JP4784094B2 - Lenticular lens sheet, surface light source device, transmissive display device - Google Patents

Description

  The present invention relates to a lenticular lens sheet, a surface light source device, and a transmissive display device using them, which are used for illumination of a liquid crystal display device or the like.

Various surface light source devices have been proposed and put into practical use as surface light sources for illuminating a transmissive liquid crystal display (LCD panel) or the like from the back. The surface light source device mainly includes an edge light type and a direct type by converting a light source that is not a surface light source into a surface light source.
For example, in the direct type, light is introduced using a cold cathode tube (light emitting tube) in parallel from the back, and the distance between the cold cathode tube and a transmissive display unit such as an LCD panel is appropriately increased, In the meantime, a diffusion plate was used, and a plurality of sheets for converging light were used.
In such a conventional method, the convergence characteristics are insufficient for the large number of optical sheets required, and the LCD panel is improved to compensate for this, and the image quality is also improved even for incident light from an oblique direction. It was set as the structure which does not drop.

However, this method has a problem in that the light use efficiency is reduced and the configuration of the LCD panel is complicated, resulting in an increase in cost.
In particular, in the direct type, the light depends on whether it is a part close to the cold cathode tube (a position close to the cold cathode tube or a position close to a gap part of the cold cathode tubes arranged in parallel). Unevenness is likely to occur in intensity (luminance). In order to suppress this, if the distance between the cold cathode tube and the LDC is made large, there is a problem that the thickness of the display becomes thick. In addition, when the diffusion is increased or the transmission amount is limited in order to suppress unevenness, there is a problem that the amount of light used is reduced.

For example, in the surface light source devices described in Patent Documents 1 and 2, uniformity is maintained by providing a light-shielding portion (lighting curtain, light-shielding dot layer). In this method, the amount of light used is as described above. Decreased.
Also, a method using a sheet provided with lenticular lenses on both sides is reported, for example, in Patent Document 3, but this is a configuration for performing diffusion control in two directions and has no function of converging light. Therefore, there is a problem in that unevenness of brightness occurs depending on the position where the screen is observed because the optical axis varies depending on the location of the LCD depending on the positional relationship with the cold cathode tube.
JP 05-119703 A JP 11-242219 A Japanese Patent Laid-Open No. 06-347613

  An object of the present invention is to provide a lenticular lens sheet, a surface light source device, and a transmissive display device that can perform uniform illumination without unevenness regardless of the position where the screen is observed.

The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to the Example of this invention is attached | subjected and demonstrated, it is not limited to this.
The invention according to claim 1 is provided in a direct-type surface light source device, and includes an incident side lens portion (14a) in which a large number of incident side unit lens shapes convexly formed on the incident surface side are arranged, and an emission surface side. An exit-side lens portion (14b) in which a large number of exit-side unit lens shapes formed in a convex shape are arranged, and the entrance-side unit lens shape and the exit-side unit lens shape are identical along the sheet surface. Are arranged in the same direction, the arrangement direction is the same direction, the half-value angle by the incident-side lens portion is in the range of 5 ° to 20 °, and the incident-side pitch at which the incident-side unit lens shapes are arranged (P1) and the exit side pitch (P2) on which the exit side unit lens shapes are arranged have different sizes, and the larger side of the entrance side pitch and the exit side pitch is the smaller side. More than 2.4 times the pitch of The incident side lens portion is arranged with one type of the incident side unit lens shape in which the minor axis is a part of a substantially elliptic cylinder that is continuous perpendicularly to the sheet surface, and the half value by the incident side lens portion. The angle is in the range of 5 ° or more and 20 ° or less, and the emission side lens portion is one type of the emission side unit in which the long axis is a part of a substantially elliptic cylinder that is continuous perpendicular to the sheet surface. A lenticular lens sheet (14) that diffuses and equalizes light emitted from a light source , in which a lens shape or a unit lens set that is a set of a plurality of types of exit side unit lens shapes is repeatedly arranged .

