Lenticular lens sheet and process for producing the same

A lenticular lens sheet comprising a base member in the form of a film or sheet, and a lens area including lenticular lenses convexly formed on the light-entering surface of the base member. The lens area is formed by using an ionizing-radiation-curable resin such as an ultraviolet-light- or electron-beam-curable resin. A non-colored layer which is substantially transparent and non-colored is formed in each lenticular lens on the base side thereof; and a colored layer is formed in each lenticular lens along the light-entering surface thereof. The colored layer has the function of enhancing the contrast of the incident-side single lenticular lens sheet. According to this lenticular lens sheet, it is possible to obtain enhanced contrast by preventing the reflection of extraneous light without lowering the intensity of imaging light so much, and to make the lenticular lens pitch extremely small.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a lenticular lens sheet suitable for 
projecting an image by using an imaging light source having cell structure 
such as an LCD (liquid crystal display) or DMD (digital micro-mirror 
device), and to a process for producing such a lenticular lens sheet. 
2. Related Art 
Heretofore, there has been known a rear-projection-type television 
comprising an imaging light source composed of three CRTs (cathode ray 
tubes) of red, green and blue, and a rear projection screen on which an 
image is projected by the imaging light source. 
In such a projection television, a screen which is a combination of a 
Fresnel lens sheet and a lenticular lens sheet is used as the rear 
projection screen. Of these lens sheets, the lenticular lens sheet is 
required to diffuse light widely, and to be less affected by extraneous 
light. 
FIG. 13 is a view showing one example of a conventional lenticular lens 
sheet. In a lenticular lens sheet 40 shown in FIG. 13, a lens area 42 
containing a plurality of lenticular lenses for condensing light 
(hereinafter sometimes referred to simply as "lenses") is formed on the 
light-entering surface 41 of the lenticular lens sheet 40; and a 
light-emerging surface 44 is formed in the vicinity of the focal point 
(condensing point) of each lens in the lens area 42. A non-light-emerging 
area 47 containing light-shielding parts (black stripes) 48 is provided on 
the light-emerging surface 44, between the focal points of each two lenses 
in the lens area 42, so that it is possible to diffuse light and to reduce 
the effect of extraneous light. 
In the field of the above-described projection television, there has also 
been developed a television using an LCD, DMD or the like as the imaging 
light source. Also in such a projection television, a lenticular lens 
sheet with black stripes as shown in FIG. 13 is used from the viewpoints 
of improvement in the light-diffusing property and prevention of the 
reflection of extraneous light. 
However, in the projection television using an LCD, DMD or the like as the 
imaging light source, a grating pattern originating from the cell 
structure of the LCD, DMD or the like is projected on the rear projection 
screen. The lenticular lens sheet for use in the rear projection screen 
has a cyclic structure with a constant pitch. Therefore, when an image is 
projected on such a lenticular lens sheet, Moire fringes formed due to the 
sampling effect of the lenticular lenses may be observed. 
In order to prevent the formation of such Moire fringes, it is preferable 
to make the lenticular lens pitch not greater than 1/3.5 of the grating 
space of the grating pattern projected. Further, in the projection 
television using an LCD, DMD or the like, glaring of the projected image 
called scintillation occurs. To make the lenticular lens pitch small is 
also useful for reducing this scintillation. It has already been known 
that, in the lenticular lens sheet with black stripes as shown in FIG. 13, 
it is generally required to make the distance between the lenticular 
lenses formed on the light-entering surface and the light-emerging surface 
not more than approximately 1.3 times the lenticular lens pitch if it is 
desired to diffuse light widely at a diffusion angle of 40 degrees or 
more, and to form black stripes on the light-emerging surface. 
For this reason, in the lenticular lens sheet with black stripes as shown 
in FIG. 13, the lenticular lens pitch is made 0.4 mm or less, and the 
thickness of the lenticular lens sheet, which corresponds to the distance 
between the lenticular lenses and the light-emerging surface, is made 0.54 
mm or less so that Moire fringes formed due to the grating pattern 
projected on the rear projection screen and the cyclic structure of the 
lenticular lenses will be vague. 
However, in the lenticular lens sheet with black stripes as shown in FIG. 
13, when the thickness of the lenticular lens sheet is made small, the 
rigidity of the lens sheet is decreased, so that it becomes difficult to 
maintain the lenticular lens sheet flat. Moreover, it is extremely 
difficult to accurately mold such a thin lenticular lens sheet by means of 
extrusion molding or the like. 
On the other hand, in the above-described projection television using an 
LCD, DMD or the like, an emergent-side single lenticular lens sheet, an 
incident-side single lenticular lens sheet or the like which has been 
colored is also used in order to improve the light-diffusing property and 
to prevent the reflection of extraneous light. 
