JP2003156629A - Optical conversion element and liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a practical optical element which has a function to convert a line light source or a point light source into a surface light source and relatively reduces light emitted to an oblique and frontward direction or controls the quantity thereof. SOLUTION: The optical conversion element 4 with a sheet like shape converts the linear light source into the surface light source by making light from the line light source incident from an end face, making it be reflected inside and making it be emitted form a front face 42. A number of prism parts 45 to reflect incident light are formed on a rear face. The angle θ which two slopes of each of the prism parts 45 form with each other is <=90 deg.. The tip of the top part which the two slopes of each of the prism parts 45 form with each other is a flat surface or a curved surface with >=0.1 μm and <=5 μm width. The pitch of each of the prism parts 45 is >=50 μm and <=300 μm and the depth d of each of the prism parts 45 is equal to or less than 10% of the total thickness t.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light conversion element suitable for use in a backlight of a liquid crystal display or the like, in which light from a line light source or a point light source is incident from an end face and reflected internally. The present invention relates to a light conversion element that converts a line light source or a point light source into a surface light source by emitting the light from the front surface or the back surface.

[0002]

2. Description of the Related Art FIG. 12 is a front sectional view showing a conventional technique. In a display that does not emit light by itself but displays by transmitting or reflecting light, like a liquid crystal display,
A surface light source with uniform brightness is required. Previously, Figure 1
As shown in FIG. 2 (1), a plurality of linear light sources 2 such as fluorescent lamps are arranged behind the liquid crystal panel 1. However, due to the demand for thinning the display, the linear light sources are formed by sheet-like or plate-like optical elements. Many configurations have been adopted in which 2 is converted into a surface light source. Specifically, the linear light source 2 is arranged along one side of the optical element, and light is incident from the end of the optical element. Then, the light is emitted forward while being reflected or scattered inside the optical element. For example, in FIG.
In the conventional example shown in (2), a plate-shaped optical element 31 having a triangular cross section is arranged, and light is reflected on an inclined surface, which is a back surface, to be emitted forward. Further, in the conventional example shown in FIG. 12C, irregular unevenness is provided on the front surface of the plate-shaped optical element 32 by a method such as printing, and light is scattered and emitted there.

[0003]

One of the important performances required for a display device such as a liquid crystal display is the brightness of the screen. In the case of a liquid crystal display using the above backlight, in order to make the screen as bright as possible with the limited power of the light source, the light emitted toward the front is increased as much as possible, and the light emitted obliquely forward is decreased. It is important to do so. This is because when the display is viewed, it is normal to look at the display while facing it, and the brightness when viewed obliquely may be reduced.

In the case of the above-mentioned conventional optical element, a relatively large amount of light is emitted obliquely forward, and as a result, there is a limit to improving the brightness of the screen. In addition, since it is necessary to increase the brightness when viewed from an angle, even if the amount of light emitted obliquely forward is increased to some extent, it is necessary to optimally adjust the amount, but this is difficult with the conventional configuration. is there. In order to improve the brightness of the screen and optimally control the light, it is effective to form regular unevenness based on optical calculation. However, since regular irregularities also have a harmful effect such as moire, fine processing with high dimensional accuracy is required.

