JPWO2006135046A1 - Fresnel lens sheet and rear projection screen using the same - Google Patents

Abstract

The present invention has a Fresnel lens shape on one surface of a Fresnel lens sheet 1 and fine irregularities on the other surface. The fine irregularities include a binder 5 containing fine particles 4 having an average particle size of 20 μm or less. A Fresnel lens sheet 1 for a transmission screen and a method for manufacturing the same, which are formed by transferring a surface fine uneven shape obtained when laminated on a substrate 3. According to the present invention, it is possible to provide an inexpensive Fresnel lens sheet 1 for a transmissive screen that is bright, speckles are suppressed, moiré is not generated, ghosts are suppressed, and the amount of light loss is small. [Selection] Figure 1

Description

  The present invention relates to a Fresnel lens sheet used for a rear projection television or the like.

  FIG. 2 shows a schematic configuration diagram of a cross section of a transmissive screen that has been conventionally used in a rear projection television. In FIG. 2, 2 is a lenticular lens sheet, and 1 is a Fresnel lens sheet. Usually, the Fresnel lens sheet 1 and the lenticular lens sheet 2 are in close contact to form a transmission screen. In general, the Fresnel lens sheet 1 is composed of a sheet in which Fresnel lenses made of concentric and fine pitch lenses at equal intervals are provided on the light exit surface. (See Patent Document 1)

  As shown in FIG. 2, the lenticular lens sheet 2 has kamaboko-type lenses arranged at equal intervals on the light incident surface side. The parallel light or convergent light emitted from the Fresnel lens sheet 1 is greatly diffused in the horizontal direction by the lenticular lens sheet 2, so that an image can be observed in a wide visual field range in the horizontal direction.

  In the lenticular lens sheet 2, as shown in FIG. 2, a light shielding layer (hereinafter referred to as a black ink) made of a light absorbing material such as black ink is provided on a portion other than the light condensing portion of each lens provided on the light incident surface side. By providing a stripe, BS, or light-shielding pattern, the contrast in a bright room is improved.

  In the Fresnel lens sheet 1, the range in which video observation is possible not only in the horizontal direction but also in the vertical direction is expanded. A vertical diffusion lenticular lens (hereinafter sometimes referred to as a V wrench) or a prism shape disclosed in Patent Document 3 has been provided on the incident surface. Further, Patent Document 4 discloses a technique of increasing the haze of the Fresnel lens sheet (increasing diffusibility) in order to suppress speckle (brightness unevenness and glare) of image light. Furthermore, Patent Document 5 discloses a technique for setting the diffusion characteristics of the Fresnel lens sheet within a specific range.

In imparting diffusibility with conventional Fresnel lens sheets,
1) Although it is conceivable to obtain a diffusion characteristic by forming a V-wrench and a prism array with equal pitch on the incident surface of the Fresnel lens sheet, there is a problem that moire occurs between the Fresnel lens sheet and the lenticular lens sheet. In addition, when imparting diffusibility using a general diffusing material,
2) The diffusion material itself causes speckle.
3) Since the diffusion characteristics are tailed (relatively small in the medium angle region and relatively large in the high angle region), the trailing component (scattering in the high angle region) of the transmitted light that has passed through the Fresnel lens sheet. Light) is blocked by the light absorption layer of the lenticular lens sheet, and a light amount loss occurs.
4) Although a ghost such as a double image is generated by the light beam path as shown in FIG. 3, the ghost cannot be sufficiently reduced by the diffusion using the conventional diffusing material.
5) It was disadvantageous in terms of cost because the diffusing agent was expensive.
There was a problem such as.

JP 59-69748 A JP 60-263932 A Japanese Patent Application Laid-Open No. 11-271884 JP-A-8-313865 JP 2000-275738 A Japanese Patent Laid-Open No. 10-803898

  The present invention has been made to solve such a problem, and provides a Fresnel lens sheet that is bright because speckle loss is small, speckles are suppressed, moiré is not generated, ghosts are suppressed, and inexpensive. For the purpose.

