WO2007046625A1

WO2007046625A1 - Light guide plate

Info

Publication number: WO2007046625A1
Application number: PCT/KR2006/004224
Authority: WO
Inventors: Jeong-Soon Kim
Original assignee: Jeong-Soon Kim
Priority date: 2005-10-19
Filing date: 2006-10-18
Publication date: 2007-04-26
Also published as: KR20070042860A; TW200717110A; KR100881332B1

Abstract

Disclosed herein is a light guide plate. In the light guide plate according to the present invention, a plurality of inclined regular reflecting surfaces, which is arranged in a direction perpendicular to incident light, is formed on the bottom surface of the light guide plate in the direction of the incident light.

Description

LIGHT GUIDE PLATE

Technical Field

[1] The present invention relates generally to a light guide plate and, more particularly, to a high-brightness light guide plate that has improved reflection efficiency and an improved reflected angle for light that enters from a light source. Background Art

[2] In general, light guide plates are known as principal elements that determine the quality and amount of light (related to the diffusion angle at the time of emission of light, directly transmitted light, and diffusively reflected light) while linear or point light is converted into surface light. For example, light guide plates are core elements of backlight units that are applied to Liquid Crystal Displays (hereinafter referred to as LCDs ) and flat panel displays.

[3] Methods of fabricating backlight units are classified into two types according to the location of the light source: a method of locating a light source immediately below a light transmitting surface and realizing surface light emission, and a method of locating a light source beside the side surface of a light guide plate and realizing surface light emission through diffuse reflection and regular reflection at the bottom surface of a light source.

[4] FIG. 1 is a schematic diagram showing the construction of a prior art backlight unit using side light sources.

[5] The backlight unit includes prism sheets 2 and 3, a diffusion sheet 4, a reflection sheet 7, side light sources 5, light source covers 6, and a light guide plate 8. In FIG. 1, reference numeral 1 designates a protection sheet.

[6] A typical light guide plate receives light from a light source using acrylic acid resin or polycarbonate, which have excellent light transmittance, diffusively reflects the received light using a printed pattern or irregularities on the bottom surface thereof, and emits the diffusively reflected light through the top surface thereof (that is, a light emitting surface), thereby forming a surface light source.

[7] The reflection sheet 7 functions to reflect light passing through the bottom surface of the light guide plate 8 and to return the light to the light guide plate 8.

[8] The diffusion sheet 4 primarily functions to diffuse light passing through the top surface of the light guide plate 8, thus being uniformly spread in front of the light guide plate.

[9] The light uniformly diffused from the diffusion sheet 4 is refracted and condensed by the prism sheets 2 and 3 appropriate to the purpose of a flat panel display, so that the light is finally emitted from the surface of the backlight unit at a uniform angle and at uniform brightness.

[10] The technologies for manufacturing light guide plates are classified into two types: a screen printing method of forming reflective patterns on the bottom surfaces of light guide plates, and a V-shaped groove cutting method of forming irregularities having minute roughness.

[11] The screen printing method is an old technology, and is currently used because it has the advantages of low manufacturing cost and suitability for mass production. However, the screen printing method is disadvantageous in that there is a limitation in the improvement of the brightness of light guide plates. Recently, although brightness is increased and is made uniform by attaching a separate film, which is a reflective material that has been provided with a printing, erosion or embossing effect, to the bottom surface of a light guide plate, the brightness of the screen printing method is not increased to the brightness level that can be achieved by the V-shaped groove cutting method.

[12] The V-shaped groove cutting method has been greatly developed and has improved efficiency from the aspects of the depth of cutting, angular arrangement and the cutting method. In particular, as a cutting method is developed from diamond blade cutting to laser cutting, the V-shaped groove cutting method can realize the accuracy of depth and arrangement and minute particles, thereby maximizing the efficiency of diffuse reflection.

[13] However, the prior art light guide plate still does not fulfill the demand for high brightness.

[14] One of the fundamental problems with the prior art technology that impedes the realization of high brightness is that the prior art light guide plate passes part of the light, which is diffusively reflected from the bottom reflection pattern, through the top surface of the light guide plate, and that part of the light is used as surface light. It is known that that part of the light is 60% of the amount of lamp light that remains after the overall loss of lamp light. The amount of lost light includes the following amounts:

[15] (1) the amount of light that is absorbed, extinguished or totally reflected based on th e light transmissivity of acrylic, and the minute amount that is not explained by light theories,

[16] (2) the amount of light that remains in the light source covers,

[17] (3) the amount of light that enters at a horizontal angle or angles close to the horizontal angle, which belongs to light that enters the light guide plate (hereinafter referred to as horizontal light ) (when light enters acrylic from the air, the light enters within a critical angle of 42.1° due to the refractive index of acrylic of 1.49, and is considerably refracted toward a horizontal direction), [18] (4) the amount of light energy reduced due to diffuse reflection because diffuse reflection, rather than regular reflection, is chiefly carried out on the bottom surface of the light guide plate,

[19] (5) the amount of light energy that is lost while light reaches the reflection pattern surface late or does not reach the reflection pattern surface and successive reflections are performed inside the light guide plate, and

[20] (6) a loss that occurs while light emitted from the light guide plate is condensed through the diffusion sheet and the prism sheets so that it is used for an LCD.

