KR20140034551A - Condensing type optical sheet - Google Patents

Abstract

The present invention relates to a condensing type optical sheet and, more specifically, to a condensing type optical sheet having a substrate, and a structure layer formed on at least one surface of the substrate and in where multiple structures are disposed. The structure comprises an internal structure composed of a low refractive index resin and an external layer formed outside the internal structure and composed of a high refractive index resin to be able to provide high light condensing efficiency and ensure a wide viewing angle.

Description

Condensing Type Optical Sheet

The present invention relates to a light collecting optical sheet used in a backlight unit.

As today's industrial society develops into a high information age, the importance of electronic displays as a medium for reaching various information is increasing day by day, and various forms of flat panel display industries such as LCD, PDP, and organic EL are expanding day by day. have. In particular, the LCD, which is the driving force behind the growth of the flat panel display industry, is a technology-intensive item that combines liquid crystal and semiconductor technology, and is thin, light, and has low power consumption. In addition to monitors and small home appliances (PDAs and mobile phones), the company has been advancing into the TV market, which has been regarded as a unique area of the CRT, which is a conventional CRT.

In the liquid crystal display (LCD) device, since the liquid crystal itself cannot play a role of light emission, a separate light source is installed at the rear of the device to shape the light emitted through the liquid crystal into the display. The light emitting device is commonly referred to as a backlight unit (BLU), and usually uses a cold cathode fluorescent lamp (CCFL) as a light source and sequentially uses an auxiliary device called a light guide plate (LGP), a light diffusion plate, and a prism sheet from the light source. The light guide plate actually converts the irregular linear light source emitted from the CCFL to the front, and the light diffusing film or sheet diffuses the front-induced light into the surface light, and the diffused light is perpendicular to the screen by the prism film or sheet. By condensing in the direction, the brightness at the front of the screen is increased to realize brighter and clearer images.

That is, since light emitted from all directions from the lamp causes light loss, a light guide plate is used to guide the light to the front side of the image, and a reflective film or sheet (hereinafter referred to as a reflector plate) is used to reuse the light lost to the back side of the image. ). However, since the light guided through the reflecting plate and the light guide plate has uneven brightness over the entire surface, the light diffusing film or sheet is used to induce the uniform surface light. In addition, since the light passing through the light diffusion film or the sheet is diffused again and the brightness of the front surface of the display device is lowered, the front brightness is lowered when the image is viewed from the right angle direction of the display device screen. Accordingly, the front brightness of the screen is increased by using a film or sheet using a prism structure to increase the light transmittance toward the front of the screen and to increase the front brightness. Such prismatic films have two orthogonal or constant angles when used separately. It is proved that the front condensing efficiency is high by arranging it by using it, and now one or two films of prism structure are orthogonally arranged.

Such a film is made of a roll or a large-area sheet in which a prism structure is formed using a transparent curable resin on a transparent film such as polyester and polycarbonate, and is cut into the size and shape required for mounting to an actual device, and the liquid crystal display is used. One or two sheets are orthogonally mounted on the backlight unit frame of the device.

At this time, a light diffusing film is used at the bottom of the prism film to evenly diffuse the light from the light guide plate or diffuser plate, and at the top of the prism film, a polarization film at the bottom of the liquid crystal module which is located at the top of the backlight and damage of the vertices of the prism by friction. To prevent damage, a light diffusing protective film is used.

However, the device manufactured with this structure uses three different optical films during the manufacturing process, resulting in a loss in cost and efficiency, and a defect in the protective film and prism film in the process of assembling the optical films of the backlight. It is a cause of reducing the use efficiency of all materials.

Accordingly, there is a need for a prism sheet capable of realizing higher light collecting performance and securing a wider viewing angle.

The present invention is to provide a light collecting optical sheet having a high light collecting performance and a wide viewing angle.

Accordingly, the present invention is a first embodiment, in the light converging optical sheet including a base layer and a structural layer formed on at least one surface of the base layer, a plurality of structures arranged, the structure is made of a low refractive resin The light converging optical sheet is formed on an inner structure and an outer surface of the inner structure and includes an outer layer made of a high refractive resin.

The structure according to the embodiment may have a triangular or semi-cylindrical cross section.

The refractive index of the inner structure of the low refractive resin and the outer layer of the high refractive resin according to the embodiment may be a difference of 0.02 or more.

The low refractive resin according to the embodiment is a polycarbonate, polymethyl methacrylate, silicone acrylate monomer, fluorene derivative diacrylate monomer, bisphenol derivative diacrylate monomer, diacrylate monomer having a thiol group, urethane acrylate monomer And acrylate photocurable resins selected from the group consisting of oligomers and mixtures thereof.