The above purpose is
A Fresnel lens sheet used for a screen for a single light source projection display device, having a Fresnel lens shape on one surface of the Fresnel lens sheet, and having fine irregularities on the other surface, It is achieved by providing a Fresnel lens sheet characterized by being formed by transferring a surface fine uneven shape obtained when a binder containing fine particles having a diameter of 20 μm or less is laminated on a substrate. .

Moreover, the effect of this invention is remarkable when the particle size of the said microparticles | fine-particles is 1-7 micrometers.
In the Fresnel lens sheet, when the diffusion characteristics satisfy the following formulas (1) and (2), the effects of the present invention are particularly remarkable.
α ≧ 2.0 ° (1)
Where α is the half-value field angle ζ ≦ 18 ° (2)
Where ζ is 1/100 angle of view

  Moreover, this invention is a rear projection type screen provided with said Fresnel lens sheet.

  With the Fresnel lens sheet of the present invention, it is possible to obtain a transmissive screen at a low cost, which is bright because there is little light loss, speckles are suppressed, moire is not generated, and ghosts are suppressed.

It is a figure which shows the formation method of the uneven | corrugated shape in this invention. It is a schematic sectional drawing of the transmissive screen generally used for the rear projection television. It is a schematic sectional drawing explaining the ghost generating optical path in a Fresnel lens sheet. It is a conceptual diagram which shows that the emitted light quantity to a large viewing angle area | region is large. It is the schematic explaining the structure of the matrix sheet | seat from which uneven | corrugated shape differs in this invention.

When the main diffusion effect is imparted by surface irregularities, the speckle can be effectively reduced because the diffusion element on the incident surface side can be more localized on the incident surface side as shown in Patent Document 6 and the like.
Further, according to the present invention, in FIG. 3, when the ghost light reflected by the Fresnel surface reaches the incident surface, the surface is an uneven surface, so that a component having an incident angle smaller than the critical angle is generated. Ghost light can be suppressed for the reason that only part of the light reaches the exit surface side. In particular, the effect of suppressing double images is remarkable.

The ratio that the surface irregularities contribute to the diffusion effect is the same as that of the present invention except that the haze measurement value of the Fresnel sheet having the diffusion characteristics of the present invention is H and no diffusing agent is included in the haze measurement method defined in JIS-K7105. When the haze measurement of the same Fresnel sheet is H1,
H1 / H> 0.5
It is desirable to satisfy. If it is outside this range, the proportion of the diffusing agent contributing to the diffusing effect increases, and the effects of the present invention may not be fully exhibited. More preferably, H1 / H> 0.8, and still more preferably H1 / H> 0.9.
The surface irregularities are preferably random. If the surface irregularities have regularity, moire may occur with Fresnel concentric circles, lenticular lens arrays, and the like.

  As a method of forming irregularities on the incident side surface of the Fresnel lens sheet, for example, there is a method of mixing a diffusing agent in the Fresnel lens sheet substrate. However, this method has a problem that the diffusion material is expensive as described above. There is also a method of forming irregularities on the surface of the mold by sandblasting and transferring the shape. However, the above-described method has problems that it is difficult to process a large area, uniformity of the uneven shape, and height adjustment, and at the same time, it is difficult to reduce the size of the uneven shape. When the size of the concavo-convex shape is large, the speckle may not be sufficiently reduced as described later.

