JP4572743B2 - Refractive light collector for backlight - Google Patents

Description

  The present invention relates to a refractive condensing plate for aligning the direction of light emitted from a light source of a backlight.

  Conventionally, in an illuminating device as a backlight of a liquid crystal display device as described in Patent Document 1, between a light source (LED light source) and an incident surface of a light guide that illuminates a liquid crystal display panel from its back surface, A refracting light collecting plate having a Fresnel lens-like refracting surface is arranged, and by this refracting light collecting plate, two-dimensional radiation light emitted radially from a light source (one that is not parallel light in two intersecting planes, for example, a plane There is a light that is refracted and collected as incident light and incident on the incident surface of the light guide.

  In the illuminating device, although the two-dimensional radiation emitted from the light source is aligned parallel to the horizontal width direction by the Fresnel lens-shaped refracting surface of the refractive condensing plate, it is not aligned parallel to the vertical direction.

For this reason, a sufficient light collecting effect cannot be obtained, and the light emission loss is large.
JP 2002-289023 A

  Accordingly, the present invention provides a refracting light concentrating plate for a backlight that can obtain a sufficient light condensing effect by aligning two-dimensional emitted light emitted from a light source in parallel in both the horizontal width direction and the vertical direction. This is the issue.

In order to solve the above problems, the following means (1) to (3) are adopted.
(1) The refracting light concentrating plate for backlight according to the present invention is a combination of a first lens unit 1 for controlling incident light in the vertical direction and a second lens unit 2 for controlling incident light in the lateral width direction. It is said.
And a first concentric axial plane that passes through the central axis, the refractive concentrating plate for aligning the direction of the two-dimensional radiation emitted from the light source with flat emission to the central axis in the thickness direction passing through the center of the light source. A Fresnel lens-shaped first lens portion for converging incident light, and a Fresnel lens-shaped for converging incident light with respect to the second central axis surface intersecting the first central axis surface and the central axis . and a second lens unit, respectively incident light side, and Ri Na in combination the exit light side,
Lens apex angles of the first lens unit and the second lens unit according to the incident angle of the emitted light from the light source viewed on the first central axis surface and the incident angle viewed on the second central axis surface Are set so that the conditions for the outgoing light to converge toward the first central axis surface and the second central axis surface are satisfied.

(2) Further, the refractive light collecting plate for backlight is
When viewed on each of the first central axis plane and the second central axis plane that intersect at the central axis, the maximum inclination angle of the incident light of the two-dimensional radiation to the refractive light collector is different on each plane,
By providing a first lens portion having a lens apex angle θ _{1 and} a second lens portion having a lens apex angle θ ₂ respectively represented by the following equations corresponding to the different incident light angles θ _L1 and θ _L2 , The refractive condensing plate for a backlight according to claim 1, wherein the two-dimensional radiation is converged on each surface.
θ _L1 <sin ⁻¹ (n × sin θ ₁ )
θ _L2 <sin ⁻¹ (n × sin (θ ₂ −sin ⁻¹ (sin θ ₂ / n)))

(3) In addition, any one of the refractive light concentrating plates for backlight is
The light source comprises a horizontally long flat transparent resin having a predetermined width W and a predetermined height H in which the LED chip is embedded at the position of the depth D, and the emission angle of the two-dimensional emitted light in the width direction represented by the following formula theta _LW, it is preferable that emission angle theta _LH in the height direction of the two-dimensional emitted light incident light angle theta _L1, corresponds to the plane of theta _L2.
θ _LW <tan ⁻¹ (n _k × W / 2D)
θ _LH <tan ⁻¹ (n _k × H / 2D)
Incidentally portion first lens unit and the second lens, on one side of the reverse side of the flat surface, respectively, the surface with (respectively first and second) formed by including a plurality of mountain-shaped array to the refractive surface , Each of the surfaces having the mountain array is combined so as to face opposite directions, and incident from the flat surface of one of the first lens portion and the second lens portion, and the other of incidence from the refractive surface, when together with the same lens apex angle theta _1, refractive surface angle of incidence is preferably greater than the flat surface of incidence angle.