The high refractive resin according to the embodiment is a fluorene derivative diacrylate monomer, a bisphenol derivative diacrylate monomer, a diacrylate monomer having a thiol group, a urethane acrylate monomer, resins including their oligomers, inorganic nanoparticles and their It may be an acrylate photocurable resin selected from the group consisting of a mixture.

The internal structure according to the embodiment may have a pitch of 25 to 70 μm and a height of 10 to 40 μm.

The light converging optical sheet according to the present invention may exhibit high light condensing performance and a wide viewing angle, and thus may exhibit improved optical efficiency as compared with a conventional light condensing optical sheet.

1 is a cross-sectional view of a light collecting optical sheet according to the present invention.
Figure 2 is a graph showing the viewing angle distribution ((a) left and right field of view, (b) top and bottom field distribution) of the light collecting optical sheet measured according to an embodiment of the present invention.

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

The present invention is a light collecting optical sheet including a base layer 10 and a structure layer 20 formed on at least one surface of the base layer, and a plurality of structures 21 are arranged, wherein the structure 21 has a low refractive index. The light converging optical sheet is characterized in that it comprises an inner structure 22 made of resin and an outer layer 23 made of a high refractive resin formed on an outer surface of the inner structure (FIG. 1).

Structure Material

In the light converging optical sheet according to the present invention, the structure formed on the structural layer includes an inner structure and an outer layer formed on the outer surface of the inner structure, the inner structure is made of low refractive resin, and the outer layer is made of high refractive resin.

A general condensing optical sheet is composed of a resin layer exhibiting a single refractive index, and when a light source emitted from a base layer such as PET is emitted through the resin layer, it is emitted at an angle that has total reflection and an invalid viewing angle distribution. Is generated based on the vertical viewing angle. However, when the structural layer is formed of a structure having a double layer having different refractive indices as in the present invention, the path of the light incident on the high refractive layer (outer layer) is different from that of the PET, thereby reducing the lost light. These lights contribute to the concentration and diffusion.

In the present invention, the low refractive resin constituting the internal structure is a polycarbonate, polymethyl methacrylate, silicone acrylate monomer, fluorene derivative diacrylate monomer, bisphenol derivative diacrylate monomer, diacrylate monomer having a thiol group, It may be an acrylate photocurable resin selected from the group consisting of urethane acrylate monomers, oligomers thereof and mixtures thereof.

In the present invention, the high refractive resin forming the outer layer includes a fluorene derivative diacrylate monomer, a bisphenol derivative diacrylate monomer, a diacrylate monomer having a thiol group, a urethane acrylate monomer, oligomers thereof, and inorganic nanoparticles. It may be an acrylate photocurable resin selected from the group consisting of resins and mixtures thereof.

The refractive index of the inner structure of the low refractive resin and the outer layer of the high refractive resin may have a difference of 0.02 or more, preferably 0.02 to 0.15. If the difference between the refractive index of the inner structure and the outer layer is less than 0.02, there is a problem that the relative difference in luminance is not enough to measure the light and diffusion effects at the same time.

In the present invention, the difference in refractive index between the inner structure and the outer layer is not an absolute reference, but is characterized by the difference in refractive index between the inner structure and the outer layer, and the material for forming the inner structure and the outer layer is described above. As may be an acrylate photocurable resin, the refractive index may be 1.49 ~ 1.70.

[Structure Shape]

Meanwhile, the structure formed in the structural layer may have a triangular or semi-circular cross section, and may be semi-cylindrical. For example, the structure having a triangular cross section may be a prism, and the structure having a semi-circular cross section may be a semi-cylindrical structure. , Lenticular, lens, or the like, but is not limited thereto.

On the other hand, in the inner structure and the outer layer included in the structure arranged in the structural layer,

The internal structure may have a pitch of 25 to 70 μm, and a height of 10 to 40 μm, and the internal structure may have a number of peaks and valleys when the pitch is less than 25 μm compared to a relatively large prism. The problem of luminance deterioration may occur, and the risk of mura occurrence increases during mold production. In addition, if the pitch is greater than 70㎛, there is a problem that the possibility of occurrence of interference fringes with the panel increases.

In addition, the outer layer formed along the outer surface of the inner structure may have a thickness of 1 ~ 5㎛, when the thickness of the outer layer is less than 1㎛ there is a problem of deterioration of the light collecting layer, if it is more than 5㎛ spray coating There is a fair difficulty in producing the method.

[Base layer]

The base material layer is not limited to this, as long as it is a transparent film such as polyethylene terephthalate film, polycarbonate film, polypropylene film, polyethylene film, polystyrene film or polyepoxy film. In addition, the thickness of the substrate may be 10 ~ 1000㎛, preferably 15 ~ 400㎛. If the thickness of the base layer is less than 10㎛, there is a problem that the mechanical strength and thermal stability is weak, if the thickness is more than 1000㎛ there is a problem that the flexibility of the film is lowered and the loss of transmitted light occurs.

