WO2016052942A1

WO2016052942A1 - Light guide plate and backlight unit comprising same

Info

Publication number: WO2016052942A1
Application number: PCT/KR2015/010176
Authority: WO
Inventors: 김민정; 김경화; 심상화; 조춘성
Original assignee: 코오롱인더스트리 주식회사
Priority date: 2014-09-30
Filing date: 2015-09-25
Publication date: 2016-04-07

Abstract

The present invention relates to a light guide plate and a backlight unit including the same and, more particularly, to a light guide plate, which has a surface layer reflecting an optical property and a hardness property, formed as a thin film on one surface of a substrate layer having an excellent optical property and reflecting a dimensional stability against an external environment, so as to have excellent workability and scratch resistance and minimize the luminance degradation, and a backlight unit including the same.

Description

Light guide plate and backlight unit including the same

The present invention relates to a light guide plate used in a liquid crystal display and a backlight unit assembly including the same.

As the industrial society develops into an advanced information age, the importance of the electronic display device as a medium for displaying and transmitting various information is increasing day by day. In particular, in the case of a liquid crystal display device (LCD), due to the advantages of thin, light, and low power consumption as a technology-intensive device in which liquid crystal and semiconductor technologies are combined, its structure and manufacturing technology have been researched and developed and used in various areas. .

Since the liquid crystal display itself cannot emit light, the liquid crystal display (LCD) device implements color and screen by installing a separate light source on the back of the device.

As the light emitting device, a backlight unit (BLU) is widely used, and instead of a cold cathode fluorescent lamp (CCFL), an LED (Light Emitting Diode) is used in accordance with the recent trend of reducing the thickness of liquid crystal display devices. The use of is increasing rapidly. Light emitting diodes (LEDs) do not use mercury and have excellent color reproducibility.

Edge-type BLUs with LEDs on the side have advantages in terms of power consumption and product thickness compared to the direct type with LEDs on the front of the backlight unit.

Edge-type BLU uses a light guide plate that can emit light from the side to the front. Light generated from the light source enters the light guide plate from the side of the light guide plate and exits to the front surface. In this method, since the light path through the light guide plate is relatively long and the light loss is increased, a material of polymethyl methacrylate (PMMA) series having high transmittance is mainly used to prevent this phenomenon. However, polymethyl methacrylate-based raw materials are vulnerable to moisture due to their chemical structure, so that the light guide plate to which these raw materials are applied has a disadvantage in that warpage and dimensional stability are poor in a high temperature and high humidity environment.

As an example of the related technology, Korean Patent Publication No. 10-2012-0088944 (2012.08.09.) Discloses a light guide plate formed of a plurality of layers. Specifically, a pattern is formed and a pattern made of a material having a high MMA content. A light guide plate formed by bonding a layer and a cover layer made of a material having a low MMA content is described. Such a light guide plate is described to solve the problem of yellowing by laser or thermal processing.

The present invention is to provide a light guide plate excellent in dimensional stability to the external environment.

The present invention is to provide a light guide plate having excellent dimensional stability to the external environment, easy laser processing and excellent scratch resistance.

The present invention aims to provide a light guide plate that can ultimately minimize dimensional stability, ease of laser processing and scratch resistance while reducing luminance.

The present invention also provides a backlight unit that can increase the workability and scratch resistance by applying such a light guide plate and can implement high brightness.

Accordingly, the present invention has a difference in refractive index of 0.05 or less on the lower surface of a base layer containing a resin having a light transmittance of at least 90%, a refractive index of 1.47 to 1.59, and a water absorption of less than 0.30% as a main component of the base layer. And a light guide plate having a hardness of at least 1H, and having a resin having a light transmittance of at least 90% as a main component.

In the light guide plate according to the embodiment, the thickness of the surface layer may be 1 to 5% of the total thickness of the light guide plate.

In the light guide plate according to the embodiment, the surface layer may have a thickness of 30㎛ to 150㎛.

In the light guide plate according to the embodiment, the surface layer may include a plurality of intaglio patterns.

In the light guide plate according to the embodiment, the plurality of intaglio patterns may exist only in the surface layer or may have a shape penetrating through the surface layer to a predetermined thickness of the base layer.

In the light guide plate according to the embodiment, the plurality of intaglio patterns may have a shape that penetrates to a thickness corresponding to 0.1 to 10% of the total thickness of the base layer.

