JP2007272161A - Front filter for pdp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a front filter for PDP (Plasma Display Panel) which has an electromagnetic wave shielding function, does not suppress a viewing angle as much as possible, and has a high contrast, and is stuck directly on an observer side of a front substrate of a PDP when used. <P>SOLUTION: The front filter for PDP has at least a contrast improvement layer and an electromagnetic wave shielding layer and is suck directly on the observer side of the plasma display panel (PDP). The contrast improvement layer has a transmission surface for PDP display light formed by arraying many lens portions which transmit light and many light absorption portions which absorb light alternately in a meashing shape. Here, the lens portions extend linearly in a predermined direction along a surface direction of the layer and a cross section perpendicular to the extension direction is in a shape of a trapezoid whose wide base is directed to the observer side. The light absorption portions extend linearly in a direction parallel to the lens portions and a cross section perpendicular to the extension direction is in a shape of a wedge whose wide base is directed to the PDP side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a PDP front filter disposed on the viewer side of a front substrate of a plasma display panel (hereinafter simply referred to as PDP), and more specifically, a PDP front filter having a contrast enhancement function. About.

In a display device such as a television set using a PDP, a protective plate including an electromagnetic wave shielding sheet and an optical filter is provided closer to the observer than the front substrate of the PDP. Although this protective plate has various functions for removing electromagnetic waves, infrared rays, and the like, it may adversely affect image quality such as a decrease in contrast due to external light.
As a method for improving the contrast of the image of the image display device, for example, Patent Document 1 describes that a large number of black or gray parallel lines, so-called black stripes, are provided on the screen or the entire surface of the cathode ray tube substantially at right angles to the scanning lines. Has been. In this patent document, a large number of parallel lines that are substantially perpendicular to the scanning lines are drawn by printing, and do not consider a reduction in contrast due to the influence of external light.
Patent Document 2 discloses a micromesh type antireflection filter for preventing reflection of a color cathode ray tube, and the micromesh is arranged at a fixed pitch with respect to the horizontal pitch and the vertical pitch of the dot pitch of the fluorescent film. It is described that the weft of the micromesh is set to a certain angle range with respect to the horizontal scanning line. However, this is an invention for preventing the occurrence of moire and is not intended to improve contrast, and the micromesh only describes a plain weave of nylon single fibers.

Japanese Patent Publication No. 37-283 JP-A-62-136741

The stripes formed by simple printing described in Patent Document 1 and the stripes described in Patent Document 2 which are composed of filaments having a circular cross section and a small diameter (thin thickness) have insufficient contrast enhancement effects. In order to improve the contrast, it is necessary to increase the area of the light absorbing portion by increasing the diameter of the filaments and narrowing the line spacing, and as a result, the aperture ratio of the grating is lowered and the image looks dark. It becomes difficult and the filaments are visually noticeable. For this reason, there is a problem that the contrast improvement effect and the image quality are not compatible.
Further, even if such a black stripe has a contrast improving effect, it does not have an electromagnetic wave shielding function or is not sufficient.

Conventionally, the protective plate of the PDP display device is disposed between the front substrate and a space. However, in such an arrangement, since the light shielding functional layer is a horizontal stripe or a vertical stripe of a fine light absorbing portion, a moire stripe may occur depending on the relationship with the pixel pitch of the PDP. There is a problem of reducing.
Therefore, when black stripes having a constant pitch are provided on such a protective plate, moire may be further promoted.

The present invention has been made to solve the above problems, has an electromagnetic wave shielding function, suppresses the viewing angle as much as possible, has a high contrast, achieves both a contrast enhancement effect and image quality, and is a front surface of the PDP. An object of the present invention is to provide a PDP front filter that is used by being directly bonded to an observer side of a substrate.
Moreover, it aims at providing PDP provided with the said front filter.

The front filter for PDP according to the present invention is a front filter for PDP that includes at least a contrast enhancement layer and an electromagnetic wave shielding layer, and is directly bonded to an observer side of a plasma display panel (PDP). A lens that is linearly connected in a predetermined direction along the surface direction of the layer, has a cross-section perpendicular to the extending direction, and has a trapezoidal shape with a wide lower base facing the viewer side, and transmits light And a section that is linearly connected in a direction parallel to the lens portion, and a cross section perpendicular to the extending direction has a wedge shape with the wide bottom bottom facing the PDP side, and absorbs light It has a transmission surface for PDP display light, which is formed by alternately engaging a plurality of light absorbing portions.
The front filter for PDP according to the present invention includes the above-described contrast improving layer, so that the contrast does not decrease even when the PDP is used in a place where external light is incident, the luminance of the image does not decrease, and the image quality is deteriorated. do not do. Further, the electromagnetic wave shielding layer can prevent the electromagnetic wave generated from the PDP from being emitted to the viewer side. In addition, by directly attaching to the observer side of the PDP and using it, moire that becomes a problem when arranged on the front surface of the PDP via an air layer is unlikely to occur.

Moreover, it is preferable that the front filter for PDP of the present invention does not include a light diffusion layer on the PDP side of the contrast improving layer, and further does not include a light diffusion layer at all.
This is because, unlike the mode in which the front filter is disposed on the front surface of the PDP through a space, the front filter of the present invention is used by directly bonding, and therefore it is not necessary to provide a light diffusion layer for preventing moire on the PDP side. .

In addition, it is preferable that the front filter for PDP of the present invention further includes one or more optical filters other than the contrast enhancement layer from the viewpoint of imparting various optical functions to the front filter.
In the PDP front filter of the present invention, a relationship of N2 <N1 is established, where N2 is a refractive index of a binder constituting the light absorbing portion and N1 is a refractive index of a material constituting the lens portion. Is preferable from the viewpoint of improving contrast.

The plasma display panel (PDP) according to the present invention is characterized in that any one of the above-mentioned PDP front filters is directly bonded to the observer side of the PDP.
In such a PDP, the contrast is improved by the functions of the contrast enhancement layer and the electromagnetic wave shielding layer of the front filter, and the emission of electromagnetic waves to the viewer side can be prevented. Furthermore, if the front filter has an optical function other than the contrast enhancement layer or the electromagnetic wave shielding layer, the PDP can also enjoy the advantages.

According to the present invention, even if the PDP is used in a place where external light is incident, the contrast does not decrease, the luminance and image quality of the image do not decrease, and the electromagnetic waves generated from the PDP are emitted to the viewer side. It is possible to provide a PDP front filter that can be prevented and is less likely to cause moire.
In addition, according to the present invention, it is possible to provide a PDP in which a PDP front filter having the above characteristics is directly bonded to the viewer side of the PDP.

The front filter for PDP according to the present invention is a front filter for PDP that includes at least a contrast enhancement layer and an electromagnetic wave shielding layer, and is directly bonded to an observer side of a plasma display panel (PDP). A lens that is linearly connected in a predetermined direction along the surface direction of the layer, has a cross-section perpendicular to the extending direction, and has a trapezoidal shape with a wide lower base facing the viewer side, and transmits light And a section that is linearly connected in a direction parallel to the lens portion, and a cross section perpendicular to the extending direction has a wedge shape with the wide bottom bottom facing the PDP side, and absorbs light It has a transmission surface for PDP display light, which is formed by alternately engaging a plurality of light absorbing portions.
The front filter for PDP according to the present invention includes the above-described contrast improving layer, so that the contrast does not decrease even when the PDP is used in a place where external light is incident. Further, the electromagnetic wave shielding layer can prevent the electromagnetic wave generated from the PDP from being emitted to the viewer side. In addition, by directly attaching to the observer side of the PDP and using it, moire that becomes a problem when it is arranged on the front surface of the PDP without an air layer hardly occurs.

In addition, being directly bonded to the observer side of the PDP means that the observer of the PDP and the front filter are bonded directly or through one adhesive layer without an air layer, It is bonded through an adhesive layer. The adhesive layer usually has only a function as an adhesive layer, but may further have an optical function described later.
Moreover, it is preferable that the PDP front filter of the present invention does not include a light diffusion layer on the PDP side of the contrast improving layer. This is because the front filter of the present invention is used by directly bonding, and therefore, unlike the mode in which the front filter is disposed on the front surface of the PDP via a space, it is not necessary to provide a light diffusion layer on the PDP side for preventing moire. .
Here, the light diffusing layer is a layer provided for the purpose of intentionally exerting a light diffusing action, and refers to a layer having a haze haze value of 50% or more, preferably 80% or more. In the case of the front filter in the form of being arranged on the front surface of the PDP via a space, it is provided in order to prevent the occurrence of moire.

