JP2003295186A - Television receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To attain a high brightness of a television receiver by limiting the number of prism sheets to one for enhancing front brightness by efficiently converting diffused light of a backlight into a viewing angle. <P>SOLUTION: A reflection plate 2 is arranged on the rear face of a light source 1 for a backlight, a diffusion plate 3 is arranged in front of the light source 1 for a backlight, and a liquid crystal panel 4 with an incident polarizing plate 5 and an emission polarizing plate 6 provided on both front and rear faces is arranged in front of the diffusion plate 3. A prism sheet 8 is arranged between the diffusion plate 3 and the liquid crystal panel 4. The ridge line direction A0 of the prism sheet 8 is defined as a horizontal direction, and the transmission axis direction B0 of the incident polarizing plate 5 is defined as the vertical direction being substantially perpendicular to the ridge line direction A0 of the prism sheet 8. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television receiver having a liquid crystal display unit having a structure in which a prism sheet is arranged between a diffusion plate on the front surface of a light source for a backlight and an incident polarizing plate on the back surface of a liquid crystal panel. In particular, the present invention relates to a technique for achieving high brightness.

A television receiver having a liquid crystal display section to which the present invention is applied is mainly a display in a personal computer, a personal digital assistant, a communication device, a display of a liquid crystal television receiver, a PALC.
The present invention is applied to a television receiver having a liquid crystal display unit capable of receiving a television such as a (plasma address liquid crystal) display.

A PALC display is composed of a light source for backlight, a plasma address substrate and three layers of liquid crystal,
In the plasma address substrate behind the liquid crystal, the discharge itself between the cathode and the anode facing the dielectric sheet forms the scanning electrode, and forms an orthogonal matrix together with the transparent column electrode on the front surface of the liquid crystal.

[0004]

2. Description of the Related Art In recent years, a television receiver having a liquid crystal display portion, particularly a television receiver having a liquid crystal display portion using a color display element, has been achieved because it is excellent in space saving, weight saving and power saving by thinning. The device is very popular. The liquid crystal display section has a structure in which polarizing plates are mounted on the entrance side and the exit side of a liquid crystal panel in which a liquid crystal layer is held by a transparent substrate such as glass, and the polarization state of linearly polarized incident light is modulated to adjust the liquid crystal. The display is performed. In the currently mainstream transmissive liquid crystal display unit, it is necessary to illuminate from behind using a backlight.

However, since the polarization direction of the incident light is random and irregular, the polarizing plate on the incident side absorbs about half of the light, resulting in low light utilization efficiency. In a laptop computer or a large PALC display of 50-60 type, which is premised on battery drive, power saving of the backlight is an important proposition.
Therefore, it has been proposed to use a prism sheet (lens film) that enhances the front brightness by efficiently using the diffused light of the backlight by condensing it within the viewing angle, and it has already been commercialized.

FIG. 9 is a perspective view showing a disassembled state of a main part of a conventional television receiving apparatus having a liquid crystal display section which requires high brightness. Reference numeral 1 is a light source for backlight, 2 is a reflecting plate arranged on the back surface thereof, 3 is a diffusion plate for uniformly diffusing the light source light of the light source 1 for backlight in all directions, and 4 is opposed to the front surface of the diffusion plate 3. The arranged liquid crystal panel, 5 is an incident polarizing plate arranged on the back surface of the liquid crystal panel 4, 6 is an outgoing polarizing plate arranged on the front surface, and 7 is composed of the liquid crystal panel 4, the incident polarizing plate 5 and the outgoing polarizing plate 6. It is a liquid crystal display board. A prism sheet 8 is arranged between the diffusion plate 3 and the liquid crystal display plate 7 with its ridge line horizontal. The ridgeline direction of the prism sheet 8 is indicated by an arrow A1.

When viewed from the front side, the transmission axis of the entrance polarizing plate 5 is inclined by 45 ° from the upper left to the lower right as shown by arrow B1, and the transmission axis of the exit polarizing plate 6 is viewed from the front side. As indicated by C1, the inclination direction is 45 ° from the upper right to the lower left. It is common in the TN type liquid crystal display unit that the transmission axis direction B1 of the incident polarization plate 5 is 45 °.

The reason is as follows. This is due to the contrast viewing angle characteristics of the liquid crystal. The conventional general TN type liquid crystal has a biased contrast viewing angle characteristic, and it is unavoidable that the contrast viewing angle characteristic is wide in the horizontal direction and narrow in the vertical direction. As a result, the transmission axis direction B1 of the incident polarizing plate 5 is inclined at 45 °.

