KR101433023B1 - Optical sheet - Google Patents

Abstract

The present invention relates to an optical sheet including a flat lens layer by a plurality of continuous and neighboring grains including a lens pattern wherein micro-lenses are regularly arranged in rows and columns. The optical sheet according to the present invention has high brightness by including the grains wherein the micro-lenses are regularly arranged in rows and columns inside the optical sheet, while viewed holistically, the micro-lenses are not arranged directly to suppress moires. At the same time, additional ultrafine lenses are included to avoid regular arrangement of the lenses, thus providing an excellent concealment and being used as an optical sheet for a surficial light source.

Description

Optical sheet {OPTICAL SHEET}

The present invention relates to an optical sheet for improving brightness in a surface light source device, and more particularly to an optical sheet used in a backlight unit for a liquid crystal display device.

Since a liquid crystal display (LCD) widely used as a flat panel display is a light-receiving device that displays an image by adjusting the amount of light coming from the outside, a backlight source form A backlight unit (BLU) is required.

A backlight unit is a device that can display information by supplying a lamp light to an LCD that can not emit light by itself, and is called a backlight unit on the back side of the LCD.

As a light source of the backlight unit, a compact fluorescent lamp or a light emitting diode (LED) is mainly used. Since the compact fluorescent lamp or LED is a linear light source or a point light source, A diffusion plate for diffusing light by scattering the light emitted to the upper side of the light guide plate and diffusing light, a light diffusion plate for uniformly diffusing according to the size of the LCD, And the optical sheet such as a prism sheet that makes the light of a strong intensity by condensing the light is used as a surface light source. In addition, various kinds of plates and films are used to transmit the light emitted from the light source toward the LCD panel as much as possible.

There is a microlens array (MLA) sheet in which a microlens shape is arranged in a single layer to exhibit both a condensing function and a hidden diffusion function at the same time.

The microlens array sheet has a higher luminance compared to a general diffusion film and has a diffusing and concealing function compared to a prism sheet, thereby being able to exhibit a composite function of correcting a viewing angle. However, The brightness is significantly lower than that of the prism sheet, and the microlenses having a single shape are arranged, which causes a problem that the concealing or diffusing function is lower than that of a general diffusion film because the density is low. Further, as in the example of the optical sheet including the conventional randomly arrayed microlens shown in FIG. 1, a lens having a relatively large diameter is included to compensate for the decrease in brightness due to the density of the low microlens (about 75% level) There is a problem in that defects are caused by sparkling called sparkling.

Accordingly, as shown in FIG. 2, in order to increase the brightness, a product in which the arrangement of the microlenses is regularized and the density of the microlenses is increased (about 85% level) has been developed. However, when the uniformity of the pattern is increased by arranging the arrangement of the microlenses in a regular manner, there is a limitation in that there are disadvantages such as occurrence of moire due to regularly arranged microlenses, loss of space between the lenses, and hiding power due to a uniform lens size.

Accordingly, development of a new optical sheet which solves such problems is urgently required.

Therefore, an object of the present invention is to provide an optical sheet for a surface light source device, which includes a micro lens such as a microlens, and which can suppress moir 辿 generation while exhibiting high brightness and exhibit excellent hiding power.

According to an aspect of the present invention, there is provided a liquid crystal display comprising a plurality of array regions including a lens pattern in which fine lenses are regularly arranged along rows and columns, The optical sheet comprising:

The optical sheet of the present invention includes an array region in which fine lenses are regularly arranged in rows and columns in an optical sheet so that the fine lenses are prevented from being orthogonally distributed in the entire optical sheet, And can provide an excellent hiding power by avoiding the regular arrangement of the lenses including the additional ultrafine lenses, and thus can be effectively used as an optical sheet for a surface light source device.

1 is a 3D micrograph showing a surface of an optical sheet including a conventional randomly arrayed microlens.
FIG. 2 is a 3D micrograph showing a surface of an optical sheet including a conventional regularly arranged microlens.
3 is a view showing a surface of an optical sheet according to an example of the present invention.
4 is a 3-D micrograph showing the surface of an optical sheet according to an example of the present invention.
5 is a 3-D microphotograph of an optical sheet according to an example of the present invention in which the area of the array area is adjusted to be small.
FIG. 6 is a 3D micrograph of an optical sheet according to an example of the present invention in which the area of the array area is largely adjusted.
7 is a photograph showing the result of stacking various optical sheets on an LED light source and an LED light source. FIG. 7 (a) is an LED light source used in a backlight unit (BLU) 7 (c) is an optical sheet of Example 2, Fig. 7 (d) is a conventional diffusion sheet, Fig. 7 (e) is an optical sheet of Comparative Example 1, (f) is an optical sheet of Comparative Example 2, and Fig. 7 (g) is an optical sheet of Comparative Example 3.