The invention of the present application was made in order to solve the above problems, and is an optical element having a function of converting a line light source or a point light source into a surface light source, which emits light emitted obliquely forward. There is a technical significance to provide a practical optical element that can be relatively decreased or the amount thereof can be adjusted.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present application is that the light from a line light source or a point light source is made incident from an end face, internally reflected and emitted from a front face or a rear face. A sheet-shaped or plate-shaped light conversion element for converting a line light source or a point light source into a surface light source by allowing a plurality of prism portions for reflecting light incident from the end face to be formed on the front surface or the back surface. The angle formed by the two slopes of each prism portion is 90 degrees or less. In order to solve the above problems, the invention according to claim 2 is the structure according to claim 1, wherein the tip of the apex formed by the two inclined surfaces of the prism portion has a flat surface with a width of 0.1 μm or more and 5 μm or less. Alternatively, it has a configuration of a curved surface. In order to solve the above-mentioned problems, the invention according to claim 3 is the structure according to claim 1 or 2, wherein the pitch of each prism portion is 50 μm or more.
It has a configuration of being 00 μm or less. In order to solve the above problems, the invention according to claim 4 is the structure according to claim 1, 2 or 3, wherein the depth or height of each prism portion is 10% or less of the total thickness. It has the structure that there is. In order to solve the above-mentioned problems, the invention according to claim 5 is a liquid crystal panel for controlling transmission and blocking of light to display an image, and a line light source or a point light source for generating light for illuminating the liquid crystal panel. , A sheet-shaped or plate-shaped light conversion element that converts a line light source or a point light source into a surface light source by allowing light from a line light source or a point light source to enter from an end surface, internally reflected, and emitted from a front surface or a back surface. 5. A liquid crystal display comprising the light conversion element according to any one of claims 1 to 4.
Any one of them is configured to illuminate the liquid crystal panel with emitted light.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments (hereinafter, embodiments) of the present invention will be described below. FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a light conversion element and a liquid crystal display including the light conversion element according to an embodiment of the present invention. In the light conversion element 4 shown in FIG. 1, the light from the linear light source 2 is made incident from the end surface 41 and internally reflected to be the front surface (the surface on the side where the light is emitted) 42 or the back surface (the surface opposite to the front surface). Four
It is an optical element that converts the linear light source 2 into a surface light source by emitting light from the light source 3. The light conversion element 4 has a rectangular sheet shape as a whole and is made of a light-transmitting resin. The linear light source 2 is arranged on one side of the light conversion element 4. The line light source 2 is arranged along one side of the rectangular light conversion element 4. A liquid crystal panel 1 is arranged in front of the light conversion element 4.
The light from the linear light source 2 enters from the end surface 41 of the light conversion element 4, is internally reflected, and is emitted toward the front liquid crystal panel 1. The light illuminates the liquid crystal panel 1, and transmission / blocking of light is controlled to display an image.

FIG. 2 is a partial cross-sectional view showing an enlarged main part of the light conversion element 4 shown in FIG. As shown in FIG. 2, the rear surface 43 of the light conversion element 4 is provided with a large number of prism portions 45 for reflecting light and emitting the light forward. The front surface 42 is a flat surface. Further, the end surface 44 on the side opposite to the side on which the light from the linear light source 2 is incident is a reflecting surface. The reflective surface is formed by forming a reflective film, for example. As shown in FIG. 2, each prism portion 45 is composed of two inclined surfaces 451 and 452 which form a concave prism. Each prism portion 45 is long in the direction of the side on which the linear light source 2 is arranged. That is, each prism portion 45
Are arranged parallel to each other in a direction intersecting with the traveling direction of light.

FIG. 3 shows the light conversion element 4 shown in FIGS.
It is a figure explaining the effect of. As shown in FIG.
The light that has entered from one end face proceeds while being totally reflected by the front surface 42 or the back surface 43 of the light conversion element 4. Then, the light is reflected by the end surface 44 on the opposite side and returns to the incident side. That is, the light conversion element 4 itself acts as a kind of light guide. The light returning to the incident side enters the light conversion element 4 again while being reflected by the mirror 21 provided behind the linear light source 2.

As described above, when the light from the linear light source 2 is guided by the light conversion element 4, few of the light travels completely parallel to the front surface 42 or the back surface 43, and the light is angled little by little. As shown in, the light reaches the prism portion 45.
Most of the light reaching the prism portion 45 is reflected by one of the inclined surfaces 451 and 452 of the prism portion 45 or transmitted through both of the inclined surfaces 451 and 452, and any of the inclined surfaces 451 and 452 of another prism portion 45. Reflect on. The reflected light is transmitted through the front surface 42 and emitted toward the front to illuminate the liquid crystal panel 1.

In the configuration of this embodiment, the prism portion 4
The angle formed by the slopes 451 and 452 of No. 5 (shown by θ1 in FIG. 2) is preferably 90 degrees or less. Hereinafter, this point will be described with reference to FIG. FIG. 4 is a diagram showing a case where the angle θ1 formed by the inclined surfaces 451 and 452 of the prism portion 45 is larger than 90 degrees.