  The backlight refracting light concentrating plate of the present invention has the above-described configuration, and the first lens unit 1 that controls the incident light in the vertical direction (first direction passing through a predetermined central axis); By combining with the second lens unit 2 controlling in the lateral width direction (second direction different from the first direction passing through the predetermined central axis), the light emitted from the light source can be transmitted in either the lateral width direction or the vertical direction. Since the directions are aligned, a high light condensing effect can be obtained and the light emission loss can be reduced.

  The refracting light concentrating plate for a backlight according to the present invention is formed by combining a lens unit 1 that controls incident light in the vertical direction and a lens unit 2 that controls incident light in the horizontal width direction.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings illustrating the embodiments. FIGS. 1 to 6 show the first embodiment of the present invention, and FIGS. 7 and 8 show the relationship between the incident angle and the lens apex angle in FIGS. 5 and 6, respectively. Moreover, FIG. 9 shows the form of Example 2 of this invention.

  FIG. 1 is an exploded perspective view showing a configuration of a backlight using a backlight refracting light collecting plate according to Embodiment 1 of the present invention. The refractive light collecting plate for backlight of the present invention is disposed between the light source 3 and the light guide 4 as indicated by the oblique lines.

  FIG. 2 is a plan view schematically showing a configuration of a backlight using the backlight refracting light collecting plate of Example 1 of the present invention. The arrows in the figure indicate the traveling direction of light. As shown in the figure, the backlight condensing condensing plate is arranged between the light source 3 (LED light source) and the incident surface of the light guide 4 in the backlight of the liquid crystal display device.

(First lens part 1, second lens part 2)
The backlight refracting light concentrating plate of Example 1 is formed by superposing two lens parts, a first lens part 1 and a second lens part 2, in a Fresnel lens shape, in opposite directions. Yes. That is, the first lens unit 1 and the second lens unit 2 face the outside of both side surfaces, and the refracting surfaces 5 (51, 52) are formed on both front and back surfaces (front and back in FIG. 4). The The two lens portions 1 and 2 converge the direction of the two-dimensional emitted light emitted from the light source on the central axis A in the thickness direction of the light source itself. More specifically, the first lens unit 1 converges the incident light on the first central axis surface F ₁ passing through the central axis A, and the second central axis surface F ₂ passing through the central axis. The second lens unit 2 for converging the light is combined so as to be positioned on the incident light side and the outgoing light side, respectively. Here, the first central axial plane of the F ₁ and a second surface different from the central axial plane F ₂ of the intersect the central axis A from one another. In the embodiment, they are orthogonal.

  Further, the first lens unit 1 and the second lens unit 2 are each provided with a plurality of mountain-shaped arrays whose surfaces are first and second refractive surfaces 51 and 52, respectively. The respective surfaces having the mountain array are combined so as to face opposite directions.

  Both lens portions 1 and 2 are plate-shaped, and one side is a refracting surface 5 and the other side is a flat surface 6. The refracting surface 5 includes a plurality of inclined surfaces arranged in parallel so that incident light is refracted.

Specifically, the first lens unit 1 positioned on the light source 4 side, light is incident to the incident angle theta _L is made large, from the first refractive surface 51 of the plurality of mountain-shaped array provided on one side thereof converges to the first central axial plane F _1. The second lens unit 2, the located opposite the light guide 5 side to the light source 4 side than the first lens unit 1, the incident light incident angle theta _L becomes small, provided on one side thereof is incident from the serving bottom of a plurality of mountain-shaped array second flat surface 62 converges with respect to the second central axial plane F _2.

