KR20120077663A - Scratch resistant light guide panel, method for preparing thereof and lcd back light unit using the same - Google Patents

Abstract

PURPOSE: A scratch resistance light guide plate, a manufacturing method thereof, and a liquid crystal display backlight unit using the same are provided to improve scratch resistance by containing a shock reinforcing agent in a skin layer. CONSTITUTION: A first skin layer(20a) is laminated at one side of a base material layer. The first skin layer contains a shock reinforcing agent(30) of 5 weight% to 50 weight% inclusive. The first skin layer forms a cubic pattern. The surface roughness of the first skin layer is 5 to 15micrometers. The difference of a refractive index between the shock reinforcing agent and the base material layer is within ±0.1. The shock reinforcing agent has a core-shell structure. A second skin layer(20b) comprises the shock reinforcing agent at the other side of the base material layer.

Description

Scratch-resistant light guide plate, manufacturing method thereof and liquid crystal display backlight unit using the same

The present invention relates to a scratch resistant light guide plate, a method of manufacturing the same, and a backlight unit using the same. More specifically, the present invention includes an impact modifier in the skin layer of the light guide plate, forms a three-dimensional pattern, and is excellent in scratch resistance and slip resistance, and the use of a protective film can be excluded.

Since the liquid crystal display device is not a self-luminous device, it should have a back light unit as a light source for generating light, and the light generated from the backlight unit is emitted from the panel portion where the liquid crystal is constantly arranged. An image and the like are displayed while adjusting the amount of permeation.

1 is an exploded perspective view illustrating a backlight unit of a general liquid crystal display device. As shown in FIG. 1, the LCD backlight unit includes a light source 105, a light guide plate 110, a reflector plate 115, a diffusion sheet 120, a prism sheet 125, and a protection sheet 130.

The light guide plate 110 is formed on the lower side of the LCD panel 100 and on one side of the light source 105, and converts spot light generated from the light source 105 into plane light to convert the light to the front surface. It serves to project.

A reflecting plate 115 is formed on the rear surface of the light guide plate 110 and reflects the light from the light source 105 in the direction of the LCD panel 100 on the front surface, and evenly distributes the light on the upper surface of the light guide plate 110. The diffusion sheet 120 is formed. A prism sheet 125 is positioned on the upper surface of the diffusion sheet 120 to increase brightness by refracting and condensing light. The protective sheet 130 is used on the upper surface of the prism sheet 125 to prevent scratches of the prism sheet 125 and to prevent moire effects.

As such, the light guide plate 110 guides the light emitted from the lamp to reach the entire light guide plate plane to have a uniform luminance distribution, and at the same time, reflects the front surface to change the linear light source of the lamp into a planar light source. It is.

The light guide plate 110 is manufactured by injection, extrusion, molding using acrylic resin, and in recent years, an extrusion method is preferred due to advantages such as production cost and large size.

Since the light guide plate by itself cannot produce a uniform distribution over the entire surface of the light guide plate, the surface of the light guide plate is printed with white ink (SiO 2 type) or a groove is formed to scatter and reflect the light by the pattern. A similar amount of light is emitted across the surface. The uniformly emitted rays show color and image quality to the observer's eye through various light paths and instruments.

However, when the light guide plate 110 has a very small defect on its surface, the light emitted to the front of the light guide plate 110 may be unnecessarily scattered, which may cause a fatal defect in the product. Therefore, the light guide plate 110 is attached to the protective film must be protected from a variety of external damage until the patterning process after extrusion and cooling.

A conventional light guide plate is extruded, polished and cooled, and then attached to upper and lower parts of the light guide plate with a protective film. Subsequently, the light guide plate raw material single piece of the desired size is produced through the cutting process with the protective film attached thereto.

After the protective film is removed in the lighting device production process to form a pattern, and then UV curable resin is applied to the surface of the light guide plate, the pattern is formed by roller pressing, etc., then cured or stored at constant temperature and humidity during pattern formation by ink printing. It is printed after pretreatment such as heating.

As described above, the conventional method requires a separate printing process such as a silk screen printing method and a pretreatment process such as constant temperature and humidity storage and heating for ink printing as well as the removal of the protective film that is already attached during the printing pattern forming process. Steps and time were required. There is also a significant cost for the treatment of the removed protective film.

Therefore, there is no problem such as external scratches and stamping even without using a protective film, cost reduction is possible by removing the protective film, and there is a need to develop a light guide plate with high productivity.

An object of the present invention is to provide a scratch-resistant light guide plate having excellent scratch resistance and slip resistance does not use a protective film.