Invention 請 Motomeko 2, in the lenticular lens sheet according to claim 1, wherein one of the exit-side unit lens shape of the exit lens part (14b), or, among the plurality of types of exit-side unit lens Where the height of the unit lens shape having the highest height is H, the width is W, and the refractive index of the exit side lens portion is N, arcsin (1 / N) <arctan (1 / ((2H / W ) -0.1)) is satisfied, which is a lenticular lens sheet (14).
According to a third aspect of the present invention, in the lenticular lens sheet according to the first or second aspect , between the incident side unit lens shape and / or the output side unit lens shape, a flat shape, a concave shape, A lenticular lens sheet characterized in that any one of fine irregularities is formed.
The invention of claim 4 is the lenticular lens sheet (14) characterized in that in the lenticular lens sheet according to any one of claims 1 to 3 , the plate thickness is 1 mm or less.

Invention of Claim 5 is a surface light source device which illuminates the transmission type display part (11) from the back, Comprising: The light source part (13) which arranged the some light source, and any one of Claim 1- Claim 4 A surface light source device comprising the lenticular lens sheet (14) according to item 1.

The invention of claim 6 is a transmission type display device comprising the transmission type display unit (11) and the surface light source device (12, 13, 14) of claim 5 .
According to a seventh aspect of the present invention, in the transmissive display device according to the sixth aspect , the transmissive display section (without diffusing a light diffusing sheet disposed on the exit side of the lenticular lens sheet (14)). 11) is a transmissive display device characterized by being laminated.

According to the present invention, the following effects can be obtained.
(1) Since the lenticular lens sheet is provided in a direct type surface light source device and diffuses and uniformizes the light emitted from the light source, the illumination light can be sufficiently diffused and uniform illumination can be achieved. it can.

(2) Since the half-value angle by the incident side lens portion is in the range of 5 ° or more and 20 ° or less, it is possible to minimize the decrease in peak luminance while obtaining a sufficient lens effect to eliminate unevenness. it can.

(3) Since the pitch on the larger side of the incident side pitch and the outgoing side pitch is 2.4 times or more the pitch on the smaller side, the occurrence of moire can be prevented.

(4) The exit side lens portion is a unit that is a single unit lens shape or a set of a plurality of types of unit lens shapes that are part of a substantially elliptic cylinder whose major axis is continuous perpendicular to the sheet surface Since the lens assembly is repeatedly arranged, it has a simple shape and can be easily manufactured.

(5) Since the exit side lens portion satisfies arcsin (1 / N) <arctan (1 / ((2H / W) −0.1)), illumination light can be emitted at a small exit angle. The above-described unevenness can be prevented from being observed when observed from an oblique direction, and the light utilization efficiency can be enhanced.

(6) Since any one of a flat shape, a concave shape, and a fine concavo-convex shape is formed between the incident side unit lens shape and / or the output side unit lens shape, the incident angle is close to the normal direction. A part of the incident light can be emitted at an emission angle close to the normal direction, an extreme decrease in luminance at a position close to the light source can be suppressed, and uniformity can be improved. Moreover, the light which goes to the diagonal direction from these flat shape, concave shape, and fine uneven | corrugated shape can inject into an adjacent unit lens, and can improve the convergence property of light.

(7) Since the plate thickness is 1 mm or less, both sides can be simultaneously molded by extrusion molding.

(8) Since the transmission type display unit is laminated on the emission side of the lenticular lens sheet without disposing a diffusion sheet having light diffusibility, a thin and inexpensive transmission type display device can be obtained. .

  The objective of uniform illumination without unevenness was achieved without increasing the number of optical sheets and while reducing the number of optical sheets.

FIG. 1 is a diagram showing an embodiment of a transmissive display device according to the present invention.
In addition, each figure shown below including FIG. 1 is the figure shown typically, and the magnitude | size and shape of each part are exaggerated suitably for easy understanding.
The transmissive display device 10 according to the present embodiment includes an LCD panel 11, a reflector 12, a light emitting tube 13, a lenticular lens sheet 14, a reflective polarizing sheet 15, and the like, and image information formed on the LCD panel 11 is reflected on the reflector. 12 is a transmissive liquid crystal display device that is illuminated from the back by a surface light source device including an arc tube 13, a lenticular lens sheet 14, and a reflective polarizing sheet 15.

