KR20090120956A - Optical film for oled - Google Patents

Abstract

PURPOSE: An optical film for an OLED is provided to extract a part of light which is totally reflected to the outside by forming a light input unit having a high refractive index layer. CONSTITUTION: An optical film includes a light input unit(10), a base member(20) and a light focusing output unit(30). The light input unit is positioned at a lower part of the base member. A high refractive index layer(12) and a low refractive index layer(14) extended in one direction are alternatively arranged in the light input unit. The light focusing output unit is positioned at an upper side of the base member. Lenticular lenses extended in one direction are continuously arranged in the light focusing output unit.

Description

Optical film for metal LED {OPTICAL FILM FOR OLED}

The present invention relates to an optical film for OLED, and more particularly, extracts a part of light that cannot be emitted to the outside due to total internal reflection to the outside to increase the amount of emitted light of the OLED, and at the same time to adjust the light distribution to adjust the luminance in a desired direction. The present invention relates to an optical film for OLED developed to be improved.

Organic light emitting diodes (OLEDs) are self-luminous devices that emit light by using an electroluminescence phenomenon that emits light when a current flows through a fluorescent organic compound.

The organic light emitting device is generally a cathode electrode (generally a metal electrode) for electron injection, an organic layer and a hole consisting of an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer and a hole injection layer It consists of an anode electrode (generally made of ITO, IZO, etc.) for hole injection.When voltage is applied, electrons move and electrons move from the cathode electrode to the light emitting layer with the help of an electron transport layer. Holes having escaped electrons move to the light emitting layer with the help of the hole transport layer. Electrons and holes encountered in the light emitting layer, which is an organic material, generate excitons with high energy. At this time, excitons fall to low energy and generate light.

Such an organic light emitting device has the advantages of excellent thermal stability and low driving voltage, and has attracted attention as a next-generation material in various industrial fields such as display and lighting.

However, in the organic light emitting device, total internal reflection occurs due to the difference in refractive index of each layer constituting the light emitting device. As a result, the amount of light finally emitted is only about 20% of the amount of light generated in the light emitting layer. It is bad and has a problem of low luminance. The present invention is a technique for reducing the total reflection at the outermost angle of the organic light emitting device having a sharp difference in refractive index.

Therefore, the present invention provides an OLED optical film developed to extract a part of light that cannot be emitted to the outside due to total internal reflection to the outside, and by applying the same to increase the output amount of the OLED, and to improve the brightness It is for that purpose.

The present invention for this purpose; And it is located under the base portion, and provides an optical film for an OLED comprising a light incident portion alternately arranged in a high refractive index layer and a low refractive index layer extending in one direction.

In this case, the optical film for OLED of the present invention may be configured to further include a light condensing light emitting unit arranged continuously on the top surface of the base portion lenticular lens, wherein the high refractive index layer and the lenticular lens is the center It is preferable that these are formed to coincide with each other.

On the other hand, the high refractive index layer is better than the refractive index (refractive index matching) of the refractive index of the OLED outermost material (glass, ITO, etc.), but may be made of a UV curable resin usually 1.50 to 1.65, the low refractive index layer is It may be an air layer, or may be made of a UV curable resin having a refractive index of 1.35 to 1.50.

On the other hand, in another aspect, the present invention; And a light incidence part disposed under the base part and having a high refractive index layer and a low refractive index layer extending in one direction, and the cross-sectional shape of the high refractive index layer formed in an inverted trapezoidal shape. to provide.

In this case, the optical film may further include a light condensing light emitter in which a lenticular lens extending in one direction is continuously arranged on an upper surface of the substrate, and in this case, an extension direction of the light condensing light emitting part and the light incidence part. The extending directions of are preferably perpendicular to each other.

The optical film may further include a buffered light-emitting part made of a polymer resin having a refractive index of 1.35 to 1.50 on an upper surface of the base part.

