JPH0915426A - Light guiding plate and surface type lighting body using the light guiding plate - Google Patents

Abstract

PURPOSE: To reduce a cost by projectingly providing the string of projected lines which are perpendicular or inclined with respect to a light incoming end surface on the light outgoing surface of a light guiding plate and guiding the light guided in the light guiding plate to the back of the light guiding plate. CONSTITUTION: Contour lines of apex parts 9 of projected lines 8 formed in a light outgoing surface S2 are made to be circular arcs and the ratio of the height of the contour part of projected line 8 to the height of the residual part is made to be 15%, the pitch of projected lines 8 is made to be 250μm and the apex angle (θ) of the projected line 8 is made to be 90 degrees. Liminous distribution is made uniform by providing white printed dots 6 which are made fine or dense so as to become denser with the going farther from a light incoming end surface S1 on a reflection surface S3. A back light device A is formed by arranging a light source 2 along the light incoming end surface S1 being one end of a light guiding plate 1, by arranging a reflector at the backward of the light source, by providing one sheet of a directivity sheet so that grooves 12 become almost parallel to the light incoming end surface S1 on the light outgoing surface S2 and also by arranging a diffusion sheet 3b and by arranging a reflection sheet 4 and an end surface reflection tape 5 along the reflection surface S3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge light type light guide plate and an improvement of a surface illumination body using the light guide plate.

[0002]

2. Description of the Related Art This type of light guide plate (1) is a light emitting surface (S2) with a large area that scatters light from a cold cathode tube which is a light source (2) arranged along a light incident end surface (S1). It is widely used as a surface light source of a planar lighting body (B) that uniformly illuminates a wide display surface, and is widely used as a backlight device for liquid crystal display devices in recent years as well as for displaying advertising lights, etc. It is used.

The above-mentioned conventional edge light type light guide plate
(1) is acrylic resin flat plate or wedge type (single lamp type) to V
Type (two-lamp type) is used, white dots (6) are printed on the reflecting surface (S3) or grain is formed, and the reflecting sheet (4) is formed along the reflecting surface (S3). ) Is provided, and the diffusion sheet (3b) and the two directional sheets (3a1) and (3a2) are provided so as to overlap each other on the flat light emitting surface (S2) side. On the directional sheets (3a1) (3a2), a plurality of groove rows (11) (12) each having an inverted V-shaped cross section are formed in parallel.
On the other hand, in the directional sheet (3a1), the groove array (11) has a light-incident end surface.
Perpendicular to (S1), to which the other directional sheet (3a2)
The groove array (12) was arranged so as to be parallel to the light incident end surface (S1), and thereby high brightness was achieved. The light source
A reflector (7) is installed behind the (2),
An end face reflection tape (5) is provided on the light reflection end face (S4) << including the side surface portion of the light guide plate (1) >> of (1).

As described above, the directional sheets (3a1) and (3a2) have a large number of fine groove rows (1) whose cross sections are inverted V-shaped.
1) and (12) are formed in parallel innumerably, and the pitch of the groove rows (11) and (12) is preferably 40 μm or less, and the apex angle portion of 100 μm or more is a cathode tube.
It becomes a bright line that is perpendicular to and horizontal to (2) and appears on the light exit surface (S2), and cannot be used as a light guide plate (1). In addition, the production of the mold for forming the directional sheets (3a1) (3a2) having a fine groove array (11) (12) with a pitch of 40 μm or less requires high technology and is expensive. However, the groove array of the mold for forming the minute groove arrays (11) and (12) is very easily damaged, and its management is very difficult. Therefore, the directional sheet (3a1) (3a2) that is the product becomes momentum and expensive,
It was one of the factors that increased the manufacturing cost. Also, light guide plate
The size of (1) is also large and small, and it is not possible to prepare many types of directional sheets (3a1) and (3a2) according to the size of the light guide plate (1). Preformed, light guide plate
The technique of cutting according to the size of (1) is used.

[0005]

However, user demands for cost reduction are becoming more and more severe, and in order to meet this demand, it is possible to reduce expensive directional sheets and roughen the pitch. It is a problem to be solved by the present invention to improve the above.