  The LCD panel 11 is a light valve formed by a so-called transmissive liquid crystal display element, and can display a 30-inch size and 800 × 600 dots. The direction along the longitudinal direction of the arc tube 13 is used as the horizontal direction, and the direction in which the arc tubes 13 are arranged is used as the vertical direction.

The arc tube 13 is a cold cathode tube of a line light source that forms a light source part of a backlight. In this embodiment, six are arranged in parallel at equal intervals of approximately 80 mm. Further, the distance between the arc tube 13 and a lenticular lens sheet 14 described later is 50 mm.
A reflector 12 is provided on the back surface of the arc tube 13, and the design allows the incident light illuminance to each part of the screen to be made uniform.
The reflective polarizing sheet 15 is a sheet that is disposed between the LCD panel 11 and the lenticular lens sheet 14 and increases the luminance without narrowing the viewing angle. In this embodiment, DBEF (manufactured by Sumitomo 3M Limited) is used.
A lenticular lens sheet 14 is provided between the arc tube 13 and the reflective polarizing sheet 15.

FIG. 2 is a perspective view showing the lenticular lens sheet 14.
The lenticular lens sheet 14 is a sheet that diffuses and equalizes the light emitted from the arc tube 13, and an incident side lens portion 14a is formed on the incident side, and an emission side lens portion 14b is formed on the emission side. Has been.
FIG. 3 is an enlarged view of the DD cross section in FIG.
The incident-side lens portion 14a has a lenticular lens shape in which incident-side unit lens shapes each formed of a partial shape of an elliptic cylinder whose short axis is continuous perpendicular to the sheet surface of the lenticular lens sheet 14 are arranged. . The incident-side unit lens shape of the incident-side lens portion 14a is a partial shape of a cylindrical surface having a radius of 20 microns. Therefore, in this embodiment, in the cross section shown in FIG. 3, the normal direction radius A1 = the radius B1 in the sheet surface direction, but one of the elliptic cylinders having a different normal direction radius A1 and a radius B1 in the sheet surface direction. It is good also as a part shape.
The incident side lens portion 14a diffuses incident light by the above-described shape, and its half-value angle is about 8 °. The diffusion half-value angle by the incident side lens portion is preferably in the range of 5 ° to 20 °.
In the present invention, the half-value angle means the diffusion half-value angle, and the luminance is measured while increasing the measurement angle (the angle in the direction matching the emission angle) with reference to the luminance measured in the normal direction. , The angle at which the luminance is ½ of the luminance in the normal direction.

  Here, Table 1 shows the results of preparing lenticular lens sheets having different diffusion half-value angles of the incident side lens part and examining the influence of the diffusion half-value angle of the incident side lens part on the peak luminance and unevenness.

  As can be seen from Table 1, when the diffusion half-value angle of the incident side lens portion is 5 ° or less, a sufficient lens effect cannot be obtained, so that unevenness cannot be eliminated, and when it is 20 ° or more. , The diffusion is too strong, and the peak luminance is drastically reduced.

The exit-side lens portion 14b has a lenticular lens shape in which exit-side unit lens shapes each having a shape of a part of an elliptic cylinder whose major axis is continuous perpendicular to the sheet surface of the lenticular lens sheet 14 are arranged side by side. . The exit side unit lens shape of the exit side lens portion 14b is a part of an elliptic cylinder having a major radius A2 = 400 μm and a minor radius B2 = 120 μm in the cross section shown in FIG. = W) = 160 μm and are arranged at equal intervals. The exit side unit lens shape of the exit side lens portion 14b is such that the protruding portion has a height H = 100 μm and a width W (= P2) = 160 μm.
The lenticular lens sheet 14 has a plate thickness of 0.7 mm and is formed of MS resin (acryl styrene copolymer) having a refractive index N = 1.55. Since the lenticular lens sheet 14 in the present embodiment has a plate thickness of 1 mm or less as described above, both surfaces can be simultaneously molded by extrusion molding.
Note that the direction in which the incident-side unit lens shape and the emission-side unit lens shape are aligned is the same as the direction in which the arc tube 13 is aligned (see FIG. 1).