In the optical film of the present invention configured as described above, the high refractive index layer may be made of a UV curable resin having a refractive index of 1.50 to 1.65, and the low refractive index layer is made of an UV curable resin having an air layer or a refractive index of 1.35 to 1.50. Can be.

The optical film for OLED of the present invention is provided with a light-receiving portion formed with a high refractive index layer, it is possible to improve the light emission efficiency of the organic light emitting device by extracting a part of the light that has been totally internally reflected inside.

In addition, the present invention has a light condensing light emitting portion on the upper surface of the optical film to improve the brightness in the desired direction.

In addition, the present invention by forming a high refractive index layer in an inverted trapezoidal shape, it was possible to perform a light condensing function with a light extraction function.

In addition, the present invention by forming a light-converging light emitting portion consisting of lenticular lenses extending in the direction perpendicular to the extending direction of the high refractive index layer, by condensing the light twice in the X-axis direction and Y-axis direction to maximize the brightness enhancement effect To make it possible.

In addition, the present invention has a buffered light emitting portion on the upper surface of the base material, to minimize the total reflection that can occur at the optical film and the air interface, it is possible to improve the amount of light output and brightness of the OLED.

Hereinafter, the OLED optical film of the present invention will be described in more detail.

As described above, the optical film for OLED of the present invention is made based on the base, the light-receiving, and the light-emitting portion, wherein the light-condensing light-emitting portion made of a lenticular lens or a buffer made of a polymer resin having a refractive index of 1.35 to 1.50. It can be made by including a sex light emitting unit.

1 and 3 to 5 show various embodiments of the optical film of the present invention.

As shown in FIG. 1, the optical film of the present invention includes a substrate unit 20; A light incidence part 10 disposed below the base part 20 and having a high refractive index layer 12 and a low refractive index layer 14 extending in one direction alternately; And a light converging light emitting part 30 positioned on an upper surface of the base part 20 and having a lenticular lens extending in one direction continuously arranged.

In addition, as shown in Figure 3, the optical film of the present invention is a base portion 20 '; Located on the lower portion of the base portion 20 ', the high refractive index layer 12' and the low refractive index layer 14 'extending in one direction are formed to include a light receiving portion 10' alternately arranged, In this case, the cross section of the high refractive index layer may be formed in an inverted trapezoid shape.

In addition, as shown in Figure 4, the optical film of the present invention is a substrate portion 20 '; A light incidence portion 10 ′ positioned below the base portion 20 ′ and having a high refractive index layer 12 ′ and a low refractive index layer 14 ′ extending in one direction; And a light condensing light emitter 30 'in which a lenticular lens extending in one direction is continuously arranged on an upper surface of the base portion 20', wherein the light condensing light emitter extends and the light incidence extends. The directions may be formed to be perpendicular to each other.

In addition, as shown in Figure 5, the optical film of the present invention is a base portion 20 '; A light incidence portion 10 ′ positioned below the base portion 20 ′ and having a high refractive index layer 12 ′ and a low refractive index layer 14 ′ extending in one direction; And positioned on the upper surface of the base portion 20 ', it may be made of a buffered light-emitting portion 40 made of a resin having a refractive index of 1.35 to 1.50.

Hereinafter, each component of the optical film of the present invention will be described in more detail.

(1) base part

The base part is for supporting the light incident part and the light exit part, and general polymer films used in the art, for example, polyester, polyvinyl chloride, polycarbonate, polymethylmethacrylate, polystyrene, polyester sulfone , Polybutadiene, polyether ketone, or the like, or a mixture of two or more kinds thereof. Preferably, one or two or more resins may be used from polycarbonate, polymethylmethacrylate, polystyrene, and polybutadiene.

(2) light receiving part

The light incident part extracts a part of the light totally reflected inside the organic light emitting device and emits the light to the outside of the organic light emitting device. The light incident part is positioned below the substrate and has a high refractive index layer and a low refractive index layer that are alternately arranged. .

