JPH1020121A - Light transmission body for surface light source element and surface light source element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to obtain high luminance and to obtain a luminance distribution uniform within the light exit surface of a light transmission body without subjecting the surface to a treatment to make dot patterns, etc., uniform by forming the light exit surface of a light transmission body of many lens arrays composed of slopes having a specific average angle of inclination. SOLUTION: The many lens arrays consisting of the slopes having the average angle of inclination of 0.5 to 7.5 deg. are formed on at least one surface of the light exit surface and rear surface of the light transmission body in such a manner that the lens arrays extend in the direction parallel with the light incident surface of the light transmission body. The reason for specifying the range described above lies in that if the average angle of inclination of the slopes constituting the lens arrays is below 0.5 deg., the exit angle (the angle to the normal of the light exit surface) of the exit light from the light exit surface increases and the directing of the exit light to the normal direction is no more possible even if an angle changing member, such as prism sheet, is used. Conversely, if the average angle of inclination of the slopes constituting the lens arrays exceeds 7.5 deg., the uniformity of the luminance as the surface light source element of the liquid crystal display device is impaired. Preferably, the average angle of inclination is in a range of 1 to 6 deg. and further preferably a range of 2 to 5 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a notebook computer,
Liquid crystal display devices used for liquid crystal televisions, etc., display devices such as guide signs and large signs at stations and public facilities, and display devices such as various traffic signs and traffic signs on expressways and general roads. The present invention relates to a surface light source element and a light guide used for the surface light source element, and more specifically, has a high luminance, and does not perform a uniform process such as a speckle pattern on a light emitting surface. The present invention relates to a surface light source element light guide and a surface light source element capable of obtaining a uniform luminance distribution.

[0002]

2. Description of the Related Art In recent years, color liquid crystal display devices have been widely used in various fields such as notebook personal computers, liquid crystal televisions, and video liquid crystal televisions. This liquid crystal display device basically includes a backlight unit and a liquid crystal display element unit. As the backlight unit, there are a direct type in which a light source is provided directly below a liquid crystal display element and an edge light type in which a light source is provided on a side surface of a light guide. I have. The edge light method is a backlight of a method in which a light source is arranged on a side surface of a plate-shaped light guide to emit light on the entire surface of the light guide, and is a so-called surface light source element.

In such a surface light source element, a plate-shaped transparent material such as an acrylic resin plate is used as a light guide, and light from a light source disposed at one end of the light guide is made to enter the light guide from a light incident surface. By providing a light emitting function such as a light scattering portion formed on the front surface (light emitting surface) or the rear surface of the light guide, the light thus emitted is emitted from the light emitting surface in a planar manner. However, when the light emitting function is formed uniformly on the front surface or the back surface of the light guide, the brightness of the emitted light decreases as the distance from the light source increases, and the brightness within the light emitting surface becomes non-uniform. It could not be obtained. This trend is
It became remarkable with the enlargement of the liquid crystal display element, and was not practically usable in a large liquid crystal display device of 10 inches or more. In particular, with the recent enlargement of the LCD screen,
2. Description of the Related Art In a liquid crystal display device used for a notebook computer, a liquid crystal television, or the like, a very high uniformity of luminance distribution in a screen is required.

In display devices such as guide sign boards and large signboards, and traffic display devices such as guide signs and traffic signs on expressways and general roads, internal lighting is used to enhance nighttime visibility and legibility. Two illumination systems, a system and an external illumination system, have been adopted. In the internal lighting method, characters, figures, photographs, etc. are formed on a translucent plastic plate such as a methacryl plate by cutting or printing to form a display plate, and a light source serving as a backlight is arranged inside the display plate. The display panel is illuminated by a light source, and a straight tube or ring-shaped fluorescent lamp is generally used as the light source.
In the external illumination system, a light source is disposed above, below, or on the front side of a display panel on which display contents are formed, and the light source illuminates the entire surface of the display panel. Tube-shaped fluorescent lamps are commonly used.

In such a display device, the luminance distribution over the entire surface of the display panel, that is, the maximum / minimum luminance value becomes very large. In such a method, uniform brightness with a small luminance distribution is obtained. It is difficult to obtain a display device having the same. This tendency was particularly remarkable in the external lighting system. In addition, the internal lighting system has a problem that a see-through phenomenon in which a fluorescent lamp or the like used as a light source can be seen through a signboard easily occurs.
Therefore, in these display devices, an attempt is being made to adopt an edge-light type backlight that arranges a light source on the side surface of a plate-shaped light guide and emits light over the entire surface of the light guide. However, such a display device requires a large surface light source element, and has a problem in that sufficient uniformity of luminance on the light emitting surface cannot be achieved similarly to the liquid crystal display device.

Various proposals have been made in order to solve the problem of non-uniform brightness of the surface light source element. For example, JP-A-1-24522 discloses a surface light source element having a light emitting function in which a light diffusing substance is densely applied or adhered to a back surface opposite to a light emitting surface of a light guide as the distance from the light incident surface increases. Has been proposed. Further, Japanese Patent Laid-Open No.
Japanese Patent Publication No. 107406 proposes that a light guide is formed by laminating a plurality of transparent plates on the surface of which fine spots made of a light scattering substance are formed in various patterns. In such a surface light source element, since a white pigment such as titanium oxide or barium sulfate is used as a light scattering substance, loss of light such as light absorption occurs when light hitting the light scattering substance is scattered. This is not preferable because it causes a decrease in the luminance of the emitted light.