On the other hand, in the present invention, as shown in FIG. 1, a Fresnel lens sheet having surface irregularities obtained by a method of forming a concave / convex shape by laminating a binder 5 containing fine particles 4 on a base material 3 and transferring the surface concave / convex shape. 1 and this method facilitates processing to a large area, uniformity of the uneven shape obtained and adjustment of the height, and adjustment of haze and transmittance of the transferred transparent sheet (base material 3). It is excellent in that it is easy.
As a more specific forming method, for example, a binder 5 such as an ultraviolet curable resin containing fine particles 4 that are inorganic fine particles or resin fine particles is laminated on a base material 3 such as a PET film or an acrylic resin sheet, and the surface of the binder 5 is laminated. There is a method of transferring the uneven shape derived from the generated fine particles 4.
The material and thickness of the substrate 3 may be appropriately selected from known materials, and are not limited to the above examples.
The material of the fine particles 4 may be appropriately selected from known materials such as glass, metal, acrylic resin, and styrene resin. In the present invention, the fine particles 4 are not particularly transparent because they are for transferring the shape. Therefore, compared with the conventional method in which a diffusing agent is mixed in the Fresnel lens substrate 3, the present invention using the fine particles 4 has a wide selection range in terms of particle size distribution, price, and the like.
Further, the shape of the fine particles 4 used in the present invention is not limited to a spherical shape, and may be appropriately selected from arbitrary shapes such as a flat shape, an elliptical spherical shape, a polygonal shape, and an indefinite shape. In the present invention, the average particle diameter means a diameter when the volume of the fine particles 4 is converted into a sphere having the same volume.

Furthermore, according to the present invention, as shown in FIGS. 5A to 5C, the height, density, and size of the uneven shape can be easily increased by increasing or decreasing the amount of the binder 5, the amount of the fine particles 4, and the particle size of the fine particles 4. You can adjust the height.
Further, when a light beam is incident on a conventional diffusion sheet containing a diffusing agent, speckles due to the light beam that is emitted without being refracted by the diffusing agent contained therein (hereinafter referred to as leak-through) become conspicuous. On the other hand, in the present invention, since the surface of the binder 5 existing between the fine particles 4 is a gently curved surface, there is an advantage that such a leak-through hardly occurs and speckles are not noticeable.

In the present invention, the average particle size of the fine particles 4 needs to be 20 μm or less. If the average particle size is larger than 20 μm, leak-through light is generated, so that sufficient diffusion performance cannot be expected. A preferable range of the average particle diameter of the fine particles 4 is 1 to 7 μm. With such a particle size, speckle is not particularly noticeable. This is because when the particle size is the above, the speckle bright spots become smaller and less noticeable.
If the particle size is smaller than 1 μm, sufficient diffusion characteristics may not be imparted. When it is larger than 7 μm, the speckle bright spots are also large and the speckle may not be sufficiently reduced. At the same time, the distance between the particles increases, and so-called leak-through light is likely to be generated. A particularly preferable range is 2 μm or more and 6 μm or less. In the present invention, two or more kinds of fine particles 4 may be used.
In the present invention, it is preferable that the average particle size of the fine particles 4 used is small. In particular, when there is a large particle size, the appearance may be uneven. In particular, if there is a small particle size, sufficient diffusion characteristics may not be imparted.
In the present invention, the preferable range of the surface roughness Ra (JIS B 0601 2001) of the transferred surface irregularities is 0.1 to 2 μm. A particularly preferable range is 0.2 to 0.6 μm. If the surface roughness is too small, sufficient diffusion characteristics may not be imparted. If the surface roughness is too large, the speckle bright spots may become large and the speckle may not be sufficiently reduced.

With the Fresnel lens sheet 1 of the present invention that satisfies the diffusion characteristics of the following formulas (1) and (2), a sufficiently wide vertical viewing angle is achieved, and at the same time, the transmitted light that has passed through the Fresnel lens sheet 1 Among them, since the trailing portion of the diffused light absorbed by the light absorption layer of the lenticular lens 2 is small, it is possible to achieve both the characteristics that the light amount loss is small.
α ≧ 2.0 ° (1)
Where α is the half-value field angle ζ ≦ 18 ° (2)
However, ζ is a 1/100 value angle of view. When light rays are incident on a conventional diffusion sheet containing a diffusing agent, the light rays are refracted by the diffusing agent contained therein. The refracted light beam is further refracted by the diffusing agent until it reaches the exit surface. In this process, there are some light components that are diffused many times by the diffusing agent and receive excessive diffusion, so it is difficult to suppress the trailing part of the diffused light that is diffused more than necessary. is there.