The high refractive index layer is better as the refractive index is the same (refractive index matching) of the OLED outermost material (glass, ITO, IZO, etc.), but is preferably made of a UV curable resin of about 1.50 to 1.65, wherein the UV-curable resin As the furnace, for example, one kind or two or more kinds thereof may be used from a radical curable resin containing a urethane acrylate, an epoxy acrylate, an ester acrylate, a radical generating monomer, or the like.

On the other hand, the low refractive index layer may be made of an air layer, a material having a lower refractive index than the high refractive index layer 12, preferably may be made of a UV curable resin having a refractive index of about 1.35 to 1.50, wherein the UV for the low refractive index layer As curable resin, 1 type (s) or 2 or more types etc. can be used from radical curable resin containing a urethane resin, urethane acrylate, epoxy acrylate, ester acrylate, a radical generating type monomer, etc., for example.

The process of extracting some of the light that has been totally reflected in the OLED through the light incident part of the present invention is as follows.

In general, total reflection refers to a phenomenon in which incident light is reflected and not reflected, and occurs when light proceeds from a material having a large refractive index (refractive index n ₁ ) to a material having a small refractive index (refractive index n ₂ ) at an incident angle greater than a critical angle. do. The critical angle θ _c is expressed by the following equation, and since the critical angle becomes smaller as the difference in refractive index between the two materials increases, total reflection easily occurs.

θ _c = arcsin (n ₂ / n ₁ )

On the other hand, conventionally, the outermost layer of the organic light emitting element in contact with air was a glass substrate on which an anode electrode (ITO electrode) was deposited (Bottom emisson method) or an anode electrode (ITO, IZO, etc.) (Top emisson method).

When the outermost layer is an anode, for example, an ITO electrode, since the refractive index n ₁ of the ITO electrode is approximately 2.0 and the refractive index n _{2 of} air is 1, the critical angle is 30 °. Therefore, light having an angle of incidence greater than 30 ° cannot be emitted to the outside, and all of them are totally reflected inside the organic light emitting diode.

However, when the optical film of the present invention is applied on the anode electrode, since the refractive index of the high refractive index layer 12 is larger than air, the difference in refractive index with the anode electrode is reduced, and as a result, the critical angle at which total reflection occurs becomes large. Therefore, some of the conventionally totally reflected light is extracted through the high refractive index layer without being totally reflected and transmitted to the substrate.

On the other hand, when the outermost layer is a glass substrate, the refractive index n ₁ of the glass is approximately 1.5, and since the refractive index n _{2 of the} air is 1, the critical angle is 41.8 °. Therefore, light having an angle of incidence exceeding 41.8 ° does not emit to the outside, and all of them are totally reflected inside the organic light emitting diode.

However, when the optical film of the present invention is applied on a glass substrate, when the refractive index of the high refractive index layer 12 is most closely matched to the glass plate refractive index in the range of approximately 1.50 to 1.65, the high refractive index layer (high refractive material) in the glass plate (low refractive material) In case of incident light, total reflection does not occur. Therefore, the light incident to the high refractive index layer among the totally reflected light is extracted through the high refractive index layer to be transmitted to the substrate portion.

The light transmitted through the substrate portion is directly emitted to the outside, or when the light collecting portion or the buffering portion is present on the upper portion of the substrate portion is emitted to the outside through the light collecting portion or the buffering portion.

Meanwhile, as shown in FIG. 1, the high refractive index layer and the low refractive index layer may have a rectangular cross section and may be formed in a sprite pattern extending in one direction, as shown in FIGS. 3 to 5. The cross section of the high refractive index layer may be formed to have an inverted trapezoidal shape. 3 to 5, when the cross-section of the high refractive index layer is formed in an inverted trapezoid with an inclination, since the path of the light is changed as the light is refracted or reflected on the inclined surface, the light extraction function can be performed together with the light extraction function. There is an advantage that it can. FIG. 6 shows a path of light traveling when the high refractive index layer is formed in an inverted trapezoid shape. Referring to FIG. 6, it can be seen that light deviating from a desired condensing direction, such as L ₁₀ , is condensed in a desired direction while being reflected from an inclined surface of the high refractive index layer. Therefore, when the high refractive index layer is formed in an inverted trapezoidal shape in this way, there is an advantage that the luminance can be improved without forming a light converging type light emitting portion on the upper surface of the base portion.