The optical sheet of the present invention includes a lens layer which is planarized by a plurality of array regions adjacent to each other and including a lens pattern in which fine lenses are regularly arranged along rows and columns.

The array region includes a lens pattern in which fine lenses are regularly arranged along rows and columns, that is, the micro lenses are regularly arranged.

Since the lens patterns included in the array area are regularly arranged along the rows and columns of the fine lenses, the density of the array area of the fine lenses is high, so that the optical sheet of the present invention can realize high brightness.

The array area may be a sheet piece shape, and the shape of the sheet piece is not particularly limited, so that the shape of the array area may be an irregular plane shape rather than a specific shape.

The array regions are contiguous and planar adjacent to each other, and may form a planar lens layer, for example, as a puzzle piece or a mosaic piece.

When the array areas are contiguous with each other to form a plane, the lens patterns included in the respective array areas have different arranging directions from the lens patterns of the adjacent array areas, and consequently, the fine patterns Lt; / RTI > That is, although the fine lenses included in the unit array region are regularly arranged along the rows and the columns, since the unit array regions are not adjacent to each other and are arranged in a specific direction when the planes are formed, When viewed in the optical sheet as a whole, it is partly regularly distributed only in a part of the optical sheet.

Therefore, since the optical sheet according to the present invention exhibits high light luminance due to the partially regularly arranged fine lenses, the fine lenses are not vertically distributed in the entire lens layer included in the optical sheet, so that the moire does not appear.

In order to compensate for the density lowering region of the fine lens due to the mismatch of the shape between the adjacent array regions on the boundary line where the array regions are adjacent to each other when the array regions are adjacent to each other, Ultrafine lenses may be included.

The diameters of the ultrafine lenses may be different from each other and may have a diameter corresponding to 5% to 70%, preferably 10% to 60%, and more preferably 15% to 50% of the diameter of the micro lenses.

By including the ultra-fine lens, the lens density of the optical sheet can be further increased, the regular arrangement of the lenses can be avoided to the maximum, and the uniformity of the lens size can be broken to form various focal lengths to improve the hiding power .

The area of each of the array areas may be equal to or different from each other, and an average of a sum of the longest width and the shortest width of the array area divided by 2 is 30 to 1,000 mu m, preferably 40 to 800 mu m, more preferably 50 To 500 m.

If the area of the unit array area is relatively small, the ratio of the regularly arranged fine lenses in the optical sheet as a whole is reduced, and when the unit array areas are adjacent to each other, It is possible to increase the number of ultrafine lenses that can be included on the boundary line between the optical sheet and the optical sheet. On the other hand, when the area of the unit array area is relatively large, the proportion of the micro-lenses that are vertically and widened in the entire optical sheet is increased, so that the brightness of the optical sheet can be relatively increased. Accordingly, the brightness and hiding power of the optical sheet can be appropriately adjusted to a desired level by adjusting the area of the unit array region according to the use, and the brightness and the hiding power can be adjusted to have an appropriate balance.

In the present invention, the micro lens may be a microlens or a lenticular lens, and preferably, it may be a microlens.

The diameter of the lens may be 5 to 50 탆, preferably 7 to 40 탆, more preferably 10 to 30 탆, and the height of the lens in relation to the diameter is 0.3 to 0.7, preferably 0.4 to 0.6, May be 0.43 to 0.53.

In the optical sheet of the present invention, the plurality of array regions may be adjacent to each other to form a planar lens layer on one side of the transparent support film.

The lens layer may be made of a thermosetting resin or a UV curing resin which is commonly used, and may be acrylic, urethane, epoxy, vinyl, polyester, polyamide resin or a mixture thereof. Specific examples thereof include (meth) acrylate resin, unsaturated polyester resin, polyester (meth) acrylate resin, silicone urethane (meth) acrylate resin, silicone polyester (meth) acrylate resin, fluorourethane Acrylate resins and mixtures thereof. Preferably, acrylic resins capable of realizing excellent coating properties, mechanical properties, adhesive strength, durability and the like can be used. Specific examples thereof include methyl methacrylate, methacrylate, ethyl acrylate, butyl acrylate, aryl acrylate, hexyl acrylate, isopropyl A homopolymer having repeating units of methacrylic, benzyl acryl, vinyl acryl, 2-methoxyethyl acryl or styrene, or a copolymer obtained by copolymerizing the above two or more components may be used.