[0006]

A light guide plate (1) according to claim 1 "scatters light incident from a light source (2) disposed on a light incident end surface (S1) and emits the light (S2). Light guide plate that emits light from (1)
The ridge (8) is projected on the light output surface (S2), and the contour line (9a) of the cross section at the apex angle portion (9) of the ridge (8) is formed in a curved shape and The ridges (8) are at right angles or inclined with respect to the light incident end surface (S1). "

On the light exit surface (S2), the ridges (8) formed at right angles to the light entrance end surface (S1) or in the inclined direction are light guide plates.
(1) A function of guiding the light introduced into the inside of the light guide plate (1) and a part of the light emitted from the light exit surface (S2) after being reflected and scattered inside the light guide plate (1), the light incident end surface (S1) ) Has a function of converging the light output angle distribution in the direction parallel to the light output surface (S2) in the direction perpendicular to the
This ridge (8) is a conventional directional sheet (3a1) installed such that the groove array (11) is perpendicular to the light-incident end surface (S1).
This directional sheet (3a1) can be omitted, and the other directional sheet (3a2) `` The groove array (12) of this directional sheet (3a2) is It is installed so that it is almost parallel to S1). " As a result, two directional sheets (3a1) and (3a2), which were required in the past, can be replaced by one sheet (3a2), which enables a significant cost reduction. Furthermore, since the contour line (9a) of the cross section at the apex angle portion (9) of the ridge (8) is formed in a curved shape, excessive light collection at the apex angle portion (9) is mitigated. Light is diffused over the entire corner portion (9), and the development of bright lines is suppressed. Therefore, the pitch of the ridges (8) can be made coarser, which facilitates die production and leads to cost reduction.

<Claim 2> is “the light guide plate according to claim 1.
In (1), the contour line (9a) of the cross section at the apex angle portion (9) of the ridge (8) is formed by an arc or a sine function, a parabola, an ellipse, or a part of an error function. '<Claim3> means “In the light guide plate according to claim 1 or 2, the apex angle (θ) of the ridge (8) << = the slopes (10) on both sides of the ridge (8)
It is the intersection angle of the virtual extension lines in (10), and is referred to below simply as the apex angle.
0 ° to 150 °, the included angle between the ridge (8) and the light incident end surface (S1) is 70 ° to 90 °, and the pitch between the ridges (8) is 10 °.
μm to 600 μm ”. Here, since the contour line (9a) of the cross section at the apex angle portion (9) of the ridge (8) is configured by a circular arc or a sine function, a parabola, an ellipse, or a part of the error function, the ridge (8 Even if the pitch between)) is 100 μm or more, the bright line does not appear, and the die manufacturing cost can be reduced. The valleys (9b) between the ridges (8) are V-shaped.

The light guide plate (1) of claim 4 is the "light emitting surface (S2)"
On the reflection surface (S3) located on the opposite side of, the white printing dots (6) or uneven wrinkles are formed so that the density thereof gradually increases as the distance from the light incident end surface (S1) increases, and on the light emitting surface (S2). The light guide plate (1) of claim 5 is characterized in that "a light diffuser is added to the conductor and the light introduced into the conductor is scattered in the conductor". To make the luminance distribution on the light emitting surface (S2) uniform ”.

The surface type illuminating body (A) of <Claim 6> includes the light guide plate (1) according to any one of claims 1 to 5, and the light guide plate (1).
Of the light source (2) disposed along the light incident end surface (S1) provided at at least one end of the light source (2) and the light source (2) disposed behind the light source (2). The reflector (7) for focusing light on the end face (S1), the diffusion sheet (3b) and the groove array (12) arranged on the light exit surface (S2) of the light guide plate (1) as necessary One directional sheet (3a2) installed substantially parallel to the light end face (S1) and along the reflecting surface (S3) on the opposite side to the light emitting surface (S2) of the light guide plate (1) Reflective sheet (4) to be arranged and light guide plate
It is composed of the end face reflection tape (5) arranged on the light reflection end face (S4) of (1).