Further, Japanese Patent Application Laid-Open Nos. 1-244490 and 1-252933 disclose an output light adjusting member and a light adjusting member having a light reflection pattern corresponding to the reciprocal of the output light distribution on the light output surface of the light guide. A surface light source element having a diffusion plate has been proposed. However, even in such a surface light source element,
Since the light reflected by the emission light adjusting member and the light diffusion plate cannot be reused, light loss occurs, and the luminance of the emission light is reduced. Further, JP-A Nos. 2-17 and 2-84618 disclose that a light emitting surface of a light guide and at least one of a back surface thereof have a matte surface, or that a large number of lens units are formed. In addition, a surface light source element in which a prism sheet is mounted on a light emitting surface has been proposed.
However, although such a surface light source element can obtain very high luminance, it has not been satisfactory in terms of uniformity on a light emitting surface.

[0008]

On the other hand, a surface light source element which increases the luminance by reducing the light loss while making the luminance of the outgoing light uniform, as disclosed in Japanese Patent Application Laid-Open No. 6-18879, has been proposed. While forming a large number of lens units on the light exit surface of the light guide, and forming a matte surface, a rough surface portion and a smooth portion are formed on the back surface so that the ratio of the rough surface portion increases as the distance from the light source increases. A surface light source element in which a prism sheet is mounted on a light exit surface has been proposed.
However, such a surface light source element can achieve uniform brightness of emitted light and reduce light loss, but when used as a display device such as a liquid crystal display device, a light guide through a liquid crystal display element or a display plate. The pattern formed by the rough surface portion and the smooth portion formed on the back surface was observed, which hindered the image observation. Also, providing a uniform light emitting function to the light guide surface is not preferable from the viewpoint of productivity of the light guide. Therefore, the present invention provides a light guide for a surface light source element and a surface light source element which have high luminance and can obtain high uniformity of luminance on a light emitting surface without performing a uniform processing of a spot pattern or the like. The purpose is to do.

[0009]

That is, in the light guide for a surface light source element of the present invention, at least one side end surface of the transparent substrate is a light incident surface, and one surface substantially orthogonal to the light incident surface is a light incident surface. In the light guide serving as an emission surface, at least one of the light emission surface and the back surface extends in a direction parallel to the light incidence surface, and has a large number of inclined surfaces having an average inclination angle of 0.5 to 7.5 °. And a lens array of Further, the surface light source element of the present invention, a light source, at least one side end surface facing the light source is a light incident surface,
The light guide includes a light guide having one surface substantially orthogonal to the light incident surface as a light exit surface, and at least one of the light exit surface and the back surface of the light guide extends in a direction parallel to the light incident surface. ,
It is characterized by comprising a large number of lens rows each having an inclined surface having an average inclination angle of 0.5 to 7.5 °.

According to the present invention, at least one of the light exit surface and the rear surface of the light guide extends in a direction parallel to the light incident surface and has an average inclination angle of 0.5 to 7.5 °. By forming a large number of lens rows composed of inclined surfaces, it is possible to reduce the emission rate of light emitted from the light emission surface of the light guide, thereby reducing light propagating in the light guide toward the tip. In many cases, high uniformity of luminance in the light emission surface can be obtained without performing a uniform processing such as a speckle pattern.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A light guide for a surface light source element according to the present invention comprises:
It is composed of a transparent substrate having at least one side end surface as a light incident surface and one surface substantially orthogonal to the light incident surface as a light emitting surface. In such a light guide, the light incident on the light guide propagates through the light guide by repeatedly reflecting light having a distribution within the critical angle on the surface of the light guide. When a rough surface portion is formed on the surface of the light guide, light exceeding the critical angle with respect to the rough surface out of the light reaching the rough surface portion is refracted and emitted out of the light guide, and the critical angle The light within is reflected and propagates through the light guide. This is because the traveling direction of light is determined by the refractive index of the medium and the angle of incidence of the light with respect to the normal to the incident surface according to Snell's law.

FIG. 1 schematically shows refraction and reflection of light on the surface of a light guide having an uneven shape. The light A incident on the slope of the uneven portion at an incident angle i exceeding the critical angle is out of the light guide at an output angle i 'that satisfies the relationship of nsini = sini' (n is the refractive index of the light guide) according to Snell's law. Out. On the other hand, light B incident at an incident angle k that is within the critical angle is
The light is reflected at an angle k ′ (k ′ = k) and propagates in the light guide.
The light once incident on the concave and convex portions and reflected therefrom has a sharp incident angle when subsequently entering the concave and convex portions, so that the light easily exceeds the critical angle and is easily emitted out of the light guide.

The inventors of the present invention have found that the relationship between the light output intensity (I) at a certain point and the output light intensity (I ₀ ) at the end of the light incident surface in the light guide for a surface light source element is expressed by (Α), the distance (L ′) from the end of the light exit surface, and the thickness (t) of the light guide were experimentally found to be expressed by the following equation (1).