As shown in FIG. 4, when the angle θ1 is larger than 90 degrees, the light reflected by the inclined surfaces 451 and 452 of the prism portion 45 transmits the front surface 42 and illuminates the liquid crystal panel 1, but obliquely forward. There will be more things to proceed. That is, when the angle formed by the thickness direction of the light conversion element 4 and the traveling direction of light is θ2 as shown in FIGS. 2 and 4, a large amount of light travels at a large θ2. Therefore, as described above, the brightness of the liquid crystal display is reduced. Also, if it is too angled, it will be reflected by the front surface 42 of the light conversion element 4,
It is attenuated in the light conversion element 4. For this reason, the light use efficiency is lowered, and the brightness of the liquid crystal display is lowered as a whole. On the other hand, as shown in FIG.
When the angle θ1 is 90 degrees or less, the proportion of the light reflected on one of the slopes 451 and 452 of the prism portion 45 advances toward the front. That is, a large amount of light travels at a small θ2. Therefore, the brightness of the liquid crystal display does not decrease and the light utilization efficiency is high.

Further, in FIG. 3, an arrangement interval of each prism portion 45 (hereinafter referred to as a pitch, indicated by p in FIG. 2) is also
This is an important factor from the viewpoint of brightly illuminating the liquid crystal panel 1. As shown in FIG. 2, when the pitch between the vertices of each prism portion 45 is a pitch p, the pitch p is preferably 50 μm or more and 300 μm or less. When the pitch p is small, more of the light from the incident surface 41 is reflected and emitted by the prism portion 45 near the incident surface 41, and is reflected and emitted by the prism portion 45 far from the incident surface. There are few things. As a result, the liquid crystal panel 1 is illuminated brightly on the side closer to the line light source 2 and darker on the side far from the line light source 2, resulting in uneven brightness on the screen. On the other hand, when the pitch p is in the optimum range, a large amount of light is reflected by the prism portion 45 far from the incident surface and is emitted. Therefore, the liquid crystal panel 1 is uniformly illuminated, and uneven brightness does not occur. It should be noted that if the pitch p is too large, the amount of light emitted from the light conversion element 4 is reduced overall, and more light is internally attenuated. For this reason, the light use efficiency is reduced, and the liquid crystal display is entirely dark.

The total thickness of the light conversion element (t in FIG. 2).
2), the depth of each prism portion 45 (d in FIG. 2).
Is preferably 10% or less. This is also for the same reason. When the depth d of the prism portion 45 becomes relatively large with respect to the thickness t, a large amount of light is reflected at a place close to the incident surface 41 and becomes difficult to be reflected at a place far away. As a result, brightness unevenness similarly occurs. If the depth d is 10% or less of the thickness t, such a problem does not occur.

Next, a second embodiment of the present invention will be described. FIG. 5 is a partial cross-sectional view showing an enlarged main part of the light conversion element of the second embodiment. In the light conversion element of the second embodiment, as in the first embodiment, the light from the linear light source 2 is made incident from the end face, reflected internally, and emitted from the front face 42 to make the linear light source 2 a surface light source. It is an optical element for conversion, and a large number of prism portions 45 are provided on the back surface 43. Each prism part 45 is similar to the first embodiment.
It consists of a concave prism.

A major feature of the light conversion element of this embodiment is that the tip of the apex formed by the two inclined surfaces 451 and 452 of each prism portion 45 is a flat surface 453 as shown in FIG. . The flat surface 453 at the tip of the apex is based on the following knowledge of the inventor. As described above, the two slopes 451 and 45 of each prism portion 45 are
The angle θ1 formed by 2 is preferably 90 degrees or less in terms of screen brightness. On the other hand, when the angle θ1 becomes smaller, the apex of the prism portion 45 becomes sharper and becomes a knife edge shape or a state close thereto. However,
When the top of the prism portion 45 becomes a knife edge shape or a state close to it, a problem occurs in manufacturing the light conversion element.

FIG. 6 is a diagram showing a manufacturing problem when the top of the prism portion 45 has a knife edge shape. As shown in FIG. 6, the light conversion element is formed by sandwiching the base material 6 between a pair of molds 5 and heating / pressurizing the base material 6. When the light conversion element is a concave prism as in the first embodiment, the mold 5 has a convex prism-shaped convex portion.

If the top of each prism portion 45 of the light conversion element as a product has a knife edge shape, the tip of the convex portion of the mold 5 also has a knife edge shape. According to the knowledge of the inventor of the present application, if molding is performed using the mold 5 having such a tip made of a knife-edge-shaped convex portion, the durability of the mold 5 is deteriorated,
It has been found that the mold 5 is deformed and the like only by repeating the molding several times to several tens of times. The deformation of the mold 5 is such that the tip of the convex portion is deformed in a wavy manner, and is considered to be a result of repeated thermal expansion and thermal contraction.

