JPH10254064A - Composite lenticular lens sheet and back projection type screen using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite lenticular lens sheet capable of obtaining a display screen with high resolution and excellent contrast, having sufficient strength and being excellent in durability to enviroment. SOLUTION: This composite lenticular lens sheet is obtained by arraying the 1st lenticular lens sheet 2 having a black stripe at a boundary part between adjacent lens units and the 2nd lenticular lens sheet 4 having the black stripe at the boundary part between the adjacent lens units so that their sheet surface directions may be parallel with each other and their lens unit directions may be orthognal to each other so as to be crosswise, and binding and integrating the 1st and the 2nd sheets 2 and 4 through a light transmissive binding layer 6. The back projection type screen is obtained by arranging a Fresnel lens sheet 8 on the side of the 1st lenticular lens sheet 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology of a lenticular lens sheet and a rear projection type screen, and more particularly, to a lenticular lens sheet and a rear projection type image display screen of a display device such as a rear projection type television. The present invention relates to a rear projection screen capable of reducing flare light, which causes high contrast, and achieving high resolution, and a composite lenticular lens sheet used therein.

[0002]

2. Description of the Related Art In recent years, clear vision, high vision,
With the progress of multimedia such as data display,
Even in rear projection screens, reduction of flare light, which causes high resolution, high contrast, and double images, has been required.

Conventionally, as a rear projection type screen, as shown in FIG. 6, a lenticular lens sheet 1 is used.
2 and a Fresnel lens sheet 14 are used. The Fresnel lens sheet 14 is arranged on the light source side (light incidence side), and the lenticular lens sheet 12 is arranged on the observation side (light emission side). On the observation-side surface of the lenticular lens sheet 12, a vertical (vertical) black stripe 13 as an external light absorbing portion is formed at a boundary between adjacent lens units. In order to meet the demand for higher resolution, a lenticular lens sheet 12 having a so-called fine pitch in which the arrangement pitch of lens units is reduced has been used. Further, in order to cope with the demand for higher contrast, the ratio of the black stripe width to the array pitch of the lens unit has been made as large as possible.

[0004]

However, the ratio of the width of the black stripe to the arrangement pitch of the lens units has almost reached the limit in manufacturing, and it is difficult to further increase the contrast by further increasing the ratio.

As one method for meeting the above-mentioned demand for improving the performance of a rear projection screen, another lenticular lens sheet having the above-mentioned black stripe is added, and the two lenticular lens sheets are used. So that the directions of the lens units are orthogonal to each other (vertically and horizontally)
Conventionally, rear projection screens simply arranged in an overlapping manner have been used. However, there is a loss in transmitted light energy due to the increase in the number of members constituting the screen, and there is a problem in terms of strength due to the thinning of the lenticular lens sheet accompanying finer pitch due to higher resolution. (Damage problem when attaching to display device)
May occur, resolution may be reduced due to poor adhesion between lenticular lens sheets (interval changes in space and time), or sufficient reliability may not be obtained in terms of environmental durability. There was such a problem.

In view of the above situation, the present invention has been made as a result of intensive studies to solve the above-mentioned problems of the prior art.

[0007]

According to the present invention, a first lenticular lens sheet having a black stripe at a boundary portion between adjacent lens units, a first lens unit having an adjacent lens unit, A second lenticular lens sheet having a black stripe at the boundary between the first lenticular lens sheet and the second lenticular lens sheet, wherein the sheet surface directions are parallel to each other and the directions of their lens units are orthogonal to each other; A light-transmitting bonding layer is interposed between the first lenticular lens sheet and the second lenticular lens sheet by the light-transmitting bonding layer. Composite lenticular lens sheet is provided.

In one aspect of the present invention, the first lenticular lens sheet has the black stripe at an interface with the translucent bonding layer, and the second lenticular lens sheet has the translucent bonding layer. The black stripe is provided on a surface opposite to the interface with the black stripe.

In one embodiment of the present invention, both the first lenticular lens sheet and the second lenticular lens sheet have a lens unit pitch of 0.1 mm.
It is not less than 05 mm and not more than 1.0 mm.

[0010] In one embodiment of the present invention, the refractive index of the translucent bonding layer is more than 1.0 and less than 1.7.

In one embodiment of the present invention, a light diffusing agent is mixed in the second lenticular lens sheet.

