is described as being “connected,” “coupled,” or “connected” to another component, the components may be directly connected or connected to each other, but there is no “connection” between each component. It should be understood that each component may be “interposed” or “connected,” “combined,” or “connected” through other components.

Spatially relative terms such as “below”, “lower”, “above”, “upper”, etc. are used to easily describe the correlation between one component and other component(s) as shown in the drawing. You can. Spatially relative terms should be understood as terms that include different directions of the element during use or operation in addition to the direction shown in the drawings. For example, if an element shown in the drawings is turned over, an element described as “below” another element may be placed “above” the other element. Accordingly, the illustrative term “down” may include both downward and upward directions.

The terminology used herein is for the purpose of describing embodiments and is therefore not intended to limit the disclosure. As used herein, singular forms also include plural forms, unless specifically stated otherwise in the context. As used in the specification, “comprise” and/or “comprising” does not exclude the presence or addition of one or more other components, steps, operations and/or elements. .

Hereinafter, preferred embodiments of the laminated optical sheet for a backlight unit according to the present invention will be described in detail with reference to the attached drawings.

The optical sheet according to the present invention is an optical sheet that processes light provided from a light source of a backlight unit. The optical sheet according to the present invention includes a half mirror that regularly reflects and transmits light on the top or bottom of the prism sheet or transparent plate.

Backlight units currently in use generally include 3 to 4 optical sheets. Although lamination between some films has been achieved, lamination between the light diffusion plate, which serves as a support layer, and the prism sheet on top thereof has not been achieved. This is because, although the effect of thickness reduction can be obtained when combining the light diffusion plate and the prism sheet, there is a problem of lowering light collection efficiency and lamp hiding power.

The present invention proposes a lamination structure between a transparent plate and a prism sheet through a half mirror that can achieve the effect of reducing thickness without reducing light collection efficiency and lamp hiding power.

Figure 2 schematically shows an optical sheet according to an embodiment of the present invention.

As shown in Figure 2 and Figures 3 to 8, the optical sheet according to the present invention does not have a structure in which a prism sheet and a transparent plate are simply stacked with an air layer in between, but the prism sheet and the transparent plate are laminated with an adhesive. It has a structure.

Referring to FIG. 2, the optical sheet shown has a structure in which a prism sheet 110 and a transparent plate 120 are laminated by an adhesive layer 130.

And, a half mirror 140 is disposed below the transparent plate 120.

The prism sheet 110 is a sheet including a prism pattern that refracts side light into front light to increase the brightness of light provided from the backlight unit.

The transparent plate 120 serves as a support for the prism sheet. The transparent plate 120 may be, for example, a polymer or glass material containing one or more of polycarbonate, polystyrene (PS), polyolefin, poly methyl methacrylate (PMMA), and MS resin (PMMA and PS copolymer). , may have a thickness of 1.0 mm or more, preferably 1.0 mm to 3.0 mm, more preferably 1.0 mm to 2.5 mm, and most preferably 1.2 mm to 2.5 mm. The transparent plate 120 may contain no diffusion agent or may contain a maximum of 0.5% by weight or less. The transparent plate 120 applied to the present invention differs from films with a thickness of only a few hundred ㎛ at most in that it has a thickness of 1.0 mm or more, and does not contain a diffusion agent or contains a maximum of 0.5% by weight or less, so that it has a thickness of about 1 weight. It is different from the existing light diffuser plate that contains % diffuser.

Additionally, an amorphous embossed shape may be provided at the bottom of the transparent plate to prevent scratches with the lamp supporter of the backlight unit, regardless of whether it is a half mirror or not.

The adhesive layer 130 may include one or more of an acrylic adhesive, a urethane adhesive, an epoxy adhesive, and a silicone adhesive, but is not limited thereto, and known transparent adhesives may be used.

The half mirror 140 reflects part of the incident light and transmits the rest. Some of the light provided from the light source passes through the half mirror 140 and the transparent plate 120, and the light reflected from the half mirror 140 toward the light source is incident again on the half mirror 140 if the light source is equipped with a reflector, etc. . Through these processes, high lamp hiding power can be achieved.