[0009]

Television receivers having a liquid crystal display section generally have lower luminance than CRTs and the like, and there is a demand for higher luminance than the current state.

In order to increase the brightness, it is necessary to narrow the brightness viewing angle. Therefore, in the case of JP-A-8-22000, two prism sheets are prepared and used in a state where their ridge lines are orthogonal to each other. However, the luminance viewing angle is narrowed both vertically and horizontally, which is not suitable for large-screen display.

The present invention was devised in order to solve the above-mentioned problems, and is intended to increase the brightness while limiting the number of prism sheets to one so as to be suitable for large-screen display. is there.

[0012]

A television receiver having a liquid crystal display section according to the present invention has the following configuration. That is, a diffusion plate is arranged on the front surface of the light source for backlight, and a liquid crystal panel having an incident polarization plate and an emission polarization plate attached to both front and back surfaces is arranged in front of the diffusion plate.
It is assumed that a prism sheet is arranged between the diffusion plate and the liquid crystal panel. Further, the transmission axis direction of the incident polarizing plate is set at a right angle with respect to the ridgeline direction of the prism sheet.

As will be described later in detail in the embodiment, in the prism sheet, the transmittance of P wave is S.
Higher than wave transmittance. The P wave is a linearly polarized light component that oscillates in the incident plane formed by the incident light ray and the normal to the object plane, and the S wave is a linearly polarized light component that oscillates in a plane perpendicular to the incident light.

Since the transmittance of the P wave is higher than that of the S wave, if the transmission axis direction of the incident polarizing plate is set along the vibration plane of the P wave as described above, the brightness becomes higher. . The vibrating surface of the P wave is perpendicular to the ridge direction of the prism sheet. As a result, by setting the transmission axis direction of the incident polarizing plate in a direction perpendicular to the ridgeline direction of the prism sheet, the brightness becomes higher.

In the above structure, when the ridgeline direction of the prism sheet is set in the left-right direction and the transmission axis direction of the incident polarizing plate is set in the vertical direction perpendicular to the ridgeline direction of the prism sheet, the following is further obtained. There are advantages. In order to increase the brightness, it is necessary to narrow the brightness viewing angle. It becomes necessary to limit the number of prism sheets to one and to narrow either the vertical or horizontal luminance visual angle.

In this case, considering the visual characteristics of the human eye,
Further, considering that a large number of people lay sideways on a large screen and view them at the same time, it is preferable to widen the luminance visual angle in the horizontal direction, and in that case, the luminance visual angle in the vertical direction is narrowed. Narrowing the vertical luminance viewing angle in the prism sheet means arranging the prism sheet so that the ridge direction is in the left-right direction.

As described above, the ridgeline direction of the prism sheet is set in the left-right direction, and correspondingly, the transmission axis direction of the incident polarizing plate is set in the vertical direction perpendicular to the ridgeline direction of the prism sheet. It is possible to achieve high brightness while having a large brightness viewing angle in the left-right direction, which is advantageous for the visual characteristics of the eyes and is advantageous for a large number of people viewing a large screen.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a television receiver according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view showing a disassembled state of a main part of a television receiver according to an embodiment of the present invention. A reflecting plate 2 is arranged on the back surface of a backlight light source 1 made of a fluorescent lamp, and a diffusion plate 3 is arranged on the front surface of the backlight light source 1 for diffusing the source light uniformly in all directions. A liquid crystal panel 4 is arranged so as to face the front surface of the diffusion plate 3, and an incident polarization plate 5 is provided on the back surface of the liquid crystal panel 4.
However, the exit polarizing plates 6 are respectively arranged on the surface, and the liquid crystal panel 4, the entrance polarizing plate 5, and the exit polarizing plate 6 constitute a liquid crystal display plate 7. Then, the prism sheet 8 for efficiently converging the diffused light from the diffuser plate 3 within the viewing angle between the diffuser plate 3 and the liquid crystal display plate 7 to increase the front brightness, has its ridgeline direction A0 in the left-right direction ( (Horizontal direction).

The transmission axis direction B0 of the incident polarization plate 5 is the vertical direction, that is, the direction perpendicular to the ridgeline direction A0 (vertical direction), and the transmission axis direction C0 of the emission polarization plate 6 is the horizontal direction (horizontal direction). In addition, the reflection plate 2 is closely attached to the back surface of the light source 1 for backlight, and the diffusion plate 3 is attached to the front surface.
Are closely attached. Further, the incident polarization plate 5 is closely attached to the back surface of the liquid crystal panel 4, and the emission polarization plate 6 is closely attached to the front surface. The prism sheet 8 is the diffusion plate 3
And is close to the incident polarization plate 5.