Another object of the present invention is to provide a scratch-resistant light guide plate without problems such as external scratches and stamping even without using a protective film.

Still another object of the present invention is to provide a scratch resistant light guide plate having high productivity as well as cost reduction by eliminating the protective film.

Still another object of the present invention is to provide a method of manufacturing a scratch resistant light guide plate having at least five times higher productivity than an injection process using a coextrusion method.

Still another object of the present invention is to provide a method of manufacturing a scratch resistant light guide plate which can be manufactured without changing equipment by using an existing equipment using a coextrusion method.

Another object of the present invention is to provide a backlight unit of a liquid crystal display device using the scratch resistant light guide plate.

Technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

One aspect of the invention relates to a scratch resistant light guide plate. The scratch resistant light guide plate may include a base layer; And a first skin layer laminated on one surface of the base layer, wherein the first skin layer contains an impact modifier and a three-dimensional pattern is formed.

In an embodiment, the first skin layer has a surface roughness of 5 to 15 μm. It is enough.

The three-dimensional pattern may be an embossed pattern, a prism pattern, a lenticular pattern, a dot pattern, a chaotic pattern, or an irregular pattern.

The impact modifier may include 5 wt% or more and less than 50 wt% of the first skin layer.

The impact modifier may be within ± 0.1 of the difference between the base layer and the refractive index.

The impact modifier may have a core-shell structure.

In another embodiment, a second skin layer including an impact modifier may be further formed on the other surface of the base layer.

The first skin layer may have a static frictional force of 0.01 to 2 N on a prism film based on a weight of 500 g and a speed of 300 mm / min, and a pencil hardness of ASTM D3363 may be 3 H or more.

In an embodiment, the base layer and the first skin layer may be integrally formed.

In an embodiment, the base layer and the first skin layer may be formed by coextrusion.

In a specific embodiment, no protective film is formed on the surface of the skin layer of the scratch resistant light guide plate.

Another aspect of the invention relates to a method of manufacturing the scratch resistant light guide plate. The method comprises: extruding a master batch comprising an impact modifier and a resin forming a skin layer onto a light guide plate surface layer to form a light guide plate having a skin layer laminated on a base layer; And forming a pattern on the surface of the skin layer.

Another aspect of the present invention relates to a liquid crystal display backlight unit using the scratch resistant light guide plate.

The present invention does not have to use a protective film because of excellent scratch resistance and slip resistance, there is no problem such as external scratches and stamping without using a protective film, cost savings by eliminating the protective film, as well as excellent productivity It has the effect of providing a scratch resistant light guide plate. In addition, using the co-extrusion method has a productivity that is at least five times higher than the injection process, and has the effect of providing a method of producing a scratch-resistant light guide plate that can be manufactured without changing equipment using existing equipment.

1 is an exploded perspective view illustrating a backlight unit of a conventional liquid crystal display device.
2 is a cross-sectional view showing a scratch resistant light guide plate according to an embodiment of the present invention.
3 is an enlarged cross-sectional view illustrating an enlarged portion A of FIG. 2.
4 is a perspective view illustrating a scratch resistant light guide plate according to another embodiment of the present invention.
5 is a perspective view illustrating a scratch resistant light guide plate according to another embodiment of the present invention.

The configuration of the present invention will be apparent with reference to the accompanying drawings. In the drawings, the sizes of components constituting the invention are exaggerated for clarity and are not limited thereto.

2 is a cross-sectional view showing a scratch resistant light guide plate according to an embodiment of the present invention.

As shown in FIG. 2, the scratch resistant light guide plate of the present invention includes a substrate layer 10; And a first skin layer 20a laminated on the surface of the base layer. The first skin layer 20a contains the impact modifier 30. A three-dimensional pattern is formed on the first skin layer 20a.

The base layer 10 may be made of an optically transparent resin. The optically transparent resin may be a resin having a refractive index of 1.49 to 1.60 and a transmittance of 90 to 93%. For example, a (meth) acrylic resin, a polycarbonate resin, a styrene resin, an olefin resin, a polyester resin, or the like may be used, but is not necessarily limited thereto. These may be used alone or in combination of two or more.

In a preferred embodiment, the olefin resin may be a cyclic olefin resin. In addition, the polyester resin may be an amorphous polyester resin.

It is most preferable to use methacryl-type resin as said optically transparent resin. Examples of the methacrylic resin include methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, Phenyl methacrylate, chloro methacrylate and the like. Of these, methyl methacrylate resin having high transmittance is most preferred.