The half mirror 140 may exhibit a light reflectance of 10 to 80% and a light transmittance of 90 to 20% depending on the layer thickness, the amount of metal in the half mirror, etc. When the half mirror 140 is included as one layer in the optical sheet, the half mirror 140 may exhibit a light reflectance of 20 to 80% and a light transmittance of 80 to 20%. When the half mirror 140 is included in a plurality of layers in the optical sheet, each half mirror 140 may exhibit a light reflectance of 10 to 80% and a light transmittance of 90 to 20%.

The half mirror 140 may be a multilayer thin film of a metal compound, for example, a metal oxide.

Additionally, the half mirror 140 may be a metal thin film containing one or more types of chromium, nickel, copper, gold, silver, aluminum, tin, stainless steel alloy, and titanium, which have excellent reflectivity.

Additionally, the half mirror 140 may be a polymer thin film in which metal powder or flakes containing one or more of chromium, nickel, copper, gold, silver, aluminum, tin, stainless steel alloy, and titanium are dispersed. Metal powder generally has a spherical shape, and metal flakes may have a flat shape. The polymer may include one or more of poly(methyl methacrylate) (PMMA), polystyrene, polycarbonate, polyethylene terephthalate (PET), polyurethane, polypropylene, polyolefin, or derivatives or copolymers thereof.

Additionally, the half mirror 140 may be a glass thin film in which metal powder or flakes containing one or more of chromium, nickel, copper, gold, silver, aluminum, tin, stainless steel alloy, and titanium are dispersed.

In addition, the half mirror 140 includes a low refractive index layer containing one or more of Al ₂ O ₃ , AlF ₃ , NaF, MgF ₂ , SiO ₂ , TiO ₂ , Ti ₂ O ₃ , Nb ₂ O ₅ , and Ta ₂ It may be a multilayer thin film in which high refractive index layers containing one or more types of O _{3 ,} ZnS, and AlN are alternately provided.

The half mirror 140 is formed by using various deposition methods, plating methods, pneumatic launching, coating methods, adhesive methods, etc. on the transparent plate 120, polymer film (210 in FIGS. 3 and 6), prism sheet (110 in FIG. 5), etc. It can be formed in layers.

Figure 3 schematically shows an optical sheet according to another embodiment of the present invention.

In the embodiment shown in FIG. 2, the half mirror 140 is formed directly on the lower surface of the transparent plate 120, but in the embodiment shown in FIG. 3, the polymer film 210 including the half mirror 140 is It is attached to the lower part of the transparent plate through the adhesive layer 220. At this time, the relative position of the half mirror layer with respect to the polymer film includes all above, below, and inside. Like the adhesive layer 130, the adhesive layer 220 may include one or more of an acrylic adhesive, a urethane adhesive, an epoxy adhesive, and a silicone adhesive, but is not limited thereto and known transparent adhesives may be used.

Figure 4 schematically shows an optical sheet according to another embodiment of the present invention.

In the embodiment shown in FIG. 2, the half mirror 140 is formed directly on the lower surface of the transparent plate 120, but in the embodiment shown in FIG. 4, the half mirror 140 is formed on the upper surface of the transparent plate 120. It is formed directly on the transparent plate 120 on which the half mirror 140 is formed and is laminated with the prism sheet 110 through the adhesive layer 130. In this case, it exhibits optical characteristics similar to the embodiment shown in FIG. 2 and can be optionally provided depending on manufacturing conditions.

Figure 5 schematically shows an optical sheet according to another embodiment of the present invention.

In the embodiment shown in FIG. 5, like the embodiment shown in FIG. 4, a half mirror 140 is disposed between the prism sheet 110 and the transparent plate 120. However, in the embodiment shown in FIG. 5, the half mirror 140 is formed directly on the lower surface of the prism sheet 110, and the prism sheet 110 on which the half mirror 140 is formed is formed through the adhesive layer 130. It is laminated with a transparent plate (120). In this case, it exhibits optical characteristics similar to the structure of FIG. 2 and can be selectively provided depending on manufacturing conditions.