[21]

[22] There are structural problems in that the amount of light that is lost due to diffuse reflection on the bottom surface of the light guide plate occupies a large part of the above-described loss of light, and a large part of the diffusively reflected light is not used as surface light and is extinguished.

[23] FIGS. 2 and 3 illustrate states in which light is diffusively reflected inside light guide plate 8 by reflection patterns S provided on the bottom surfaces of the light guide plate 8.

[24] As illustrated in FlG. 2, while light is diffusively reflected by the bottom surface of the light guide plate 8 and is emitted through the top surface of the light guide plate 8, a large amount of light is not emitted but is re-reflected, therefore the light rapidly loses the energy thereof. Although the reflection patterns S are perceived as bright by a person s eye, only light diffused within an angular range of 84.2° (42.1° + 42.1°) around a vertical line is emitted, but light diffused outside of that angular range remains in the light guide plate 8 due to the refractive index of acrylic, is re-reflected and is diffusively reflected by another reflection pattern S again, and the above process is repeated, with the result that light energy is rapidly reduced.

[25] Meanwhile, light having right and left angles of 20° around a normal line perpendicular to the top surface of the light guide plate, that is, an internal angle equal to or less than 40°, which belongs to light emitted within an angular range of 84.2° around the normal line, has strong energy, whereas light having an interval angle in a range of 40°~84.2°, which belongs to the remaining emitted light, has weak energy, therefore it is not effectively used.

[26] The phenomenon can be easily ascertained.

[27] That is, as shown in FlG. 4, short 1 -shaped, V-shaped groove cutting G is performed on the bottom surface of a light guide plate 8, single red linear light is radiated onto it, and an examination is made using the naked eye or a white plate W above a groove G. In this case, only light emitted within an angular range of about 40° is transmitted through the light guide plate 8, light having an angle greater than the angle has weak intensity or is emitted at an angle close to the horizontal angle of the light guide plate, or a large amount of light is re-reflected inside the light guide plate and is not used as surface light.

[28] Furthermore, the prior art light guide plate 8 has a problem in that light is diffusively reflected to a position below the reflection patterns S, therefore great loss is incurred while the light is re-reflected by the reflection sheet 7 and enters the light guide plate 8. This can be sufficiently ascertained based on the fact that the measured brightness of an upper layer varies depending on the presence of the reflection sheet and the type of reflection sheet. Disclosure of Invention Technical Problem

[29] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a high-brightness, high efficiency light guide plate, which regularly reflects incident light vertically or approximately vertically through the top surface (light emitting surface) of a light guide plate so that the diffuse reflection of the light in the light guide plate is prevented and, thus, the loss of light energy is minimized, thereby emitting a maximal amount of light and achieving high light energy.

Technical Solution

[30] That is, the present invention is intended to change a reflection structure so that regular reflection, rather than diffuse reflection by prior art V-shaped grooves having minute roughness, can occur, thereby regularly reflecting as much of the light that is incident on a light guide plate as possible.

[31] Furthermore, another object of the present invention is to provide a uniform, high- brightness light guide plate, which utilizes the light guide plate of the present invention as a separate light guide plate at the time of use of a point light source, thereby converting point light into linear or surface light, and using the resulting linear or surface light for a light source.

[32] In order to accomplish the above objects, the present invention provides a light guide plate, wherein a plurality of inclined regular reflecting surfaces, which is arranged in a direction perpendicular to incident light, is formed on the bottom surface of the light guide plate in the direction of the incident light. Advantageous Effects

[33] According to the present invention, regular reflection other than prior art diffuse reflection is utilized, thereby achieving the high-brightness and high efficiency of an LCD, and a reflection sheet, a diffusion sheet and prism sheets are not required, thereby reducing manufacturing cost due to the simplification of parts and the reduction in assembly cost, and thereby simplifying and improving assembly due to the use of a small number of parts. [34] Furthermore, the assembly structure or module structure of the light guide plate is simplified, therefore the overall thickness of a complete light guide plate is reduced, thereby improving the design of related products. [35] Furthermore, high-definition image quality can be realized in an LCD using a uniform surface light source, and power consumption is reduced due to the efficiency of a light source based on high brightness, thereby increasing the useful lifetime of portable products. [36] Moreover, the amount of emitted light per light source is considerably increased and the emitted angle of light can be arbitrary adjusted, therefore backlight units, to which the light guide plate of the present invention is applied, can be used as various light sources for commercialized display panels, architectural illumination, lighting equipment and so on. [37]

Brief Description of the Drawings [38] The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: [39] FIG. 1 is an exploded view of a prior art backlight unit;

[40] FIGS. 2 to 4 are diagrams illustrating the characteristics of light inside a light guide plate;

[41] FIG. 5 is a diagram illustrating the refraction of light;

[42] FIG. 6 is a diagram 3-dimensionally illustrating the refraction of light incident on a light guide plate; [43] FIGS. 8 to 11 are diagrams illustrating the theory of regular reflection according to the present invention; [44] FIG. 12 is a diagram illustrating the fundamental theory of a reflection pattern according to the present invention; and [45] FIGS. 13 to 23 are diagrams illustrating various embodiments according to the present invention. [46]

Best Mode for Carrying Out the Invention [47] Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar components. [48] In a light guide plate according to the present invention, a plurality of inclined regular reflecting surfaces, which is arranged in a direction perpendicular to incident light, is formed on the bottom surface of the light guide plate in the direction of the incident light.