〔Layer structure〕
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, each figure shown below exaggerated the dimension and the shape suitably for description.
FIG. 1 is a perspective view showing a display device in which a front filter of the present invention is bonded to a front substrate of a PDP without an air layer. In FIG. 1, the front side of the paper is the back side of the PDP, and the back side of the paper is the observation side.
The display device 100 includes a PDP (plasma display panel) 1 and a front filter 101 bonded to the observation side of the PDP 1. The front filter 101 is formed by laminating at least a contrast improving layer 4 and an electromagnetic wave shielding layer 5. In the following, a laminate formed by laminating the contrast improving layer 4 and the electromagnetic wave shielding layer 5 may be expressed as contrast improving layer 4 / electromagnetic wave shielding layer 5.
The contrast enhancement layer 4 is a layer including a lens portion 2 that transmits light and a light absorption portion 3 that absorbs light, and is a layer that has a function of improving contrast. The light referred to here is light in the visible light region that affects the contrast, that is, in the wavelength region of 380 nm to 780 nm.
The electromagnetic wave shielding layer 5 is a layer having a function of absorbing electromagnetic waves emitted from the PDP.

FIG. 2 is a diagram in which PDP 1 is omitted from FIG. The contrast enhancement layer 4 is connected in a straight line in a predetermined direction along the surface direction of the layer, and the lens unit 2 has a shape in which a cross section perpendicular to the extending direction becomes a trapezoidal shape with a wide bottom base facing the viewer side. And a light absorbing section 3 having a wedge-shaped shape that is linearly connected in a direction parallel to the lens section and whose cross section perpendicular to the extending direction has a wide lower base toward the PDP side. A transmission surface for PDP display light, which is formed by meshing many, is provided.
In addition, the arrangement in which a large number are alternately meshed means that a plurality of lens portions and light absorption portions are alternately adjacent to each other to form a part of the other. Further, the transmission surface of the PDP display light is not limited to the interface of the layers, and has a certain thickness.

3A is a cross-sectional view showing the most basic layer configuration of the front filter according to the present invention, and is a cross-sectional view parallel to AA of FIG. 2 and perpendicular to the plane of the front filter.
The lens portion 2 has a trapezoidal cross-sectional shape, and the cross-sectional shape of a portion sandwiched between the oblique sides of adjacent lens portions is a wedge shape having a wide lower base 28 on the PDP side and a narrow upper base 27 on the observer side. A light absorbing portion 3 having a light absorbing effect is provided by forming a groove and filling the wedge-shaped groove with the same or different material as the lens portion 2.

FIG. 3B is a PDP front filter of the present invention further including an optical filter 6 other than the contrast improving layer and the electromagnetic wave shielding layer. The optical filter has one or more functions selected from, for example, a near infrared absorption function, a neon light absorption function, a toning function, an ultraviolet absorption function, an antireflection function, an antiglare function, and an anti-scratch function. It is a layer which has and can be included in a front filter by 1 layer or 2 layers or more. The optical filter 6 also serves as a protective film for the conductor mesh layer (electromagnetic wave shielding layer).
Between each of the above layers, a layer structure including an adhesive (adhesive) layer necessary for laminating each of the above layers and a transparent substrate used as a supporting substrate necessary for forming each of the above layers may be used. May be. The adhesive layer and the transparent base material may be mixed with materials for imparting various functions such as the near-infrared absorption function, and may also serve as an optical filter.
The contrast enhancement layer may be located in any part of the layer structure of the front filter in order to develop a contrast enhancement function.

For example, as an example in which the contrast improving layer is positioned on the PDP side, a layer configuration as in Embodiment 1 shown in FIG.
(Embodiment 1)
Antireflection layer (or antiglare layer) 7 / UV absorber-containing polyethylene terephthalate (UVAPET) film 8 / Near infrared absorption / neon light absorption layer 9 / Toning adhesive layer 10 / Electromagnetic wave shielding layer 5 / Transparent adhesive layer 11 / Contrast improving layer 4 / Transparent adhesive layer (or impact resistant layer) 12
(In addition, the first layer (in this embodiment, the antireflection layer (or antiglare layer)) side is the observer side, and the last layer (in this embodiment, the transparent adhesive layer (or impact resistant layer)) side is the PDP panel. The front filter is arranged so as to be located on the side. The same applies to the following modes.)

In addition, the following layer structure is mentioned as a similar layer structure.
(Embodiment 2)
Antireflection layer (or antiglare layer) / UVAPET film / Near infrared absorption / neon light absorption layer / Toning adhesive layer / Electromagnetic wave shielding layer / Transparent adhesive layer / Polyethylene terephthalate (PET) film / Contrast improving layer / Transparent adhesive Agent layer (or impact resistant layer)
(Embodiment 3)
Antireflection layer (or antiglare layer) / PET film / UV absorber-containing pressure-sensitive adhesive layer / PET film / Near-infrared absorption / neon light absorption layer / toning pressure-sensitive adhesive layer / electromagnetic wave shielding layer / transparent pressure-sensitive adhesive layer / contrast improvement Layer / transparent adhesive layer (or impact-resistant layer)
(Embodiment 4)
Antireflection layer (or antiglare layer) / Polyethylene terephthalate (PET) film / UV absorber-containing pressure-sensitive adhesive layer / PET film / Near-infrared absorption / neon light absorption layer / toning pressure-sensitive adhesive layer / electromagnetic wave shielding layer / transparent pressure-sensitive adhesive Layer / contrast improving layer / transparent adhesive layer (or impact resistant layer)

(Embodiment 5)
Antireflection layer (or antiglare layer) / polyethylene terephthalate (PET) film / UV-absorbing agent-containing adhesive layer / electromagnetic wave shielding layer / Near-infrared absorbing function, neon light absorbing function, and toning function adhesive layer / contrast Improvement layer / transparent adhesive layer (or impact-resistant layer)
(Embodiment 6)
Hard coat layer / electromagnetic wave shielding layer / UV absorber-containing PET film / adhesive layer having near infrared absorption function, neon light absorption function, and toning function / contrast improving layer / transparent adhesive layer (or impact resistant layer)

Further, since the contrast enhancement layer exhibits its performance regardless of the layer configuration of the front filter, for example, the front filter may have the following layer configuration.
(Embodiment 7)
Hard coat layer / polyethylene terephthalate (PET) film / contrast improving layer / ultraviolet absorber-containing adhesive layer / electromagnetic wave shielding sheet / adhesive layer having near infrared absorption, neon light absorption, and toning function The embodiments are illustrative and are not intended to limit the invention by these descriptions.

Hereinafter, the respective layers constituting the front filter of the present invention will be described in order.
[Contrast improvement layer]
The contrast enhancement layer 4 constituting the front filter of the present invention is used for the purpose of imparting a contrast enhancement function to the front filter.
FIG. 4 shows an enlarged cross-sectional view of the contrast improving layer constituting the front filter of the present invention. The contrast enhancement layer 4 includes a lens unit 2 and a light absorption unit 3.
As shown in FIG. 2, the wedge-shaped cross-sectional shape of the light absorbing portion 3 extends in the horizontal direction (the direction connecting the front and the back of the paper), and this is the vertical direction (the direction connecting the top and bottom of the paper). ) At a pitch of 100 μm.
The light absorbing portion 3 is filled with a material in which light absorbing particles 29 are added in a transparent binder (hereinafter referred to as “transparent binder 26”). The light-absorbing part 3 having a trapezoidal cross-sectional shape includes a wide lower base 28 on the PDP side and a narrow upper base 27 on the observer side. The angle between the inclined surface where the light absorbing portion 3 and the lens portion 2 are in contact with the normal line V of the light exit surface (a line parallel to the perpendicular incident light with respect to the front filter) is formed at a predetermined angle θ41. θ41 is preferably in the range of 3 ° ≦ θ ≦ 15 °. If θ41 is less than 3 °, the display light from the PDP does not reach the front side of the observation side sufficiently, and a brightness enhancement effect cannot be obtained. On the other hand, if θ exceeds 15 °, the bottom of the light absorber 3 This is because the area of the lens portion through which the display light from the PDP is transmitted becomes too small and the luminance is lowered.

  As a method for forming the lens portion 2, a hot pressing method in which a heated mold is pressed against a thermoplastic resin, a casting method in which a thermoplastic resin composition is injected into a mold and solidified, an injection molding method, an ultraviolet curable mold Conventionally known methods such as a UV method in which a resin composition is injected into a mold and cured by ultraviolet rays are used. Among these methods, a UV method excellent in mass productivity is more preferable. The UV method can be produced by continuously embossing lens units using a roll-shaped mold while supplying a continuous sheet. For example, the lens unit 2 is usually made of a material such as epoxy acrylate having ionizing radiation curability.

At the same time as the lens portion 2 is formed in this way, a wedge-shaped groove is formed. The light-absorbing portion 3 is formed by filling the wedge-shaped groove with ink containing the light-absorbing particles 29 and the transparent binder 26 that acts as a binder and curing the ink. Since the light absorbing particles 29 have a light absorbing action, the light incident on the inside of the light absorbing portion 3 is absorbed by the light absorbing particles and is not emitted outside the light absorbing portion.
As a material for forming the transparent binder 26 of the light absorbing portion 3, it is preferable to use a material such as a resin having ionizing radiation curability. Commercially available colored particles can be used as the light-absorbing particles 29 constituting the light-absorbing part 3, and are used after being dispersed in a transparent binder 26 as a binder.
In order to improve the ease of production, an additive such as a defoaming agent or a leveling agent may be added to the above ink in an appropriate amount if necessary.