Figure 6 schematically shows an optical sheet according to another embodiment of the present invention. In the embodiment shown in FIG. 6, like the embodiment shown in FIGS. 4 and 5, a half mirror 140 is disposed between the prism sheet 110 and the transparent plate 120. However, in the embodiment shown in FIG. 6, the polymer film 210 including the half mirror 140 is attached to the prism sheet 110 and the transparent plate 120 through

adhesive layers

130 and 220, respectively. . In this case, it exhibits optical characteristics similar to the embodiment shown in FIG. 2 and can be optionally provided depending on manufacturing conditions.

Meanwhile, additional sheets may be laminated or laminated on the top or bottom of the prism sheet 110 and on the top or bottom of the transparent plate 120. That is, the optical sheet according to the present invention includes at least one half mirror below the prism sheet (when two or more prism sheets are included, the lower part based on the uppermost prism sheet).

For example, one or more intermediate sheets may be additionally disposed between the prism sheet 110 and the transparent plate 120. As another example, one or more upper sheets may be additionally disposed on the prism sheet 110. The middle sheet can be a lens array sheet such as a diffusion sheet, a prism sheet, etc., and the top sheet can be a lens array sheet, a prism sheet, etc. The lens array sheet includes a bead coating and a bead array imprinted sheet, and the beads may be arranged amorphously or regularly.

Referring to FIG. 7, when additional prism sheets 810 are laminated on the prism sheet 110 through the adhesive layer 820, the directions of the prism patterns of these prism sheets are preferably perpendicular to each other.

Figure 8 schematically shows that there is an air layer between the prism sheet and the top sheet. As in the example shown in FIG. 8, when the upper sheet 910 is laminated on the prism sheet 110 through the adhesive layer 920, an air layer 925 is formed between the upper sheet 910 and the prism sheet 110. This may be included.

The air layer 925 may be formed when the sheet on the lower side has a non-flat three-dimensional structure such as a lens shape or a prism shape, and the adhesive layer 920 for laminating the upper sheet 910 is sufficiently thin. This can be achieved when it is formed in thickness. More preferably, a method may be used to make the thickness of the adhesive layer 920 smaller than the height of the prism pattern of the prism sheet 110. This air layer 925 can minimize the loss of the prism-shaped light condensing effect caused by lamination.

As shown in FIGS. 2 to 8, the lower surface of the transparent plate may be flat. Differently, although not shown in the drawings in FIGS. 1 to 8, an amorphous emboss shape is provided on the bottom of the transparent plate to prevent scratches with the lamp supporter of the backlight unit, regardless of whether a half mirror is provided on the bottom of the transparent plate. It can be.

Figure 9a shows a laminated optical sheet (diffuser prism sheet lamination) in which a light diffusion plate and a prism sheet are simply laminated with an air layer in between (structure of Figure 1a), and a light diffusion plate and a prism sheet laminated with an acrylate adhesive. This is a comparison of the vertical viewing angles of laminated optical sheets (laminated diffuser prism sheets) (structure in Figure 1b). In FIG. 9A, the x-axis is the 'vertical viewing angle' angle, which can be seen as the angle at which the TV is moved in the vertical direction, for example, and is set as 0° when viewed from the front. In Figure 9A, the y-axis is luminance.

Referring to Figure 9a, when the x value is 0, that is, the luminance from the front is at the level of 65 for the stacked type, while it can be seen that the luminance of the stacked type is about 33, which is lowered by almost half. In other words, it can be said that the light-gathering function of the prism sheet is almost lost due to the lamination. In the case of a laminated optical sheet (diffusion plate prism sheet lamination) in which a diffusion sheet and a prism sheet are simply laminated with an air layer in between, the angle of incidence of light incident on the prism pattern of the prism sheet is approximately -45° to 45°, but the laminated In the case of the diffusion sheet prism sheet, the angle of incidence of light incident on the prism sheet is approximately -90° to 90°, and it can be seen that the light-collecting function of the prism is lost. In other words, the light outside the -45 to 45 range is totally reflected between the diffusion plate and the air layer, goes down to the bottom, hits the reflector again, and is reused. However, when laminated, the light outside the -45 to 45 range travels to the prism pattern without total reflection or significant angle change. It is not concentrated and is emitted as high-angle light.