[49] The term inclined regular reflection surface refers to an inclined surface that is processed to maximize regular reflection while maximally suppressing diffuse reflection. The present invention is realized using V-shaped projections, at least one of surfaces of each of which are inclined regular reflection surfaces, and is realized using the inclined regular reflection surfaces, which have an inclined angle of 45°.

[50] In the above and following descriptions, the term light guide plate means a light guide plate which is used as a light guide plate bar and a light guide plate assembly in which a light guide plate bar is attached to a light guide plate in a broad sense, as well as a light guide plate in a narrow sense. It can be understood that those skilled in the art can apply the concept of the present invention to the light guide plate, the light guide plate bar and the light guide plate assembly without difficulty.

[51] Since the present invention aims to change the structure of the light guide plate and thus achieve high brightness as described above, existing light theories known in association with the light guide plate are described first below.

[52] The incident angle θl and refracted angle 02 of light, which starts from a light source and enters a light guide plate (made of acrylic) 100, have the relationship illustrated in FlG. 5.

[53] In this case, the medium nl has an air refractive index of 1, and n2 has an acrylic refractive index of 1.49.

[54] In this case, the relative refractive index is 1.49/1.

[55] Of course, since the refractive index of light, which is emitted into the air from acrylic, is a relative refractive index of 1/1.49, the relationships between the incident angle and the refracted angle are the opposite of the table of FlG. 5.

[56] In the case where the incident angle is 90° when light enters acrylic from the air, the critical angle of the acrylic is 42.1° (in the following description, 42.1° is denoted as 42° in some cases).

[57] Furthermore, in the case where the incident angle is greater than 73.5°, the refracted angle is 40°. Since the effective components of light having the incident angle greater than 73.5° are insignificant, they will be disregarded in some cases.

[58]

[59] The moment light starting from a side surface light source enters the light guide plate (acrylic), as illustrated in FlG. 6(a), refraction having directionality, that is, three components(x-axis, y-axis and z-axis), is generated based on the refractive index of acrylic.

[60] Meanwhile, unless specifically described otherwise in the above and following descriptions, the term incident direction of light refers to the x-axis direction in the cases of FIGS. 6(a).

[61] This is described below with respect to the x-z section, the x-y section and the y-z section, as shown in FIGS. 6B, 6C and 6D. The graphs shown in the right parts of the drawings are diagrams illustrating the distributions of light vector amounts based on refracted angles.

[62] In the case of the x-z section of FlG. 6, since all of the incident light can enter within the angular range of 0°~ 90°, the amount of entering light varies with the degree of the angle due to the influence of total reflection, and the amount of entering light decreases in a direction from 0° to 90°. Furthermore, the light entered in the acrylic may have an angle in a range of 0°~ 42.1° due to the refractive index of acrylic.

[63] Meanwhile, when the light entered in the acrylic is emitted through the top surface of the light guide plate, the emission angle of the light is in a range of 47.9°~90° with respect to a normal line perpendicular to the top surface of the light guide plate. Since the angle is greater than a critical angle of 42.1° for the acrylic, the light cannot be emitted to the outside, and all of the light is totally reflected.

[64] This can be easily understood from the fact that, when light is radiated onto one surface of a transparent light guide plate, on which no reflection pattern is formed, no light is emitted through the top or bottom surface of the light guide plate, but instead exits in the direction opposite the light source.

[65] As viewed from the x-y section and y-z section of FIGS. 6C and 6D, all of the light has angles equal to or less than 42.1°, therefore all of the light has angles capable of being emitted. However, since the light itself has the characteristic of the x-z section also, all of the light is not emitted in lateral, upward and downward directions and exits in the direction opposite to a light source.

[66] Accordingly, as understood from FlG. 6, light propagating throughout the light guide plate has the following characteristics.

[67] (1) Incident light propagates throughout a light guide plate at an angle in a range of

0°-critical angle (42.1°).

[68] (2) Within a light guide plate, the energy of incident light increases at angles close to 0°.

[69] (3) Within a light guide plate, the energy of incident light decreases at angles close to a critical angle.

[70]

[71] The fundamental principles of the present invention are described below.

[72] V-shaped projections having the best reflected angle are formed on the bottom surface of a light guide plate using the propagation of light having the above-described characteristics, and regular reflection processing (reflective layer coating for regular reflection) is applied to the surfaces of the V-shaped projections or to the entire bottom surface of the light guide plate, therefore the regular reflection of light can be generated, thereby realizing a high-brightness light guide plate. [73] First, the regular reflection processing (reflective layer coating for regular reflection) is described below. [74] As in diffuse reflection or a reflection sheet in the conventional dot printing (printed dot) method or the V-shaped groove cutting method, radiation from a medium itself causes the loss of light. [75] In order to eliminate such a loss, arriving light must be regularly reflected as it is.