[0014]

I = I ₀ (1−α) ^{L ′ / 20t} (1) If the length (L) and the thickness (t) of the light guide are determined from the equation (1), the light is emitted. It can be seen that the uniformity of luminance in the light emitting surface is determined by the rate (α). The emission ratio (α) of the light guide having a thickness of tmm is 20 m from the light incident surface end of the light guide.
The luminance was measured at intervals of m, and from the graph of the distance (l) from the light incident surface end and the logarithm of the luminance, the gradient (K (mm)
^-1 )) is obtained by the following equation (2).

[0015]

Α = (1−10 ^{20 K} ) × 100 (2) In the present invention, a degree of variation (R%) represented by the following equation (3) is used as a measure of luminance uniformity. Then, the uniformity of luminance in the light guide for the surface light source element was evaluated and examined. For the degree of variation (R%), the luminance was measured at intervals of 20 mm in a range from a point 5 mm away from the end of the light incident surface to the opposite end in the approximate center of the light guide, and the maximum value of the measured luminance (I _max ), the minimum value of the measured luminance (I _min ), and the average value of the measured luminance (I _av ) are obtained by the following equation (3).

[0016]

Equation 3] _{R% = {(I max -I} min) / I av} × 100 ··· (3) As a result, the output rate and (alpha) and variation degree (R%), the length of the light guide It has been found that there is a specific relationship depending on the thickness (L) and the thickness (t). When the emission rate (α) increases, the degree of variation (R%) increases accordingly, and the emission rate (α) increases. ) Is constant, the ratio (L) of the length (L) to the thickness (t) of the light guide is obtained.
/ T) increases, the degree of variation (R%) also increases. That is, in a light guide of a certain size,
Luminance uniformity (degree of variation) within the light exit surface of the light guide
Depends on the emission rate (α) from the light guide,
It can be seen that uniformity of luminance can be achieved by controlling the emission ratio (α).

On the other hand, the present inventors, when forming a large number of lens arrays extending in a direction parallel to the light incident surface on the surface of the light guide, depend on the gradient of the inclined surface forming such a lens array. As a result, they found that the emission direction and the emission rate of the light emitted from the light guide changed. Here, as this gradient, ISO
4287 / 1-1987.
a) can be used. That is, the average inclination angle (θ
When the value of a) increases, the light emitted from the light guide has a smaller emission angle and becomes closer to the normal direction. Also, as the average inclination angle (θa) increases, the emission rate from the light guide increases accordingly. From this, the uniformity of the luminance on the light emission surface of the surface light source element can be increased by lowering the emission rate from the light guide, and the average inclination angle (θ
It has been found that uniformity can be achieved by reducing a). The uniformity of the brightness of the light guide varies depending on the application. However, in a large display device such as a guide sign board, a large signboard, a guide sign or a traffic sign, the degree of variation (R%) is 2%.
It is 50% or less, preferably 200% or less. Further, a surface light source element used in a liquid crystal display device such as a notebook computer or a liquid crystal television is required to have extremely high uniformity, and the degree of variation (R%) is 25% or less, preferably 20% or less. .

In order to make the brightness uniform within the light exit surface of the light guide for a surface light source element, the average inclination angle (at least one of the light exit surface and the back surface of the light guide) is required. θa) It is necessary to form a large number of lens rows each having a slope of 0.5 to 7.5 ° so as to extend in a direction parallel to the light incident surface of the light guide. This is because if the average inclination angle (θa) of the slopes constituting the lens array is less than 0.5 °,
The emission angle of the light emitted from the light emission surface (the angle with respect to the normal line of the light emission surface) becomes large, so that it is not possible to sufficiently direct the emitted light in the normal direction even if a variable angle member such as a prism sheet is used. That's why. Conversely, if the average inclination angle (θa) of the inclined surfaces constituting the lens array exceeds 7.5 °, the uniformity of luminance is impaired as the surface light source element of the liquid crystal display device. Preferably, the average inclination angle (θa) is in the range of 1 to 6 °, and more preferably in the range of 2 to 5 °. A large number of lens arrays each having an inclined surface having an average inclination angle (θa) of 0.5 to 7.5 ° may be formed on the light emitting surface of the light guide from the viewpoint of uniform luminance and high luminance. preferable.

Although the size of the light guide for a surface light source element of the present invention is not particularly limited, the length (L) of the light guide in order to more remarkably exert the effects of the present invention. )
It is preferable to use as a light guide having a ratio (L / t) of 150 or less to the thickness (t). When L / t exceeds 150, even if the average inclination angle (θa) of the light guide is reduced, there is a tendency that uniformity of luminance on the light emission surface cannot be sufficiently achieved. It is in the range of 130 or less, more preferably 80 or less.

In the present invention, as the light guide, a transparent plate made of glass, synthetic resin or the like can be used. As the synthetic resin, for example, an acrylic resin, a polycarbonate resin, various highly transparent synthetic resins such as a vinyl chloride resin can be used, and this resin is extruded by a normal molding method such as injection molding. The light guide can be manufactured by molding into a plate-like body. In particular, methacrylic resin has high light transmittance, heat resistance, mechanical properties,
It has excellent moldability and is optimal as a light guide material. Such a methacrylic resin is a resin containing methyl methacrylate as a main component, and it is preferable that methyl methacrylate is 80% by weight or more. Further, a light diffusing agent, fine particles, or the like may be mixed in the light guide as needed.