When the light guide plate (1) of the present invention is used, not only can the conventional directional sheet (3a1) be omitted,
The pitch of the ridges (8) formed on the light exit surface (S2) of the light guide plate (1) can be made coarse, and the surface lighting body (A) such as a backlight device can be manufactured by reducing the die manufacturing cost. We were able to significantly reduce manufacturing costs.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. First, various examples of the light guide plate (1) used in the present invention and a planar illuminator (A) using the light guide plate (1) will be described. As shown in FIGS. 1 and 2, the first embodiment of the light guide plate (1) is formed in a wedge shape, the reflective surface (S3) is provided with white printed dots (6) or grain, and the light emitting surface (6) is further provided. This is an example in which the rows of the ridges (8) are formed at S2) at right angles or inclines with respect to the light incident end surface (S1). The vertical angle of the ridge (8) is 30 ° ~
150 ° (preferably 50 ° to 110 °), the included angle n between the ridge (8) and the light incident end surface (S1) is 70 ° to 90 °, and the pitch between the ridges (8) is It is 10 μm to 600 μm. The contour line (9a) of the cross section at the apex angle portion (9) of the ridge (8) is formed in a curved shape, and the curve is represented by, for example, an arc or a sine function, a parabola or an error function, and a part of an ellipse. It
From the standpoint of ease of mold making, a circular arc is preferable, but from the viewpoint of light converging ability, a sine function, parabola, ellipse or error function is preferable.

Next, the height (a) of the contour portion of the cross section at the apex angle portion (9) of the ridge (8) << = the height from the intersection of the contour line (9a) and the slope (10) to the apex , And the height (b) from the intersection of the contour line (9a) and the slope (10) to the valley (9b) will be described with reference to FIG. An appropriate value is selected for the ratio of the height (a) to the height (b) depending on the performance required of the light guide plate (1). That is, height
As the ratio of (a) increases, the light diffusivity increases and conversely the light condensing property decreases. Therefore, it becomes difficult for a bright line to appear in the apex angle portion (9) of the ridge (8), resulting in a soft surface type illumination body (A).
Therefore, the pitch (P) between the ridges (8) can be made coarse, and 1
Even if the thickness is 00 μm or more, no bright line may appear.
Conversely, if the height (a) is made smaller and the height (b) ratio is made larger, the appearance of bright lines becomes easier, and the pitch (P) between the ridges (8) must be made tight and the die cost Therefore, the relationship between both (a) and (b) is determined by the required performance. Generally speaking, the height (a) is small when high brightness is required, and the height (a) is important when reducing die manufacturing cost is important.
And the pitch (P) of the ridges (8) are increased. In addition, the slope (10) and the apex (9) that make up the ridge (8)
The curved surface of is processed into an optical mirror surface.

As shown in FIG. 1, the wedge-shaped light guide plate (1) has a wide light entrance end surface (S1), and a narrow light reflection end surface (S4) opposite to the light entrance end surface (S1). It is formed on both ends (S
1) The reflecting surface (S3) is formed so as to be inclined with respect to the light emitting surface (S2) between (S4), and its cross section is formed to have a wedge shape. (Note that the light-incident end surface of the light guide plate (1) (S
The side surface between 1) and the light-reflecting end surface (S4) also reflects light here, so it is shown as (S4), but the end surface reflection tape (5) does not necessarily have to be provided on the side surface portion. ) In this embodiment, the light exit surface (S2) is perpendicular to the light entrance end surface (S1), and the reflection surface (S3) is inclined with respect to the light entrance end surface (S1). However, conversely, the light exit surface (S2) is the light entrance end surface (S1).
It is needless to say that the reflecting surface (S3) may be inclined with respect to the light incident end surface (S1) at a right angle. As a material, an acrylic plate having excellent light transmission is generally used.

A cold cathode tube which serves as a light source (2) is arranged along the light incident end surface (S1) of the wedge-shaped light guide plate (1). Behind the cold cathode tube (2), a reflector (7) formed in a concave surface is generally installed. Furthermore, a reflection sheet (4) is installed on the lower side of the reflecting surface (S3) of the wedge-shaped light guide plate (1).
On top of 2), one directional sheet (3a2) and, if necessary, one scattering sheet (3b) are installed. Directional sheet
A large number of groove rows (12) are formed in parallel in (3a2), and the groove rows (12) are installed so as to be parallel or slightly inclined to the light incident end surface (S1) of the wedge-shaped light guide plate (1). It That is, generally, the ridge (8) formed on the light exit surface (S2) of the wedge-shaped light guide plate (1) is the light entrance end surface.
When it is perpendicular to (S1), in order to prevent the occurrence of the moire phenomenon, the directional sheet (3a2) has its groove row (12) with respect to the light incident end surface (S1) of the wedge-shaped light guide plate (1). When the convex stripes (8) formed on the light exit surface (S2) of the wedge-shaped light guide plate (1) are arranged so as to be slightly inclined, and are formed to be inclined with respect to the light incident end surface (S1). The directional sheet (3a2) is arranged such that its groove array (12) is parallel to the light incident end surface (S1) of the wedge-shaped light guide plate (1). Of course, when the ridge (8) is perpendicular to the light incident end surface (S1), the groove array (12) of the directional sheet (3a2) becomes parallel to the light incident end surface (S1) of the wedge-shaped light guide plate (1). Or the ridges (8)
The groove array (12) may be arranged so as to be inclined with respect to the light incident end surface (S1) of the wedge-shaped light guide plate (1) when inclined with respect to 1).