For this purpose, the formation of a mirror surface and the formation of a reflective layer coating are useful. [76] Such regular reflection processing allows all of the light to be regularly reflected.

That is, the regular reflection processing regularly reflects all of the light without refraction, transmission or diffuse reflection even when light incident on an inclined regular reflection surface has an incident angle greater than a critical angle. [77] Accordingly, regular reflection processing (reflective layer coating for regular reflection) is applied to the surfaces of V-shaped projections (or the entire bottom surfaces of light guide plate) that are realized in the present invention. Methods for regular reflection processing includes various methods, such as general mirror surface formation techniques, for example, aluminum deposition and silver nitrate deposition using a vacuum deposition method, chrome plating, and white reflective film coating film formation. [78] The reflective layer coating includes reflective layer coating for regular reflection and reflective layer coating for diffuse reflection. The technique applied to the present invention is the reflective layer coating for regular reflection. [79] [80] FIG. 7 shows states in which linear light enters a light guide plate, is refracted at angles in a range of 0°~ 42° and is then reflected by V-shaped projections. [81] When regular reflection occurs, the incident angle of light is identical to the reflected angle of the light with respect to inclined regular reflection surfaces. [82] As understood from FIG. 7, in order to construct a V-shaped projection so that the center of the light is reflected in a vertical direction, the interior angle of the V-shaped projection must be 111°. The interior angle of a V-shaped projection capable of emitting all of the light is in a range of 90°~132°. [83] In FIG. 7, light incident on inclined regular reflection surfaces is indicated by dotted arrows, and light reflected by the inclined regular reflection surfaces is indicated by solid arrows. [84] Furthermore, in the present embodiment, it is assumed that the sides of each of the

V-shaped projections have the same angle with respect to a normal line perpendicular to the top surface of a light guide plate. The reason for this is that, when light sources are placed beside two side surfaces of a light guide plate, each of the V-shaped projections is defined by two inclined regular reflection surfaces and the two inclined regular reflection surfaces have the same inclined angle with respect to a normal line perpendicular to the top surface of the light guide plate.

[85] However, when a light source is placed beside one side surface of a light guide plate, only one inclined regular reflection surface of each V-shaped projection is required to regularly reflect light. That is, although each V-shaped projection is basically defined by two inclined surfaces, only one of the two inclined surfaces is significant for an inclined regular reflection surface. In this case, the inclined regular reflection surface requires a predetermined inclined angle with respect to a normal line perpendicular to the top surface of a light guide plate. In the cases of FIGS. 7(a), 7(b) and 7(c), the inclined angle is in a range of 45°~66°. In this case, an inclined surface that is not used as an inclined regular reflection surface may have an angle that is different from that of the inclined surface that is used as the inclined regular reflection surface.

[86] FlG. 8 shows reflected angles at V-shaped projections when point light having a light width of 130° enters light guide plate.

[87] Point light having a light width of 130° is chiefly used. When a light width is 130°, light enters a light guide plate at an upward angle of 65° and a downward angle of 65° with respect to a horizontal direction. In this case, a generated refracted angle is in a range of -37.5°~0^o(horizontal)~37.5° based on the relationship of FlG. 5. At this time, light refracted upward within a range of -37.5°~0° is totally reflected by the top surface of the light guide plate and is converted into light within a range of 0°~37.5°, with the result that all of the light is oriented to the bottom surface of the light guide plate throughout the light guide plate within an angular range of 0°~37.5°.

[88] Accordingly, light having a light width of 130° has a refracted angle in a range of

0°~37.5°. As illustrated in FlG. 8, in order to construct a V-shaped projection so that the center of light is reflected in a vertical direction, the interior angle of the V-shaped projection is 108.75°, and the interior angle of a V-shaped projection capable of reflecting all of the light is in a range of 85.5°~132°.

[89] Of course, in this case, when only one inclined surface of a V-shaped projection is significant for an inclined regular reflection surface, all of the light can be emitted when the inclined regular reflection surface has an inclined angle in a range of 42.75°~66° with respect to a normal line perpendicular to the top surface of the light guide plate.

[90]

[91] Meanwhile, when point light, that is, horizontal light, has a light width of about 0°~10°, the refracted angle of the light that enters the light guide plate is about 0° (that is, horizontal) based on the relationship of FlG. 5. In this case, the interior angle of a V-shaped projection that reflects light having a refracted angle of 0° in a vertical direction is 90°. However, when horizontal light enters, the V-shaped projection shown in FlG. 9(a) is not necessary, in which case the inclined regular reflection surface having an inclined angle of 45° shown in FlG. 9(b) is sufficient. That is, the inclined regular reflection surface having an angle of 45° is raised in steps of the height of a projection, and the incident angle of 45° for the inclined regular reflection surface is greater than the critical angle of a light guide plate, thus all of the light is regularly reflected and is vertically emitted through the top surface (light emitting surface) even when no reflective layer coating for regular reflection is applied to the inclined regular reflection surface (or to the entire bottom surface of the light guide plate).

