JP4673199B2 - Fresnel lens sheet, transmissive screen and rear projection display - Google Patents

Description

  The present invention relates to a Fresnel lens sheet having a shape that can be manufactured at low cost, a transmissive screen having the Fresnel lens sheet, and a rear projection display device.

  A large-screen display device such as a rear projection display device often sees images projected on a transmissive screen (hereinafter simply referred to as “screen”) by a plurality of people, compared to a small display device. A wide viewing angle is required. For example, a projection television, which is a rear projection display device, includes a transmissive screen that projects video light emitted from a light source. In general, this transmissive screen diffuses the substantially parallel light and a Fresnel lens sheet that is a lens member for deflecting the image light projected from the light source to the observer side into substantially parallel light (including parallel light). And a lenticular lens sheet which is a light diffusion sheet for widening the viewing angle of the image.

In recent years, there has been a demand for a thinner rear projection display device. In order to meet the demand, use of a total reflection type Fresnel lens sheet has been proposed (for example, see Patent Document 1). The total reflection type Fresnel lens sheet is a type of Fresnel lens sheet in which the center of the Fresnel does not exist within the sheet surface, and diffuses the image light projected toward the screen from the lower back or upper back of the transmissive screen. This is a sheet for deflecting light into substantially parallel light toward the sheet. Such a total reflection type Fresnel lens sheet has a large number of prisms, and each prism has a refracting surface (referred to as an “incident surface” in Patent Document 1) that refracts image light. It has a reflection surface (referred to as “total reflection surface” in Patent Document 1) that totally reflects light transmitted through the refracting surface in the normal direction of the screen surface (screen).
Japanese Patent Laid-Open No. 61-208041

  As described above, with the increase in size and thickness of the rear projection display device, the incident angle of the image light to the transmissive screen (however, the incident angle when the back surface of the screen is assumed to be a plane parallel to the screen surface) ) Means a relatively large difference of about 35 ° on the side close to the light source and about 80 ° on the side far from the light source. As a result, in the Fresnel lens sheet that totally reflects the image light in the normal direction on the screen surface, the inclination angle of the total reflection surface of each prism (when the plane perpendicular to the thickness direction of the Fresnel lens sheet is used as a reference) It is necessary to select the angle of inclination within a range of about 15 to 40 ° depending on the position of the prism.

  The Fresnel lens sheet is generally manufactured using a mold. In this mold, a large number of grooves corresponding to a large number of prisms to be formed on the Fresnel lens sheet are formed at a fine pitch, and these large numbers of grooves are usually formed by cutting. In order to obtain a Fresnel lens sheet in which the angle of inclination of the total reflection surface of the prism differs according to the position of the prism, it is necessary to change the angle of inclination of the side wall of the groove portion formed in the mold according to the position. Become. Such a groove can be formed, for example, by preparing a plurality of types of cutting tools having a shape corresponding to the cross-sectional shape in the width direction of the groove to be formed and using them properly.

  However, the pitch of the grooves to be formed in the mold is fine as described above, and in order to form a large number of grooves with fine pitches using different types of cutting tools, the cutting tools must be changed. It is necessary to increase the alignment accuracy when starting a new cutting. In this way, it is extremely difficult to produce a mold, and as a result, the manufacturing cost of the Fresnel lens sheet increases.

  The present invention has been made in view of the above circumstances, and the object thereof is to produce the low-cost even when the inclination angle of the total reflection surface of the prism is varied according to the position of the prism. The object is to provide a Fresnel lens sheet having a shape. Another object of the present invention is to provide a transmission screen and a rear projection display device having the Fresnel lens sheet.

  The Fresnel lens sheet of the present invention for solving the above problems is a Fresnel lens sheet having at least a total reflection Fresnel lens part formed on one surface in the thickness direction, and the total reflection Fresnel lens part is incident The prism includes a plurality of prisms each having a refracting surface that refracts light and a reflecting surface that reflects light refracted by the refracting surface, and the reflecting surface includes a first reflecting surface on a top side of the prism, and the first reflecting surface. A second reflecting surface continuous with the reflecting surface, and an angle formed between the first reflecting surface and the refracting surface is smaller than an angle formed between the second reflecting surface and the refracting surface. (Hereinafter, this Fresnel lens sheet may be referred to as “Fresnel lens sheet I”).

  In this Fresnel lens sheet I, the second reflecting surface of the reflecting surfaces constituting the prism corresponds to the total reflecting surface referred to in Patent Document 1. Such a Fresnel lens sheet I can be manufactured using a mold in the same manner as a conventional Fresnel lens sheet. The reflecting surfaces of the individual prisms are formed so that the angle formed between the first reflecting surface and the refracting surface is smaller than the angle formed between the second reflecting surface and the refracting surface. Even when trying to obtain a Fresnel lens sheet I having a different inclination angle of the second reflecting surface (total reflecting surface), the mold used for manufacturing the die has a required number of grooves formed by one cutting tool. Can be obtained. That is, this Fresnel lens sheet I has a shape that can suppress the manufacturing cost of the mold, and as a result, even when the inclination angle of the second reflecting surface is varied depending on the position of the prism, It presents a structure that can be obtained at low cost.

  In the Fresnel lens sheet I of the present invention, the angle formed between the first reflecting surface and the refracting surface is the same regardless of the distance from the Fresnel center of the Fresnel lens sheet, and the second reflecting surface and the The angle formed with the refracting surface is gradually increased with increasing distance from the Fresnel center of the Fresnel lens sheet (hereinafter, this Fresnel lens sheet may be referred to as “Fresnel lens sheet II”).

  According to this Fresnel lens sheet II, since the angle formed by the first reflecting surface and the refracting surface is the same regardless of the distance from the center of the Fresnel, it has a structure that makes it easy to manufacture a mold used for manufacturing the same. ing. Furthermore, since the angle formed by the second reflecting surface and the refracting surface gradually increases as the distance from the Fresnel center increases, the image light projected when the light source is arranged vertically below or above the Fresnel lens sheet surface, It has a structure that facilitates the production of a mold that can be deflected into light that is parallel or substantially parallel to the thickness direction of the Fresnel lens sheet. As used herein, “deflecting visible light, which is image light, into light that is parallel or substantially parallel to the thickness direction of the Fresnel lens sheet” means that the image light incident on the prism is converted to the thickness of the Fresnel lens sheet. This means that the light is deflected so as to emit light within 5 ° from the direction.

  In any of the Fresnel lens sheets I and II of the present invention, it is preferable that the angle formed between the second reflecting surface and the refracting surface is in a range of 35 ° to 45 ° and gradually increases within the range ( Hereinafter, this Fresnel lens sheet may be referred to as “Fresnel lens sheet III”.)

  In any of the Fresnel lens sheets I to III of the present invention, it is preferable that the bottom of the valley formed by adjacent prisms is curved toward the refractive surface side of one of the adjacent prisms ( Hereinafter, this Fresnel lens sheet may be referred to as “Fresnel lens sheet IV”.)

  In a mold used for manufacturing a Fresnel lens sheet, a large number of grooves corresponding to a large number of prisms of the Fresnel lens sheet are formed at a fine pitch. In a mold produced using a mold base material that is easy to cut, the upper end of the boundary between adjacent grooves, that is, the tip of the molded part corresponding to the valley formed by adjacent prisms in the Fresnel lens sheet, It is characterized by being easily bent in a certain direction during the molding process. The Fresnel lens sheet manufactured using such a mold has a characteristic structure in which the bottoms of the valleys formed by adjacent prisms are also curved in a certain direction.

  According to the Fresnel lens sheet IV of the present invention, the bottom of the valley formed by the adjacent prisms exhibits a structure that is curved toward the refractive surface side of one of the adjacent prisms. There is an advantage that the reflected light can be prevented from entering the curved bottom. Therefore, according to this Fresnel lens sheet VII, it is easy to obtain this even when the inclination angle of the second reflecting surface of the prism is varied according to the position of the prism, and the image quality when the image is projected It becomes easier to obtain a high transmission screen.

  In any of the Fresnel lens sheets I to IV of the present invention, the height of the first reflecting surface in the thickness direction is not less than 5% and not more than 25% of the height of the prism having the first reflecting surface. It is preferable that the Fresnel lens sheet is hereinafter referred to as “Fresnel lens sheet V”.

  In the Fresnel lens sheets I to IV of the present invention, the light totally reflected by the first reflecting surface of each prism becomes light that is substantially parallel or non-parallel to the thickness direction of the Fresnel lens sheet. Light may become stray light on the transmission screen having the Fresnel lens sheet. However, according to the Fresnel lens sheet V, the height of the first reflecting surface in the thickness direction is not less than 5% and not more than 25% of the height of the prism. The amount of light can be suppressed. As a result, even when the inclination angle of the second reflecting surface of the prism is changed according to the position of the prism, it is easy to obtain this, and a transmission screen with high image quality when an image is projected is obtained. Becomes even easier. In the present invention, “light that is not parallel to the thickness direction of the Fresnel lens sheet” is light that is emitted at an angle that exceeds the above-mentioned parallel or substantially parallel light, and from the thickness direction of the Fresnel lens sheet. It means light emitted with a deviation within 20 ° in any direction.

  In any of the Fresnel lens sheets I to V of the present invention, the top shape of each of the plurality of prisms can be formed to be a curved surface shape or a chamfered shape (hereinafter, this Fresnel lens sheet is referred to as “Fresnel lens sheet”). VI ").