As shown in FIG. 3 or FIG. 4, as the number of lens rows formed on the surface of the light guide, a lens row composed of inclined surfaces having an average inclination angle (θa) within the above range can be used. It is not particularly limited, and examples include a lenticular lens array having an arc-shaped cross section, a prism array having a serrated cross section, and a concavo-convex array having a continuous cross section having a waveform. Among them, a prism array and a lenticular lens array whose cross sections are symmetrical are particularly preferable. Also, such a lens row,
The lens rows are formed so as to extend in a direction parallel to the light incident surface of the light guide, and preferably, each lens row is formed continuously in parallel. The pitch of the lens rows is appropriately selected depending on the application, but is usually preferably in the range of 20 μm to 5 mm.

A specific average inclination angle (θ
The processing method for forming a large number of lens rows composed of the inclined surfaces a) is not particularly limited as long as the average inclination angle (θa) falls within a specific range. Using a mold or the like with a lens pattern formed by laser processing, etc., heat-press the transparent substrate, apply active energy ray-curable resin on the transparent substrate, and form and cure by irradiation with active energy rays. Examples thereof include a method of transferring a lens pattern, a method of forming a lens pattern by injection molding, and a method of directly processing a light guide by etching, cutting with a tool, laser processing, or the like.

As shown in FIG. 2, the surface light source element of the present invention has a light source 2 such as a fluorescent lamp arranged at one end of the light guide 1 as described above, and a back surface facing the light emitting surface. The reflective layer 4 is formed by a reflective film or the like. In order to effectively introduce light from the light source 2 to the light guide 1, the light incident surfaces of the light source 2 and the light guide 1 are configured to be covered with a case or film coated with a reflective agent on the inside. Further, as the light guide 1,
Various shapes such as a plate shape, a wedge shape, and a boat shape can be used.

In the surface light source element of the present invention, the emission direction of the light emitted from the light guide 1 is usually shifted from the normal direction, so that the surface light source element is used for the purpose of observing from the normal direction. In this case, it is preferable to take measures such as placing the lens sheet 3 on the light guide 1 to change the angle of the emitted light in the normal direction. In this case, the lens sheet 3 used
Has a lens surface in which a large number of lens units are formed in parallel on at least one surface. As the lens shape to be formed, various shapes are used depending on the purpose, and examples thereof include a prism shape, a lenticular lens shape, and a corrugated shape. The lens unit pitch of the lens sheet 3 is preferably about 20 μm to 5 mm, and when a prism sheet is used, the prism apex angle is appropriately selected according to the emission angle of light emitted from the light guide. Generally, it is preferable to be in the range of 50 to 120 °. Also, regarding the orientation of the prism sheet,
It is appropriately selected according to the emission angle of the light emitted from the light guide, and may be mounted so that the lens surface is on the light guide side, or may be mounted in the opposite direction. When a large number of lens arrays composed of inclined surfaces having an average inclination angle (θa) of 0.5 to 7.5 ° are formed on the light emitting surface of the light guide, the light emitted from the light emitting surface has a normal line. Since the light is emitted at a relatively large angle of about 80 to 60 ° with respect to the prism sheet, the prism surface on which the prism row having the prism apex angle of about 55 to 70 ° is formed has the prism surface on the light emitting surface side of the light guide. With such mounting, the light emitted from the light guide can be deflected in the normal direction, and the luminance in the normal direction can be improved.

The lens sheet 3 of the present invention is preferably manufactured using a material having a high visible light transmittance and a relatively high refractive index. For example, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, Energy ray-curable resins and the like. Among them, an active energy ray-curable resin is preferred from the viewpoints of scratch resistance, handleability, productivity and the like of the lens sheet. If necessary, additives such as an antioxidant, an ultraviolet absorber, a yellowing inhibitor, a bluing agent, a pigment, and a diffusing agent may be added to the lens sheet. As a method for producing the lens sheet, a usual molding method such as extrusion molding and injection molding can be used. When manufacturing a lens sheet using an active energy ray-curable resin, it is made of a transparent resin such as a polyester resin, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, a polymethacrylimide resin, and a polyolefin resin. On a transparent substrate such as a transparent film or sheet,
A lens part is formed of an active energy ray-curable resin. First, an active energy ray-curable resin liquid is injected into a lens mold having a predetermined lens pattern formed thereon, and a transparent substrate is overlaid. Next, an active energy ray such as an ultraviolet ray or an electron beam is irradiated through a transparent base material, and the active energy ray-curable resin liquid is polymerized and cured, and is separated from a lens mold to obtain a lens sheet.

In the surface light source device of the present invention, in addition to the lens sheet as described above, a diffusion sheet, a color filter, a polarizing film, etc., optically change, converge, and diffuse light, and adjust its optical characteristics. Various optical elements that vary can be used. The surface light source element of the present invention is a notebook computer using a liquid crystal display element, a backlight of a color liquid crystal display device such as a liquid crystal television or a video integrated liquid crystal television, or a character such as cutout or printing on a translucent plastic plate. It is suitable as a backlight of a display device such as a guide sign board or a large signboard using a display board formed with figures, photographs, or the like, or a guide sign or a traffic sign on an expressway or a general road.