In the emergent-side single lenticular lens sheet, the shape of a part of a 
circle or ellipse, or a shape utilizing total reflection is adopted as the 
shape of the cross section of the lenticular lens. However, in the case 
where the shape of the cross section of the lenticular lens is a part of a 
circle or ellipse, total reflection occurs when the lens angle formed with 
incident light at the base of the lens exceeds the critical angle. 
Therefore, the viewing angle cannot be made wide. Further, in the case of 
the shape utilizing total reflection, it is impossible to accurately 
transfer the lens pattern by means of extrusion molding because of its 
peculiar shape. Consequently, it is inevitable to produce such a 
lenticular lens sheet by a cast molding method which is poor in 
productivity. 
FIG. 14 is a view for illustrating the relationship between the inclination 
of a lens at the point at which light enters into an incident-side single 
lenticular lens sheet, and the emergent angle of this light. As shown in 
FIG. 14, in an incident-side single lenticular lens sheet 60, a lens area 
62 containing a plurality of lenticular lenses for condensing light is 
formed on the light-entering surface 61 of the lenticular lens sheet 60. 
In FIG. 14, the symbol .phi. represents the lens angle (inclination) at 
the base of each lens in the lens area 62; the symbol .theta. represents 
the emergent angle of light which has entered into the base of each lens 
in the lens area 62; the symbol h represents the height of the lens area 
62; and the symbol L represents the distance between the incident point 
(the base of each lens in the lens area 62) and the condensing point. 
The relationship between the lens angle .phi. at the base of the lens, and 
the emergent angle .theta. and the position of the condensing point is 
shown in the following Table 1, where the refractive index n of the 
lenticular lens sheet is 1.5, and the lens pitch p is 1.0 mm. 
TABLE 1 
______________________________________ 
(n = 1.5, p = 1.0 mm) 
.phi.[deg] 
.theta.[deg] L[mm] H[mm] 
______________________________________ 
30 15.9 2.69 0.14 
40 22.3 1.92 
0.19 
50 29.7 1.42 
0.26 
60 38.9 1.08 
0.33 
70 51.0 0.83 
0.42 
______________________________________ 
It can be understood from the data shown in the above Table 1 hat, in the 
incident-side single lenticular lens sheet 60 as shown in FIG. 14, it is 
necessary to make the lens angle .phi. at the base of the lens sixty 
degrees or more in order to obtain a wide viewing angle with an emergent 
angle .theta. of 40 degrees or more. 
However, in such an incident-side single lenticular lens sheet 60, when the 
lens angle .phi. at the base of the lens is made large, extraneous light D 
which has entered from the light-emerging surface 64 side is totally 
reflected at the lens, and emerges again from the light-emerging surface 
64 as shown in FIG. 3B, and this light is observed (see symbols D1, D2, D3 
and D4). For this reason, the image contrast is drastically decreased. 
It is noted that, in the case of a conventional lenticular lens sheet with 
black stripes, the light-emerging surface is formed in the vicinity of the 
focal point (condensing point) of each lens in the lens area and that the 
distance between the lens area formed on the light-entering surface and 
the light-emerging surface is equal to "h+L". In the above Table 1, the 
distance "h+L" is 1.41 when the lens angle .phi. is 60 degrees, and 1.25 
when .phi. is 70 degrees. It can thus be understood that it is necessary 
to make the distance between the lens area formed on the tight-entering 
surface and the light-emerging surface approximately 1.3 times the lens 
pitch. For this reason, in the case of the conventional lenticular lens 
sheet with black stripes, when the lens pitch is made small, the 
lenticular lens sheet becomes thin, so that such problems that the 
rigidity of the lens sheet is decreased and that it becomes difficult to 
mold such a lens sheet are brought about as contrasted in the case of the 
incident-side single lenticular lens sheet in which it is not always 
necessary to make the distance between the lens area and the 
light-emerging surface "h+L". 
SUMMARY OF THE INVENTION 
The present invention was accomplished by taking the aforementioned 
problems in the prior art into consideration. An object of the present 
invention is therefore to provide a lenticular lens sheet that can prevent 
the reflection of extraneous light without lowering the intensity of 
imaging light so much to obtain enhanced contrast and in which the 
lenticular lens pitch can be made extremely small, and a process for 
producing such a lenticular lens sheet. 
A first aspect of the present invention is a lenticular lens sheet 
comprising a base member in the form of a film or sheet; and a lens area 
including a plurality of lenticular lenses convexly formed on a 
light-entering surface of the base member, wherein a non-colored layer is 
formed in the base member, or each lenticular lens of the lens area on the 
base side thereof, and a colored layer is formed in each lenticular lens 
of the lens area at least at the apex thereof. 