Further, according to the present invention, there is provided a rear projection type screen comprising the above composite lenticular lens sheet to achieve the above object. In this rear projection screen, a Fresnel lens sheet can be arranged on the side of the first lenticular lens sheet.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a first embodiment of a composite lenticular lens sheet according to the present invention, and FIG. 2 is a partial sectional view thereof. FIG. 1 also shows the configuration of an embodiment of the rear projection screen of the present invention in which a composite lenticular lens sheet is combined with a Fresnel lens sheet.

In these figures, reference numeral 2 denotes a first lenticular lens sheet, 4 denotes a second lenticular lens sheet, and 6 denotes a translucent bonding layer. Also,
8 is a Fresnel lens sheet. The arrows indicate the directions of light entering and exiting the composite lenticular lens sheet or rear projection type screen when used.

As shown in FIG. 2, the first lenticular lens sheet 2 has a light incident side lens surface 2a and a light exit side lens surface 2b which are respectively paired on the light incident side and the light exit side. The one lens unit defined by the pair of lens surfaces extends in the vertical direction as shown in FIG. A large number of such lens units are arranged, and a black stripe 2c is formed on the light emission side at the boundary between adjacent lens units.

The second lenticular lens sheet 4 is
Basically, it has the same configuration as the first lenticular lens sheet 2, and as shown in FIG. 2, a light incident side lens surface 4a and a light incident side It has a light exit side lens surface 4b. However,
One lens unit defined by a pair of lens surfaces extends laterally as shown in FIG. A large number of such lens units are arranged, and a black stripe 4c is formed on the light emission side at the boundary between adjacent lens units.

The arrangement pitch of the lens units of the lenticular lens sheets 2 and 4 is 0.0 from the viewpoint of high resolution.
It is preferably from 5 mm to 1.0 mm. In particular, in order to support a high-resolution and high-definition image such as a high-definition television, the arrangement pitch of the lens unit is preferably 0.05 mm or more and 0.5 mm or less.

The lenticular lens sheets 2 and 4 are made of, for example, an acrylic resin, a polycarbonate resin, or another resin, by an extrusion molding method, a cell casting method, a hot pressing method, or a photopolymer method using an active energy ray-curable resin. And a production method using melt spinning as described in JP-A-3-200948.

As the translucent bonding layer 6, an adhesive or a pressure-sensitive adhesive can be used. Examples of such adhesives and pressure-sensitive adhesives include aqueous type, solvent type, non-solvent type, chemical reaction type, active energy ray curing type, pressure sensitive type, hot melt type, etc.
For example, vinyl acetate, CR, synthetic rubber, natural rubber, vinyl acetate emulsion, vinyl acetate copolymer, EVA, acrylic, isocyanate, latex, epoxy, cyano, polyurethane, silicone Etc. can be used. Further, a primer such as a silane coupling agent may be interposed between the base material (the lenticular lens sheets 2 and 4) and the adhesive or the pressure-sensitive adhesive.

The method for forming the light-transmissive bonding layer 6 includes coating with a hand roller, a bar coater, a roll coater, a flow coater, a spray, or the like, and the properties (viscosity, composition, etc.) of the adhesive or the pressure-sensitive adhesive. An appropriate method can be selected in consideration of the application area and the like.

The refractive index of the translucent bonding layer 6 is not particularly limited, but may be, for example, in a range of more than 1.0 and less than 1.7. The refractive index of the translucent bonding layer 6 is the refractive index of the lenticular lens sheets 2 and 4 (for example, 1.45).
~ 1.60) and close to the refractive index (1.0) of air. If a material having a refractive index higher than that of the lenticular lens sheets 2 and 4 is used as the translucent bonding layer 6, the lens surfaces 2 b and 4 of the lenticular lens sheets 2 and 4 on the side of the translucent bonding layer 6 are used.
What is necessary is just to make the shape of a concave.