As the colored particles, black pigments such as carbon black or resin particles such as those obtained by staining transparent particles such as acrylic with black pigments such as carbon black are used. In addition, a mixture of various pigments and / or dyes of blue, purple, yellow, and red other than black pigments, or a material that is substantially black by mixing and dispersing the black colorant in a blue, purple, yellow, and red colorant May be used. As the blue pigment, copper phthalocyanine, etc., as the purple pigment, dioxazine violet, etc., as the yellow pigment, disazo yellow, etc., as the red pigment, chromophthal red typel, etc. are used. Alternatively, a dye may be used instead of a pigment. Further, a colored pigment or dye obtained by mixing and dispersing a blue, purple, yellow, red, black pigment or dye, and colored particles obtained by coloring transparent particles such as resin particles such as acrylic may be used.
Among the above colored particles, in the present invention, black particles are the preferred material because they have the highest light absorption.

The light absorbing particles 29 in the front filter of the present invention preferably have an average particle size of 1 μm or more and half or less of the width of the upper bottom surface 28 of the light absorbing portion 3. If the size of the light absorbing particles 29 is too small, a sufficient light absorbing effect cannot be obtained. On the other hand, if the size of the light-absorbing particles 29 exceeds the half of the width of the upper bottom surface 28 of the light-absorbing portion 3, it becomes difficult to fill the wedge-shaped grooves with ink at the time of manufacturing, and the filling rate is deteriorated. The filling rate varies among the groove units, which is not preferable because of optical unevenness.
Moreover, it is preferable that the light absorption particle | grains 29 in the front filter of this invention are 10-50 volume% with respect to the whole volume of the light absorption part 3. FIG. By maintaining this ratio, it is possible to provide easy manufacturing conditions while maintaining a sufficient light absorption effect.

  As the binder, for example, a transparent resin having a predetermined refractive index, an ultraviolet curable resin having an ionizing radiation curing function, an electron beam curable resin, or the like is used. Some of them are directly cured by ionizing radiation, but the curing reaction is generally caused through a substance called a catalyst or an initiator that excites a reaction. In order to cause a curing action with ultraviolet light having a wavelength of 300 to 400 nm, it is common to mix several percent of a substance called a photoinitiator that excites a reaction in the ultraviolet region. Photoinitiators include those based on ketones and acetophenones, such as Sandley 1000, Darocure 1163, Darocure 1173, Irgacure 183, Irgacure 651, and the like, and are appropriately selected according to the type (wavelength characteristics) of ionizing radiation for curing. it can. Examples of ionizing radiation curable resins include reactive oligomers (epoxy acrylate, urethane acrylate, polyether acrylate, polyester acrylate, polythiol, etc.) and reactive monomers (vinyl pyrrolidone, 2-ethylhexyl acrylate, β-hydroxy). Acrylate, tetrahydrofurfuryl acrylate, etc.) are appropriately selected. In order to adjust the fluidity of the ionizing radiation curable light absorbing material before curing, the kind of reactive oligomer and the composition ratio of the low molecular weight reactive monomer having low viscosity may be appropriately changed.

  A material appropriately selected from the above is used after being uniformly dispersed (mixed) by a three-roll dispersion method or the like to form an ink. The composition ratio may be appropriately determined by evaluating the curability by ionizing radiation and various physical properties after curing. The colorant is 10 to 50 parts, the binder is 50 to 90 parts, and the photoinitiator is 1 to 10 parts. The degree is preferred.

  The ink is filled into a wedge-shaped groove by a method such as a wiping method, and then cured and fixed with ionizing radiation such as ultraviolet rays.

  In the present invention, a form in which a black stripe is provided on the bottom surface of the wedge-shaped groove may be used. External light 35 incident on the black stripe from the observer side is absorbed by the black stripe, and the contrast is further improved.

When a PDP front filter having such a contrast enhancement layer is installed and used in a PDP, the contrast of the PDP is hardly lowered even in an environment where external light hits the display surface.
The type of external light differs depending on the environment in which the PDP is used, but is usually incident light from a window or ceiling illumination when used indoors, and is mainly sunlight when used outdoors. Normally, these external lights rarely enter from almost the front surface of the PDP display surface as indicated by L24 in FIG. 4, and are incident at a relatively shallow angle with respect to the display surface of the PDP as indicated by L25. It is characterized by. It is only necessary that the external light incident at such a shallow angle can be efficiently absorbed by the light absorber.

  The light absorbing portion according to the present invention has a rectangular cross section because the shape of the light absorbing portion in the contrast improving layer has a wide lower base 28 on the PDP side and a narrow upper base 27 on the viewer side. Compared with the case of the front filter having the light absorption part, the incident angle of the external light on the inclined surface of the light absorption part (angle α in FIG. 4) even if the incident angle of the external light with respect to the outermost surface on the observer side is the same Will grow. Therefore, when the refractive index of the binder constituting the light absorbing portion 3 is N2, and the refractive index of the material constituting the lens portion 2 is N1, the relationship N1-N2> 0 is satisfied, that is, total reflection is Even if there is a possibility that this will occur, the amount of external light absorbed into the light absorbing portion increases, and the amount of external light that is totally reflected decreases. As a result, less external light reaches the front surface of the PDP, and scattered light from the front surface of the PDP is suppressed.

  On the other hand, it is preferable that the light emitted from the PDP main body reaches the observer side as much as possible without being absorbed by the light absorbing portion. For this reason, when the refractive index of the transparent binder constituting the light absorbing portion is N2, and the refractive index of the material constituting the lens portion is N1, the relationship N1-N2> 0 holds from the PDP body. It is preferable because the amount of the outgoing light reaching the observer side is increased by the total reflection of the outgoing light on the surface of the light absorbing portion. In FIG. 4, the vertical light L21 incident on the vicinity of the center portion of the lens unit 2 from the light source side passes straight through the inside of the contrast improving layer as it is and reaches the observer. The light L22 obliquely incident on the vicinity of the end of the lens unit 2 from the PDP side is totally reflected on the slope due to the refractive index difference between the lens unit 2 and the transparent binder 26 and is emitted to the observer side as vertical light. The The incident light L23 having an even larger angle from the PDP side to the vicinity of the end of the lens unit 2 is totally reflected by the inclined surface, and has a smaller angle than that at the time of incidence in a direction opposite to that at the time of incidence and an angle close to that of vertical light. Light is emitted to the observer side. As described above, the light from the PDP can be totally reflected by the slope of the light absorbing portion and can be emitted efficiently, which contributes to the improvement of luminance and contrast.

In the case of N1-N2 ≦ 0, since total reflection does not occur on the slope of the light absorption part, the external light from the observer side can be efficiently absorbed by the light absorption part, but the light emitted from the PDP main body is also excessively absorbed. This is not preferable.
The value of N1-N2 depends on the materials of the lens unit 2 and the transparent binder 26. Usually, a material is used so that light emitted from the PDP main body is efficiently totally reflected on the surface of the light absorption unit, and external light incident at a shallow angle with respect to the display surface of the PDP is sufficiently absorbed by the light absorption unit. Must be selected. It is determined appropriately in consideration of the design of the PDP and other design factors.
From the viewpoint of efficiently totally reflecting the emitted light from the PDP main body on the inclined surface of the light absorbing portion, it is preferable that N1−N2 ≧ 0.05 and further N1−N2 ≧ 0.1.

On the other hand, as the value of N1-N2 increases, the amount of external light that is totally reflected and absorbed by the light absorption unit decreases, so that the external light that reaches the front surface of the PDP increases and irregular reflection tends to increase. Since the range of the refractive index of a practical transparent material is about 1.3 to 1.7, the value of N1-N2 is usually about 0.4 at the maximum, and in the range of about 0.4 or less The light absorption part can sufficiently absorb external light.
In FIG. 4, the optical paths of the lights L21 to L25 are schematically shown.

  FIG. 5 is a diagram showing various aspects of the shape of the slope portion of the wedge-shaped groove (light absorbing portion). The wedge-shaped groove has a substantially isosceles trapezoidal shape formed between two adjacent unit lenses. FIG. 5A shows a case where the slope of the wedge-shaped groove is formed in a straight line. In this case, the angle θ51 formed by the slope and the light exit surface normal is constant at any point on the slope. FIG. 5B shows a case where the slope of the wedge-shaped groove is formed with a smooth curve. FIG. 5C shows a case where the slope of the wedge-shaped groove is composed of two straight lines. In these cases, the angle θ52, θ53, or θ54 formed by the slope and the light exit surface normal line varies depending on the position on the slope. In the present invention, when the angle formed between the slope and the light exit surface normal is not constant as in FIGS. 5B and 5C, the slope and the light exit surface normal are at least 50% of the length of the slope. The effect of the present invention can be obtained if the angle between the angles exceeds 3 °.