More preferably, the methacrylic resin is copolymerized with a monofunctional unsaturated monomer, and the methacrylic resin is preferably copolymerized with a monofunctional unsaturated monomer within about 40% by weight, and more preferably within 30% by weight. Even more preferably copolymerized to within about 20% by weight.

Examples of the monofunctional unsaturated monomer copolymerized with the methacrylic resin include ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxy methacrylate. Acrylic acid including ethyl, phenyl methacrylate, chloro methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate and the like Ester compound is preferable.

Examples of the monofunctional unsaturated monomer copolymerized with the methacrylic resin include unsaturated acid compounds including methacrylic acid and acrylic acid, styrene, acrylonitrile, maleic anhydride, phenyl maleimide, cyclohexyl maleimide, and the like. These may be used alone or in combination of two or more.

Copolymerization of the methacrylic resin with a monofunctional unsaturated monomer can be easily carried out by those skilled in the art.

In embodiments, the thickness of the base layer 10 may be 1 to 10 mm, preferably 2 to 6 mm.

A three-dimensional pattern is formed in the first skin layer 20a. The three-dimensional pattern includes an embossed pattern, a prism pattern, a lenticular pattern, a dot pattern, a chaotic pattern or an irregular pattern, but is not necessarily limited thereto.

For example, the three-dimensional pattern may have a lenticular pattern as shown in FIG. 5. The pitch p of the lenticular pattern may be 50 to 500 μm, and the height h may be 10 to 300 μm. Preferably, the pitch p may be 100 to 300 μm, and the height h may be 50 to 150 μm, and the friction force may be lowered in the above range.

In another embodiment, it may have a prism pattern (not shown). In another embodiment, the apex portion of the prism pattern may have a chaotic pattern.

In another embodiment, the projection pattern may have a predetermined pattern surface.

In any case, the first skin layer has a surface roughness in the range of 5 to 15 μm, preferably 8 to 12, so as to compensate for slippage due to the exclusion of the protective film.

The first skin layer 20a contains the impact modifier 30. 3 is an enlarged cross-sectional view illustrating an enlarged portion A of FIG. 2. As shown, the impact modifier 30 is dispersed in the resin base material 21 in the first skin layer 20a. The dispersion may be dispersed uniformly or nonuniformly, preferably uniformly dispersed.

The impact modifier 30 may have a core-shell structure. In an embodiment, the impact modifier 30 may have a structure in which a shell is formed by grafting an unsaturated monomer to a core of a rubber component.

The rubber may be a diene rubber having 4 to 6 carbon atoms, an acrylic rubber, a silicone rubber, or a combination thereof.

Butadiene, isoprene, butadiene-styrene rubber may be used as the diene rubber.

As said acrylic rubber, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hexyl (meth) It is superposed | polymerized from (meth) acrylate 'monomers, such as) acrylate. Ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1, 3- butylene glycol di (meth) acrylate, 1, 4- butylene glycol di (meth) acrylate, allyl (meth) ) Crosslinking agents, such as an acrylate and a triallyl cyanurate, can be used further.

The silicone rubber is polymerized from an organosiloxane, and specific examples thereof include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane, and tetramethyltetra. Phenylcyclotetrosiloxane, octaphenylcyclotetrasiloxane, or combinations thereof can be used. At this time, a crosslinking agent such as trimethoxymethylsilane, triethoxyphenylsilane, tetramethoxysilane and tetraethoxysilane can be further used. In another embodiment, the chlorosilanes such as dimethyldichlorosilane, diphenyldichlorosilane, phenylmethyldichlorosilane, methyltrichlorosilane, and phenyltrichlorosilane can be prepared by hydrolysis and condensation.

The average particle diameter of the rubber may be 0.4 to 1 ㎛. It may have excellent impact resistance and scratch resistance in the above range.

Unsaturated monomers grafted to the rubber include 1 to 10 alkyl (meth) acrylates, (meth) acrylates, acid anhydrides, and alkyl or phenyl-substituted maleimides. These may be used alone or in combination.

Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and the like, of which methyl methacrylate. Can be preferably used.

Examples of the acid anhydride include carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride.

The impact modifier may comprise 5 wt% or more and less than 50 wt%, preferably 10 to 40 wt%, more preferably 20 to 30 wt% of the first skin layer. In the above range, there are advantages such as productivity and optical properties.

The impact modifier may be within ± 0.1 of the difference between the base layer and the refractive index. As such, using particles having almost no difference in refractive index with the base layer or having the same refractive index, there is an advantage of minimizing reflection and refraction of light, and decreasing luminance and color coordinate difference. In addition, the impact modifier may be applied to the skin resin to improve the light guide plate impact.