  The transmissive screen of the present invention for solving the above-described problems has any one of the above-described Fresnel lens sheets I to VI of the present invention and a light diffusion sheet (hereinafter, this transmissive screen is referred to as “ Screen I ”).

  According to this screen I, since it has any of the Fresnel lens sheets I to VI of the present invention described above, a transmissive screen applicable to a thin rear projection display device can be obtained at low cost. Can do.

  In the screen I of the present invention, the light diffusion sheet has at least a light diffusion portion that diffuses light incident from the Fresnel lens sheet side by total reflection, and the light diffusion portion is directed toward the Fresnel lens sheet side. It is characterized by having a light absorbing portion in which a resin containing a light absorbing material is filled in a number of tapering substantially V-shaped grooves (hereinafter, this transmissive screen may be referred to as “screen II”). .)

  A rear projection display device of the present invention for solving the above problems includes any one of the screens I and II of the present invention described above, and a light source for projecting image light from the rear obliquely lower side or the rear oblique upper side of the transmissive screen. It is characterized by having.

  According to the rear projection type display device, since any one of the screens I and II of the present invention described above is provided, it is possible to reduce the thickness and the cost.

  As described above, according to the Fresnel lens sheet of the present invention, even when the inclination angle of the second reflecting surface is varied according to the position of the prism, a structure that can be obtained at low cost is presented. Yes. According to the transmissive screen of the present invention using such a Fresnel lens sheet, a transmissive screen applicable to a thin rear projection display device can be obtained at low cost. According to the provided rear projection display device of the present invention, it is possible to reduce the thickness and cost, and to further promote the rear projection display device.

  Hereinafter, each form of the Fresnel lens sheet, the transmission screen, and the rear projection display device of the present invention will be described in detail.

(Fresnel lens sheet: 1st form)
FIG. 1 is a perspective view schematically showing an example of the Fresnel lens sheet of the present invention. The Fresnel lens sheet 10 is made of, for example, a transparent resin having a refractive index (meaning a refractive index with light having a wavelength of 587 nm; the same shall apply hereinafter) of about 1.45 to 1.65. The shape of 10 when viewed from the front is a rectangular shape that is long in the left-right direction.

On one surface S ₁ in the thickness direction of the Fresnel lens sheet 10, and the total reflection Fresnel lens portion comprising a plurality of prisms 5 formed, the other surface S ₂ in the thickness direction is formed in a flat shape Yes. Each prism 5 is formed in an arc shape so as the center point O is a fresnel center outside surface S _1. The point O is located on an extension line of the vertical axis A _x (which means an axis extending in the height direction of the Fresnel lens sheet 10 in the illustrated state) when the Fresnel lens sheet 10 is viewed from the front. Yes.

The pitch between adjacent prisms 5 and 5 (meaning the distance between the tops) is the same regardless of the distance from the Fresnel center (point O) of the Fresnel lens sheet, and the pitch is the Fresnel lens sheet. 10 is selected so that each prism 5 is not visually recognized when a transmissive screen is configured by using 10. The pitch is preferably about 1.0 mm or less, and more preferably about 0.1 mm or less. The shape of each prism 5 is selected so as to be able to deflect the image light incident from the obliquely lower rear side of the surface S ₁ as viewed from the surface S ₂ into light parallel to or substantially parallel to the thickness direction of the Fresnel lens sheet 10. Has been. Hereinafter, the shape of each prism 5 will be described in detail with reference to FIG.

FIG. 2 is a schematic view of a vertical section of the Fresnel lens sheet 10 shown in FIG. As shown in FIG. 2, each prism 5 has a refracting surface 1 that refracts at least part of image light (also referred to as incident light) projected from a light source, and a reflection that reflects light refracted by the refracting surface 1. Surface 3. The reflecting surface 3 has a first reflecting surface 3a located on the top T side of the prism 5, and a second reflecting surface 3b continuous with the first reflecting surface 3a. The second reflecting surface 3b is located on the base _BP side of the prism 5.

The first reflecting surface 3a has a shape corresponding to a part of the conical surface, and the second reflecting surface 3b has a shape corresponding to a part of the peripheral surface of the truncated cone. Further, the refracting surface 1 and the first reflecting surface 3a are in contact with each other at the apex T to form an arcuate ridgeline. Bottom B _V valley V prism 5 adjacent to each other to form is curved refractive surface 1 side in one of the prism 5 of these adjacent prism 5.

Since the above-mentioned bottom B _V is curved refractive surface 1 side, as compared with the case where curved on the second reflecting surface 3b side, the light totally reflected by the second reflecting surface 3b is the curved portion of the Incidence can be easily suppressed. As a result, when a transmissive screen is configured using the Fresnel lens sheet 10, it is easy to obtain a transmissive screen with high image quality of the projected image. The surface of the curved portion is not included in either the refracting surface 1 or the second reflecting surface 3b.

In any of these prisms 5, the angle θ ₁ formed by the first reflecting surface 3 a and the refracting surface 1 is smaller than the angle θ ₂ formed by the second reflecting surface 3 b and the refracting surface 1. The inclination angle theta ₃ of each of the second reflecting surface 3b is normal of at least part of the surface S ₂ light incident at an incident angle larger than the critical angle to the second reflecting surface 3b passes through the refractive surface 1 NL Is selected so as to be totally reflected in a direction parallel to or substantially parallel to. The normal line NL extends in the thickness direction of the Fresnel lens sheet 10. The “inclination angle of the second reflection surface” in the present invention means the inclination angle of the second reflection surface with reference to a plane orthogonal to the thickness direction of the Fresnel lens sheet.

A transparent resin having a refractive index of about 1.45 to 1.65 is used as the material of the Fresnel lens sheet 10, and a transmissive screen applied to a thin rear projection display device is obtained using the Fresnel lens sheet 10. , The above-mentioned angles θ ₁ , θ ₂ , the inclination angle θ ₃ of the second reflecting surface, and the inclination angle θ ₄ of the refracting surface 1 (on the basis of a plane orthogonal to the thickness direction of the Fresnel lens sheet) The inclination angle of the refracting surface is preferably selected as follows.

That is, the angle θ ₁ in each prism 5 can be appropriately changed according to the position of the prism 5 in the surface S ₁ , but the Fresnel lens sheet 10 is formed using one cutting tool. From the viewpoint of obtaining the Fresnel lens sheet 10 at a low cost by producing a mold for use, it is preferable to set the same value within the range of about 30 to 37 °, and particularly preferably about 35 °. .

Further, the angle θ ₂ in each prism 5 can be the same value between the prisms 5, but the image light projected on the transmission screen described above is divergent light, and this image light can be used as much as possible. From the standpoint of total reflection in a direction parallel or substantially parallel to many normal lines NL, it is preferably within a range of about 35 to 45 ° depending on the position of each prism 5 in the surface S ₁ . More preferably, it is in the range of about ~ 43 °. Specifically, it is preferable to gradually increase the angle θ ₂ within the above range from the prism 5 close to the point O shown in FIG.

The inclination angle θ ₄ of the refracting surface 1 in each prism 5 is preferably in the range of about 87.5 to 90 ° from the viewpoint of making the incident angle of the image light less than the critical angle, and 88 to 88.5. More preferably, it is within a range of about 0 °. The inclination angle θ ₄ can be constant between the prisms 5 or can be changed as appropriate according to the position of the prism 5.

As these results, the inclination angle theta ₃ of the second reflecting surface 3b of each prism 5, depending on the position of each prism 5 in the surface S _1, falls within the range of about 1 ° ~ 43 °. The height H of each prism 5 in the thickness direction of the Fresnel lens sheet 10 can be appropriately selected within a range of about 150 to 300 μm.

  FIG. 3 is a schematic view showing an example of an optical path of light in the Fresnel lens sheet 10 described above. This figure shows an example of an optical path of light in the same vertical section as the vertical section shown in FIG. 2, but hatching is omitted in the figure for easy understanding of the optical path. Each prism shown below the broken line in the center of FIG. 3 is a prism close to the point O shown in FIG. 1 (hereinafter, these prisms are referred to as “prism 5n”, and in FIG. Each prism shown above the broken line in the center of FIG. 3 is a prism far from the point O shown in FIG. 1 (hereinafter, these prisms are referred to as “prism 5f”). In FIG. 3, it is indicated by the reference numeral “5f”.

In the transmissive screen using the Fresnel lens sheet 10, image light is projected onto each prism 5 in a divergent light state. At this time, the incident angle of image light ML ₁ to the refractive surface 1 of the prism 5n is relatively large, the incident angle of the image light ML ₂ to the refractive surface 1 of the prism 5f is relatively small. In each of the prisms 5n and 5f, the image lights ML ₁ and ML ₂ pass through the refracting surface 1, and most of them enter the reflecting surface 3.

Of the image lights ML ₁ and ML ₂ incident on the reflecting surface 3, the light incident on the first reflecting surface 3 a is totally reflected here and then totally reflected on the refracting surface 1, and is substantially the normal line NL of the surface S _2. Parallel image light is emitted from the Fresnel lens sheet 10. On the other hand, the image light ML _1, ML ₂ incident on the second reflecting surface 3b is totally reflected here, is emitted from the Fresnel lens sheet 10 becomes the normal line NL of the surface S ₂ parallel or approximately parallel image light . Each prism 5n, totally reflected image light ML ₁ are selected inclination angle of the second reflecting surface 3b so as to be parallel or substantially parallel to the normal line NL at the second reflecting surface 3b, in each prism 5f, the inclination angle of the second reflecting surface 3b as image light ML ₂ totally reflected by the second reflecting surface 3b are parallel or substantially parallel to the normal line NL is selected.