Figure 9b shows a laminated optical sheet (diffuser plate prism sheet lamination) in which a light diffusion plate and a prism sheet are simply stacked with an air layer in between (structure of Figure 1a), and a polymer transparent plate and prism sheet with a half mirror formed on the lower surface. This is a comparison of the vertical viewing angles of laminated optical sheets (polymer plate prism sheet lamination) (structure in FIG. 2) laminated with an acrylate adhesive.

Referring to Figure 9b, in the case of a diffusion sheet prism sheet laminated by adding a half mirror and an adhesive layer, it can be seen that the light-collecting function of the prism is maintained, unlike Figure 9a. In the case of a polymer plate, since there is no diffuser, light outside the range of -45° to 45° cannot exist, and due to the presence of a half mirror, it can exhibit a reflectance similar to that in the presence of a light diffuser.

The light coming from the light source of the backlight unit travels at an angle of about -90° to 90°, but when it enters the polymer plate or light diffusion plate, it travels in the range of about -45° to 45° according to Snell's law. In the case of a light diffusion plate, the light from -45° to 45° is diffused to the range of -90° to 90° by the dispersed diffuser, but in the case of a polymer transparent plate, the light propagates within -45° to 45° without diffusion. do.

Table 1 shows the results of optical property analysis for optical sheets of various structures.

In Table 1, the diffused light transmittance and front luminance were each measured using Light Tools, an optical simulation tool. The half mirror included in the examples used a dielectric multilayer thin film, and the reflectance was different depending on the refractive index and film thickness.

The meaning of each symbol in Table 1 is as follows:

PS: polystyrene plate

A: Adhesive layer

Air is the air layer

H: Half mirror,

D: Diffusion plate (60% transmittance with mie scattering)

P: Prism sheet

L: Lens array sheet (total light transmittance 75%), haze 99%

[Table 1]

Referring to Table 1, it can be seen that Examples 1 to 13 including a half mirror showed frontal luminance equal to or better than Comparative Examples 1 to 5 including a light diffusion plate rather than a half mirror, and that additional lamination was possible.

Comparing Comparative Example 1 and Comparative Example 2, it can be seen that the structure in which the light diffusion plate and the prism sheet are combined has a very low light collection ability compared to the laminated structure, and the diffused light transmittance, which is one of the measures of lamp concealment, is significantly lowered. There is (Figure 9a).

Comparing Comparative Example 1 and Example 1, in the case of the optical sheet of Example 1 in which transparent plates including a half mirror are laminated, the optical sheet of Comparative Example 1 is simply laminated with a conventional light diffusion plate and a prism sheet with an air layer interposed therebetween. It showed the same effect as the sheet (FIG. 9b).

In particular, comparing Example 2 and Comparative Example 1, the optical sheet of Example 2 was provided with a half mirror with a reflectivity of 50%, resulting in a lower diffused light transmittance along with frontal luminance equivalent to that of the optical sheet of Comparative Example 1. , through which a higher light source hiding effect can be achieved.

In addition, as can be seen from Examples 1, 3, and 4, it can be seen that both examples of providing a plurality of half mirrors with a low reflectance and examples of providing a single half mirror with a high reflectance exhibit similar effects.

In addition, Comparative Examples 3 and 4 are representative optical sheet combinations of backlights currently applied, and when comparing Examples 5 to 9 with Comparative Example 3 and Examples 10 to 13 and Comparative Example 4, Examples 5 to 9 and 10 It can be seen that the optical sheet of ~13 shows the same effect as Comparative Examples 3 to 4 even though the light diffusion plate is omitted.