In one embodiment, the impact modifier may have an average particle size of 1 to 100 µm, preferably 10 to 40 µm. In the above range there is an advantage that the skin roughness can be easily adjusted.

The resin substrate 21 constituting the matrix of the skin layer may use the same or different material as that of the base layer 10. In one embodiment, the resin substrate 21 may be an optically transparent resin. The optically transparent resin may be a (meth) acrylic resin, polycarbonate resin, styrene resin, olefin resin, polyester resin and the like, but is not necessarily limited thereto. Preferably it is (meth) acrylic-type resin.

The average thickness of the first skin layer 20a may be 10 to 500 μm, preferably 50 to 300 μm.

In one embodiment, the ratio of the thickness of the base layer 10 and the average thickness of the first skin layer 20a may be 500: 1 to 10: 1. Preferably it may be 100: 1 to 10: 1. Excellent optical properties and process manufacturing are possible in the above range.

4 is a cross-sectional view illustrating a scratch resistant light guide plate according to another embodiment of the present invention. In another embodiment, the second skin layer 20b including the impact modifier may be further formed on the other surface of the base layer 10. The second skin layer 20b may be made of the same material as or different from the first skin layer 20a. In addition, the impact modifier included in the second skin layer 20b may be the same as the type and content of the impact modifier used in the first skin layer 20a. Although not shown, the second skin layer 20b may have a three-dimensional pattern.

In an embodiment, the first skin layer 20a and the second skin layer 20b may be integrally formed with the base layer. For example, the first skin layer 20a, the base layer 10, and the second skin layer 20b form a single layer, but the impact modifiers are evenly distributed throughout the single layer, and a three-dimensional pattern is formed on one surface. It may be. Alternatively, the impact modifier may be distributed only on the surface of the single layer, and a three-dimensional pattern may be formed.

In another embodiment, the first skin layer 20a, the base layer 10, and the second skin layer 20b may be laminated by co-extrusion and integrally formed.

The first skin layer 20a may have a static frictional force of 0.01 to 2 N with respect to the prism film based on a weight of 500 g and a speed of 300 mm / min. When the static frictional force of the skin layer is within the above range, the slipperiness of the light guide plate and the film adjacent thereto may be improved. Preferably, the static frictional force on the prism film of the skin layer may be 0.01 to 1.5 N. The frictional force is a value measured based on a condition that a prism film (BEF, 3M) is placed on the surface of the skin layer, a weight of 500 g is placed on a scratch resistant light guide plate, and a line speed of 300 mm / min.

In addition, the first and second skin layer 20a has a pencil hardness of 3H or more according to ASTM D3363.

Another aspect of the invention relates to a method of manufacturing the scratch resistant light guide plate. The method can be preferably produced by the coextrusion method. In this way, the substrate layer and the skin layer are formed by coextrusion, thereby increasing productivity. In addition, by using the co-extrusion method, it is possible to improve the optical properties and slip properties of the light guide plate without changing the existing equipment.

In a specific embodiment, the method comprises: extruding a master batch including an impact modifier and a resin forming a skin layer onto a light guide plate surface layer to form a light guide plate having a skin layer laminated on a base layer; And forming a pattern on the surface of the skin layer.

In this case, the transparent resin forming the base layer and the resin forming the skin layer may be coextruded to form a film in which the base layer and the skin layer are laminated. The pattern may be formed by passing an extruded light guide plate through a pattern roll, or transferring a UV resin after coating.

Another aspect of the present invention relates to a liquid crystal display backlight unit using the scratch resistant light guide plate. The backlight unit of the present invention is characterized in that a protective film is not formed on the surface of the skin layer of the scratch resistant light guide plate.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention, and the manner of achieving them, will be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, only the present embodiments to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims.

Example  One

100 parts by weight of polymethyl methacrylate (PMMA) resin (Sumitomo EXN) is added to the master batch Was extruded, and the master batch and polymethyl methacrylate resin were melt extruded to the light guide plate surface layer to prepare a co-extruded light guide plate having a three-layer structure having a transparent base layer and a skin layer including an impact modifier on the surface. At this time, the impact modifier content in the skin layer was 20%. The first skin layer was in-line patterned with a lenticular shape having a pitch of 300 μm and a height of 100 μm. The total thickness of the light guide plate was 3 mm, and the thicknesses of the first and second skin layers were 150 μm, respectively.

Example  2

The impact modifier content in the skin layer was carried out in the same manner as in Example 1 except that the content was changed to 30%.