FIG. 4 is a diagram showing a typical trajectory of light incident on the lenticular lens sheet 14.
Immediately above the arc tube 13, the illumination light having the same angle increases. However, by arranging the lenticular lens sheet 14, the effect that the illumination light having the same angle is diffused becomes very high, and is emitted from the lenticular lens sheet 14. The illumination light to be made is made uniform. Therefore, in the transmissive display device 10 according to the present embodiment, uniform illumination can be performed without disposing a diffusion sheet having a light diffusion property such as a so-called mat film between the lenticular lens sheet 14 and the LCD panel 11. it can.

As described above, the exit-side unit lens shape of the exit-side lens portion 14b is such that the protruding portion has a height H = 100 μm, a width W = 160 μm, and a refractive index N = 1.55. These values satisfy the following formula (1).
arcsin (1 / N) <arctan (1 / ((2H / W) −0.1)) (1)
This expression (1) is an expression for determining whether or not the light totally reflected at the position of 10% of the height from the end of the lens valley is totally reflected at the top of the lens.

FIG. 5 is a diagram showing how light travels in the lenticular lens sheet 14 in the present embodiment compared to the comparative example. FIG. 5A shows the case of this example, and FIG. 5B shows the case of a lenticular lens sheet having a shape that does not satisfy the above formula (1) on the exit side as a comparative example.
The light reaches the top of the lens from various directions, but when the light coming from a certain direction is totally reflected in the valley between the unit lenses and exits from the top, it proceeds in an oblique direction (FIG. 5B). ) (See the light ray L2 in the middle), so that it looks uneven when observed from an oblique direction. By satisfying the expression (1), it is possible to emit light with a small emission angle like the light beam L1 in FIG. 5A, and to prevent the above-described unevenness from being observed when observed from an oblique direction. In addition, the light utilization efficiency can be increased.

In this embodiment, the incident side unit lens shape is arranged at the incident side pitch P1 = 10 μm, and the output side unit lens shape is arranged at the output side pitch P2 = 160 μm. Therefore, P2 / P1 = 16. Yes. Here, the pitch on the larger side of the incident side pitch and the outgoing side pitch is preferably 2.4 times or more the pitch on the smaller side.
Here, a lenticular lens sheet is prepared by changing the lens pitch ratio obtained by dividing the larger pitch of the incident side pitch and the outgoing side pitch by the smaller pitch, and the results of examining the presence or absence of moire are shown in Table 2. .

From Table 2, it can be seen that moire occurs when the difference in pitch is small. Therefore, the lens pitch ratio is desirably 2.4 or more.
In the present embodiment, this condition of 2.4 times or more is satisfied.
Even if this lens pitch ratio is less than 2.4 times, it is known from experiments that if the lens pitch ratio is around 1.5 times, the moire is small. Therefore, the lens pitch ratio is assumed to be around 1.5 times. Also good.

  According to the present embodiment, since the lenticular lens sheet 14 is used in a direct type surface light source device, a sufficient diffusion effect can be obtained and luminance unevenness can be eliminated. Further, since a sufficient diffusion effect can be obtained only by the lenticular lens sheet 14, it is not necessary to additionally use a diffusion sheet having a light diffusibility such as a so-called mat film, which has been conventionally required, and is thin. Can be cheaper.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the equivalent scope of the present invention.
(1) In the present embodiment, the homogenization sheet 14 has an example in which the incident side pitch of the incident side lens unit 14a is small and the output side pitch of the output side lens unit 14b is large. That is, the incident side pitch of the incident side lens unit may be large, and the output side pitch of the output side lens unit may be small.

(2) In the present embodiment, the example in which the surface light source device and the transmissive display device are formed by combining the homogenizing sheet 14 and the reflective polarizing sheet 15 is shown. However, the present invention is not limited to this. When the property is required, a diffusion sheet may be added, or a surface light source device and a transmissive display device may be formed by combining various optical sheets other than these and the uniformizing sheet 14.