In the first aspect of the present invention, it is preferable that the 
lenticular lens sheet further comprises a substantially transparent front 
sheet provided on the light-emerging surface side of the base member, and 
a surface-treatment layer provided on the light-emerging surface side of 
the base member or on the front surface of the front sheet. It is 
preferable that at least one layer selected from an antireflection layer, 
an antistatic layer, a scratch resistant layer, a polarized light filter 
layer, an antistaining layer, a magnetic-wave-shielding layer, an 
antiglaring layer and a layer functioning as a touch sensor be included in 
the surface-treatment layer. Further, it is preferable that the lens area 
be formed by using an ionizing-radiation-curable resin. 
A second aspect of the present invention is a process for producing a 
lenticular lens sheet, comprising the steps of coating a non-colored 
ionizing-radiation-curable resin onto one surface of a base member in the 
form of a film or sheet; coating a colored ionizing-radiation-curable 
resin onto a lens-shaping mold on which a lenticular lens pattern has been 
formed; nipping the base member against the lens-shaping mold with the 
non-colored resin and the colored resin facing each other; and curing the 
non-colored resin and the colored resin by applying thereto ionizing 
radiation. 
In the second aspect of the present invention, it is preferable that the 
process further comprises the step of drying the non-colored resin coated 
onto the base member and that the fluidity of the non-colored resin coated 
onto the base member be lower than that of the colored resin at the time 
when the lens is shaped. Moreover, it is preferable that the process 
further comprises the step of integrating the base member and a 
substantially transparent front sheet by means of coating and/or 
lamination, and the step of forming a surface-treatment layer on the 
light-emerging surface of the base member or on the front surface of the 
front sheet by means of coating and/or lamination. It is preferable that 
the base member be fed as a continuous film or sheet. 
According to the first and second aspects of the present invention, 
enhanced contrast can be obtained by preventing the reflection of 
extraneous light without lowering the intensity of imaging light so much, 
and a lenticular lens sheet in which lenticular lens pitch is extremely 
small can be obtained.

DETAILED DESCRIPTION OF THE INVENTION 
By referring to the accompanying drawings, embodiments of the present 
invention will now be described in detail. 
FIG. 1A is a view showing a rear projection screen in which a lenticular 
lens sheet according to the first embodiment of the present invention is 
used; and FIG. 1B is an enlarged view of the part B in FIG. 1A, showing 
the lenticular lens sheet according to the first embodiment of the present 
invention. FIG. 2 is a view for illustrating the reflection of extraneous 
light in the lenticular lens sheet shown in FIGS. 1A and 1B. 
As shown in FIG. 1A, a lenticular lens sheet 10 according to this 
embodiment constitutes a rear projection screen 1 together with a Fresnel 
lens sheet 20. Further, this rear projection screen 1 constitutes a rear 
projection system together with a light source 2 such as an LCD projector. 
As shown in FIG. 1B, the lenticular lens sheet includes a base member 15 in 
the form of a film or sheet, and a lens area 12 including lenticular 
lenses convexly formed on the light-entering surface 11 side of the base 
member 15. 
The lens area 12 is formed by using an ionizing-radiation-curable resin 
such as an ultraviolet-light- or electron-beam-curable resin. A 
non-colored layer 12A which is substantially transparent and non-colored 
is formed in each lenticular lens on the base side thereof; and a colored 
layer 13 is formed in each lenticular lens along the light-entering 
surface 11 thereof. It is noted that the colored layer 13 has the function 
of enhancing the contrast of the incident-side single lenticular lens 
sheet 10. 
FIGS. 3A and 3B are views for illustrating the function of the colored 
layer in the lenticular lens sheet 10 according to this embodiment by 
comparison with a conventional incident-side single lenticular lens sheet 
60. 
As shown in FIG. 3B, the conventional lenticular lens sheet 60 is an 
incident-side single lenticular lens sheet of body colored type in which a 
base layer 65 is colored entirely. In the lenticular lens sheet 60 shown 
in FIG. 3B, extraneous light D (D1) which has entered from the observation 
side is totally reflected at a lens area 62 formed on the light-entering 
surface 61 of the lenticular lens sheet 60, and emerges again toward the 
observation side as extraneous light D4. In this process, the extraneous 
light D1 is repeatedly reflected along, the outline of the lenticular lens 
in the lens area 62 (D1.fwdarw.D2.fwdarw.D3.fwdarw.D4). 