[92] The light emitted from the light guide plate enters the light incident polarization sheet of an LCD, and then passes through all of the elements of the LCD. In this case, the efficiency of the light width of light that can effectively enter the LCD gradually increases with the development of technologies of a polarization sheet, liquid crystal, a liquid crystal drive device and exposure printing. Recently, in the case of a prism light guide plate and a prism sheet, in which prisms are formed on the upper light emitting surface of a light guide plate, a prism angle of about 90° is chiefly used, in which case the maximum emission angle is about 45°.

[93] The interior angle of a V-shaped projection suitable for a maximum emission angle of 45° is 118.3°, as shown in HG. 10.

[94] A thinner light guide plate is required from the aspects of the efficiency of light and finished product design.

[95] For example, when point light having a light width of 130° is used as a light source for a 2-inch light guide plate having a thickness of 0.4 mm, the width of strong emitted light is about 0.14 mm in a V-shaped projection having an interior angle of 108.75° (refer to FlG. 1 l(a)). It is desirable that strong emitted light be sufficiently wide as to overlap itself at least two times so as to form uniform surface light. For this purpose, the interval between V-shaped projections (pitch) is 0.07 mm, the number of V-shaped projections is about 640 when the length of a light guide plate is 45mm, the minimum height of V-shaped projections is about 0.006 mm, the maximum height of V-shaped projections is about 0.020 mm, the difference between the maximum height and the minimum height is 0.014 mm, and the average height difference between respective V- shaped projections is about 0.000022 mm. These specifications require a mold that requires 10 nm-level machining precision, therefore it is not easy to fabricate a mold and to apply to mass production.

[96] Therefore, it is desirable to utilize the maximum emission angle of an LCD (for example, about 45°). FlG. 1 l(b) illustrates a light guide plate that uses the maximum emission angle. In this case, the distribution of light having strong energy is broader and more uniform, therefore the uniformity of surface light can be also improved.

[97] Hence, in order to maximally utilize light energy and form uniform surface light, an angle within a range of 100°~120° is suitable for the interior angle of V-shaped projections. The interior angle of V-shaped projections may be wide for commercialized display panels, illumination equipment and architectural illumination.

[98] When only one inclined surfaces of V-shaped projections are used as inclined regular reflection surfaces, V-shaped projections having an interior angle in a range of 100°~120° correspond to inclined regular reflection surfaces having an inclined angle in a range of 50°~60° with respect to a normal line perpendicular to the top surface of a light guide plate.

[99] In FlG. 11, upper graphs illustrate light energy at points at which light is emitted.

[100] As described above, horizontal light can be achieved using only inclined regular reflection surfaces that are formed stepwise at an angle of 45° without using V-shaped projections.

[101]

[102] The patterns of inclined regular reflection surfaces are described below.

[103] While a screen printing method has been used for the last 20 years, patterns have been significantly developed.

[104] The principle of all the pattern structures of light guide plate is the same as the principle of the patterns of a dot screen printing method.

[105] That is, the patterns of light guide plate have two functions. One of them is the function of printed portions, that is, a function of diffusively reflecting and emitting light, as in dots, and the other is the function of non-printed portions, that is, a function of regularly reflecting light. The latter function is transferring light from a light source to a remote dot so that the remote dot diffusively reflects the light and emits the light.

[106] A gradation etching method is based on the same principle that uses printed portions and non-printed portions that are minutely distributed.

[107] The dot pattern is configured such that the sizes of dots increase in the X-axis direction (refer to FlG. 6) away from a light source and dots having the same size are arranged in the Y-axis direction (refer to FlG. 6).

[108] The configuration of the pattern of the present invention is similar to that of the dot pattern.

[109] FlG. 12(a) is a schematic diagram of the prior art dot pattern, and FlG. 12(b) is a diagram of a V-shaped projection pattern according to the present invention.

[110] In FlG. 12(a), section a-b is a light incident part that diffusively reflects and emits light, and section b-c is a part that regularly reflects light and transfers the light rearward.

[Ill] In FlG. 12(b), section e-f is a light incident part, section f-i is a part that regularly reflects and emits light, and section f-g is a part that regularly reflects light and transfers light rearward.

[112] Although ( section a-b and section e-f ), and ( section b-c and section f-g ) are different in the size of the cross section, the sum of the areas of respective dots of section a-b are identical to that of section e-f, and that of section b-c is identical to that of section f-g from the aspect of a horizontal plane (x-y plane). As a result, the sum of the areas of all dots in a light guide plate (the sum of the areas of section a-b in FlG. 12) is identical to the sum of the areas of all V-shaped projections (the sum of the areas of section e-f in FlG. 12). Accordingly, the two patterns are different only in shape, and have the same pattern principle and the same function.

[113] The two patterns are compared with each other below. In the dot pattern, light is diffusively reflected, therefore the amount of emitted light is much smaller than the amount of incident light, and light energy and the emitted angle are poor after the emission of the light. In contrast, in the V-shaped projection pattern, all of the light is regularly reflected and is emitted at high light energy in a vertical direction.

[114] Furthermore, although the dot pattern realizes only precision corresponding to a screen mesh size of 5/100 mm, the V-shaped projection pattern realizes a precision of 10 nm, and provides a high-brightness light guide plate that supports the uniformity of surface light and the efficiency of light.