In the light guide plate according to the above embodiment, the plurality of intaglio patterns may be one selected from the group consisting of semicircles, triangles, squares, and irregular shapes of three-dimensional shapes of longitudinal sections thereof.

The light guide plate according to the preferred embodiment may be manufactured by a coextrusion method.

In the light guide plate according to the above embodiment, the co-extrusion method heat melts each resin composition constituting the substrate layer and the surface layer by using an extruder to make a fluid state, and then simultaneously melt-discharges through a feed block (T die). While pressing through continuously while extruding, the thickness uniformity of the surface layer can be performed to satisfy 20% or less.

In the light guide plate according to the embodiment, the base layer is a resin selected from polycarbonate resin, polystyrene resin, acrylic resin, olefin resin, polyester resin and polyamide resin, copolymers thereof, mixtures thereof, and It may be based on a resin selected from the group consisting of these derivatives.

In the light guide plate according to the embodiment, the surface layer is a resin selected from polycarbonate resin, polystyrene resin, acrylic resin, olefin resin, polyester resin and polyamide resin, copolymers thereof, mixtures thereof and these It may be based on a resin selected from the group consisting of derivatives of.

In the light guide plate according to the embodiment, the base layer may be a copolymer containing methyl methacrylate at 60 wt% or less as a main component.

In the light guide plate according to the embodiment, the surface layer may be a copolymer containing at least 70% by weight of polymethyl methacrylate resin or methyl methacrylate.

In the light guide plate according to the embodiment, the substrate layer may be made of methyl methacrylate-styrene resin, and the surface layer may be made of polymethyl methacrylate resin.

An exemplary embodiment of the present invention provides a backlight unit including the light guide plate according to the above embodiments.

According to the present invention, it is possible to provide a light guide plate which is excellent in dimensional stability, ease of laser processing and scratch resistance to an external environment, and can minimize luminance deterioration. Not only can it increase scratchability, but it can also contribute to high brightness.

1 to 3 are cross-sectional views of a light guide plate according to an embodiment of the present invention.

1 is an example of a light guide plate having a surface layer not including an intaglio pattern;

2 is an example of a light guide plate having a surface layer including a plurality of negative patterns;

FIG. 3 is formed at a predetermined height h such that a plurality of intaglio patterns included in the light guide plate according to the exemplary embodiment of the present invention penetrate the surface layer thickness x to penetrate to a part of the thickness of the substrate layer y. Are shown to facilitate

4 is an example of a light guide plate having a base layer on which the upper pattern 100 is formed and a surface layer including a plurality of intaglio patterns on the bottom surface of the base layer.

10: base material layer,

20: surface layer, 40: engraved pattern

100: upper pattern

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

An example of the light guide plate of the present invention may be the same as that of FIG. 1, which is a lower surface of the base layer 10 including a resin having a light transmittance of at least 90%, a refractive index of 1.47 to 1.59, and a water absorption of less than 0.30%. The surface layer 20 is mainly composed of a resin having a difference in refractive index of 0.05 or less, a hardness of at least 1H, and a light transmittance of at least 90%, as compared with the main component resin of the base layer.

[Base layer]

In the light guide plate according to the present invention, the base layer preferably contains a resin having excellent optical properties as a main component, specifically, a light transmittance of at least 90% or more, and a refractive index of at least 1.47 to 1.59 as a main component. have.

In the above and the following descriptions, the term 'main component' in the resin composition is at least 95% by weight or more in the total resin composition of the layer within a range not impairing the optical properties required for the light guide plate. It is intended to be defined as 'components included in amounts'.

Resins satisfying the above-described physical properties are resins having excellent optical properties, and examples thereof include polycarbonate-based resins, polystyrene-based resins, acrylic resins, olefin-based resins, polyester-based resins, and polyamide-based resins. And a resin selected from the group consisting of copolymers thereof, mixtures thereof and derivatives thereof.

In particular, in terms of excellent dimensional stability to the external environment, the base layer preferably has a water absorption of less than 0.30%, and in this regard, it may be preferable that the copolymer includes methyl methacrylate at 60 wt% or less. In particular, it may be preferable that the copolymer of methyl methacrylate and styrene (abbreviated as "MS resin").

MS resins are lightweight, inexpensive thermoplastics and have low water absorption. In the case of using this as a main component, the dimensional stability of the light guide plate may be improved as a result.

