KR20150113689A - Optical Sheet and Back Light Unit Comprising the Same - Google Patents

Abstract

The present invention relates to an optical sheet and a backlight unit including the same. More specifically, the optical sheet includes: a substrate layer; and a structure layer which is formed on the surface of the substrate layer and has a pattern formed thereon. The structure layer includes: a first pattern unit having multiple patterns arranged thereon; and a second pattern unit which has multiple patterns formed and arranged to cross the patterns of the first pattern by 60-150 degrees.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an optical sheet and a backlight unit including the optical sheet.

The present invention relates to an optical sheet used in a liquid crystal display (hereinafter referred to as LCD) and a backlight unit including the optical sheet.

BACKGROUND ART An LCD used as an optical display device is an indirect light emitting type in which an image is displayed by adjusting the transmittance of an external light source, and a backlight unit as a light source device is used as an important component for determining the characteristics of an LCD.

In particular, with the development of LCD panel manufacturing technology, there has been a demand for a thin and bright LCD display. Accordingly, various attempts have been made to increase the brightness of a backlight unit. For example, a monitor, a PDA Is a measure of its superiority in that a liquid crystal display used as a light source emits bright light from a small energy source. Therefore, the front brightness of LCD is very important.

Since the structure of the LCD diffuses the light passing through the light diffusion layer in all directions, the light exerted on the front surface is very scarce, and thus efforts to develop higher luminance with less power consumption are continuing. In addition, efforts are being made to enlarge the viewing angle so that more users can view the display as the size becomes larger.

If the backlight power is increased for this purpose, the power consumption increases and the power loss due to heat increases. As a result, the battery capacity and the battery life of the portable display are reduced.

In order to improve the luminance, a method of directing light has been proposed, and various lens sheets have been developed for this purpose. The representative optical sheet has a prism arrangement on its surface.

In general, an optical sheet having a prism arrangement has a triangular array structure having an inclined plane of 45 DEG in order to improve luminance in the front direction.

As such, the optical structure surface has a mountain shape, and there is a problem that the upper part of the mountain is easily broken or distorted by the small external scratches to damage the prism structure. The angles emitted from the prism structures of the same shape are the same for each array. Therefore, even when the prisms are arranged in a small crushed state or a fine scratch on the inclined surface, the luminance is lowered And a failure occurs. Therefore, even in the case of producing a prism sheet, even if a slight defect occurs, the entire surface of the produced prism sheet may not be used depending on the position. This leads to a decrease in productivity and soon becomes a burden on the cost increase. Even in companies that assemble an actual backlight module, defects due to scratch damage due to scratches during prism sheet handling are a serious problem.

In addition, a plurality of sheets and films are stacked when the backlight unit is mounted. In order to increase the brightness, a plurality of prism films can be mounted. In this case, the upper portion of the lower prism film and the lower portion of the upper prism film are in contact with each other Thereby damaging the prism structure.

Therefore, there has been a case where a conventional protective film is laminated in order to prevent damage to the prism structure. However, since the LCD panel is becoming thinner, there is a tendency to omit the film or use a sheet having a multifunctional function, and there is also a problem of reducing the increase in the production cost, the temporal and physical efficiency due to the addition of the process of laminating the protective film .

In addition to damage to the prism structure due to handling during manufacturing, the use of portable displays such as notebooks and PDAs is increasing, and the display is frequently moved into a bag or the like. In this case, when a shock is applied to the display by jumping during traveling or by a vehicle stop, the prism structure mounted in the display is damaged even if there is a protective film, thereby causing serious problems affecting the screen.

On the other hand, recently, the demand for high-quality and high-reliability products in the display market has been increased, and the sensitivity of the touch panel has increased due to an increase in the number of touch screens. .

Therefore, it is inevitable to develop a light collecting type optical sheet which not only includes an optical structure surface capable of flexibly coping with the force externally applied, but also has no defect when dropped or subjected to a physical impact.

The present invention provides an optical sheet having excellent viewing angle, color by angle, and scratch resistance, and a backlight unit including the optical sheet.