Of course, not all of the image lights ML ₁ and ML ₂ incident on the second reflecting surface 3b are emitted from the Fresnel lens sheet 10 as image lights parallel or substantially parallel to the normal line NL, but parallel to the normal line NL. Alternatively, only the image lights ML ₁ and ML ₂ in which the incident angle to the second reflecting surface 3b and, consequently, the incident angle to the refracting surface 1 are in a specific angle range become the substantially parallel image light. When a transmissive screen is configured using the Fresnel lens sheet 10, the video light ML ₁ , ML applied to each refractive surface 1 according to the configuration of the light source in the rear projection display device to which the transmissive screen is applied. _Since the value of the incident angle of ₂ is determined, the second reflecting surface 3b is converted so that as much of the image light ML ₁ and ML ₂ as possible is converted into image light parallel or substantially parallel to the normal line NL according to these values. the inclination angle theta ₃ and the refractive surface 1 of the inclination angle theta _{4 (see} FIG. 2) is pre-selected.

In many cases, the image lights ML ₁ and ML ₂ totally reflected by the first reflecting surface 3a and further totally reflected by the refracting surface 1 with respect to the normal line NL when the angle θ ₁ is 30 to 37 °. Since the light is emitted from the Fresnel lens sheet 10 at an emission angle of about 10 °, the viewing angle in the vertical direction becomes large in the transmission screen manufactured using the Fresnel lens sheet 10. From the viewpoint of suppressing the decrease in brightness in front of the transmissive screen, or from the viewpoint of suppressing the generation of stray light on the transmissive screen, the first reflecting surface 3a in the thickness direction of the Fresnel lens sheet 10 is used. Is preferably 5% or more of the height H of the corresponding prism 5, more preferably 25% or less, and still more preferably 10% or less.

  In the Fresnel lens sheet 10 having the above-described configuration, the reflecting surfaces 3 of the individual prisms 5 include the first reflecting surface 3a and the second reflecting surface 3b, so that a necessary number of grooves are formed using one cutting tool. Can be produced using a mold produced by forming a mold base material. That is, the manufacturing cost of the mold can be suppressed. Therefore, the technology that the Fresnel lens sheet 10 can be easily obtained at a low cost even when the inclination angle of the second reflecting surface 3b of the prism 5 is varied depending on the position of the prism 5. There is a special effect.

  In addition, by a large number of prisms 5 arranged in concentric arcs, most of the light incident on each prism 5 in the form of divergent light is converted into light that is parallel or substantially parallel to the thickness direction of the Fresnel lens sheet 10. Therefore, by constructing a transmissive screen using this Fresnel lens sheet, there is also a technical effect that it is easy to obtain a transmissive screen with high image quality when an image is projected.

  Hereinafter, for the manufacturing method of the mold used for manufacturing the Fresnel lens sheet 10 described above, refer to FIGS. 4A to 4E while appropriately quoting the reference numerals used in FIG. 2 or FIG. To explain. FIG. 4A to FIG. 4E are process diagrams schematically showing a manufacturing process of a mold used for manufacturing the Fresnel lens sheet 10.

In manufacturing the mold for the Fresnel lens sheet 10, first, as shown in FIG. 4A, a mold base material M having a predetermined shape and size and a cutting tool B are prepared. As the material of the mold base material M, for example, a material that is not easily deformed, such as a steel material, can be used, and a material with good cutting properties, such as aluminum, copper, nickel, or the like can also be used. Further, as the cutting tool B, the bottom angle of the groove formed in the mold base material M by the cutting tool B is the same as the angle θ ₁ (see FIG. 2) in the Fresnel lens sheet 10. It is preferable to use

  Next, a required number of grooves are formed in a concentric arc shape on one side of the mold base M. One groove corresponds to one prism 5 in the Fresnel lens sheet 10. The groove portion is formed by the cutting tool B by attaching the mold base material M to the lathe and rotating it, and pressing the cutting tool B against the mold base material M. At this time, it is preferable to sequentially form the grooves corresponding to the prism 5 farthest from the point O shown in FIG.

  When forming each groove, the cutting tool B is gradually pushed into the mold base M. As shown in FIG. 4B, when the cutting depth by the cutting tool B becomes equal to the height H of the prism 5, the pushing of the cutting tool B is stopped. Thereby, the groove part which has the shaping | molding surface corresponding to the refractive surface 1 in the prism 5, and the shaping | molding surface corresponding to the 1st reflective surface 3a is formed.

  Next, as shown in FIG. 4C, the die base material M is cut by changing the angle of the cutting bit B while the tip of the cutting bit B is inserted into the groove, and the prism 5 is used. A groove portion g having a molding surface corresponding to the refractive surface 1, a molding surface corresponding to the first reflection surface 3a, and a molding surface corresponding to the second reflection surface 3b, that is, a groove portion g having a shape corresponding to the prism 5. Form. As shown in FIG. 4D, the cutting tool B is once extracted from the mold base material M after the formation of the groove g.

  Thereafter, the position of the cutting tool B is changed, and the steps shown in FIGS. 4B, 4C, and 4D are repeated in this order. The inclination angle of the molding surface corresponding to the second reflecting surface 3b in each groove part g can be controlled by appropriately selecting the angle of the cutting tool B when forming this molding surface. By forming the necessary number of grooves g in the arc shape concentric with the mold base material M in this way, a mold D corresponding to the Fresnel lens sheet 10 can be obtained as shown in FIG. .

In addition, when a shaping | molding die is produced using the mold | die base material with good machinability, as shown in FIG.4 (e), the upper end part of the boundary of adjacent groove part g will be easy to curve in a fixed direction. That is, when forming the molding surface corresponding to the second reflecting surface 3b, the upper end portion is easily curved toward the groove portion g formed earlier. With mold this curvature occurs, the Fresnel lens sheet bottom B _V valley V prism 5 adjacent to each other to form the curved refracting surface 1 side in one of the prism 5 of the prism 5 adjacent the is can get. The bending of the upper end portion in the mold can be suppressed by producing the mold D using a mold base material that is difficult to deform.

  The production of the Fresnel lens sheet 10 using the molding die D can be performed by a method such as press molding, injection molding, or casting molding using the molding die D, for example. As a raw material of the Fresnel lens sheet 10, for example, light that becomes a transparent thermoplastic resin having a refractive index of about 1.45 to 1.65 or a transparent resin having a refractive index of about 1.45 to 1.65 by being cured. A curable (including ultraviolet curable) or electron beam curable resin composition can be used. Specific examples of the transparent resin used as the material for the Fresnel lens sheet 10 include acrylic resins, polycarbonate resins, vinyl chloride resins, styrene resins, cellulose resins, and cycloolefin resins.

(Fresnel lens sheet: modification)
In the Fresnel lens sheet of the present invention, a large number of prisms are formed on one surface in the thickness direction, and each prism has a reflecting surface including a first reflecting surface and a second reflecting surface. The overall configuration of such a Fresnel lens sheet is not limited to the configuration shown in FIGS. Various modifications, modifications, combinations, and the like are possible.

  For example, like the prism 5A in the Fresnel lens sheet 10A shown in FIG. 5A, the apex T of each prism may be formed into a curved surface (curved curved surface outward). Further, like the prism 5B in the Fresnel lens sheet 10B shown in FIG. 5B, the apex T of each prism may be formed into a chamfered shape. Of the components shown in FIG. 5A or FIG. 5B, the components other than the prism are given the same reference numerals as those used in FIG.

  By making the shape of the top of the prism a curved surface or a chamfered shape, it becomes easy to obtain Fresnel lens sheets that are difficult to damage individual prisms, and molding for Fresnel lens sheets. It becomes easy to suppress breakage of the cutting tool in the process of producing the mold. A Fresnel lens sheet having such a prism can be manufactured, for example, with a cutting tool whose tip is molded into a curved surface, or a molding die made using a cutting tool whose tip is chamfered.

  Further, like the valley Va formed by adjacent prisms 5C in the Fresnel lens sheet 10C shown in FIG. 6, the bottom of the valley formed by adjacent prisms has a V-shaped cross section in the width direction. Also good. In addition, about the component except the prism 5C and the trough Va among the components shown in FIG. 6, the same referential mark as the referential mark used in FIG. 2 is attached | subjected, and the description is abbreviate | omitted.

  Such a Fresnel lens sheet is difficult to deform a steel material or the like as a material of the mold base material M when producing a mold according to the manufacturing method described with reference to FIGS. 4 (a) to 4 (e), for example. It is obtained by producing a mold D using the material and manufacturing using the mold D.

  Although the Fresnel lens sheet 10 shown in FIGS. 1 to 3 has a single layer structure, the Fresnel lens sheet of the present invention may have a multilayer structure of two or more layers.

FIG. 7A is a vertical sectional view schematically showing an example of a Fresnel lens sheet having a two-layer structure. The Fresnel lens sheet 20 shown in Fig has a structure in which a colored layer 15 on the surface S ₂ of the Fresnel lens sheet 10 shown in FIGS. The configuration other than the colored layer 15 is the same as that of the Fresnel lens sheet 10 shown in FIGS.

  The colored layer 15 is for reducing the amount of light that becomes stray light among the light emitted from the Fresnel lens sheet 20 when a transmissive screen is configured using the Fresnel lens sheet 20. It is formed of a material containing carbon black, pigment, dye or the like in a resin. From the viewpoint of suppressing the stray light and obtaining a transmissive screen with a bright image, it is preferable that the total light transmittance of light (visible light) in the colored layer 15 is in the range of about 70 to 95%.