MS resins are usually named MS500, MS600 or MS750 according to the content of methyl methacrylate, and in the present invention, it may be preferable to use MS600 or MS500 among these MS resins. Most preferably, the entire base layer resin may be such an MS resin.

Meanwhile, the substrate layer may have a thickness of 0.5 to 4.5 mm in consideration of stable thickness formation and thinning of the display during extrusion.

The substrate layer may have a structure in which various three-dimensional patterns are formed within a range in which the emission light surface, that is, the upper surface of the substrate layer does not have a pattern structurally or impair the effects of the present invention. In terms of improving luminance, the lenticular pattern may be, but is not limited thereto.

When the upper surface of the substrate layer has a pattern, the thickness of the substrate layer means the entire thickness including the upper pattern portion.

[Surface layer]

In the light guide plate, the surface layer is a layer in which various patterns in consideration of the optical path are formed, and in general, a printing technique or a V-cut technique has been applied as a pattern formation method.

In the pattern formation method, laser processing enables the processing of large-area micropatterns, the ability to form various types of micropatterns, and high impact ultra-precision fineness due to less impact on the processed sample with short time and high output. Although processing technology, depending on the material is not easy processing, or scratches occur, such as constraints.

In consideration of this point, the surface layer of the light guide plate of the present invention is composed of a resin having a refractive index difference of 0.05 or less, a hardness of at least 1H high, and a light transmittance of at least 90%, as compared with the main component resin of the base layer.

Resins that can satisfy such physical properties include selected resins of polycarbonate resins, polystyrene resins, acrylic resins, olefin resins, polyester resins, and polyamide resins, copolymers thereof, mixtures thereof, and derivatives thereof. The resin selected from the group consisting of, may be selected and used within the range of satisfying the above-described physical properties in consideration of the main component resin of the base layer.

In particular, in view of excellent processability and scratch resistance, the surface layer may be a copolymer including methyl methacrylate at least 70% by weight or more, or a polymethyl methacrylate resin (hereinafter, abbreviated as 'PMMA resin'). have.

For example, when the base material layer contains MS resin as a main component, the surface layer containing PMMA resin having a higher hardness than the MS resin as a main component is excellent in scratch resistance and workability.

Most preferably, the surface layer may be one in which the entire surface layer resin is a PMMA resin.

In the present invention, although the surface layer is disposed in consideration of workability and scratch resistance, the light guide plate made of only the base layer may be the best when considering the optical path. If a layer other than the base layer is provided, luminance loss is inevitable.

In consideration of this point, in the light guide plate of the present invention, the surface layer is preferably formed as thin as possible.

Here, the degree of the thin film is about 1 to 5% of the total thickness of the light guide plate, and a specific example is about 30 μm to 150 μm, and particularly preferably, the surface layer is formed to a thickness of 30 to 90 μm.

When the surface layer is formed within the range of the above degree, the surface layer is formed to such an extent that it does not substantially form an interface with the substrate layer, thereby minimizing optical path inhibition by the interlayer interface.

The light guide plate according to the preferred embodiment of the present invention may be manufactured by a coextrusion method. Specifically, each resin composition constituting the base layer and the surface layer is melted by heating using an extruder to be in a fluid state, and then a feed block ( At the same time through melt feed through the feed block) and extruded to the film through the T-die while pressing continuously, it may be desirable to perform so that the uniformity of the thickness of the surface layer is 20% or less.

When the thickness uniformity of the surface layer is more than 20%, a decrease in luminance uniformity and light degradation due to an interlayer interface may appear.

The factors for adjusting the thickness of the surface layer in coextrusion vary, among which the discharge rate corresponds to an element which is fixed fairly according to a predetermined thickness. For example, when the surface layer thickness is 40 μm, extrusion may be performed at a discharge rate of 15 kg / hr of surface layer resin composition through an extruder having a screw diameter of 65 mm, and at a discharge rate of 700 kg / hr of a base layer resin composition through an extruder having a screw diameter of 120 mm. Can be.

The thickness uniformity of the surface layer is important to match the flow rate of each of the base layer and the surface layer, because the pressure of each layer and the flow rate is different depending on the melting temperature and the screw speed when the resin is molten. Therefore, the flow velocity of each layer should be similar, and the pressure of each layer should be similar. Variables for this are screw speed, gear pump speed (rpm) and melting temperature.

It is preferable to control the thickness uniformity of the surface layer to 20% or less through the control of such process elements.

Thereby, the surface layer which is a thin film is formed, and the light-guide plate which is excellent in scratch resistance and workability can be obtained, without impairing brightness.