Accordingly, the present invention provides, as a first preferred embodiment, a substrate layer; And a structure layer formed on one surface of the substrate layer, wherein the structure layer has a first pattern portion in which a plurality of patterns are arranged and a second pattern portion in which a plurality of patterns are arranged, And a second pattern portion in which a plurality of patterns formed by crossing at an angle are arranged.

The shapes of the patterns formed in the first pattern portion and the second pattern portion according to the embodiment may be polyhedron shapes in which the vertical cross-sections are selected from among triangular, polygonal, semicircular, and semi-elliptical shapes. A triangular shape whose longitudinal section is a triangle, a polygon, a triangle whose peak is streamline, a polygon whose peak is streamline, a columnar shape selected from a semicircular shape and a semielliptic shape; A triangular, polygonal, or triangular shape whose peak plane is streamline, a curved column shape selected from polygonal, semicircular, and semi-elliptical shapes whose peak is streamlined; Cones and polyhedra horns. The term " horn "

The pattern formed on the second pattern unit according to the embodiment may have an aspect ratio of 0.05 to 10 in the longitudinal direction.

The pattern formed on the second pattern unit according to the embodiment may have a pattern interval of 50 to 10000 m.

The pattern formed in the second pattern unit according to the embodiment may have a regular or irregular interval between adjacent patterns.

The prism pattern of the first pattern portion and the pattern of the second pattern portion according to the embodiment have a height difference (| H1-H2 |) of less than 500 μm, wherein H1 is the height of the prism pattern of the first pattern portion, H2 May be the height of the pattern of the second pattern portion.

The present invention also provides, as a second preferred embodiment, a backlight unit including the optical sheet.

According to the optical sheet of the present invention, not only the light-condensing effect but also the diffusion effect can be simultaneously exhibited due to the morphological characteristics of the pattern formed on the structure layer. Further, the optical sheet of the present invention not only improves hue and angle-specific hue but also exhibits excellent scratch resistance.

1 schematically shows a longitudinal section of an optical sheet of the present invention.
2 is a SEM (scanning electron microscope) photograph of the optical sheet of the present invention.
3 shows a top view and an intersection angle of the optical sheet of the present invention.
4 is an image of a method of manufacturing the optical sheet of the present invention.

Hereinafter, the present invention will be described in more detail.

The present invention relates to a substrate layer; And a structure layer formed on one surface of the substrate layer, wherein the structure layer has a first pattern portion in which a plurality of patterns are arranged and a second pattern portion in which a plurality of patterns are arranged, And a second pattern portion in which a plurality of patterns formed by crossing at an angle are arranged.

[Base layer]

In the present invention, the base layer can be used without any particular limitation as long as it is a film that can be generally used for the base layer of the optical sheet. Examples of the base layer include polyethylene terephthalate film, polycarbonate film, polypropylene film, polyethylene film, polystyrene film, Film, and the like.

The thickness of the substrate layer is preferably 10 to 1000 mu m. When the thickness of the base layer is less than 10 탆, the mechanical strength and thermal stability become poor. When the thickness exceeds 1000 탆, the flexibility of the film is deteriorated and the light transmittance may be lost.

[Structure layer]

In the present invention, the structure layer is formed on one surface of the substrate layer, and includes a first pattern portion 10 in which a plurality of prism patterns are arranged and a second pattern portion 10 having an angle of 60 to 150 degrees with the pattern of the first pattern portion 10 And a second pattern portion 20 in which a plurality of patterns formed in an intersecting manner are arranged (Figs. 1 and 2).

Wherein the structural layer comprises at least one compound (a) selected from a urethane acrylate compound, a styrene compound, a butadiene compound and an isoprene compound, or at least one compound selected from a bisphenol acrylate compound and a fluorene acrylate compound b), and a thermosetting resin may be used as the ultraviolet curable resin.

In the present invention, the first pattern portion may include a plurality of patterns, and the plurality of patterns may be continuously arranged.