[0027]

The present invention will be described below in detail with reference to examples. Inverter the cold cathode tube of the measuring light guide luminance (TDK Corp. CXA-
M10L) to connect to a DC power supply, and apply DC 12 V to light up. Place the surface light source element on the measuring table and adjust the measurement distance so that the surface light source element is perpendicular to the center line of the luminance meter (Minolta nt-1 ゜) and the measuring circle has a diameter of 8 to 9 mm. did. Next, after aging the cold cathode tubes for 30 minutes or more, the luminance was measured. The measurement is 20 mm x 20 m except for the 5 mm near the light source.
m, and the brightness of each area was measured by making the center of the measurement circle of the luminance meter coincide with the center of each area, and the average value of these was defined as the brightness in the normal direction. In the case of a large-sized display device, the measurement was performed by turning on a 30 W fluorescent lamp instead of a cold cathode tube.

The degree of variation (R%) was calculated from the measured value of the brightness in each region from the light source side at the center of the surface light source element to the other end face, based on the equation (3). The emission ratio (α) was calculated from the measured value of the luminance in each region from the light source side at the center of the surface light source element to the other end surface based on the equation (2).

Average tilt angle (θa) Determined according to ISO 4287 / 1-1984. Using a stylus type surface roughness meter (Surfcom 570A, manufactured by Tokyo Seiki Co., Ltd.) using E-DT-S04A (1 μmR, 55 ° cone, diamond) as a stylus, the surface roughness of the rough surface was adjusted to a drive speed of 0. It was measured at 03 mm / sec. The inclination is corrected by subtracting the average line from the measured average line, and the following (4)
５ (5)

[0030]

[Number 4] Δa = (1 / L) ∫ 0 L | (d / dx) f (x) | dx ··· (4)

[0031]

[Equation 5] θa = tan ⁻¹ Δa (5) Example 1 A large number of prism rows having a vertical angle of 172 ° and a pitch of 50 μm as shown in FIG. The prism surface was transferred by thermal transfer to one surface of a 4 mm × 210 mm × 165 mm transparent acrylic resin plate using a mold on which the formed prism pattern was formed to obtain a light guide. The average inclination angle of the obtained light guide (θ
a) was 4.2 °. 165 mm of the obtained light guide
PET with silver deposited on the two end faces and the other end face
The film was adhered by adhesive processing, and a PET film on which silver was vapor-deposited was taped to the back surface opposite to the light emission surface serving as the prism surface to form a reflection surface. A cold cathode tube (KC230T4E, 4 mmφ × 230 mm, manufactured by Matsushita Electric Industrial Co., Ltd., 4 mmφ × 230 mm) is wound around a PET film on which silver is deposited on the other end surface of the light guide, and the light guide is installed as a light source lamp. A prism sheet is formed by forming a large number of parallel prism rows with a vertical angle of 63 ° and a pitch of 50 μm using an acrylic ultraviolet curable resin having a refractive index of 1.53 so that the prism surface faces the light emitting surface side of the light guide. To provide a surface light source element. The normal luminance and the degree of variation (R
%) Are shown in Table 1. On the other hand, 3mm x 90mm x
Using a transparent acrylic resin plate of 300 mm, a light guide was produced in the same procedure. A surface light source element was prepared in the same manner as described above, except that a PET film on which silver was vapor-deposited was adhered to two end faces of 90 mm of the obtained light guide, and the obtained film was adhered. The emission ratio was determined and is shown in Table 1.

Example 2 Using a mold having a lens pattern in which a large number of lenticular lens rows having a pitch of 50 μm as shown in FIG. 4 were continuously formed in parallel using a diamond tool on a brass plate, 4 mm × 210 mm × The prism surface was transferred to one surface of a 165 mm transparent acrylic resin plate by thermal transfer to form a light guide. Average tilt angle (θa) of the obtained light guide
Was 4.3 ゜. A silver-evaporated PET film was attached to two end surfaces of 165 mm and the other end surface of the obtained light guide by adhesive processing, and a silver-evaporated PET film was applied to the back surface opposite to the light emission surface which was a prism surface. The tape was fixed to form a reflective surface. A cold cathode tube (KC230T4E, 4 mmφ × 230 mm, manufactured by Matsushita Electric Industrial Co., Ltd., 4 mmφ × 230 mm) is wound around a PET film on which silver is vapor-deposited on the other end surface of the light guide, and the light guide is installed as a light source lamp.
A prism sheet in which a number of prism rows having a vertical angle of 63 ° and a pitch of 50 μm are formed in parallel with an acrylic ultraviolet curable resin having a refractive index of 1.53 on a T film so that the prism surface faces the light emitting surface side of the light guide. To provide a surface light source element.
The normal luminance and the degree of variation (R%) of the obtained surface light source element were determined and are shown in Table 1. On the other hand, 3mm x 90mm x 300
Using a transparent acrylic resin plate having a thickness of 2 mm, a light guide was produced in the same procedure. A surface light source element was prepared in the same manner as described above, except that a PET film on which silver was vapor-deposited was adhered to two end faces of 90 mm of the obtained light guide, and the obtained film was adhered. The emission ratio was determined and is shown in Table 1.