The transparent support film is preferably a transparent plastic. The transparent support film should have good adhesion with the binder resin, transmittance of light incident from the rear surface should be 90% or more, and smoothness of the surface should be uniform.

Specific examples of suitable materials for the transparent support film include polyether sulfone (PES), polyacrylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN), polyethylene terephthalate It is also possible to use polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyallylate, polyimide, polycarbonate (PC), cellulose triacetate (TAC), cellulose acetate propionate cellulose acetate propionate, CAP), and mixtures thereof. Particularly preferred is polyethylene terephthalate (PET).

The thickness of the transparent support film may be 50 to 300 mu m, preferably 75 to 270 mu m, and more preferably 100 to 250 mu m.

In the optical sheet of the present invention, the coating layer may be formed on the other surface of the surface of the transparent support film on which the lens layer is formed. The coating layer may prevent wet-out and scratches, and may impart diffusing and / or hiding properties to the optical sheet.

The coating layer may be composed of a thermosetting resin and a UV curing resin, and specific examples thereof may include resins exemplified as material of the lens layer.

Meanwhile, the coating layer may include beads for diffusing and / or hiding functions. The beads may be organic polymer beads comprising a material selected from the group consisting of hard acrylate, polystyrene, nylon, soft acrylate and silicone. Among them, hard acrylate having good solvent resistance and easy dispersion is preferable. The beads are preferably spherical, and may have an average particle diameter of 0.5 to 10 mu m, preferably 0.8 to 6 mu m.

The optical sheet of the present invention can be used in the form of a composite optical sheet by laminating a prism sheet on the other surface of the lens layer formed on the transparent support film or by providing a prism shape on the other surface of the transparent support film.

The prism sheet is not particularly limited, and any prism sheet known in the art can be used without limitation.

In the optical sheet of the present invention, a master mold is produced by arranging a large-sized bead (bead) on a flat substrate made of a material capable of being embedded and arranging small beads sequentially so as to have an appropriate depth, And proceeding the replication process. Specifically,

(1) preparing a flat substrate made of a soft material capable of embedding beads;

(2) arranging and embedding beads of a size capable of realizing the shape of a fine lens on the flat substrate;

(3) further arranging and embedding beads between the arranged beads, the beads being capable of realizing the shape of an ultrafine lens having a size smaller than that of the fine lenses;

(4) preparing a primary intaglio replication sheet by applying and curing a liquid resin composition capable of being thermally cured or UV-curable on a flat substrate on which the beads are arranged, and replicating the fine lens and ultrafine lens shapes ;

(5) A liquid resin composition capable of being thermosetting or UV-curable is applied onto the above-prepared primary intaglio replication sheet and cured to prepare a secondary embossed sheet including a lens layer on one side, Can be prepared through a manufacturing step.

At this time, a coating layer for preventing wet-out or scratching may be formed on the other surface of the surface of the secondary embossed sheet on which the lens layer is formed.

Further, in the production of the secondary embossed sheet, instead of applying the liquid resin composition directly onto the primary engraved replica sheet, the liquid resin composition is applied on a separate transparent supporting film, The secondary embossed sheet can also be produced by curing the resin composition after lapping with the sheet, and then separating the resin composition cured on the transparent support film from the primary intaglio replication sheet.

On the other hand, the regular-array array region can be adjusted by arranging and embedding beads having a size capable of realizing the shape of a fine lens on the flat substrate in the step (2), and arranging the beads with a high density by controlling the density A large area array area can be formed, and when arranged at a lower density, a small area array area can be constituted.

Hereinafter, the optical sheet of the present invention will be described in detail with reference to the drawings, but the drawings are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

3 is a view showing a surface of an optical sheet according to an example of the present invention.

3, a lens layer included in an optical sheet according to an exemplary embodiment of the present invention includes a plurality of array areas 10, 20 including a lens pattern in which fine lenses 100 are regularly arranged along rows and columns , 30, and 40 are contiguous to each other to form a plane. At this time, the shape of the array regions 10, 20, 30, 40 is an irregular plane shape rather than a specific shape, and the array regions 10, 20, 30, The lens patterns included in the respective array regions 10, 20, 30, and 40 have alignment directions different from those of the adjacent array regions 10, 20, 30, and 40, Moire can be prevented by avoiding the regular distribution of the fine lenses in the entire lens layer as a whole.

