Projection type display device

Abstract

To provide a projection-type display device which can effectively heat a refractive-type liquid crystal display element by a heat generation source, the heat generation source rarely reducing the cooling performance of cooling the refractive liquid crystal display element.SOLUTION: In at least one of the longer direction and the shorter direction of a refractive liquid crystal display element 1, the length of the refractive liquid crystal display element 1 is L1, the length of the heat generation source 3 is L3, and the thickness of a base 21 of a heat sink 2 is t. The refractive liquid crystal display element 1 and the heat generation source 3 face each other across the base 21 so that the length L3 of the heat generation source is within the length L1 of the refractive liquid crystal display element 1. The length L3 of the heat generation source 3 satisfies the relation of L3≥L1-2 t.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a projection display device.

Background Art

[0002] A projection display device that modulates illumination light in accordance with an image signal by a reflective liquid crystal display element and projects it onto a screen has become widespread. It is not preferable to operate a projection display device with a reflective liquid crystal display element in a low-temperature state, nor is it preferable for the reflective liquid crystal display element to become high-temperature. Therefore, a projection display device is provided with a configuration for heating the reflective liquid crystal display element or a configuration for cooling the reflective liquid crystal display element (see Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is desired to provide a projection display device that can effectively heat a reflective liquid crystal display element by a heat source and that hardly reduces the cooling performance of the heat source for cooling the reflective liquid crystal display element. The present invention aims to provide a projection display device that includes both a heating function and a cooling function for a reflective liquid crystal display element, which can effectively heat the reflective liquid crystal display element by a heat source and hardly reduces the cooling performance of the heat source for cooling the reflective liquid crystal display element.

Means for Solving the Problems

[0005] The present invention provides a projection display device comprising a heat sink having a plate-shaped base, a reflective liquid crystal display element fixed to a first surface of the base, a heat source fixed to a second surface of the base facing the first surface, and a cooling fan for blowing cooling air onto the heat sink, wherein, in at least one of the longitudinal or transverse directions of the reflective liquid crystal display element, if the length of the reflective liquid crystal display element is L1, the length of the heat source is L3, and the plate thickness of the base is t, the reflective liquid crystal display element and the heat source face each other across the base such that the length L3 of the heat source is located within the length L1 of the reflective liquid crystal display element, and the length L3 of the heat source satisfies L3 ≥ L1 - 2t. [Effects of the Invention]

[0006] According to the projection-type display device of the present invention, the heat source can effectively heat the reflective liquid crystal display element, and the heat source hardly reduces the cooling performance of the reflective liquid crystal display element, so that the reflective liquid crystal display element can be operated at an optimal temperature. [Brief explanation of the drawing]

[0007] [Figure 1] This figure shows a projection-type display device according to one embodiment. [Figure 2] This is a perspective view showing a heat sink and heat source in a projection-type display device according to one embodiment. [Figure 3] This is a cross-sectional view of the Y1-Y2 line in Figure 2. [Figure 4] This is a characteristic diagram showing the relationship between ambient temperature and element temperature in a projection-type display device according to one embodiment. [Figure 5] This is a characteristic diagram showing the relationship between the current value of the light source driving current and the element temperature in a projection-type display device according to one embodiment. [Modes for carrying out the invention]

[0008] Hereinafter, a projection display device according to one embodiment will be described with reference to the attached drawings. The projection display device 100 according to one embodiment shown in Figure 1 comprises a reflective liquid crystal display element 1, a heat sink 2, a heat source 3, a cooling fan 5, drive circuits 30a and 30b for the heat source 3, temperature sensors 41 and 42, and a drive circuit 50 for the cooling fan 5. The reflective liquid crystal display element 1 is fixed to the first surface of the base 21 of the heat sink 2, and the heat source 3 is fixed to the second surface of the base 21 facing the first surface. The cooling fan 5 is located behind the heat sink 2.

[0009] The projection display device 100 includes three reflective liquid crystal display elements 1 that modulate red light (R light), green light (G light), and blue light (B light). Preferably, the projection display device 100 is configured as shown in Figure 1 for each of the reflective liquid crystal display elements 1 for R light, G light, and B light. Alternatively, the projection display device 100 may be configured as shown in Figure 1 only for the reflective liquid crystal display element 1 for B light.

[0010] In the projection display device 100, the illumination optical system that irradiates the reflective liquid crystal display element 1 with illumination light, the synthesis optical system that combines the illumination light modulated by each of the reflective liquid crystal display elements 1 for R light, G light, and B light, and the projection optical system that projects the synthesized light combined by the synthesis optical system onto the screen are no different from conventional configurations, so their configurations are omitted in Figure 1. The configurations of the illumination optical system, synthesis optical system, and projection optical system may be those described in Patent Document 2.