When such a deformation of the mold 5 occurs, the shape of the prism portion 45 of the finished light conversion element cannot satisfy the performance as a product. For example, as a result of the prism portion 45 being deformed and formed, there is a risk that light may be abnormally scattered by the prism portion 45, or light may be lost due to irregular reflection. On the other hand, if the tip of the top of each prism portion 45 is a flat surface 453 as in the second embodiment, deformation does not occur even if molding is repeated as many times as practically required, and defects of defects do not occur. You can continue to make products that do not exist.

The width of the flat surface 453 (indicated by w in FIG. 5) is
It is important for preventing the deformation of the mold 5. The width w is 0.
If it is smaller than 1 μm, it becomes close to the knife edge, and the problem due to the deformation of the mold 5 becomes apparent. On the other hand, the width w is 5 μm
If it exceeds, there is a problem that the utilization efficiency of light is reduced due to irregular reflection at the flat surface 453. Therefore, the flat surface 4
The width of 53w is preferably 0.1 μm or more and 5 μm or less.

Next, a third embodiment of the present invention will be described. FIG. 7 is a partial cross-sectional view showing an enlarged main part of the light conversion element of the third embodiment. In the third embodiment, each prism portion 45 is composed of a convex prism. Other configurations are almost the same as those in the first embodiment. Also in the third embodiment, as shown in FIG. 7, the light guided inside is reflected by one of the inclined surfaces 451 and 452 of the prism portion 45 and is emitted from the front surface 42. Also in this embodiment, the angle formed by the two inclined surfaces 451 and 452 of each prism portion 45 is 90 degrees or less. Therefore, the screen of the liquid crystal display can be made brighter. In the third embodiment, in order to prevent uneven brightness,
The height of each prism portion 45 (shown by h in FIG. 7) is preferably 10% or less with respect to the thickness t.

FIG. 8 is a partial cross-sectional view showing an enlarged main part of the fourth embodiment of the present invention. The fourth embodiment has a configuration in which the top end of each prism portion 45 in the third embodiment is a flat surface 453. In the above-described third embodiment, since each prism portion 45 is a convex prism, the mold for molding the light conversion element has a shape having a large number of concave prism-shaped concave portions. The type is often
It is manufactured by cutting a metal block, but if the tip of the prism portion 45 of the light conversion element has a knife edge shape, the cutting edge of the cutting tool has to be a knife edge shape, and the cutting tool There is a problem in terms of durability.

Further, when the top of each prism portion 45 has a knife-edge shape, there is a problem that the finished light conversion element is difficult to handle. That is, since the tops of the prism parts 45 are sharp, cracks or chips are likely to occur at the tops of the prism parts 45 during transportation or attachment to a liquid crystal display. On the other hand, if the tip of the top of each prism portion 45 is a flat surface 453 as in the fourth embodiment, such a problem does not occur. That is, the durability of the bite does not become a problem and the handling of the product does not become difficult. The width of the flat surface 453 is the same as in the case of the second embodiment described above.

FIG. 9 is a partial cross-sectional view showing an enlarged main part of the fifth embodiment of the present invention. In the fifth embodiment, the top end of each prism portion 45 has a curved surface 454. FIG. 9 (1) corresponds to a configuration in which the tip of the top is a curved surface 454 in the second embodiment. FIG. 9 (2) corresponds to the configuration in which the tip of the top portion is the curved surface 454 in the fourth embodiment. Figure 9 (1)
(2) In any of the configurations, as in the second and fourth embodiments, it is possible to improve the durability of the mold and the cutting tool and to easily handle the product. Also, the width of the curved surface 454 is preferably 0.1 μm or more and 5 μm or less, as in the second and fourth embodiments.

FIG. 10 is a schematic sectional view of another embodiment of the liquid crystal display of the present invention. In the liquid crystal display shown in FIG. 10, a lenticular sheet 7 is provided between the light conversion element 4 and the liquid crystal panel 1. The lenticular sheet 7 has a flat surface on the side of the light conversion element 4 and a liquid crystal panel 1.
The side surface is the lenticular surface 71. As shown in the enlarged view of FIG. 10, the lenticular surface 71 has a cross-sectional shape in which a large number of small convex lenses are packed and arranged. Each convex lens is long in the length direction of the linear light source 2, like each prism part 45 of the light conversion element 4. The lenticular sheet 7 improves the visibility (improves the viewing angle) when the liquid crystal display is viewed obliquely. That is, it has a function of slightly spreading the light from the light conversion element 4 in the lateral direction and making the screen easy to see even when viewed obliquely from a certain extent.