[115]

[116] Embodiments of the present invention are described below.

[117]

[118] - First embodiment (refer to HG. 13)

[119] A plurality of V-shaped projections 121 having a specific interior angle is formed on the bottom surface 120 of each light guide plate 100 having a uniform thickness. Each of the plurality of V-shaped projections 121 is configured to have the same shape, that is, the same cross section, in a direction(that is, the y-axis direction of FlG. 6) perpendicular to incident light. Furthermore, the plurality of V-shaped projections 121 is formed in the direction of incident light from a light source. In this case, the V- shaped projections 121 have the same interior angle.

[120] The sizes of the V-shaped projections 121 (that is, in the present embodiment, the heights of the V-shaped projections 121), which are adjacent to surfaces facing light sources, that is, light incident surfaces 130, are small. And the widths of the surfaces of the bottom surface 120, on which no V-shaped projections 121 are formed, (the intervals between V-shaped projections 121 and their adjacent V-shaped projections 121), which are adjacent to surfaces facing light sources, are narrow. [121] The heights of the V-shaped projections 121 increase in proportion to the distances from corresponding light sources, and the widths of the surfaces of the bottom surface

120, on which no V-shaped projections 121 are formed, (the intervals between V- shaped projections 121 and their adjacent V-shaped projections 121), decrease in proportion to the distances from corresponding light sources.

[122] That is, when, as illustrated in FlG. 13(a), light sources are respectively located beside two side surfaces of the light guide plate 100, V-shaped projections 121 having the smallest height are respectively formed on two sides of the bottom surface 120, and V-shaped projections 121 having heights inversely proportional to the distances to the center of the bottom surface 120 are formed between the side V-shaped projections

121. The heights of the V-shaped projections are symmetrical around the center of the bottom surface 120.

[123] When, as illustrated in FlG. 13(b), a light source is located beside one side of a light guide plate 100, the V-shaped projection 121 having the smallest height is formed beside a light incident surface 130 and V-shaped projections 121 having heights proportional to the distances from the light incident surface 130 are formed.

[124] In this case, as the interval between V-shaped projections 121 decreases, the accuracy of regular reflection patterns increases and the uniformity of surface light increases.

[125] Meanwhile, the difference in size between adjacent V-projections in the direction of incident light increases in proportion to the distance to the light source. Accordingly, by repeatedly and respectively connecting the three vertices of a V-shaped projection with the three vertices of an adjacent V-shaped projection, aspheric quadratic curve, the increment of which increases in proportion to the distance to the light source, other than straight lines that increase in equal ratio, can be found.

[126]

[127] - Second embodiment (refer to FlG. 14)

[128] By locating the lower ends of the V-shaped projections 121 of the first embodiment at the same horizontal level (that is, in the same horizontal plane), the V-shaped projections 121 are formed stepwise and are raised in proportion to the height of a V- shaped projection 121. That is, the bottom surface 120 of the light guide plate 100 is formed stepwise in the direction of incident light, and the V-shaped projections 121 are formed on the start or end portions of respective steps. The present embodiment can utilize horizontal light to an extent corresponding to the heights of the step, therefore brightness is increased.

[129]

[130] - Third embodiment (refer to HG. 15)

[131] The present embodiment is realized by gradually increasing the height of one inclined surface of each V-shaped projection 121 in proportion to the distance to the light source and raising the lower vertex of the V-shaped projection 121 by the increased height. The present embodiment can utilize horizontal light to an extent corresponding to the increased height, therefore brightness is increased further.

[132]

[133] - Fourth embodiment (refer to HG. 16)

[134] The present embodiment of FIG. 16 is realized by dividing a V-shaped projection

121 of the first embodiment into a plurality of split V-shaped projections 121a, as illustrated in FIG. 16. The sum of the areas of the light incident surfaces of the plurality of split V-shaped projections 121a is equal to the area of the light incident surface of the original V-shaped projection 121. In this case, for both the split V-shaped projections 121a and the original V-shaped projection 121, the amount of incident light is basically equal to the amount of reflected light.

[135] The split V-shaped projections 121a into which the single V-shaped projection 121 is divided can realize more uniform surface light than the single V-shaped projection 121.

[136]

[137] - Fifth embodiment (refer to FIG. 17)

[138] As shown in FIG. 17, a plurality of V-shaped projections 121 having the same size and the same interior angle may be formed on the bottom surface 120 of a light guide plate 100.

[139] In this case, the interval between V-shaped projections 121 adjacent to a light incident surface 130 is wide, and the interval between adjacent V-shaped projections 121 decreases in a direction away from a light source.

[140] When a pattern is formed as described above, a process of manufacturing a mold can be simplified, and a precise pattern in which the intervals between the V-shaped projections 121 are narrow can be obtained, therefore a uniform surface light source can be realized.

[141]

[142] - Sixth embodiment (refer to HG. 18)

[143] In the present embodiment, the bottom surface 120 of a light guide plate 100 is configured to be inclined. That is, the bottom surface 120 of the light guide plate 100 is a bottom surface the height of which increases in the direction of incident light.