[0011] However, the effects of this embodiment are particularly evident in a projection-type display device 100 that uses a blue laser light source that emits blue laser light as the light source for illumination.

[0012] As shown in Figure 2, the heat sink 2 has a plate-shaped base 21 and a plurality of fins 22 integrally formed on the upper surface of the base 21. The heat sink 2 is made of, for example, aluminum or an aluminum alloy. In the central part of the heat sink 2, there is a finless portion 23 where no fins 22 are formed and the upper surface of the base 21 is exposed over a predetermined area. A heat source 3 is fixed to the upper surface of the base 21 in the finless portion 23.

[0013] It is preferable to use a ceramic heater as the heat source 3. The ceramic on the surface of the ceramic heater has a relatively high thermal conductivity of about 150 W / m·K. Therefore, when a ceramic heater is used as the heat source 3, the heat generated by the reflective liquid crystal display element 1 is transferred to the heat sink 2, and further to the ceramic heater on the finless portion 23, allowing the heat to be efficiently dissipated into the air. On the other hand, when a silicone rubber heater is used as the heat source 3, the thermal conductivity of the rubber on the surface of the silicone rubber heater is 1.4 to 8 W / m·K, which is low. Therefore, although the heat generated by the reflective liquid crystal display element 1 is transferred to the heat sink 2, it is not easily transferred to the silicone rubber heater on the finless portion 23, and the heat cannot be efficiently dissipated into the air.

[0014] In Figure 2, the X direction is the longitudinal direction of the reflective liquid crystal display element 1, and the Y direction is the short direction of the reflective liquid crystal display element 1. Figure 3 is a cross-sectional view of Figure 2 along the Y1-Y2 line. In Figure 1, the reflective liquid crystal display element 1 and heat sink 2 are shown as viewed from the side of the heat sink 2 along the X direction.

[0015] In FIG. 1, temperature sensors 41 and 42 are respectively attached to the reflective liquid crystal display element 1 and the heat sink 2. The output of the temperature sensor 41 is supplied to the drive circuit 30a, and the output of the temperature sensor 42 is supplied to the drive circuit 30b. For example, the drive circuit 30a may be configured using a microprocessor, and the drive circuit 30b may be a simple circuit without using a microprocessor. The temperature sensor 41 may be configured as a circuit within the reflective liquid crystal display element 1. In this case, when power is not supplied to the reflective liquid crystal display element 1, the temperature sensor 42 may be used, and when power is supplied to the reflective liquid crystal display element 1, the temperature sensor 41 may be used. As the temperature sensor 42 attached to the heat sink 2, a thermistor whose resistance value changes with temperature can be used.

[0016] The drive circuit 30a drives the heat source 3 according to the temperature detected by the temperature sensor 41. The drive circuit 30b drives the heat source 3 according to the temperature detected by the temperature sensor 42.

[0017] When the projection display device 100 is operating and the reflective liquid crystal display element 1 is being driven, and the temperature detected by the temperature sensor 41 is below a predetermined temperature, the drive circuit 30a drives the heat source 3 to generate heat. At this time, if the drive circuit 30a is configured using a microprocessor, the drive circuit 30a can control the temperature of the reflective liquid crystal display element 1 with high precision.

[0018] When the projection display device 100 is not operating and the reflective liquid crystal display element 1 is not being driven, and the temperature detected by the temperature sensor 42 is below a predetermined temperature, the drive circuit 30b drives the heat source 3 to generate heat. At this time, if a thermistor is used as the temperature sensor 42, the temperature of the heat sink 2 can be detected by flowing only a small current through the temperature sensor 42. Also, if the drive circuit 30b is a simple circuit, a large amount of power is not required to operate the drive circuit 30b, and the heat source 3 can be driven according to the temperature detected by the temperature sensor 42.

[0019] Thus, if the projection display device 100 includes the temperature sensors 41 and 42 and the drive circuits 30a and 30b, the heat source 3 can be appropriately driven in both the state where the projection display device 100 is not operating and the state where it is operating. Even if the projection display device 100 has been exposed to a low ambient temperature for a long time while not operating, the drive circuit 30b can drive the heat source 3 to raise the temperature of the reflective liquid crystal display element 1. Therefore, after the power of the projection display device 100 is turned on and the projection display device 100 starts operating, the reflective liquid crystal display element 1 can be set to a desired temperature in a short time, and the startup time of the projection display device 100 can be shortened.

