KR20100076335A - Lenticular optical film with reduced moire and backlight unit comprising the same - Google Patents

Abstract

PURPOSE: A lenticular optical film and a backlight unit including the same according to the present invention are provided to improve the moire without the degradation of the brightness. CONSTITUTION: First lenses(10) of cylindrical shape are expanded in one direction, and are arranged with a constant interval continuously. A second lens(20) of the cylinder shape is expanded in the same direction with the extension direction of the first lens. The second lens is formed on the boundary of first lenses, and has the size smaller than the first lens.

Description

LENTICULAR OPTICAL FILM WITH REDUCED MOIRE AND BACKLIGHT UNIT COMPRISING THE SAME}

The present invention relates to a lenticular optical film having improved moiré and a backlight unit including the same. More particularly, a lenticular optical designed to improve moiré without lowering luminance by additionally disposing small lenses in a valley between the lenticular lenses. It relates to a film and a backlight unit including the same.

The lenticular optical sheet is a product that performs a function of condensing light in a predetermined direction. The lenticular optical sheet is a light collecting sheet which is typically used together with a prism sheet, and is widely used in a backlight unit.

In such a lenticular optical sheet, cylindrical lenses having a size of several tens of micrometers to several hundreds of micrometers are periodically arranged on a surface of the lenticular optical sheet. However, when the optical sheet having the periodic array overlaps with the optical sheet having the other periodic array or pattern or the panels composed of pixels of constant period, the moire phenomenon occurs due to geometric interference. .

1 is a view for explaining the moiré phenomenon. As shown in FIG. 1, when two film masks having a similar contrast pattern are overlapped, light causes an interference phenomenon, and a new contrast pattern as shown on the far right is generated, which is called a moiré phenomenon. .

When the moiré phenomenon occurs, an unnecessary pattern is generated in the image implemented on the display, and the image quality is deteriorated. Therefore, various efforts have been made to improve such moiré.

In general, a moiré improvement method is to form a pitch of a lenticular lens at a pitch that can minimize moiré in relation to an optical sheet or panel having a different periodic arrangement or pattern, or to remove periodicity by changing the height or pitch of the lens. Has been used. However, the former method has a problem that it cannot be used when the optical sheet or display panel used together is changed. The latter method may be useful for a prism lens sheet, but the lenticular having a curved surface of the lens surface may be used. In the case of the lens, if the pitch is arbitrarily changed, the curved portion of the lens exposed to light is greatly changed, so that the luminance may be greatly reduced. In addition, since the pitch must be arbitrarily changed, there is a problem that the manufacturing difficulty is high.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a lenticular optical film capable of improving moiré while minimizing brightness reduction by additionally disposing small lenses in the valleys between the lenticular lenses. .

To this end, the present invention extends in one direction, the primary lens of the cylindrical form continuously arranged at a constant cycle; And extending in the same direction as the extension direction of the primary lens, formed on the boundary of the primary lenses, and comprising secondary lenses having a cylindrical shape smaller than the primary lens.

In this case, it is preferable that the secondary lens has a height, a width, or both of which are modulated in a curved function form along the extension direction, and in particular, is modulated in a sinusoidal form.

In this case, it is preferable that the curve function has a modulation amplitude (Mod. Amp.) Of about 20% to 100% of the maximum height of the secondary lens and the maximum height of the secondary lens does not exceed 70% of the primary lens. .

In addition, when the secondary lenses are modulated in the form of a sine function, the respective secondary lenses are preferably modulated in a sine function having different initial phases.

Meanwhile, the primary lens and the secondary lens may have a spherical semicircular shape or an aspherical oval shape, a parabolic shape, and a hyperbolic shape. The pitch of the primary lens may be about 50 μm to 500 μm, and the height of the lens may be about 10 μm to 10 μm. It is preferable that it is about 300 micrometers. In addition, the width of the secondary lens is preferably about 5% to 75% of the primary lens pitch, and the height of the secondary lens is preferably about 0.1% to 70% of the height of the primary lens.

The present invention also provides a backlight unit comprising a lenticular optical film made as described above.

The lenticular optical film of the present invention has almost no reduction in luminance because the condensing performance is maintained by the primary lens maintaining a constant period and shape, and the vertices and valleys of the primary lens are reduced by the secondary lenses disposed between the primary lenses. Moire is improved because the difference in luminance of the portion is reduced to reduce the intensity of the contrast pattern.

In addition, the present invention curve-modulated the height or pitch of the secondary lens in the extension direction, thereby maximizing the moiré improvement effect by eliminating the periodicity of the lenticular lens pattern. On the other hand, even in this case, since the condensing performance is maintained by the primary lens, the luminance does not decrease significantly.