  In the present invention, the case where the wedge-shaped groove has a substantially isosceles trapezoidal cross-sectional shape is mainly described, but a good front filter can be obtained even when the wedge-shaped groove has a substantially isosceles triangular cross-sectional shape. . Further, in the present invention, the cross-sectional shape forming the wedge-shaped groove is substantially trapezoidal or substantially triangular, and each angle formed by the two slope portions of the wedge-shaped groove and the normal line of the light emitting surface is different depending on the location. Good. Further, along with the cross-sectional shape of the wedge-shaped groove, in the cross-sectional shape of the lens portion, each angle formed by the trapezoidal slope portion with the normal line of the light exit surface may be different depending on the location.

(Electromagnetic wave shielding layer)
The electromagnetic wave shielding layer constituting the front filter of the present invention is a layer provided to shield electromagnetic waves generated from the PDP.
The material and form used for the electromagnetic wave shielding layer are not particularly limited, and a known electromagnetic wave shielding layer for PDP can be used. As a known electromagnetic wave shielding layer, an ITO (indium tin oxide) film (JP-A-1-278800, etc.) provided on the front surface of a transparent substrate or a transparent substrate made of a resin film is bonded with an adhesive. The thing etc. which etched metal foil, such as copper foil, and made it mesh shape etc. are mentioned.

Hereinafter, the case of an electromagnetic wave shielding layer including a mesh-like conductor layer will be described.
The mesh-shaped conductor layer is usually provided on a transparent substrate. FIG. 6 shows an example of the electromagnetic wave shielding layer provided on the transparent substrate. 6A is a cross-sectional view of an example of the electromagnetic wave shielding layer, and FIG. 6B is a plan view of an example of the electromagnetic wave shielding layer. An electromagnetic wave shielding layer 5 including a mesh-like conductor layer 301 and a grounding frame portion 302 is laminated on one surface of the transparent substrate 31. Hereinafter, this laminate may be referred to as an electromagnetic wave shielding sheet for convenience.

The grounding frame portion 302 is usually a portion that has the same layer configuration as the mesh-like conductor layer 301 but does not form an opening, and is provided to facilitate grounding when the front filter is installed on the PDP. It is done. As the grounding frame portion 302, a portion that does not affect the image display around the four sides of a generally rectangular electromagnetic shielding sheet is often provided in a frame shape. But it ’s okay. Further, the electromagnetic wave shielding layer 5 that is entirely made of the mesh-like conductor layer 301 without providing the ground frame 302 may be grounded from the mesh-like conductor layer.
The electromagnetic wave shielding layer further includes a grounding frame portion as described above, a rust prevention layer, a blackening layer, and the like that can be further formed in the mesh-like conductor layer.

(Transparent substrate of electromagnetic shielding layer)
The transparent substrate 31 is a layer for reinforcing a mesh layer having a low mechanical strength. Therefore, as long as it has light transmittance as well as mechanical strength, it may be selected and used depending on the application, taking into account heat resistance, insulation, etc. as appropriate. Specific examples of the transparent substrate include a resin sheet (or a film, the same applies hereinafter) and the like.
Examples of the transparent resin used as the resin sheet include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, terephthalic acid-isophthalic acid-ethylene glycol copolymer, terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer, and the like. Resin, polyamide resin such as nylon 6, polyolefin resin such as polypropylene and polymethylpentene, acrylic resin such as polyacrylate, polymethacrylate and polymethyl methacrylate, styrene resin such as polystyrene and styrene-acrylonitrile copolymer And cellulose resins such as triacetyl cellulose, imide resins, polycarbonate resins and the like.

In addition, these resins are used as a single or a plurality of types of mixed resins (including polymer alloys) as a resin material, and as a layer, they are used as a single layer or a laminate of two or more layers.
The thickness of the transparent substrate is not particularly limited as long as it depends on the application, and when made of a transparent resin, it is usually about 12 to 1000 μm, preferably 50 to 700 μm, more preferably 100 to 500 μm. Is desirable. If the thickness is less than the above, the mechanical strength is insufficient and warping, slackening, breakage or the like occurs, and if the thickness exceeds the above, the cost is increased due to excessive performance and it is difficult to reduce the thickness.

Hereinafter, the electromagnetic wave shielding layer including the mesh-shaped conductor layer will be described in detail.
(Mesh-like conductor layer)
The conductor layer 301 is a layer having conductivity and is responsible for the electromagnetic wave shielding function, and even if the conductive layer 301 itself is opaque, the presence of a mesh-shaped opening portion improves the electromagnetic wave shielding performance. Both light transmittance is achieved. An example of the mesh-like conductor layer 301 is shown in FIG. The conductor layer 301 has a mesh shape in which the openings 303 are densely arranged, and the mesh includes the openings 303 and a line 304 forming a frame.
The material and forming method of the mesh-like conductor layer are not particularly limited, and various conductor layers in a conventionally known light-transmitting electromagnetic wave shielding sheet can be appropriately employed. In general, the conductor layer is mainly a metal layer, and in addition to this, a conductive treatment layer as described later and, if necessary, a blackening layer or a rust prevention layer may be included.

  The shape of the mesh is arbitrary and not particularly limited, but the shape of the opening is typically a square. Examples of the shape of the opening include a triangle such as a regular triangle, a square such as a square, a rectangle, a rhombus, and a trapezoid, a polygon such as a hexagon, a circle, and an ellipse. The mesh has a plurality of openings having these shapes, and the openings are usually line-like line portions having a uniform width, and the openings and the openings are generally the same shape and the same size on the entire surface.

  As an example of a specific size, the width of the line part 304 between the openings is referred to as a line width W as shown in FIG. 7 in terms of the aperture ratio and the invisibility of the mesh, and is 25 μm or less, preferably 20 μm or less. It is preferable that The opening width is represented by (line pitch P) − (line width W). In the present invention, it is preferably 150 μm or more, preferably 200 μm or more from the viewpoint of light transmittance. Moreover, it is preferable that the thickness of at least the mesh part of the finally obtained electromagnetic wave shielding layer, that is, the height H of the line part 304 between the openings is 3 μm or less. In view of the electromagnetic wave shielding function, it is more preferable that the electric resistance value of the metal be 1 to 3 μm so that the electromagnetic wave shielding effect is not easily impaired. Note that the bias angle of the mesh portion (the angle formed between the mesh line portion and the outer periphery of the electromagnetic wave shielding sheet) may be appropriately set to an angle at which moire is difficult to occur in consideration of the pixel pitch of the display and the light emission characteristics.

The method for preparing such a mesh-shaped conductor layer is not particularly limited, and examples thereof include the following four methods.
(1) A method in which a conductive ink is printed in a pattern on a transparent substrate, and metal plating is performed on the conductive ink layer (for example, JP 2000-13088 A).
(2) A method in which a conductive ink or a chemical plating catalyst-containing photosensitive coating solution is applied to the entire surface of a transparent substrate, and the coating layer is made into a mesh by photolithography, followed by metal plating on the mesh (for example, , Sumitomo Osaka Cement Co., Ltd. New Materials Division, New Materials Research Institute, New Materials Research Group, “Photoresolvable Chemical Plating Catalyst”, [online], date not listed, Sumitomo Osaka Cement Co., Ltd. [2003 Search on January 7], Internet <URL: http://www.socnb.com/product/hproduct/display.html>).
(3) After laminating a transparent base material and a metal foil with an adhesive, the metal foil is formed into a mesh by a photolithography method (for example, JP-A-11-145678).
(4) A conductive substrate is formed on one surface of a transparent substrate, a transparent substrate on which a metal layer is formed as a metal plating layer by electrolytic plating is prepared, and the metal of the metal-plated transparent substrate The plating layer and the conductive treatment layer are formed into a mesh shape by photolithography. (For example, JP2003-86991A)

Among them, particularly in the present invention, since the transparency and the mesh accuracy are excellent, the display image can be seen well, and in the manufacturing process, there is little warpage or mixing of bubbles, etc., and the yield is good and inexpensive in a short process. From the viewpoint of production, it is particularly preferable to use the method (4).
Then, the method to prepare the electromagnetic wave shielding sheet which has a mesh-shaped conductor layer by the method of said (4) is demonstrated in detail.

  An example of an electromagnetic wave shielding sheet formed by the method (4) above, in which an electromagnetic wave shielding layer including at least a mesh-like conductor layer is laminated on one surface of a transparent substrate, is shown in FIG. . 8 is a BB cross-sectional view and a CC cross-sectional view of FIG. 8A shows a cross section that crosses the opening, and the openings 303 and the lines 304 are alternately formed. FIG. 8B shows a cross section that cuts the line 304 vertically, and the line 304 including the conductor layer 301 is formed. Are formed continuously. In FIG. 8, the conductor layer 301 includes a conductive treatment layer 33 and a metal plating layer (hereinafter also simply referred to as a metal layer) 34.