The light guide plate obtained as described above may have a surface layer not acting as an optical foreign material layer even though it further includes a surface layer in addition to the substrate layer.

[Intaglio pattern]

On the other hand, the light guide plate of the present invention may further improve the brightness by having a pattern on the surface layer surface, specifically, may have a plurality of intaglio patterns. A plurality of intaglio patterns may exist within the surface layer thickness, and may be formed in a shape that penetrates the surface layer and penetrates up to a predetermined thickness of the substrate layer thickness as shown in FIGS. 2 to 3.

Although the intaglio patterns represented on the drawings are expressed as successive intaglio patterns of the same standard, the size and / or spacing of the patterns may be changed in consideration of the light incident surface / the light facing surface. Here, the light incident surface refers to one side of the light guide plate on which the light of the LED package is incident, and the light incident surface refers to the other side opposite to the light incident surface.

For example, the distance between the patterns may be narrower as the distance from the light source is closer to the light incident surface.

Referring to FIG. 3, the height h of the intaglio pattern is the thickness x of the surface layer and the thickness y of the base layer. It can be expressed as a sum with a thickness corresponding to 0.1 to 10% of), which can be formulated by Equation 1.

x + (1/1000) y ≤ h ≤ x + (1/10) y

Where x is the thickness of the surface layer, y is the thickness of the base layer, and h is the height of the intaglio pattern.

If the height (h) of the intaglio pattern is less than "x + (1/1000) y" in Equation 1, there is a slight problem that the luminance increase effect due to the intaglio pattern is formed. Laser processing takes a long time and there is a light visibility problem.

On the other hand, the intaglio pattern is not limited to the three-dimensional structure as long as it satisfies the above-described degree of penetration shape, for example, the shape of the longitudinal section may be selected from the group consisting of semicircles, triangles, squares and irregular shapes.

In addition, the engraved pattern may be formed adjacent to each other continuously or discontinuously.

In the present invention, the intaglio pattern is formed to penetrate to a predetermined range of the total thickness of the base layer as described above, thereby preventing the light incident from one side of the light guide plate from escaping to the other side, thereby ultimately reducing luminance. It can prevent.

The light guide plate of the present invention as described above, due to the intaglio pattern formed in the form of the base layer having excellent dimensional stability, the surface layer having excellent hardness, and penetrates to a part of the thickness of the base layer, has excellent scratch resistance and workability, while reducing luminance. Minimizing the light guide plate can be provided.

The backlight unit including the light guide plate may exhibit an effect of preventing luminance deterioration, scratch resistance, and workability.

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

MS (Denka, MS500, copolymer of 50% by weight of methyl methacrylate with 50% by weight of styrene, light transmittance of 91%, refractive index 1.54, pencil hardness (ASTM D3363) 1H, water absorption 0.25%) 700kg / hr Extruder with screw diameter of 120mm, extruded at 230 ~ 240 ℃, PMMA (LGMMA, HP202, light transmittance of 94%, refractive index of 1.49, pencil hardness (ASTM D3363) 2H) 15kg / hr It was added to the extrusion at 240 ~ 250 ℃, melt discharged through the feed block (feed block) at the same time to produce a light guide plate by extruding and pressing through a T-die.

At this time, the surface layer was formed so that the thickness uniformity was 20% by controlling the speed of the screw, the gear pump rpm and the melting temperature.

A laser pattern was processed on the surface layer to form a light-curved plate having a height of 50 µm, a width of 60 µm, and a semicircular intaglio pattern of a longitudinal section thereof.

Here, the resin properties and the surface layer thickness uniformity were evaluated by the following method.

(1) Light transmittance: Total light transmittance and haze were measured using the ASTM D1003 method and the NDH-2000 measuring apparatus manufactured by Nitto.

In the above and the following description, "light transmittance" means total light transmittance unless there is a specific limitation.

(2) Refractive index: According to ASTM D1218, the refractive index was measured using the Abbe refractometer.

(3) pencil hardness

According to ASTM D3363, using a pencil hardness tester (manufactured by Mitsubishi Corporation, uni) using a pencil hardness tester (manufactured by Heidon, 14FW) at a load of 500 kg / cm and a speed of 0.5 mm / sec, the pencil hardness was measured and The results are shown in Table 2 below.