  A first ridge line is formed by the top of the first chevron array, and a second ridge line is formed by the top of the second chevron array. In the front view, the first ridge line and the second ridge line intersect each other. In the embodiment, the cross-section of each mountain array is a right triangle, and increases in order toward the inclined surface side next to each other (see FIG. 4). The hypotenuse is the refracting surface 5 (first refracting surface 51, second refracting surface 52), and the base is parallel to the flat surface 6 (first flat surface 61, second flat surface 62). It is.

In addition, the angle formed by the refracting surface 5 which is the oblique side of the cross section and the flat surface having the same angle as the base of the cross section (synonymous with the first flat surface 61 and the second flat surface 62 which are the cross section base) is The lens apex angle θ ₁ is set.

  The first lens unit 1 and the second lens unit 2 are combined so that the directions in which the inclined surfaces of the refractive surface 5 are arranged are orthogonal to each other, and the first lens unit 1 moves incident light up and down. The lens unit 2 on the right side in the figure controls incident light in the lateral width direction (left and right direction in the figure).

  With this configuration, the radial light emitted from the light source 3 is aligned in the vertical direction by the Fresnel lens as the first lens unit 1, and is aligned in the horizontal direction by the Fresnel lens as the second lens unit 2. The light is incident on the light guide 4 in a state aligned in both the vertical direction and the vertical direction.

  In addition, incident light may be aligned in the horizontal width direction by the first lens unit 1 and aligned in the vertical direction by the second lens unit 2.

(Explanation of FIGS. 3 and 4)
FIG. 3 is an exploded perspective view of a part of FIG. 1, showing the positional relationship between the light source 3, the refractive light collecting plate for backlight of the present invention, and the light guide 4, and the virtual center in this specification. This shows the positional relationship between the axis A and the central axis plane F (F ₁ , F ₂ ). FIG. 4 is a layout explanatory diagram showing FIG. 3 in a plan view and a side view.

The central axis A is an axis (horizontal axis in the embodiment) in a direction passing through the center of the light source 3 and connecting the light source 3 and the light guide 4. It faces the thickness direction of the refractive light collecting plate for backlight of the present invention. A first central axis plane F ₁ is the second central axial plane F ₂ together through the center axis A, and the central axis A intersects the 90 degrees.

The light sources 3 are LED light sources that emit two-dimensional emitted light, and a plurality of light sources 3 are installed at equal intervals in the planar view width direction (see FIG. 1). Each light source 3 is embedded in a box-shaped colored resin (flat rectangular solid indicated by a solid line in FIG. 4, white resin in the figure), and a transparent resin (flat rectangular solid indicated by a solid line in FIG. 4) is embedded. Smaller LED chips are embedded in the resin. One surface of the transparent resin on the back surface side on the light guide 4 side is exposed as a radiation surface of the light source 3. An LED chip is affixed and embedded in the bottom surface (side surface) of the transparent resin viewed from the radiation surface (see FIG. 4). The width W, depth D, and height H of the rectangular parallelepiped of the transparent resin define the spread, size, and amount of light of the two-dimensional radiated light for each unit of the light source 3, and as will be described later, the lens apex angle θ _This is a required value when ₁ is set.

(Explanation of FIGS. 5 and 7)
FIG. 5 is an enlarged view of the vicinity of the second refractive surface 52 (refractive surface 5) of the second lens unit 2 shown in the side view of FIG. The triangle of FIG. 5 shows a second flat surface 62 whose hypotenuse is parallel to the second refracting surface 52 (refracting surface 5) and whose horizontal base is parallel to the flat surface 6 (shown by a horizontal dotted line).

As shown in FIG. 5, the emission angle θ _L (θ _L2 ) of the emitted light from the light source with respect to the central axis A is equal to the lens incident angle θ ₂ with respect to the central axis A of the emitted light because of the complex angle. The second flat surface emission angle theta ₃ becomes the incident light lens refraction to a flat surface 62 which is incident in the lens incident angle theta _2, enters the refractive surface incident angle theta ₄ to the refractive surface 52. Further, light incident on the refracting surface 52 is emitted at a lens exit angle θ ₅ with respect to the refracting surface. At this time, the following relationship is established including the refractive index n and the bottom lens apex angle θ ₁ .