On the other hand, when a light beam is incident on a sheet that diffuses due to the unevenness of the incident surface of the present invention, the diffusion characteristic is determined only by receiving a refracting action once on the incident surface, so that the trailing portion of the diffused diffused light can be suppressed.
Conventionally, by imparting diffusibility to the Fresnel lens sheet 1 for the purpose of reducing speckles, and increasing the diffusion characteristics of the Fresnel lens sheet 1 at that time, the light shielding portion of the lenticular lens sheet 2 disposed on the exit side As described above, a light amount loss occurs because the amount of light to be blocked increases. As a result of intensive studies, the inventors of the present invention have obtained a screen that achieves both reduction of speckle and avoidance of light loss by using the Fresnel lens sheet 1 having the above-mentioned diffusion characteristics. This achievement has been achieved especially by paying attention to the visual field 1/100 value angle (ζ). In the viewing angle region where the luminance is 1/100 compared to the front, the luminance is literally only 1/100 of the front as shown in FIGS. However, as shown in FIG. 4c, even in such an angular region, the total amount of light emitted to the entire periphery with the front direction as an axis in a certain angular range is much larger than that considered from the luminance that is the amount of light in only one direction. Has increased. This is because the total amount of light emitted in the direction of a certain angle θ is a function of sin θ because the luminance value at the angle θ is multiplied by the circumference of the unit sphere. In general, increasing the diffusivity is accompanied by an increase in the visual field half-value angle as well as the above-described visual field 1/100 value angle. Such an increase in the amount of light over the entire angle region becomes large. In the Fresnel lens sheet 1 of the present invention, the visual field half-value angle is set to be equal to or greater than the above-described constant value, and the value of the visual field 1/100 value angle is set to be equal to or less than the above-described constant value. In the rear projection type screen in which the Fresnel lens sheet 1 and the lenticular lens sheet 2 according to the present invention are combined, the present invention of reducing both light loss and reducing speckles is achieved. The effect of this will be exhibited.

When the viewing half-value angle α is smaller than 2.0 °, the diffusion characteristics are insufficient, the vertical viewing angle becomes narrow, and moiré, ghost, etc. may not be sufficiently suppressed. A preferable range of the half-value angle α is 2.5 ° or more.
If the visual field 1/100 value angle ζ is larger than 18 °, the trailing component of the light absorbed by the light shielding pattern portion of the lenticular lens sheet 2 increases, so that a necessary gain may not be obtained. A particularly preferable range of the visual field 1/100 value angle ζ is 16 ° or less. For the same reason, the visual field 1/10 value angle γ is preferably 12 ° or less.
The visual field 1/100 value angle ζ is preferably 12 ° or more. If the angle is less than 12 °, the so-called hot band phenomenon, in which the brightness of the screen suddenly becomes dark at a vertical viewing angle of a certain range or more, may be a problem. For the same reason, the visual field 1/10 value angle γ is preferably 7 ° or more.
The ratio ζ / α of the visual field 1/100 value angle ζ to the visual field half-value angle α is preferably smaller than 7. This is because the ratio of the light beam toward the peripheral portion becomes smaller than the light beam near the front surface, and the ratio of the light amount loss to the emitted light amount decreases.

As a method for transferring the uneven shape to the surface of the Fresnel lens sheet 2 in the present invention, for example, there is the following method. First, a binder 5 containing fine particles 4 is laminated on the base material 3 to produce a concave / convex matrix sheet, and a metal film having a predetermined thickness is formed on the concave / convex surface by metal vapor deposition, plating, or the like. Thereafter, if necessary, the metal film surface of the concavo-convex matrix sheet is laminated on a rigid sheet made of metal, and the concavo-convex matrix sheet is removed to produce a metal mold to which the concavo-convex shape is transferred.
Moreover, after producing the said uneven | corrugated matrix sheet | seat, a transfer sheet | seat is produced, for example using ultraviolet curable resin, a metal film may be formed in the transfer sheet surface, and a metal mold | die may be manufactured.