When the low refractive index layer 14 is an air layer, the light incident part 10 has a pattern corresponding to the high refractive index layer 12 (that is, a pattern having a cross section of a square or an inverted diagonal shape and extending in one direction). After the UV curable resin is injected between the mold and the base part film, it may be manufactured by a method of curing. When the low refractive index layer is formed of a curable resin, a high refractive index layer is formed by the above method, and then a low refractive index is formed in the empty portion. It can manufacture by the method of filling and hardening UV curable resin for layers. Methods of forming patterns using UV curable resins and molds are well known in the art, and the light incident portion of the present invention can be fabricated using such conventional techniques.

(3) condenser

As shown in FIGS. 1 and 4, the optical film of the present invention additionally includes condensed light exit parts 30 and 30 ′ in addition to the substrate parts 20 and 20 ′ and the light incident parts 10 and 10 ′. Can be configured.

The light collecting part adjusts the direction of light emitted from the film to focus the light in a desired direction, and at the same time, when light is emitted from the film to the outside, the total reflection caused by the difference in refractive index between the film and the outer air layer is reduced. It is to perform a role to make, generally consisting of lenticular lenses arranged in succession.

As such, when the light converging light emitting part is formed on the upper surface of the base part, the light extracted through the light incidence part is incident on the light condensing light exiting part through the base part, and the traveling direction is changed by the lenticular lens of the light condensing light exiting part. Therefore, the light can be deflected in the desired direction (for example, the front direction), and as a result, the luminance in the desired direction can be improved.

On the other hand, since the optical film of the present invention also has a refractive index different from that of air, total reflection occurs when light proceeds from the film into the air, and the light condensing light emitting part also serves to reduce the total reflection. The total reflection occurring at the interface of materials with different refractive indices is significantly reduced when there is a curvature at the interface. Therefore, when the light condensing light-emitting part made of the curved lenticular lens is formed at the outermost portion of the film, total reflection is significantly reduced.

On the other hand, when the cross section of the high refractive index layer is rectangular, the extending direction of the light incident portion and the extending direction of the light condensing light emitting portion are formed parallel to each other, and the center of the lenticular lens and the high refractive index layer of the light condensing light emitting portion 30 is formed. It is preferable from the viewpoint of the light collection efficiency that these are formed to coincide with each other. In this case, the light condensing range may be adjusted by adjusting the width of the high refractive index layer.

On the other hand, when the cross section of the high refractive index layer is formed in an inverted trapezoid, it is preferable that the extending direction of the light incident portion and the extending direction of the light condensing light emitting portion are formed perpendicular to each other.

4 shows an optical film of the present invention in which the cross section of the high refractive index layer is formed in an inverted trapezoid, and the extending direction of the light incident portion and the extending direction of the light converging light exit portion are perpendicular to each other.

As shown in FIG. 4, when the high refractive index layer and the light condensing light emitting part of the inverse dihedron are formed perpendicular to each other, the light is condensed twice in the light incidence part 10 ′ and the light condensing light emitting part 30 ′. That is, after light is focused once on the inclined surface of the high refractive index layer (L ₁₀ of FIG. 6) The light is collected once again (see L ₁₂ of FIG. 6) while passing through the lenticular lens of the light condensing light emitting unit. However, at this time, since the extending direction of the light incident portion 10 'is the horizontal direction (x-axis), and the extending direction of the lenticular lens is the vertical direction (y-axis), condensing by the high refractive index layer occurs in the horizontal direction and the lenticular Condensing by the lens occurs in the longitudinal direction.