A part of the light emitted from the light source (2) is part of the light incident end surface (S
The light is directly incident on 1), and the rest is reflected by the reflector (7) and incident. The incident light travels straight in the wedge-shaped light guide plate (1), and most of the light is reflected by the reflection surface (S3) or the reflection sheet (4), its course is changed, and countless reflections are repeated. Most of the light is emitted from the light emitting surface (S2). Part of the light that is incident substantially parallel to the light emitting surface (S2) or the reflecting surface (S3) is reflected on the reflecting surface (S3).
It is reflected by the end face reflection tape (5) arranged on the light reflection end face (S4) without being reflected by the light reflection end face (S1), and is reflected again by the reflector (7). The course has changed, and the light is finally coming out.

Here, since the ridge (8) is formed so as to be inclined at a right angle or at an included angle n (70 ° to 90 °) with respect to the light incident end surface (S1), the ridge (8) is formed. The light introduced into the light guide plate (1) is guided to the back of the light guide plate (1), and the light reflection end surface
Reach (S4). At the same time, of the light emitted from the light exit surface (S2), the light exit angle distribution in the direction parallel to the light entrance end surface (S1) is displayed.
Focus in a direction perpendicular to (S2). Here, since the contour line (9a) of the cross section in the apex angle portion (9) of the ridge (8) is formed in a curved shape, excessive light collection to the apex angle portion (9) is mitigated. Light diffuses over the entire apex (9), the development of bright lines is suppressed,
Therefore, the pitch of the ridges (8) can be made coarser.

Subsequently, since the groove array (12) of the directional sheet (3a2) installed on the ridge (8) is installed so as to be substantially parallel to the light incident end surface (S1). , Here, the light output angle distribution in the direction perpendicular to the light incident end surface (S1) is condensed in the direction perpendicular to the light output surface (S2). As a result, the directional sheet (3
The exit angle distribution of the light passing through a2) will be focused on the optical axis perpendicular to the exit surface (S2). If this condensed light is too sharp, place a diffusion sheet on the directional sheet (3a2).
(3b) is installed, and the diffusion sheet (3b) diffuses light uniformly, and as a result, light is emitted uniformly and with high brightness over the entire light emitting surface (S2). In the case where the contour line of the cross section at the apex portion of the groove array (12) of the directional sheet (3a2) is formed in a curved shape, excessive light condensing to the apex portion is alleviated here as well, and the entire apex portion is relieved. The light is diffused and the development of the bright line is suppressed, the degree of light collection is reduced, and the diffusion sheet (3b) can be omitted.

In the above, the case where the light guide plate (1) is wedge-shaped has been described as an example, but of course, the present invention is not limited to this, and a one-lamp parallel plate type (not shown) or a two-lamp parallel plate type is used. Various things such as a thing (not shown) or a two-lamp type V type as shown in FIG. 5 are also included. Further, the material of the light guide plate (1) is preferably an acrylic plate as described above, but is not limited to this, of course,
Any material may be used as long as it has excellent light transmittance. Further, in the above, the case where the light guide plate (1) is transparent is taken as an example, but it is needless to say that the present invention is not limited to this, and may be an in-conductor diffuser plate in which fine particles are diffused.