The light converging optical sheet according to the present invention may be manufactured by relative coextrusion to have two layers having different refractive indices using resins having different refractive indices.

In addition, after forming a photocurable resin layer having a different refractive index on the base film, it can be manufactured through a laser processing process.

In addition, after forming a low refractive index layer and a high refractive index layer using a cylindrical mold, it can be manufactured by final processing into a pattern mold mold.

Most preferably, a cylindrical mold mold may be used to form a low refractive index layer (inner structure), followed by final processing of the high refractive layer (outer layer) by spray coating.

The light converging optical sheet manufactured as described above not only exhibits high condensing performance and wide viewing angle, but also obtains high condensing performance even when a lot of low-refractive resins are relatively inexpensive than high refractive resins. have.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

Example 1

A light converging optical sheet was manufactured in the form as shown in Table 1.

As a substrate layer, 188 ± 2 μm ultra-transparent polyethylene terephthalate film Astroll (KOLON) was used.

In the structural layer, a prism is formed as an inner structure, and as a resin for forming an outer layer of the prism, 70% by weight of 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene and tris ( 2-hydroxyethyl) isocyanurate triacrylate 10% by weight, 1,6-hexanedioldiacrylate 3% by weight, phenoxyethylacrylate 10% by weight, 2,4,6-trimethylbenzoyl diphenol phosphate 3% by weight of pinoxide, 2% by weight of 2 (2-hydroxy-5-t-octoxybenzotriazole), bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate By mixing 2% by weight to prepare a resin composition for forming an outer layer,

50% by weight of 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene as a resin for forming a prism as an internal structure, tris (2-hydroxyethyl) isocyanurate tri 15% by weight of acrylate, 15% by weight of 1,6-hexanedioldiacrylate, 13% by weight of phenoxyethylacrylate, 3% by weight of 2,4,6-trimethylbenzoyl diphenolphosphine oxide, 2 (2-hydr) Resin for forming an internal structure by mixing 2% by weight of oxy-5-t-octoxybenzotriazole) and 2% by weight of bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate The composition was prepared.

The polyethylene terephthalate film, a resin composition for forming an outer layer, and a resin composition for forming an internal structure are put into a cylindrical mold mold and cured, and then a light converging optical sheet having a structure including an outer layer and an internal structure is formed using a laser processing machine. Was prepared.

At this time, on the polyethylene terephthalate film, the resin composition for forming the internal structure is first coated by using a cylindrical mold mold in which the pattern is not molded, and then the resin composition for forming the outer layer is used thereon, without being semi-cured or cured. Using a roll having a prism pattern imprinted on the cylindrical mold mold, a prism pattern was formed, and a structure including an outer layer and an inner structure was formed and finally cured to produce a light collecting optical sheet.

Example 2

The structural layer forms a prism as a structure, and 70 wt% of 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene as a resin for forming the outer layer of the prism, tris (2- Hydroxyethyl) isocyanurate triacrylate 10% by weight, 1,6-hexanedioldiacrylate 3% by weight, phenoxyethylacrylate 10% by weight, 2,4,6-trimethylbenzoyl diphenolphosphine oxide 3 weight%, 2 (2-hydroxy-5-t-octoxybenzotriazole) 2 weight%, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate 2 weight % Was mixed to prepare a resin composition for forming an outer layer,

As a resin for forming the internal structure, 60% by weight of 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene, tris (2-hydroxyethyl) isocyanurate triacrylate 10% by weight, 1,6-hexanedioldiacrylate 3% by weight, phenoxyethylacrylate 20% by weight, 2,4,6-trimethylbenzoyl diphenolphosphine oxide 3% by weight, 2 (2-hydroxy- 2 wt% of 5-t-octoxybenzotriazole) and 2 wt% of bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate were mixed to form a resin composition for forming an internal structure. A light converging optical sheet was manufactured in the same manner as in Example 1, except that the compound was manufactured and used.