[144] Accordingly, the thickness of the light guide plate 100 is large at the location adjacent to the light incident surface 130, and the thickness of the light guide plate 100 decreases in proportion to the distance from the light incident surface 130.

[145] The light guide plate 100 of the present embodiment is different from the light guide plate 100 of the first to fifth embodiments, in which the bottom surfaces 120 are parallel to the top surfaces 110.

[146] Each of the light guide plates 100 of HGS. 18(a) and 18(b) has a wedge shape, and is provided with a light source beside one surface thereof. The light guide plate 100 of FIG. 18(c) has a butterfly shape, the thickness of which decreases in a direction toward the center of the light guide plate 100, and is provided with light sources beside two surfaces thereof.

[147] The embodiments are formed by inclining bottom surfaces 120 and forming V- shaped projections 121 on the bottom surfaces 120.

[148] The concept of the first embodiment (FIG. 13) has been applied to the embodiment of FIG. 18(a), and the concept of the fifth embodiment (FIG. 17) has been applied to the embodiments of HGS. 18(b) and 18(c).

[149] The above embodiments having the above shapes can partially utilize horizontal light, therefore brightness can increase. Although the above embodiments have a low rate of utilization of horizontal light compared to the third embodiment (FIG. 15), they can achieve uniform light emission amounts using accurate patterns.

[150]

[151] - Seventh embodiment (refer to FIG. 19)

[152] In the case of the light guide plate of the first to sixth embodiments that are provided with the V-shaped projections, regular reflection processing (reflective layer coating for regular reflection) must be applied only to the surfaces of the V-shaped projections or to the entire bottom surfaces of the light guide plate (including the V- shaped projections).

[153] However, in light guide plate using horizontal or approximately horizontal light as source light, it is effective to form inclined regular reflection surfaces 122 having an inclined angle of 45° on stepped bottom surfaces 120 without forming V-shaped projections. In this case, it is not necessary to perform reflective layer coating on the inclined regular reflection surfaces 122 having an inclined angle of 45°.

[154] In the light guide plate of FIG. 19(a), the inclined regular reflection surfaces 122 having an inclined angle of 45° are formed on the stepped bottom surface 120 so that the inclined surfaces 122 are gradually raised in the direction away from a light source or a light incident surface 130. In the light guide plate of FIG. 19(b), the interval between adjacent inclined regular reflection surfaces 122 having the same size decreases in the direction away from the light incident surface 130.

[155] That is, the bottom surface 120 of the light guide plate 100 is raised stepwise in the direction of incident light, and the inclined regular reflection surfaces 122 are formed at the start or end portions of respective steps of the light guide plate 100.

[156]

[157] - Eighth embodiment (refer to HG. 20) [158] In order to utilize small-sized light guide plate having two or fewer point light sources as uniform surface light sources, light guide plate bar 200 is separately manufactured using the patterns selected from the first to seventh embodiments, and is attached onto light guide plate 100, as illustrated in FlG. 20, therefore uniform surface light can be formed by the light guide plate bar 200 and can enter the light guide plate 100. That is, the concept of the present invention is applied to the light guide plate bar 200.

[159] The light guide plate 100 of the present embodiment increases the efficiency of light sources when point light sources are used, can realize uniform surface light sources free from bright lines that may be generated in light guide plate on the incident surface of which prisms are formed, and allow regular reflection condensation to be achieved on the x-y sections through the use of the light guide plate bar, thereby realizing high-brightness, high-efficiency light guide plate that does not require diffusive prism sheets. The light guide plate can provide uniform surface light sources for LCDs.

[160]

[161] - Ninth embodiment (refer to FlG. 21 )

[162] In small-sized light guide plate using two or less horizontal light point light sources shown in FlG. 20, light guide plate bar is not separately provided, unlike the eighth embodiment, and the patterns of the seventh embodiment are formed on side surface of a light guide plate, thereby the light guide plate bar and the light guide plate are integrated into single bodies.

[163] As a result, in the present embodiment, inclined regular reflection surfaces are formed on the side surface 140 of the light guide plate 100.

[164]

[ 165] - Tenth embodiment (refer to HGS . 22 and 23)

[166] In the present embodiment, a plurality of V-shaped projections is arranged to have a check pattern.

[167] In the case of the first embodiment, the V-shaped projections formed on the bottom surface 120 are continuously and longitudinally extended in a direction perpendicular to incident light. In this case, light, which is reflected by the V-shaped projections 121 formed on the bottom surface 120 and then emitted, can form more uniform light in proportion to the extent of the overlap of emitted light. The extent of the overlap of emitted light, in turn, increases in proportion to the width of the light incident parts of the V-shaped projections 121 (section e-f of FlG. 12 (b)).

[168] Meanwhile, to increase the width of the light incident parts (section e-f of FlG.

12(b)) in relation to the area of the V-shaped projections 121 determined according to the pattern rule for the light guide plate, that is, to allow light to be emitted while overlapping itself much more, it is preferred that the V-shaped projections 121 be configured to be regularly spaced apart from each other, as illustrated in FlG. 22, rather than to be continuously and longitudinally formed, as in the first embodiment, with respect to light incident on the bottom surface of a light guide plate.