  In the present invention, the metal mold may be a mold, or a transfer mold of the metal mold may be produced and used as a mold. Depending on the number of times of transfer, the surface concavo-convex shape of the Fresnel sheet product may be the same shape as the concavo-convex matrix sheet, or the concavo-convex shape may be reversed. In the present invention, any case may be used, and an appropriate stool may be set by evaluating light transmittance, speckle, ghost and the like.

  In the present invention, a molded product can be produced by using the above-mentioned mold, for example, by a press molding method, an extrusion molding method, an ultraviolet curable resin molding method, an injection molding method, or the like. Of these, the injection molding method and the ultraviolet curable resin molding method are suitable. One of the features of the unevenness of the present invention is that its pitch and height are small. This is because the injection molding method and the ultraviolet curable resin molding method have good transferability of such a shape. In view of the fact that the resin material is expensive in the ultraviolet curable resin molding, the injection molding method is particularly suitable.

  The transmission type screen of the present invention is characterized by including the Fresnel lens sheet 1 described above, and usually includes a lenticular lens sheet 2 in many cases. Here, in addition to the lenticular lens sheet 2 having a horizontal diffusion performance, a plate may be provided with a lenticular lens sheet having a vertical diffusion performance. Instead of the lenticular lens sheet 2, a microlens array sheet (also referred to as a fly-eye lens sheet) may be used. May be provided). Moreover, you may provide the protective sheet to which the diffusion performance was provided by the spreading | diffusion agent etc.

Examples of the present invention will be described below.
<Example 1>
Base sheet: PET 100 μm sheet Binder: UV curable resin and organic solvent Fine particles: Beads having an average particle diameter of 3 μm (Material: methacrylic crosslinked resin)
Mixing ratio of binder and fine particles by weight: 24 parts of UV curable resin, 65 parts of organic solvent, 11 parts of fine particles 9 g / m ² of the above mixture of binder and fine particles is applied to one side of the base sheet. (This is called sheet 1)
Next, metal deposition and plating were performed, and after a 0.3 mm metal film was laminated on the uneven surface, the metal film was bonded to a 2 mm thick stainless steel sheet via a polyimide sheet and an adhesive sheet.
Thereafter, the sheet 1 was removed, and a metal mold in which the uneven shape of the sheet 1 was transferred was produced.

  Subsequently, the metal mold and a separately prepared mirror-shaped metal mold were attached to an injection molding apparatus to produce a sheet made of polymethacryl / styrene copolymer resin. A Fresnel lens was formed on the mirror surface side with an ultraviolet curable resin to produce a Fresnel lens sheet 1. The MS resin sheet has a refractive index of 1.54 and does not contain a diffusing agent. The thickness of the Fresnel lens sheet 1 was 2 mm, the surface roughness Ra (JIS B 0601 2001) of the matte surface was 0.3 μm, and the haze value was 60%. Table 1 shows the viewing angle characteristics of the acrylic resin sheet. The Fresnel lens sheet 1 is arranged on the projector side, and the lenticular lens sheet with a pitch of 0.1 mm is arranged on the viewer side to form a transmission screen, which is attached to the LCD projection television apparatus, and the front screen brightness. And speckles were visually evaluated. The results are shown in Table 1. The transmission screen using the Fresnel lens sheet 1 of the present invention was bright and the speckle was sufficiently reduced.