The present inventors have steadily studied to improve the moiré of the lenticular sheet without reducing the luminance, and as a result, by additionally arranging a small secondary lens in the valley portion formed at the interface of the lenses while maintaining the structure of the conventional lenticular lens, It has been found that the moiré can be effectively improved with little reduction in the light collection performance of the lenticular sheet, thus completing the present invention.

The lenticular optical film of the present invention includes cylindrical primary lenses extending in one direction and continuously arranged at regular intervals; And secondary lenses of a cylindrical shape extending in the same direction as the extension direction of the primary lens, formed at the boundary of the primary lenses, and smaller in size than the primary lens.

The root cause of moiré in the lenticular sheet is that brightness differences occur near the vertices and valleys of the lens, resulting in a constant contrast pattern. 4 shows the light behavior in a conventional lenticular sheet. In general, the lens shape of the lenticular sheet is designed to optimize the luminance and the viewing angle for a given pitch, where both ends of the unit lens have a relatively large change in curvature, so that light is more likely to be reflected rather than transmitted. In many cases, light is incident on an adjacent unit lens and recycled. Therefore, as shown in FIG. 4, since the amount of transmitted light is small at both end portions of the unit lens, that is, at the boundary surface (bone portion) of the unit lenses, the luminance is lower than that near the vertex of the lens. Contrast patterns will occur.

However, in the case of the present invention, as shown in Figure 5, since the light incident to the boundary of the primary lens is transmitted by the secondary lens, the brightness difference between the peak and the valley of the primary lens is not large, the contrast pattern This appears weak, and as a result, it is possible to improve the moiré phenomenon.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

2 illustrates an embodiment of the present invention. As shown in FIG. 2, two types of lenses having different sizes, that is, the primary lens 10 and the secondary lens 20 are formed on the surface of the lenticular optical film of the present invention.

The primary lens 10 performs a light condensing function and is formed in a cylindrical shape extending in one direction. At this time, the cross-sectional shape, height, pitch, etc. of the primary lens is not particularly limited, and may be suitably designed in consideration of the use of the optical film, desired luminance, viewing angle, and the like. For example, the primary lens of the present invention may be formed in a semicircular or spherical oval, parabolic, hyperbolic, or the like in a cross section, wherein the pitch of the lens is about 50 μm to 500 μm, and the height of the lens is about 10 μm. It is preferable that it is about micrometers-300 micrometers. In this case, the pitch of the primary lens refers to the distance P between the floor of the primary lens and the floor, and the height of the primary lens refers to the floor of the primary lens from the design reference line L0 of the primary lens. , Corresponds to H ₁ in FIG. 5. The design baseline of the primary lens or the height of the primary lens can be defined through the following calculation process. Find the radius of curvature ( R ) and the conical constant ( k ) by substituting any two points of the primary lens into the conic curvature equation of Equation 1 below to define the lens shape. The pitch P may be used to define the height H ₁ of the primary lens such as Equation 2.

(식 1)

(Equation 1)

Here, x and y are coordinates within a single lens shape and are defined as the distance from the lens center and the distance from the lens ridge, respectively.

(식 2)

(Equation 2)

On the other hand, the primary lenses 10 are continuously arranged at a predetermined period, wherein the continuously arranged primary lenses are preferably arranged in parallel to each other.

Next, the secondary lens 20 is to improve the moire by transmitting the light incident to the boundary of the primary lens to improve the brightness of the lens boundary, it is formed on the boundary of the primary lens.

At this time, the secondary lens is formed extending in the same direction as the extension direction of the primary lens, the cross-sectional shape may be formed of a spherical semi-circular or aspherical oval, parabolic, hyperbolic.

On the other hand, the secondary lens is preferably formed of a smaller size than the primary lens, but is not limited to this, the height of the secondary lens is about 0.1% to 70% of the height of the primary lens, the secondary lens is Preferably, the width is formed to be about 5% to 75% of the primary lens pitch. In this case, the height of the secondary lens refers to the distance H ₂ from the design reference line L0 of the primary lens to the floor of the secondary lens, and the width of the secondary lens is a unit applied when designing the secondary lens. The width of the lens, as in FIG. 5, is the width W of the unit lens of the secondary lens at the primary lens design reference line LO. This can be obtained using any two points of the cross-sectional shape of the secondary lens, the height H ₂ of the secondary lens, and Equation 1. On the other hand, when the height of the secondary lens is less than 0.1% of the height of the primary lens, the effect of improving moiré is insignificant, and when it exceeds 70%, the disappearance of the curved surface of the primary lens, which functions as a light collecting function, greatly increases the luminance. do.