On the other hand, in the lenticular lens sheet 10 according to this 
embodiment, the colored layer 13 is formed along the optical path of light 
which is totally reflected along the outline of the lenticular lens in the 
lens area as shown in FIG. 3A. Therefore, the optical path length of 
extraneous light D in the colored layer 13 is approximately 5 to 10 times 
the optical path length of imaging light A in the colored layer 13. It is 
noted that, in the case of the conventional lenticular lens sheet 60 of 
body-colored type shown in FIG. 3B, the optical path length of extraneous 
light D in the colored layer (base layer 65) is only about 2 to 3 times 
the optical path length of imaging light A in the colored layer (base 
layer 65). 
For this reason, according to the lenticular lens sheet 10 of this 
embodiment, it is possible to prevent the reflection of extraneous light D 
without lowering the intensity of imaging light A so much. It is thus 
possible to obtain a screen excellent in contrast. 
The lenticular lens sheet 10 according to this embodiment is characterized 
by efficiently absorbing extraneous light D which is totally reflected at 
each lens in the lens area 12 formed on the light-entering surface 11. 
Therefore, in order to allow each lens in the lens area 12 to totally 
reflect the extraneous light D, each lens in the lens area 12 is required 
to have a portion whose inclination is such that the angle .phi. formed 
with the screen surface (see FIG. 4) is at least equal to the critical 
angle (approximately 42 degrees). A lenticular lens sheet including a lens 
area 12 having a portion whose inclination is smaller than the 
above-described value cannot be superior to the lenticular lens sheet 60 
of body colored type. 
FIG. 4 is a view for illustrating the relationship between the angle of the 
lens area in the lenticular lens sheet formed with the screen surface, and 
the incident angle of extraneous light. As shown in FIG. 4, the incident 
angle .phi.' at the time when extraneous light which has vertically 
entered into the lenticular lens sheet emerges from or is totally 
reflected at the lens area 12, is equal to the lens angle .phi. formed 
with screen surface at this site. Namely, in FIG. 4, the line L-L' 
(tangent) and the line M-M' (normal) intersect at a right angle, and i=i', 
so that .phi. is equal to .phi.'. 
For this reason, in order to allow each lens in the lens area 12 to totally 
reflect the extraneous light D, each lens in the lens area 12 is required 
to have a portion at which the lens angle .phi. is equal to or more than 
the critical angle sin.sup.-1 (1/n) (wherein n represents the refractive 
index of the lenticular lens sheet). 
However, as shown in the above Table 1, when the inclination is 
approximately 42 degrees, only a narrow diffusion angle of approximately 
25 degrees can be obtained. It is, therefore, generally desirable that 
each lens in the lens area 12 has a portion at which the lens angle is 
approximately 60 degrees or more so that the diffusion angle will be 40 
degrees or more. 
The coloring method for obtaining the above-described colored layer 13, and 
the color, color density, shape and thickness of the colored layer 13 will 
be described in detail hereinafter. 
The Coloring Method for Obtaining Colored Layer) 
It is preferable that coloring for obtaining the colored layer 13 be 
effected by incorporating or dispersing a dye or pigment in a molding 
resin of ionizing radiation curable type. 
(Color of Colored Layer) 
As the color of the colored layer 13, it is preferable to use an achromatic 
color such as gray, or a color capable of selectively absorbing or 
transmitting light of a specific color to control the balance of three 
primary colors (red, green and blue) in the spectral properties of the 
light source. 
(Color Density of Colored Layer) 
It is preferable that the color density of the colored layer 13 be made 
higher than those of the layers positioned on the light-emerging surface 
14 side in terms of the colored layer 13 (the non-colored layer 12A and 
the base member 15) and that the color density of the non-colored layer 
12A and that of the base member 15 be made either 0 or low, thereby 
reducing the effect of extraneous light without lowering so much the 
transmittance of projection light (imaging light) emitted by the light 
source 2. 
Specifically, it is preferable that the color density of the colored layer 
13 be so made that the transmittance of the lenticular lens sheet 10 will 
be from 40 to 70%. When the color density is made low so that the 
transmittance will be higher than 70%, although the transmittance is 
increased, the intensity of extraneous light which is totally reflected at 
the lens area 12 and returned to the observation side is increased; the 
contrast is thus lowered. On the contrary, when the color density is made 
high so that the transmittance will be lower than 40%, the transmittance 
of imaging light is merely decreased, and the reflection of extraneous 
light at the light-emerging surface 14 becomes relatively outstanding. The 
contrast is thus lowered also in this case. 
FIG. 5 is a view showing the relationship between the transmittance of the 
lenticular lens sheet according to this embodiment, and contrast. 