FIG. 7B is a vertical sectional view schematically showing another example of a Fresnel lens sheet having a two-layer structure. The Fresnel lens sheet 30 shown in the figure has a structure in which a base sheet 25 is bonded to one side of a Fresnel lens sheet main body 10D on which a large number of prisms are formed in the same manner as the Fresnel lens sheet 10 shown in FIGS. Have. Since the shape of each prism in the Fresnel lens sheet main body 10D is the same as the shape of the prism 5 in the Fresnel lens sheet 10 shown in FIGS. 1 to 3, each prism and the surfaces or regions constituting the prism are described. The same reference numerals as those used in FIG. Further, in the Fresnel lens sheet 30, since the main surface of the outer of the base sheet 25 corresponds to the surface S ₂ as shown in FIG. 2, also indicated by reference numeral "S _2" in FIG. 7 (b).

  Since the Fresnel lens sheet 30 includes the base sheet 25, the base sheet 25 can be formed of a material different from the material of the prism 5, and as a result, characteristics that are difficult to obtain with the material of the prism 5 alone. And functions such as scratch resistance, heat distortion resistance, and water absorption resistance resistance can be easily added. The material of the base sheet 25 is appropriately selected from organic materials and inorganic materials according to the characteristics and functions to be added by the base sheet 25.

  Such a Fresnel lens sheet 30 is, for example, a raw material (photocurable or electronic) of the Fresnel lens sheet main body 10D on the molding die D so as to fill each groove g of the molding die D shown in FIG. The base material of the base sheet 25 is stacked after the application of the linear curable resin composition, and in this state, the raw material of the Fresnel lens sheet main body 10D is cured and then released, and after releasing, the desired size is obtained. Obtained by cutting.

  It should be noted that characteristics and functions that are difficult to obtain with only the material of the prism 5 by providing a layer, film, or sheet corresponding to the base sheet 25 in place of the colored layer 15 shown in FIG. Can be obtained.

  When the Fresnel lens sheet of the present invention is used as a transmissive screen material, the arrangement of a large number of prisms in the Fresnel lens sheet is concentric arcs as in the Fresnel lens sheet 10 shown in FIGS. However, it is also possible to arrange a large number of prisms having a strip shape or a line shape in parallel with each other. In this case, by arranging the Fresnel lens sheet so that the arrangement direction of the prisms is the vertical direction on the screen surface and configuring the transmissive screen, the light incident on the prisms in the divergent light state is It is possible to convert the light into a divergent light that is parallel or substantially parallel to a plane orthogonal to the arrangement direction of the prisms. The converted light includes light that is parallel or substantially parallel to the thickness direction of the Fresnel lens sheet.

(Transmissive screen: 1st form)
Transmission screen of the present invention includes a Fresnel lens sheet of the present invention described above, arranged in (corresponding to the plane S ₂ shown in FIG. 2) side the other face in the thickness direction of the Fresnel lens sheet light The light diffusing sheet is capable of diffusing light emitted from the Fresnel lens sheet in at least the horizontal direction on the screen surface.

FIG. 8 is a perspective view schematically showing an example of a transmission screen having the above-described structure. Transmission screen 50 illustrated includes a Fresnel lens sheet 10 shown in FIGS. 1 to 3, and a lenticular lens sheet 40 as a light diffusing sheet which is bonded on surface S ₂ in the Fresnel lens sheet 10 Yes.

Since the Fresnel lens sheet 10 among the constituent elements shown in FIG. 8 has already been described, the same reference numerals as those used in FIG. Is omitted. The reference symbol “O” in the figure indicates the center of the arrangement of the prisms 5 arranged in concentric arcs, and the reference symbol “A _x ” indicates the vertical axis of the Fresnel lens sheet 10. Yes.

Lenticular lens sheet 40 of the above are those having a number of cylindrical lenses 35 on one surface in the thickness direction, each cylindrical lens 35 has its longitudinal axis is parallel to the vertical axis A _x of the Fresnel lens sheet 10 They are oriented and parallel to each other. The pitch between the adjacent cylindrical lenses 35 (interval between the optical axes) is appropriately selected within a range of, for example, about several μm to several hundred μm.

Transmission screen 50 has the other surface in the thickness direction are joined with each other and the surface S ₂ of the Fresnel lens sheet 10 structured in the lenticular lens sheet 40, and the normal line of the surface S ₂ from the Fresnel lens sheet 10 The light emitted in parallel or substantially parallel is diffused by the lenticular lens sheet 40 in the horizontal direction on the screen surface (screen). As a result, the transmissive screen 50 has good viewing angle characteristics in the horizontal direction.

  In addition, as described above, the Fresnel lens sheet 10 can be manufactured at low cost even when the inclination angle of the total reflection surface (second reflection surface) of the prism 5 is changed according to the position of the prism 5. Since the technical effect that it is easy to obtain can be obtained, the transmission screen 50 configured using the Fresnel lens sheet 10 can be applied to a thin rear projection display device at low cost. There is a technical effect that it is easy to obtain.

(Transmissive screen: second form)
FIG. 9 is a perspective view schematically showing another example of the transmission screen of the present invention. Transmission screen 70 shown in the figure, has a Fresnel lens sheet 10 shown in FIGS. 1 to 3, and a light diffusing sheet 60 joined onto the surface S ₂ in the Fresnel lens sheet 10.

Since the Fresnel lens sheet 10 among the components shown in FIG. 9 has already been described, the same reference numerals as those used in FIG. Is omitted. The reference symbol “O” in the figure indicates a virtual point that is the center of the arrangement of the respective prisms 5 arranged in concentric arcs, and the reference symbol “A _x ” indicates the upper and lower sides of the Fresnel lens sheet 10. An axis is shown.

  The light diffusing sheet 60 has at least a light diffusing portion for diffusing light incident from the Fresnel lens sheet side by total reflection, and the light diffusing portion tapers toward the Fresnel lens sheet side. A number of grooves have a light absorbing portion 55 that is filled with a resin containing a light absorbing material. The light diffusing portion has a so-called light guide function, and a light absorbing portion 55 having a substantially wedge-shaped (substantially V-shaped) cross section extends in the vertical direction on the surface on the observer side serving as the light output surface and is constant in the horizontal direction. It is formed with a pitch. The light absorbing portion 55 is formed by filling a large number of substantially V-shaped grooves with a low refractive index resin containing light absorbing particles, and constitutes a low refractive index portion.

  FIG. 10 is a schematic view of a cross section when the light diffusion sheet 60 is cut along a direction orthogonal to the longitudinal axis of each of the substantially trapezoidal portion 53 and each light absorbing portion 55 in front view. In this light diffusing sheet 60, a substantially trapezoidal section (also referred to as an isosceles trapezoidal section) 53, which is a part other than the groove, constitutes a high refractive index part, and the slope forming the groove has a low refractive index. This is an interface between the portion and the high refractive index portion. The slope is composed of two slopes, and these slopes function as a light guide that totally reflects the substantially parallel light deflected by the Fresnel lens sheet 10. Further, the light absorbing portion 55 which is a low refractive index portion containing a light absorbing resin acts to absorb stray light in the transmission screen and to absorb external light to improve contrast.

In FIG. 10, each substantially trapezoidal portion 53 constitutes a part of the high refractive index portion 51, and this high refractive index portion 51 is composed of a substantially trapezoidal portion 53 and a layered region 52. . In FIG. 10, the boundary between each substantially trapezoidal portion 53 and the layered region 52 is indicated by a two-dot chain line CL. The outer surface S ₃ in the thickness direction of the layer region 52 is joined to the surface S ₂ of the Fresnel lens sheet 10, the upper surface S ₄ of the substantially trapezoidal section 53 when referred to this layered region 52 are respectively outer surface S ₃ parallel to each other.

  The light diffusing sheet 60 is formed with a fine pitch corresponding to a recent single light source, and the material for forming the light diffusing sheet 60 is also a radiation curable resin, specifically an acrylate resin such as urethane, polyester or epoxy. Material is used. The light diffusing sheet 60 is formed by first applying the radiation curable resin on a mold roll in which the inverted shape of the groove is formed, and usually applying a base film (see reference numeral 125 in FIG. 13) from above. Bonding is performed, and radiation (for example, ultraviolet rays or electron beams) is applied from the base film side to cure the radiation curable resin. After that, the sheet is peeled off from the mold roll, and a large number of V-shaped grooves formed are filled with a low refractive index resin containing a light absorbing material. If necessary, an extra low refractive index is obtained with a squeegee or doctor blade. The light diffusion sheet 60 is formed by removing the resin.

  As a material of the high refractive index portion 51 and the substantially trapezoidal portion 53, for example, the total light transmittance of light (visible light) when the refractive index is about 1.5 to 1.65 and the film thickness is 100 μm is 80. A transparent resin that is about% or more can be used. Specifically, resins such as acrylic resins, styrene resins, vinyl resins and polycarbonate resins, synthetic resins such as diene rubbers and non-diene rubbers, or natural resins of these resins, particularly acrylic resins, or natural resins What added the rubber | gum about 1-5 mass% can be used.