[0020] When the temperature detected by the temperature sensor 41 or 42 is equal to or higher than a predetermined high temperature, the drive circuit 50 drives the cooling fan 5 so that the cooling air from the cooling fan 5 hits the heat sink 2.

[0021] As described above, when the heat source 3 generates heat, the heat is transmitted to the reflective liquid crystal display element 1 through the base 21 of the heat sink 2, and the temperature of the reflective liquid crystal display element 1 rises. When the reflective liquid crystal display element 1 generates heat in a state where the heat source 3 is not generating heat, the heat is transmitted to the fins 22 through the base 21 of the heat sink 2. Since the cooling air from the cooling fan 5 hits the heat sink 2, the heat sink 2 dissipates heat and the temperature of the reflective liquid crystal display element 1 decreases.

[0022] In the projection display device 100 configured as described above, if the area of the heat source 3 in contact with the base 21 of the heat sink 2 is small, the reflective liquid crystal display element 1 cannot be effectively heated. On the other hand, if the area of the heat source 3 in contact with the base 21 of the heat sink 2 is large, there is a risk of deteriorating the heat dissipation performance (cooling performance) of the heat sink 2.

[0023] Therefore, it is necessary to effectively heat the reflective liquid crystal display element 1 with the heat source 3, while ensuring that the heat source 3 does not significantly reduce the cooling performance of the reflective liquid crystal display element 1. In other words, it is necessary to effectively balance the heating function of the heat source 3 with the cooling function of the heat sink 2.

[0024] As shown in Figure 1, the reflective liquid crystal display element 1 and the heat source 3 are positioned opposite each other with the base 21 in between, such that the length L3 of the heat source 3 is located within the length L1 of the reflective liquid crystal display element 1. Preferably, the reflective liquid crystal display element 1 and the heat source 3 are positioned so that their longitudinal centers coincide.

[0025] In Figure 1, the heat generated by the heat source 3 is efficiently transferred in the region between 3hcR and 3hcL, which are at an angle of approximately 45 degrees indicated by the dashed arrow, in a direction perpendicular to the surface of the base 21. Therefore, it is preferable that the length L3 of the heat source 3 satisfies equation (1) using the length L1 of the reflective liquid crystal display element 1 and the thickness t of the base 21. If equation (1) is satisfied, the heat generated by the heat source 3 can be efficiently transferred to the reflective liquid crystal display element 1 via the heat sink 2 (base 21). L3 ≥ L1 - 2t …(1)

[0026] When the heat source 3 is not generating heat, the heat generated by the reflective liquid crystal display element 1 is efficiently transferred in a direction perpendicular to the surface of the base 21, in the region between 1hcR and 1hcL at approximately 45 degrees, as indicated by the dashed arrow. Therefore, in order to improve the cooling efficiency of the heat sink 2, it is preferable that the length L2 of the heat sink 2 (base 21) satisfies equation (2) using the length L1 of the reflective liquid crystal display element 1 and the plate thickness t of the base 21. L2 ≥ L1 + 2t …(2)

[0027] In Figure 1, the lengths L1 of the reflective liquid crystal display element 1, L2 of the heat sink 2, and L3 of the heat source 3, as described above, represent the lengths in the X direction, which is the longitudinal direction of the reflective liquid crystal display element 1. The projection display device 100 preferably satisfies equation (1) in the X direction, and more preferably satisfies both equations (1) and (2). Similarly, in the Y direction shown in Figure 3, it is preferable that equation (1) is satisfied, and more preferably that both equations (1) and (2) are satisfied.

[0028] The projection display device 100 may satisfy equation (1) in only one of the two directions, the length in the X direction and the length in the Y direction, or it may satisfy both equation (1) and equation (2) in only one of the two directions. Compared to the case where equation (1) (or equations (1) and (2)) are not satisfied in both the X direction and the Y direction, a predetermined effect can be obtained if equation (1) (or equations (1) and (2)) is satisfied in only one of the directions.

[0029] It is preferable that the projection display device 100 satisfies equation (1) in both the length in the X direction and the length in the Y direction. It is even more preferable that the projection display device 100 satisfies both equation (1) and equation (2) in both the length in the X direction and the length in the Y direction.

[0030] Thus, the projection display device 100 only needs to satisfy equation (1) in at least one of its lengths in the X direction and Y direction. Preferably, the projection display device 100 satisfies both equation (1) and equation (2) in at least one of its lengths in the X direction and Y direction.