(4) water absorption

It was measured through the ASTM D570 test method. After weighing by drying in an oven at 60 ° C. for 24 hours, it is impregnated with moisture at 23 ° C. for 24 hours. The water absorption rate was calculated based on the following formula 1 from the weight before drying and the weight after the impregnation after drying.

Water Absorption Rate (%) = (Weight after impregnation-Weight after impregnation) / Weight after impregnation * 100

(5) surface layer thickness uniformity

The cross section of the light guide plate was analyzed by a microscope (VK-X100, manufactured by KEYENCE), and 30 points were measured, and then expressed as a percentage of the tolerance.

Tolerance refers to the extent to which the measured value is tolerable to errors in the surface layer thickness. Often expressed as a percentage.

Thickness uniformity is defined as a value calculated based on Equation 2.

Thickness uniformity (%) = {(measurement maximum-reference value) + (reference value-measurement minimum value)} / reference value × 100

Examples 2-4

A light guide plate was manufactured in the same manner as in Example 1, except that the thickness of the surface layer was changed as described in Table 1.

At this time, by controlling the speed of the screw, the gear pump rpm and the melting temperature to form a surface layer to meet the thickness uniformity as shown in Table 1.

Examples 5-8

A light guide plate was manufactured in the same manner as in Example 1, except that the surface layer was processed with a laser pattern to form a semi-circular intaglio pattern having the same height as that described in Table 1.

Examples 9-10

A light guide plate was manufactured in the same manner as in Example 1, except that the thickness uniformity of the surface layer was set as described in Table 1, and the intaglio pattern having the semicircular shape of the longitudinal section thereof was formed.

Examples 11-12

Example 1 and the above except that a pattern roll having the pattern was formed to form a lenticular pattern (Example 11-200 μm in width, Height 50 μm, Example 12 in width 300 μm, height 50 μm) in the substrate layer. In the same manner, a light guide plate was manufactured.

A typical structure of a light guide plate according to these embodiments is shown in FIG. 4.

Reference Examples 1 to 3

Reference Examples 4 to 5

A light guide plate was manufactured in the same manner as in Example 1, except that the intaglio pattern height of the surface layer was changed as described in Table 1.

Reference Examples 6 to 7

For the light guide plates manufactured in Examples and Reference Examples, luminance and pattern visibility were measured by the following method, and pencil hardness was measured by the method described above, and the results are shown in Table 2. The pencil hardness at this time is the value measured about the lower surface of a base material layer.

After sequentially stacking a light guide plate (Example or Comparative Example), a diffusion film (KOLON), a prism film (KOLON), and a DBEF (3M) on a BLU (Backlight Unit, 27 inch LED 1vertical), the luminance measuring equipment (BM-7A) After measuring 13 points using, TOPCON), the average value was calculated.

The relative luminance value with respect to Ref. Was measured using the luminance of Comparative Example 1 as a reference (Ref., 100%).

Here, in Comparative Example 1, without forming a surface layer, MS (Denka, MS500, copolymer of 50% by weight of methyl methacrylate and 50% by weight of styrene, light transmittance of 91%, refractive index of 1.54, pencil hardness (ASTM D3363) 1H And a light guide plate having a semicircular intaglio pattern having a semicircular shape of a longitudinal section on a lower surface of the base material layer having a water absorption of 0.25%).

Comparative Example 2 was a light guide plate was manufactured in the same manner as in Comparative Example 1 except that the base layer contained a lenticular pattern of the same standard as in Example 11.

The light guide plate was visually observed to determine whether the pattern formed on the lower part was visible.

Table 1

	Substrate layer		Surface layer		Engraved pattern
	Thickness (㎛)	Top pattern formation	Thickness (㎛)	Thickness uniformity (%)	Height (㎛)	Profile
Example 1	2960	radish	40	20	50	Semicircular
Example 2	2950	radish	50	20	50	Semicircular
Example 3	2900	radish	100	20	50	Semicircular
Example 4	2870	radish	130	20	50	Semicircular
Example 5	2960	radish	40	20	30	Semicircular
Example 6	2960	radish	40	20	40	Semicircular
Example 7	2960	radish	40	20	60	Semicircular
Example 8	2960	radish	40	20	100	Semicircular
Example 9	2960	radish	40	5	50	Semicircular
Example 10	2960	radish	40	10	50	Semicircular
Example 11	2960	Lenticular pattern (200㎛ pitch)	40	20	50	Semicircular
Example 12	2960	Lenticular pattern (300㎛ pitch)	40	20	50	Semicircular
Comparative Example 1	3000	radish	No formation	-	50	Semicircular
Comparative Example 2	3000	Lenticular pattern (200㎛ pitch)	No formation	-	50	Semicircular
Reference Example 1	2980	radish	20	20	50	Semicircular
Reference Example 2	2830	radish	170	20	50	Semicircular
Reference Example 3	2750	radish	250	20	50	Semicircular
Reference Example 4	2960	radish	40	20	0.3	Semicircular
Reference Example 5	2960	radish	40	20	310	Semicircular
Reference Example 6	2960	radish	40	30	50	Semicircular
Reference Example 7	2960	radish	40	50	50	Semicircular