On the other hand, the cross-sectional shape of each light absorption part 55 is an isosceles triangle shape of substantially V shape or a wedge shape like illustration. These light absorbing portion 55, when the thickness direction and parallel or substantially parallel light of the light diffusion sheet 60 is incident from the outer surface S ₃ side in a substantially trapezoidal shape portion 55, the direction distribution by using total reflection Is for selectively changing. Therefore, the inclination angle θ5 of the interface between the light absorbing portion 55 and the substantially trapezoidal portion 53 is selected so that the incident angle of the parallel or substantially parallel light to the interface is equal to or greater than the critical angle. Here, the “inclination angle of the interface between the light absorbing portion and the substantially trapezoidal portion” means the above-mentioned interface when a plane whose normal is parallel to the thickness direction of the light diffusion sheet 60 is a reference plane. Means the inclination angle.

The width of each light absorbing portion 55 in a front view (plan view) is preferably in the range of about several μm to several hundred μm, and more preferably in the range of about 10 to 100 μm. By the width of the front view of the light absorbing portion 55 (plan view) in the range of the aperture ratio of the light diffusion sheet 60 (when the light diffusing sheet 60 from the upper surface S ₄ side described above is viewed from the front it means the percentage of the total area of the upper surface S ₄ occupied in the total area.) the can be easily set to about 30% to 80%, it is easy to enhance the quality of images in the transmissive type screen 70. The height of each light absorbing portion 55 in side view, that is, the height in side view of each substantially trapezoidal portion 53 is the width of the light absorbing portion 55 in front view (plan view) and the substantially trapezoidal portion 53. Depending on the difference in refractive index between the material and the material of the light absorbing portion 55, it can be appropriately selected within a range of about 5 to 20 times the width of the upper portion of the light absorbing portion.

  The light absorbing portion 55 is formed of a light absorbing material having a refractive index smaller than that of the material of the substantially trapezoidal portion 53. Specifically, the light absorbing portion 55 is light absorbing in a transparent resin material having a small refractive index. It is formed by a light-absorbing material containing a pigment or dye. For example, a transparent resin having a refractive index of approximately 80 to 99% of the refractive index of the material of the substantially trapezoidal portion 53 can be used, and specific examples include urethane acrylate resins and epoxy acrylate resins.

In the transmission screen 70 having a light diffusion sheet 60 having the above structure, the parallel or substantially parallel to the direction distribution of the emergent light from the Fresnel lens sheet 10 and the normal line of the surface S _2, substantially trapezoidal portion 53 and the light The total reflection at the interface with the absorber 55 can be selectively changed. For example, among the light emitted from the Fresnel lens sheet 10 in parallel with the normal of the surface S ₂ , the light incident on the region where the outer surface 3 of the layered region 52 and the upper surface S ₄ of the substantially trapezoidal part 53 overlap in front view. Is emitted from the light diffusing sheet 60 without being refracted, and the light incident on the interface between the substantially trapezoidal portion 53 and the light absorbing portion 55 is totally reflected here and horizontally in the screen surface (screen). Diffused. As a result, the transmissive screen 70 has good horizontal viewing angle characteristics.

  In addition, as described above, the Fresnel lens sheet 10 can be manufactured at low cost even when the inclination angle of the total reflection surface (second reflection surface) of the prism 5 is changed according to the position of the prism 5. Since the technical effect that it is easy to obtain is obtained, the transmission screen 70 configured using the Fresnel lens sheet 10 can be applied to a thin rear projection display device at a low cost. There is a technical effect that it is easy to obtain.

(Transparent screen: modification)
Transmission screen of the present invention includes a Fresnel lens sheet of the present invention described above, the thickness direction of the Fresnel lens sheet other surface light disposed (corresponding to the plane S ₂ shown in FIG. 2) side The light diffusion sheet can diffuse light emitted from the Fresnel lens sheet at least in the horizontal direction on the screen surface. The overall configuration of such a transmission screen is not limited to the configuration shown in FIGS.

  For example, as the Fresnel lens sheet constituting the transmission screen of the present invention, a Fresnel lens sheet other than the Fresnel lens sheet 10 shown in FIGS. 1 to 3 can be used as long as it is the Fresnel lens sheet of the present invention. Similarly, as the light diffusing sheet constituting the transmission screen of the present invention, any light diffusion sheet can be used as long as the light emitted from the Fresnel lens sheet of the present invention can be diffused at least in the horizontal direction on the screen surface. Light diffusion sheets other than the light diffusion sheets 40 and 60 shown in FIG. 10 can be used.

  When a lenticular lens sheet is used as the light diffusion sheet, this lenticular lens sheet may have a large number of cylindrical lenses 35 formed on only one side as shown in FIG. 8, or a large number of cylindrical lenses on each side. It may be formed. In either case, it is preferable to provide a light shielding layer (black stripe layer) between the cylindrical lenses that are adjacent in the horizontal direction of the screen. Providing these light shielding layers makes it easy to obtain a transmission screen with high image contrast.

  FIG. 11A is a cross-sectional view schematically showing another example of a light diffusion sheet that can be used as a constituent member of the transmission screen of the present invention. The light diffusion sheet 80 shown in the figure has a structure in which a large number of light shielding layers 75 are formed on the surface opposite to the surface on which a large number of cylindrical lenses 35 are formed. These light shielding layers 75 are disposed between the cylindrical lenses 35 while overlapping each adjacent cylindrical lens 35 with a desired width in a front view (plan view). Each light shielding layer 75 is formed of a resin containing, for example, carbon black or a black pigment.

  The light diffusion sheet 80 is arranged on the display surface side of the above-described Fresnel lens sheet of the present invention with the respective light shielding layers 75 facing outward to constitute the transmission screen of the present invention.

  FIG. 11B is a cross-sectional view schematically showing still another example of a light diffusion sheet that can be used as a constituent member of the transmission screen of the present invention. The light diffusing sheet 90 shown in the figure has a structure in which a plurality of light shielding layers 87 are formed on one side of a lenticular lens sheet 85 having cylindrical lenses formed on both sides.

  The lenticular lens sheet 85 is formed by forming a plurality of cylindrical lenses 82 on one side and alternately forming cylindrical lenses 83 and bowl-shaped portions 84 having a lens diameter smaller than that of the cylindrical lens 82 on the other side. A bowl-shaped portion 84 is formed between the cylindrical lenses 83. A light shielding layer 87 is provided on each ridge upper portion 84. Each hook-shaped portion 84 and each light shielding layer 87 are positioned between these cylindrical lenses 82 while overlapping each adjacent cylindrical lens 82 with a desired width in a front view (plan view).

The light diffusion sheet 90, in the orientation the cylindrical lenses 82 and the cylindrical lens 83 is parallel to the vertical axis A _x shown in FIG. 8, respectively, and, of the present invention where the light-shielding layer 87 is described above in the outer direction In combination with the Fresnel lens sheet, the transmissive screen of the present invention is configured.

  A functional layer can be provided on the outer surface of the light diffusing sheet (the outer surface when a transmissive screen is configured), if necessary. Here, the “functional layer” in the present specification is a layer for improving the optical characteristics, visibility, mechanical characteristics, electrical characteristics, etc. of the light diffusion sheet. Examples thereof include a prevention layer, an antiglare layer, a hard coat layer, and an antistatic layer.

  By providing the antireflection layer as the functional layer, reflection of external light on the light diffusion sheet can be suppressed, and as a result, the reflected light is suppressed from being superimposed on the diffused light by the light diffusion sheet. In addition, by providing an antiglare layer as a functional layer, it is possible to suppress glare when viewing the light diffusion sheet. When the transmissive screen of the present invention is configured using a light diffusion sheet provided with an antireflection layer or an antiglare layer as a functional layer, it is easy to increase the contrast of an image.

  The antireflection layer may have a single layer structure or a multilayer structure. The layer constituting the antireflection layer can be formed of an inorganic material or an organic material. The design wavelength of the antireflection layer can be selected as appropriate, but is preferably set within a wavelength range of about 500 to 600 nm where the standard relative luminous sensitivity is high.

  The antiglare layer is, for example, a transparent resin such as an acrylic resin (including a methacrylic resin), a polycarbonate, a polyolefin resin, a methacryl-styrene copolymer resin (MS resin), a polyurethane resin, or a polyester resin. Is used as a matrix material, and a layer having an uneven surface is formed by a material in which a light diffusing material such as transparent resin beads or glass beads is dispersed in the matrix material. As said transparent resin bead, what was formed with resin, such as an acrylic resin, a styrene resin, a vinyl resin, a polycarbonate resin, or a polyolefin resin, can be used, for example. The shape of the light diffusing material can be appropriately selected from a spherical shape, a lump shape, a foil shape, a scale shape, and the like. When the light diffusing material 143 has a spherical shape, the average particle diameter can be appropriately selected within a range of about 5 to 15 μm. Moreover, when making the shape of the light-diffusion material 143 into shapes other than spherical shape, it is preferable to make the maximum length into 5-15 micrometers or less. The content of the light diffusing material 143 in the antiglare layer can be appropriately selected within a range of about 5 to 40 parts by weight with respect to 100 parts by weight of the matrix material.

  On the other hand, by providing a hard coat layer as the functional layer, the impact resistance and scratch resistance of the light diffusion sheet can be improved, and as a result, the durability of the light diffusion sheet can be improved. For example, the hard coat layer is formed of an acrylic, epoxy, urethane, polyester, or other light (including ultraviolet) curable resin composition or electron beam curable resin composition. It can be obtained by curing. By dispersing the light diffusing material described above in the hard coat layer, the hard coat layer can be provided with a function as an antiglare layer.

  Moreover, by providing an antistatic layer as a functional layer, it is possible to suppress the adhesion of dust to the surface of the light diffusion sheet, and as a result, the optical characteristics of the light diffusion sheet are good even if the frequency of cleaning is low. It becomes easy to keep in a state.