The two components of linearly polarized light will be described with reference to FIG. As shown in FIG. 3 (a), a P wave that is a linearly polarized light component that oscillates in the incident surface 41 created by the incident light ray 20 and the normal 31 of the object surface 30, and as shown in FIG. 3 (b), There are two components, the S wave, which is a linearly polarized light component that oscillates in a plane 42 perpendicular to the incident surface 41.

[Embodiment 1] FIG. 4 shows the relationship between the incident angle and the reflectance when incident on the transparent light guide (acrylic) from the air layer, and FIG. 5 shows the relationship between the transparent light guide (acrylic) and the air layer. The relationship between the incident angle and the reflectance when incident is shown. Here, acrylic is a constituent material of the prism sheet 8. The transmittance is (100-reflectance).

FIG. 6 shows a light path in the prism sheet 8 made of acrylic. If the refractive index of acrylic resin that constitutes the prism sheet 8 is 1.49 and the apex angle of the prism is 90 °, the slope 8b of the prism sheet 8 is perpendicular to the flat back surface 8a of the prism sheet 8 as indicated by L3. In order to emit light in the front direction, the following conditions are required.

Since the angle of refraction from the inclined surface 8b of the prism of the prism sheet 8 must be 45 °, the incident angle θ2 of the light ray L2 in the prism with respect to the inclined surface 8b must be θ2 = 28 °. That is, according to Snell's law, 1.49
From sin θ2 = 1.0 · sin 45 °, θ2 = 28.33. As a result, β = 45−28 = 17 ° is required. β = α. Refraction angle in prism is 1
Since it is 7 °, it is necessary that the incident angle θ1 of the light L1 entering the prism sheet 8 from the air layer behind is θ = 26 °. That is, from 1.0 · sin θ1 = 1.49 · sin 17 °,
θ1 = 25.82.

In FIG. 4, when the reflectance at the incident angle θ1 = 26 ° from the air layer to acrylic is examined, both the reflectance of P wave and the reflectance of S wave are about 4%, and there is no difference between them. The transmittance at that time is 100-4 = 96%. Further, in FIG. 5, the incident angle θ2 from the acrylic layer to the air layer is 28 °.
The reflectance of P wave is about 2%,
The reflectance of S wave is about 8%. At that time, the transmittance of P waves is 98%, and the transmittance of S waves is 92%.

[Comparative Example 1] Here, as Comparative Example 1, FIG.
The conventional television receiver shown in will be verified. In the case of a conventional television receiver, the transmission axis direction B1 of the incident polarizing plate 5 is the ridgeline direction A1 of the prism sheet 8.
It has an angle of 45 ° with respect to. In FIG. 6, the P-wave vibration surface 41 is parallel to the paper surface, and the S-wave vibration surface 42 is perpendicular to the paper surface.

In the case of the prior art, in FIG. 6, the transmission axis direction B1 of the incident polarization plate 5 is 45 ° with respect to both the P-wave vibration surface 41 and the S-wave vibration surface 42 perpendicular thereto.
It means that it is inclined.

From the prism sheet 8, a P wave along the vibrating surface 41 and an S wave along the vibrating surface 42 are emitted toward the liquid crystal panel 4. However, it will pass through the incident polarization plate 5 before entering the liquid crystal panel 4. This incident polarization plate 5
Since the transmission axis direction B1 of 4 has an angle of 45 ° with respect to both of the vibrating surfaces 41 and 42, both the P wave and the S wave pass through the incident polarization plate 5 by about 50% and are cut by about 50%. Since the reflectance of the P wave on the slope 8b of the prism sheet 8 is 2%, the transmittance of the P wave is 100-2 =
It becomes 98%. Further, since the S wave reflectance on the slope 8b is 8%, the S wave transmittance is 100-9 = 92%.
Becomes Since the ratio of the P wave and the S wave that pass through the incident polarization plate 5 and enter the liquid crystal panel 4 is approximately 50%: 50%,
The substantial transmittance of the incident polarizing plate 5 is (98 + 9
2) / 2 = 95%.

[Embodiment 1] Next, the description of Embodiment 1 is resumed. In the case of Example 1, since the ridgeline direction A0 of the prism sheet 8 is the horizontal direction (horizontal direction) and the transmission axis direction B0 of the incident polarizing plate 5 is the vertical direction (vertical direction),
The transmission axis direction B0 of the incident polarization plate 5 has an angle of 90 ° with the ridgeline direction A0 of the prism sheet 8. This is the transmission axis direction B0 of the incident polarization plate 5 in FIG.
Is parallel to the vibration surface 41 of the P wave and is 90 ° with respect to the vibration surface 42 of the S wave.