Ultrafine lenses 200 and 210 having a smaller diameter than the fine lenses 100 of the array area may be included on the boundary line 50 where the array areas 10, 20, 30 and 40 are adjacent to each other.

In this case, the size of the ultrafine lenses may be different from each other, and may be a relatively small size (200) or a relatively large size (210).

4 is a 3D micrograph showing a surface of an optical sheet according to an example of the present invention.

Referring to FIG. 4, it can be seen that there are array areas including lens patterns in which fine lenses are regularly arranged, and ultrafine lenses smaller in size than the fine lenses are included in the boundary surfaces between the array areas .

The optical sheet of the present invention can control the extent to which the lens pattern coincides with the entire optical sheet by adjusting the area of each unit array area.

5 and 6 are photographs showing the appearance of the optical sheet according to an example of the present invention in which the area of the array area is adjusted to be small and the appearance of the optical sheet according to an example of the present invention in which the area of the array area is largely adjusted The picture is shown.

As shown in Fig. 5, when it is required that the objective optical sheet has a higher hiding power than the high brightness, the area of each unit array area is reduced to reduce the degree of matching of the patterns, The hiding power can be maximized by including a large number of ultrafine lenses on adjacent boundary lines of the respective unit array areas which are relatively increased as the number of ultrafine lenses increases.

On the other hand, as shown in Fig. 6, when it is important to have a high brightness as compared with a high hiding power, the area of each unit array area is increased to increase the degree of coincidence of patterns, The brightness can be maximized by reducing the number of ultrafine lenses included on adjacent borderlines of the respective unit array regions that are relatively reduced as the number of regions decreases.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are intended to illustrate the present invention, but the scope of the present invention is not limited thereto.

Example  One

In order to realize a shape for realizing an array area in which fine lenses are regularly arranged along rows and columns, beads having a particle diameter of 20 mu m are arranged on a flat plate made of a polyethylene material and heated to 90 DEG C , And a pressure of about 0.5 MPa was applied thereto. At this time, the beads have a number of beads ranging from several to ten, and the rows are arranged by several to ten, so that the micro lenses are regularly arranged along the rows and the columns to realize the array region .

Beads having a particle diameter of 3 to 5 占 퐉 are further arranged and buried at the boundaries of the patterns to realize an ultrafine lens shape having a size smaller than that of the fine lenses.

A resin composition capable of UV curing was applied on a flat substrate on which the beads were buried, and after curing and then releasing, a first duplicate sheet of an engraved was produced through duplication using a flat plate on which beads were embedded.

A resin composition capable of being cured by UV irradiation is applied on the first copying sheet again, and after curing and releasing the resin composition, an embossed second copying sheet is produced to manufacture an optical sheet including a planar lens layer Respectively.

Example  2

Except that in the arrangement of the fine lenses in Embodiment 1, a larger number of fine lenses are arranged in rows than in Embodiment 1, and the arrangement is adjusted so that the number of rows is larger than that in Embodiment 1 so as to form heat , An optical sheet was prepared in the same manner as in Example 1.

Comparative Example  1 to 3

(UTE23, MNtech) including a conventional diffusion sheet (CH273, SKC-Haas), an optical sheet (ML13XM, SKC-Haas) including randomly arranged microlenses, and a regularly arrayed microlens, Were used as Comparative Examples 1 to 3, respectively.

Comparison of optical properties

A prism sheet was formed on each of the optical sheets prepared in Examples 1 and 2 and the optical sheets of Comparative Examples 1 to 3 and each of them was applied to a backlight unit (BLU for 32 inch LG TV) The viewing angle was measured, and the optical sheets prepared in Examples 1 and 2 and the optical sheets of Comparative Examples 1 to 3 were placed on a single LED of the BLU, and pictures were taken to compare hiding power.

≪ Measurement of light luminance &

A prism sheet was superimposed on each of the optical sheets prepared in Examples 1 and 2 and the optical sheets of Comparative Examples 1 to 3 and then each of them was placed on a light guide panel of a backlight unit (BLU for 32-inch LG TV) And the measured value when the light receiving unit is perpendicular to the backlight unit was measured as a luminance value using a spectrometer (SR-3 of Topcon). At this time, the relative luminance value was obtained by setting the optical luminance of the optical sheet of Comparative Example 1 to 100.0%. The values are shown in Table 1.