Comparative Examples 1-2 After the surface of a glass plate was subjected to chemical etching by performing a fluorine treatment after being subjected to a sandblast treatment, a thickness of 3 m was obtained using an electroforming mold obtained by taking a replica mold by electroforming.
mx 210mm x 165mm and 4mm x 210mm
The rough surface was transferred by heat transfer to one surface of two types of transparent acrylic resin plates of × 165 mm to obtain a light guide. The average inclination angle (θa) of the obtained light guide was 8.4 °. A silver-deposited PET film was adhered to two end faces of 165 mm and the other end face of the obtained light guide by adhesive processing, and a PET film having silver deposited on the back face opposite to the roughened light emission face was applied. The tape was fixed to form a reflective surface. A cold cathode tube (KC130T4E72, manufactured by Matsushita Electric Co., Ltd., 4 mm) is formed of a PET film on which silver is deposited on the other end surface of the light guide.
(φ × 130 mm) is wound and installed as a light source lamp, and the refractive index of the PET film on the light emitting surface of the light guide is 1.
A surface light source is prepared by placing a prism sheet made of a number of 53 acrylic ultraviolet-curing resins in parallel with a number of prism rows having a vertical angle of 63 ° and a pitch of 50 μm so that the prism surface faces the light exit surface side of the light guide. It was an element. The normal luminance and the degree of variation (R%) of the obtained surface light source element were determined and are shown in Table 1. On the other hand, using a transparent acrylic resin plate of 3 mm × 90 mm × 300 mm, the light guide 1 was produced in the same procedure. PET on which silver was deposited on two 90 mm end faces of the obtained light guide 1
A surface light source device was prepared in the same manner as described above except that the film was adhered by sticking, and the emission ratio of the obtained surface light source device was obtained and shown in Table 1.

COMPARATIVE EXAMPLE 3 Using a diamond tool on a brass plate, using a mold having a prism pattern in which a large number of prism rows having a vertical angle of 164 ° and a pitch of 50 μm were formed in parallel and continuous as shown in FIG. The prism surface was transferred by thermal transfer to one surface of a 4 mm × 210 mm × 165 mm transparent acrylic resin plate to form a light guide. The average inclination angle of the obtained light guide (θ
a) was 8.2%. 165 mm of the obtained light guide
PET with silver deposited on the two end faces and the other end face
The film was adhered by adhesive processing, and a PET film on which silver was vapor-deposited was taped to the back surface opposite to the light emission surface serving as the prism surface to form a reflection surface. A cold cathode tube (KC230T4E, 4 mmφ × 230 mm, manufactured by Matsushita Electric Industrial Co., Ltd., 4 mmφ × 230 mm) is wound around a PET film on which silver is deposited on the other end surface of the light guide, and the light guide is installed as a light source lamp. A prism sheet is formed by forming a large number of parallel prism rows with a vertical angle of 63 ° and a pitch of 50 μm using an acrylic ultraviolet curable resin having a refractive index of 1.53 so that the prism surface faces the light emitting surface side of the light guide. To provide a surface light source element. The normal luminance and the degree of variation (R
%) Are shown in Table 1. On the other hand, 3mm x 90mm x
Using a transparent acrylic resin plate of 300 mm, a light guide was produced in the same procedure. A surface light source element was prepared in the same manner as described above, except that a PET film on which silver was vapor-deposited was adhered to two end faces of 90 mm of the obtained light guide, and the obtained film was adhered. The emission ratio was determined and is shown in Table 1.

COMPARATIVE EXAMPLE 4 Using a mold having a lens pattern in which a large number of lenticular lens rows having a pitch of 50 μm were continuously formed in parallel as shown in FIG. 6 using a diamond tool on a brass plate, 4 mm × 210 mm × The prism surface was transferred to one surface of a 165 mm transparent acrylic resin plate by thermal transfer to form a light guide. Average tilt angle (θa) of the obtained light guide
Was 8.3 ゜. A silver-evaporated PET film was attached to two end surfaces of 165 mm and the other end surface of the obtained light guide by adhesive processing, and a silver-evaporated PET film was applied to the back surface opposite to the light emission surface which was a prism surface. The tape was fixed to form a reflective surface. A cold cathode tube (KC230T4E, 4 mmφ × 230 mm, manufactured by Matsushita Electric Industrial Co., Ltd., 4 mmφ × 230 mm) is wound around a PET film on which silver is vapor-deposited on the other end surface of the light guide, and the light guide is installed as a light source lamp.
A prism sheet in which a number of prism rows having a vertical angle of 63 ° and a pitch of 50 μm are formed in parallel with an acrylic ultraviolet curable resin having a refractive index of 1.53 on a T film so that the prism surface faces the light emitting surface side of the light guide. To provide a surface light source element.
The normal luminance and the degree of variation (R%) of the obtained surface light source element were determined and are shown in Table 1. On the other hand, 3mm x 90mm x 300
Using a transparent acrylic resin plate having a thickness of 2 mm, a light guide was produced in the same procedure. A surface light source element was prepared in the same manner as described above, except that a PET film on which silver was vapor-deposited was adhered to two end faces of 90 mm of the obtained light guide, and the obtained film was adhered. The emission ratio was determined and is shown in Table 1.