Wherein the shape of the pattern formed on the first pattern portion is a polyhedron shape in which the vertical cross-section is selected from a triangle, a polygon, a semicircle, and a semi-ellipse; A triangular shape whose longitudinal section is a triangle, a polygon, a triangle whose peak is streamline, a polygon whose peak is streamline, a columnar shape selected from a semicircular shape and a semielliptic shape; A triangular, polygonal, or triangular shape whose peak plane is streamline, a curved column shape selected from polygonal, semicircular, and semi-elliptical shapes whose peak is streamlined; Cones and polyhedra horns. The term " horn "

In this case, the columnar shape in which the vertical cross-section of the pattern formed in the first pattern portion is triangular may be a prism pattern. In the prism pattern, optical characteristics such as front brightness and light intensity distribution within a viewing angle are severely changed according to the upper apex angle, and the upper apex angle of the triangular prism structure is preferably 80 ° to 100 °. When the angle is less than 80 °, the front luminance due to light collection is good but the light intensity distribution in the viewing angle is poor and it is difficult to apply. When the angle is more than 100 °, the light intensity distribution characteristic in the viewing angle is good, .

In the present invention, the second pattern portion may include a plurality of patterns formed by intersecting the pattern of the first pattern portion at an angle of 60 to 150 degrees, and the plurality of patterns may be arranged continuously or discontinuously, May be arranged regularly or irregularly. The term " continuous " refers to a form in which the patterns are formed adjacent to each other, and " discontinuous " refers to a form in which the patterns are formed at intervals apart from each other. Also, the term " regular " means that patterns are arranged such that the interval between adjacent patterns is constant, and " irregular " means that patterns are arranged such that the interval between adjacent patterns is not constant.

The shape of the pattern formed on the second pattern portion may be a polyhedral shape in which the vertical cross-section is selected from a triangle, a polygon, a semicircle, and a semi-ellipse; A triangular shape whose longitudinal section is a triangle, a polygon, a triangle whose peak is streamline, a polygon whose peak is streamline, a columnar shape selected from a semicircular shape and a semielliptic shape; A triangular, polygonal, or triangular shape whose peak plane is streamline, a curved column shape selected from polygonal, semicircular, and semi-elliptical shapes whose peak is streamlined; Cones and polyhedra horns. The term " horn "

Also, the second pattern portion may have a structure in which at least one or more concentric circles are arranged in a plan view, and a structure in which an obtuse and a valley are formed along concentric circles.

In this case, the columnar shape in which the vertical cross-section of the pattern formed in the second pattern portion is triangular may be a prism pattern. It is preferable that the angle of the peak portion is 80 to 100 DEG and the angle of the peak portion is 85 to 95 DEG in consideration of the luminance and the wide viewing angle due to the light condensation, since the characteristics of the luminance and the wide viewing angle are greatly changed according to the angle of the peak portion of the prism pattern. Is more preferable.

Or when the longitudinal section of the second pattern portion is polygonal, the peak portion may be rounded so that the peak is streamlined. In this case, the aspect ratio of the longitudinal portion may be 0.05 to 10, and if the aspect ratio is less than 0.05, There is a problem in that the front luminance is greatly reduced. When it is more than 10, there arises a problem in the manufacturing process, and the scratch resistance and the viewing angle improving effect are deteriorated.

In the present invention, the aspect ratio of the longitudinal section means a value obtained by dividing the height of the pattern longitudinal section by the width.

The pattern formed on the second pattern unit according to the embodiment may have an interval between the patterns of 50 to 10,000 mu m. When the interval between the patterns is less than 50 mu m, there is a problem that a moiré which is regular and has periodicity and a regular or wavy pattern is seen on the prism film. When it exceeds 10000 mu m, the front luminance due to the light- But the light intensity distribution in the viewing angle is small. According to the interval between the patterns, the pattern formed in the second pattern portion may be formed regularly or irregularly. Here, the term " regular " refers to a form in which the interval between patterns is constant (see FIG. 3), and " irregular " refers to a form in which the interval between patterns is not constant.

It is preferable that the height difference (| H1-H2 |) of the height H1 of the prism pattern of the first pattern portion and the height H2 of the pattern of the second pattern portion is less than 500 mu m. If the height difference exceeds 500 mu m, there arises a difficulty in the manufacturing process, and there is a problem in production quality such as scratch resistance and chop roll control.