Lenticular lens sheets 10 including colored layers with different color 
densities were prepared, and the transmittance and reflectance of each of 
these lenticular lens sheets were respectively measured by a 
spectrophotometer ("UV 2100" manufactured by Shimadzu Corp., Japan). The 
reflectance and transmittance/reflectance ratio were plotted against 
transmittance (abscissa). The reflectance can be read from the ordinate on 
the left-hand side; and the transmittance/reflectance ratio can be read 
from the ordinate on the right-hand side. 
The transmittance is increased when the color density is decreased, and the 
reflectance is drastically increased at around the point at which the 
transmittance exceeds 70% as shown in FIG. 5. This is because it becomes 
difficult for the colored layer 13 to sufficiently absorb extraneous light 
when the color density of the colored layer 13 is decreased. The 
lenticular lens sheet 10 according to this embodiment does not absorb 
extraneous light reflected at the light-emerging surface 14 on the 
observation side. Therefore, also in the case where the transmittance is 
decreased by increasing the color density, the transmittance/reflectance 
ratio is decreased, and a peak is observed when the transmittance is 50%. 
For this reason, it is preferable as mentioned above that the color density 
of the colored layer 13 be made so that the transmittance of the 
lenticular lens sheet 10 will be from 40 to 70%. 
In the case where a transmission-type LCD light source is used as the light 
source 2, the output of the LCD light source is not so great, and there is 
also a limitation to sacrifice the transmittance. Therefore, it is more 
preferable that the color density of the colored layer 13 be so made that 
the transmittance will be from 45 to 60%. 
(Shape of Colored Layer) 
FIG. 6 is a view for illustrating the optimum thickness of the colored 
layer in the lenticular lens sheet according to this embodiment. 
As mentioned previously, the lenticular lens sheet 10 according to this 
embodiment utilizes such a phenomenon that extraneous light which has 
entered into the light-emerging surface 14 on the observation side travels 
along the lens area 12. It is therefore preferable to make the colored 
layer 13 follow the outline of the lens area 12. 
In this case, the minimum geometrical optical thickness t.sub.min of the 
colored layer 13 is equal to the height of the lens at the position at 
which the inclination .phi. of the tangent T to the lens area 12 is 45 
degrees. When the shape of the cross section of the lens is an ellipse, 
this thickness can be calculated from the following equation (1): 
EQU t.sub.min =b-b.sup.2 (a.sup.2 +b.sup.2).sup.1/2 (1) 
wherein a and b are the transverse diameter (minor axis) and longitudinal 
diameter (major axis) of the ellipse, respectively (see FIG. 1B). It is 
noted that, when the thickness of the colored layer 13 is made equal to 
the value of t.sub.min calculated from the above equation (1), the best 
contrast can be obtained. 
In the case of an elliptical lenticular lens whose cone constant k is 
approximately 0.45 (=a.sup.2 /b.sup.2 -1) and whose lens angle at the base 
of the lens is approximately 60 degrees, the above-described t.sub.min is 
approximately 1/10 of the lens pitch. 
On the other hand, even in the case where the colored layer 13 does not 
follow the outline of the lens area 12, for instance, even when the lens 
area 12 in whole is made as the colored layer 13 while the base member 15 
is made as the non-colored layer 12A, or even when the boundary face 
between the colored layer 13 and the non-colored layer 12A is flat, a 
lenticular lens sheet 10 which is superior to the lenticular lens sheet 60 
of body-colored type can be obtained as can be expected from the 
comparison shown in FIGS. 3A and 3B. 
In the case where the lens area 12 in whole is made as the colored layer 
13, the colored layer 13 is made thinner as much as possible. It is 
therefore preferable to make the thickness of the colored layer 13 equal 
to or smaller than the lenticular lens pitch, or not greater than 1/2 of 
the thickness of the lenticular lens sheet. 
(Distribution of Thickness of Colored Layer) 
FIG. 7 is a view for illustrating the optimum distribution of the thickness 
of the colored layer in the lenticular lens sheet according to this 
embodiment. 
In one lens in the lens area 12, it is preferable that the colored layer 13 
be so made that the thickness t1b at the base 12b of the lens will be 
smaller than the thickness t1a at the apex 12a of the lens (t.sub.1a 
&gt;t.sub.1b). This is because, when the thickness of the colored layer 13 is 
made uniform, the optical path length in the colored layer 13 of imaging 
light which has entered into the base 12b of the lens becomes longer than 
that of imaging light which has entered into the apex 12a of the lens area 
12, so that the former imaging light is absorbed greatly by the colored 
layer 13 as compared with the latter imaging light. As a result, the 
intensity of light which emerges at a diffusion angle of 30 to 40 degrees 
is decreased (see FIG. 8). 