In this embodiment, the light is aligned in the front direction (thickness direction of the light converting element 4) by the light converting element 4, so that each convex lens of the lenticular sheet 7 is optimally designed to obtain a desired light. The effect of improving the viewing angle can be obtained. On the other hand, in the conventional configuration, light is not aligned in the front direction (thickness direction of the light conversion element 4), and thus it is difficult to obtain the desired effect of improving the viewing angle only by optimally designing the lenticular sheet 7.

FIG. 11 is a schematic plan view of still another embodiment of the liquid crystal display of the present invention. In the embodiment shown in FIG. 11, a point light source 20 is used. The light conversion element 4 has a substantially rectangular plate shape as shown in FIG. The point light source 20 is provided near one corner of the rectangular light conversion element 4. The light conversion element 4 has a small flat surface at the corner where the point light source 20 is provided. The light from the point light source 20 enters from the flat surface and propagates in the light conversion element 4. In some cases, the light that has entered the light conversion element 4 is transmitted to the end surface of the light conversion element while being totally reflected.

As shown in FIG. 11, the light conversion element 4 has a plurality of prism portions 45 extending in a concentric arc shape.
The center of the arc of each prism portion 45 substantially coincides with the position of the point light source 20. The cross-sectional shape and action of each prism portion 45 are the same as those in the above-described embodiments. Also in this embodiment, the light from the point light source 20 is emitted from each prism portion 45.
At, the light is reflected toward the front to illuminate a liquid crystal panel (not shown in FIG. 11). Since the angle formed by the two slopes of each prism portion 45 is 90 degrees or less, the ratio of forward movement increases, and a high optical path changing function can be obtained. Therefore, a bright liquid crystal display with an efficient screen is obtained.
The surface of the corner where the light from the point light source 20 is incident may be a concave lens surface, if necessary.

In each embodiment, as the material of the light conversion element, PMMA (methacryl or methacryl) resin excellent in light transmittance, PC (polycarbonate) resin excellent in heat resistance and moisture absorption, non-bornene resin, etc. are adopted. be able to. Although each prism portion 45 is formed on the back surface 43 and the front surface 42 is the flat surface 453 in the above description, this may be reversed. In this case, a reflective film or the like may be provided on the back surface 43 so that light does not leak to the side opposite to the liquid crystal panel 1 through the back surface 43. Further, the terms “front” and “rear surface” mean that the side that emits light is “front” and the opposite side is “rear”, and does not define the front and back in an actual use state or the like.

Further, the pitch of the prism portions 45 may refer to the distance between the ends of each prism portion 45 as well as the distance between the top portions. In each of the above embodiments, the light conversion element has a sheet shape, but it may be an optical element having a certain thickness. In this case, it may be better to call it a plate shape rather than a sheet shape. In any case, they are merely differences in relative thickness and have the same function and technical significance.

As an embodiment using a point light source, in addition to the above-mentioned one, there is a case where point light sources are arranged in a line on one side of the light conversion element 4 and light is incident from one end face. There is also a case where one point light source is once converted into a linear light source by an optical system and the light is made incident from one end face of the light conversion element 4 of the present embodiment. Further, the line light source that constitutes the liquid crystal display means a long and thin light source, and is not limited to a thin light emitting portion that can be regarded as a line. The same applies to the point light source, and the light emitting unit is not limited to a small size that can be regarded as a point.

[0032]

[Examples] Next, examples of the second embodiment will be described. As an example belonging to the second embodiment, the material of the light conversion element is PMMA resin, the angle θ1 formed by the two slopes 451 and 452 is 50 degrees, and the prism portion 45 is formed.
It is possible to adopt a configuration in which the depth d is 10 μm, the pitch p is 100 μm, and the width w of the flat surface 453 at the tip is 1 μm. The entire light conversion element is a sheet having a width of 500 mm, a depth of 400 mm and a thickness of 1 mm. In addition, as an example belonging to the fourth embodiment, the material is PM as well.
The angle θ1 formed by the MA resin and the two slopes 451 and 452 is 5
0 degree, the height of the prism portion 45 (indicated by h in FIG. 4) is 12
It is possible to adopt a configuration in which the pitch is 200 μm, the pitch p is 200 μm, and the width of the flat surface 453 at the tip is 1.5 μm.