[0031] Considering the balance between heating by the heat source 3 and cooling by the heat sink 2, the best balance is achieved when equation (3) is used. Therefore, it is preferable to satisfy equation (3). L3 = L1 - 2t …(3)

[0032] Figure 4 shows the temperature (element temperature) of the reflective liquid crystal display element 1 when the ambient temperature changes. The dashed line shows the temperature characteristics when the heat source 3 and cooling fan 5 are not operating, and the solid line shows the temperature characteristics when the heat source 3 and cooling fan 5 are operating. Figure 4 shows the temperature characteristics when both equations (1) and (2) are satisfied for both the length in the X direction and the length in the Y direction.

[0033] When the ambient temperature is low and the temperature of the reflective liquid crystal display element 1 is low, the heat source 3 is activated, allowing the reflective liquid crystal display element 1 to operate at an optimal element temperature. When the ambient temperature is high and the temperature of the reflective liquid crystal display element 1 is high, the cooling fan 5 is activated, allowing the reflective liquid crystal display element 1 to operate at an optimal element temperature. The projection display device 100 can maintain the element temperature at an optimal element temperature regardless of the ambient temperature.

[0034] Figure 5 shows the element temperature of the reflective liquid crystal display element 1 when the current value of the light source driving current changes. The dashed line shows the temperature characteristics when the heat source 3 and cooling fan 5 are not operating, and the solid line shows the temperature characteristics when the heat source 3 and cooling fan 5 are operating. Figure 5 shows the temperature characteristics when both equations (1) and (2) are satisfied for both the length in the X direction and the length in the Y direction.

[0035] When the current value of the light source drive current is small and the temperature of the reflective liquid crystal display element 1 is low, the heat source 3 is activated, allowing the reflective liquid crystal display element 1 to operate at an optimal element temperature. When the current value of the light source drive current is large and the temperature of the reflective liquid crystal display element 1 is high, the cooling fan 5 is activated, allowing the reflective liquid crystal display element 1 to operate at an optimal element temperature. The projection display device 100 can maintain the element temperature at an optimal element temperature regardless of the current value of the light source drive current.

[0036] When a blue laser light source is used as the light source for illumination, if the element temperature is too low or too high and deviates from the optimal element temperature, interference fringes are likely to occur, especially in the image of the blue light. According to the projection display device 100 of this embodiment, interference fringes can be reduced. Of course, according to the projection display device 100 of this embodiment, it is possible to display high-quality images even if the light source for illumination is not a blue laser light source.

[0037] Three reflective liquid crystal display elements 1 that modulate R light, G light, and B light are designated as the first to third reflective liquid crystal display elements, respectively. When the blue light source is a blue laser light source, it is sufficient to obtain the effect of reducing interference fringes by using only the third reflective liquid crystal display element 1 among the first to third reflective liquid crystal display elements as the reflective liquid crystal display element 1 in Figure 1. The first and second reflective liquid crystal display elements only need to be fixed to a normal heat sink to which the heat source 3 is not fixed.

[0038] The present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0039] 1. Reflective liquid crystal display element 2 Heatsink 3. Heat source 5 Cooling fan 21 Base 22 fins 23 Fin-less section 30a, 30b, 50 drive circuit 41,42 Temperature Sensor 100 Projection display device

Claims

1. A heat sink having a plate-shaped base, A reflective liquid crystal display element fixed to the first surface of the base, A heat source is fixed to a second surface of the base that is opposite to the first surface, A cooling fan that blows cooling air onto the heatsink, Equipped with, In at least one of the longitudinal or transverse directions of the reflective liquid crystal display element, if the length of the reflective liquid crystal display element is L1, the length of the heat source is L3, and the thickness of the base is t, The reflective liquid crystal display element and the heat source are positioned opposite each other with the base in between, such that the length L3 of the heat source is located within the length L1 of the reflective liquid crystal display element. The length L3 of the heat source satisfies L3 ≥ L1 - 2t. Projection type display device.

2. The projection display device according to claim 1, wherein, in at least one direction of the longitudinal or transverse direction of the reflective liquid crystal display element, if the length of the base is L2, then the length of the base L2 satisfies L2 ≥ L1 + 2t.

3. The aforementioned heatsink is The base has a plurality of fins integrally formed on the second surface, The second surface is provided with a finless portion where the second surface on which the fins are not formed is exposed. The heat source is fixed to the fin-less portion. The projection display device according to claim 1 or 2.

4. The projection display device according to claim 1 or 2, wherein the heat source is a ceramic heater.

5. It comprises a first reflective liquid crystal display element that modulates red light, a second reflective liquid crystal display element that modulates green light, and a third reflective liquid crystal display element that modulates blue light. The aforementioned blue light source is a blue laser light source, Of the first to third reflective liquid crystal display elements, only the third reflective liquid crystal display element is referred to as the reflective liquid crystal display element. The projection display device according to claim 1 or 2.

Images