  Only one type of functional layer may be formed on the light diffusion sheet, or a plurality of types of functional layers may be laminated. When a plurality of types of functional layers are stacked, the stacking order is appropriately selected according to the type of functional layers to be provided. The functional layer can be formed directly on the lenticular lens sheet constituting the light diffusion sheet, or one or more functional layers are laminated on a desired transparent substrate, and this is used as a lenticular lens sheet. You may use it in combination.

  FIG. 11C is a cross-sectional view schematically showing still another example of a light diffusion sheet that can be used as a constituent member of the transmission screen of the present invention. In the light diffusion sheet 100 shown in the figure, the transparent base 94 having the functional layer 92 formed on one side is formed on the surface on which the light shielding layer 75 is provided in the lenticular lens sheet 80 shown in FIG. And a transparent adhesive layer 96.

  The transparent substrate 94 preferably has a total light transmittance of light (visible light) of about 80% or more. Examples of such a transparent substrate 94 include polyethylene terephthalate, polycarbonate, and acrylic resin. (Including methacrylic resins), plate-like materials, sheet-like materials, or film-like materials made of transparent resins such as polyolefin resins can be used. The refractive index of the transparent substrate 94 is not particularly limited, but it may be smaller than the refractive index of the lenticular lens sheet 80 from the viewpoint of suppressing reflection of external light at the interface with the lenticular lens sheet 80. preferable.

The light diffusion sheet 100, in the orientation the cylindrical lenses 35 is parallel to the vertical axis A _x shown in FIG. 8, respectively, and combined with the Fresnel lens sheet of the present invention the functional layer 92 described above in the outer direction Thus, the transmissive screen of the present invention is constituted.

  The lenticular lens sheet 80 and the transparent substrate 94 on which the functional layer 92 is formed may be integrated with each other by a bonding agent such as an adhesive or a pressure-sensitive adhesive, or may be separate from each other. . When separate from each other, a spacer, a support member, or the like is appropriately used. Instead of the lenticular lens sheet 80, the lenticular lens sheet 40 shown in FIG. 8 or the lenticular lens sheet 90 shown in FIG. 11B can be used.

  FIG. 12 is a cross-sectional view schematically showing still another example of a light diffusion sheet that can be used as a constituent member of the transmission screen of the present invention. The light diffusing sheet 120 shown in the figure is different from the light diffusing sheet 60 shown in FIG. 10 in that it has a light absorbing portion 115 made of a material in which a large number of light absorbing particles 113 are dispersed in a transparent resin. . Since the other structure in the light diffusion sheet 120 is the same as that of the light diffusion sheet 60 shown in FIG. 10, constituent elements other than the light absorbing portion 115 among the constituent elements shown in FIG. The same reference numerals as those used in FIG.

  Also in the light diffusing sheet 120 having such a configuration, light can be absorbed by the light absorbing portion 115 as in the case of the light diffusing sheet 60 shown in FIG. That is, light that has entered the interface between the substantially trapezoidal portion 53 and the light absorbing portion 115 at an incident angle less than the critical angle and propagated into the light absorbing portion 115 can be absorbed by the light absorbing particles 113. Moreover, the light directly incident on the light absorbing portion 115 can be absorbed without passing through the interface. Therefore, in the transmissive screen using the light diffusion sheet 120, stray light and external light can be absorbed by the light absorption unit 115, and as a result, the image quality when an image is projected is improved.

  As the light absorbing particles 113, particles having the same color can be used as long as they exhibit desired light absorption characteristics when a large number of the light absorbing particles 113 are gathered, and based on the surface color. Particles that can be classified into a plurality of types can also be used. The color when many light-absorbing particles 113 gather is preferably black.

  As such light-absorbing particles 113, those formed of an organic material, an inorganic material, or an organic-inorganic composite material can be used, and in particular, a core formed of a transparent material is covered with a coloring material. It is preferable to use particles comprising a transparent material and particles made of a transparent material and a colorant dispersed in the transparent material. As the transparent material, a transparent resin such as urethane resin or acrylic resin, or glass can be used, and its refractive index is not particularly limited. It is preferable that the refractive index of the matrix material is substantially the same as that for obtaining the material of the absorbing portion 115. Moreover, as said coloring material, carbon black, various dyes, various pigments, etc. can be used. The colorant constituting each particle may be only one type, or two or more types. The content of the colorant in the particles is preferably in the range of about 5 to 30% by mass, and more preferably in the range of about 15 to 25% by mass.

  FIG. 13A is a cross-sectional view schematically showing still another example of a light diffusion sheet that can be used as a constituent member of the transmission screen of the present invention. The light diffusing sheet 130 shown in the figure has a high refractive index portion 121 having a single layered region 122 and a plurality of substantially trapezoidal portions 123, except that the first transparent base material 125 is joined. It has the same configuration as the light diffusion sheet 120 shown in FIG. Of the constituent elements shown in FIG. 13A, those common to the constituent elements shown in FIG. 12 are given the same reference numerals as those used in FIG. 12, and descriptions thereof are omitted. A two-dot difference line CL in FIG. 13A represents the boundary between the layered region 122 and the substantially trapezoidal portion 123.

  The first transparent substrate 125 preferably has a total light transmittance of light (visible light) of about 80% or more. Examples of the first transparent substrate 125 include polyethylene terephthalate and polycarbonate. A plate-like material, a sheet-like material, or a film-like material made of a transparent resin such as an acrylic resin (including a methacrylic resin) or a polyolefin resin can be used. Although the refractive index of the first transparent base material 125 is not particularly limited, from the viewpoint of suppressing reflection of external light at the interface with the substantially trapezoidal portion 123, the refractive index of the approximately transparent trapezoidal portion 123. Is preferably small.

In the light diffusing sheet 130 having the above-described structure, stray light and external light can be absorbed by the light absorbing unit 115 as in the light diffusing sheet 120 shown in FIG. The light diffusion sheet 130 has an outer surface S ₅ of the first transparent substrate 125 is disposed in an orientation which is a Fresnel lens sheet side, constituting the transmission screen of the present invention.

  Similarly to the light diffusion sheet 60 of FIG. 10, the light diffusion sheet 130 is also formed with a fine pitch corresponding to a recent single light source. As a material for forming the light diffusion sheet 130, a radiation curable resin, specifically, a urethane-based resin is used. Acrylic resin materials such as polyester and epoxy are used. The light diffusing sheet 130 is formed by first applying the radiation curable resin on a mold roll having a groove inverted shape, and bonding the first transparent base material 125 from the top, and then the base film side. Then, radiation (for example, ultraviolet rays or electron beams) is applied to cure the radiation curable resin. After that, the sheet is peeled off from the mold roll, and a large number of V-shaped grooves formed are filled with a low refractive index resin containing light-absorbing fine particles. If necessary, an extra low refractive index is obtained with a squeegee or doctor blade. The light diffusion sheet 130 is formed by removing the resin.

  FIG. 13B is a cross-sectional view schematically showing still another example of a light diffusion sheet that can be used as a constituent member of the transmission screen of the present invention. The light diffusing sheet 140 shown in FIG. 13 has a second transparent base material 135 bonded to each substantially trapezoidal portion 123 and each light absorbing portion 115 via a bonding agent layer 131, except that FIG. It has the same configuration as the light diffusion sheet 130 shown in FIG. Among the constituent elements shown in FIG. 13B, those common to the constituent elements shown in FIG. 13A are given the same reference numerals as those used in FIG. Is omitted. A two-dot chain line CL in FIG. 13B represents the boundary between the layered region 122 and the substantially trapezoidal portion 123.

The bonding material layer 131 is made of, for example, the upper surface S ₄ of each substantially trapezoidal portion 123 and each of the substantially trapezoidal portions 123 by a transparent adhesive or transparent adhesive having a refractive index of about 90 to 110% of the refractive index of the substantially trapezoidal portion 123. It is formed on the upper surface of the light absorbing portion 115 (upper surface when the first transparent base material 125 is used as a reference), and the film thickness is appropriately selected within a range of about 1 μm to several tens of μm.

The second transparent substrate 135 described above, is bonded to the bonding agent layer 131 covers the upper surface of the upper surface S ₄ and the light absorbing portion 115 of the substantially trapezoidal section 123. Examples of the material of the second transparent substrate 135 include the same materials as those of the first transparent substrate 125 already described.

The light diffusion sheet 140 having such a structure has the same function as the light diffusion sheet 130 shown in FIG. Furthermore, since the second transparent base material 135 is provided, there is an advantage that the light absorbing portion 115 is suppressed from dropping off during or after the manufacturing process. The light diffusion sheet 140 has an outer surface S ₅ of the first transparent substrate 125 is disposed in an orientation which is a Fresnel lens sheet side, constituting the transmission screen of the present invention.

  The light diffusion sheet 140 is, for example, a bonding agent so as to cover each substantially trapezoidal portion 123 and each light absorption portion 115 in the light diffusion sheet 130 after the light diffusion sheet 130 shown in FIG. The layer 131 is formed, and the second transparent substrate 135 is disposed thereon and bonded to the bonding material layer 131. Alternatively, the base material of the second transparent substrate 135 is disposed on the bonding agent layer 131. Can be obtained by cutting into a desired size after joining.