(3) In the present embodiment, the exit side lens portion 14b has shown an example in which one type of exit side unit lens shape is arranged side by side. However, the present invention is not limited to this. For example, a plurality of types of exit side unit lens shapes are arranged. You may arrange.
FIG. 6 is a view showing a uniformizing sheet in which a plurality of types of exit side unit lens shapes are arranged side by side.
The homogenization sheet 20 is formed by arranging three sets of exit side unit lens shapes 21, 22, and 23 as one set on the exit side. In such a case, the height of the exit side unit lens shape having the highest height may be substituted for the height H in the above formula (1) to satisfy the formula (1).

(4) In the present embodiment, the incident-side unit lens shape and the exit-side unit lens shape have been described with reference to an example in which they are continuously arranged. In the meantime, a flat portion, a concave shape, or a fine uneven shape may be formed in at least one of the exit side unit lens shapes to improve the light uniformity and convergence.

It is a figure which shows the Example of the transmissive display apparatus by this invention. FIG. 3 is a perspective view showing a lenticular lens sheet 14. It is the figure which expanded and showed DD cross section in FIG. 4 is a diagram showing a typical trajectory of light incident on a lenticular lens sheet 14. FIG. It is the figure which showed how the light progresses in the lenticular lens sheet 14 in a present Example compared with a comparative example. It is a figure which shows the homogenization sheet | seat which has arrange | positioned and arranged the multiple types of exit side unit lens shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Transmission type display apparatus 11 LCD panel 12 Reflector 13 Light emission tube 14 Lenticular lens sheet 14a Incident side lens part 14b Outgoing side lens part 15 Reflective polarizing sheet

Claims (7)

Provided in the direct type surface light source device,
An incident-side lens unit in which a large number of incident-side unit lens shapes formed in a convex shape on the incident surface side are arranged;
An exit side lens portion in which a large number of exit side unit lens shapes formed in a convex shape on the exit surface side are arranged;
With
The incident side unit lens shape and the emission side unit lens shape are aligned in one direction along the sheet surface, and the alignment direction is the same direction,
The incident-side pitch in which the incident-side unit lens shape is arranged and the outgoing-side pitch in which the outgoing-side unit lens shape is arranged have different sizes, and is larger in the incident-side pitch and the outgoing-side pitch. The pitch on the side is at least 2.4 times the pitch on the small side,
The incident side lens portion is arranged with one type of the incident side unit lens shape that is a part of a substantially elliptic cylinder whose short axis is orthogonal to the sheet surface and continues.
The half-value angle by the incident side lens part is in the range of 5 ° or more and 20 ° or less,
The exit-side lens portion has one kind of exit-side unit lens shape, or a plurality of kinds of exit-side unit lens shapes, each of which is a part of a substantially elliptic cylinder whose major axis is orthogonal to the sheet surface. The unit lens set which is a set is repeatedly arranged,
A lenticular lens sheet that diffuses and equalizes light emitted from a light source. In the lenticular lens sheet according to claim 1 ,
The height of the one-side exit-side unit lens shape of the exit-side lens unit or the unit lens shape having the highest height among the plurality of types of exit-side unit lenses is H, the width is W, and the exit side When the refractive index of the lens part is N,
arcsin (1 / N) <arctan (1 / ((2H / W) −0.1))
Be satisfied,
Lenticular lens sheet characterized by In the lenticular lens sheet according to claim 1 or 2 ,
Between the incident side unit lens shape and / or the emission side unit lens shape, either a flat shape, a concave shape, or a fine uneven shape is formed,
Lenticular lens sheet characterized by In the lenticular lens sheet according to any one of claims 1 to 3 ,
The plate thickness is 1 mm or less,
Lenticular lens sheet characterized by A surface light source device that illuminates a transmissive display unit from the back,
A light source section in which a plurality of light sources are arranged;
The lenticular lens sheet according to any one of claims 1 to 4 ,
A surface light source device comprising: A transmissive display;
A surface light source device according to claim 5 ;
A transmissive display device. The transmissive display device according to claim 6 ,
The transmission type display unit is laminated on the emission side of the lenticular lens sheet without disposing a diffusion sheet having light diffusibility,
A transmissive display device characterized by the above.

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