(Formation of conductive treatment layer)
In the above method (4), a conductive treatment layer is formed on the transparent substrate 31 as described above prior to metal electrolytic plating described later. As a method for the conductive treatment, a thin film of a known conductive material may be formed. Examples of the conductive material include metals such as gold, silver, copper, iron, nickel, and chromium, or alloys of these metals. Moreover, transparent metal oxides, such as a tin oxide, ITO, and ATO, may be sufficient. The conductive treatment may be a single layer or multiple layers, and these materials are formed by a known method such as a vacuum deposition method, a sputtering method, or an electroless plating method to form the conductive treatment layer 33. The conductive treatment layer 33 is preferably a very thin layer having a thickness of about 0.001 to 1 μm, as long as the necessary conductivity can be obtained during plating.

(Metal plating layer)
A metal plating layer 34 is formed on the surface of the conductive treatment layer 33 to form a metal plating transparent substrate. As the material of the metal plating layer 34, for example, a metal having sufficient conductivity to shield electromagnetic waves, such as gold, silver, copper, iron, nickel, chromium, or an alloy containing these metals can be applied. The metal plating layer 34 may be a single layer or a multilayer, and copper or copper alloy is preferable from the viewpoint of easiness of electrolytic plating and conductivity. Moreover, when providing a blackening layer and / or a chromate (process) layer, copper or a copper alloy is preferable also from adhesiveness etc. As described above, the thickness of at least the mesh part of the finally obtained electromagnetic wave shielding layer is preferably 3 μm or less, more preferably 2 to 3 μm. When the electromagnetic shielding layer is formed by the above method (4), in addition to the thickness of the conductive treatment layer 33 and the thickness of the metal plating layer 34, the blackening layer and the rust preventive layer are formed as necessary. The sum is obtained by adding the thickness of the layer or the like.

(Blackening layer)
In order to absorb external light to the electromagnetic wave shielding layer and improve the visibility of the image on the display, it is preferable to perform a blackening process on the observation side of the mesh-like conductor layer 301 to give a sense of contrast. . For this purpose, as shown in FIG. 9, a blackening layer 35 </ b> A and / or 35 </ b> B is provided on at least one surface of the metal plating layer 34 as necessary. The blackened layer may be roughened and / or blackened on the surface of the metal plating layer 34. Further, when a blackened layer is provided on the surface of the transparent base 31, the metal plated layer 34 may be provided after conducting a conductive treatment on the transparent base and providing the black plated layer.

  As the blackening layers 35A and 35B, formation of metal oxides and metal sulfides and various methods can be applied. In the case of iron, it is usually exposed to steam at a temperature of about 450 to 470 ° C. for 10 to 20 minutes to form an oxide film (blackened film) of about 1 to 2 μm. An oxide film (blackened film) may be used. Further, in the case of copper, cathodic electrodeposition in which the cathode particles are attached by performing cathodic electrolysis in an electrolytic solution composed of sulfuric acid, copper sulfate, cobalt sulfate, and the like is preferable. By providing the cationic particles, the surface becomes more rough, and at the same time, black is obtained. As the cationic particles, copper particles and alloy particles of copper and other metals can be applied, but copper-cobalt alloy particles are preferred. The average particle diameter of the cationic particles is preferably about 0.1 to 1 μm from the viewpoint of black density.

(Rust prevention layer)
Further, the rust preventive layers 36A and / or 36B are formed so as to cover at least one side of the metal plating layer 34 and, when a blackened layer is provided, to cover at least one side of the blackened layers 35A and / or 35B. Is preferably provided.
The rust prevention layers 36A and 36B are preferably provided at least on the blackening layer in order to prevent the rust prevention function and the blackening layer from dropping or deforming. As the rust prevention layer 36B, nickel, zinc, and / or copper oxide, or a chromate treatment layer can be applied. The nickel, zinc, and / or copper oxide may be formed by a known plating method, and the thickness is about 0.001 to 1 μm, preferably 0.001 to 0.1 μm.

In the case where the rust prevention layer 36A is provided on the blackened layer 35A surface of the transparent substrate 31, the conductive treatment is performed on the transparent substrate, and the rust prevention layer 36A is provided by the same material and method as the above 36B. Good. In this case, a black plating layer (corresponding to the blackening layer 35A), a metal plating layer 34, and, if necessary, a blackening layer 35B and a rust prevention layer 36B are sequentially provided on the surface of the rust prevention layer 36A.
The blackening layers 35A and 35B and the rust prevention layers 36A and 36B may be provided at least on the observation side, and the contrast is improved and the visibility of the image on the display is improved. Further, it may be provided on the other surface, that is, on the display surface side, and stray light generated from the display can be suppressed, so that the visibility of the image is further improved.

Next, the process of making the conductor layer on the transparent substrate provided as described above into a mesh by a photolithography method will be described.
First, a resist layer is provided on the conductive layer on the transparent base material prepared as described above, for example, the metal layer (metal plating layer) 34 surface on the transparent base material, mesh-patterned, and not covered with the resist layer. After removing a portion of the metal layer 34 by etching, a mesh-like metal layer is formed by a so-called photolithography method in which the resist layer is removed. Furthermore, existing equipment can be used, and by performing many of these manufacturing processes continuously, quality is high, production efficiency is high, yield is high, and production can be performed at low cost.

(Photolithography method)
A resist layer is provided in a mesh pattern on the conductor layer surface of the laminate, and a portion of the conductor layer that is not covered with the resist layer is removed by etching, and then the resist layer is removed by photolithography to obtain a mesh shape. To do. The conductor layer is a general term for the conductive layer 33, the metal layer 34, and the blackened layers 35A and / or 35B and the anticorrosive layers 36A and / or 36B as necessary.

(masking)
First, the electromagnetic wave shielding layer surface of the laminate of the transparent base material 31 and the electromagnetic wave shielding layer 5 is formed into a mesh shape by photolithography to form a mesh-shaped conductor layer 301 in the electromagnetic wave shielding layer. Also in this step, it is preferable to process a roll-shaped laminated body continuously wound in a band shape (referred to as a winding process or a roll-to-roll process). While the laminate is conveyed continuously or intermittently, masking, etching, and resist peeling are performed in a stretched state without looseness. When glass is used as the transparent substrate 31, it is processed one by one (referred to as single wafer processing or single wafer processing).

  First, in the masking, for example, a photosensitive resist is applied onto the conductor layer 301 and dried, and then, contact exposure with a predetermined pattern plate (photomask), water development, film hardening, etc. are performed, and baking is performed. To do. Note that either a negative type or a positive type of photosensitive resist can be used. When the photosensitive resist is a negative type, the mesh pattern of the pattern plate is a positive (positive image) with transparent line portions. When the photosensitive resist is positive, the mesh pattern of the pattern plate is a negative (negative image) with a transparent opening. Further, the exposure pattern is a desired pattern as an electromagnetic wave shielding sheet, and is composed of a minimum mesh pattern. Further, as necessary, a ground frame pattern is added to the outer periphery of the mesh portion as shown in FIG.

  In the winding of the resist, the conductor layer 301 is conveyed while continuously or intermittently transporting a belt-like laminate (a laminate of the transparent base material 31 and the electromagnetic wave shielding layer 5 including the conductor layer 301). A resist such as casein, PVA, or gelatin is applied to the surface by dipping (dipping), curtain coating, pouring, or the like. Moreover, a dry film resist may be used instead of application | coating, and workability | operativity can be improved. In the case of a casein resist, baking is performed at 200 to 300 ° C., but the lowest possible temperature is preferable in order to prevent warping of the laminate.

(etching)
Etching is performed after masking. As the etching solution used for the etching, a solution of ferric chloride or cupric chloride that can be easily circulated when etching is continuously performed is preferable. The etching is basically the same as the equipment for manufacturing a shadow mask for a color TV cathode ray tube that etches a strip-like continuous steel material, particularly a thin plate having a thickness of 20 to 80 μm. In other words, the existing manufacturing equipment for the shadow mask can be diverted, and from masking to etching can be produced consistently and continuously, which is extremely efficient. Single-wafer processing in the case of using glass as the transparent substrate 31 has also been performed for a long time. After etching, the substrate may be dried after washing with water, stripping the resist with an alkaline solution, and washing. Since the transparent base material is exposed on the surface of the mesh opening thus formed, the transparency of the mesh opening is good.

(Flattening layer)
In order to fill the roughness of the adhesive surface of the mesh opening and / or to prevent contamination by bubbles and to make it transparent, the mesh opening is filled with a transparent resin called a flattening resin as necessary. Alternatively, it may be coated as a planarizing layer.
The flattening layer may be one having high transparency, good adhesion to the conductive layer of the mesh, and good adhesion to the adhesive in the next step. However, if there are protrusions, dents, or unevenness on the surface of the flattening layer, moire, interference unevenness, and Newton rings may occur when installed on the front surface of the display. In order to prevent such problems, as a preferred method, after applying a heat or ultraviolet curable resin as a resin, a substrate having excellent planarity and a peelable property is laminated, and the applied resin is cured with heat or ultraviolet light to be peeled off. A method of peeling and removing the conductive substrate. As for the surface of the planarization layer, the surface of the planar substrate is transferred to form a smooth surface. The resin used for the planarization layer is not particularly limited, and various natural or synthetic resins, heat or ionizing radiation curable resins can be applied. From the viewpoint of durability, applicability, ease of planarization, flatness, etc. of the resin. Acrylic ultraviolet curable resins are preferred.