From the prism sheet 8, a P wave along the vibrating surface 41 and an S wave along the vibrating surface 42 are emitted toward the liquid crystal panel 4. However, it will pass through the incident polarization plate 5 before entering the liquid crystal panel 4. This incident polarization plate 5
Since the transmission axis direction B0 of is along the vibration surface 41, almost 100% of the P wave passes and almost 100% of the S wave is cut. Since the reflectance of P waves on the slope 8b of the prism sheet 8 is 2%, the transmittance of P waves on the incident polarizing plate 5 is 100-2 = 98%. There is no need to think about S waves. Comparing 98% of P-wave transmission with 95% of the conventional technique of Comparative Example 1, 98/95 = 1.03.
157 ..., and the brightness can be improved by about 3.1%.

Comparative Example 2 As another Comparative Example 2,
Let us consider a television receiver in which the transmission axis direction of the incident polarizing plate 5 is parallel to the ridgeline direction of the prism sheet 8, that is, horizontal. In this case, in FIG. 6, it means that the transmission axis direction of the incident polarization plate 5 is parallel to the vibration surface 42 of the S wave and is 90 ° with respect to the vibration surface 41 of the P wave. Therefore, almost 100% of S waves pass through the incident polarization plate 5, and almost 100% of P waves pass through.
Be cut. S on the slope 8b of the prism sheet 8
Since the wave reflectance is 8%, S in the incident polarization plate 5 is
The wave transmittance is 100-8 = 92%. There is no need to think about P waves. When the transmittance of 98% in the case of the above-mentioned Example 1 is compared with this Comparative Example 2, 98/92 =
1.0652 ... That is, when using only the P wave, the brightness is about 6.5 as compared with when using only the S wave.
% Can be improved.

Further, the significance of utilizing the P wave in the embodiment (example) of the present invention will be described in detail. FIG. 7 is a diagram showing the relationship between the vertical viewing angle in the plane perpendicular to the ridgeline direction A0 of the prism sheet 8 and the luminance for the P wave and the S wave. This corresponds to the material 101 in FIG. Ridge direction A0 is used to represent the material 101
Vertical to. The data was obtained in the range of −40 ° below to + 40 ° above as the range of visual angle. Overall, P
The brightness of the wave is higher than that of the S wave. As described above, the brightness of the P wave is about 6.5% higher than the brightness of the S wave when it is directly in front, that is, when the viewing angle is 0 °.

FIG. 8 is a diagram showing the relationship between the viewing angle in the horizontal direction in the plane parallel to the ridgeline direction A0 of the prism sheet 8 and the brightness of the P wave and the S wave. This corresponds to the material 102 in FIG. The representation of the material 102 is parallel to the ridge direction A0. The data was obtained in the range of −40 ° to the left and + 40 ° to the right as the viewing angle range. The brightness of the P wave is higher than the brightness of the S wave in the range of −20 ° to the left and + 20 ° to the right. Similarly, when it is directly in front, that is, when the viewing angle is 0 °, the brightness of the P wave is about 6.5% higher than that of the S wave. The brightness of the S wave is higher than the brightness of the P wave in the range outside the left -20 ° and outside the right + 20 °.

From a total view of FIG. 7 and FIG. 8, it can be seen that the use of P-waves with high brightness in the viewing angle range near the normal direction is better as a backlight. The P wave vibrates in the vibrating surface 41 parallel to the paper surface in FIG.
The directionality of the incident polarization plate 5 in the transmission axis direction B0 required for making the P wave incident on the liquid crystal panel 4 is also parallel to the paper surface in FIG. That is, the transmission axis direction B0 should be perpendicular to the ridgeline direction A0 of the prism sheet 8. Therefore, the arrangement relationship is as shown in FIG. In this case, the front brightness is increased by about 6.5% as compared with the case of using the S wave.

[Embodiment 2] Embodiment 2 is applied to a vertically long television receiver. In FIG. 2, the prism sheet 8 is arranged with the ridgeline direction A0 set in the vertical direction (vertical direction), and the transmission axis direction B0 is perpendicular to the ridgeline direction A0, that is, in the state of being oriented in the left-right direction (horizontal direction). A perspective view of a disassembled state of the television receiving device in which the incident polarizing plate 5 is arranged and the outgoing polarizing plate 6 is arranged in a state where the transmission axis direction C0 is perpendicular to the transmission axis direction B0 of the incident polarizing plate 5. Is. The orientation of the material 101 corresponding to FIG. 7 and the orientation of the material 102 corresponding to FIG. 8 are different from those of FIG. 1 by 90 °. Also in this case, the P wave is used, and the front luminance is increased by about 6.5% as compared with the case of using the S wave.