In the present invention, the pattern of the first pattern portion and the pattern of the second pattern portion are formed to intersect at an angle of 60 to 150 degrees. When the intersection angle is less than 60 or more than 150, the light converging effect is reduced and the front luminance is greatly reduced.

In the present invention, the intersection angle is shown in Fig. Refers to an angle at which the pattern of the first pattern portion intersects the pattern of the second pattern portion.

[Manufacturing method]

The optical sheet according to the present invention may be manufactured by manufacturing a pull roll so that the structure layer including the first pattern portion and the second pattern portion can be formed by a single process, The optical sheet can be manufactured by coating and hardening the layer and forming the structure layer including the first pattern portion and the second pattern portion.

The optical sheet as described above can exhibit a condensing effect and a diffusion effect at the same time by the morphological characteristic of the pattern formed on the structure layer.

Further, the optical sheet is applied to a backlight unit to improve the viewing angle and color by angle and exhibit scratch resistance.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these embodiments are only for describing the present invention in more detail and that the scope of the present invention is not limited by these embodiments.

Example  One

As the substrate layer, a polyethylene terephthalate film (KOLON) having a thickness of 188 占 퐉 was prepared.

(Sartomer, SR339), 15 weight% of phenoxyethyl acrylate (Sartomer, SR339), and 6 weight parts of photoinitiators 2,4,6 1.5% by weight of trimethylbenzoyldiphenylphosphine oxide, 1.5% by weight of photoinitiator methylbenzoylformate, 2% by weight of additive bis (1,2,2,6,6-pentamethyl-4-piperidyl sebacate) Acrylate were mixed and mixed at 60 DEG C for 1 hour to prepare a composition for forming a structure layer.

A composition for forming a structure layer was applied to one surface of a substrate layer and placed on a frame of a patterned roller including a first pattern portion and a second pattern portion at 35 ° C and irradiated with ultraviolet rays of a type D (600Watt / inch2) bulb and irradiated with a light quantity of 300 mJ / cm ^{2 in} the direction of the base layer to form a structure layer including a first pattern portion and a second pattern portion perpendicular to the first pattern portion, thereby producing an optical sheet. The shapes and sizes of the first prism portion and the second prism are shown in Table 1.

Example  2 ~ Example  3

An optical sheet was prepared in the same manner as in Example 1, except that the shape of the pattern formed on the second pattern portion was changed as shown in Table 1.

Example  4 ~ Example  5

An optical sheet was prepared in the same manner as in Example 1, except that the interval between patterns of the patterns formed in the second pattern portion was changed as shown in Table 1. [

Example  6 ~ Example  7

An optical sheet was produced in the same manner as in Example 1 except that the aspect ratio of the pattern formed on the second pattern portion was changed as shown in Table 1. [

Example  8 ~ Example  9

An optical sheet was prepared in the same manner as in Example 1, except that the crossing angles of the pattern of the first pattern portion and the pattern of the second pattern portion were changed as shown in Table 1.

Comparative Example  One

A general prism sheet (KOLON) in which prisms having a vertex angle of 90 DEG, a pitch of 50 mu m and a height of 25 mu m were continuously formed was manufactured.

Comparative Example  2 ~ Comparative Example  3

An optical sheet was prepared in the same manner as in Example 1, except that the interval between patterns of the patterns formed in the second pattern portion was changed as shown in Table 1. [

Comparative Example  4 ~ Comparative Example  5

An optical sheet was produced in the same manner as in Example 1 except that the aspect ratio of the pattern formed on the second pattern portion was changed as shown in Table 1. [

Comparative Example  6

The difference in height H1-H2 between the height H1 of the pattern formed on the first pattern portion and the height H2 of the pattern formed on the second pattern portion was changed as shown in Table 1. In Examples 1 and 2, An optical sheet was prepared in the same manner.

Comparative Example  7

An optical sheet was prepared in the same manner as in Example 1, except that the crossing angles of the pattern of the first pattern portion and the pattern of the second pattern portion were changed as shown in Table 1.