  The condition that the emitted light is parallel to the central axis A is that the following relationship is established.

At this time, the relationship between the emission angle θ _L = θ _{2 of} the light source and the lens apex angle θ ₁ is as follows.

  It is desirable to set “the condition under which the emitted light is parallel to the central axis” expressed by the above formula 7 at the farthest corner of the lens, that is, the central axis. In such a case, since the incident light angle to the lens becomes smaller as it approaches the central axis, the outgoing angle is condensed (converged) toward the central axis.

FIG. 7 shows the relationship between the incident light angle θ _L2 (θ _L ) (vertical axis) and the lens apex angle θ ₁ (horizontal axis) based on Equation 7 above. It is. If it is in a region below this curve, the emitted light will converge toward the central axis. On the contrary, if it exists in the area | region above this curve, emitted light will leave | separate from a central axis. That is, the outgoing light incident from the second flat surface 62 (flat surface 6) is classified into convergence, parallel, and divergence, respectively, according to the conditions of the following equations.

The lens apex angle θ ₁ can be set by setting so as to be in the lower region of FIG. 7 (that is, Formula 8 is satisfied) according to the incident angle of the radiated light from the light source 4. That is, by using the lower area in FIG. 7 or Expression 8, the apex angle corresponding to the incident angle can be easily set as that of a lens that reliably exhibits the convergence function. In addition, regarding the existing backlight refracting / condensing plate, a preferable one can be easily determined based on the arrangement state, the shape of the backlight refracting / condensing plate, and the type of the light source.

(Explanation of FIGS. 6 and 8)
FIG. 6 is an enlarged view of the vicinity of the first refractive surface 51 (refractive surface 5) of the first lens unit 1 shown in the plan view of FIG. The triangle in FIG. 6 shows a first flat surface 61 whose hypotenuse is parallel to the first refracting surface 51 (refracting surface 5) and whose horizontal base is parallel to the flat surface 6 (shown by a horizontal dotted line). In FIG. 6, the refractive index n, the base angle of the base angle θ ₁ composed of the base (first flat surface 61) and the hypotenuse (first refracting surface 51), and the incident angle (center axis A) to the lens. Is an incident angle θ _L (θ _L1 ) with respect to, an incident angle θ _{2 with} respect to light incident on the first refracting surface 51, and a reflection angle θ ₃ with respect to the hypotenuse (first refracting surface 51).

As shown in FIG. 6, (the exit angle θ _{L with} respect to the central axis A of the emitted light from the light source) and (the difference between the incident angle θ ₂ and the reflection angle θ ₃ ) are equal because of the complex angle. Describing in order of the traveling direction of the radiated light indicated by the arrows in FIG. 6, the incident light to the first refraction 51 incident at an inclination angle of the lens incident angle θ _{2 with} respect to the central axis is an exit angle with respect to the refracting surface due to lens refraction. the θ _3. Then, the light is emitted to the first flat surface 61. At this time, as shown in FIG. 6, in order for the emitted light to be in the same direction (zero angle) as the central axis, that is, in the direction perpendicular to the first flat surface 61, the following relationship must be satisfied.

FIG. 8 shows curves illustrating the relationship between the incident angle θ _L1 and the lens apex angle θ ₁ in Equation 13 as the horizontal axis and the vertical axis, respectively. On this curve, the lens output light and the central axis A are parallel. In FIG. 8, if it is an area below the same curve, the light emitted from the lens converges in the direction of the central axis A. Conversely, if it is an area above the same curve, it diverges (diffuses). That is, the outgoing light incident from the second flat surface 62 (flat surface 6) is classified into convergence, parallel, and divergence, respectively, according to the conditions of the following equations.