<Example 2>
Fine particles: Beads with an average particle size of 5 μm (Material: methacrylic crosslinked resin)
Mixing ratio of binder and fine particles: 24 parts of UV curable resin, 65 parts of organic solvent, 11 parts of fine particles 12 g / m ² of the above mixture of binder and fine particles is applied to one side of the base sheet. (This is called sheet 2)
A Fresnel lens sheet 2 was produced in the same manner as in Example 1 except that.
The thickness of the Fresnel lens sheet 2 was 2 mm, the surface roughness of the matte surface was Ra = 0.55 μm, and the haze value was 58%. Table 1 shows the viewing angle characteristics of the Fresnel lens sheet 2.
A transmissive screen constructed in the same manner as in Example 1 except that this Fresnel lens sheet 2 was used was also mounted on an LCD projection television set and observed in the same manner as in Example 1. As a result, it was bright and speckles were sufficient. Has been reduced.

<Example 3>
Fine particles: beads having an average particle diameter of 20 μm (material: methacrylic crosslinked resin)
Mixing ratio of binder and fine particles: 24 parts of UV curable resin, 65 parts of organic solvent, 11 parts of fine particles 12 g / m ² of the above mixture of binder and fine particles is applied to one side of the base sheet. (This is called sheet 3)
A Fresnel lens sheet 3 was produced in the same manner as in Example 1 except that.
The thickness of the Fresnel lens sheet 2 was 2 mm, the surface roughness of the matte surface was Ra = 0.6 μm, and the haze value was 57%. Table 1 shows the viewing angle characteristics of the Fresnel lens sheet 2.

<Example 4>
A Fresnel lens sheet 3 was formed in the same manner as in Example 1 except that the amount of fine particles was 14 parts and the coating amount was 12 g / m ² . The results are shown in Table 1.

<Example 5>
A Fresnel lens sheet was formed in the same manner as in Example 1 except that 17 parts of fine particles and the coating amount were 14 g / m 2, and evaluated in the same manner. The results are shown in Table 1.

<Comparative Example 1>
Using two mirror-shaped molds, a diffusing agent made of glass particles (average particle size 3 μm, refractive index 1.56) was mixed, and the concentration was adjusted so that the haze value was 60% to produce a resin sheet. Except for the above, an MS resin sheet having a mirror surface of 2 mm in thickness was prepared in the same manner as in Example 1.
A Fresnel lens sheet 3 was produced in the same manner as in Example 1 except that the resin sheet of Comparative Example 1 was used, a transmission type screen was constructed, and it was mounted on an LCD projection television device. The brightness and speckle were visually evaluated. The results are shown in Table 1. The transmissive screen using the Fresnel lens sheet of Comparative Example 1 had a high gain as in Example 1, but the speckle was not sufficiently reduced and the quality of the image was impaired.

<Comparative example 2>
A transmissive screen was prepared in the same manner as in Comparative Example 1 except that the particle size of the diffusing agent was 5 μm, and the haze value was adjusted to 70% by adjusting the concentration. Were visually evaluated. The results are shown in Table 1. The speckle of the transmission type screen using the Fresnel lens sheet 4 of Comparative Example 2 was relatively small, but a dark image was obtained.

Table 1 summarizes the results of the above examples and comparative examples.

Claims (5)

A Fresnel lens sheet used for a screen for a single light source projection display device,
It has a Fresnel lens shape on one side of the Fresnel lens sheet, and has fine irregularities on the other side,
The Fresnel lens sheet, wherein the fine unevenness is formed by transferring a surface fine unevenness shape obtained when a binder containing fine particles having an average particle diameter of 20 μm or less is laminated on a substrate. . The Fresnel lens sheet according to claim 1, wherein an average particle diameter of the fine particles is 1 to 7 μm. The Fresnel lens sheet according to claim 1, wherein the diffusion characteristics of the Fresnel lens sheet satisfy the following expressions (1) and (2).
α ≧ 2.0 ° (1)
Where α is the half-value field angle ζ ≦ 18 ° (2)
Where ζ is 1/100 angle of view A rear projection screen comprising the Fresnel lens sheet according to claim 1. A rear projection screen comprising the Fresnel lens sheet according to claim 3.

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