[0033]

As described above, according to the invention described in claim 1 of the present application, the angle formed by the two inclined surfaces of each prism portion for reflecting the light incident from the end is 90 degrees or less, so The ratio of the light traveling toward the direction increases, and a high optical path changing function can be obtained. Therefore, when used in a liquid crystal display, the brightness of the screen does not decrease, and the light utilization efficiency is improved. According to the invention of claim 2, in addition to the above effects, the tip of the apex formed by the two slopes of the prism portion is a flat surface or a curved surface having a width of 0.1 μm or more and 5 μm or less, It is possible to improve the durability of the mold used for manufacturing the mold, the durability of the cutting tool used for manufacturing the mold, and to facilitate the handling of the product. According to the invention of claim 3, in addition to the above effect, the pitch of each prism portion is 5
Since the thickness is 0 μm or more and 300 μm or less, it is possible to obtain an effect that uneven brightness does not occur and light utilization efficiency does not decrease. Further, according to the invention of claim 4, in addition to the above effects, since the depth or height of each prism portion is 10% or less of the total thickness, uneven brightness or light is generated. It is possible to obtain the effect that the utilization efficiency of the is not reduced. Further, according to the invention described in claim 5, it is possible to obtain the effect that the liquid crystal display having the above-mentioned effect is provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a light conversion element and a liquid crystal display including the light conversion element according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing an enlarged main part of the light conversion element 4 shown in FIG.

FIG. 3 is a diagram illustrating an operation of the light conversion element 4 shown in FIGS. 1 and 2.

FIG. 4 is a diagram showing a case where an angle θ1 formed by inclined surfaces 451 and 452 of the prism portion 45 is larger than 90 degrees.

FIG. 5 is a partial cross-sectional view showing an enlarged main part of the light conversion element according to the second embodiment.

FIG. 6 is a diagram showing a manufacturing problem when the top of the prism portion 45 has a knife edge shape.

FIG. 7 is a partial cross-sectional view showing an enlarged main part of a light conversion element according to a third embodiment.

FIG. 8 is a partial cross-sectional view showing an enlarged main part of a fourth embodiment of the present invention.

FIG. 9 is a partial cross-sectional view showing an enlarged main part of a fifth embodiment of the present invention.

FIG. 10 is a schematic cross-sectional view of another embodiment of the liquid crystal display of the present invention.

FIG. 11 is a schematic plan view of still another embodiment of the liquid crystal display of the present invention.

FIG. 12 is a front sectional view showing a conventional technique.

[Explanation of symbols]

1 LCD panel 2 line light source 20 point light source 4 Optical conversion element 41 incident surface 42 front 43 back 44 Reflective surface 45 Prism part 451 slope 452 slope 453 flat surface 454 curved surface 7 Lenticular sheet

Claims (5)

[Claims] 1. A sheet-like or plate-like light for converting a line light source or a point light source into a surface light source by allowing light from a line light source or a point light source to enter from an end surface, internally reflected and emitted from a front surface or a back surface. In the conversion element, a large number of prism portions that reflect the light incident from the end face are formed on the front surface or the back surface, and the angle formed by the two inclined surfaces of each prism portion is 90 degrees or less. Characteristic light conversion element. 2. The light conversion element according to claim 2, wherein the tip of the apex formed by the two slopes of the prism portion is a flat surface or a curved surface having a width of 0.1 μm or more and 5 μm or less. 3. The pitch of each prism portion is 50 μm
3. The light conversion element according to claim 1, wherein the light conversion element has a thickness of 300 μm or less. 4. The light conversion element according to claim 1, wherein the depth or height of each prism portion is 10% or less of the total thickness. 5. A liquid crystal panel for displaying an image by controlling transmission and blocking of light, a line light source or a point light source for generating light for illuminating the liquid crystal panel, and light from the line light source or the point light source from an end surface. A liquid crystal display comprising a sheet-shaped or plate-shaped light conversion element that converts a line light source or a point light source into a surface light source by making the light incident, internally reflected, and emitted from the front surface or the back surface, wherein the light conversion element comprises: The liquid crystal display according to any one of claims 1 to 4, wherein the liquid crystal panel is illuminated by emitted light.