[0036]

[Table 1]

As is clear from Table 1, the surface light source devices of Examples 1 to 4 of the present invention have excellent uniformity with a luminance variation (R%) of 20% or less in the light emitting surface. Thus, it was sufficiently practical as a surface light source element for a liquid crystal display device. On the other hand, in the surface light source elements of Comparative Examples 1 to 4, the degree of variation (R%) of the luminance in the light emitting surface exceeds 100%, and the uniformity of the luminance is not sufficiently obtained. Was.

Embodiment 3 Using a diamond tool on a brass plate, using a mold having a prism pattern in which a large number of prism rows having a vertical angle of 172 ° and a pitch of 50 μm are formed in parallel and continuous as shown in FIG. The prism surface was transferred by thermal transfer to one surface of a transparent acrylic resin plate of 10 mm × 600 mm × 1250 mm to form a light guide. The average inclination angle (θa) of the obtained light guide was 4.2 °. 125 of the obtained light guide
The silver-deposited PET film is adhered to the two end surfaces of 0 mm and the other end surface by adhesive processing, and the silver-deposited PET film is taped to the back surface opposite to the light emission surface serving as the prism surface, and the reflection surface is formed. Formed. A 30 W fluorescent lamp (FSL30T6 manufactured by Matsushita Electric Industrial Co., Ltd.) was wound around a PET film on which silver was deposited on the other end surface of the light guide, and the light guide was installed as a light source lamp. A prism sheet made of 1.53 acrylic ultraviolet curable resin and having a large number of parallelly arranged prism rows with a vertical angle of 63 ° and a pitch of 50 μm is placed so that the prism surface faces the light emitting surface side of the light guide. A surface light source element was used. Table 2 shows the normal luminance and the degree of variation (R%) of the obtained surface light source element. On the other hand, 10mm x 600mm x 1250m
Using a transparent acrylic resin plate of m, a light guide was produced in the same procedure. A surface light source element was prepared in the same manner as described above, except that a silver-evaporated PET film was adhered to two end surfaces of 1250 mm of the obtained light guide and adhered.
The emission ratio of the obtained surface light source element was determined and is shown in Table 2.

Example 4 A diamond tool was used for a brass plate, and a mold having a lens pattern in which a large number of lenticular lens rows with a pitch of 50 μm were continuously formed in parallel as shown in FIG. The prism surface was transferred by heat transfer to one surface of a 1250 mm transparent acrylic resin plate to form a light guide. The average inclination angle of the obtained light guide (θ
a) was 4.3%. 1250m of the obtained light guide
silver-evaporated PE on the two end faces and the other end face
A T film was adhered by adhesive processing, and a PET film on which silver was vapor-deposited was taped on the back surface opposite to the light emission surface serving as a prism surface to form a reflection surface. A 30 W fluorescent lamp (FSL30T6 manufactured by Matsushita Electric Industrial Co., Ltd.) was wound around a PET film on which silver was deposited on the other end surface of the light guide, and the light guide was installed as a light source lamp. A prism sheet made of 1.53 acrylic ultraviolet curable resin and having a large number of parallelly arranged prism rows with a vertical angle of 63 ° and a pitch of 50 μm is placed so that the prism surface faces the light emitting surface side of the light guide. A surface light source element was used. The normal luminance and the degree of variation (R%) of the obtained surface light source element were determined, and Table 2 was obtained.
It was shown to. On the other hand, 10 mm x 600 mm x 1250 mm
Using the transparent acrylic resin plate described above, a light guide was produced in the same procedure. A surface light source device was prepared in the same manner as described above, except that a silver-evaporated PET film was adhered to two end surfaces of 1250 mm of the obtained light guide, and the resulting film was adhered to the surface light source device. The emission ratio was determined and is shown in Table 2.

COMPARATIVE EXAMPLE 5 Using a diamond tool on a brass plate, a mold having a prism pattern in which a number of prism rows having a vertical angle of 164 ° and a pitch of 50 μm were formed in parallel and continuous as shown in FIG. The prism surface was transferred by thermal transfer to one surface of a transparent acrylic resin plate of 10 mm × 600 mm × 1250 mm to form a light guide. The average inclination angle (θa) of the obtained light guide was 8.2 °. 125 of the obtained light guide
The silver-deposited PET film is adhered to the two end surfaces of 0 mm and the other end surface by adhesive processing, and the silver-deposited PET film is taped to the back surface opposite to the light emission surface serving as the prism surface, and the reflection surface is formed. Formed. A 30 W fluorescent lamp (FSL30T6 manufactured by Matsushita Electric Industrial Co., Ltd.) was wound around a PET film on which silver was deposited on the other end surface of the light guide, and the light guide was installed as a light source lamp. A prism sheet made of 1.53 acrylic ultraviolet curable resin and having a large number of parallelly arranged prism rows with a vertical angle of 63 ° and a pitch of 50 μm is placed so that the prism surface faces the light emitting surface side of the light guide. A surface light source element was used. Table 2 shows the normal luminance and the degree of variation (R%) of the obtained surface light source element. On the other hand, 10mm x 600mm x 1250m
Using a transparent acrylic resin plate of m, a light guide was produced in the same procedure. A surface light source element was prepared in the same manner as described above, except that a silver-evaporated PET film was adhered to two end surfaces of 1250 mm of the obtained light guide and adhered.
The emission ratio of the obtained surface light source element was determined and is shown in Table 2.