In this embodiment, as shown, a vertical lenticular lens sheet (a black stripe extending in the vertical direction) 2 is disposed on the light source side, and a horizontal lenticular lens sheet (black) is disposed on the observation side. Since the stripes 4 are arranged in the horizontal direction, a relatively large viewing angle is obtained in the horizontal direction (horizontal direction) as compared with the vertical direction (vertical direction), which is preferable in view of the intended use ( In image display, a wide viewing angle is required in the horizontal direction, and only a narrower viewing angle is required in the vertical direction than in the horizontal direction. That is, the size of the viewing angle
Since the shape and curvature of the lens surface on the light incident side are greatly involved and it is currently difficult to industrially use adhesives and pressure-sensitive adhesives with a refractive index close to air, a wide viewing angle range in the horizontal direction is required. In order to obtain, the light incident side lens surface 2a is air (refractive index 1.
The direction of the lens unit of the first lenticular lens sheet 2 on the light incident side in contact with 0) is the vertical direction. As a result, as shown in FIG. 3, the viewing angle range in the horizontal direction can be widened. On the other hand, the viewing angle in the vertical direction may be considerably narrower than that in the horizontal direction, and the αV value (the angle between the direction in which the peak luminance is obtained and the direction in which half the luminance is obtained) may be about 5 to 20 degrees. Therefore, the second lenticular lens sheet 4 on the light exit side where the light incident side lens surface 4a is in contact with the translucent bonding layer (the refractive index is more than 1.0 and not practically close to 1.0). Let the direction of the lens unit be the horizontal direction. As a result, as shown in FIG. 4, the viewing angle range in the vertical direction is considerably narrower than that in the horizontal direction.

Lateral lenticular lens sheet 4
Since the light incident side lens surface 4a is in contact with the light transmissive bonding layer 6, the curvature of the light incident side lens surface 4a and the light incident side lens surface 4a and the light exit side The distance from the lens surface 4b (corresponding to the thickness of the lenticular lens sheet 4) is adjusted so that the absorption by the black stripe 4c does not cause a loss in the amount of image light.
That is, when the light enters the lenticular lens sheet 4 from the translucent bonding layer 6 having a refractive index of more than 1.0, the refraction angle of the light on the light incident side lens surface 4a becomes smaller than when the light enters from the air layer. As shown in FIG. 4, the incidence-side lens surface 4a is formed so that the curvature of the entrance-side lens surface 4a is as large as possible and light does not enter the black stripe 4c.
The distance between the lens surfaces between the lens and the exit side lens surface 4b is set appropriately. Then, the shape and the curvature of the light exit side lens surface 4b are set so that the vertical viewing angle is about 5 to 20 degrees.

A method of setting the curvature of the lens surface of the lenticular lens sheet 4 will be described below.

A quadratic curve passing through the origin of the XY coordinates is expressed as follows: Y = CX ² / {1 + {(1−KCX ² )}} (1) Here, C indicates the curvature at the origin, and K
Is a parameter and the quadratic curve is a circle when K = 1, K
When> 0, it is an ellipse (including a circle), when K = 0, it is a parabola, and when K <0, it is a hyperbola.

When the object point is at infinity (that is, when parallel light is incident), in order for the incident light to converge at one point (spherical aberration = 0), the quadratic curve is made elliptical. In
Assuming that the eccentricity is e, the condition of e = n ₁ / n ₂ ... (2) is required. Here, n ₁ is the refractive index of the translucent bonding layer 6 and n ₂ is the refractive index of the lenticular lens sheet 4.

For example, when polycarbonate (refractive index: 1.59) is used as the material of the lenticular lens sheet 4 and an adhesive having a refractive index of 1.4 is used as the material of the translucent bonding layer 6, K = b ² / a ² e = √ (a ² −b ² ) / a. Here, a is the major axis length of the ellipse, and b is the minor axis length of the ellipse.

Therefore, from equation (2), √ (a ² −b ² ) / a = n ₁ / n ₂₁ 1−b ² / a ² = (n ₁ / n ₂ ) ²¹ 1−K = (n ₁ / ^{_{n 2) 2 K = 1- (}} n 1 / n 2) 2 = 1-1.4 2 /1.59 2 = 0.2247 is derived.

If K = −0.2247 is used in equation (1), spherical aberration = 0. Using this K value, a C value may be used such that the αV value is 5 to 20 degrees, and the range of this C value is 0.454 ≦ C ≦ 1.53.

A light diffusing agent can be mixed in the composite lenticular lens sheet as described above. It is preferable to mix all or most of the light diffusing agent into the lenticular lens sheet 4 on the observation side from the viewpoint of preventing the resolution from deteriorating.