According to the incident angle θ _L of the radiated light from the light source 4, the arrangement of the refractive light collecting plate for the backlight of the present invention and the transparent resin of the light source 3 as shown in the lower region of FIG. shape (width W, depth D, height H) to adjust the, also, it is possible to set the lens apex angle theta _1. That is, by using the lower region in FIG. 8 or Expression 14, the apex angle corresponding to the incident angle can be easily set as that of a lens that reliably exhibits the convergence function. In addition, regarding the existing backlight refracting light collecting plate, a preferable one can be easily determined based on the arrangement state, the shape of the backlight refracting light collecting plate, and the type of the light source.

(Comparison of FIG. 7 and FIG. 8)
7 and FIG. 8, when the incident angles to the refracting surfaces 5 (51, 52) and the flat surfaces 6 (61, 62) are compared, the incidence from the flat surface 6 as shown in FIG. When the incident from the refracting surface 5 is the same lens apex angle θ ₁ , the refracting surface incident angle is larger than the flat surface incident angle. This is because when the curve of FIG. 7 and the curve of FIG. 8 are overlapped, the curve of FIG. 8 is located on the lower side, and the value of the parallel lens apex angle θ ₁ is lower.

Specifically, when the lens apex angle θ ₁ is 10 °, 20 °, and 30 °, the refractive surface incident angle θ _L1 (FIG. 8) is 15.6 °, 32.0 °, and 50.8 °, respectively. The flat surface incident angle θ _L2 (FIG. 7) is 5.5 °, 11.0 °, and 16.6 °, respectively. From this, under the condition of the same lens apex angle θ ₁ , the refractive surface incident angle θ _L1 (FIG. 8) is about three times the critical value (from the convergence region to the diverging region) of the flat surface incident angle θ _L2 (FIG. 7). Critical value to be transferred). This means that refracting surface incidence (FIG. 6) is more excellent in wide-angle lens function.

(Concrete example)
In general, when the light source 3 is an LED light source, a slightly horizontally long transparent resin is provided as described above (description of FIGS. 3 and 4). As described above, generally, the two-dimensional emitted light is a radiation angle, that is, incident light on the refracting light collecting plate when viewed on each of two surfaces intersecting with the central axis A (that is, two surfaces in a side view and a plan view). The maximum inclination angle differs between the two surfaces. That is, it is a two-dimensional radiation that emits flatly. Corresponding to each surface of the two-dimensional radiated light that radiates flatly, the radiated light can be efficiently converged on each of the surfaces by providing lenses in the directions shown in FIGS. In this way, the lens surface is formed as the backlight refractive condensing plate of Example 1, and the first lens portion 1 and the second lens portion 2 are disposed on both surfaces (outside of each other so that the ridge lines are orthogonal to each other). ).

When the LED chip is considered to be a point light source at the position of the depth D of the transparent resin for simplification, the emission angle θ _{LW in the} width W direction and the emission angle θ _LH in the height H direction are expressed by the following equations, respectively. The

For example, when nk = 1.55, W = D, and H = W / 4, the emission angle θ _{LW in the} width W direction is 37.8 °, and the emission angle θ _{LH in the} height H direction is 10.9 °. . With reference to these values and FIG. 7 (or Formula 8) and FIG. 8 (or Formula 14), the lens apex angle θ ₁ of the first lens unit 1 on the light source 4 side, and the second lens unit 2 on the light guide 5 side. It can be determined that the lens apex angle θ ₁ of the second refracting surface 62 is optimally 24 ° or more and 20 ° or more, respectively.

  Example 2 is shown in FIG. 9 as another embodiment of the present invention. In the first embodiment, the side on which the refractive surface 5 of the left lens portion 1 in the figure is formed faces the light source 3 side, and the side on which the refractive surface 5 of the right lens portion 2 in the drawing is formed is on the light guide 4 side. In contrast, the flat surfaces 6 and 6 of the lens portions 1 and 2 are combined so that they face each other, but in Example 2, the side on which the refractive surface 5 of the left lens portion 1 is formed is shown in the drawing. The lens unit 2 on the middle right side may be combined so as to face the side on which the flat surface 6 is formed.