≪ Measurement of viewing angle &

A prism sheet was laminated on each of the optical sheets prepared in Examples 1 and 2 and the optical sheets of Comparative Examples 1 to 3 and then each of them was placed on a light guide panel of a backlight unit (BLU for 32 inch LG TV) The distance between the light receiving unit and the backlight unit is fixed at 500 mm. The light receiving unit is tilted at an interval of 1 degree in the left / right / up and down directions of the backlight unit using a light intensity meter (SR- Value was compared with the measured value in the case where the light receiving unit was perpendicular to the backlight unit, and the angle at which the 1/2 luminance value was measured and the angle at which the 1/3 luminance value was measured were obtained. The values are shown in Table 1.

< Hiding power  Evaluation>

The optical sheets prepared in Examples 1 and 2, the optical sheets of Comparative Examples 1 to 3, and the conventional diffusion sheet were each fixed on a 25 mm LED light source using a transparent acrylic plate, and the degree of hiding power for the LED light source Observed, which is shown in Fig.

7 is a photograph showing the result of stacking various optical sheets on an LED light source and an LED light source. FIG. 7 (a) is an LED light source used in a backlight unit (BLU) 7 (c) is an optical sheet of Example 2, Fig. 7 (d) is a conventional diffusion sheet, Fig. 7 (e) is an optical sheet of Comparative Example 1, ) Relates to the optical sheet of Comparative Example 2, and Fig. 7 (g) relates to the optical sheet of Comparative Example 3.

Experimental Example Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Optical sheet
Overlapped structure The upper sheet Prism sheet Prism sheet Prism sheet Prism sheet Prism sheet Bottom sheet Example 1
(Small area
Array region) Example 2
(Large area
Array region) Comparative Example 1
(Diffusion sheet
2 pieces) Comparative Example 2
(random
Micro lens sheet) Comparative Example 3
(regular
Micro lens sheet) Diameter of micro lens 20 탆 20 탆 - 60 탆 24 탆 Relative luminance (%) 101.4 102.5 100.0 101.1 103.3 Viewing angle
(°) Left and right '1/2' 97 97 98 96 95 Left and right '1/3' 106 107 106 105 106 Up and down '1/2' 65 65 67 64 63 Up and down '1/2' 72 72 73 72 72

Referring to Table 1, in the case of the optical sheet according to Example 2, in which the brightness of the optical sheet according to the present invention is higher than that of the conventional two diffusion sheets, the area of the array region is increased, It was confirmed that the optical sheet had a luminance close to that of the optical sheet including the microlenses.

7 (b) and 7 (c) show the optical sheets according to Examples 1 and 2 of the present invention, compared to the case of using a conventional diffusion sheet (FIG. 7 (d) ), And it was also found that the hiding power against the LED light source is superior to that of the optical sheet including the conventional random array microlens or the regular array microlens, (b), it was confirmed that when the area of the array area is made smaller, the hiding power can be further increased.

10, 20, 30, 40: array area
50: boundary between adjacent array regions
100: Micro lens
200, 210: ultrafine lens

Claims (8)

A plurality of array regions 10, 20, 30, and 40 including a lens pattern in which fine lenses 100 are regularly arranged along rows and columns are contiguous and adjacent to each other, Wherein the array regions (10, 20, 30 and 40) have an irregular shape.
delete The method according to claim 1,
Wherein when the array areas (10, 20, 30 and 40) are adjacent to each other, the lens patterns included in the respective array areas have different arranging directions from the lens patterns of adjacent array areas.
The method according to claim 1,
Wherein ultrafine lenses (200 and 210) having diameters smaller than the micro lenses (100) are included on a boundary line (50) where the array areas (10, 20, 30 and 40) are adjacent to each other.
The method according to claim 1,
Wherein the micro lens (100) is a micro lens or a lenticular lens, and the diameter of the lens is 5 to 50 mu m.
The method according to claim 1,
And the height of the fine lenses (100) is 0.43 to 0.53 in diameter.
The method according to claim 1,
Wherein the optical sheet further comprises a transparent support film, the lens layer is formed on one side of the transparent support film, and a coating layer is further formed on the other side of the transparent support film.
5. The method of claim 4,
Wherein the diameter of the ultrafine lenses (200 and 210) is 15% to 50% of the diameter of the micro lenses (100).

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