COMPARATIVE EXAMPLE 6 A diamond tool was used for a brass plate, and a mold having a lens pattern in which a large number of lenticular lens rows with a pitch of 50 μm were continuously formed in parallel as shown in FIG. The prism surface was transferred by heat transfer to one surface of a 1250 mm transparent acrylic resin plate to form a light guide. The average inclination angle of the obtained light guide (θ
a) was 8.3 °. 1250m of the obtained light guide
silver-evaporated PE on the two end faces and the other end face
A T film was adhered by adhesive processing, and a PET film on which silver was vapor-deposited was taped on the back surface opposite to the light emission surface serving as a prism surface to form a reflection surface. A 30 W fluorescent lamp (FSL30T6 manufactured by Matsushita Electric Industrial Co., Ltd.) was wound around a PET film on which silver was deposited on the other end surface of the light guide, and the light guide was installed as a light source lamp. A prism sheet made of 1.53 acrylic ultraviolet curable resin and having a large number of parallelly arranged prism rows with a vertical angle of 63 ° and a pitch of 50 μm is placed so that the prism surface faces the light emitting surface side of the light guide. A surface light source element was used. The normal luminance and the degree of variation (R%) of the obtained surface light source element were determined, and Table 2 was obtained.
It was shown to. On the other hand, 10 mm x 600 mm x 1250 mm
Using the transparent acrylic resin plate described above, a light guide was produced in the same procedure. A surface light source device was prepared in the same manner as described above, except that a silver-evaporated PET film was adhered to two end surfaces of 1250 mm of the obtained light guide, and the resulting film was adhered to the surface light source device. The emission ratio was determined and is shown in Table 2.

[0042]

[Table 2]

As is clear from Table 2, the surface light source devices of Examples 3 and 4 of the present invention have excellent uniformity with a luminance variation (R%) in the light emitting surface of 200% or less. Thus, it was sufficiently practicable as a surface light source element for a large display device. On the other hand, in the surface light source devices of Comparative Examples 5 and 6, the degree of variation (R%) of the luminance in the light emitting surface exceeds 600%, and the uniformity of the luminance is not sufficiently obtained. Was.

[0044]

According to the present invention, at least one of the light emitting surface of the light guide and the back surface facing the light emitting surface is constituted by an inclined surface having an average inclination angle (θa) of 0.5 to 7.5 °. By forming a large number of lens rows, it is possible to obtain a high brightness and to obtain a uniform brightness distribution in the light emitting surface without performing uniform processing such as a speckle pattern. The present invention can provide a surface light source element suitable for a display device such as a liquid crystal display device, a signboard, a large signboard, a guide sign or a traffic sign on a highway or a general road.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an optical path of light on a lens surface of a light guide according to the present invention.

FIG. 2 is a partial perspective view showing a surface light source element of the present invention.

FIG. 3 is a partial cross-sectional view illustrating a prism surface of a light guide according to an embodiment.

FIG. 4 is a partial cross-sectional view showing a lenticular lens surface of a light guide according to an example.

FIG. 5 is a partial cross-sectional view illustrating a prism surface of a light guide according to a comparative example.

FIG. 6 is a partial cross-sectional view illustrating a lenticular lens surface of a light guide according to a comparative example.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuko Hayashi 3816 Notobe, Tama-ku, Kawasaki City, Kanagawa Prefecture Mitsubishi Rayon Co., Ltd. Tokyo Technology and Information Center

Claims (5)

[Claims] 1. A light guide in which at least one side end surface of a transparent substrate is a light incident surface and one surface substantially orthogonal to the light incident surface is a light exit surface, at least one of a light exit surface and a back surface thereof. A surface extending in a direction parallel to the light incident surface and comprising a number of lens rows each having an inclined surface having an average inclination angle of 0.5 to 7.5 °. Light body. 2. A light guide for a surface light source device according to claim 1, wherein said lens array is formed of a lenticular lens array having an arc-shaped cross section. 3. The light guide for a surface light source device according to claim 1, wherein said lens array comprises a prism array. 4. A light source and at least one light source facing the light source.
A light guide having one side end surface as a light incident surface and one surface substantially orthogonal to the light incident surface as a light exit surface, wherein at least one of the light exit surface of the light guide and the back surface thereof is It extends in a direction parallel to the light incident surface, and has an average inclination angle of 0.5 to 7.
A surface light source element comprising a large number of lens rows each having a slope of 5 °. 5. The surface according to claim 4, wherein a prism sheet having a large number of prism rows formed in parallel on at least one surface is disposed on the light emitting surface side of the light guide. Light source element.