[169] That is, in the embodiment of FlG. 22, the V-shaped projections 121 are formed in short bar shapes, and respective short bars are located in a direction perpendicular to incident light at regular intervals.

[170] In this case, short bar-shaped, V-shaped projections 121 allow incident light to overlap itself much more due to their wide width, and the gaps between the V-shaped projections 121 function to totally reflect incident light and transfer the light rearward.

[171] In FlG. 23, the tenth embodiment and the first embodiment are compared with each other.

[172] In FlG. 23, left views are conceptual perspective views of the bottom surfaces of the light guide plate, and right views are bottom views of the V-shaped projections. Furthermore, upper views illustrate the tenth embodiment and lower views illustrate the first embodiment.

[173] As illustrated in the drawings, the width of the light incident parts of the V-shaped projections of the tenth embodiment is greater than the width of the light incident parts of the first embodiment.

[174] Furthermore, the sum of the areas of the V-shaped projections of the tenth embodiment is identical to the sum of the areas of the V-shaped projections of the first embodiment.

[175] The light guide plate of the tenth embodiment may be manufactured by fabricating a light guide plate having the shape of the first embodiment first and precisely forming gaps in the V-shaped projections of the first embodiment.

[176] Of course, the pattern of the V-shaped projections that are formed in a direction perpendicular to the direction of incident light at regular intervals may be applied to the fifth and sixth embodiments.

[177]

[178] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

[179]

Industrial Applicability

[180] According to the present invention, regular reflection other than prior art diffuse reflection is utilized, thereby achieving the high-brightness and high efficiency of an LCD, and a reflection sheet, a diffusion sheet and prism sheets are not required, thereby reducing manufacturing cost due to the simplification of parts and the reduction in assembly cost, and thereby simplifying and improving assembly due to the use of a small number of parts.

[181] Moreover, the amount of emitted light per light source is considerably increased and the emitted angle of light can be arbitrary adjusted, therefore backlight units, to which the light guide plate of the present invention is applied, can be used as various light sources for commercialized display panels, architectural illumination, lighting equipment and so on.

Claims

[I] A light guide plate, wherein a plurality of inclined regular reflecting surfaces, which is arranged in a direction perpendicular to incident light, are formed on a bottom surface of the light guide plate in a direction of the incident light.

[2] The light guide plate as set forth in claim 1, wherein the inclined regular reflecting surfaces are at least one of surfaces of each V-shaped projections that are formed on the bottom surface of the light guide plate, the V-shaped projections having an identical interior angle and surfaces on which regular reflection processing has been performed.

[3] The light guide plate as set forth in claim 2, wherein the V-shaped projections are continuously and longitudinally extended on the bottom surface of the light guide plate in a direction perpendicular to the incident light.

[4] The light guide plate as set forth in claim 2, wherein the V-shaped projections are extended on the bottom surface of the light guide plate at regular intervals in a direction perpendicular to the incident light.

[5] The light guide plate as set forth in claim 2, wherein the inclined regular reflecting surfaces of the V-shaped projections have an inclined angle in a range of 50°~60° with respect to a normal line perpendicular to a top surface of the light guide plate.

[6] The light guide plate as set forth in claim 2, wherein the regular reflection processing is regular reflective layer coating.

[7] The light guide plate as set forth in claim 2, wherein the regular reflection processing is performed on the entire bottom surface of the light guide plate.

[8] The light guide plate as set forth in claim 2, wherein the V-shaped projections have sizes that increase in a direction away from a light source.

[9] The light guide plate as set forth in claim 8, wherein the differences in size between adjacent V-shaped projections increase in a direction away from a light source.

[10] The light guide plate as set forth in claim 9, wherein the bottom surface of the light guide plate is formed stepwise in the direction of incident light, and the V- shaped projections are respectively formed at start portions of steps.

[II] The light guide plate as set forth in claim 2, wherein the V-shaped projections have intervals that decrease in the direction away from a light source.

[12] The light guide plate as set forth in claim 2, wherein the bottom surface of the light guide plate is an inclined bottom surface that is raised in the direction of the incident light.

[13] The light guide plate as set forth in claim 1, wherein the inclined regular reflection surfaces have an inclined angle of 45° with respect to the direction of the incident light, the bottom surface of the light guide plate is formed stepwise in the direction of the incident light, and the inclined regular reflection surfaces are respectively formed at the start portions of the steps.

[14] The light guide plate as set forth in claim 13, wherein the inclined regular reflection surfaces have sizes that increase in a direction away from a light source.

[15] The light guide plate as set forth in claim 13, wherein the inclined regular reflection surfaces have intervals that decrease in the direction away from a light source.

[16] The light guide plate as set forth in claim 1, wherein the light guide plate is used as a light guide plate bar.

[17] A light guide plate, wherein a plurality of inclined regular reflecting surfaces, which are formed in a direction perpendicular to incident light, are formed on a side surface of the light guide plate in a direction of the incident light and have an inclined angle of 45° with respect to a direction of the incident light, the side surface of the light guide plate is formed stepwise in the direction of the incident light, and the inclined regular reflection surfaces are respectively formed at least at start portions of the steps.