In addition, when the width of the secondary lens is less than 5% of the pitch of the primary lens, the effect of improving moiré is insignificant, and when the width of the secondary lens is greater than 75%, the disappearance of the curved surface of the primary lens, which functions as a light collecting function, greatly reduces the luminance. Because.

Meanwhile, the secondary lenses of the present invention may be formed in a stripe shape having a constant height and width (see FIG. 2), or may be formed in a shape in which the height or width of the secondary lens is curved-modulated along the extending direction. (See Figure 3).

When the secondary lens is formed in a curved modulated form, the curved modulation may be in various forms, for example, a sine function, a random function (any curve without periodicity), and the like. It is particularly preferable to be modulated. This is because sine function modulation can be easily implemented in actual product application and can increase reproducibility in mold manufacturing required for optical sheet manufacturing.

In addition, when the secondary lens is modulated by a sine function, the phases of the secondary lens formed in one film may be differently formed by changing the initial phase for each secondary lens. In this case, the irregularity is increased, there is an advantage that can maximize the effect of improving the moire.

The lenticular optical film of the present invention may be manufactured using a mold in which a desired shape is engraved. In this case, the mold may be manufactured by, for example, engraving the secondary lens shape through a bite process on a mold in which the primary lens shape is engraved, that is, a mold for a conventional lenticular lens sheet.

Meanwhile, by shaking the bite in the vertical direction and / or the horizontal direction during the bite processing, the secondary lens shape in which the height or width of the lens is modulated in a curved shape can be engraved.

3 shows a lenticular optical film in which the height of the secondary lens is modulated in the form of a sine function. The lenticular optical film of FIG. 3 was manufactured by using a mold in which a secondary lens was engraved by vibrating a bite in the form of a sine function in the vertical direction. In this case, since the end portion of the bite is spherical, the width (width) of the engraved cross section is changed along with the depth of the engraved portion while moving the bite vertically. As a result, as shown in Figure 3, not only the height of the secondary lens, but also the width is modulated together. As such, when the height and / or width of the lens is changed according to the position, the degree of condensing is changed, and as a result, the periodicity of the light pattern is weakened, and as a result, the moiré can be more effectively improved.

In addition, in the optical film of FIG. 3, the initial phase of the sine function is different for each of the secondary lenses during the sine function modulation, thereby increasing the irregularity and maximizing the moiré improvement effect.

On the other hand, it is preferable that the function of modulating the secondary lens is a modulation amplitude (Mod. Amp.) Is 20% to 100% of the maximum height of the secondary lens. If the modulation amplitude of the modulation function exceeds 100% of the height of the secondary lens, there is a problem that the brightness is lowered, and if less than 20% of the maximum height of the secondary lens, the moiré improvement effect is insignificant.

The lenticular optical film of the present invention configured as described above may be used as a light collecting film of a backlight unit such as an LCD. When the lenticular optical film of the present invention is used in the backlight unit, it may bring an effect of improving the moire.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

Comparative example

The intensity change of the contrast pattern for the lenticular sheet having an elliptic unit lens having R = ˜93 μm, k = −0.4, and a pitch of 200 μm was formed through a ray-tracing program. The results are shown in FIG. 6, and the maximum luminance difference was found to be 4.6 × 10 ⁵ .

In addition, the vertical viewing angle luminance distribution and the horizontal viewing angle luminance distribution of the lenticular sheet of this comparative example were measured using a ray-tracing program, and the results are shown in FIGS. 11 and 12, respectively.

Example 1

A lenticular sheet having an elliptic primary lens having R = ˜93 μm, k = −0.4 and a pitch of 200 μm, and a stripe secondary lens having R = ˜93 μm, k = −0.4 and a pitch of 60 μm. The intensity change of the contrast pattern for was measured through a Ray-tracing program. The results are shown in FIG. 7, and the maximum luminance difference was 4.1 × 10 ⁵ .

In addition, the vertical viewing angle luminance distribution and the horizontal viewing angle luminance distribution of the lenticular sheet of this embodiment were measured using a Ray-tracing program, and the results are shown in FIGS. 11 and 12, respectively.

Example 2

A lenticular sheet having an elliptic primary lens having R = ˜93 μm, k = −0.4 and a pitch of 200 μm, and a stripe secondary lens having R = ˜93 μm, k = −0.4 and a pitch of 100 μm. The intensity change of the contrast pattern for was measured through a Ray-tracing program. The results are shown in FIG. 8, and the maximum luminance difference was found to be 2.8 × 10 ⁵ .

In addition, the vertical viewing angle luminance distribution and the horizontal viewing angle luminance distribution of the lenticular sheet of this embodiment were measured using a Ray-tracing program, and the results are shown in FIGS. 11 and 12, respectively.