FIG. 8 is a graph showing the light-diffusing property of the lenticular 
lens sheet according to this embodiment, by comparing a case where the 
thickness of the colored layer is made uniform with a case where the 
thickness of the colored layer at the base of the lens is made small. 
As shown in FIG. 8, in the lenticular lens sheet 10 according to this 
embodiment, the above-described phenomenon (decrease in the intensity of 
light emerging at a diffusion angle of 30 to 40 degrees) can be prevented 
by making thickness of the colored layer 13 at the base 12b of the lens 
small. 
It is preferable to vary the thickness of the colored layer 13 depending 
upon the optical path length of incident light. By doing so, it is 
possible to obtain the desired light-diffusing property corresponding to 
lens design. Further, it is also possible to diffuse incident light 
without incorporating any diffusing agent into the colored layer 13, but 
(1) by forming a diffusing agent layer in the non-colored layer 12A, or 
(2) by forming a matte layer on the light source side in terms of the 
lenticular lens sheet by the use of a metal mold having a matte surface or 
by making the surface of the molded lens matted. 
It is noted that the light-emerging surface 14 of the lenticular lens sheet 
10 according to this embodiment is smooth or matted. 
In the case where the light-emerging surface 14 is made smooth, clearness 
can be given to the image projected. In this case, it is not necessary to 
place a transparent flat panel in front of the screen, so that the screen 
is free from unfavorable reflection from the light-entering surface (back 
surface) of the flat panel. Consequently, a favorable image can be 
obtained. Further, when the light-emerging surface 14 is made smooth, an 
antireflection layer, a low-reflection layer, a polarized light filter 
layer or the like can be provided as the surface-treatment layer. In this 
case, contrast comparable to contrast obtainable by the conventional 
lenticular lens sheet with black stripes can be obtained. Furthermore, it 
is also possible to form, on the light-emerging surface 14, an antistatic 
layer, a scratch resistant layer (hard coat layer), an antiglaring layer, 
an antistaining layer, a magnetic-wave-shielding layer, or a layer 
functioning as a touch sensor. 
On the contrary, when the light-emerging surface 14 is matted, it becomes 
antiglaring. Therefore, to matting the light-emerging surface 14 is useful 
for protecting the screen surface from unfavorable reflection. 
Thus, the light-emerging surface 14 of the lenticular lens sheet 10 
according to this embodiment is flat, so that it is possible to form 
thereon a variety of surface-treatment layers (function layers). Further, 
by laminating a substantially transparent sheet to the lenticular lens 
sheet 10 in order to make the lens sheet rigid, a front panel which is 
usually used for a screen including the conventional lenticular lens sheet 
with black stripes can be omitted. 
In the lenticular lens sheet 10 according to this embodiment, an optical 
axis correcting lens is not formed on the light-emerging surface 14. It is 
therefore preferable to use, as the light source 2, a projector of single 
lens or tube type which projects imaging light from one lens. Further, as 
the light source 2, it is preferable to use an LCD or DMD projector or the 
like in which light from a lamp is split into spectra of three primary 
colors by a dichromic mirror, image information is given by transmitting 
the spectra through an LCD, and the spectra are then combined again and 
projected. 
Second Embodiment 
By referring now to FIG. 9, a second embodiment of the lenticular lens 
sheet according to the present invention will be described. The second 
embodiment of the present invention is almost the same as the first 
embodiment shown in FIGS. 1A and 1B except that a front sheet and a 
surface-treatment layer are provided on the light-emerging surface side of 
a base member. In the second embodiment of the present invention, the same 
parts as in the first embodiment shown in FIGS. 1A and 1B are represented 
by the same symbols, and detailed explanations for these parts are 
omitted. 
As shown in FIG. 9, in a lenticular lens sheet 10 according to this 
embodiment, a substantially transparent and non-colored front sheet 17 is 
provided on the light-emerging surface of a base member 15. The front 
sheet 17 is useful for increasing the rigidity of the lenticular lens 
sheet 10. A resin sheet such as an acrylic resin, polycarbonate, styrene 
or polyolefin resin sheet can desirably be used as the front sheet 17. 
Further, a surface-treatment layer 18 is provided on the front surface of 
the front sheet 17. As the surface-treatment layer 18, it is preferable to 
form at least one of the following layers: an antireflection layer, an 
antistatic layer, a scratch resistant layer (hard coat layer), a polarized 
light filter layer, an antistaining layer, a magnetic-wave-shielding 
layer, an antiglaring layer, and a layer functioning as a touch sensor. 