The first pattern portion The second pattern portion pattern
Height car
(| H1-H2 |, 占 퐉) The pattern crossing angle of the first and second pattern portions The longitudinal section of the pattern Longitudinal section Between patterns
interval
(D, 占 퐉) shape width
(탆) Height
(H1, 占 퐉) shape width
(탆) Height
(H2, 占 퐉) Aspect ratio Example 1 triangle 50 25 triangle 50 25 0.5 100 0 90 ° Example 2 triangle 50 25 Semicircular 50 25 0.5 100 0 90 ° Example 3 triangle 50 25 Square 50 25 0.5 100 0 90 ° Example 4 triangle 50 25 triangle 50 25 0.5 1000 0 90 ° Example 5 triangle 50 25 triangle 50 25 0.5 10000 0 90 ° Example 6 triangle 50 25 Circular column 50 50 1.0 100 25 90 ° Example 7 triangle 50 25 Circular column 50 100 2.0 100 75 90 ° Example 8 triangle 50 25 triangle 50 25 0.5 100 0 60 ° Example 9 triangle 50 25 triangle 50 25 0.5 100 0 90 ° Comparative Example 1 triangle 50 25 - - - - - - - Comparative Example 2 triangle 50 25 triangle 50 25 0.5 20 0 90 ° Comparative Example 3 triangle 50 25 triangle 50 25 0.5 11000 0 90 ° Comparative Example 4 triangle 50 25 Circular column 50 2 0.04 100 23 90 ° Comparative Example 5 triangle 50 25 Circular column 50 600 12 100 575 90 ° Comparative Example 6 triangle 50 25 Circular column 50 1000 20 100 975 90 ° Comparative Example 7 triangle 50 25 triangle 50 25 0.5 100 0 30 °

The optical sheets prepared in Examples and Comparative Examples were measured for brightness, half value angle, color by angle and scratch resistance according to the following method, and the results are shown in Table 2.

(1) Evaluation of luminance (Cd / m ² )

Two prism sheets of the above-described example and comparative example were stacked in an orthogonal direction on a backlight unit for a 27-inch liquid crystal display panel, and a viewing angle improving film was stacked thereon and fixed thereon, and the resultant was fixed with a luminance meter (Model: BM- The luminance of the arbitrary 13 points was measured using the measurement apparatus and the average value thereof was obtained. Comparative Example 1 is represented by a luminance of 100%.

(2)

Two prism sheets of the above-described example and comparative example were stacked and fixed in the orthogonal direction on a 27-inch liquid crystal display panel backlight unit, and they were fixed at an angle of 80 degrees at right and left using a luminance meter (Model: BM- Was measured at intervals of 1 deg., And an angle representing a half brightness of the maximum luminance was obtained.

(3) Color by angle

Two prism sheets of the above-described example and comparative example were stacked and fixed in the orthogonal direction on a backlight unit for a 27-inch liquid crystal display panel, and they were fixed at an angle of 80 degrees at right and left using a luminance meter (model name: SR-3, Japan TOPCON) Was measured at intervals of 1 deg., And the value of max-min of hues x and y was determined. This means that the smaller the number, the less the color difference is by angle.

(4) moire

Two prism sheets of the above-described example and comparative example were stacked in an orthogonal direction on a backlight unit for a 27-inch liquid crystal display panel, the diffusion sheets were laminated and fixed, and straight or wavy stripes or patterns It was considered that moire occurred and relative evaluation was made according to the degree of occurrence of moire.

Occurrence ← ◎ - ○ - Δ - × → Not occur

(5) Scratch resistance

When the optical sheets of Examples and Comparative Examples were subjected to a minimum pressure using a basic weight of a Big Heart test apparatus manufactured by IMOTO, the occurrence of scratches on the structure layer was measured. The degree of damage was visually judged, and the criteria were as follows.