Example 3

The structural layer forms a prism as a structure, and 70% by weight of 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene as a resin for forming the outer layer of the prism, tris (2 -Hydroxyethyl) isocyanurate triacrylate 10% by weight, 1,6-hexanedioldiacrylate 3% by weight, phenoxyethylacrylate 10% by weight, 2,4,6-trimethylbenzoyl diphenolphosphine 3% by weight of oxide, 2% by weight of 2 (2-hydroxy-5-t-octoxybenzotriazole), bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate 2 By mixing the weight% to prepare a resin composition for forming the outer layer,

As a resin for forming the internal structure, 65% by weight of 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene, tris (2-hydroxyethyl) isocyanurate triacrylate 10% by weight, 1,6-hexanedioldiacrylate 8% by weight, phenoxyethylacrylate 10% by weight, 2,4,6-trimethylbenzoyl diphenolphosphine oxide 3% by weight, 2 (2-hydroxy- 2 wt% of 5-t-octoxybenzotriazole) and 2 wt% of bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate were mixed to form a resin composition for forming an internal structure. A light converging optical sheet was manufactured in the same manner as in Example 1, except that the compound was manufactured and used.

Example 4

A light converging optical sheet was manufactured in the same manner as in Example 2, except that the height of the outer layer was 3 μm.

Comparative Example 1

3M BEFII was prepared as a light condensing optical sheet.

Comparative Example 2

Condensing was carried out in the same manner as in Example 2 except that the outer layer was formed of the resin composition used as the resin composition for forming the internal structure, and the inner prism was formed from the resin composition used as the resin composition for forming the outer structure. A type optical sheet was prepared.

With respect to the optical sheets prepared in Examples and Comparative Examples, the brightness and viewing angle were measured by the following method, and the results are shown in Table 2.

Using LightTools ver 7.3, the brightness and viewing angles were simulated under the following conditions, and the luminance and viewing angles of the light-converging optical sheet of the example were determined as relative properties of the brightness and viewing angle of 3M BEF II of Comparative Example 1. Measured.

All simulated values were compared relative to peak values of luminance values gathered in each mesh based on 3M BEFII, and viewing angle was defined as an angle corresponding to 10% of luminance intensity peak values.

Light source setting: 4.9 mm x 4.9 mm Lambertian light source (light source through the diffusion sheet), comparing only the performance of film (5 mm x 5 mm)

Light source wavelength: use 550 nm wavelength

Refractive Index of Medium: PET-Set to 1.49

The refractive indices for the film layers of each model are based on the following data:

Internal structure Outer layer Refractive index Pitch (μm) Height (㎛) Refractive index Thickness (㎛) Example 1 1.52 50 25 1.57 One Example 2 1.54 50 25 1.57 One Example 3 1.56 50 25 1.57 One Example 4 1.54 50 25 1.57 3 Comparative Example 1 3M company BEFII Comparative Example 2 1.57 50 25 1.54 One

Luminance Right and left viewing angle
(V, degree) Vertical angle
(H, degree) Example 1 1.0528 83.93 114.98 Example 2 1.0317 82.46 113.44 Example 3 1.0154 81.27 110.87 Example 4 1.0113 80.42 110.75 Comparative Example 1 1.00 79.62 110.89 Comparative Example 2 0.9814 85.11 114.22

As a result of measuring the physical properties, as shown in Table 1 and Figure 2, compared to BEF II of 3M company of Comparative Example 1 containing a prism formed of a single resin, the light converging optical sheet of the Example is increased by about 5%, the viewing angle of the viewing angle The upper, lower, left, and right viewing angles were enlarged by 4.3 degrees and 4.1 degrees, respectively.

10: base material layer,
20: structural layer, 21: structure, 22: internal structure, 23; Outer layer

Claims (7)

In the light collecting optical sheet comprising a base layer and a structural layer formed on at least one surface of the base layer, a plurality of structures are arranged,
The structure is a light converging optical sheet, characterized in that it comprises an inner structure made of a low refractive resin and an outer layer made of a high refractive resin formed on the outer surface of the inner structure. The method of claim 1,
The structure is a light converging optical sheet, characterized in that the cross section is triangular or semicircular. The method of claim 1,
The refractive index of the inner structure of the low refractive resin and the outer layer of the high refractive resin is the difference between the refractive index is 0.02 or more. The method of claim 1,
The low refractive resin is a polycarbonate, polymethyl methacrylate, silicone acrylate monomer, fluorene derivative diacrylate monomer, bisphenol derivative diacrylate monomer, diacrylate monomer having a thiol group, urethane acrylate monomer, oligomers thereof And an acrylate photocurable resin selected from the group consisting of mixtures thereof. The method of claim 1,
The high refractive resin is a group consisting of a fluorene derivative diacrylate monomer, a bisphenol derivative diacrylate monomer, a diacrylate monomer having a thiol group, a urethane acrylate monomer, resins including oligomers, inorganic nanoparticles, and mixtures thereof. Condensing optical sheet, characterized in that selected from. The method of claim 1,
The inner structure has a pitch of 25 ~ 70㎛, condensing optical sheet, characterized in that the height is 10 ~ 40㎛. The method of claim 1,
The outer layer is a light converging optical sheet, characterized in that the thickness of 1 ~ 5㎛.

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