Meanwhile, in Examples 14 and 15, the prism sheet and the transparent plate were laminated through an adhesive layer, and a half mirror was placed on the prism sheet. For example, when comparing Comparative Example 5 and Example 15, it can be seen that even when a half mirror is provided on the prism sheet, front luminance of the same or higher level can be obtained compared to the case where the half mirror is not provided.

Although the preferred embodiments of the present invention have been described in detail above, those skilled in the art will understand that various modifications and other equivalent embodiments are possible. Accordingly, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

An optical sheet that processes light provided from a light source of a backlight unit,

prism sheet;

a transparent plate laminated with the prism sheet through an adhesive layer at the bottom of the prism sheet; and

It includes a half mirror disposed below the transparent plate,

The transparent plate contains no or less than 0.5% by weight of a diffusion agent and has a thickness of 1.0 to 2.5 mm.
According to paragraph 1,

The half mirror is placed directly on the bottom of the transparent plate, or

An optical sheet, characterized in that the polymer film on which the half mirror is disposed is laminated to the lower surface of the transparent plate through an adhesive layer.
An optical sheet that processes light provided from a light source of a backlight unit,

prism sheet;

a transparent plate disposed below the prism sheet;

A half mirror disposed between the prism sheet and the transparent plate and laminated with at least one of the prism sheet or the transparent plate through an adhesive,

The transparent plate does not contain a diffusion agent or contains less than 0.5% by weight of the diffusion agent, and has a thickness of 1.0 to 2.5 mm.
According to paragraph 3,

The half mirror is placed directly on one of the prism sheet and the transparent plate and is laminated to the other one of the prism sheet and the transparent plate through an adhesive, or

An optical sheet, characterized in that the polymer film on which the half mirror is disposed is laminated to the prism sheet and the transparent plate through an adhesive layer.
According to any one of claims 1 to 4,

The transparent plate is a laminated optical sheet for a backlight unit, characterized in that it contains one or more types of glass, polycarbonate, polystyrene, polyolefin, PMMA (poly methyl methacrylate), and MS resin.
According to any one of claims 1 to 4,

A laminated optical sheet for a backlight unit, characterized in that the lower surface of the transparent plate is flat or has an amorphous embossed shape.
According to any one of claims 1 to 4,

The half mirror is a laminated optical sheet for a backlight unit, characterized in that it exhibits a light reflectance of 10 to 80% and a light transmittance of 20 to 90%.
According to any one of claims 1 to 4,

The half mirror is a laminated optical sheet for a backlight unit, characterized in that selected from the following i) to v).

i) metal compound multilayer thin film,

ii) a metal thin film containing one or more of chromium, nickel, copper, gold, silver, aluminum, tin, stainless steel alloy and titanium,

iii) a polymer thin film in which metal powder or flakes containing one or more of chromium, nickel, copper, gold, silver, aluminum, tin, stainless steel alloy and titanium are dispersed,

iv) A thin film of glass in which metal powder or flakes are dispersed, containing one or more of chromium, nickel, copper, gold, silver, aluminum, tin, stainless steel alloy and titanium.

v) a low refractive index layer containing one or more of Al 2 O 3 , AlF 3 , NaF, MgF 2 , SiO 2 , TiO 2 , Ti 2 O 3 , Nb 2 O 5 , Ta 2 O 3 , ZnS, and AlN A multilayer thin film provided alternately with high refractive index layers containing one or more of the following.
According to any one of claims 1 to 4,

Laminated optical sheet for a backlight unit, characterized in that it further comprises one or more intermediate sheets disposed between the transparent plate and the prism sheet or one or more upper sheets disposed on top of the prism sheet.
According to any one of claims 1 to 4,

A laminated optical sheet for a backlight unit, further comprising an upper sheet laminated with the prism sheet through an adhesive layer on the upper part of the prism sheet, and comprising an air layer between the upper sheet and the prism sheet.