It is also possible to directly form the surface-treatment layer 18 on the 
front surface of the base member 15 without providing the front sheet 17 
as described above. 
Process for Producing Lenticular Lens Sheet 
A process for producing a lenticular lens sheet according to the 
above-described first or second embodiment of the present invention will 
be described hereinafter. 
An example of a system for producing a lenticular lens sheet is shown in 
FIG. 10. 
As shown in FIG. 10, a production system 50 is composed of a roll 51 around 
which a base member 15 in the form of a continuous film is wound, a coater 
52 for coating a non-colored ultraviolet-light-curable resin 12A which is 
substantially transparent and non-colored and which has been diluted with 
a solvent onto one surface (light-entering surface) of the base member 15, 
a dryer 53 for drying the non-colored resin 12A coated onto the base 
member 15, a metal mold roll (lens-shaping mold) 54 on which a lenticular 
lens pattern has been formed, a dispenser 55 for coating a colored 
ultraviolet-light-curable resin 13 onto the metal mold roll 54, a nip roll 
56 for nipping the base member 15 against the metal mold roll 54 with the 
colored resin 13 and the non-colored resin 12A facing each other, a UV 
lamp 57 for applying ultraviolet light to the colored resin 13 and the 
non-colored resin 12A on the metal mold roll 54, and a release roll 58 for 
releasing the shaped lenticular lens sheet from the metal mold roll 54. 
Next, a process for producing a lenticular lens sheet according to the 
first or second embodiment of the present invention, by using the 
production system shown in FIG. 10 will be described. 
FIG. 11 is a flow sheet for illustrating one example of a process for 
producing a lenticular lens sheet according to the first embodiment of the 
present invention. 
At first, a highly-viscous non-colored resin 12A is diluted with a solvent, 
and the diluted resin solution is coated onto one surface of a base member 
15 in the form of a film by the coater 52 (step 101). Subsequently, the 
coated resin is dried by the dryer 53 using hot air to form a non-colored 
resin layer having restrained fluidity (step 102). It is noted that this 
step 102 can be omitted depending upon the production conditions to be 
employed. 
Next, a colored ultraviolet-light-curable resin 13 is coated onto the metal 
mold roll 54 (step 103), and the base member on which the non-colored 
resin 12A has been coated is then nipped against the metal mold roll 54 on 
which the colored resin 13 has been coated so that the colored resin 13 
and the non-colored resin 12A can be laminated to each other (step 104). 
Thereafter, ultraviolet light is applied by the UV lamp 57 from the base 
member 15 side to cure the colored resin 13 and the non-colored resin 12A 
(step 105). 
Finally, a lenticular lens sheet 10 in which a lens area 12 composed of the 
colored resin 13 and the non-colored resin 12A has been formed on the base 
member 15 is released from the metal mold roll 54 (step 106). 
In this production process, a urethane acrylate or epoxy acrylate resin can 
be used as the ionizing-radiation-curable resin. The colored resin 13 can 
be obtained by mixing a dye or pigment, or a colored UV ink with the 
above-described resin. 
It is preferable that the fluidity of the non-colored resin 12A be lower 
than that of the colored resin 13 at the time when a lens is shaped. This 
is effective to obtain a two- layer structure without bringing about 
unfavorable mixing of the pre coat resin (non-colored resin 12A) with the 
colored resin 13 during the step of nipping. To attain this, a polymer may 
be added to the non-colored resin 12A; or the molecular weight of an 
oligomer or polymer may be increased. 
FIG. 12 is a flow sheet for illustrating one example of a process for 
producing a lenticular lens sheet according to the second embodiment of 
the present invention. The steps 101 to 106 shown in FIG. 12 are identical 
with the steps 101 to 106 shown in 11. 
To provide a front sheet on the lenticular lens sheet 10, the step of 
forming a substantially transparent, and non-colored front sheet 17 on the 
base member 15 by means of coating or lamination (step 107) is added, as 
shown in FIG. 12, to the process shown in FIG. 11. 
Further, to provide a surface-treatment layer 18, the step of forming a 
surface-treatment layer 18 which is at least one of an antireflection 
layer, an antistatic layer, a scratch resistant layer, a polarized light 
filter layer, an antistaining layer, a magnetic-wave-shielding layer, an 
antiglaring layer, and a layer functioning as a touch sensor on the base 
member 15 or on the front surface of the front sheet 17 by means of 
coating and/or lamination (step 108) is added to the process shown in FIG. 
11. 
It is noted that the step of forming a front sheet 17 onto the base member 
15 (step 107) may be conducted after the surface-treatment layer 18 is 
formed onto the front sheet 17 (step 108). 