  FIG. 14A is a cross-sectional view schematically showing still another example of a light diffusion sheet that can be used as a constituent member of the transmission screen of the present invention. A light diffusing sheet 150 shown in the figure is provided with a second transparent base material 145 in which a large number of light diffusing materials 143 are dispersed instead of the second transparent base material 135 shown in FIG. In addition, the configuration other than the second transparent substrate 145 is the same as the configuration of the light diffusion sheet 140 shown in FIG. Of the constituent elements shown in FIG. 14A, those common to the constituent elements shown in FIG. 13B are given the same reference numerals as those used in FIG. Is omitted. A two-dot chain line CL in FIG. 14 represents the boundary between the layered region 122 and the substantially trapezoidal portion 123.

  As the light diffusing material 143, for example, the same light diffusing material used as the material of the above-described antiglare layer can be used, but when the shape is spherical, the average particle diameter is 5 μm to 5 μm. It is preferable to select appropriately within the range of about 15 μm. Moreover, when making the shape of the light-diffusion material 143 into shapes other than a spherical shape, it is preferable to make the maximum length into tens of micrometers or less. On the other hand, as a matrix material in the second transparent substrate 145, for example, an acrylic resin (including a methacrylic resin), a polycarbonate, a polyolefin resin, a methacryl-styrene copolymer resin (MS resin), or the like has a refractive index. A transparent resin of about 1.4 to 1.7 can be used. The content of the light diffusing material 143 in the second transparent base material 145 can be appropriately selected within a range of about 0.5 to 30 parts by weight with respect to 100 parts by weight of the matrix material.

  Such a 2nd transparent base material 145 can be obtained by knead | mixing matrix material and the light-diffusion material 143, for example, and shape | molding it in a film form, a sheet form, or plate shape.

The light diffusion sheet 150 having the above-described structure has the same function as the light diffusion sheet 140 shown in FIG. Further, since the number of light diffusing material 143 in the second transparent substrate 145 are dispersed, the directional distribution of the collimated light incident from the outer surface S ₅ side of the first transparent substrate 125, the substantially trapezoidal shape 123 It has the function of changing in directions other than the arrangement direction. The light diffusion sheet 150 has an outer surface S ₅ of the first transparent substrate 125 is disposed in an orientation which is a Fresnel lens sheet side, constituting the transmission screen of the present invention.

  When the transmissive screen of the present invention is configured using the light diffusion sheet 150, the transmissive screen has good viewing angle characteristics in the horizontal direction and viewing angle characteristics in the vertical direction.

  FIG. 14B is a cross-sectional view schematically showing still another example of a light diffusion sheet that can be used as a constituent member of the transmission screen of the present invention. The light diffusing sheet 160 shown in the figure has a functional layer 155 provided on the second transparent base material 135 in the light diffusing sheet 140 shown in FIG. 13B, and the configuration other than the functional layer 155 is as follows. The configuration of the light diffusing sheet 140 shown in FIG. Among the constituent elements shown in FIG. 14B, those common to the constituent elements shown in FIG. 13B are given the same reference numerals as those used in FIG. Is omitted. Moreover, as the functional layer 155, the thing similar to the functional layer 92 shown in FIG.11 (c) can be used, Since this functional layer was already demonstrated, the description is abbreviate | omitted here.

  Only one type of functional layer 155 or a plurality of types of functional layers 155 may be stacked on the second transparent substrate 135. When a plurality of types of functional layers 155 are stacked, the stacking order is appropriately selected according to the type of functional layer 155 to be provided.

  In addition, the 2nd transparent base material 135 shown in FIG.13 (b) and the 2nd transparent base material 145 shown in FIG.14 (a) can also be provided in the light-diffusion sheet 120 shown in FIG. Moreover, the functional layer 155 shown in FIG.14 (b) can be provided in the various light-diffusion sheet which has a 2nd transparent base material.

The light diffusing sheet that can be used as a constituent member of the transmission screen of the present invention includes a plurality of substantially trapezoidal portions arranged while forming a gap between adjacent ones, and these substantially trapezoidal shapes. In the light diffusion sheet provided with the light absorbing portion so as to fill the gap between the portions, the cross-sectional shape when the light absorbing portion is cut along the plane orthogonal to the longitudinal direction is other than the isosceles triangle It can also be shaped. Specifically, (1) as shown in FIG. 15 (a), one end of each of the _two arcs A ₁ and A ₂ touches at one point, and the other end of each of the _two arcs A ₁ and A ₂ Morning glory connected by one side SI, (2) As shown in FIG. 15B, one end of each of the two first sides SI ₁ , SI ₁ touches at one point, and these two first sides SI _1, SI ₁ tilt angle is contiguous smaller second side end of SI ₂ than each of the first side SI ₁ to the other end, further second side SI ₂ of each other end connected by one side SI ₃ (3) As shown in FIG. 15C, the base (lower base) BS may have an isosceles trapezoid whose length is shorter than the length of the upper base US. In FIGS. 15A to 15C, the substantially trapezoidal portion is indicated by reference numeral “53”, and the high refractive index portion where the substantially trapezoidal portion is formed is indicated by reference numeral “51”. The light absorbing portion is indicated by reference numeral “55”.

  The transmission type screen of the present invention may be one in which the Fresnel lens sheet and the light diffusion sheet of the present invention described above are joined in surface contact with each other, or the Fresnel lens sheet and the light diffusion sheet are spacers. Or may be superposed or arranged via a support member. The transmission screen of the present invention can be variously modified, modified, combined, etc. in addition to those described above.

(Rear projection display)
The rear projection type display device according to the present invention includes the above-described transmission type screen according to the present invention and the image light on the Fresnel lens sheet constituting the transmission type screen from the lower rear side or the upper rear side of the transmission screen. And a light source capable of projecting.

FIG. 16 is a partial sectional view schematically showing an example of the rear projection type display device of the present invention. In the rear projection type display device 210 shown in the figure, a light source 204 is disposed at the bottom of a thin casing 202, close to the inner surface of the rear wall of the casing 202, and parallel to the vertical direction on the screen surface (screen). A mirror 206 is arranged. The transmission screen 70 shown in FIG. 9 is provided so as to close the window provided on the front wall of the housing 202. This transmissive screen 70 is arranged with the light diffusing sheet 60 facing outward with the vertical axis A _x (see FIG. 9) of the Fresnel lens sheet 10 oriented in the vertical direction on the screen surface (screen). Yes.

  In the rear projection display device 210 having such a structure, the image light ML emitted from the light source 204 is reflected by the mirror 206 toward the transmission screen 70 and enters the transmission screen 70 in a divergent light state. The image light ML that has entered the transmission screen 70 is converted into image light parallel or substantially parallel to the thickness direction of the Fresnel lens sheet 10 by the Fresnel lens sheet 10 (see FIG. 9), and further the light diffusion sheet 60. The light is diffused by (see FIG. 9) and emitted from the transmission screen 70.

  The rear projection display device 210 described above includes the transmissive screen 70 of the present invention, and the transmissive screen 70 can be easily obtained at low cost as described above. The projection display device 210 is also easy to obtain at low cost.

  The light source in the rear projection type display device of the present invention can project image light onto the transmissive screen when viewed from the front obliquely downward or obliquely upward and obliquely upward. Any configuration may be used, and the configuration can be appropriately selected according to the use, grade, and the like of the rear projection display device. Further, as the transmissive screen in the rear projection display device of the present invention, a screen other than the transmissive screen 70 shown in FIG. 16 can be used as long as it is the transmissive screen of the present invention described above.

Example 1 Production of Fresnel Lens Sheet
First, a mold base material made of a flat metal plate was prepared. Further, as a cutting tool for cutting the mold base material, a tool having a tip angle of 35 ° with a tip formed into a curved surface having a curvature radius of 2 μm (a curved surface convex outward) was prepared. Next, according to the method described with reference to FIGS. 4A to 4E, one side of the mold base material is cut with the cutting tool described above, and a virtual point outside the one side is obtained. A large number of grooves were formed in a concentric arc shape at the center, thereby obtaining a mold for a Fresnel lens sheet.

  Next, as a raw material for the Fresnel lens sheet, a resin composition layer is formed by casting an ultraviolet curable resin composition, which is cured by irradiation with ultraviolet rays to become an epoxy acrylate resin having a refractive index of 1.55, in the mold. The surface was flattened and then cured by irradiating with ultraviolet rays. Thereafter, release and cutting were performed to obtain a Fresnel lens sheet having a 135 cm × 75 cm rectangle when viewed in plan.

  Similar to the prism 5 in the Fresnel lens sheet shown in FIGS. 1 to 2, this Fresnel lens sheet has a large number of prisms on one surface around a virtual point outside one surface in the thickness direction. It is formed in a concentric arc shape at a pitch of 0.1 mm, and the other surface in the thickness direction is formed into a flat surface.

  The top of each prism is formed into a curved surface (curved convex surface) having a radius of curvature of 2 μm, and its height H (see FIG. 3) is 0.1 to 0.2 mm depending on the position of each prism. Within the range, the height h (see FIG. 3) of the first reflecting surface at each prism varies depending on the position of each prism, but is within 30% of the height H of the corresponding prism.

The angle θ ₁ (see FIG. 2) formed by the refracting surface and the first reflecting surface in each prism is 35 ° in any prism, and the angle θ ₂ formed by the refracting surface and the second reflecting surface (see FIG. 2). ) Is 37 ° for the prism closest to the virtual point and 40 ° for the farthest prism. This angle θ ₂ gradually increases from the prism closest to the virtual point toward the prism farthest from the virtual point. Further, the inclination angle θ ₄ (see FIG. 2) of the refracting surface in each prism is constant at 87 °.