Poor scratch resistance ← × <Δ <○ <◎ → excellent scratch resistance

Luminance Half angle Color by angle Moire Scratch resistance Example 1 106 42 0.0040 X ◎ Example 2 103 45 0.0040 X ◎ Example 3 110 47 0.0045 X ◎ Example 4 118 42 0.0055 X ◎ Example 5 118 32 0.0050 X ◎ Example 6 116 32 0.0050 X ◎ Example 7 120 32 0.0050 X ◎ Example 8 110 43 0.0050 X ◎ Example 9 108 42 0.0055 X ◎ Comparative Example 1 100 28 0.008 ◎ X Comparative Example 2 80 38 0.007 ◎ ◎ Comparative Example 3 110 28 0.008 ○ X Comparative Example 4 75 30 0.008 ◎ ○ Comparative Example 5 95 28 0.007 ◎ X Comparative Example 6 101 30 0.008 ◎ X Comparative Example 7 70 30 0.007 ◎ X

As a result of measurement of physical properties, as shown in Table 2, in the case of the general prism sheet of Comparative Example 1, the color difference by angle was relatively larger than that in Examples, and the scratch resistance was poor.

Also, as in Comparative Example 2, when the interval between the patterns of the second pattern portion was narrower than the proper range, the brightness was lowered, the color difference was great depending on the angle, and moire occurred.

In addition, as in Comparative Example 3, when the interval between the patterns of the second pattern portion was wider than the proper range, the viewing angle improvement effect was not obtained, and the color difference by angle was large.

Also, as in Comparative Example 4, when the aspect ratio of the pattern formed on the second pattern portion was smaller than the proper range, the luminance was lowered and the color difference by angle was large.

As in Comparative Example 5, when the aspect ratio of the pattern formed on the second pattern portion was larger than the proper range, the viewing angle was not improved and the scratch resistance was bad.

Also, as in Comparative Example 6, when the height difference between the patterns of the prism pattern of the first pattern portion and the pattern of the second pattern portion deviates from an appropriate range, the color difference by angle was large and the scratch resistance was poor.

Also, as in Comparative Example 7, when the intersection angle between the pattern of the first pattern portion and the pattern of the second pattern portion was smaller than the proper range, the luminance was lowered, and the color difference by angle was large and moire occurred.

As a result, according to the first to tenth embodiments showing various examples of the optical sheet according to the present invention, it is possible to provide an optical sheet having excellent brightness and half-angle characteristics, small color difference by angle, preventing moire, It was confirmed that an optical sheet can be produced.

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereto will be. Accordingly, the actual scope of the present invention will be defined by the appended claims and their equivalents.

10: first pattern portion
20: second pattern portion
D1: Inter-pattern spacing of the second pattern portion
W1: Width of the prism pattern of the first pattern portion
W2: Width of the pattern of the second pattern portion
H1: Height of the prism pattern of the first pattern portion
H2: height of the pattern of the second pattern portion
?: The intersecting angle of the first pattern portion and the second pattern portion

Claims (7)

A base layer; And a structure layer formed on one surface of the base layer and having a pattern formed thereon,
Wherein the structure layer includes a first pattern portion in which a plurality of patterns are arranged and a second pattern portion in which a plurality of patterns formed by intersecting the pattern of the first pattern portion at an angle of 60 to 150 degrees are arranged. .
The method according to claim 1,
The shape of the pattern formed on the first pattern portion and the second pattern portion may be a polyhedron shape in which the vertical cross-section is selected from a triangular shape, a polygonal shape, a semicircular shape, and a semi-elliptical shape; A triangular shape whose longitudinal section is a triangle, a polygon, a triangle whose peak is streamline, a polygon whose peak is streamline, a columnar shape selected from a semicircular shape and a semielliptic shape; A triangular, polygonal, or triangular shape whose peak plane is streamline, a curved column shape selected from polygonal, semicircular, and semi-elliptical shapes whose peak is streamlined; Wherein the optical sheet is at least one selected from the group consisting of cones and polyhedral horns.
The method according to claim 1,
Wherein the pattern formed on the second pattern portion has an aspect ratio of 0.05 to 10 in the longitudinal direction.
The method according to claim 1,
Wherein an interval between the patterns formed on the second pattern portion is 50 to 10000 m.
The method according to claim 1,
Wherein an interval between adjacent patterns of the pattern formed on the second pattern portion is regular or irregular.
The method according to claim 1,
The prism pattern of the first pattern portion and the pattern of the second pattern portion have a height difference (| H1-H2 |) of less than 500 mu m, wherein H1 is the height of the prism pattern of the first pattern portion, Is a height of a negative pattern.
A backlight unit comprising the optical sheet according to any one of claims 1 to 6.

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