As described above, when the light incidence portion 10 'and the lenticular lens 30' extend in the vertical direction, the light is condensed twice in the horizontal direction (X-axis direction) and in the vertical direction (Y-axis direction) (L ₁₀ and L in FIG. 5). ₁₂ ) occurs, the advantage that the brightness enhancement effect can be maximized.

Methods for producing a lenticular lens sheet are well known in the art, and the light converging light emitting portion of the present invention can be formed using these conventional techniques. For example, the light converging light exiting part may be formed by injecting a UV curable resin between the mold and the base part film in which the lenticular lens shape is continuously engraved, and then UV curing.

(4) buffering light emitting part

On the other hand, the optical film of the present invention, as shown in Figure 5, may comprise a buffered light-emitting portion 40. The buffered light-emitting part is a polymer resin layer having a refractive index of 1.35 to 1.50 formed on the upper surface of the substrate, and is intended to suppress total reflection that may occur when light travels from the optical film to the external air layer.

As described above, since the high refractive index layer of the present invention has a larger refractive index than air, some total reflection occurs when light is emitted from the optical film. Therefore, in the present invention, the total light reflection part can be suppressed by forming a buffered light-emitting part using a polymer resin having a lower refractive index than a high refractive index layer, preferably a polymer resin having a refractive index of 1.35 to 1.50, on the upper surface of the base part. .

1 is a diagram showing a first embodiment of the optical film of the present invention.

FIG. 2 is a view for explaining a propagation path of light in the optical film of FIG. 1. FIG.

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

4 is a view showing a third embodiment of the optical film of the present invention.

5 is a view showing a fourth embodiment of the optical film of the present invention.

6 is a view for explaining a path of light propagation in the optical film of FIG. 4.

<Key Symbols in Drawing>

10, 10 ': light incident part

20, 20 ': description

30, 30 ': light collecting part

40: buffer light emitting unit

Claims (12)

Base unit; And Located in the lower portion of the base portion, the high refractive index layer and the low refractive index layer extending in one direction comprising an incident light portion arranged alternately. The method of claim 1, The optical film is positioned on the upper surface of the base portion, the optical film for OLED further comprises a light condensing light emitting portion arranged in a continuous direction lenticular lens. The method of claim 2, Wherein the high refractive index layer is formed such that its center coincides with the center of the lenticular lens. The method according to any one of claims 1 to 3, The high refractive index layer is an optical film for OLED, characterized in that made of a UV curable resin having a refractive index of 1.50 to 1.65. The method according to any one of claims 1 to 3, The low refractive index layer is an optical film for OLED, characterized in that the air layer. The method according to any one of claims 1 to 3, The low refractive index layer is an optical film for OLED, characterized in that made of a UV curable resin having a refractive index of 1.35 to 1.50. The method of claim 1, The optical film for OLED, characterized in that the cross section of the high refractive index layer is formed in an inverted trapezoidal shape. The method of claim 7, wherein The optical film may further include a light condensing light emitting part in which a lenticular lens extending in one direction is continuously arranged on an upper surface of the base part, The extending direction of the light converging light-emitting part and the extending direction of the light-receiving part are perpendicular to each other. The method of claim 7, wherein Located on the upper surface of the base portion, the optical film for OLED, characterized in that further comprises a buffer outgoing portion made of a resin having a refractive index of 1.35 to 1.50. The method according to claim 7 or 9, The high refractive index layer is an optical film for OLED, characterized in that made of a UV curable resin having a refractive index of 1.50 to 1.65. The method according to claim 7 or 9, The low refractive index layer is an optical film for OLED, characterized in that the air layer. The method according to claim 7 or 9, The low refractive index layer is an optical film for OLED, characterized in that made of a UV curable resin having a refractive index of 1.35 to 1.50.

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