In a television receiver, it is generally necessary to narrow the luminance viewing angle in order to increase the luminance. As one of the countermeasures, there is a method in which two prism sheets are prepared and used in a state where their ridge lines are orthogonal to each other (Japanese Patent Laid-Open No. 8-22000). However, the luminance viewing angle is narrowed both vertically and horizontally, which is not suitable for large-screen display.

Therefore, the number of prism sheets is limited to one,
It becomes necessary to choose to narrow either the vertical or horizontal luminance visual angle.
In this case, considering the visual characteristics of the human eye, and considering that a large number of people lie side by side on a large screen at the same time, it is preferable to widen the luminance viewing angle in the left-right direction. Therefore, if it is necessary to narrow one of the vertical and horizontal luminance visual angles, it is preferable to select the narrower vertical luminance visual angle. In this way, it is possible to achieve a high luminance while ensuring a relatively large luminance visual angle and making it suitable for large-screen display.

The following is given as a background to the establishment of the present invention. Recently, a wide viewing angle liquid crystal has been developed, and the contrast viewing angle characteristic of the liquid crystal has been widened. It is not necessary to tilt the transmission axis direction B0 of the incident polarizing plate 5 to 45 °, and the vertical direction is set as described above. It doesn't matter.

[0039]

According to the present invention of a television receiver having a structure in which a prism sheet is arranged between a diffuser plate on the front surface of a light source for a backlight and an incident polarizing plate on the rear surface of a liquid crystal panel, according to the present invention. In order to use the P wave with higher transmittance, the transmission axis direction of the incident polarization plate is set at a right angle with respect to the ridgeline direction of the prism sheet. Therefore, only one prism sheet is used to compare the luminance viewing angle. It is possible to realize a higher brightness display while securing a large size and suitable for a large screen display.

Particularly, by setting the ridge direction of the prism sheet in the left and right direction and the transmission axis direction of the incident polarizing plate in the up and down direction, it is advantageous for human visual characteristics and also advantageous for a large number of people to see a large screen. It is possible to achieve high brightness while maintaining a large brightness viewing angle in the left-right direction.

[Brief description of drawings]

FIG. 1 is a perspective view of a disassembled state of a main part of a television receiving apparatus according to an embodiment (Example 1) of the present invention.

FIG. 2 is a perspective view of a disassembled state of a main part of a television receiving device in a case of a second embodiment.

FIG. 3 is an explanatory diagram of P waves and S waves.

FIG. 4 is a diagram showing the relationship between the incident angle and the reflectance when incident on acrylic from an air layer.

FIG. 5 is a relationship diagram between the incident angle and the reflectance when the light enters the air layer from acrylic.

FIG. 6 is an explanatory diagram of a light path in an acrylic prism sheet.

FIG. 7 is a diagram showing the relationship between the vertical viewing angle in a plane perpendicular to the ridgeline direction of the prism sheet and the luminances of P waves and S waves.

FIG. 8 is a diagram showing the relationship between the viewing angle in the left-right direction and the brightness of P waves and S waves in a plane parallel to the ridge direction of the prism sheet.

FIG. 9 is a perspective view of a disassembled state of a main part of a conventional television receiver (Comparative Example 1).

[Explanation of symbols]

1 Light source for backlight 2 reflector 3 diffuser 4 LCD panel 5 Incident polarization plate 6 Output polarizing plate 7 Liquid crystal display board 8 prism sheet 20 incident rays 30 Object plane 31 Normal 41 P wave vibration surface 42 S wave vibration plane A0 Prism sheet ridge direction B0 Direction of transmission axis of incident polarizer C0 Transmitting polarization direction of output polarizing plate

Claims (2)

[Claims] 1. A liquid crystal panel comprising a light source for a backlight, a diffusion plate arranged in front of the light source for the backlight, and an incident polarization plate and an emission polarization plate arranged on the front and back sides of the diffusion plate. And a direct-type backlight device composed of one prism sheet disposed between the diffusion plate and the liquid crystal panel, wherein the ridge line direction of the prism sheet is the left-right direction of the screen. And the transmission axis of the incident polarizing plate facing the prism sheet is set to a transmission axis having a high transmittance with respect to the prism sheet. 2. The television receiver according to claim 1, wherein a transmission axis direction of the incident polarizing plate is set to a direction along a vibration plane of P waves.