[Optical filter]
In this invention, the optical filter which comprises the front filter for PDP means optical filters other than a contrast improvement layer and an electromagnetic wave shielding layer of a sheet | seat, plate shape, or coating film shape, for example.
The optical filter is, for example, one or more filter functions selected from a near infrared absorption function, a neon light absorption function, a toning function, an ultraviolet absorption function, an antireflection function, an antiglare function, an anti-scratch function, etc. 1 or 2 or more in the front filter. The optical filter also serves as a protective film for the conductor mesh layer (electromagnetic wave shielding layer).

The layer configuration of the optical filter may be a single layer, or the transparent substrate described in the description of the electromagnetic wave shielding layer may be used as a support substrate, and a layer having a filter function may be laminated thereon, or the filter There may be a configuration in which a layer having a function and a transparent substrate are laminated to each other.
An adhesive (adhesive) layer may be provided between the layers of each filter. Each of the transparent substrate and the adhesive layer may be a single layer or a multilayer.

[Near infrared absorption filter]
As the near-infrared absorbing filter, a commercially available film having a near-infrared absorber (for example, Toyobo Co., Ltd., trade name No. 2832) is used, or a composition containing a near-infrared absorbing dye in a binder is formed, or The composition may be applied and laminated on a transparent substrate. As a near-infrared absorbing dye, when an optical filter is applied to the front surface of a plasma display panel, it absorbs a near-infrared region caused by a xenon gas discharge emitted by the plasma display panel, that is, a wavelength region of 800 nm to 1100 nm. Is used. The near-infrared transmittance of the band is preferably 20% or less, more preferably 10% or less. At the same time, it is desirable that the near-infrared absorbing filter has a sufficient light transmittance in the visible light region, that is, in the wavelength region of 380 nm to 780 nm.

  Specific examples of near-infrared absorbing dyes include polymethine compounds, cyanine compounds, phthalocyanine compounds, naphthalocyanine compounds, naphthoquinone compounds, anthraquinone compounds, dithiol compounds, imonium compounds, diimonium compounds, and aminium. Compounds, pyrylium compounds, cerium compounds, squarylium compounds, copper complexes, nickel complexes, dithiol metal complexes organic near infrared absorbing dyes, tin oxide, indium oxide, magnesium oxide, titanium oxide, chromium oxide Zirconium oxide, nickel oxide, aluminum oxide, zinc oxide, iron oxide, ammonium oxide, lead oxide, bismuth oxide, inorganic near-infrared absorbing dyes such as lanthanum oxide, etc. can be used alone or in combination of two or more. . As the binder resin, a resin such as a polyester resin, a polyurethane resin, an acrylic resin, or an epoxy resin is used. Binder resin drying and curing methods include a drying and solidification method by drying a solvent (or dispersion medium) from a solution (or emulsion), a polymerization method using heat, ultraviolet light, electron beam energy, and a crosslinking reaction. Alternatively, a curing method utilizing a reaction such as crosslinking or polymerization between a functional group such as a hydroxyl group or an epoxy group in a resin and an isocyanate group in a curing agent can be applied.

[Neon light absorption filter]
The neon light absorption filter is installed to absorb neon light emitted from the plasma display panel, that is, an emission spectrum of neon atoms when the optical filter is used for a plasma display. Since the emission spectrum band of neon light has a wavelength of 550 to 640 nm, it is preferable to design the neon light absorption filter so that the spectral transmittance is 50% or less at the wavelength of 550 to 640 nm. The neon light absorption filter may be formed by dispersing a dye conventionally used as a dye having an absorption maximum in a wavelength region of at least 550 to 640 nm in a binder resin as mentioned in the near infrared absorption filter. it can. Specific examples of the dye include cyanine, oxonol, methine, subphthalocyanine or porphyrin.

[Toning filter]
The toning filter is for adjusting the color of the front filter for PDP in order to improve the color purity of light emitted from the PDP, the color reproduction range, the display color when the power is turned off, and the like. For example, a composition in which a toning dye is dispersed in a binder resin can be formed into a film, or it can be formed on a transparent substrate or other functional filter, and dried or cured as necessary. it can. As the toning dye, a known dye having a maximum absorption wavelength in the visible region of 380 to 780 nm can be used in any combination depending on the purpose. Known dyes that can be used as toning dyes include the dyes described in JP 2000-275432 A, JP 2001-188121 A, JP 2001-350013 A, JP 2002-131530 A, and the like. Can be suitably used. In addition, other dyes such as anthraquinone, naphthalene, azo, phthalocyanine, pyromethene, tetraazaporphyrin, squarylium, and cyanine that absorb visible light such as yellow light, red light, and blue light. Can be used. As the binder resin, resins such as those listed above for the near infrared absorption filter can be used.

[Ultraviolet absorption filter]
Moreover, as an ultraviolet absorption filter, it can form by disperse | distributing an ultraviolet absorber to binder resin, for example. Examples of the ultraviolet absorber include organic compounds such as benzotriazole and benzophenone, and inorganic compounds composed of particulate zinc oxide, cerium oxide, and the like. As the binder resin, resins such as those listed above for the near infrared absorption filter can be used.

[Antireflection filter]
Moreover, as an antireflection (AR) filter, for example, a multi-layer structure in which low refractive index layers and high refractive index layers are alternately laminated is generally used, and a dry method such as vapor deposition or sputtering, or coating is used. The wet method can also be used. Note that silicon oxide, magnesium fluoride, fluorine-containing resin, or the like is used for the low refractive index layer, and titanium oxide, zinc sulfide, zirconium oxide, niobium oxide, or the like is used for the high refractive index layer.

[Anti-glare filter]
In addition, anti-glare (AG) filters can be applied to the surface of the layer by forming a coating using an inorganic filler such as silica in a resin binder, or by shaping using a shaping sheet or shaping plate. It can be formed as a layer provided with fine irregularities that diffusely reflect. As the resin of the resin binder, a curable acrylic resin, an ionizing radiation curable resin, or the like is preferably used in the same manner as the hard coat layer described below because surface strength is desired as the surface layer.

In addition, you may laminate | stack the protective film for protecting these layers from an abrasion and contamination on the surface of a conductor mesh layer and an optical filter as needed. Examples of the protective film include a hard coat layer (HC layer) and an antifouling layer.
Among the protective films, as the hard coat layer, for example, a polyfunctional (meth) acrylate prepolymer such as polyester (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, or trimethylolpropane tri (meth) Ionization in which trifunctional or higher polyfunctional (meth) acrylate monomers such as acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. are used alone or in combination of two or more selected from these It can be formed as a coating film using a radiation curable resin. Here, (meth) acrylate is a composite notation meaning acrylate or methacrylate.

Of the protective films, the antifouling layer is generally a water-repellent or oil-repellent coat, and a siloxane-based or fluorinated alkylsilyl compound can be applied. A fluorine-based or silicone-based resin used as a water-repellent paint can be preferably used. For example, when the low refractive index layer of the antireflection filter is formed of SiO2, a fluorosilicate water-repellent paint is preferably used.
In addition, the material used with the electromagnetic wave shielding sheet mentioned above can be used suitably for the transparent base material and adhesive bond layer which comprise an optical filter.

[Adhesive layer]
Next, an adhesive layer that can be used for the front filter of the present invention will be described.
The adhesive layer is not particularly limited as long as it is a layer capable of bonding the optical filter and the electromagnetic wave shielding sheet, and various natural or synthetic resins, heat or ionizing radiation curable resins, etc. Is applicable.

  As the adhesive layer used in the present invention, an adhesive is preferred. Here, the pressure-sensitive adhesive refers to one type of adhesive. Of the adhesives, the adhesive is bonded only by the pressure on the surface, only by pressing moderately, usually by light pressure. Say what you can. In order to develop the adhesive strength of the pressure-sensitive adhesive, usually, physical energy or action other than pressurization such as heating, humidification, and radiation (ultraviolet ray, electron beam, etc.) is unnecessary, and chemical reaction such as polymerization reaction is also unnecessary. is there. In addition, the pressure-sensitive adhesive can maintain the adhesive strength to the extent that it can be re-peeled after bonding. There is no restriction | limiting in particular as such an adhesive, It has moderate adhesiveness (adhesive force), transparency, and coating suitability from what is conventionally used as a well-known adhesive, and it is used in this invention. An optical filter that does not substantially change the transmission spectrum of the optical filter is appropriately selected.

  An acrylic adhesive is mentioned as an adhesive suitably used. The acrylic pressure-sensitive adhesive is a polymer containing at least a (meth) acrylic acid alkyl ester monomer. Generally, it is a copolymer of a (meth) acrylic acid alkyl ester monomer having an alkyl group having about 1 to 18 carbon atoms and a monomer having a carboxyl group. In the present invention, (meth) acrylic acid refers to acrylic acid and / or methacrylic acid.