Example 3

An elliptic primary lens having R = ˜93 μm, k = −0.4, pitch 200 μm, and R = ˜93 μm, k = −0.4, width 60 μm, and Mod. The intensity change of the intensity pattern for the lenticular sheet having a secondary lens modulated with a sine function having an Amp. = 3.8 μm and a period of 0.5 mm was measured through a ray-tracing program. The results are shown in FIG. 9, and the maximum luminance difference was 3.2 × 10 ⁵ .

In addition, the vertical viewing angle luminance distribution and the horizontal viewing angle luminance distribution of the lenticular sheet of this embodiment were measured using a Ray-tracing program, and the results are shown in FIGS. 11 and 12, respectively.

Example 4

An elliptical primary lens having R = ˜93 μm, k = −0.4 and a pitch of 200 μm, and R = ˜93 μm, k = −0.4 and a width of 100 μm, and Mod. The change in intensity of the intensity pattern for the lenticular sheet having a secondary lens modulated with a sine function having an Amp. = 10.9 mu m and a period of 0.5 mm was measured through a ray-tracing program. The results are shown in FIG. 10, and the maximum luminance difference was 2.5 × 10 ⁵ .

In addition, the vertical viewing angle luminance distribution and the horizontal viewing angle luminance distribution of the lenticular sheet of this embodiment were measured using a Ray-tracing program, and the results are shown in FIGS. 11 and 12, respectively.

Through Examples 1 to 4 and Comparative Examples, as shown in the present invention, when the secondary lens is formed, it can be seen that the moiré phenomenon is improved compared to the conventional. In particular, when the secondary lens is modulated with a curve, it can be seen that the moiré improvement effect is more excellent.

On the other hand, it can be seen from Figure 11 and 12, the luminance in the optical film of Examples 1 to 4 is maintained almost similar to the case of the comparative example.

1 is a view for explaining the moiré phenomenon.

2 is a view showing an embodiment of a lenticular optical film of the present invention.

3 is a view showing another embodiment of the lenticular optical film of the present invention.

4 is a view showing light behavior in a conventional lenticular optical film.

5 is a view showing the light behavior in the lenticular optical film of the present invention.

FIG. 6 is a diagram illustrating a result of measuring a ray-tracing program of a comparative example. FIG.

FIG. 7 is a diagram illustrating a result of measuring a ray-tracing program of Example 1. FIG.

FIG. 8 is a diagram illustrating a result of measuring a ray-tracing program of Example 2. FIG.

FIG. 9 is a diagram illustrating a result of measuring a ray-tracing program of Example 3. FIG.

FIG. 10 is a diagram illustrating a result of measuring a ray-tracing program of Example 4. FIG.

FIG. 11 is a graph showing the vertical viewing angle luminance distribution of the optical sheets of Comparative Examples and Examples 1 to 4. FIG.

12 is a graph showing a horizontal viewing angle luminance distribution of the optical sheets of Comparative Examples and Examples 1 to 4;

Claims (12)

Primary lenses extending in one direction and continuously arranged at regular intervals; And A lenticular optical film extending in the same direction as the extending direction of the primary lens, and formed on the boundary of the primary lenses, the secondary lens of the cylindrical shape smaller than the primary lens. The method of claim 1, A lenticular optical film, characterized in that the height, width or both of the secondary lens is modulated in the form of a curve function along the extension direction. The method of claim 2, The curve function is a lenticular optical film, characterized in that the form of a sine function. The method of claim 2, The curve function is a lenticular optical film, characterized in that the modulation amplitude (mod. Amp.) Is 20% to 100% of the maximum height of the secondary lens. The method of claim 3, And the secondary lenses are modulated by a sine function having different initial phases, respectively. The method of claim 1, The primary lens is a lenticular optical film, characterized in that the cross-sectional shape is spherical semicircular or aspherical oval, parabolic, hyperbolic. The method of claim 1, The primary lens has a lenticular optical film, characterized in that the pitch of 50㎛ to 500㎛. The method of claim 1, The primary lens has a lenticular optical film, characterized in that the height of 10㎛ to 300㎛. The method of claim 1, The secondary lens is a lenticular optical film, characterized in that the cross-sectional shape is semi-circular, elliptical, parabolic or hyperbolic. The method of claim 1, The width of the secondary lens is lenticular optical film, characterized in that 5% to 75% of the primary lens pitch. The method of claim 1, The height of the secondary lens is lenticular optical film, characterized in that 0.1% to 70% of the height of the primary lens. The backlight unit which comprises the lenticular optical film of any one of Claims 1-11.

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