(Embodiment 1) In a single-lamp wedge-shaped light guide plate (1) having an area of 9.4 ", a ridge (8) formed on its light emitting surface (S2).
The contour line (9a) of the apex angle portion (9) is a circular arc, and the ratio of the height (a) of the contour portion of the ridge (8) to the remaining height (b) is 15
%, The pitch (P) of the ridge (8) is 250 μm, the apex angle of the ridge (8)
(θ) was set to 90 °. White dots printed on the reflective surface (S3) with a density that increases with distance from the light-incident end surface.
(6) is provided to make the brightness distribution uniform. This light guide plate (1)
Light source (2) along the light incident end surface (S1) provided at one end of
And a reflector (7) on the back of the light source (2), and the groove array (12) on the light exit surface (S2) of the light guide plate (1) is the light entrance end surface.
A sheet of directional sheet << Mitsubishi Rayon Corp. apex angle 68 ° >> (3a2) is installed so that it is almost parallel to (S1), and a diffusion sheet (3b) is placed on top of it, and reflection is performed. The reflection sheet (4) is arranged along the surface (S3), the end face reflection tape (5) << Rivik tape (product name) >> is arranged on the light reflection end face (S4), and the backlight unit (A) is installed. Formed. When the luminance performance of the backlight device (A) thus formed was measured, the average luminance was 1,670 cd / m ² . In addition, the row of the ridges (8) is inclined with respect to the light incident end surface (S1) (= the ridge (8) and the light incident end surface.
The included angle with (S1) is 80 °, and the pitch (P) of the ridges (8)
Was 250 μm, but no bright line was observed, and the surface type illuminator (A) with soft light was obtained.

[0021]

As described above, since the light emitting surface of the light guide plate of the present invention is provided with a row of ridges projecting at right angles or inclined with respect to the light incident end face, it is introduced into the light guide plate. The reflected light will be guided to the back of the light guide plate, and it is possible to omit the conventional directional sheet for laying the lower side, which is installed so that the groove rows are in a direction perpendicular to the light incident end surface. , Other directional sheet "The groove array of this directional sheet is installed so that it is almost parallel to the light-incident end face", and it is possible to reduce the cost significantly. Further, since the contour line of the cross section at the apex angle portion of the ridge is formed in a curved shape, excessive light condensing at the apex angle portion is alleviated, light is diffused over the entire apex angle portion, and a bright line is expressed. As a result, the pitch of the ridges can be made coarser, which facilitates die manufacturing and leads to cost reduction.

[Brief description of the drawings]

FIG. 1 is a perspective view of a first embodiment of a planar lighting body according to the present invention.

FIG. 2 is a schematic sectional view of FIG.

FIG. 3 is a plan view of FIG. 1;

FIG. 4 is an enlarged perspective view of a ridge portion of FIG.

FIG. 5 is a perspective view of a second embodiment of the planar illuminator according to the present invention.

FIG. 6 is a perspective view of a conventional example.

[Explanation of symbols]

 (1)… Light guide plate (2)… Light source (6)… White dot (8)… Convex ridge (9)… Vertical corner (9a)… Contour line (S1)… Incoming end face (S2)… Emitting face ( S3) ... Reflecting surface (S4) ... Light reflecting end surface

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[Procedure amendment]

[Submission date] May 29, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

Title: Light guide plate and planar illuminator using the light guide plate

Claims (6)

[Claims] 1. A light guide plate which scatters light incident from a light source disposed on a light incident end surface and emits the light from the light emitting surface, wherein a convex stripe is provided on the light outgoing surface. 2. The light guide plate, wherein the contour line of the cross section at the apex angle portion is formed in a curved shape, and the convex line is orthogonal or inclined to the light incident end face. 2. The light guide plate according to claim 1, wherein the contour line of the cross section at the apex angle portion of the ridge is formed by an arc or a sine function, a parabola, an ellipse, or a part of an error function. And a light guide plate. 3. The light guide plate according to claim 1, wherein the convex line has an apex angle of 30 ° to 150 °, and the angle between the convex line and the light incident end face is 70 ° to 90 °. The pitch between the ridges is 1
A light guide plate having a thickness of 0 μm to 600 μm. 4. A white printed dot or uneven wrinkles are formed on the reflecting surface located on the opposite side of the light exit surface so that the density thereof gradually increases as the distance from the light entrance end surface increases, and the brightness distribution on the light exit surface is made uniform. Claim 1 characterized by the fact that
3. The light guide plate described in any one of 3. 5. The light diffusing agent is added to the conductor to diffuse the light in the conductor to make the luminance distribution on the light emitting surface uniform. Light guide plate. 6. The light guide plate according to claim 1, a light source arranged along a light incident end face provided at at least one end of the light guide plate, and a light source arranged behind the light source. A reflector that is provided to collect the light from the light source on the light incident end surface, a diffusion sheet that is arranged on the light exit surface of the light guide plate as necessary, and its groove array are substantially parallel to the light incident end surface. One directional sheet installed on the light guide plate, a reflection sheet arranged along the reflection surface opposite to the light exit surface of the light guide plate, and an end face reflection tape arranged on the light reflection end surface of the light guide plate. A planar lighting body characterized by being composed of and.