  There may be a gap between the lens parts 1 and 2. Each of the lens portions 1 and 2 can be manufactured by processing one side of a film or sheet-like material such as a PET resin to form the refractive surface 5, or can be manufactured by injection molding. Further, by forming the refracting surfaces 5 on the front and back surfaces of one plate, both lens portions 1 and 2 can be integrated.

  Furthermore, one lens part can be an appropriate lens such as a prism lens or a lenticular lens, in addition to the Fresnel lens.

  It can be used in a backlight of a liquid crystal display device.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 2 is an arrangement explanatory plan view schematically showing a configuration of a backlight using the backlight light-reflecting light concentrating plate of Example 1. FIG. 2 is a perspective enlarged explanatory view showing a configuration of a backlight using the backlight light converging plate of Example 1 shown in FIG. 1. The top view and side view which showed typically the structure of the backlight using the refractive condensing plate for backlights of Example 1 shown in FIG. The expanded side view which showed the 2nd lens part of the refractive light condensing plate for backlights of Example 1 shown in FIG. The enlarged plan view which showed the 1st lens part of the refractive light condensing plate for backlights of Example 1 shown in FIG. The graph which shows the relationship between the incident angle in the case of incidence from the flat surface of the 2nd lens part of the refractive condensing plate for backlights of Example 1 shown in FIG. 4 and a lens apex angle. The graph which shows the relationship between the incident angle in the case of incidence from the refractive surface of the 1st lens part, and a lens vertex angle of the refractive condensing plate for backlights of Example 1 shown in FIG. Explanatory drawing of the refractive condensing plate for backlights of other embodiment (Example 2) of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st lens part 2 2nd lens part 3 Light source 4 Light guide 5 Refractive surface 51 1st refractive surface 52 2nd refractive surface 6 Flat surface 61 1st flat surface 62 2nd flat surface A Center Axis F ₁ first central axis plane F ₂ second central axis plane

Claims (3)

A refraction condensing plate for aligning the direction of two-dimensional radiation emitted from a light source and flattened with a central axis in a thickness direction passing through the center of the light source, with respect to the first central axis plane passing through the central axis a first lens portion of the Fresnel lens shape for converging the incident light Te, Fresnel lens-shaped second to converge the incident light to the second central axial plane of the intersecting with the first central axis plane and the central axis and a lens portion of each incident light side, and Ri Na in combination the exit light side,
Lens apex angles of the first lens unit and the second lens unit according to the incident angle of the emitted light from the light source viewed on the first central axis surface and the incident angle viewed on the second central axis surface Is set so that the conditions for the outgoing light to converge toward the first central axis surface and the second central axis surface, respectively, are satisfied. When viewed on each of the first central axis plane and the second central axis plane that intersect at the central axis, the maximum inclination angle of the incident light of the two-dimensional radiation to the refractive light collector is different on each plane,
By providing a first lens portion having a lens apex angle θ _{1 and} a second lens portion having a lens apex angle θ ₂ respectively represented by the following equations corresponding to the different incident light angles θ _L1 and θ _L2 , The refractive condensing plate for a backlight according to claim 1, wherein the two-dimensional radiation is converged on each surface.
θ _L1 <sin ⁻¹ (n × sin θ ₁ )
θ _L2 <sin ⁻¹ (n × sin (θ ₂ −sin ⁻¹ (sin θ ₂ / n))) The light source includes a rectangular parallelepiped transparent resin having a predetermined width W and a predetermined height H in which the LED chip is embedded at the position of the depth D, and the emission angle θ of the two-dimensional emitted light in the width direction represented by the following formula: _The refractive condensing plate for a backlight according to claim 1 or 2, wherein an emission angle θ _LH of the two-dimensional radiation light in the height direction corresponds to the plane of the incident light angles θ _L1 and θ _L2 .
θ _LW <tan ⁻¹ (n _k × W / 2D)
θ _LH <tan ⁻¹ (n _k × H / 2D)

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