TABLE 2

	Luminance (%)	Pattern visibility	Pencil Hardness (ASTM D3363)
Example 1	120	Invisible	2H
Example 2	117	Invisible	2H
Example 3	113	Invisible	2H
Example 4	110	Invisible	2H
Example 5	110	Invisible	2H
Example 6	115	Invisible	2H
Example 7	126	Invisible	2H
Example 8	132	Invisible	2H
Example 9	129	Invisible	2H
Example 10	125	Invisible	2H
Example 11	128	Invisible	2H
Example 12	130	Invisible	2H
Comparative Example 1	100	Invisible	H
Comparative Example 2	104	Invisible	H
Reference Example 1	98	Invisible	2H
Reference Example 2	92	Invisible	2H
Reference Example 3	84	Invisible	2H
Reference Example 4	81	Invisible	2H
Reference Example 5	148	show	2H
Reference Example 6	98	Invisible	2H
Reference Example 7	86	Invisible	2H

Claims

On the lower surface of the base material layer containing resin having a light transmittance of at least 90%, a refractive index of 1.47 to 1.59, and a water absorption of less than 0.30%,

A light guide plate comprising a surface layer composed mainly of a resin having a difference in refractive index of 0.05 or less, a hardness of at least 1H, and a light transmittance of at least 90%, as compared with the main component resin of the base layer.
The light guide plate according to claim 1, wherein the surface layer has a thickness of 1 to 5% of the total thickness of the light guide plate.
The light guide plate according to claim 1, wherein the surface layer has a thickness of 30 µm to 150 µm.
The light guide plate according to any one of claims 1 to 3, wherein the surface layer comprises a plurality of intaglio patterns.
The light guide plate of claim 4, wherein the plurality of intaglio patterns exist only in the surface layer or penetrate the surface layer to penetrate to a predetermined thickness of the base layer.
The light guide plate according to claim 4, wherein the plurality of intaglio patterns have a shape penetrating up to a thickness corresponding to 0.1 to 10% of the total thickness of the base layer.
The light guide plate according to claim 4, wherein the plurality of intaglio patterns are selected from the group consisting of semicircles, triangles, squares, and irregular shapes of three-dimensional shapes of longitudinal sections thereof.
The light guide plate according to any one of claims 1 to 3, which is produced by a coextrusion method.
The method of claim 8, wherein in the co-extrusion method, each resin composition constituting the substrate layer and the surface layer is melted by heating using an extruder to be in a fluid state, and then simultaneously melt-discharged through a feed block and extruded through a T die. While pressing continuously, the thickness uniformity of the surface layer is performed to satisfy 20% or less Light guide plate, characterized in that.
The method of claim 1, wherein the substrate layer is selected from polycarbonate resins, polystyrene resins, acrylic resins, olefin resins, polyester resins and polyamide resins, copolymers thereof, mixtures thereof and derivatives thereof. A light guide plate comprising a resin selected from the group consisting of as a main component.
The method of claim 1, wherein the surface layer is selected from polycarbonate resins, polystyrene resins, acrylic resins, olefin resins, polyester resins and polyamide resins, copolymers thereof, mixtures thereof and derivatives thereof. A light guide plate comprising a resin selected from the group consisting of as main components.
The light guide plate according to claim 1, wherein the base layer contains a copolymer containing methyl methacrylate in an amount of 60% by weight or less.
The light guide plate according to claim 1, wherein the surface layer is mainly composed of a polymethyl methacrylate resin or a copolymer containing at least 70% by weight of methyl methacrylate.
The light guide plate according to claim 1, wherein the light guide plate is made of a methyl methacrylate-styrene resin, and the surface layer is made of a polymethyl methacrylate resin.
A backlight unit comprising the light guide plate of claim 1.