According to this production process, since a lenticular lens sheet is 
formed by the use of an ultraviolet-light-curable resin, it is possible to 
obtain a lenticular lens sheet having an ultrafine lens pitch of 100 
micrometers or less. 
Further, the base member 15 is fed as a continuous film or sheet, so that 
it is continuously, subjected to shaping. Consequently, it is possible to 
attain improved productivity. 
EXAMPLES 
Specific examples of a lenticular lens sheet according to the 
aforementioned first embodiment will be given hereinafter. 
Example 1 
A lenticular lens sheet 10 according to the above-described first 
embodiment was prepared, in which the shape of the cross section of the 
lenticular lens in the lens area 12 was an ellipse, the lens pitch p was 
50 micrometers, the transverse diameter a of the ellipse was 24 
micrometers, and the longitudinal diameter b of the ellipse was 26 
micrometers. An ultraviolet-light-curable resin having a refractive index 
of 1.55 was used for forming the non-colored layer 12A; the resin was 
coated onto the base member 15 so that the thickness t.sub.2 of the 
resulting non-colored layer 12A would be 10 micrometers. Further, a 
mixture obtained by dispersing black pigment in the above-described 
ultraviolet-light-curable resin was used for forming the colored layer 13; 
the mixture was coated onto the metal mold roll on which the reverse 
pattern of the lenticular lens was formed. As the base member 15, a PET 
film having a thickness t.sub.3 of 0.25 mm was used. The lenticular lens 
sheet 10 was produced in accordance with the production process shown in 
FIG. 11, by using the production system 50 shown in FIG. 10. In this case, 
the colored layer 13 having a thickness of 7 .mu.m at the apex thereof was 
formed by adjusting the nipping pressure of the nipping roll. 
Example 2 
A lenticular lens sheet 10 was prepared by laminating a transparent film 
having an antireflection layer 18 to the light-emerging surface 14 of a 
lenticular lens sheet 10 prepared in accordance with the same manner as in 
Example 1. 
Comparative Example 1 
An incident-side single lenticular lens sheet 60 of body-colored type in 
the same shape as that of the lenticular lens sheet 10 of Example 1, 
capable of giving screen gain comparable to one given by the lenticular 
lens sheet 10 of Example 1 was prepared. 
Comparative Example 2 
A lenticular lens sheet was prepared by forming black stripes with a pitch 
p of 0.72 mm (black stripe rate: 45%) on the lenticular lens sheet of 
Comparative Example 1. 
Results of Evaluation 
The lenticular lens sheets of Example 1 and Comparative Example 1 were 
respectively combined with a Fresnel lens sheet into which a diffusing 
agent, acrylic beads having a mean particle diameter of 30 micrometers, 
had been incorporated, thereby forming rear projection screens. These 
screens were respectively set in a rear-projection-type television using 
an LCD light source, and a comparative test was carried out. Specifically, 
the lenticular lens sheet of Example 1 and that of Comparative Example 1 
were set on the right side and left side of the television, respectively, 
and images projected on the screens were observed in a room lighted by a 
fluorescent lamp. As a result, it was found that the screen using the 
lenticular lens sheet of Example 1 was excellent in contrast as compared 
with the screen using the lenticular lens sheet of Comparative Example 1. 
Subsequently, the lenticular lens sheets of Examples 1 and 2 and 
Comparative Examples 1 and 2were respectively combined with a Fresnel lens 
sheet into which a diffusing agent, acrylic beads having a mean particle 
diameter of 30 micrometers, had been incorporated, thereby forming rear 
projection screens. The transmittance and reflectance at a wavelength of 
550 nm of each of these screens were measured by a spectrophotometer ("UV 
2100" manufactured by Shimadzu Corp., Japan), and the 
transmittance/reflectance ratio was obtained by calculation. As a result, 
as shown in the following Table 2, the ratio of the screen using the 
lenticular lens sheet of Example 1 was 4 times or more the ratio of the 
screen using the lenticular lens sheet of Comparative Example 1 
(lenticular lens sheet of body-colored type); and the ratio of the screen 
using the lenticular lens sheet of Example 2 was considerably higher than 
that of the screen using the lenticular lens sheet of Comparative Example 
2(lenticular lens sheet with black stripes). 
TABLE 2 
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Transmittance 
Reflectance 
Transmittance/ 
[%] [%] Reflectance 
______________________________________ 
Example 1 60.0 6.0 10.0 
Example 2 60.0 3.0 
20.0 
Comparative 
63.3 27.8 
2.3 
Example 1 
Comparative 
70.4 9.4 
7.5 
Example 2 
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