Comparative Example  One

The same procedure as in Example 1 was conducted except that no impact modifier was applied.

Comparative Example  2

The impact modifier content in the skin layer was performed in the same manner as in Example 1 except that the content was changed to 10%.

Comparative Example  3

The same procedure as in Example 1 was carried out except that the impact modifier was excessively applied.

Comparative Example  4

The impact modifier content in the skin layer was changed to 10%, and the same procedure as in Example 1 was carried out except that no pattern was formed.

Comparative Example  5

The same procedure as in Example 1 was conducted except that no pattern was formed.

Comparative Example  6

The same procedure as in Example 2 was conducted except that no pattern was formed.

Skin layer
PMMA content (%) Skin layer
Impact modifier content Skin layer
Patterning Example 1 80 20 U Example 2 70 30 U Comparative Example 1 100 0 U Comparative Example 2 90 10 U Comparative Example 3 50 50 U Comparative Example 4 90 10 radish Comparative Example 5 80 20 radish Comparative Example 6 70 30 radish

(1) Friction force: A prism film (BEF, 3M) was placed on the light guide plate manufactured above, and then the friction force was measured using a surface property tester (manufactured by HEIDON) while slipping them. Measurement conditions of the frictional force was based on the weight of 500g, line speed 300mm / min.

(2) Scratch resistance: The pencil hardness was measured according to ASTM D3363.

(3) Surface roughness: Surface roughness measuring instrument (ET4000A, manufactured by Kasaka laboratory)

The results are summarized in Table 2 below.

Pencil hardness Friction force (N) Total light transmittance (%) Surface roughness
Ra (μm) stop Exercise Example 1 2H 1.539 0.927 91.7 22.67 Example 2 3H 1.436 1.029 92.2 20.13 Comparative Example 1 H 1.431 0.984 91.9 21.64 Comparative Example 2 H 1.397 1.052 91.8 22.68 Comparative Example 3 H 1.485 1.077 88.34 20.65 Comparative Example 4 H More than 20 Over 20 92.0 0.02 Comparative Example 5 2H More than 20 More than 20 92.1 0.03 Comparative Example 6 3H More than 20 More than 20 92.1 0.02

As shown in Table 2, Example 1-2 has a significantly lower friction than the Comparative Example 3-6, it can be seen that the scratch resistance is superior to Comparative Example 1-2.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and may be manufactured in various forms, and a person of ordinary skill in the art to which the present invention belongs may have the technical idea of the present invention. However, it will be understood that other specific forms may be practiced without changing the essential features. It is therefore to be understood that the embodiments described above are in all respects illustrative and not restrictive.

100: panel 110: light guide plate
120: diffusion film 125: prism film
130: protective sheet 200: light guide plate
10: base layer 20a, 20b: first and second skin layers
30: impact modifier

Claims (11)

A base layer; And
A first skin layer laminated on one surface of the base layer;
And the first skin layer contains at least 5 wt% and less than 50 wt% of an impact modifier, and the scratch resistant light guide plate is formed.

The method of claim 1, wherein the first skin layer has a surface roughness of 5 to 15 ㎛ Scratch resistant light guide plate.
The scratch resistant light guide plate of claim 1, wherein the three-dimensional pattern is an embossed pattern, a prism pattern, a lenticular pattern, a dot pattern, a chaotic pattern, or an irregular pattern.
The scratch resistant light guide plate according to claim 1, wherein the impact modifier has a refractive index difference of ± 0.1 within the substrate layer.
The scratch resistant light guide plate of claim 1, wherein the impact modifier has a core-shell structure.
The scratch resistant light guide plate of claim 1, further comprising a second skin layer including an impact modifier on the other surface of the base layer.
The method of claim 1, wherein the first skin layer has a static frictional force of 0.01 to 2 N for the prism film on the basis of weight 500g, speed 300mm / min, pencil hardness according to ASTM D3363 3 H or more Scratchable light guide plate.
The scratch resistant light guide plate of claim 1, wherein the base layer and the first skin layer are integrally formed.
The scratch resistant light guide plate according to claim 1, wherein the base layer and the first skin layer are formed by coextrusion.
Extruding the master batch containing the impact modifier and the resin forming the skin layer onto the light guide plate surface layer to form a light guide plate having a skin layer laminated on the base layer; And
Forming a pattern on the skin layer surface;
Method for producing a scratch-resistant light guide plate comprising a step.
A liquid crystal display backlight unit using the scratch resistant light guide plate according to any one of claims 1 to 9.

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