  Examples of (meth) acrylic acid alkyl ester monomers used here include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, sec-propyl (meth) acrylate, N-butyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, Examples thereof include n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, undecyl (meth) acrylate, and lauryl (meth) acrylate. Moreover, the said (meth) acrylic-acid alkylester is copolymerized in the quantity of 30-99.5 weight part normally in an acrylic adhesive.

  Moreover, as a monomer which has a carboxyl group which forms an acrylic adhesive, monomers containing a carboxyl group such as (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, monobutyl maleate and β-carboxyethyl acrylate are used. Can be mentioned.

  The adhesive layer may contain one or more near infrared absorbing dyes, ultraviolet absorbers, and / or neon light absorbing dyes as described above. By doing so, the functions of a plurality of optical filters can be combined with one layer, and this can be integrated with the adhesive layer, so that the total thickness, the number of steps, and the cost as a composite filter can be reduced. This is possible and preferable. In that case, the light transmittance in the wavelength region of 800 nm to 1100 nm is 20% or less, particularly 15% or less, and the light transmittance in the wavelength region of 560 to 630 nm is preferably 30% or less, particularly preferably 25% or less. .

(Shock resistant layer)
Moreover, you may provide an impact-resistant layer in the surface at the side of PDP of a front filter from a viewpoint of improving an impact-resistant effect. As the impact resistant layer, acrylic resin, rubber resin, silicon resin, vinyl resin, urethane resin, epoxy resin, polyester resin, and the like can be applied. Among these resins, acrylic resin or urethane resin is preferable. For example, what formed the 100-200-micrometer-thick adhesive layer using the said adhesive used for the said adhesive bond layer can be used conveniently.

  In addition, contrast evaluation of the front filter for PDP of this invention is performed by sensory evaluation (visual evaluation). Contrast calculated from the values obtained by pasting the front filter for PDP on the viewer side of the PDP using the luminance meter to measure the luminance during black display (black luminance) and the luminance during white display (white luminance). This is because the chromaticity measured with a spectral colorimeter or the like does not always match the quality of the contrast and the color tone based on human senses.

  The sensory evaluation of contrast is, for example, two colors consisting of image data of the highest density of achromatic color (perfect black) and the lowest density of achromatic color (perfect white), with grid lines (rectangular grids) alternately (white Place the filter on the front of the image data (Fig. 13) of the pattern that has been arranged (shown in black next to it and all white next to black). The quality can be judged by whether or not the black and white border of the pattern is clearly visible.

[Plasma Display Panel (PDP)]
The plasma display panel (PDP) according to the present invention is characterized in that the above-mentioned front filter is directly bonded to the observer side of the PDP.
In such a PDP, the contrast is improved by the functions of the contrast improving layer and the electromagnetic wave shielding layer of the front filter, and the emission of electromagnetic waves to the viewer side can be prevented. Furthermore, if the front filter has the optical function, the PDP can enjoy the advantages.

The front filter is directly attached to the front surface of the PDP with the travel axis of the light absorption part of the front filter tilted by 3 to 15 ° with respect to the horizontal axis of the PDP pixel, thereby restricting the horizontal viewing angle. This is preferable because it is not necessary and generation of moire can be prevented.
If the inclination of the traveling axis of the light absorption part of the front filter is less than 3 ° with respect to the horizontal axis of the PDP pixel, moire may occur, and if it exceeds 15 °, the viewing angle may be regulated. .

  Hereinafter, the present invention will be specifically described with reference to examples. These descriptions do not limit the present invention. In the examples, parts represent parts by weight unless otherwise specified.

<Example 1>
The front filter of the present invention is created by the following steps.
(1) The antireflection layer 7 was laminated on a 100 μm-thick (manufactured by Teijin DuPont Films, trade name “HBPF8W”) to obtain a laminate shown in FIG.
The antireflection layer was formed by sequentially forming a high refractive index layer and a low refractive index layer one by one on the UVAPET film.
Here, the high refractive index layer is a cured product having a thickness of 3 μm and a refractive index of 1.69 of a composition (trade name “KZ7973” manufactured by JSR Corporation) in which ultrafine zirconia particles are dispersed in an ultraviolet curable resin. Consists of layers.
The low refractive index resin layer is made of a cured product having a thickness of 100 nm and a refractive index of 1.41 made of a fluororesin-based ultraviolet curable resin (manufactured by JSR Corporation, trade name “TM086”).

(2) The near infrared absorption / neon light absorption layer 9 was laminated on the back surface of the UVAPET film 8 on which the antireflection layer was laminated to obtain a laminate shown in FIG.
A gravure roll is a coating liquid obtained by mixing a diimonium dye and a phthalocyanine dye as a near infrared absorber, a cyanine dye as a neon light absorber, and an acrylic resin binder as a binder resin. Coating was performed to form a near infrared absorption / neon light absorption layer 9 having a thickness of 5 μm.

(3) The toned pressure-sensitive adhesive layer 10 was laminated on the near infrared absorption and neon light absorption layer 9 to obtain a laminate shown in FIG.
A coating liquid obtained by mixing a pigment for toning and an acrylic resin-based pressure-sensitive adhesive for imparting tackiness is applied with a gravure roll, and a toning adhesive layer 10 having a thickness of 25 μm is formed. Formed.

(4) An electromagnetic wave shielding sheet 30 including an electromagnetic wave shielding layer was laminated on the toning pressure-sensitive adhesive layer 10 to obtain a laminate shown in FIG.
First, the electromagnetic wave shielding sheet 30 shown in FIG. 11 was produced as follows.
As the transparent base material 31, a continuous belt-like uncolored transparent biaxially stretched polyethylene terephthalate film having a thickness of 100 μm and a polyester resin primer layer formed on one surface was prepared.
On the primer layer of the transparent substrate, a nickel-chromium alloy layer having a thickness of 0.1 μm and a copper layer having a thickness of 0.2 μm (a part of the conductor layer) are sequentially provided by sputtering. A treatment layer 33 was obtained.
A copper metal plating layer 34 having a thickness of 2.0 μm was provided on the surface of the conductive treatment layer by an electrolytic plating method using a copper sulfate bath.

  Next, a blackened layer 35B was formed on the conductor layer. Specifically, a nickel plate is used for the anode, and the mesh-shaped conductor layer is formed on a transparent base material in a blackening plating bath made of a mixed aqueous solution of a nickel ammonium sulfate aqueous solution, a zinc sulfate aqueous solution and a sodium thiocyanate aqueous solution. The laminated sheet formed above is immersed and electrolytically plated to blacken, and a blackened layer 35B made of a nickel-zinc alloy is formed on the entire surface of the exposed metal plated layer. A sheet on which the body layer 32 (the conductive treatment layer 33, the metal plating layer 34, and the blackening layer 35B) was laminated was obtained.

Next, the conductive layer of the laminated sheet is etched by using a photolithography method, and the mesh region 301 including the opening 303 and the line portion 304, and the outer edge that surrounds the four circumferences of the mesh region 301. A frame-shaped grounding region 302 was formed in the part.
Specifically, using a production line for a color TV shadow mask, the etching was performed consistently from masking to etching on the continuous belt-like laminated sheet. That is, after applying a photosensitive etching resist to the entire surface of the conductor layer of the laminated sheet, it is closely exposed using a mask having a negative pattern of a desired mesh pattern, developed, hardened, and baked to form a mesh line. After processing the resist layer into a pattern in which the resist layer remains on the region corresponding to the portion and the resist layer does not exist on the region corresponding to the opening, the conductor layer and the black The chemical layer was removed by etching to form a mesh-shaped opening, followed by sequential washing with water, stripping of the resist, washing and drying.

  The mesh shape of the mesh region 301 is such that the line width of the linear portion where the opening is a square and a non-opening is 10 μm, the line interval (pitch) is 300 μm, the height of the line is 2.3 μm, rectangular When the sheet was cut into a single sheet, the bias angle defined as the subordinate angle with respect to the long side of the rectangle was 49 degrees. Further, the mesh region 301 has a portion facing the image display region of the display when the completed front filter is bonded to the front surface of the PDP, and the periphery of the mesh region has a front surface. When the filter was cut into a rectangular sheet, the pattern was designed to leave a frame portion with a width of 15 mm without an opening as a grounding region on the outer periphery of the four sides. In this way, an electromagnetic wave shielding sheet 30 was obtained.

  Next, the portion of the mesh-like region 301 of the obtained electromagnetic wave shielding sheet is laminated on the toning pressure-sensitive adhesive layer 10 using a laminator (trade name “LAMIPACKER” manufactured by Fuji Plastics) and shown in FIG. A laminate was obtained.

(5) The transparent adhesive layer 11 was provided on the polyethylene terephthalate (PET) film 13, and the laminated body shown to FIG.10 (E) was obtained.
On a colorless and transparent PET film 125 having a thickness of 188 μm, an acrylic resin adhesive was laminated using a laminator (manufactured by Fuji Plastics, trade name “LAMIPACKER”) to obtain a transparent adhesive layer. In addition, on the obtained transparent adhesive layer, the releasable release film is bonded together (not shown), and a transparent adhesive layer is protected.