The composite lenticular lens sheet of the present embodiment can be used as a rear projection type screen. At that time, as shown in FIG. 1, the first lenticular lens sheet 2 side (light incident side) The Fresnel lens sheet 8 can be arranged in (2). As the Fresnel lens sheet 8, a conventionally known one as shown in FIG. 6 can be used.

As described above, by joining and integrating the two lenticular lens sheets 2 and 4 with the translucent joining layer 6, even when the two lenticular lens sheets 2 and 4 are mounted on the screen of the display device, the distance between the two lenticular lens sheets 2 and 4 can be increased. Is properly maintained over the entire surface, and deterioration of resolution is prevented. Further, the reflection at the interface between each of the lenticular lens sheets 2 and 4 and the translucent bonding layer 6 is reduced, the energy loss of the transmitted light is small, and the contrast is less reduced. In addition, 2
Since no outside air can enter between the two lenticular lens sheets 2 and 4, the durability against the environment is also improved.

Conventionally, a multiple image (based on flare light) mainly due to the thickness of the Fresnel lens sheet
In order to suppress the occurrence of the light, a thin Fresnel lens sheet was used, or a light diffusing agent was mixed into the Fresnel lens sheet. However, there is a limit in strength in reducing the thickness, and the Fresnel lens When a light diffusing agent is mixed in the sheet, there is a problem that image light is blurred and resolution is deteriorated. However, according to the composite lenticular lens sheet of the present invention as described above, even when multiple images appear on the left, right, top and bottom of the screen, the multiple stripes can be absorbed by the black stripes 2c and 4c, so that the multiple images can be seen from the observation side. There is an advantage that the light diffusing agent can be prevented from being mixed into the Fresnel lens sheet.

FIG. 5 is a perspective view showing a second embodiment of the composite lenticular lens sheet according to the present invention. In this drawing, members having the same functions as those in FIGS. 1 to 4 are denoted by the same reference numerals.

In the present embodiment, the first lenticular lens sheet 2 and the second lenticular lens sheet 4
In particular, one obtained by a production method using the above melt spinning and having a different cross-sectional shape from that of the first embodiment is used. Here, each lens unit of the lenticular lens sheets 2 and 4 is constituted by a translucent cylindrical rod having a substantially circular cross section, and the black stripe is constituted by a light shielding cylindrical rod having a substantially circular cross section. In this embodiment, the same operation and effect as those of the first embodiment can be obtained.

In the rear projection screen of the present invention, a transparent substrate made of glass or plastic (an acrylic plate or a polycarbonate plate) is provided on the observation side (ie, the light emitting side of the second lenticular lens sheet 4). ) Is arranged or adhered with a transparent adhesive or the like, thereby further improving the strength.

[0038]

The present invention will be specifically described below with reference to examples.

(Embodiment 1) The shape of the entrance lens surface is K =
-1.43, C = 1.215, the shape of the exit side lens surface is K = -0.2, C = 1.284, the arrangement pitch of the lens unit is 0.42 mm, and the thickness is 0.5 mm. A first lenticular lens sheet made of polycarbonate provided with a vertical black stripe is prepared, and the shape of the incident side lens surface is K = 0.225, C = 0.875, and the shape of the exit side lens surface is K = A second lenticular lens sheet made of polycarbonate having 0, C = 0, an arrangement pitch of 0.42 mm in lens units, a thickness of 2.0 mm, and a horizontal black stripe was prepared, and these are shown in FIG. As shown in the figure, a two-part curable silicone-based adhesive having a refractive index of 1.4 was joined and integrated using a 0.3 mm-thick translucent joining layer to obtain a composite lenticular lens sheet.

On the light-incident side of the first lenticular lens sheet of the composite lenticular lens sheet, a Fresnel lens sheet having a focal length of 1000 mm, a pitch of 0.3 mm, and a thickness of 1.5 mm is arranged, and a 40-inch liquid crystal type ( (1 beam) projection television and observed the image. In this observation, the contrast is improved by 20% compared to the conventional one in which two lenticular lens sheets are simply arranged vertically and horizontally without being joined by the translucent joining layer and combined with a superposed Fresnel lens sheet. As a result, a good image in which multiple image generation was reduced as much as possible was obtained, and the resolution was sufficiently good.

Further, when a heat resistance test was conducted at 60 ° C. for 100 hours, the vertical and horizontal lenticular lens sheets joined and integrated by the translucent bonding layer were peeled off or partially floated even after the heat resistance test was completed. In the image observation, the flare light was as low as before the heat resistance test, and the intensity was good.