  The Fresnel lens sheet having the prism having the above-described shape means the incident angle of the image light at the lower end of the display surface (however, the incident angle when the back surface of the transmissive screen is assumed to be a plane parallel to the screen surface. The same) is 45 °, the incident angle of the image light at the upper end of the display surface is 70 °, and the transmission screen used in the thin rear projection display device in which the image light is projected obliquely from the lower rear of the display surface. It can be used as a component.

(Comparative Example 1; Production of Fresnel lens sheet)
A Fresnel lens sheet was produced in the same manner as in Example 1 except that when the mold for the Fresnel lens sheet was produced, the inclination angles of the left and right side walls in each groove were set to different values. Each prism in this Fresnel lens sheet does not have a surface corresponding to the second reflecting surface, and the angle formed between the refracting surface and the reflecting surface in each prism is constant at 38 ° in any prism. . Further, the inclination angle θ ₄ (see FIG. 2) of the refracting surface in each prism is variable within a range of about 90 ° to 70 °.

Example 2 Production of Transmission Screen
A 135 cm × 75 cm × 0.5 mm thick light diffusing sheet having the same structure as the light diffusing sheet 140 shown in FIG. 13 (b) was prepared, and this light diffusing sheet and the Fresnel lens sheet produced in Example 1 Were bonded to each other using a UV curable resin to obtain a transmission screen having a total thickness of 5 mm having the same configuration as that of the transmission screen 70 shown in FIG.

  Hereinafter, the light diffusion sheet and the method for manufacturing the same will be specifically described with reference to the reference numerals used in FIG.

  First, as a raw material of the high refractive index portion 121 (each substantially trapezoidal portion 123), an epoxy acrylate ultraviolet curable resin composition (hereinafter referred to as “high refractive index resin”) having a refractive index after curing of 1.55. Prepared). Further, as a raw material of each light absorbing portion 115, 20 parts by weight of a light diffusing material dispersed in 100 parts by weight of a urethane acrylate ultraviolet curable resin composition having a refractive index after curing of 1.48 (hereinafter, "Low refractive index resin raw material") was prepared. The light diffusing material is a spherical material in which styrene particles are dispersed in a urethane acrylate resin, and the average particle diameter is 4 μm.

  Separately, a polyethylene terephthalate film with a film thickness of 188 μm was prepared as a base material for the first transparent base material 125, and a polyethylene terephthalate film with a film thickness of 188 μm was prepared as a base material for the second transparent base material 135. Furthermore, an acrylic adhesive having a refractive index of about 1.5 was prepared as a material for the bonding agent layer 131.

  Next, according to the manufacturing method described in the description of the light diffusion sheet 140, a light diffusion sheet with an aperture ratio of 40% was produced. The film thickness of the high refractive index portion 121 in this light diffusion sheet is 130 μm, and the height of each substantially trapezoidal portion 123 formed in the high refractive index portion 121 (the height of each light absorbing portion 115) is 120 μm. is there. Further, the inclination angle of the interface between the substantially trapezoidal portion 123 and the light absorbing portion 115 is about 20 °. The thickness of the bonding agent layer 131 is 20 μm.

(Comparative Example 2: Production of transmission type screen)
A transmissive screen was produced under the same conditions as in Example 2 except that the Fresnel lens sheet produced in Comparative Example 1 was used.

(Evaluation)
The transmissive screen of Example 2 and the transmissive screen of Comparative Example 2 were mounted on a rear projection display device, and the image quality of each was visually evaluated. The one using the transmissive screen of Example 2 was caused by stray light. While no deterioration in image quality was observed, in the case of using the transmissive screen of Comparative Example 2, a decrease in image quality due to stray light was observed at the bottom of the screen. As a rear projection display device, a 50-inch projection television equipped with a 50 W-DLP light source (manufactured by Samsung Electronics Co., Ltd., HLM5065W) was used, and a transmissive screen used for the test was mounted on a screen fixing frame. Was fixed with tape.

It is a perspective view showing roughly an example of the Fresnel lens sheet of the present invention. It is the schematic of the vertical cross section of the Fresnel lens sheet shown in FIG. It is the schematic which shows an example of the optical path of the light in the Fresnel lens sheet shown in FIG. 4 (a) to 4 (e) are process diagrams schematically showing a manufacturing process of a mold used for manufacturing the Fresnel lens sheet shown in FIGS. 1 to 3, respectively. FIG. 5A is a cross-sectional view schematically showing the Fresnel lens sheet of the present invention in which the tops of the individual prisms are formed into curved surfaces, and FIG. 5B is the Fresnel lens of the present invention. It is sectional drawing which shows schematically what was shape | molded in the shape by which the top part of each prism was chamfered among the lens sheets. It is sectional drawing which shows schematically the cross section of the bottom part of the trough which adjacent prisms form among the Fresnel lens sheets of this invention becomes V shape. FIG. 7A is a vertical sectional view schematically showing an example of the Fresnel lens sheet of the present invention having a two-layer structure, and FIG. 7B is a diagram of the Fresnel lens sheet of the present invention having a two-layer structure. It is a vertical sectional view schematically showing another example. It is a perspective view which shows roughly an example of the transmission type screen of this invention. It is a perspective view which shows roughly the other example of the transmission type screen of this invention. It is the schematic of the cross section of the light-diffusion sheet | seat which comprises the transmissive screen shown in FIG. 11 (a), 11 (b), and 11 (c) are cross sections each schematically showing still another example of a light diffusing sheet that can be used as a constituent member of the transmission screen of the present invention. FIG. It is sectional drawing which shows roughly another example of the light-diffusion sheet which can be used as a structural member of the transmission type screen of this invention. FIG. 13A and FIG. 13B are cross-sectional views schematically showing still another example of a light diffusion sheet that can be used as a constituent member of the transmission screen of the present invention. FIG. 14A and FIG. 14B are cross-sectional views schematically showing still another example of a light diffusion sheet that can be used as a constituent member of the transmission screen of the present invention. FIG. 15A to FIG. 15C are arranged while forming a gap between adjacent ones of the light diffusion sheets that can be used as the constituent members of the transmission screen of the present invention. FIG. 2 schematically shows another example of the cross-sectional shape of the light absorbing portion in the light diffusion sheet provided with a plurality of substantially trapezoidal portions and filled with a light absorbing portion so as to fill a gap between the substantially trapezoidal portions. It is sectional drawing. It is a fragmentary sectional view which shows roughly an example of the rear projection type display apparatus of this invention.

Explanation of symbols

10, 10A, 10B, 10C, 20, 30 Fresnel lens sheet 1 Refractive surface 3, 3A Reflective surface 3a, 3a2 First reflective surface 3b Second reflective surface 5, 5A, 5B, 5C, 5D, 5f, 5n Prism 40 Light Diffusion sheet (lenticular lens sheet)
DESCRIPTION OF SYMBOLS 50 Transmission type | mold screen 53,123 Substantially trapezoid part 55,105,115 Light absorption part 60 Light diffusion sheet 70 Transmission type screen 80,90,100 Light diffusion sheet 113 Light absorption particle 110,120,130,140,150, 160 Light Diffusing Sheet 210 Rear Projection Display Device S _{1 One} surface in the thickness direction of the Fresnel lens sheet S ₂ The other surface in the thickness direction of the Fresnel lens sheet θ ₁ The first reflecting surface and the refracting surface of the prism are formed. Angle θ Angle formed by the second reflecting surface and the refracting surface of the ₂ prism _BP Prism base O Fresnel center V Valley formed by adjacent prisms B _V Valley bottom formed by adjacent prisms T Prism top h Height of first reflecting surface ML, ML ₁ , ML ₂ video light OS light source

Claims (8)

A Fresnel lens sheet having at least a total reflection Fresnel lens part formed on one surface in the thickness direction,
The total reflection Fresnel lens unit includes a plurality of prisms having a refracting surface that refracts incident light and a reflecting surface that reflects light refracted by the refracting surface, and the reflecting surface is on the top side of the prism. A first reflecting surface and a second reflecting surface continuous to the first reflecting surface;
An angle formed between the first reflecting surface and the refracting surface is smaller than an angle formed between the second reflecting surface and the refracting surface ;
A Fresnel lens sheet , wherein bottom portions of valleys formed by adjacent prisms are curved toward the refractive surface side of one of the adjacent prisms .   The angle formed by the first reflective surface and the refractive surface is the same regardless of the distance from the Fresnel center of the Fresnel lens sheet, and the angle formed by the second reflective surface and the refractive surface is a virtual one. The Fresnel lens sheet according to claim 1, which gradually increases as the distance from the center of the Fresnel increases.   3. The Fresnel lens sheet according to claim 2, wherein an angle formed by the second reflecting surface and the refracting surface is in a range of 35 to 45 °, and gradually increases within the range. The height of the first reflecting surface in the thickness direction, any one of claims 1-3, characterized in that the first 25% or less than 5% of the height of the prism having a reflective surface The Fresnel lens sheet according to Item 1. Top shape of the prism, a Fresnel lens sheet according to any one of claims 1 to 4, characterized in that a curved shape or chamfered shape. A Fresnel lens sheet according to any one of claims 1 to 5 transmissive screen and having a light diffusing sheet. The light diffusing sheet has at least a light diffusing portion that diffuses light incident from the Fresnel lens sheet side by total reflection, and the light diffusing portion has a substantially V-shape that tapers toward the Fresnel lens sheet side. The transmissive screen according to claim 6 , further comprising a light absorbing portion in which a plurality of grooves are filled with a resin containing a light absorbing material. 8. A rear projection display device comprising: the transmissive screen according to claim 6; and a light source that projects image light from a rear obliquely lower side or a rear oblique upper side of the transmissive screen.

Images