(6) The contrast improving layer 4 was laminated on the back surface of the PET film 13 provided with the transparent pressure-sensitive adhesive layer 11 to obtain a laminate shown in FIG.
FIG. 12 is a diagram illustrating a manufacturing process of the contrast improving layer 4.
First, a liquid mixture of an ultraviolet curable resin composed of a liquid urethane acrylate prepolymer and an acrylate monomer and a benzophenone photoinitiator is applied to the back surface of the PET film 13 provided with the transparent adhesive layer 11. (FIG. 12A). Next, the lens part 2 is formed by irradiating ultraviolet rays in a state where the applied ultraviolet curable resin is sandwiched between the roll mold having the inverted shape and the PET film 13 (FIG. 12B). ).

Between the lens portions 2 formed by the above-described process, the light absorbing portion 3 is formed by squeezing a material in which black light absorbing particles are added in a transparent resin, and the black stripe 3a is formed. Then, the contrast improving layer 4 is completed (FIG. 12C).
Here, the specification of the contrast enhancement layer 4 in the present embodiment is shown below. The aperture ratio indicates the ratio of the area through which the light excluding the black stripe 3a is transmitted with respect to the entire area when the contrast improving layer 4 is observed from the PDP 1 side. The trapezoidal taper angle is a cross-sectional shape. The angle formed by the trapezoidal slope portion and the normal line of the boundary surface (light-emitting surface) between the contrast improving layer 4 and the PET film 125.

Opening ratio: 70%
Lens unit 2 pitch: 100 μm
Refractive index of the material of the lens part 2: 1.56
Refractive index of transparent resin: 1.55
Upper bottom surface width of light absorbing portion 3: 7 μm
Trapezoid taper angle: 6 °
Particle size of light absorbing particles: 5 μm
Concentration of light absorbing particles: 25%
Next, the observer side surface of the obtained contrast enhancement layer 4 and the PET film 13 were bonded together using a laminator (manufactured by Fuji Plastics, trade name “LAMIPACKER”).

(7) A transparent adhesive layer was laminated as the impact resistant layer 12 on the contrast improving layer 4 to obtain a laminate shown in FIG.
An acrylic resin-based adhesive (trade name “TU-41A”, thickness 25 μm, manufactured by Yodogawa Paper Mill, thickness 25 μm) is laminated on the contrast enhancement layer 4 using a laminator (trade name “LAMIPACKER” manufactured by Fuji Plastics). The impact resistant layer 12 was obtained.

(8) By laminating the electromagnetic wave shielding sheet 30 of the laminate obtained in (4) and the transparent adhesive layer 11 of the laminate obtained in (7), the PDP of the present invention shown in FIG. A front filter was obtained. Prior to lamination, the release film laminated to protect the transparent adhesive layer 11 was peeled off. Lamination was performed using a laminator (manufactured by Fuji Plastics, trade name “LAMIPACKER”).

<Comparative example>
A laminated body was obtained in the same manner as in Example 1 except that the transparent adhesive layer 11 was formed directly on the back surface of the electromagnetic wave shielding sheet 30 and the PET film 13 and the contrast improving layer 4 were not laminated.

[Evaluation]
The following evaluation was performed about the said Example.
(1) Visual contrast evaluation The existing optical film was removed from the front substrate of a commercially available PDP display device (Pioneer, product name “PDP-435HDL (42 inches)”. The front filter of the example was applied to the outermost adhesive layer. The (11 or 12) side was brought into contact with the front surface of the PDP and pressed with a rubber roller and pasted.PDP1 with the front filter 102 and 40 W white fluorescent lamp 404 (manufactured by Toshiba Corporation, trade name “ Two neoline white FL40S-W ") are arranged as shown in FIG. 13, and the outside light is set so that the illuminance at the center of the surface of the PDP display unit is 370 lx as measured by a luminance meter. The following visual evaluation was performed from the position of
The front filter of the comparative example was also evaluated in the same procedure.

  For the sensory evaluation of contrast, the image quality (brightness, contrast, etc.) of the PDP 1 is set to the “standard” mode, and the highest density of achromatic color (complete black) and the lowest density of achromatic color (complete white) are set. The image data (FIG. 14) of the pattern in which grids (rectangular grids) are alternately arranged in two colors consisting of image data is displayed, and whether or not the black-and-white border of the pattern is clearly visible can be judged as good or bad. Judged. The case where the black-and-white border was clearly visible was marked with ○, and the case where it was not so was marked with ×.

In addition, each above sensory evaluation was performed by evaluation of 20 evaluators. The criteria for each evaluation are as follows.
[Criteria]
Good: When 11 or more evaluators are ○ Acceptable: When 10 evaluators are ○ Poor: When 9 or less evaluators are ○ The evaluation results of the examples and comparative examples used the front filter of the example. In this case, the evaluation was “good”, and when the front filter of the comparative example was used, the evaluation was “bad”.

<Summary of results>
The following can be seen from the above examples and comparative examples.
In the display device of the present embodiment in which the front filter 101 described above is disposed in combination with the PDP 1, the contrast enhancement layer 4 is provided so that an image with a high contrast can be displayed without a decrease in contrast due to external light. did it.

It is a perspective view which shows the display apparatus which bonded the front filter which concerns on this invention on the front substrate of PDP. It is a perspective view of the front filter concerning the present invention. It is sectional drawing which shows the layer structure of the front filter which concerns on this invention. The expanded sectional view of the contrast improvement layer which constitutes the front filter of the present invention is shown. It is sectional drawing which shows the various aspects of the shape of the slope part of a light absorption part (wedge-shaped groove | channel). It is sectional drawing of the electromagnetic wave shielding layer provided on the transparent base material. It is a perspective view of the electromagnetic wave shielding layer which consists of a mesh-shaped conductor layer. It is sectional drawing which shows an example of an electromagnetic wave shielding layer. It is sectional drawing which shows an example of an electromagnetic wave shielding layer. It is sectional drawing which shows the front filter which concerns on an Example. It is sectional drawing of the electromagnetic wave shielding layer used for the front filter of an Example. It is sectional drawing which shows the manufacturing process of a contrast improvement layer. It is a figure which shows the evaluation method of the visual contrast of the front filter which concerns on this invention. 3 shows image data for sensory evaluation of contrast of a front filter according to the present invention.

Explanation of symbols

1 PDP (Plasma Display Panel)
2 Lens part 3 Light absorption part (wedge-shaped groove)
3a Black stripe 4 Contrast improving layer 5 Electromagnetic wave shielding layer 6 Optical filter 7 Antireflection layer (or antiglare layer)
8 UV absorber-containing polyethylene terephthalate (UVAPPET) film 9 Near infrared absorption / neon light absorption layer 10 Toning adhesive layer 11 Transparent adhesive layer 12 Transparent adhesive layer (or impact resistant layer)
DESCRIPTION OF SYMBOLS 13 Transparent base material 14 Ultraviolet curable resin 25 Polyethylene terephthalate (PET) film 26 Transparent binder 27 Wide bottom surface 28 Narrow top surface 29 Light absorption particle 30 Electromagnetic wave shielding sheet 31 Transparent base material 32 Conductor layer 33 Conductive treatment layer 34 Metal layer (metal plating layer)
35A, 35B Blackening layer 100 Display device 101 Front filter 121 Transparent resin 122 Light absorbing particles 125 PET film 301 Mesh-like conductor layer 302 Grounding frame 303 Opening 304 Line part 403 Evaluator 404 White fluorescent lamp

Claims (6)

A front filter for PDP comprising at least a contrast enhancement layer and an electromagnetic wave shielding layer, and directly bonded to an observer side of a plasma display panel (PDP),
The contrast enhancement layer is
A lens that is linearly connected in a predetermined direction along the surface direction of the layer, has a cross-section perpendicular to the extending direction, and has a trapezoidal shape with a wide lower base facing the viewer side, and transmits light And
A light-absorbing part that is linearly connected in a direction parallel to the lens part and has a wedge-shaped shape in which a cross section perpendicular to the extending direction has a wide lower base toward the PDP side, and absorbs light And a front surface filter for PDP, comprising a transmission surface for transmitting PDP display light.   The front filter for a PDP according to claim 1, wherein a light diffusion layer is not provided on the PDP side of the contrast enhancement layer.   The front filter for a PDP according to claim 2, wherein the front filter for a PDP has no light diffusion layer.   The front filter for PDP according to claim 1, further comprising one or more optical filters other than the contrast enhancement layer.   The relationship N1-N2> 0 is established, where N2 is a refractive index of the binder constituting the light absorbing portion and N1 is a refractive index of the material constituting the lens portion. A front filter for PDP as described in 1.   5. A plasma display panel, wherein the PDP front filter according to claim 1 is directly bonded to an observer side of the plasma display panel.

Images