Comparative Example 1 A commercially available lenticular lens sheet with a black stripe having a pitch of 0.6 mm was prepared by
When combined with the same Fresnel lens sheet as in Example 1 above and attached to a projection television in the same manner and observed for images, the contrast was not sufficient.
A high-resolution image was not obtained, and when the still screen was observed from a horizontal direction and a direction inclined by 45 degrees with respect to the front, a double image or a triple image appeared, and characters and the like were very difficult to read.

(Comparative Example 2) The shape of the incident side lens surface was K = -1.43, and C was the same as that used in Example 1 above.
= 1.215, and the shape of the exit-side lens surface is K = −0.
2, C = 1.284, array pitch of lens unit 0.4
Two polycarbonate lenticular lens sheets each having a thickness of 2 mm and a thickness of 0.5 mm and having a black stripe are prepared, and these are overlapped so that the directions of the lens units are orthogonal to each other. When combined with the sheet and attached to the projection television in the same way and observed images, each lenticular lens sheet is thin, so floating occurs between the superimposed lenticular lens sheets, multiple images are generated, and the resolution is increased. Screen became low.

Further, after the heat resistance test at 60 ° C. for 100 hours was completed, the adhesiveness of the vertical and horizontal lenticular lens sheets was further reduced, and the image was more deteriorated in image observation than before the heat resistance test.

[0045]

As described above, according to the composite lenticular lens sheet and the rear projection screen using the same according to the present invention, the two lenticular lens sheets are joined and integrated by the translucent joining layer. Therefore, even when the lenticular lens sheet is formed into a fine pitch to obtain a high resolution, the interval between the two lenticular lens sheets is always kept properly and constant, and a display screen with good contrast can be obtained. Sufficient strength can be obtained, and environmental durability is also good.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a first embodiment of a composite lenticular lens sheet according to the present invention.

FIG. 2 is a partial sectional view of a first embodiment of the composite lenticular lens sheet according to the present invention.

FIG. 3 is a diagram showing light passing through the first lenticular lens sheet in the first embodiment of the composite lenticular lens sheet according to the present invention.

FIG. 4 is a diagram showing light passing through a second lenticular lens sheet in the first embodiment of the composite lenticular lens sheet according to the present invention.

FIG. 5 is a perspective view showing a second embodiment of the composite lenticular lens sheet according to the present invention.

FIG. 6 is a perspective view showing a conventional rear projection screen.

[Explanation of symbols]

 2,4 Lenticular lens sheet 2a, 4a Light incidence side lens surface 2b, 4b Light emission side lens surface 2c, 4c Black stripe 6 Translucent bonding layer 8 Fresnel lens sheet

Claims (7)

[Claims] 1. A first lenticular lens sheet having a black stripe at the boundary between adjacent lens units and a second lenticular lens sheet having a black stripe at the boundary between adjacent lens units. The lens units are arranged so that the plane directions are parallel and the directions of the lens units are orthogonal to each other, and a light-transmissive bonding layer is interposed between the first lenticular lens sheet and the second lenticular lens sheet. A composite lenticular lens sheet, wherein the first lenticular lens sheet and the second lenticular lens sheet are joined and integrated by an optical joining layer. 2. The first lenticular lens sheet has the black stripe at an interface with the translucent bonding layer, and the second lenticular lens sheet has an opposite side to the interface with the translucent bonding layer. The composite lenticular lens sheet according to claim 1, wherein the composite lenticular lens sheet has the black stripe on a surface of the lenticular lens. 3. An arrangement pitch of each of the first lenticular lens sheet and the second lenticular lens sheet is 0.05 mm or more and 1.0 mm or more.
The composite lenticular lens sheet according to claim 1, wherein: 4. The composite lenticular lens sheet according to claim 1, wherein a refractive index of said translucent bonding layer is more than 1.0 and less than 1.7. 5. The composite lenticular lens sheet according to claim 1, wherein a light diffusing agent is mixed in the second lenticular lens sheet. 6. A rear projection type screen comprising the composite lenticular lens sheet according to claim 1. 7. The rear projection type screen according to claim 6, wherein a Fresnel lens sheet is arranged on the side of the first lenticular lens sheet.